Modern Printed Circuits: February 2015

FEBRUARY ‘15

Raspberry Pi A+ Overview

Tips For Low-cost Designs

Interview with Anaya Vardya CEO of American Standard Circuits

CompetitiveADVANTAGE

The

American Standard Circuits Offers Customers the COMPLETE PACKAGE

http://bit.ly/jd6Wcw

CONTENTS

eeweb.com/register

Join Today

READY TO LAUNCH

For the launch of the Tiva C Series Connected LaunchPad, TI has partnered with Exosite, mentioned briefly above, to provide easy access to the LaunchPad from the Internet. The LaunchPad takes about 10 minutes to set up and you can immediately interact with it across the Internet and do things like turn an LED on and off remotely from the website and see the reported temperature as well. It can also display approximate geographic location based on the assigned IP address and display a map of all other connected LaunchPad owners if they are active and plugged-in to Exosite. “In addition, it supports a basic game by enabling someone to interface to the Connected LaunchPad through a serial port from a terminal while someone else is playing with them through their browser. It is basically showing how you can interact remotely with this product and a user even if you are across the globe,” Folkens explained.

START DEVELOPING

The Tiva C Series Connected LaunchPad is shipping now and the price is right; at $19.99 USD, it is less than half the price of other Ethernet-ready kits. The LaunchPad comes complete with quick start and user guides, and ample online support to ensure developers of all backgrounds are well equipped to begin creating cloud-based applications. “We have assembled an online support team to monitor the Engineering-to-Engineering (or E2E) Community,” Folkens said. “Along with this, you also got a free Code Composer Studio Integrated Development Environment, which allows developers to use the full capability. We also support other tool chains like Keil, IAR and Mentor Embedded.

Affordable, versatile, and easy to use, the Tiva Series Connected LaunchPad is well suited for a broad audience and promises to facilitate the expansion of ingenious IoT applications in the cloud. As Folkens concluded, “The target audiences actually are the hobbyists, students and professional engineers. A better way of looking at it is that we are targeting people with innovative ideas and trying to help them get those ideas launched into the cloud.”

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CONTENTS

CONTENTS

Modern Printed Circuits

3

4

12

18

26

32

TECH REPORTAvoiding Flux Residue in Advanced PCB Designs

TECH REPORTThe Raspberry Pi A+A Look at the World’s Most Popular Microcomputer

Cost Saving Steps for Your Next Design

INDUSTRY INTERVIEWThe Competitive AdvantageAmerican Standard Circuits’ Anaya Vardya, CEO

TECH SERIESPCB Reliability:Using Vias in Your Design

FLUX RESIDUEToday’s advanced PCB technologies demand more aggressive steps in cleaning up residues left by conventional no-clean flux cleaning processes.

By Zulki Khan, President and Founder NexLogic Technologies, Inc.

T The PCB world is seeing more

technology advancements

today than ever before. With

so much attention given to a growing

number of PCB design, fabrication, and

manufacturing concerns introduced by

these new technologies, it is no surprise

that little consideration is given to board

cleanliness on the manufacturing floor.

To make matters worse, today’s PCB

cleaning agents are lackluster at best.

As a result, there is a high probability of

leaving residues on the board, ultimately

leading to undesirable performance.

That is a key reason for placing special

emphasis on cleaning no-clean fluxes.

in Advanced PCB Designs

Avoiding

Raspberry Pi A+

The world’s most affordable microcomputer just got CHEAPER, and SMALLER.

The Raspberry Pi, perhaps the

most popular microcomputer,

just got even smaller. This

past November, the Raspberry Pi

Foundation released the Raspberry

Pi Model A+ computer—its smallest

form factor yet, perfect for projects

that need a bite-sized punch. This

allows makers to install virtually

invisible mini electronics all over

the house in order to make the

home more digitized. A device this

size can discretely fit on the side of

a planter’s pot in order to monitor

the soil content of a plant; or it can

squeeze behind a touchscreen display

in order to monitor and control the

climate of any room of the house;

or it can be fitted to a device like

a telescope that allows it to track

different celestial bodies. The

possibilities are endless. The discrete

form factor arrives just in time, as

the Internet of Things is gaining

more momentum and smaller, more

robust computer systems are needed

to enable these new applications.

The

A+ Source: www.adafruit.com

The American printed circuit industry has had a turbulent decade. With

more and more companies opting to outsource their PCB designs for cheaper rates, the once-popular “board shop” is becoming harder to find. However, despite the downturn in the industry, American Standard Circuits has implemented unique process technology to develop one of the broadest portfolios available, resulting in its fifth year of consistent growth. Founded in 1988, American Standard Circuits quickly grew from its small, family-run shop to acquiring larger Chicago facilities to support growing demand for its services. EEWeb spoke with Anaya Vardya, CEO of American Standard Circuits, about how the company migrated up the technology curve in order to supply customers with increasingly complex boards.

American Standard Circuits Offers Customers the Complete Package of PCB Solutions—All Under One Roof

Competitive Advantage

Interview with Anaya Vardya CEO of American Standard CircuitsThe

About Anaya Vardya

Anaya Vardya has 30 years in the electronics manufacturing business and is currently the CEO of American Standard Circuits, Inc (ASC). Founded in 1988, Chicago-based ASC is a total solutions provider, manufacturing quality rigid, metal-backed, and flex PCBs on various substrates for a variety of applications and markets. With customers in the medical, automotive, industrial, and defense and aerospace markets, and volumes from small test and prototype quantities to large volume production, ASC has the expertise to provide all technologies in a time-critical environment. Anaya was previously COO of Canadian-based Coretec Inc. and Sr. VP Operations of Merix (now part of Via Systems). Prior to that he had a variety of positions within IBM. Anaya also has a Master’s in Chemical Engineering from the University of Cincinnati and a Bachelor’s of Technology from Indian Institute of Technology (Bombay).

6:1

The first rule for via design is simple: bigger is better. Larger vias have greater mechanical strength as well as greater electrical and thermal conductivity. While space is always a consideration when it comes to PCB design, vias should have large drill holes with large aspect ratios. While manufacturers can achieve drill holes significantly smaller than this, 20 mil drill width with an annular ring of 7 mil and an aspect ratio of 6:1 should be used if space allows. For many boards this may be an unachievable goal, requiring drill holes in the realm of 8 to 12 mils, or even smaller. Check with your manufacturer to establish what their capabilities are. However, even if they are capable of providing smaller, the basic premise of bigger is better stands true. When a PCB is exposed to thermal changes in its processing or in its end working environment, the varying coefficient of thermal expansion (CTE) between the laminate and the copper can cause issues. PCBs are constrained through structural latticework to limit horizontal expansion but can expand and contract significantly in the vertical

direction. As copper expands and contracts at slightly less than one fourth of the rate of FR-4 laminate, vias are literally being pulled apart every time the board is heated. If the board is too thick and the copper in the via too thin, then the board will expand too much and the copper will break, literally tearing the via apart. In the example above, to get the appropriate aspect ratio with a drill width of 20 mil, this would result in a total pad diameter of 34 mil and allow a max board thickness of 120 mil.

Size is important with vias, but location is tantamount. If a via is located close to a solder pad, a myriad of problems may arise. Foremost is the problem with solder wicking. As the via heats up, it pulls the solder from the solder pad, through the via, and onto the other side of the board, leaving the pad either solder deficient or completely solder free. The larger the via, the more solder will likely wick away, making it less likely that you will have a solid mechanical and electrical joint. Fortunately, this concern can be fixed by any of three no-cost methods.

Aspect Ratio Solder Wicking

Providing a solder mask between the lead and the via creates a barrier to the movement of the solder. This is a simple yet effective method, though it does have its drawbacks. Due to the minimum width required for a solder mask, this may require the via to be moved even farther from the lead. The distances required may seem minimal, in the 2 - 5 mil range, however, when space is at a premium or the board is carrying high frequency signals, this may have a profound effect on your design. However, when these aren’t issues, this is a great way to avoid the solder wicking concerns.

If there is no space to move the via and you need to minimize the via size, it is possible to use an encroached or tented via. By masking the via pad, you save space and also make it possible to silkscreen over the via. However, this makes it impossible to use the via as a test point as the copper will no longer be accessible from the side that is tented. At this point, you need to make a decision on whether an encroached or tented via is best. A tented via is completely sealed and will create a better surface for silkscreening as well as a better barrier against contamination. This barrier works both ways, though. If a

Solder Dam

Encroached Via

Tented Via

Size is important with vias, but location is tantamount. If a via is located close to a solder pad, a myriad of problems may arise.

44





















Avoiding

5

TECH REPORT

5




















Avoiding

66


The PCB world is seeing more technology advancements today than ever before. With so much attention given to a growing number of PCB design, fabrication, and manufacturing concerns introduced by these new technologies, it is no surprise that little consideration is given to board cleanliness on the manufacturing floor. To make matters worse, today’s PCB cleaning agents are lackluster at best. As a result, there is a high probability of leaving residues on the board, ultimately leading to undesirable performance. That is a key reason for placing special emphasis on cleaning no-clean fluxes.

Residues and contaminants left over on PCBs could be ionic contaminations or non-ionic contaminations. Typically, these are non-conductive, organic species that are left over due to fabrication and assembly handling. These residues result mostly from resins, oils, greases, hand lotions, or silicone, and they don’t change a cleaning solution’s conductivity. However, these need to be cleaned after the board is assembled.

Conversely, ionic contaminations are ones containing molecules or atoms, which are conductive when a cleaning solution is applied to it. Moisture or ionic residues can completely dissociate into negative or positive particles, which change the overall conductivity of the solution. Therefore, if certain solution-like water is applied, it becomes either positive or negative. These are ionic contaminants or residues.

Some examples of ionic residues are ionic surfactants, flux activators, human perspiration, and plating chemistries, which are the ones that get charged during PCB fabrication. By taking a positive or negative ion charge, these residues change the cleaning solution’s conductivity, thereby making the cleanliness process different from what it should be.

These scenarios make it imperative that the EMS Provide or CM must not be complacent in its PCB regular cleaning process. Rather, extraordinary steps must be taken in assuring the correct cleaning technologies or techniques are applied based on a PCB’s application.

Otherwise, unexpected reactions can be created, resulting in subsequent board damage when inappropriate or non-compatible cleaning agents are used with fluxes and solder pastes.

The right cleaning agents are required to remove flux residues, especially when higher-reliability mil/aero and medical electronics PCB applications are involved. Proper cleaning agents improve the integrity of the process such as bonding and conformal coating. Residues can also cause improper adhesion of a bond that can lead to failures such as heel liftoff of certain gull wing components. During the coating process, if these residues are left in poor wetting or de-lamination, they can cause assembly failures and ultimately lead to field failures. These reliability risks are extraordinarily high, especially when using lead-free solder paste.

Switch to No-Clean Paste

Up to now, using water-soluble paste for cleaning PCBs has been the predominant method. However, today, increasing numbers of EMS providers and contract manufacturers (CMs) are switching to no-clean paste due to greater usage of quad flat no-leads (QFN) packages and flip-chip devices on the PCB, which are better assembled using no-clean paste. In those cases, special chemistries and aqueous batch cleaning take on a more important role compared to de-ionized water.

There are two main reasons for using no-clean paste for QFN and flip chip device-populated PCBs. One, it provides better wetting processes. Two, it is

more aggressive and compatible with those packaged devices in that no-clean paste penetrates through tight and tiny board packaging areas and crevices, which, otherwise, is not completely possible with water-soluble paste. Plus, no-clean paste offers better solder ability with fine-pitch BGAs and CSPs.

From a broader perspective, the challenge is to use no-clean paste and flux and still be able to clean the board and components to 99.5% - 99.9% level of cleanliness. Due to their tenacious nature, residues left behind by no-clean flux are especially difficult to clean even with special cleaning agents. In some cases, even some residues remain, which produce

Fig. 1. Ionograph tester for checking ionic contamination after batch cleaning is finished.

Extraordinary steps must be taken in assuring the correct cleaning technologies or techniques are applied based on a PCB’s application.

7

TECH REPORT

7

The PCB world is seeing more technology advancements today than ever before. With so much attention given to a growing number of PCB design, fabrication, and manufacturing concerns introduced by these new technologies, it is no surprise that little consideration is given to board cleanliness on the manufacturing floor. To make matters worse, today’s PCB cleaning agents are lackluster at best. As a result, there is a high probability of leaving residues on the board, ultimately leading to undesirable performance. That is a key reason for placing special emphasis on cleaning no-clean fluxes.

Residues and contaminants left over on PCBs could be ionic contaminations or non-ionic contaminations. Typically, these are non-conductive, organic species that are left over due to fabrication and assembly handling. These residues result mostly from resins, oils, greases, hand lotions, or silicone, and they don’t change a cleaning solution’s conductivity. However, these need to be cleaned after the board is assembled.

Conversely, ionic contaminations are ones containing molecules or atoms, which are conductive when a cleaning solution is applied to it. Moisture or ionic residues can completely dissociate into negative or positive particles, which change the overall conductivity of the solution. Therefore, if certain solution-like water is applied, it becomes either positive or negative. These are ionic contaminants or residues.

Some examples of ionic residues are ionic surfactants, flux activators, human perspiration, and plating chemistries, which are the ones that get charged during PCB fabrication. By taking a positive or negative ion charge, these residues change the cleaning solution’s conductivity, thereby making the cleanliness process different from what it should be.

These scenarios make it imperative that the EMS Provide or CM must not be complacent in its PCB regular cleaning process. Rather, extraordinary steps must be taken in assuring the correct cleaning technologies or techniques are applied based on a PCB’s application.

Otherwise, unexpected reactions can be created, resulting in subsequent board damage when inappropriate or non-compatible cleaning agents are used with fluxes and solder pastes.

The right cleaning agents are required to remove flux residues, especially when higher-reliability mil/aero and medical electronics PCB applications are involved. Proper cleaning agents improve the integrity of the process such as bonding and conformal coating. Residues can also cause improper adhesion of a bond that can lead to failures such as heel liftoff of certain gull wing components. During the coating process, if these residues are left in poor wetting or de-lamination, they can cause assembly failures and ultimately lead to field failures. These reliability risks are extraordinarily high, especially when using lead-free solder paste.

Switch to No-Clean Paste

Up to now, using water-soluble paste for cleaning PCBs has been the predominant method. However, today, increasing numbers of EMS providers and contract manufacturers (CMs) are switching to no-clean paste due to greater usage of quad flat no-leads (QFN) packages and flip-chip devices on the PCB, which are better assembled using no-clean paste. In those cases, special chemistries and aqueous batch cleaning take on a more important role compared to de-ionized water.

There are two main reasons for using no-clean paste for QFN and flip chip device-populated PCBs. One, it provides better wetting processes. Two, it is

more aggressive and compatible with those packaged devices in that no-clean paste penetrates through tight and tiny board packaging areas and crevices, which, otherwise, is not completely possible with water-soluble paste. Plus, no-clean paste offers better solder ability with fine-pitch BGAs and CSPs.

From a broader perspective, the challenge is to use no-clean paste and flux and still be able to clean the board and components to 99.5% - 99.9% level of cleanliness. Due to their tenacious nature, residues left behind by no-clean flux are especially difficult to clean even with special cleaning agents. In some cases, even some residues remain, which produce

Fig. 1. Ionograph tester for checking ionic contamination after batch cleaning is finished.

Extraordinary steps must be taken in assuring the correct cleaning technologies or techniques are applied based on a PCB’s application.

88


undesirable results on extra high-speed PCBs, like improper eye diagrams.

If the proper cleaning agents aren’t applied, a board may still have flux and solder paste residues that are trapped inside the small cavities, which will hinder the board’s optimal performance since transmission and return signals are not 100% clean, especially with high-speed designs. When this occurs, assembly personnel have to resort to another cleaning cycle and then use an ionograph machine, as shown in Fig. 1, to assure targeted cleanliness is performed to a satisfactory level, which can be quantitatively proven.

It’s also worth noting that no-clean paste means PCBs cannot be cleaned with de-ionized water. The reason is the chemistry of no-clean flux doesn’t gel well with water. As a result, it leaves white residue on the PCB that is not attractive to the

eye; plus, these boards are difficult to clean. Special chemistries are needed because composition of that chemistry effectively gels with the chemistry of the no-clean flux. This way, PCBs can be cleaned properly to eliminate flux residues.

In this instance, there are flux residues that not only contaminate a board, but also have some fingerprints, which have human body oils, as shown in Fig. 2. All these residues and contaminants can get stuck in different portions of a board’s surface and cause undesirable performance. Those performance symptoms can show up within a short time period; others can linger and subsequently emerge as major system flaws in the field.

For example, conformal coatings may fail, creating a huge issue. If no-clean flux residues are left, voids within the conformal coating are created, resulting in air gaps or pockets. This is a major issue, especially when these improperly cleaned PCBs are exposed to a harsh and rugged environment. Conformal coating deteriorates when incorrect chemistries adversely react with the conformal coating material. Also, bonding or encapsulation may deteriorate due to highly active flux ingredients.

The reaction in this case would be such that they break hermetically sealed packaging, which is intended to keep moisture or humidity from entering and damaging the circuitry it houses. If such a thing happens, moisture seeps in and assembly joints may be compromised and may get damaged. Also, flux residues

can cause corrosions and dendrite growth, which often causes intermittent failures. Similar in nature to tin whiskers, dendrite growth comprises tiny conductive metal filaments that extend between PCB pads or bridge across tracks to cause short circuits.

Problems at High Frequency & High Voltage

Flux residues cannot be tolerated in high-voltage PCBs. Leftover and undesired flux residues have the highest probability of creating a spark between two points and short the circuit. For example, a flux residue may adversely affect analog or digital conversion in A/D circuits. This is especially true with extremely high-speed digital signals. If there are flux residues, rosins or gooey types of agents left on the PCB and device packaging, they will hinder the A/D conversion process. It will not optimally occur as it is intended, especially at high-speed levels when flux and paste residues are left over.

Also, the higher the frequency, the cleaner the PCB surface has to be. Both transmit and return paths need to operate at high-speed levels, which must be very clean of any contaminations. Even the slightest speed transfer change in the return path compared to the transmit path can have a devastating effect on performance. If improper, non-compatible cleaning agents are used, undesirable residues and rosins will hinder signal propagation at those high-speed levels.

Fig. 2. PCB with red solder mask

shows fingerprints from handling of

this board.

Fig. 3. A clean video link channel may be distorted as a result of miniscule flux residues on a PCB. compromising that product.

The higher the frequency, the cleaner the PCB surface has to be.

Both transmit and return paths need to operate at high-speed levels, which must

be very clean of any contaminations.

In particular, flux residues can have a damaging effect on image processing based applications for medical device markets. Take for example oncology products, where a clean video link channel, as shown in Fig. 3, may be distorted as a result of miniscule flux residues on a PCB, ultimately compromising that product. Due to that distortion, an inaccurate reading can mislead a healthcare giver using such a product, or worst case, medical specialists aren’t able to determine healthy versus cancerous cells in the video link because channel transmission is not clean. Therefore, flux residues can prevent PCB circuitry from achieving optimal results.

9

TECH REPORT

9

undesirable results on extra high-speed PCBs, like improper eye diagrams.

If the proper cleaning agents aren’t applied, a board may still have flux and solder paste residues that are trapped inside the small cavities, which will hinder the board’s optimal performance since transmission and return signals are not 100% clean, especially with high-speed designs. When this occurs, assembly personnel have to resort to another cleaning cycle and then use an ionograph machine, as shown in Fig. 1, to assure targeted cleanliness is performed to a satisfactory level, which can be quantitatively proven.

It’s also worth noting that no-clean paste means PCBs cannot be cleaned with de-ionized water. The reason is the chemistry of no-clean flux doesn’t gel well with water. As a result, it leaves white residue on the PCB that is not attractive to the

eye; plus, these boards are difficult to clean. Special chemistries are needed because composition of that chemistry effectively gels with the chemistry of the no-clean flux. This way, PCBs can be cleaned properly to eliminate flux residues.

In this instance, there are flux residues that not only contaminate a board, but also have some fingerprints, which have human body oils, as shown in Fig. 2. All these residues and contaminants can get stuck in different portions of a board’s surface and cause undesirable performance. Those performance symptoms can show up within a short time period; others can linger and subsequently emerge as major system flaws in the field.

For example, conformal coatings may fail, creating a huge issue. If no-clean flux residues are left, voids within the conformal coating are created, resulting in air gaps or pockets. This is a major issue, especially when these improperly cleaned PCBs are exposed to a harsh and rugged environment. Conformal coating deteriorates when incorrect chemistries adversely react with the conformal coating material. Also, bonding or encapsulation may deteriorate due to highly active flux ingredients.

The reaction in this case would be such that they break hermetically sealed packaging, which is intended to keep moisture or humidity from entering and damaging the circuitry it houses. If such a thing happens, moisture seeps in and assembly joints may be compromised and may get damaged. Also, flux residues

can cause corrosions and dendrite growth, which often causes intermittent failures. Similar in nature to tin whiskers, dendrite growth comprises tiny conductive metal filaments that extend between PCB pads or bridge across tracks to cause short circuits.

Problems at High Frequency & High Voltage

Flux residues cannot be tolerated in high-voltage PCBs. Leftover and undesired flux residues have the highest probability of creating a spark between two points and short the circuit. For example, a flux residue may adversely affect analog or digital conversion in A/D circuits. This is especially true with extremely high-speed digital signals. If there are flux residues, rosins or gooey types of agents left on the PCB and device packaging, they will hinder the A/D conversion process. It will not optimally occur as it is intended, especially at high-speed levels when flux and paste residues are left over.

Also, the higher the frequency, the cleaner the PCB surface has to be. Both transmit and return paths need to operate at high-speed levels, which must be very clean of any contaminations. Even the slightest speed transfer change in the return path compared to the transmit path can have a devastating effect on performance. If improper, non-compatible cleaning agents are used, undesirable residues and rosins will hinder signal propagation at those high-speed levels.

Fig. 2. PCB with red solder mask

shows fingerprints from handling of

this board.

Fig. 3. A clean video link channel may be distorted as a result of miniscule flux residues on a PCB. compromising that product.

The higher the frequency, the cleaner the PCB surface has to be.

Both transmit and return paths need to operate at high-speed levels, which must

be very clean of any contaminations.

In particular, flux residues can have a damaging effect on image processing based applications for medical device markets. Take for example oncology products, where a clean video link channel, as shown in Fig. 3, may be distorted as a result of miniscule flux residues on a PCB, ultimately compromising that product. Due to that distortion, an inaccurate reading can mislead a healthcare giver using such a product, or worst case, medical specialists aren’t able to determine healthy versus cancerous cells in the video link because channel transmission is not clean. Therefore, flux residues can prevent PCB circuitry from achieving optimal results.

1010


Difficult to Remove

Residues from no-clean paste and fluxes are more difficult to remove than water-soluble-based ones. At times, a special batch cleaning process with certain chemistries is required to prevent these residues and contaminations. A word of caution; using too strong a chemistry for cleaning the PCB may cause creepage of chemical agents into the solder mask, thus jeopardizing solder integrity, as shown in Fig. 4.

The advantage of cleaning is to prevent electrochemical migration from one side of the board to another, or so-called “creep corrosion,” either by stopping it or preventing it from happening altogether. Creep corrosion occurs from electrochemical oxidation of metals in reaction to an oxidant such as oxygen. It is difficult to mitigate due

to the very nature of the corrosion, i.e. reaction between metal contents in no-clean flux and oxygen.

To mitigate corrosion, control leakage currents and improve in-circuit testing (ICT) yield by improving the cleanliness in a batch cleaning process using special chemistry instead of de-ionized water. Also, this provides a better point of contact for flying probe testing so that the probe points can effectively touch pads on the board when there is no obstruction due to flux or high chemical residues. Moreover, when boards are clean, there is improved conformal coating and underfill adhesion.

Two other factors playing a part in improved cleaning include better point of contact for testing and improved underfill conditions. De-ionized (DI) water alone

cannot clean 100 percent of all the rosin in the flux. It leaves white powdery foam and the solvent saponifier chemistry is often needed to clean that foam. This increases the capital expenditure of the CM, as well as increases the cost since a special cleaner is required, along with the extended cleaning time requirements.

Consequently, equipment is needed to clean it, and additional chemistries are needed. Rosin, which is in the no-clean flux, provides inert and, in some cases, non-hygroscopic covers on the top. This coating on the top prevents ions from having an electromagnetic migration path.

Expertise on Manufacturing Floor

EMS providers and CMs are faced with a vast selection of PCB cleaning agents from a considerable number of large well-known commercial vendors. Each has different types of cleaning agents with varying kinds of chemicals in those products. There are also lesser-known, smaller vendors producing different cleaning agents with different characteristics. Some are conducive to no-clean flux cleaning, while others are not as compatible.

It’s also important to know that sometimes vendors add or delete certain chemical properties from their cleaning agents. When this occurs and the changes go unannounced, it leaves the EMS provider and CM guessing as to the proper PCB cleaning mix to avoid damaging boards.

Therefore, it’s highly important for the EMS provider and CM to be at the top of their game and have up-to-date knowledge, expertise, and experience about today’s cleaning agents and their characteristics. This includes matching the right cleaning agents with the right PCB applications, knowledge of chemical properties in cleaning agents produced by specific vendors, understanding technical specification sheets, and making the right decisions based on precise know how. If that expertise isn’t found on a PCB manufacturing floor, the chances are high that the wrong cleaning agents will be used. As a result, those boards will incur some level of damage, leading to undesirable performance and latent field failures.

Fig. 4. Too strong a chemistry used for

cleaning a PCB may cause creepage of

chemical agents into the solder mask and

jeopardize solder integrity.

Creep corrosion

occurs from electro-

chemical oxidation

of metals in reaction to an oxidant such

as oxygen.

Author Bio

Zulki Khan is the Founder and President of NexLogic Technologies, Inc., San Jose, CA, an ISO 9001:2008 Certified Company, ISO 13485 certified for medical electronics, and a RoHS compliant EMS provider. Prior to NexLogic, he was General Manager for Imagineering, Inc., Schaumburg, IL. He has also worked on high-speed PCB designs with signal integrity analysis. He holds B.S.E.E from N.E.D University and M.B.A from University of Iowa and is a frequent author of contributed articles to EMS industry publications.

11

TECH REPORT

11

Difficult to Remove

Residues from no-clean paste and fluxes are more difficult to remove than water-soluble-based ones. At times, a special batch cleaning process with certain chemistries is required to prevent these residues and contaminations. A word of caution; using too strong a chemistry for cleaning the PCB may cause creepage of chemical agents into the solder mask, thus jeopardizing solder integrity, as shown in Fig. 4.

The advantage of cleaning is to prevent electrochemical migration from one side of the board to another, or so-called “creep corrosion,” either by stopping it or preventing it from happening altogether. Creep corrosion occurs from electrochemical oxidation of metals in reaction to an oxidant such as oxygen. It is difficult to mitigate due

to the very nature of the corrosion, i.e. reaction between metal contents in no-clean flux and oxygen.

To mitigate corrosion, control leakage currents and improve in-circuit testing (ICT) yield by improving the cleanliness in a batch cleaning process using special chemistry instead of de-ionized water. Also, this provides a better point of contact for flying probe testing so that the probe points can effectively touch pads on the board when there is no obstruction due to flux or high chemical residues. Moreover, when boards are clean, there is improved conformal coating and underfill adhesion.

Two other factors playing a part in improved cleaning include better point of contact for testing and improved underfill conditions. De-ionized (DI) water alone

cannot clean 100 percent of all the rosin in the flux. It leaves white powdery foam and the solvent saponifier chemistry is often needed to clean that foam. This increases the capital expenditure of the CM, as well as increases the cost since a special cleaner is required, along with the extended cleaning time requirements.

Consequently, equipment is needed to clean it, and additional chemistries are needed. Rosin, which is in the no-clean flux, provides inert and, in some cases, non-hygroscopic covers on the top. This coating on the top prevents ions from having an electromagnetic migration path.

Expertise on Manufacturing Floor

EMS providers and CMs are faced with a vast selection of PCB cleaning agents from a considerable number of large well-known commercial vendors. Each has different types of cleaning agents with varying kinds of chemicals in those products. There are also lesser-known, smaller vendors producing different cleaning agents with different characteristics. Some are conducive to no-clean flux cleaning, while others are not as compatible.

It’s also important to know that sometimes vendors add or delete certain chemical properties from their cleaning agents. When this occurs and the changes go unannounced, it leaves the EMS provider and CM guessing as to the proper PCB cleaning mix to avoid damaging boards.

Therefore, it’s highly important for the EMS provider and CM to be at the top of their game and have up-to-date knowledge, expertise, and experience about today’s cleaning agents and their characteristics. This includes matching the right cleaning agents with the right PCB applications, knowledge of chemical properties in cleaning agents produced by specific vendors, understanding technical specification sheets, and making the right decisions based on precise know how. If that expertise isn’t found on a PCB manufacturing floor, the chances are high that the wrong cleaning agents will be used. As a result, those boards will incur some level of damage, leading to undesirable performance and latent field failures.

Fig. 4. Too strong a chemistry used for

cleaning a PCB may cause creepage of

chemical agents into the solder mask and

jeopardize solder integrity.

Creep corrosion

occurs from electro-

chemical oxidation

of metals in reaction to an oxidant such

as oxygen.

Author Bio

Zulki Khan is the Founder and President of NexLogic Technologies, Inc., San Jose, CA, an ISO 9001:2008 Certified Company, ISO 13485 certified for medical electronics, and a RoHS compliant EMS provider. Prior to NexLogic, he was General Manager for Imagineering, Inc., Schaumburg, IL. He has also worked on high-speed PCB designs with signal integrity analysis. He holds B.S.E.E from N.E.D University and M.B.A from University of Iowa and is a frequent author of contributed articles to EMS industry publications.

1212


When considering the long term reliability

of a PCB, you must take into account the

vias that you have on your board. While

an invaluable and essential part of board design, vias

introduce weaknesses and affect solderability. This

article will discuss vias, the potential concerns that are

introduced into your board through their implementation,

and how to minimize those concerns to acceptable levels.VIADESIGN

PCB Reliability:

13

TECH SERIES

13

When considering the long term reliability

of a PCB, you must take into account the

vias that you have on your board. While

an invaluable and essential part of board design, vias

introduce weaknesses and affect solderability. This

article will discuss vias, the potential concerns that are

introduced into your board through their implementation,

and how to minimize those concerns to acceptable levels.VIADESIGN

PCB Reliability:

1414


6:1







Solder Dam

Encroached Via

Tented Via


15

TECH SERIES

15

6:1







Solder Dam

Encroached Via

Tented Via


www.aapcb.com

1616


Filled vias are also an option, which increase strength, electrical/thermal conductivity, and protect the via from solderwicking and contamination. The main drawback to filled vias is that they can add significant costs to the board. The other methods should have no impact on cost whatsoever.

Every design has different requirements and constraints. However, when possible, utilize these tips by using the largest vias, the appropriate aspect ratio, and by thoughtfully choosing the solder masking style that suits your needs. This will help reduce the overall lifetime costs by increasing reliability of your products.

via is tented on both sides of the board, contamination can fill the void during the board construction. At elevated temperatures, such as when the PCB is being reflowed or wave soldered, the contamination can outgas and destroy the via and thus the board. When you tent a via, make certain you only do it on one side. An encroached via eliminates this issue by keeping the hole itself open and also has the added benefit versus a tented via of being possible no matter the via size. While tented vias need to be small enough for the solder mask to bridge the drill hole, the encroached via only covers the annular ring and can be as big or small as needed.

Advanced Assembly was founded to help engineers assemble their prototype and low-volume PCB orders. Based on years of experience within the printed circuit board industry, Advanced Assembly developed a proprietary system to deliver consistent, machine surface mount technology (SMT) assembly in 1-5 days. It’s our only focus. We take the hassle out of PCB assembly and make it easy, so you can spend time on other aspects of your design.

20100 E. 32nd Pkwy #225 | Aurora, CO 80011 | www.aapcb.com | 1-800-838-5650

Every design has different requirements and constraints.

http://www.aapcb.com

CLICK HERESMT Assembly for Engineers

SMT Assembly for Engineers

SMT Assembly for Engineers

http://www.aa-pcbassembly.com

1818


Large or small, every company wants to decrease costs without

affecting the quality of their products or services. There is rarely a perfect way to achieve this and PCB design and assembly is no exception. Accurately assembling PCBs is not an easy task; it takes experience, technology and, above all, dedicated people to ensure your projects are done right. When searching for a low-volume assembly shop to populate your boards, it may

be tempting to use a low-cost shop to save money. However, doing so may end up costing more in the long term due to reliability concerns and lower throughput, which could result in a damaged reputation. As the famous adage goes—you get what you pay for. With thoughtful planning, you can incorporate the following eight design principles to bring the overall price down while still using a high quality shop and getting high quality results.

STEPSYour Next Design

for

Cost Saving8

19

TECH SERIES

19

Large or small, every company wants to decrease costs without

affecting the quality of their products or services. There is rarely a perfect way to achieve this and PCB design and assembly is no exception. Accurately assembling PCBs is not an easy task; it takes experience, technology and, above all, dedicated people to ensure your projects are done right. When searching for a low-volume assembly shop to populate your boards, it may

be tempting to use a low-cost shop to save money. However, doing so may end up costing more in the long term due to reliability concerns and lower throughput, which could result in a damaged reputation. As the famous adage goes—you get what you pay for. With thoughtful planning, you can incorporate the following eight design principles to bring the overall price down while still using a high quality shop and getting high quality results.

STEPSYour Next Design

for

Cost Saving8

2020


One-sided SMT and Through-Hole

One-side SMT / One-side Through-Hole

Mixed SMT and Through-Hole

Mixed Technology PCBs

1 2DESIGN WITHIN STANDARD SPECIFICATIONS

By using industry standard sizes and components, the assembly team can use processes that have already been established and thoroughly tested. They will also be able to automate large portions of the process and avoid costly and time-consuming hand placement and soldering. Knowing what the assembly house is capable of is a matter of experience and research. Assembly houses should include their capabilities on their websites or provide a link in brochures which should answer most questions of what they can successfully handle. Any questions that are not answered by these sources can be directed to the company itself. The responsiveness of the company to your questions about their capabilities should be a good indicator of the type of service that you will receive if you become a customer.

When asked for capabilities, assembly houses will provide what they are capable of but not necessarily what is cost-effective. As a general rule, it’s always a good idea to not push the design limitations as much as possible. If it is possible to use larger traces, or greater spacing between components, then why not do it? It may or may not make the process easier but if it does not affect the operation of the board, then it only has the potential of helping.Also, when speaking with the assembly house, ask if there is anything specific to their process that may help bring the overall cost down. These suggestions may have a considerable impact on the design of your PCB, so it may be a good idea to start looking into assembly houses towards the beginning of the design of the board once you have a general idea of what you will need.

CONSIDER THE COSTS OF MIXED MOUNT TECHNOLOGIES

When building a board with solely surface mount technology parts, the boards typically have solder paste applied and are then populated and run through a reflow oven to complete the soldering process. Even for low volume assembly where most components are hand soldered, mixed technology requires more time and effort. Depending on the disparity of sizes between through-hole and surface-mount components, different soldering iron tips, temperatures, and solders may need to be used. If this low volume assembly is a pre-cursor to larger volume and more automated assembly, the difference in complexity becomes even more pronounced and is a larger concern. In the case of through-hole components during high volume assembly, when they are placed on the board they are then wave soldered. However, when there is a combination, things become more complicated. There are three combinations of mixed technology: single sided SMT and through-hole, double sided with SMT on one side and through-hole on the other, and double-sided with both SMT and through-hole on either side. Each of these scenarios is dealt with differently, but require significantly more steps and have more stringent requirements than a single technology on the board. For example, even placing SMT and through-hole components on one side requires the additional steps of applying an adhesive

to the SMT components, allowing the adhesive to cure, flipping the board and then wave soldering it. As the solder bath temperatures can destroy some SMT components, you will need to verify that the SMT components are wave solderable, making your component selection criteria even more stringent. When there is mixed technology on both sides of the board, this becomes even more complex and frequently requires hand soldering of certain components after the automated process. This is not to say that you cannot mix technologies or utilize both sides of your boards for components, merely that you should weigh the benefits and drawbacks of each and make sure that mixing the technologies is worth the additional cost and assembly time for your application.

Avoid Design Limitations Mixed Technology PCBs Panelized PCBs

21

TECH SERIES

21

One-sided SMT and Through-Hole

One-side SMT / One-side Through-Hole

Mixed SMT and Through-Hole

Mixed Technology PCBs

1 2DESIGN WITHIN STANDARD SPECIFICATIONS

By using industry standard sizes and components, the assembly team can use processes that have already been established and thoroughly tested. They will also be able to automate large portions of the process and avoid costly and time-consuming hand placement and soldering. Knowing what the assembly house is capable of is a matter of experience and research. Assembly houses should include their capabilities on their websites or provide a link in brochures which should answer most questions of what they can successfully handle. Any questions that are not answered by these sources can be directed to the company itself. The responsiveness of the company to your questions about their capabilities should be a good indicator of the type of service that you will receive if you become a customer.

When asked for capabilities, assembly houses will provide what they are capable of but not necessarily what is cost-effective. As a general rule, it’s always a good idea to not push the design limitations as much as possible. If it is possible to use larger traces, or greater spacing between components, then why not do it? It may or may not make the process easier but if it does not affect the operation of the board, then it only has the potential of helping.Also, when speaking with the assembly house, ask if there is anything specific to their process that may help bring the overall cost down. These suggestions may have a considerable impact on the design of your PCB, so it may be a good idea to start looking into assembly houses towards the beginning of the design of the board once you have a general idea of what you will need.

CONSIDER THE COSTS OF MIXED MOUNT TECHNOLOGIES

When building a board with solely surface mount technology parts, the boards typically have solder paste applied and are then populated and run through a reflow oven to complete the soldering process. Even for low volume assembly where most components are hand soldered, mixed technology requires more time and effort. Depending on the disparity of sizes between through-hole and surface-mount components, different soldering iron tips, temperatures, and solders may need to be used. If this low volume assembly is a pre-cursor to larger volume and more automated assembly, the difference in complexity becomes even more pronounced and is a larger concern. In the case of through-hole components during high volume assembly, when they are placed on the board they are then wave soldered. However, when there is a combination, things become more complicated. There are three combinations of mixed technology: single sided SMT and through-hole, double sided with SMT on one side and through-hole on the other, and double-sided with both SMT and through-hole on either side. Each of these scenarios is dealt with differently, but require significantly more steps and have more stringent requirements than a single technology on the board. For example, even placing SMT and through-hole components on one side requires the additional steps of applying an adhesive

to the SMT components, allowing the adhesive to cure, flipping the board and then wave soldering it. As the solder bath temperatures can destroy some SMT components, you will need to verify that the SMT components are wave solderable, making your component selection criteria even more stringent. When there is mixed technology on both sides of the board, this becomes even more complex and frequently requires hand soldering of certain components after the automated process. This is not to say that you cannot mix technologies or utilize both sides of your boards for components, merely that you should weigh the benefits and drawbacks of each and make sure that mixing the technologies is worth the additional cost and assembly time for your application.

Avoid Design Limitations Mixed Technology PCBs Panelized PCBs

2222


3

45 6

size your assembly house can handle, and put as many iterations of your design on that single panel as possible.

It should be noted that the benefits of panelizing boards are only applicable if it is the same design repeated multiple times on a single panel. Including multiple designs on one panel will not provide any cost savings as the panel will, in essence, be a larger, more complex single board.

MINIMIZE OVERAGES

If you are producing a low volume of boards, use an assembly house that does not require reels or major parts overages. If you only need 30 boards and only one or two of each component on each board, it does not make sense to buy a reel of

literally thousands of parts. At the prototyping stage, components can be changed out quite frequently in the design and you may end up with a great deal of parts that serve no purpose and may have cost considerable amounts of money. Some assembly houses can machine place parts without needing large reels or tubes of parts. While researching the company, find what each is capable of handling—if they require you to purchase large reels for small prototyping runs, look elsewhere.

While you do want to minimize the parts necessary for your build, do not forget to include a small amount of overage in your requirements calculations. Parts, particularly

the incredibly small 0402 and 0201 components, can be dropped by the pick-and-place machine or damaged at some point in the process, so your assembly house should have general guidelines on how many extra parts you need to provide. Excess parts after the assembly will be shipped back with the parts.

SEEK EXTERNAL REVIEW

Whenever possible, have someone else review your work. When your circuit boards are submitted to a PCB manufacturer or assembly house, trained technicians or engineers will look at the design and verify that it is manufacturable. This is an invaluable service that has saved many designs from basic errors over the years. However, these technicians and engineers are focused on the manufacturability and do not know the purpose of the board. By asking a member of your team to review your work and provide a fresh perspective, you reduce the risk of missing simple

PANELIZE YOUR BOARDS

The size of panel that is acceptable depends on the assembly house, but this information can save considerable amounts of money. By using the largest panel size possible, you can drop assembly costs by eliminating pick and place downtime. For an example, assume a single sided SMT board with 200 parts and a pick and place speed of 6,000 components an hour. In this scenario, it would only take two minutes to fully populate each board once the board was fully situated. After the board is complete, it will then need to be removed and replaced with a new unpopulated board, either manually or via some form of conveyor. At best, this could take approximately 15 seconds and potentially much more. If the board needs to be moved and replaced by hand it could either take a minute or two for a worker to make the switch, or require the worker to stand there and watch the pick and place work. Both of these options require a significant amount of labor. If the process is automated and takes 15 seconds to switch out a board, over 10% of the component placement time will be in moving boards. If you are able to get 10 boards on a panel, those 15 seconds will only apply to every 10 boards, meaning only slightly over 1% of the time spent populating the board will be moving the board into position. If it takes longer than 15 seconds to switch out a board or the pick and place is faster than 6,000 components an hour, the time savings—and therefore cost savings—will be even greater. It is in your best interest to find the largest panel

Collaboration

yet crucial errors. If you are unable to find someone with the experience to provide feedback, even explaining the board to someone who is not particularly knowledge in the field will help you to step through and verify the functionality of the design to yourself.

TAKE ADVANTAGE OF FIRST ARTICLE SERVICE

With prototypes, even after thorough and repeated review, it is still likely that there will be concerns. With final designs, while less likely, it is still possible that there is some error that will be manifest in the end product. Many assembly houses will populate one board and send it out for review, testing, and verification before continuing on the process. If they offer this service, take advantage of it. Hopefully all is well with the board, but if not, it could save a tremendous amount

of money to catch the problems before potentially expensive

components are attached to boards with errors on them.

23

TECH SERIES

23

3

45 6

size your assembly house can handle, and put as many iterations of your design on that single panel as possible.

It should be noted that the benefits of panelizing boards are only applicable if it is the same design repeated multiple times on a single panel. Including multiple designs on one panel will not provide any cost savings as the panel will, in essence, be a larger, more complex single board.

MINIMIZE OVERAGES

If you are producing a low volume of boards, use an assembly house that does not require reels or major parts overages. If you only need 30 boards and only one or two of each component on each board, it does not make sense to buy a reel of

literally thousands of parts. At the prototyping stage, components can be changed out quite frequently in the design and you may end up with a great deal of parts that serve no purpose and may have cost considerable amounts of money. Some assembly houses can machine place parts without needing large reels or tubes of parts. While researching the company, find what each is capable of handling—if they require you to purchase large reels for small prototyping runs, look elsewhere.

While you do want to minimize the parts necessary for your build, do not forget to include a small amount of overage in your requirements calculations. Parts, particularly

the incredibly small 0402 and 0201 components, can be dropped by the pick-and-place machine or damaged at some point in the process, so your assembly house should have general guidelines on how many extra parts you need to provide. Excess parts after the assembly will be shipped back with the parts.

SEEK EXTERNAL REVIEW

Whenever possible, have someone else review your work. When your circuit boards are submitted to a PCB manufacturer or assembly house, trained technicians or engineers will look at the design and verify that it is manufacturable. This is an invaluable service that has saved many designs from basic errors over the years. However, these technicians and engineers are focused on the manufacturability and do not know the purpose of the board. By asking a member of your team to review your work and provide a fresh perspective, you reduce the risk of missing simple

PANELIZE YOUR BOARDS

The size of panel that is acceptable depends on the assembly house, but this information can save considerable amounts of money. By using the largest panel size possible, you can drop assembly costs by eliminating pick and place downtime. For an example, assume a single sided SMT board with 200 parts and a pick and place speed of 6,000 components an hour. In this scenario, it would only take two minutes to fully populate each board once the board was fully situated. After the board is complete, it will then need to be removed and replaced with a new unpopulated board, either manually or via some form of conveyor. At best, this could take approximately 15 seconds and potentially much more. If the board needs to be moved and replaced by hand it could either take a minute or two for a worker to make the switch, or require the worker to stand there and watch the pick and place work. Both of these options require a significant amount of labor. If the process is automated and takes 15 seconds to switch out a board, over 10% of the component placement time will be in moving boards. If you are able to get 10 boards on a panel, those 15 seconds will only apply to every 10 boards, meaning only slightly over 1% of the time spent populating the board will be moving the board into position. If it takes longer than 15 seconds to switch out a board or the pick and place is faster than 6,000 components an hour, the time savings—and therefore cost savings—will be even greater. It is in your best interest to find the largest panel

Collaboration

yet crucial errors. If you are unable to find someone with the experience to provide feedback, even explaining the board to someone who is not particularly knowledge in the field will help you to step through and verify the functionality of the design to yourself.

TAKE ADVANTAGE OF FIRST ARTICLE SERVICE

With prototypes, even after thorough and repeated review, it is still likely that there will be concerns. With final designs, while less likely, it is still possible that there is some error that will be manifest in the end product. Many assembly houses will populate one board and send it out for review, testing, and verification before continuing on the process. If they offer this service, take advantage of it. Hopefully all is well with the board, but if not, it could save a tremendous amount

of money to catch the problems before potentially expensive

components are attached to boards with errors on them.

2424


7

8Advanced Assembly was founded to help engineers assemble their prototype and low-volume PCB orders. Based on years of experience within the printed circuit board industry, Advanced Assembly developed a proprietary system to deliver consistent, machine surface mount technology (SMT) assembly in 1-5 days. It’s our only focus. We take the hassle out of PCB assembly and make it easy, so you can spend time on other aspects of your design.


ORDER IN VOLUME

Once you are confident with your design and do not expect many changes, it would be best to get boards manufactured and populated in as large of quantities as possible. Economies of scale is a familiar concept, but in regards to PCBs, it is even more relevant than usual. The actual materials involved in the production of the PCBs are relatively minimal and the assembly of a PCB only has the cost of solder, electricity, and maintenance for the machines who place and reflow the boards. However, the time it takes to ready designs for these steps is quite extensive. There are a multitude of steps required before the actual boards are even placed into the pick and place machine. The assembly house needs to review the provided design and clarify any confusion or discrepancy, before loading the design into the pick and place machine. The parts provided are then placed into the machine, which depending on the amount of parts, could be a long and tedious process. Even if the placing will be done by hand, the process will accelerate substantially after the first few boards as the workers become more familiar with the components and where they go.

Many of the assembly houses that perform prototyping assembly are also fully capable of providing large-scale assembly. There are many benefits of using the same assembly house for both levels of production, the largest benefit being that they are already aware of your project and requirements whereas a new assembly house would need to gain familiarity with the project requirements and the production pitfalls associated with their particular system. Ordering in volume is always a gamble as everyone in the industry has had the experience of creating large piles of very costly coasters. By using the same assembly house, you can further reduce the risks of high volume ordering as you will already be familiar with the way they work and they will be familiar with your needs. However, in the end, it is up to you and the engineers on your team to reach the level of confidence where the benefit of the cost savings is no longer outweighed by the risk of having design flaws.

PROVIDE HELPFUL INFORMATION TO THE MANUFACTURER

If there are any special requirements or areas that you believe will cause concerns, contact the company and

discuss it with them. They may be able to provide design advice that eliminates these concerns or maybe let you know that the design is unmanufacturable. Most likely, however, they will pay special attention to where you have indicated and perhaps make minor tweaks to their processes to ensure that it is done correctly. Knowing beforehand can save a lot of time and money on rework that could have been avoided.

There is rarely too much information provided when submitting boards for manufacturing and assembly. If there is information that is recommended but not required, include it when you can. For example, Advanced Assembly does not require fiducials in order to process and successfully assemble circuit boards. However, the fiducials are an additional help that could reduce the difficulties in the assembling process and could improve the final product due to increased accuracy. If it is possible to include fiducials on either the PCB or panel, do so.

CONCLUSION

It is possible to decrease costs without giving up quality. Instead of using cut-rate manufacturers and assembly houses, follow these low-to-no cost recommendations that will save you the money you need to make sure that your designs are produced to the highest quality possible. Never settle for less than the standards that you and your customers expect.

www.aapcb.com

25

TECH SERIES

25

7

8Advanced Assembly was founded to help engineers assemble their prototype and low-volume PCB orders. Based on years of experience within the printed circuit board industry, Advanced Assembly developed a proprietary system to deliver consistent, machine surface mount technology (SMT) assembly in 1-5 days. It’s our only focus. We take the hassle out of PCB assembly and make it easy, so you can spend time on other aspects of your design.


ORDER IN VOLUME

Once you are confident with your design and do not expect many changes, it would be best to get boards manufactured and populated in as large of quantities as possible. Economies of scale is a familiar concept, but in regards to PCBs, it is even more relevant than usual. The actual materials involved in the production of the PCBs are relatively minimal and the assembly of a PCB only has the cost of solder, electricity, and maintenance for the machines who place and reflow the boards. However, the time it takes to ready designs for these steps is quite extensive. There are a multitude of steps required before the actual boards are even placed into the pick and place machine. The assembly house needs to review the provided design and clarify any confusion or discrepancy, before loading the design into the pick and place machine. The parts provided are then placed into the machine, which depending on the amount of parts, could be a long and tedious process. Even if the placing will be done by hand, the process will accelerate substantially after the first few boards as the workers become more familiar with the components and where they go.

Many of the assembly houses that perform prototyping assembly are also fully capable of providing large-scale assembly. There are many benefits of using the same assembly house for both levels of production, the largest benefit being that they are already aware of your project and requirements whereas a new assembly house would need to gain familiarity with the project requirements and the production pitfalls associated with their particular system. Ordering in volume is always a gamble as everyone in the industry has had the experience of creating large piles of very costly coasters. By using the same assembly house, you can further reduce the risks of high volume ordering as you will already be familiar with the way they work and they will be familiar with your needs. However, in the end, it is up to you and the engineers on your team to reach the level of confidence where the benefit of the cost savings is no longer outweighed by the risk of having design flaws.

PROVIDE HELPFUL INFORMATION TO THE MANUFACTURER

If there are any special requirements or areas that you believe will cause concerns, contact the company and

discuss it with them. They may be able to provide design advice that eliminates these concerns or maybe let you know that the design is unmanufacturable. Most likely, however, they will pay special attention to where you have indicated and perhaps make minor tweaks to their processes to ensure that it is done correctly. Knowing beforehand can save a lot of time and money on rework that could have been avoided.

There is rarely too much information provided when submitting boards for manufacturing and assembly. If there is information that is recommended but not required, include it when you can. For example, Advanced Assembly does not require fiducials in order to process and successfully assemble circuit boards. However, the fiducials are an additional help that could reduce the difficulties in the assembling process and could improve the final product due to increased accuracy. If it is possible to include fiducials on either the PCB or panel, do so.

CONCLUSION

It is possible to decrease costs without giving up quality. Instead of using cut-rate manufacturers and assembly houses, follow these low-to-no cost recommendations that will save you the money you need to make sure that your designs are produced to the highest quality possible. Never settle for less than the standards that you and your customers expect.

http://www.aapcb.com

26







About Anaya Vardya


INDUSTRY INTERVIEW

27






About Anaya Vardya


28


You have been in the printed circuits industry for quite some time now. In your opinion, what have been some of the most significant changes you have seen and how has American Standard Circuits adapted to them?

I was very fortunate to have started my career at IBM-Endicott. At the time, they were developing very complex circuit boards, so I had the opportunity to start my career at the high end of technology. In general, the American printed circuit industry back then had very low-complexity technology, so I felt I had a major advantage starting out. Throughout my career, I have worked at various levels of technology. The one thing I have been successful in doing is helping each company migrate up the technology curve.

At American Standard Circuits, we have a very holistic capability scenario right now. American Standard Circuits is really good at running a diversified product line. We do things as simple as single-sided printed circuit boards in our facility up to complicated microwave/RF hybrid circuit boards. We also do a metal-backed

board, where we build the circuit board, build the metal and then bond them together for grounding and thermal management. We also utilize pre-bonded materials (RF materials bonded to metal by the laminate supplier) to produce a circuit board on these pre-built, metal-backed boards, which is fairly complex. In addition to these processes, we are capable of producing flex and rigid-flex boards. We have really developed a wide product mix. We are one of the few circuit board shops that does as many different things as we do under one roof.

Does American Standard Circuits do its own R&D?

Yes we do. We have a number of patents in the RF/microwave space, which are primarily associated with materials that can be used for bonding circuit boards to metals. In addition, we do what we call customer-based R&D, where customers come to us with some of their unique problems and we will take the time and the energy to develop what is needed for their particular requirement. One of the biggest things we have invested in over the years is the capability to build pre-bonded RF circuit boards that are built on aluminum. We can drill blind holes which go through the RF dielectric and aluminum. We are then able to plate the circuit board material and the aluminum simultaneously, which is extremely difficult to do.

What is the key factor that sets American Standard apart from its competitors?

There are a number of factors. First of all, we are able to process things very quickly. We are also uniquely qualified to handle the full range of products from diverse customers. In addition, we can work with customers from an R&D standpoint, so we can help them resolve issues that they are having trouble resolving. Lastly, 65 percent of the products done in our facilities are microwave and there are not that many shops in this country that are able to say that. We have a very diverse set of materials that we not only work with, but we also stock—we have almost a million dollars’ worth of raw material in our inventories ready for when our customers place orders.

The latest report from IPC states that the printed circuit industry is starting to improve. How has American Standard Circuits performed over the last year or two?

While the market has either remained stagnant or shrinking, American Standard Circuits has actually grown. We have grown year after year for the past six years, and we expect the same for 2015.

What are some of the challenges you see on the horizon in addressing the customer’s needs?

The biggest thing that we see is the trend towards higher and higher frequencies. The automotive sector is one of our largest segments and we are currently building boards that are at 24GHz—and some of those boards are migrating towards 77GHz. We have actually done boards for one of our customers that are operating at 100GHz, which comes with its own significant material and circuit formation challenges..

What kinds of hybrid constructions are you capable of doing?

We are able to actually mix different kinds of dielectric materials. For example, we can have a customer requiring a PCB with eight layers which may have one core of RO3003 material with the balance of the layers being FR-4 because they only need two layers of RF / Microwave capability. We tell our customers that if they need a microwave board, they need to design it with as few RF layers as possible in order to make it cost-effective. The other thing we see our customers doing is putting cavities in boards like this because there are specific

We are one of the few circuit board shops that does as many different things as we do under one roof.

We do what we call customer-based R&D, where customers come to us with some of their unique problems and we will take the time and the energy to develop what is needed for their particular requirement.

INDUSTRY INTERVIEW

29

You have been in the printed circuits industry for quite some time now. In your opinion, what have been some of the most significant changes you have seen and how has American Standard Circuits adapted to them?

I was very fortunate to have started my career at IBM-Endicott. At the time, they were developing very complex circuit boards, so I had the opportunity to start my career at the high end of technology. In general, the American printed circuit industry back then had very low-complexity technology, so I felt I had a major advantage starting out. Throughout my career, I have worked at various levels of technology. The one thing I have been successful in doing is helping each company migrate up the technology curve.

At American Standard Circuits, we have a very holistic capability scenario right now. American Standard Circuits is really good at running a diversified product line. We do things as simple as single-sided printed circuit boards in our facility up to complicated microwave/RF hybrid circuit boards. We also do a metal-backed

board, where we build the circuit board, build the metal and then bond them together for grounding and thermal management. We also utilize pre-bonded materials (RF materials bonded to metal by the laminate supplier) to produce a circuit board on these pre-built, metal-backed boards, which is fairly complex. In addition to these processes, we are capable of producing flex and rigid-flex boards. We have really developed a wide product mix. We are one of the few circuit board shops that does as many different things as we do under one roof.

Does American Standard Circuits do its own R&D?

Yes we do. We have a number of patents in the RF/microwave space, which are primarily associated with materials that can be used for bonding circuit boards to metals. In addition, we do what we call customer-based R&D, where customers come to us with some of their unique problems and we will take the time and the energy to develop what is needed for their particular requirement. One of the biggest things we have invested in over the years is the capability to build pre-bonded RF circuit boards that are built on aluminum. We can drill blind holes which go through the RF dielectric and aluminum. We are then able to plate the circuit board material and the aluminum simultaneously, which is extremely difficult to do.

What is the key factor that sets American Standard apart from its competitors?

There are a number of factors. First of all, we are able to process things very quickly. We are also uniquely qualified to handle the full range of products from diverse customers. In addition, we can work with customers from an R&D standpoint, so we can help them resolve issues that they are having trouble resolving. Lastly, 65 percent of the products done in our facilities are microwave and there are not that many shops in this country that are able to say that. We have a very diverse set of materials that we not only work with, but we also stock—we have almost a million dollars’ worth of raw material in our inventories ready for when our customers place orders.

The latest report from IPC states that the printed circuit industry is starting to improve. How has American Standard Circuits performed over the last year or two?

While the market has either remained stagnant or shrinking, American Standard Circuits has actually grown. We have grown year after year for the past six years, and we expect the same for 2015.

What are some of the challenges you see on the horizon in addressing the customer’s needs?

The biggest thing that we see is the trend towards higher and higher frequencies. The automotive sector is one of our largest segments and we are currently building boards that are at 24GHz—and some of those boards are migrating towards 77GHz. We have actually done boards for one of our customers that are operating at 100GHz, which comes with its own significant material and circuit formation challenges..

What kinds of hybrid constructions are you capable of doing?

We are able to actually mix different kinds of dielectric materials. For example, we can have a customer requiring a PCB with eight layers which may have one core of RO3003 material with the balance of the layers being FR-4 because they only need two layers of RF / Microwave capability. We tell our customers that if they need a microwave board, they need to design it with as few RF layers as possible in order to make it cost-effective. The other thing we see our customers doing is putting cavities in boards like this because there are specific

We are one of the few circuit board shops that does as many different things as we do under one roof.

We do what we call customer-based R&D, where customers come to us with some of their unique problems and we will take the time and the energy to develop what is needed for their particular requirement.

www.asc-i.com

30


About American Standard Circuits

American Standard Circuits (ASC) prides itself on being a total solutions provider, manufacturing quality rigid, metal-backed, flex and rigid-flex PCBs as well as RF/microwave PCBs to the medical, automotive, industrial, defense, and aerospace markets in volumes from test and prototypes to large production orders. ASC has the expertise to provide all technologies in a time-critical environment. Company qualifications include ISO9001:2008, MIL-PRF 31032, and ITAR registration. It holds a number of key patents for metal bonding processes as well. For more information, visit www.asc-i.com.

areas where you want to access from the outside. This results in cavities, more blind holes, and buried vias. There is a lot of complexity you can add in some of these circuit boards; obviously, the more complicated it becomes, the more expensive it is to manufacture it.

What are your goals for growth and development over the next five years?

Our goal is to continue to grow our company while we continue to grow our technology portfolio. In general, we have made investments based on market situations, but we are trying to take customer input and develop what the marketplace is looking for. What I see at American Standard is more metal-backed work as well as flex and rigid-flex. We are also seeing more hybrid construction with RF/microwave and FR4 high-speed material going through our facility. Some of our target market segments that we expect to grow are aerospace/defense, medical, and the LED market space.

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Raspberry Pi A+





























The


33

TECH REPORT

33

Raspberry Pi A+





























The


3434


Along with the miniaturization, the Raspberry Pi A+ now has a microSD rather than a full size SD card. The microSD card slot is now also a push-push fit, and while this does not really affect the overall performance of the Pi, it does remove the speculation of whether or not the SD card will fall out. If the user is migrating from a Raspberry Pi Model A or B, then this will be the first time they can use MicroSD cards. The SD card will no longer hang off the edge, allowing for the size to become even smaller.

A smaller form factor isn’t the only thing that is new about the Raspberry Pi A+—it also has more general purpose I/O. The Raspberry Pi Model A/B had only 26 GPIO pins while the new model A+ has 40 pins. More pins means more capabilities; with more data lanes, more complex systems can be developed; with more push buttons, sensors and switches can now be programmed with one Raspberry Pi. This allows the user to create a complex system involving many sources of data in order to monitor and use the data for personal gain.

Even with the expanded pin-out, the Raspberry Pi Model A+ has lower power consumption. This is because the

Raspberry Pi foundation replaced linear regulators with switching regulators. Linear regulators have to pass the entire load current through a series transistor, which wastes a lot of power as heat. With switching regulators, the transistors operate as a switch, so when the transistor is conducting current, the voltage drops, resulting in a smaller power path. If the transistor is not conducting current, there is no bleed through like there would be in a linear regulator. This allows for a drop in power between 0.5W and 1W, making the A+ a low-power solution for many projects.

The composite video of the Raspberry Pi Models A and B has been removed, leaving the HDMI port as the sole video-out component. The HDMI interface is capable of providing both sound and video, which removes the need for the use of the composite video and the audio jack. In this day and age, it is hard to find a monitor that uses composite video, so the use of an HDMI port most definitely coincides with programmers’ needs. The video produced through HDMI is also much better quality than the video produced from composite video, and removing an unused video port also helps the power consumption.

The Raspberry Pi A+ is perfect for projects that need a bite-sized punch.

40 PIN GPIO

DISPLAY PORT

MICRO USB POWER SOURCE

FULL SIZE HDMI

CAMERA PORT

USB PORT

STEREO OUTPUT AND COMPOSITE

VIDEO OUT

A+Source: www.raspberrypi.org

35

TECH REPORT

35

Along with the miniaturization, the Raspberry Pi A+ now has a microSD rather than a full size SD card. The microSD card slot is now also a push-push fit, and while this does not really affect the overall performance of the Pi, it does remove the speculation of whether or not the SD card will fall out. If the user is migrating from a Raspberry Pi Model A or B, then this will be the first time they can use MicroSD cards. The SD card will no longer hang off the edge, allowing for the size to become even smaller.

A smaller form factor isn’t the only thing that is new about the Raspberry Pi A+—it also has more general purpose I/O. The Raspberry Pi Model A/B had only 26 GPIO pins while the new model A+ has 40 pins. More pins means more capabilities; with more data lanes, more complex systems can be developed; with more push buttons, sensors and switches can now be programmed with one Raspberry Pi. This allows the user to create a complex system involving many sources of data in order to monitor and use the data for personal gain.

Even with the expanded pin-out, the Raspberry Pi Model A+ has lower power consumption. This is because the

Raspberry Pi foundation replaced linear regulators with switching regulators. Linear regulators have to pass the entire load current through a series transistor, which wastes a lot of power as heat. With switching regulators, the transistors operate as a switch, so when the transistor is conducting current, the voltage drops, resulting in a smaller power path. If the transistor is not conducting current, there is no bleed through like there would be in a linear regulator. This allows for a drop in power between 0.5W and 1W, making the A+ a low-power solution for many projects.

The composite video of the Raspberry Pi Models A and B has been removed, leaving the HDMI port as the sole video-out component. The HDMI interface is capable of providing both sound and video, which removes the need for the use of the composite video and the audio jack. In this day and age, it is hard to find a monitor that uses composite video, so the use of an HDMI port most definitely coincides with programmers’ needs. The video produced through HDMI is also much better quality than the video produced from composite video, and removing an unused video port also helps the power consumption.

The Raspberry Pi A+ is perfect for projects that need a bite-sized punch.

40 PIN GPIO

DISPLAY PORT

MICRO USB POWER SOURCE

FULL SIZE HDMI

CAMERA PORT

USB PORT

STEREO OUTPUT AND COMPOSITE

VIDEO OUT

A+Source: www.raspberrypi.org

3636


There are some limitations to the Model A+ that allow it to have such a small form factor. The Model A+ does not have LAN port, which keeps in line with the Model A, but Model B lovers will have to deal with a micro wireless USB dongle, or a USB to Ethernet converter. With the LAN port gone, the user will most likely use the USB port for network connectivity. If the USB port is used as a network connection, be aware that the only USB port is not consumed, another unfortunate limitation of a smaller form factor. USB hubs may be a solution, but they can suck up a lot of power out of a single USB port, effectively disabling some of the devices. Even with reduced power consumption, it might still be difficult to use a lot of different USB powered devices. If a project requires a network connection, but the USB port will be used for other devices, make sure there is a solution to code and troubleshoot the Pi.

The discrete form factor arrives just in time, as the Internet of Things is gaining more momentum and smaller, more robust computer systems are needed to enable these new applications.

Keep in mind that the hardware has not been upgraded. The Model A+ uses the ARM1176JZF-S single-core, 700 MHz processor. It has 256MB of SDRAM and uses the same Broadcom VideoCore IV that runs at 250 MHz with OpenGL ES 2.0, which computes at a rate of 24 GFLOPS. Although the Model A+ will be used in projects that don’t need a lot of processing power, it is good to keep this in mind as some applications will need a faster computer.

The Raspberry Pi A+ is a wonderful little computer that can be useful in many different situations. The Raspberry Pi has transformed from a learning tool into a useful mini-computer that can be applied to many applications, though the user might still learn a lot throughout the duration of the project. With a price tag of only $20 USD, it might just be the world’s most accessible computing platform.

A+

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Modern Printed Circuits: February 2015