Elimination of Wave Exactalloy Tape and Reel Preforms

an Alent plc Company

Preform Product

Elimination of Wave Exactalloy T&R Preforms

Highly Confidential and Privileged Information of Alpha an Alent plc Company

Introduction of “Elimination of Wave”

• The desire to reduce cost and improve reliability in assembly for our customers continues to drive Alpha’s marketplace today. Transitioning mixed technology or traditional wave applications to SMT or what we like to call the “elimination of wave” is a value proposition demonstrating both cost, reliability, and environmental benefits.

• The most common methodology to accomplish a transition from wave to surface mount technology is known as pin-in-paste or P-i-P. Pin-in-Paste provides manufacturers with a high-yield process that simultaneously reflows solder for surface mount and through hole components - without the need for wave soldering. By eliminating that step of the assembly process altogether, pin-in-paste not only saves time, reduces production costs, and increases throughput, but also enhances solder reliability while reducing dross in the manufacturing environment

• Once a PiP application has been identified, there are a number of challenges that can arise which can be overcome by using Alpha T&R preforms with PiP. In this presentation, we will focus on those applications. Upon completion, you will have the ability to assess your mixed technology process quickly and determine if it is a candidate for elimination of wave using Alpha Exactalloy Tape and Reel (T&R) preforms. Let’s get started!


Alpha’s Tape and Reel Preforms can enable PiP technology

Overprinting

Typical

Thru-hole Connector

Alpha’s Exactalloy T&R Preforms

can supplement solder volume

when overprinting is not possible or

insufficient


Exactalloy T&R Solder Preform Sizes

0.020

mm inch mm inch mm inch mm^3 in^3

0201 0.51 0.020 0.25 0.010 0.25 0.010 0.03 0.000002

0202 0.51 0.020 0.51 0.020 0.25 0.010 0.07 0.000004

03015 0.76 0.030 0.38 0.015 0.25 0.010 0.07 0.000005

0402H 1.00 0.039 0.60 0.020 0.25 0.010 0.15 0.000008

0402 1.00 0.039 0.50 0.020 0.50 0.020 0.25 0.000016

0402B 1.00 0.039 0.55 0.022 0.55 0.022 0.30 0.000019

0603H 1.60 0.063 0.80 0.031 0.50 0.031 0.64 0.000061

0603 1.60 0.063 0.80 0.031 0.80 0.031 1.02 0.000061

0805 2.01 0.079 1.30 0.051 0.76 0.028 1.99 0.000113

1406 3.56 0.140 1.52 0.060 0.77 0.030 4.17 0.000252

VolumePart

Type

Part Dimensions

a b c

Free 1,000 piece

reels available

for testing

Other standard sizes available, contact you salesperson for more information


No

tem

pera

ture

dif

fere

nti

al

= n

o t

herm

al

sh

ock

2150C

(>2350C)

>2300C

(>2450C)

Sn/Pb Soldering

(Pb-Free Soldering)

1100C

Tem

pera

ture

dif

fere

nti

al

cre

ate

s t

herm

al

sh

ock

Internal planes

act as

heat-sinks

inhibiting

barrel fill

during wave

solder ONLY,

not PIP reflow

215oC

(>2350C)

Preform in Paste

Process Comparison

Wave Soldering

Less than 75%

hole fill

100% hole fill

SMT Reflow Soldering


Reflow Wave

Hole fill Comparison

Reflow vs. Wave


Hole Fill Reflow

T&R Preforms allow precise solder

volume control

• Multiple preforms can be placed at

each pin location

• Fillet generation can be controlled


Value Proposition

• What would be the value of eliminating wave

soldering or selective wave and re-work in a

“mixed technology” process?

SMT1 SMT2 WAVE Re-Work

•Print Paste

•Pick & Place

•Reflow

•Flip PCBA

•Print Paste

•Pick & Place

•Reflow

•Inspect

•Place Comp.

•Flux

•Wave Solder

•Inspect

•Inspect

•Rework/Touch-up

(optional)


Savings by Elimination of Wave

$$

SMT1

SMT2

Cost of Wave Cost of

Preforms

$$ SAVINGS $$

Cost Stack for Elimination of Wave Solder

WAVE is an expensive additional process

which most would eliminate if possible

¢¢


Implementing

Paste-plus-Preform

to Eliminate Wave


General Guidelines

1. Overprinting should always be considered the first option for filling plated through holes.

2. Preforms are placed in solder paste to accurately increase solder volume to the plated through hole component.

• Inadequate solder volume from overpinting.

• Limited space around the throu hole component.

3. Preforms are placed first with chip caps and resistors. SMT components are placed next, and through hole components are placed last, automatically or manually.

4. Through hole components are soldered pin down during the SMT2 process.


Checklist for Success (Identifying a Candidate for Elimination of Wave)

All through-hole components can tolerate the reflow

temperature

All components meet the minimum standoff heights for

the selected preforms.

Pins do not have a shoulder that blocks hole

No paste is printed underneath standoffs

Pin protrusion is not excessive

Pin to hole ratio is reasonable


Components Can Tolerate the Reflow

Temperatures

Component Temperature: – The Through Hole components must withstand

SMT reflow temperature. • For SnPb, it must withstand 230 °C for 10 to 20

seconds

• For Pb-Free, it must withstand 260 °C for 10 to 20 seconds

– Check with connector supplier to determine if the component is SMT rated.


Component Standoff Height is Adequate

• Standoff = clearance between bottom of the

component and the board.

• Minimum Standoff Clearance

– Paste height (stencil thickness) + Preform thickness

+ tolerance (0.003”)

– Preform must be allowed to move freely to the hole

(under the component body) during reflow.

Insufficient clearance under the

body of the component will

prevent preforms from flowing to

the plated through hole.

Resulting in large solder

sphere defects outside the

hole Through-hole

Component


Calculating Allowable Preform Height

Allowable Preform Height = Comp. Standoff Height – Stencil Thickness – 3 mils

Component Standoff Height

Allowable preform Height

Paste on Pad

Preform



Standoff Built into Pin is Not Desirable

• Example component with pin standoff

– Standoff built into the pin will block the hole during

reflow

Standoff on pin


Comparing Standoff Styles Both components have identical standoff height

Permits paste printing and Preform

Placement

Pin standoff blocks the hole, preventing

top side hole fill

Standoff built into the component body Standoff built into the component pin


Improved Pin Standoff Design

With notched standoffs in the pin, the pad and plated through hole are exposed, allowing solder to flow to the hole.



• Components with multiple

standoffs can interfere with

solder paste printing

• Components with standoff

at the end of the

component body are

preferred

Minitek Header


Pin Protrusion is Not Excessive

• Excessive pin protrusion can reduce hole fill • Paste can fall off during handling or reflow

• Stranded paste can cause large solder balls to form at the tip of the pin.

– Pin protrusions longer than 60 mils (1.5 mm) can cause solder balls to form at the tip of the pin.

• Blunt ended pins are not desirable. – Worsen excessive pin protrusion issues

– Used tapered or rounded pin whenever possible

Solder ball formed at the

tip of a pin after reflow

Solder ball (shown in X-ray)

BLUNT ENDED PIN

INSUFFICIENT SOLDER


Pin Protrusion

It is possible to use a stencil that totally blocks the

hole to enable paste plus preforms with very

long or blunted ended pin protrusions.


Pin to Hole Ratio Acceptable

• A wide variety of pin to hole ratios can be

reflow soldered using paste plus preforms

• Pin to Hole Ratios: – Minimum Pin to Hole Ratio: Pin + 15 mils (0.38 mm).

• Going lower will create problems of solder flow and

placement issues.

– Maximum Pin to Hole Ratio: Pin + 40 mils (1 mm)

• Exceeding this value may create voids or gaps in

barrel.


Checklist for Success

Summary

Components can tolerate the reflow temperature

All components have a minimum standoff height

Pins do not have a shoulder that blocks hole


Pin protrusion is not excessive

Pin to hole ratio is reasonable

** If you can confirm all the items in the checklist, you surely have an excellent candidate for a preform application.


Parameters Needed:

1. Board thickness - Th

2. Hole diameter - Hd

3. Lead diameter - Ld

4. Solder pad diameter Pd

Th

Ld

Hd

Solder Volume Calculation

Pd


Steps for Selecting a Preform

1. Calculate the total solder volume needed (Vsldr):

Vsldr = (Vhole – Vpin) + 2(Vfillet)

2. Calculate the paste volume (Vpaste) from the allowable stencil aperture:

Vpaste = Aapp x THstncl

3. If, Vsldr > ½ Vpaste, then Preform(s) is needed.

4. Calculate the target Preform volume:

Vpf = Vsldr – ½ Vpaste

5. Check PF / Paste Ratio (4X and 8X rules):

Vpf / Vpaste < 4* (Air)

< 8* (Nitrogen)

* Values less than 4 or 8, indicate inadequate flux volume

6. Calculate target PF height:

Comp. Standoff Hgt. – THKstncl – 0.003”

7. Select the most appropriate Preform(s) from the list of available standard

sizes

Fillets


Get your Alpha Reference bulletin entitled “Checklist for Success”

from your Alpha Sales representative


28

Summary • Alpha Tape and Reel Preforms can be used to aid in the

Elimination of Wave in a mixed technology process.

• Tape and Reel Preforms are an economical alternative to increasing solder volume when overprinting solder paste is not adequate.

• There are a wide variety of Alpha T&R preform sizes to address most every through hole application.

• The implementation of Alpha T&R Preforms into an existing SMT process is not complicated.

• Alpha T&R preforms are a more reliable solution then overprinting:

– Very little flux residue

– 100% hole fill is routinely achieved

– A large overprint can be reduced or eliminated

– Random solder balls can be significantly reduced.

• Not all Wave applications can benefit from preform in paste techniques. Use the Checklist for Success tool to help you decide.

Business

Elimination of Wave Exactalloy Tape and Reel Preforms