Computer and Information Engineering Lab II ECE 3102 & ECE 4102

Designing Printed Circuit Board (PCB )

(Tutorial Five)

فهما رزقني و علما زدني ربMy Lord! Advance me in Knowledge and true understanding .

Computer and Information Engineering Lab IIECE 3102 & ECE 4102

2

Lecturer: Dr. Nor Farahidah Za’bah

Demonstrator:Br. Akhter

Lab technician:Br. Shahlan

Laboratory:Mechatronics Workshop, Room# E2-2-13.12

فهما رزقني و علما زدني ربMy Lord! Advance me in Knowledge and true understanding .

3

Contents

Basic PCB Skills and Tools.

PCB design using Crocodile.

PCB design using Eagle.

4

Need to know about……

• Types of Circuit Board .• Soldering Guide.• Tools required for electronics.• Starter kit of components.• Making a workbench for

electronics.

Basic PCB Skills and Tools

Construction of Electronics Projects

5

Breadboard Stripboard Printed Circuit Board


Types of Circuit Board

Breadboard Stripboard Printed Circuit Board

6

Breadboard Temporary use, Normally for testing purpose. No soldering required . This is a way of making a temporary circuit. No soldering is

required and all the components can be re-used afterwards. It is easy to change connections and replace components. Almost all the Electronics Club projects started life on a breadboard to check that the circuit worked as intended.


Types of Circuit Board (Con.)

Breadboard

7

Stripboard Permanent, Soldered . Stripboard has parallel strips of copper track on one side. The

strips are 0.1" (2.54mm) apart and there are holes every 0.1" (2.54mm). Stripboard requires no special preparation other than cutting to size. It can be cut with a junior hacksaw, or simply snap it along the lines of holes by putting it over the edge of a bench or table and pushing hard.



Stripboard

8

Printed Circuit Board Permanent, soldered . Printed circuit boards have copper tracks connecting the holes

where the components are placed. They are designed specially for each circuit and make construction very easy. However, producing the PCB requires special equipment so this method is not recommended if you are a beginner unless the PCB is provided for you.



Printed Circuit Board

Single sided layer• Positive board & Negative board


Working With PCB

A sample of positive board

the desired circuit will be the one with black color.

A sample of negative board

the desired circuit will be the one with white color.

9

FLOWCHART


Working With PCB (Con.)

10



After making the PCB …..

11



1.Circuit

Schematic diagram

PCB Layout

12

Step 1

When the PCB layout (Using software) is finished it is printed on a Transparent Paper and becomes a PCB mask.



13

Step 2

Photo-resist Positive Board

PHOTO-RESIST BOARD is a piece of glass reinforced plastic.

One of the sides is copper clad with photosensitive coating.

When the plastic film is peeled back this sensitive coating is revealed.

After processing this will be the PCB.



14

Step 3

The PCB mask (transparent page) is placed underneath the photo-resist board, touching the sensitive surface.

The plastic film must be removed.

PCB mask and board are then transferred to the UV light Box.

Be careful to ensure that the PCB mask is the right way up, otherwise when the circuit is etched you will discover that the tracks are also the wrong way round.

15

Placing Photo-resistive board on Mask

Step 4



The lid is shut and the box switched on.

The photo-resist board, with PCB mask are left underneath the lid for 2 minutes (120 sec.)

Note: for negative board, the exposure will be for 25 seconds

16

Using UV Light BoxStep 5



The photo-resist board is then placed in a tank filled with developer solution.

It is important that the board is only left in the developer for approximately ten seconds.

When the board is taken out of the developer it must be washed in clean water before transferring to the etching tank.

Always use plastic tongs or gloves.

17

Using UV Light BoxStep 6 & 7



The etchant used is Ferric Chloride.

This solution slowly etches away the unwanted copper, leaving the tracks only. ◦ At this stage it is important to keep

checking that the PCB is completed If it is left in the tank too

long the copper tracks will also be removed or damaged.

18

Using UV Light BoxStep 6 & 7



The last stage is drilling the holes for the components. A small PCB drill is used for this purpose.

Again care is needed as a good PCB can be ruined by careless drilling.

19

Cleaning & DrillingStep 8 & 9



20

1. Use a soldering iron in good condition. Inspect the tip to make sure that it is not past good operation. If it looks in bad condition it will not help you solder a good joint. The shape of the tip may vary from one soldering iron to the next but generally they should look clean and not burnt.

2. A PCB eraser is used to remove any film from the tracks. This must be done carefully because the film will prevent good soldering of the components to the PCB. The tracks can be checked using a magnifying glass. If there are gaps in the tracks, sometimes they can be repaired using wire but usually a new PCB has to be etched.

Soldering Techniques Step 10



21

3. Place the PCB, with its components in position, in the bull clip. This will steady the PCB when you try to use the soldering iron.4. The heated soldering iron should then be placed in contact with the track and the component and allowed to heat them up. Once they are heated the solder can be applied. The solder should flow through and around the component and the track

Soldering Techniques (Con.)Step 10



22

5. Having completed soldering the circuit the extended legs on the components need to be trimmed using wire clippers. The circuit is now ready for testing.

Soldering Techniques (Con.)Step 10



Below are some of the warning symbols that appear on etchants and ferric chloride solutions. They are present to warn the user of their potential danger if mishandled. Why should etchants and solutions such as ferric chloride be handle with great care ?

23

Checking & TestingStep 11



24

Checking & Testing (Con.)Step 11



25

The ProductFinally



26

Soldering iron

A soldering iron is a hand tool used in soldering. It supplies heat to melt the solder so that it can flow into the joint between two work-pieces.

A soldering iron is composed of a heated metal tip and an insulated handle. Heating is often achieved electrically, by passing an electric current through a resistive heating element.

The iron's power rating should be 15 to 25W and it should be fitted with a small bit of 2 to 3mm diameter.


Tools Required for Circuit Construction

27

Soldering iron stand

You must have a safe place to put the iron when you are not holding it.

The stand should include a sponge which can be dampened for cleaning the tip of the iron.


Tools Required for Circuit Construction (Con.)

28

De-soldering pump (solder sucker)

A tool for removing solder when de-soldering a joint to correct a mistake or replace a component.



29

Reel of solder

The best size for electronics is 22swg (swg = standard wire gauge).



30

Cutters

For trimming component leads close to the circuit board.



31

Small pliers

Usually called 'snipe nose' pliers, these are for bending component leads etc. If you put a strong rubber band across the handles the pliers make a convenient holder for parts such as switches while you solder the contacts.



32

Small flat-blade screwdriver

For scraping away excess flux and dirt between tracks, as well as driving screws.



33

Small electric drill

Ideally this should be mounted in a drill stand. We will need a range of small drill bits, but for most holes a

1mm bit is suitable. Larger holes can be drilled with a hand drill but 1mm bits are too fragile to use reliably in a hand drill.



34

A few safety precautions:

Never touch the element or tip of the soldering iron. • They are very hot (about 400°C) and will give you a nasty

burn. • Take great care to avoid touching the mains flex with the tip of

the iron. • The iron should have a heatproof flex for extra protection. An

ordinary plastic flex will melt immediately if touched by a hot iron and there is a serious risk of burns and electric shock.

Always return the soldering iron to its stand when not in use.

• Never put it down on your workbench, even for a moment! Work in a well-ventilated area.

• The smoke formed as you melt solder is mostly from the flux and quite irritating. Avoid breathing it by keeping you head to the side of, not above, your work.

Wash your hands after using solder. • Solder contains lead which is a poisonous metal.


Soldering Guide: HOW TO SOLDER

35

Use a damp sponge, frequently, to keep the bit clean.

Always return the soldering iron to its stand when not in use.


Soldering Guide: HOW TO SOLDER (Con.)

36

Tinning the bit, Heating the joint and applying the solder. Tin the bit for good heat conduction. (This means putting a small blob of solder on the tip of the bit).

Hold the iron like a pen. Rest your hands on the workbench to make them steady. Take precautions against the work moving (use a small vice or sticky tape). Heat the biggest part of the joint for 2-3 seconds.



37

PRACTICE MAKES PERFECT !!!



38


Important Components

39


Important Components (Con.)

40

Take great care to avoid damage. Components cost a few pence, an assembled printed circuit board may be worth several hundred pounds.

Ensure the iron bit is well tinned. Heat up the joint to be de-soldered until the solder runs. Apply the solder sucker and remove the solder. This should only take two or three seconds.

Tools required: pliers, cutters, soldering iron, and solder sucker (de-soldering tool).


De-soldering Components

Working on a double-sided PCB (where copper tracks are on both sides of the PCB) is more difficult and requires more care.

It is often safer to cut the component leads and discard the component, then desolder the leads individually.

Circuit Design UsingCrocodile Technology

3D

41

Crocodile is a compilation of circuit design tools and simulation tools.

This application is also good for beginners who wanted to learn electronics.

The simulation tools help learners / users to experiment circuit connections without being worried about component get burns because of wrongly connected.

You can always replace burnt component with a new one by simply drag and drop.

42

Circuit Design Using Crocodile Technology 3D

Crocodile Technology 3D

43

1. Click File >> New2. Click “Rectangular PCB space” from the Parts Library pane and drag it

to the scene space


Creating New File

44

Schematic space

3D / PCB space

Parts tray

Parts tray

Click and drag parts to PCB space


Working Space

No. Component Value Qty1. Resistor 470 Ohm 32. Resistor 10 kOhm 23. Capacitor 100 uF 14. Diode 1N914 15. IC 555 timer - 16. 4027 dual JK flip flop - 17. LED - 3

45

Find and drag all the components below to the PCB space


Circuit Designing Practice

46

Draw the schematic below on the schematic space.

See the circuit simulation by clicking the switch button on the schematic


Drawing the Schematic

47

Once a circuit has been designed and simulated/tested in Crocodile Technology and any necessary alterations made, the completed circuit is ready for export to ‘real PCB’.

Both Crocodile Technology and Real PCB software must be running at the same time for this to be possible.

The conversion to PCB layout can be achieved through a menu in Crocodile Technology. Real PCB converts the circuit diagram effortlessly to PCB layout and usually with 100% accuracy.


Crocodile Technology to Real PCB

48

Real PCB can also be used to construct a circuit as a PCB layout, from scratch, by selecting components from a series of menus and drawing the tracks connecting them. It can be used by both beginners and experts to produce accurate PCBs. Quality checks can be carried out automatically and the software will also produce a bill for the components used on any PCB.

The ‘Pour Copper’ menu changes the final PCB by only removing enough copper so that the tracks can be seen. This means that only the necessary copper is removed to ensure the final circuit works. This extends the life of etchant used in the etchant tank.

Two more ways of presenting the PCB. The 'artwork' layout is the most likely to be printed out on a transparency, ready for conversion to PCB. The ‘real life’ layout style shows the PCB with its components. This is useful when arranging the components on the PCB, as the position of each can be check against a real life printed.


Working with Real PCB

49

When the PCB layout is finished it is printed on a transparency and becomes known as a PCB mask. The PCB mask is transferred to the UV box, which is the next stage in the manufacture of a printed circuit board.

Advantages of using circuit and PCB software:

1. Circuits can be simulated on screen without the need to build a circuit on a breadboard with real components.

2. Errors can be corrected and alterations made to the circuit by simply replacing components from menus.

3. No soldering is needed, simply move components with a mouse.4. Using simulation software is safer than soldering with hot soldering irons and avoids

dangerous fumes being produced whilst soldering.5. Once a PCB has been designed it can be printed onto transparencies repeatedly, all to

the same high quality.6. PCB layout software is more accurate than drawing a circuit by hand.


Working with Real PCB (Con.)

50

Jumper wires exist when Real PCB finds out that there are no possibilities of copper connection.

But you can always eliminate jumper wires by rearranging the components position.

Try rearranging the components until a PCB artwork with minimum or no jumper wires at all.

Jumper wires



51



Exporting to Real PCB

52

Real PCB window option

• For the first time, simply click “Quick” button.

• Take note on the “circuit warnings” down below…



53

12

Click this button to see error log

Click this button to open Real PCB


Working with Real PCB (Con.)Real PCB Progress

54

Tools pane

Jumper wire



Real PCB

55



No Jumpers

56

It will always be a good practice to print the artwork to a white paper first.

This will allow you to check the arrangement and the orientation of the components easily.

If you’ve satisfied with the artwork than print it on a transparency film to create a PCB mask.


Working with Real PCB (Con.)Printing PCB Artworks

PCB – SCHEMATIC AND LAYOUT

USING EAGLE SOFTWARE

57

Eagle software is used to design schematic diagram i.e. the circuit and then transfer it into a PCB layout

However, Eagle does not perform circuit analysis like PSPICE or ORCAD.

Circuit Design Using EAGLE Software

EAGLE Software

58

File >> New >> Project


Creating New Project

59


Creating New Project (Con.)

60

Right click on the New Project folder icon to access the menu.Rename the project before creating a new schematic since it is not

possible to change the project’s name while it is in use.


Rename Project & Schematic

61

• Set up the library before working on the schematic .• Right click on the Library, and choose “Use all”.• Some user might drop components that he/she don’t want. This will

make sure that all the components library is selected


LIBRARY

62

Add Parts – This is where all the parts needed stored in the library

Connecting Wires

Copy

Select / Move

NOTE: Right hand click to rotate your parts


Designing Space

63

Now construct the circuit using the schematic.

Output will be connected to an oscillator

An AC signal produced by a function generator


Example: Rectifier Circuit

64

This window will appear if ‘Add Part’ Icon is clicked.Write the type of component (Ex. DIODE), Choose the model D1N4148.


Selecting Components

65

To select the part just click OK and the part will be displayed on the schematic window.

WARNING!!! NEVER CLICK "Drop". By clicking the "Drop" button, this part is deleted from the list. If you’ve clicked the "Drop" button by mistake, you can reset the library on Control Panel.


Selecting Components

66


Selecting Components (Con.)To position the component simply click the left mouse button anywhere on the window.

Click again to get another same component.

To stop the addition function of the component, strike the ESC key and click "Cancel”. ORPress STOP in the toolbar.

67

Adjust the display screen using Fit, In and Out button.

To delete, click delete button, click on the parts to delete press STOP to end this operation.


Selecting Components (Con.)

68


Wiring the parts

After putting the component, wiring can be done by the Wire function.

Left click the lead wire of the part and double-click at the end point

which of wiring.

It isn't necessary to keep to push the mouse button during wiring work.

To stop this feature, press STOP button.

The drawn line can be erased using the Delete button.

Can also wire the components using bus icon.

69


Wiring the parts (Con.)A circular black mark is put to the node of the wiring. This mark isn't

related to the wiring of the printed board. It is to confirm the connection of the wire when the person sees the schematic.

When pushing the Junction button, the circular mark which moves with the mouse pointer appears.

A mark is drawn to the schematic when left clicking at the node. To stop this feature, it clicks the Cancel button.

70


PracticeDraw this circuit: A 5volt voltage regulator circuit using IC 7805 .

After drawing a schematic, the mistake can be automatically detected by the ERC (Electrical Rule Check) button.

71

We need to have PADs included in schematic so that PCB can be connected to power supply, GND and the output node

So, again click Add parts, search for Pad, and find wire pads.

Use the ( 1,6 /0,8) package.


WIREPADS

72


WIREPADS (Con.)

WIREPADS

73


Tips

Can label the wire pads by clicking the icons and then select the items to rename or put values for the resistors/capacitors. Can do this in schematic diagram.

74


Related Instructions Invoke

◦ Use when it involves ICs.

◦ It is common for an IC to have more than 1 logic circuit in it, for example, an IC for NOT gate ( 74LS04N ).

◦ There are 6 NOT gates in the IC. Hence, invoke allows you to connect other logic circuits accordingly.

75

ERC is performed to check schematic before transforming them into a PCB layout.

Once the icon is clicked, a text file will appear producing list of errors and warnings.

Correct schematic and perform ERC again. IT IS VERY IMPORTANT TO GET A CORRECT

SCHEMATIC

Icon associated with ERC


Electrical Rule Check (ERC)

76


Example of ERC

EAGLE Version 4.09r2 Copyright (c) 1988-2002 CadSoft

Electrical Rule Check for C:/PROGRAM FILES/EAGLE-4.09R2/projects/test/test.sch

WARNING: Sheet 1/1: POWER Pin IC1P VCC connected to +5V

Board and schematic are consistent

0 errors 1 warning

77


Starting New Project: Board File

Click "Board" icon in the schematic window.

When a board isn't made yet, board creating is confirmed by following dialog.

78


Creating Board FileThe yellow line among the parts is the line which shows a connection

among them. But, these lines are not wiring for the printed board yet.

79

Can still rotate parts even though using in the PCB layout window.

Need to move your parts into the frame.Click on

Select all the parts, click onRight hand click the grouped parts.And then left hand click to place them in the frame. Once all parts are place in the frame, click on the

Ratsnest icon.


Creating Board File

80

The yellow line shows a connection among the parts. The part should be arranged for the yellow line to be simpler.


Parts Arrangement on the Board

81

A Ratsnest display: ◦ the program will draw a straight line (not a track)

between the pads of components which are connected on the schematic.

◦ it shows the connectivity of circuit before starting laying out tracks.

◦ At the start of board layout with all components, placed down randomly, this will appear as a huge and complicated random maze of lines. Hence the name Ratsnest.


What is RATNEST

82

Place all the components that need to be in specific locations.◦ e.g. connectors, switches, LEDs

Pay attention to orientation of each part placed. Give careful thought when placing components to minimize trace

lengths. Put parts next to other parts they connect to.

◦ a good job here makes routing the traces much easier.◦ Again, the orientation of each part matters too.

Arrange ICs in only one or two orientations:◦ vertically or horizontally.

if possible, align each IC so that pin #1 is in the same place for each part, say, on the top ( if horizontal ) and/or left sides ( if vertical ).


Placing Components

83

Firstly, set the rules for PCB layout. Examples of what can be set with a DRC:

◦ Circuit connectivity. It checks that every track on board matches the connectivity of schematic.

◦ Electrical clearance. Can check the clearance between tracks, pads, and components.

◦ Manufacturing tolerances like min/max hole sizes, track widths.

A complete DRC is performed again after finishing PCB.


Design Rule Check (DRC)

84

The default is 8 mil. Since 1 inch is 25.4mm and 1mil is 1/1000 inches, so 8mil is about 0.2mm. 40mil is about 1mm. Normally, we set it to be higher, around 16-20mil.


Design Rule Check (DRC) (Con.)

85


AUTOROUTE – connecting the partsNext, click Autorouter icon and a window

will appear.

Make sure your Autorouter is setup as shown

86


Autorouting on the Board In EAGLE, a pattern is drawn using 2 layers which are component side and wiring side. The blue line is the wiring on the wiring side and the red line is wiring on the component side.

87

If you don’t like the design of your PCB or if there is an error, need to re-route.

Click the RipUp icon basically to cancelled PCB connections.

Once clicked that, go to and a window will popped out.

Click Yes

Once done, rearrange the parts again, Ratsnest and Autoroute until not satisfied with PCB design.


RIP - up

88


Before & After

The PCB route is marked in blue

89

Since we use one sided PCB, change the red line (1top) to blue (16 bottom) without violating the board/circuit consistency. Use right click on the red line.


Customizing the Board

90

To see exactly how the PCB board would look like,

click the display icon and highlight these portions only.


Customizing the Board (Con.)

91


Before & After

92

Select the frame and move it so that it fits nicely with PCB layout.

Finally, print out the PCB layout on the transparency.


Other responsibilities

93

The size of the PCB can be seen by click Info and click the frame line (length in inch).

If necessary adjust the size using Move to drag the frame line.


Customizing the board (Con.)

94


Printing the Layout

File >> Export

• Browse and write a filename, for example, rectifier.

• Open using Paint and then print.

95


Circuit is Framed

You can add ‘copper text’ by clicking the icon.

The white lines will be the conducting lines and nodes

96


Prototype Circuit

555 timer IC. One 1N914 "switching" diode. Two 10 kΩ resistors.One 100 µF capacitor .4027 dual J-K flip-flop. Ten-segment LED. Three 470 Ω resistors. One 6 volt battery.

97


Pin-diagram of 555 & JK Flip-Flop (4027) 1234

8765

555 Timer

JK Flip-Flop(4027)

98


Printing the Mask PatternAt the board, the component side pattern, the wiring side pattern, the

shape of the parts and the name of the parts are drawn together. When doing print in this condition, all of them have been printed. So, it is

necessary to set to print only a necessary part; the bottom copper for 1 sided PCB.

Set at least tPlace, tDocu, tNames, tValues, tOrigin to OFF, set other display as necessary. And set the print setting also as below.

99

100

Thank You

Documents

Computer and Information Engineering Lab II ECE 3102 & ECE 4102