PCB Design

ECE304 PCB Design

2015 Fall

Hailing Yue

[email protected]

Department of Electrical and Computer Engineering

University of Dayton

Printed Circuit Board

 Multilayer boards made of alternating layers of conducting and insulating materials.  FR4: A type of fiberglass used as substrate/Base material. The solid core gives the PCB its rigidity and

thickness.  Copper: Can be applied on one side or double sides.  Solder mask: It is overlaid onto the copper layer to insulate the copper traces from accidental contact

with other metal, solder, or conductive bits.  Silkscreen: The white silkscreen layer is applied on top of the soldermask layer. The silkscreen adds

letters, numbers, and symbols to the PCB that allow for easier assembly and indicators for humans to better understand the board.

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Why PCB?

• Features • Surprisingly Affordable

• Highly reliable

• Compact

• Drawbacks • Requires more layout than other board types

• Higher initial cost than wire wrap or point-to-point construction

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PCB Design Steps

1.Paper and pencil: Circuit with simulated results.

Circuit layout for simple routing.

Each circuit components has to be specified.

2. PCB board design: Place the components.

Route the wires.

3. Manufacture

4. Soldering and test

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Download Software from: http://www.expresspcb.com/free-cad-software/

ExpressPCB Environment

Example 1: Schematic

Components in ExpressPCB

Two-port Connector Resistor LED

Resistor

Semiconductor BJT

8 pin Opamp Capacitor Potentiometer

Example 1: PCB Layout

Example 2

 3.8” x 2.5”

 2 Layer (top and bottom)

 0.1’’ power & ground traces, 0.03’’ signal traces

 0.1’’ power & ground input pads with silkscreen Labels

 0.1’’ output signal pads

Step 1: Schematic Model

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Step 2: Place Major Components

These are standard components which can be found in the components library.

Step 3: Place Customized Components

Buzzer and Photoresistor are the two components we have to make. Details will be explained later.

Step 4: Add Power Trace

• The power trace is made big (0.1’’) to endure high current.

• Orient the components to minimize routing.

Step 5: Add Ground Trace

• The ground trace is set to the bottom layer to avoid trace interconnection

Step 6: Wire the Components

• The signal trace is set to 0.025’’.

Step 7: NAME YOUR BOARD

• Put your names and project name on one of the METAL layers, NOT the silkscreen layers.

Make a Customized Components- Buzzer

• The lead spacing of a buzzer is 15mm=0.6’’; • The hole diameter is 0.8+/- 0.1mm~=0.035’’, choose 0.1’’ pad with 0.046 hole. • The diameter of the buzzer is 24mm=0.94’’

1mm=0.04inch

Make a Customized Components- Buzzer

Step 2: Select a component with same lead spacing

In this case, cap with 0.6’’ leading spacing

Step 3: Ungroup the component and add a arc on

silkscreen layer with 0.5’’ radius

Step 4: Change the hole size to be 0.1’’ pad with 0.046’’ hole

Step 5: Label the positive port, group and save the

component

Make a Customized Components- PhotoResistor

Step 1: Look at the component datasheet. The lead spacing of a PR is 0.1’’

Step 2: Select a component with same lead spacing In this case, cap with 0.1’’ leading spacing

Step 3: Ungroup the component and change the silkscreen layer

Step 4: Save the component

ECE304 PCB Homework Summing Audio Amplifier

1. Inputs: +/- Power Connection Two AC Inputs One DC Input

2. Output: Speaker

3. Other components: Op-amp, BJT, Potentiometer, Resistors&Caps, GND

Steps: 1. Components: LF353D: DIP-8PIN BJT: semiconductor TO-92 Potentiometer: 3386F R&C: 0.25’’ Lead spacing 2. Customize the speaker 3. Power Traces: 0.1’’, +,-,GND 4. Input connection: 0.03’’-0.05’’

two AC input, one DC input. 5. Output connection: speaker 6. Labelling 7. Signal routing 8. Naming

• The lead spacing of a speaker is 15mm=0.6’’; • The hole diameter is 0.8+/- 0.1mm~=0.035’’, choose 0.1’’ pad with 0.046 hole.

ECE304 PCB Homework Summing Audio Amplifier