part ii: using pcb layout software – custom component libraries

Part II: Using PCB Layout Software – Custom Component Libraries

September 24-28, 2012Carol Lenk

Introduction to Prototyping a LED Driver

What’s in a Component

Board SymbolPad Footprint:

copper, maskReference NameSilkscreen, Document

Board SymbolPad Footprint:

copper, maskReference NameSilkscreen, Document

Schematic SymbolSchematic ShapePins

Schematic SymbolSchematic ShapePins

ComponentConnection between pins

and padsValues, Component height,

Digikey/Mfr part number

ComponentConnection between pins

and padsValues, Component height,

Digikey/Mfr part number

HV9910

• Component not in library.• Package is standard.• Schematic symbol is standard.• Need to make a new Component that uses

existing SO-8 PCB symbol and schematic symbol.

• Library Manager• PCB Symbol Tab• Use All Libraries• Find…• Search for “SO” and 8

pads• Click on 8-SOIC

[prolib]

Find SO-8 PCB Symbol

• Library Manager• Schematic Symbol

Tab• Use All Libraries• Find…• Search for “SO” and 8

pads• Click on FCH-SO8

[fairchild1]

Find SO-8 Schematic Symbol

New Component• Library Manager• Components Tab• New Item…

HV9910• Assign pins 1 to 1• Enter Terminal Name• Save to our custom library

Custom Footprint

• Download datasheet from Digikey.• Find component size and recommended land

pattern.

Create custom PCB Symbol library• Library Manger• PCB Symbols Tab: New Lib… : 9910Demo.psl

Custom PCB Symbol

Copy a 2 pad footprint• In prolib.psl, copy

SMD1 to custom library• Name new pcb symbol

DR1050

Edit Custom PCB Symbol• Library Manager, go to 9910Demo.psl, select DR1050, click Edit• Right click on S (symbol origin) : Origins : Set System Origin at Item• Menu: Units: mm• Double click on pad to bring up Properties

• Change position (center of pad)

4.45

3.65

0.8

4.45

X

• Menu: Settings: Grids: Step Size 0.1mm.• Double click on corners to add chamfer.• Move R reference locator to outside of body• Pads underneath part makes it hard to hand solder.

– Increase pad size by 1 mm.

• Library Manager: Component Tab: New Item

Component Editor• Connect Sch

Terminals to PCB Pads

• Save to custom library

• Add Component to schematic.

MOSFET

MOSFET• Add pad numbers• Add description in Properties window.

• Schematic Symbol– Use Diode-2 in diode.ssl

library

• Need to create custom PCB symbol– Copy pcb symbol “1206”

from sm.psl library.– Name new symbol “SMA”

Diode

Diode PCB Symbol• With line selected, hit “L” to change layers.• Purple items are on Top Document layer to show components.

Layer not printed on PCB.• Yellow items are on Top Silkscreen layer. They are printed on

the PCB.• With line selected, hit “s” to change line style thickness.• For closed shape, use Properties and click on Filled.

Footprint Guidelines

• Reduce production errors.– Alignment, solderability, inspectable.

• IPC Standards.• From datasheets for resistors,

capacitors, etc.• Generally ~ 0.005” wider overall,

0.020” longer on each side.• Hand solderable for prototypes.

How is a PCB Made?1 2

3 4

Looking at a PCB

Pin connector

Green Solder Mask

Copper Trace visible under solder mask

White Silkscreen

Reference Designator on Silkscreen Layer

Tinned Pad

Layers

• Hit “c” to bring up colors.

• In Interaction Bar (Menu: View or F9), Layers Tab is at bottom.

Thank You