Making it at home

What is a PCB ? A PCB contains a fiber glass epoxy board with

thin copper layers attached to it. A photographic process is used to etch off the

copper where it is not needed to connect ICs. Prior to etching, all holes are drilled in the PCB

and it is electroplated so that the feed through holes connect to the different copper layers.

Electronic parts are soldered to copper mounting pads left after etching, and thin copper traces are used to connect the parts.

More on PCBs The designer must use a PCB layout CAD

tool to design the pads and interconnect lines.

The PCB layout tool produces the artwork for the photographic mask that is used to chemically etch the PCB.

Small simple boards have two copper layers.

Boards like PC motherboards are very complex and have 8-12 stacked layers of copper (more expensive setup charge – too high for student projects!)

Why we need PCB?

No wires Makes a design permanent In industrial scale production of circuits

Steps in making a PCB

Design schematic Design layout Fabricate the layout

Parts / Components Electronic components

Schematic symbol Description (used for BOM) Footprint (Simulation model)

Footprint examples:

DIP16 SOT23

Footprint examples:

SOIC8 PQFP240

Footprint examples:

FineLine BGA484 BGA256 TSOP48

Schematic capture

Export schematic to PCB

Place components on PCB

Distance from pad to trace > 10 mil

• Distance between components > 10 mil

PCB making softwares Autocrat EDA EAGLE FreePCB (open-source Win2K/XP) FreeRouting Cadstar Electronics Workbench gEDA, open-source PCB software

project OrCAD Allegro (Cadence) PADS Dip Trace

Dip Trace – Draw the Schematichttp://www.diptrace.com/http://www.diptrace.com/

Diptrace has a Free Version: Freeware edition does not support Diptrace has a Free Version: Freeware edition does not support export to DXF, Gerber and N/C Drill, max. number of pins — 250.export to DXF, Gerber and N/C Drill, max. number of pins — 250.

PCB Rapid Prototyping Systems

CNC machine mills out copper traces with small cutting tools and drills

OK for small quantity simple boards Interfaces to PCB design software files

Methods of etching Silk screen printing uses etch-resistant inks to protect the copper foil.

Subsequent etching removes the unwanted copper. Alternatively, the ink may be conductive, printed on a blank (non-conductive) board. The latter technique is also used in the manufacture of hybrid circuits.

Photoengraving uses a photomask and chemical etching to remove the copper foil from the substrate. The photomask is usually prepared with a photoplotter from data produced by a technician using CAM, or computer-aided manufacturing software. Laser-printed transparencies are typically employed for phototools; however, direct laser imaging techniques are being employed to replace phototools for high-resolution requirements.

PCB milling uses a two or three-axis mechanical milling system to mill away the copper foil from the substrate. A PCB milling machine (referred to as a 'PCB Prototyper') operates in a similar way to a plotter, receiving commands from the host software that control the position of the milling head in the x, y, and (if relevant) z axis. Data to drive the Prototyper is extracted from files generated in PCB design software and stored in HPGL or Gerber file format.

Toner Transfer Method

• A method of creating a printed circuit board (PCB) using a copy machine or a laser printer to make apply the etchant resist pattern

• Software now available to create schematic and PCB layout

• No expensive equipment is required but can be helpful in the home

• A simple process once the basics are mastered

Print to Transfer Paper

Transfer Toner to Board

Remove Paper from Toner

Soak 20+ Min. Warm, Soapy Water

Rub off the paper

Circuit Ready for Etching

Wash off the unwanted copper

Laser Printer

Toner is plastic based

Soldering

Troubleshooting

References http://www.kpsec.freeuk.com/solder.htm

http://ezinearticles.com/?The-3-Different-Types-of-Printed-Circuit-Boards&id=3133963

http://en.wikipedia.org/wiki/Printed_circuit_board

http://www.qsl.net/vk5cu/

http://bot-thoughts.blogspot.com/2009/08/simple-diy-pcb-etching.html

http://www.kpsec.freeuk.com/boards.htm

http://www.diptrace.com/books/

http://www.youtube.com/watch?v=urv6jArKp6M

http://gilmore2.chem.northwestern.edu/projects/garbz2_prj.php

Thank You