homemade printed circuit boards 6/22/2015 jonathan weaver, km4fik with special thanks to paul...

Homemade Printed Circuit Boards

6/22/2015Jonathan Weaver, KM4FIK

With special thanks to Paul (WA7ZVY)

Overview• Creating PCB Artwork• Getting the PCB Artwork to copper• Preparation before Etching• Etching• Work after Etching• Supplies and Suppliers

Creating PCB Artwork: Circuit Design

• Find and use• Magazines, books, and references• Online• Component datasheets

• Find and modify• Use specialized tools (logic tools,

filter tools, etc)• Create from Scratch

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Creating PCB Artwork: Circuit Simulation

• Verify that it “works”• Tool: LTSpice (freeware downloadable at

www.linear.com/ltspice)• Alternative: Pspice Student, OrCAD Lite

(free versions of production software with limitations)

Creating PCB Artwork: Schematic• Easy to read• Incorporates notes• Generates a bill of materials (list of parts)• Generates a net list (how the parts are

connected)• Tools: TinyCAD

(http://sourceforge.net/projects/tinycad/)• Alternative Tools:

• ExpressPCB (easiest to learn)• Eagle (freeware has limitations, but very popular)• KiCAD• GEDA (Linux only)• DesignSpark PCB

Creating PCB Artwork: PCB Layout• Physical Layout

• 600 dpi printing limits the minimum sizes• 15 to 20 mil (1/1000 inch) trace width where

possible. 5 mil trace width minimum (3 dots)• Similar on spacing• 30 to 40 mil holes on 55 to 60 mil pads• Use copper “fill” areas to minimize etching

• Imports net list (parts and hookups)• Includes an auto router (I usually never

use)• Generates manufacturing files (usually

Gerbers)

Creating PCB Artwork: PCB Layout Cont.d

• Free PCB plus ViewMate Gerber Viewer• Alternatives:

• ExpressPCB (easiest to learn but tied to vendor if you want PCB's manufactured)

• Eagle (freeware has limitations)• KiCAD• GEDA (Linux only)• DesignSpark PCB

• At this point you can send the PCB files to a manufacturer or etch a board yourself

Printing a PCB• Print to verify size, etc.• Print for etching (to PDF using PDF Creator)

• Mirror the top side• Bottom side is already mirrored

• Keep the PDF file for easy printing later on• Print using LASER printer on magazine paper

• Alternative papers include • Epson Glossy Ink Jet Photo Paper P/N S041141• Pulsar Toner Transfer System (http://pulsarprofx.com).

Digikey P/N 182-1003-ND and P/N 182-1021-ND.• Line up top and bottom using light under glass

table or light table• Tape two sides down

Getting the PCB Artwork to Copper

• Clean the copper clad board with a scotchbrite pad

• Insert the board in the print out “pocket”• Iron on high. Cover entire board with iron.

About a minute. Apply good pressure (I usually iron on a counter top).

• Let board “sandwich” cool (sets the ink to the copper).

• Soak the “sandwich” in a sink of cool water• Gently remove paper. Use toothbrush or

sponge to remove small bits of paper stuck to the ink.

Board Prep before Etching• Inspect!!!!• Use an Exacto knife to cut any "shorted" traces

or pins apart.• Use a fine point sharpie marker to draw in

traces that may have been lifted with the paper removal.

• If it is unrepairable, clean off failed transfer with Acetone, and start over.

• Cut out the board with a Dremel tool (SAFETY GLASSES). Use care not to scratch the design.

Etching• Bath of hot water• Float bath of etchant (Ferrious Chloride)• SAFETY TOOLS: Latex gloves, safety

glasses, apron or disposable clothes (etchant stains)

• Submerge PCBs. Agitate Etchant. Flip PCBs.

• Repeat until all exposed copper is removed.

• Submerge PCBs in cold water to remove etchant and stop chemical reaction

• Dry PCBs.

After Etching• CLEAN UP – I store used etchant and reuse.

Etchant can be neutralized with wash powder, dilluted, and disposed down the drain.

• Clean ink off the PCB using acetone (nail polish remover) and scotchbrite pad.

• Drill holes with drill press (etched holes in pads help line up the bit)

• Solder vias through holes (use bare bus wire)• Solder components and jumpers (soldering

would be a whole other presentation)

Suppliers• Parts

• Digikey (www.digikey.com)• Jameco (www.jameco.com)• Mouser (www.mouser.com)• Others (Radioshack, Element 44, Allied, etc)

• Copper Clad boards and drill bits• Far Circuits (www.farcircuits.net) operated by

KF9GX• He will also etch your boards for you• He accepts ExpressPCB files