Homemade Printed Circuit Boards 6/22/2015 Jonathan 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 More Knowledge and Experience

Creating PCB Artwork: Circuit Simulation Verify that it “works” Tool: LTSpice (freeware downloadable at 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 ( 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 S Pulsar Toner Transfer System ( Digikey P/N ND and P/N 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 ( Jameco ( Mouser ( Others (Radioshack, Element 44, Allied, etc) Copper Clad boards and drill bits Far Circuits ( operated by KF9GX He will also etch your boards for you He accepts ExpressPCB files