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A guide to printing your own circuit boards

by Jay Couture

jcouture@latte.memphis.edu

Introduction

This article was written to try and help others avoid the pitfalls I have encountered while printing my first circuit boards. I do not claim that this is the best way, nor that it'll work for you. With that being said, here are my methods:

1) I used a product called PRESS-N-PEEL BLUE from Techniks, Inc. This product allows you to print your circuit out and iron it onto a copper-clad board. The only stipulation is that the printer use toner (so a photocopier will work also).
2) The PCB art. My image came from a PDF from National Semiconductor. The LM2595 Simple Switcher circuit is provided in the PDF at 2x size. I tried different methods to capture the image but this one worked the best. Print the image in as high a DPI as your printer allows (600 is good but I went with 1200). Then scan in this image at 1200DPI black and white (if your printer only prints 600DPI, then you should only scan at 600DPI). You can now adjust the circuit in the art program of your choice. You will need the ability to flip the image (either horizontally or vertically). Make sure you flip your image, otherwise your art will be backwards when you transfer it to your copper board. A picture of the test printout.
3) The instructions that came with the PRESS-N-PEEL BLUE never quite tell you what a pain it is to get the sheet to feed. The transfer sheet is basically a transparency with a blue film on one side (the documentation refers to is as the dull side). The dull side was too slick for the pick-up mechanism, both in my laser printer and copier, to grab hold. After several paper jams and unfused toner stains, I found two simple solutions. The first is to use several lines of masking tape at the top of the page to give the pick-up something to grab onto. One the page was in , the friction feed rollers were able to grab hold. The second method is to tape a small section of the sheet to a "carrier" piece of paper. This worked the best for me, but others might have more luck with their particular printer. I use 600 DPI on the printout to avoid getting "too much" toner. Too much toner results in a "fuzzy" circuit. That is, the toner tends to spread out (kinda like the jelly in a P&J sandwich when your squish it). A picture of the printed mask.
4) Now you need to transfer your art to the board. The instructions say to set your iron to the polyester to acrylic settings. I use the acrylic. Prepare your board just like the instructions say. Be sure to use steel wool and not an abrasive pad (like 3M). I used Brillo pads with no trouble, but tried a 3M pad with mixed results. I have tried ironing on a flat surface with and without a towel. I recommend the towel. Also, be sure to file the edges, if the iron doesn't make good contact you'll know when you try to remove the transparency backing. You can usually look at the transfer to tell if the toner is fusing to the copper. The image will appear to darken. Wherever you see "lighter" spots, use the tip of the iron to heat those areas up. When everything looks good, quench the board in water. Using tweezers slowly peel the backing off. If the art is sticking to the transfer, reheat that area with the iron. Do not overheat, or the backing will start to wrinkle. The instructions tell you to use tape to remove any fills. Only bother with this step if there are fills between traces. Don't worry about filled in donuts, you'll have to drill them anyway. I picture of the board after ironing then etching.
5) Now just etch your PCB. I use ferric chloride I bought from Radio Shack for $3.58 a bottle.
6) Now just drill your board. When you are ready to populate it, use a Brillo pad (or abrasive pad) to remove the transfer and toner. I also recommend you get TINNIT tin plating material. Although on my first board I left the mask on, on the rest of my projects I used TINNIT to protect the copper and help with soldering.
A picture of my Dremel drill press.
This last photo shows one of my first attempts. You'll notice I forgot to flip the art before I printed it. Now I have a backwards example to show you what not to do :) A picture of a PCB with the Blue mask removed.
The LM2595 5 volt Switching Regulator
Here is the finished product. I added a power LED and recommend the same. A picture of the finished LM2595.
These final photos show the LM2595 in action.
A powered up LM2595. LM2595 powering a Bot Board 1.

Good luck, Jay


List of materials needed:

PRESS-N-PEEL BLUE Techniks Inc. $30
Ferric Chloride Radio Shack $ 3.58
Clothes Iron Permission from your spouse :)  
Copper clad board Circuit Specialist  
Small drill bits and TINNIT All Electronics Around $5 for 9 used bits
  or Walmart I bought a Dremel drill bit set for $9.00
Laser printer/photocopier    
Parts needed for the LM2595 (all parts from Digikey)
Schott 67144130 Digikey PN:257-1044-ND $10.91
1N5820 3A 20V Digikey PN:1N5820CT-ND $1.13
180mF/35V Electrolytic Cap Digikey PN:P5733-ND $0.49
330mF/10V Electrolytic Cap Digikey PN:P1203-ND $0.43
This document last modified 01/25/1999 11:00:20 AM