Wednesday, July 16, 2014

PC Board Fabrication

Coworker Tony DeRose wrote up his experience in fabbing his own PCBs, and has graciously allowed me to post them here.  Check out his drain cleaner comment in step 7 and you'll know why he's such a great guy to work with! 

 I've finally started to look into making my own 1 and 2 layer pcbs. I've experimented with a few inexpensive methods. Here's a description of the best I've found so far. Let me know if you have a better process.

Step 1: Laser print the layout on transparency film (costs 80 cents at Kinko's). Layout was created in Eagle (lite).

 Step 2: Buy pretreated photosensitive pcb board. About $7 for this size at Lasher's.
 Step 3: Cut a piece from the board to size.
 Step 4: Using a "safelight" that won't expose the board (a 40W incandescent bulb), peel off the protective white layer.
 Step 5: Lay the pattern on the board (treated side up) and cover with an acrylic plate to hold it in place.
 Step 6: Expose under a photo lamp for 5-8 minutes.
 Step 7: UV light makes the exposed parts of the board susceptible to removal using NaOH solution. Place in a NaOH bath until the pattern becomes clearly visible. In my experiment last night this took about 30 seconds. Immediately rinse in a water bath to remove excess NaOH. The bottle says 1 part concentrated solution to 7 parts water. I got better results with a ration of 1:10 using the product below. I think you can go even cheaper and use drain cleaner, but I haven't tried that yet.

Step 8: Etch away the copper using equal parts 14% HCL and 3% H2O2. OSH carries the HCL as a pool chemical (also called muriatic acid). Any drug store has peroxide. Takes about 10 mins.

Step 9: Rinse in water and dry.

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