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Step 2Print the masks
This is a tricky step. You need to print the masks onto special paper, and make them as dark as possible. Here's how I did it. I used Jet Print Multi-Project glossy photo paper. I had to order it online, but it might be available at larger office supply stores. Tom Gootee recommends Staples "Picture Paper"; that seems easier to obtain. Unfortunately I didn't read Gootee's article until AFTER I'd already gotten the Jet Print paper. So the Staples paper might be better.
These papers are marketed as ink-jet papers. But for this process, you need to run them through a laser printer. The toner creates the mask. And, you want the toner to be as dark and dense as possible. I found that if you tell the printer that you're printing a transparency, it'll apply more toner. I also adjust various settings on the printer menus (e.g., toner density, optimization, etc.) to get the densest possible print -- your printer settings will vary. Experiment to see what works best, and take notes as you go so you'll be able to duplicate your best efforts later. I burned through quite a bit of paper before I got it right, but now I get it right the first time.
If your PCB design has long vertical traces, you might orient the design on the page so that the long traces are angled. Because of the direction that paper travles through laser printers, long vertical traces might lose toner density near the bottom. Angling the long traces helps keep the toner dense on the full length.
Remember to print the copper mask "right-reading" -- i.e. NOT a mirror image -- but the "silkscreen" mask shold be printed in reverse.
Make a print or two and find a mask that is uniformly dense with a minimum of pinholes. Make sure all the traces and pads are complete.
These papers are marketed as ink-jet papers. But for this process, you need to run them through a laser printer. The toner creates the mask. And, you want the toner to be as dark and dense as possible. I found that if you tell the printer that you're printing a transparency, it'll apply more toner. I also adjust various settings on the printer menus (e.g., toner density, optimization, etc.) to get the densest possible print -- your printer settings will vary. Experiment to see what works best, and take notes as you go so you'll be able to duplicate your best efforts later. I burned through quite a bit of paper before I got it right, but now I get it right the first time.
If your PCB design has long vertical traces, you might orient the design on the page so that the long traces are angled. Because of the direction that paper travles through laser printers, long vertical traces might lose toner density near the bottom. Angling the long traces helps keep the toner dense on the full length.
Remember to print the copper mask "right-reading" -- i.e. NOT a mirror image -- but the "silkscreen" mask shold be printed in reverse.
Make a print or two and find a mask that is uniformly dense with a minimum of pinholes. Make sure all the traces and pads are complete.
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