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Homebrew_PCBs@yahoogroups.com, "smilingcat90254" wrote:
>
> First of all, HP toner has a melting point (commonly written as MP###) of around 95C to 105C.
Thanks very much for sharing your experience and suggestions. Just knowing the melting point puts a different light on things -- I'd mostly been concerned about not having enough heat, when it's pretty clear now I had way too much.
Today I made two attempts with a simple little board. I wasn't able to use my IR thermometer to measure the temperature of the iron (too shiny) but a meat probe thermometer did the job, and on the "Silk" setting my iron runs right at 250 deg. F., which seemed about right based on the MP of the toner. The first attempt was for 60 seconds with moderate pressure, and while the toner transferred, a large area flaked off. The second time I kept the iron set on Silk but increased the time to 90 seconds. In each case I moved the iron around 3-4 times but didn't "iron it", just held steady pressure.
The result of #2 can be seen here:
http://img849.imageshack.us/img849/5864/tonertest90secsilk250de.jpgThe traces transferred well and are much clearer, but some areas of the ground plane didn't transfer too well as can be seen by the exposed copper areas. Seeing this, I followed your suggestion and baked the board in the oven at 200 deg. F for 20 minutes, which seems to have helped adhesion. Since it doesn't affect the operation I'm going ahead and etching this one, and next time I will vary the temperature or time a bit and see what effect that has.
Overall - much improved! And to answer my own original question, I can see how the hot-roll laminator could help insure equal heat and pressure all across the board.
73, Bob W9RAN