Some followup --
I made a board last night, and etched, drilled, and tinned it this morning. The process was the same as described below, except I managed to regulate the temperature on the hot plate much better. Here is the new board:
http://home.earthlink.net/~a_wake/tt_test_board2.jpgand here it is in comparison to the over-cooked board from yesterday:
http://home.earthlink.net/~a_wake/tt_test_comparison.jpgThere is still a little browning of the new board, but nothing like what happened to the one from yesterday. I took an old board and put it on the hot plate, and kept turning the heat up a little at a time until I saw the solder melt. When I put the new board on, I wound up still needing to turn the heat up a bit more -- basically, it was melting the solder only on the heating cycle. I wonder if it browned a bit in part because it took me so long to get it all tinned, because it wasn't quite hot enough.
Now that I know where the setting is, I may try the next time with a 3/4" thick plate of aluminum, with the idea that it should keep a pretty stable temperature across the heating cycle.
In any case, I am very pleased with the latest results. BTW, the fine traces on the board are 10 mil, and the lettering is using .004" thick strokes.
Thanks for all the input, and for all that you all have taught me to get me to this point!
Andy
--- In Homebrew_PCBs@yahoogroups.com, "awakephd" <a_wake@...> wrote:
>
> I have only done three or four toner-transfer boards, with acceptable results. But recently I acquired a laminator, and I picked up an inexpensive hotplate, so I did some experimenting to test my techniques. Here are some results; if you read all the way to the end, I have a couple of questions. :)
>
> Test results showing patterns for 10/10, 8/8, 6/6, and 5/5 (left to right):
>
> http://home.earthlink.net/~a_wake/tt_test_closeup.jpg
>
> The patterns have two inner blocks and traces of the designated size and spacing spiraling outward to two outer blocks. If the inner block and the matching outer block show continuity, then the trace is intact; if there is continuity between two inner or two outer blocks, then there is a short. All of these test patterns worked except the 8/8 -- there is a break in one of the traces, but not the other. No shorts anywhere. Surprisingly (to me, anyway!) the 5/5 pattern worked perfectly. I'm not sure I'd be ready to trust it for a real project, though! :)
>
> Here is what I used to produce the patterns.
>
> HP LaserJet P2015dn printer with HP toner
>
> HP Presentation Paper, Laser Glossy, 34lb. I can't find the part number anywhere ...
>
> GBC 2130 laminator. This has a built-in temperature control that will go up to 320 degrees -- which is where I set it to do this test. I ran it through on speed 2 (next to slowest) three times. Here is a picture of the laminator:
>
> http://home.earthlink.net/~a_wake/laminator.jpg
>
> ∗∗∗ very important: I peeled the paper off the board immediately after removing from the laminator! In the past, I have found that it is nearly impossible to get this paper off if you let it cool and soak it, but it seems to come right off, leaving the toner behind, if you peel it off immediately.
>
> I etched in 2 parts drug-store variety hydrogen peroxide plus 1 part muriatic acid. Usually this is super fast, but today it took more than 10 minutes ... maybe because the chemicals were really cold, and I etched it outside in the cold.
>
> After cleaning the board with acetone to remove the remaining toner, I put it on a small hotplate -- a 110v single burner with an 8" x 8" piece of 1/4" thick aluminum on top. I fluxed the board and then heated it up until I could tin it with some solder. I wiped the excess solder off while still hot.
>
> Now for some questions: 1) The PC board turned a chocolate brown color after heating on the hot plate. If you look at the second picture above, you'll see the now-brown board at the bottom of the picture next to a light-green board that came from the same stock. IOW, the light green is the color it was before heating on the hot plate. Is this color change normal? Ominous?
>
> 2) Does anyone else use the glossy laser paper as I've described above, peeling it off immediately after laminating?
>
> 3) Any suggestions about any of the technique described above?
>
> Many thanks to anyone who has actually read this lengthy post all the way to the end!
>
> Andy
>