[sdiy] PCB making

[Batz Goodfortune]

Y-ellow Samppa 'n' all.

At 09:14 PM 1/2/07 +0200, Samppa Tolvanen wrote:
>And here´s Tom Gootee´s "classic" description of the toner transfer method:
>
>http://www.fullnet.com/~tomg/gooteepc.htm#1
>
>This method does work when You find the correct setup. One thing I do
>differently: I´ve found, pre-etching the board before the transfer
>will make toner to stick better, than transferring diretly to bare
>clean copper.

Mmmm. Never thought of doing that with Toner transfer. Doh!. Ironically, I 
use to do that with Postiv20 and photo-etching. But usually, not by choice 
initially. :( Tip of the hat for that one. But I've never done it with TTS. 
However one of the tricks I use to do was to go over the board with some 
wet and dry paper in several directions to rough up the board a bit. 
pre-etching would undoubtedly be better.

Here's another helpful hint which I had meant to mention. Another sort of 
accidental discovery. Clean your blanks with a very nasty solution of 
caustic soda.

Positiv20 (And some other photo etch resists) develop in a weak solution of 
caustic soda. The rule of thumb is 1 teaspoon of caustic to 1 litre of 
water. The guy who taught me this trick use to say that if the solution is 
right, it should feel a little bit soapy between your fingers. That's 
actually the caustic turning the oils in your fingers to soap. You can buy 
expensive developer but essentially it's just pre-mixed caustic solution. 
Mix well because any large grains of the stuff unmixed, and settling on 
your board, will take out the etc resist exposed or not.

When I use to stuff up a board (And that was about half the time.) the 
quickest thing to do in order to get the remaining resist off the board and 
re-start the process was to ramp up the caustic developer solution. IE: 
dump a heap of caustic into the developer, put the botched piece of blank 
board into it and wait tell all the remnants of resist are gone. It then 
dawned on me that this was the magic bullet for cleaning down blank PCBs.

A strong caustic solution will rip any dirt or oil right off the board like 
it had been chemically sand blasted. If you like that shiny, fresh from the 
Fab look to your boards, this is the way to do it. No more power scrubbing 
over the wash trough out the back. A light scrub with a scourer, a bit of a 
going over with some wet & dry and then a nice relaxing bath in caustic.

NOTE: Don't try the finger test with this mix. It'll take your finger off 
as well. :(

Caustic will lift the dirt out from places you didn't know there could be 
places. Best of all, it's dirt cheap. :)

Hope this helps.

Be absolutely Icebox.

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