RE: [Homebrew_PCBs] Digest Number 768
2004-07-30 by Thomas P. Gootee
Richard, I think that using soap or detergent is not necessarily a bad thing, as long as you also use something else, after that, to get rid of every trace of the soap or detergent and its additives. The isopropyl probably accomplished that, in your case. I now do ONLY TWO things to prepare a new piece of board for TT. (See farther below.) Cleaning of the PCB blank IS a CRITICAL part of the toner transfer process. I USED to go through many more steps than I do now, including either sanding and/or scrubbing with an abrasive pad, and washing with soap and water, and washing with isopropyl alcohol (IPA), and washing with acetone and/or laquer thinner, drying with a new paper towel after each step, etc. BUT, I have found that ALL that is needed is the abrasive pad and the acetone. Results are always perfect. [It works for me, anyway. But I also use a certain magic glossy paper, from Staples office supply stores, which is just called "Staples Picture Paper", on the package. (Complete/exact details of the Staples paper's UPC and SKU numbers, ordering it on line from Staples, etc, etc, are on my pcb webpage, at: http://www.fullnet.com/u/tomg/gooteepc.htm .)] *** PROCEDURE FOR PREPARING PCB BLANKS FOR TONER TRANSFER: *** (After this point, don't touch the surface of the board with bare skin. I use a clean paper towel to hold the edges of the board, during the procedures below.) ** STEP 1: ** Rub/scrub the whole surface of the pcb blank with a nylon abrasive pad (usually green, e.g. "Scotchbrite", often sold for kitchen use(?); some types are also sold for painting and varnishing prep; also sometimes referred to as "artificial steel wool", usually equivalent to '0' grade steel wool. (But DON'T use REAL steel wool, since it will embed steel particles in the copper, which WILL rust.)). I lay the board on a flat surface and go all the way across the board and partially off of each side with each motion of the pad, and work my way from one end to the other while doing that. At that point, the board should be uniformly shiny and clean-looking, with no remaining discoloration or marring or irregularities. Then, you need to do the same thing again, but in a perpendicular direction, and probably not quite as vigorously or firmly. The board should look like the example I show at http://www.fullnet.com/u/tomg/gooteepc.htm , with a pattern of nice fine scratches that run in two more-or-less-perpendicular directions (high directional precision is not required, hehe). You usually don't have to press TOO hard. But I press the pad down with the flats of several of my fingertips, in a manner that I would called "firmly", and use a fast and vigorous side-to-side motion. ** STEP 2: ** Wet a clean paper towel with Acetone and rub the board very firmly, to clean it. Note the huge amount of "dirt" that comes off (probably composed mostly of particles of the abrasive pad and the copper). Keep using a completely clean part of the paper towel, or another towel, with more acetone, and repeat, until you can't see anything else come off onto the towel. (Rub hard!) [Also, you have to take care to not re-introduce any dirt or contaminants back onto the board from the work surface, via the paper towel. I always clean the work surface with acetone and a paper towel, after using the abrasive pad and before cleaning the board with the acetone. I usally also clean my hands, and quickly wipe both sides of the board, AND the edges, just before starting the main cleaning process.] The entire process takes about a minute, at the most, if the materials are all at hand and you've done it before. If you're one of those who's worried about getting cancer from the acetone, you might want to wear some type of protective gloves, and have good ventilation. Also, remember that many household finishes and materials can be harmed, or destroyed, by acetone. (So don't do this on the lady of the house's good dinner table, for example.) Remember, too, that acetone is *extremely* flammable! By the way, I also usually use a paper towel and acetone to remove the toner, after etching. Good luck! Regards, Tom Gootee http://www.fullnet.com/u/tomg ------------------------------------ Date: Thu, 29 Jul 2004 18:43:10 -0700
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From: Richard Mustakos <rmustakos@...> Subject: Re: What cleaner to use for preparing for TT I have scrubbed the surface of boards , and washed them with detergents, but until I used IPA, I was never able to get the toner to stick reliably. Does anyone know why the detergent doesn't clean the oils off? Does it leave it's own coating? Richard [Non-text portions of this message have been removed]