Homebrew PCBs

Correction: "... negative FILM photoresist ..."

No matter how many times you proof read ... Awww Crap!!!

--
Phil M.

----- Original Message ----- 
From: "Phil@Yahoo" <yahoo@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Tuesday, May 21, 2013 12:30 PM
Subject: Re: printer


> Hmmm...
>
> I'm a (relatively) new member here. I've been lurking. This is the first 
> urination competition I've seen in this group but, human nature being what 
> it is, I suppose they are inevitable. When I was in the first grade we 
> used to see who could stand farthest back from the urinal. I could do more 
> than six feet. Now that I'm almost 60 (yikes!) well, you don't want to 
> know. A sad story.
>
> Anyway, the topic: This is in fact the reason I joined. I make double 
> sided PCBs with plated-thru holes, but have trouble going beyond 2 or 3 
> inches on a side because of the distortion caused by printing laser 
> transparencies. I used negative file photoresist which works quite well, 
> bit printing negatives exacerbates the distortion problem because of the 
> large areas of black.
>
> The contrast of the laser printer (I have a Brother MFC8500) is fairly 
> poor so I have to stack up 3 prints to make it dark enough. Last time I 
> tried inkjet (HP 932C) the ink wouldn't stick well enough to the plastic, 
> so large dark areas had lots of gaps (too much surface tension in the 
> ink.) Recently I picked up a used Epson Workforce 630 for my wife [only 
> $25 :-) but $70 for ink :-( ] and decided to try printing a mask on that. 
> I was thrilled! It looked perfect, with excellent contrast. But the test 
> was a positive image, no flood fill.
>
> Next board I made I printed on the Epson, but found the ink smearing and 
> bleeding wherever there were large dark areas, and the fine traces 
> (~12mil) tending to close up. Back to the laser. I know I could use flood 
> fill to reduce the black areas on negatives, but that is not foolproof 
> because the flood fill often cannot reach some spaces.
>
> I recently picked up some Oracal to experiment with, but even with that I 
> doubt TT will work for me because of inadequate contrast (too many 
> pinholes in the black areas) though I am in the process of making a 
> temperature controller for my Royal PL2112 laminator. I looked at 
> replacing the thermostats but decided I'd rather have continuous control 
> from hand-warmer to melt-down. Who knew a simple 1N4148 made such a swell 
> temp. sensor? I have actually tried multiple applications of toner to a 
> PCB. Too hard to align. But there are other interesting applications for 
> TT.
>
> Anyway, I would be very interested in learning which printers produce the 
> best contrast with little or no distortion. I can't afford to keep buying 
> inkjet and/or laser printers till I get it right, and I don't want to 
> spend a fortune on equipment or consumables. If I could just throw money 
> at the problem I wouldn't bother with DIY. I have a pretty good supply of 
> NuKote laser transparencies and would prefer to continue using those. They 
> seem to work pretty well with the Epson inkjet, though I'd grant there may 
> be something that works better. If so, I'd like to know why. But again, I 
> don't want to accumulate a stack of useless transparencies searching for 
> The One That Works.
>
> OT; FWIW, I've found that conductive ink made from Silver Acetate is very 
> effective as a hole wall activator. After drying and annealing at ~92C it 
> forms a layer of metallic silver with a very strong mechanical bond to the 
> hole walls, and as such is impervious to solvents. It is more expensive 
> than conventional DIY activators, and is quite toxic, but the shelf life 
> is virtually indefinite, and I can make it in small batches. I thought 
> about selling it in small vials but the toxicity argues against that. Some 
> putz would probably sue me because his kid tried to snort it or something. 
> Anyway, FWIW.
> --
> Phil M.