Hi Rob, On Mon, 29 May 2006, Robert Spanton wrote:
Then once you've got those vias, you've got to get some sort of conducting stuff through them. I don't think sodlering anything through them is an option, as they wouldn't be flat enough to go beneath the BGA. The only chemicals I've seen for plating PCBs seem quite expensive (for a student!). I'd be interested to know if there's anyone who can suggest cheap ways of copper plating the holes. Rob
I think I can help you out on that one as I happen to study chemistry and also do quite a lot of it as a hobby. Basically one can't make those vias without some expensive chemicals, but very small amounts of the expensive ones are needed. They are used as catalysts or 'nucleation promoters'. Copper is one of the easiest metals to plate electrolytically and autocatalytically, so it definitely is possible @home/garage. Also none of the materials is really toxic or environmentally nasty, which is a good thing (tm). The tricky part is that one has to drill and plate holes before etching, and then those vias have to be protected during the etch.
One working way is by making a 'negative mask' (tracks and vias exposed) and a thin silver plating. Silver then works as a real mask in chloride based etch, and voila, one gets a nice silver plated pcb. The actual protective layer is silver chloride which forms on silver surface, but is practically insoluble in the etch. The dull coating of chloride is finally washed away with ammonia, photo fix, bromide... Then just go ahead and solder stuff on :)
Really helpful for plating is a software that can calculate the real permanent copper area, as plating current, speed and thickness are sometimes better calculated than guessed. Also it may be worthwhile to make some of the needed materials from the common industrial chemicals, especially precisious metal salts. For example silver is really cheap as silver compared to silver nitrate from research chemicals supplier, and it just takes a few cents worth of nitric acid to make 100g or so. The needed equipment one is going to need anyway...
This is going strongly off-topic to OGP I think, so maybe we should continue details pm. Any opinions from the others (also you)? The way or another, great to see people doing stuff like that. All my best wishes to the projet (of yours and The OGP) ;)
-Vesa _______________________________________________ Open-graphics mailing list [email protected] http://lists.duskglow.com/mailman/listinfo/open-graphics List service provided by Duskglow Consulting, LLC (www.duskglow.com)
