Homebrew PCBs

----- Original Message ----- 
From: "rmustakos" <rmustakos@...>
> When you say "real dry-film soldermask", you mean photo sensitive,
> right? Where can it be had?

http://www.thinktink.com/stack/volumes/voli/store/specs/8130spec.htm, about 
$3 to $5/sq.ft, depending on quantity ($240/80', or $200/40' x 12" rolls). A 
group purchase makes sense. Do you think we can find 12 US list members to 
split an 80' roll, for $30 each (to cover repackaging and shipping)?

Also, BGA is a bit more problematic because traces are usually run out 
through micro-vias in 4- or 7-layer boards. Soldermask is needed there to 
prevent wicking away solder in the micro-vias. I don't expect our manual 
processes can hold the required tolerances even if we were able to route 
them on just 2 layers.