Homebrew PCBs

Hmmm,

I intend to use dryfilm laminate on both sides. The idea is to etch from 
both sides which I think might help keeping the undercuts at about half 
your rate. Just guessing though, and again, I definately will try this soon.

Markus

DJ Delorie schrieb:
>
>
> Markus Zingg <homebrew-pcb@... 
> <mailto:homebrew-pcb%40shdesign.info>> writes:
> > Were you using dryfilm resist laminate?
>
> No, toner transfer. Packing tape on the back side.
>
> > What's the thickness of the brass sheet?
>
> It varied from 2 to 5 mil. I've been favoring the thinner stuff.
>
> > Does this not lead to too much solderpaste on the pads?
>
> Yes, thicker means too much paste. A 5 mil thick sheet vs a 8 mil
> wide opening is a big chunk of paste.
>
> The other issue is thickness of the brass vs the space between pins.
> The undercutting is significant in this case; the holes end up being
> wider on one side than on the other; sometimes the undercutting can
> connect between openings. In general, an N mil thick sheet will be N
> mils wider on the "near" (toner, photomask) side.
>
>