Homebrew PCBs

----- Original Message ----- 
From: "Stuart Wallace" <stuartw@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Tuesday, June 13, 2006 1:00 PM
Subject: Re: [Homebrew_PCBs] My best fine-pitch PCB so far


> Hi Leon,
>
>>I've just made another PCB with a footprint for a Hirose 50 way DF12
>>connector with 0.5 mm lead spacing, it turned out very well. The DF12
>>pads are 0.38x1.00 mm.
>>
>>
> That's very impressive! It's pretty much what I'm aiming for, but I just
> can't seem to get my process right. It's good to see some results in
> context: I often find that people advocating one method or another
> without revealing the level of complexity (principally trace and space
> width) that they're attempting.

What are you printing the transparencies on?

>
> I'd like to be able to make double-sided boards with 8/8 traces and
> spaces but this seems problematic. I'd be interested to hear from anyone
> who's done this! My two biggest problems are contamination of the board
> while handling it between stages of the process, and alignment between
> the two layers. I need aligment errors of less than 1mm, and I'm not
> sure that this is achievable in a DIY set-up. At the moment I drill
> guide holes before exposure and use PCB pins to tack each side of
> artwork in place, in turn, before taping the artwork to the board and
> placing it in my UV box.

8/8 is feasible, but I prefer using 10/10 or 12/12. That board of mine has 
12 mil tracks. I have done one or two double-sided boards with tracks on 
both sides, by making a sort of envelope of the two transparencies with 
masking tape. The registration was slightly off (better than 1 mm, though) 
but I was able to assemble the boards OK.

Leon