DIY PCB plated thru holes?

[jbv]

>
>
> > Any ideas out there on how to do diy plated through holes?
>
>
> > I'm working on a super compact design that is going to require a two
> > sided pcb but I still want them to be DIY. I really don't want to have
> > to solder one side and then the other side.  Any ideas?

I've been facing a similar problem for the past couple of years, and finally
decided to take an alternate path. Soldering on both sides is fine as long as

it concerns condos & resistors, but becomes more difficult when it comes
to ICs (especially if you use sockets).
The solution I use is to extend the IC pin connection on the PCB and drill
a 2nd hole next to it (at a distance of 0.01 inch) in which I simulate a PTH
by inserting a short piece of component trail and soldering it on both sides.

I know, it's not really elegant, but it works (for prototyping it's OK, and
it keeps PCB cost quite low; but it requires more time for extra driling &
soldering). I usually place these fake PTH under (beneath) the IC, so that
it doesn't waste too much PCB room...

> However, there are other problems which make producing double-sided boards
> very tricky, the main one being registration of the top and bottom photo
> masks.  I print mine out onto transparent film in my laser printer, and I
> need two foils for each side to ensure adequate opaqueness.  Add to that
> the variability of the printing process, and you soon run out of
> resolution on your track width/separation (as in, make the tracks too thin
> and they disappear, put them too close together and they merge into one
> big track :-(



A nice solution (if you can output postcript files for your PCB designs)
is to print films on a linotype (just like a film for regular magazines
printing).
A friend of mine works in a desktop publishing company nearby and
I can get the films for free, but I know that such equipment is widespread
now, and many companies will print you an A4 size film (on which you
can put 2 eurocards, or both sides of a double-side PCB) for less than
$10. I know, it's somewhat more expensive than printing at home on
transparent films with a laser printer, but then you get top quality
(1200 dpi resolution + top quality professional opaqueness), and also
photo marks that make film positioning for double-side PCBs much
easier. I've brought such films to a small components shop (in my small
city) that also makes PCBs and I've got very professional & compact
PCB, with 0.5 mm between tracks, and tracks of 0.1 mm width...

>
>
> So, the upshot of this is: given your requirements, go to a board
> shop.  They will produce a very nice board, with all the extras you get
> when done professionally (optional solder mask, optional silkscreen,
> tinned, machined, etc) that you wouldn't get with home-made.
>

BTW, I think I remember someone posting on this very list a few months
ago an adress of a company (in Poland AFAIR) making cheap PTH PCBs...
When I have a minute I'll check my archives...

jbv