On 15 Dec 2010, at 07:39, Vicent Colomar Prats wrote:
> Hi Donald,
>
> I think your idea of putting a thin wire in a slotted pad could work, but it
> is going to be a lot of work. A friend of mine also tried to flat the vias
> (normal ones with a simple piece of wire) with a dremel and did a good job.
> It is also a lot of work but never did it enought to put an IC on top of
> those vias.
>
> Another idea I have, but not tried yet, is with sodder paste. First try one
> side, then the other. Or maybe helped with a very thin wire in the hole?
> Anybody tried something similar?
>
I mill out PCBs at home using my Everprecision 2002 machine, and then I make connections with solder-paste. Using paste is a lot faster than using solder IMHO - takes about 3 secs/hole.
You can't just use solder-paste though. It wicks away from the center-hole and you don't get an electrical connection through the FR4. My method is:
- lay out the vias using squares rather than circles - it makes it easier to see which ones are vias :)
- put a blob of solder-paste on each square via
- poke a thin-gauge wire through the hole, touch the soldering iron to the paste, move the iron away then wait for the solder to 'set'
- snip the wire
- repeat for each via
- turn the board over, put a blob of solder-paste on each via
- touch the paste with the soldering iron
(optionally) turn the board over again to the component-side
melt each via with the soldering iron and push the wire through so it sticks out the reverse side, not the component side
drag the iron down the copper trace to smooth out the solder
The optional stage can make the surface on the component side pretty smooth - not perfect though, and I wouldn't like to put any SMT chips on top of that sort of via
I was recently looking at plated-through-holes myself. I found the LPKF solution (circa $10k), or a Chinese PTH machine (circa $1400 + $500 shipping). The Chinese one is not a pulse-plating system, it's just a DC plating machine.
So, I thought about how to DIY one of these. LPKF will sell the chemistry in small doses (it'll still cost you $300 or so I reckon, but that's "small" :), so that's not an issue. I'm busy with other projects (my reef tank started leaking, and I have to re-install everything. A 240-gallon fishtank takes a lot of time to set up properly :) at the moment, so it hasn't got very far, but I put up the design at
http://platepcb.com/ The SSR's will arrive in January next year, so perhaps I'll have a chance to work on it then.
Apart from the chemistry, you're still looking at the high-hundreds for a reverse-pulse-plating machine if you DIY it. I can't see the price being much more "affordable" than that if it's sold commercially.
Simon
(BTW: What on earth does 'quimical' mean ?)
>
> Anyway, some of this "inventions" can work with more o less result, but I'm
> convinced the way is to go to a quimical or electrolytical plated process.
> Is there anything affordable for the hobbyier?
>
> 2010/12/15 Donald H Locker <dhlocker@...>
>
> >
> >
> > I have no personal experience. I think a plated-through-holes (PTH) process
> > is usually a bit beyond the hobbyist level, but is the only way of achieving
> > no-bulge vias. All other methods (eyelets, fine-gauge wire) leave
> > protrusions on the surface that prevent flat mounting of components.
> >
> > It _might_ be possible to put down a pad with a slot in the copper
> > (extending radially from the hole) just wide enough to lay a fine gauge wire
> > in and bridge the pad's slot and the wire with solder, producing a
> > nearly-flat surface, but I wouldn't want to do many of those. Never mind.
> > 1oz copper is about 0.0013 inches thick, while 30AWG wire is 0.010 inch
> > diameter - that's about a 0.009 inch ridge on the board.
> >
> > Donald.
> > --
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