Homebrew PCBs

Stephan

>...the solder will bead up, never form continuous useable traces.
>try it with copper and solder filings and colophony powder.
>  If you have enough copper to make it stay you still have no adhesion to 
>the board.
>
>
>  
>
  This has been a issue in my mind, though I'm not sure what the effect 
of the copper powder will have on the process is.  I am also looking 
into water activated adhesives, as a back up.  I wonder whether sanding 
the fiberglass would make a difference, since even though the wetting 
won't happen, there could be a good mechanical adhesion if the reflowed 
solder can get 'around' the flayed fibers.  FR-4 might not be the 
preferred substrate for this:  I believe it is expressly engineered (or 
the flux was) to not be wetted with flux, to not be solderable.  I have 
not looked into other possibilities, but one possibility is card stock, 
since I think it can stand up to reflow temps, it should not have worse 
wicking problems than anything else, and is relatively cheap (buy a pack 
of 3x5s and your golden for 50-100 small prototype boards).  This is 
directly aimed at short lived prototype boards.  Longer life boards 
would be made the regular way.
   I will look at the colophony powder, but a reference I've found says:

"Colophony is pine resin after the turpentine has been removed. It has 
such a strong affinity for Fire that if kept in a powder form (this is 
chunk), it can spontaneously combust."
<www.alchemy-works.com/incense_colophony.html>

  I would want a fine powder for this application (more likely to take 
detail), and spontaneous combustion of working materials is right up 
there with muiriatic acid cocktails for the kids. ;)

>Then you have "sucking" of ink, no resolution at all, how narroy parallel 
>traces
>do you think are possible with this?
>  
>
  I'm not really worried about the capillary action of the water into 
the powders and how it effects the trace, as paper is a tough target 
that way, and the ink jets have gotten over that problem for the most 
part.  So my first thought is that the effect will be negligible, but 
that's what experiments are for.

>When you solder you have to solder in the soft solder/copper traces, that 
>will not be easy.
>  
>
I actually have a full size syringe of silver/solder conductive inks, 
and I was thinking using that for component mechanical and electrical 
placement and bonding.

>I don't see any advantage of this process, i would not waste my time even 
>if the
>odds were better that it works.
>(Even in an ideal case the work and result are much worse than many other 
>processes (like TT)).
>
  My target audience for this is, well, me.
  I have children at home, and am not all that interested in having the 
liquid chemicals around the house (of course keeping lead, flux and 
copper powders in the house is perfectly safe <G>, that and a little 
vodka seem to make the kids much easier to deal with (the powders for 
them, the drink for me ;) )), or of going through the imaging/etching 
process.  While I'm going to end up doing smt, for the most part I'm 
sticking to pdip, where I can, so I come from the low to medium 
resolution camp.
Thanks for the comments
RM


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