Homebrew PCBs

In a message dated 10/18/2004 6:17:55 PM Central Standard Time,  
BWeiss@... writes:

What  does one use to protect the copper when your finished with the board?  
Tinning?




BW:  Yes, the bare copper SHOULD be at least tinned, except for  "throw-away, 
one-each" hobby-PC work that doesn't have to last.  A firm I  THINK I read is 
no longer with us, Kepro, sold a "Tinnit" solid which, when  dissolved in hot 
water, would "electrolessly" tin all the bare copper that came  into contact 
with it.  I used this religiously for a time until TWO  things:  First, the 
stuff just plain "went bad" (which I learned later it  DOES), and then, I 
couldn't get in touch with that firm any longer, and seems I  READ (here?) that 
Kepro was either out of business, or had at least ceased  selling to "home shop 
folks".  
 
What I always do when doing an "important" board is solder nicely, then  
using either Acetone or lacquer thinner and an old toothbrush (using the one you  
actually still use is not tasty!) and "scrub off" all the solder-flux ("rosin  
core") melted all over the board.  Be very careful not to let that  goop run 
into IC sockets, etc.!   Hold the board essentially  vertically over a metal 
pan large enough to catch drippings, and give you also a  place to dip/re-wet 
your brush.  I do this "solvent brushing" ONLY on the  "solder side"!  If there 
are nasty spots on the top (where you soldered a  "through-hole" 
resistor-lead, etc.) I use a tiny piece of paper napkin and  swab-off that tiny spot of 
nasty on top, here and there, being super  careful not to use so much that it 
runs all over, into sockets and  non-hermetically-sealed components, etc. 
 
Then I "mask off" all the IC-sockets, trim-pots, later-to-be-soldered pins,  
etc., and then clear-spray the board, both sides, parts and all.  Then  
carefully remove all that masking tape, and use a fresh piece of it to "pull  off" 
any nasties that peeled off onto the board as you removed the  masking.  This 
keeps the nasty atmosphere off the "shiny metal", but, as  you had so carefully 
masked the sockets, etc., you can still plug in IC's,  certain of good 
contact.  
 
Takes some patience and experience.  Did I say patience?  
 
Lotsa  luck!                Jan  Rowland


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