Jon,
You have likely seen my other message explaining for Dennis. You're
basically correct except about the solder plated part, it is not part of
pattern plating, it would be part of the etching process and is the etch
resist. I believe that most manufacturers have switched (a fair period ago)
from using solder as the etch resist because the lead in the Solder made it a
environmental/recycling/disposal/reclamation problem.
Then as well, if you have solder plated traces you don't have SMOBC.
SMOBC is literally Solder Mask Over Bare Copper. The assembly/soldering problem
that you first raised is due to solder already being plated under the
soldermask. Solder plated traces wick and flow under the mask during soldering,
they also wick additional solder from the pads being soldered exactly as you
described. So for SMOBC the solder (or any other etch resist) is
removed/stripped prior to soldermask application. Leaving only bare copper
under the soldermask and you don't get the solder wicking/flowing problems
under the soldermask.
Sincerely,
Brad Velander
Senior PCB Designer
Northern Airborne Technology
#14 - 1925 Kirschner Road,
Kelowna, BC, V1Y 4N7.
tel (250) 763-2329 ext. 225
fax (250) 762-3374
-----Original Message-----
From: Jon Elson [mailto:[EMAIL PROTECTED]
Sent: Thursday, January 19, 2006 12:42 PM
To: Protel EDA Discussion List
Subject: Re: [PEDA] Solder Masks for vias.
That may well have been 10+ years ago, I just remember seeing this
happen.
OK, I guess I have forgotten the name of the process using the solder as the
etch resist. I guess that is called solder resist. I seem to recall a
process where
a laminate with a very thin foil is masked with a negative resist
pattern, and then
copper plated until the desired trace thickness is built up. Then, the
exposed trace
surface is (electro)plated with solder. Then, the resist is stripped,
and a quick
dip in etchant removes the thin foil, leaving the solder-plated traces
isolated.
This process accomplishes both the through-hole plating and the defining
of the
traces in one step. I thought this process was called pattern plating,
and most
fabricators leave the solder plating on the traces, and then solder mask it.
Jon
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