Tinning on old PCBs

From: Louis Schulman <louiss_at_gate.net>
Date: Thu Dec 20 18:59:28 2001

Yes, this is the actual lead/tin that is peeling off. There is no coating on this PCB, just the bare tinned traces
on a bare board. I will admit, this is quite unusual, since the solder must have flowed out to tin the traces in
the first place, yet it did not bond properly.

Louis

On Thu, 20 Dec 2001 08:22:17 -0500, Allison wrote:

#Are you sure it was the solder plating and not the resist(solder)
#mask(a plastic like over coating material)? If it was the tinning,
#that's there to improve solderability and appearance as well.
#
#The tinning adds very little to the current carrying capability as
#tin and lead have significantly more resistance than copper.
#
#Allison
#
#-----Original Message-----
#From: Louis Schulman <louiss_at_gate.net>
#To: classiccmp_at_classiccmp.org <classiccmp_at_classiccmp.org>
#Date: Wednesday, December 19, 2001 10:34 PM
#Subject: Tinning on old PCBs
#
#
#>I was cleaning a 20+ year old printed circuit board today, in the manner
#recently discussed here at length
#>(but by hand, I don't have a dishwasher). I was somewhat alarmed when some
#of the tinning flaked off the
#>copper tracks in places. The tracks themselves are fine, but evidently
#they had not been properly prepared
#>before tinning, so the tinning lost its grip.
#>
#>My questions is this: Is the copper itself sufficient to carry the
#currents, or is the tinning required to reduce
#>resistance? Or, putting it another way, is the tinning required, or is it
#just to assist in attaching components?
#>Or, putting it one last way, do I need to re-tin the bare spots?
#>
#>For what it's worth, this took place on the motherboard of my newly
#acquired Exidy Sorcerer #2, a Mark I
#>32K unit. This one came with a fair number of manuals and software (on
#tape, of course).
#>
#>Thanks,
#>
#>Louis
#>
#>
#
Received on Thu Dec 20 2001 - 18:59:28 GMT