Richard:

Let us first identify the fact that you are in the UK, and what is "tinning"
for you is not tinning to much of the rest of the world.  The "tinning" you
refer to is probably Tin/Lead solder?   The key question is how is it
applied, via hot air leveling (HAL, or HASL?) or is it fused/reflowed
electroplated Tin/Lead?

In either case the problem is almost certainly dirty Copper as the Tin/Lead
is applied, but if it is fused/reflowed Tin/Lead, it is most likely
oxidation, and I actually wrote a paper more than 10 years ago about the
problem.

Get back to us on how the "Tinning" is applied, and we can assist more.

And incidently, do you do business with my friends at W. Canning, now
MacDermid-Canning?

Rudy Sedlak
RD Chemical Company

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