Nicholas,
As you know, solderablity is a surface problem. Wetting of solder on the copper of the
printed circuit may be ok in your case, but the plating defects inside the hole -
missing copper on several little areas , is the cause of the "pinhole" as you call it.
On the suface of the solder joint it looks like that, but generally inside the printed
circuit hole you discover a much larger void. People usually don't bother with details
and call it a solderability problem, but in fact it is not. It is a problem related to
the hole plating process with its many aspects. The subject is very vast and the
reliability of such joints must be judged individually, multilayer circuits having more
"what if"s than double sided boards.
To avoid the problem if considered only "cosmetic" manufacturers dry the boards prior
to soldering, and absorbed water or organics from the plating process are eliminated,
hoping to eliminate the visual defect, but defective hole plating can not be
"repaired", and heat is bad for the "real" solderability.
There is a lot more, you'll get it, I am sure.
Gaby

Nicholas LAI wrote:

> Hello all
>
> Is there anyone can give me some info of pin hole in PTH.
> Our end-customer complain that there is poor solderanility of our product.
> After micro-section teh problem hole. there is some pin hole on teh PTH wall. Is
> this is teh root cause of the poor solderability.
> Any comment?
>
> More, is there any reasons can cause poor solderability(non-wetting)?
>
> Is there any good source can know more about the poor
> solderability(non-wetting)?
>
> Best Regard,
> Nicholas Lai
> 9/18/99
>
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