YOU WROTE:
>Hello TechNetters,
>
>I am a bare board fabricator and writing on behalf of one of our customers.
>They are having a solderability problem with one of the components, a press-fit
>pin, and are seeking any advice I can collect.
>
>These pins are .028" diameter and are pushed through .062" thick PC-75 laminate
>until just .010" protrudes out the other side, and held in place by friction.
>The .010" stub of the pin is surrounded by a pad to which solder paste is
>conventionally applied and flowed. After soldering, inspection shows excellent
>wetting of the pad surface, but *no bond to the pin*. Specifics of the pin
>materials are not available at this time, but visually they appear to be tin-
>coated brass. Mechanical scraping/brushing of the pin and hand soldering fixes
>the problem, they obviously want to avoid this in production.
>
>Personally, I think that the pin is being coated with resin as it is press fit
>through the hole wall (this is not a plated-through-hole board). Can anyone
>shed some light on this problem?
>
>Thanks!
>
>Bill Parlin

We continually have problems with solderability of tin plated brass, swaged
standoffs.  Shelf life seems to be a real problem and the way they are
stored can greatly affect the solderable life.  We use a piece of 3M OAP in
a sealed bag (not pink poly or paper).  This seems to help but we still see
a problem from time to time.

Hope this helps a little.

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