Yehuda,

After your first reflow cycle the original solder thickness is
unimportant...

Thickness will also not be a major contributor to shelf-life...what
would affect this is the quality of the solder coating...

Most HASL processes should be able to produce acceptable solderability
up to a year after fabrication provided they are package accordingly,
and stored in an decent storage facility (average temperature/humidity).

My suggestion would be to state the quality level you expect, at
receiving, after 6 months, a year, etc, etc. Writing a requirement for
continued solderability up to and beyond 3 thermal cycles may be a bit
much, unless you're able to work well with the supplier...

My $12.00 worth ~my time is more expensive then a mere two cents
~grins~~

Franklin D Asbell

> Yehuda Weisz wrote:
>
> Dear Technetters,
> I am trying to write a spec. for solder levelled boards received from
> an outside vendor. The boards contain SMD (some - 0.019" pitch) and
> some pressfit connectors.
> What solder thickness should I ask for if I wish the boards to
> maintain solderability after at least one year of storage (under
> normal conditions) and 3 reflow assembly cycles (sometimes even more).
>
> Probably, all of you had seen specs that made no sense, I don't want
> to write another one.
>
> I'll appreciate very much your inputs.
>
> Yours,
> Yehuda Weisz

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