On a related side note, we've been seeing exposed copper recently after HASL
boards have been assembled (2 reflow and wave solder) - almost like the
solder coating has been eaten off. We think there's a correlation between
the HASL thickness and this phenomenon, since we've been seeing it on parts
that seem to have 20-30 uinches. It only seems to happen on small annular
ring holes and large areas with no componants soldered to them, and we
haven't been seeing solderability problems. Has anyone seen anything like
this happen?

Matt Sanders

Matthew Sanders
PWB Procurement Engineer, Trimble Navigation Limited
[log in to unmask]
Phone: (408) 481-7817
Fax: (408) 481-8590

> -----Original Message-----
> From: Charles Barker [SMTP:[log in to unmask]]
> Sent: Friday, July 10, 1998 10:21 AM
> To:   [log in to unmask]
> Subject:      [TN] Solder thickness needed after HASL
>
> I am getting differing information from different suppliers of PWB's with
> regard to solder thickness requirements after HASL. Some say 100 to 500
> u-inches, others say 500-800 u-inches and yet others say 1200-3000
> u-inches
> (.0012" to .003"). We are looking for 6 months to one year of
> solderability
> with storage being in an air-conditioned environment with well less than
> saturation humidity in the stockroom. (Generally temp is in the 70 to 75
> deg F range, relative humidity 50 percentish +/- 10 percentage points.)
>
> Can some one tell me what the height of the "normal" intermetallics is on
> a
> HASLed SMT pad and how much additional solder coating is needed to prevent
> deterioration of the solderability of the pads?
>
> Thanks all,
>
> Charlie B.
>
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