Hi Bill! I don't know of an IPC specification that designates a given
period of shelf life for an of the available pwb finishes. The general
consensus for shelf life of either components or pwbs within the JSTD-002
and JSTD-003 committees is one year. However, that one year figure is not a
requirement. The shelf life of a specific pwb finish is negotiable between
yourself and your pwb fabricator. Many of the pwb finishes types (immersion
gold, immersion silver, immersion tin, HASL, OSP) can easily have one year
shelf life when properly applied, properly handled and adequately stored.
Also realize that some pwb finishes (e.g. thin OSP coating family) are not
designed for one year storage. Good Luck.
Dave Hillman
JSTD-002/003 Chairman
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Bill Page
<bill.page@SANMIN To: [log in to unmask]
A-SCI.COM> cc:
Sent by: TechNet Subject: [TN] Raw card solderability
<[log in to unmask]>
04/25/2003 03:48
PM
Please respond to
"TechNet E-Mail
Forum."; Please
respond to Bill
Page
Consider this a hypothetical question :)
We have some fabs that, due to reduced production requirements, have been
in
house for an extended period of time (more than a year). In investigating
some solderability concerns, the board house suggested that with thinner
HASL coatings, copper migrates through the tin-lead coating, reducing
solderability. The vendor seemed to think that a six-month shelf life is
now an industry standard...indeed, he involved the magic name of IPC.
It has, admittedly, been a long time since I considered myself up to date
on
PCB fabrication issues.
a. Is this a legitimate observation from our supplier?
b. Should we expect only a six month shelf life on PCB?
c. What rework method is recommended to bring these back in spec?
Thanks,
Bill Page
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