Kerry - as part of a longterm wetting balance study I tested solderability
versus real time storage - laid out on strips to allow air flow. For ENIG I
ran out of coupons after 899 days. Solderability was still okay after this
time but wetting force was reduced 30+ % versus the original values. Your
parts are slightly older and your assembly flux will be stronger than my
test flux so you may not have any issues. Baking of the boards if FR4 should
not be necessary - their moisture uptake is very little, if Polyimide that's
another issue.
For HASL I ran the same test with HASL at a minimum thickness of 80
micro-inches - ran out of samples after 650+ days - not such a significant %
reduction in wetting force. Provided you have sufficient HASL deposit this
deposit should also be no problem


Regards


Gerard O'Brien

Photocircuits Corporation


-----Original Message-----
From: McMullen, Kerry [mailto:[log in to unmask]]
Sent: Tuesday, May 11, 2004 10:33 AM
To: [log in to unmask]
Subject: [TN] Bare PWB's - Storage Limits

Fellow Technetters,

I have two different boards (unpopulated) that have been in inventory since
May 2001.
One of the boards is ENIG, and the other is HASL.
They were stored in bags, but not sealed.
I want to populate them.  I will inspect the plating on both boards, and
bake them prior to assembly.
Any other steps I should take?

Thanks,
Kerry

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