I wrote a paper on the subject of testing shelf life of five surface
finishes in real time a number of years ago - published in Surfin 99. This
paper details the performance of ENIG, HASL, OSP, Palladium and Silver as a
function of storage conditions and tested using a wetting balance. To sum it
up for you these are the results I obtained - I should re-iterate that the
test coupons were stored in the open in two different locations,  one being
temp humidity controlled the other not. Testing was carried out until either
I ran out of coupons (ten tests/day /location/surface finish) or I suffered
with solderability problems.
ENIG - ran out of coupons after 899 days - still soldering - increased
wetting time, but still very acceptable.
HASL - ran out of coupons after 750 days - nothing to remark -
OSP - ran out of coupon after 630 days - nothing to remark
Palladium - poor solderability after 538 days
Silver - dead after 28 days in temp/humidity controlled area. Dead in 52
days in unprotected environment (picked up chloride and retarded sulfide
formation). Tested it stored in a bag - still soldering after 750+ days.


Gerard O'Brien
Co-chairman 4552
Photocircuits Corporation
-----Original Message-----
From: Bissonnette, Jean-Francois [mailto:[log in to unmask]]
Sent: Wednesday, January 29, 2003 3:55 PM
To: [log in to unmask]
Subject: [TN] Shelf life of PWB


What is the shelf live of a PWB.  After how long can I expect to have
solderability problem?

Thanks!

Jean-François Bissonnette
Vérificateur, Contrôle de la Qualité
Électronique
Produits et Procédés
Vapor Rail Inc.
10655 Henri-Bourassa O.
St-Laurent, Qc
H4S 1A1

(514) 335-4200 x2021
(514) 335-4231 fax



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