Hi Joe - if only predicting solderability was that easy! The industry
"norms", if there is really such a unit of measure, is that a majority of
component manufacturers will state that the component solderability is good
for 12 months and many will extend that out for 24 months. After that
everyone becomes silent. Three forcing functions become part of the
equation: 1) what is the condition of the component finish?; 2) what is the
storage environment?; 3) what flux will be used during the soldering
process? A good, thick tin lead surface finish(e.g. 120 microinches) can
last for several years but a thin tin lead surface finish could oxidize or
have intermetallic exposure problems within months. A gold finish could
last indefinitely but if it has too much porosity then the basis metal
oxidizes very quickly. The storage environment you mention is very benign
but lack of humidity and temperature controls will impact the surface
finish. Last, the flux used in the soldering operation may be active enough
to overcome any surface finish oxidation/intermetallic problems that may be
present. The interaction of these three variables is why getting a
black&white answer to storage life prediction for a component finish is so
tough. Steam aging is NOT a simulation of storage life but only a condition
method that can be used to understand how robust a surface finish is (that
is a widely misunderstood concept). The Alternative Finishes task group is
going to be looking into conditioning methods for surface finishes in the
next year including reassessment of steam aging (maybe we should say steam
conditioning) so hopefully some good information will become available for
the industry to use.

Dave Hillman
Rockwell Collins
[log in to unmask]





[log in to unmask] on 10/23/97 07:12:53 PM

Please respond to [log in to unmask]; Please respond to [log in to unmask]

To:   [log in to unmask]
cc:    (bcc: David D Hillman/CedarRapids/Collins/Rockwell)
Subject:  [TN] Axial Part Age




Technetters- As the industry moves more and more toward SMT, our TH line
continues to mfg mature products. The problem is that as qty rises on SMT,
the qty are dropping on TH. We are seeing older and older parts on the
shelf and would like to avoid solderability problems proactively. I
understand that solderability can vary widely between manufacturers, parts
and lots....but is there an industry standard for how long axial parts can
sit on the shelf (reels in an air conditioned factory, 65-75F, 45-55RH)? I
am looking for a broad guideline (something like: don't use anything older
than X, test parts that are Y-Z, incoming test for new parts). Thanks in
advance. Joe
Joe Wackerman
Sr. Mechanical Engineer
Parker Hannifin
Compumotor Division
http://www.compumotor.com
voice 707-584-2522
FAX 707-584-8015
e-mail [log in to unmask]
##############################################################
TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c
##############################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following
text in the body:
To subscribe:   SUBSCRIBE TECHNET <your full name>
To unsubscribe:   SIGNOFF TECHNET
##############################################################
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for
additional information.
For the technical support contact Dmitriy Sklyar at [log in to unmask] or
847-509-9700 ext.311
##############################################################

##############################################################
TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c
##############################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body:
To subscribe:   SUBSCRIBE TECHNET <your full name>
To unsubscribe:   SIGNOFF TECHNET
##############################################################
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information.
For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311
##############################################################