Some RTV materials emit acidic acid as they cure and some are alcohol based.
We had one case several years ago where the copper core of a tin plated lead
was eaten up by the acidic acid. We changed to one of the alcohol based
RTV's and have had no problems since. Ask your Dow Corning rep for a
recommendation for non acid emitting RTV.
Ron Dieselberg

-----Original Message-----
From: Sherman Banks [mailto:[log in to unmask]]
Sent: Wednesday, November 24, 1999 19:37
To: [log in to unmask]
Subject: [TN] ASSY: RTV vs. Solder Joints


Hi Technetters:

I have recently joined this company and a legacy product has been having a
few field failures. The nature of the failure is a fractured solder joint.
It is a lap configuration of a Kovar (gold plated) lead onto a HASL SMT pad.
The fracture seems to originate at the point of the joint where the exposed
base metal is from clipping. The solder looks especially grainy although it
has not seen significant temperature cycles or time at temperature.
The solder joint is encased in RTV 128 as a conformal coating. According to
GE tech support, RTV 128 outgases ammonia as it cures.
My question is: Has anyone any experience using RTV in this situation? Has
anyone seen or heard about RTV attacking solder joints to this extent?

As this is sent late on Thanksgiving eve, if you see it before Thursday,
Happy Thanksgiving, if after, I hope you had a Happy Thanksgiving.

Regards,
Sherman Banks
[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.
If you need assistance - contact Gayatri Sardeshpande at [log in to unmask] or
847-509-9700 ext.5365
##############################################################

##############################################################
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.
If you need assistance - contact Gayatri Sardeshpande at [log in to unmask] or
847-509-9700 ext.5365
##############################################################