Dear fellow Technets:
        I am conducting research into solder fatigue of solder joints. I am
currently postulating a viscous flow model for low cycle fatigue. I am
curious to know if anyone out there in industry has any empirical
observations or models similiar to viscous flow?

Brian J. Van De Wal
Mechanical Engineer
Benet Weapons Lab, Tank Turret Branch
U.S. Army Research, Development, and Engineering Command
Watervliet Arsenal
Comm 518-266-4287
Fax 518-266-4851



-----Original Message-----
From: Nancy Trumbull [mailto:[log in to unmask]]
Sent: Wednesday, July 21, 1999 3:00 PM
To: [log in to unmask]
Subject: [TN] Horns on Tin Plated Screw


Hi  Everyone,

I'm new to the Technetters.  I have been a Trainernet for just a short time
and have discovered that I also need you as well.

So here goes.

Problem: We ( TRMI ) are periodically experiencing horns on a
 screw head. After wave solder process.

Information:
Screw:               Tin plated
Flux:                   Christopher JF900 2LF
Solder:                Alpha Metals 63%  37%
Process Profile:  Not changed

Self Tapping screw is securing a 4 terminal connector to the PCB.
 Design indicated this type of screw is to be used to ensure proper
 torque setting of screw in  finished product.
 Covering the screw is not an option. Designer has a plating
 around the screw to aid soldering process.

Questions:
 1) Could Nitrogen be a factor in creating horns during the
       wave solder process.
  2) Could Nitrogen place a part with other defects as bridges
        and missing solder
  Japan and USA make the same product.  Japan does not have
 this problem.  Difference in process is Nitrogen.
   3) Any ideas  on why we get horns.

Thank you for your time
Nancy

##############################################################
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
##############################################################