I went out and processed some of these boards myself and found no problem. 
On the bad batch of boards I found poor topside fill on most everything. To top it off, the leads of the Thermistors were cut after Wave Solder. I'm pretty sure there was not enough contact time with the wave and the cutting of the leads created enough stress on the joint to fracture it. 
 Is there a way to check the joints for a fracture without clipping the leads? (There's really no reason for us to be clipping them, so we stopped.)
Thanks for your input.

Jonathan

>>> Phil Nutting <[log in to unmask]> 02/24 6:30 AM >>>
Jonathan,

Is this fracture occurring during wave solder?  In some of our applications
we put the thermistors in by hand after wave solder and use a high
temperature solder (10Sb90Pb).

Regards,

Phil Nutting
Manufacturing Engineer
Kaiser Systems, Inc.
High Voltage Power Supplies That Work(tm)
126 Sohier Road
Beverly, MA 01915
ph: 978-922-9300
fx: 978-922-8374
[log in to unmask] 


-----Original Message-----
From: Jonathan Boyle [mailto:[log in to unmask]] 
Sent: Friday, February 23, 2001 3:25 PM
To: [log in to unmask] 
Subject: [TN] Fractured Joints!


Hello Technetters,

I have a problem with fractured joints on a thermistor. We only see this on
the thermistor.  I've got to clip off the lead and examine under a
magnifying glass to find it. Does anyone have some insight as to the
cause/solution? Maybe increase the preheat?

Thanks in advance!

Jonathan

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