John Devore at GE E-labs reported on a condition, years ago (circa. 1970s)
on PWAs where the
solder joints look perfect, however, a push with an orange stick allowed the
solder joint to
be pushed off the pad with little force. He termed this slippery solder.
This was blame on
Tin/Lead plating organic levelers and other types of contaminates that
interferred with solder wetting of the pads.

-----Original Message-----
From: Don Vischulis [mailto:[log in to unmask]]
Sent: Wednesday, October 03, 2001 12:41 PM
To: [log in to unmask]
Subject: Re: [TN] Solder joints not bonded to copper


Warren:

What you're seeing is often referred to a double reflow.  George Wenger at
Lucent knows a lot about this defect.  In a former life, we encountered the
same type of failures.  Assemblies passed through the plant but failed in
the field after 1 to 3 years.  The SMT solder joints lift off of the board
surface with almost no distortion of the solder joint (leads one to suspect
that the inter-metallic alloy is failing or the copper was contaminated).
The pads on the board appear to be dark gray or look like tarnished copper.

The problem is a combination of wave soldering conditions and board design.
When the board passes over the wave, the top side solder joints reflow or
come close to reflow temperature which induces stress in the top side
component attachment points.  I'm sure others can explain it better than me.

The bottom line is that this defect is caused by assembly conditions not by
manufacturing defects in the bare board.  Check the archives for more on
this subject.

Don Vischulis

-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Warren crow
Sent: Wednesday, October 03, 2001 10:08 AM
To: [log in to unmask]
Subject: [TN] Solder joints not bonded to copper


I have a 3 year old assembly that has most of the SMT joints coming off the
pads. The PCB was HASL finished and the SMT components were pasted and
convection re-flow The joints appear to be good visually, but if probed
lightly the components will pop off, leaving only a dull copper pad
exposed. Appears the copper was contaminated prior to HASL, but we should
have noticed an obvious exposed copper prior to assembly. Also the assy.
has thur hole that get wave solder on bottom side after SMT. Could the 2nd
process re-flow the smt without flux and start oxide on copper. I am open
to any input.

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