Bryan,
        I will be interested in seeing the responses to this, we also
see this issue/phenomena occasionally. We solder some assemblies with
HMP Sn5/Pb93.5/Ag1.5, and sometimes see this occur at the lead/joint
interface or in the fillet itself. We preheat the assemblies using a
benchtop convection preheater before soldering, and are using adequate
soldering times/temperatures for the alloy. It can appear at the initial
soldering step, or will sometimes appear after first inspection after
the boards have passed through a vapor degrease cleaning cycle. It is
more prevalent on large mass parts such as terminals or connector pins,
and can make life difficult for both manufacturing and inspection. With
these alloys having a high meltpoint, multiple soldering excursions is a
recipe for lifted pads and excessive thermal stress on the
components....

Mike

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Kerr, Bryan
Sent: Wednesday, September 15, 2004 9:35 AM
To: [log in to unmask]
Subject: [TN] HMP Solder Joint Cracking


Hi

We are fitting a swaged turret terminal and soldering using 96% Tin 4%
Silver alloy and have experienced cracks running around the edge of the
swage solder joint - between the pin and the solder. Re-soldering gets
rid of it in most but not all cases. I have thought that perhaps some
stress relaxation is occurring in the swage area (brass base material)
during soldering resulting in these cracks. Can anyone shed any light on
this problem ?

Cheers

Bryan Kerr
Principal Quality Engineer
Process and Materials Laboratory
AMS Hillend


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