Hi Scott! Here are a couple of things to check - (a) your reflow profile, 
specifically the temperature of the SMT inductors solder joints; (b) the 
amount of solderpaste you are depositing for the SMT inductors. Ag/Pd/PT 
terminations will produce a gritty/grainy solder joint appearance if the 
finish is allowed to excessively "leach" into the solder joint. The 
Ag/Pd/Pt termination is much happier to be in the solder than on the 
component and you don't mention if you have a barrier layer on the 
inductor to prevent leaching (I am guessing there is no barrier layer). 
Also, if you have a lower solderpaste volume, you will increase the amount 
of tin/silver and tin/palladium phases in the solder joint which could 
lead to a rougher joint appearance. Good Luck.

Dave Hillman
Rockwell Collins
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[TN] Dull and Grainy Leaded Solder Joints






We are suddenly seeing a rash of dull and grainy solder joints on SMT
inductors that use silver-palladium-platinum-glass frit terminations.
Otherwise the exterior of the joint looks good. The terminations as
supplied have no leaded or lead free solder or tin finish, just the
glass frit. In cross section the joint is also unique in that there is
no real IM layer and the grain structure near the joint is a bit odd.
The solder joints are fully re-flowed.  All the other solder joints on
the CCA look good with no indication of solder process issues.

 

The vendor claims they have been supplying this type of termination for
years and nothing has changed, also this issue has just sprung up in the
last couple of months.

 

As far as we can tell the joints look different, but reliable.

 

Any suggestions or comments?

 

Scott Newland

Chief Mechanical Engineer - Fighter Enterprise
Harris GCSD
321 768 4272 (W)
321 720 1756 (C)
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