Subject: ASSY: Encapsulant/underfill of TSOP              1997.07.1111:33 AM

Hi TechNetters,

I am posting this on behalf of a co-worker who is investigating the
reliability of TSOP solder joints.  I understand that the leadframe material
(Alloy42 vs Cu) and particular geometry of TSOPs reduces the board level
reliability (relative to other leaded devices).  We intend to include an
"encapsulated/underfilled" TSOP in the study.  

Any recommendations as to which type of material to use to restrain the solder
joints ?  If you have a specific material which you have used, this would be
of interest (spec, name, etc).  Is it better to underfill the complete
component (my opinion) or only the joints ?

Thanks in advance.
Charles Elliott
NPI Process Engineering
Newbridge Networks
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