RE>>BGA Solder joint crackin                 2/20/96

Hi Peter,

Thanks for your suggestion for an alternative BGA underfill material, but we've tried a couple of Dymax formulations (including the 9000 series) for this application without much luck.  The problems that we run into with them include inadequate adhesion and a very narrow cure processing window (too little: gummy; too much:  "cracked mudflats").  The processing window problem can be explained by the fact that these formulations are targeted for UV cure, but heat curing is an option.  Since these materials are located beneath BGAs, UV cure isn't workable.  

It was very disappointing to see these problems.  The Dymax formulations are reworkable, have longer shelf/pot lives, and are cheaper than the Hysol versions.  

Regards,
Greg Bartlett
Mercury Computer Systems
Chelmsford, MA