Dear Net Member,

     Underfill material should be categorised as those for CSP and
     Flipchip. In the market, there are a lot of underfill material with
     CTE about 25ppm and Young's modules 6 Gpa. Those kind of material
     match the eutectic solder  bumb (CTE=25ppm) with substrate of FR4
     (CTE=15ppm)
     and silicon chip (CTE=3ppm). But for CSP such as uBGA, the passivision
     is not a silicon. So the diffirent underfill from flip chip should be
     used.

     The underfill is used for CSP due to our particular concern.


     Does anyone know some underfill especially designed for CSP?


     Eden

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