Characterization of underfill materials for functional solder bumped flip chips on board applications

The curing conditions and material properties such as the TCE (thermal coef ficient of expansion), T-g (glass transition temperature), flexural storage modulus, tangent delta, and moisture content of nine different underfill m aterials from three different vendors are measured. Their Bow rate and the effect of moisture content on mechanical (shear) strength in solder bumped flip chips on organic substrate are also determined experimentally. Further more, their effects on the electrical performance (voltage) of functional f lip chip devices on organic substrate are measured. Finally, a simple metho dology is presented for the selection of underfills from the measurement re sults of these nine different underfill materials.