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

The curing conditions and material properties such as the TCE (thermal coefficient of expansion), T-g (glass transition temperature), flexural storage modulus, tangent delta, and moisture content of nine different underfill materials from three different vendors are measured. Their flow sate and the effect of moisture content on mechanical (shear) strength in solder bumped flip chips on organic substrate are also determined experimentally. Furthermore, their effects on the electrical performance (voltage) of functional flip chip devices on organic substrate are measured. Finally, a simple methodology is presented for the selection of underfills from the measurement results of these nine different underfill materials.