How to select underfill materials for solder bumped flip chips on low cost substrates

Ten different underfill materials with different size and content of filler, and epoxy from four different vendors are studied in this paper. Their curing conditions such as time and temperature are measured by a differential scanning calorimeter (DSC) unit. Their material properties such as the TCE (thermal coefficient of expansion), T g (glass transition temperature), dynamic storage modulus, tangent delta, and moisture content are carried out using the thermal mechanical analysis (TMA), dynamic mechanical analysis (DMA), and thermal gravimetric analysis (TGA). Their flow rate and the effect of moisture content on mechanical (shear) strength in a solder bumped flip chip on board are measured. Finally, based on the present results, a simple guideline is presented for the selection of underfill materials.

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