Thermal method to control underfill flow in semiconductor devices

Abstract

A method and apparatus for assembling a semiconductor device. A chip () with solder bodies () on its contact pads is flipped onto a substrate (). After the reflow process, a gap () spaces chip and substrate apart. A polymer precursor is selected for its viscosity of known temperature dependence. The apparatus has a plate () with heating and cooling means to select and control a temperature profile from location to location across the plate. After preheating, the assembly is placed on a mesa () of the plate configured to heat only a portion of the substrate. Movable capillaries () blow cooled gas onto selected locations of the assembly. After the temperature profile is reached, a quantity of the precursor is deposited at a chip side and pulled into the gap by capillary action. The capillary flow is controlled by controlling the precursor viscosity based on the temperature profile, resulting in a substantially linear front, until the gap is filled substantially without voids.