Development of processing diagrams for underfill resins

Due to high pin counts, PQFP technology is being replaced by flip chip on organic substrates. The assembly scheme is very different for flip chip technology. After soldering the chip directly to the printed circuit board, the assembly is heated to a “flow temperature” of 80°C and the underfill resin is dispensed. Capillary action is required to flow the dispensed underfill resin under the die. Once the flow or underfilling process is completed, the assembly is heated to elevated temperatures to cure the underfill resin (150-165°C). The underfill process has been shown to increase the life of a flip chip assembly by a factor of ten. The objective of this work is to combine cure characterization and flow modeling studies to develop processing diagrams for underfill resins. Input from the cure characterization is used to predict flow during the underfill process and is summarized using a processing diagram