What underfill properties contribute to its flow characteristics?
The fillers used in underfills, in addition to the viscosity of the underfill, have the most significant impact on the flow characteristics. Filler properties that affect flow include morphology, size, loading, and surface of the filler. In general, lower viscosity indicates faster flow, but the flow rate will also depend on the filler characteristics. Viscosity at the actual underfilling temperatures is important for flow, while viscosity at ambient conditions is important for dispensing in the pump.
