Off-line control of time-pressure dispensing processes for electronics packaging

Fluid dispensing is one critical process in electronics packaging, in which fluid materials (such as encapsulant, adhesive) are delivered controllably onto substrates for the purpose of encapsulation. Time-pressure dispensing is recently the most widely used approach, and its control has proven to be a challenging task due to the fact that the dispensing process performance is significantly affected by the behavior of the fluid dispensed. Moreover, if the fluid exhibits time-dependent behavior, the control becomes more difficult and demanding. This paper presents a method to model the time-pressure dispensing process, taking into account the time-dependent fluid behavior. Based on the model developed, an off-line control strategy is developed for improving the process performance. Experiments on a typical commercial dispensing system were carried out to verify the effectiveness of the modeling method and the off-line control strategy.