Study on the pressurized underfill encapsulation of flip chips

Flip-chip technology generally requires encapsulation of the solder joints to reduce the loads on such joints during thermal excursions. At present, the encapsulation process by dispensing constitutes the primary obstacle to widespread acceptance and implementation of flip-chip technology because of the long process times involved and the subsequent reliability and reparability problem. A new process to encapsulate flip-chips has been developed. This process uses a special mold to surround the chip to be encapsulated and injects the encapsulation material at elevated pressure. The experimental results show that the pressurized encapsulation process reduces the fill time (by as much as a factor of 1000), is able to perform the encapsulation at room temperature, fills the cavity completely without any voids and increases the capability of handling highly viscous encapsulants (1000 times more viscous than current commercial encapsulants) relative to the customary dispensing process for the particular case used in the current experiment.