| 摘要 |
A semiconductor assembly comprising an integrated circuit chip with a first plurality of metallic contact pads exposed, having a pitch center-to-center of less than 180 mum. A metallic bump of reflowable metal is attached to each of these contact pads. The assembly further has an electrically insulating substrate with a second plurality of metallic terminal pads in locations matching the locations of the contact pads. Each of the bumps also attached to these matching terminal pads, respectively, whereby the chip is interconnected with the substrate spaced apart by a gap. An adherent polymeric encapsulant fills the gap so that the encapsulant is free of voids. It is a pivotal feature in the method that vibration energy, up to ultrasonic frequencies, is used while the encapsulant is still in a low-viscosity precursor state in order to ensure the void-free spreading of the precursor throughout the gap between chip and substrate. The vibration energy ensures uniform underfill distribution even when the gap and the bump pitch are narrow, with uniform distribution of any fillers, and enhanced adhesion to chip, substrate and bumps.
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