Effect of scale size, orientation type and dispensing method on void formation in the CUF encapsulation of BGA

Abstract

Prediction of void occurrence during capillary underfill encapsulation process is vital to avoid package failure due to incomplete filling during the encapsulation process. Two design variables, namely the gap height and package orientations, together with different types of industrial standard design of dispensing methods were identified as possible influences to the void formation in encapsulated package. In this paper, all these factors have been closely related to the void formation and subsequently the best chip design has been formulated to improve package reliability. From the study, air entrapment is clearly visualized in the experiment, which can be detrimental as it contains trapped oxygen, which can combust at high temperature. A series of experiments eventually showed higher possibility of air void formation by U-type dispensing method compared with the L-type dispensing method. In addition, it is found that the chip design parameters that include the scaling size and ball grid array orientation have an effect on the size of void formed. Our experimental findings were validated using lattice-Boltzmann method simulation and great consensus is found between both approaches. These findings provide additional insights to the electronic packaging developer to effectively reduce the formation of void during encapsulation process.