Abstract:

Underfills can improve flip chip reliability. However, the fillers used in some underfills to enhance coefficient of thermal expansion (CTE) properties can be dispersed unevenly, causing less than optimal reliability. In this study, underfill dispensing was conducted using various fill patterns. Experimental results show that particle migration is a secondary mechanism, which causes uneven filler distribution. Particle settling mainly occurred during the curing process, rather than during dispensing, and was affected by the surface tension.

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