Effects of Underfill Materials on Behavior of Intermetallic Compound Thickness of Ball Grid Array Solder Joints Using ANOVA

Abstract

Underfill material has normally been used to improve the ball grid array (BGA) component's reliability and performance by allowing ruggedness and portability. However, the excessive thickness of the intermetallic compound (IMC) layer development on BGA balls can decrease the reliability of the solder joints. This paper investigated the IMC layer growth variances on BGA component solder joints with and without underfill post thermal cycle test using ANOVA. Four variables were observed; sample a: BGA ball without underfill, sample b: BGA ball with underfill, sample c: post rework BGA ball without underfill, and sample d: post rework BGA ball with underfill. The investigation revealed the comparison of the IMC layer growth variances between the samples using ANOVA can determine the differences between the means and estimate whether the variance was practically significant. Each confidence interval has a confidence level of 98.96%. This result indicated that we can be 98.96% confident that each interval contains the true difference between a specific pair of group means. The individual confidence level for each comparison produces a 95% simultaneous confidence level for all six comparisons in the Tukey simultaneous test. With the empirical data, solder joints' quality was observed to justify the application of the underfill for better solder joint reliability concerning the IMC layer thickness.