Solder joint height impact on temperature cycle reliability of BGA components with thermal enabling load

Thinner organic BGA packages typically lead to higher warpage before surface mount which, after reflow, causes package corner solder joints (SJ) to have higher stand-off compared to solder joints in the package center. Hence the solder joints at package corners can change from typical barrel shape to an elongated hour-glass shape. Conventional understanding of the impact of SJ height on temperature cycling (TC) reliability states that taller SJs results in longer life. Since that understanding was derived based on the evaluations of BGAs without an enabling load applied, the question was if the same conclusions can be extended to BGAs with an enabling load, where critical SJs are in the package corner. To answer that question, a comprehensive experimental-modeling study was conducted. To investigate the solder joint height impact on temperature cycle reliability of BGA components with thermal enabling load, empirical data was collected on identical BGA packages that were intentionally deformed to create different incoming warpage and as a result different SJ height. The experimental results showed the solder joint shape impacts reliability under temperature cycle condition and that reliability is highly correlated with SJ height. Finite Element Method (FEM) modeling studies was conducted to provide physical explanation of observed behaviors. The modeling results correlate very well with experimental data. The key result of the study is that incoming warpage driven SJ height variations will impact reliability of BGAs with enabling load, that taller SJs will results in shorter life then “normal” barrel shaped joint which is contrary to the understanding held in the past.