Effect of passivation opening design on electromigration reliability issue in flip-chip solder joints

This study investigates the effect of passivation opening design on electromigration reliability issue in flip-chip solder joints by using statistical analysis. Eutectic SnAg solder joints were used in this study with two different filling condition of polyimide (PI), ie with or without contact opening. The bump height is 50 µm. The four point probe method was used to monitor the bump resistance of a specific solder joint with downward election flow, under 0.8 A at 155°C. The failure criteria are defined as the resistances rose to 1.2 times and 2 times of their initial values. In addition, three-dimensional finite element analysis (3D-FEA) was employed to show the distribution of current density, and the different failure modes were also discussed. The solder joints without PI performed longer failure time from the statistical analysis results. In other words, the set without PI shows better reliability than that with PI.