Electromigration of C4 bumps in ceramic and organic flip-chip packages

As technology continues to scale, there is increasing demands on I/O counts and power requirements, leading to decreasing solder pitch and increasing current density for solder bumps in high-density flip-chip packages. At the same time, increasing performance requirements has led to the use of organic packages instead of the conventional ceramic packages. Hence it is very important to be able to measure the current carrying capability of solder bumps and evaluate the impact of reduced bump pitch and use of organic packages on EM reliability. In this paper, we run conventional EM test configuration using mechanically shorted dies and making the connection to the solder bumps through the flip-chip package directly mounted on the test boards to evaluate the effect of varying bump pitches on the electromigration performance of the solder bumps. Our results show that electromigration resistance is very high on ceramic packages with high lead solders and degrades significantly when high lead solder is used in conjunction with eutectic solder on organic packages