Reliability Study of High-Density EBGA Packages Using the Cu Metallized Silicon

Abstract

The reliability of high-density enhanced ball grid array (EBGA) packages using the eight-layer Cu metallization silicon was discussed. The key failure mechanisms included the die cracking (in the vicinity of the edge) and thin film delamination. It was noticed that the failure was unique to the Cu metallization silicon. The large package body size (45 mm2) and the die size (approximately 15 mm2 ) provided additional manufacturing and reliability challenges. The die-edge defects induced during the wafer sawing process were exhibited to be the culprits of the die cracking and the thin film delamination failures. Additionally, the height of die attach fillets significantly influenced the stresses on the die edge, and the excessive fillet height was found to help extend initial cracks at the edge of the silicon. The results demonstrated the adoption of a dual-step wafer sawing scheme and resin blades would control the defects and reduce the failure rate dramatically. A mixture of low-stress encapsulation and die attach materials would help improve the overall reliability of the packages as well. The solder joint reliability of the package was very robust based on the board-level reliability testing results. The statistical analysis of the test results confirmed that most of the die cracking and thin film delamination failures were early-life failures and random. A good sample screening scheme and the process improvement procedure would help improve the reliability and insure the customer a low failure rate for the lifetime of the product. The predicted reliability of the package met the application life needs for the products with process improvement plans in place.