Thermal Cycling Effects on Eutectic Flip-Chip Die on Organic Packages

Increasing I/O density and power distribution requirements have driven the industry towards flip-chip BGA pack-aging. Cost and performance considerations areforcing a movefrom ceramic to organic based substrate technology. Assembly development and reliability evaluations of large flip-chip die an organic substrates have progressed such that the packages have been qualified and used in volume applications. However, the first level reliability of these new packages has remained of some concern because of the larger difference in CTE between the die and substrate (compared to ceramic substrates, and the relatively limited quantity of publicly available data on thermal cycling behavior in these packages. In order to gain knowledge on expected lifetimes of the first-level package, computer models of the possible failure mechanisms have been prepared and experimental assemblies have been cycled to failure in a liquid-to-liquid test apparatus. Thermal profiles of -65 to 150°C and -40 to 125°C were studied. Appropriately modifying the assembly process has resulted in an organic flip-chip package that can satisfy industry requirements for first level reliability.