Proper choice of the encapsulant volumetric CTE for different PGBA substrates

摘要

The present invention describes a method and apparatus for packaging a flip chip by matching the z-direction CTE of the IC solder joint with the z-direction CTE of the encapsulant. Consideration of the z-direction CTE's is important when determining the volumetric CTE of the encapsulant. This invention first requires a determination of the z-direction CTE of the IC solder joint and a determination of the z-direction CTE of the encapsulant. The invention next matches the z-direction CTE of the IC solder joint to the z-direction CTE of the encapsulant. The matching of the two z-direction CTE's reduces the z-direction tensile or compression stresses on the IC solder joint and the encapsulant.