ABSTRACT
The purpose of temperature cycling is to check on package integrity in spite of the coefficient of thermal expansion mismatches between the various materials and their respective interfaces within the plastic package. The typical failure modes seen with temperature cycling are delamination between interfaces or cracking somewhere in the die, whether it be the passivation, the interlayer dielectric, or through the bulk silicon. Temperature cycling and thermal shock are the cause of numerous failure modes in semiconductor packages. Some of these modes include broken bond wire or lifted bonds from pads, solder joint/bump/ball fatigue, cracked molding compound, and the aforementioned interface delamination. Corrosion is the primary mechanism for failure with these types of tests. The phenomenon of corrosion is more easily seen in a humid environment than in a dry one. The intent of reliability tests is to elicit known failure mechanisms through a set of accelerated tests and provide an accurate level of field life prediction.
