The influence of autoclave on plastic encapsulated microcircuit

Plastic encapsulated microcircuit (PEM) is widely used due to its great advantages in size, weight, cost and performance, especially in industries. However, there are many problems that cannot be ignored. The most significant one is that PEM is not hermetical, which means that moisture can infiltrate in the PEM. The infiltration may lead to the delamination, even result in corrosion. Autoclave is one of the powerful reliability tests applied primarily to evaluate the moisture resistance integrity of non-hermetic packaged. The PEM is subjected to a condensing, highly humid environment under pressure to force moisture into the package. In this paper, the influence of autoclave on plastic encapsulated microcircuit is deeply discussed. Totally 80 PEMs from 8 devices are used as samples, containing different companies (TI, NXP, IDT, etc), different packages (TSSOP, SOIC, BGA, etc.) and different operating temperature scales (-55□~125□, -40□~85□, etc.). Before autoclave, scanning acoustic microscope (SAM) is used to check the delamination. Then, autoclave is operated. After 48h autoclave, delamination between plastic mold and silicon chip can be observed in some of the samples obviously. Meanwhile, the leads of few samples are oxidized. Followed with another 48 hours autoclave, the degree of delamination is extended and oxidizing material can be seen not only on the leads, but also on the surface. When autoclave operated to 168h, the delamination is more serious. What is more, some samples failed in the electrical characteristic test. Failure analysis is operated afterwards. The result shows that there are many factors may have contributed to the failures. The most important one is strongly related to the delamination of molding compound and passivation glass on the surface of the die. The oxidizing material also plays a very important role to the failure.