Package Related Failure Mechanisms in Plastic BGA Packages Used for ASIC Devices

Abstract

This paper describes various package related failure mechanisms observed in the plastic surface mount Ball Grid Array (BGA) package. Two types of plastic BGA packages commonly known as 225 OMPAC™ (Over Molded Pad Array Carrier) and 225 GTPAC (Glob Top Pad Array Carrier) are covered in this paper. The GTPAC is not offered as a production package, but it is used for commercial prototypes and evaluations. The failure analysis results discussed in this paper are primarily of the devices which failed at different times during various reliability and qualification testing over a period of two years. The failure analysis results of field returns (about 10% of al the devices analyzed) from customers for the same period are also included in this study. Of all the devices in the BGA packages which were failure analyzed, about 50% lailed due to package related problems. All the package related failures fall into two major categories of failure mechanisms, package delamination and cracked open copper traces on the printed circuit board (PCB). The delamination resulted in a variety of physical damage such as lifted ball bonds at the die pads, fractured bond wires in the span as well as at the heel of the crescent bonds on the PCB substrate, and cracking of the encapsulant. The copper traces cracked from two types of stresses, mechanical and thermal. In addition, some of the techniques used for the failure analysis are briefly discussed in this paper.

Effectiveness of conformal coatings on a PBGA subjected to unbiased high humidity, high temperature tests

“…In addition to assembly related moisture reliability, moisture-induced failures also constitute a field-related reliability concern with PBGA packages (Sawada et al, 1998;Parekh, 1996;Scalise, 1996). When PBGA packages are exposed to humid environments, moisture is absorbed through the package into the epoxy molding compound and substrate, and rapidly diffuses into the package.…”