EFFECTS OF BOARD SURFACE FINISH ON FAILURE MECHANISMS AND RELIABILITY OF BGAs
Author: Reza Ghaffarian Company: California Institute of Tech Date Published: 8/23/1998
Surface Mount International
Abstract: Ball Grid Array (BGA) is an important technology for utilizing higher pin counts, without the handling and processing problems of the peripheral array packages. The assembly reliability of BGAs was investigated under a JPL- led consortium. A large number of test vehicles with two ceramic (361 and 625 I/OS) and five plastic (256,313,352- two types, 560 I/OS) packages and three surface finishes were assembled and subjected to two thermal cycling environments, The number of cycles to failure was determined. This paper will present cycles to failure in Weibull plots as well as their failure characteristics up to 7,000 cycles. The effect of three surface finishes (HASL, OSP, and NiiAu) on cycles to failures and their failure mechanisms will also discussed in detail. The SEM microphotographs and elemental surface chemistry for random brittle failure of Ni/Au will be presented. Possible reasons for ductile and brittle failure behavior will also be discussed.