Reliability and moisture sensitivity evaluation of 225-pin, 2 layered overmolded (OMPAC) ball grid array package

Abstract

With trends in electronic devices towards more circuitry and higher pin count, Ball Grid Array (BGA) packages are now becoming popular in Integrated Circuit (IC) products. The BGA technology also provides space savings, higher yield during solder reflow attachment, and utilization of existing surface mount technology processes. This paper reviews OMPAC BGA packages, their structure and technology. In addition, we investigate the moisture sensitivity and reliability of 225 I/O 2-layered (2L) OMPAC BGA packages with Metal Oxide Semiconductor (MOS) ICs. This paper presents the experimental results of (i) percent weight gain measurements of four different BGAs that were preconditioned at various moisture levels, (ii) internal package damage as a function of ingressed moisture content, (iii) reliability concerns of BGAs, and (iv) qualification test data. Reliability performance of moisture plus solder reflow preconditioned BGAs demonstrated no failures after 1,000 hours of Temperature Humidity Bias (THB) stressing, when a low level of moisture (0.12%) was present in the BGA packages. The results of this study also suggest that 2L BGA packages with moisture content higher than 0.12% by weight exhibit serious delamination at different package interfaces during solder reflow. In addition, it was established that 4L, overmolded BGA packages appear to absorb 20-25% less moisture than a 2L BGA package.