Thermo-Mechanical Reliability of High-End Flip Chip BGA Packages: Comparison Heat Spreader and Motherboard Construction

Abstract

The major concern regarding the high-end flip chip ball grid array (FCBGA) package as of now, is the solder joint fatigue failure. This problem was induced by thermal expansion mismatch. In this experiment, the experimental stress analysis (which is to measure the stress distribution at FCBGA package by using finite element analysis and Moire interferometry analysis) were performed to predict the number of solder joint fatigue failures which would occur during the board level reliability test. These analysis results were compared with the actual accelerated thermal cycling test on board level, monotonic 4-point bend test, FEA(finite element analysis) and Moire interferometry analysis. This comparison was conducted to verify the effectiveness of the lid heat spreader construction, the package substrate material, and of the motherboard thickness. To validate the 3 major factors, two types of heat spreader types, (One-piece lid and two-piece lid) two package substrate materials, (organic and ceramic substrate) and 2 types of motherboard thickness, (93mil 8 layer PCB and 197mil 14 layer PCB) were compared. From the analysis above and from the actual reliability test results, NECEL can predict the behavior of the strain and solder joint fatigue failure comparison of high-end FCBGA packages. The information derived from the various tests also reveal that the heat spreader construction of the FCGBA packages and the mother board thickness play a role in the effectiveness of the solder joint reliability.