Authored By:
Laurene Yip, Ace Ng
Xilinx Inc.
San Jose, CA, USA
Summary
The drive for higher performance and smaller electronic components make flip chip ball grid array (FCBGA) packages attractive for automotive applications. As automobiles rely more heavily on electronics for passenger safety, efficiency, and comfort, component reliability has become increasingly important. Since automotive components operate in extreme environmental conditions, with a temperature range of -40 Celsius to +125 Celsius, solder joint reliability of ball grid array packages is a major concern in automotive systems. Because of the difference in thermal expansion of the different packaging materials and the printed circuit board (PCB), temperature variations create thermal mismatch, resulting in solder joint stress. After repeated thermal cycling, the solder joints can crack and lead to system failures.
In our study, the board level reliability of different FCBGA packages was evaluated in the automotive thermal cycling environment. The effect of different factors, such as package construction, underfill type, and ball pitch, have on board level reliability of flip chip packages will be discussed. Our studies showed FCBGA packages using organic substrates can achieve high board level reliability under automotive operating conditions.
Key words: flip chip, ball grid array, automotive, board level reliability; solder joint fatigue
Conclusions
In our study, the board level reliability of flip-chip BGA assemblies on laminate substrates was evaluated for automotive use by temperature cycling -40 Celsius to 125 Celsius. The influence of assembly materials and package design on package warpage and board reliability was presented. The results showed that samples assembled with higher Tg underfill had a negative effect on warpage and thermal fatigue solder ball life of the flip chip packages. Lidded packages reduced warpage variation during thermal cycling loading and resulted in higher board level reliability compared to the bare die package. For the same die size and package ball count, reducing package size by reducing the solder ball pitch and increasing the ball density under the die resulted in higher board reliability. This suggest that package miniaturization by moving to a finer ball pitch could be a feasible lower cost package option. An increase in the thermal cycling range decreased the number of cycles to failure for the solder joints due to fatigue. Thus, proper selection of package materials and design is necessary to achieve high board level reliability in high temperature applications.
Initially Published in the SMTA Proceedings
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