Modeling and Analysis of Signal Integrity of Ball Grid Array Packages With Failed Ground Solder Balls

As an integrated circuit (IC) package, ball grid arrays (BGA) are widely used in various electronic systems, playing an important role in energy transfer and electrical signal transmission. In general, a signal solder ball is usually surrounded by ground solder balls. Compared with the signal solder ball, some ground solder balls are closer to the corner position of printed circuit boards (PCB), which leads to a higher failure risk for the ground solder balls in harsh environments. In this research, the impact of failed ground solder balls on the signal integrity of BGA packages was investigated using both theoretical analysis and experimental testing. A 3-D electromagnetic field model of a BGA high-frequency transmission channel with failed ground solder balls was developed. The
$S_{11}$
and
$S_{21}$
parameters before and after degradation were analyzed and discussed. Based on transmission line theory, an equivalent circuit model of a soldering transition section with failed ground solder balls was also developed. It was found that the 3-D electromagnetic field model results were in a good agreement with the high-frequency parameters obtained from the equivalent circuit model. Both the 3-D electromagnetic field model and the circuit model results are validated by experimental tests. This study fully considers the return path discontinuity (RPD) aggravated by failed ground solder balls and provides a better understanding of this effect on signal transmission. It provides theoretical understanding and support for the application of fault detection strategies to electronic systems.