Interposer connection reliability using double-side solder bump for board-level vertical interconnection

For the miniaturization and multifunction of electronic devices, the vertical interconnection technology has been developed to replace the traditional planar packaging technology. The interposer connection using double-side solder bump is used as the vertical interconnection technology in this study. Three kinds of solder bumps with different diameters of 0.76mm, 1.2 mm and 2mm were prepared and mounted to different interposers separately. Vertical interconnect circuit boards with different solder bumps were then fabricated and undergone the reliability tests under thermal cycling and vibration environments. The interconnecting resistances were measured to evaluate the electrical stability and the microstructures of solder joints were analyzed to find out the failure mode. During the thermal cycling test, cracks initiate as a result of the mismatch in the thermal expansion coefficients (CTEs) in the solder matrix on the board side and propagate parallel to the bonding pad. The joints with the diameter of 0.76mm eventually cracked. After the vibration test, 0.76mm solder balls were all fractured on the board side. Our work shows that 0.76mm solder balls are unsuitable for the vertical interconnection and 1.2mm and 2mm solder balls are recommended. This paper will contribute to build a comprehensive understanding of the interposer connection reliability.