The solder joint and runner metal reliability of wafer-level CSP (Omega-CSP)

Wafer-level Chip Size Package (Wafer Level CSP)s are competing with normal CSPs because they provide the benefits of real chip size package with low manufacturing cost. However, solder joint and runner metal reliability in board level are still critical to the acceptance of WLCSP as an alternative package. In Hyundai Electronics, Wafer-Level CSP without underfill, called Omega-CSP, has been developed for a high speed DRAM application. Omega CSP has a newly developed dielectric polymer as a stress buffer and modified redistribution process. This work aimed at the assessment of the solder joint reliability characteristics and the runner metal reliability. We studied and examined the reliability in terms of the property of dielectric polymer and the runner structure. According to the results, it was found that solder joint reliability strongly depended on the solder ball size and runner thickness. In addition, the effects of CTE/modulus of dielectric polymer on the reliability solder joint will be discussed.