A process method for making BGA solder mask using nickel oxide

Advanced wafer level packaging technology allows multiple chips to be integrated into a single package in a side-by-side or vertically stacked manner. Advanced packaging technologies, represented by wafer-level chip packaging (WL-CSP), system-in-package (SiP) and fan-out wafer-level packaging (FOWLP) technologies, can not only improve the integration of devices, but also significantly shorten the product development cycle and reduce development costs. The external interface of advanced packages is usually BGA (Ball Grid Array) or bump. The conventional practice is to use UBM (Under Bump Metallization) to define the ball implantation area. This paper introduces a direct method to define the ball implantation area using nickel oxide. Through design and practical verification, this method proves that the process flow can be reduced compared to the traditional UBM method and facilitates rapid verification of prototype’s performance.