Wafer level CSP process by VPES (vacuum printing encapsulation systems)

BGA and CSP markets are increasing, but these technologies use plastic or ceramic substrates as interposers, and the packaging size is really larger than chip size. Recently, wafer level CSP as extremity packaging has been introduced. This packaging method starts with the transfer molding method. However, transfer molding of epoxy resin can cause large warpage due to thermal expansion mismatch between wafer and insulating layer after molding, and reliability is poor. In this paper, we developed low cost and high reliability wafer level CSP packaging. We developed very low warpage, low expansion, high adhesive strength, and high purity encapsulating liquid epoxy resin. The coating method used VPES (vacuum printing encapsulation systems) to produce void-free packaging. VPES is very suitable for large scale production. We achieved low cost and high reliability wafer level CSPs as extremity packaging with a good combination of low warpage epoxy resin and VPES.