Challenges and improvement of reliability in advanced wafer level packaging technology

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The number of WLCSP (Wafer Level Packages) used in semiconductor packaging has experienced significant growth since its introduction in 1998. The growth has been driven primarily by mobile consumer products because of the small form factor and high performance enabled in the package design. And it is also attractive to WE (wearable electronics) and IoT (Internet of Things) products. Although WLCSP is now a widely accepted package option, the initial acceptance of WLCSP was limited by concerns with the SMT assembly process and the fragile nature of the exposed silicon inherent in the package design. Assembly skills and methods have improved since the introduction of the package; however, damage to the silicon remains a concern. The side or top of the die continue to be exposed after dicing the wafer and the silicon continues to be at risk for chipping, cracking, and other handling damage during the assembly process. This paper introduces eWLB (embedded Wafer Level Ball Grid Array) /FO-WLP (fanout-WLP) and eWLCSP (encapsulated WLCSP) for its improved and advanced reliability [1], In these new packages EMC is applied to all exposed silicon surfaces on the die. The manufacturing process leverages existing high volume manufacturing methods with exceptionally high process yields. eWLB is a type of FO-WLP that has the potential to realize any number of interconnects with standard pitches at any shrink stage of the wafer node technology. For eWLCSP, the applied coating protects the silicon and fragile dielectrics to prevent handling damage during dicing and assembly operations, effectively providing a packaged part in the form factor of a WLCSP. In manufacturing process, the product wafer is thinned and diced first. The dies are then reconstituted into a wafer form and standard methods are used to apply dielectrics, thin film metals, and solder bumps. The resulting structure is identical to conventional WLCSP products with the exception of the protective sidewall coating. This paper discusses the improvement of reliability, both component level and board level (drop and Temperature Cycle on Board). The key attributes of the new package as well as the manufacturing process used to create it are to be presented. Experimental reliability data and failure mode are studied and compared to conventional WLCSP products.