Advanced flip chip package on package technology for mobile applications

With the rapid technology developments in the semiconductor industry, the mobile phone has evolved from a simple communication device to a complicated and highly integrated system with multiple functions and heterogeneous devices. Based on the fast growth in emerging markets for mobile applications, many wireless devices have jumped to 4G Long Term Evolution (LTE) communication platform and may ramp to 5G generation technology in the next two to three years. Moving forward with this trend, packaging semiconductor devices for mobile electronics is more challenging than ever before. As the demand of higher performance, higher bandwidth, lower power consumption and smaller form factor are increasingly required in portable mobile devices, standard flip chip packages such as fcCSP are not able to meet these requirements. Three-dimensional (3D) package-on-package solution with flip chip interconnect (fcPoP) has been widely utilized to successfully achieve these goals. With the ability to stack a logic processor and memory device in a single package, the utilization of fcPoP is becoming a preferred solution in the mobile market segment. It is well known that fcPoP technology developments are related to the evolution of mobile low power double data rate (LPDDR) memory, requiring lower voltage, lower power consumption and higher transition rates, a significant number of 4G LTE mobile devices are adopting fcPoP with LPDDR3 and are now migrating to LPDDR4 as well as finer silicon nodes (below 20nm). Challenges in finer pitch memory devices, thinner package profiles, stringent package warpage/coplanarity requirements and Surface Mount Technology (SMT) processes are successfully met with fcPoP technology. This paper reports the 3D package developments with flip chip technology, including bare die package-on-package (BD-PoP), molded laser package-on-package (MLP-PoP) as well as interposer package-on-package (I-PoP) to support high bandwidth or wide I/O memory. Various fcPoP vehicles have been designed and fabricated to demonstrate low profile (total package height less than 1.2mm) and much finer top ball pitch solutions for mobile applications. Package warpage/coplanarity control and reliability characterization are also illustrated. These results show fcPoP architecture is an enabling technology for highly integrated, miniaturized, low profile and cost-effective 3D packaging solutions