Novel Molded FCBGA Package Platform for Highly Reliable Automotive Applications

As the number of automotive applications and performance of automotive electronic components increase, the demand for flip chip ball grid array (FCBGA) packages has also increased. However, conventional FCBGAs experience cracking or fracture toughness degradation of underfill and solder resist materials during the package-level reliability tests required by the Automotive Electronics Council (AEC). To achieve Automotive Grade 1/0 reliability, a new package (PKG) platform is proposed. This new platform is designated as a molded flip chip ball grid array (mFCBGA). The mFCBGA offers an exposed surface of a silicon die for better thermal performance. By applying a proper epoxy molding compound (EMC) material, package coplanarity can be improved without an additional mechanical support such as a stiffener or lid compared to a conventional FCBGA PKG. This new mFCBGA platform enables a reduced substrate thickness by applying thinner substrate core material in the molded structure.This paper investigates the assembly steps and materials for the entire process of the mFCBGA. Specifically, various EMCs are tested for optimizing the warpage of the package and carrier. The EMC material properties of Young’s modulus, coefficient of thermal expansion (CTE), glass transition temperature (Tg), and volume shrinkage for molding are validated and simulated. An EMC material design of experiments (DOE) was conducted at the mold process to achieve carrier warpage under 1.0-mm. To support the EMC material DOE matrix, statistical analysis was performed using JMP software. Through JMP analysis, hierarchical cluster and, K means cluster and principal component analysis were conducted. Based on EMC material properties, the carrier warpage value was predicted by warpage simulation. Then, warpage simulation results and the measurement results during processing were compared.Finally, a best-known method (BKM) was proposed for the mFCBGA overall process including module array, mold, de-bonding, mold grinding and singulation process. PKG warpage was improved for 5,500-mm
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body size compared to a conventional FCBGA design. Reliability tests for Highly Accelerated Stress Test (HAST) 264 hours [1], temperature cycling condition H (TCH) 2,000x [2], and high temperature storage (HTS) 2,000x [3] conditions are verified for two types of PKG designs - lidded and no lid versions with 1,225-mm
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body size.