Evaluation of liquid crystal polymers for high performance SOP application

Electronic devices increasingly rely on new materials with improved properties such as lower coefficient of thermal expansion (preferably close to silicon), higher modulus, lower permittivity and dielectric loss, lower moisture absorption better thermal conductivity, higher dimensional stability, and most importantly reduced warpage particularly after the build-up process. Liquid crystal polymers (LCPs) have led to increasing interest for the packaging community due to their superior thermal and electrical properties. The targeted applications areas for LCPs are RF packaging, due to their low loss and low dielectric constant over a wide frequency range (Fukutake and Inoue, 2002; Fukutake, 1998; Jayaraj et al, 1995; Lawrence, 2000; Jayaraj et al, 1996; Yue et al, 1999,), near hermitic plastic sealing due to superior moisture barrier properties (Jayaraj et al, 1997), flex circuits and microvia laminates for high density interconnection (Corbett et al, 2000; Yue and Chan, 1998). This paper is focused toward possible application of LCP as a dielectric material for lamination on PWB and other engineered organic substrates. Commercially available LCP samples were analyzed using a variety of thermal analysis techniques. Based on thermal properties such as coefficient of thermal expansion (CTE), thermal degradation temperature and modulus, samples were selected for applications as a dielectric material. It is expected that a low CTE dielectric such as LCP will further reduce the dielectric film stress even when the CTE of the chip is matched with that of the substrate.