Next Generation High Dk, Low Df Organic Laminate for RF Modules and High Frequency Applications

Abstract

In this paper, we present a novel high density high performance ultra-thin organic laminate, X-R-1, with low cost standard PCB fabrication processes for RF and high frequency applications. The X-R-1 substrate, developed at Zeon Corporation is a new generation halogen-free high dielectric constant (Dk) and low loss tangent (Df) dielectric laminate material. Its dielectric constant is 6.5–6.7 in the range of 1–20GHz, similar to typical LTCC substrates but larger than most organic materials such as LCP, PTFE and Epoxy based materials. Its dielectric loss tangent is 0.003, similar to that of LTCC, LCP and PTFE but much lower than epoxy based materials. The thicknesses of the core used in this study are 50um. The clad copper on both sides is a 12um thick profile-free copper foil which provides extremely smooth surface. Microminiaturization of RF devices can be achieved by the combination of high Dk and ultra-thin substrate. The combination of low Df and smooth surface leads to RF and high frequency signals having minimum propagation loss. The material is suitable for mechanical and laser through hole drilling and fully compatible with the low cost standard PCB facilities and processes. Because of the smooth surface, 25um very fine copper lines and spaces were achieved by wet etching process. Copper filled through holes with 40um diameter drilled by CO2 laser have been demonstrated. Panel size of 6″×6″ test vehicles with RF filters and transmission lines was fabricated and measured. Test data on the filters at 2.4GHz and 5GHz has been presented in this paper. This high Dk and low Df laminate with standard PCB processes provides a low cost organic platform for RF and high frequency circuit applications.