Development of SOP Module Technology Based on LCP Substrate for High Frequency Electronics Applications

Abstract

Liquid crystalpolymer (LCP) materials are considered to be promising substrates for RF-applications. In this work, the high frequency characteristics o LCP were investigated using a microstrip ring resonator.The purpose is to verify the possibility ofthe application of the material in RFpackaging. The metallization ofLCP was studiedfor the purpose ofboardfabrication. The adhesions between deposited copper and LCP layer were also measured by the shear-off-method. The standardplanarfabrication techniques were employed to complete the LCP based substrate and a multi-stagedfabricationflowfor LCP substrate has been optimized. Furthermore, flip chip (FC) bonding was carried out to bond a daisy chain chip onto the LCP substrate by using anisotropic conductive films (ACF), and thefunctionality was tested by thefour point resistance measurements. The results indicate that LCP has a dielectric constant ofabout 3 and a loss tangent ofabout 3.5x]0-3 in thefrequency range between 2 and 35 GHz. Flip-Chip bonding ofACA joint on LCP substrate shows an resistance ofabout 0. 7 Ohm. Finally, embedded technique ofactive devices into the LCP substrate has been demonstrated. IntroductionFuture electronic packaging requires better materials to handle extremely high frequency, low cost, 3D packaging and large thermal dissipation capacities [1]. Although System on a Chip (SOC) solution may work for specific application areas, System on Package (SOP) is generally considered as the best, cost effective system level package solution [2][3].With radio frequency (RF) systems' operating frequencies continuing to rise, system reliability becomes increasingly reliant on hermetic or near hermetic packaging materials [4]. Earlier, Teflon and ceramics based materials were used for the RF applications. But both of the materials were expensive. LCP has been identified as a good candidate for high frequency packaging materials [5][6]. The advantages of using LCP substrate for RF functionalities are [7-10]: high rigidity and strength, high heat resistance, low moisture absorption, adjustable CTE, near-hermeticity, high frequency properties, environmental friendliness and relatively low cost.The purpose of this paper is to present a summary of the research work carried out so far. Section 2 introduces the high frequency characteristics of LCP investigated using a microstrip ring resonator. This is to verify the possibility of the application of the material in RF packaging. Section 3 summaries the metallization of

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