Improvement of Cu-Pillar Structure Using Advanced Plating Method

Abstract

The recent appearance of mobile application processor now plays an important role in the semiconductor industry. Additionally, there have been endless demands for small form factor, thin profile, outstanding thermal, mechanical properties and electrical performances in the field of IC packages for mobile application processors. MIS (Molded Interconnect Substrate) can provide ideal and this solution in the mobile industry as it contains multiple solutions for the complicated requirement of the IC packages for application processors. Based on the embedded pattern technology, this solution can provide high I/O count, fine pattern for small form factor, and stable flip chip mounting methods. Other advantages of this solution include stable properties required for high-frequency transmission and high thermal dissipation rate as it is only composed of copper and epoxy mold compound materials. These core techniques for MIS technology can be divided into below major concepts. First, Cu pillar electrolytic plating technology electrically connects the inner and the outer layers using photo-lithography method, instead of laser method. The shape of Cu pillar and the plating thickness tolerance control are the key parameters. Second, grinding technology is to precisely grind the plated Cu pillars and applied mold epoxy. And deposition of Cu layer on top of grinded mold surface can construct fine pattern traces.