Strong Adhesion of Electroless Plated Copper by Optimizing Lamination Temperature of Epoxy Composite Film for Advanced Chip Packaging Substrates

Abstract

Semi-additive process (SAP) is a pivotal technique for fabricating integrated circuit (IC) packaging substrates, achieving fine line/space resolution below 20 μm. The adhesion strength between the epoxy composite dielectric layer and electroplated copper is critical for ensuring the long-term service reliability of high-performance substrates. Herein, an epoxy composite film suitable for SAP is deposited with copper layer via electroless plating followed by electroplating. The effects of lamination and pre-curing temperatures in SAP on the butter layer thickness, desmear weight, surface roughness (R_a), and adhesion strength of the plated copper are systematically investigated. The desmear weight decreases with the rising of lamination temperature attributed to the increased butter layer thickness. The lamination temperature is demonstrated to be one of the most influential factors in determining the adhesion strength between the plated copper and the epoxy composite. A high and stable peel strength exceeding 6.0 N cm⁻¹ is achieved under the circumstance of a low R_a of merely 0.95 μm, indicating significant potential for these epoxy composite films in the fabrication of fine-line and high-density packaging substrates.