Sheet-bulk metal forming of copper heat spreader with controllable deformation zone

Abstract

In this paper a novel precision forging process for the manufacture of CPU heat spreaders is presented. The study included numerical and simulation verification and the purpose was to replace the commonly used forging methods used for heat spreader manufacture with sheet-bulk metal forming (SBMF). The process includes roughing, finishing and trimming from a pre-formed shape. The finite element method (FEM) was used to optimize the design of the width and variable flash controllable deformation zones (W-CDZ/VF-CDZ) to ensure the dimensions were within the 0.1 mm critical specifications for flatness and parallelism. Simulation analysis took into account all the related microscopic phenomena: forming, material flow, flow velocity and strain distribution. The simulations and experiments showed that the occurrence of SBMF overlapping defects could be successfully avoided by the proper design of W-CDZ and VF-CDZ. The forming load, material flow, flow velocity and strain related distribution were thoroughly investigated within the controllable and stable deformation zones. It was found that the forming sequence and filling ratio could be improved, and uniform distributed cross-sectional hardness could be attained which augmented uniform heat dissipation.