Mitigation of distortion in fiber laser welded ultra-thin vapor chamber

The ever-increasing demand for higher integration and performance in mobile devices underscores the necessity of finding superior cooling solutions. Miniaturization results in a larger heat flux and local high temperatures that impact the lifetime and reliability of these devices. Vapor chambers (VC) are extensively utilized in the thermal management of electronic systems due to their passive operation, reliability, and effective heat transport. However, there remains a need to manufacture much thinner vapor chambers to address tight space limitations while ensuring the required thermal performance and sufficient structural integrity. The purpose of this work is to fabricate ultra-thin vapor chambers (UTVC) meeting these requirements by utilizing a novel fiber laser welding process to join stainless steel. The unavoidable issue of distortion due to welding is tackled by developing finite element models to simulate heat transfer and stress development. Various methods for mitigating welding-induced distortion are examined. Characteristic parameters, including laser power, travel speed, and cooling and clamping systems, are thoroughly studied and optimized. The results indicate that minimizing the net heat input during welding, along with adequate cooling and constraining of the central region of the vapor chamber, significantly reduces waviness and distortion to meet tolerance requirements.