Experimental Study on Diffusion Bonding of OFHC Cu for Vacuum Tube Applications

This paper presents the experimental investigation on feasibility of using diffusion bonding (DB), an advanced bonding technique, for the manufacturing of microwave vacuum devices. In this study, the diffusion bonding of OxygenFree High-Conductivity (OFHC) copper in a controlled hydrogen furnace was investigated under different bonding conditions. This investigation assesses the impact of temperature, surface roughness, and flatness on the quality of the bond for vacuum applications. Bonding was conducted at temperatures ranging from 550 to 800° C, with an external pressure applied at the bonding interface under the rated load. The bonded interface characterization involved surface preparation methods, such as grinding, polishing, and cleaning, followed by a comprehensive analysis of bond quality using scanning electron microscopy (SEM) and vacuum testing. The experimental findings indicate that diffusion bonding, when optimized with the right parameters, produces high-quality joints with properties comparable to those achieved through conventional brazing.