Temperature effects on microstructures of brazing porous copper to copper using Cubased filler metal

摘要

Open-cell structures of porous copper have many interesting combinations of physical and mechanical properties. It consists of cells, which all are interconnected (without walls) that allowing a fluid to pass through. Due to its attractive properties, it is crucial to utilize this material as heat exchanger for electronic devices. Therefore, brazing porous copper to copper has been conducted in this research using copper-based (Cu-9.7Sn-5.7Ni-7P) filler metal. The study is mainly focusing on the effects of different temperatures to the microstructures of brazed joint. The brazing process was conducted in a tube furnace with a flow of argon gas to limit contamination at different temperatures; 660℃, 680℃ and 700℃ for 15 minutes holding time with heating rate and cooling rate of 10℃/min, respectively. The bonding joints were characterized using Scanning Electron Microscopy (SEM) equipped with Energy dispersive X-Ray Spectroscopy (EDS) and X-Ray Diffraction (XRD) analysis. Interestingly, it was observed that the porous copper was joined on both sides, changed its colour and become more rigid after brazing even though the filler metal was put on one side only. The analysis using SEM-EDS and XRD shows that the phosphorus (P) was diffused into the porous metal and formed Cu-P containing phase regions. The phase also contributed to the bonding of porous copper to copper and the rigidity of porous copper after brazing. With increasing of brazing temperature, the less formation of Cu-P containing phase regions was observed. It is hoped that the analysis may provide guides for the design of heat exchanger for high power electronic devices.