Abstract

Au-Ge-Ni solder was chosen for brazing of the Cu-Cr-Zr alloy cylinder and a part with a cylindrical hole (sleeve) below 550 °C. The Au based solder was first sintered on the surface of the cylinder and then brazed to the inner surface of the sleeve. The effects of the heating process, the temperature and the holding time at the temperature on the microstructure of the sintered layer on the surface of the cylinder, the brazed interfacial microstructure, and the brazed shear strength between the cylinder and the sleeve were investigated by scanning electron microscope, energy dispersive X-ray spectroscopy analysis, and tensile shear tests. By approach of side solder melt feeding and brazing under proper parameters, the voids and micro cracks due to a lack of enough solder melt feeding are greatly lessened and the brazed shear strength of 100 MPa is ensured even with large clearances around 0.01 mm.

Highlights

  • Cu and Cu based alloys have found wide and important applications in many fields, especially in electrical appliances and electronic products [1,2]

  • It should be noted that a piece of solder sheet with a thickness of 0.5 mm is set at one side of the brazing seam

  • In the results in Section 3.3.1, it can be seen that the brazed shear strength is below 90 MPa and there are many voids and micro cracks related to lack of solder melt feeding during solidification of the solder melt in the brazing seam

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Summary

Introduction

Cu and Cu based alloys have found wide and important applications in many fields, especially in electrical appliances and electronic products [1,2]. As for brazing of copper and its alloys, Au based solders are widely used due to their excellent electrical conductivity, good electromigration resistance, and high fatigue resistance [15,16,17,18,19]. These mainly include Au-Sn, Au-Ge, Au-In, and Au-Ni. As for Au-Sn solder, the eutectic point of Au-Sn is 282 ◦ C, the brazed tensile strength is only about 48 MPa [15,16]. Au-Ge solder with an addition of minor Ni and Cu were tested; the effect of the wrapping of the solder foil and the sintering process on the microstructure of the sintered layer on the surface of the cylinder were investigated by scanning electron microscope (SEM) and Energy dispersive X-ray spectroscopy (EDS), and the effect of the brazing process and the side solder melt feeding on the interfacial microstructure, including micro defects and the brazed shear strength, were studied by SEM and tensile shear tests

Materials and Methods
Properties of the spectroscopy
Properties of the Au Based Solder
Cross-sectional
Effect of the Brazing Temperature and the Holding Time
Section 3.3.1
Conclusions

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