Joining of Hypereutectic Al-50Si Alloys Using Lead-Free Brazing Filler Glass in Air.

Zhenjiang Wang,Peng He,Jitai Niu,Zeng Gao,Xianli Ba,Junlong Chu

doi:10.3390/ma13245658

Abstract

Hypereutectic Al-Si alloys are attractive materials in the fields of electronic packaging and aerospace. A Bi2O3-ZnO-B2O3 system lead-free brazing filler glass was employed to braze hypereutectic Al-50Si alloys in air. The hypereutectic Al-50Si alloys were pre-oxidized and the low-temperature glass powder was flake-shaped in the brazing process. The effects of brazing temperature and time on joints microstructure evolution, resulting mechanical strength, and air tightness were systematically investigated. The results indicated that the maximum shear strength of the joint was 34.49 MPa and leakage rate was 1.0 × 10−10 Pa m3/s at a temperature of 495 °C for 30 min. Crystalline phases, including Bi24B2O39 and Bi2O3, were generated in the glass joint. The formation of a diffusion transition layer with a thickness of 3 μm, including elements of Al, Si, Zn, Bi, Na, and B, was the key to form an effective joint. The elements of Al, Si, and Bi had a short diffusion distance while the elements of Zn, Na, and B diffused in a long way under brazing condition.

Highlights

With the rapid development of electronic information technology, the integrated circuits of electronic devices require high power, high integration, and miniaturization [1,2]
Thermophysical properties of the brazing filler glass were detected by differential scanning
Thermophysical analysis, microstructure evolution observation, shearing strength tests, and leakage rate tests of air tightness were implemented to characterize the performance of brazing filler glass and the brazing joints

Summary

Introduction

With the rapid development of electronic information technology, the integrated circuits of electronic devices require high power, high integration, and miniaturization [1,2]. As the most commonly used electronic packaging material, has been used for a long time and played a huge role in electronic packaging in the past for its similar linear expansion coefficient to borosilicate hard glass It has the disadvantages of poor thermal conductivity and heavy weight. Silicon carbide particle-reinforced aluminum metal matrix composites (SiCp /Al MMCs) and hypereutectic Al-Si alloys have become popular candidates for a new generation of electronic packaging materials for their outstanding advantages such as high thermal conductivity, low density and low adjustable thermal expansion coefficient. They have potential applications in aerospace, automobiles, electronics, optical instruments, Materials 2020, 13, 5658; doi:10.3390/ma13245658 www.mdpi.com/journal/materials

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