Abstract
As an undisputed material of choice to guarantee reliability in a broad range of high performance and safety-critical applications in the electrical contacts and connectors, AuAgCu alloy was soldered with Ag-plated Cu wire using Sn-based solder. To clarify the embrittlement and strength reduction of the gold soldered joint, the microstructure and its influence on the macroand micro-mechanical properties of the soldered joint under various thermal aging conditions were studied. The result indicated that, taking the mechanical property consideration alone, Sn-based solder could be used to join AuAgCu alloy. Different from the embrittlement and strength reduction of the soldered joint of pure gold, although the brittle fracture features appeared in mechanical test of the soldered joints, the shear strength of soldered joint after thermal aging at 125 °C almost did not decrease in comparison with that before thermal aging. Nevertheless, too high temperature and long time still had bad influence on mechanical properties. Otherwise, thermal aging had a large effect on the IMCs layer, as aging temperature elevated and aging time increased, IMCs layer became thicker, more complex components and multiply-sublayers structure with different microhardness. The study provides a fundamental understanding for gold alloy soldering.
Highlights
Gold and its alloy have many unique advantages, such as high ductility, resistance to corrosion, oxidation and most other chemical reactions, and good conductivity of heat and electricity etc [1]
The rapid dissolution of Au into the molten Sn-based solder will induce a large amount of Au-Sn intermetallic compounds (IMCs) formation along the interface between Sn-based solder and gold alloy [9-18]
As aging temperature elevated and aging time increased, IMCs layer divided into the different compound layer, indicating different composition IMCs layer formed
Summary
Gold and its alloy have many unique advantages, such as high ductility, resistance to corrosion, oxidation and most other chemical reactions, and good conductivity of heat and electricity etc [1]. Additions of silver and copper into gold will improve the electrical conductivity of pure gold based on maintaining its excellent chemical stability, enhance its hardness, strength and abrasive resistance, and decrease the temperature-resistance coefficient and thermoelectric potential to copper [5]. These versatility and unique properties make the AuAgCu alloy an indispensible and widespread industrial use in the electrical contacts and connectors, such as low resistance wire resistor, electronic brush, and electronic sliding ring etc [6, 7]. For a thin Au film, Au forms dispersed Au-Sn IMCs in the solder as a minor phase which does not cause embrittlement [34-37]
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