Rapid Ag/Sn/Ag transient liquid phase bonding for high-temperature power devices packaging by the assistance of ultrasound

Abstract

Rapid transient liquid phase (TLP) bonding process on Ag/Sn/Ag system is achieved in air by the assistance of ultrasonic, which has great potential to be applied to high-temperature power devices packaging. In this study, the influence of ultrasonic effect on the morphology and growth kinetics of AgSn grains, and the joint microstructure, mechanical property and thermal reliability were systematically investigated. Experimental results indicated that the rapid consumption of the "dynamic" transient liquid phase was attributed to the accelerated dissolution of Ag substrate and the extrusion of liquid Sn, which were entirely induced by the complex sonochemical effects on the liquid/solid intermetallic compounds (IMCs) interface. An elongated scallop-like morphology of AgSn grains was developed during Ag/Sn interfacial reaction with ultrasonic, accompanied by widening of grooves between neighbored grains. This phenomenon is called as a strengthening thermal grooving, in which the grooves at grain boundaries provide stable molten channels for Ag atoms diffusion from the substrate. Consequently, the improved elemental diffusion was evaluated through the growth kinetics of AgSn IMCs, with conservative estimation of 6-16.5 times faster than the traditional TLP process. In addition, both excellent mechanical property and thermal reliability of the Ag-Sn intermetallic joint were experimentally verified by shear test and high-temperature storage test, respectively.

Microstructure and Formation Mechanism of Ultrasound-Assisted Transient Liquid Phase Bonded Magnesium Alloys with Ni Interlayer

“…The formation of the Mg 2 Ni means that the oxide film on the surface of the Mg was eliminated by USV within 10 s [18,20,25]. It was said in [14] that due to the acoustic plasticity effects, the BM and the oxide film were triggered in varying deformation and this plastic mismatch between the BM and the oxide film led to the breakage of the oxide film. So, the mutual diffusion between the Mg BM and the Ni interlayer proceeded and the Mg 2 Ni IMC layer was created after the fresh Mg and Ni atoms came into contact with each other.…”

“…Ultrasound-assisted transient liquid phase bonding (U-TLP), which has been developed from the TLP method, is a low-cost, high-efficiency, green, and reliable joining method, which has been applied to join different kinds of alloys [14,15] or dissimilar alloys [16,17,18]. Xu et al joined the Mg alloy within 1 s using a Zn layer via U-TLP; however, the joint was filled with MgZn and MgZn 2 , which led to a 42 MPa shear strength [19].…”

Low Temperature Bonding by Infiltrating Sn3.5Ag Solder into Porous Ag Sheet for High Temperature Die Attachment in Power Device Packaging

“…Compared with other IMCs, Ag 3 Sn shows excellent ability to absorb stress with a low Young’s modulus of 78.9 GPa and a low hardness of 3.25 GPa; in fact, Ag 3 Sn is the most ductile IMCs among the common reaction products in electronic packaging, such as AuSn 4 , Cu 6 Sn 5 , Cu 3 Sn, and Ni 3 Sn 4 40 , 41 . In addition, Ag 3 Sn shows the lowest electrical resistivity among them, which would contribute greatly to the overall electrical performance of the formed bondline 41 . That is to say, the porous Ag sheet infiltrated with Sn-Ag solder can be a promising high temperature die attach material with good thermal and electrical conductivities and mechanical properties.…”

Strategies to Reduce Transient Liquid Phase Bonding Time for the Die Attach of Power Semiconductors

“…Ultrasonic-assisted TLPB is a recent process that has been actively studied. Ultrasonic wave is applied to TLPB to produce microbubble in the joint 28,29) . Forming microbubbles in the liquid interlayer, the temperature and pressure reached locally 5000 K and 0.1 GPa, respectively, due to the of bubble implosion 29) .…”