In this study, a novel Cu@Sn TLPS joint was fabricated for high-temperature power electronics application. Cu@Sn core–shell composite powder was firstly prepared by a methylate electroplating method, and then pressed into a preformed sheet. The Cu@Sn preform was reflowed at 250 ∼ 280 °C for 40 min under the pressure of 0.1 × 10⁻³ MPa, and the resulting bondline can withstand high temperatures up to 600 °C. During the process, the Sn layer was transformed to Cu₃Sn, and the Cu₃Sn surrounded the outside of the residual Cu particles. The joint characteristics were controlled by size gradation of Cu particles, the ratio of Cu/Sn, preform forming pressure and TLPS process. The joint shear strength was no less than 48 MPa after aging at 400 °C for 1000 h. Young's modulus and hardness were 98.35 GPa and 2.62 GPa, respectively, which are much lower than the pure Cu₃Sn joint. The electrical resistivity and thermal conductivity of the joint were 5.1 μΩ cm and 148 W m⁻¹ K⁻¹, respectively. It is superior to pure Cu₃Sn joints and the other Cu/Sn system TLPS joints. The high shear strength, high thermal conductivity and high melting temperature demonstrate that Cu@Sn TLPS joint is a promising interconnect technology for high power density modules.

Herein, a 110 A commercial, Si continuous current diode with high heat dissipation power is attached to Cu@Sn@Ag preform, formed by electroplating and physical vapor deposition, and pressed into a preformed sheet under a pressure of 5–10 MPa. The prepared dense three-dimensional network of Cu/Cu₃Sn/Ag₃Sn joint, based on Cu@Sn@Ag preform obtained using transient liquid-phase diffusion soldering technology, can withstand high temperatures up to 600 °C in power device applications. The mechanical and thermal performance and power cycle reliability of the Cu@Sn@Ag joint are investigated and comparatively analyzed with PbSn5Ag2.5 joints. The results show that the average shear strength of the Cu@Sn@Ag joint is ∼35 MPa, which exceeds that of PbSn5Ag2.5 solder joint, and is similar to that of sintered nano-silver solder joint; the minimum thermal resistance of the corresponding device is ∼0.18 K W⁻¹, near to that of PbSn5Ag2.5 joint. The growth rate of the forward voltage drops below 2% following 150 000 active power cycles, with a junction temperature difference below 60 °C, meeting the requirements of reliability test standards for vehicle specifications. It is concluded that the performance and power cycle reliability of the Cu@Sn@Ag joint are better than those of the PbSn5Ag2.5 joint.

This paper presents a novel Cu-based die attachment material for interconnection with bare Cu substrate, verifying the successful sintering process between power chip and Cu substrate. The attachment materials are based on Cu/Ni/Ag preform by pressing the mixture of Cu@Ni@Ag powders and Ag nanoparticles. By inserting a dense layer of Ni interface between Cu and Ag, this material can solve the problem that Cu or Cu@Ag powders are prone to oxidation during the process of sintering. Also, the shear strength can reach over 20 MPa of the joint after sintering at 300 °C under a pressure of 15 MPa. The Cu/Ni/Ag preform shows great potential for the application of power electronics packaging with high power density, high integration and high-temperature working environments.