A low-temperature bonding method for high power device packaging based on In-infiltrated nanoporous Cu

Abstract

With the rapid development of the third-generation semiconductor materials, an appropriate high-temperature-resistant die attach material has become one of the bottlenecks to fully exploit the excellent properties of the third-generation semiconductor power devices. At the same time, a low-bonding temperature is always the pursuit goal of packaging engineers to reduce the thermal residual stress in electronic devices. In this paper, a low-temperature bonding method was proposed to address the above-mentioned issue based on In infiltrating the nanoporous Cu. In, as a low melting point metal, can significantly reduce the bonding temperature, and the nanoporous Cu structure can provide a very large specific surface area, which greatly increases the consumption rate of In. Furthermore, the formed Cu-In IMCs with high-remelting temperature can withstand the high operating temperature. The microstructures of the bondlines before and after bonding were studied in detail. The results show that the bondline can completely consume the low melting point In, within 10 min at 165 °C under a pressure of 0.75 MPa. When the bonding temperature was further increased to 310 °C, the bondline was composed of η-Cu₂In and δ-Cu₇In₃ phases, whose melting points were more than 600 °C. The average electrical resistivity was determined to be 5.53 ± 0.65 μΩ cm, and the thermal conductivities were 144.33 W m⁻¹ K⁻¹, 139.24 W m⁻¹ K⁻¹ and 129.79 W m⁻¹ K⁻¹ at 30 °C, 150 °C and 300 °C, respectively. The average shear strength were 19.09 ± 3.4 MPa, 20.47 ± 4.6 MPa and 30.73 ± 5.2 MPa at 30 °C, 250 °C, 310 °C, respectively. These results indicate that the nanoporous Cu infiltrated with In could meet the requirements of electrical, thermal conduction, and mechanical support as a die attachment for high-power devices.