Copper Die-Bonding Sinter Paste: Sintering and Bonding Properties

This paper describes the sintering properties and bonding properties of copper (Cu) die-bonding sinter paste for power devices operating at high temperatures. The Cu paste can be sintered pressureless in 100% 112 or under pressure in 100% N ₂ atmospheres. The as-sintered density, thermal conductivity and resistivity of pressureless-sintered Cu (in 100% 112, 300 °C, 1 h) is found to be 78%, 180 Wm ^-1 K ^-1 and 4.3 μΩ·cm, respectively. The pressureless-sintered Cu has higher 0.2% proof stress than the pressure-sintered Ag (sintered density = 87%, in air, 300 °C, 10 MPa, 10 min) as a comparison material in a three-point bending test. The die-shear strength of appropriate pressure-less-sintered Cu on four different metal adherends (Cu, Ni, Ag and Au) was 30 MPa or higher. The die-shear strength of pressure-sintered Cu in 100% N ₂ was 36 MPa or higher. A thermal cycle tolerance of 1000 cycles or greater was shown in a power device test package which was bonded using the pressureless-sintered Cu and encapsulated with an epoxy molding compound. The Cu sinter paste can be used as a reliable die-bonding material for power modules operating at high temperatures.