Thermal stability of low-temperature sintered joint using Sn-coated Cu particles during isothermal aging at 250 °C

摘要

In this paper, we investigate the microstructural stability of a Cu-Cu joint sintered with microscale Cu particles and Sn-coated Cu (Cu@Sn) particles during an isothermal aging. Using Cu particles and Cu@Sn particles as die attach materials, pure Cu discs were bonded at 200 °C for 20 min with an applied pressure of 10 MPa in a formic acid atmosphere. After the bonding, the Cu sintered joint showed a loosely sintered structure, while the Cu@Sn sintered joint exhibited a microstructure comprised of a Cu_3Sn network with a dispersion of Cu particles. The isothermal aging test was conducted at 250 °C in an air atmosphere. Debonding of the Cu sintered joint happened after the aging for only 100 h, due to a severe oxidation of the sintered Cu layer and Cu substrate. On the other hand, the Cu@Sn sintered joints showed better thermal stability. The joint presented nearly 20 MPa shear strength after the aging for 1000 h. The Cu_3Sn IMC network suppressed the oxidation of Cu both in the sintered layer and on the substrate, thereby maintaining the microstructural integrity of the Cu@Sn sintered joint.