Pressure and Pressure-less Cu Sintering Paste Developed for Next Generation Interconnection Material

Because of their high thermal and electrical conductivity, copper (Cu) sintering pastes were developed to meet the requirements for high-power applications. Compared to mature silver (Ag) sintering pastes, which are also designed for high-power applications, the Cu sintering paste advantages, such as low cost and insusceptibility to Ag migration, are appealing. Through extensive research, another important feature for Cu sintering paste was found: Cu sintering paste sinters well on bare Cu. In other words, no special precious metal plating (e.g. gold (Au) or Ag) is required for die or activate metal brazing (AMB). This eliminates the step of plating with Au or Ag for die or AMB and can potentially reduce costs. In this paper, pressure and pressure-less Cu sinter pastes with high-reliability were developed for high-power applications. The bonding performance of both pastes was determined on the Cu substrate. At 250-270°C, 15-25 MPa, 3-7.5 min, and under a nitrogen (N<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2)</inf> atmosphere, the pressure Cu sintering paste reached 40-70 MPa shear strength. For pressureless Cu sintering paste, a shear strength of >25 MPa was demonstrated under the sintering conditions of 250°C, 30 min, and an N<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> atmosphere. Meanwhile, both pressure and pressureless Cu pastes have passed 1,000 cycles of thermo-cycling tests (TCT) (-65-150°C), which indicates its high-reliability.