Non-Pressure Cu Sinter Paste for High Density Power Device Interconnection

With the rapid development of power electronic devices, miniaturization, high-power density, and high thermal reliability have become the standard for next-generation semiconductor devices. As silicon-based materials are difficult to meet the application requirements for high power density and high-temperature operation, wide-band-gap (WBG) semiconductor, such as silicon carbide (SiC) and gallium nitride (GaN), have taken the main role. Though high-power density and high switching frequency characteristics ensured those materials can lead to high performance power devices, the excessive junction temperatures (Tj) could lead to the deterioration risk for relative packaging material. Especially the die-attach materials, which integrate power chips to substrate, are easily influenced by thermal fatigue and frequency thermal cycling environment. Some new technologies, such as. high-temperature brazing materials, transient liquid phase bonding technology, and sintered silver (Ag) technology, have been investigated. All those materials have their own drawbacks such as serious processing condition, high risk of fragile, and price costing. In comparison, metal copper (Cu) sinter paste is considered an ideal wide-bandgap semiconductor connection material due to its cost-effectiveness, excellent thermoelectric properties, and good thermal reliability. However, for efficient sintering of Cu paste, most research applied pressure, reductive atmosphere and/or high processing temperature, which limited the widely application of Cu sinter paste for high density power device interconnection [1]–[3]. Therefore, it is necessary to study the bonding strength, bonding mechanism, and reliability of copper paste on metal plates in high-power devices. To address these issues, this paper reports a non-pressure Cu sinter paste interconnection technology with nano-particles and reductive solvent included. The paste could form efficient sintering in N2. So that high reliable interconnection between chips and substrate could be achieved. The shear strength, SEM and EDS were applied on sintered interconnection for evaluation. And the result showed that the Cu sinter paste showed good bondability on both Cu and Ag surface, and the key factors for high rank sintering were explored. This work provides both experimental and theoretical research for creating high-strength connections by sintered Cu pastes, and extended the potential of Cu sinter paste in high density power devices.