Enhancing Device Performance Through Non-Pressure Sintering on Copper Leadframes

Efficient energy conversion is crucial for power conversion systems, driving the need for advancements in semiconductor materials and packaging techniques. Silicon Carbide (SiC) offers superior properties, including increased critical breakdown strength, low On-state resistance, and high switching frequency, which significantly enhance energy efficiency. However, effective heat dissipation remains a critical challenge, limiting the maximum operating voltage and temperature of SiC-based devices. A matured technique to overcome this challenge is pressure-assist sinter and is widely deployed in power modules packaging. Expanding to Leadframe (LF)-based devices brings about a new set of challenges. Despite much progress, demand for non-pressure solution that can increase thermal dissipation remains strong. Most interviewees have expressed resistance to plate die pad of copper LF. To address these challenges, this paper introduces non-pressure silver (Ag) sintering on copper surfaces. By enhancing thermal conductivity and reliability, sintering on copper LF enables power devices to operate cooler and more reliably over extended periods. A key aspect of this approach involves understanding LF surface roughness, which exhibits a moderate negative correlation to die shear. By meticulously controlling surface roughness, the effectiveness of sintering techniques can be optimized, facilitating improved heat dissipation and overall device performance. Additionally, the paper presents the advantages of non-pressure sintering over conventional soldering methods for copper LF. These advantages include lower processing temperatures, potentially reducing thermal stress on the die, and improved compatibility with temperature-sensitive components. A processing temperature of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$250^{\circ}\mathrm{C}$</tex> was considered an optimal temperature for achieving a robust bonding strength [1]. Furthermore, the elimination of pressure during sintering simplifies the assembly process and reduces equipment requirements.