Tens-of-seconds solid-state sinter-bonding technique in air using in situ reduction of surface oxide layers on easily bendable dendritic Cu particles

Solid-state sinter bonding using metal particles, such as Ag and Cu, are emerging for the development of the next-generation die-attachment technique of a semiconductor chip that operates at high temperature or generates huge heat, thereby requiring a significant decrease in bonding time for industrial applications. However, this process still requires at least several minutes, even when using pastes containing expensive Ag nanoparticles that are limited in terms of handling and mixing. Here, we present an easily applicable and ultrafast sinter-bonding method that can be applied in air, using a combination of a micron-scale surface-area-enhanced Cu particles and an effective reducing solvent. Using uniquely-shaped semi-dendritic particles of 2.89 mu m in D50 size, the bonding under a 5-MPa compression at 300 degrees C forms a Cu bondline that exhibits a sufficient shear strength of 23.7 MPa after heating for only 10 s to reach 300 degrees C. Subsequently, the strength increased to 29.0 MPa with the bondline microstructure of near-full density after 60 s. This strategy will provide enhanced sustainability at temperatures above 200 degrees C, long-term mechanical reliability, and significantly higher thermal conductivity than those in solder joints.

Automated summary

This study presents an easily applicable and ultrafast sinter-bonding method using micron-scale surface-area-enhanced Cu particles and an effective reducing solvent. The Cu bond formed after only 10 seconds of heating exhibited sufficient shear strength, and the strength increased further after 60 seconds of heating, with a near-full density bondline microstructure.