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

Abstract

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 μm in D50 size, the bonding under a 5-MPa compression at 300 °C forms a Cu bondline that exhibits a sufficient shear strength of 23.7 MPa after heating for only 10 s to reach 300 °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 °C, long-term mechanical reliability, and significantly higher thermal conductivity than those in solder joints.