Air-sinterable copper pastes for next-generation electronics: a review

Abstract

In recent years, in addition to the pursuit of miniaturization and integration, electronic devices have exhibited an increasingly prominent demand for high power and intelligent functions, which has become a key driving force for the development of next-generation products. However, traditional soldering technologies, characterized by low melting temperatures, restricted thermal conductivity, inadequate fatigue resistance, and intrinsic brittleness, are unable to provide reliable joining for electronics under demanding service conditions involving high temperatures and cyclic deformation.Metal pastes, which exhibit low-temperature sinter-joining behavior, excellent thermal and electrical conductivity, and favorable mechanical compliance, provide a novel approach to overcoming above challenges. Among metal pastes, copper pastes are regarded as ideal candidates for replacing traditional solders due to their high electrical conductivity, excellent resistance to electromigration, and significant cost advantages.However, the high chemical reactivity of copper makes it highly susceptible to oxidation, and current atmosphere-protected sintering processes not only increase process complexity and cost but also hinder its practical implementation. In this work, a comprehensive overview of recent advances in air-sinterable copper pastes is presented, which is of great significance for the development and application of copper pastes. Specifically, the design strategies are systematically elaborated, encompassing the fabrication of oxidation-resistant copper particles and the development of reductive solvent systems. Furthermore, sintering process compatible with air conditions including pressure-assisted sintering, laser sintering, and other emerging sintering approaches are analyzed in detail. Finally, their current application status in flexible electronics and power devices is summarized, followed by a discussion on the existing challenges and prospective research directions.