Micro-nanostructures fabricated by femtosecond laser for interface joint strengthening of Cu/sapphire

The reliability of the sapphire-metal joint technology in electronic devices determines its performance for industrial applications. Hence, we propose a method to enhance the connection strength between sapphire and metal based on micro-nanostructures on the substrate surface fabricated by femtosecond laser technology. The micro-nano modification of the substrate surface effectively improves the wettability of the silver paste, contributing to the spreading of the solder. The influence of different substrate surface morphologies on the joint strength is also investigated. It is found that the Cu/ sapphire substrate with cone microstructure arrays has the highest joint strength, reaching 27.2 MPa at a sintering temperature of 300 °C, which is about 4 times increase compared to the flat substrate (7.3 MPa). Further, the effect of different sintering parameters on the joint strength of the cone-structured array substrate is studied. The morphology of the cross-section and shear damage surfaces for connecting structures is analyzed, revealing that the mechanism of interface strength enhancement is mechanical interlocking. This fabrication of micro-nanostructures on substrate surfaces by femtosecond lasers provides a simple and efficient approach for the high-performance joining of ceramics and metals.