Capillarity-promoted laser re-sintering of printed semisolid Cu nanoparticles for facile fabrication of conductive patterns with voidless structure and improved conductivity

Abstract

In this work, we propose a capillarity-promoted laser re-sintering method of printed semisolid Cu nanoparticles for facile fabrication of conductive patterns with voidless structure and improved conductivity. Conductive circuits with a thickness of 5 μm are fabricated. By using a semisolid Cu particle paste instead of a dry paste, a more compact sintered structure is obtained, and the resistivity is reduced from 18 to 9.2 μΩ cm. Thermal diffusion tests reveal that the semisolid paste exhibits a much higher thermal diffusion coefficient (∼7 × 10−6 m2/s) than the dry paste (∼3 × 10−6 m2/s). Through four repeated laser scannings, the fully sintered layer on the upper surface of the circuits thickens and transits into a solid structure without internal voids. The resistivity is further reduced to 3.8 μΩ cm, which is only two times that of bulk copper. The capillary phenomena of the semisolid paste also promotes the closure of large-scale voids. These effects drive the improvement of the properties and formable thickness of the sintered circuits. These findings could provide new experimental basis for structure and property modifications of printed circuits by similar techniques.

Keywords

• Metal nanoparticles
• Laser sintering
• Thermal diffusion
• Fully sintered layer