Enhanced thermal conductivity of metallic nanoparticle packed bed by sintering treatment

Highlights: • Thermal conductivity could be enhanced 1.45 times by sintering treatment. • Higher sintering temperature leads to a higher thermal conductivity. • Hardness and thermal conductivity both depend on the contact condition. • Nanoparticle contact conditions can be greatly influenced by sintering treatment. - Abstract: In this paper, for the first time, the sintering treatment is applied to enhance the thermal conductivity and the mechanical property of the copper and the nickel nanoparticle packed beds (NPBs) which could realize low-temperature joining and high-temperature service as a soldering material used in the electronic device. Following the sintering treatment of NPBs, the hot-wire method and the Vickers hardness tester are applied to measure the thermal conductivity and the hardness of NPBs respectively. The sintering temperature and the tableting pressure both influence the thermal conductivity of NPBs greatly and the sintering temperature has a lager advantages than the tableting pressure in enhancing the thermal conductivity. With a sintering temperature larger than 800 K, the thermal conductivity can be enlarged even 2.45-folds than that without sintering treatment, because of the decreased porosity and the importantly improved nanoparticle contact conditions. On the other hand, with a large tableting pressure which will lead to a small porosity and a large nanoparticle coordination number, the thermal conductivity is only increased more than 0.41 times. Meanwhile, with the increase of the sintering temperature, the hardness of NPBs follows the same increase trend as that of the thermal conductivity. This study provides a simple and effective way in increasing the thermal conductivity and the hardness of NPBs simultaneously for a soldering application.