機能性ナノワイヤ面ファスナーの接着強度および熱伝導性の向上

抄録

Solder has been used for the conventional bonding technology in electronic assembly for a long time. However, the traditional reflow soldering technique is characterized by high heating temperatures. Moreover, due to the progress of power devices, the working temperature in the electrical packages is increased. Therefore, we have proposed nanowire surface fastener (NSF) based on Cu nanowire arrays by which cold bonding for electrical packaging can be realized. Since copper is a high thermal conductive material, a satisfactory heat transfer characteristic is expected. In this paper, we investigated the improvements of the strength and thermal properties by changing the connecting load. The template method was used for fabricating Cu nanowire arrays, and the bonding strength of Cu NSF was evaluated by a tensile test. The highest bonding strength (205.06 N/cm²) was recorded when two nanowire arrays were connected by the connecting load of 125 N. Simultaneously, we measured the electrical resistance of Cu NSF by a four－terminal method. The electrical resistance showed the opposite behaviour to the bonding strength. Specifically, the larger connecting load we applied, the lower electrical resistance it showed. In metallic materials, since free electrons are carriers of the electric current and heat transfer, the electric conductivity and the thermal conductivity are closely related. Therefore, improvements of the electric and thermal conductivity are expected when electrical resistance decreases.