Effect of temperature on the electrical conduction and dielectric behavior of solder

Solder is widely used as an electrical conductor in electronics. This paper reports the effect of heating up to 70 °C on the conduction and dielectric behavior of solder (Sn–4Ag lead-free eutectic solder). The effect of temperature on the electric permittivity is reported for the first time for metals in general. The electrical resistivity increases linearly with the temperature, with the temperature coefficient of resistivity equaling 3.59 × 10^–3/°C. The relative permittivity is 3.24 × 10⁶ (100 kHz) and does not change with the temperature. This suggests that the increase in the amplitude of thermal vibration as the temperature increases impacts the conduction behavior more than the dielectric behavior, which hinges on the electron–atom interaction. The increase in the thermal vibration amplitude apparently enhances the electron scattering without affecting the electron–atom interaction, which occurs primarily at defects such as the interfaces in the solder microstructure. The absence of change of the permittivity with the increase in temperature is attractive for the practical use of solder as electrical conductors in electronics.