Electrical and thermal conductivities and thermopower of some lead free solders (LFS) in the liquid and solid state

We have measured the electrical resistivity and thermopower of industrial liquid and solid lead–tin alloys and of several lead free solders (Sn–Ag; Sn–Cu; Sn–Sb; Sn–Ag–Cu), and have deduced the thermal conductivity as a function of the temperature by using the relations between the electronic transport coefficients. The resistivity of lead free solders are smaller than those of lead–tin alloys, which is desired. Similarly the algebraic value of the thermopower is increased in the liquid. From an electronic and thermal point of view, lead free solders have better properties than lead–tin alloys. Calculated values are compared to our experimental ones and give good results for the alloys. It is shown that the best lead free solders have an increased thermal conductivity up to 30% in liquid and solid state.