Homologous temperature

The homologous temperature of a substance is useful for determining the rate of steady state creep (diffusion-dependent deformation).

[1] Additionally, for a given fixed homologous temperature, two materials with different melting points would have similar diffusion-dependent deformation behaviour.

In electronics applications, where circuits typically operate over a −55 °C to +125 °C range, eutectic tin-lead (Sn63) solder is working at 0.48Tmp to 0.87Tmp.

The upper temperature is high relative to the melting point; from this we can deduce that solder will have limited mechanical strength (as a bulk material) and significant creep under stress.

Copper, on the other hand, has a much higher melting point, so foils are working at only 0.16Tmp to 0.29Tmp and their properties are little affected by temperature.