Homologous temperature
Encyclopedia
Homologous temperature expresses the temperature
of a material as a fraction of its melting point
temperature using the Kelvin scale. For example, the homologous temperature of lead at room temperature is approximately 0.50 (TH = T/Tmp = 298K/601K = 0.50).
Solder (Tmp: 183°C = 456K) at 0.85Tmp or 115°C (= 388K), would thus be expected to have comparable properties to copper (Tmp: 1085°C = 1358K) at 0.85Tmp or 881°C (= 1154K).
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. This is borne out by its comparatively low values for tensile strength, shear strength and modulus of elasticity.
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.
Temperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...
of a material as a fraction of its melting point
Melting point
The melting point of a solid is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depends on pressure and is usually specified at standard atmospheric pressure...
temperature using the Kelvin scale. For example, the homologous temperature of lead at room temperature is approximately 0.50 (TH = T/Tmp = 298K/601K = 0.50).
Solder (Tmp: 183°C = 456K) at 0.85Tmp or 115°C (= 388K), would thus be expected to have comparable properties to copper (Tmp: 1085°C = 1358K) at 0.85Tmp or 881°C (= 1154K).
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
Creep (deformation)
In materials science, creep is the tendency of a solid material to slowly move or deform permanently under the influence of stresses. It occurs as a result of long term exposure to high levels of stress that are below the yield strength of the material....
under stress. This is borne out by its comparatively low values for tensile strength, shear strength and modulus of elasticity.
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.