Dynamic measurement of the thermal resistance of contacts on thermoelectric samples

摘要

Method for dynamically measuring the contact thermal resistance R _C^th between two joining partners, wherein at least one of the partners is a substrate (1) comprising a thermoelectric material, wherein the substrate (1) between two equally or differently tempered blocks (2a, 2b ) is arranged and with these via a contact material (3a, 3b) is brought into surface, wherein at each block (2a, 2b) at least one power supply, via which a direct electrical current through the substrate (1) can be passed, an electrical probe line for measuring the voltage over which the voltage drop between the blocks (2a, 2b) can be measured, and at least one temperature measuring point, comprising: a) supplying a direct current through the blocks (2a, 2b) such that an electric current I _{0 flows} from one block (2a, 2b) to the other block (2a, 2b), the current flowing through the contact material (3a, 3b ), the substrate (1) and again the contact material (3a, 3b) flows, b) switching off or switching the current to another constant value at time t ₀ , wherein the change of the current is denoted by I, and c) time-resolved measurement of the voltage over a period of time immediately after the current has been switched off, the time period occurring at least during a fast decay half-life and at a sampling rate allowing at least 10 to 100 measured values (voltage values) to be recorded within the first half-life; or by another methodology that allows back to the initial value of the relaxing measurement voltage immediately after switching off the current v ₁ (t ₀ ), d) subsequent time-resolved measurement of the voltage over a period of time, beginning after the first relaxation has largely subsided, in which the system substantially conforms to the new equilibrium state, with a data rate of at least 5 to 20 values per half-time of slow decay on entry into the new equilibrium state, or by means of another methodology which allows _{one to deduce} the initial value v _{1, fit} (t ₀ ) of the second, slower relaxation with respect to the switch-off / switchover instant of the current t ₀ , e) linear or exponential extrapolation of the measured voltage drop in step c) to obtain an initial value v ₁ (t ₀ ) at time t ₀ and linear or exponential extrapolation of the measured voltage drop in step d) to obtain a baseline v _{1, fit} (t) until time t ₀ , f) Determining the temperature difference ΔT = (V ₁ (t ₀ ) -V _{1, fit} (t ₀ )) / S between the baseline obtained in step e) at time t ₀ and the extrapolated measured value from step c) at time t ₀ where S denotes the difference of the Seebeck coefficients of the thermoelectric material (substrate (1)) and the joining partner (contact material (3a, 3b)), and g) calculation of the contact thermal resistance R _C^th after $R_C{}^{\text{th}}=\frac{\Delta T}{P}\left(P=PeltierwärmestrOm\right),$