Method and apparatus for determination of junction-to-case thermal resistance for a hybrid circuit element

Claim 1

A method for determining the junction-to-case thermal resistance θ jc of a solid-state circuit element mounted in a case, the circuit element having at least one semiconductor p-n junction, including the steps of: (a) applying a calibration current through the junction; (b) measuring a voltage drop across said junction for a plurality of temperatures to determine a temperature coefficient T c with said calibration current flowing through said junction; (c) applying a substantial increase in power to said solid-state circuit element and allowing said solid-state circuit element to reach a state of thermal equilibrium with a surrounding environment; (d) measuring a total power dissipation P T of said solid-state circuit element while keeping said base of said solid-state circuit element at a constant temperature; (e) removing said increase in power to said solid-state circuit element and measuring a change in junction voltage drop ΔV BE between low-power operation (only a small calibration current flowing) and high-power operation (substantially increased power to said solid-state circuit element); and (f) determining said junction-to-case thermal resistance θ jc by dividing said ΔV BE with the product of said total power P T and said temperature coefficient T c .

Claim 2

A method for determining the junction-to-case thermal resistance θ jc of a solid-state circuit element mounted in a case, the circuit element having at least one semiconductor p-n junction, including the steps of: (a) applying a calibration current through the junction; (b) measuring a voltage drop across said junction for a plurality of temperatures to determine a temperature coefficient T c with said calibration current flowing through said junction; (c) applying a substantial increase in power to said solid-state circuit element and allowing said solid-state circuit element to reach a state of thermal equilibrium with a surrounding environment; (d) measuring a total power dissipation P T of said solid-state circuit element while keeping said base of said solid-state circuit element at a constant temperature; (e) removing said increase in power to said solid-state circuit element and measuring a change in junction voltage drop ΔV BE between low-power operation (only a small calibration current flowing) and high-power operation (substantially increased power to said solid-state circuit element); and (f) determining said junction-to-case thermal resistance θ jc by dividing said ΔV BE with the product of said total power P T and said temperature coefficient T c .

Claim 5

A method for determining the junction-to-case thermal resistance of a solid state hybrid circuit element, said hybdrid circuit element being mounted in a case and including at least one semiconductor p-n junction, said method comprising the steps of: (a) applying a calibration current through the junction; (b) calculating a temperature coefficient for the junction; (c) applying additional power to the circuit element and measuring the power dissipated thereby; (d) lowering the power to the circuit element until only the calibration current is applied to the junction; (e) measuring the voltage drop across the junction between steps (c) and (d); and (f) determining the junction-to-case thermal resistance by dividing the voltage drop with product of the measured power dissipated by the circuit and the temperature coefficient of the junction.

Claim 6

A method for determining the junction-to-case thermal resistance of a solid state hybrid circuit element, said hybdrid circuit element being mounted in a case and including at least one semiconductor p-n junction, said method comprising the steps of: (a) applying a calibration current through the junction; (b) calculating a temperature coefficient for the junction; (c) applying additional power to the circuit element and measuring the power dissipated thereby; (d) lowering the power to the circuit element until only the calibration current is applied to the junction; (e) measuring the voltage drop across the junction between steps (c) and (d); and (f) determining the junction-to-case thermal resistance by dividing the voltage drop with product of the measured power dissipated by the circuit and the temperature coefficient of the junction.

Claim 11

A method for determining the junction-to-case thermal resistance of a hybrid circuit element mounted in a case, the circuit element including at least one semiconductor p-n junction therein, said method including the steps of: (a) placing the circuit element in a fixture; (b) measuring changes in voltage across said junction as a function of temperature to thereby determine the temperature coefficient of said junction while a small calibration current is flowing therethrough; (c) measuring the voltage drop across the junction with said calibration curent flowing therethrough; (d) increasing the power to the circuit element; (e) measuring total power dissipation in said circuit element while maintaining the case at a substantially constant temperature; (f) thereafter, removing power to the circuit element except for said calibration current being applied to said junction; (g) measuring the voltage drop across the junction within about 3 seconds after the power is removed in step (f); (h) calculating the difference between the voltage drop across the junction measured in step (c) and step (g); and (i) determining the junction-to-case thermal resistance by dividing said voltage drop difference calculated in step (h) with the product of the total power dissipated as measured in step (e) and said temperature coefficient as measured in step (b).

Claim 12

A method for determining the junction-to-case thermal resistance of a hybrid circuit element mounted in a case, the circuit element including at least one semiconductor p-n junction therein, said method including the steps of: (a) placing the circuit element in a fixture; (b) measuring changes in voltage across said junction as a function of temperature to thereby determine the temperature coefficient of said junction while a small calibration current is flowing therethrough; (c) measuring the voltage drop across the junction with said calibration curent flowing therethrough; (d) increasing the power to the circuit element; (e) measuring total power dissipation in said circuit element while maintaining the case at a substantially constant temperature; (f) thereafter, removing power to the circuit element except for said calibration current being applied to said junction; (g) measuring the voltage drop across the junction within about 3 seconds after the power is removed in step (f); (h) calculating the difference between the voltage drop across the junction measured in step (c) and step (g); and (i) determining the junction-to-case thermal resistance by dividing said voltage drop difference calculated in step (h) with the product of the total power dissipated as measured in step (e) and said temperature coefficient as measured in step (b).