Apparatus for measuring heat of circuit module

Claim 1

Testing apparatus for measuring the heat of a circuit module mounted on a circuit board, the board having a planar surface that defines a plane for the orientation of the circuit module, the circuit module having a major heat dissipating surface facing outward from the board the apparatus comprising, a tubular housing having a central axis and having a shape to be positioned over the circuit module with the axis of the housing generally perpendicular to the plane of the board, whereby a thermal path is formed through the axis of the housing for substantially all of the heat from the module surface, a first horizontal partition of high thermal conductivity located inside the housing at a position spaced from the heat dissipating surface to form a top of a first chamber that is open to receive the circuit module and forming a bottom of a second chamber, a second horizontal partition of high thermal conductivity located inside the housing to form a top of the second chamber, and a bottom of a third chamber, means in the first chamber for making a good thermal path between the circuit module and the first horizontal partition, a second thermally conductive material having a predetermined thermal resistance filling the second chamber, whereby a temperature drop will be produced between the first and second partitions according to a heat flow through the housing, an electric fan located above the second partition for blowing cooling air against the upper surface of the second partition means for measuring the temperature drop through the thermal resistance of the second chamber, comprising a first temperature sensing element located to measure the temperature of the first partition and a second temperature sensing element located to measure the temperature of the second partition, the walls of the housing being poor heat conductors to restrict the thermal path to substantially said axis of the housing whereby the heat transferred from the circuit module can be calculated according to an equation relating the temperature drop across the thermally conductive material to the thermal resistance established by the material.