Chapter 15 Steady Heat Conduction3-46 Six identical power transistors are attached on a copper plate. For a maximum case temperature of 85°C, the maximum power dissipation and the temperature jump at the interface are to be determined. Assumptions1Steady operating conditions exist. 2Heat transfer can be approximated as being one-dimensional, although it is recognized that heat conduction in some parts of the plate will be two-dimensional since the plate area is much larger than the base area of the transistor. But the large thermal conductivity of copper will minimize this effect. 3 All the heat generated at the junction is dissipated through the back surface of the plate since the transistors are covered by a thick plexiglas layer. 4 Thermal conductivities are constant. PropertiesThe thermal conductivity of copper is given to be k= 386 W/m⋅°C. The contact conductance at the interface of copper-aluminum plates for the case of 1.3-1.4 μm roughness and 10 MPa pressure is hc= 49,000 W/m2⋅°C (Table 3-2).
This is the end of the preview. Sign up
access the rest of the document.
This note was uploaded on 01/14/2012 for the course PHY 4803 taught by Professor Dr.danielarenas during the Fall '10 term at UNF.