Allocation of Chip Modules by Superposition Technique for Controlling Module Temperatures

ALLOCATION OF CHIP MODULES BY SUPERPOSITION TECHNIQUE FOR CONTROLLING MODULE TEMPERATURES

Suriyon Chomdee Tanongkiat Kiatsiriroat Department of Mechanical Engineering, Faculty of Engineering, Chiang Mai University, Chiang Mai 50200

ABSTRACT This paper presents the approach of superposition technique that includes the adiabatic convective heat transfer coefficient and the thermal wake function for calculating module temperatures mounted on printed circuit board with air cooling. The technique has been modified for adjusting the positions of the chip modules for controlling their temperatures not to exceed a set value. Some examples have been carried out and the procedure developed has been used to allocate the modules with various conditions effectively. Keywords: Module temperature, Module allocation, Superposition technique

INTRODUCTION Temperature rise in an electronic module comes from two sources. The first one is due to its self-heating within the module and the second one is due to heat releases from its upstream components and raise the temperature of coolant which passes over the considered module. The second heating is named the thermal wake effect. There are two methods for predicting the module temperatures mounted on circuit board. The first one has used the heat transfer coefficient based on the temperature difference of the module and the ambient air over the module[Azar, 1997]. Then the method will take the thermal wake effect into the heat transfer coefficient. The second approach has used a superposition technique that includes the convection from adiabatic heat transfer coefficient based on the temperature difference between the module and the entering air at the leading edge and the heat due to the heat generation from the upstream module [Arvisu and Moffat, 1982].

The second method is more versatile to be used for predicting the module temperatures even each module generates different heat flux while the first one has to developed...