1984-07-01

Thermal Evaluation of Plastic Cases for Electronic Equipment 840951

An analytical study using computer thermal models to investigate the feasibility of replacing the MRA (Missile Radar Altimeter) aluminum case with TORLON 5030, a polyamide-imide thermoplastic (1)*, is presented. The MRA case was selected because the MRA is used for several different missiles, and the resultant higher quantities provides a cost saving potential.
The feasibility of using TORLON cases in electronic equipment is determined by heat generation rates, methods of cooling and the severity of the thermal environment. Since TORLON has considerably lower thermal conductivity compared to aluminum, knowing the critical thermal paths in the electronic equipment case is essential in arriving at an optimum design/combination of TORLON and aluminum.
Five different designs using TORLON were analyzed by computing component temperatures and comparing them with those of an all-aluminum baseline design. The five design concepts are: 1. An all-TORLON (sidewalls and baseplate) case; 2. TORLON sidewalls and a TORLON baseplate with aluminum plugs; 3. TORLON sidewalls with an aluminum baseplate; 4. Aluminum inserts in TORLON sidewalls with an aluminum baseplate; and 5. Aluminum film coated TORLON sidewalls with an aluminum baseplate. For each design concept, three different sets of boundary conditions were imposed: 1. baseplate actively cooled; 2. baseplate passively cooled; and 3. baseplate not cooled.
The study indicates that an all-TORLON design is not suitable for the MRA because of heat dissipation problems. Only for the actively cooled baseplate condition, can TORLON be incorporated into the MRA case sidewalls because most of the heat is transferred out through the aluminum baseplate.

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