Motorola Single Board Computer, MVME5100 manual Component Temperature Measurement, Preparation

E

Thermal Analysis

Component Temperature Measurement

This section outlines general temperature measurement methods. For the specific types of measurements required for thermal evaluation of this board, see Table E-1.

Preparation

We recommend 40-gage thermocouples for all thermal measurements. Larger gage thermocouples can wick heat away from the components and disturb air flowing past the board.

Allow the board to reach thermal equilibrium before taking measurements. Most circuit boards reach thermal equilibrium within 30 minutes. After the warm up period, monitor a small number of components over time to assure that equilibrium is reached.

Measuring Junction Temperature

Some components have an on-chip thermal measuring device such as a thermal diode. For instructions on measuring temperatures using the on- board device, refer to the MVME5100 component manufacturer’s documentation listed in Appendix C, Related Documentation.

Measuring Case Temperature

Measure the case temperature at the center of the top of the component. Make sure there is good thermal contact between the thermocouple junction and the component. We recommend you use a thermally conductive adhesive such as Loctite 384.

If components are covered by mechanical parts such as heatsinks, you need to machine these parts to route the thermocouple wire. Make sure that the thermocouple junction contacts only the electrical component. Also make sure that heatsinks lay flat on electrical components. Figure E-3shows one method of machining a heatsink base to provide a thermocouple routing path.

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