Personal Computer User Manual

E-6 Computer Group Literature Center Web Site
Thermal Analysis
E
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-3 shows one
method of machining a heatsink base to provide a thermocouple routing
path.