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An Application-Oriented TIM Thermal Measurement Approach
Keywords: TIM, thermal , interface
IMAPS ATW 2013 Presentation Abstract An Application-Oriented TIM Thermal Measurement Approach Bernie Siegal, Thermal Engineering Associates, Inc. Tom Tart, Package Science Services, LLC George Meyer, Celsia Technologies Selection of TIM for thermal management designs is usually based on reviewing vendor datasheets and selecting the material based on the thermal conductivity specification value. However, this specification is for the bulk thermal conductivity (BTC) and does not take into account the thermal resistance (typically referred to as Bond Line Resistance [BLR]) associated with the thermal interfaces on both sides of the material. Thus, it is possible to select a material with a high BTC that actually has lower thermal performance in an application-oriented environment than a material of lower conductivity due to the BLR differences. A second step should be added to the TIM selection process. This step could be a thermal resistance measurement from device junction to the ambient reference in an actual application. However, this is often difficult to implement and time consuming for a variety of reasons. An alternative approach is to make application-oriented measurements in a manner that is simpler to implement, less time consuming and can lead to a standardized measurement approach for comparing materials. This presentation will provide a suggestion for implementing an application-oriented TIM thermal measurement approach. Results of testing of a representative sample of various TIMs will be presented. These TIMs were tested on actual shipping hardware on real thermal test sets. Presentation Details (for planning purposes of work needed to gather data – not submitted with abstract.) 1) Use the apparatus at right to make thermal resistance measurements on several TIM greases and/or pads that have difference KΘ values. 2) Apparatus is setup to provide 8lbs of force on a 10.23mm X 10.23mm Flip Chip. 3) The plate at the bottom of the heat sink is a OFV with a slot of embedding a TC or Thermistor. 4) ΔT measurements between the chip junction and the plate embedded sensor will be made with uniform heating at a level of ~15W. The device will be configured for uniform heating. 5) The data will be compared to TIM grease BTC values. 6) If time allows, the board can be reconfigured for non-uniform heating and measurements can be made to demonstrate the resultant impact on the thermal resistance values. 7) Further, a vapor chamber heat spreader can be inserted in to the heat flux path to measure the impact with non-uniform heating.
George Meyer/Bernie Segal, CEO
Celsia Inc/ Thermal Eng Assoc
Morgan Hill, CA

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