Pan Pacific Symposium Conference Proceedings


Author: Roger Emigh
Company: Advanced Thermal Solutions
Date Published: 1/25/2000   Conference: Pan Pacific Symposium

Abstract: This paper discusses in situ thermal characterization techniques for temperature mapping and measurement of airflow velocity fields. These techniques can be applied to a wide variety of micro-electronic systems (packages, boards, full computer or telecom systems, etc.) to aid in understanding and improving their thermal design. Temperature mapping is accomplished using a liquid crystal technique that provides a visual temperature profile over any area of interest, from an individual die to an entire motherboard. This is accomplished by applying an electrically insulating material to the entire surface. The material changes color with temperatures and can be tailored to respond over various temperature ranges. Standard image analysis techniques can then be applied as desired. For testing of enclosed systems, transparent materials can be used to visually expose the components without altering the airflow characteristics. Airflow velocity fields are measured using special thermistor sensors that are small enough to be placed in very tight spaces, such as between the fins of a heat sink, with minimal disruption of the ambient airflow. These solid state devices measure both airflow and temperature with a single sensor, providing accuracy and minimal disruption. The thermal designer can find great benefit from this combination of accurate, in situ measurement of local airflow and temperature along with the ability to visually illuminate the temperature distribution over any desired area. Experimental results for both techniques are presented as applied to a network switching system. Also presented is an example of the liquid crystal technique to a bare, operational die. The techniques described are seen to be effective methods of obtaining a thorough understanding of the thermal environment within micro-electronic systems.

Keywords: Liquid crystal, thermal measurements, thermal characterization, air velocity measurement, thermistor.

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