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Project: Infrared Images of Two Amplifier Circuits

Document: Thermal Test Report

Prepared by: Michael A. Tharp P.E.

Principal Engineer

Test Date: Dec 17^th, 2004

Scope: This report provides the infrared thermal images of two sample amplifier assemblies operated at room temperature to measure transistor surface temperature and case temperatures under normal operating conditions.

Qsigma Associates

3020 Zaharias Drive

Orlando FL 32837

Ph. 407-694-4865

Fax 407-888-1190

1.0 Test Objectives

The primary test objective was to measure the surface temperature and the case temperature of two amplifier transistor assemblies by using a non-contact FLIR Systems infrared camera to determine if the junction temperatures calculated for the devices using Excel spreadsheet techniques and ICEPAK models are close to the measured test values. Test images are to aid in the determination of the impact on junction temperatures of mounting the circuits on either ALN (Alumina Nitride) or non-ALN substrates and the impact of thermally conductive silver epoxy versus non-conductive epoxy.

A secondary objective of the tests was to compare the client’s amplifier to a competitor’s device to determine if the client’s device provides a cooler and therefore a more reliable product.

2.0 Test Setup

1) Test set up and thermocouple instrumentation are shown in Figure 1.

2) Test sample size: two amplifier modules

3) Test Equipment

Description Manufacturer Model/Series

Infrared Camera FLIR Systems ThermaCam E-Series

Digital Multimeter Extech MP510

15 VDC Power Supply Paradyne A41506

Digital Thermometer Fluke HH501DK

Laptop Computer Dell Inspiron 8200

3.0 Test Procedure

Thermocouple data was measured for room ambient and the back surface of the metal housing. The units were each run one at a time off 15 VDC capable of supplying 600 mA and allowed to warm up for 15 minutes before taking infrared images. Thermocouples readings were monitored until a steady state temperature was reached on the outer metal case before close up thermal images were captured and stored for each amplifier assembly.

4.0 Test Results

Test samples are shown along with their corresponding thermal images in Figures 2 and 3. For sample amplifier Test Item #1, the measured lab ambient air temperature surrounding module was 23 ^oC and measured temperature of the back metal case after steady state was achieved was 43 ^oC. For Test Item #1 circuitry the maximum surface temperature measured was 166 ^oC at the lower left corner amplifier, which is the circled amplifier, highlighted in the close-up photo provided in Figure 2. The measured temperature at the circled amplifier on the lower right side of Figure 2 was 107 ^oC. The ceramic substrate surface temperature near the left lower high temperature amplifier was 110 ^oC.

For sample amplifier module Test Item #2 the measured lab ambient temperature was 22.4 ^oC and the metal case temperature at the back of the module was 51.7 ^oC. A maximum surface temperature of 150 ^oC was recorded in the lower left amplifier that was circled in the accompanying Figure 3. Maximum surface temperature of the amplifier on the right side of the module was 109 ^oC. and the measured temperature of the white ceramic substrate on the left circuit was 104 ^oC.

Figure 1. Thermal Test Set-Up