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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 17th, 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

 

 

 

 

 

Figure 2. Sample Amplifier Test Item #1 and Thermal Image

 

 

Figure 3. Sample Amplifier Test Item #2

 

 

 

 

 

Figure 4. Test Sample #1 in Black and White and Iron Palettes

 

 

 

 

 

 

 

Figure 5. Test Sample #2 in Black and White and Iron Palettes

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Thermal Model of Amplifier Tharp 1/19/05

 

 

ICEPAK Model of Test Amplifer Sample #1

Adaptive Hexa Mesh with 24,169 Elements and 26,462 Nodes

 

 

ICEPAK Model of Amplifier #1

Hex Fine Mesh with 49,856 Elements and 54,054 Nodes

 

 

 

 

 

 

ICEPAK Model Showing Mesh of Surround Air and Boundary Conditions

 

 

 

ICEPAK Model Showing Heat Air Velocity Vectors above Die