Thermal Model Comparison
For use with Thermalyze thermal image analysis software
Thermal Model Comparison (TMC) tests are used to troubleshoot populated circuit board to detect and locate the following faults:
How It Works
TMC (see Figure 1) is a process of comparing the thermal behavior of an electronic device to known operational devices as the devices are electrically exercised. Comparison tests can detect small temperature differences between functional and defective devices that are nearly impossible to detect using other methods. Entire circuit boards can be analyzed at once.
Thermalyze Software: See Thermalyze Operation documentation for Thermal Model Comparison features and operation.
Test Tip: For a thermal model comparison test to be performed properly, the camera and device must not move while testing both the golden boards and defective boards.
Figure 1: Thermal Model Comparison window
Powering Circuit Boards
When performing TMC tests, boards can be electrically exercised in several different ways, depending on the nature of suspected defects. For example, in no fault found conditions, circuit boards can be powered for normal boot-up. If a full boot-up comparison test is inconclusive however, voltage can be applied to individual power rails to narrow down the search area and number of suspect components. When in-circuit test identifies a short between nodes, the circuit on which the fault lies can be separately powered using probes or by soldering leads onto the board.
One or more known good boards must first be tested under power to develop a thermal model that defines how non-defective boards should behave. After the model has been created, test boards are powered in the same manner as the golden boards and their thermal behavior is compared to the golden board model. Thermal deviations from the model are used to identify suspect board areas and components.
Unlike lock-in thermography that typically pinpoint isolated heating, TMC tests may detect and display several areas with different thermal behavior than the golden board model. Engineers and technicians use this information, along with technical schematics, to determine likely fault modes. Success is highly dependent on the troubleshooter’s knowledge and experience.
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