Power Cycle Test Methods
The following description provides a step by step procedure for setting up a power cycling test for a chosen device. The first step is to perform a complete thermal characterization of the device. This includes the usual preliminary step of junction-thermal-calibration and measurement of the transient thermal impedance, junction-to-coolant with the device mounted on the intended test fixture. This fixture can be either a single device liquid-cooled test fixture such as the Rjc Liquid Cooled Fixture, Rjc Liquid Universal XY, or the Power Cycler for testing multiple devices simultaneously. The following plot shows a heating curve for a particular device mounted to a particular test fixture with a particular base-plate thermal grease mounting.
The associated cumulative structure function is computed automatically from the transient thermal characterization:
Once the thermal transient characterization is completed, the response of the device can be simulated with the Power Cycle Wizard to determine the expected thermal response of this device to any prospective power cycle. The Power Cycle Wizard application allows the user to explore the complete range of power cycle options and interactively design the desired junction temperature cycle prior to commencing power cycle testing. The following Power Cycle Wizard input screen is shown with the associated junction temperature projection plot.
Once the desired power cycle has been designed with the Power Cycle Wizard, power cycling can commence. The following two screens show the Power Cycle Condition setting screen, device Recalibration screen and then the Power Cycle Test screen.
The following sample data plot shows the progressive deterioration of the thermal impedance of the device caused by cyclic thermal aging.
Without the Power Cycler hardware accessory, users are limited to minimum duration intervals of 1 second for power-ON and for power-OFF, and can of course only test one device at time. Otherwise the Power Cycling software features of WinTherm offer long-term cyclic thermal testing with contiguous periodic monitoring of the device thermal properties and their progressive deterioration with time.