How to Plan and Conduct Highly Accelerated Life Testing |
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Conducting a HALT HALT is comprehensive and encompasses several testing phases, each with specific parameters to follow. Thermal Step StressThermal step-stress testing applies incremental temperature stress levels throughout the product life cycle in order to identify product failure modes. Connect the power and functional test equipment to the DUTs. Additional product-specific stresses may or may not be applied depending on the application.Begin with cold step stress, followed by hot step stress.Initially use 10 °C increments, decreasing to 5 °C increments as limits are approached.Set the dwell time minimum at 10 minutes plus the time needed to run a functional test. Timing should commence once the temperature being monitored on the DUT has reached its set point.Continue the test until operating and destruct limits are determined, or maximum stress as dictated by the test plan.Thermal Shock CyclingThermal shock cycling is conducted between the DUT’s operating limits determined above. This exposes the DUT to fast thermal transitions, sometimes 60 ˚C per minute or as fast as the testing equipment/chamber allows. Connect the power and functional test equipment to the DUTs. Additional product-specific stresses may or may not be applied depending on the application.Keep the temperature range between 10 °C below the upper operating limit and 10 ˚C above the lower operating limit determined during step-stress testing.If the sample cannot withstand maximum thermal transitions, decrease the transition rate by 10 °C per minute until the allowable rate is found.Continue hot and cold thermal transitions with 10-minute dwells at each extreme for five total cycles. Vibration Step StressVibration step stress testing applies incremental vibrational stress levels in order to identify product failure modes. Connect the power and functional test equipment to the DUTs. Additional product-specific stresses may or may not be applied (power cycling, line voltage/frequency margining, etc.), depending on the application.Determine the G-level root mean square (Grms) increments, typically ranging from 3-5 Grms on product.Set the dwell time minimum at 10 minutes plus the time needed to run a functional test.At 30 Grms and above, perform “tickle” vibration between setpoint vibrations. The tickle vibration is performed at 5 Grms while performing the functional check.Continue the test until the operating and destruct limits are determined, or maximum stress as dictated by the test plan.Combine Vibration and Thermal Shock TestingMerge testing results and methodologies to further test products. Connect the power and functional test equipment to the DUTs. Additional product-specific stresses may or may not be applied (power cycling, line voltage/frequency margining, etc.), depending on the application.Use the vibration destruct limit and divide by 5 to determine the step increase at each of the five thermal cycles for this test.Use the thermal shock cycle limits and ramp rate for the five thermal cycles.At 30 Grms and above, perform a “tickle” vibration between setpoint vibrations (to manifest failure modes not evident under high vibration amplitudes or static conditions). The tickle vibration is performed at 5 Grms while performing the functional check.Post-HALT ProcessOnce HALT is completed, the design engineers’ focus becomes determining the root causes of all failures and corrective action. This can include identifying the failure site and failure mechanism for each failure mode. Afterwards, a verification HALT needs to be implemented to evaluate if testing adjustments fixed the problems. Ansys Sherlock can shortcut this process by creating simulations based on testing models before any physical sample modification or the verification HALT takes place, saving time and money. In addition, our Reliability Engineering Services team can perform Accelerated Life Testing once the weak points in the design have been resolved and final testing required. Contact us today to discuss how we can help streamline your HALT process and accurately confirm results. |
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