IEC 62047-37:2020 pdf download-Semiconductor devices – Micro-electromechanical devices.
4.4 Post-treatment After completion of the tests, first the application of mechanical stress and strain, or vibration, is halted, and then the DUT is removed from the chamber and returned to standard conditions. However, this shall not apply to cases in which the DUT clearly recovers from its degraded state after the application of mechanical stress and strain, or vibration, is halted at the testing temperature because a correct result is not possible. 4.5 Final measurements The methods of measurement used in moist heat tests shall conform to the methods set forth in IEC 62047-30. The degraded state of a DUT is evaluated by comparing the final measurements to the initial measurements. The environmental conditions for measurements shall include: • ambient temperature: 25 °C ± 3 °C; • relative humidity: 45 % to 75 %; • atmospheric pressure: 86 kPa to 1 06 kPa. As a general rule, final measurements shall be conducted within 48 h from the completion of tests after verifying that the surface of the DUT is dry. When conducting intermediate measurements prior to the final measurements, the DUT shall be deposited back into the testing chamber within 96 h after being removed for measurements. Final measurements are preferably completed within 96 h after halting voltage application to the DUT. 5 Environmental and dielectric withstand testing 5.1 Environmental testing 5.1.1 General Equipment used in these experiments includes: • a chamber or a room capable of maintaining predetermined test temperature and humidity and allowable temperature and humidity; • a vibrator or an external actuator for generating a predetermined deflection of the unimorph beam; • a mechanical stress and strain, or vibration, application equipment having sufficient resistance for withstanding the test temperatures and humidity.
The chamber shall be capable of maintaining its entire interior at the set temperature ±2 °C and the set humidity ±5 % during the test. The applied mechanical stress and strain, and the operating method shall be established with consideration for the limits of the DUT. The application circuit shall be considered to account for load conditions and other factors in order that the operating state of the DUT be suitably maintained. NOTE 1 The degree of degradation in a device under test (DUT) is evaluated by measuring the piezoelectric properties of the DUT before and after applying the environmental stress of temperature and humidity. NOTE 2 The degree of degradation in a DUT is evaluated using the measurement methods in IEC 62047-30. NOTE 3 A test circuit for testing a plurality of DUT simultaneously is designed so that failure of one DUT during a test does not affect the other DUT.