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MIL-STD 883 Steady-State Life Testing

MIL-STD 883 steady-state life testing demonstrates the reliability of devices subjected to the specified conditions over extended time periods. Tests should last long enough to assure results are not characteristic of early failures or “infant mortality.” Periodic observations of results should be made before completing the test to indicate significant variations of failure rate with time.

Valid results at shorter intervals or at lower stresses require accelerated test conditions or a sufficiently large sample size. This provides a reasonable probability of detecting failures in the sample. This will correspond to the distribution of potential failures in the lot(s) from which the sample was drawn. The test conditions that will be provided below are intended to reflect these considerations.

This test may be employed for the purpose of assessing the general capability of a device. It may also be used as a device qualification test in support of future device applications requiring high reliability. In these cases, the test conditions should be selected to represent the maximum operating or testing ratings of the device. This includes electrical input, load and bias and the corresponding maximum operating temperature or other specified environment.

Keystone Compliance is a full equipped reliability testing lab. Our test engineers have significant MIL-883 steady-state life testing experience. The following information is extremely technical as it provides a summary of the testing requirements of  Method 1005.11 MIL-STD 883 reliability testing.

What Equipment is Needed in a Steady-State Life Laboratory?

All MIL-883 reliability testing must be performed in a fully equipped reliability laboratory. A fully equipped steady-state life testing lab includes the following. Suitable sockets or mounting means are needed. This helps to make firm electrical contact to the terminals of devices in the specific configuration order.

Mounting means should not remove internally-dissipated heat from the device by conduction. Heat may be removed through the device terminals, the necessary electrical contacts and the gas or liquid chamber medium. The apparatus should provide for maintaining the specified biases at the terminals of the device. It should also provide for monitoring of the input excitation or output response, when specified.

Power supplies and current-setting resistors should be able to maintain the minimal specified operating conditions throughout the test. They must be able to maintain these conditions despite normal variations in source voltages, ambient temperatures, etc. When power dissipation occurs, the test apparatus should be arranged so the approximate average power dissipation for each device results.

The test circuits need not compensate for normal variations in individual device characteristics. However, they should allow for abnormal devices in a group without negating the effect of the test for other devices.

What Procedure Results in the Best Reliability Testing?

The microelectronic device is subjected to the specified test condition for the specified duration at the specified test temperature. The required measurements are made at the specified intermediate points and end points. QML manufactures who are certified and qualified may modify the time or the condition. The modification must be contained in the manufacturer’s QM plan, and “Q” certification identifier must be marked on the device.

Lead-, stud-, or case-mounted devices are mounted by the leads, stud, or case in their normal mounting configuration. The point of connection is maintained at a temperature not less than the specified ambient temperature. The test condition, duration, sample size, and temperature selected prior to the test is recorded and governs the entire test. Test boards can not employ load resistors which are common to more than one device or output pin.

What is the Appropriate Test Duration for the Best Steady-State Life Testing?

When testing for the standard life of devices, the test duration is 1,000 hours minimum at 125°C. After the specified duration, the device is removed from the test conditions and allowed to reach standard test conditions. When this test is used to demonstrate compliance with a specified lambda, it may end at the specified duration. Or it may end at the point of rejection if this occurs prior to the specified test duration.

When testing for accelerated life duration, the time is equivalent to 1,000 hours at 125°C for the ambient temperature specified. Within 72 hours of the specified duration of the test, the device is removed from the specified test conditions. It is then allowed to reach standard test conditions without removal of bias. Bias interruption for one minute as the device is moved to cool-down positions, is not considered removal of bias.

What Test Temperatures are Used for Steady-State Life Compliance Testing?

The specified test temperature is the minimum ambient temperature all devices in the working area of the chamber are exposed to. To ensure this, adjust chamber profile, loading, location of control/monitoring instruments, and flow of air or other suitable gases/liquids . Chamber calibration requires a fully loaded, unpowered configuration, with the indicator sensor reflecting the coldest point in the working area. Regardless of power level, devices shall be able to be life-tested at their maximum rated operating temperature.

For hybrid devices the ambient or case life test temperature is specified. Case temperature life testing is performed at the maximum operating case temperature (TC) specified for the device. The device should be life tested at the maximum specified operating temperature, voltage, and loading conditions. Case and junction temperature are normally much higher than ambient temperature.

The circuit should be structured so the maximum rated junction temperature and the cure temperature of polymeric materials are not exceeded. If no maximum junction temperature is specified, a maximum of 175°C is assumed. The specified test temperature is the minimum ambient or case temperature that must be maintained for all devices in the chamber.  To ensure this, adjust chamber profile, loading, location of control/monitoring instruments, and flow of air or other suitable gases/liquids.

For accelerated life testing, the minimum ambient test temperature is +175°C , unless otherwise specified. Accelerated testing is normally performed at temperatures higher than the maximum rated operating junction temperature of the device. Therefore, care should be taken to ensure that the device does not go into thermal runaway.

Special considerations are made for devices with internal thermal limitations. For these devices, extended exposure at a greater temperature, does not provide a realistic indicator of long-term operating reliability. For devices equipped with thermal shutdown, operating life test shall be performed at an ambient temperature. At this temperature, the worst case junction temperature is at least 5°C below the worst case thermal shutdown threshold.

Where is the Best Reliability Lab for Steady-State Life Certification?

Keystone Compliance is one of the best steady-state life labs in the country. Our test engineers understand the nuances of reliability compliance testing. This enables us to provide reliability certifications for various commercial, military, and  aerospace products. Contact us to learn why so many manufacturers rely on Keystone Compliance’s testing services to meet their compliance testing needs.

MIL-STD-883 testing contains several test methods. For more information about these test methods, please click on one of the links below.