Although environmental testing is closely related to reliability testing, they are quite different in some respects. Next, we will talk about the differences between the two and their related standards from the aspects of test purpose, test type, test time, the number of environmental stresses used, and the selection criteria for environmental force values.
Test purposes:
The environmental test examines the adaptability of the product to the environment, determines whether the environmental adaptability design of the product meets the requirements of the contract, and provides a decision-making basis for acceptance and rejection.
The reliability test is to quantitatively evaluate the reliability of the product, that is, the probability that the product will complete the specified function within the specified time under specified environmental conditions.
Test type:
Environmental tests usually use single-factor tests and multi-factor combination tests to act on the product in a certain order.
Reliability tests mostly use comprehensive stress tests, where multiple environmental stresses are applied to the samples in the same space and at the same time to more realistically simulate the influence of environmental conditions. In order to improve the accuracy and reliability of test results, environmental testing has also begun to focus on the development of comprehensive testing, and actively develop large-scale multifunctional environmental testing equipment that can simultaneously apply stress such as temperature, humidity, vibration, radiation, dust, wind, and rain.
Test time:
In the environmental test, the time of each test basically depends on the selected test and the specific test procedure, but there are some differences due to the different time required for performance testing at each stage, and the test time is much shorter than the reliability test.
The reliability test time depends on the reliability index value to be verified, the selected statistical test plan and the quality of the product itself. The time cannot be determined, until the total station hours of the tested product reaches the specified value or the decision of acceptance or rejection can be made.
Number of environmental stresses used:
Environmental test: GJB150 stipulates 19 test items, MIL-STD-810 D stipulates 20 environmental test items, 810F increases to 24 test items, including environmental stress that has a more important impact on the product, such as: temperature, humidity , salt spray, vibration shock, pressure, solar radiation, sand dust, rain, etc. The test items should be selected according to the environmental conditions of its future use and the degree of impact. Generally, more than 10 environmental stresses should be investigated.
Reliability test: Due to the need for comprehensive simulation, only comprehensive environmental stress (temperature, humidity, vibration) and electrical stress are combined for testing. It can be seen that the number of environmental stresses used in the reliability test is much less than that of the environmental test.
Environmental stress value selection criteria:
The environmental test basically adopts extreme value conditions, and replaces mildness with harshness, that is, the most extreme environmental conditions that the product may encounter during its life cycle are used as test conditions. Many tests are destructive and generally do not need to simulate the working state of the product during the test.
The reliability test adopts the actual effect test, that is to truly simulate the main environmental conditions encountered in the process of storage, transportation and use and their dynamic change process. In GJB-889 and the corresponding MIL-STD-781 D, a set of methods to determine the environmental profile according to the task profile, and then simplify the environmental profile to the test profile for long-term reliability assessment of the product is specified. Generally, the reliability test will not cause damage to the product. It needs to simulate the working state of the product. Most of the test conditions used simulate the milder stress environment often encountered in the work, and the value is much lower than that of the environmental test.
Main Types of Environmental Tests
1. Climatic environment test
Including high temperature test, low temperature test, rapid temperature change test, temperature shock test, constant temperature and humidity test, temperature and humidity cycle test, salt spray test, waterproof and dustproof test, ultraviolet aging test and xenon lamp aging test, etc. It is one of the important test methods to evaluate the product reliability and assess the adaptability of the product under various environmental conditions.
Execution test standards include GB2423, GJB150A, GJB4, IEC60068, GJB1032, GJB322A, GJB360A, GJB548, GB4208, GJB899, TB3021, etc.
2. Mechanical environmental test
It mainly includes mechanical vibration, mechanical shock, other tests (drop, collision, acceleration test), etc.
Execution test standards include GB2423, GJB150A, GJB4, IEC60068, GJB1032, GJB322A, GJB360A, GJB548, TB3058, GJB899, GB/T21563, ISO16750, etc.
3. Comprehensive environmental reliability test
Including temperature and humidity combination test, temperature + humidity + vibration comprehensive test (three comprehensive tests).
Meet the requirements of GJB, GB, GB/T, IEC, ISO, EN, MIL-STD, SAE, ASTM, ISTA, JIS, IPC, JEDEC, GM, NISSAN and other international and domestic environmental and reliability test standards, and meet relevant Military standard requirements.
List of environmental and reliability test standards (excluding GJB)
Climatic environment test:
Mechanical tests:
Comprehensive test:
