Reliability testing should be after the reliability design, but the current reliability work in China is still in the testing stage, and the test will be put in front here. In order to measure the reliability of the product (that is, to measure the MTBF of the product), we need to take out certain samples and do a long-term running test to find the failure time of each sample and calculate it according to the formula in the first section Out of MTBF, of course, the more samples, the more accurate the test results. However, such an ideal test is actually impossible, because for this test, it is necessary to wait until the last sample fails-the test time required is unimaginably long, and it takes all samples to fail-the cost required Unimaginably high.
In order to test the reliability, here is introduced: accelerated testing (that is, increasing stress *) to make defects appear quickly; after a large number of experts and long-term statistics, some methods of increasing stress have been found and converted into some test items. If the product is tested through these items and there are still no obvious defects, it means that the reliability of the product can reach at least a certain level, and MTBF can be calculated after conversion (because the product can pass these tests, no obvious defects appear, indicating that it has not been reached The ultimate capacity of the product, so the corresponding MTBF at this time is the minimum value of the product). See below for other calculation methods. (* Stress: refers to the destructive power of the external environment on the product. For example, the stress at 85 ℃ is greater than the stress at 25 ℃; working under high stress, the possibility of product failure is greatly increased);
1. Environmental testing
In the process of using the product, there are different use environments (some are installed outdoors, some are carried around, some are installed on the ship, etc.), and they will be stressed by different environments (some are exposed to wind and rain, some are subject to vibration and drop, some are Subject to salt spray corrosion, etc.); in order to confirm that the product can work normally in these environments, the national standard and the industrial standard require the product to simulate some test items in the environmental method. These test items include:
1. High temperature test (high temperature operation, high temperature storage);
2. Low temperature test (low temperature operation, low temperature storage);
3. High and low temperature alternating test (temperature cycle test, thermal shock test);
4. High temperature and high humidity test (damp heat storage, damp heat cycle);
5. Mechanical vibration test (random vibration test, sweep frequency vibration test);
6. Automobile transportation test (simulated transportation test, crash test);
7. Mechanical shock test;
8. Switching electrical test;
9. Power bias test;
10. Cold start test;
11. Salt spray test;
12. Rain test;
13. Dust and sand test;
The relevant national standards for the above environmental tests are as follows (some tests may not have relevant national standards, or I have not found them yet):
1. Low temperature test According to GB / T2423.1-89 "Part 2 of Environmental Test for Electrical and Electronic Products: Test Method Low Temperature Test";
GB / T2423.22—87 "Part 2 of Environmental Test for Electrical and Electronic Products: Test Method Temperature Change Test Method"
Carry out low temperature test and temperature change test.
Temperature range: -70 ℃ ～ 10 ℃.
2. High temperature test According to GB / T2423.2-89 "Part 2 of Environmental Test for Electrical and Electronic Products: Test Method High Temperature Test";
GB / T2423.22—87 "Part 2 of Environmental Test for Electrical and Electronic Products: Test Method Temperature Change Test Method"
Carry out high temperature test and temperature change test.
Temperature range: 10 ℃ ～ 210 ℃
3. Damp heat test
According to GB / T2423.3-93 "Part 2 of Environmental Test for Electrical and Electronic Products: Test Method Constant Damp Heat Test";
GB / T2423.4-93 "Part 2 of Environmental Test for Electrical and Electronic Products: Test Method Alternating Damp Heat Test"
Carry out constant humid heat test and alternating humid heat test.
Humidity range: 30% RH ～ 100% RH
4. Mold test
According to GB / T2423.16-90 "Electrical and Electronic Products Environmental Test Part II: Test Method Long Mold Test" for mold testing.
5. Salt spray test
Carry out the salt spray test according to GB / T2423.17-93 "Part 2 of Environmental Tests for Electrical and Electronic Products: Test Method Salt Spray Test".
6. Low pressure test
According to GB / T2423.21-92 "Part 2 of Environmental Test for Electrical and Electronic Products: Test Method Low Pressure Test";
GB / T2423.25—92 "Part 2 of Environmental Test for Electrical and Electronic Products: Test Method Low Temperature / Low Pressure Test";
GB / T2423.26-92 "Part 2 of Environmental Test for Electrical and Electronic Products: Test Method High Temperature / Low Pressure Test";
Conduct low pressure test, high and low temperature / low pressure test. Test range: -70 ℃ ～ 100 ℃ 0 ～ 760mmHg20% ～ 95% RH.
7. Vibration test
Carry out the vibration test according to GB / T2423.10-95 "Part 2 of Environmental Tests for Electrical and Electronic Products: Test Method Vibration Test".
Frequency range (mechanical vibration table): 5 ~ 60Hz (fixed frequency vibration 5 ~ 80Hz), maximum displacement amplitude 3.5mm (full load). Frequency range (electromagnetic vibration table): 5 ～ 3000Hz, maximum displacement 25mmP-P.
8. Impact test
Carry out the impact test according to GB / T2423.5-95 "Part 2 of Environmental Tests for Electrical and Electronic Products: Test Method Impact Test". Impact acceleration range: (50 ～ 1500) m / s2.
9. Crash test
Carry out the crash test according to GB / T2423.6-95 "Part 2 of Environmental Tests for Electrical and Electronic Products: Test Method Crash Test"
10. Drop test
According to GB / T2423.7-95 "Part 2 of Environmental Tests for Electrical and Electronic Products: Test Methods for Dipping and Overturning Test";
GB / T2423.8-95 "Electrical and Electronic Products Environmental Test Part II: Test Method Free Drop Test" for drop test.
Note: The above 13 items provide a more comprehensive overview of the external environment encountered during the use of the product; during actual testing, because the differences in the properties of the products themselves are far away, and the use environment is also very different, companies can choose according to the characteristics of the products , Appropriately select and add some items to test (the required test items required by the national / line standard corresponding to this product, of course, must be tested); you can also design some new test items according to the specific use environment and use method of the product To verify that the product can work for a long time.
Test conditions: Different products have different test conditions; for high temperature test, some products require high temperature storage test, some require high temperature operation test, some products use high temperature test at 85 ℃, and some products use 65 Test at ℃. However, there is only one purpose, and that is to at least meet the national standards. To test the reliability of a product, it is necessary to find the national / line standard of this product. According to the requirements and guidelines of the national / line standard, find the necessary test items and test methods for each item to carry out environmental testing;
The same product has different test conditions at different stages; in general, the product will go through three different stages of research and development, small batch trial production, and mass production. In the R & D phase, the test conditions are the most stringent (the stress is greatest) and the test duration is the shortest; the small batch trial production stage, the test stress is moderate and the test time is moderate; the mass production stage, the test stress is the minimum and the test time is short; the three stages The main differences are shown in the table below:
The purpose of the phase experiment is the experimental characteristics. The experiment requires R & D to find design defects, expand the design margin, high stress, short-term failure-free pilot test to check whether the product reaches the basic reliability level, medium stress, and long-term no obvious failure. The production process conditions are stable Low-stress, short-term and conditionally allow faults to occur. Identify the reliability of the product, calculate the MTBF of the product. Low stress, no special requirements for a long time
Accelerated environmental test technology The traditional environmental test is a test method based on real environment simulation, called environmental simulation test. The characteristics of this test method are: simulation of the real environment, plus design margins, to ensure that the test passes. The disadvantage is that the efficiency of the test is not high, and the resource consumption of the test is huge.
In order to test the reliability, here is introduced: accelerated testing (that is, increasing stress *) to make defects appear quickly; after a large number of experts and long-term statistics, some methods of increasing stress have been found and converted into some test items. If the product is tested through these items and there are still no obvious defects, it means that the reliability of the product can reach at least a certain level, and MTBF can be calculated after conversion (because the product can pass these tests, no obvious defects appear, indicating that it has not been reached The ultimate capacity of the product, so the corresponding MTBF at this time is the minimum value of the product). See below for other calculation methods. (* Stress: refers to the destructive power of the external environment on the product. For example, the stress at 85 ℃ is greater than the stress at 25 ℃; working under high stress, the possibility of product failure is greatly increased);
1. Environmental testing
In the process of using the product, there are different use environments (some are installed outdoors, some are carried around, some are installed on the ship, etc.), and they will be stressed by different environments (some are exposed to wind and rain, some are subject to vibration and drop, some are Subject to salt spray corrosion, etc.); in order to confirm that the product can work normally in these environments, the national standard and the industrial standard require the product to simulate some test items in the environmental method. These test items include:
1. High temperature test (high temperature operation, high temperature storage);
2. Low temperature test (low temperature operation, low temperature storage);
3. High and low temperature alternating test (temperature cycle test, thermal shock test);
4. High temperature and high humidity test (damp heat storage, damp heat cycle);
5. Mechanical vibration test (random vibration test, sweep frequency vibration test);
6. Automobile transportation test (simulated transportation test, crash test);
7. Mechanical shock test;
8. Switching electrical test;
9. Power bias test;
10. Cold start test;
11. Salt spray test;
12. Rain test;
13. Dust and sand test;
The relevant national standards for the above environmental tests are as follows (some tests may not have relevant national standards, or I have not found them yet):
1. Low temperature test According to GB / T2423.1-89 "Part 2 of Environmental Test for Electrical and Electronic Products: Test Method Low Temperature Test";
GB / T2423.22—87 "Part 2 of Environmental Test for Electrical and Electronic Products: Test Method Temperature Change Test Method"
Carry out low temperature test and temperature change test.
Temperature range: -70 ℃ ～ 10 ℃.
2. High temperature test According to GB / T2423.2-89 "Part 2 of Environmental Test for Electrical and Electronic Products: Test Method High Temperature Test";
GB / T2423.22—87 "Part 2 of Environmental Test for Electrical and Electronic Products: Test Method Temperature Change Test Method"
Carry out high temperature test and temperature change test.
Temperature range: 10 ℃ ～ 210 ℃
3. Damp heat test
According to GB / T2423.3-93 "Part 2 of Environmental Test for Electrical and Electronic Products: Test Method Constant Damp Heat Test";
GB / T2423.4-93 "Part 2 of Environmental Test for Electrical and Electronic Products: Test Method Alternating Damp Heat Test"
Carry out constant humid heat test and alternating humid heat test.
Humidity range: 30% RH ～ 100% RH
4. Mold test
According to GB / T2423.16-90 "Electrical and Electronic Products Environmental Test Part II: Test Method Long Mold Test" for mold testing.
5. Salt spray test
Carry out the salt spray test according to GB / T2423.17-93 "Part 2 of Environmental Tests for Electrical and Electronic Products: Test Method Salt Spray Test".
6. Low pressure test
According to GB / T2423.21-92 "Part 2 of Environmental Test for Electrical and Electronic Products: Test Method Low Pressure Test";
GB / T2423.25—92 "Part 2 of Environmental Test for Electrical and Electronic Products: Test Method Low Temperature / Low Pressure Test";
GB / T2423.26-92 "Part 2 of Environmental Test for Electrical and Electronic Products: Test Method High Temperature / Low Pressure Test";
Conduct low pressure test, high and low temperature / low pressure test. Test range: -70 ℃ ～ 100 ℃ 0 ～ 760mmHg20% ～ 95% RH.
7. Vibration test
Carry out the vibration test according to GB / T2423.10-95 "Part 2 of Environmental Tests for Electrical and Electronic Products: Test Method Vibration Test".
Frequency range (mechanical vibration table): 5 ~ 60Hz (fixed frequency vibration 5 ~ 80Hz), maximum displacement amplitude 3.5mm (full load). Frequency range (electromagnetic vibration table): 5 ～ 3000Hz, maximum displacement 25mmP-P.
8. Impact test
Carry out the impact test according to GB / T2423.5-95 "Part 2 of Environmental Tests for Electrical and Electronic Products: Test Method Impact Test". Impact acceleration range: (50 ～ 1500) m / s2.
9. Crash test
Carry out the crash test according to GB / T2423.6-95 "Part 2 of Environmental Tests for Electrical and Electronic Products: Test Method Crash Test"
10. Drop test
According to GB / T2423.7-95 "Part 2 of Environmental Tests for Electrical and Electronic Products: Test Methods for Dipping and Overturning Test";
GB / T2423.8-95 "Electrical and Electronic Products Environmental Test Part II: Test Method Free Drop Test" for drop test.
Note: The above 13 items provide a more comprehensive overview of the external environment encountered during the use of the product; during actual testing, because the differences in the properties of the products themselves are far away, and the use environment is also very different, companies can choose according to the characteristics of the products , Appropriately select and add some items to test (the required test items required by the national / line standard corresponding to this product, of course, must be tested); you can also design some new test items according to the specific use environment and use method of the product To verify that the product can work for a long time.
Test conditions: Different products have different test conditions; for high temperature test, some products require high temperature storage test, some require high temperature operation test, some products use high temperature test at 85 ℃, and some products use 65 Test at ℃. However, there is only one purpose, and that is to at least meet the national standards. To test the reliability of a product, it is necessary to find the national / line standard of this product. According to the requirements and guidelines of the national / line standard, find the necessary test items and test methods for each item to carry out environmental testing;
The same product has different test conditions at different stages; in general, the product will go through three different stages of research and development, small batch trial production, and mass production. In the R & D phase, the test conditions are the most stringent (the stress is greatest) and the test duration is the shortest; the small batch trial production stage, the test stress is moderate and the test time is moderate; the mass production stage, the test stress is the minimum and the test time is short; the three stages The main differences are shown in the table below:
The purpose of the phase experiment is the experimental characteristics. The experiment requires R & D to find design defects, expand the design margin, high stress, short-term failure-free pilot test to check whether the product reaches the basic reliability level, medium stress, and long-term no obvious failure. The production process conditions are stable Low-stress, short-term and conditionally allow faults to occur. Identify the reliability of the product, calculate the MTBF of the product. Low stress, no special requirements for a long time
Accelerated environmental test technology The traditional environmental test is a test method based on real environment simulation, called environmental simulation test. The characteristics of this test method are: simulation of the real environment, plus design margins, to ensure that the test passes. The disadvantage is that the efficiency of the test is not high, and the resource consumption of the test is huge.
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