Accelerated storage life test evaluation method for electronic products

Abstract

The present invention relates to an accelerated storage life test and evaluation method for electronic products, belonging to the technical field of accelerated storage life testing. This method addresses the deficiencies in prior art domestic equipment storage life and reliability research, as well as the low storage life testing and evaluation capabilities of electronic products. The method comprises: performing a high-temperature stress test on the product to be evaluated to determine the number and duration of failures that occurred during the high-temperature stress test; calculating the total test time under normal temperature stress based on the number and duration of failures during the high-temperature stress test; and evaluating the product's storage life based on the total test time under normal temperature stress.

Description

Technical Field

[0001] The present invention relates to the technical field of accelerated storage life test, and in particular to an accelerated storage life test evaluation method for electronic products. Background Art

[0002] With the rapid advancement of contemporary high-tech, newer, higher and stricter technical requirements have been put forward for various electronic product systems. Subsystem-level and important equipment-level products are required to have a longer lifespan and higher reliability indicators.

[0003] Currently, the development of electronic product systems has shifted its focus to comprehensively improving system performance and meeting actual operational needs, placing higher demands on the overall performance of the system throughout its lifecycle. Relevant data indicates that storage reliability is as important as mission reliability. To reduce support requirements and shorten technical preparation time, newly developed products are required to be shipped, tested, and maintained in full lifecycle condition. This requires higher storage reliability for their subsystems and key equipment. To ensure operational integrity and mission success, it is essential to understand the product's storage life in order to effectively improve its storage reliability.

[0004] The research on accelerated life test methods abroad has a history of more than 50 years. The test method of increasing stress is used to accelerate product failure, shorten the test time, and select the corresponding acceleration model to estimate the life (or reliability) characteristic value of the product under normal stress.

[0005] The United States and Russia are the primary foreign countries conducting accelerated life testing research. Russia has implemented a series of measures to improve the storage reliability of electronic product systems. The widespread, standardized, and effective application of accelerated life testing during engineering development has been highly successful. A six-month accelerated storage life test can yield a 10-year storage life, ensuring that the system meets the required unpacking pass rate and mission success rate requirements without requiring repairs during the 10-year storage period. This enables the electronic system to achieve the very high storage reliability indicators typically expected of electromechanical products. This accelerated testing methodology, developed in Russia, draws upon years of engineering practice. It simulates the product on simulated equipment and requires the development of several models. The test loading conditions include electrical stress, temperature stress, and mechanical stress (vibration and shock). This method can be used to perform accelerated storage life testing not only on components and materials, but also on equipment, subsystems, and systems, making it highly cost-effective. In the early stages of storage life and reliability research in the United States, natural storage methods were employed, as well as information from field storage tests. After new models were delivered, most were stored for long periods without testing, while a small number underwent periodic testing. Testing of small batches allows monitoring of the entire batch and estimation of the storage reliability of the entire batch.

[0006] For a long time, domestic storage life and reliability research has relied on analysis of system-wide vibration test data, comprehensive stress test data, system benchtop joint test data, inventory inspection data, field storage test data, and other relevant test data. Determining the storage reliability and lifespan of electronic product systems requires years of use. This approach is not only time-consuming but also requires significant human, material, and financial resources. Especially for newly developed equipment, the inability to determine the storage lifespan at the time of finalization severely impacts its use and maintenance. During the development phase, it is difficult to simulate the full lifecycle environment for testing and verification, thereby providing scientific storage reliability and lifespan indicators.

[0007] Overall, the level of equipment storage life and reliability research in China lags far behind that of international research, and storage reliability testing and evaluation capabilities are severely inadequate. Incomplete data on basic materials and corresponding accelerated performance, particularly the lack of accelerated testing methods and corresponding data, has severely hampered the implementation of accelerated storage testing for system-level, subsystem-level, and critical equipment-level products.

[0008] Typical electronic product storage life assessment methods utilize a combination of engineering and statistical analysis, assessing the storage life based on the specific product characteristics. During the engineering development phase, simulated storage testing under laboratory conditions identifies weaknesses, calculates the actual environmental conditions or aging processes to which the product will be subjected throughout its storage period, and implements effective improvement measures to achieve a product storage life that meets specified requirements. Evaluating product storage periods of up to ten or even twenty years through relatively short testing periods can improve testing efficiency, reduce testing costs, and achieve significant financial savings. In-depth research on this topic will significantly advance the development of product life extension technology.

[0009] By studying electronic product storage life assessment tests, appropriate and reasonable recommendations can be made for the development and optimization of product storage environments and related packaging technologies. Furthermore, this research can enable hierarchical management of electronic equipment storage, ensuring the integrity of electronic equipment at the lowest possible lifecycle cost, improving availability, and reducing maintenance and logistics costs, ultimately achieving the goal of "doubling reliability and halving maintenance or costs." Therefore, this research has strong practical significance. Summary of the Invention

[0010] In view of the above analysis, the embodiments of the present invention aim to provide an accelerated storage life test evaluation method for electronic products to address the deficiencies in existing domestic equipment storage life and reliability research, and the low storage life test and evaluation capabilities of electronic products.

[0011] In one aspect, an embodiment of the present invention provides a method for evaluating an electronic product's accelerated storage life test, comprising:

[0012] Perform high temperature stress tests on the products to be evaluated to obtain the number of failures and failure time of the electronic products during the high temperature stress tests;

[0013] Calculate the total test time under normal temperature stress based on the number of failures and failure time during the high temperature stress test;

[0014] The product storage life is evaluated based on the total test time under the normal temperature stress.

[0015] Furthermore, the high temperature stress test is performed on the product to be evaluated to obtain the number of failures and the failure time of the electronic product during the high temperature stress test, including:

[0016] Stage high temperature stress test, including: j The high temperature stress of the j-th stage high temperature stress test is tested on n products. j After keeping warm for M days, the device is restored to normal temperature stress T0. After keeping warm for N hours under normal temperature stress, a power-on test is performed, where the initial value of j is 1.

[0017] If there is no fault or a Class B fault occurs after power-on, the j+1 stage high temperature stress test will be continued with the current stage test temperature as the high temperature stress of the j+1 stage high temperature stress test;

[0018] If a type A fault occurs after power is turned on, the high temperature stress T j Minus T th Afterwards, the j+1 stage high temperature stress test is performed as the high temperature stress of the j+1 stage high temperature stress test;

[0019] When the test time reaches the total test time T z , or when the number of Class A faults reaches k, the test ends;

[0020] Count the number of Class A failures i of the product to be evaluated during the high temperature stress test and the failure time t corresponding to the i-th Class A failure i .

[0021] Furthermore, the failure time is the time corresponding to the start of the first stage high temperature stress test to the detection of the i-th type A failure;

[0022] The product to be evaluated is in a powered-on state during normal temperature stress testing and is in a powered-off state during other stages of the test.

[0023] Furthermore, the total test time under normal temperature stress is calculated based on the number of failures and failure time during the high temperature stress test, including:

[0024] Obtain the test time conversion coefficient of the product to be evaluated, and calculate the test time conversion coefficient based on the test time conversion coefficient, the number of Class A failures i in the high temperature stress test, and the failure time t corresponding to the i-th Class A failure. i , calculate the total test time of the product under normal temperature stress through the product test time conversion formula.

[0025] Furthermore, the conversion formula is expressed as:

[0026]

[0027] Where T is the total test time of n products converted to normal stress, b is the product test time conversion coefficient, T0 is normal stress, t1 is the failure time corresponding to the first failure, t i is the failure time corresponding to the i-th failure, and k is the upper limit of the number of failures.

[0028] Furthermore, the evaluation of the product storage life according to the total test time under normal temperature stress includes:

[0029] Obtain the critical value and confidence level of the chi-square distribution of the product, and calculate the storage life of the product by evaluating the product storage life formula based on the critical value and confidence level of the chi-square distribution of the product and the total test time under the normal temperature stress.

[0030] Furthermore, the formula for evaluating the shelf life of the product is expressed as:

[0031]

[0032] in, is the evaluation life of the product, T is the total test time of n products converted to normal stress, χ is the critical value of chi-square distribution, α is the confidence level, 1-α is the confidence level, and n is the number of products.

[0033] Furthermore, the high temperature stress is less than the test extreme temperature of the electronic product;

[0034] During the accelerated storage life test, the temperature change rate of the electronic product is 5℃ / min.

[0035] Furthermore, the insulation for M days and N hours must satisfy the temperature balance inside the electronic product during the test.

[0036] Furthermore, the Class A failure refers to a failure of the test product caused by improper production or component defects during the test, which is the basis for determining the environmental stress limit value of the test product, including:

[0037] Failure caused by improper production of parts or defective components; or

[0038] Unconfirmed fault: refers to a fault that cannot be reproduced or the cause of which has not yet been determined;

[0039] The Class B failures mentioned above refer to failures of the test product caused by reasons other than design. Class B failures are not used as a basis for determining the environmental stress limit values ​​of the test product, and include:

[0040] Failure of the test product due to failure of the test equipment provided by the laboratory, or the instruments and meters used for testing; or

[0041] Failures caused by improper operation, maintenance and repair of the test products by personnel.

[0042] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0043] 1. The accelerated storage life test of electronic products proposed by the method of the present invention fills the gap in the relevant field in China;

[0044] 2. The present invention is applicable to my country's existing industrial base and experimental conditions and is easy to industrialize;

[0045] 3. The present invention solves the problem of life assessment of electronic products by evaluating the storage life of small samples of electronic products, while minimizing the loss of equipment or inventory equipment;

[0046] 4. Compared with existing evaluation methods, the life evaluation results obtained by the present invention are more realistic, accurate, and reasonable in that the test starting temperature of the present invention is selected to be close to the temperature limit of the product components. At the same time, the test time of the electronic product storage life test is shortened. The temperature range is covered widely, the time efficiency is high, the number of samples consumed is small, and the results are more realistic, accurate, and reasonable.

[0047] 5. Compared with the previous method of using large-scale comprehensive stress test data, regular inspection data and other related test data, the method proposed by the present invention for estimating the storage life of electronic products saves more manpower, material resources, financial resources and other resources;

[0048] 6. Based on the results obtained by this invention, measures to extend the life of the product can be implemented to achieve the goal of extending the life of the product.

[0049] In the present invention, the above-mentioned technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of the present invention will be described in the following description, and some advantages will become apparent from the description or be learned through practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] The accompanying drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like parts throughout the drawings.

[0051] Figure 1 This is a flow chart of an accelerated storage life test evaluation method for electronic products according to one embodiment of the present application;

[0052] Figure 2 This is a cross-sectional view of a high-temperature stress test at different stages of accelerated storage life shown in one embodiment of the present application;

[0053] Figure 3 This is a schematic diagram of an accelerated storage life evaluation test shown in one embodiment of the present application. DETAILED DESCRIPTION

[0054] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, and are not used to limit the scope of the present invention.

[0055] A specific embodiment of the present invention discloses a method for evaluating the accelerated storage life test of an electronic product, such as Figure 1 As shown, including:

[0056] S10. Perform a high-temperature stress test on the product to be evaluated to obtain the number of failures and failure time of the electronic product during the high-temperature stress test; optionally, in order to ensure the authenticity, accuracy, rationality and effectiveness of the test results, at least 6 sets of products to be evaluated are selected for testing based on the rationality of sampling and the minimum sample data requirements for evaluation implementation.

[0057] Specifically, to ensure the accuracy of the product life assessment results, the performance test for the accelerated storage life test should be conducted after the product is installed in the experimental equipment, ensuring that the equipment is in a normal state before the test. During the test, the test product needs to be returned to room temperature. However, the product is powered on during the normal temperature stress test and is not powered on during the other stages of the test.

[0058] Specifically, the accelerated storage life test of the product is conducted using a step-back stress profile. The step-back stress test begins at the highest stress level and is performed using a constant truncation method. Each time a Class A failure occurs, the stress level is reduced by one. This process is repeated. When three Class A failures occur during the test, the test is terminated and the life assessment is performed. More specifically, the high-temperature stress test is performed on the product to be assessed, and the number of failures and the time of failure of the electronic product during the high-temperature stress test are obtained, including:

[0059] S101, stage high temperature stress test, including:j The high temperature stress of the j-th stage high temperature stress test is tested on n products. j After keeping the temperature at room temperature for M days, the device is restored to normal temperature stress T0. After keeping the temperature at normal temperature stress for N hours, a power-on test is performed, where the initial value of j is 1. If a product failure occurs, the failure mechanism is analyzed and the next test method is determined.

[0060] Specifically, the high-temperature stress is lower than the test extreme temperature of the electronic product; optionally, the preliminary test is replaced by an accelerated storage test. For example, when the test extreme temperature of the product to be tested is 115°C, the temperature stress of the first-stage high-temperature stress test can be reduced by 5°C based on 115°C, that is, the maximum temperature in the high-temperature stress test can be 110°C.

[0061] Specifically, in order to avoid temperature shock during the accelerated storage life test, the temperature change rate of the electronic product during the test is 5°C / min; for example, from the high temperature stress T j Return to normal temperature stress T0, or increase from normal temperature stress T0 to high temperature stress T j , the temperature change rate is 5℃ / min;

[0062] The M days and N hours of insulation must ensure that the electronic product maintains internal temperature equilibrium during testing. This is to ensure that the electronic product is heated and cooled thoroughly during testing, thereby achieving internal temperature equilibrium. Optionally, in this embodiment, M = 7 days and N = 2 hours.

[0063] S102. If there is no fault or a Class B fault occurs after power-on, the j+1 stage high-temperature stress test is continued using the current stage test temperature as the high-temperature stress of the j+1 stage high-temperature stress test. Specifically, no fault is found and the product is qualified when the following conditions are met: that is, the appearance inspection shows no new blistering, wrinkling, or peeling of the paint film, and no expansion, cracking, or deformation of non-metallic parts, and the product's technical parameters meet the predetermined values.

[0064] Specifically, if a Class B fault occurs, after the fault is eliminated, continue to perform high-temperature stress testing at the original test temperature.

[0065] The so-called Class B failure refers to the failure of the test product caused by non-design reasons. Class B failure is not used as the basis for judging the environmental stress limit value of the test product. Specifically, Class B failure includes: failure of the test product caused by failure of the test equipment provided by the laboratory, and the instruments and meters used for testing; or failure caused by improper operation, maintenance and repair of the test product by personnel.

[0066] S103. If a Class A fault occurs after power is turned on, such as Figure 2 As shown, the high temperature stress T j Minus T th Afterwards, the j+1 stage high temperature stress test is conducted as the high temperature stress of the j+1 stage high temperature stress test; specifically, the Class A failure refers to a failure of the test product caused by improper production or component defects during the test, which is the basis for judging the environmental stress limit value of the test product, including: failures caused by improper production of parts and components, or unconfirmed failures: refers to failures that cannot be reproduced or the cause of which has not yet been determined;

[0067] Optionally, because the test is carried out in a high temperature section, which is close to the high temperature stress limit of the product, even a small temperature change can cause the failure of some components. In order to ensure that the test life evaluation information of the product to be tested is obtained accurately, T th =5℃.

[0068] S104. When the test time reaches the total test time, or the number of Class A faults is k, the test is terminated. Optionally, to ensure that a sufficient amount of test information is obtained, the total test time T z = 6 months, the number of Class A failures is k = 3, that is, if the number of Class A failures within the set 6 months does not reach 3, the test will continue to 6 months and end the experiment on time.

[0069] S105: Count the number of Class A failures i that occur in the product to be evaluated during the high temperature stress test and the failure time t corresponding to the i-th Class A failure. i Specifically, the failure time is the time from the start of the first stage high temperature stress test to the detection of the i-th type A failure;

[0070] S20, calculating the total test time under normal temperature stress according to the number of failures and failure time during the high temperature stress test;

[0071] Specifically, various methods can be used in engineering to obtain the total test time T of the product converted to normal stress. For example, the test can be conducted under high stress and then the time measured in the test can be converted to normal stress. Alternatively, when the product cannot withstand excessively high stress, the test can be conducted for a sufficiently long time under the highest stress condition that the product can withstand, and then the time measured in the test can be converted to normal stress. Optionally, in this embodiment, the total test time is calculated by converting the test time under high temperature stress to that under normal temperature stress. Specifically, the total test time under normal temperature stress is calculated based on the number of failures and failure times that occurred during the high temperature stress test, including:

[0072] Obtain the test time conversion coefficient of the product to be evaluated, and calculate the test time conversion coefficient based on the test time conversion coefficient, the number of Class A failures i in the high temperature stress test, and the failure time t corresponding to the i-th Class A failure. i , calculate the total test time of the product under normal temperature stress by the product test time conversion formula. The conversion formula is expressed as:

[0073]

[0074] Where T is the total test time of n products converted to normal stress, b is the product test time conversion coefficient, T0 is the normal temperature stress, t1 is the failure time corresponding to the first failure, t i is the failure time corresponding to the i-th failure, and k is the upper limit of the number of failures.

[0075] S30. Evaluate the product storage life according to the total test time under the normal temperature stress.

[0076] Specifically, the evaluation of the product storage life based on the total test time under normal temperature stress includes: obtaining the critical value and confidence level of the chi-square distribution of the product, and calculating the product storage life using a formula for evaluating the product storage life based on the critical value and confidence level of the chi-square distribution of the product and the total test time under normal temperature stress. The formula for evaluating the product storage life is expressed as:

[0077]

[0078] in, is the evaluation life of the product, T is the total test time of n products converted to normal stress, χ is the critical value of chi-square distribution, α is the confidence level, 1-α is the confidence level, and n is the number of products.

[0079] Compared with the existing technology, the accelerated storage life test of electronic products proposed by the method of the present invention fills the gap in the domestic related fields; the present invention is applicable to my country's existing industrial foundation and test conditions and is easy to industrialize; the present invention solves the problem of life assessment of electronic products by evaluating the storage life of electronic products on a small sample, while minimizing the loss of equipment or inventory equipment; compared with the existing evaluation methods, the life assessment results obtained by the present invention are obtained in that the test starting temperature of the present invention selects the temperature tolerance limit value of the product component components, while shortening the test time of the electronic product storage life test, covering a wide temperature range, with high time efficiency and a small number of samples consumed, and the results are more real, accurate and reasonable; the method for the storage life of electronic products proposed by the present invention saves more manpower, material resources, financial resources and other resources than the previous methods through large-scale comprehensive stress test data, regular inspection data and other related test data; product life extension measures can be implemented based on the results obtained by the present invention to achieve the goal of life extension.

[0080] Hereinafter, how to obtain the number of failures and the failure time during a high-temperature stress test in an accelerated storage life test evaluation method for electronic products will be described in detail by way of specific embodiments:

[0081] (1) Select 6 sets of products to be evaluated, install them into the test equipment, and conduct performance tests. The measured performance meets the requirements of the product performance indicators;

[0082] (2) 110°C was used as the high temperature stress for the first stage of high temperature stress test. After reaching 110°C, the temperature was kept constant for 7 days, then the temperature was restored to 25°C. After being kept constant at 25°C for 2 hours, a power-on test was performed. Specifically, the temperature change rate during the temperature change was 5°C / min.

[0083] (3) If it is determined that the product to be evaluated has no faults or has a Class B fault after being powered on, the temperature is raised to 110°C and the next stage of high temperature stress testing is continued at 110°C;

[0084] (4) If it is determined that a Class A failure occurs after the product to be evaluated is powered on, the high-temperature stress of the current stage is reduced by 5°C and the high-temperature stress is used as the high-temperature stress for the next stage of high-temperature stress test; (For example, if a failure occurs after the first stage of high-temperature stress test, 110°C is reduced by 5°C, that is, 105°C is used as the high-temperature stress for the second stage of high-temperature stress test);

[0085] (5) The test is terminated when the test time reaches 6 months of the total test time or when Class A failures occur 3 times.

[0086] Specifically, Table 1 below describes the number of samples, test conditions, and stress of the accelerated storage life test.

[0087] Table 1

[0088]

[0089]

[0090] Hereinafter, how to evaluate the product storage life in the accelerated storage life test evaluation method of electronic products is described in detail by way of specific embodiments:

[0091] First, according to the requirements of the accelerated storage test, 6 sets of products were selected for the step-back stress accelerated storage test. The accelerated storage test was carried out for 4320 hours under the condition of accelerated stress not less than 100℃. The product function test was normal without any fault. Figure 3To estimate the product life under natural storage conditions, three failures were artificially added. Specifically, one product failure was assumed at each of the step-back accelerated stresses of 110°C, 105°C, and 100°C, with one sample reduced for each failure. The failure times at 110°C, 105°C, and 100°C were also assumed to be 3600 hours, 3960 hours, and 4320 hours, respectively. Based on the experimental description of the accelerated storage test, the test data for the step-back test are shown in Table 2. Assuming α = 0.05 and b = 346.43, the 95% confidence lower limit for the product life under natural storage conditions is 11.32 years; this means that the product life under static storage at room temperature (25°C) is estimated to be 11.32 years. Because the number of failures was artificially increased for a conservative estimate, the actual product life should be no less than 11.32 years. Furthermore, the product had been stored under natural storage conditions for seven years before the accelerated storage life test, so the minimum static storage life under natural storage conditions is 18.32 years.

[0092] Table 2

[0093]

[0094]

[0095] As can be seen from the above-described specific embodiments, the present invention provides an accelerated storage life test evaluation method for electronic products. This method uses a starting temperature that approximates the temperature tolerance limits of the product's components and parts, ensuring full coverage of the product's temperature range. Compared to previous evaluation processes, this method offers a wider temperature range, is more time-efficient, requires fewer samples, and provides authentic, accurate, and reasonable test results, achieving the goals of increasing lifespan and extending the lifespan of equipment while also enabling cost-effective upgrades.

[0096] Those skilled in the art will appreciate that all or part of the process steps of the above-described embodiments can be implemented by instructing related hardware through a computer program, and the program can be stored in a computer-readable storage medium, such as a magnetic disk, an optical disk, a read-only memory, or a random access memory.

[0097] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed by the present invention should be covered by the scope of protection of the present invention.

Claims

1. A method for evaluating the accelerated storage life test of an electronic product, characterized in that: include: Perform high-temperature stress testing on the product to be evaluated to obtain the number of failures and failure time of the electronic product during the high-temperature stress test, including: Stage high temperature stress test, including: j The high temperature stress of the j-th stage high temperature stress test is tested on n products. j After keeping warm for M days, the device is restored to normal temperature stress T0. After keeping warm for N hours under normal temperature stress, a power-on test is performed, where the initial value of j is 1. If there is no fault or a Class B fault occurs after power-on, the j+1 stage high temperature stress test will be continued with the current stage test temperature as the high temperature stress of the j+1 stage high temperature stress test; If a type A fault occurs after power is turned on, the high temperature stress T j Minus T th Afterwards, the j+1 stage high temperature stress test is performed as the high temperature stress of the j+1 stage high temperature stress test; When the test time reaches the total test time T z , or when the number of Class A faults reaches k, the test ends; Count the number of Class A failures i of the product to be evaluated during the high temperature stress test and the failure time t corresponding to the i-th Class A failure i ; The failure time is the time corresponding to the start of the first stage high temperature stress test to the detection of the i-th type A failure; The product to be evaluated is powered on during normal temperature stress testing and is not powered on during other stages of the test. Calculate the total test time under normal temperature stress based on the number of failures and failure time during the high temperature stress test; The product storage life is evaluated based on the total test time under the normal temperature stress.

2. The electronic product accelerated storage life test evaluation method according to claim 1, characterized in that: The calculating of the total test time under normal temperature stress according to the number of failures and failure time during the high temperature stress test comprises: Obtain the test time conversion coefficient of the product to be evaluated, and calculate the test time conversion coefficient based on the test time conversion coefficient, the number of Class A failures i in the high temperature stress test, and the failure time t corresponding to the i-th Class A failure. i , calculate the total test time of the product under normal temperature stress through the product test time conversion formula.

3. The electronic product accelerated storage life test evaluation method according to claim 2, characterized in that: The conversion formula is expressed as: Where T is the total test time of n products converted to normal stress, b is the product test time conversion coefficient, T0 is normal stress, t1 is the failure time corresponding to the first failure, t i is the failure time corresponding to the i-th failure, and k is the upper limit of the number of failures.

4. The electronic product accelerated storage life test evaluation method according to claim 3, characterized in that: The evaluation of the product storage life according to the total test time under the normal temperature stress includes: Obtain the critical value and confidence level of the chi-square distribution of the product, and calculate the storage life of the product by evaluating the product storage life formula based on the critical value and confidence level of the chi-square distribution of the product and the total test time under the normal temperature stress.

5. The electronic product accelerated storage life test evaluation method according to claim 4, characterized in that: The formula for evaluating the shelf life of the product is expressed as: in, is the evaluation life of the product, T is the total test time of n products converted to normal stress, χ is the critical value of chi-square distribution, α is the confidence level, 1-α is the confidence level, and n is the number of products.

6. The electronic product accelerated storage life test evaluation method according to claim 1, characterized in that: The high temperature stress is less than the test extreme temperature of the electronic product; During the accelerated storage life test, the temperature change rate of the electronic product is 5℃ / min.

7. The electronic product accelerated storage life test evaluation method according to claim 1, characterized in that: The insulation for M days and N hours must ensure the temperature balance inside the electronic product during the test.

8. The electronic product accelerated storage life test evaluation method according to claim 1, characterized in that: The aforementioned Class A failures refer to failures of the test product caused by improper production or component defects during the test. They are the basis for determining the environmental stress limit values ​​of the test product and include: Failure caused by improper production of parts or defective components; or Unconfirmed fault: refers to a fault that cannot be reproduced or the cause of which has not yet been determined; The Class B failures mentioned above refer to failures of the test product caused by reasons other than design. Class B failures are not used as a basis for determining the environmental stress limit values ​​of the test product, and include: Failure of the test product due to failure of the test equipment provided by the laboratory, or the instruments and meters used for testing; or Failures caused by improper operation, maintenance and repair of the test products by personnel.

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