The reliability of electronic products is affected by many factors. In addition to human operation, the environment in which the products are located is also an important reason for their work failure. Among them, temperature, humidity and vibration are the three main environmental factors that have the greatest impact on the product equipment. This paper analyzes the main types and causes of product failure caused by these three environmental stresses, and discusses the application of temperature, humidity and vibration comprehensive environmental testing technology in product reliability testing.

Environmental stress can lead to the failure of products and equipment, which has been widely recognized by the manufacturing industry. In order to improve the quality of products, relevant technicians and manufacturing enterprises have conducted a detailed study on the relationship between environmental application and product failure. Environmental tests for product equipment can be divided into three categories: mechanical environment test, climate environment test and comprehensive environment test. Among them, the mechanical environment test mainly includes vibration, impact, collision, constant acceleration, voice, etc.; the climate environment test mainly includes temperature, humidity, low pressure, salt fog, rain, mold, solar radiation, dust, etc; Comprehensive environmental test includes various environmental factors combined with mechanical environment and climatic environment. Therefore, the comprehensive environmental test is the most comprehensive and effective for detecting the failure rate of products.

1.Relationship between temperature, humidity, vibration stress and failure

(1) Relationship between temperature stress and failure

Temperature stress is one of the most important factors causing product failure. It is mainly caused by aging, heat accumulation, migration and spread caused by high temperature, low temperature brittleness caused by low temperature, and product expansion or contraction caused by temperature cycle or temperature impact.

(2) Relationship between humidity stress and failure

The humid environment caused by high temperature will also cause product failure. In a humid environment, the material absorbs moisture in the air, causing expansion, strength reduction and performance changes, which will reduce the electrical performance of the insulating materials of the product equipment, resulting in corrosion, short circuit and mold.

(3) Relationship between vibration application and failure

The resonance of vibration stress on product equipment will cause displacement of product equipment, resulting in looseness, separation, poor contact, wear, fatigue deformation, cracking and fracture of product equipment.

2.The relationship between the comprehensive application of temperature, humidity and vibration and product failure

According to the long-term research on the relationship between the three applications of temperature, humidity and vibration and product failure, it is found that any of the three environmental stresses applied to the product can bow the failure of the product. If the three environmental stresses are applied to the product at the same time, the probability of product failure increases by 3-5 times. The comprehensive effect of these environmental stresses, due to different comprehensive conditions, causes different fault performances.

For example, during the impact test of temperature cycle on the interior of the product, due to the difference of material thermal expansion coefficient, the structure of the product expands and contracts, resulting in the loosening of the joint of components. At this time, increasing the environmental humidity, the moisture will invade the interior of the product equipment along the gap, reducing the friction coefficient between the joint and the joint. If the vibration stress is applied again, a new failure result different from the three environmental application tests will be produced. Therefore, for the test of the relationship between these three environmental stresses and product failure, the most effective method is to conduct a comprehensive test.

3.Application of temperature, humidity and vibration comprehensive test technology

(1) Vibration stress

During the operation of the equipment, select 24 h for vibration stress test, randomly select 25% of the working cycle time to apply vibration stress, and the vibration cycle time of vibration stress is 3 h.

(2) Temperature and humidity stress

• The temperature during product test shall be controlled at 22 ℃ and 25%. Then start the test, first quickly reduce the temperature to -50 ℃ for 1.75 h, and then rise to -32 ℃;

• Reduce the temperature to -34.5 ℃ in 3.25 h;

• Take 13 h to raise the temperature to -28 ℃:

• Take 5 h to raise the temperature to 22 ℃.

• Keep the temperature at 22 ℃  and adjust the relative humidity to 25% – 75%;

• Raise the temperature to 25 ℃ and the relative humidity to 95% in 2 h:

• Take 10 h to raise the temperature to 29 ℃, and the relative humidity remains unchanged at 95%;

• Take 5 h to reduce the temperature to 25 ℃, and at this time, the relative humidity remains unchanged at 95%;

• Reduce the temperature to 22 ℃ and the relative humidity to 25% – 75% in 2 h;

• Raise the temperature to 25 ℃ and reduce the relative humidity to 65% in 2 h;

• Raise the temperature to 48 ℃ and reduce the relative humidity to 25% in 12 hours;

• Raise the temperature to 60 ℃ and the relative humidity to 95%. Keep it under this condition for 2 h, and then reduce the temperature to 48 ℃;

• Take 6 h to reduce the temperature to 22 ℃ and the relative humidity to 25% – 75%. Through the above steps, the comprehensive test of temperature, humidity and vibration can fully understand the condition of the equipment in the reliability test of the equipment installed outside the naval surface ship. Based on the test of the temperature, humidity and vibration of the environment in which the equipment is located, the relevant data can be used as the basis for continuously optimizing the equipment design for the response of the test surface under different test conditions.

4.Application direction of temperature, humidity and vibration comprehensive environmental test technology

(1)Product reliability enhancement test technology

The test technology of strengthening the reliability of products in the temperature, humidity and vibration comprehensive environmental test technology can enable technicians to understand the weak links in the structure and function of the product for which type of environmental stress, find out the causes of product failure according to the fault location, and analyze the improved process and design, so that the environmental adaptability and reliability of the product can be continuously strengthened. Through the continuous round-trip process of test → fault discovery → problem analysis → process improvement → retest → new problem discovery → re analysis → re improvement → re test, the ability of the product to cope with environmental stress is continuously strengthened, and finally the weak links existing in the product are completely eliminated in the product development stage, so that the product design and manufacturing technology reach a mature state.

(2)Development trend of temperature, humidity and vibration comprehensive environmental test technology

In the past, the test technology for environmental stress of products mainly used environmental simulation technology and effect simulation technology. Although these technologies still have some application space at present, with the continuous improvement of temperature, humidity and vibration comprehensive environmental test technology, it will eventually become the mainstream technology of environmental application test of products in the future:

The test focus of temperature, humidity and vibration comprehensive environmental test technology mainly focuses on the search and analysis of weak links and potential faults in product design and manufacturing, and has become a test technology combining various technical means.

5.Conclusion

The comprehensive test of temperature, humidity and vibration is to highly restore the operating environment of the equipment, so as to use the changes of temperature, humidity and vibration to stimulate product faults, and find the design and technical defects of the products, so as to continuously improve the relevant design and manufacturing processes, so that the products have a stronger function of resisting environmental impact in practical applications. Based on the application of the temperature, humidity and vibration comprehensive test technology introduced in this paper, it can be seen that this test is a very important means to improve the reliability of products.