The temperature cycling stress test of the high and low temperature alternating test chamber is an important means of inspecting product quality, which is of great significance for evaluating product quality. The following is the analysis and discussion of the cause of product failure by the temperature cyclic stress test of Beijing Yashilin Technology Department:
1. Basic parameters of temperature cycling stress:
There are six basic parameters of temperature cycling stress: ①upper limit temperature; ② lower limit temperature; ③ temperature change rate; ④ upper limit temperature holding time; ⑤ lower limit temperature holding time; ⑥ cycle number.
2. Analysis of temperature cycle stress characteristics:
In the environmental reliability test, when the temperature cycle changes, the high temperature stress, low temperature stress and thermal fatigue interact on the product, and the material will show different degrees of thermal expansion and contraction. Its characteristic is that increasing the temperature change range and temperature change rate can strengthen this process, thus enhancing the thermal stress and increasing the number of cycles, which will directly affect the excited stress.
In the temperature cycle test, the airflow uniformity in the high and low temperature alternating test chamber is an important parameter, which will affect the temperature change rate of the product. This requires that when multiple test products are tested at the same time, there should be appropriate intervals between the test products, between the test product and the test box wall, so that the airflow can circulate freely between the test products, between the test product and the box wall .
In the temperature cycle test, when the low temperature and high humidity condition is changed to the high temperature and high humidity condition, the air temperature rises faster than the product temperature, and when a certain temperature difference is reached, condensation will occur on the product. The greater the temperature difference, the more obvious the condensation phenomenon. The condensation water cannot be discharged in time, which will increase the chance of corrosion of the product and reduce the insulation strength. For the whole equipment, it will lead to sensitivity reduction, frequency drift, etc., which will seriously affect product quality.
3. The mechanism and sensitive components of temperature cycle stress-induced failure
Temperature cycling makes the expansion of different materials with different expansion coefficients different, causing peeling, cracking, and sensitive components such as paint coating, etc .; temperature cycling loosens screw connections or riveted joints, and sensitive components such as screws and riveting Components, etc .; temperature cycling relaxes the press-fit joints with insufficient mechanical tension; high and low temperature alternating test chamber temperature cycling increases the brazing contact resistance of poor materials or induces an open circuit, and its sensitive components such as resistance components; temperature cycling causes contact Pitting corrosion and pollution, its sensitive components such as alloy materials.
Create harmony and unity between energy and the environment. ——Beijing Yashilin Test Equipment Co., Ltd.
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