So far, there are still a lot of people think that the temperature shock and temperature cycle test process and principle of the difference is not big, are to raise or drop the temperature of the test product test; Some people are cheated by the testers because they don’t know enough about the differences between them. If you think there is no difference between temperature shock and temperature cycle, you are wrong. How much do you know about the difference between temperature shock and temperature cycle? Now let’s look at the differences in definition, purpose, application area, and effect.
How much do you know about temperature shock?
Definition of temperature shock
Thermal shock test is often called temperature shock test or temperature cycle, high and low temperature cold and hot shock test. Temperature shock According to GJB 150.5A-2009 3.1, temperature shock is A sharp change in the temperature of the atmosphere around the equipment. The temperature change rate is greater than 10 degrees/minute. Temperature shock test temperature rise/drop rate is not less than 30℃/ min. The temperature variation range is very large, and the test severity also increases with the increase of the temperature change rate. The two-slot test device is allowed to be used in the temperature shock test. Temperature cycle test using a single tank test device. In the two-groove box, the temperature change rate should be greater than 50℃/ min.
Purpose of temperature shock test
The engineering development stage can be used to find product design and process defects, product finalization or design identification and mass production stage can be used to verify the adaptability of the product to the temperature impact environment, to provide a basis for design finalization and mass production acceptance decisions; When applied as environmental stress screening, the aim is to eliminate early failures of the product.
Application of temperature shock
Temperature changes are common in electronic equipment and components. When the device is not energized, the inner parts of the device experience temperature changes more slowly than the parts on the outer surfaces. Rapid temperature changes can be expected under the following conditions:
— When equipment moves from a warm indoor environment to a cold outdoor environment, or vice versa
— When the equipment is caught in the rain or immersed in cold water and suddenly cools
— Mounted in external airborne equipment
— Under certain transportation and storage conditions
After energizing the device, there is a high de temperature gradient. Due to the temperature change, the component will undergo stress. For example, near a high-power resistor, radiation will cause the surface temperature of the adjacent component to rise, while the rest of the component will remain cold. When the cooling system is energized, manually cooled components undergo rapid temperature changes. It can also cause rapid temperature changes of components during the manufacturing process of the equipment. The number and magnitude of temperature changes, as well as the time interval, are important.
The effect of temperature shock
The impact of temperature shock is usually more severe on the part close to the outer surface of the equipment, and the further away from the outer surface (depending, of course, on the properties of the relevant material), the slower the temperature change, the less obvious the effect. Transportation boxes, packaging, etc. also reduce the impact of temperature shocks on enclosed equipment. Dramatic temperature changes may temporarily or permanently affect the operation of equipment. Here are some examples of problems that can arise when equipment is exposed to temperature shocks. Consider the following typical questions to help determine if this experiment is applicable to the equipment under test
(1) Typical physical effects: broken glass containers and optical instruments; The moving parts are tight or loose; Cracking of solid pills or charge columns in explosives; The shrinkage or expansion rate of different materials, or the induced strain rate is different; Deformation or rupture of parts; Surface coating cracking; Leaky cabin; Insulation protection failure
(2) Typical chemical effects: separation of components; Chemical reagent protection failure
(3) Typical electrical effects: changes in electrical and electronic components; Electrical or mechanical failure caused by rapid condensation or frosting; Electrostatic excessive
The product is suitable for the safety performance test of electronic components to provide reliability test, product screening test, etc. At the same time, through this equipment test, the reliability of the product can be improved and the quality control of the product. High and low temperature impact test chamber is aviation, automobile, home appliances, research in areas such as the necessary test equipment, test and determine the electrician, electronics, automotive electronics, materials and other products, in the high and low temperature test the temperature of the environment impact parameter and the performance after the change, use flexibility, suitable for schools, factories, military industry, research, etc.
Now that we have a brief look at temperature shocks, let’s look at a few things about temperature cycles.
What is the temperature cycle?
The temperature cycle is to expose the test sample to a set of alternating high and low temperature test environment. In order to avoid the impact of temperature shock, the temperature change rate during the test must be less than 20℃/ min. At the same time, in order to achieve the effect of creep and fatigue damage, it is recommended that the test temperature cycle be 25℃ ~ 100℃, or the cycle test of 0℃ ~ 100℃ can be used according to the purpose of the product, and the exposure time is 15 minutes each.
Purpose of temperature cycle test
In order to investigate the resistance and adaptability of the test sample when suddenly subjected to drastic changes in temperature. This experiment generally uses a rapid temperature change chamber or a temperature cycle chamber.
The principle of temperature cycling
The drastic change of temperature is accompanied by the drastic change of heat, and the drastic change of heat leads to the drastic change of thermal deformation, which leads to the drastic change of stress. When the stress exceeds the ultimate stress, there will be crack or even fracture. Rapid temperature test is to investigate the creep failure of components, and its intensity is not as severe as temperature shock test, so it can be used as stress screening.
The difference between temperature shock test and temperature cycle test is mainly due to the different stress loading mechanism. The temperature shock test mainly investigates the failure caused by creep and fatigue damage, while the temperature cycle mainly investigates the failure caused by shear fatigue. Temperature shock test allows the use of two tank test device; Temperature cycle test using a single tank test device. In the two-groove box, the temperature change rate should be greater than 50℃/ min. Therefore, the fundamental difference between the temperature cycle test and the temperature shock test is that the temperature conversion is carried out at a constant rate.
Generally, the rate of change above 5℃/min can be considered as a rapid temperature change test. The temperature shock is to realize the exchange of high temperature zone and low temperature zone within the specified time. The general AIR-AIR test method requires the switch of temperature zone within 20S. The outlet temperature of the test chamber can be stabilized within 5min, and the sample temperature can be stabilized within 15min.
It can accurately simulate the complex natural environment of low temperature, high temperature, high temperature and high humidity, low temperature and low humidity. It is suitable for reliability testing of products in plastic, electronics, food, clothing, vehicles, metal, chemical, building materials and other industries. 2. The temperature cycle test chamber can provide a high temperature and humidity environment to compare the material changes of rubber and plastic before and after the test and the degree of strong decay reduction; It can also simulate the container environment to detect the fading and shrinkage of rubber and plastic under high temperature and humidity.
The machine is specially designed to test the heat resistance, cold resistance and moisture resistance of various materials. The temperature shock is mainly used in the furnace heat test and heating test in the battery safety performance test, but compared with the temperature cycle test box, the temperature shock test box has no humidity.