Up to now, there are still many people who think that the temperature cycle test process and thermal shock and the principle of the difference is not big, it is to raise or lower the temperature of the test product test; Testers fool some people because they don’t know enough about the differences between them. How much do you know about the difference between thermal shock and thermal cycling? Now let’s look at the differences in definition, purpose, area of application and effect.
How much do you know about thermal shock?
Definition of thermal shock
Thermal shock test is often called thermal shock test or temperature cycling, high and low temperature hot and cold shock test. Thermal shock According to GJB 150.5A-2009 3.1, thermal shock is a sudden change in the temperature of the atmosphere around the equipment. The rate of temperature change is more than 10 degrees/minute. The temperature rise/fall rate of the heat shock test is not less than 30℃/min. The range of temperature change is very large, and the severity of the test also increases as the rate of temperature change increases. The two-slot test fixture can be used in thermal shock tests. Temperature cycling testing using a single tank test device.
Purpose of the thermal shock test
The engineering development phase can be used to find product design and process defects, product completion or project identification, and the mass production phase can be used to verify the adaptability of the product to the environment of temperature impact, to provide a basis for project completion and mass production. acceptance decisions; When applied as environmental stress detection, the goal is to eliminate early product failures.
Thermal shock application
Temperature variations are common in electronic equipment and components. When the device is not powered, the internal parts of the device experience slower temperature changes than the parts on the external surfaces. Rapid changes in temperature can be expected under the following conditions:
— When the equipment is moved 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 becomes cold
— Mounted on external airborne equipment
— Under certain transport and storage conditions
After powering up the device, there is a high temperature gradient. Due to the temperature change, the component will experience stress. For example, in close proximity to a high-power resistor, the radiation will cause the surface temperature of the adjacent component to rise, while the rest of the component will remain cool. When the cooling system is energized, manually cooled components experience rapid temperature changes. It can also cause rapid temperature changes of components during the equipment manufacturing process.
What is the temperature cycle?
Temperature cycling consists of exposing the test sample to a series of alternating high and low temperature test environments. To avoid the impact of thermal shock, the temperature change rate during the test should 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 is 25 ℃ ~ 100 ℃, or 0 ℃ ~ 100 ℃ can be used cycle test according to for the purpose of the product, and the exposure time is 15 minutes each.
The principle of temperature cycles.
The drastic change in temperature is accompanied by the drastic change in heat, and the drastic change in heat leads to the drastic change in thermal strain, which leads to the drastic change in stress. When the stress exceeds the maximum stress, it will cause cracks or even fractures. The difference between the thermal shock test and the temperature cycle test is mainly due to the different stress loading mechanism. Thermal shock testing mainly investigates failure caused by creep and fatigue damage, while temperature cycling mainly investigates failure caused by shear fatigue. The thermal shock test allows the use of a two tank test fixture; Temperature cycling testing using a single tank test device. In the two-slot box, the temperature change rate should be more than 50℃/min. In general, the rate of change above 5℃/min can be regarded as a rapid temperature change test. Thermal shock is to realize the exchange of high temperature area and low temperature area within the specified time. The general AIR-AIR test method requires the temperature zone to change within 20S.
The machine is specially designed for testing the heat, cold and moisture resistance of various materials. Thermal shock is mainly used in the furnace heating test and the heating test in the battery safety performance test, but compared to the temperature cycle test box; the temperature of the thermal shock test box has no humidity.
