1, the temperature shock is defined thermal shock test (Thermal Shock Testing) Impact test is often called a temperature (Temperature Shock Testing), or temperature cycling (Temperature Cycling), high and low temperature thermal shock test. According to GJB 150.5A-2009 3.1, the temperature shock is a sharp change in the ambient temperature of the equipment. The temperature change rate is greater than 10 degrees/min, which is the temperature shock. MIL-STD-810F 503.4 (2001) holds a similar view.
2. Purpose of temperature impact test The purpose of temperature impact test: engineering development stage can be used to find product design and process defects; product stereotype or design identification and mass production stage is used to verify the adaptability of products to temperature impact environment, design stereotypes And provide basis for mass production acceptance decisions; as an environmental stress screening application, the goal is to eliminate early failure of the product.
3. Temperature shock applications Temperature changes in electronic devices and components are common. When the device is not powered, its internal parts are slower than the temperature changes experienced by the parts on its outer surface.
Rapid temperature changes can be foreseen in the following cases: - when the equipment is transferred from a warm indoor environment to a cold outdoor environment, or vice versa; - when the equipment is exposed to rain or immersed in cold water and suddenly cooled; - installed in external onboard equipment; - under certain transportation and storage conditions.
High voltage gradients occur in the device after power-on. Components are subject to stress due to temperature changes. For example, next to a high-power resistor, radiation causes an increase in the temperature of the adjacent component surface while the other parts are still cold. When the cooling system is energized, the manually cooled components experience rapid temperature changes. It also causes rapid temperature changes in the components during the manufacturing process of the device. The number and magnitude of temperature changes as well as the time interval are important.
4. Effect of temperature shock The temperature shock usually affects the part close to the outer surface of the equipment more seriously. The farther away from the outer surface (of course, related to the characteristics of the relevant material), the slower the temperature change, the less obvious the effect. Transport boxes, packaging, etc. also reduce the impact of temperature shocks on closed equipment. Rapid temperature changes can temporarily or permanently affect the work of the equipment. The following are examples of problems that may arise when the equipment is exposed to a temperature shock environment. Consider the following typical questions to help determine if the test is applicable to the equipment under test.
(1) Typical physical effects are: 1) chipping of glass containers and optical instruments; 2) clamping or loosening of moving parts; 3) cracking of solid pellets or grains in explosives; 4) shrinkage or expansion of different materials Rate, or induced strain rate is different; 5) deformation or cracking of parts; 6) cracking of surface coating; 7) leakage of sealed compartment; 8) failure of insulation protection.
(2) Typical chemical effects are: 1) separation of components; 2) failure of chemical reagent protection.
(3) Typical electrical effects are: 1) changes in electrical and electronic components; 2) rapid condensation or frosting causing electrical or mechanical failure; 3) excessive static.
5. Types of thermal shock test methods are classified into three types according to IEC and national standards: 1. Test Na: rapid temperature change for specified conversion time; air; 2. Test Nb: temperature change for specified change rate; air; , test Nc: rapid change of temperature in the two-tank method; liquid;
In the above three tests, 1, 2 uses air as a medium, and the third uses a liquid (water or other liquid) as a medium. The conversion time of 1, 2 is longer, and the conversion time of 3 is shorter.
| Serial number | International standard | Domestic corresponding standard | Be applicable | medium | Conversion time |
| 1 | IEC 60068-2-14:2009 "Environmental test Part 2-14: Test method test N: Temperature change" | GB/T 2423.22-2012 "Environmental test - Part 2: Test method test N: Temperature change" | Assembly level of components, components, equipment, etc. | air | Within 3 minutes or longer |
| 2 | MIL-STD-810F Method 503.4: Temperature Shock Test | GJB 150.5A-2009 "Laboratory test methods for military equipment - Part 5: Temperature impact test" | equipment | air | 1 minute |
| 3 | MIL-STD-202G Method 107G: Thermal Shock Test | GJB 360B-2009 Method 107 Temperature Shock Test in Test Methods for Electronic and Electrical Components | Components | liquid | short |
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