What are the effects of high temperature and high humidity testing on products? What is the standard?

Date：2022-12-01 15:34:43 Views：2147

High temperature and high humidity test is to simulate the temperature and humidity environment in which products are stored and operated, and to check whether the impact on products after a period of time under this environment is within the acceptable range. The product storage and working environment has a certain temperature and humidity, and some environments have high temperature and humidity. The performance and service life of the product will be affected to some extent if the product is in such a high temperature and humidity environment for a long time. Therefore, the product needs to be tested at high temperature and high humidity to understand its performance. If it fails to meet the requirements, the product needs to be improved accordingly.

The high temperature and high humidity test is to use the equipment temperature and humidity box with heating, cooling, humidification and dehumidification functions. Before the test, check whether the relevant functions and performance of the product are normal and take photos. Then place the product in the temperature and humidity box, start the machine and set the temperature, humidity and test duration of the temperature and humidity box. For example, test for 168 hours at 70 ℃ and 95% humidity. After setting, let the temperature and humidity box work, and the test starts. After reaching the set end time, take out the product, and check again whether there are any changes in the relevant functions and performance of the product before the test, so as to judge whether the product meets the test requirements. Sometimes it is also necessary to take the product out for inspection during the test process to understand the state of the product at different test times. If the impact on the product has exceeded the acceptable range before the preset test completion time, the test can be terminated in advance to find solutions to the problem, and the product can be retested after improvement.

High temperature and high humidity test includes high temperature and high humidity storage and high temperature and high humidity operation. High temperature and high humidity storage is to test the product under non working conditions. High temperature and high humidity operation is a test for electronic products when the product is powered on.

Effect of high temperature on products

With the increase of temperature, the movement speed of material molecules will increase, and the increase of molecular kinetic energy will lead to the expansion of objects, phase transition and changes in physical and chemical properties, leading to:

a) Failure of thermal insulation materials - thermal aging of materials (increase of thermal conductivity);

b) Deformation, jamming and bursting (structural damage) - expansion or size increase of gaseous, liquid and solid objects under high temperature;

c) Electrical performance changes, poor electrical contact, dielectric breakdown - resistivity and conductivity increase, surface oxidation at high temperature, and mutual diffusion between materials intensifies

d) Deterioration (wear) or loss (structural damage) of lubricating performance - chemical reaction causes lubricant deterioration, and viscosity decreases with temperature increase;

e) Change of material phase state - material softening, melting, evaporation and upgrading at high temperature;

f) At higher temperatures, if the solid reaches the distance point, it will lose its magnetism, and the object will lose its polarity in the strong electric medium. When the critical temperature of superconductivity is reached, the object will have super conductivity

g) Discoloration, cracking or crazing of organic materials;

h) The material in the sealed shell (shell, bomb, etc.) is subject to high pressure due to thermal expansion;

1) The synthetic material deflates at high temperature and loses vacuum.

Effect of humidity on products

Humidity will affect the external physical and chemical properties of products. Humidity and temperature are always coupled environmental factors. The combined action of heat and humidity can cause:

a) Accelerate oxidation and electric corrosion of metal surface;

b) Accelerate the electrochemical reaction of the surface organic coating and damage the protective effect of the surface coating;

c) . The adsorption of materials leads to material expansion, which leads to structural damage;

d) . Due to the influence of physical phenomena such as moisture absorption and adsorption, the electrical insulation performance will be reduced);

e) . Condensation and free water vapor will lead to electrical short circuit, poor heat transfer characteristics, and poor imaging and transmission quality of optical devices.

Common standards

IEC 60068, GB/T 2423: the most widely used environmental test standard, which specifies the main parameters, test conditions, severity levels, etc. of equipment.

ISO 16750-4: A common standard for European cars, and gradually referred to by national standards and enterprise standards.

SAE J1211, SAE J1455: Environmental test standards for automotive electrical components developed by the Society of Automotive Engineers.

High temperature test: IEC 60068-2-2 GB/T 2423.2

Low temperature test: IEC 60068-2-1 GB/T 2423.1

Temperature cycling test: IEC 60068-2-14 GB/T 2423.22

Temperature impact test: IEC 60068-2-14 GB/T 2423.22 EIA-364 IPC － TM650

Damp heat test: IEC 60068-2-30 GB/T 2423.3 (constant damp heat) GB/T 2423.4 (alternating damp heat)

The environmental reliability test items of the same type as the high temperature and high humidity test include: high temperature test, constant temperature and humidity test, low temperature test, high and low temperature cycle test, alternating damp heat test, high and low temperature impact test, etc.

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