How to choose wet heat test? What is the impact on the product?

Date：2022-08-12 18:17:42Views：1139

Damp heat test is also a method to test the corrosion resistance of the coating. The main test process is the damage of saturated water vapor to the coating. Generally, it is conducted simultaneously with the salt spray test. The humid and hot environment generally exists in the whole life cycle of electronic products during transportation, storage and use. Under the influence of the humid and hot environment, the insulating materials and metals in electronic products will absorb water vapor, resulting in product degradation. At the same time, under the joint action of humidity, temperature and electrical stress, it will cause electrochemical reaction and metal corrosion, resulting in the decrease of insulation resistance and increase of leakage of electronic equipment, and in serious cases, arcing, breakdown and circuit damage. The following is a brief analysis of the damp heat test for your reference.

Action mechanism of damp heat test

Damp heat test is an environmental test under the combined action of temperature stress and humidity stress. The typical environmental effect of damp heat test is mainly caused by the two phenomena of product surface and volume.

Moisture on the surface means that more water vapor stays on the surface of the product, causing it to condense. This is a common adsorption phenomenon in the humid and hot environment. The humid and hot test includes two environmental stresses: temperature and humidity. When the temperature rises, the thermal inertia of the product surface lags behind the rate of temperature rise, and condensation occurs on the product surface. This phenomenon is also a form of adsorption.

The volume moisture is mainly caused by the diffusion and absorption phenomena in the damp heat test. It refers to the process in which the water vapor diffuses from the area with high concentration to the area with low concentration, so as to damp the inside of the product and may be absorbed by the material of the product itself.

There is also a physical phenomenon of respiration in the damp heat test. This phenomenon generally occurs in the airtight products with cavities. When the temperature rises and falls in the environment, the pressure inside and outside the cavity will change, resulting in the internal and external flow of steam, and the volume will be affected by moisture.

After adsorption and condensation on the product surface, the insulation performance of the product surface will be greatly reduced or even short circuited with the help of dust and corrosion on the product surface. This environmental effect will directly affect the electrical performance of the product.

When the material of the product itself is a relatively active metal, it is prone to electrochemical corrosion after contacting with oxygen and water vapor in the air.

Influence of damp heat on products

1. Humidity of damp heat test chamber. Due to moisture absorption, the sealing performance of the sealing product is reduced or damaged, the coating layer on the product surface is peeled off, and the product mark is blurred.

2. The wet and hot corrosion is the indirect chemical and electrochemical corrosion caused by a small amount of acid and alkaline impurities in the air, or by pollutants such as welding slag and sweat on the product surface.

3. Damp heat test chamber. For the whole equipment, it will cause sensitivity reduction and frequency drift.

4. Due to the absorption and diffusion of moisture, the volume resistance of the insulating material decreases, thereby generating leakage current.

5. The surface insulation resistance of the insulating material decreases due to condensation and adsorption.

6. Damp heat test chamber. For different metal materials, metal and non-metal materials, even in the absence of pollutants, as long as there are appropriate humidity conditions or condensation, due to chemical or electrochemical effects, they will cause different degrees of corrosion.

7. Wet environment can cause changes in mechanical and chemical properties of materials, such as volume expansion and mechanical strength reduction.

Selection of damp heat test type

1. The damp heat test method is selected according to the characteristics of the sample itself. The test sample is solid or insulating material, and constant damp heat test is usually used to test the electrical performance or insulation performance of the product in the humid atmosphere; If the test sample is sealed or hollow, the alternating damp heat test is often used, because the sample will undergo thermal expansion and contraction under the action of thermal stress, resulting in the product being affected by moisture.

2. The damp heat test method is selected according to the damp mechanism of the sample. The sample is affected by moisture after absorbing or absorbing moisture, and the constant damp heat test shall be adopted generally; If the influence of humidity on the product is enhanced by condensation or respiration, the alternating damp heat test shall be adopted.

That's all for the above. On the one hand, the damp heat test can simulate the impact of the damp heat environment on the product in actual use, on the other hand, it can also identify the moisture-proof ability of the product and evaluate the safety and reliability of the product under high temperature and humidity conditions. I hope I can provide you with some reference, and we will bring more wonderful content later. The company's testing services cover: electronic component testing and verification, IC authenticity identification, product design and material selection, failure analysis, function testing, factory incoming material inspection, braiding and other test items. Welcome to call Chuangxin testing, we will serve you wholeheartedly.