With the process of industrialization, almost all industrial products now need to be tested in a simulated environment for reliability. Among them, constant temperature and humidity test (also called high and low temperature test, high and low temperature damp heat test) plays a pivotal role in the reliability test Among them, the temperature of 85°C and the humidity of 85% (also commonly known as the double 85 test) are the test conditions with the highest utilization rate.
Why not use 90℃ temperature and 85% humidity? Why not use a temperature of 85°C and a humidity of 90%? I believe that many experimenters have had this question, and the following is the explanation of this question. What exactly is
"double 85"?
The double 85 test refers to the aging test of the test body under the condition that the temperature is set to 85°C and the humidity is 85%, that is, a severe reliability test. Usually the time is 1000 hours, mainly to test the limit that the product can withstand in the harsh environment of high temperature and high humidity.
The constant temperature and humidity test is used to test the heat resistance, cold resistance, dry resistance and humidity resistance of materials or products in various environments, while the double 85 test is a performance test for the product's resistance to heat and humidity. The double 85 test refers to the comparison of the performance changes before and after aging after aging the product under the condition of 85℃/85%RH, such as the photoelectric performance parameters of lamps, mechanical properties of materials, yellowing index, etc. The smaller the difference, the better , so as to test the heat and humidity resistance of the product.
Application of "Double 85" in various industries
The "Dual 85" test of reliability is widely used in the LED and photovoltaic industries. LED light sources, modules and accessories need to be tested for reliability. Reproduce the damage to its components in a high temperature and humidity environment, and this is also an environmental test condition often used in product life testing. For soldered assemblies, the reliability "Dual 85" test can test its ability to resist long-term penetration of high temperature moisture.For plastic components, the "Double 85" test of reliability can assess the properties of the material in terms of mechanics, yellowing resistance, heat resistance, acid and alkali resistance, etc., especially the data comparison before and after the test can show this trend. The "Double 85" test of reliability has penetrated into all walks of life, and is widely used in electronics, electrical, communication technology, instrumentation, vehicles, medical, plastic products, aerospace and other industries.
Reference standard for commonly used reliability "Double 85" test
1. GB/T 2423.50 [Environmental Testing Part 2: Test Method Test Cy Constant damp heat is mainly used for accelerated testing of components]
2. IEC60068-2-67 [ Environmental testing - Part 2-67: Tests - Test Cy: Damp heat, steady state, accelerated test primarily intended for components 】
3. JESD22-A101D 【Steady-State Temperature-Humidity Bias Life Test】
Choose "Dual 85" temperature and humidity test chamber 1. Box size
When putting the tested product (components, components, parts or whole machine) into the constant temperature and humidity chamber for test, in order to ensure that the surrounding environment of the tested product can meet the environment specified in the test specification The test conditions, the working size of the climate box and the outer dimension of the tested product should follow the following regulations:
a. The volume of the tested product (W×D×H) shall not exceed the effective working space of the test chamber (20～35 )% (20% is recommended). It is recommended to use no more than 10% for products that generate heat during the test.
b. The ratio of the windward cross-sectional area of the tested product to the total area of the test chamber studio on the cross-section is not greater than (35-50)% (35% is recommended).
c. The distance between the outer surface of the tested product and the wall of the test chamber should be at least 100-120 mm (120 mm is recommended).
The above three-point regulations are actually interdependent and unified.Taking a 1m³ cube box as an example, an area ratio of 1:(0.35~0.5) is equivalent to a volume ratio of 1:(0.207~0.354). 100～150mm from the box wall is equivalent to a volume ratio of 1:(0.343～0.512).
summarizes the above three points and stipulates that the working chamber volume of the climate environmental test chamber should be at least 3 to 5 times the outer volume of the tested product.
Second, the temperature range
The temperature range of Keming equipment can reach -70 ℃ ~ 150 ℃. This temperature range can usually meet the temperature test needs of most domestic military and civilian products. Unless there are special needs, such as products whose installation position is close to the heat source such as the engine, the upper limit of the temperature should not be blindly increased. Because the higher the upper limit temperature, the greater the temperature difference inside and outside the box, and the worse the uniformity of the flow field inside the box. The available studio volume is also smaller. On the other hand, the higher the upper limit temperature value is, the higher the heat resistance requirement is for the thermal insulation material (such as glass wool, etc.) in the interlayer of the box wall. The higher the requirements for the tightness of the box body, the higher the production cost of the box body; while the low temperature involves the cost of the product. The lower the temperature, the greater the power and cooling capacity of the refrigeration system and the corresponding equipment cost.
3. Humidity range
Under the above temperature range, the humidity range of Kemin equipment can reach 10%～98% RH. Generally speaking, for the same absolute moisture content, the higher the temperature, the smaller the relative humidity , such as the absolute moisture content of 5g/Kg (refers to 1 kg dry air contains 5 grams of water vapor , when the temperature is 29°C, the relative humidity is 20%RH, when the temperature is 6°C, the relative humidity is 90%RH, when the temperature drops below 4°C and the relative humidity exceeds 100%, condensation will occur in the box If there is no dehumidification system in the damp heat test box, the humidity range is 60~98% RH, this type of test box can only do high humidity test, but its price is much lower.
Fourth, cooling method
There are two cooling methods, air cooling and water cooling. Which cooling method to choose should be determined according to the actual situation of the laboratory. When conditions permit, preference is given to water cooling. After understanding the basic content of the "Double 85" test,
hopes to help customers and friends to choose the constant temperature and humidity test chamber that is more in line with the product test requirements. Keming has been deeply involved in the environmental testing industry for 31 years, and continues to create value for customers. With high-quality, high-efficiency and high-sincere environmental test chambers, we can assist you in completing the "Double 85" and all temperature and humidity tests, and speed up the pace of product development.
