High and low temperature testing is a method to determine the adaptability of a product under storage, transportation, and usage in high or low temperature climatic conditions. The severity of the experiment depends on the temperature of high or low temperatures and the duration of exposure.
High and Low Temperature Test Standards:
GB/T 2423.2-2008 Environmental Tests for Electrical and Electronic Products - Part 2: Test Methods - Test B: High Temperature
GBT 2423.1-2008 Environmental Tests for Electrical and Electronic Products Part 2: Test Methods Test A: Low Temperature
IEC 60068-2-2 Fundamental Environmental Testing Procedures, Part 2-2: Test Test B: Dry Heat
IEC 60068-2-1:2007 Environmental Test for Electrical and Electronic Products: Low Temperature
Section II: Applicable Industries Include:
Electronics, components, circuit boards, telecommunications, LED, LCD screens, instruments, capacitors, vehicles, plastics, metals, chemicals, construction materials, and more.
Three, the high and low temperature experiment chamber is mainly capable of conducting the following experimental projects:
(1) High-Temperature Test
Experimental Objective: To verify the adaptability of the experimental samples for storage or use under high-temperature conditions. Applies to equipment and instruments operating in high-temperature environments such as tropical weather or steel mills.
High and Low Temperature (Humidity) Test Chamber for Experimental Equipment
Test Conditions: Generally, a stable temperature stress and duration are selected.
Preferred Common Temperatures: 200°C, 175°C, 155°C, 125°C, 100°C, 85°C, 70°C, 55°C, etc.
Preferred experimental time points include: 2h, 16h, 72h, 96h, etc.
(2) Low-Temperature Test
Test Objective: To verify the adaptability of the experimental samples for storage or use under low-temperature conditions. Commonly used in type tests during the product development stage and for the selection of components.
High-Temperature and Low-Temperature (Humidity) Test Chamber
Experimental Conditions: Generally, a stable temperature and experimental time are selected.
Preferred temperatures include: -65°C, -55°C, -40°C, -25°C, -10°C, -5°C, +5°C, etc.
Preferred common experimental times include: 2h, 16h, 72h, 96h, etc.
(3) Rapid Temperature Change Test.
Experiment Objective: Rapid temperature variation refers to temperature changes with a regular rate of change, often mimicking environments with significant diurnal temperature differences, and can also be used for lifespan experiments to evaluate the appearance, mechanical, and electrical functions of components or products.
Test Equipment: Rapid Temperature Change Experimental Box.
Test Conditions:
1) High and low temperature values with scale changes in temperature;
2) Retention time at high and low temperatures for the sample.
3) Rate of temperature change from low to high or between high and low temperatures;
4) Number of condition testing cycles.
(4) Temperature shock test.
Test Objective: To evaluate the product's adaptability to rapid changes in environmental temperature. The objective of the thermal shock test is fundamentally the same as that of the temperature cycle test, but the conditions of the thermal shock test are much more stringent than those of the temperature cycle test.
Test Equipment: Two sets of cold and heat shock test chambers and three sets of cold and heat shock test chambers.
Test Conditions:
1) High and low temperature values for temperature change scale;
2) Retention time at high and low temperatures for the sample.
3) Moment of change from low to high temperature, or from high to low temperature.
4) Number of condition test cycles.
(5) Stable Temperature and Humidity Test
Experimental Objective: To assess the adaptability of the product for use and storage under humid and hot conditions, observe the effects on the experimental samples under stable temperatures, without condensation, and at regular intervals in a high-humidity environment, to accelerate the evaluation of the method's effectiveness in resisting humid and hot deterioration.
Laboratory Equipment: Constant Temperature and Humidity Chamber.
Test Conditions: Test Temperature; Test Humidity; Test Time.
Preferred temperature/humidity combinations include: 40°C, 85%; 40°C, 93%; 85°C, 85% etc.
Preferred common experimental intervals include: 48h, 96h, etc.
(6) Temperature and Humidity Cycle Test
Test Objective: To determine the adaptability of the experimental sample for use and storage under humid conditions with temperature cycling and condensation on the surface.
High and Low Temperature (Humidity) Test Chamber
Test Conditions: Selected temperature, humidity, cycle count, temperature change rate, duration.
High and low temperature testing requirements
1. The product surface is free from any damage, deformation, or defects. If it's coated or plated, there should be no peeling, bubbling, or discoloration on the surface.
2. Plastic parts shall be free of cracks, bubbles, and deformation.
3. Rubber products free from aging, bonding, softening, and cracking.
4. No drips are present at the welding parts of the product.
5. Product functional data and structural features comply with technical specifications and requirements; no other defects should be present that could hinder the normal operation of the product.
High and Low Temperature Test Applications
Computers and accessories: computers, monitors, servers, computer components, equipment, and other precision instruments.
2. Electronics & Communication: Mobile phones, radio frequency devices, electronic communication components, etc.
3. Electrical Appliances: Household electronics, lighting fixtures, transformers, and other electrical equipment.
4. Other: Packaging boxes, shipping equipment, etc.
High and low temperature testing methods
Preheat the chamber to 25 ± 3 ℃ and maintain this temperature, adjusting the relative humidity to 45% - 75% for a stable temperature treatment of 2 to 6 hours. In the last hour, increase the chamber's relative humidity to no less than 95%, while keeping the temperature at 25 ± 3 ℃.
After the stable phase, initiate the cycle so that the box temperature rises continuously from 25 ± 3℃ to 55 ± 2℃ within 2.5 to 3 hours. During this warming phase, the relative humidity should not fall below 95% except for the last 15 minutes, when it should be at least 90%, to allow condensation on the test sample surface but not excessive condensation on large experimental samples. Then maintain this high-temperature and high-humidity environment of 55 ± 2℃ for 12 ± 0.5 hours from the start of the cycle. The relative humidity during this stage should be (93 ± 3)% except for the initial and final 15 minutes, which should not be below 90%.
Then, within 3 to 6 hours, reduce the box temperature from 55 ± 2℃ to 25 ± 3℃. The initial 1.5 hours cooling rate is 10℃/h, with relative humidity not falling below 90% in the first 15 minutes, and at least 95% throughout the rest of the period.
After cooling, the temperature must maintain at 25℃±3℃ with relative humidity not less than 95%, with a cycle of 24 hours starting from the beginning of the circulation.
Differences in Testing Methods
1. Non-heat sink samples and heat sink samples
Under natural air conditions, a sample is referred to as a heat dissipation test sample if the surface temperature remains above the ambient atmospheric temperature by more than 5℃ after reaching a stable state. A sample with a temperature increase of 5℃ or less is considered a non-heat dissipation test sample. All non-operational storage and transportation tests are classified as non-heat dissipation tests. During operational testing, if the temperature increase of the test sample is less than 5℃ after reaching a stable state, it is also classified as a non-heat dissipation test.
If the surface temperatures of the externally accessible parts of an electric fan do not exceed 20℃ after testing, it is a heat dissipation test.
2. Temperature Shock Test and Temperature Ramping Test
Upon reaching or dropping to the specified temperature, the sample is immediately placed in the testing chamber for a temperature shock test. Conversely, placing the sample in a testing chamber at room temperature first, then gradually increasing or decreasing the chamber's temperature to the specified experimental temperature, is referred to as a temperature ramp test.
Generally speaking, if sudden temperature changes have no other harmful effects on the test sample, sudden temperature change testing should be used to save time. Otherwise, gradual temperature change testing should be chosen.
3. Forced Air Circulation Test Without Compulsion and Forced Air Circulation Test With Compulsion
During non-heat dissipation testing, forced air circulation is recommended to enhance heat exchange efficiency. The higher the air circulation speed, the greater the heat exchange efficiency. Therefore, it is advisable to use an air circulation speed of ≥2 m/s during such forced tests.
During heat dissipation testing, a better approach is to opt for non-forceful air circulation testing. If non-forceful air circulation does not meet the experimental requirements, forced air circulation testing should be chosen.
What is a high and low temperature test? A high and low temperature test primarily imitates the changes in high and low temperatures in natural environments to test how well a product withstands heat, cold, and dryness. It usually includes high-temperature tests, low-temperature tests, and tests for changes in temperature and humidity.
High and low temperature testing equipment primarily simulates environmental conditions according to national standards or customer-specific requirements to assess the physical and other related properties of products under various low and high temperature conditions. After testing, it can preliminarily determine if the product's functionality still meets the预定 requirements, and is mainly used for product design, improvement, certification, and factory inspection.
