1、 The Origin, Purpose, and Introduction of Environmental Testing
Origin: It originated from the military and was first recorded in literature as conducting metal sample hanging tests on the edge of rivers entering the sea, which was the earliest natural environmental experiment.
During World War I, a large proportion of weapons were transported to the battlefield and could not work. Many weapons were stored for a period of time and could not work, resulting in a high proportion. Therefore, a series of environmental adaptability tests were developed.
During World War II, in order to further promote the environmental adaptation of weapons, the United States established the 'Center for Deterioration Protection' to develop environmental testing standards for military products.
Purpose: Quality is the foundation of product value. When quality problems occur after a product is launched on the market, the degree of performance damage does not directly affect product costs. The biggest loss for manufacturers is the loss of brand reputation. To avoid these losses, it is necessary to conduct quality appraisal of the product before it is put on the market. Environmental testing is not only capable of identifying product quality through simulation testing and product life aging testing, but also an essential part of the quality assurance system.
Introduction: Environmental testing is a simulation test conducted based on the (extreme) environment that may occur during product transportation and use, aiming to identify the vast majority of problems during the product development stage, so that no major problems will occur after the product is launched into the market. All guidelines are based on the actual user profile of the product.
Environmental testing is more focused on verifying the design objectives of products, mainly in terms of transportation, storage, and work environments. However, environmental testing can only say that the product can work in specific environments and does not necessarily demonstrate its ability to work continuously under specific conditions for a long time. In other words, environmental testing cannot tell us the reliability level of the product.
2、 Classification of environmental tests
1. Environmental testing can be classified according to its methods:
1.1 Natural exposure test:
Natural environment exposure test refers to a test conducted in a natural environment for a long time, usually under outdoor natural conditions. Environmental exposure test is usually used to study the environmental adaptability of materials and production processes (coatings and coatings) of outdoor products, with a focus on corrosion and deterioration of materials.
1.1.1 Effect of natural exposure test:
Through natural exposure testing, the variation pattern, failure situation, failure level, and cause of electrical parameters of products under natural environmental conditions can be obtained. It is also possible to understand the stability and protective ability of materials, processes, coating layers, and other properties during the product manufacturing process.
Natural exposure testing can provide data for studying artificial simulation testing methods and their conversion relationships, and can also be used to verify and compare the effectiveness of accelerated testing.
1.1.2 Limitations of natural exposure tests:
The uncontrollable experimental conditions have to some extent affected the reproducibility of the experiment.
In addition, the natural exposure test has a long testing cycle and sometimes cannot keep up with the development of the product.
1.2. Artificial simulation test:
Simulate the climate and mechanical environment of products during storage, transportation, and use through testing instruments such as temperature and humidity chambers, vibration tables, salt spray chambers, and light aging test chambers.
1.2.1 Classification of artificial simulation experiments:
According to the environmental conditions encountered during storage, transportation, and use of products, they can be divided into:
Climate environment - temperature and humidity category: high temperature, low temperature, constant humidity, alternating humidity, temperature and humidity combined cycle, rapid temperature change, cold and hot shock, low pressure (highly simulated).
Climate environment - Lighting category: UV ultraviolet test, xenon lamp test, metal halide lamp, carbon arc lamp.
Mechanical environment: random vibration test, sine vibration test, resonance search and dwell, sine+random vibration test, random+random vibration test, mechanical impact test, collision test, steady-state acceleration, drop test.
Comprehensive environment: temperature+humidity+vibration, temperature+humidity+impact, temperature+humidity+collision, HALT/HASS/HASA, temperature+humidity+stacking, high-pressure cooking.
Protection level: IP protection (waterproof, dustproof), IK protection (external mechanical collision protection).
Biological and chemical active substance environment: salt spray test, mold test, gas corrosion, resistance to chemical reagents, artificial sweat.
1.2.2 Advantages and disadvantages of manual simulation testing
Compared with natural exposure testing, artificial simulation testing can accelerate and strengthen testing, save time, and can be conducted at any time. The test parameters are easy to control, and the reproducibility is good.
The disadvantage is that when the conditions and test procedures are not chosen properly, it can distort the test and even lead to incorrect conclusions.
1.3. On site testing:
Conduct inspection and testing on the product under actual usage conditions.
1.3.1. Role of on-site usage testing
For large products, especially mobile and large complete sets of equipment (such as environmental adaptability tests when testing cars at high speeds), on-site testing can only be conducted.
In addition, for those who need to collect on-site actual data, on-site tests need to be conducted in actual environments, such as high-speed train operation and actual packaging road test of large equipment.
1.3.2 Advantages and disadvantages of on-site use testing
During the on-site use of the product, it is subject to the comprehensive effects of various environmental factors, so it can better expose the problems of the product than single or combined tests. It can be seen that the results of on-site use experiments are the most authentic and persuasive.
Its shortcomings are long cycles and high costs.
2. Environmental tests are classified according to environmental conditions:
2.1. GB/T 4796-2017/IEC 60721-1:2002 'Classification of Environmental Conditions - Environmental Parameters and Their Severity' divides the environmental conditions of products into seven categories: climatic conditions, biological conditions, chemically active substances, mechanically active substances, polluting liquids, mechanical conditions, electrical and electromagnetic interference.
2.2. ETSI 300 019 'Environmental Testing Series for European Communication Products' divides the environmental conditions of products into categories such as air temperature, humidity, air (pressure and velocity), water, radiation, chemical active substances, mechanical active substances, biology, vibration, impact, earthquake, etc.
3、 The role of environmental testing
3.1. During the design and development stages of the product, environmental testing is used to assess whether the selected components, designed structures, and adopted processes can meet the requirements of the actual environment and the existing defects. To save time and fully expose the weak links of the product, an accelerated life aging test is used, which uses different acceleration factors based on different environmental stress factors to strengthen and accelerate the process.
3.2. During the product design stage, environmental testing is used to determine whether the technical indicators of the product can meet the design requirements in the predetermined environment, whether the design life can be guaranteed under normal working conditions, and whether the safety requirements can be met. The environmental test at this stage is an environmental adaptability test, which is conducted under the actual environmental conditions during product storage, transportation, and use.
3.3. During the normal production stage of the product, there are significant changes in the production process, or after a considerable period of production, environmental testing is used to check the process quality of the product or to check its quality stability. The environmental test at this stage is also an environmental adaptability test.
3.4. In the final inspection stage of the product, environmental testing checks all products by applying non-destructive stress to eliminate early failures, reduce the number of non-conforming products, and test work for a period of time to stabilize product performance before qualified products are put into use. The environmental test at this stage is an environmental screening test.
3.5. Environmental testing can also be used for safety checks to check whether the product has any health, life, and property hazards. For example, using vibration tests to check the firmness of installation and connections. When environmental testing is used to assess safety, higher test conditions than normal testing are usually used.
4、 The Importance of Environmental Testing
Environmental testing is an important means of evaluating the environmental adaptability of product components, systems, and their packaging under actual storage, transportation, and usage environmental conditions. It is also an important means of inspecting and ensuring the quality of products.
5、 When to conduct environmental tests
5.1. Environmental testing runs through the entire process of design, trial production, production, sales, and use of electronic and electrical products, and its role and manifestation vary at different stages.
5.2. Environmental testing can play an important role in raw material certification during the product design stage, reliability growth during the development stage, reliability statistics during the finalization stage, environmental adaptability during the production process, and environmental screening before leaving the factory.