Environmental testing is an important method for evaluating product reliability, which assesses the adaptability of products under various environmental conditions, such as vibration, shock, centrifugation, temperature(high temperature test and low temperature test), thermal shock(thermal shock reliability test), humidity, salt spray, low pressure, and so on.
Life testing is a method of studying the life characteristics of a product, which simulates various usage conditions in the laboratory. Life testing is one of the most important and basic projects in ort ongoing reliability test, which examines the failure (damage) of the product under specific test conditions over time. Through life testing, the life characteristics, failure rules, failure rate, average life, and various failure modes that may occur during the life testing process of the product can be understood. By combining failure analysis, the main failure mechanism leading to the product failure can be further clarified, which provides the basis for reliability design, reliability prediction, improvement of new product quality, and determining reasonable screening and routine (batch assurance) test conditions. If the test time can be shortened by increasing stress without changing the failure mechanism, it is called accelerated life testing. Life testing can be used to evaluate the reliability level of products and improve the reliability level of new products through quality feedback.
Screening test is a non-destructive test of all products. Its purpose is to select products with certain characteristics or eliminate early failures of products to improve the reliability of product use. During the manufacturing process, due to defects in materials or process control, some products may have early defects or failures. If these defects or failures can be eliminated early, the reliability level of the product can be guaranteed during actual use. The characteristics of reliability test are that this test is not a sampling test, but a 100% test; this test can improve the total reliability level of qualified products, but cannot improve the inherent reliability of each product, that is, it cannot improve the life of each product; the effectiveness of the screening cannot be simply evaluated by the screening rejection rate. A high rejection rate may be due to serious defects in product design, components, or processes, but it may also be due to the high intensity of screening stress. A low rejection rate may be due to few product defects, but it may also be due to insufficient screening stress intensity and test time.
The above-mentioned tests are all conducted by simulating on-site conditions. Due to equipment limitations, simulated tests often only apply a single stress to the product, and sometimes double stresses can be applied. There is a significant difference between such simulated tests and actual usage environment conditions, so they cannot truly and comprehensively expose the quality of the product. Field use testing is different because it is performed in the actual usage environment, so it can most realistically reflect the reliability issues of products. The data obtained from the field use testing has high value for reliability prediction, design, and assurance. Field use testing is also important for developing reliability test plans, verifying reliability test, and evaluating test accuracy.
