The focus of five common electronic components screening projects has come

Date：2021-07-19 13:17:06 Views：1757

Components are the basis of the whole machine. The inherent reliability of electronic components depends on the reliability design of products. In the manufacturing process, due to its inherent defects or improper control of manufacturing process, the final finished products cannot achieve the expected inherent reliability. How to accurately and effectively detect the relevant parameters of components and determine whether the components are normal or not, different methods must be adopted according to different components, so as to detect whether the components are normal or not. Therefore, before the electronic components are installed on the whole machine and equipment, we should try to eliminate the components with early failure as much as possible. Therefore, we should screen the components. Several common electronic components screening items are introduced below.

1) High temperature storage

The failure of electronic components is mostly caused by various physical and chemical changes in their body and surface, which are closely related to temperature. After the temperature rises, the chemical reaction speed is greatly accelerated and the failure process is accelerated, so that the defective components can be exposed and removed in time.

High temperature screening is widely used in semiconductor devices. It can effectively eliminate devices with failure mechanisms such as surface contamination, poor bonding and oxide defects. Usually, the device needs to be stored at the maximum junction temperature for 24 ~ 168 hours.

High temperature screening is simple and inexpensive, and can be implemented on many components. After high-temperature storage, the parameter performance of components can be stabilized and the parameter drift in use can be reduced. The thermal stress and screening time of various components shall be properly selected to avoid new failure mechanism.

2) Power aging

When screening, under the combined action of thermoelectric stress, it can well expose a variety of potential defects in the body and surface of components. It is an important item of reliability screening.

Various electronic components are usually aged for several hours to 168 hours under rated power conditions. Some products, such as integrated circuits, can not change the conditions at will, but can adopt high-temperature working mode to improve the working junction temperature and achieve high stress state. The electrical stress of various components shall be properly selected, which can be equal to or slightly higher than the rated conditions, but can not lead to new failure mechanism.

The power aging needs special test equipment and its cost is high, so the screening time should not be too long. Civil products usually take several hours, military highly reliable products can choose 100 or 168 hours, and aerospace components can choose 240 hours or even longer.

3) Temperature cycle

Electronic products will encounter different ambient temperature conditions in the process of use. Under the stress of thermal expansion and cold contraction, components with poor thermal matching performance are easy to fail. Temperature cycle screening uses the thermal expansion and contraction stress between extreme high temperature and extreme low temperature, which can effectively eliminate the products with thermal performance defects. The common screening conditions for components are - 55 ℃ to + 125 ℃, with 5-10 cycles.

4) Centrifugal acceleration

Centrifugal acceleration test is also called constant stress acceleration test. This screening is usually carried out on semiconductor devices. The centrifugal force generated by high-speed rotation is applied to the devices to eliminate devices with too weak bonding strength, poor internal lead matching and poor mounting. Usually, the centrifugal acceleration of 20000g is selected and the test is continued for one minute.

5) Monitoring vibration and shock

It is often called monitoring vibration or monitoring impact test to monitor the electrical performance of products at the same time of vibration or impact test. This test can simulate the vibration and impact environment during the use of the product, effectively eliminate components with poor mechanical structure such as instantaneous short circuit and open circuit, and find faults such as false welding in the whole machine. Monitoring vibration and shock is an important screening item in highly reliable relays, connectors and military electronic equipment.

Typical vibration conditions: the frequency is 20-2000hz, the acceleration is 2-20g, the scanning period is 1 ~ 2 cycles, and it is necessary to stay near the resonance point for an additional period of time. The typical impact screening conditions are 1500-3000g and impact for 3 ~ 5 times. This test is only applicable to components. Monitoring vibration and shock requires special test equipment, which is expensive and generally not used in civil electronic products. In addition to the above screening items, there are commonly used thickness leak detection, microscopic inspection, linear discrimination screening, precision screening, etc.

This article introduces that the inherent reliability of electronic components depends on the reliability design of products. In the manufacturing process of products, due to human factors or fluctuations in raw materials, process conditions and equipment conditions, the final finished products cannot all achieve the expected inherent reliability. In each batch of finished products, there are always some potential defects and weaknesses in some products, which show early failure under certain stress conditions. Therefore, whether military products or civil products, screening is an important means to ensure reliability. For military products, screening is more important. According to national requirements, each component in each batch of military products should be tested through screening test to find and eliminate defects and hidden dangers in manufacturing, technology and materials, so as to ensure the reliability of components.