Reliability analysis of electronic components in low pressure environment

Date：2022-05-17 15:10:36Views：849

Reliability can comprehensively reflect the quality of products. The reliability of electronic components is the basis of the reliability of electronic equipment. In order to improve the reliability of equipment or system, we must improve the reliability of electronic components. Reliability is an important quality index of electronic components, which must be examined and tested. In order to help you have an in-depth understanding, this paper will summarize the relevant knowledge of the reliability of electronic components in low pressure environment. If you are interested in what this article will cover, read on.

1、 Low pressure environment

Under the action of the earth's gravity, the air is attached to the earth to form an atmosphere, which extends upward from the ground to hundreds of kilometers high. The gravity of the earth makes the air have a certain weight to form atmospheric pressure. The atmospheric pressure at a certain height is the weight of the whole air column per unit area perpendicular to the ground above that point. The atmospheric pressure is isotropic, that is, at a certain point, the atmospheric pressure is equal no matter which direction is measured. The atmospheric pressure mainly depends on the altitude. With the increase of altitude, the atmospheric pressure gradually decreases and the atmosphere gradually becomes thinner. When the altitude is close to 5.5km, the atmospheric pressure decreases to about half of the standard atmospheric pressure at sea level; The atmospheric pressure near 16km is 1 / 10 of the standard sea level value; The atmospheric pressure near 31km is 1 / 100 of the standard atmospheric pressure at sea level The reduction of atmospheric pressure will inevitably have an impact on the electrical and electronic products used in high-altitude areas. About 50% of the earth's surface area in China is 1000m above sea level, and about 25% is 2000m above sea level The greater the pressure gradient, the faster the pressure changes, and the more chance the components will be damaged.

2、 Influence of low pressure environment on electronic components

1. Impact on heat dissipation products

A considerable part of electrical and electronic products are heat dissipation products, such as motors and transformers. These products consume part of electric energy in use to turn it into heat energy and raise the product temperature. The temperature rise of heat dissipation products increases with the decrease of atmospheric pressure.

The heat dissipation of heat dissipation products can be divided into three forms: conduction, convection and radiation. The heat dissipation of a large number of heat dissipation products mainly depends on convection, that is, it depends on the air flow around the products to dissipate heat. Convective heat dissipation can generally be divided into forced ventilation heat dissipation and natural convection heat dissipation. Natural convection heat dissipation relies on the temperature field generated by product heating, resulting in the temperature gradient of the air around the product, which makes the air flow and heat dissipation. Forced ventilation and heat dissipation is to force the air to flow through the product and take away the heat generated by the product through compulsory measures. For forced convection heat dissipation, when the volume flow remains unchanged, the atmospheric pressure will decrease with the increase of height. The reduction of air density will directly affect the effect of forced convection heat dissipation. This is because forced convection heat dissipation depends on the flow of gas to take away heat. The cooling fan for general motor is to ensure that the volume flow through the motor remains unchanged. When the height increases, the mass flow of air flow will decrease due to the decrease of air density, even if the volume flow remains unchanged.

2. Influence on the performance of electronic components

The increase of height and the decrease of air pressure will also affect the performance of electronic components. Especially for the equipment with air as the insulating medium, the influence of low air pressure is more significant. Under normal atmospheric conditions, air is an excellent insulating medium, and many electrical products use air as the insulating medium. When these products are used as mechanical equipment in high altitude areas, partial discharge often occurs near the electrode with strong electric field strength due to the reduction of atmospheric pressure. More seriously, sometimes air gap breakdown occurs, which means that the normal operation of the equipment is damaged.

3、 Reliability control of electronic components in low pressure environment

1. Reasonable selection of components

The reliability of components is based on the design analysis and reasonable selection of components according to the service characteristics of components in the circuit. The reliability control point of electronic components should move forward and start from the source, that is, from design selection, optimization of manufacturers, compression of varieties, reliability test and improvement of quality level, so that the preventive measures exchanged for cost can play a role at the source, rather than always in the state of remedial measures. In addition, from the perspective of component reliability physical analysis, the quality and reliability analysis technology of components such as failure information collection and analysis, failure analysis, destructive physical analysis, internal atmosphere analysis of sealed components, correlation analysis of failure mode and mechanism and process, failure mode and impact analysis should be systematically carried out, and the quality and reliability analysis technology of components should be integrated into the product design and manufacturing process of components, Realize the reliability growth of components.

2. Supervision, test and acceptance of components

The production, test and acceptance of components are not only an important link to ensure the quality of components, but also a key control point for the reliability of components of aerospace products. The inherent quality of components is determined by the quality of its process control. Electronic components are divided by function, including electronic components, discrete devices and microcircuits; According to procurement channels, there are imported and domestic components; According to product maturity, there are shelf products and new devices. Different components have different control requirements, and there should be different treatment methods and procedures during off-site supervision, acceptance and arrival inspection. Therefore, the components shall be classified, the supervision mode, special test requirements and acceptance methods of various components shall be specified, and the corresponding procedures and execution units or departments shall be specified.

3. Destructive physical analysis

The main purpose of DPA (destructive physical analysis) of components is to prevent the installation and use of components with obvious or potential defects. In addition to the quality identification of components, in aerospace products, it is also used for the acceptance of components, quality review of components before installation, overdue re inspection of components and failure analysis of components. In general products, DPA is usually used for quality verification of installed components. In aerospace products, DPA must be completed before components are installed. Therefore, it is necessary to clarify the timing of DPA for components used in aerospace products, the test items of DPA, the organization implementing DPA, the data recording requirements of DPA and the processing method of DPA results.

4. Failure analysis method of components

The main task of component failure analysis is to conduct necessary electrical, physical and chemical tests on the failed components, and analyze them in combination with the specific conditions before and after the component failure and relevant technical documents, so as to determine the failure mode, failure mechanism and causes of the component failure. Through failure analysis, the inherent quality problems of failed components can be found, and the service quality problems of components that fail due to failure to use according to the specified conditions can also be found. Through feedback to relevant parties, the responsible party can be prompted to take corrective measures to improve the inherent quality or service quality of components.

Relatively speaking, the determination of failure mode is relatively simple, while the determination of failure mechanism is more difficult. Analysts must master the design, process and relevant physical and chemical knowledge of components, and have certain practical experience. In addition, it also has more complex instruments and equipment. After clarifying the failure mechanism, we must also find out the failure causes in order to avoid repeated failure and improve the inherent quality or service quality of components. However, determining the failure cause according to the failure mechanism often involves the specific conditions such as the failure site and the person in charge, which is quite difficult to determine. Therefore, it is necessary to first determine the unit for failure analysis, specify the procedures and failure information for submitting failure analysis, as well as the failure information recording requirements of failed components in each stage of product development, and then zero the causes of failure according to the conclusion of failure analysis. If it is a design defect, work with the manufacturer to find out the problem and make improvement; If it is an operation error, the operation specification must be strictly enforced to avoid introducing human error. The purpose of manufacturing and operation is to reach a higher level.

5. Management of component quality information

In the process of component selection, procurement, supervision and acceptance, screening and re inspection and failure analysis quality assurance, there is a lot of component quality information, such as the specification, model, manufacturer, quality grade and application of components outside the catalog; Domestic manufacturers of new devices and the use of new devices; Quality assurance of imported devices; Failure analysis report and treatment of components, etc.

To sum up, low air pressure will greatly affect the performance of electronic components and sometimes lead to direct damage.

The impact of low-pressure environmental conditions on components cannot be simulated under normal atmospheric conditions, and the test must be carried out according to relevant standards. Therefore, we must strengthen the standardization of environmental condition test, consider the impact of environmental changes on products from the design link, and enhance the adaptability of products to the environment, so as to improve the reliability of products.