How to inspect and screen electronic components

Date：2021-10-27 18:05:49 Views：2054

In the formal industrial production, there are special component screening and testing workshops, equipped with many general and special screening and testing equipment and instruments, but for amateurs, these conditions cannot be met. Even so, they must not give up the screening and testing of components, because many electronic enthusiasts use mail orders, including authentic products, There are also defective products, most of which are surplus or profit products. For example, they are not screened and tested before installation. Once welded into the printed circuit board, it is found that the circuit can not work normally, and then check it. It will not only waste a lot of time and energy, but also easily damage the components and printed circuit board. This paper has collected and sorted out some materials, and I hope this paper can be of great reference value to all readers.

1、 Inspection of appearance quality

This is a simple and feasible inspection method, which can find the early defects of some electronic components and the damage in the procurement process. When identifying and testing electronic components, the following operations shall be carried out:

1) Check that the model, specification, manufacturer and place of origin of components must meet the design requirements, and the outer packaging must be intact.

2) Check that the appearance of components must be intact, and the surface must be free of defects such as depression, scratch and crack. Components with coating on the outside must be free of falling off and scratch.

3) The electrode leads of components shall be free from crimping and bending, and the coating shall be intact and smooth without oxidation and corrosion.

4) The model and specification marks on the components shall be clear and complete, the color code position and color shall meet the standards, and the characters on the integrated circuit shall be carefully checked.

5) The size of components of mechanical structure shall be qualified, the thread shall be flexible and the rotation feel shall be appropriate.

6) Switch components are flexible and feel good; The connector shall have proper tightness and good contact. The components in various electronic products have their own characteristics. During inspection, the inspection contents shall be determined according to the specific requirements of each component.

2、 About electrical performance screening

In order to ensure the stability and reliability of electronic products, screening the components on the computer is an important link. During screening, one or more stresses shall be applied to electronic components according to the use requirements of components to expose their defects and eliminate early failure. The screening test and applied stress shall be in an appropriate range to make the defective components invalid, and the components with good quality will pass the test.

1. Component efficiency curve

The efficiency curve of electronic components, i.e. bathtub curve, reflects the failure law of components in use. Generally, when the components are just put into use, the failure rate is high due to the defects of raw materials, equipment and technology in the manufacturing process of components. After components are used for a period of time, the failure rate of components is low, that is, accidental failure period. After the normal service life, the components enter the aging failure period, that is, the loss failure period. The working life of the components ends. In the aging failure period, the failure rate of components increases.

2. Screening and aging of electronic components

For the aging screening of components, the early working conditions of components shall be artificially manufactured, so that the components are in the simulated working voltage state, and the early failure products shall be removed before use to improve the reliability of products. In the production process, screening aging includes high temperature storage aging, high and low temperature cycle aging, high and low temperature impact aging and high temperature power aging. With the improvement of the production level of components, different aging screening requirements and processes should be selected according to different product requirements and national and enterprise standards. 100% screening shall be conducted for typical components used in electronic products or equipment with high reliability requirements, and sampling inspection shall be adopted for components used in civil products with low requirements; Natural aging and simple electrical aging methods shall be adopted for the components used in the development and manufacturing of general electronic products.

3. Parameter performance test

After appearance inspection and aging of electronic components, the performance index shall be tested to eliminate the failed components. Before testing, you should have a comprehensive understanding of the common problems and solutions in the testing of electronic components. It is required to have a variety of general or special testing instruments. The components used in general electronic design or electronic equipment shall be tested by common instruments such as multimeter. When using a multimeter for testing, pay attention to the use requirements of the multimeter and use it correctly.

1) General multimeter has analog pointer type and digital type. The former is reliable, durable and intuitive, but the reading is inaccurate and the resolution is low; The latter has accurate and intuitive reading, high input resistance and high requirements for use and maintenance.

2) Two kinds of multimeter require to select functions and jacks when using: pointer type generally has a special jack when measuring high current and high voltage; The special jack is used when measuring the current above 200mA, and the special jack is used for the current gear of some types of multimeter.

3) When selecting the measuring range, it should be noted that the indication error of the pointer multimeter is small at about 30% ~ 35% and 65% ~ 70% of the full scale. If it is difficult to determine the measurement range, it shall be gradually converted from the maximum range.

4) When using a multimeter, the human body shall not touch the metal part of the probe to ensure accurate measurement and personal safety.

5) When measuring high voltage or large current, do not shift during measurement. Disconnect the probe when shifting. After selecting the range, connect the probe for measurement, otherwise the multimeter will be damaged.

6) When measuring diode, rectifier, triode, aluminum electrolytic capacitor and other polar components, pay attention to the polarity of the probe. In the resistance block, the red lead of the pointer multimeter is connected to the negative pole of the internal power supply of the multimeter, the black lead is connected to the positive pole of the internal power supply, the red lead of the digital multimeter is connected to the positive pole of the internal power supply of the multimeter, and the black lead is connected to the negative pole of the internal power supply.

When the multimeter cannot meet the test requirements, the LRC handheld bridge shall be selected to measure the parameters such as resistance, capacitance, inductance and quality factor, and the combined multimeter shall be selected to measure the parameters such as voltage, current, resistance and frequency. Handheld bridge and desktop multimeter are selected to measure relevant parameters. The test accuracy is higher than that of multimeter, and it also has the measurement function that multimeter does not have.

In conclusion, we should pay attention to quality control in electronic product screening, reasonably use the performance parameters of components, simplify circuit design, improve reliability, and reduce the use to improve reliability. I hope it can help you. We will bring more wonderful content later. The company's testing services cover: electronic component testing and verification, IC authenticity identification, product design and material selection, failure analysis, function testing, factory incoming material inspection, tape braiding and other testing items. Welcome to call Chuangxin testing, we will serve you wholeheartedly.