Incoming inspection and judgment method of PCBA electronic components

Date：2021-12-22 14:04:41 Views：2204

For PCBA industry, the incoming inspection of components is the first barrier to be guarded by the whole quality management, and it is also a very important link. By strictly controlling the incoming links, it has an important impact on the final product quality. If the standards of various devices are different, the supplier's specifications shall be consulted before incoming materials. The main purpose is to prevent the outflow of defective products from adversely affecting the company's reputation and reputation, and the problems of repair, rework and return of defective products will bring economic losses to the company.

Incoming inspection sampling method:

1. Prepare inspection tools.

2. Overall inspection: whether the outer packaging is intact, whether the label is clear and correct, whether the inner packaging is intact, whether the label is clear and correct, whether there are a few, and whether the packing is disordered.

3. Sampling inspection.

4. Single product inspection: appearance and size inspection, function inspection and reliability inspection. Judgment result: if it passes, the packaging shall be restored, the pass seal shall be affixed, and the aging label shall be affixed; If it fails, the packaging shall be restored and the reject seal shall be affixed.

Incoming inspection method of electronic components:

1. Component performance and appearance quality inspection

The performance and appearance quality of components have a direct impact on the reliability of SMA. First, check the incoming components according to relevant standards and specifications. Pay special attention to whether the performance, specification and packaging of components meet the ordering requirements, product performance requirements, assembly process and equipment requirements, storage requirements, etc.

2. Solderability test of components

The solderability of component pins (electrode terminals) is the main factor affecting the welding reliability of SMA. The main reason for the problem of solderability is the oxidation on the surface of component pins. Since oxidation is easy to occur, in order to ensure the reliability of welding, on the one hand, measures should be taken to prevent the components from being exposed to the air for a long time before welding, and avoid long-term storage, etc; On the other hand, pay attention to the weldability test before welding, so as to find problems and deal with them in time.

The original method of solderability test is visual evaluation. The basic test procedure is: immerse the sample in the flux, remove the excess flux, and then immerse it in the molten solder tank. When the immersion time is about twice the actual production welding time, take it out for visual evaluation. This test experiment is usually carried out with an immersion tester, which can control the immersion depth, speed and immersion residence time of the sample according to the specified accuracy.

3. Other requirements

① The components shall have good pin coplanarity. The basic requirement is no more than 0.1mm. Under special circumstances, it can be relaxed to the same thickness as the pin.

Surface assembly technology is to mount components on the surface of PCB. Therefore, there are strict requirements for the coplanarity of component pins. Generally, it must be within the tolerance area of 0.1mm. This tolerance zone consists of two planes, one is the welding area plane of PCB and the other is the device pin plane. If the same plane of the three lowest points of all pins of the device is parallel to the plane of the PCB welding area, and the distance error between each pin and the plane does not exceed the tolerance range, the mounting and welding can be carried out reliably, otherwise there may be welding faults such as pin false welding and lack of welding.

② The thickness of solder coating layer at the pin or welding end of components shall meet the process requirements, and it is recommended to be greater than 8 μ m. The tin content in the coating shall be between 60% and 63%.

③ The dimensional tolerance of components shall comply with the provisions of relevant standards and meet the requirements of pad design, mounting, welding and other processes.

④ Components must be able to withstand heating for 10 welding cycles at 215 ℃. Generally, each welding shall be able to withstand the following conditions: vapor phase reflow is 215 ℃ for 60s; Infrared reflow soldering: 230 ℃, 20s; Wave soldering is 260 ℃ for 10s.

⑤ The components shall be solvent resistant at the cleaning temperature (about 40 ℃), such as staying in Freon for 4min. Under the condition of ultrasonic cleaning, they can stay in the ultrasonic with frequency of 40KHz and power of 20W for at least 1min. The marks will not fall off and will not affect the performance and reliability of components.

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