PCB Tech - Basic knowledge and methods of PCB board inspection

The reason why PCBs that are exposed to in life can be more and more widely used because of its unique advantages such as high reliability, high density, designability, manufacturability, etc. are closely related to PCB No matter in terms of output and performance indicators, there has been rapid growth in the demand for many years. Correspondingly, higher requirements have been put forward for the quality inspection of PCB. Traditional inspection methods can no longer meet the requirements of the PCB industry for quality control. PCB board is an important part of modern electronic equipment. Due to the small size and high mounting density of SMD components, the required integration level is further improved. The quality of PCB directly affects the quality of the entire electronic product, so PCB testing equipment is particularly important and critical. Various PCB tests are an inspection method to discover problems in time, and it is also a necessary means to prevent more defective products and reduce losses.

When inspecting PCB boards, the following points should be paid attention to:

1. Do not cause a short circuit between the pins when testing the PCB board

2. Pay attention to the insulation performance of the soldering iron when testing the PCB board

3. The internal resistance of the PCB board test instrument should be large

4. Pay attention to the heat dissipation of the power integrated circuit when testing the PCB board

5. The lead wire of the PCB board should be reasonable

6. Inspect PCB board to ensure welding quality

7. Do not easily determine the damage of the integrated circuit when testing the PCB board

8. Before testing the PCB board, understand the working principle of integrated circuits and related circuits

What should be done before? First understand the working environment of the device, mainly consider the possible impact of external electrical parameters on the device; ask what happens when the circuit board fails, and analyze the cause of the failure; carefully check the components on the circuit board to find out what is wrong Which components the circuit board plays a key role? Take measures to prevent electromagnetic interference and static electricity.

So, what are the commonly used inspection methods for PCB boards in the production process?

In addition to the high cost of manual visual inspection, certain errors are generated due to long-term visual inspection, coupled with the reduction of the wire spacing and component volume on the PCB, the requirements for manual visual inspection are also increasing. Obviously, with the continuous increase in PCB production This method is becoming more and more inappropriate.

There is also a PCB board function test. The functional system test uses special test equipment in the middle and end of the production line to conduct a comprehensive test on the functional modules of the circuit board to confirm the quality of the circuit board. It requires special equipment and a specially designed test process, and it is complicated to write functional test programs, so it is not suitable for most circuit board production lines. But nowadays, there is a kind of size detection that is relatively widely used. It uses a two-dimensional image measuring instrument. Measure dimensions such as hole position, length and width, and position.

Since PCB is a small, thin and soft type of product, contact measurement can easily produce deformation and cause inaccurate measurement. The two-dimensional image measuring instrument has become the choice of high-precision size measuring instruments.

It is precisely because the PCB has a wide range of applications in today’s society that there may be questions about the PCB inspection process. Here are some practical methods of operability that have been summarized after years of testing. Provided in this way For everyone, I hope to provide useful references for everyone in the practice of circuit board testing.