PCB Tech - Basic inspection methods and procedures for PCB

Basic inspection methods and procedures for printed circuit boards

Since the first batch of computers were produced, the progress of electronic technology has been very magnificent, but the hero of all this is the integration of the circuit system. Whether it is a semiconductor chip or a circuit board, it is essentially to save space and integrate complex cables into a small space. But this also brings a problem, that is, after it is manufactured, the integration level is very high, and repair is basically impossible in the later stage, and it can only be tested and guarded at the factory. At present, the lightweight of various equipment puts forward higher requirements for the quality inspection of PCBs, and traditional inspections can no longer meet the quality control requirements of the printed circuit board production industry. As the most important component and connection unit of modern electronic equipment, PCB circuit boards have high mounting density and small size of SMD components. Therefore, the integration of PCB boards is required to continue to increase. The quality of the motherboard directly affects the quality of the entire electronic product, so PCB testing equipment is very important. The final step of PCB production is to carry out quality inspection. Various tests in the factory are an inspection method to discover problems in time and provide reliable products. It is also a necessary means to prevent losses due to product quality.

Main points of PCB board testing:

1. Check the insulation performance of the soldering iron when the PCB board is soldered;

2. Test whether there is a short circuit between the pins of the circuit board;

3. The PCB board test instrument meets the standard, and the built-in resistance should be sufficient for testing;

4. Pay attention to the power when detecting the circuit board and monitor the heat dissipation of the integrated circuit to avoid danger;

5. The lead wire of the PCB board is reasonable and reliable;

6. Detect the welding quality of the PCB board in the case of welding;

7. Do not arbitrarily judge whether the integrated circuit is damaged when testing the PCB board

8.Before testing the PCB board, you must be proficient in the working principle of integrated circuits and related circuits

What should be done before PCB testing? First of all, clarify the environment and requirements of the equipment when it is working. The first factor is the possible impact of external electrical parameters on the equipment. Subsequently, observe the phenomenon that occurs when the PCB fails, and analyze the cause of the failure. Then carefully check the chip components on the circuit board to find out the important components in the circuit board and their influence on the function of the circuit board. Finally, anti-interference measures such as anti-static and anti-electromagnetic must be taken.

PCB inspection methods include the following: The first is manual visual inspection, but this method is expensive, and due to long-term visual inspection of PCB, human eye fatigue may produce certain errors. In addition, the integration of modern PCBs continues to increase, and the wire spacing With the shrinking of SMD components, the requirements for visual inspection are also increasing. With the specialization of PCB production and output factors, manual visual inspection methods are becoming more and more backward; the other is the functional testing of circuit boards. Functional system testing refers to the use of special test equipment in the intermediate process stage of the production line and the early stage of shipment. Comprehensively test the functional modules of the circuit board to confirm whether the circuit board is malfunctioning. It requires special equipment and a specially designed test process, and it is cumbersome to write a functional test program, so it is not suitable for most circuit board production lines. But nowadays, a single-size inspection is relatively widely used. It uses a plane imaging system measuring instrument to measure the position, length, width, hole position and other shape data. PCB is a delicately processed and fragile product. Contact measurement is prone to PCB deformation and inaccurate measurement. Planar image measuring instruments have become the best choice for high-precision size measuring instruments. After the plane image measuring instrument is programmed, it can realize fully automatic measurement. At the same time, it has the triple effect of high measurement accuracy, greatly shortening the measurement time, and improving the measurement efficiency.

The above is the step that has the greatest impact on quality in PCB production, so that the quality of the product can be guaranteed. This should also be because the PCB factory has introduced the latest plane testing equipment to ensure the quality of shipments.