Several common sense of PCB manufacturers proofing

How many 9 small knowledges do you know about PCB proofing? The following knowledge is included in detail, and the details should be understood with PCB proofing manufacturers.

1. Pay attention to the insulation function of the electric soldering iron when detecting the PCB board

It is not allowed to use a soldering iron for soldering with power. It is necessary to admit that the soldering iron is not charged. Ground the shell of the soldering iron. Be more careful with the MOS circuit. It is safer to use a low-voltage circuit iron of 6~8V.

2. Before inspecting the PCB board, understand the working principle of integrated circuits and related circuits. Before inspecting and repairing integrated circuits, you must first understand the functions of the integrated circuits used, the internal circuits, the main electrical parameters, the role of each pin, and the normal voltage of the pins. The working principle of the circuit composed of waveforms and peripheral components. If the above conditions are met, the analysis and inspection will be much simpler.

3. It is strictly forbidden to use grounded test equipment to touch the live TV, audio, video and other equipment on the bottom plate to detect the PCB board without a blocking transformer. Audio, video and other equipment. Although the general radio cassette recorder has a power transformer, when you come into contact with more special TV or audio equipment, especially the output power or the nature of the selected power supply, you must first clarify whether the chassis of the machine is charged, otherwise it will be very easy to interact with The TVs, audios and other equipment with live baseboards form power short circuits, which involve integrated circuits, which cause further expansion of the faults.

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

When measuring the DC voltage of the integrated circuit pins, a multimeter with an internal resistance greater than 20KO/V in the header should be used, otherwise there will be larger measurement errors for some pin voltages.

5. Pay attention to the heat dissipation of the power integrated circuit when testing the PCB. The power integrated circuit should have good heat dissipation, and it is not allowed to work in a high-power state without a heat sink.

6. When inspecting the PCB board, it is necessary to ensure that the welding quality is firmly welded, and the accumulation of solder and the pores simply form a virtual weld. The soldering time generally does not exceed 3 seconds, and the power of the soldering iron should be about 25W using internal heating. The integrated circuit that has been soldered should be checked carefully, use an ohmmeter to measure whether there is a short circuit between the pins, and then turn on the power after admitting that there is no solder adhesion.