A complete PCB board needs to go through many processes from planning to production. Once all processes are implemented, it will eventually enter the testing stage. Only PCB boards that pass the testing will be applied to the product. So, how to do a good job in PCB circuit board testing is a topic that we are all concerned about. Below, the editor will talk about the relevant knowledge of circuit board testing for us!

When measuring voltage or testing waveforms with oscilloscope probes, do not cause a short circuit between the pins of the integrated circuit due to sliding of the probe or probe. Measure on the peripheral printed circuit directly connected to the pins. Any momentary short circuit can easily damage the integrated circuit, and extra caution should be taken when testing flat packaged CMOS integrated circuits.

2. It is not allowed to use a live soldering iron for welding. It is necessary to confirm that the soldering iron is not live, ground the outer shell of the soldering iron, and be more careful with MOS circuits. Low voltage circuit iron with a voltage of 6-8V can be used for safety.

If it is necessary to add peripheral components to replace damaged parts inside the integrated circuit, small components should be selected, and the wiring should be reasonable to avoid unnecessary parasitic coupling, especially to handle the grounding terminal between the audio power amplifier integrated circuit and the preamplifier circuit.

4. It is strictly prohibited to directly test television, audio, video and other equipment without power isolation transformers using instruments and equipment with grounded casings. Although most tape recorders have power transformers, when in contact with special television or audio equipment, especially those with high output power or unfamiliar with the nature of the selected power source, the first thing to do is to determine whether the chassis of the machine is charged. Otherwise, it is very easy to form a power short circuit with the charged television, sound and other equipment on the chassis, involving integrated circuits and further expanding the problem.

Before inspecting and repairing integrated circuits, it is necessary to familiarize oneself with the functions, internal circuits, main electrical parameters, effects of each pin, as well as the normal voltage and waveform of the pins and the working principle of the circuit composed of peripheral components. If the above conditions are met, analysis and viewing will be much simpler.

6. Do not easily judge that the integrated circuit is damaged. Due to the fact that the vast majority of integrated circuits are directly coupled, if a circuit is not functioning properly, it may cause multiple voltage changes, which may not necessarily be caused by damage to the integrated circuit. In some cases, when the measured voltage of each pin matches or is close to the normal value, it may not necessarily indicate that the integrated circuit is good. Due to some soft defects, it does not cause changes in DC voltage.

Article source: Jiangmen single-sided and double-sided circuit boardhttp://www.yonghongpcb.com/