PCB Tech - What are the methods of PCB cleaning

Circuit board cleaning

Before cleaning, all connectors on the PCB circuit board including jumpers, card boards, batteries and ICs must be carefully unplugged one by one. Potentiometers, transformers and solenoid coils (inductance coils) must also be removed from the circuit board. Down. [Note: Non-electronic professionals should not perform this operation, because if you do not have electronic expertise, it is easy to damage the parts and circuit boards during disassembly. Fortunately, computer-related circuit boards basically do not have these components].

Therefore, once water enters the components, the water droplets in the gap or between the turns are difficult to be swept out by the compressed air and the moisture is difficult to be dried. The disassembly must be recorded one by one to ensure that there will be no errors in the restoration after cleaning. At the same time, check whether the electrolytic capacitor on the circuit board is leaking or bulging on the top. If so, remove it and make a record so that it can be replaced with a new product of equivalent value after the circuit board is cleaned.

For the circuit board of the computer power supply, you should also check whether there are cracks and unsoldering between the pads of the printed circuit and the component feet, especially the high-power components. If there are cracks and unsoldering, they should be repaired immediately. One repair welds one place, otherwise it is easy to miss.

cleaning method

1. Before cleaning, use a clean soft paint brush (1 inch wide brush is better) and dry compressed air with a pressure of about 0.1Mpa (that is, 1kg/cm2) to remove the dust on the circuit board.

2. For cleaning, a special cleaning fluid (commonly known as board washing water) for washing circuit boards can be used. This fluid can be bought at a specialized store. If there is no board washing water, you can do as follows: (now we generally don’t use board washing water) rinse with tap water first, pay attention to the water flow to be soft, not too strong, carefully brush with a soft brush while flushing, both sides of the circuit board The same is true.

3. Then use a soft brush with neutral soap to carefully and gently clean every part of the circuit board, especially the jumper plugs, the inside and bottom of the slots (CPU slot, AGP slot, PCI slot, memory slot), The bottom of the IC socket, the north-south bridge chip, the BIOS chip and the bottom of each other IC chip, the bottom of the large capacitor, etc. should be carefully cleaned, and the small capacitors and other components that are installed upright should not be touched when operating; If the soap foam is very dirty, it must be rinsed with clean water and then scrubbed with soap again until the soap foam is white.

4. Then slowly rinse the circuit board thoroughly with clean water. Note: The soapy water must be rinsed thoroughly.

5. After washing, use dry compressed air with a pressure of about 0.1Mpa [ie 1kg/cm2] to blow away the water droplets, especially jumper plugs, slots (CPU slot, AGP slot, PCI slot, memory slot) The inside and the bottom, the bottom of the IC socket, the north-south bridge chip, the BIOS chip and every other IC chip, the bottom of the large capacitor, etc., should be blown from different directions, and strive to blow all the water droplets in the gap. clean. If you don't have compressed air, you can use a rubber hand pump for watch repair professionals or camera repair professionals, but this stuff can be tiring.

6. Use double distilled water or anhydrous alcohol to wash the circuit board once again (make the side where the components are soldered face up, place the circuit board diagonally, and use a clean oil paint brush of No. 10 to 12 to dip it in anhydrous alcohol. From top to top Go to the ground for cleaning). Carbon tetrachloride is more effective, but this thing is toxic, and you must be careful when using it. Don't use it unless it is necessary. It is generally recommended not to use carbon tetrachloride.

At this point, the cleaning is over. This cleaning is not only clean and thorough, saves money, and is environmentally friendly and healthy.