PCB News - Circuit board cleaning and maintenance methods

Circuit board cleaning and maintenance methods

Ordinary electronic products have been used for a long time, and the circuit board will be covered with dust. If there is more dust or air humidity, it will corrode and short-circuit the circuit board and damage the components and circuit board. So when you find dust on the circuit board When there are more, it is necessary to clean and nurture them. The system board graphics card, sound card, network card and other more sophisticated circuit boards are cleaned before leaving the factory. The purpose is to clean the flux and hand sweat attached to the circuit board during the consumption process (although all operations on the consumption line Personnel wear gloves) and other harmful substances. Regarding circuit board manufacturers, they use special cleaning fluid (commonly known as board washing water) to wash the boards. Regarding ordinary users, due to limited conditions, it is impossible to operate like a circuit board manufacturer, but only need to be careful and careful when operating; cleaning the circuit board is not a difficult and terrible thing.

1. Preparation before cleaning. Before cleaning, all connectors on the circuit board, including jumpers, card boards, batteries and ICs, must be unplugged one by one. Potentiometers, transformers and solenoid coils (inductance coils) must also be removed from the circuit board. Remove the circuit board, [Note: Non-electronic professionals should not stop 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 are basically not These components] Therefore, once water enters the components, the water droplets in the gaps or between the turns are difficult to be swept out by the compressed air and the moisture is difficult to be dried. When disassembling, it is necessary to record them one by one to ensure that they will not be restored after cleaning. Something went wrong. 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 cleared. . Regarding the circuit board of the computer power supply, it should also be checked whether there is a crack or live unsoldering between the printed circuit pad and the component foot, especially the high-power components. If there is a crack or unsoldering, it should be repaired immediately. One repair weld is found, otherwise it is easy to miss.
2, cleaning
⑴. Before cleaning, use a clean soft paint brush (a 1-inch wide brush is better) and a monotonous compressed air with a pressure of about 0.1Mpa [ie 1kg/cm2] to remove dust on the circuit board.
⑵. For cleaning, a special cleaning solution for washing circuit boards (commonly known as board washing water) can be used. This solution can be bought at special stores. If there is no board washing water, you can do as follows: (usually we don’t usually 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.
⑶. Then use a soft brush dipped in neutral soap to carefully and quietly clean each center 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 every other IC chip, the bottom of the large capacitor, etc. should be carefully cleaned. During operation, be careful not to bump the small capacitors and other components installed upright; suppose it is washed out If the soap foam is very dirty, it must be rinsed with water and then scrubbed again with soap until the soap foam washed out is white.

⑷. Then slowly rinse the circuit board thoroughly with clean water. Note: The soapy water must be rinsed thoroughly.
⑸. After washing, use monotonous compressed air with a pressure of about 0.1Mpa [ie 1kg/cm2] to blow away the water droplets, especially jumper plugs, slots (CPU slots, AGP slots, PCI slots, memory slots) The inside and the bottom, the bottom of the IC socket, the bottom of the north and south bridge chip, the BIOS chip and the bottom of each other IC chip, the bottom of the large capacitor, etc., should stop blowing from different directions, and try to blow all the water droplets in the gap. clean. Assuming that there is no compressed air, you can use a rubber hand pump for watch repair professionals or camera repair professionals, but this stuff can be tiring.
⑹. Use double distilled water or anhydrous alcohol to wash the circuit board again (make the side where the components are soldered face up, place the circuit board diagonally, and use a clean oil paint brush No. 10 to 12 to dip it with absolute alcohol from top to top Go to the ground to stop 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, but also healthy; because the washing water is harmful to the body, it will definitely not be a good thing to say that the waste liquid after washing is poured into the sewer.
3. Use monotonous compressed air with a pressure of about 0.1Mpa [ie 1kg/cm2] to blow away the water droplets, 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 and south bridge chips, the BIOS chip and the bottom of every other IC chip, the bottom of the large capacitor, etc. should stop blowing from different directions, trying to blow all the water droplets in the gap.
4. After cleaning, the circuit board must be completely monotonous before it can be put into use. There are many ways to do it. You can refer to the following methods:
⑴. Put it in an air-conditioned room and let it dry naturally for more than 36 hours.
⑵. Dry in an oven, the temperature of the oven is adjusted to about 80 degrees Celsius, which lasts about 24 hours.
⑶. Dry with a hair dryer (for industrial use or for household use). This method requires holding the hair dryer and constantly swinging it, which is very annoying! And if the technique is improper, it may be monotonous and uneven, especially in the center of those gaps.
5. Follow the records made when disassembling the components as a guide, and restore all the originals that were disassembled one by one.
6. Check whether the installation is qualified. The circuit boards of other equipment can also be cleaned and maintained according to the above methods.