Solder paste and rosin do not cause defects on PCB board, but some solder paste and rosin contain more water, and moisture will remain on the surface of the board after use, which may cause short circuit. In addition, after using flux , some solid or powdery residue will remain on the circuit board. These residues will not short-circuit under normal conditions, but when the circuit board is under pressure detection, it is found that the high pressure will pass through the residue. The material penetrates the circuit board components or runs in a low-temperature and high-humidity environment. These residues absorb the moisture in the air, so that the moisture layer is enough to reduce the insulation resistance of the surface of the circuit board and the board causes corrosion or metal dendrites. Below are the solutions for cleaning flux residues.
Use a cotton swab to clean the residual flux and dirt on the solder joints. The manual cleaning method is applicable to all kinds of welding points, the method is simple, the cleaning effect is good, but the efficiency is low.Pay attention to the following points when cleaning:
1. Do not damage the solder joints and components, the cleaning action should be light, do not twist and pull the leads of the wires or components on the solder joints.
2. The cleaning solution should not be dispersed. Do not use the cleaning solution excessively to prevent the cleaning liquid from flowing into the product and reduce the performance of the product.
3. When the cleaning solution becomes dirty, it should be replaced in time. The cleaning solution is usually a flammable chemical and should be used with fire protection.
Ultrasonic cleaning is a method in which cleaning is performed by a cleaning effect by high-frequency oscillation of ultrasonic waves. he cleaning solution generates a effect under the action of ultrasonic waves, and the high-intensity shock wave generated by the effect causes the dirt on the solder joint and the slit to be detached, and accelerates the process of dissolving the dirt in the cleaning liquid. The ultrasonic cleaning method is characterized by fast cleaning speed, good cleaning quality, cleaning of complicated welding parts and dirt in the gap, and easy automation of cleaning.The effect of ultrasonic cleaning is related to many factors, such as the frequency of ultrasonic waves, the sound intensity, the nature of the cleaning solution, the temperature and the cleaning time.
How to improve the cleaning effect？
1. Wash as soon as possible after welding (within 1 hour).
2. Improve the working temperature of the cleaning agent.
3. Extend the cleaning time.
4. Change the new cleaning agent frequently.