The reasons of PCB lacks tin
PCB design and production process, you have not encountered PCB bad situation of lacking tin? For engineers, once a PCB board appears poor tin, often means that the need to re-welding or even re-production, the consequences are very troublesome. So, PCB tin bad situation is due to what causes it? In what ways can we avoid the emergence of this problem?
The main reason is that the surface of the circuit is partially uncoated with tin.
There are many reasons that lead to the bad situation of PCB eating tin, usually can be summarized as the following aspects.
PCB board surface with grease, impurities and other debris, or the substrate in the manufacturing process of grinding particles left in the line surface, or there is a residual silicone oil, will lead to poor PCB to eat tin. In the inspection process if the above situation occurs, you can use solvents to clean debris. However, if it is silicone oil, then you need to use a special cleaning solvent for scrubbing, otherwise it is not easy to be cleaned.
There is also a situation can lead to poor PCB tin eat, that is stored in the storage time is too long or humid environment, the manufacturing process is not rigorous, resulting in the substrate or parts of the tin surface oxidation and copper surface dull serious situation. When this happens, the use of flux has been unable to solve this problem, the technician must re-welding, so as to be able to improve the tin-eating effect of the PCB.
PCB welding process did not ensure adequate temperature or time, or not properly used flux, also can lead to poor PCB tin. General operating temperature solder than its melting point temperature 55 ~ 80 ℃, preheating time is not enough to easily lead to the emergence of tin bad situation. The amount of flux distribution on the surface of the line is affected by the proportion of the amount. Check the proportion can also be ruled out due to the wrong labels, poor storage conditions and other reasons caused improper use of improper flux.
The process of welding, solder the pros and cons of the material and the terminal is also directly related to the final result of the cleanliness. If the solder impurities in too many components or terminals are defaced, can also cause bad PCB tin. During welding, the impurities in the solder can be measured in time and the cleaning of each terminal can be ensured. If the solder quality is not normal, the standard solder needs to be replaced.