Causes Of Poor Tin Eating In PCB
Causes of poor tin eating in PCB
During the design and production of PCB, have you ever had a bad tin-eating experience for PCB? For engineers, once a PCB plate has a problem of eating tin, it often means rewelding or even remaking. The consequences are very painful. So what is the cause of poor tin eating on PCBs? What can be done to avoid this problem?
Generally speaking, the main reason why the poor eating of tin on the PCB board is due to the lack of tin on the surface of the circuit. This kind of PCB board with poor tin eating usually appears in reality as shown in the following figure:
There are a number of reasons for poor tin consumption in PCB, which can be summed up in the following areas.
The surface of the PCB board is covered with grease, impurities, etc., or the grinding particles left on the circuit surface during the manufacture of the substrate, or the residue of silicon oil, can lead to poor tin eating by PCB. Solvent can be used to clean the sundries. But if it is silicone oil, it is necessary to use a special cleaning solvent to wash, otherwise it is not easy to be cleaned.
There is also a condition that can lead to poor tin eating on PCB plates, which can be caused by excessive storage time or wet conditions, and the process of making it is not rigorous. Therefore, the oxidation of the tin surface of the substrate or parts and the darkening of the copper surface are serious. When this happens, the problem can no longer be solved by changing the flux, and the technician must reweld it once to improve the tin eating effect of PCB.
The failure to ensure adequate temperature or time during PCB welding, or the improper use of flux, can also lead to poor eating of tin by PCB. Generally, the operating temperature of solder is 5580 ℃ higher than its solution temperature. Not enough preheating time can easily lead to bad eating tin. The amount of flux distribution on the surface of the line is affected by the specific gravity. Improper use of flux due to poor storage conditions.
In the process of welding, the quality of solder material and the cleanliness of the terminal are also directly related to the final result. If there are too many impurities in the solder or if the terminal is tainted, During welding, the impurities in the solder can be measured on time and every terminal clean. If the solder quality is not regulated, the standard solder needs to be replaced.
In addition to the above mentioned cases, there is also a problem similar to the adverse situation of PCB eating tin, that is, the situation of removing tin from the PCB occurs mostly on the tin plated lead substrate. Its specific performance is very similar to that of poor tin eating. But when the tin path surface to be welded is separated from the tin wave, most of the solder that is already on it will be pulled back into the tin furnace. Therefore, the situation of tin removal is more serious than that of poor tin eating. Rewelding the substrate will not necessarily improve at this time. Therefore, once this happens, the engineer must return the PCB plate to the factory for repair.
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