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Analysis Of PCB Surface Mount Welding Of The Bad Causes And Solutions
Oct 16, 2017

Analysis of PCB surface mount welding of the bad causes and solutions

One, bridge

The cause of the bridge is mostly due to the excess of solder or the serious collapse of the solder after printing, or the size of the PCB substrate, the SMD placement offset caused by the SOP, QFP circuit tends to miniaturization stage, Resulting in electrical short circuit, affecting the use of the product.

Second, poor wetting

Poor wetting refers to the solder and PCB substrate during the welding process, after the infiltration does not produce the reaction between the metal, resulting in leakage welding or less welding failure. The reason is that the surface of the weld is contaminated, or stained with solder resist, or the metal compound layer is formed on the surface of the conjugate. For example, the surface of the silver has a sulfide, and the surface of the tin has an oxide The In addition, when the residual aluminum, zinc and cadmium in the solder exceeds 0.005%, the degree of activity is reduced by the moisture absorption of the flux, and the wetting may occur. Wave soldering, if the gas exists in the PCB substrate surface, but also prone to this failure. Therefore, in addition to the implementation of the appropriate welding process, the PCB substrate surface and the surface of the components to be anti-pollution measures, select the appropriate solder, and set a reasonable welding temperature and time.