PCB Fabrication

The solderability of circuit board holes affects soldering quality

by:A-TECH      2021-03-20
The poor solderability of the printed circuit board holes will result in false soldering defects, which will affect the parameters of the components in the circuit, resulting in unstable conduction of the components and the inner wires of the multilayer board, causing the entire circuit to fail. The so-called solderability is the property that the metal surface is wetted by molten solder, that is, a relatively uniform continuous smooth adhesion film is formed on the metal surface where the solder is located. The main factors affecting the solderability of printed circuit boards are: (1) The composition of the solder and the nature of the solder. Solder is an important part of the welding chemical treatment process. It is composed of chemical materials containing flux. Commonly used low-melting eutectic metals are Sn-Pb or Sn-Pb-Ag. The impurity content must be controlled in a certain proportion to prevent the oxides generated by the impurities from being dissolved by the flux. The function of the flux is to help the solder wetting the surface of the circuit to be soldered by transferring heat and removing rust. White rosin and isopropanol solvents are generally used. (2) The welding temperature and the cleanliness of the metal plate surface will also affect the weldability. If the temperature is too high, the solder diffusion speed will increase. At this time, it will have high activity, which will cause the circuit board and the molten surface of the solder to oxidize rapidly, resulting in soldering defects. Contamination of the circuit board surface will also affect the solderability and cause defects. Including tin beads, tin balls, open circuits, poor gloss, etc.
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