Compared with the single-sided circuit board, the wiring density of the double-sided circuit board becomes larger and the aperture is smaller. The metallized holes on which the layer-to-layer interconnection relies are directly related to the reliability of the printed circuit board. As the pore size shrinks, some debris, such as brush debris, volcanic ash, etc., PCBA manufacturing once remaining in the small hole, will make electroless copper and electroplating useless.

In order to ensure the reliable conductive effect of the double-sided circuit, the connecting holes on the board should be welded with wires first, and the protruding part of the connecting wire tip should be cut to avoid injuring the operator's hand. This is the board connection preparation work. So, what problems should be paid attention to when welding double-sided circuit boards?
1. For devices that require shaping, they should be shaped first and then plug-in according to the requirements of the process drawings.
2. After shaping, the model side of the diode should face up, and there should be no discrepancies in the length of the two pins.
3. When inserting devices with polarity requirements, pay attention to their polarity not to be reversed. After inserting, no matter it is a vertical or horizontal device, there must be no obvious tilt.
4. The power of the soldering iron used for soldering is between 25~40W, the temperature of the soldering iron tip should be controlled at about 242℃, and the soldering time should be controlled at 3 to 4 seconds.
5. When welding, generally operate according to the welding principle of the device from short to high and from the inside out. The welding time should be mastered. If the time is too long, the device will be burnt, and the copper line on the copper clad board will also be burnt.
6. Because it is double-sided soldering, a process frame for placing the circuit board should also be made, so as not to squash the components below.
7. After the soldering is completed, a comprehensive inspection should be carried out to find out where there are missing insertion and soldering. After confirmation, trim the excess device pins and then flow into the next process.
8. The specific operation should also strictly follow the relevant process standards to ensure the welding quality.
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