Factors that affect soldering in SMT processing

Factors that affect soldering in SMT processing

Abstract: Welding is the most important link in smt chip processing. If it is not done well in the welding link, it will affect the entire production of the PCB board. If it is slightly unqualified, there will be unable products, and if it is severe, the product will be scrapped. To avoid the impact on the quality of smt processing due to poor welding, it is necessary to pay attention to the welding process.

To this end, we have summarized the following seven factors that will affect welding, and we hope that everyone can help after reading them.

Welding heating bridge – Factors that affect soldering

The soldering thermal bridge in the chip processing is to prevent the solder from forming a bridge. If there is an error in this process, it will lead to uneven distribution of the solder. The correct soldering method is to put the tip of the soldering iron in the middle of the pins of the soldering pad, make the tin wire close to the tip of the soldering iron, and when the solder paste melts, move the tin wire between the pad and the pins, and place the soldering iron on the tin wire. In this way, good solder joints can be produced and the impact on processing can be reduced.

Pin welding force – Factors that affect soldering

In the process of processing, if the soldering force of the pin is too large, it is easy to cause problems such as lifting, delamination, or depression of the pad of the patch. Therefore, to ensure the quality of the smt chip processing during the soldering process, it is not necessary to use too much force, only the soldering iron tip needs to be in contact with the pad.

The choice of the soldering iron tip

In the process of soldering, the size selection of the soldering iron tip is also very critical. If the size is too small, it will increase the residence time of the soldering iron tip, resulting in the appearance of cold solder joints. Too large a size will heat up too fast and burn the patch. Therefore, we need to choose a suitable size for the soldering iron tip according to the length and shape of the soldering iron tip, as well as the heat capacity and contact surface.

Temperature setting

Temperature is also a very important step in the soldering process. If the temperature is set too high, the pad will warp, and if the solder is overheated, it will damage the patch. Therefore, it is necessary to pay attention to the temperature setting. Setting a suitable temperature is also very important for the processing quality.

The use of flux

In the process of implementing related processes, if too much flux is used, it will cause the problem of whether the lower solder leg is stable, and if it is serious, corrosion or electron transfer may also occur.

Operation of transfer welding

Transfer soldering is when the solder is first placed on the tip of the iron and then transferred to the connection. Poor wetting can result if done incorrectly. Therefore, we should first place the soldering iron tip between the pad and the pin, and when the tin wire is close to the soldering iron tip, move the tin wire to the opposite side when the tin melts. Then place the tin wire between the pad and the pin. Place the soldering iron on the tin wire, and move the tin wire to the opposite side when the tin melts.

Modification or rework

The biggest taboo in the welding process is to modify or rework in pursuit of perfection. And this approach is not only unavoidable but also repeated modification or rework to pursue the perfection of product quality, which is easy to cause the metal layer of the circuit board/PCB circuit board to break and the board to be delaminated, which is not only time-consuming but also may cause The scrapping of the PCB board, so don’t do unnecessary modification and rework. Factors that affect soldering.

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