How to deal with the phenomenon of tin tip in PCB wave soldering

SMT processing plants are as numerous as a cow's hair. In order to meet the needs of products, many medium and large companies have also quietly launched SMT production lines. Among the numerous SMT factories, how to choose a reliable supplier? This article from the perspective of industry professionals suggested from the following aspects of screening, to ensure that your choice of minimum cost, conducive to long-term cooperation. The following to explain how to select SMT manufacturers and PCB wave soldering tin tip phenomenon how to deal with the relevant knowledge.

1. How to deal with the phenomenon of tin tip in PCB wave soldering

Cause of the tin tip phenomenon in wave soldering long pin components: During welding, as the solder wets and covers the board surface, most of the flux on the board is washed away, leaving the flux between the PCB board and the tin wave. When the PCB board leaves the tin wave, the flux left on the PCB board prevents oxidation of the solder. If the space between the joints is small, there is not much flux left in the process, so there is little protection against oxidation. As a result, when the tin wave is separated from the PCB board, oxidation occurs in the solder and an oxide layer is formed on the surface. During the final phase of separation, the surface tension of the liquid solder causes part of the solder to remain on the element pin; If this part of the solder surface is oxidized, the solder will become encased in an oxide layer, forming a tin tip.

This is especially true if a large area is covered with solder and there is little flux to help prevent oxidation. Therefore, we can understand why a long pin is more likely to cause the tin tip phenomenon, because only the flux left on the PCB board surface can help prevent oxidation, and during the separation process of PCB board and tin wave, due to the distance between the long pin and the PCB board surface, the flux on the PCB board surface to the pin oxidation resistance is significantly weakened. Similarly, the tin tip phenomenon is also easy to occur in the place where the solder pad area is larger on the PCB board. Due to the heat dissipation effect, the solder joint on the shield is also prone to tin tip phenomenon. If the heat from the solder to the solder joint is quickly absorbed by the shield, the solder will cure almost immediately after separating from the tin wave. As a result, the cured tin cannot flow back to the solder joint to form a tin tip.

2. How to select SMT manufacturer

As a link in the entire electronic product manufacturing process, with highly developed equipment and perfect management, the professional Cooperation of SMT processing plant seems to determine whether your PCBA board can be delivered on time, whether the quality can be controlled, and whether it can be repaired in time. The added value is much higher than the unit price difference between 8 and 9 per cent. How to check the cooperation degree of SMT factory? Start with people. Talk with the management and even the boss of the SMT factory to see if they have a sincere attitude and belief. In addition, the third party can also know the reputation of the processing plant and the customer cases served and so on.

2, Quality Control process (Quality Control) Many SMT processing plants in order to reduce the unit price in the market, at the risk of sacrificing quality, reduce QC personnel or do not equip with AOI for testing and other means. In the process of evaluating SMT processing plant, it is necessary to observe and understand in detail whether IQC, post-furnace inspection, QC and other series positions are set up in the warehouse, whether AOI inspection equipment is reasonably equipped, whether it is opened and used, and how engineers introduce quality management methods and documents, etc. Only with a comprehensive understanding, can you ensure that your products can be perfectly processed.

The spiritual outlook of front-line employees and managers determines whether your products can maintain high yield, consistency, etc., because products are made by people or operating equipment. Whether the communication with the manager is smooth, whether there is passion, whether the staff work meticulously, each does his job.

4. Give Up These Audits · Look at factory scale: Unless your order is enough for 100k, any SMT factory can do it · Look at SMT equipment: Unless PCB board has very small material (such as 0201 and below) or complex process (POP, etc.), general factory SMT equipment can be done. · Look at the quotation: If the quotation is slightly out of line at the first glance, one SMT factory will be rejected, and it may be a very good one. Those who dare to say anything are competent and have requirements on quality. The initial quotation can only be referred to, or even not referred to. It is very risky to choose this supplier based on the chest pounding promise of SMT factory or happy chat. Good companies have long-term stable SMT processing plants, but poor companies are always looking for, repeat yesterday's story. It's time to reflect on your purchasing behavior. Grasp the above several methods to select SMT factory, can be in the choice of suppliers without disadvantage.