PCBA scheme design, development, processing, SMT patch welding production

Tin tip phenomenon in long pin components during wave soldering

The cause of tin tip phenomenon in long pin components during peak soldering is that during the soldering process, as the solder wets and covers the surface of the circuit board, most of the flux on the circuit board is washed away, leaving the remaining flux between the PCB board and the tin wave. When the PCB board leaves the solder wave, the flux left on the PCB board will prevent oxidation of the solder. If the space between solder joints is relatively small, there will not be too much flux left during this process, so it is almost impossible to prevent solder oxidation. As a result, when the tin wave separates from the PCB board, the solder will oxidize and form an oxide layer on the surface. In the final stage of separation, the surface tension of liquid solder will cause some solder to remain on the pins of the component; If this part of the solder surface is oxidized, the solder will be wrapped in the oxide layer, forming a tin tip. If there is a large area covered with solder and almost no flux can help prevent oxidation, this phenomenon will be more pronounced. Therefore, we can understand why long pins are more prone to tin tip phenomenon, because only the flux left on the surface of the PCB board can help prevent oxidation. In the separation process between the PCB board and the tin wave, due to the long pins being far from the surface of the PCB board, the anti oxidation effect of the flux on the PCB board surface is significantly weakened. Similarly, tin tip phenomenon is also prone to occur in areas with larger solder pads on PCB boards. Due to the heat dissipation effect, solder joints on the shielding cover are also prone to tin tip phenomenon. If the heat brought by solder to the solder joint is quickly absorbed by the shielding cover, the solder will almost immediately solidify after separation from the solder wave, resulting in the solidified tin cannot flow back to the solder joint and form a tin tip. Solution to the tin tip phenomenon of long pin components during peak soldering: Shorten the protruding component pins so that the solder flux remaining on the PCB can still provide anti oxidation effect. Increasing the usage of soldering flux generally does not have an effect, as these fluxes are likely to be washed away when the PCB board passes through solder waves; Of course, more flux helps to wet the solder pads; If a soldering flux with strong adhesion to PCB boards is used, it may help prevent the occurrence of tin tip phenomenon. When PCB boards pass through tin waves, covering them with inert gas or creating an environment that helps reduce oxidation can also avoid tin tip phenomenon. If the tin tip is caused by the heat dissipation effect near the solder joint, it is necessary to optimize the solder joint design.