What is SMT?(十三) -- Assembly process -- Wave peak

author: Hellen

2022-10-12

What is SMT?(十三) -- Assembly process -- Wave peak

In the wave soldering process, the wave is central. Preheated, flux-coated, dirt-free metal can be delivered to the soldering workstation via a conveyor belt to contact the wave solder - wave soldering diagram with a certain temperature of the solder, which is later heated so that the flux reacts chemically and the solder alloy forms an interconnection through the wave power, which is the most critical step. The commonly used symmetrical wave crest is called the main wave crest. Setting the pump speed, wave crest height, immersion depth, transfer angle and transfer speed provides a full range of conditions to achieve good soldering characteristics. The data should be adjusted appropriately, and the solder run should be made to slow down and stop slowly just after leaving the back of the wave (exit end). the PCB with the wave run should eventually push the solder to the exit. In the best case, the surface tension of the solder and optimizing the wave run of the board, zero relative motion can be achieved between the component and the wave at the exit end. This deshell area is what achieves the removal of the solder from the board. Adequate inclination should be provided without defects such as bridging, burrs, pulls and solder balls. The wave exit needs to have a hot air flow to ensure that bridging that may form is excluded. After surface mount components are mounted on the bottom of the board, sometimes, to compensate for bubbles in the solder or in the "harsh wave" area that forms behind while performing wave leveling prior to using turbulent chip cresting. The high vertical speed of the turbulent wave crest helps ensure contact between the solder and the leads or pads. The vibrating portion behind the leveled laminar wave crest can also be used to eliminate bubbles and ensure that the solder achieves satisfactory contact with the component. The soldering workstation should basically achieve: high purity solder (as per standard), wave temperature (230~250°C), total time to contact the wave (3~5 seconds), depth of immersion of the printed board into the wave (50~80%), realization of a parallel transfer track and solder content in the solder pot in the parallel state of wave and track.