The mysterious assistant of selective wave soldering
发布时间：2022-04-23 浏览次数：605
Development status of selective wave soldering
With the increasing difficulty of welding through-hole components (especially large-capacity or fine-pitch components), especially for lead-free and high-reliability products, the welding quality of manual welding has been unable to meet the requirements of high-quality Denso production, and wave soldering in specific use can not fully meet the small batch and multi-variety production applications. Therefore, the application of selective wave soldering has been rapidly developed in recent years.
Why does selective wave soldering need nitrogen protection?
The main purpose of nitrogen protection in selective wave soldering is to reduce the oxidation of solder and improve the quality of solder joints.
Nitrogen-filled welding usually adopts gas dispersion technology, which means that solder is sprayed into the solder wave required by design through electric pump or electromagnetic pump, and nitrogen is injected into the solder pool to distribute evenly on the surface of the wave crest to achieve inert gas protection. At the same time, this technology enables PCB boards pre-loaded with components to be soft soldered through the solder wave, thus realizing the mechanical and electrical connection between components and printed boards.
The advantages of selective wave soldering in a nitrogen environment compared to welding in an air environment can reduce the required welding temperature, reduce process defects, and form a perfect solder joint. In addition, according to the incomplete statistics of an auto parts manufacturer, the amount of tin slag produced by selective wave soldering equipment using nitrogen and not using nitrogen is also significantly different. When nitrogen is used, there is almost no tin residue for eight hours of normal operation, and when no nitrogen is used, the tin residue is produced at a hundred times the rate，So more cost saving.
Why nitrogen?What about other gases?
So why nitrogen protection, can other gases? The use of nitrogen protection is mainly because the chemical properties of nitrogen are stable and generally do not react with other metals. In addition to nitrogen, other chemically stable gases can also be used, such as rare gases: He, Ne, Ar, Kr, etc., but the acquisition cost of rare gases is too high, and nitrogen accounts for 78.08% of the total atmosphere, which is relatively easier to prepare, so nitrogen is the best choice.
Nitrogen protection for selective wave soldering equipment can effectively reduce the amount of tin slag, save costs, and improve welding quality and reliability. Nitrogen can be obtained by purchasing high-pressure gas cylinders or liquid dewar tanks from an external supplier, or by purchasing a nitrogen generator for on-site production.
The nitrogen generator produced by Holang (NPM02 Pro&NPM04 Pro&NPM06 Pro can be selected according to welding requirements), uses PSA technology to continuously separate oxygen from compressed air to extract pure nitrogen, and the flow rate and nitrogen purity can be set independently on demand (nitrogen purity can reach 99.999%). The feature of Holang nitrogen generator is modular design, small and delicate, on-site nitrogen production, nitrogen production efficiency and better quality, simple and flexible operation, safe, reliable and more environmentally friendly.
According to the characteristics of the SMT industry, on-site nitrogen generation with nitrogen generators is an ideal alternative to delivery nitrogen supply. At present, Holang nitrogen generator has been maturely applied in a number of selective wave soldering manufacturers, and has been unanimously recognized and praised.