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There are two kinds of circuit boards PCB assembly, welding and manual welding machine, welding machine is not to talk, manual welding need to soldering iron, soldering iron power according to the size of the welding on the size of the components, typically 25 ℃ environment, choose 30 w small iron can welding general of original such as resistors, capacitors, such as welding with large-area metal original to power larger soldering iron, this depends on by welding for like, 45 w, optional 60 w, etc. Before welding, the welding feet of electronic components should be removed and oxidized, otherwise it is easy to occur virtual welding. Welding wire has a diameter of 0.2, 0.5, 0.8 and other specifications, the selection of welding wire should be based on the size of the foot, the general electronic components can choose a 0.5mm specification of the wire, if you want to welding integrated circuit choose 0.2mm wire, for the ground area of the metal version of the original need a larger diameter of the wire. Flux is generally rosin, solder paste and solder fluid. Flux will be liquefied and then vaporized when it meets the high temperature of soldering tip. In this process, it will spread to all sides, which can guide the liquefied solder wire to fill the gap of solder joint and fuse everything in the gap together. Deal with rosin, other flux has strong acid, this basically is can rise to the surface of the weldment to oxidation, but they also have a very strong corrosive, so after using flux welding must be used for solder joint of pure alcohol for cleaning, or in after a few time will be corrosion solder joints, causing damage of circuit board.
Five-step PCB assembly method:
1. Preparation for welding: preparation before welding includes cleaning of welding parts, installation of components and preparation of solder, flux and tools. Solder wire in left hand and electric iron in right hand (keep the soldering tip clean and keep the soldering tip in welding state at all times).
2. Heating welding parts: the whole welding part should be heated evenly.
3. Feed the welding wire: when the welding part reaches a certain temperature, the welding wire soldering iron contacts the welding part from the opposite side.
4. Remove the welding wire: when the welding wire melts a certain amount, remove the welding wire immediately.
5. Remove the soldering iron: remove the soldering iron after soldering the soldering pad or welding part.