Before welding, can be prepared according to the size of the boundary parts, prepared electric lattice silver oblique silver sharp mouth pliers，preparation work such as tin plating.
1. Preparation of electric soldering iron
1)Preparation of electric soldering iron should usually be carried out in the following aspects prior to manual welding.
Check the performance of electric soldering iron, especially its power line, see that it is the place where there is leakage of electricity, the shell of electric iron has no leakage of electricity, and the connection of ground wire is good or not. The purpose of this inspection is to ensure personal safety.
2) for the electric iron which can adjust the temperature, the work of the electric iron should be adjusted according to the specific condition of the welding piece degree for the prepared soldering iron. It should be tinned first so that the soldering iron can carry a suitable amount of welding easy. Dip the rosin with the iron head from time to time, so that the solder and electric iron face is always covered with the oil film of the rosin layer.
2. Instrumentation of components
There are two types of inserts on printed circuit boards, one horizontal and the other vertical. Horizontal and vertical interpolation have their own advantages and disadvantages, the components should be flexibly selected according to the actual situation.
Horizontal insertion refers to the state in which components are laid flat on a printed circuit board and placed parallel to each other. Horizontal insert is not easily disturbed by the external extrusion and dynamic, so the mechanical stability is good. From the appearance, the arrangement of the whole circuit board is also relatively neat and beautiful. But the horizontal type inserts the occupation area to be big, therefore is suitable for the bigger printed circuit board.
Vertical intercalation means that components stand upright on a printed circuit board and are almost vertical between them. Vertical insertion occupies a small area, but after the components are squeezed or vibrated, it is easy to cause a short circuit caused by the touch of the component pin.
Therefore, this method is suitable for smaller printed circuit boards and more components, requiring compact and dense arrangement of components on printed circuit boards our products.
When each component is inserted on a printed circuit board, the component cannot be attached to or separated from the printed circuit board
Circuit board is not only neat and beautiful tImm, vertical insert components of the long lead need a heat shrink tube sleeve. This welding good printing view, but also has a basic level of technology.
3. Lead bending
When the lead bending of components is made, it should be treated according to the distance between the pad holes and the assembly requirements. In general, the span of the device pin is approximately the same as the span of the pad hole.
In addition, the shape of component pin and T should be favorable to the heat dissipation and mechanical strength after welding. During processing, the lead wire can be clamped with tweezers or small screwdrivers at 1 ~ 2 mm from the root of the component, and then bent to form a shape. Note: do not bend the component lead from the root to prevent damage to the component by bending the lead.
After the forming of the components, in welding, it should be kept as neat as possible, the same kind of components to maintain the height of the cause. The symbol marks of each component are upward when the horizontal type is inserted, and the symbol mark of each component is outward for convenience of checking when the vertical type is inserted.
4. Tin plating treatment of component lead wire
Before welding, the lead wire of components should be scraped clean, and the oxide, rust, grease, dust and impurities on the surface of the welding piece should be cleaned up, preferably tinned before welding.
Component leads are generally coated with a thin layer of solder, mostly tin, gold, hate or nickel metal. The welding properties of these metals themselves are different, and long time placement will lead to the formation of oxide film on the surface of the lead, which has a greater impact on the quality of welding. Therefore, with the exception of a few silver and gold coated lead wires with good weldability, most of the components need to be tinned again before welding.
Tin plating is to moisten the surface of welded metal with liquid flux to form a bonding layer which is different from both welded metal and solder. When the bonding layer is formed, the solder will be firmly connected to the material whose properties and components are not the same as those of the solder to be welded.
Before tin plating, the oxide should be treated clean, if the lead wire is silver plated, the oxide should be completely scraped off with a knife; if the lead wire is gold-plated, it can not be scratched with a knife, but erased the oxide with an eraser. New components are usually made of aluminum-tin alloy, as long as the coating is bright and erased with an eraser. After removing the oxides, dip their leads in rosin or rosin water and coat the lead wire with a thin layer of tin with an electric iron.