Kemaolong professional to undertake the production of circuit board prototype, small batch processing, assembling, welding and debugging, debugging, PCB development, circuit board, electronic components and circuit board to modify the matching purchase welding, to provide customers with one-stop service the company specialized in all kinds of electronic products sample, product batch SMT (SMD, plug-in) welding processing, BGA processing and OEM professional welding and processing, according to the customer to provide a test environment for debugging, maintenance and other services to the entire process of all kinds of industrial control board. The company adopts the machine and manual matching operation, manual printing, patch, plug-in, lead-free reflow soldering, with strict scientific management, welding, maintenance, commissioning team of professional and precision instruments and equipment provides excellent service and quality products to customers.
Matters needing attention in SMT welding process
Welding is a very important technical problem in the process of electronic production, and the quality of welding affects the quality of manufacture directly. Electronic beginners tend to ignore this question. I'd like to talk about the basics of welding.
1, the choice of electric iron
The main tool for welding is electric iron. In addition to the internal and external heat type electric iron, there are tin soldering iron and constant temperature electric iron. At present, the sale of more heat type electric iron, commonly used specifications are 20W, 40W, 70W several. Which type of electric iron is selected depends on the specific welding object. If you install a semiconductor radio or other small electronic components, you should choose 20W electric iron, because it has a fast heating, power consumption, small size and light weight and so on. If you install a TV set or repair a larger home appliance, use a larger power, such as a 40W electric iron. Power electric iron must choose appropriate, will spoil the transistor or other heat element, often too small will not firm welding components on the surface of each pull, is actually very easy to produce false welding or weld phenomenon.
Electric soldering iron head is usually made of copper, commonly used iron head has straight and bend type two. The new electric soldering iron head edge or just in the surface layer of the oxide layer, therefore not on the tin, when in use, the first tip edge surface oxide layer with sandpaper to polish, and then to the electric iron heating after a period of time, a layer of rosin in polished clean place painted and then coated with a layer of tin tin, this process is called. An electric soldering iron with a good tin can be used properly. In the future use of the process, the iron head of the blade will be oxidized, tin, this phenomenon is called "burn", but also must use the above methods to re tin processing.
2. Selection of soldering tin
When welding solder solder is used, the most suitable is called a solder solder supply on the market, its low melting point, good conductivity, the coexistence of a certain strength, internal pre filled rosin, welding is very convenient, the most suitable for the production of electronic circuit.
3 、 flux selection
Prevent the effect of surface oxidation of soldering flux in welding. The commonly used flux is rosin, which is neutral and will not corrode the circuit elements and the soldering iron head. There is a flux is also called welded oil, solder paste, soldering results than rosin, but she took a little corrosive, general welding components after soldering paste clean.
4 、 preparation before welding
Firstly, the surface of the printed circuit board is processed, and the surface of the copper on the printed circuit board is polished by a piece of fine sand paper. After washing, the resin is coated with a layer of rosin alcohol solution, and then it can be carried out. The ratio of rosin to alcohol is 1:2. The surface treated printed circuit board not only guarantees the quality of welding, but also increases the speed of welding.
5 、 welding method
The first ready element into the printed circuit board provides a good position, at the point of connection components and the printed circuit board copper foil, coated with a little flux, for electric heater with tip edge on some amount of solder, the solder joint number according to the size of the decision. When welding will tip edge contact pads and component leads, make some moves according to the shape of solder, solder and solder joint with the flow into the slot is welded, the contact time is about 3-5 seconds, then take off the electric iron. Take electric soldering time, direction and speed, determines the correct method of the quality and appearance of welding is to be left in the solder joint, fast electric iron back, quickly after leaving the spot, the spot welding is so bright, smooth, without burr.
When welding, the welding time is not too long, lest the element burns, but also not too short, resulting in false welding or weld. After welding, with appropriate welding components Liezi is clamped by the pull dial, check whether the element is welded. If it is found to be loose, welding must be performed again.