Classification and selection of electric soldering iron
Electric soldering irons are classified according to the form of heating:
Internal and external heating
Soldering irons are classified according to temperature control methods:
Ordinary electric soldering iron; temperature-adjusting electric soldering iron; constant temperature electric soldering iron
The internal heating electric soldering iron has the advantages of low power consumption, small size, light weight, and fast heating. It has two rated powers of 20W and 25W, and is suitable for soldering small electronic devices, such as semiconductor radios.
External heat soldering iron
The rated power of the external heating electric soldering iron is 25W, 30W, 45W, 75W, 300W, etc.
If the power of the electric soldering iron is too high, the components will be scalded; if the power is too small, there will be virtual soldering or difficulty in melting the solder.
Soldering materials (divided into solder and flux):
The solder is a fusible metal, and the solder used in manual soldering is a tin-lead alloy. It has the advantages of low melting point, high mechanical strength, small surface tension and strong oxidation resistance.
The function of the flux is to remove oxides, sulfides, oils and other contaminants on the metal surface, and to prevent the solder from continuing to oxidize during the heating process. At the same time, it also has the effect of enhancing the activity of solder and metal surface and increasing wetting.
(1) It has the effect of cleaning the surface of the metal to be welded and the solder.
(2) The melting point should be lower than that of all solders.
(3) It can form a liquid at the welding temperature and has the function of protecting the metal surface.
(4) It has low surface tension and can flow quickly and evenly after being heated.
Solder resist is a kind of high temperature resistant coating, its function is to protect the parts that do not need to be soldered on the printed circuit board.
Types of solder resist:
Heat curable solder resist; UV light curable solder resist (photosensitive solder resist); Electron radiation curable solder resist
Solder wire is the solder used for manual soldering. Solder wire is tubular, made of flux and solder together, and solid flux is entrained in the solder tube. The flux generally uses super-grade rosin as the matrix material, and a certain activator, such as diethylamine hydrochloride, is added. Different tin-lead components have different melting points.
Commonly used solder wires such as Sn63Pb37 have a melting point of 183°C, and Sn62Pb36Ag2 have a melting point of 179°C. The diameter of tubular solder wire is 0.2, 0.3, 0.4, 0.5, 0.6, 0.8, 1.0 and other specifications. 0.5, 0.6 solder wire can be used for soldering perforated components.
The choice of soldering iron
Reasonable selection of electric soldering iron is directly related to improving welding quality and efficiency. If the power of the electric soldering iron used is small, the soldering temperature is too low, making the solder joints not smooth and firm, and even the solder cannot be melted, making the soldering impossible. If the power of the electric soldering iron is too high, the solder joints of the components will be overheated, causing damage to the components and causing the copper foil of the printed circuit board to fall off.
