Basic knowledge of soldering iron
1. Classification of welding technology
Welding techniques are generally divided into three categories: fusion welding (arc welding, etc.), contact welding (ultrasonic, pulse) and brazing (soldering iron).
2. The function, type, structure, selection and grip of electric soldering iron
1. Function:
Provide the heat source required for welding, heat the metal to be welded, melt the solder, and promote their mutual fusion to form close contact.
2. Type and structure:
(1) External heating electric soldering iron
①Structure: It consists of a soldering iron tip, a soldering iron core, a shell, a wooden handle, a power cord and a lead plug.
②Specification: 25W, 45W, 75W, 100W, 150W, etc. (The higher the power, the higher the temperature of the soldering iron tip)
(2) Internal heating type electric soldering iron
①Structure: It consists of a soldering iron tip, a soldering iron core, a shell, a wooden handle, a power cord and a lead plug.
②Specification: 20W, 30W, 50W, etc.
③The internal heat soldering iron has high efficiency, and the 20W internal heat soldering iron is equivalent to about 40W external heat soldering iron.
3. Choose
(1) General printed circuit boards, electronic components, and installation wires: 20W internal heating type, 30W external heating type;
(2) Integrated circuit: 20W internal heating type;
(3) Solder tabs, potentiometers, 2~8W resistors, large electrolytic capacitors, high-power tubes: 30~50 W internal heating type, 50~75W external heating type;
(4) Resistance above 8W, wire above 2mm: 100W internal heating type, 150~200W external heating type;
4. Grip
(1) Reverse grip method: suitable for the operation of high-power electric soldering iron, welding parts with large heat dissipation;
(2) Overhand grip: It is suitable for the operation of high-power electric soldering irons and most of them are elbow-type electric soldering irons;
(3) Pen-holding style: suitable for low-power (below 35W) electric soldering irons, mostly used in electronic production, such as general soldering of printed circuit boards.
5. Several issues that should be paid attention to when using electric soldering iron
(1) Before using a new electric soldering iron, first use a file to file the soldering iron tip into a certain shape as required, and then turn on the power supply. When the temperature of the soldering iron tip rises to the point where the solder can be melted, apply rosin to the soldering iron tip, etc. After the rosin smokes, apply a layer of solder, and repeat this until the blade surface is completely coated with solder.
(2) Soldering iron tip does not "eat tin" treatment: use fine sandpaper or file to re-polish the soldering iron tip or file out new stubble, and re-tinn it.
(3) Treatment of excess solder on the soldering iron tip during soldering: wipe off with a damp cloth, and avoid shaking the soldering iron.
3. The role and classification of flux
1. The role of flux
(1) Destroy the oxidized impurities on the surface of the metal to be welded and prevent the metal surface from being oxidized again during welding;
(2) Reduce the surface tension of solder and improve the wettability and adsorption of solder to promote the formation of alloy solder joints.
2. Flux type
Rosin, rosin alcohol solution, solder paste and hydrochloric acid, etc. The most suitable flux for electronic circuit making is rosin.
