Introduction to selecting electric soldering irons
When we use electric soldering irons to weld electronic components, do we feel inadequate due to the unsatisfactory function or design of the soldering iron? Have you ever blindly worshipped 'certain light 936' while listening to the teachings of various great gods?
（1） Selection of electric soldering iron types
1. Internally heated electric soldering iron. The internal heating electric soldering iron has a simple structure, high thermal efficiency, and is lightweight and flexible, making it the preferred choice. It consists of a connecting rod, handle, spring clip, soldering iron core, and soldering iron head (also known as copper head). The soldering iron core is installed inside the soldering iron head. The soldering iron core is made of nickel chromium resistance wire wrapped around a porcelain tube. Generally, the resistance of a 20W electric soldering iron is about 2.4k Ω, while that of a 35W electric soldering iron is about 1.4k Ω.
Internally heated electric soldering iron
2. Externally heated electric soldering iron. This type of electric soldering iron has a complex manufacturing process, low efficiency, and high price, generally consisting of soldering iron head, soldering iron core, shell, handle, plug, and other parts. The soldering iron head is installed inside the soldering iron core and is made of copper alloy material based on copper with good thermal conductivity.
The length of the soldering iron head can be adjusted (the shorter the soldering iron head, the higher the temperature of the soldering iron head). The commonly used shapes in practice include chisel, pointed cone, circular face, circle, pointed cone, and semicircular groove to meet the needs of different welding surfaces.
Externally heated electric soldering iron
3. Thermostatic electric soldering iron. Install a magnetic temperature controller inside the soldering iron head to control the power on time, which is a constant temperature electric soldering iron. When welding components that should not be too high in temperature or too long in welding time, a constant temperature electric soldering iron should be used, but its price is high. Although the automatic constant temperature electric soldering iron has many parts, is difficult to repair, and has a high price, it can ensure the quality of the solder joints, especially when conducting circuit experiments and repairing a large number of printed boards, it works very well. The electric soldering iron used on the production line adopts an automatic voltage regulation method for constant temperature, which may result in lower costs. In some areas, the power supply is unstable, and the soldering iron is often burned without dipping in tin, or the temperature is not enough to solder. To ensure the quality of brazing, the only option is to use an automatic constant temperature series soldering iron or configure a voltage regulating system. Even if the temperature is too high, a series step-down resistor can also be used.
Thermostatic soldering iron
4. Tin absorbing electric soldering iron. Tin suction electric soldering iron is a soldering tool that integrates a piston type tin suction device with an electric soldering iron. It has the characteristics of convenient use, flexibility, and wide applicability. The disadvantage is that only one solder joint can be removed at a time.
Tin absorbing soldering iron
5. Gas welding soldering iron. It is a type of soldering iron that uses combustible gases such as liquefied gas and methane to burn and heat the soldering head. In situations where power supply is inconvenient or AC power cannot be supplied, you can choose to use it. Due to the risk of explosion, this article does not discuss the selection of such soldering irons here.
（2） Power selection of electric soldering iron
The power of the soldering iron used is too high, which can easily burn out the components (usually when the temperature of the junction of the transistor and transistor exceeds 200 ℃, it will burn out) and cause the printed wires to detach from the substrate; The power of the soldering iron used is too low, the soldering tin cannot be fully melted, the flux cannot evaporate, the solder joints are not smooth and firm, and it is prone to false soldering. Generally, it is used for welding integrated circuits, printed circuit boards, CMOS circuits, decorating transistors, IC type recorders, televisions, and conducting ordinary circuit experiments. It is generally recommended to use 20W. For repairing vacuum tube machines such as biliary machines and old instruments, it is recommended to use 35W, while for externally heated ones, it is recommended to use 45W. For welding the wiring of large transformers and grounding main lines on metal substrates, it is recommended to use internally heated 50W, externally heated 75W, and some higher power applications.
There are various shapes of soldering iron heads, and the key to choosing one is to regularly maintain a certain amount of solder, quickly and effectively melt the solder on the joint, without producing solder joints, overlap, or hanging, without burrs, and without damaging the board and components. If the solder joints on the machine are brand new and bright, the tin dipping section of the soldering iron head can be larger, and a flat or elliptical head can be used for fast heat transfer, natural operation, and convenience. The tin oxide layer is thick, and the soldering iron tip is relatively sharp, making it easy to break through.
Due to the high density of components, it is necessary to use corresponding sharp iron alloy heads to avoid burns and soldering. When assembling and disassembling IC blocks, special shaped soldering iron heads are often used. Sometimes, due to the inability to solder and the need to avoid damaging plastic parts, bent soldering iron heads are used. Of course, it also depends on each person's operating habits and hobbies.
How to choose an electric soldering iron
1. Selection of heating method based on electric soldering iron
(1) Selection of internal and external heating: When the power is the same, the temperature of the internal heating electric soldering iron is higher than that of the external heating electric soldering iron.
(2) When low-temperature welding is required, a voltage regulator should be used to control the temperature of the electric soldering iron. The temperature of the electric soldering iron is closely related to the power supply voltage. In practical use, the temperature of the electric soldering iron is often reduced by lowering the power supply voltage.
(3) Control the temperature by adjusting the extension length of the soldering iron head.
(4) There are several methods to stabilize the temperature of electric soldering irons: installing a regulated power supply to prevent changes in the power supply network; Maintain a certain volume, length, and shape of the soldering iron head; Using a constant temperature electric soldering iron; Maintain a constant indoor temperature; Avoid natural wind or electric fans, etc.
