Soldering iron is an indispensable tool for electronic production and electrical maintenance. Its main purpose is to weld components and wires. According to the mechanical structure, it can be divided into internal heating type electric iron and external heating type electric iron. According to the function, it can be divided into non-suction soldering iron and suction. Tin-type soldering irons are divided into high-power soldering irons and low-power soldering irons depending on the application.
The soldering iron is divided into two types: external heat type and internal heat type:
The external heating type soldering iron is composed of a soldering iron head, a soldering iron core, a casing, a wooden handle, a power lead, a plug and the like. Since the tip is mounted inside the iron core, it is called an external heating type soldering iron. The iron core is a key component of the soldering iron. It is formed by winding the heating wire in parallel on a hollow ceramic tube. The mica sheet in the middle is insulated, and two wires are connected to the 220V AC power supply. There are many specifications for external thermal soldering irons, such as 25W, 45W, 75W, 100W, etc. The higher the power, the higher the temperature of the soldering iron.
The internal heat type soldering iron is composed of a handle, a connecting rod, a spring clip, a soldering iron core and a soldering iron head. Since the iron core is installed inside the soldering iron tip, the heat is fast and the heat utilization rate is high, so it is called an internal heat type soldering iron. The common specifications of the internal heating type soldering iron are 20W and 50W. Due to its high thermal efficiency, the 20W internal thermal soldering iron is equivalent to an external thermal soldering iron of about 40W. The rear end of the internal heat type soldering iron is hollow, and is sleeved on the connecting rod and fixed by the spring clip. When the soldering iron head needs to be replaced, the spring clip must be first removed, and the front end of the soldering iron head is clamped with the pliers. Pull out slowly, remember not to use too much force to avoid damaging the connecting rod.
1. For the selection of suitable solder, the low melting point solder wire for soldering electronic components should be used.
2. Flux is dissolved in 75% alcohol (by weight) as a flux with 25% rosin.
3. The soldering iron should be tinned before use. The specific method is: heat the soldering iron. When the solder can be melted, apply flux, and then evenly spread the soldering iron on the soldering iron to make the soldering iron evenly eat. A layer of tin.
4, the welding method, the pads and components of the pins are polished with fine sandpaper, coated with flux. Dip a proper amount of solder with a soldering iron tip and contact the solder joint. After the solder on the solder joint is completely melted and immersed in the component lead, the soldering iron tip gently lifts up the solder joint along the lead of the component.
5, the welding time should not be too long, otherwise it is easy to burn the components, if necessary, you can use the tweezers to clamp the pins to help dissipate heat.
6, the solder joint should be sinusoidal peak shape, the surface should be bright and smooth, no tin thorn, moderate amount of tin.
7. After the welding is completed, the residual flux on the circuit board should be cleaned with alcohol to prevent the flux after the carbonization from affecting the normal operation of the circuit.
8. The integrated circuit should be soldered at the end, and the soldering iron should be grounded reliably or after the power is turned off. Or use an integrated circuit socket, solder the socket and then plug the integrated circuit.
9. The soldering iron should be placed on the soldering iron frame.
The temperature range of the soldering iron is 100 ° C ~ 400 ° C, the temperature adjustment mark indicates low, medium and high position, the temperature control accuracy is nominally ± 5%, and a thermocouple sensor is used. The control circuit adopts the direct current step-down, filtering and regulated power supply scheme of the AC mains. The working principle is shown in the figure below.
The mains AC220V is used as the power supply voltage and temperature setting voltage source of the comparison device IC after R1 step-down, D1 half-wave rectification, D2 clipping regulation, and C1 filtering. The IC-A3 pin is the thermocouple detection voltage input terminal (corresponding to the temperature value); the 2 pin is the thermostat setting voltage. After the voltages at both ends of pins 2 and 3 are compared, they are output by pin 1. The role of R5 is to feed back a small part of the input to the non-inverting input pin 3, so that the output lock does not change when the small signal fluctuates. When the thermocouple detects that the temperature is low; the level of the 3 pin is lower than the 2 pin, so that the output pin 1 is also low. Further, the IC-B amplifier 6 pin is lowered relative to the fixed bias 5 pin, so that the output 7 pin is high. Since the voltage of the IC-B5 pin is obtained by dividing the AC220V by R6 and R7, the frequency and phase are completely the same as those of the AC220V. After comparing with 6-pin DC, the AC voltage is output at 7 feet. The AC voltage is reversely connected in parallel with C2, D4, D3 and D4 (acting as a bidirectional diode) to trigger the bidirectional thyristor, so that the corresponding voltage is applied to the soldering iron heating wire to achieve the purpose of constant temperature.
One 220V/20W internal electric iron, one 220V/500W electric iron. There is also a 12V/10AH battery for the low voltage soldering iron power supply.
Second, the production steps1. Remove the 20W soldering iron core from the soldering iron. Carefully remove the fine porcelain tube wrapped with electric heating wire, soak it in alcohol for half an hour, then remove all the heating wire (the fine porcelain tube is very brittle and must be handled with care).
2. Remove the heating wire on the electric iron core of the electric iron, and cut the total length of it by 1/14. The resistance is about 7Ω measured by a multimeter (the resistance of the 500W electric iron heating wire is about 97Ω). The electric heating wire is neat. The ground is tightly wound around the fine porcelain tube, and the lead wire is taken out, and then the thick porcelain tube is placed, and it is put into the original electric soldering iron to connect the wire, and a low-voltage electric soldering iron is completed.
The power of the 12V low-voltage soldering iron is 20w (12÷7×12), and it can be used with the 12V/10AH battery. The larger the battery capacity, the longer the working time.
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