Five-step training method of electric soldering iron and precautions for using electric soldering iron
Commonly used electric soldering irons are divided into two types: internal heating type and external heating type.
The soldering iron tip of the internal heating type electric soldering iron is outside the heating wire. This electric soldering iron heats up quickly and is light in weight.
The soldering iron tip of the external heating electric soldering iron is inserted into the heating wire. Although it heats slowly, it is relatively firm.
The electric soldering iron is directly heated by a 220V AC power supply. The power cord and the case should be insulated, and the resistance between the power cord and the case should be greater than 200M ohms.
Electronic hobbyists usually use 30W, 35W, 40W, 45W, 50W soldering irons. A more powerful electric soldering iron has a lower heating wire resistance. Ohm's law derived formula: R=U/I=U/I*U/U=U^2/P.
How to use a soldering iron?
1. Welding operation posture and hygiene
The chemical substances volatilized by heating the flux are harmful to the human body. If the nose is too close to the tip of the soldering iron during operation, it is easy to inhale the harmful gas. Generally, the distance from the soldering iron to the nose should be at least not less than 30cm, usually 40cm is appropriate.
There are three ways to hold the electric soldering iron, as shown in Figure 1. The anti-grip method is stable in action, and it is not suitable for fatigue after long-term operation. It is suitable for the operation of high-power soldering irons. The overhand grip is suitable for operation with medium-power soldering irons or irons with an angled tip. Generally, when welding printed circuit boards and other weldments on the operating table, the pen holding method is often used.
"Using a Soldering Iron"
There are generally two ways to hold solder wire, as shown in Figure 2. Since lead accounts for a certain proportion in the welding wire composition, it is well known that lead is a heavy metal harmful to the human body, so you should wear gloves or wash your hands after operation to avoid ingestion.
Use a soldering iron to configure a soldering iron stand, which is generally placed on the right front of the workbench. After using the soldering iron, it must be placed on the soldering iron stand safely, and be careful not to touch the tip of the soldering iron with wires and other objects, so as to avoid short circuit after the insulation is damaged by the soldering iron.
Two, five-step training
As a training method for beginners to master manual soldering technology, the five-step method is very effective and deserves to be discussed as a separate section.
Many electronic enthusiasts re-use a soldering operation method, that is, first dip some solder on the tip of the soldering iron, and then put the soldering iron on the solder joint to wait for heating and then solder to wet the weldment.
This method is not the correct method of operation. Although the weldment can also be welded in this way, the quality cannot be guaranteed. This is not difficult to understand from what we know about the soldering mechanism.
When we melt the solder onto the soldering iron tip, the flux in the solder wire will lie on the surface of the solder. Since the temperature of the soldering iron tip is generally above 250°C-350°C, the rosin flux will continue to volatilize before the soldering iron is put on the solder joint. , and when the soldering iron is placed on the solder joint, due to the low temperature of the weldment, it will take a while to heat up. During this period, most of the flux is likely to volatilize or even completely volatilize, so the wetting process is poor due to the lack of flux during the wetting process. At the same time, due to the large temperature difference between the solder and the weldment, the bonding layer is not easy to form, and it is difficult to avoid virtual welding.
Moreover, after the protective effect of the flux is lost, the solder is easy to oxidize, and it is inevitable that the quality cannot be guaranteed.
