Understanding how to use an electric soldering iron and weld
How to use a soldering iron
1. Preparation tools: electric soldering iron, solder wire, rosin (you can buy them in general hardware stores);
2. The newly bought electric soldering iron can hang the soldering iron head with a knife (because there is an oxide layer), and then plug in the power. Be careful that the temperature is very high when you plug in the power;
3. When the temperature of the soldering iron comes up, put rosin on the tip of the soldering iron and solder;
4. First put rosin on the wires that need to be welded, and then solder on the dots;
5. Then solder on the components that need to be soldered, pay attention to the speed, otherwise the components will be burned if the temperature is too high;
6. When the soldering iron is not in use, put solder on the tip of the soldering iron (to prevent the soldering iron from drying);
7. Use rosin as the flux as much as possible, and the solder paste will be a little corrosive;
The method of hanging tin is very simple. Before powering on, clean the end face of the soldering iron tip with sandpaper or a knife. A layer of tin. The tip of the soldering iron after tinning can be used for soldering at any time.
Note: Any electric soldering iron must have three terminals, two of which are connected to the soldering iron core for connecting to 220V AC power supply, and the other is connected to the soldering iron shell as a grounding protection terminal for connecting to the ground wire. For safety reasons, Before use, it is best to use a multimeter to identify whether the soldering iron core is broken or mixed. Generally, the resistance of the soldering iron core of a 20-30W electric soldering iron is: 1500-2500 ohms.
Precautions for using electric soldering iron
The pins of various components should not be cut too short, otherwise it is not conducive to heat dissipation and soldering.
1. When soldering, place the lead wire of the component with tin hanging on the position to be soldered, such as the pad hole of the printed board or the small hole of the solder piece of various joints, sockets and switches, and use a soldering iron tip with an appropriate amount of tin to solder The part stays for about 3 seconds, and after the soldering iron is removed, a smooth solder joint is formed at the soldering place.
In order to ensure the quality of welding, it is best to hang tin in advance at the position of the lead wire of the welding component. When welding, make sure that the position of the lead wire does not change, otherwise it is very easy to cause false welding. The soldering iron tip should not stay for too long, otherwise it will burn the components, and if it is too short, it will cause false welding due to insufficient welding melting.
2 Before soldering, the excess part of the lead wire of the component should be cut off and tinned. If the surface of the component is oxidized and not easy to tin, you can use fine sandpaper or a knife to clean the surface of the lead, and use a soldering iron tip to dip an appropriate amount of rosin core solder to tin the lead.
If you still can't hang tin, you can put the component lead on the rosin block, then touch the lead lightly with the tip of the soldering iron, and turn the lead at the same time, so that the surface of the lead can be evenly tinned.
The tinning time of each lead wire should not be too long, generally 2~3 seconds is appropriate, so as not to burn the inside of the component, especially when tinning the pins of diodes and triodes, it is best to use metal tweezers to clamp the lead wires against the shell part, so as to transfer part of the heat away. in addition,
3. After welding, carefully observe the shape and appearance of the solder joints. The solder joints should be hemispherical and the height is slightly smaller than the radius. They should not be too bulging or flat. The appearance should be smooth and uniform without obvious pores or depressions, otherwise it will easily cause false or false welding. When welding the leads of several components at the same time, more attention should be paid to the quality of the solder joints.
Basic steps of welding operation
Step 1: Prepare for welding. Hold the welding wire in your left hand and the soldering iron in your right hand, and enter the welding preparation state. The tip of the soldering iron is required to be kept clean, free of oxides such as welding slag, and coated with a layer of solder on the surface.
Step 2: Heating the weldment The tip of the soldering iron rests on the junction of the two weldments, and heats the entire weldment for about 1 to 2 seconds. For soldering components on printed boards, care should be taken to make the tip of the soldering iron touch both objects to be soldered at the same time. Wires and terminals, component leads and pads should be heated evenly at the same time.
Step 3: When the welding surface of the welding piece fed with the welding wire is heated to a certain temperature, the solder wire contacts the welding piece from the opposite side of the soldering iron. Note: Do not send solder wire to the tip of the soldering iron!
Step 4: Remove the welding wire. When the welding wire has melted for a certain amount, immediately remove the welding wire to the upper left at 45°.
Step 5: Remove the soldering iron, after the solder infiltrates the pad and the welding part of the weldment, remove the soldering iron in the upper right direction of 45°, and end the welding. From the third step to the end of the fifth step, the time is about 1 to 2s.
Precautions for Welding Operation
1. Do not move or vibrate the weldment before the solder is solidified, otherwise it will easily cause loose solder joint structure or virtual welding.
2. The amount of flux should be moderate. Excessive use of rosin flux will inevitably wipe off excess flux after welding, and prolong the heating time and reduce work efficiency. When the heating time is insufficient, it is easy to form the defect of "slag inclusion".
3. The evacuation of the soldering iron should pay attention to the evacuation of the soldering iron in time, and the angle and direction of the evacuation are related to the formation of solder joints.
4. When increasing the contact area to speed up heat transfer and heating, the parts on the weldment that need to be infiltrated by solder should be heated evenly, instead of only heating a part of the weldment, let alone using the soldering iron to increase the pressure on the weldment.
5. Keep the tip of the soldering iron clean and maintained. When soldering, the tip of the soldering iron is in a high-temperature state for a long time, and it is easy to oxidize and get a layer of black impurities. Therefore, pay attention to wipe the tip of the soldering iron with a wet sponge at any time, and add tin to the tip of the soldering iron when it has not been used for a long time to prevent the tip of the soldering iron from oxidizing and making it impossible to stick tin.
6. The amount of solder should be moderate. The tin wire is already filled with flux made of rosin and activator.
7. Do not use the soldering iron tip as a tool for transporting solder (soldering with tin) Some people are used to using the soldering iron tip as a tool for transporting solder for soldering, which results in oxidation of the solder.
Because the temperature of the tip of the soldering iron is generally above 300°C, the flux in the solder wire is easy to decompose and fail at high temperature, and the solder is also in a low-quality state of overheating.
