Introduction of soldering iron welding skills
Electric soldering iron is the most commonly used tool in electronic circuit welding. Its function is to convert electric energy into heat energy to heat and weld the soldering point. Whether it is successful or not depends largely on how it is controlled. Therefore, from a certain point of view, electric soldering iron The use of it depends on a sense of technique.
Generally speaking, the greater the power of the electric soldering iron, the greater the heat, and the higher the temperature of the soldering iron tip. A 20W internal heating type electric soldering iron is sufficient for general transistors and integrated circuit electronic components. If the power is too high, the components will be easily burned out, because the junction temperature of diodes and triodes will burn out if the junction temperature exceeds 200°C. However, in the production of amplifiers mainly for scaffolding welding, the power of the electric soldering iron should be higher, and the power of the electric soldering iron can be selected from 35W-45W, or even higher.
It is worth noting that when welding the circuit, the time should not be too long or too short. If the time is too long, it will be easily damaged, but if the time is too short, the solder will not be able to fully melt, resulting in uneven solder joints and false soldering. For the most appropriate time must be completed within 1.5s ~ 4s.
Solder is a fusible metal, and the most commonly used is generally solder wire. The role of solder is to connect the component pins with the connection points of the printed circuit board, and the choice of solder has a great influence on the soldering quality. Now the most commonly used is rosin solder wire, but it is also very particular about the subdivision. Among them, the silver solder wire that is really not mixed with water is of course the first-class product.
It is also worth mentioning the solder suction device, which is very practical for novices. It is always easy to get solder everywhere when using a soldering iron for the first time. The solder suction device can help you dispose of excess solder on the circuit board. In addition, the tin suction device is very effective when removing multi-pin integrated circuit devices. It can suck off all the solder joints, but it is completely unnecessary for those who can skillfully use the soldering iron. It can completely replace its function with a soldering iron. The components can be easily removed by melting off the solder joints.
Before soldering, pre-soldering treatment should be performed on the component pins or the soldering parts of the circuit board.
Remove the oxide layer on the soldering part - a knife can be made from a broken saw blade to scrape off the oxide layer on the surface of the metal lead to expose the metal luster of the lead. The printed circuit board can be polished with fine gauze paper, and then coated with a layer of rosin alcohol solution.
Component tinning - tinning on scraped leads. After dipping the lead wire in the rosin alcohol solution, press the tip of the hot soldering iron with tin on the lead wire and turn the lead wire. The leads can be evenly plated with a very thin layer of tin. Before the wire is welded, the insulation sheath should be peeled off, and then the above two treatments can be performed before formal welding. In the case of multi-strand wires, they should be twisted together after polishing, and then tinned.
(1) Hold the electric soldering iron in the right hand. Use needle-nose pliers or tweezers with your left hand to hold components or wires. Before soldering, the electric soldering iron should be fully preheated. Tin should be eaten on the blade surface of the soldering iron head, that is, a certain amount of solder should be brought on.
(2) Place the blade of the soldering iron tip against the solder joint. The electric soldering iron is at an angle of about 60° to the horizontal plane. To facilitate the flow of molten tin from the tip of the soldering iron to the solder joint. The time the soldering iron tip stays at the solder joint is controlled within 2 to 3 seconds.
(3) Lift the tip of the soldering iron. The left hand still holds the component. The left hand can only be released after the tin at the solder joint is cooled and solidified.
(4) Rotate the lead wire with tweezers to confirm that it is not loose, and then use the pliers to cut off the excess lead wire.
Welding quality ----- When welding, it is necessary to ensure that each solder joint is firmly welded and in good contact. To ensure the quality of welding, its typical features are bright tin spots, smooth without burrs, and moderate tin content. The tin and the object to be welded are firmly fused, and there should be no false welding or false welding.
False soldering means that only a small amount of tin is welded at the solder joint, resulting in poor contact and intermittent on and off. False welding means that it seems to be welded on the surface, but it is not actually welded. Sometimes the lead wire can be pulled out from the solder joint by pulling it out by hand.
When soldering the circuit board, be sure to control the time. If it is too long, the circuit board will be burnt, or the copper foil will fall off. When removing components from the circuit board, stick the tip of the electric soldering iron on the solder joint, and pull out the component after the tin on the solder joint melts.
How to replace components ------ In fact, replacing components could not be simpler. It can be easily done with a solder suction device, and all the solder on the component pins will be sucked off. Here is a little trick for you. The current circuit Most of the boards are finely crafted, the solder is rarely used, and it is difficult to melt off, so it is much easier for us to add some solder to the pins and then use the solder absorber.
Another method is as mentioned above, directly use the electric soldering iron to melt off the solder, but there is a lot of danger in this way, not only to be careful that the solder joints are not completely melted, but also to be afraid of burning out the components if they are in contact for too long. The common method is to use tweezers to hold the component and pull it out when the temperature is high. When the temperature reaches, the component will be pulled out, but remember not to use too much force, otherwise it will be troublesome if the pin breaks in the solder.
Of course, for the sake of safety, it is better to use the two methods in combination, because sometimes the suction soldering is difficult to be sucked clean because the component socket is too small. Heat the soldering iron and remove it.
