What are the basic methods and operating essentials of manual welding?

There are two basic methods of manual welding:

One is welding with tin, which is suitable for welding with solid welding rod; Another spot welding method is suitable for welding solder wires with rosin. The former is a traditional method, and the latter is a commonly used method at present.

1) spot welding method. Spot welding is also called double-hand welding. When welding, hold the electric soldering iron in the right hand and the rosin core solder wire in the left hand. When welding, two hands should cooperate with each other and coordinate. Not only that, but also master the correct operation method and welding essentials to make the solder joints bright, smooth and uniform in size, and prevent false welding and false welding.

Generally, there are three ways to hold rosin solder wire in your left hand.

Continuous tin wire drawing method:

That is, the thumb and four fingers hold the welding wire, and the other three fingers cooperate with the thumb and forefinger to continuously feed the welding wire forward. Suitable for manual welding of coiled welding wire; Intermittent tin wire holding method: hold the tin wire with thumb, forefinger and middle finger. This method that the welding wire can't advance continuously is suitable for manual welding of a short section of welding wire.

Spot welding method has the characteristics of fast welding speed and high quality of solder joints, and is suitable for rapid welding of multi-components. The specific welding process can be divided into the following four processes.

A) heating process. Use a heated soldering head to contact the component pin and the pad of the printed circuit board at the same time. The electric soldering iron forms an included angle of about 450 with the plane of the printed circuit board, and is heated for about 1-2s, so that the components pins and pads on the printed circuit board are heated evenly.

B) wire feeding process. When heated to a certain temperature, the left hand will send the rosin-cored wire to the root of the component pin from the left side, instead of to the welding head. When the solder wire of the rosin core began to melt, the solder joint formed quickly. The length of this process depends on the amount of solder needed by the solder joint, so it is necessary to control the wire feeding time to make the solder joint size uniform. Wire feeding process. Pay special attention to the best wire feeding position at the intersection of welding head, welding hole and component lead.

C) silk removal process. When the size of the solder joint is moderate, the welding wire held by the left hand quickly spreads out and the soldering iron remains heated.

D) heat removal process. After the wire is removed, the surrounding heating state is maintained, so that the solder is in full thermal contact with the object to be welded, thereby improving the welding reliability. After this process is completed, the soldering iron quickly departs from the inclined direction of 45 0, leaving a bright and smooth solder joint, and the whole process is over. Note: the solder joint is formed by the fluidity of the solder after it is completely melted. Do not use a soldering iron to wipe the solder joint when it is not ideal. When welding solder wire with spot soldering, rosin should be used in the middle of solder wire, otherwise it will be difficult to weld and the welding quality will be difficult to guarantee.

2) Welding with tin. When welding, first hang a proper amount of solder on the edge of the soldering iron, then accurately contact the solder joint with the edge of the soldering iron within 3s, and quickly remove the soldering iron after the solder joint is formed. Pay attention to the included angle of 450 between the cutting edge of soldering iron and the plane of printed circuit board when welding. The included angle is too small, and the solder joint is small; If the included angle is too large, the solder joint will be large. In this welding method, the amount of tin hanging on the soldering iron should be just enough for one solder joint. Too much tin will make the solder joint too big, and too little tin will make the solder joint insufficient. You should master the amount of tin in welding through practice. When welding by this method, the welding head should be immersed in rosin from time to time, so that the solder and welding head are always wrapped by a layer of rosin oil film. Otherwise, when the soldering iron hangs tin, the tin will not become beads, and the amount of tin hanging cannot be controlled.

(2) Operating Steps of Manual Soldering In electronic manufacturing, the manual soldering process is often summed up in eight words: "one scraping, two plating, three measuring and four welding". 1) Scraping-refers to cleaning the surface of the parts or wires to be welded before welding. Generally, the pins of integrated circuits are scrubbed with alcohol; For gold-plated silver alloy pins, the coating can not be scraped off, and the surface dirt can be removed with an eraser; If an oxide layer is found on the pin of the component, scrape off the oxide layer with a knife or fine sandpaper and wipe off the oil stain.

2) Electroplating-that is, tin plating on scraped parts. Tin plating is a very important step in manual welding. The specific method is to dip the rosin alcohol solution in the scratched part of the component, then press the hot welding head with tin on the component, and rotate the component to evenly coat it with a thin tin layer. If it is multi-stranded, it should be twisted together after grinding and then tinned.

3) Testing —— Test the tinned components, and test whether the quality of all tinned components is reliable with multimeter. If there are parts with unreliable or damaged quality, they should be replaced with parts with the same specifications.

4) Welding-refers to the final welding of components that have passed the test and completed the above three steps into the circuit. After welding, clean and coat the protective layer, and check the welding quality according to the different requirements of welding parts.