One: Fundamentals of Welding
Currently soldering electronic components mainly soldering techniques. Soldering technique using tin as a primary material for the tin alloy of the solder, the solder melts at a certain temperature, the mutual attraction between the metal and the tin atoms weldments, diffusion, combine to form a binding layer of infiltration. In appearance, platinum and copper printing plate component leads are very smooth, in fact they have a lot of tiny surface irregularities gap, tin solder melt flow state by means of a weld surface diffusion along the capillary attraction, with solder to form a solder infiltration member, the component and the printed board firmly bonded together, but also has good electrical conductivity.
Soldering conditions are: welding surface should be clean, grease, rust will affect the welding; metal can be tin solder wetting only weldable, brass and other materials on the surface of the oxide film is easy to generate, can aid after flux, the surface of the first member welded tin infiltration, re-welding; have appropriate heating temperature of the solder material has a certain fluidity, weld can achieve the purpose, but the temperature is not too high, too easy to form an oxide film is high and affect the quality of welding.
II: electric iron
The main tool is the electric iron hand soldering. Many types of electric iron, there are direct thermal, sensing, energy storage and temperature controlled multiple electric power has 15W, 2OW, 35w ...... 300W variety, based primarily on the size of the weldment to decide. In general components of the welding heat-type electric iron 2OW appropriate; energy storage can be used electric iron welding consumables and IC components; available 150W ~ 300W high-power external thermal electric iron welding large weldments. Low-power electric iron tip temperature is generally between 300 ~ 400 ℃.
Tip generally use copper material. To protect from oxidation at high temperature welding rust, often the tip after the plating process, and some also with alloy tip easily oxidized material. The new soldering tip should be preceded formal tinning process. The tip is to clean and polished with spinning paper, then dipped pine fragrance, stained solder hard objects (such as wood) repeatedly on the ground so that all the faces tip tinned. If you use a very long time, the tip has been oxidized, use a small file rasp light to the surface oxide layer is treated with with new tip tinned copper exposed in the same way as light. When only a soldering iron, you can use the tip inserted iron core different shades method of adjusting the temperature of the tip. Tip from the iron core is pulled out longer, relatively lower tip temperature, whereas the temperature is higher. It can also be used to replace the tip size and shape to achieve the purpose of regulating the tip temperature. The finer the tip, the higher the temperature; the thicker the tip, the lower the relative humidity.
Depending on the type of welding element can select the appropriate shape of the tip. Tip top shape of the conical, beveled oval and chisel and other. Small solder joints can be used conical, welding large joints can chisel-shaped or cylindrical.
There is also a suction tin soldering iron, is in direct thermal electric iron absorption tin increases the body composition. To use this electric iron components in the circuit for desoldering
And solder paste
Solder is a major welding materials. Soldering of electronic components is actually a tin-lead alloy, different proportions of tin-lead solder melting temperature of different, usually 180 ~ 230 ℃. Hand soldering is best suited for use tubular solder wire, solder wire sandwiching a quality rosin and activator, and extremely easy to use. Tubular solder has 0.5,0.8,1.0,1.5 ... and other specifications can be easily selected.
Solder flux also known, is a kind of post-welding heat can play a clean metal surface and the protective effect of the material. Air metal surface easily generates an oxide film, an oxide film that can prevent solder wetting effect of the weld metal. Proper use of flux removes the oxide film, the welding quality, more reliable solder joint surface is smooth, mellow.
Flux series are inorganic, organic and rosin series series three, including the most active inorganic flux, but has a strong corrosive effect on metal, welding electronic components are not allowed. Organic flux (such as hydrochloric acid diethyl gum) activity followed, there are slightly aggressive. The most widely used is a rosin flux. Rosin melt in alcohol (1: 3) to form a "pine fragrance," welding dipped in a small amount of solder joints pine fragrance, you can achieve good flux effect. Excessive amount or more welding to form a black film, the rosin flux has lost its role, the need to clean up after the line welding. For the rosin flux is difficult to weld metal components can be added about 4% hydrochloric acid diethyl gum or tri-ethanol gel (6%). As a variety of flux on the market, we must understand its composition and corrosion on components, the re-use. Do not blindly use, resulting in corrosion of components in the future, its endless trouble.
Manual welding method
Hand soldering is the traditional welding methods, although the bulk of electronic products has been less used manual welding, but for electronic products, maintenance, testing inevitably will be used in manual welding. Welding quality is good or bad has a direct impact to the service results. Manual welding is a very practical skills in understanding the general method, the practice should be more; more practice, in order to have a better quality of welding.
Manual welding electric iron grip approach, positive grip, reverse grip and hold a pen three. Repair welding components and circuit boards to hold a pen type is more convenient.
Manual welding generally divided into four steps. ① welding preparation: Clean dust and oil components to be welded at, and then welded components are breaking around about a breaking of components, so that the tip can touch the electrical components are soldered at solder to avoid tip toward weld scorch when other components. When welding new components to deal with lead tin components. ② heat welding: The moistened with a little solder and rosin soldering iron tip contacts are welded components for about a few seconds. If you want to remove the printed board after the components are to be heated tip, gently pull the hand or silver components, see if you can remove it. ③ clean up the weld surface: If the bond portion excess solder, soldering iron can get rid of the head (be careful not to burn the skin, and do not flung the printed circuit board!), Branded tin optical head "stick" some solder out . If too little solder joints, is not smooth, electric iron head can "dip" some solder joints to repair welding. ④ Check the joints: joints to see if mellow, bright, solid, with the surrounding components whether there is even welding phenomenon.
Cause welding quality is not high
Hand soldering solder joint requirements are: ① good electrical connection performance; ② a certain mechanical strength; ③ smooth and mellow.
Common causes welding quality is not high: ① excessive amount of solder to form solder tin accumulation; solder is too small, not enough to wrap joints. ② cold welding. Soldering iron temperature is too low or insufficient heating time, the solder is not completely melted, invasion, and the solder surface is not bright (not smooth), there is a small crack (like tofu, like!). ③ mixed with a layer sandwiched between rosin rosin soldering, solder or printed board and components, resulting in poor electrical connection. If the lack of inclusion of heating rosin, the next layer of brown rosin solder film; if the heating temperature is too high, there is a layer of black coating carbonized under rosin solder joints. For lack of heating rosin film case, you can use a soldering iron repair welding. For black film has been formed, will have to "eat" clean solder, clean printing plates are welded components or surface, re-welding job. ④ solder connecting bridge. It refers to the excessive amount of solder, causing a short circuit between solder components. This should particularly pay attention to when the ultra-small components and small printed circuit board welding. ⑤ excess flux, solder rosin residue around a lot. When a small amount of rosin residues can then gently heated electric iron and let evaporate rosin be moistened with anhydrous alcohol cotton ball, wipe off the excess rosin or flux. ⑥ solder joints formed on the surface of a sharp cusp. This is mostly due to the heating temperature is less than or too little solder, and solder irons leaving improper angle.
Welding consumable components
Vulnerability refers to the installation of components in the welding process, likely to cause damage to the components when exposed to heat or touch a soldering iron, for example, organic casting components, MOS integrated circuits. Vulnerable components prior to welding to carefully prepare surface cleaning, tin, and other preparatory work, avoid prolonged repetitive welding iron welding, soldering iron tip and to select the appropriate temperature, to ensure a successful welding. In addition, to use less flux, solder prevent electrical contact points invasion of components (for example relay contacts). Welding MOS integrated circuit is best to use energy storage type electric iron, in order to prevent the leakage weak electric iron damage integrated circuits. Since the IC lead pitch is small, to choose the right tip and temperature to prevent bridging between the leads. IC is best to weld welding ground terminal, an output terminal, a power supply terminal, and then welded input. For those who are particularly sensitive to temperature components can be picked up with tweezers dipped yuan on water ethanol (alcohol) of cotton root protection components, the heat spread as little as possible on the components.