(one). Soldering basic conditions 1. Weldability of weldments Not all materials can be connected by soldering. Only a portion of the metal has good solderability (strictly speaking, it should be solderable) to be soldered. General copper and its alloys, gold, silver, zinc, nickel, etc. have good weldability, but aluminum, stainless steel, cast iron and other weldability is very poor, generally require the use of special welding agents and methods for soldering. 2. Qualified solder Pb-Sn solder components that are out of specification or have excessive impurities can affect solder quality, especially certain impurity contents such as zinc, aluminum, cadmium, etc. Even if the content is 0.001%, the solder wettability and fluidity will be significantly affected, which will reduce the solder quality. Welding quality. It is obvious that even a clever cook can't produce delicacies with inferior ingredients. 3. Suitable for flux Different materials are used to weld different materials. Even if they are of the same kind of material, different fluxes are often used when the welding process is different. For example, hand soldering and dip soldering are used. Different solder fluxes are required for cleaning and non-cleaning after soldering. . For hand soldering, the use of rosin and active rosin can meet most of the electronic product assembly requirements. It should also be pointed out that the amount of flux must also be taken care of. Too much or too little is not conducive to soldering. 4. Solder joint design is reasonable Reasonable solder joint geometries are essential to ensure the quality of soldering. The contacts shown in Figure 1(a) are difficult to guarantee adequate solder joint strength due to the limited strength of lead-tin solder, as shown in Figure 1(b). Joint design is greatly improved. Figure 2 shows the effect on the soldering quality when the dimensions of the lead and mounting holes on the printed board are different. (two). Hand soldering points The following points are derived from the soldering mechanism and are proven by practical experience to have universal applicability. 1. Master heating time Different heating speeds can be used for soldering. For example, the shape of the soldering iron head is poor. We have to extend the time to meet the solder temperature requirement when soldering a large soldering iron with a small soldering iron. In most cases, prolonging the heating time is detrimental to electronic product assembly because (1) The bonding layer of the solder joint exceeds a suitable thickness due to prolonged heating, resulting in deteriorated solder joint performance.邋邋 (2) Printed boards, plastics, and other materials that are subject to excessive heat will deform and deteriorate. (3) After the components are heated, the performance changes or even fails. (4) The surface of the solder joint loses protection and oxidizes due to volatilization of the solder. Conclusion: The shorter the time is, the better it is to ensure that the solder wets the weldment. 2. Maintain the right temperature If high-temperature soldering iron welding spot is used in order to shorten the heating time, there will be another problem: the flux in the solder wire does not have enough time to flow through the surface to be welded and prematurely evaporate; the solder melts too fast. Affects the function of the flux; due to the high temperature, the heating time is short but also causes overheating. Conclusion: Keep the iron tip at a reasonable temperature range. The general rule of thumb is that the tip temperature is 50°C above the solder melting temperature. The ideal condition is to shorten the heating time at a lower temperature. Although this is contradictory, in practice, we can obtain a satisfactory solution by operating techniques. 3. Using a soldering iron to apply force to solder joints is harmful The heat transfer from the iron head to the solder joints mainly depends on the increase of the contact area, and it is futile to heat the solder joint with a soldering iron. In many cases, the welded parts may be damaged. For example, potentiometers, switches, and the solder joints of the connectors are often fixed on the plastic components. The result of the force may easily cause the original to fail. WEISS MACHINERY CO., LTD. , https://www.weissmachinery.com
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