|
Arabic
Bengali
Chinese
English
French
German
Hebrew
Hindi
Italian
Japanese
Korean
Malay
Polish
Portuguese
Spanish
Turkish
Ukrainian
Vietnamese|
ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING Solders and fluxes. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Ham Radio Technologies One of the main elements of electrical and radio installation work is soldering. The quality of installation is largely determined by the correct choice of the necessary solders and fluxes used when soldering wires, resistances, capacitors, etc. To facilitate this choice, below is a summary of hard and soft solders and fluxes, their use and their manufacture. Soldering is the joining of hard metals with the help of molten solder having a melting point lower than the melting point of the base metal. The solder should dissolve the base metal well, spread easily over its surface, wet the entire soldering surface well, which is ensured only when the wetted surface of the base metal is completely clean. To remove oxides and contaminants from the surface of the metal being soldered, protect it from oxidation and better wetting with solder, chemicals called fluxes are used. The melting point of fluxes is lower than the melting point of solder. There are two groups of fluxes: 1) chemically active, dissolving oxide films, and often the metal itself (hydrochloric acid, borax, ammonium chloride, zinc chloride) and 2) chemically passive, protecting only soldered surfaces from oxidation (rosin, wax, stearin and etc.). Depending on the chemical composition and melting point of solders, soldering with hard and soft solders is distinguished. Hard solders include solders with a melting point above 400°C, light solders include solders with a melting point up to 400°C. The main materials used for soldering. Lead- soft, malleable metal of silver-white color. Specific gravity at 20°C - 7,31. Melting point 231,9°C. It dissolves well in concentrated hydrochloric or sulfuric acid. Hydrogen sulfide has almost no effect on it. A valuable property of tin is its stability in many organic acids. At room temperature, it is little susceptible to oxidation, but when exposed to temperatures below 18 ° C, it can turn into a gray modification (“tin plague”). In places where gray tin particles appear, the metal is destroyed. The transition of white tin to gray sharply accelerates when the temperature drops to -50°C. For soldering, it can be used both in pure form and in the form of alloys with other metals. Lead - bluish-gray metal, soft, easy to process, cut with a knife. Specific gravity at 20°C 11,34. Melting point 327qC. In air, it oxidizes only from the surface. It dissolves easily in alkalis, as well as in nitric and organic acids. Resistant to the effects of sulfuric acid and sulfuric compounds. Used for making solders. Cadmium- silver-white metal, soft, ductile, mechanically fragile. Specific gravity 8,6. Melting point 321°C. It is used both for anti-corrosion coatings and in alloys with lead, tin, bismuth for low-melting solders. Antimony- brittle silvery-white metal. Specific gravity 6,68. Melting point 630,5°C. It does not oxidize in air. It is used in alloys with lead, tin, bismuth, cadmium for low-melting solders. Bismuth- brittle silver-gray metal. Specific gravity 9,82. Melting point 271°C. It dissolves in nitric and hot sulfuric acids. It is used in alloys with tin, lead, cadmium to obtain low-melting solders. Zinc- bluish-gray metal. Brittle when cold. Specific gravity 7,1. Melting point 419°C. In dry air it oxidizes, in moist air it is covered with an oxide film, which protects it from destruction. In combination with copper, it gives a number of strong alloys. Easily soluble in weak acids. It is used for the manufacture of hard solders and acid fluxes. Copper- reddish metal, malleable and soft. Specific gravity 8,6 - 8,9. Melting point 1083 C. It dissolves in sulfuric and nitric acids and in ammonia. In dry air, it almost does not give in to oxidation, in damp air it is covered with green oxide. It is used for the manufacture of refractory solders and alloys. Rosin- a product of processing the resin of coniferous trees Lighter grades of rosin (more thoroughly cleaned) are considered the best. The softening point of rosin is from 55 to 83°C. It is used as a flux for soft soldering. Soft solders Soldering with soft solders has become widespread, especially in the production of installation work. The most commonly used soft solders contain a significant amount of tin. In table. 1 shows the compositions of some lead-tin solders. Table 1
When choosing the type of solder, it is necessary to take into account its features and apply it depending on the purpose of the soldered parts. When soldering parts that do not allow overheating, solders with a low melting point are used. Solder brand POS-40 finds the greatest application. It is used for soldering connecting wires, resistances, capacitors. Solder POS-30 is used for soldering shielding coatings, brass plates and other parts. Along with the use of standard grades, POS-60 solder (60% tin and 40% lead) is also used. Soft solders are made in the form of rods, ingots, wire (up to 3 mm in diameter) and tubes filled with flux. The technology of these solders without special impurities is simple and quite feasible in a workshop: lead is melted in a graphite or metal crucible and tin is added in small parts to it, the content of which is determined depending on the brand of solder. The liquid alloy is mixed, carbon deposits are removed from the surface and the molten solder is poured into wooden or steel molds. The addition of bismuth, cadmium and other additives is optional. For soldering various parts that do not allow significant overheating, especially low-melting solders are used, which are obtained by adding bismuth and cadmium or one of these metals to lead-tin solders. In table. 2 shows the compositions of some fusible solders. Table 2
When using bismuth and cadmium solders, it should be taken into account that they are very brittle and create a less durable solder than lead-tin solders. Hard solders Hard solders create high seam strength. In electrical and radio installation work, they are used much less frequently than soft solders. In table. 3 shows the compositions of some copper-zinc solders. Table 3
The color of the solder changes depending on the zinc content. These solders are used for soldering bronze, brass, steel and other metals with a high melting point. Solder PMTs-42 is used when soldering brass with a content of 60-68% copper. Solder PMTs-52 is used for soldering copper and bronze. Copper-zinc solders are made by alloying copper and zinc in electric furnaces, in a graphite crucible. As the copper melts, zinc is added to the crucible; after the zinc melts, about 0,05% of phosphoric copper is added. Molten solder is poured into molds. The melting temperature of the solder must be less than the melting temperature of the soldered metal. In addition to the indicated copper-zinc solders, silver solders are also used. The compositions of the latter are given in table. four. Table 4
Silver solders have great strength, the seams soldered by them are well bent and easily processed. Solders PSR-10 and PSR-12 are used for soldering brass containing at least 58% copper, solders PSR-25 and PSR-45 - for soldering copper, bronze and brass, solder PSR-70 with the highest silver content - for soldering waveguides , volume contours, etc. In addition to standard silver solders, others are used, the compositions of which are given in Table. 5. Table 5
The first of them is used for soldering copper, steel, nickel, the second, which has a high conductivity, for soldering wires; the third can be used for soldering copper, but is not suitable for ferrous metals; the fourth solder has a special fusibility, is universal for soldering copper, its alloys, nickel, steel. In some cases, commercially pure copper with a melting point of 1083°C is used as solder. Solders for aluminum brazing Soldering aluminum causes great difficulty due to its ability to easily oxidize in air. Recently, aluminum soldering with the help of ultrasonic soldering irons has been used. In table. 6 shows the compositions of some solders for soldering aluminum. Table 6
When soldering aluminum, organic substances are used as fluxes: rosin, stearin, etc. The last solder (solid) is used with a complex flux, which includes: lithium chloride (25-30%), potassium fluoride (8-12%), zinc chloride (8-15%), potassium chloride (59-43%) . The melting point of the flux is about 450°C. Fluxes The good wetting of solder joints and the formation of strong seams largely depend on the quality of the flux. At the soldering temperature, the flux should melt and spread in a uniform layer, while at the moment of soldering it should float to the outer surface of the solder. The melting point of the flux should be somewhat lower than the melting point of the solder being used. Reactive fluxes(acid) - these are fluxes that in most cases have free hydrochloric acid in their composition. A significant disadvantage of acid fluxes is the intense formation of corrosion of solder joints. The chemically active fluxes primarily include hydrochloric acid, which is used for soldering steel parts with soft solders. The acid remaining on the surface of the metal after soldering dissolves it and causes corrosion. After soldering, the product must be washed with hot running water. The use of hydrochloric acid when soldering radio equipment is prohibited, since during operation it is possible to break electrical contacts at the soldering points. It should be borne in mind that hydrochloric acid causes burns when it enters the body. zinc chloride(etched acid), depending on the soldering conditions, is used in the form of a powder or solution. Used for soldering brass, copper and steel. To prepare the flux, it is necessary to dissolve one weight part of zinc in five weight parts of 50% hydrochloric acid in lead or glassware. A sign of the formation of zinc chloride is the cessation of the release of hydrogen bubbles. Due to the fact that there is always a small amount of free acid in the solution, corrosion occurs at the soldering points, therefore, after soldering, the soldering point must be thoroughly washed in running hot water. Soldering with zinc chloride in the room where the radio equipment is located is not allowed. It is also impossible to use zinc chloride for soldering electrical and radio equipment. Store zinc chloride in a glass container with a tightly closed glass stopper. Bura(aqueous sodium salt of pyroboric acid) is used as a flux when soldering with brass and silver solders. Easily soluble in water. When heated, it turns into a glassy mass. Melting point 741°C. Salts formed during soldering with borax must be removed by mechanical cleaning. Borax powder should be stored in hermetically sealed glass jars. Sal ammoniac(ammonium chloride) is used as a powder to clean the working surface of the soldering iron before tinning. Chemically passive fluxes (acid-free) Acid-free fluxes include various organic substances: rosin, fats, oils and glycerin. The most widely used in electrical and radio installation work is rosin (in dry form or its solution in alcohol). The most valuable property of rosin as a flux is that its residues after soldering do not cause metal corrosion. Rosin has neither reducing nor dissolving properties. It serves solely to protect the soldering point from oxidation. For the preparation of alcohol-in-rosin flux, one weight part of crushed rosin is taken, which is dissolved in six parts by weight of alcohol. After complete dissolution of rosin, the flux is considered ready. When using rosin, the soldering points must be thoroughly cleaned of oxides. Often, for soldering with rosin, parts must be pre-tinned. stearindoes not cause corrosion. It is used for soldering lead sheaths of cables, couplings, etc. with extra soft solders. Melting temperature is about 50°С. Recently, it has been widely used flux group LTIused for soldering metals with soft solders. In terms of their anti-corrosion properties, LTI fluxes are not inferior to acid-free ones, but at the same time, they can be used to solder metals that could not be soldered before, for example, parts with galvanized coatings. LTI fluxes can also be used for brazing iron and its alloys (including stainless steel), copper and its alloys, and metals with high resistivity (see Table 7). Table 7
When soldering with LTI flux, it is enough to clean the soldering points only from oils, rust and other contaminants. When soldering galvanized parts, zinc should not be removed from the place of soldering. Before soldering parts with scale, the latter must be removed by etching in acids. Pre-etching of brass is not required. The flux is applied to the junction with a brush, which can be done in advance. Flux should be stored in a glass or ceramic container. When soldering parts with a complex profile, you can use solder paste with the addition of LTI-120 flux. It consists of 70-80 g of petroleum jelly, 20-25 g of rosin and 50-70 ml of LTI-120 flux. But LTI-1 and LTI-115 fluxes have one big drawback: dark spots remain after soldering, and intensive ventilation is also necessary when working with them. Flux LTI-120 does not leave dark spots after soldering and does not require intensive ventilation, so its use is much wider. Usually, flux residues after soldering can not be removed. But if the product will be operated in severe corrosive conditions, then after soldering, the flux residues are removed using ends moistened with alcohol or acetone. The production of flux is technologically simple: alcohol is poured into clean wooden or glassware, crushed rosin is poured until a homogeneous solution is obtained, then triethanolamine is introduced, and then active additives. After loading all the components, the mixture is stirred for 20-25 minutes. The flux produced must be checked for a neutral reaction with litmus or methyl orange. The shelf life of the flux is not more than 6 months. Publication: cxem.net
Artificial leather for touch emulation
15.04.2024 Petgugu Global cat litter
15.04.2024 The attractiveness of caring men
14.04.2024
▪ XNUMXD materials change shape and store energy ▪ Created an elastic form of carbon ▪ AMD will combine x86 and ARM architectures in one processor
▪ site section Clocks, timers, relays, load switches. Article selection ▪ article A slap in the face to public taste. Popular expression ▪ article How did you find out that animals do not distinguish colors? Detailed answer ▪ article Deputy director of the school for academic work. Job description ▪ article Merging paper. Focus Secret
Home page | Library | Articles | Website map | Site Reviews
www.diagram.com.ua | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
See other articles Section 
Latest news of science and technology, new electronics:
All languages of this page