General information about soldering. Solders and fluxes

General information. Soldering- this is the process of obtaining a permanent connection of materials with heating below the temperature of their autonomous melting by wetting, spreading and filling the gap between them with molten solder and their adhesion during the crystallization of the seam. Soldering is widely used in various industries.

The advantages of soldering include: slight heating of the connecting parts, which preserves the structure and mechanical properties of the metal; maintaining the dimensions and shapes of the part; connection strength.

Modern methods allow brazing carbon, alloy and stainless steels, non-ferrous metals and their alloys.

Solders - this is the quality, strength and operational reliability of the solder joint. Solders must have the following properties:

have a melting point below the melting point of the soldered materials;

provide a sufficiently high adhesion, strength, plasticity and tightness of the solder joint;

have a coefficient of thermal expansion close to the corresponding coefficient of the brazed material.

Low-melting solders widely used in various industries and households; they are an alloy of tin and lead.

Low-melting solders are used for soldering steel, copper, zinc, lead, tin and their alloys, gray cast iron, aluminum, ceramics, glass, etc. Antimony, bismuth, cadmium, indium, mercury and other metals are added to tin-lead solders to obtain special properties. . In locksmith work, solder POS 40 is more often used.

Refractory solders are refractory metals and alloys, of which copper-zinc and silver are widely used.

The addition of small amounts of boron increases the hardness and strength of the solder, but increases the brittleness of the solder joints.

According to GOST, copper-zinc solders are produced in three grades: PMC-38 for soldering brass with 60 ... 68% copper; PMC-48 - for soldering copper alloys, copper over 68%; PMTs-54 - for soldering bronze, copper, tompak and steel. Copper-zinc solders melt at 700 ... 950 degrees.

Fluxes used to remove oxide chemicals. Fluxes improve the surface wetting conditions by dissolving the oxide films present on the surface of the soldered metal and solder.

There are fluxes for soft and hard solders, as well as for soldering aluminum alloys, stainless steels and cast iron.

Soldering tools. Types of solder joints

Soldering irons. A special group is made up of soldering irons for special purposes: ultrasonic with an ultrasonic frequency generator (UP-21); with arc heating; with vibrating devices, etc.

Periodically heated soldering irons subdivided into angular, or hammer, and straight, or end. The former are the most widely used. A soldering iron is a piece of copper of a certain shape, mounted on an iron rod with a wooden handle at the end.

To soldering irons continuous heating include gas and petrol.

Electric soldering irons widely used, as they are simple in design and easy to use. No harmful gases are formed during their operation, and they heat up quickly - within 2 ... 8 minutes, which improves the quality of soldering. Electric soldering irons are (a) straight and (b) angled.

Types of soldered seams. Depending on the requirements for soldered products, soldered seams are divided into three groups:

durable having a certain mechanical strength, but not necessarily tightness;

dense- solid sealed seams that do not allow the penetration of any substance;

dense-strength with both strength and tightness.

The parts to be joined must fit well together.

Soldering with soft and hard solders

Soft soldering is divided into acidic And acid-free. For acid soldering, zinc chloride or technical hydrochloric acid is used as a flux; for acid-free soldering, fluxes that do not contain acids: rosin, turpentine, stearin, solder paste, etc. Acid-free soldering produces a clean seam; after acid soldering, the possibility of corrosion is not excluded.

Brazing is used to obtain strong and heat-resistant seams and is carried out as follows:

surfaces are adjusted to each other by sawing and thoroughly cleaned of dirt, oxide films and fats mechanically or chemically;

fitted surfaces at the junction are covered with flux; pieces of solder are placed on the place of the solder - copper plates and fixed with a soft knitting wire; prepared parts are heated with a blowtorch;

when the solder melts, the part is removed from the fire and kept in such a position that the solder cannot drain from the seam;

then the part is slowly cooled (it is impossible to cool the part with the soldered plate in water, as this will weaken the strength of the connection).

Safety. When soldering and tinning, the following safety rules must be observed:

the solderer's workplace must be equipped with local ventilation (air velocity not less than 0.6 m/s);

work in polluted premises is not allowed;

at the end of work and eating, you should wash your hands thoroughly with soap and water;

sulfuric acid should be stored in glass bottles with ground stoppers; you need to use only diluted acid;

when heating the soldering iron, the general rules for safe handling of the heat source should be observed;

for an electric soldering iron, the handle must be dry and non-conductive.

Tinning

The coating of the surface of metal products with a thin layer of an alloy corresponding to the purpose of the products (tin, tin-lead alloy, etc.) is called tinned.

Tinning, as a rule, is used in preparing parts for soldering, as well as to protect products from corrosion and oxidation.

The tinning process consists of preparing the surface, preparing the polish and applying it to the surface.

Surface preparation for tinning depends on the requirements for the products, and the method of applying the floor. Before coating with tin, the surface is brushed, polished, degreased and etched.

Irregularities on products are removed by grinding with abrasive wheels and skins.

Fatty substances are removed with Viennese lime, mineral oils - with gasoline, kerosene and other solvents.

Tinning methods. Tinning is carried out in two ways - by immersion in a semi-dude (small products) and rubbing (large products).

Immersion tinning performed in a clean metal container, in which they lay, and then melt the half-dude, pouring small pieces of charcoal onto the surface to protect it from oxidation. Then the product is washed in water and dried in sawdust.

Rubbing tinning perform by first applying zinc chloride to the cleaned area with a hair brush or tow. Then the surface of the product is evenly heated to the melting temperature of the half-day, which is applied from the rod. After that, they heat up and serve other places in the same order. At the end of tinning, the cooled product is washed with water and dried.

Gluing

General information. Gluing- this is the process of connecting machine parts, building structures and other products using adhesives.

Adhesive joints have sufficient tightness, water and oil resistance, high resistance to vibration and shock loads. Gluing in many cases can replace soldering, riveting, welding, interference fit.

Reliable connection of parts of small thickness is possible, as a rule, only by gluing.

Adhesives. There are several types of BF glue, produced under the brands BF-2, BF-4, BF-6, etc.

Universal glue BF-2 is used for bonding metals, glass, porcelain, bakelite, textolite and other materials.

Glue BF-4 and BF-6 is used to obtain an elastic seam when joining fabrics, rubber, fert. Compared to other adhesives, they have little strength.

Carbinol glue may be liquid or pasty (with filler). The adhesive is suitable for joining steel, cast iron, aluminium, porcelain, ebonite and plastics and ensures bonding strength within 3..5 hours after preparation.

bakelite lacquer- a solution of resins in ethyl alcohol. Used for gluing linings on clutch discs.

Technological process of gluing regardless of the materials to be glued and brands of adhesives, it consists of the following stages: preparation of surfaces for gluing - mutual preparation, cleaning from dust and grease and giving the necessary roughness; applying glue with a brush, spatula, spray gun; adhesive hardening and quality control of adhesive joints.

Defects. Reasons for the fragility of adhesive joints:

poor cleaning of bonded surfaces;

uneven application of the layer on the surfaces to be glued;

hardening of the glue applied on the surface until they are connected;

insufficient pressure on the connected parts of the parts to be glued;

incorrect temperature conditions and insufficient drying time for the adhesive joint.

The choice of solder depends on the metals or alloys to be joined, on the method of soldering, temperature restrictions, dimensions of parts, required mechanical strength, corrosion resistance, etc. Low-melting solders are most widely used in amateur practice. Recommendations for their use, on the basis of which you can choose a solder, are shown in the table. The letters POS in the brand of solder mean tin-lead solder, the numbers - the tin content in percent (POS 61, POS 40). To obtain special properties, antimony, cadmium, bismuth and other metals are introduced into the composition of tin-lead solders. The composition of some of these solders is given in the table. Low-melting solders are produced in the form of cast ingots, rods, wires, foil tapes, powders, tubes with a diameter of 1 to 5 mm filled with rosin, and also in the form of pastes composed of solder powder and liquid flux.

Lightweight solders.

brand	Melting temperature, ° С	Application area
POS90	222	Soldering parts and assemblies subjected to further galvanic treatment (silvering, gilding)
POS61	190	Tinning and soldering of thin spiral springs in measuring instruments and other critical parts made of steel, copper, brass, bronze, when high heating in the soldering zone is unacceptable or undesirable. Soldering thin (0.05-0.08 mm in diameter) winding wires, including high-frequency (litz wire), winding leads, radioelements and microcircuits, mounting wires in PVC insulation, as well as soldering in cases where increased mechanical strength and electrical conductivity
POS50	222	The same, but when higher heating is allowed than with POS 61
POS40	235	Tinning and soldering non-critical conductive parts, lugs, wire connections with petals, when higher heating is allowed than with POS 50 or POS 61
POSZO	256	Tinning and soldering non-critical mechanical parts made of copper and its alloys, steel and iron
POS 18	277	Tinning and soldering with reduced requirements for the strength of the seam, non-critical parts made of copper and its alloys, galvanized iron, steel
POSSu 4-6	265	Tinning and soldering of copper and iron parts by immersion in a bath of molten solder
POSK 50	145	Soldering parts made of copper and its alloys that do not allow local overheating. Soldering semiconductor devices
POSV 33 POSK 47-17	130 180	Soldering fuses Soldering wires and leads of elements to a layer of silver deposited on ceramics by burning
P200 P250	200 280	Soldering of thin-walled parts made of aluminum and its alloys
Alloy Rosé Alloy d "Arsenral Wood's fusion	92-95 79 60	Soldering when a particularly low solder melting temperature is required

The composition of some special low-melting solders.

brand	Content of elements, %						Melting temperature, ° С
	sn	Pb	Sb	Bi	CD	Zn
POSSu 4-6	3-4	90-92	5-6	-		-	265
POSK 50-18	49-51	29,8-33,8	0,2	-	17-19	-	222
POSV 33	33,4	33,3	-	33,3	-	-	130
P250	80	-	-	-	-	20	280
P200	90	-	-	-	-	10	200
Rose Alloys	15,5	32	-	52,5	-	-	95
	25	25	-	50	-	-	94
	-	40	-	52	8	-	92
Alloy d "Arsenval	9,4	45,1	-	45,5	-	-	79
Wood's fusion	12,5	25	-	50	12,5	-	60

Fluxes

Fluxes dissolve and remove oxides and contaminants from the surface of the solder joint. In addition, during soldering, they protect the surface of the heated metal and molten solder from oxidation. All this contributes to an increase in solder spreadability and, consequently, to an improvement in soldering quality. The flux is chosen depending on the properties of the metals or alloys being joined by soldering and the solder used, as well as on the soldering method. Flux residues, especially active ones, and the products of its decomposition must be removed immediately after soldering, as they contaminate the joints and are corrosion centers. When installing electrical and radio equipment, rosin and fluxes are most widely used, prepared on its basis with the addition of inactive substances - alcohol, glycerin and even turpentine. Rosin is not hygroscopic, it is a good dielectric, so its unremoved residue does not pose a danger to the solder joint. Data on the fluxes most commonly used in amateur practice are given in the tables.

Inactive (acid-free) fluxes

Active (acidic) fluxes

Composition, %	Application area	Residue removal method
Zinc chloride - 25-30; concentrated hydrochloric acid - 0.6-0.7; water - the rest	Soldering parts made of ferrous and non-ferrous metals	Thorough rinsing with water
Zinc chloride (saturated solution) - 3.7; technical vaseline - 85; distilled water - the rest (flux paste)	The same when, by the nature of the work, it is more convenient to use paste	Also
Zinc chloride - 1.4; glycerin - 3; ethyl alcohol - 40; distilled water - the rest	Soldering nickel, platinum and its alloys	Also
Rosin - 24; zinc chloride - 1; ethyl alcohol - rest	Soldering non-ferrous and precious metals (including gold), critical parts made of ferrous metals	Acetone flush
Rosin - 16; zinc chloride - 4; technical vaseline - 80 (flux paste)	The same, for obtaining joints of increased strength, but only parts of a simple configuration that does not impede washing	Also

Soldering aluminum with POS solders

It is difficult, but still possible, if the tin-lead solder contains at least 50% tin (POS 50, POS 61, POS 90). Mineral oil is used as a flux. Best results are obtained when using alkaline oil (for cleaning weapons after shooting). Satisfactory soldering quality is provided by mineral oil for sewing machines and precision mechanisms. A flux is applied to the place of soldering and the aluminum surface under a layer of oil is cleaned with a scraper or a knife blade to remove the oxide film that is always present on the aluminum surface. Solder with a well-heated soldering iron. For soldering thin aluminum, a soldering iron power of 50 W is sufficient, for aluminum with a thickness of 1 mm or more, a power of 90 W is more desirable. When soldering aluminum with a thickness of more than 2 mm, the place to be soldered must be preheated with a soldering iron and only then the flux should be applied.

Soldering aluminum with solders P200 and P250

The corrosion resistance of solder joints made with these solders is somewhat lower than those made with tin-lead solders. The flux is a mixture of oleic acid and lithium iodide. Lithium iodide (2-3 g) is placed in a test tube or flask and 20 ml (about 20 g) of oleic acid are added (from 5 to 17% lithium iodide.) The mixture is slightly heated by lowering the test tube into hot water and stirred until the salt is completely dissolved. Ready flux is poured into clean glassware and cooled. If an aqueous lithium salt is used, then when it dissolves, a layer of an aqueous mixture descends to the bottom of the test tube, and the flux floats up and is carefully drained. Before soldering, the tip of a well-heated soldering iron (the temperature of the tip should be about 270-350 ° C) is cleaned and tinned with solder using pure rosin. The parts to be joined are wetted with flux, tinned and soldered. After cooling, the flux residues are removed with a swab from a cloth dipped in alcohol, acetone or gasoline, and the seam is covered with a protective varnish. The flux during the soldering process does not emit toxic.and..substances with a pungent odor. It is easily washed off with soap and water from the fabric and skin of the hands.

Nichrome soldering (nichrome with nichrome, nichrome with copper and its alloys, nichrome with steel)

It can be carried out by soldering POS 61, POS 50 (worse - POS 40) using a flux of the following composition (in grams): vaseline - 100, zinc chloride powder -. 7, glycerin - 5. The flux is prepared in a porcelain mortar, in which petroleum jelly is placed, and then added, stirring well until a homogeneous mass is obtained, sequentially zinc chloride and glycerin. The surfaces to be joined are carefully cleaned with a sandpaper and wiped with a cotton swab dipped in a 10% alcohol solution of copper chloride, flux is applied, tinned, and only then soldered.

Soldering of galvanized steels

Soldering of steels plated with zinc or cadmium is possible with tin-lead solders with a soldering iron using zinc chloride as a flux (clause 10.13). Soldering with rosin fluxes does not give a quality connection.

solder paste

When soldering at home, solder is usually collected and applied with a soldering iron. It is extremely difficult to control the amount of molten solder carried by a soldering iron: it depends on the melting temperature of the solder, the temperature and cleanliness of the tip, and other factors. It is not excluded in this case that drops of molten solder will get on the conductors, the housings of the elements, the insulation, which sometimes leads to undesirable consequences. You have to work extremely carefully and accurately, and yet it can be difficult to achieve good soldering quality. Soldering can be made easier and improved by using solder paste. To prepare the paste, grind the solder with a file with a large notch (the fine one is clogged with solder) and mix the sawdust with an alcohol-rosin flux. The amount of solder in the paste is selected empirically. If the paste is too thick, alcohol is added to it. Store the paste in a tightly sealed container. The paste is applied to the place of soldering with the necessary doses with a metal spatula. The use of solder paste, in addition, avoids overheating of small parts and semiconductor devices.

"Solder Tape"

It is indispensable for splicing conductors, tubes, rods, when it is not possible to use an electric soldering iron. To make "solder tape", you must first prepare a paste of solder chips, rosin, and petroleum jelly. The paste is applied in a thin even layer on a calico tape. The place of soldering is wrapped in one layer with a “soldering tape”, moistened with gasoline or kerosene and set on fire. It is advisable to tin the pre-joined surfaces.

Tinning wires in enamel insulation

When stripping the lead ends of the winding wire LESHO, PELSHO, PEL and PEV with sandpaper or a blade, cuts and breaks in thin wire strands are not uncommon. Stripping by firing also does not always give satisfactory results due to the possible melting of wires of small cross section. In addition, at the place of firing, the wire loses its strength and breaks easily. PVC tubing can be used to strip small wires with enamel insulation. A piece of the tube is placed on a plank and, pressing the wire to the tube with the plane of the tip of a well-heated soldering iron, pull the wire 2-3 times with a light effort. In this case, the destruction of the enamel coating and the tinning of the wire occur simultaneously. The use of rosin is optional. Instead of a PVC tube, you can use scraps of a mounting wire or cable in PVC insulation. Wire in enamel insulation of any diameter can be tinned with aspirin-rosin paste. Aspirin and rosin must be crushed into powder and mixed (in a mass ratio of 2: 1). Dilute the resulting mixture with ethyl alcohol to a paste-like state. The end of the wire is immersed in the paste and the tip of a hot soldering iron is passed along the wire with little effort or the wire is moved under the tip, while the enamel is destroyed and the wire is tinned. To remove residues of acetylsalicylic acid (aspirin), the wire is tinned again using pure rosin.

Solder instead of glue

It is often necessary to solder a wire to a metal part that is difficult to solder: stainless steel, chromium, nickel, aluminum alloys, etc. In such cases, the following method can be used to ensure reliable electrical and mechanical contact. The part at the point of connection of the wire is thoroughly cleaned of dirt and oxides and degreased. The tinned end of the wire is dipped in BF-2 glue and pressed to the junction with the tip of a heated soldering iron for 5-6 s. After cooling, 1-2 drops of epoxy glue are applied to the contact point and dried until completely hardened.

Welding instead of soldering

Electric welding significantly reduces the time spent on installation work, provides connections that can withstand high-temperature heating, does not require solders, fluxes, pre-tinning, allows you to connect conductors from metals and alloys that are difficult to solder, such as wires of electric heaters. For welding, it is necessary to have a source of direct or alternating current with a voltage of 6-30 V, providing a current of at least 1 A. The electrode for welding is a graphite rod from used KBS batteries or others, sharpened at an angle of 30-40 °. As an electrode holder, you can use a probe from an ammeter voltmeter with a crocodile tip. In places of future welding, pre-stripped conductors are twisted with a bundle and connected to one of the poles of the current source. An electrode connected to the other pole of the current source heats up the place to be welded. The molten metal forms a drop-shaped compound. As the graphite burns out during operation, the electrode should be sharpened. With the acquisition of the skill, welding is clean, without scale. It is necessary to work in light-protective glasses.

"Practical advice to the master-amateur", 1991. O.G. Verkhovtsev, K.P. Lyutov

Soldering with a soldering iron is one of the most common and simple soldering methods, but it has two significant limitations. Firstly, a soldering iron can only be soldered with low-melting (soft) solders, and secondly, they cannot (or, in any case, it is difficult) to solder massive parts with a large heat sink - due to the impossibility of heating them to the melting temperature of the solder. The latter limitation is overcome by heating the part to be soldered with an external heat source - a gas burner, an electric or gas stove, or in some other way - but this complicates the soldering process.

Before you solder with a soldering iron, you need to get everything you need. The main tools and materials without which soldering is impossible include the soldering iron itself, solder and flux.

Soldering irons

Depending on the method of heating, soldering irons are "normal" - electric (with a spiral or ceramic heater), gas (with a gas burner), hot air (heat is transferred by air flow), induction. Massive hammer soldering irons can be heated not only with electricity, but also in the old fashioned way - with an open flame.

How to use such a soldering iron, you can learn from the descriptions of the technology of tin work, it was there that they were used most often. Nowadays, electric soldering irons are usually used due to their availability and ease of use. But the first soldering irons were heated by an open flame.

The main parameter by which a soldering iron is selected is its power, which determines the amount of heat flow transmitted to the soldered parts. For soldering electronic components, devices with a power of up to 40 W are used. Thin-walled parts (with a wall thickness of up to 1 mm) require a power of 80-100 watts.

For parts with a wall thickness of 2 mm or more, you will need soldering irons with a power higher than 100 watts. These are, in particular, hammer electric soldering irons that consume up to 250 W and more. The most energy-intensive soldering irons include, for example, the Ersa Hammer 550 hammer soldering iron with a power of 550 W. It is capable of heating up to a temperature of 600°C and is designed for soldering particularly massive parts - radiators, machine parts. But he has an inadequate price.

In addition to the massiveness of the part, the thermal conductivity of the soldered metal also affects the required power of the soldering iron. With its increase, the power of the device and the temperature of its heating must be increased. When soldering copper parts with a soldering iron, it must be heated more strongly than when soldering a part of the same mass, but made of steel. By the way, when working with copper products, a situation may arise when, due to the high thermal conductivity of the metal, during soldering, desoldering of previously completed places will occur.

Solders

When soldering with electric soldering irons, low-temperature tin-lead (POS-30, POS-40, POS-61), tin-silver (PSr-2, PSr-2.5) or other solders and pure tin are used. The disadvantages of solders containing lead include the harmfulness of the latter, the advantages are the better quality of soldering than lead-free solders. Pure tin is used for soldering food utensils.

Fluxes

It is generally accepted that tin, silver, gold, copper, brass, bronze, lead, nickel silver are well soldered. Satisfactory - carbon and low alloy steels, nickel, zinc. Poor - aluminum, high-alloy and stainless steels, aluminum bronze, cast iron, chromium, titanium, magnesium. However, without disputing these data, it can be argued that there is no poorly soldered metal, there is poor preparation of the part, incorrectly selected flux and incorrect temperature conditions.

Choosing the right flux for soldering means solving the main soldering problem. It is the quality of the flux that determines, first of all, the solderability of a particular metal, the ease or difficulty of the soldering process itself, and the strength of the joint. The flux must correspond to the material of the soldered products - its ability to destroy its oxide film.

Acidic (active) fluxes, such as "Soldering Acid" based on zinc chloride, cannot be used when soldering electronic components, as they conduct electricity well and cause corrosion, however, due to their aggressiveness, they prepare the surface very well and are therefore indispensable when soldering metal structures, and the more chemically resistant the metal, the more active the flux should be. Residues of active fluxes must be carefully removed after soldering is completed.

Effective fluxes for soldering steel are an aqueous solution of zinc chloride, soldering acids based on it, flux LTI-120. You can use other, stronger fluxes, which abound on the market.

The main difference between soldering stainless steels and soldering carbon and low-alloy steels is the need to use more active fluxes, which are required to destroy the chemically resistant oxides with which stainless steels are coated. As for cast iron, it must be soldered with high-temperature soldering, and, therefore, an electric soldering iron is not suitable for this purpose.

For stainless steel, phosphoric acid is used. Well cope with a chemically resistant oxide film and specialized fluxes, such as, for example, F-38.

For galvanized iron, you can use a composition containing rosin, ethyl alcohol, zinc chloride and ammonium chloride (flux LK-2).

Auxiliary materials and devices

You can do without some devices and materials used for soldering, but their presence makes the work much more convenient and comfortable.

Soldering iron stand serves to ensure that the heated soldering iron does not touch the table or other objects. If it does not come with a soldering iron, it is purchased separately or made independently. The simplest stand can be made from a thin sheet of tin by cutting grooves in it for laying the tool.

Wet rayon or foam sponge, placed in a nest to prevent falling out, it is much more convenient to clean the tip of the soldering iron than with a regular cloth. Brass shavings can also serve for the same purposes.

You can remove excess solder from the surface of the parts using special suction or braids. The first in appearance and design resembles a syringe equipped with a spring. Before use, it must be cocked by drowning the stem head. Bringing the spout to the molten solder, the spring is lowered by pressing the release button. As a result, excess solder is drawn into the removable head.

It is a braid of fluxed thin copper wires. By attaching its end to the solder and pressing it on top with a soldering iron, thanks to capillary forces, you can collect all the excess solder in it like a blotter. The tip of the braid, saturated with solder, is simply cut off.

A very useful device is called third hand(Third-Hand Tool). When working with a soldering iron, sometimes there are catastrophically "not enough hands" - one is busy with the soldering iron itself, the other with solder, but you still need to keep the parts to be soldered in a certain position. The "third hand" is convenient in that its clamps can be easily installed in any position relative to each other.

Solder holder "Third hand"

The soldered parts are heated to a high temperature, touching them can cause burns. Therefore, it is desirable to have various clamping devices that allow you to manipulate heated parts - pliers, tweezers, clamps.

Preparing the soldering iron for work

The first time you turn on the soldering iron, it may start to smoke. There is nothing wrong with this, the oils used to preserve the soldering iron just burn out. You just need to ventilate the room.

Before using the soldering iron, you need to prepare its tip. Preparation depends on its original form. If the tip is bare copper, the tip can be forged into a screwdriver shape, which will compact the copper and make it more resistant to wear. You can simply sharpen it with sandpaper or a file, giving it the necessary shape - in the form of an acute or truncated cone with a different angle, a tetrahedral pyramid, an angular bevel on one side. Nickel metal coatings are used to protect copper from oxidation. If the soldering iron has such a coating, then it cannot be forged and sharpened in order to avoid damage to the coating layer.

There is a unified range of tip shapes, but you can, of course, use any shape suitable for a particular job.

When soldering massive parts, the area of ​​contact between the soldering iron and the part should be as large as possible to ensure better heat transfer. In this case, the angular sharpening of a round rod is considered the best (2 in the photo above). If you intend to solder small parts, then a sharp cone (4), knife or other forms with small angles will do.

The instructions for working with a soldering iron with an uncoated copper tip contain one mandatory requirement - tinning the "sting" of a new soldering iron in order to protect it from oxidation and wear. And this should be done at the first heating, without delay. Otherwise, the "sting" will be covered with a thin layer of scale, and the solder will not want to stick to it. This can be done in different ways. Warm up the soldering iron to operating temperature, touch the "sting" to the rosin, melt the solder on it and grind the latter on a piece of wood. Or wipe the heated tip with a rag moistened with a solution of zinc chloride, melt solder on it and rub it over the tip with a piece of ammonia or rock salt. The main thing is that as a result of these operations, the working part of the tip is completely covered with a thin layer of solder.

The need to tin the tip is due to the fact that the flux gradually corrodes, and the solder dissolves the tip. Due to the loss of shape, it is necessary to sharpen the sting regularly, and the more active the flux, the more often, sometimes several times a day. For nickel-plated tips, nickel closes access to copper, protecting it, but such tips require careful handling, they are afraid of overheating, and it’s not a fact that the manufacturer has made a sufficiently high-quality coating for which it requires an overpayment.

Preparation of parts for soldering

Preparing parts for soldering involves performing the same operations, regardless of what type (low-temperature or high-temperature) soldering is performed, and what heating source (electric or gas soldering iron, gas burner, inductor, or something else) is used.

First of all, this is cleaning the part from dirt and degreasing. There are no special subtleties here - you need to clean the part from oils, fats, dirt with the help of solvents (gasoline, acetone or others). If there is rust, it must be removed by any suitable mechanical means - using an emery wheel, wire brush or sandpaper. In the case of high-alloy and stainless steels, it is desirable to grind the joined edges with an abrasive tool, since the oxide film of these metals is especially strong.

Soldering temperature

The heating temperature of the soldering iron is the most important parameter; the quality of the soldering depends on the temperature. Insufficient temperature manifests itself in the fact that the solder does not spread over the surface of the product, but lies in a lump, despite the preparation of the surface with flux. But even if the soldering turned out externally (the solder melted and spread over the joint), the solder joint turns out to be loose, matte in color, and has low mechanical strength.

The soldering temperature (the temperature of the soldered parts) should be 40-80°C higher than the melting temperature of the solder, and the tip heating temperature should be 20-40°C higher than the soldering temperature. The last requirement is due to the fact that in contact with the parts to be soldered, the temperature of the soldering iron will decrease due to heat removal. Thus, the heating temperature of the tip should exceed the melting temperature of the solder by 60-120°C. If a soldering station is used, then the required temperature is simply set by the regulator. When using a soldering iron without temperature control, it is possible to evaluate its actual value, when using rosin as a flux, by the behavior of rosin when the soldering iron is touched. It should boil and release steam profusely, but not burn out instantly, but remain on the tip in the form of boiling drops.

Overheating of the soldering iron is also harmful, it causes the flux to burn and char before it activates the solder surface. Overheating is evidenced by a dark film of oxides that appears on the solder located at the tip of the soldering iron, as well as the fact that it does not stay on the “sting”, flowing from it.

soldering technique

There are two main ways to solder with a soldering iron:

• Supply (drain) of solder to soldered parts from the tip of the soldering iron.
• Supply of solder directly to the parts to be soldered (to the pad).

With any method, it is necessary to first prepare the parts for soldering, install and fix them in their original position, heat up the soldering iron and moisten the place of the solder with flux. Further steps differ depending on which method is used.

When supplying solder from a soldering iron, a certain amount of solder is melted on it (to be held at the tip) and the "sting" is pressed against the parts to be soldered. In this case, the flux will begin to boil and evaporate, and the molten solder passes from the soldering iron to the junction. By moving the tip along the future seam, the solder is distributed over the joint.

Solder on the jelly may be enough if the tip has just acquired a metallic sheen. If the shape of the tip has changed noticeably, then there is too much solder.

When applying solder directly to the junction, the soldering iron first heats up the parts to the soldering temperature, and then the solder is fed to the part or to the joint between the soldering iron and the part. Melting, the solder will fill the joint between the soldered parts. Choose how to solder with a soldering iron - the first or second way - should be depending on the nature of the work performed. For small parts, the first method is better, for large ones, the second.

The main requirements for high-quality soldering include:

• good heating of the soldering iron and soldered parts;
• a sufficient amount of flux;
• entering the required amount of solder - exactly as much as required, but no more.

Here are some tips on how to properly solder with a soldering iron.

If the solder does not flow, but smears, then the temperature of the parts has not reached the desired values, you need to increase the heating temperature of the soldering iron or take a more powerful device.

You don't need to add too much solder. High-quality soldering implies the presence of a minimum sufficient amount of material in the joint, at which the seam turns out to be slightly concave. If there is too much solder, you do not need to try to attach it somewhere at the junction, it is better to remove it with suction or a braid.

The quality of the junction is indicated by its color. High quality - the junction has a bright sheen. Insufficient temperature makes the structure of the junction grainy, spongy - this is an unambiguous marriage. Burnt solder looks dull and has reduced strength, which in some cases may be quite acceptable.

When using active (acidic) fluxes, it is imperative to wash off their residues after soldering - with some kind of detergent or ordinary alkaline soap. Otherwise, no guarantee can be given that after some time the connection will not be destroyed by corrosion from the remaining acids.

Tinning

Tinning - covering the metal surface with a thin layer of solder - can be either an independent, final operation, or an intermediate, preparatory stage of soldering. When this is the preparatory stage, successful tinning of the part in most cases means that the hardest part of the soldering job (joining the solder to the metal) is done, and soldering the tinned parts together is usually no longer difficult.

Wire tinning. Tinning the ends of electrical wires is one of the most frequent operations. It is carried out before soldering the wires to the contacts, soldering together or to ensure better contact with the terminals when connecting with bolts. It is convenient to make a ring from a tinned stranded wire, which provides convenience when attached to the terminal and good contact.

Wires can be solid and stranded, copper and aluminum, varnished or not, clean new or acidified old. Depending on these features, their service differs.

The easiest way to tin is a single-core copper wire. If it is new, it is not covered with oxides and is tinned even without stripping, you just need to apply flux to the surface of the wire, apply solder to the heated soldering iron and move the soldering iron along the wire, slightly turning the wire. As a rule, tinning passes without problems.

If the conductor does not want to be tinned - due to the presence of varnish (enamel) - ordinary aspirin helps. Knowing how to solder with an aspirin (acetylsalicylic acid) tablet can be very helpful in some cases. You need to put it on a board, press the conductor against it and warm it up for a few seconds with a soldering iron. In this case, the tablet begins to melt, and the resulting acid destroys the varnish. After that, the wire usually tins easily.

If there is no aspirin, vinyl chloride insulation from electrical wires also helps to remove varnish that interferes with tinning from the surface of the conductor, which, when heated, releases substances that destroy the varnish coating. It is necessary to press the wires with a soldering iron to a piece of insulation and drag it several times between the insulation and the soldering iron. Then irradiate the wire in the usual way. When stripping varnish with sandpaper or a knife, cuts and breaks in thin wire strands are not uncommon. When stripping by firing, the wire may lose strength and break easily.

It should be borne in mind that molten PVC and aspirin release substances harmful to health into the air.

Also, for varnished (enamelled) wires, you can purchase a special flux that removes varnish.

The new stranded copper wire can be tinned just as easily as a single strand. The only feature is to rotate it in the direction in which the wires will be twisted and not untwisted.

Old wires can be coated with oxides that prevent tinning. The same aspirin tablet will help to cope with them. You need to unwind the conductor, put it on aspirin and warm it up with a soldering iron for several seconds, moving the conductor back and forth - and the problem of tinning will disappear.

For tinning aluminum wire, you will need a special flux - for example, the one that is called "Aluminum Brazing Flux". This flux is universal and is also suitable for soldering metals with a chemically resistant oxide film - stainless steel in particular. When using it, you just need to remember to clean the connection from flux residues afterward in order to avoid corrosion.

If during tinning the wires an excess of surf has formed on them, you can remove it by placing the wire vertically with the end down and pressing a heated soldering iron to its end. Excess solder will drain from the wire to the soldering iron.

Tinning of a large metal surface

Tinning of the metal surface may be necessary to protect it from corrosion or to subsequently solder another part to it. Even if a completely new sheet is tinned, which outwardly looks clean, foreign substances can always be on its surface - preservative lubricant, various contaminants. If a sheet covered with rust is tinned, then it needs to be cleaned all the more. Therefore, tinning always begins with a thorough cleaning of the surface. Rust is cleaned with an emery cloth or a metal brush, fats and oils are removed with gasoline, acetone or other solvent.

Then, with a brush or other tool that matches the flux, a flux is applied to the surface of the sheet (this may not be a pasty flux as in the photo below, but, for example, a solution of zinc chloride or another active flux).

A soldering iron with a relatively large flat surface of the tip is heated to the required temperature and solder is applied to the surface of the part. It is desirable that the power of the soldering iron be about 100 W or higher.

Then apply the soldering iron to the solder on the part with the largest plane and keep it in that position. The heating time of the part depends on its size, the power of the soldering iron and the contact area. The achievement of the required temperature is evidenced by the boiling of the flux, the melting of the solder and its spreading over the surface. Gradually, the solder is distributed over the surface.

After tinning, the metal surface is cleaned of flux residues with alcohol, acetone, gasoline, soapy water (depending on the chemical composition of the flux).

If the solder does not spread over the metal surface, then this may be due to poor cleaning of the surface before tinning, poor heating of the metal (due to insufficient soldering iron power, small contact area, insufficient heating time of the metal part), dirty soldering iron tip. Another reason may be the wrong choice of flux or solder.

Tinning can be carried out by applying (draining) solder from a soldering iron and distributing it with a "sting" over the surface, or by supplying solder directly to the site - the solder melts when it touches the heated metal of the part.

Lap soldering of sheet metal

When repairing car bodies, all kinds of tin work, it becomes necessary to solder sheet metal overlaid. There are two ways to solder sheet parts overlapping each other - by pre-irradiating them, or using solder paste containing solder and flux.

In the first case, the overlapping zones of the parts are pre-tinned after mechanical cleaning and degreasing. Then the parts of the connection are applied to each other with tinned surfaces, fixed with clamping devices and heated with a soldering iron from different sides to the melting temperature of the solder. Evidence of successful soldering is the flow of melted solder from the gap.

In the second method, after preparing the parts, the contact area of ​​one of the parts is covered with solder paste. Then the parts are fixed in the desired position, tightened with clamps and, as in the first case, the seam is heated with a soldering iron from both sides.

When buying solder paste, you need to pay attention to its purpose, because. many solder pastes are designed for soldering electronics and do not contain active fluxes that allow soldering steel.

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Soldering is a technological process of joining metal (or metallized) parts with molten solder, which, when hardened, holds the soldered parts together. The connection of parts occurs due to the diffusion of the solder into the base metal without the latter being molten. In this case, the melting temperature of the solder is much lower than the melting temperature of the base metal.

A soldering iron is a hand tool of various shapes and weights. The part of the soldering iron that is directly soldered is made of copper, the heating of the copper part of the soldering iron can be done using electricity (electric soldering iron), over a gas flame (gas soldering iron) or in a furnace.

Solders are some non-ferrous metals and their alloys. Depending on the mechanical properties, solders are usually divided into soft and hard solders. Solder is available in the form of a sheet, tape, rods, wire, mesh, blocks, foil, grains, powders and solder paste.

Soft solders are low-melting solders with a melting point up to about 400 ° C. These solders have a low tensile strength - usually not higher than 50 - 70 MPa. The most common are tin-lead solders with a tin content of 18 to 90% grades POS-18 - POS-90. Reliable contact connection gives POS-30 solder. It has a high fluidity and gives better surface wettability compared to the less expensive POS-18. For soldering aluminum parts, tin-zinc and other solders are used.

Hard solders have a melting point above 500°C. They have a tensile strength of up to 500 MPa. The most common are copper-zinc solders PMC, copper-silver PSR and copper-phosphorus PMF, in particular PMF-7 (the latter solders do not require flux when soldering copper parts).

The technological process of soldering consists of the following operations: preparing the surfaces of parts, coating the surfaces to be soldered with flux, tinning the surfaces, and soldering.

Surface preparation of parts is to remove contaminants of fatty and oxide films. Cleaning is carried out by mechanical and chemical methods.

Surfaces are coated with flux immediately before tinning and soldering.

The flux forms a liquid and gaseous protective zone that protects the surface of the metal and molten solder from oxidation. In addition, it dissolves oxide films and impurities, forming a slag that is easily removed. Most fluxes promote better wetting of the soldered surface with molten solder and reduce the surface tension of the solder. According to the action on the metal, fluxes are divided into acidic (zinc chloride and fluxes based on it);

Acid-free (rosin and fluxes based on it),

Activated (based on rosin with the addition of some reagents and acids, used for metals that are difficult to tin and solder), etc.

When soldering with hard solders, borax and fluxes based on it are used as a flux.

Flux residues and slag must be carefully removed mechanically and by washing to prevent corrosion of the soldering point. The exception is rosin fluxes, which do not need to be removed. Therefore, they are used for soldering insulated wires that cannot be washed.

Safety precautions:

It is extremely important to take safety precautions very seriously, since during soldering and tinning, various harmful factors can affect the worker. These include increased air pollution with vapors of chemicals, fire hazard, splashes of fluxes and solders, and increased air temperature in the working area. In this case, it is extremely important to have personal protective equipment.

In the work it is important to use high-quality materials and tools. Solders are used when soldering products made of brass, bronze, copper. Managers should conduct competent briefing on how to work with this tool.

Work related to soldering and tinning should be carried out in specially equipped and pre-prepared rooms. There must be a ventilation system. Ventilation units must be equipped with sound and light alarms.

In work, it is important to use high-quality and serviceable tools. According to the rules of technical documentation, the soldering iron must undergo special checks and tests. The class of this equipment must necessarily correspond to the conditions of production and the category of the premises. You also need to take care of protecting the soldering iron cable from contact with hot objects and protecting it from accidental mechanical damage.

Equally important is the preparation of the workplace. They must be equipped with ventilation. It is not allowed to solder and plow without the use of special protective glasses. The workplace should be equipped with luminaires with non-translucent reflectors. Lighting devices must be positioned in such a way that the light does not "hit" the worker's eyes.

Tinning is the application of a ton layer of tin or its alloy to the surface of a metal product. Experts call this layer half-day. Metal tinning is used today in many industries: in radio engineering, electrical engineering, mechanical engineering and the aviation industry.

The tip of the soldering iron is tinned so that it holds the solder well and does not oxidize. The main requirement for the process is a dense and thin tin coating, which is a protective layer for the metal in the fight against corrosion. There are two technologies for tinning metals: hot and galvanic.

Hot tinning is carried out by two methods: immersion and rubbing. In the first case, a metal product is immersed in a bath of molten tin. In the second, the alloy is applied to the plane of the product and the tow is rubbed over it with a thin layer.

These methods have been known for a long time, the technologies have been worked out to the smallest detail. They are simple and do not require sophisticated equipment, fixtures and tools.

When talking about tinning and soldering, they often mean the hot method. But this technology also has its drawbacks. Firstly, it is unevenly distributed tin over the surface of metal products.

This is especially true for immersion. The differences in one plane can be significant, especially if the product has a complex design. Therefore, they have to be improved.

If metal is tinned with holes of small diameter or with fine cuts, then the hot option will not work here.

And the third disadvantage of hot tinning is the difficulty of removing contaminants that form inside the alloy and remain inside the half. These impurities come with the solder, so it is very important to use a high purity tin alloy.

Galvanic technology

The galvanic version of tinning is also divided into two methods: in alkaline and acidic electrolytes. The name suggests that the process of applying tin is based on the use of electric current.

Hence the cost of the process. But it is this technology that guarantees strong adhesion of the applied alloy to the metal surface. There are other positives as well:

• the tin layer is even and uniform;
• you can set the required coating thickness, even on the most complex metal structures;
• low porosity of the coated layer;
• saving tin solder.

Typically, products with complex shapes are tinned with alkaline electrolytes, because this tinning option has a high covering and scattering power.

The disadvantages of galvanic tinning technology include the fact that this method is complex. It can be carried out by highly qualified employees, and these are salary costs. That is, it is impossible to tin metal in this way at home. In addition, special baths are required for the process.

If we talk about the technology of tinning with alkaline electrolytes, then the solution itself is unstable, it is difficult to prepare it, and you will have to constantly monitor the concentration of alkali and the quality of the anodes.

Product preparation

The cleaner the surface of the metal, the stronger the solder will attach to it. Therefore, depending on the requirements for the workpiece itself, different methods of preparing metal for tinning are used.

The first way is to clean the metal surface with brushes. Usually scale and rust are removed with such a tool. First, the product is washed with water, and then cleaned with a brush. Often lime, sand, pumice are used at this stage.

The next way to prepare for tinning is to grind the metal with sandpaper and discs. This stage is the finalization of the product, that is, bringing its surface to maximum evenness.

Apply degreasing with sodium compounds: caustic soda - 10-15%, sodium phosphate - 10-15%, sodium carbonate - 10-15% solution. We add that chemical solutions must be heated to 50-80C before use.

Etching is also used. For this, sulfuric acid is used.

Features of rubbing and immersion

Rubbing tinning technology basically contains such a process when solder is applied to a metal product and rubbed with tow. In this case, a flux is used in the form of ammonia and zinc chloride. Here is the sequence of operations:

1. zinc chloride is applied to the metal and heated with a blowtorch;
2. when it boils, solder is introduced into it, which melts;
3. ammonia is sprinkled on top in the form of a powder;
4. then the tow liquid tin is rubbed over the surface of the metal product.

For the immersion method, tin baths are used, in which tin is heated to +300 ℃. A metal product is lowered into the molten alloy, which is covered with a layer of solder.

Moreover, the longer it lies in the bath, the thicker the tin layer will settle on it. When a soldering iron is tinned, it is first heated, then immersed in rosin, and only then a small piece of tin is melted with it, thereby providing a coating.

Solution for galvanizing

In principle, both tinning technologies (with alkaline and acidic electrolytes) differ from each other by the presence of an alkaline or acidic solution in the electrolyte bath. The very process of tin sticking is the same for them, and it occurs with the help of an electric current.

The composition of acidic solutions includes tin sulfate, sulfuric acid, substances of the capillary-active type (phenol or cresol), colloidal substances (glue, nicotine, gelatin or similar substances).

It is very important to accurately observe the proportions of the main components: tin sulfate - 65 g / l, sulfuric acid - 100 g / l.

As for alkaline solutions for tinning metals, their diversity is not determined by one recipe. Therefore, the composition of the solutions is different. Some use stannous chloride, others use sodium tin chloride, and still others use stannous chloride.

The same goes for solvents. Here and caustic nart, and sodium acetate, and caustic potash. Based on the presence of certain components, you can choose your own solution formulation.

In this case, each will necessarily have its own concentration of substances. Of course, the current density and the heating temperature of the solution in the bath are selected for each recipe.

Tinning, as a protective process of metals against corrosion, is one of the most popular. It is not very cheap, but effective compared to many technologies. Therefore, it is often used in various industries.