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 adhesion during 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 make it possible to solder 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 lower than the melting point of the materials being soldered;

ensure sufficiently high adhesion, strength, ductility and tightness of the solder joint;

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

Low melting point 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 of gray cast iron, aluminum, ceramics, glass, etc. To obtain special properties, antimony, bismuth, cadmium, indium, mercury and other metals are added to tin-lead solders . For plumbing work, POS 40 solder is most often used.

Refractory solders They 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 fragility of the soldered seams.

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

Fluxes used to remove oxide from chemicals. Fluxes improve surface wetting conditions by dissolving 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 soldered seams

Soldering irons. A special group consists of special-purpose soldering irons: ultrasonic with an ultrasonic frequency generator (UP-21); with arc heating; with vibrating devices, etc.

Intermittent soldering irons are divided into angular, or hammer, and straight, or end. The first ones are used most widely. A soldering iron is a shaped piece of copper mounted on an iron rod with a wooden handle at the end.

To soldering irons continuous heating include gas and gasoline.

Electric soldering irons They are widely used because they are simple in design and easy to use. During their operation, no harmful gases are formed, 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 the products being soldered, soldered seams are divided into three groups:

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

dense– continuous sealed seams that do not allow the penetration of any substance;

densely durable, possessing both strength and tightness.

The parts to be connected must fit well together.

Soldering with soft and hard solders

Soft soldering is divided into acidic And acid-free. In acid soldering, zinc chloride or commercial hydrochloric acid is used as a flux; in acid-free soldering, fluxes that do not contain acids are used: rosin, turpentine, stearin, solder paste, etc. Acid-free soldering produces a clean seam; After acid soldering, the possibility of corrosion cannot be ruled out.

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;

the fitted surfaces at the junction are covered with flux; Pieces of solder - copper plates - are placed in place of the solder joint and secured with soft knitting wire; the prepared parts are heated with a blowtorch;

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

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

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

The soldering workplace must be equipped with local ventilation (air velocity of at least 0.6 m/s);

work in gas-polluted areas is not allowed;

After finishing work and eating, you should wash your hands thoroughly with soap;

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

When heating the soldering iron, you should follow the general rules for safe handling of the heating source;

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

Tinning

Coating the surface of metal products with a thin layer of an alloy (tin, tin-lead alloy, etc.) appropriate for the purpose of the product is called tinning.

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 plating and applying it to the surface.

Preparing the surface for tinning depends on the requirements for the products and the method of applying the poluda. Before tin coating, the surface is brushed, polished, degreased and etched.

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

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

Tinning methods. Tinning is carried out in two ways - immersion in half (small products) and grinding (large products).

Immersion tinning It is performed in a clean metal container, in which it is placed and then melted, pouring small pieces of charcoal onto the surface to protect it from oxidation. The product is then washed in water and dried in sawdust.

Rubbing tinning This is done by first applying zinc chloride to the cleaned area with a hair brush or tow. Then the surface of the product is uniformly heated to the melting temperature of the half-plate, which is applied from the rod. After this, they are heated and other places are served in the same order. At the end of tinning, the cooled product is washed with water and dried.

Bonding

General information. Bonding is the process of joining machine parts, building structures and other products using adhesives.

Adhesive joints have sufficient tightness, water and oil resistance, and high resistance to vibration and shock loads. In many cases, gluing can replace soldering, riveting, welding, and 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 gluing metals, glass, porcelain, bakelite, textolite and other materials.

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

Carbinol glue can be liquid or paste-like (with filler). The adhesive is suitable for joining steel, cast iron, aluminum, porcelain, ebonite and plastics and provides bonding strength within 3..5 hours after preparation.

Bakelite varnish– solution of resins in ethyl alcohol. Used for gluing linings on clutch discs.

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

Defects. Reasons for the weakness of adhesive joints:

poor cleaning of bonded surfaces;

uneven application of the layer on the bonded surfaces;

hardening of the glue applied to the surface before joining;

insufficient pressure on the connecting parts of the parts being glued;

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

The choice of solder depends on the metals or alloys being joined, on the soldering method, temperature limits, 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 solder, are given in the table. The letters POS in the solder brand mean tin-lead solder, the numbers indicate 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, wire, foil strips, powders, tubes with a diameter of 1 to 5 mm, filled with rosin, as well as in the form of pastes composed of solder powder and liquid flux.

Low-melting solders.

Brand	Melting temperature, °C	Scope of application
POS90	222	Soldering of parts and assemblies subjected to further galvanic processing (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 of thin (0.05-0.08 mm in diameter) winding wires, including high-frequency (Litz wire), winding leads, radio elements and microcircuits, installation 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 of conductive parts for non-essential purposes, tips, connections of wires with petals, when higher heating is allowed than with POS 50 or POS 61
POSZO	256	Tinning and soldering of non-critical mechanical parts made of copper and its alloys, steel and iron
POS 18	277	Tinning and soldering with reduced requirements for weld strength, 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 of parts made of copper and its alloys that prevent local overheating. Soldering of semiconductor devices
POSV 33 POSK 47-17	130 180	Soldering fuses Soldering wires and element leads to a layer of silver deposited on ceramics using the burning method
P200 P250	200 280	Soldering of thin-walled parts made of aluminum and its alloys
Alloy Rose Alloy d'Arsenral Wood's alloy	92-95 79 60	Soldering when a particularly low melting point of solder is required

Composition of some special low-melting solders.

Brand	Element content, %						Melting temperature, °C
	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
Alloys Rose	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 alloy	12,5	25	-	50	12,5	-	60

Fluxes

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

Inactive (acid-free) fluxes

Active (acid) fluxes

Compound, %	Scope of application	Residue removal method
Zinc chloride - 25-30; concentrated hydrochloric acid - 0.6-0.7; water - the rest	Soldering of parts made of ferrous and non-ferrous metals	Thorough rinsing with water
Zinc chloride (saturated solution) - 3.7; technical petroleum jelly - 85; distilled water - the rest (flux paste)	The same thing when, due to the type of work, it is more convenient to use paste	Same
Zinc chloride - 1.4; glycerin - 3; ethyl alcohol - 40; distilled water - the rest	Soldering of nickel, platinum and its alloys	Same
Rosin - 24; zinc chloride - 1; ethyl alcohol - the rest	Soldering of non-ferrous and precious metals (including gold), critical parts made of ferrous metals	Washing with acetone
Rosin - 16; zinc chloride - 4; technical petroleum jelly - 80 (flux paste)	The same, for obtaining connections of increased strength, but only parts of a simple configuration that does not complicate washing	Same

Soldering aluminum with POS solders

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. The best results are obtained when using alkaline oil (for cleaning the weapon after shooting). Satisfactory soldering quality is ensured by mineral oil for sewing machines and precision mechanisms. Flux is applied to the soldering site and the surface of the aluminum under the oil layer is cleaned with a scraper or a knife blade to remove the oxide film that is always present on the surface of the aluminum. Solder with a well-heated soldering iron. For soldering thin aluminum, a soldering iron power of 50 W is sufficient; for aluminum 1 mm thick or more, a power of 90 W is desirable. When soldering aluminum with a thickness of more than 2 mm, the soldering area must be preheated with a soldering iron and only then apply flux.

Soldering aluminum with P200 and P250 solders

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 is added (the flux can contain from 5 to 17% lithium iodide.) The mixture is slightly heated by immersing the test tube in hot water and stirred until the salt is completely dissolved. The finished flux is poured into a clean glass container and cooled. If an aqueous lithium salt is used, then when it is dissolved, a layer of the aqueous mixture is lowered to the bottom of the test tube, and the flux floats to the surface and is carefully poured off. Before soldering, the tip of a well-heated soldering iron (tip temperature should be about 270-350 °C) is cleaned and tinned with solder, using clean rosin. The surfaces of the parts to be joined are moistened with flux, tinned and soldered. After cooling, the remaining flux is removed with a cloth swab soaked in alcohol, acetone or gasoline, and the seam is covered with a protective varnish. During the soldering process, flux does not emit toxic or pungent odor substances. It is easily washed off from fabric and skin with soap and water.

Soldering nichrome (nichrome with nichrome, nichrome with copper and its alloys, nichrome with steel)

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

Brazing of galvanized steels

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

Solder paste

When soldering at home, solder is usually picked up and applied with a soldering iron. It is extremely difficult to control the amount of molten solder transferred 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 possible that drops of molten solder will get on conductors, element housings, and 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. You can make soldering easier and improve it using solder paste. To prepare the paste, grind the solder with a file with a large notch (fine ones are clogged with solder) and mix the sawdust with alcohol-rosin flux. The amount of solder in the paste is selected experimentally. If the paste turns out to be too thick, alcohol is added to it. The paste should be stored in a tightly sealed container. The paste is applied to the soldering site in the required doses with a metal spatula. The use of solder paste, in addition, avoids overheating of small parts and semiconductor devices.

"Soldering tape"

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

Tinning of wires in enamel insulation

When stripping the output ends of the winding wire LESHO, PELSHO, PEL and PEV using sandpaper or a blade, cuts and breaks of thin wire strands are common. Stripping by firing also does not always give satisfactory results due to the possible melting of small-section wires. In addition, at the place of firing, the wire loses strength and breaks easily. To strip small cross-section wires in enamel insulation, you can use a polyvinyl chloride tube. A piece of tube is placed on a board and, pressing the wire to the tube with the flat of the tip of a well-heated soldering iron, pull the wire 2-3 times with light force. In this case, the enamel coating is destroyed and the wire is tinning at the same time. The use of rosin is not necessary. Instead of a PVC tube, you can use scraps of installation wire or cable in PVC insulation. Enameled wire of any diameter can be tinned using 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. 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 force or the wire is moved under the tip, while the enamel is destroyed and the wire is tinned. To remove residual acetylsalicylic acid (aspirin), the wire is tinned again using clean rosin.

Instead of solder - glue

It is often necessary to solder a wire to a part made of a metal 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 where the wire is connected 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, apply 1-2 drops of epoxy glue to the contact area and dry until completely hardened.

Welding instead of soldering

Electric welding significantly reduces the time spent on installation work, produces connections that can withstand high-temperature heating, does not require solders, fluxes, or pre-tinning, and allows you to connect conductors made of metals and alloys that are difficult to solder, for example, wires of electric heating devices. For welding, you must 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 ampere-voltmeter with a crocodile tip. In places of future welding, pre-stripped conductors are twisted into 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 area to be welded. The molten metal forms a teardrop-shaped compound. As the graphite burns out during operation, the electrode should be sharpened. With the acquisition of skill, welding turns out clean, without scale. It is necessary to work in light-protective glasses.

"Practical advice for an amateur craftsman", 1991. O.G. Verkhovtsev, K.P. Lyutov

Soldering with a soldering iron is one of the most common and simplest soldering methods, but it has two significant limitations. Firstly, a soldering iron can only be soldered with low-melting (soft) solders, and secondly, it cannot (or, in any case, 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 last limitation is overcome by heating the part to be soldered with an external heat source - a gas burner, electric or gas stove, or some other method - 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 heating method, soldering irons can be “conventional” - electric (with a spiral or ceramic heater), gas (with a gas burner), hot-air (heat is transferred by air flow), and induction. Massive hammer soldering irons can be heated not only with electricity, but also in the old fashioned way - with an open flame.

You can learn how to use such a soldering iron from descriptions of the technology of tin work, which is where 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 over an open flame.

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

For parts with a wall thickness of 2 mm or more, soldering irons with a power above 100 W will be needed. These are, in particular, electric hammer soldering irons that consume up to 250 W and higher. 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 it has an inadequate price.

In addition to the massiveness of the part, the required power of the soldering iron is also affected by the thermal conductivity of the metal being soldered. As it increases, the power of the device and its heating temperature must be increased. When soldering parts made of copper with a soldering iron, it must be heated more 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 areas 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, and the advantages include better soldering quality than that of lead-free solders. Pure tin is used for soldering food utensils.

Fluxes

It is generally accepted that tin, silver, gold, copper, brass, bronze, lead, and nickel silver can be soldered well. Satisfactory - carbon and low-alloy steels, nickel, zinc. Poor - aluminum, high-alloy and stainless steels, aluminum bronze, cast iron, chrome, titanium, magnesium. However, without disputing these data, we can say 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 problem of soldering. It is the quality of the flux that primarily determines the solderability of a particular metal, the ease or difficulty of the soldering process itself, and the strength of the connection. The flux must correspond to the material of the products being soldered - in 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 irreplaceable 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, and LTI-120 flux. You can use other, stronger fluxes, of which there are plenty on the market.

The main difference between soldering stainless steels with a soldering iron 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 needs to 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. Specialized fluxes, such as F-38, also cope well with chemically resistant oxide films.

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

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, you can purchase it separately or make it yourself. The simplest stand can be made from a thin sheet of tin, cutting grooves in it for storing tools.

Wet viscose or foam rubber sponge, placed in a socket 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 parts using special suction or braids. The first one, in appearance and design, resembles a syringe equipped with a spring. Before use, it must be cocked by recessing the rod head. By bringing the nose to the molten solder, the spring is released by pressing the release button. As a result, excess solder is drawn into the removal head.

It is a braid of fluxed thin copper wires. By placing its end on 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 occupied with the soldering iron itself, the other with the solder, but you still need to hold the soldered parts in a certain position. The “third hand” is convenient because its clamps can be easily installed in any position relative to each other.

Soldering holder "Third hand"

The parts being soldered are heated to high temperatures; touching them can cause you to get burned. Therefore, it is desirable to have various clamping devices that allow the manipulation of heated parts - pliers, tweezers, clamps.

Preparing the soldering iron for use

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

Before using a soldering iron, you need to prepare its tip. Preparation depends on its original form. If the tip is made of bare copper, the tip can be forged into a screwdriver shape, this will seal the copper and make it more resistant to wear. You can simply sharpen it with sandpaper or a file, giving it the required shape - in the form of a sharp 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 or sharpened to avoid damaging the coating layer.

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

When soldering massive parts, the contact area between the soldering iron and the part should be maximum to ensure better heat transfer. In this case, angular sharpening of a round rod (2 in the photo above) is considered the best. If you plan to solder small parts, then a sharp cone (4), knife or other shapes with small angles are suitable.

Instructions for working with a soldering iron that has an uncoated copper tip contain one mandatory requirement - tinning the “tip” of the new soldering iron in order to protect it from oxidation and wear. Moreover, this should be done at the first heating, without delay. Otherwise, the “tip” 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 “tip” to the rosin, melt the solder on it and rub the solder 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 table 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 caused by the fact that the flux gradually corrodes, and the solder dissolves the tip. Due to loss of shape, the tip has to be sharpened regularly, and the more active the flux, the more often, sometimes several times a day. For nickel-plated tips, nickel blocks access to copper, protecting it, but such tips require careful handling, they are afraid of overheating, and it is not a fact that the manufacturer has made a sufficiently high-quality coating, for which they require an overpayment.

Preparing parts for soldering

Preparing parts for soldering involves performing the same operations regardless of what type of soldering (low-temperature or high-temperature) is performed, and what heating source (electric or gas soldering iron, gas torch, 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 use solvents (gasoline, acetone or others) to clean the part from oils, fats, and dirt. If there is rust, it must be removed by any suitable mechanical method - using an emery wheel, wire brush or sandpaper. In the case of high-alloy and stainless steels, it is advisable to treat the edges being joined with an abrasive tool, since the oxide film of these metals is particularly strong.

Soldering temperature

The heating temperature of the soldering iron is the most important parameter; the quality of 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 forms a lump, despite the preparation of the surface with flux. But even if the soldering is successful in appearance (the solder has melted and spread over the joint), the soldered joint turns out to be loose, matte in color, and has low mechanical strength.

The soldering temperature (temperature of the parts being soldered) should be 40-80°C higher than the melting temperature of the solder, and the heating temperature of the tip should be 20-40°C higher than the soldering temperature. The last requirement is due to the fact that when it comes into contact with the parts being soldered, the temperature of the soldering iron will decrease due to heat dissipation. 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, the required temperature is simply set by the regulator. When using a soldering iron without temperature control, its actual value, when using rosin as a flux, can be assessed by the behavior of the rosin when touched by the soldering iron. It should boil and release abundant steam, but not burn instantly, but remain on the tip in the form of boiling drops.

Overheating the soldering iron is also harmful; it causes combustion and charring of the flux until it activates the junction surface. Overheating is indicated by a dark film of oxides appearing on the solder located at the tip of the soldering iron, as well as by the fact that it does not stay on the “tip” and flows off it.

Soldering technique with a soldering iron

There are two main methods of soldering with a soldering iron:

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

With any method, you must first prepare the parts for soldering, install and secure them in their original position, heat the soldering iron and moisten the joint with flux. Further steps differ depending on which method is used.

When feeding solder from a soldering iron, a certain amount of solder is melted on it (to keep it on the tip) and the “tip” is pressed against the parts being soldered. In this case, the flux will begin to boil and evaporate, and the molten solder will move from the soldering iron to the soldering joint. The movement of the tip along the future seam ensures the distribution of solder along the joint.

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

When applying solder directly to a junction, use a soldering iron to first heat the parts to soldering temperature, and then apply solder to the part or to the joint between the soldering iron and the part. As the solder melts, it will fill the joint between the parts being soldered. You should choose exactly how to solder with a soldering iron - the first or second method - depending on the nature of the work being performed. The first method is better for small parts, the second for large parts.

The basic requirements for high-quality soldering include:

• good heating of the soldering iron and parts being soldered;
• 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 solder correctly with a soldering iron.

If the solder does not flow, but is smeared, it means that the temperature of the parts has not reached the required values, you need to increase the heating temperature of the soldering iron or use a more powerful device.

There is no need to add too much solder. High-quality soldering requires 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, there is no need to try to attach it somewhere at the joint; it is better to remove it with suction or braiding.

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

When using active (acidic) fluxes, be sure to wash off their residues after soldering - with some detergent or ordinary alkaline soap. Otherwise, there is no guarantee that after some time the connection will not be destroyed by corrosion from 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 most difficult part of the soldering job (joining the solder to the metal) is done; soldering the tinned parts to each other is usually no longer difficult.

Wire tinning. Tinning the ends of electrical wires is one of the most common operations. It is carried out before soldering the wires to the contacts, soldering them 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 ensures ease of attachment to the terminal and good contact.

Wires can be single-core or stranded, copper or aluminum, varnished or not, clean new or acidified old. Depending on these features, their servicing differs.

The easiest way to tin is single-core copper wire. If it is new, it is not covered with oxides and tins 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 proceeds without problems.

If the conductor does not want to tinker - due to the presence of varnish (enamel) - regular aspirin helps. Knowing how to solder with a soldering iron using an aspirin tablet (acetylsalicylic acid) can be very useful in some cases. You need to put it on a board, press the conductor to it and heat it for a few seconds with a soldering iron. At the same time, the tablet begins to melt, and the resulting acid destroys the varnish. After this, the wire usually tins easily.

If there is no aspirin, vinyl chloride insulation from electrical wires, which, when heated, releases substances that destroy the varnish coating, also helps to remove the varnish that interferes with tinning from the surface of the conductor. You need to press the wires to a piece of insulation with a soldering iron and drag it several times between the insulation and the soldering iron. Then tin the wire as usual. When removing varnish using sandpaper or a knife, cuts and breaks of thin wire strands are common. When stripped by firing, the wire may lose strength and break easily.

It should be taken into account that melted polyvinyl chloride and aspirin release substances harmful to health into the air.

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

New stranded copper wire can be tinned just as easily as solid copper wire. The only peculiarity is to rotate it in the direction in which the wires will twist and not unwind.

Old wires may be coated with oxides that prevent tinning. The same aspirin tablet will help to cope with them. You need to untwist the conductor, put it on aspirin and heat it for a few seconds with a soldering iron, moving the conductor back and forth - and the tinning problem will disappear.

To tinning an aluminum wire, you will need a special flux - for example, the one called “Flux for soldering aluminum”. 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 afterwards to avoid corrosion.

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

Tinning a large metal surface

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

Then, using a brush or other tool that matches the flux, flux is applied to the surface of the sheet (this may not be a paste-like 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 tip surface is heated to the required temperature and solder is applied to the surface of the part. It is advisable that the soldering iron power 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 this 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 indicated by boiling of the flux, melting of the solder and its spreading over the surface. The solder is gradually distributed over the surface.

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

If the solder does not spread over the metal surface, 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 time to warm up the metal of the part), or a 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 “tip” over the surface, or by supplying solder directly to the pad - the solder melts upon touching the heated metal of the part.

Overlapping sheet metal soldering

When repairing car bodies, all kinds of tin work, there is a need for overlay soldering of sheet metal. There are two ways to solder sheet parts overlapping each other - by pre-tinning them, or by using soldering paste containing solder and flux.

In the first case, the overlapping areas of parts after mechanical cleaning and degreasing are pre-tinned. 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 molten 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 on both sides.

When purchasing 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 you to solder steel.

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Soldering is a technological process of joining metal (or metallized) parts with molten solder, which, when solidified, holds the parts being soldered together. The joining of parts occurs due to the diffusion of solder into the base metal without the latter being molten. In this case, the melting temperature of the solder is significantly 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 copper part of the soldering iron can be heated using electricity (electric soldering iron), over a gas flame (gas soldering iron) or in a forge.

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

Soft solders are low-melting solders with a melting point of approximately 400°C. These solders have low tensile strength - usually no 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. POS-30 solder provides a reliable contact connection. It has greater fluidity and provides better surface wettability compared to the less expensive POS-18. Tin-zinc and other solders are used for soldering aluminum parts.

Brazing alloys 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.

Preparing the surfaces of parts involves removing contaminants from fatty and oxide films. Cleaning is carried out by mechanical and chemical methods.

Surfaces are coated with flux immediately before tinning and soldering.

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 contaminants, forming 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. Based on their effect on 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 tinning and soldering), etc.

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

To prevent corrosion of the soldering area, flux residues and slag must be carefully removed mechanically and by washing. 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, the worker can be exposed to various harmful factors. These include increased air pollution with chemical vapors, 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.

It is important to use high-quality materials and tools in your work. Solders are used when soldering products made of brass, bronze, and copper. Managers must provide competent instruction on how to use this tool.

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

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

Preparation of the workplace is no less important. They must be equipped with ventilation. Soldering and patching are not allowed without the use of special safety glasses. The workplace must be equipped with lamps with non-translucent reflectors. Lighting fixtures must be positioned in such a way that the light does not “shine” into the worker’s eyes.

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

The soldering iron tip is tinned so that it holds the solder well and does not oxidize. The main requirement for the process is a dense and thin coating of tin, 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 using 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 tow is rubbed over it in 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 complex equipment, devices and tools.

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

This is especially true for the method of immersion. Differences in one plane can be significant, especially if the product has a complex design. Therefore they have to be modified.

If you are tinning metal with small diameter holes or 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 important to use a high purity tin alloy.

Galvanic technology

The galvanic option of servicing 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 positive aspects:

• the tin layer is smooth 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 using alkaline electrolytes, because this version of tinning has high covering and dispersive power.

The disadvantages of galvanic tinning technology include the fact that this method is complex. It can be carried out by highly qualified workers, but this costs wages. That is, it is impossible to tin the metal using this method at home. In addition, the process requires special baths.

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

Preparation of products

The cleaner the metal surface, the more firmly 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 method is to clean the metal surface with brushes. Typically, this tool removes scale and rust. First, the product is washed with water and then cleaned with a brush. Lime, sand, and pumice are often 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.

Degreasing is used using sodium compounds: sodium hydroxide – 10-15%, sodium phosphate – 10-15%, sodium carbonate – 10-15% solution. Let us 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 involves a process where solder is applied to a metal product and rubbed with tow. In this case, 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 added to it, which melts;
3. ammonia in powder form is sprinkled on top;
4. then the liquid tin is rubbed with tow over the surface of the metal product.

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

Moreover, the longer it lies in the bath, the thicker the layer of tin will settle on it. When tinning a soldering iron, they first heat it, then dip it in rosin, and only then melt a small piece of tin with it, thereby providing a coating.

Solution for galvanic treatment

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 process of tin adhesion is the same for them, and it occurs with the help of electric current.

The composition of acidic solutions includes tin sulfate, sulfuric acid, substances of boilillary-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 tin chloride, others sodium stannous, and others stannous chloride.

The same applies to solvents. There is caustic sled, sodium acetate, and caustic potassium. You can choose your own solution recipe based on the presence of certain components.

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

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