Classification of solders for soldering, technical characteristics and recommendations for selection

Classification

Solders are classified according to several main criteria.
First of all, they are divided into soft and hard. Soft ones include those brands whose melting point reaches 300 degrees Celsius. The maximum tensile strength in this case is 100 MPa, while the minimum is only 16 MPa. These include alloys of lead, tin, cadmium, zinc, antimony and other light-melting metals, including lead-free solders. https://youtube.com/watch?v=cyCXjjhN6xc

Hard grades include those brands with a melting point above 300 degrees Celsius. This also increases the tensile strength, since the minimum value here is about 100 MPa, and the maximum value can reach 500 MPa. These are alloys of copper, zinc, nickel, silver and other metals that have a high melting point.

Brazing Solder

In addition, there is a division into which base metal is contained in the filler material. It could be:

• Silver solder;
• Copper;
• Tin;
• Aluminum;
• Solder for soldering stainless steel.

It is also worth highlighting fluxed brands, which contain flux inside, into a separate class; therefore, they do not require its additional use.

According to delivery options, the following are distinguished:

• Rods are small dense elements that are melted with a soldering iron;
• Wire – well suited for both gas soldering and a soldering iron;
• Tubular - made in the form of a tube, inside of which flux is often located;
• Sheets are thin sheets of alloy that are suitable for both flat surface soldering and other purposes.

There are different manufacturing technologies that also create different grades of solder solders. Among them are drawn, crushed, cast, pressed, sintered, stamped, amorphous and rolled.

Lead free

Lead-free solder must not contain harmful metals and is considered environmentally friendly, not causing harm to the environment and the solder performers. The simplest example is tin solder, which contains pure tin, has increased wettability and high electrical conductivity. To combat deficiencies, copper, silver and gold are added to them, which helps make the substance harder.

Such a product has an increased melting temperature, but it has not yet been possible to find a complete alternative to standard types of solder, but the main indicator is harmlessness. Tin occupies a major place in the chemical composition, so its inherent properties have a great influence on the solder, because of this, the melting point of lead-free solder is lower, and the material is softer.

V. I. Blinov, vocational school education, specialty welder of the sixth category, admission from NAKS to NGDO and GO, work experience since 2004: “If there is no option suitable in all respects, during soldering, use the PSR-45 grade, which contains harmful lead is minimal and amounts to no more than 0.5% of the total weight.”

Release form

Solder comes in various forms. Initially, at the factory, these are pigs. The letter Ch is then added to the brand designation. For example, Ch POS-40. GOST 21930-76 determines the shape and size of pigs for each material and type.

Solder for retail sale comes in rods with a diameter of 8 mm, in the form of solder wire wound on a spool or rolled into a spiral and placed in a plastic tube.

Very often, soldering wire is a tube made of tin-lead alloy, inside of which there is flux - a substance that helps improve the quality of soldering.

Flux destroys the oxide film on the parts being soldered and prevents further oxidation of the soldered joint during its cooling.

Rosin, a product of the distillation of pine resin, is often used as a flux. It melts at a temperature of 68 ℃, under normal conditions it is hard, brittle, and yellow in color.

3.3. Classification of fluxes and their designation system

Soldering fluxes

- substances and compounds used to prevent the formation of an oxide film on the surface of the solder and soldered material, as well as to remove oxidation products from the soldering zone. The melting point of fluxes is lower than the melting point of solder. Fluxes are used in solid, paste and powder form, as well as in the form of aqueous, alcohol or glycerin solutions.

Fluxes

used for soldering are classified according to: temperature range of activity;
nature of the solvent; the nature of the activator of the determining action; mechanism of action; state of aggregation. Depending on the temperature range of activity,
soldering fluxes are divided into: low-temperature (≤ 450 ° C); high temperature (> 450 °C).

By the nature of the solvent

soldering fluxes are divided into: water-based; non-aquatic

By the nature of activators

Low-temperature soldering fluxes
that determine their action are divided into: rosin; acidic; halide; hydrazine; fluoroborate; aniline; stearic.

By the nature of the activators of the determining action, high-temperature soldering fluxes

divided into: halide; fluoroborate; boride-carbon dioxide.

If the flux contains several activators, all activators must be named. For example, rosin-halide, fluoroborate-halide flux.

By mechanism of action

soldering fluxes are divided into: protective;
chemical action; electrochemical action; reactive. According to their state of aggregation,
soldering fluxes are divided into: solid; liquid; pasty.

Printed circuit boards and components. Surface cleanliness of printed circuit boards and components

is one of the most important factors influencing the soldering process. Oxides and other surface contaminants significantly impair solder wettability and heat transfer from the soldering iron tip to the soldered surfaces, increasing soldering time. To improve solderability, printed circuit boards with a long shelf life can be pre-cleaned using special solvents, for example, VIGON SC 200, ZESTRON SD 100, ZESTRON SD 301.

Recommended operating sequence

When working with multi-channel tubular solders, soldering is carried out with two hands. To get the best results when soldering, it is recommended to use the following process:

1. Bring the soldering iron tip to the work surface. The soldering iron tip must be in contact with both the board pad and the component lead at the same time in order to heat both soldered surfaces. The excess solder on the tip, applied during tinning, will aid the heat transfer process by increasing the contact area between the pad and the lead. It takes no more than a split second to properly heat both surfaces.

2. At this time, a rod of tubular solder brought to the joint on the side opposite to the soldering iron tip will allow the formation of a fillet of solder. This takes about 0.5 seconds

Attention! If solder is applied directly to the soldering iron tip, the active components of the flux will burn out prematurely, and its effectiveness will sharply decrease. Do not apply excess solder to the solder joint.

This can lead to an increase in flux residues and deterioration in the appearance of the product. It is recommended to choose a solder rod diameter equal to half the diameter of the soldering iron tip.

3. Remove solder from the solder joint and then remove the soldering iron tip.

The entire soldering process should take from 0.5 to 2.0 s per solder joint, depending on the mass, temperature and configuration of the soldering iron tip, as well as the solderability of the surfaces. Excessive time or temperature can, firstly, deplete the flux before the solder is wetted, which can lead to more residue, and secondly, increase the brittleness of the solder joint. Shutdown

To ensure a long service life of the soldering iron tip after finishing work, it is necessary to irradiate it.
It is convenient to use tubular solder for this purpose: wrap several turns of solder (as shown in Fig. 5) around the tip of the tip and heat it. Practical examples
At the initial stage, working with tubular solders (two-handed soldering) can be difficult. How to work correctly with tubular solders? The examples below will help you quickly master two-handed soldering technology.

Fig.4

Fig.5

Soldering of chip components: resistors, capacitors, tantalum capacitors, inductors, varistors, MELF-Kopnyca.

1. Irradiate one of the contact pads (hereinafter referred to as CP). It is necessary to supply a sufficient amount of solder for the subsequent formation of the fillet.

2. Install the chip component on the gearbox.

3. Holding the chip component with tweezers, bring the soldering iron tip up, ensuring simultaneous contact of the tip with the terminal of the chip component and the tinned CP.

4. Solder for 0.5-1.5 s. Remove the soldering iron tip.

5. Solder the second terminal: bring the soldering iron tip up, ensuring simultaneous contact of the tip with the terminal and the gearbox. On the opposite side of the soldering iron tip, apply tubular solder at an angle of 45° to the plane of the CP and the component lead

Attention! When soldering chip components, the correct selection of solder diameter is important. Excessively thick solder will cause

lead to the formation of excess solder fillet.

Containing antimony

To reduce the degree of oxidation of the alloy in the liquid state and give the soldering a better appearance, antimony is introduced into its composition. According to GOST 21930-76, all tin-lead solders for soldering, depending on the chemical composition, are classified into:

• antimony-free;
• low antimony, with antimony content up to 0.5%;
• antimonous, containing more than 0.5% antimony.

The same GOST also determines the areas of primary use of each brand.

Table 1. Chemical composition of solders

Basic properties

A variety of metal alloys are used as soldering materials. However, there are compositions consisting entirely of metal. In order for the connections to be of high quality, the solder must have certain properties.

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Any materials must have high wettability - a phenomenon in which the bond strength between solid and liquid substances is higher than that of the liquid. At high values, the liquid spreads over the surface, filling the smallest cavities. If the solder does not sufficiently wet the metal, it cannot be used for soldering. For example, lead is not used to work with copper, otherwise the result will be a low-quality compound.

There are two temperature limits. The first is the one in which the most fusible elements begin to melt during the soldering process, the second is when all the solder becomes liquid. The interval between these indicators is scientifically called the crystallization interval.

If the switching point is in such a temperature range, the soldering can quickly fail even under minimal load. This is due to the fact that the connection has high resistance and fragility. It should be noted: until the solder has completely hardened, you cannot have any impact on it.

Refractory and low-melting

Solders for soldering are divided into refractory and low-melting.
They are also called hard and soft. All types of solders are widely used in mechanical engineering, electrical engineering, and electronics. Hard solders are used when it is necessary to achieve high joint strength. Probably, such connections could be called constructive. Their melting point reaches 500 ℃ and above.

This temperature is dangerous for most components of electronic circuits, especially for semiconductor devices and limits their use, so other alloys are used for soldering - low-melting alloys.

They are obtained by adding more lead to tin. All low-melting solders have a melting point of about 200 - 240 ℃.

Soldering components mounted through holes.

1. Install the component into the mounting holes, if necessary, bend the leads.

2. Apply the soldering iron tip in such a way that simultaneous contact is ensured with the mounting hole CP and the component lead, warm up for 0.5-1.0 s.

Struck No. 1.
It is necessary to ensure good thermal contact between the soldering iron tip and the soldered surfaces.
3. Apply a small amount of solder to the soldering iron tip so that a solder bridge is formed between the CP and the terminal (see figure).

4. Move the tubular solder in a circle along the CP in the opposite direction from the soldering iron tip (see figure).

5. Once the solder joint is formed, remove the solder rod.

6. At the same time, remove the soldering iron tip. To form the correct fillet shape, the soldering iron tip must move upward along the component lead.

Rule No. 2.
It is necessary to ensure contact between the soldering iron tip and the soldered surfaces until a solder fillet is formed.
Attention! Avoid applying strong pressure with the soldering iron tip to the gearbox. Do not allow the soldering iron tip to contact the solder fillet without using tubular solder, this may cause degradation of the solder joint.

Possible problems and solutions
Spattering.
High heating rate. Apply the solder rod to the heated contact surfaces (component terminal and CP), do not apply solder to the soldering iron tip.

Brushed solder joints.

Long-term contact of the soldering iron tip with the soldered joint after the solder rod is removed from the soldering zone.

Residues after soldering in the form of soot.

Clean the soldering iron tip and sponge or replace the soldering iron tip.

Excessive flux residue around the solder joint.

1. Large diameter tubular solder, use smaller diameter solder.

2. Excessive supply of tubular solder to the soldering point.

3. Low soldering temperature, use a higher power soldering iron or increase the soldering temperature.

Foreign stamps

There are also foreign-made compounds. They are marked differently, but the mark can determine the composition of the alloy. An example is the Sb62Pb36Ag2 alloy produced by the American company.

It contains 62% tin, 36% lead and 2% silver. Silver is often added to the composition to increase fluidity after the solder has melted.

Another example is a product produced by Canadian. Its marking is SN62/36/2 NC. This material is in the form of a paste and from the marking it follows that its composition is: 62% tin, 36% lead, 2% silver. NC (No Clean) means that the solder balls are contained within a flux gel.

Heating Methods

Soldering materials can be heated in different ways. If we talk about home use of the metal soldering process, the most common option is a soldering iron or torch.

The first tool is used if it is necessary to carry out a low-temperature process, the second - if a high-temperature one. The variety of modern soldering irons is great. Among them there are devices with automatic temperature control and other useful functions.

The production uses mainly other technologies: oven soldering, using induction heaters, immersion in special baths with metal or salts.

Electrical resistance heating is used, when the solder and the workpieces being connected are heated due to the flow of electric current through them, and others.

3.2. Properties of solders

Brazing

carried out by electric contact method, graphite or copper electrodes or using arc welding. Small parts are soldered using an autogen. With the electric contact method, solder is placed in advance between the parts to be joined or introduced into the joint during the soldering process; welding is carried out without metal additives by fusing the ends of the parts being connected.

For electrical contact soldering with silver solders

Borax is usually used as a flux. Soldering with self-fluxing solders, which contain phosphorus, and welding in a protective atmosphere are carried out without the use of flux.

Solders containing phosphorus cannot be used for soldering steel and cast iron and joints subject to shock and vibration due to the brittleness of the soldered seam. The classification and chemical composition of soft and semi-hard solders are given in table. 3.1.

Table 3.1
Classification and chemical composition of soft and semi-hard solders

The physical and mechanical properties of soft and semi-hard solders are given in Table. 3.2.

Table 3.2
Physical and mechanical properties of soft and semi-hard solders

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Preferred areas of application for soft and semi-hard solders:

O2

— tinning and soldering of collectors, armature sections and windings of electrical machines with class H insulation, tinning of critical fixed contacts, including those containing zinc;

POS90

— tinning and soldering of internal seams of food utensils and medical equipment;

POS61

- tinning and soldering of electrical and radio equipment, printed circuit boards, precision instruments with highly sealed seams where overheating is not allowed;

POS40

— tinning and soldering of electrical equipment, galvanized iron parts with sealed seams;

POS10

— tinning and soldering of contact surfaces of electrical devices, instruments, relays;

POSK50-18

— soldering of parts made of copper and its alloys that are sensitive to overheating, including soldering of copper-clad aluminum. Soldering of ceramics, glass and plastics metallized with tin, silver, nickel;

POS61M

— soldering of food utensils, medical equipment, electrical and radio equipment, printed circuit boards, parts sensitive to overheating;

POSSu61-0.5

— tinning and soldering of electrical equipment, soldering of printed circuit boards, windings of electrical machines, galvanized radio components under strict temperature requirements;

POSSu50-0.5

— tinning and soldering of aircraft radiators;

POSSu40-0.5

— tinning and soldering of sheet metal, windings of electrical machines, for soldering mounting elements of winding and cable products;

POSSu35-0.5

— tinning and soldering of lead cable sheaths;

POSSu30-0.5

– tinning and soldering of zinc sheets, carbon and stainless steels. Tinning and soldering of wires, cables, bands, radiators, various parts of equipment and devices operating at temperatures up to 160 ° C;

POSSu25-0.5

— tinning and soldering of radiators;

POSSu18-0.5

— tinning and soldering of heat exchanger tubes, electric lamps;

POSSu95-5

;
PSr3Kd
- hot tinning and soldering of collectors, armature sections, bandages and current-carrying connections of heat-resistant electric machines with high rotation speeds. Soldering of pipelines and various parts of electrical equipment.

POSSu40-2

— general-purpose solder;

POSSu30-2

— tinning and soldering in refrigeration equipment manufacturing, electric lamp production;

POSSu18-2, POSSu15-2, POSSu10-2

— soldering in the automotive industry;

POSSu8-3

— tinning and soldering in electric lamp production;

POSSu5-1

— tinning and soldering of parts operating at elevated temperatures;

POSSu4-6

— soldering of tinplate, tinning and soldering of parts with rolled and riveted seams made of brass and copper;

POSSu4

—
4
— tinning and soldering in the automotive industry;

POSK2-18

— tinning and soldering of metallized ceramic parts;

POSI30

;
PSr3I
- soldering of copper and its alloys and other metals, non-metallic materials and glass with metal coatings. Soldering of electronic equipment parts. It has high fluidity and provides good adhesion of soldered surfaces.

The parameters of soft solders with low melting points are given in table. 3.3.

Table 3.3
Soft solders (alloys) with low melting points

Note. They are used in radio circuits with semiconductor devices and in circuits where solder is used as a temperature fuse.

The chemical composition and physical and mechanical properties of solid silver and copper-phosphorus solders are given in Table. 3.4.

Table 3.4
Chemical composition and physical and mechanical properties of solid silver and copper-phosphorus solders

The parameters of copper-zinc and copper-nickel hard solders are given in table. 3.5.

Table 3.5
Copper-zinc and copper-nickel hard solders

The parameters of silver solders with a low melting point are given in table. 3.6.

Table 3.6
Silver solders with lower melting points

The preferred areas of application of hard solders are given in table. 3.7.

Table 3.7
Preferred applications of brazing alloys

The parameters of copper-phosphorus solders are given in table. 3.8.

Table 3.8
Copper-phosphorus solders

Note. For copper-phosphorus and silver solders, borax is used as a flux in powder form or mixed with table salt.

The parameters of solders for soldering aluminum are given in table. 3.9, 3.10.

Table 3.9
Chemical composition and physical properties of solders for aluminum soldering

Table 3.10
Other solders for aluminum soldering

The primary areas of application of solders for soldering aluminum P250A, P300A and P300B are given in table. 3.11.

Table 3.11
Preferred areas of application of solders for aluminum soldering

According to condition

Fluxes also come in different shapes and conditions. There are solid, liquid and paste-like. In general, they differ almost completely in their parameters and properties.

Liquid

Liquid fluxes already have better properties compared to solid ones. They are much easier to apply and significantly reduce soldering time. The disadvantage is that it dries quickly in the open air; if such a composition is spilled on the surface, it will be difficult to wipe it off. This type includes, for example, liquid rosin. It is usually sold in jars with a brush.

If you use liquid rosin, do not apply it to a hot surface with a brush. Due to high temperature, the brush may become deformed and cannot be returned to its previous state.

Solid

The hard ones include the most common rosin and solder fat. The advantage of such fluxes is their price and neutral properties. The disadvantage is the inconvenience of application (first on a soldering iron, then on the soldering site, etc.), some types of soldering are not available, poor removal of oxides before and during soldering, extremely low surface tension effect, many marks on the work site and a large amount of fumes when soldering.

Pasty

Paste fluxes are the best of the presented types. For example, they are very convenient to apply. They do not dry out in the air, have excellent soldering properties (depending, of course, on the price) and all types of soldering are possible. The only disadvantages include the fact that there are many fakes of famous manufacturers on sale (however, some fakes are close in level to the standard), harmful fumes and, of course, the price.

Fluxes that are too cheap are terribly solderable. Another undeniable advantage of paste is that you can use syringes with thin needles (the sharp tip of the needle must be cut off), thereby very accurately dosing a portion of the flux and without smearing it all over the board. In addition, they are easy to wash and some of them can not be washed off at all (which are used in BGA soldering, where cleaning is, in principle, very difficult).

The best way to apply flux is with a syringe. You can accurately and economically dose the flux using a syringe. In addition, a metal needle does not deform from high temperature as much as a brush, and you can safely add flux during the soldering process.

Convenient application of paste-like flux is another plus in the collection of advantages of paste-like substances.

It is very convenient to apply and store flux in a syringe with a thin needle. A simple pharmaceutical syringe is enough, we cut off the sharp part of the needle and you can freely make the length of the dispenser as convenient for you. There are also so-called flux guns, but they are much larger and are not very convenient for micro-soldering due to their dimensions.

Pastes for microcircuits

Solder is also available in the form of solder paste. It is a plastic mass consisting of flux and a binder, which contains many tiny balls of tin-lead solder with flux.

Such pastes are used for stencil soldering, that is, when the use of conventional soldering methods is impossible due to the small size of the components.

These can be microcircuits or components in BGA packages. The pastes are applied to the terminals with a spatula and melted with a hairdryer or infrared soldering iron.

Due to the fact that solder pastes dry out quickly, they should be stored in special, hermetically sealed tubes.

To restore BGA packages, that is, to update the solder balls on their terminals, also called reballing, solder balls are produced. It can be either tin-lead or lead-free.

This is a high quality pure product with a very precise chemical composition.

The balls are stored in tightly closed jars at a temperature of +20 - +30 ℃ and a humidity of no more than 60-70%. The shelf life of such solder is usually no more than 12 months. Used for soldering critical components.

Types of soldering irons

A soldering iron is a tool that is used for soldering and tinning, for heating flux and elements, melting solder, etc. The working part of the device is called a tip; heating occurs from a blowtorch or electric current.

Typically, the electrical power of such tools is 30-40 W; they are designed for repairing and installing electronic devices. But when working with semiconductor equipment, this product can cause unacceptable overheating. To prevent such situations, it is advisable to purchase a low-power unit with ratings of no more than 15 V. Soldering irons come with both periodic and constant heating. The latter are divided:

• Electrical. They have a built-in heating element that operates from an outlet, battery or transformer.
• Gas. Equipped with a built-in burner, fuel is usually supplied from a cylinder with liquefied material. An external source is rarely used.
• Liquid fuel. They are similar in design to gas ones, but are heated by the combustion flame of liquid fuel.
• Thermal air. The work is carried out thanks to a stream of hot air. The principle of operation is similar to a hair dryer, but in this case a thin air stream is used.
• Infrared. Heated by a source of infrared radiation.

Devices with periodic heating are hammer and end-type. They are presented in the form of a massive tip attached to a metal handle, the length of which ensures the safety of work. Heating is carried out from external heat sources.

There are different types of solders and fluxes that are suitable for working with specific metals. Having understood the features of the drugs, choosing the right material will not take much time and will not cause difficulties.

How to replace flux

Regardless of what flux is used, the finished soldering must be wiped with a cloth soaked in rectified alcohol or acetone, and also cleaned with a stiff brush or brush moistened with a solvent to remove flux residues and dirt. In some exceptional cases, instead of rosin, you can use its substitutes:

• rosin varnish, available in hardware stores. It can be used as a liquid flux instead of a solution of rosin in alcohol. The same varnish can also be used for anti-corrosion coating of metals.
• resin - pine or spruce resin - is an accessible material, especially for amateurs living in rural areas. You can prepare this flux yourself. Resin collected from trees in the forest must be melted in a tin over low heat (the resin may ignite over high heat). Pour the melted mass into matchboxes.
• an aspirin tablet available in any home medicine cabinet. The disadvantage of this flux is the unpleasant smell of smoke released when aspirin melts.

Nowadays a large number of different so-called “no-clean” fluxes are produced, both liquid and in the form of a semi-liquid gel. Their peculiarity is that they do not contain components that cause oxidation and corrosion of the parts being connected, do not conduct electric current and do not require washing the board after soldering. Although it is still better to remove all flux residues from the soldered parts after completing soldering.

To apply liquid flux, you can use a brush, a cotton swab or just a match, but it is more convenient to use the so-called “flux applicator”. You can try to buy a branded flux applicator that costs about $20-30. It is also convenient to use flux in the form of a gel or paste. To apply it, you can use a disposable syringe, but because of its thickness, you will have to use a thicker syringe needle.

Amateur radio solder for soldering

Nowadays, solder wire with a cross-section of 1 to 5 mm is used for soldering. The most common are 1.5-2 mm multi-channel solders. Multi-channel means that inside the tin wire there are several channels of flux, which ensures the formation of an even, shiny and reliable solder. Such solder is sold in coils - at radio markets, in flasks - in which it is rolled into a spiral, and in reels (the amount of solder in them is such that it will last for more than one year). It is recommended to purchase it in the form of a wire, the thickness of a match - it is more convenient to solder.

When soldering installation wires of radio equipment, it is convenient to use tin-lead solders, cast in the form of thin rods with a diameter of 2 - 2.5 mm. You can make such rods yourself by pouring molten solder into a vessel with a hole pre-made in the bottom. The vessel should be held above a sheet of tin or a metal plate. After cooling, the rods should be cut into pieces of the required length.

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Modern solders used in soldering electronic circuits are produced in the form of thin tubes filled with a special resin (colophonium), which acts as a flux. Heated solder creates an internal connection with metals such as copper, brass, silver, etc., if the following conditions are met: the surfaces of the parts to be soldered must be cleaned, that is, the oxide films formed over time must be removed from them, the part is in place Soldering joints must be heated to a temperature above the melting point of the solder. Certain difficulties arise in the case of large surfaces with good thermal conductivity, since the power of the soldering iron may not be enough to heat it.

With a melting point less than 200 degrees

There are also solders with very low melting points. This is, for example, POSK-50-18. From the marking it follows that this solder contains 50% tin, 18% cadmium, and 32% lead.

This solder melts at a temperature of 142 – 145 ℃. It is very plastic, but due to its cadmium content, it is toxic.

Another example of such low-melting solders is POSV-50 (it has the name Rose). Here the number 50 indicates a bismuth content of 50%, and tin and lead are present in the composition in equal proportions - 25% each.

Solder melting temperature is 90 – 94 ℃. These two soldering products most often come in tablet-like shape and size. Wood's third alloy contains 10% tin, 40% lead, 40% bismuth, 10% cadmium.

Its melting point does not exceed 72°C. Due to the presence of cadmium in its composition, it is toxic. Rose and Wood alloys are quite expensive.

Indium solders are often used for soldering semiconductors, since their melting point is about 117 ℃. In this alloy, indium replaces tin, and lead is also added to soften it and make it more fluid.

Some indium solders can be used to solder glass. In this case, the edges of the latter are simply rubbed with paste before soldering.

Brands of soft solders for soldering with a soldering iron

The main component when soldering with an electric soldering iron is tin-lead solder. It is available in the form of wire or tube of different diameters. The tubular solder inside is filled with rosin. This type of solder is very convenient when working, since it does not require additional flux to the soldering iron tip.

Solder is an alloy of low-melting metals. As a rule, solder contains tin. You can solder with pure tin, but it is expensive and therefore cheap lead is added to the tin. Tin is an environmentally friendly metal and can be used as solder for soldering food utensils and medical instruments in its pure form. If you bend or squeeze a tube made of pure tin, it crunches. The more lead in the solder, the darker the surface of the solder.

Solders are marked with letters and numbers. For example, POS-61, which means P - solder, O - tin, S - lead, 61 - % tin content. POS-61 is the most common, as it is suitable for soldering in most cases. Popularly, POS-61 is often called a tertiary, since it contains a third of lead (Pb).

Solders can be soft or hard. The melting point of soft solders is below 450˚C. Hard solders melt when heated above 450˚C and are not used for soldering with an electric soldering iron.

Main technical characteristics of soft solders for soldering with an electric soldering iron

The electrical resistivity of tin-lead solder (conductivity) is 0.1-0.2 Ohm/meter, aluminum 0.0271, and copper 0.0175. As you can see, solder conducts current ten times less than copper or aluminum.

The most common solder is POS-61, also called tertiary. It is excellent for soldering and tinning of live parts made of copper, brass and bronze with a sealed seam and is not expensive. Suitable for almost all household soldering situations.

Using PIC

The discoverers of this alloy were pleasantly surprised that it turns into a molten state at a lower temperature, and the eutectic mixture can act as a solvent for the added metal. This is how the very first brands of POS solders were developed.

Lead options

Such mixtures containing lead are characterized by softness, rapid melting and easy processing, which is why they are called lead-containing solders. They are harmful and have been banned for use in soldering electrical components around the world . The percentage of cadmium, mercury, and similar harmful components in equipment is strictly regulated and verified by relevant organizations.

Solder for soldering aluminum 34A

The composition of the solder allows it to be used for soldering pure aluminum and its alloys, aluminum with copper and its alloys. Product 34A has found application in many areas of traditional and modern industry.

The alloy is suitable for soldering using acetyl-oxygen, propane-butane and propane gas torches. It is not recommended for use with alloys D1 and D16, as well as with compositions containing more than 3% magnesium.

The shelf life of the product is unlimited.

Manufacturers specifically develop high-tech solders for the restoration and repair of aluminum parts, so that the use of expensive welding equipment is not required during the soldering process. With such products you can easily achieve elasticity and strength in the seam, which will withstand even high loads on the repaired part. With the right solders, aluminum products can be repaired or joined in a matter of minutes.

Requirements for amateur radio fluxes

The choice of flux is an important issue. Previously, only rosin was used, there was no other flux. Why rosin is bad - rosin, alcohol rosin flux belong to the category of active fluxes. The first disadvantage is that at high temperatures, not only the metal oxide is removed, but also the metal itself. The second drawback is that cleaning the board after soldering with rosin is a big problem. You can only wash off the residue with alcohol or solvents (and even then, sometimes it’s easier to pick it out with something sharp). Flux residues on the board are not only unsightly from an aesthetic point of view, but also harmful. On boards with small gaps between conductors, the growth of dendrites (in other words, short circuits) caused by galvanic processes on a contaminated surface is possible. What is the solution - on the modern materials market you can find a wide range of fluxes that are washed off with ordinary water, do not destroy the soldering iron tip and provide high quality soldering. Such fluxes are usually sold in syringes, which is very convenient for use.