What is solder for a soldering iron

Tin for soldering: melting point, solder composition

Everyone knows from school that tin with the chemical symbol “Sn” is used for soldering microcircuits and other radio components. The main requirement for this alloy is a low melting point.

This is because the solder must melt during the process, not the part being joined.

Pure tin with a melting temperature of 232 °C is quite suitable for these purposes, but in practice, pure tin is not actually used for soldering due to its high cost; alloys with lead and other metals are more often used.

Characteristics

Tin is indispensable in the production of electronic devices. Due to its properties, it is used for welding components in radio engineering. The alloy, called Eutectica, consists of lead (Pb), silver (Ag), copper (Cu) and nickel (Ni). Thanks to these additives, tin melts at different temperatures depending on the percentage of each of them.

Tin for soldering

Tin is soft and malleable, but very resistant to corrosion and does not form rust, has very good electrical conductivity and a relatively low melting point. All these characteristics make it indispensable for creating electronic devices.

The soldering process takes place in soft welding, which consists of combining two base elements by introducing a third element with a lower melting point into the base.

For example, soldering a copper circuit board pad to a capacitor leg uses molten tin, which melts at a much lower temperature than the base elements.

During the heating process, liquid tin, due to its capillary properties, is attracted to the base components, and then cools in soft soldering mode.

Eutectica alloy

Types of solders and fluxes

In our country, the POS brand of solder has become widespread - an alloy of tin Pb and lead Sn. Depending on the type, cadmium, nickel, copper, and other metals may be added to it. PIC is mainly produced in the form of rods, wires, balls and paste. Its chemical composition is strictly regulated by GOST 21930-76. In Russia, the following types of solder are widely used: POS18, POS30, POS50, POS90, which are soft alloys with a melting temperature of up to 300 degrees.

POS brands

POS-18

Solder is regulated by state standards; in addition to Pb (0.8%) and Sn (17-19%), it contains impurities of many metals. Regulatory authorities strictly ensure that the manufacturer limits the presence of toxic arsenic in the composition, which reduces the fluidity of the liquid alloy and increases fragility under conditions of alternating loads.

Composition of POS-18 impurities in percent:

• Cu - 0.1;
• Bi0 - 0.05;
• S—0.02;
• Fe - 0.02;
• Al, Ni, Zn - 0.002 each.

Technical data:

1. Density—10.3g/cm2.
2. The resistivity indicator is 0.200 µOhm•cm.
3. The Brinnel hardness index is 11 HB.
4. Thermal conductivity—0.37 kcal/cm*C*deg.
5. T at which the solder will melt solidus/liquidus—183/285 C.

Solder Advantages:

• Wide area of ​​alloy in liquid state;
• reduced content of impurities that cause brittleness;
• corrosion resistance of the soldering area, which is important for parts located in humid environments.

Disadvantages of POS-18:

• Special solder, not mass produced.
• The presence of harmful additives in the composition - Pb.

POS-18

POS-18 belongs to the universal alloys and is a substitute for antimony-free alloys; it is used:

• For the production of radio equipment;
• soldering low power printed circuit boards;
• car body repair in the form of tinning;
• connections of units made of copper-zinc alloys;
• repair of equipment in heating systems: boilers, radiators and other heating elements.

The price of POS-18 solder as of September 1, 2019 is from 710 rubles/kg.

POS-30

Solder is standardized by GOST 21930.76 / 21931.76 and belongs to soft alloys with a melting temperature of 256.0 C. Its properties are similar to grades with POS-40 and 50 and consists of Pb and Sn in a percentage ratio of 30:70, as well as other elements no more than 1 %. It differs from pure tin in its dark color and increased hardness of the alloy.

Solder POS-30

Composition of impurities in percentage:

• Sb - 0.1;
• Cu - 0.05;
• Bi0 - 0.2;
• S, As, Fe - 0.02 each;
• Al, Zn - 0.002 each.

Technical data:

1. Density - 9.72 g/cm2.
2. The resistivity indicator is 0.185 µOhm•cm.
3. The Brinell hardness index is 12 HB.
4. Thermal conductivity - 0.37 kcal/cm*C*deg.
5. Solidus/liquidus melting temperature - 183/256 C.

Solder Advantages:

• High fluidity;
• low melting temperature;
• low resistance allows you to work with small parts;
• high impact strength equal to pure tin;
• high scope of application, with the possibility of replacing expensive materials, for example, for soldering zinc or brass plates;
• Possibility of use for repairing household appliances.

The disadvantage of POS-30 is the presence of harmful additives in the composition - Pb.

The price of POS-30 as of September 1, 2019 is from 766 rubles/kg.

POS-50

It is produced in accordance with the requirements of GOST 21931.76, it is distinguished by a practically equal ratio of lead and tin.

Solder POS -50

Composition of POS-50 impurities in percent:

• Sb - 0.8;
• Cu - 0.1;
• Bi - 0.05;
• As - 0.05;
• S, Fe - 0.02 each;
• Ni, Al, Zn - 0.002 each.

Technical data:

1. Density - 8.87 g/cm2.
2. The resistivity indicator is 0.158 µOhm•cm.
3. The Brinell hardness index is 14 HB.
4. Thermal conductivity - 0.48 kcal/cm*C*deg.
5. Solidus/liquidus melting temperature - 183/209 C.

Solder Advantages:

• Good fluidity;
• good thermal and electrical conductivity;
• Possibility of use in wet environments;
• good ductility of the seam allows it to be used for products with increased requirements for tightness, for example, in measuring instruments and low-power PC circuits.

Disadvantages of POS-50:

• Ineffective when soldering thick products due to unstable heating; the presence of harmful additives in the composition - Pb;
• accelerated crystallization of the melt does not make it possible to use the alloy in manual soldering technology.

The price of POS-50 solder as of September 1, 2019 is from RUB 1,102.00/kg.

POS-90

The solder is characterized by low thermal conductivity and high hardness, which is explained by the high content of tin 90, the material is silver in color, which gives the resulting joints an aesthetic appeal.

Solder POS - 90

Composition of POS-90 impurities in percent:

• Sb - 0.1;
• Cu - 0.05;
• Bi - 0.2;
• As - 0.01;
• S, Fe - 0.02 each;
• Ni, Al, Zn - 0.002 each.

Technical data:

1. Density - 7.6 g/cm2.
2. The resistivity indicator is 0.120 µOhm•cm.
3. The Brinell hardness index is 15.4 HB.
4. Thermal conductivity - 0.13 kcal/cm*C*deg.
5. Solidus/liquidus melting temperature - 183/220 C.

Advantages of POS-90:

• Wide range of applications from household, medical to industrial sectors;
• good fluidity;
• high level of wettability in the liquid state;
• low melting temperature;
• good electrical conductivity;
• good tightness, the ability to use in water and gas environments; good plasticity of the seam allows it to be used for products with high
• sealing requirements, for example in measuring instruments and low-power PC circuits.

The disadvantages of POS-90 are the presence of harmful additives in the composition (lead).

The price of POS-90 solder as of September 1, 2019 is from RUB 1,778.00/kg.

What is the melting point

Tin, which is used in electronics, is usually a eutectic type, meaning that it is an alloy with a lower melting point for each of its constituent elements. So, if there is a 60% tin alloy (melting temperature - 232 C) and 40% lead (melting temperature - 327 C), then the total melting temperature of the alloy will be approximately 183 C.

Melting tin

The most common solder used in EU countries for electronic work is 63/37 SnPb. It is a eutectic alloy with a melting point of 183 C. The 60Sn alloy has a working range of 183-238. There is a lower temperature alloy Sn43Pb43Bi14, which has a melting point of 144-163.

Solder composition

The lead contained in the alloy is gradually being phased out in accordance with new EU directives (RoHS and WEEE) and is being replaced by solders consisting of tin-antimony alloys. Already today in the EU many stores do not sell it. Things are different here for now; it will probably be many years before lead solder in our country is replaced forever.

Important! Lead-free alloy has a higher melting point than lead alloy and uses more aggressive fluxes. This means that the soldering iron must be made for lead-free soldering to ensure the correct temperature of around 230 C. Lead-free solder is generally about 20-50% more expensive than lead solder.

How to choose the right one

The choice of solder depends on the type of work and purpose of the finished product, as well as on the conditions under which the product will be used.
Criteria to consider before choosing solder for soldering:

1. Soldering iron type.
2. Wire size. Diameters vary from centimeters or millimeters, the size of the wire depends on the work being performed.
3. The flux cleans the soldering area, making it easier for the solder to flow and therefore a perfect solder joint. Flux changes surface tension as it increases adhesive properties in the solder joint.
4. Before purchasing, you need to know at what temperature tin melts for soldering.
   Compound. The debate about whether to use lead or lead-free solder on PCBs is still ongoing. Despite debates caused by environmental and health concerns, many electrical technicians use lead.

Note! The expiration date and industry guidelines require its use within three years from the date of manufacture. The expiration date is indicated on the product and can be found in the store upon purchase. If you use expired solder paste, oxidation may occur on the solder surface, rendering the connection ineffective.

Usage

Experts give useful tips that are very helpful for novice radio amateurs to solder correctly:

1. Choose solder with a minimum lead content.
2. It is necessary to ensure the cleanliness of the soldering iron tip; it should not have dirty deposits.
3. For cleaning, use a file or sandpaper. After cleaning, the tip is tinned with rosin.
4. It is not recommended to hold the device at the solder point for a long time, since the parts being connected can suffer high temperature damage. To reduce the harmful effect of T on the part, it is held with tweezers, which will act as a heat sink.
5. The product is cleaned before soldering, and the contact contacts are additionally tinned to ensure excellent adhesion.

Soldering technology

Additional Information. When soldering, safety precautions must be taken. Always wear safety glasses to protect your eyes from flying drops of hot liquid solder. The tip of the soldering iron is very hot by design, exceeding 370 C. Do not allow the tip to come into contact with skin, clothing or other objects. When working, you need to use a special holder for a soldering iron.

To summarize, we can say that soldering tin is still widely used in the domestic electronics industry and everyday life. The product is widely represented on the Russian and foreign markets, in the form of lead and lead-free solders. In order to protect the environment and the requirements of international organizations, consumption of the first type will be steadily reduced.

Source: https://rusenergetics.ru/ustroistvo/olovo-dlya-payki

Solders for soldering. Types and properties. Composition and fluxes. Melting

Soldering is often used to connect various metal parts together. This type of connection is popular in various areas of life and production. It is most often used by radio amateurs and home craftsmen.

Soldering can help out both when repairing computers, TVs, radio equipment, and in industry, repairing refrigerators. Soldering is good at creating a tight connection. And some materials simply cannot be combined in any other way.

Not all metals can be joined by welding. And in order for the soldering to be high-quality and airtight, you need work skills, good tools and appropriate solders and fluxes.

The compositions and types of solders and fluxes are selected in accordance with the materials from which the materials being joined are made. For example, aluminum requires a completely different flux than copper. Let's consider the basic properties of solders, their applicability, and features of use.

Basic properties

Various metal alloys are used as solder. There are alloys based on one pure metal, usually tin. The metals that make up solder differ from each other in different parameters.

Wettability

Any solder for soldering must necessarily have the property of wettability, otherwise the parts to be joined will not be connected by high-quality soldering.

Wettability is a phenomenon in which the reliability of the bond between the molecules of a solid and a liquid is greater than that of the liquid. If there is good wettability, the liquid disperses over the surface and fills all its cavities. When solder does not sufficiently wet the metal, it is not used for that metal. Pure lead is not used for soldering copper; it does not wet the copper.

Melting temperature

Regardless of the type of solder, the melting point of any type should not be higher than the temperature of the parts being soldered. However, it must be higher than the operating temperatures of the materials so that the solder does not melt during operation of the soldered device.

There are two temperature thresholds in this matter. The first is the temperature at which the melting of the most fusible components of the solder just begins, and the second is when all the solder has turned into liquid. The interval between these two values ​​is called the solder solidification interval.

If the place connected by soldering is at a crystallization temperature, then the soldering place can quickly collapse, even from a small load, since the connection will have increased electrical resistance and fragility. When soldering, you need to know that until the solder has completely hardened, you cannot apply any loads to it.

Properties of solders

Any solder composition should not contain substances that have toxic properties to humans beyond the norm. Solders for soldering must have the properties of thermal stability and electrical stability. When choosing a solder, the thermal conductivity of the solder and its thermal expansion are taken into account. They must be level with the soldered parts.

Types of solders

All solders for soldering are divided into hard and soft. The melting point of hard solders is more than 450 degrees, and soft solders - up to this value.

Soft wires for soldering

The most popular of them are alloys of tin and lead with different percentages. To impart special properties to the solder, auxiliary components can be added to it. Cadmium and bismuth are used to reduce the melting point. Antimony increases soldering strength.

Tin and lead solders have a low melting point and low strength. It is better not to use such solder for critical parts. If you have to soft solder parts that are subject to heavy loads, it is recommended to increase the soldering area of ​​the parts.

The most popular soft steel solders are from POS - 18 to POS - 90. The numbers in the marking indicate the percentage of tin in the solder. These brands of solders are used in the production of instruments and electronic devices.

POS-90 is used for soldering parts that are subsequently subjected to galvanization. POS-61 is used for soldering precision devices and critical parts made of various materials.

They are used for soldering brass and copper when connection strength and increased electrical conductivity are needed.

POS-40 is used for non-critical parts that do not require special precision. The soldering area can be heated to a high temperature. POS-30 goes well with brass and copper, as well as steel alloys.

Brazing alloys for soldering

Among hard solders with a high melting point there are two groups: alloys of copper and silver. Copper types of solders include solders based on zinc and copper, which are well combined for connections intended for static loads. These alloys are brittle, so they should not be used for soldering materials subject to shock or vibration.

Other types of solder

There are other types of solder that are rarely used. They are necessary for soldering rare metals, or for special special conditions. There are nickel-based solders used for parts operating at high temperatures or made of stainless steel. Gold solders are used for vacuum tubes. Magnesium solders are also available.

Release form

Solders are produced in various forms and packaging. Most often, solders are made in the form of wire, foil, or powder or tablets. There are also granular solders and solder pastes. The shape of the solder is selected depending on the type of soldering zone.

Soldering aluminum

Aluminum parts are connected by soldering, using special solders. Aluminum soldering is used in industry and domestic conditions.

In general, soldering aluminum is considered a difficult job. This happens when the type of solder is chosen incorrectly. They take the wrong kind of solder, which is intended for other metals. The reason for difficult soldering is the formation of an oxide film, which does not allow good wettability of aluminum.

To solder an aluminum part, a solder containing zinc, silver, copper, aluminum and silicon is used. There are many solders with such components in different proportions in the trading network. When choosing, it should be taken into account that the greatest corrosion resistance and joint strength is achieved by solder with a significant zinc content.

Aluminum can also be soldered with ordinary lead and tin solder, but this requires high-quality surface preparation, which includes cleaning with a stainless steel wire brush. When soldering, you need to use active flux. But this method is rarely used.

Aluminum soldering is carried out at high temperatures. The most commonly used solders for soldering aluminum are aluminum-copper-silicon compounds.

Soldering copper

Copper is the easiest to solder. Almost all types of solders are combined with it. Both soft low-melting solders and hard types are used, as well as alloys of tin, lead, silver, zinc, etc.

Any soft solder is suitable for repairing a computer or TV. Hard solders are used for soldering pipes, plumbing, and refrigerators. By following these simple rules you can get a good result.

Soldering stainless steel

To connect parts made of stainless steel by soldering, experts recommend using solder consisting of lead and tin. A good result is obtained with solder containing cadmium. Zinc-based soft solders can be used.

They cannot be used in conjunction with low-alloy steels, as well as carbon alloys. The best solder option for stainless steel is pure tin solder, especially if the soldering will come into contact with food products.

When soldering is carried out in a dry place or in an oven, use manganese with silver, pure copper or nickel and chromium solders. During soldering under corrosive conditions, silver-based tinols with a portion of nickel are used.

Soldering steel

An effective solder for joining steel parts is POS-41. Other soldering alloys can also be used, but they are not entirely suitable for this purpose. Zinc-based solder does not combine well with steel, especially low-alloy and carbon alloys.

How to make your own solder

To prepare your own solder, the component parts (usually lead and tin) are weighed on a scale. This mixture is melted in a crucible on a gas burner. The molten composition is stirred with a metal rod.

Next, using a small steel plate, remove the slag from the surface of the molten solder, then carefully pour it into molds made of tin or plaster.

Melting is carried out in a ventilated area, in compliance with safety measures, that is, wear glasses, an apron, and gloves.

Types of fluxes

No soldering can be done without flux, just as without solder. It is a chemical that dissolves and absorbs oxides. Flux protects the metal from oxidation and promotes wetting of the parts to be joined.

For the soldering process with solder based on tin and lead, a flux based on hydrochloric acid or zinc chloride is used. Ammonium chloride or borax can also serve as a flux. These fluxes are active. Passive fluxes consist of rosin, oil, petroleum jelly and other similar substances.

For example, with soft types of solders, you can use a solution of hydrochloric acid. Zinc chloride is used with steel, copper and brass. Ammonia can dissolve fatty substances. For soldering aluminum alloys, a mixture of tung oil, zinc chloride, and rosin is used as a flux. Phosphoric acid also has its uses.

Related topics:

Source: https://electrosam.ru/glavnaja/slabotochnye-seti/pripoi-dlia-paiki/

Brands of soft solders and fluxes for soldering with a soldering iron

For soldering with a soldering iron, solder is used, and in order for the solder to spread well over the surface of the parts being connected by soldering, a substance called flux is used. Depending on the metal of the parts and their size, the strength and tightness of the soldering, it is necessary to choose a specific brand of solder and flux. The information in the tables will help you select the required solder and flux for 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.

Flux is an auxiliary substance necessary for freeing the surfaces of parts being soldered from oxides and for better spreading of solder over the metal surface during soldering. Without using flux, it is almost impossible to perform high-quality soldering with a soldering iron.

When preparing the most popular fluxes for soldering with an electric soldering iron, rosin is used. It is obtained from the wood of coniferous trees, mainly pine. At a temperature of about 50°C, rosin softens, and at 250°C it begins to boil.

Rosin is not resistant to atmospheric moisture - it hydrolyzes. It consists of 85-90% abietic acid. If you do not remove the remaining rosin after soldering, oxidation of the soldering area occurs. Many people do not know this and believe that rosin is harmless to metal. In addition, by absorbing water from the atmosphere, rosin increases its conductivity and can disrupt the operation of electronic devices, especially their high-voltage circuits.

Popular fluxes for soldering with an electric soldering iron

Flux based on alcohol and solvents must be stored in an airtight container, otherwise the liquid will quickly evaporate. A bottle of manicure polish is very convenient for this purpose. Always have a brush at hand, which is convenient for applying flux to the soldering area.

You can find such a bottle in almost any home. Another advantage is that the brush and twist are not dissolved by alcohol and solvent. Before filling with flux, be sure to thoroughly wash the bottle and varnish brush. If the varnish has hardened too much, pour in acetone and leave.

After a while the varnish will dissolve.

I prepare alcohol-rosin flux in a bottle. First, I pour rosin powder through a paper funnel and then fill it with alcohol. It is easy to pour alcohol into the narrow neck of the bottle if you touch the neck of the bottle with alcohol to a brush previously soaked in alcohol. You need to pour it very slowly and you won’t spill a single drop. Over time, the alcohol evaporates and the flux becomes thick. Then you need to dilute it with alcohol to the required consistency.

As a flux, I often use the undocumented flux of aspirin (acetyl salicylic acid), which is used as a medicine. With its help, you can tin copper and steel surfaces without prior preparation. Liquid flux for soldering with a soldering iron can easily be prepared on the basis of aspirin; just dissolve the tablet in a small amount of alcohol, acetone or water.

Solder pastes (tinol) for soldering

Solder paste (tinol) is a composition of solder and flux. The paste is irreplaceable when soldering with a soldering iron in hard-to-reach places, and when installing unframed radio components. The paste is applied with a spatula in the required amount to the soldering area and then heated with an electric soldering iron. The result is a beautiful and high-quality soldering. Its use is especially convenient if you have no experience working with a soldering iron.

You can make your own pasta. To do this, you need to select a brand of solder suitable for soldering the required metal. Next, use a file with a large notch to cut sawdust from the rod. Then add the liquid soldering flux selected from the table, mixing the sawdust until a paste-like composition is obtained. The paste should be stored in an airtight container. The shelf life of the paste is no more than six months, since solder filings oxidize over time.

Source: https://YDoma.info/tehnologii-remonta/kak-payat/kak-payat-pripoi-flyusy.html

Solder for soldering

The process of repairing electronics and performing work in radio engineering occurs with the help of a soldering iron. High-quality work serves as the basis for durable connection of parts.

The work is done with a soldering iron; reliable connections are made not only with a high-quality tool, but also with flux and solder. The main solder is an alloy of light-alloy metals, which melts when a certain temperature is reached.

Tin in its pure form is considered the most suitable option, but the material is very expensive.

Solder for soldering

What types of solders are there?

There are a large number of materials for soldering, the main division is into soft and hard. Radio equipment is installed using low-melting material; its melting point ranges from 300 to 450 °C. In terms of strength, soft types of solders are not inferior to others when soldering; they are used in the assembly of almost all electronic products.

The soldering process is based on an alloy of tin and lead with a certain standard and quantity.

Some refractory solders have steel alloys, which makes it possible to implement certain parameters when connecting. Impurities are used to achieve certain characteristics, anti-corrosion properties, and strength levels. Solder for soldering is used in most cases of the POS brand, which means tin-lead solders. The number indicates the percentage of tin in the composition.

Tin-lead solder

If a situation occurs where solders and fluxes used in soldering are of unknown origin, they can be distinguished by the following physiological properties:

• The melting point of lead-tin solders varies from 183 to 265 °C.
• A bright metallic sheen indicates a high tin content, presumably grade POS-61 and higher.
• A high lead content is indicated by a dull gray tint and matte surface.
• A large amount of lead increases the ductility of the wire; a product with a diameter of 6 mm can be easily bent by hand, but a higher quality product cannot be bent.

Different types of solder are produced by manufacturers depending on certain factors. Most modern soldering materials use a flux tolerance of 1 to 3%, which significantly improves working conditions.

There is no need to bring the tip of the soldering tool to the flux each time if it is contained in the solder core. A type of lead-tin product is POSSu brand solder.

The designation involves the addition of antimony, is used in various industries, and is suitable for use with tin parts.

Solder Sn63Pb37

The most common type of solder used for soldering and tinning copper and bronze parts through which current flows is tertiary solder. The melting point of this variety is 190 °C, resulting in a sealed seam. The foreign analogue is Sn63Pb37, where the content of tin to lead corresponds to the name.

Low temperature solders

Low-melting solders have a transition temperature to the liquid state of up to 450 °C. They are used in radio engineering connections, when soldering wires, and other works. The main components of such soldering products are alloys of tin, lead, cadmium or bismuth. In the process of degreasing and tinning technical boards, Wood or Rose alloys are used. Such substances become liquid already at around 70 °C.

Low temperature solder

Metals have different melting points, it is important to familiarize yourself with the composition of the solder before purchasing.

1. Tin is a low-melting metal that is dissolved by sulfuric or hydrochloric acid. The metal melts at 232 °C; exposure to standard room temperatures does not affect it, but at -50 °C the composite crystal lattice is destroyed.
2. Lead is popular due to its fusibility and easy processing. Only the surface exposed to ambient air is oxidized.
3. Cadmium is used for anti-corrosion purposes when soldering tin and lead products. The material itself is toxic, melting at 321 °C.
4. Bismuth is added to the composition due to its solubility in sulfuric acid and nitrogen media.

The most convenient form of release for soldering radio components is wire with a diameter of 2-2.5 cm. The composition of modern products is rosin, which acts as a flux.

Soft solders are used in conjunction with an electric soldering iron and flux. The tin included in the composition is an environmentally friendly product and can be used to connect elements of the food industry. The most common soldering product is the tertiary, which got its name due to the composition containing a third of lead . Soft solders are divided into varieties according to their purpose and melting temperature.

Solder POSV-33

Low-melting solders are used for soldering heat-sensitive parts such as fuses and transistors. The composition includes lead, tin, bismuth and cadmium, the latter material is toxic and is not used in all areas of activity. Melting of Wood's products begins at the lowest temperature - 69 °C.

Domestic brands of products are labeled POS; with the addition of some substances, the name changes. For example, POSV - 33 has equal parts of lead, tin and copper, and is applied to brass and copper parts that require a sealed seam.

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

The technical characteristics of materials used for soldering are divided into several parameters:

• conductivity or electrical resistivity is 0.1 ohm per meter. Tin-lead type solder conducts electric current an order of magnitude worse than aluminum or copper;
• Tensile strength is measured kg/mm; low-temperature solders do not include this parameter, because not designed for load. The parameter depends on the amount of tin; the more there is, the higher the number. For example, POS-61 brand solder has a strength of 4.3 kg per mm, and POS-90 solder has a strength of 4.9 kg/mm.
• The melting point depends on the purpose and components.

An auxiliary substance that promotes the spreading of soldering materials over the surface of the parts being soldered is flux. High-quality connections are created by solders and fluxes ; without one of the components, soldering is impossible. A common type of flux is rosin, made from hard coniferous trees. Softening occurs at 50 °C, and when the temperature reaches 250 °C, the process begins to boil the composition.

Flux for soldering aluminum

Due to the hydrolysis provided for in the manufacture of rosin, the material is not resistant to atmospheric influences. After soldering, it is necessary to remove flux residues, because... the compound may undergo an oxidation process. By absorbing moisture from the atmosphere, rosin can disrupt the operation of radio components.

Tinol soldering pastes for soldering

Among the substances offered, there are solder pastes that are produced with a mixed type of flux. It is used when installing open-frame elements in hard-to-reach places. Application occurs with a special spatula, then heating with an electric tool. The result is a reliable, high-quality connection, which is actively used by novice craftsmen in the absence of appropriate experience.

Tinol pasta

It is possible to prepare an alloy for soldering with your own hands; for this you will need the solder required by the element. Using a medium-grain file, tin for soldering in the form of wire is crushed to the state of metal chips. A flux selected from the above in a liquid state is added to the composition, after which the elements are mixed. The composition must be prepared in a small container, the shelf life is limited to 6 months, after which the metal oxidizes in an acidic environment.

Use of tin-lead group alloys

The soldering process is the joining of several metallized parts together. In this case, the exposure temperature does not exceed the critical threshold at which destruction of parts or circuit boards occurs. The main objectives of using soldering products are to ensure the most even temperature viscosity, at which uniform spreading occurs over the surface.

Tin is used for soldering quite often; the material serves as a component of the largest number of solders. In its pure form, the metal is very expensive and is used for soldering important products and elements. Divided into categories with and without lead.

Lead solders

Various soldering materials are used using lead. The material is fusible, soft and easy to process. Easily dissolves in an alkaline environment and acidic impurities.

Lead solder

Products labeled PIC are considered the most popular in use. The percentage of elements allows you to work with different environments and materials. They differ in temperature and other parameters that are important for a reliable connection. Zinc, bismuth or antimony are added to lead compounds to provide protection against oxidation and other destructive factors.

How to choose solder

The main task for the master is to create a high-quality, reliable fastening that will last for a long time. Solder selection is based on the following parameters:

• Materials that are processed. It is necessary to accurately familiarize yourself with the characteristics of the materials being soldered. There is a temperature threshold for melting fragile elements, transistors, capacitors, etc. Radio amateurs use fusible substances.
• The composition of the solder is selected according to the parameters of thickness and purpose of the product. When soldering wires and other large elements, it is possible to use refractory elements.
• Some cases require choosing the optimal conductivity. The resistance of tin is lower than that of lead; more expensive brands of solder are used on high-frequency boards.

In any situation, it is necessary to be scrupulous about the compliance of soldering parameters and the product. High-quality products are used for soldering, the price is not high, and the choice on the market is huge.

Source: https://stankiexpert.ru/spravochnik/svarka/pripoj-dlya-pajki.html

What do you need for soldering with a soldering iron?

When a novice electrician watches a master work with a soldering iron, all the actions seem simple and understandable.

However, as soon as you pick up the tool yourself, troubles immediately begin: the solder does not hold, the contacts fall off, the insulation burns, the tip becomes covered with soot.

To prevent this from happening, certain rules must be followed.

The master knows them and fulfills them. For a beginner, I advise you to first understand how to solder correctly with a soldering iron. Only after that do you take on this work.

3 main secrets: posture, light and air

Even at home, to perform high-quality soldering, a comfortable worker position with good lighting is required. I recommend installing a desktop near a window that receives sunlight during the day and an artificial source of light in the evening.

Soldering involves heating substances and releasing fumes. Although heated rosin smells like pine needles, this smell is still harmful if inhaled frequently. And other fluxes and acids are even more dangerous. Entering the body through the respiratory system, they accumulate and cause chronic diseases.

Therefore, ventilation is important. Work with an open window, or even better, use forced exhaust.

Useful devices

A short tin with a paper lining is necessary for working with solder and rosin.

A special stand helps to store a heated soldering iron, and a sponge allows you to clean the hot tip from oxides.

It is convenient to remove excess melted solder with a desoldering pump.

Working with small objects is made easier by tweezers, small vices, and “third hand” devices. The simplest option: regular pliers with an elastic band.

You can make other simple designs with your own hands.

Selecting and preparing a soldering iron

The sale offers various models with voltage from 12 to 220 or 380 volts. Each soldering iron is created for a specific job, although it has universal capabilities.

They are assessed by the power consumption of electrical energy, which is spent on heating the tip of the tip.

It is convenient to solder radio components with a soldering iron with a power of 40÷60 watts, and for wires choose 80÷100.

For beginner soldering ironers, it is enough to use simple models of two soldering iron designs with:

1. heating from nichrome wire and a copper rod;
2. ceramic insert and copper tip with nickel coating.

The first type of soldering iron is cheaper, but it requires constant care of the tip, takes longer to heat up to the desired temperature, and wears out faster.

A soldering iron with a ceramic insert works better, but is more expensive. In addition, ceramics require careful handling. It can break due to mechanical shock.

Personal preferences

I have been using transformer soldering irons of the “Moment” type for more than 30 years.

Some people don't like it because of the extra weight. But for me this indicator is not critical. The industrial wattage of 65 is good for amateur radio soldering, but it is not enough for connecting electrical wires.

Therefore, I assembled a more powerful structure with my own hands.

This technology is described in a separate article on the website.

About counterfeit brands

For a long time I could not understand why I like transformer soldering irons, but they are massively criticized on the Internet. Even in the above article, readers expressed a negative opinion about them, criticizing their fragility and poor quality.

I realized this only after a visitor to my site sent me a burnt-out soldering iron from the Chinese company Licota for experiments.

It looks very nice, is light in weight, fits comfortably in the hand and is originally packaged. Upon closer examination of it, I discovered many installation and design defects. I wrote them down in separate articles:

When buying cheap soldering irons from dubious sellers, you can end up with low-quality products, lose money and time. Please pay attention to electrical performance and warranties.

There are other different types of soldering irons designed to get professional work done well. But it’s better to start learning soldering using the models described above.

About sharpening the tip

Cleanliness is not only a guarantee of our health, but also a guarantee of high-quality soldering. It must be observed during work.

The copper tip of the soldering iron heats up to such a state that oxides and carbon deposits form on it. When they penetrate the solder, you can forget about the quality of the soldering. Therefore, the tip of the tip should always be clean and well sharpened.

Its shape is created for a specific type of parts to be soldered:

• The “flat head screwdriver” transfers heat well. It is used to heat massive parts;
• A “pyramid” or “sharp cone” makes it more convenient to control the amount of heating. It is used to connect small radio elements or thin wires;
• The “blunted cone” is sharpened for soldering medium-section wires.

The first type of sharpening is more popular. It can be formed by hammer blows. Then the metal is better compacted and retains its properties longer.

By placing this tip on the part to be soldered with a plane or an acute angle, you can regulate the degree of its heating.

Modern ceramic soldering irons have a set of removable tips of the most necessary shapes. They are coated with a layer of nickel on top and do not require sharpening or preparatory treatment.

How to tin a copper tip

The tip of a new soldering iron without a protective nickel coating must be coated with a thin layer of solder, which will protect it from carbon deposits and premature wear. For this:

1. the soldering iron is turned on under voltage, heating the tip to working condition;
2. immerse it in a piece of rosin;
3. melt the solder, distributing it over the surface of the tip tip. It is convenient to use a wooden object.

What are the soldering steps?

The main objective of this technology is to connect two metal parts, most often conductors, with a low-melting alloy so that they hold firmly and pass electric current with the lowest possible resistance.

To do this, you need to perform a series of actions sequentially. Let's look at them using the example of soldering wires. This:

• removing insulation from the connected ends of the wire;
• mechanical stripping of metal cores to an ideal state of oxides;
• heat treatment with flux - tinning the ends with a thin layer;
• heating the solder and applying it to the soldering area.

Removing insulation

The dielectric layer of the wire can be made of polyethylene, fabric, varnish or other similar material. It needs to be removed.

This work is best done with a sharp knife, placing its blade almost parallel to the axis of the metal core. This prevents cutting and deep scratches. They weaken mechanical strength and increase electrical resistance. This cannot be allowed.

Thin wires coated with varnish can simply be treated with an open flame of matches or a lighter. The same method is suitable for twisted pair and even thicker wires.

There are special pliers of various designs on sale for stripping insulation from the end of a wire of any diameter. They allow this work to be done professionally without damaging the core.

After removing the insulation, the condition of the metal surface is assessed. Pay attention to cleanliness, absence of dents and cuts.

Removing dirt and oxide film

Only pure metal can ensure a high-quality connection of parts when soldering. It is created by mechanical cleaning of the surface and chemical solutions.

First, they work with a knife blade, lightly pressing it against the contaminated metal at an obtuse angle. The core is pulled from the insulation layer to the bare end, rotating slightly in one direction. The metal will immediately lose its dullness and begin to shine.

Chemical cleaning involves treatment with solvents, alcohol, and FES flux.

Tinning of contact pads

The final cleaning of the metal surface of the conductor is carried out by heat treatment with flux, using a tinned soldering iron tip. The most popular and universal remedy is rosin. It is used in a solid state, dissolved in alcohol or jelly-like.

The sale allows you to purchase rosin in any form and provides a wide range of other fluxes.

For soldering parts of electrical circuits, it is not recommended to use fluxes containing acids . They are quite difficult to completely neutralize, and even minor residues quickly oxidize the metal and destroy its structure.

The sequence of tinning a wire core with solid rosin:

1. Heat the soldering iron to the desired temperature. It can range from 180 to 240 degrees and depends on the solder and the metal parts being connected. To control the heating, the tips are touched with a tip of solid rosin. If it begins to rapidly form steam, then heating is normal.
2. The cleaned conductor is placed on the rosin and touched with the tip of the soldering iron. The wire is rotated to coat it evenly with molten flux.
3. The tip of a soldering iron melts the solder and applies it to the rosin-treated wire, evenly distributing it over the surface.

A solution of rosin in alcohol is applied with a brush to the surface to be tinned or simply dripped through a dropper tube.

Jelly-like rosin is squeezed out of a special syringe, which is very convenient to do.

The conductor treated with liquid or jelly-like rosin is heated with a heated soldering iron tip with a drop of solder, accelerating it over the entire contact area.

Direct soldering

It is started after both contact pads are prepared for connection: cleaned of dirt and oxides, tinned.

The soldered ends are connected together. A piece of solder is placed on them with a heated soldering iron, ensuring that it spreads over both areas. After this, the tip is sharply retracted to the side, and the parts remain motionless until the tin completely hardens. This is judged by a slight darkening of its color.

Correctly performed soldering is distinguished by a strong connection of contacts and a smooth surface of the solidified solder, which is slightly shiny. Its quality is checked using a small mechanical tensile force.

If the surface of the solder has darkening and unevenness, then the soldering is unreliable and needs to be corrected.

5 Tips for Creating Reliable Soldering

These include:

1. Warming up of the parts to be connected should be done not with the tip of the tip, but with its side surface. This provides greater contact and better temperature transfer. However, when working with a tip with a blunt tip or a transformer soldering iron, this advice will practically not help.
2. To give increased strength to the connection being created, additional twisting of the wires is done.
3. A mechanical device, the third hand, makes it easier to fix the stationary position of the parts being connected.
4. New electronic components are manufactured with tinned contact surfaces. If they are not contaminated in any way, then flux and solder can be immediately applied to them without prior tinning. This speeds up the soldering process.
5. The sale offers craftsmen tubular solder, inside of which there is a flux. Usually this is rosin. This combination is easier to work with: the number of intermediate operations is reduced due to the simultaneous supply of both components.

4 signs of high-quality soldering

The reliability of the connection is assessed by:

1. the bright shine of the created surface layer;
2. absence of excess solder on parts;
3. tensile strength of control mechanical force;
4. integrity of the insulation layer, absence of traces of melting.

Additionally, I recommend watching the video from the owner of AutoAndElectronics “How to solder correctly with a soldering iron.”

Source: https://rem-serv.com/chto-nuzhno-dlya-payki-payalnikom/

Hand soldering and tinning technology

This instruction establishes the technology for manual soldering and tinning of electrical and radio products (ERI). The instructions were developed on the basis and development of OST 4G 0.033.200 “Solders and fluxes for soldering”, OST 4GO 054. 267 “Soldering of electrical connections. Typical technological operations."

The instructions apply to workshop workers performing technological operations of manual installation and soldering of electronic components on printed circuit boards.

Safety precautions

Solders, fluxes, and washing liquids used for manual soldering and tinning are generally toxic and irritating substances.

To prevent their exposure, it is necessary to keep the workplace clean and work under local exhaust ventilation at the workplace.

Personal protective equipment is:

robe, knitted gloves with polymer coating of the “Multex” type, protective respirator masks.

Harmful components in tubular and wire solders, fluxes, flushing liquids

Modified rosin (contained in X39, JM-20, Crystal 502 solders)	May cause irritation upon contact with skin and inhalation of soldering fumes.
Lead in solders	At soldering temperatures above 500ºC, lead vapor reaches a high concentration, which can cause nausea, weakness, and convulsions.
Flushing liquid VIGON EFM Flux MF 210 (X33-12i), WF-9942.	May cause irritation upon contact with skin.

I. Technical data:

Soldering is the basis for assembling a printed circuit assembly. Soldering combines two or more metal surfaces into one metallurgical joint.

The soldering process is the application of molten solder to flux-treated surfaces; the flux is applied to wet the soldered surfaces with solder; wetting is required to obtain a metallurgical joint during soldering.

Wettability is defined as the formation of a uniform, smooth, unbroken, non-adhesive film of solder on the base metal.

 Solderability is a property of a metal surface that allows it to be wetted with solder.

The process of soldering a printed circuit assembly involves simultaneously applying heat and solder.

For manual soldering and tinning the following are used:

• flux: pine rosin grade “A” GOST 19113-84, requiring cleaning after soldering;
• alcohol-rosin flux FKSp OST 4G 0.033.200, requiring cleaning;
• flux MF 210 (X33-12i), which does not require cleaning, from Multicore Solders (England);
• flux WF-9942, which does not require cleaning, INDIUM Corporation (USA);
• solder wires of various diameters, brand POS-61;
• tubular solders of various diameters, brand POS-61, with flux that requires cleaning;   
• multi-channel tubular solders of various diameters, brands 60EN X39, 60EN Crystal 502 from Multicore Solders (England), CW-801 from INDIUM Corporation (USA), JM-20 from KOKI (Japan), containing flux that does not require cleaning;   
• alcohol-gasoline washing liquid (a mixture of ethyl alcohol and nefras);
• flushing liquid VIGON EFM from ZESTRON (Germany).

FLUXES

Fluxes are necessary to ensure high quality solder joints.

The purpose of fluxes is to dissolve oxides and sulfides that prevent solder from wetting metal surfaces, protect soldered surfaces from re-oxidation, reduce the surface tension of molten solder at the metal-solder-flux interface, and improve the spreadability of solder. 

When manual soldering, flux must be applied only to the areas to be soldered.

The need to remove flux residues after soldering is indicated in the technological processes.

• Fluxes MF 210 (X33-12i), WF-9942, no-clean, low solids, do not contain halogens (corrosive components), leave virtually no residue after soldering. Transparent flux residues after soldering are compatible with moisture-proof coatings on boards. Fluxes MF 210, WF-9942 have a high ability to penetrate through metallized holes.
• Flux FKSp OST 4G 0.033.200 leaves residues on the board that require washing with an alcohol-gasoline mixture.
• Flux “pine rosin grade “A” in a solid state is used to clean the tips of the fingertips from carbon deposits.     

SOLDER

Solder is a metal alloy used to create mechanical connections between electronic components and printed circuit board pads.

The diameter of the wire or tubular solder should be half the diameter of the soldering iron tip.

Domestic solders brand POS 61 – alloy of tin (61%) and lead (39%),

example notation: 

• PRv KR1 POS 61 GOST 21930-76 – solder wire, round, 1 mm in diameter, tin-lead;
• POS 61T1A GOST 21930-76 – tin-lead solder, tubular, 1 mm in diameter, single-channel, filler – pine rosin grade “A” flux.

Imported tubular solders:

• SN62 X39 – alloy of tin (62%), lead (36%), silver (2%), multi-channel tubular solder f. Multicore Solders (England), contains 1% solid flux X39, which does not require cleaning. The presence of silver in solder increases the mechanical strength of solder joints and prevents the migration of silver from the contact surfaces of electronic components into the solder during the soldering process.
• 60EN X39 – alloy of tin (60%) and lead (40%), multi-channel tubular solder f. Multicore Solders, contains 1% solid flux X39, which does not require cleaning. Analog – JM-20 solder from KOKI (Japan),
• СW-801 - alloy of tin (63%) and lead (37%), multi-channel tubular solder f. Indium (USA), contains 2% CW-801 flux, which does not require cleaning.
• 60EN Crystal 502 - an alloy of tin (60%) and lead (40%), multi-channel tubular solder, contains 3% Crystal solid flux, which does not require cleaning. Used for soldering metals with a high melting point, such as nickel.

Multichannel solders (up to 5 flux channels in a solder rod, see Fig. 1) have an advantage over single-channel ones:      

the increased number of flux channels ensures uniform distribution of flux without gaps along the length of the rod, which prevents the possibility of dry soldering - without flux, as is the case with single-channel solders.

After soldering, the flux in imported solder leaves transparent residues around the soldering area that do not interfere with inspection and are electrically insulating (non-conducting currents).

Rice. 1. Cross-section of a multi-channel solder rod

WASHING LIQUIDS

Flushing liquids are designed to clean solder joints and printed circuit boards from contamination in order to ensure the operational durability of products.

There are three main sources of pollutants:

Printed circuit boards (typical contaminants include:

• fat from processing;
• food residues;
• tobacco;
• epoxy resin;
• fiberglass;
• internal copper contamination).

PCB mounted components (typical contaminants include:

• fat from processing,
• leftover food products,
• tobacco,
• defects in component materials,
• internal contamination of component leads).

Soldering technology used (typical contaminants include:

• flux,
• flux residues
• solder balls,
• internal contamination of the solder,
• fat from processing,
• leftover food products,
• tobacco.

1. The washing liquid “alcohol-gasoline mixture” is used to remove residues of alcohol-rosin flux, mechanical contaminants, dust, grease prints, but does not remove salts released from board coatings, components, or fingerprints. After washing with an alcohol-gasoline mixture, whitish stains remain on the board.

2. VIGON EFM washing liquid (based on alcohol compounds) is used to remove flux residues from the printed circuit assembly during manual cleaning and repair. Effectively removes grease and salt contaminants, solder balls, chemical residues from the etching process in the manufacture of printed circuit boards, flux activators, which, under intense operating conditions of products, can lead to corrosion processes on the board.

3. The washing liquid is applied to the area to be cleaned with a KFK file brush and dried in air. If there is a large amount of flux residue on the board after soldering, you can wash the board by placing a cotton napkin on it and applying washing liquid to the napkin with a brush.  

The need to clean the printed circuit assembly after soldering with flushing liquids is indicated in the technological processes.

PREPARATION FOR WORK

when working with personal soldering irons of the BM type and copper tips of our own factory production (including Solomon soldering irons equipped with copper tips of our own factory production):  

The tip of the pin (tip) can be of different shapes and sizes for the best contact and heat transfer to the soldered surfaces.

The copper tip of the soldering iron must be cleaned of carbon deposits and oxide with rosin: dip the heated tip into solid pine rosin flux and clean it on a calico napkin. If necessary, sharpen the copper tip for an individual soldering iron with a file.

Attention: When sharpening the soldering iron, sharp edges must be dulled.

Before tinning or soldering, the tip must be tinned. For this purpose, use wire or tubular solder: wrap several turns of solder (as shown in Figure 2) around the tip of the tip and heat it until the solder melts.

                                Rice. 2. Maintenance of the soldering iron tip

when working with original soldering irons of PACE, HAKKO, Solomon, Lukey soldering stations using original imported tips:

It is strictly forbidden to strip the original soldering iron tips.

Source: https://gostost.ru/paika-pechatnie-platy/

Solders

Radio electronics for beginners

At the beginning of their amateur radio activities, many novice radio amateurs rarely ask themselves about the types of solders and what their properties are.

To assemble the simplest homemade devices, the most common POS-61 or similar is sufficient. As they say: “It would be something to solder with”

You don't even have to buy solder. It is enough to take an old printed circuit board from some electronic device and assemble it with a heated soldering iron tip from the soldered contacts.

This method of “extraction” is especially relevant for those who live far from cities and large populated areas, where there is no opportunity to visit a radio store.

Solder collected from printed circuit boards

But still, solder to solder is different. In his practice, a person dealing with electronics must understand the issue of his choice. Therefore, we will consider in detail what types of solders there are, what they are used for, which one is better to use for installing electronic circuits and repairing household radio equipment.

What types of solders are there?

Solders are divided into soft (low-melting) and hard. For the installation of radio equipment, low-melting ones are used, i.e. those whose melting temperature ranges from 300 to 4500C. Soft solders are inferior in strength to hard solders, but they are used for assembling electronic devices.

Solder is an alloy of metals. For low-melting solders, this is usually an alloy of tin and lead. It is these metals that make up the majority of the alloy. Alloying metals may also be present in it, but their quantity in the composition is small. Impurities of other metals are introduced into the alloy to obtain certain characteristics (melting point, ductility, strength, corrosion resistance).

The most widely used type of solder is POS (Tin-Lead Solder). Next, a brief designation of its brand is followed by a number that shows the percentage of tin in it. So POS-40 contains 40% tin, and POS-60, respectively, 60%.

It happens that solder of an unknown brand comes into use. Its composition can be roughly assessed by indirect signs:

• Solders of the tin-lead group have a melting point of 183 – 2650C.

• If the solder has a bright metallic sheen, then it contains a fairly high tin content (POS-61, POS-90).

  And, conversely, if it is dark gray in color and the surface is matte, then this indicates a high lead content. It is lead that gives the surface a peculiar grayish tint.

• Solders containing a lot of lead are very ductile.

  So, for example, a solder bar with a diameter of 8 mm. with a high lead content (POS-30, POS-40) is easily bent by hand. Tin, unlike lead, gives the alloy strength and rigidity. If there is a lot of tin in the alloy, then it will no longer be possible to bend such a rod easily.

POS-40 (bar)

Let's consider the purposes for which solders of the tin-lead group (POS) are used.

• POS-90 (Sn 90%, Pb 10%). Used for repairing food utensils and medical equipment. As you can see, it contains a small lead content (10%), which is quite toxic and its use in things that come into contact with food and water is unacceptable.

• POS-40 (Sn 40%, Pb 60%). Mainly used for soldering electrical equipment and parts made of galvanized iron, used for repairing radiators, brass and copper pipelines.

• POS-30 (Sn 30%, Pb 70%). It is used in the cable industry, and is also used for tinning and soldering zinc sheets.

• And finally, POS-61 (Sn 61%, Pb 39%). Same as POS-60. I don't think there's much difference between them.

POS-61 is used for tinning and soldering printed circuit boards of radio equipment. It is mainly used as a material for assembling electronics. Its melting point starts at 1830C, and complete melting is achieved at a temperature of 1900C.

Soldering with such solder can be done using a conventional soldering tool without fear of overheating of the radioelements, since its complete melting is achieved already at 1900C.

POS-30, POS-40, POS-90 completely melt at temperatures of 220 – 2650C. For many radio-electronic components, this temperature is subcritical. Therefore, it is better to use POS-61 for assembling homemade electronic devices.

A foreign analogue of POS-61 can be considered Sn63Pb37 (63% tin, 37% lead). It is also used for soldering radio equipment and for making homemade electronics. Radio amateurs choose it as an alternative to the domestic POS-61.

As a rule, any solder is sold in coils or tubes of 10 ~ 100 grams. The composition of the alloy is indicated on the packaging, for example, like this: Alloy 60/40 (“Alloy 60/40” - also known as POS-60). It has the shape of a wire of different diameters (from 0.25 to 3 mm).

It is also not uncommon that it contains flux (FLUX), which fills the core of the wire. flux is indicated as a percentage (usually from 1 to 3.5%). This form factor is very convenient. During operation, there is no need to separately supply flux to the soldering area.

One of the varieties of POS solders is POSSu . Yes, if you say it out loud, it doesn’t sound very presentable.

But, despite this, tin-lead solder with antimony (this is how the abbreviated designation stands for) is used in the automotive industry, in refrigeration equipment, for soldering the windings of electrical machines, elements of electrical equipment, winding parts and cable products. Well suited for soldering galvanized parts. In such an alloy, in addition to lead and tin, there is from 0.5% to 2% antimony.

Solder	Initial melting t0 (Solidus)	Full meltdown (Liquidus), t0
POSSu-61-0.5	183	189
POSSu-40-2	185	229
POSSu-40-0.5	183	235
POSSu-30-2	185	250
POSSu-30-0.5	183	255

As we can see from the table, POSSu-61-0.5 solder is most suitable for replacing POS-61, since it has a complete melting temperature of 1890C.

It is worth noting that there is also a completely lead-free tin-antimony solder POSu 95-5 (Sn 95%, Sb 5%). Its melting point is 234 – 2400C.