Melting point of tin for soldering microcircuits

Greetings to dear readers! In this material I tried to collect all the data about PIC solder. This Tin-Lead Solder is the most popular solder for mounting radio components and is used more often than others in radio engineering. I will try to explain why this is so and tell you about the types and technical characteristics of POS series solders. I’ll also tell you a terrible secret about POS-60 and POS-62 solders. Go!

Melting point and other properties of tin and lead based solders

The table shows the melting point of solders of common brands based on tin and lead, as well as their thermophysical and mechanical properties.
The properties of solders are given at room temperature. The table shows the following properties: melting point of solders (solidus and liquidus) in degrees Celsius, solder density, electrical resistivity, thermal conductivity, tensile strength, elongation, impact strength, Brinell hardness, HB.

The melting point of solders (liquidus - the liquid state of solder) based on lead and tin is in the range from 145 to 308 ° C. It should be noted that the melting temperature of the solder, equal to 145°C, corresponds to POSK 50-18 solder, which belongs to the category of low-melting solders. At a temperature of 308 degrees Celsius, POSSu 5-1 solder is in liquid form.

The properties of the following solders are considered: POS 90, POS 61, POS 40, POS 10, POS 61M, POSK 50-18, POSSU61-0.5, POSSU 50-0.5, POSSU 40-0.5, POSSU 35-0, 5, POSSU 30-0.5, POSSU 25-0.5, POSSU 18-0.5, POSSU 95-5, POSSU 40-2, POSSU 35-2, POSSU 30-2, POSSU 25-2, POSSU 18 -2, POSSU 15-2, POSSU 10-2, POSSU 8-3, POSSU 5-1, POSSU 4-6.

According to the table, it can be seen that the density of solders varies from 7300 to 11200 kg/m3 . The solder with the minimum density is tin-lead solder POSu 95-5. The heaviest of the solders considered is POSSu 5-1 solder - the density of such solder is 11200 kg/m 3.

The thermal conductivity of solders in the table is given in kcal/(cm·s·deg). Solders with maximum thermal conductivity are POS 90 and POSK 50-18 - their thermal conductivity is 0.13 kcal/(cm s deg).

Technical characteristics of POS-10 solder

POS 10 solder has a distinctive chemical composition. It contains 9-10% tin, about 89% lead, 0.2% bismuth, 0.1% antimony and other impurities in small quantities. POS-10 solder is used for soldering and tinning contact surfaces of electronics. For example, they solder relays and fill control plugs in radio electronics housings.

The POS-10 soldering temperature is 299 degrees Celsius. The solidus point is 268 degrees.

Advantages of POS-10 solder:

• high melting point is useful when soldering equipment cases.

Disadvantages of POS-10 solder:

• low strength and tensile strength of about 3.2 kgf/sq.mm.;
• high resistivity - 0.2 Ohm x sq.mm./m;
• high content of lead, which is hazardous to health.

Melting temperature of solders and low-melting alloys

The table shows the melting temperatures of solders and low-melting alloys based on mercury Hg, cesium Cs, potassium K, bismuth Bi, thallium Tl, indium In, tin Sn, lead Pb, cadmium Cd, Wood's alloy, Rose alloys, gold Au , magnesium Mg, zinc Zn, silver Ag.

The melting temperatures of solders and alloys in the table are given starting with the most fusible alloys and range from -48.2 to 262°C. In alloys with a negative melting point (from minus 48.2°C), the content of mercury and alkali metals predominates. Low-melting alloys with a melting point from 200 to 260°C have a predominant content of bismuth and thallium in their composition.

Note: eut - eutectic alloys or close to them; For non-eutectic alloys, solidus temperatures are given.

Melting temperature of tin for soldering, POS-40 and POS-60 solder, technical characteristics

Solder is a metal or mixture of metals used in soldering to join parts together. Typically, alloys based on tin, copper and nickel are used. Tin-based solder is included in the group of low-melting solders.

And the melting temperature of the solder here does not exceed 450 °C. These compounds are widely used to work with radio equipment.

Solders based on tin and lead are very common; they are widely used in our metal industry: the abbreviation POS.

To assemble homemade devices of the simplest design, the most common solder POS-61 or similar is sufficient. The alloy can be obtained from an old printed circuit board from an electronic device and assembled with a soldering iron from the soldered contacts.

Types and characteristics of solders

They are soft (low-melting) and hard. For installation of radio equipment, low-melting materials are used, with a melting point of 300−450 °C. Soft solders are inferior in strength to hard solders, although they are the ones used for assembling electrical appliances.

Low-melting alloys are usually an alloy of lead and tin primarily. There are few alloying elements.

Impurities of other metals are introduced to obtain certain characteristics:

• plasticity;
• melting point;
• strength;
• corrosion resistance.

The number in the brand designation indicates the percentage of tin it contains. So, the technical characteristics of POS-40 solder are such that it contains 40% Sn, and POS-60 - 60%.

If the brand is unknown, the composition can be assessed by indirect signs:

• The melting point of POS is 183−265 °C.
• If the solder has a metallic sheen, it means there is a lot of Sn in it (POS-61, POS-90). If the color is dark gray and the surface is matte, this indicates a high lead content, which is what gives the grayish tint.
• Solders containing large amounts of lead are very ductile, and tin imparts strength and rigidity.

Use of tin-lead group alloys

These alloys include the following:

• POS-90 contains: Pb - 10%, Sn - 90%. Used for repairing medical equipment and food utensils. There is little toxic lead, as it should not come into contact with food and water.
• POS-40: Pb - 60%, Sn - 40%. Mainly used for soldering electrical equipment and galvanized iron products; it is also used to repair radiators, brass and copper pipelines.
• POS-30: Sn - 30%, Pb - 70%. Used in the cable industry, for soldering and tinning and zinc sheeting.
• POS-61: Pb 39%, Sn 61%. Like with POS-60. There's not much difference.

Using POS-61, tinning and soldering of printed circuit boards of radio equipment is carried out. This is the main material for assembling electronics. It begins to melt at 183 °C, complete melting at 190 °C. You can solder with this solder using an ordinary soldering iron without fear that the radioelements will overheat.

POS-30, POS-40, POS-90 melt at 220−265 °C. For many radio-electronic elements this temperature is subcritical. It is better to assemble homemade electronic devices with POS-61, whose foreign analogue can be considered Sn63Pb37 (where Sn is 63% and Pb is 37%). It is also used to solder radio equipment and homemade electronics.

Solders are usually sold in tubes or coils of 10-100 g. The composition of the alloy can be read on the packaging, for example: Alloy 60/40 (“Alloy 60/40” - POS-60). It looks like a wire with a diameter of 0.25-3 mm.

It often contains flux (FLUX), which fills the core of the wire . indicated as a percentage and amounts to 1−3.5%. Thanks to this form factor, there is no need to supply flux separately during operation.

A variety of POS - POSSu is a tin-lead alloy with antimony, and is used in the automotive industry, in refrigeration equipment, for soldering electrical equipment elements, electrical machine windings, cable products and winding parts; Suitable for soldering galvanized parts. In addition to lead and tin, the alloy contains 0.5−2% antimony.

As the table shows, POSSU-61−0.5 is most suitable for replacing POS-61, because its complete melting temperature is 189 °C. There is also a completely lead-free , tin-antimony POSu 95−5 (Sb 5%, Sn 95%) with a melting point of 234−240 °C.

There are solders designed specifically for soldering parts that are highly sensitive to overheating. The most “high-temperature” among low-temperature ones is POSK-50−18 with a melting point of 142−145 °C. POSK-50−18 contains 8% cadmium, 50% tin and 32% lead. Cadmium enhances corrosion resistance, but at the same time imparts toxicity .

In descending order of temperature comes ROSE (Sn 25%, Pb 25%, Bi 50%), marked POSV-50. T pl. - 90−94 °C. Designed for soldering brass and copper. This alloy contains 25% tin, 25% lead, and 50% bismuth.

The ratio of metals in percentage may vary slightly, and their quantity is usually indicated on the package in the “Composition” column. This solder is extremely popular among electronics engineers. Used when dismantling/installing elements sensitive to overheating.

Among other things, the alloy is ideal for tinning the copper tracks of a brand new printed circuit board.

Used in protective fuses in radio equipment.

An even lower temperature WOOD alloy (Sn 10%, Cd 10%, Pb 40%, Bi 40%). Melting point - 65−72 °C. Since the alloy contains 10% cadmium, it is toxic, unlike ROSE.

Both ROSE and WOOD are quite expensive solders.

Density of solders and babbits, their thermal conductivity and thermal conductivity

The tables give the thermophysical properties of some solders and babbitts (anti-friction bearing materials) at room temperature. Properties such as density, coefficient of thermal expansion and thermal conductivity are presented.

The properties of the following solders and babbitts are indicated: POS-30, POS-18, PSr45, POTs70, POTs60, 34A, eutectic silumin; babbits, B83, B16, BKA, B88, B89, B6.

It should be noted that the density of solders, coefficient of thermal expansion (CTEL) and thermal conductivity of solders and babbitts have similar values, with the exception of solder 34A and eutectic silumin, which are 2-4 times lighter.

Composition and thermal conductivity of solders and babbitts at different temperatures

The table shows the composition and value of the thermal conductivity coefficient of aluminum antifriction alloys, babbitts and solders at temperatures from 4 to 300 K (from -269 to 27 ° C).

The following solders and bearing materials were considered: AN2.5, AO6-1, BKA, B16, B83, B88, POS61, POS18, POSSu18-2, POSSu40-2, Wood's alloy, Rose's alloy, PSr25, PSr44, PSr70.

The most thermally conductive antifriction alloy, according to the table, is the AO6-1 alloy - its thermal conductivity is 180 W/(m deg). Silver solder PSr70 (based on silver and copper) has the highest thermal conductivity among the considered solders - the thermal conductivity of this solder is 170 W/(m deg).

Sources:

1. Physical quantities. Directory. A.P. Babichev, N.A. Babushkina, A.M. Bratkovsky and others; Ed. I.S. Grigorieva, E.Z. Meilikhova. - M.: Energoatomizdat, 1991. - 1232 p.
2. Chirkin V.S. Thermophysical properties of nuclear technology materials.
3. Tables of physical quantities. Directory. Ed. acad. I.K. Kikoina. M.: Atomizdat, 1976. - 1008 p.
4. Non-ferrous metals. Directory. - Nizhny Novgorod: "Venta-2", 2001. - 279 p.

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Solder

- a material [1] used in soldering to join workpieces and having a melting point lower than the metals being joined. Alloys based on tin, lead, cadmium, copper, nickel, silver and others are used.

There are non-metallic solders [2].

The service life of a solder joint depends on the correct soldering technology and environmental parameters during operation.

Description [edit | edit code ]

Solders are produced in the form of granules, rods, wire, powder, foil, pastes and embedded parts.

Soldering is carried out either to create a mechanically strong (sometimes hermetically sealed) seam, or to obtain electrical contact with low contact resistance. When soldering joints, the solder is heated above its melting point. Since solder has a melting point lower than the melting point of the metal (or metals) being joined, from which the parts being joined are made, it melts, while the metal of the parts remains solid. At the interface between molten solder and solid metal, various physical and chemical processes occur. Solder wets the metal, spreads over it and fills the gaps between the parts being connected. In this case, the components of the solder diffuse into the base metal, the base metal dissolves in the solder, resulting in the formation of an intermediate layer, which, after solidification, connects the parts into one whole.

Solder is selected taking into account the physical and chemical properties of the metals being joined (for example, melting point), the required mechanical strength of the solder, its corrosion resistance and cost. When soldering live parts, it is necessary to take into account the specific conductivity of the solder.

The fluidity of low-temperature solders makes it possible to solder products of complex shapes.

Classification of solders [edit | edit code ]

Solders are usually divided into two groups:

Soft solders include those with a melting point of up to 300 °C, and hard solders - above 300 °C. In addition, solders vary significantly in mechanical strength. Soft solders have a tensile strength of 16-100 MPa, and hard solders - 100-500 MPa.

Soft solders include tin-lead alloys (POS) with a tin content of 10 (POS-10) to 90% (POS-90), the rest is lead. The electrical conductivity of these solders is 9-15% of the electrical conductivity of pure copper. Melting of these solders begins at a temperature of 183 °C (melting point of the eutectic of the tin-lead system) and ends at the following liquidus melting temperatures:

Solders POS-61 and POS-63 melt at a constant temperature of 183 °C, since their composition practically coincides with the composition of the tin-lead eutectic.

In addition to these compounds, the following are also used as soft solders:

• antimony solders (POSSu), used for soldering galvanized and zinc products and increased requirements for the strength of the soldered joint,
• tin-lead-cadmium (POSK) for soldering parts sensitive to overheating and soldering leads to capacitors and piezoceramics,
• tin-zinc (TS) for aluminum soldering,
• lead-free solders containing, along with tin, copper, silver, bismuth and other metals.

Brazing alloys [ edit | edit code ]

The most common hard solders are copper-zinc (PMZ) and silver (PSr) with various additives:

Melting temperatures of PSR and PMC grade solders:

PSr-10 - 830 °C. PSr-12 - 785 °C. PSr-25 - 765 °C. PSr-45 - 720 °C. PSr-65 - 740 °C. PSr-70 - 780 °C. PMC-36 - 825 °C. PMC-42 - 833 °C. PMC-51 — 870 °C

Copper-phosphorus solders are widely used. Copper-phosphorus solders include alloys of copper and tin with phosphorus additives. Such solders are used for soldering copper, copper alloys, silver, cast iron, and hard alloys.

Melting temperatures of copper-phosphorus solders:

P81 - 660 °C P14 - 680 °C MF7 - 820 °C P47 - 810 °C

Silver solders [edit | edit code ]

Silver solders have a melting point from 183 to 1133 ° C and are silver-lead-tin alloys; silver-lead; silver-copper; silver-copper-zinc; silver-copper-zinc-cadmium; etc.

Silver solders have a fairly wide range of applications:

• tinning and soldering of copper, copper-nickel alloys, nickel, kovar, nickel silver, brass and bronze;
• soldering iron-nickel alloys with silver-plated steel parts;
• soldering steel with copper, nickel, copper and copper-nickel alloys;
• soldering copper with nickel-plated tungsten;
• soldering titanium and titanium alloys with stainless steel;
• soldering of copper and copper alloys with heat-resistant alloys and stainless steels;
• soldering of copper and brass with kovar, nickel, stainless steels and heat-resistant alloys, soldering of lead-tin bronzes;
• soldering and tinning of copper, nickel, copper and copper-nickel alloys with silver-plated ceramics, soldering of silver-plated parts;
• soldering of copper and nickel with glass enamel and ceramics;
• soldering and tinning of jewelry;
• soldering copper to bronze, copper to copper, bronze to bronze;
• soldering of copper, copper alloys and steels over a freshly deposited copper galvanic coating with a thickness of at least 10 microns;
• soldering and tinning of non-ferrous metals and steels;
• soldering and tinning of silver parts.

Technical characteristics of POS-61 solder

The designation of solder, as we found out, is quite controversial, but you can’t argue against GOST. POS-61 is used for soldering and tinning of electronic components and printed circuit boards of precision instruments with highly hermetic seams, for which overheating is not allowed.

Composition of POS-61 solder

The chemical composition of POS-61 solder is as follows:

• Tin 59 - 61%;
• Antimony - no more than 0.1%;
• Copper - no more than 0.05%;
• Bismuth - no more than 0.02%;
• Arsenic - no more than 0.02%;
• Iron - no more than 0.02%;
• Nickel - no more than 0.02%;
• Sulfur - no more than 0.02%;
• Zinc - no more than 0.002%;
• Aluminum - no more than 0.002%;
• Lead - everything else - about 38.7 - 40.7%.

The soldering temperature of POS-61 solder is 220 degrees Celsius. Solidus is 183 degrees. I even shot a slow motion video of this solder melting on my Olympus Tough TG-860 at 240fps.

Solder POS 61 GOST 21931-76 has the following technical characteristics:

• Density determines weight and is equal to 8.5 g/cu. cm.;
• The electrical resistivity is 0.139 Ohm x mm2/m;
• Thermal conductivity is 0.12 kcal/cm x s x deg;
• Temporary tensile strength is 4.3 kgf/sq.mm.;
• The relative elongation is 46%.

Advantages of POS-61 brand solder:

• the best ratio of melting temperature and strength;
• good adhesion to metal surfaces;
• universal solder for soldering and most radio installation work;
• accessibility and prevalence;
• low cost;
• often produced in the form of wire, for example POS 61 T2A solder.

Disadvantages of POS-61 type solder:

• versatility reduces performance in special cases, for example when soldering zinc;
• melting temperature is not suitable for all devices;
• solder fumes (lead in it) are harmful to health.

Other [edit | edit code]

Special types of metal alloys not related to solders themselves are used in electric vacuum technology for electrical leads that are fused into glass and operate at relatively low temperatures, when the use of refractory but relatively expensive metals (tungsten, molybdenum, platinum) is not required. For these materials, the temperature coefficient of linear expansion ( α l > ) is of particular importance, which, in order to obtain a vacuum-tight input, must be matched as accurately as possible with α l > glass. For example, kovar (alloy grade 29NK), used for the manufacture of electrical leads through glass flasks for various gas-filled and electric vacuum electronic devices and lighting lamps, has an approximate composition: Ni - 29%, Co - 18%, Fe - the rest; its resistivity is about 0.49 μOhm m, and α l > about 4...5·10 −6 K −1.

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.

Melting point of tin for soldering microcircuits

Working with microcircuits is very delicate, as they are complex devices with many contacts. All of them are made in fairly small sizes, so if you need to solder something, then you need to select the appropriate equipment and consumables, not to mention experience working with such things.

Naturally, to facilitate the work, it is necessary that the temperature of the solder be relatively low, so that the temperature does not damage other parts located nearby. When choosing which solder to use for soldering microcircuits, you need to pay attention to its quality.

Even at a high cost, it will be quite justified, since during soldering of this kind a relatively small amount of material is used.

Using solder when soldering a microcircuit

Solder is used both in the private sphere, among many radio amateurs, and in factory production and repair shops. Unlike other varieties, when choosing which solder to solder microcircuits with, you need to pay attention not to strength, temperature resistance and other mechanical parameters. Electrical conductivity, soldering properties and melting point are more important here.

Suitable brands

There are different types of solders for soldering, but it is worth highlighting the most suitable for working with microcircuits that can be found on the modern market. One of the most common options is POS 61. It has the following chemical composition:

The technical characteristics of the material are as follows:

An analogue from the same POS 30 series can also be used. It is inferior in quality, but has a sufficiently low melting point to provide comfortable working conditions. Its composition has virtually no impurities:

The technical characteristics of this brand are as follows:

Criterias of choice

In addition to this, there are other brands, so people often have a question about which solder to choose for microcircuits, based on the parameters. First of all, you need to pay attention to the conductivity of the composition.

If it has high resistance, then it may not be suitable for complex circuits.

For ordinary home soldering, the criteria are not so significant, but if there is serious work to be done, then it is better to pay attention to silver solders rather than tin-lead solders, although they are cheaper.

Silver solders

One of the important parameters is the swimming temperature. There is no need for high strength and the temperature itself in the diagram will not rise above a hundred degrees. At a low melting point, solder melts better and adheres to the surface. It is also easier to remove residues that may stick if not handled carefully.

It is better if the material is made in the form of a rod or wire, as this is more convenient in practical use. After all, you need to measure out relatively small portions, therefore, you need to be able to take a minimum amount of material with a soldering iron.

"Important!

You should always have a supply of flux for the solder that will be used.”

Soldering Features

When choosing which solder is best for SMD soldering, it is worth considering that the soldering process itself has some differences. Firstly, for the job you need to choose a thin soldering iron that has a sharp flat tip. Its power should not exceed the melting point of the consumable material too much. Flux should be used liberally to improve the speed and reliability of the connection.

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.

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.

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.

Technical characteristics of POS-30 solder

Solder for soldering of the POS 30 brand is an intermediate link between POS 10 and POS 40. The composition of POS 30 solder is as follows: 30% tin and 69.5% lead. The rest is impurities and doping. Solder POS 30 can be easily replaced with POS 40, which is described below. The melting point (liquidus) is 238 degrees, and the plasticity temperature (solidus) is 183 degrees Celsius. According to the technical characteristics, POS 30 solder is most often used for soldering and tinning of zinc sheets and radiators.

Advantages of POS-30 solder:

• good adhesion;
• high strength.

Disadvantages of POS 30 brand solder:

• high lead content;
• often produced in rods.

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.

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.

Technical characteristics of POS-90 solder

POS-90 brand solder consists of 90% tin and 10% lead. It also contains about 0.1% antimony and 0.05% copper. It is mainly used for soldering and tinning internal seams of food utensils and medical equipment. Yes, 10% lead can already be put into food products - surprisingly, everything is in accordance with GOST 1976. According to the technical characteristics, the melting temperature of solder type POS 90 is 220 degrees.

Advantages of POS-90 solder:

• low lead content;
• rarely counterfeited;
• low resistance;
• high strength.

Disadvantages of POS-90 brand solder:

• high cost (higher than pos-61);
• low plasticity.

Brands of soft solders for soldering with a soldering iron

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.

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.

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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.

About the composition of solder

The name of the solder of the tin-lead group indicates the tin content in it. For example, POS-40 contains 40% tin, and POS-61 contains almost 61% tin. The rest consists of lead and additional impurities. By appearance, you can estimate the composition . If the PIC solder is more matte and dark, then it contains more lead. If it is lighter and shiny, then there is more tin. This is best understood by comparison. Look at the photo to see what a sheet of tin and a sheet of lead look like.

The strength of solder depends not only on the alloy alloy, but also on the metal being soldered. For example, to solder copper or zinc, several percent of copper or zinc are added to the POS solder, respectively. This reduces chemical erosion of the metal and increases the surface strength of the joint.

Solder alloying

To improve performance characteristics, alloying of solder with the following substances is used:

• adhesion is improved by the addition of copper, cadmium, antimony, aluminum, silver and zinc;
• ductility and resistance to thermal cycling are improved by the addition of indium, silver, manganese, bismuth, and lithium;
• Nickel, cobalt, zinc, silicon, boron, iron add strength
• The corrosion resistance of solder is increased by nickel and copper;
• Heat resistance is increased by silicon, zirconium, tungsten, vanadium, cobalt, niobium, hafnium.

Flux for soldering with a soldering iron

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.

Popular fluxes for soldering with an electric soldering iron

Soldering of metal joints occurs using various substances. Fluxes are divided into three main categories, differing in their area of ​​application and method of preparation. The process of preparing elements for work may vary; after soldering, it is necessary to remove residues in the manner described in the instructions.

1. Inactive rosin fluxes are used for soldering copper and other types of soft metals. There is a light rosin that is ready for use and does not include additional substances. Alcohol-rosin solution is made from components with a concentration of 1 to 5. It is used for soldering in hard-to-reach places, it is produced in powder form, and must be mixed with alcohol before use. Glycerin - rosin materials are used when a hermetic connection is necessary.
2. Active fluxes suitable for soldering precious and non-ferrous metals include zinc chloride, alcohol or petroleum jelly. The last parameter differs in its composition, when used in a liquid or paste state. It is more convenient to work with flux as a paste; it is possible to apply it directly to the product in the required amount.
3. Acid-active flux is divided into zinc chloride and phosphoric acid. It is performed in the form of liquid solutions or paste, using rosin, zinc chloride, alcohol or petroleum jelly.

Orthophosphoric acid consists of water, ethyl alcohol and the acid itself with a density of 1.7. It is used for soldering stainless materials, copper, and silver. Alcohol-based fluxes must be stored in airtight containers. A convenient container for storage is a nail polish jar, the brush does not react to the active medium, and the lid allows you to tightly close the container, avoiding evaporation of the 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.

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.

Diameter of holes

Solder Solder T 2.0 POS 61 is POS solder in the form of a tube with flux with a diameter of 2 mm. Supplied in a coil or reel

Other markings are possible. For example, Solder POS-61-T1 And this is also solder POS-61, but in the form of a tube with a diameter of 1 mm

If you come across the marking Solder POS-61 (wire d-3 mm), then this is POS-61 solder produced in the form of wire with a diameter of 3 mm, without rosin, supplied in the form of a coil.

Marking Solder POS-30 or Solder POS-30 ⌀8 means the same thing. This is POS-30 solder, supplied in the form of a rod with a diameter of 8 mm.

Solder “A”, what is it for?

Solder “A” is a tin-zinc alloy, with the obligatory alloying additives of copper and aluminum. Used for tinning the aluminum cable sheath before applying PIC solder. Pre-treatment of the cable surface with solder “A” dramatically increases the electrical and mechanical strength of the soldered contact. However, applying solder "A" requires a lot of attention and skill. Solder “A” is a fairly refractory solder and there is a risk of overheating the cable sheath if unsuccessful attempts are made to rub it with solder “A”. It is very important to use a high-quality gas burner with adjustable flame sharpness for this.

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.

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.

Tin-lead solders POS

Tin-lead solders in products, GOST 21931-76

Solders are filler metals (alloys) that, in the molten state, are capable of filling the gap between the products being soldered and, as a result of solidification, forming a permanent, strong connection.

Available in round wire, strip, triangular, round rods, flux-filled round tubes and powder

Some types of solders:

• POS - 90 - for tinning and soldering internal seams of food utensils and medical equipment;

• POSSU 4-4 - for tinning and soldering in the automotive industry.

Tin-lead solders in ingots, GOST 21930-79

This standard applies to tin-lead solders (PLS) in ingots and in products used mainly for tinning and soldering parts. The indicators of this standard correspond to the highest quality category.

Low antimony

Antimony

One of the main elements of electrical and radio installation work is soldering. The quality of installation is largely determined by the correct choice of the necessary solders and fluxes used when soldering wires, resistances, capacitors, etc.

To facilitate this choice, below is brief information about hard and light solders and fluxes, their use and their manufacture.

Soldering is the joining of hard metals using molten solder, which has a melting point lower than the melting point of the base metal.

The solder should dissolve the base metal well, spread easily over its surface, and well wet the entire soldering surface, which is ensured only if the wetted surface of the base metal is completely clean.

To remove oxides and contaminants from the surface of the metal being soldered, to protect it from oxidation and to provide better wetting with solder, chemicals called fluxes are used.

The melting point of fluxes is lower than the melting point of solder. There are two groups of fluxes: 1) chemically active, dissolving oxide films, and often the metal itself (hydrochloric acid, borax, ammonium chloride, zinc chloride) and 2) chemically passive, protecting only the surfaces to be soldered from oxidation (rosin, wax, stearin and etc.). .

Depending on the chemical composition and melting temperature of the solders, soldering is distinguished between hard and soft solders. Hard solders include solders with a melting point above 400°C, while light solders include solders with a melting point up to 400°C.

Basic materials used for soldering.

Tin is a soft, malleable metal with a silvery-white color. Specific gravity at a temperature of 20°C - 7.31. Melting point 231.9°C. It dissolves well in concentrated hydrochloric or sulfuric acid. Hydrogen sulfide has almost no effect on it. A valuable property of tin is its stability in many organic acids. At room temperature it is difficult to oxidize, but when exposed to temperatures below 18°C ​​it can transform into a gray modification (“tin plague”). In places where gray tin particles appear, the metal is destroyed. The transition of white tin to gray accelerates sharply when the temperature drops to -50°C. For soldering it can be used both in pure form and in the form of alloys with other metals.

Lead is a bluish-gray metal, soft, easy to process, and can be cut with a knife. Specific gravity at a temperature of 20°C is 11.34. Melting point 327qC. In air it oxidizes only from the surface. It dissolves easily in alkalis, as well as in nitric and organic acids. Resistant to the effects of sulfuric acid and sulfuric acid compounds. Used for the manufacture of solders.

Cadmium is a silver-white metal, soft, ductile, and mechanically fragile. Specific gravity 8.6. Melting point 321°C. It is used both for anti-corrosion coatings and in alloys with lead, tin, bismuth for low-melting solders.

Antimony is a brittle, silvery-white metal. Specific gravity 6.68. Melting point 630.5°C. Does not oxidize in air. It is used in alloys with lead, tin, bismuth, cadmium for low-melting solders.

Bismuth is a brittle silver-gray metal. Specific gravity 9.82. Melting point 271°C. Dissolves in nitric and hot sulfuric acids. It is used in alloys with tin, lead, and cadmium to produce low-melting solders.

Zinc is a bluish-gray metal. When cold it is fragile. Specific gravity 7.1. Melting point 419°C. In dry air it oxidizes, in humid air it becomes covered with a film of oxide, which protects it from destruction. When combined with copper, it produces a number of durable alloys. Easily dissolves in weak acids. Used for the manufacture of hard solders and acid fluxes.

Copper is a reddish metal, malleable and soft. Specific gravity 8.6 - 8.9. Melting point 1083 C. Dissolves in sulfuric and nitric acids and ammonia. In dry air it is almost impossible to oxidize; in damp air it becomes covered with green oxide. Used for the manufacture of refractory solders and alloys.

Rosin is a product of processing the resin of coniferous trees. Lighter varieties of rosin (more thoroughly purified) are considered the best. The softening temperature of rosin is from 55 to 83°C. Used as a flux for soft soldering.

Tin-lead solder in products and ingots GOST 21930-76, this standard applies to tin-lead solders used for tinning and soldering parts. Depending on the chemical composition, tin-lead solders are manufactured in the following grades:

Antimony-free - POS-90, POS-63, POS-61, POS-50, POS-40, POS-30, POS-10;

Low antimony - POSSU 61-05, POSSU 50-05, POSSU 40-05, POSSU 35-05, POSSU 30-05, POSSU 25-05, POSSU 18-05;

Antimony - POSSu 40-2, POSSu 30-2, POSSu 25-2, POSSu 18-2.

Tin-lead solders are manufactured in accordance with the requirements of this standard according to technological instructions approved in the prescribed manner. The chemical composition of solders must comply with the requirements of Table 1, the mass fraction of impurities is indicated in Table 2.

Chemical composition of tin-lead solders GOST 21931-76

Table 1

Impurity composition of tin-lead solders GOST 21931-76

table 2

Soft solders.

Soldering with soft solders has become widespread, especially during installation work. The most commonly used soft solders contain significant amounts of tin. In table Table 1 shows the compositions of some lead-tin solders.

Table 1

When choosing the type of solder, it is necessary to take into account its characteristics and use it depending on the purpose of the parts being soldered. When soldering parts that do not allow overheating, solders with a low melting point are used.

The most commonly used solder is POS-40 grade solder. It is used for soldering connecting wires, resistances, and capacitors. POS-30 solder is used for soldering shielding coatings, brass plates and other parts. Along with the use of standard grades, POS-60 solder (60% tin and 40% lead) is also used.

Soft solders are manufactured in the form of rods, ingots, wire (up to 3 mm in diameter) and tubes filled with flux. The technology of these solders without special impurities is simple and quite feasible in a workshop: lead is melted in a graphite or metal crucible and tin is added in small parts, the content of which is determined depending on the brand of solder. The liquid alloy is mixed, carbon deposits are removed from the surface and the molten solder is poured into wooden or steel molds. The addition of bismuth, cadmium and other additives is not necessary.

For soldering various parts that do not allow significant overheating, especially low-melting solders are used, which are obtained by adding bismuth and cadmium or one of these metals to lead-tin solders. In table Table 2 shows the compositions of some low-melting solders.

table 2

When using bismuth and cadmium solders, it should be taken into account that they are very brittle and create a less strong junction than lead-tin solders.

Hard solders.

Hard solders create high weld strength. In electrical and radio installation work they are used much less frequently than soft solders. In table Table 3 shows the compositions of some copper-zinc solders.

Table 3

The color of the solder changes depending on the zinc content. These solders are used for soldering bronze, brass, steel and other metals with a high melting point. PMC-42 solder is used when soldering brass containing 60-68% copper. PMC-52 solder is used for soldering copper and bronze. Copper-zinc solders are made by alloying copper and zinc in electric furnaces in a graphite crucible. As the copper melts, zinc is added to the crucible; after the zinc has melted, about 0.05% phosphorus copper is added. Molten solder is poured into molds. The melting temperature of the solder must be less than the melting temperature of the metal being soldered. In addition to the above-mentioned copper-zinc solders, silver solders are also used. The compositions of the latter are given in table. 4.

Table 4

Silver solders have great strength; the seams soldered by them bend well and are easy to process. PSR-10 and PSR-12 solders are used for soldering brass containing at least 58% copper, PSR-25 and PSR-45 solders are used for soldering copper, bronze and brass, PSR-70 solder with the highest silver content is for soldering waveguides , volumetric contours, etc.

In addition to standard silver solders, others are used, the compositions of which are given in table. 5.

Table 5

The first of them is used for soldering copper, steel, nickel, the second, which has high conductivity, is used for soldering wires; the third can be used for soldering copper, but is not suitable for ferrous metals; The fourth solder has a special fusibility and is universal for soldering copper, its alloys, nickel, and steel.

In some cases, commercially pure copper with a melting point of 1083°C is used as solder.

Solders for soldering aluminum.

Soldering aluminum is very difficult due to its ability to easily oxidize in air. Recently, aluminum soldering using ultrasonic soldering irons has found application. In table Table 6 shows the compositions of some solders for soldering aluminum.

Table 6

When soldering aluminum, organic substances are used as fluxes: rosin, stearin, etc.

The last solder (hard) is used with a complex flux, which includes: lithium chloride (25-30%), potassium fluoride (8-12%), zinc chloride (8-15%), potassium chloride (59-43%) . The melting point of the flux is about 450°C.

Fluxes.

Good wetting of solder joints and the formation of strong seams largely depends on the quality of the flux. At the soldering temperature, the flux should melt and spread in an even layer, and at the moment of soldering it should float to the outer surface of the solder. The melting point of the flux should be somewhat lower than the melting temperature of the solder used.

Chemically active fluxes (acid) are fluxes that in most cases contain free hydrochloric acid. A significant disadvantage of acid fluxes is the intense formation of corrosion of solder seams.

Chemically active fluxes primarily include hydrochloric acid, which is used for soldering steel parts with soft solders. The acid remaining on the surface of the metal after soldering dissolves it and causes corrosion. After soldering, the products must be rinsed with hot running water. The use of hydrochloric acid when soldering radio equipment is prohibited, since during operation it is possible to break the electrical contacts at the soldering points. Please note that hydrochloric acid causes burns if it comes into contact with the body.

Zinc chloride (etching acid), depending on the soldering conditions, is used in the form of a powder or solution. Used for soldering brass, copper and steel. To prepare the flux, it is necessary to dissolve one part by weight of zinc in five parts by weight of 50% hydrochloric acid in a lead or glass container. A sign of the formation of zinc chloride is the cessation of the release of hydrogen bubbles. Due to the fact that there is always a small amount of free acid in the solution, corrosion occurs at the soldering joints, so after soldering the joint must be thoroughly washed in running hot water. Soldering with zinc chloride should not be carried out in the room where the radio equipment is located. It is also prohibited to use zinc chloride for soldering electrical and radio equipment. Zinc chloride should be stored in a glass container with a tightly closed glass stopper.

Borax (aqueous sodium salt of pyroboric acid) is used as a flux when soldering with brass and silver solders. Easily dissolves in water. When heated, it turns into a glassy mass. Melting point 741°C. Salts formed during brown soldering must be removed by mechanical cleaning. Borax powder should be stored in hermetically sealed glass jars.

Ammonia (ammonium chloride) is used in powder form to clean the working surface of a soldering iron before tinning.

Chemically passive fluxes (acid-free).

Acid-free fluxes include various organic substances: rosin, fats, oils and glycerin. Rosin (in dry form or a solution in alcohol) is most widely used in electrical and radio installation work. The most valuable property of rosin as a flux is that its residues after soldering do not cause corrosion of metals. Rosin has neither reducing nor dissolving properties. It serves solely to protect the soldering area from oxidation. To prepare alcohol-rosin flux, take one part by weight of crushed rosin, which is dissolved in six parts by weight of alcohol. After the rosin has completely dissolved, the flux is considered ready. When using rosin, soldering areas must be thoroughly cleaned of oxides. Often, for soldering with rosin, parts must be pre-tinned.

Stearin is non-corrosive. Used for soldering lead sheaths of cables, couplings, etc. with especially soft solders. Melting point is about 50°C.

Recently, the LTI group of fluxes used for soldering metals with soft solders has become widely used. In terms of their anti-corrosion properties, LTI fluxes are not inferior to acid-free ones, but at the same time, they can be used to solder metals that previously could not be soldered, for example, parts with galvanic coatings. LTI fluxes can also be used for soldering iron and its alloys (including stainless steel), copper and its alloys and metals with high resistivity (see Table 7).

Table 7

When soldering with LTI flux, it is enough to clean the soldering areas only from oils, rust and other contaminants. When soldering galvanized parts, you should not remove zinc from the soldering area. Before soldering parts with scale, the latter must be removed by etching in acids. Pre-etching of brass is not required. Flux is applied to the joint using a brush, which can be done in advance. Flux should be stored in glass or ceramic containers. When soldering parts with complex profiles, you can use solder paste with the addition of LTI-120 flux. It consists of 70-80 g of petroleum jelly, 20-25 g of rosin and 50-70 ml of LTI-120 flux.

But fluxes LTI-1 and LTI-115 have one big drawback: after soldering, dark spots remain, and intensive ventilation is required when working with them. Flux LTI-120 does not leave dark spots after soldering and does not require intensive ventilation, so its use is much wider. Usually, flux residues after soldering do not need to be removed. But if the product will be used in severe corrosive conditions, then after soldering, flux residues are removed using ends moistened with alcohol or acetone. The production of flux is technologically simple: alcohol is poured into a clean wooden or glass container, crushed rosin is poured until a homogeneous solution is obtained, then triethanolamine is added, and then active additives. After loading all the components, the mixture is stirred for 20-25 minutes. The prepared flux must be checked for a neutral reaction with litmus or methyl orange. The shelf life of the flux is no more than 6 months.

PHYSICAL AND MECHANICAL PROPERTIES OF SOLDER

LOW FUSE SOLDER

1 For soldering of metals with a melting point of 200AC and above 2 For soldering to glass 3 Soldering of signal fuses 4 For soldering of aluminum and its alloys 5 For soldering of mounting wires with PVC insulation, winding wires, sealed seams, products made of hardened steel 6 For soldering of current-carrying parts made of brass, silver, tin-plated nickel 7 For soldering parts and assemblies for electroplating, silver, gold-plated (solder with high corrosion resistance) 8 For tinning and soldering of cable products 9 For tinning and soldering of current-carrying parts made of copper, zinc and their alloys, for soldering parts of devices and radio equipment, for tinning before soldering with lower-melting solders 10 Cheap solder for various jobs 11 Solder with increased creep resistance 12 Solder with high resistance to alkali corrosion 13 For soldering molybdenum and tungsten 14 For soldering silver, glass and ceramics 15 For soldering food utensils, containers for medicines and water (POS-90 solder is suitable for these purposes) 16 For soldering magnesium and its alloys 17 For soldering parts made of galvanized steel, zinc, copper alloys, for soldering external parts of devices

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.

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