Technical characteristics and melting temperature of POS 61 solder

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!

Types of POS solders

First, let's remember what types of solders are made from alloys of the tin-lead group. The most popular are antimony-free solders POS-10, POS-40, POS-61 and POS-90. POS solder containing antimony is called POSSU. Antimony in the solder adds several percent to its strength.

When we talk about melting a mixture of tin and lead, we need to remember the definitions of solidus and liquidus . When any mixture of two or more metals is heated, the melting (transformation from solid to liquid phase) of the lightest particles occurs first. This temperature mark is called the solidus of the alloy.

With a further increase in temperature, more refractory components begin to melt. As soon as they melt, the liquidus . The PIC solder is now completely melted. This process is explained in more detail by a picture taken from a presentation on the topic of alloys.

Between these two points is a state of increased ductility of the solder . In this state, the solder can be pulled and deformed without losing integrity.

There are eutectic alloys - solders, in which the solidus and liquidus points coincide. This is very convenient when soldering and indicates the high quality of the solder.

Chemicals for work

Due to the fact that the soldering iron tip is clean and dry, and the soldering technology involves fluxes, a set of chemicals is required. For high-quality work, the following list of fluxes is recommended:

• Rosin is a universal and popular substance, without which no soldering worker will start working. Application is mandatory. Sold dry.
• Flux LTI-120 is a chemically active substance that contains orthophosphoric acid for removing oxides from metal. The principle of action is the same as that of ordinary rosin. Used to work with oxidized metal. There is no need to rinse off after completing the process.
• Flux F-38M is an active acidic substance that must be washed off after work. Used for soldering nichrome, aluminum, stainless steel. Washable with low-fat gasoline.
• Soldering acid, a cheaper version of F-38M flux. It is used in exceptional cases, as it tends to corrode metal. Helps with soldering stainless steel, bronze, nickel, nichrome.
• Glycerin is an oily liquid, does not have oxidizing properties, is safe, and does not harm products. Wash off with plain water.
• Homemade flux - add 200 grams of ethyl alcohol to 200 grams of isobutyl alcohol; vodka is not suitable as it contains water. 50 grams of glycerin and 100 grams of rosin are added to the alcohol mixture. The result is a concentrated solution that has inactive properties and is washed off with water.
• TT indicator flux . Gel density. It has a paste-like structure, does not flow, and does not require cleaning. The manufacturer's recommendation is on the label: do not wash off, protects contacts from oxidation.

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.

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.

Technical characteristics of POS and POSSu solders

In order not to describe all the technical characteristics of solders of the tin-lead group, I will simply provide a table of parameters. It can be used to determine the melting point, density, electrical resistivity, thermal conductivity, tensile strength, elongation, impact strength and Brinell hardness of solders.

An analysis of the table shows that the most fusible among the list is cadmium with a melting point characteristic of 145 degrees Celsius. The strongest solder is POSSu 4-6 solder with a tensile strength of 6.5 kgf/sq.m. mm.

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.

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.

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.

Technical characteristics of POS-40 solder

The chemical composition consists of 39-41% tin, 59% lead. The remaining impurities are in the same ratio as in POS-10. Soldering solder POS-40 is often used for soldering and tinning radio equipment casings made of galvanized iron with galvanized seams.

The soldering temperature of the solder is 238 degrees Celsius, and the solidus is 183 degrees.

Advantages of POS-40 solder:

• good ratio of ductility and melting point;
• because of this, it tolerates thermal cycling better than POS-61.

Disadvantages of POS-40 solder:

• high lead content, which is harmful to health;
• elevated liquidus temperature.

The terrible secret of POS-60 solder

Now the time has come for the terrible secret of POS 60 solder . According to GOST 21930-76 entitled “Tin-lead solders in ingots. Technical specifications" and GOST 21930-76 "Tin-lead solders in products. Technical specifications", solder such as POS-60 simply does not exist. GOST 21930-76 itself can. Here is the complete table from this GOST.

So “ POS-60 ” is jargon or a popular designation for “the solder that everyone solders with.” It seems to me that this is due to confusion in the designation of POS-61. Because when the tin content in the solder according to GOST is from 59 to 61%, it is more logical to call it POS-60 rather than POS-61.

Among the solders produced according to international standards there is Sn60Pb40 solder . This is a solder solder containing 60% tin and 40% lead. It could be called POS-60, if at least specifications for it were developed. According to international data describing the characteristics, the melting point of 60/40 solder is 191 degrees Celsius.

The same story with POS-62 type solder . Such lead solder according to GOST has not yet been invented. So, if they ask me “what is the melting temperature of POS-62 solder,” I know that the answer with the figure 184 degrees Celsius must be looked for in the imported solder catalog. For example, you can use the Kester solder catalog.

General information about soldering

What is more important in a soldering job: the tool or the material? Everything is important: the soldering iron, the solder, and the flux. The variety of soldering irons is related to the object of soldering. Massive parts are heated with powerful soldering irons, and microscopic circuits of chips are heated with low-power ones. Professional soldering workers use several types of these heating tools.

Classification of soldering irons by power:

• A soldering iron with a nichrome insert with a power of 25 watts is a common household tool used by craftsmen, radio amateurs, and electronics engineers. They are still popular to this day, quite cheap, and last up to 10 years. A metal insert in the form of a copper rod, the tip of which is cut at 60 degrees. It is used in 90% of cases that arise in business situations; even many repair shops use them.
• The second type is more powerful with a 40-watt heater and a nichrome insert, twice as heavy and larger than its 25-watt counterpart. Used for more complex work. The tip is sharpened into a wedge, similar to a screwdriver, but it cannot be used for screwing screws. This sharpening is made for the convenience of soldering massive parts, for heating up to 190 C. They are used by professionals, but not recommended for home use.
• The third type is a gas soldering iron, three in one. The soldering iron itself has a copper core sharpened for a needle. The second function is a hair dryer that can heat an object up to 600 degrees. Gas burner - in this case the nozzle is changed, the tool performs the functions of a gas burner, heats the parts to a temperature of 1300 degrees.
• The fourth type is a modern ceramic soldering iron. Champion compared to all presented instruments. It has a very thin tip, capable of soldering millimeter dots, and is used to perform very precise work. Power - 100 watts. It is equipped with a soldering station with a temperature range from 200 to 480 degrees. Among specialists it is used as a universal tool.

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.

Varieties

Individual types of product are characterized more by different appearance, rather than by the content of components in the product. These varieties include:

• wire 1-7 mm thick in increments of 0.5 mm is the most popular type, supplied in coils, used in conjunction with a torch and soldering iron;

Solder POS 61. Wire 5 mm

• additive with spruce rosin. The thickness of the additional layer in the form of a tube is 1 mm, which ensures good connection quality;

Solder POS 61 with rosin

• solder POS 61 rods of 8 mm, as well as other sections, are long thin elements that are widely used for soldering in domestic conditions;

• antimony-free, supplied in thin strips, no additives.

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Technical characteristics of POS-63 solder

Solder POS 63 is described in GOST and in the industry standard OCT 4G 0.033.200. POS-63 solder is understood as an alloy that consists of 63% tin and 37% lead. This is a kind of modernization of POS-61 solder, adjusted to the international standard J-STD 006B. Most are also labeled Sn63Pb37 . These are eutectic alloys with a melting point of 183 degrees Celsius.

POS-63 is used for soldering and tinning the leads of microcircuits and packaged radio components, printed circuit boards, wires and cables. In general, of modern solders, this is the most common. The technical characteristics of POS 63 solder are approximately the same as those of POS-61. But I haven’t found the exact values ​​yet.

Advantages of POS-63 solder:

• the most common POS series solder;
• relatively low melting point;
• coincidence of solidus and liquidus points;
• low cost;
• supplied in the form of wire filled with flux.

Disadvantages of POS-63 solder:

• often counterfeited, especially by the Chinese;
• contains lead, which increases the cost of recycling electronic equipment in accordance with modern safety standards.

Description of solder

The main requirement for the solder used is a lower melting temperature than the melting temperature of the workpiece. different together . In this regard, there are different types of materials that differ from each other in physical and chemical properties and are part of the alloy components.

So, there are two groups of solders: soft and hard. Soft ones are those whose melting point is below 300 degrees, therefore, the melting of hard solders will be above this value.

One of the most common filler materials is POS - tin-lead. There are several materials in this category, depending on the percentage composition of tin in the alloy, which is indicated by a number. They are characterized by a relatively low melting point and low strength.

This somewhat limits their scope of application. For example, these solders are convenient to use in radio installation and are undesirable for use in parts that experience great physical stress.

Technical characteristics of solder POSSu-61-0.5

Solder marking POSSu-61-0.5 indicates a type of antimony solder containing 61% tin, up to 0.5% antimony and about 38% lead. This solder is used for soldering and tinning of printed circuit boards and galvanized radio components under increased operating temperature requirements. But its melting point is 189 degrees.

Advantages of POSSu-61-0.5 solder:

• increased adhesion to the metal surface due to the antimony content;
• technical characteristics are almost the same as POS-61.

Disadvantages of POSSu-61-0.5 solder:

• difficult to find on sale;
• increased cost.

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.

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.

Flux for soldering with a soldering iron

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.