To create a sealed, reliable connection of metal parts, soldering is most often used. The essence of the process lies in the bonding of materials when heated with the help of an alloy - solder, the melting point of which is lower than the melting temperature of the substances to be joined. When heated, the solder, spreading between the areas to be joined, provides strong adhesion (adhesion) of metals to each other at the molecular level, which gives high strength and electrical conductivity of the connection. The molten solder should wet the metal well. That is, the connection between the molecules of a solid and a liquid must be more reliable than between particles of a liquid material. In this article we will tell the readers of the site Electrician himself, what are the types of solders for soldering, having considered the purpose and scope of each of the brands.
Content:
- Solder selection
- Varieties
- Soft or fusible
- Solid or refractory
- Low temperature
- Other types
- Solder paste
- For aluminum
- For copper
- Outcome
Solder selection
For the connection to be of good quality, it is necessary to choose the right solder. To do this, you need to consider:
- types of metals or alloys to be joined;
- soldering method;
- temperature limits;
- the size of the parts to be connected;
- required mechanical strength;
- corrosion resistance.
Varieties
The types of alloys intended for the brazing process, depending on the melting temperature, are divided into hard refractory and soft low-melting compositions. The former melt at 450 degrees and above, the latter below this value. Hard alloy brazing is more durable. But soft types of solders are indispensable for radio installation work.
Soft or fusible
The most widespread are tin-lead solders, the abbreviated name is POS. The number indicated in the marking after the letter abbreviation corresponds to the percentage in the composition of tin. For example, POS-60 contains 60% tin. These types are used in the manufacture of devices, electronic devices.
POS-90 contains only 10% of toxic lead, so this variety is used to repair food utensils and medical instruments.
POS-40 is used for soldering brass and copper pipes, electrical equipment, elements made of galvanized iron.
POS-30 is used for brazing zinc sheets, in the cable industry, for brazing galvanized iron.
POS-61 is used for soldering radio components to printed circuit boards. Its melting point is 183 degrees, and a complete transition to a liquid state occurs at 190 degrees, which helps to avoid overheating, and prevents the failure of radioelements.
There is a versatile and convenient version of POS-61, which is a hollow tin-lead tube with rosin inside. This form is very convenient, since soldering is carried out without additional flux supply.
The next type of POS is POSSu grade solder. In addition to the lead and tin components, it contains up to 2% antimony. This material can be used to solder the windings of electrical machines, elements of electrical equipment, cable products, galvanized parts.
The table summarizes some types of POS and their main properties.
Currently, lead-free alloys are widely used in the manufacture of electronics. For example, lead-free POSu95-5 solder. Determination of its composition is possible by marking. The number 95 means the percentage of tin, 5 - antimony. The melting point is in the range of 234 - 240 degrees.
Solid or refractory
Brazing alloys provide high bond strength. The disadvantage of their use is the need for intensive heating over 500 degrees, which can disable some types of devices.
Among the refractory ones with a high melting point, two groups are divided: copper and silver alloys. Copper brazing alloys based on zinc and copper are used in joints intended for static loading due to their brittleness. They should not be used to solder materials that are subject to dynamic - shock or vibration loading.
Silver types of solders are universal, they can be used to solder various materials. The disadvantage is the high cost, so the use of the composition must be economically justified. Silver alloy is used for soldering stainless steel, copper, in orthopedic dentistry, for repairing silver jewelry.
Compositions with a silver content are designated by the letters PSr. There are markings PSr-15, PSr-25, PSr-45, PSr-65, PSr-70, where the number indicates the percentage of silver.
Low temperature
POSK 50-18 contains 50% tin, 18% cadmium, 32% lead. Cadmium enhances corrosion resistance but makes the material toxic. The purpose of the solder is to mount components that are sensitive to overheating. The melting point of the material is 142-145 degrees.
The melting point of the ROSE alloy is in the range from 90 to 94 degrees. This species is marked as POSV-50. The composition contains 25% tin, 25% lead, bismuth - 50%. The percentage of metals may vary slightly. The material is produced in the form of rods, granules, ingots.
The composition is used in jewelry production, for mounting electronic devices, tinning copper tracks on printed circuit boards. It is used in electromechanics for protective fuses, fuse links. And also for dismantling radio-electronic components and connectors with plastic housings
Benefits of ROSE:
- emits a minimum amount of toxic substances, since it does not contain cadmium;
- easy to melt, contact with boiling water is enough;
- can be used at home without the use of special equipment;
- economical to use.
The melting point of the VUDA alloy is in the range of 65-72 degrees, which expands the scope of its application. But 10% of the cadmium in its composition makes the material toxic. The rest of the alloy: 13% tin, 27% lead, 50% bismuth.
It applies:
- in sensors of fire alarm systems;
- in microcircuits;
- in electroplating;
- in dentistry;
- for the manufacture of cast elements;
- in the typographic business for the production of fonts, matrices, cliches;
- in mechanical engineering and shipbuilding;
- in the aviation industry;
- in the metallurgical industry.
Other types
There are rare solders used for special conditions. These include:
- Nickel-based compounds used in high-temperature parts;
- gold, used for vacuum tubes;
- magnesium, used in ferrous and non-ferrous metallurgy.
We will give examples of some of them, since there are a lot of them and it will not be possible to consider all types within the article.
Solder paste
Soldering of microcircuits, assembly of SMD components on printed circuit boards, complex repair of mobile phones can be carried out using solder paste consisting of no-clean flux and Sn62Pb36Ag2 alloy. The composition contains 62% tin, 36% lead and 2% silver.
The paste meets the basic requirements for surface mount technology (SMD components) in the electronics industry.
For aluminum
Lucas-Milhaupt Filalu 1192 NC solder has good fluidity, high adhesion to aluminum. They can be used to solder refrigeration equipment, car radiators, air conditioners. Soldering aluminum to aluminum is straightforward, even for non-professionals. It is produced in the form of a bar with a flux inside. Melting point 577 degrees.
Composition structure: Si-11.94%, Fe-0.18%, Cu-0.01%, Mn-0.03%, Mg <0.01%, Zn-0.01%, Al-rest, FLUX - 32%
For copper
Almost any kind, both soft and hard, are suitable for brazing copper. For example, tin, lead, zinc, silver solders can be used.
Outcome
A great variety of solders for soldering various products are produced, it is simply not realistic to list them in the volume of one article. But summing up the above, we note:
- For the installation of electronic components, radio amateurs use a relatively low-melting POS-61, parts on lead-free solder unsoldered by preliminary tinning with a ROSE alloy to reduce the melting temperature, subsequently the parts are dismantled easily. Hard-melt grades are used for pipes and refrigeration equipment.
- The alloy should not contain toxic substances in excess of the established norm. Work must be carried out only in a ventilated area, observing safety measures.
Related materials:
- How to solder radio components from boards
- How to choose a soldering iron for soldering wires
- How to solder wires correctly