The smell of heated rosin is familiar to many people. Many people know that rosin is used for Tinning and soldering of metals. What is the value of this substance and what role it plays in the process - this is to be understood.
Contents
Why are soldering fluxes needed?
High-quality soldering impossible without flux. Without its use the solder will not "stick" to the metal to be soldered. The tasks of flux:
- Dissolve dirt and oxides on the surface;
- Prevent surface oxidation when heated with a soldering iron;
- Reduce surface tension of molten solder droplets.
These tasks are well performed by rosin.
Basic properties of rosin
Rosin represents a fragile amorphous substance with a softening point from +50 to +150 degrees - depending on the composition and the method of reception. One version of the origin of the name is from the ancient city of Colophon, where pine resin of high quality was extracted. Rosin has a color from pale yellow to dark brown (sometimes almost black) with a reddish hue. It consists mainly of resins, fatty acids and some other substances. The composition is to a certain extent similar to that of amber.
Rosin is insoluble in water, but it is well soluble in ethyl alcohol, acetone and other organic solvents.
In addition to the qualities listed above, the substance has other properties required for fluxes:
- Chemical inertness to solders and soldered metals, as well as low corrosive activity;
- rosin in the molten form has a good flowability and wettability;
- its melting point is low, in some kinds of the substance it does not exceed 70 degrees, which is enough for soldering even with the Rosé alloy;
- flux residues can be easily removed with organic solvents.
The disadvantages include weak activity. Rosin is good for soldering metals that are easy to this kind of connection - copper, brass, bronze, etc. For soldering steel, not to mention aluminum, more active substances are needed. As a rule, fluxes based on inorganic acids are used for this purpose.
Rosin is often used not only in solid form, but also in liquid alcoholic solutions or thick gels. The advantages of such a design are:
- lower consumption of rosin (a small concentration of the active substance is enough without reducing efficiency);
- Reduced smoke formation for the same reason;
- The liquid composition is more convenient to apply (for example, with a brush);
- the amount of flux is easier to dose;
- Flux in the form of a liquid penetrates even into small cracks.
Moreover, this composition is applied directly to the soldering point, and the solid substance is first taken by the sting of the soldering iron. In the process of transferring to the area to be soldered, some of the flux evaporates or burns off before the process even begins, which further increases the consumption and the amount of smoke.
Other additives can also be added to the alcohol solution to improve the effectiveness of the flux, such as glycerin. You should know that this substance is hygroscopic, easily absorbs water, becoming more conductive, so after soldering with such flux you need to rinse off the remains more carefully. Also saturated with moisture glycerin over time can cause corrosion of the contact place.
How rosin is made
The main source of the substance is the natural resin of coniferous trees, which contains about one third of volatile substances (turpentine and others). After they are evaporated, a solid residue is formed, which is the pine rosin, also called harpyus. Sometimes you can also find rosin made of spruce, fir or cedar resin. This type of rosin is called oleoresin. The technology of its production can be reproduced even in artisanal conditions.
Collection of resins is a time-consuming process, so it is more rational to extract rosin directly from the wood pulp. In this case the sawdust of coniferous trees is treated with a solvent, which draws the raw material for further purification and evaporation. In this case, the final product has a darker color, but the quality is not affected. Such rosin is called extraction rosin. It is cheaper than oleoresin, but it contains additional substances from the wood pulp and solvents. It practically does not affect the quality of soldering, but for other uses of rosin it may be important.
Rosin is also obtained by distilling tall oil, a byproduct of cellulose production. The result is tallow rosin, which is more expensive than regular rosin. In addition, this product and its vapors have a pungent, unpleasant odor. The advantages of such rosin include a lower softening point.
Other applications of rosin
This substance is not only used for soldering. Powdered rosin is used where it is necessary to increase friction, but abrasion is undesirable. Powder rosin is commonly used mixed with other substances for rubbing bows of string musical instruments and shoes of ballet dancers. Grinded rosin is used in various sports equipment (to reduce the likelihood of slipping of hands), etc.
As a chemical agent rosin is used in production of varnishes, paints, plastics, rubber, etc. Its water-repellent properties are used to impregnate paper and, in the past, wooden structures.
Rosin has good dielectric propertiesbut its mechanical qualities (brittleness, susceptibility to external factors) do not allow its use in engineering as an independent dielectric. It is part of various dielectric compounds.
Is rosin harmful?
The advantage of rosin is its relative harmlessness. It contains no toxic substances. However, when overheated with a soldering iron, non-toxic resins can break down into more harmful constituents (some acids, pinolin, etc.). These substances are also low-toxic, but may cause allergic reactions, mucosal irritation, etc. if inhaled for a long time.
Synthetic rosin types are less harmful in this regard, as they do not contain abietic acid, but such compositions are expensive. Prolonged inhalation of rosin particles is also harmful - it can lead to asthma. Therefore, to work with rosin in production conditions can not be without a hood and personal respiratory protection.
In home conditions, it is difficult to imagine the master in a respirator, but also the scale of smoke formation in such a situation is small. It is unlikely that infrequent occasional use of rosin in the home can cause noticeable harm, however, work in a ventilated room is very desirable.
Important! All of the above applies to pure rosin. In industrial fluxes based on it (for example, LTI series) other substances are added that make the composition more active, but also more harmful. When working with them you need to take serious safety measures.
Over the past few decades, the chemical industry has taken a giant step forward. No one needs natural rubber anymore, many natural dyes have also been replaced by artificial ones. But rosin will long remain in use as it was hundreds of years ago. An inexpensive and effective alternative is yet to be seen.
Related articles:
