What fluxes are used for soldering. Likbez on soldering. What should we know about flux

The most important element in the repair of any equipment is soldering. Solder, fluxes, solder paste - all this must be taken into account when performing repair work. If everything is relatively clear with solder - usually tin-lead solders are used for this with different ones (depending on the composition of the alloy), then what about the flux? What is it for?

The main purpose of the flux is to remove oxides from the surface, as well as to reduce surface tension in order to improve solder spreading. In addition, the flux for soldering serves to protect the joint from the effects of the external environment.

What are fluxes

According to their effect on metal surfaces, fluxes are of the following types.

In addition, for soldering products made of cast iron, carbon steels, as well as copper and its alloys, borax is used, which is a white crystalline powder with a melting point of 741 ° C.

Also, borax (more precisely, its mixture with boric acid in a ratio of 1: 1) is used for soldering stainless steel and hard

As a flux for brass products, a mixture consisting of equal parts of common salt and calcium chloride is used.

Soldering aluminum products requires a flux that has a low melting point. Flux usually contains 30 to 50% potassium chloride.

Soldering flux can be in powder, liquid, or paste form. In addition, there are special solder pastes in which the solder particles are already contained with the flux.

What is important to know when soldering

When choosing a flux for soldering, not only the material of the parts to be soldered is taken into account, but also what kind of solder is used. The melting point of the flux must not exceed the melting point of the solder.

Regardless of the type of flux used, the place to be soldered after completion of work must be wiped with a cloth soaked in acetone or rectified alcohol. Then clean this place with a brush or brush moistened with any solvent to remove flux residues. This is especially true of the active flux, since the products of its decomposition not only pollute the place of soldering, but are also a source of corrosion.

All the best! This rating contains the best fluxes for soldering and is compiled from personal preferences and feedback from electronics repairmen. Many readers will now think - “Well, finally! Master Soldering has started to write something about soldering!” and they will be right - for almost 4 years, not a single decent article about the soldering process has been written on the blog, although the name of the blog seems to oblige. I admit, I confess, I will correct the situation.

I plan to publish reviews of soldering processes, soldering tools, soldering videos and new technologies in the soldering world. And today I will give my rating of the 10 best fluxes for soldering. This rating is based on personal preferences and all kinds of feedback from familiar electronics repairmen of various levels and does not claim to be exclusive. Let's go - fluxes for soldering.

Rating of the most popular soldering fluxes

What should we know about flux?

The flux is designed to improve the quality of the process of soldering two metal surfaces by soldering and, when heated, cleans the surfaces from oxide and greasy films. A good flux should have a low melting point and low specific gravity. Before the solder melts, it must have time to dissolve the oxides and not penetrate deep into the solder joint during the soldering process. The flux should spread well and wet the surface of the solder and the metal at the place of soldering.

In fifth place is the most popular flux of all time, the muse of musicians, gift of nature, her majesty rosin. Rosin is gum (from the resin of coniferous trees, has almost no fatty acids), extraction (extraction of coniferous sawdust with gasoline, contains more fatty acids than gum) and tall (residues after sulfate-cellulose production of soap).

In fourth place is the beloved alcohol-rosin flux SKF or FKSp (soldering alcohol-rosin flux). It consists of 60-80% alcohol and 20-40% rosin. Such a mixture can be prepared at home with your own hands. For example, many simply crumble rosin into alcohol in a ratio of about 1 to 3. It is convenient to use in a syringe with a needle. But when stored in a loosely closed syringe, it begins to dry out on the needle and stops flowing.

Advantages:

affordable and popular inactive flux, easy to apply, does not smoke much.

Disadvantages:

when heated, the alcohol begins to rapidly evaporate and hiss.

What to solder: copper wires, gold-plated and silver-plated contacts of microcircuits and radioelements, brass, zinc.

How to rinse: alcohol, solvents, gasoline, alcohol-gasoline mixture.

So we got to the Top 3 best soldering fluxes. On the prizes, I placed professional fluxes, which in ordinary life may not be useful. But in the craft - they are very necessary.

Fluxes Amtech RMA-223 and Kingbo RMA-218

The third bronze place is occupied by Amtech RMA-223 - it is a gel flux - a mixture of crushed rosin and solvent.

I also suspect that there may be activators and fragrance in the composition. - the biggest sign of a fake- on the sticker there is an inscription in small print “Coliformia” instead of “California”, however, oddly enough, the Chinese fake flux is very good in operation, and many services just sit on it. Although the masters from mysku do not advise to take this flux for Ali, but it is better to take an analogue.

Advantages:

it is convenient to apply the gel, good solderability, you can not wash it, a fake is cheap (about 200 rubles), but it soldered very well with it and smelled of perfume.

Expensive (a 10 g tube can cost 1,500 rubles), smelly, fakes come across. The price is a limiting factor, for example, a 30 g tube can cost from 2,000 rubles.

What to solder: mainly responsible lead-free and lead soldering.

How to rinse: most can not be washed off, alcohol, solvent, there is a proprietary solvent T2005M.

This concludes the Top 10 best soldering fluxes. Of course, there are a lot of other fluxes, including good Chinese and top German and Japanese ones. But I haven't used them, so I can't adequately describe them.

If you, dear readers, use any other flux and consider it the best in the world, then be sure to write to me about it in the comments. Perhaps it will appear in the rating after testing.

Soldering Master tried for you.

A good solder joint can be obtained by following certain requirements, among which the correct choice of flux is important. There are many compounds of organic, mineral and mixed origin. They have differences in properties and recommendations for use.

A novice solderer does not always appreciate the importance of the functions performed by fluxes. There are parts, solder, soldering iron or other soldering tools. All warmed up, connected, cooled, washed - and you're done.

In fact, the process is more complicated. Only surfaces that are free from oxide deposits and other impurities can reliably connect.

The solder should spread evenly in the required place, and not just anywhere. The materials must have a suitable combination in which adhesion is maximized.

To do this, you need to reduce the tension forces on the surfaces. For many types of soldering, the influence of the external environment is not allowed. It is necessary to isolate the working area from the surrounding atmosphere.

Therefore, the main functions of the flux are as follows:

A good flux composition can handle all tasks. There are many for sale. You can make good compositions at home, but it is better to buy ready-made compositions that have been tested many times in the work.

Choosing a flux for soldering is easy. It is necessary to have information about the available brands and take into account the specifics of the upcoming soldering.

Popular varieties

Compositions of different consistency are widely used. Among the most famous fluxes that you can choose for soldering certain parts include:

• rosin and its alcohol solutions;
• glycerin solutions;
• borax;
• soldering fat;
• phosphoric acid;
• soldering acid (solution of zinc chloride in hydrochloric acid);
• some brands of gel fluxes (Flux-Plus, RMA-223).

There are compositions in the form of tubes or briquettes of paste containing both flux and solder. In many cases, this is a very convenient option that simplifies soldering.

When thinking about what kind of flux you can use for soldering with a hair dryer, do not hesitate, choose a paste. It is acceptable mainly for surface mounting, work in hard-to-reach places, with SMD parts.

The best soldering flux performs all the necessary functions at once. There are different classifications of auxiliary compositions for soldering.

Fluxes can be very active, good at removing oxides and other impurities on the surface. The reverse, unpleasant side of their action is the possibility of oxidation of the metal of the part. Soldering should be carried out carefully, followed by washing the working area.

There are compositions with a moderate effect, providing sufficient surface cleaning, good solder distribution.

with rosin

When planning the installation of electrical circuits or radio components using easily melting solders as a flux, it makes sense to choose pure rosin or mixtures based on it.

The advantage of natural resin lies in its inertness. It perfectly protects the junction from oxidation, does not cause corrosion, recovery, dissolution of metal parts.

After applying the usual light rosin, it is enough to clean the working area with a brush or a cotton swab slightly moistened with alcohol. You can use acetone as a solvent.

For soldering in hard-to-reach places, it is advisable to choose. If there is no rosin, you can take coniferous resin. The result will not disappoint. Alcohol is sometimes replaced with cologne, gasoline, acetone, ethyl acetate.

If the place of soldering will be subjected to high thermal loads in the future, it makes sense to add glycerin to the mixture of rosin and alcohol.

Ethyl alcohol of any degree of purification is suitable for the preparation of solutions. Rosin should be taken ordinary, and not specially prepared for rubbing bows. "Musical" types may have impurities that interfere with soldering.

Based on hydrochloric acid

A common component with great activity are compounds based on hydrochloric acid. It quickly removes all oxides when soldering steel products with soft solders.

For radio installation work, the use of hydrochloric acid is not recommended. Acid activity can backfire. Places of processing are easily exposed to subsequent corrosion, so the working area should be thoroughly washed with hot water after soldering.

Work with hydrochloric acid should be carried out carefully, under a fume hood. Vapors can damage the mucous membranes of the eyes and respiratory tract.

For working with brass, copper and steel alloys, it is advisable to choose zinc chloride in a hydrochloric acid solution. It is easily obtained at home by adding metal to acid.

Specific it is convenient to carry out with a flux paste consisting of a saturated aqueous solution of zinc chloride, petroleum jelly.

Non-ferrous and noble metals are repaired by soldering with a flux consisting of rosin and zinc chloride in alcohol. The joint after work is washed with acetone.

If you need to obtain joints with increased strength when soldering the same alloys, you should choose a flux paste from rosin, zinc chloride and technical petroleum jelly. Washing is carried out with swabs moistened with acetone.

With weak acids and borax

Many craftsmen try to choose time-tested tools for soldering. They prefer to work with stainless steel, nichrome, some other metals and alloys, using concentrated phosphoric acid.

Flux is available and inexpensive. Its main disadvantages include the ability to form products that conduct electricity well. If this circumstance significantly impairs the performance of the brazed part, a different flux should be selected.

For soldering metal parts with soft solders, a group of mixtures with the designation LTI is recommended. There are several varieties of these products containing different ratios of several nitrogen-containing compounds.

For each type of flux of the LTI group, there are strictly defined recommendations that must be taken into account.

High-temperature, copper alloys, steels with a high carbon content are carried out by choosing borax as a flux. Its melt removes oxides and other impurities well. After work the place of the soldering is easily cleared mechanically.

No wash required

In recent years, the popularity of no-clean soldering fluxes has increased. The advantage of such solutions, gels is to save time.

After work, there is no need to thoroughly rinse the joint, because the mixtures do not contain components that cause damage to metals.

Apply no-clean flux gels with special applicators that are commercially available. You can make such devices yourself from a disposable syringe and a rubber or silicone tube. The non-cleaning flux is chemically inert, but it is still better to wipe off its residues from the surface of the joint.

In order to choose a good flux for soldering, you need to think through all the nuances of the work ahead, study the composition of the metal, and provide for acceptable cleaning methods.

An important factor is the requirements for the quality of the future connection, the operating conditions of the part. In many situations, one should take an interest in the electrical conductivity of the flux, the residual resistance of the future junction.

Analysis of all information will allow you to choose a good flux, get a good soldering result.

And so you decided to plunge into electronics with your head, stocked up with a soldering iron, bought solder and ... And what's next? If the worst is poor, then everyone represents how to solder, but the subtleties of the technology are far from known to many and come with experience. Well, I will speed up this disastrous process and tell you a couple of tricks.

So, you probably already read about a, so we will dance from him. In addition to a soldering iron, you will need solder and flux. More about them.

Solder.
This is a special alloy that melts at a temperature of about 200 degrees. The most common is 60/40 Alloy, aka POS-61. An alloy containing 60% tin and 40% lead. Its melting point is 183-230 degrees. Usually sold in the form of wire wound on spools.
For small installations, it is better to take the one where the diameter of the wire is smaller - it is easier to dose. I have two coils, one with 0.3mm solder wire, the other 0.6mm. Well, there is still one and a half millimeters, but I hardly use it. Only if I massively solder massive parts, where a lot of solder is needed.
It is better to buy imported solder, unfortunately the Russian product sucks all the time. Maybe there is a quality one, but usually I came across low-grade slag. A solder coil, as in the picture, should cost from 150-200 rubles, more expensive is possible, cheaper is not desirable. It is better to spend money once, but then have a beautiful and high-quality soldering and not take a steam bath. And the coil usually lasts for a year and a half or two, which is at least.
It is also useful to buy yourself some Rosé alloy. This is also like solder, but its melting point is completely ridiculous - somewhere in the region of 90-100 degrees. This alloy is sometimes useful when dismantling, but there will be a separate article on this later.

Fluxes
In the process of soldering, from heating, the parts are oxidized and the solder ceases to wet them. To prevent this from happening, fluxes are used - substances that dissolve the oxide film, contribute to soldering. By the way, if someone is not in the know, the process of coating one metal with another is called tinning. I say banal things? Well, after all, educational program is educational program! :)

Rosin

The simplest and most popular flux. It's just pure pine resin. When soldering, they first take a little solder on the tip, then they poke it into rosin to collect resin on the tip, and then quickly, until the resin has evaporated, they solder. The method is not very convenient, so they often do it differently. They take ordinary ethyl (medical) alcohol and dissolve crushed rosin in it until it dissolves. After this solution is applied with a brush to the parts to be soldered and soldered. The activity of rosin is not high, so sometimes nothing happens - the details are not tinned, but rosin has one huge advantage, which sometimes covers all its shortcomings. Rosin is completely passive. That is, it does not need to be removed from the place of soldering, since it does not oxidize or reduce metals, while being an excellent dielectric. That is why I try to make the most responsible solderings with alcohol-rosin flux.

One of my favorite fluxes. It is a red liquid, it contains rosin and a number of additives. Solder them as well as the usual alcohol-rosin flux - smear with a brush on the parts and solder. But there is one trick. In the original version, the liquid infection is smeared with a thin layer and dries instantly, in general, it is not very convenient to use it. I figured out how to overcome it.
I made myself a palette of fluxes - I pasted a bunch of caps from bottles on a small company, poured various fluxes into them and pasted this case onto a spool of solder. It turned out very convenient and compact. So, pouring into the lid, I let it stand for a couple of days. During this time, it will dry out and thicken to the state of liquid honey. Now it is already convenient to spread it with a sharp toothpick exactly where you need it. And if it thickens beyond measure, then either I’ll drop a little alcohol there, or add a little more fresh flux and stir it. The manufacturer claims that it is not necessary to rinse. In principle, it seems to be the way it is, it is not active. But something confuses me with the additives that are in it, so I always wash it off. It is washed off with a wide brush dipped in alcohol. Or just brush under running tap water. There is nothing wrong with washing the finished board with water, the main thing is to dry it well afterwards.

Rosin gel
Great stuff. Not so long ago appeared in the radio stores and has already earned my love and respect. It is a thick brown rosin-based paste, sold in syringes. It is excellently smeared directly where it is needed, does not leave carbon deposits on the soldering iron, like LTI-120. Easily washed off with water or alcohol, in general, rulez!

Killer active flux, which is easily washed off with water, does not leave dirty sticky marks and oxides. But it must be washed off. Rinse thoroughly. Otherwise, in a couple of years, it can corrode the tracks of the board or its remains will become conductive and there will be terrible leaks on the surface of the board between the tracks, which will have an extremely negative effect on the operation of the circuit. I'm also not sure about the safety of his fumes. You can use it for two times, but constantly using it somehow does not smile at me. But in general, this is an awesome flux, soldering them is a pleasure.

Glycerin-Salicylic Flux.
He's FSGL. Honestly, I have no idea where this crap comes from. I have had a bank of this flux since childhood (which is why I practically never soldered rosin) - dad stole it from a defense enterprise. I have never seen it for free sale. Solders as vigorously as Glycerin-hydrazine, but does not contain impurities that are questionable from the point of view of toxicity. It's 90% glycerin, 5% salicylic acid, 5% water. Buy chtol in the pharmacy salicylic acid and save yourself? Pretty crazy recipe. One drawback - you need to wash it off, it is active. But it washes off easily with water.

F-34A
Hellish acid mix. When soldering, it has a terrible caustic exhaust, with which I poisoned half of our laboratory. You can solder this muck only in a gas mask and with a powerful hood, but this shit solders everything that other fluxes never dreamed of even in a nightmare. This slurry tins in flight - rust, oxides, steel, coatings, even aluminum can be soldered. So if you need to solder to a rusty nail, drop that shit, hold your breath, and LUDI!

Imported non-cleaning fluxes.
To be honest, I haven't used them. They say they are cool, but IMHO it’s not rational to solder them just like that - they are too expensive, and they don’t sell them in our city, but I’m sick of ordering. Rather, they are for professional use, such as repairing cellular or soldering BGA cases (this is when the legs are in the form of an array of balls under the microcircuit case). If you are interested, then look for information on the forums of cell repairers, they know everything about this matter.

Hemp Dutch Flux
I have no idea who makes it and where they sell it, but I know for sure that it is! I was especially convinced of this after picking the product diagrams of the company where I used to work. The developers are obviously soldering them. Since I have not yet seen such stoned circuit solutions.

Soldering iron in hand and go!!!
I told you about fluxes, now, in fact, about the soldering process.
This is not a tricky thing. To begin with, it is desirable to irradiate the details. Wet them with flux, pick up a little bit of solder with a soldering iron tip and smear it over the surface. There is no need to hurry, the details should be covered with an even thin shiny layer. The conclusions of microcircuits and radio components do not need to be tinned - they are already tinned at the factory.

Solder should be liquid, like water. If it is lumpy, with pronounced graininess and matte, then there are two reasons - soldering iron temperature incorrect, or solder base shit. If the soldering iron is too cold, then the solder will be on the verge of a solid and liquid state, it will be viscous and will not wet. If the soldering iron is overheated, then the solder will instantly be covered with a gray film of oxide and will also be disgusting to tin. The ideal temperature of the soldering iron when soldering with solder POS-40 ( 60/40 Alloy), in my opinion, this is about 240-300 degrees. At ST-96 it is enough to set the regulator to 2/3 in the direction of increase.

If you solder a printed circuit board, then the tracks also need to be tinned. But this must be done carefully. Textolite, which is sold in the expanses of the Motherland, often also turns out to be rare shit, and when heated, the foil falls off from it at the moment. Therefore, it is impossible to heat the board for a long time - the tracks will fall off. Usually I just smear all the tracks well with flux and quickly run a flat tip of a soldering iron with a drop of solder over each track. As a result, I have perfectly tinned tracks, with an almost mirror-like surface.

There is a folk way for quickly tinning large boards:

A braid is taken to remove solder, this is such a copper washcloth, it is sold in coils of 30 rubles per meter. If you can't find it, you can pick out a shield braid from a thick television coaxial cable - the same garbage, only fuss more. The board is properly lubricated with flux, the braid is properly impregnated with solder and also watered with flux. Further, this crap is being soldered on the surface of the board with a soldering iron. So that the fibers of the braid do not stick to the tracks, it is better to take a larger and more massive soldering iron.

I have perfected the method.
I took an old powerful 60W soldering iron, wrapped the tip with this braid, impregnated it with Rose alloy and now a puddle of the board in one motion. Why Rose? And it’s easier for them to tinker, the soldering iron cools down sharply when it touches the board. gives off heat. If the braid is moistened with ordinary solder, then it is immediately welded to the board with separate fibers, and the Rosé alloy is light-melting and does not stick.

Soldering transistors, diodes and microcircuits.
Here I would like to draw special attention. The point is that semiconductors destroyed by too high a temperature, so there is a risk of overheating the chip. To prevent this from happening, it is advisable to set the soldering iron 230 degrees or so. This is quite a tolerable temperature, which the chip can withstand for quite a long time. You can solder and take your time. For conventional, non-adjustable soldering irons, the tip temperature is about 350-400 degrees, so you need to solder quickly, with one touch. No longer than a second on each leg and take at least a 10-15 second break before proceeding to solder the other leg. You can also hold the leg with metal tweezers - it will serve as a heat sink.

Soldering wires
It is better to service the ends separately before soldering, and if the wire is soldered to the printed circuit board, then it is very desirable to drill a hole in the board, bring it in from the other side and only then solder. In this case, the risk of tearing off the droshky when jerking the wire is reduced to zero.

Soldering with solder wire.
This is how microcircuits are usually soldered. They grab it diagonally by the extreme legs, lubricate everything with flux, and then, holding a soldering iron with one hand and a thin wire of solder with the other, quickly solder all the legs.

Soldering wires in varnish insulation
Any winding wire, such as those with which the transformer is wound, is covered with a thin layer of varnish. To solder to it, this layer of varnish must be torn off. How to do it? If the wire is thick, then you can burn it a little with the fire of a lighter, the varnish will burn, and the soot can be cleaned off with a rough cardboard. If the wire is thin, then either gently scrape it with a scalpel, holding the scalpel strictly perpendicular to the wire, or take an aspirin tablet and press and shove the hot tip of the soldering iron over the wire on the aspirin. When heated, aspirin will release a substance that will gobble up the varnish insulation and clean the wire. The truth will stink a lot :)

third hand

I recommend getting one like this. Damn handy thing, allows you to hold some Cthulhu while soldering, the ends do not hang from side to side. By the way, beware of spring-loaded conductors! When soldering, it can jump off and throw a drop of solder in your face, how many times this has already flown into my face and I don’t remember, but it could have been in the eye! So follow the safety precautions!

Sponge
The tip of the soldering iron is gradually fouled and covered with soot. This is normal, usually the flux is to blame, the same LTI-120 burns, God forbid. To clean the soldering iron, you can use a special sponge. Such a yellow garbage, comes complete with soldering iron stands. It must be moistened with water and squeezed out, leaving it damp. By the way, the sponge constantly dries up, so that it does not get wet every time, it can be soaked with ordinary medical glycerin. Then it won't dry out at all! Damn convenient! If there is no sponge, then take a cotton cloth, put it in an iron tray and also soak it with water or glycerin. Our installers kept an ordinary waffle towel on the table and wiped the soldering iron on it.

By the way, about safety.

• First, arrange everything so that it is convenient.
• Watch your power cords. soldering iron very likes to burn his own wire. He's got mania. And this is fraught at best with a wire repair, at worst with a short circuit and fire.
• Do not leave the soldering iron on even for a short time. Rule " Gone - turned off"must be done ironically.
• Rule two - the soldering iron should be either in hand or on its reliable stand. And nothing else! In no case should you put it on the table or on the first thing that popped on the table. The cord will drag him along in a moment.
• Don't forget about exhaust and ventilation. If you are soldering, then at least open the window, ventilate the room, or better, put a fan on the table (at least 80mm from the computer) or a hood.

It is better to see once than to read a hundred times:
No problems! At your service a bunch of videos from You Tube for the query "solder". See how the professionals do it. Watch and learn!