What flux is needed for soldering microcircuits. Appointment of different types of fluxes for soldering

Soldering is the process of connecting radio elements together, and this requires the use of various filler materials, such as solder and flux.

Solder is a metal or an alloy of various metals that has a melting point lower than that of the metals being joined. It provides a strong connection and fills the gaps between the connected parts of the workpiece.

Flux Requirements

Various fluxes are used to improve the soldering of parts and the quality of the resulting joint, as well as to clean the surface from the oxide film and fatty contaminants. Any flux used in the work must meet the following requirements:

The melting temperature must be below the melting temperature of the solder. This is the main condition for high-quality connection of parts.
Must not react with solder.
Must provide good spreading of the solder over the surface and wet all workpieces.
Should remove and destroy all oxide and fatty films.
Residues should be well washed off surfaces.

Fluxes are usually divided into active and neutral, depending on the presence of acids in their composition. Acidic actively interact with many soluble oxide films and fats.

However, they release toxic fumes when they evaporate and can damage the PCB over time if they are not removed. This is due to the fact that the active acid, which is part of these fluxes, dissolves various metals well, for example, those that make up the radio components and the board itself.

Neutral options are often devoid of these shortcomings, but soldering is not as good as with acid ones.

Flux groups

All existing drugs can be divided by efficiency into three groups according to GOST:

Overview of various soldering fluxes

The above materials are the most accessible and popular. In addition to them, there are special fluxes in the form of gels, but they are very expensive and are unlikely to be required in amateur radio.

How to replace flux for soldering

In the absence of a flux and the impossibility of acquiring it, some improvised materials can be used, but it should be remembered that the quality of soldering will be very low, and material residues are often difficult to remove or toxic. However, you should be aware of some adequate options.

It should be remembered that soldering will be of high quality when the flux is selected correctly. There are perfect fluxes for every metal, and others may not work. In addition, it is highly discouraged to solder boards with active fluxes, especially those containing acids, since if the flux residues are not completely removed from the surface of the printed circuit board, the active components will destroy the conductive copper tracks.

The parts should be soldered with a soldering iron with a perfectly tinned tip, and when soot appears, try to clean the tip in oxidal, this will allow for very good soldering. Upon completion of work, flux residues from the surface of soldered parts and boards must be removed in a suitable way. The tracks of the board can be coated with special varnishes, for example, zaponlak, this will protect them from moisture.

Today, on the shelves of radio markets and electronics stores, you can find a huge number of soldering fluxes of various purposes and prices.

Flux manufacturers offer really high quality products, but it is quite difficult to find them on the market. The number and variants of fakes are simply amazing in their diversity. Even if you are lucky and you find an original product, its cost will differ significantly from the cost of a fake. Most potential buyers after comparing prices decide to save money and look for a cheaper flux. Masters, on the other hand, select the optimal set of soldering chemicals according to their requirements, which suits them in terms of technical parameters and price. But for this they have to go through unknown fluxes and, through experiments, select the most suitable option for a particular job.

Almost every corner sells hundreds of cheap fluxes with high performance on the label. But inside the package you may expect a very unpleasant surprise.
And now let's figure it out how fluxes are bred and how this affects their technical characteristics.

Rosin instead of flux

Imagine the situation: you bought a superflux, open a tube, and instead of a high-quality flux, there is low-quality rosin (waste after rosin production). Moreover, the same rosin is also very diluted with some kind of contaminated technical petroleum jelly.

Soldering or tinning with such a mixture is simply impossible. The so-called "flux" begins to "run away" from the place of soldering. As a result, we get undeserved conclusions, poor-quality "cold" soldering, and contact pads and tracks instantly fall off the board due to overheating.

Flux diluted with acid

Very often, acids (citric, orthophosphoric) or chlorides (zinc chloride) are added to an already low-quality flux. Compared to rosin, the picture immediately changes - everything is tinned and soldered. It seems that the flux is just super, but electronic boards cannot be soldered with such a flux. It is very difficult and sometimes almost impossible to remove acid residues, especially from under SMD elements. Acid can even remain inside the solder, in the pores of the solder.

As a result, after a month or two, soldering with acid (or zinc chloride) crumbles into powder along with the conclusions of the radioelement. Repair then will be very, very time-consuming, and sometimes it is completely impossible.

Flux diluted with glycerine

It also happens that glycerin is generously poured into the flux. Glycerin flux solders great, it's cheap and plentiful, but try covering the board with it. And then measure the resistance of the PCB board. That's bad luck: it conducts current from a few to tens of ohms where it should not. Even if you try to wash off the glycerin, and it is washed off easily, the “conductivity” of the board will still remain! Glycerin is absorbed into the textolite (resistance of textolite not covered with copper is 10 to 50 ohm). For most devices, this is simply unacceptable. Even the most simple and banal schemes will be “buggy”. To somehow make the device work, try scratching the textolite between the tracks with a needle.

Conclusion: glycerin, acids, chlorides in non-cleaning fluxes for working with radio electronics, BGA and SMD components should not be used.

Basic requirements for a high-quality flux for working with lead elements, BGA and SMD:

no corrosivity
good lubricating properties
high wetting ability
no boiling when heated to operating temperature
lack of electrical conductivity
ease of removal of residues if necessary
support for lead-free and lead-containing solders
no-clean soldering technology (remains can not be washed off)
ease of application (gel, paste)
affordable price.

Now let's see what they offer us on the market.

All of the above requirements are met by trademarked fluxes CHIPSOLDER FLUX.

The fluxes of the series are also of sufficient quality. SP (SP-10+, SP-15+, SP-18+, SP20+, SP30+).

They do not contain acids, chlorides or glycerin. SP fluxes are available in different consistency: paste, gel, liquid (L-NC-3200, L-NC-3600). They do not conduct electricity, and it is not necessary to wash off the residue.

These fluxes comply with all declared standards and have been tested when soldering lead parts, conductors, BGA and SMD elements, as well as sensitive solar panels.

Flux characteristics and their features

Let's now look at some of them in more detail.
First, let's deal with the name. What do all those big letters stand for?

G(gel) - gel-like flux.
NC(no clean) - does not require rinsing.
5268 - flux index.
LF(lead free) - suitable for lead-free solders.

CHIPSOLDER G-NC-5268-LF

This flux is suitable for soldering tinned contacts. It has good thermal conductivity, the contact pad remains on the board, and not on the soldering iron tip. Flux gel CHIPSOLDER G-NC-5268 LF is a high quality, translucent, synthetic no-clean flux with resin-like characteristics. Used for soldering and desoldering BGA/SMD components. Suitable for working with a soldering iron, hot air gun, IR station, as well as for reballing.

The flux is made from highly purified components. Conveniently fixes BGA and SMD components when soldering ("landing"). Fully supports both conventional and lead-free soldering technology. Halogen-free for long-term reliability and excellent soldering characteristics.

It has a minimal, "soft" activity during soldering, which allows you to not wash off residues. It does not boil, does not leave a dark "soot", after soldering it remains a transparent gel. It loses transparency only at a temperature of -5 ° C, but at the same time retains its properties. Easily removed with any universal alcohol-based (alcohol-petrol) based cleaner and a paper towel.

It has excellent thermal conductivity (the component heats up as evenly as possible), it is very convenient to use. Solvent-free, does not dry out in the open air and does not harden after soldering. Suitable for multiple use.

CHIPSOLDER-G-NC-6500-LF

These fluxes are similar in characteristics to the CHIPSOLDER flux series, but they are slightly cheaper. It should be noted that the cost did not affect the quality. They can also work great and get good results. And now let's dwell on each of them in more detail.

SP-10+

This is a cheap and pretty good low-active flux. Recommended for mounting and dismounting FLIP CHIP, BGA and SMD components, crystals, as well as for repair work using a soldering iron, hot air gun, IR equipment.

Has almost zero activity. Used for soldering and desoldering tinned leads. Suitable for lead-free solders. SP-10+ is absolutely safe for radio components. Evenly distributes soldering temperature and prevents peeling of printed conductors. It has a sticky consistency (viscous, sticky), does not cause corrosion, securely fixes the elements during soldering. It also does not conduct electricity.

The flux is used without subsequent cleaning in printed circuit assemblies. Suitable for working in various environmental conditions.

SP-15+

The main difference is in the consistency.
SP-30 It is a translucent, sticky gel. Flux is intended for repair and production of electronics. Can be used with all standard solders.

So, let's sum up.

All fluxes are formulated for high quality soldering. All of the above fluxes are used in various environmental conditions and with different process features.
The main differences between SP fluxes are consistency and potency. Therefore, it is necessary to select the flux based on the scope and convenience during operation.

As for CHIPSOLDER brand fluxes, they are not as versatile as SP fluxes. When choosing a CHIPSOLDER flux, you definitely need to know how to use it and for what purpose.

Natalia Zinko

Flux for soldering, of course, you can do yourself. To do this, the resin collected in the forest from coniferous trees must be melted in a tin over low heat, stirring occasionally, and then simply poured into containers. When the mixture hardens, it will turn into rosin. But let's not engage in amateur performances, it's not worth it, but rather consider different types of fluxes that can be purchased at any electronic store.

Requirements for fluxes used in soldering work

The melting point of the flux must be less than the melting point of the solder.
The flux must be completely molten and flow well during the soldering process.
Should quickly and completely dissolve the oxides of the soldered metal.
Must not form chemical bonds with metal or solder.
It should evenly cover the surface of the metal at the place of soldering, preventing its oxidation during the soldering process.
Should not evaporate quickly during soldering, and its decay products should be displaced by solder and easily washed off after soldering without causing corrosion of the soldering point

Gel fluxes are, in principle, ordinary rosin, but in a gel state. They are best used for delicate soldering of radio components and repair of mobile phones, laptops, smartphones, etc. Their main feature is that they are very easy to wash off with Flux-Plus, acetone or gasoline, alcohol can also be used.

Currently, two types of gel fluxes can be found on sale: Flux-Plus and its cheap Chinese counterpart RMA-223

Flux-Plus is considered the best among gel products. Even a full one will be able to solder with him. But its price of 20 green pieces of paper is not at all encouraging. So before you take it, think about it, is it worth the money? If you are a repairer of smartphones or tablets, then it will definitely pay off for you, and for simple lovers of soldering, I would advise its Chinese counterpart.

RMA-223 Soldering Gel Flux is a Chinese counterfeit of the proprietary Flux-Plus. The cheapest way to order it is in Chinese online stores. When soldering, it also spreads well and envelops the solder. I advise everyone to use it and you will not regret it.

For cooking at home and with our own hands, we need the following ingredients, medical or technical alcohol for dissolving rosin, a hammer or something similar for grinding rosin, a container for storing the resulting liquid composition. Then we crush the pieces of rosin with a hammer, I advise you to wrap them in a bandage or any piece of cloth before that. Pour the resulting powder into a vial and fill it with alcohol (I’ll immediately answer your question “Vodka will not work”), after a few days of settling, the product will serve perfectly for soldering operations.

Why can't you solder with rosin? It is possible, but not very convenient, since it is necessary to quickly bring the evaporating rosin to the place and it will still have to be smeared a little with a soldering iron on all soldered surfaces.

It is used in soldering work as a liquid agent for oxidized copper, ferrous metal and stainless steel. Can also be used to remove rust. After use, a protective film forms on the treated surface, which prevents the corrosion process.

Used for brazing carbon and low alloy steels, nickel and alloys. The liquid is active at a temperature of 290-350 °C. After using a special agent, the surfaces must be washed with a solution of soda ash

Manufactured on a vaseline base, suitable for soldering highly oxidized metals from ferrous and non-ferrous metals

The active agent is used in the radio assembly of electronic components and printed circuit boards. Rinse with water or alcohol after use

This liquid can be purchased at a regular pharmacy, it costs much less than alcohol, and the effect is the same, although it contains 90% ethyl alcohol.

Clean-free. If desired, excess liquid can be wiped off with a rag. In addition to soldering aluminum, it can be used for soldering stainless steels, nickel, copper and other metals.

In terms of its properties and characteristics, rosin fully meets the requirements for fluxes, it just needs to be able to solder.

The specific gravity and melting point of rosin are lower than those of solder
It melts completely and has good fluidity at the correct soldering temperature. At the same time, there is a small plus compared to standard fluxes, namely, molten rosin does not “leak out” from the soldering point
Rosin completely dissolves oxides, and this reaction proceeds at a temperature that is several degrees lower than the melting temperature of the solder
Rosin is always neutral, it does not react and does not form chemical compounds with solder and base metal.
It evenly covers the surface of the soldered metal, creating protection against oxidation.
Rosin does not burn out at the soldering temperature, while the solder completely expels all its decomposition products
After the soldering process, the rosin residue left on the PCB is easily washed out

It is a transparent glassy resin, light yellow in color, hard but brittle. It is obtained from the resin of various coniferous trees. Rosin is essentially a mixture of resin acids (their chemical formula is C 20 H 30 O 2), various types of fatty acids and a small amount of oxidized and neutral substances. The basis for high-quality rosin is abietic acid.

Rosin dissolves perfectly in alcohol, ether, turpentine, worse - in kerosene, gasoline. It is completely insoluble in ordinary water.

According to the method of obtaining rosin, it happens:

gum- obtained from the resin of coniferous trees. Mostly pines. This type of rosin has practically no fatty acids in its composition.
extraction- obtained by extracting with gasoline the crushed wood of coniferous trees. This type of rosin is darker, with a lower softening point and a fairly high content of fatty acids.
tall rosin is a by-product of cellulose sulphate production in the manufacture of soap.

Rosin soldering technique

Soldering with rosin is easy enough. Before soldering, parts must be tinned. To do this, a soldering iron heated to operating temperature with a clean tip is lowered into rosin.

Then you need to cover with solder and apply it to the surface to be soldered. After that, the parts are fixed and in the place of their contact they are briefly touched with a sting. The solder spreading over the surface with a thin film after cooling will create a good connection. After soldering, the remains of rosin are washed off with alcohol or a solvent.

And so you decided to plunge into electronics with your head, stock up on a soldering iron, buy 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 mixture. 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 a 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 burn. 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 snort the hot tip of the soldering iron along 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 problem! At your service a bunch of videos from You Tube for the query "solder". See how the professionals do it. Watch and learn!

what types are there, for what purposes they are used. The quality and reliability of soldering depends on them, and sometimes there are situations when soldering metal without flux does not work at all (for example, aluminum). Of those fluxes that are used when soldering radio components, the most common, and of course the well-known flux, isrosin.

Rosin is an ordinary resin, after distillation, yellow or orange, taken from coniferous trees. In Soviet times, those who could not buy rosin in the store for some reason were invited to collect resin from coniferous trees in the forest and heat it in a metal container over low heat, preventing ignition, pour it into matchboxes or plastic jars. This resin could be used for soldering. Fluxes are used to remove the oxide film from the surface of the soldered part. They are soldered with soldering irons of the EPSN type in this way: they dip the heated tip of the soldering iron into rosin, collect a little solder on the tip and transfer this solder to the place of soldering. If the flux is liquid, it is applied with a brush, if the flux is pasty, then it is applied with a stick, or if it is in a syringe, then the required amount is squeezed out to the place of soldering.

The photo above shows a jar of rosin sold in stores, which was probably poured in liquid form in a similar way. Fluxes are divided into two types:active And neutral. On sale in stores, rosin is found not only in solid form, but also in the form of a special rosin - gel in a syringe.

According to manufacturers, rosin-gel is also suitable for soldering SMD parts.

Both types of fluxes, both active and neutral, must be washed off the board after soldering. If traces of neutral flux remain on the board, the device is possible and will work normally, it all depends on the electrical conductivity of the flux.

The figure shows a brush for washing away traces of flux from boards. If you do not wash off the remnants of the active flux, after soldering with it, traces of active salts and other hazardous substances remain on the board, which over time can corrode the solder or the soldered wire. In general, I recommend after soldering, when it is possible to wash the place of soldering with a brush dipped in technical alcohol or acetone.

Recently, I have been washing boards instead of alcohol with Aseptolin, (simply because it has already been bought), a liquid that is sold in pharmacies. Great results and inexpensive. Contains 92.5% ethyl alcohol and costs only 30 rubles per 100 milliliters. Bottles last a long time. Flux based on rosin and alcohol exists and is widely used. Which is called alcohol-rosin flux, or abbreviatedGFR.

I often use the one in the photo above. Such a flux can be easily prepared by yourself, it is enough to grind the rosin into powder, pour it into the container in which it will be stored, and pour it with technical alcohol. The ratio of rosin and alcohol should be 3 to 5. After that, we wait one or two days until the rosin dissolves in alcohol, and you can use it.

The photo above shows two flux storage containers that I use when soldering.Convenient to use, as a container for flux, turned out to be a bottle of nail polish, as it comes immediately with a brush. Previously, before use, the bottle must be washed from traces of varnish with acetone or a solvent. With the help of alcohol-rosin flux, you can solder in those places where you simply cannot crawl with rosin. Or those surfaces that rosin "does not take." For example, using SKF, you can solder wires to battery terminals, to a nickel-plated surface. Of course, the surface to be soldered will need to be mechanically cleaned before that. on etched boards in a hot way.To do this, we cover the tracks on the SKF board, apply the flux with a brush.

Conditionally neutral fluxes includeneutralsolder fat, the photo is shown above. But it is still recommended to wash it off the board after soldering. Sold in the same jars andactive soldering fat :

Many people like to use fluxLTI-120, which also needs to be flushed, because when it is used on boards with digital devices, unstable operation is sometimes observed.

For soldering device cases made of tin and other similar materials, soldering acid is used. Soldering acid is also a flux, very active, much stronger than SCF, but you can’t solder radio components with it! If you solder the radio components on the board with acid, the soldering will look strong and reliable, but the place on the board where the acid got into will certainly corrode over time. Acid, moreover, has a high electrical conductivity. Acid bottle photo:

There are special fluxes for soldering steel and even aluminum. They are highly active fluxes, and they cannot be used for soldering radio components either. In general, it is better to solder radio components, only with neutral fluxes, the same SCF. One of the fluxes for soldering stainless steel and aluminum is shown in the photo below:

In Soviet times, when many fluxes were in short supply, acetylsalicylic acid tablets or, in other words, aspirin, were used as active flux for soldering. In this case, the output or the part on which the flux had to be applied was placed on a tablet and heated with a soldering iron. The smell at the same time, according to the stories of those who used it, was, to put it mildly, not pleasant, and besides, it was harmful to health.

Also a strong active flux is food citric acid. Many used it in order to tin a damaged non-burning soldering iron tip. Such a sting is durable in use, if it is not overheated much.

But if a soldering station or a soldering iron with a regulator is left turned on for a long time at a tip temperature of 480 degrees (maximum), the tip loses its properties and the solder stops sticking to it.In this case, using citric acid as a flux, we can tin a damaged soldering iron tip. After tinning, the sting must be thoroughly washed. Generally, after , which are not based on rosin, it is necessary to rinse the board after soldering. There are specialno-clean fluxes for soldering SMD parts.

For soldering steel and cast iron, a flux is also used calledBura.

For use in conjunction with Boer's flux, special medium-temperature solders are needed. Also, for soldering with this flux, you need a powerful soldering iron in the form of an ax or similar. Author - AKV.