All about solder fat

What it is

Solder fat is a thick viscous paste used as a flux additive when soldering with tin-lead solders. Its main function is to remove the oxide film from the parts being soldered and prevent its reoccurrence.

The use of solder fat can significantly improve the quality of tinning and soldering, making solder joints strong and durable. Soldering fat has long earned popularity among professional solders, but only recently began to spread among home craftsmen.

Composition and properties

The chemical composition of the flux depends on its type. It may include:

for neutral fat:

• rosin;
• stearin.

for active:

• paraffin;
• technical petroleum jelly;
• water with reduced ion content;
• zinc and ammonium chlorides.

The physical and chemical properties make solder fat an excellent flux additive. Under its influence, the tin spreads over the surface of the joint, forming an extremely smooth and uniform layer. During the tinning process, a layer of tin envelops the material of the part without protrusions or depressions. Few other soldering chemistry can guarantee a similar result the first time.

Soldering with solder fat

Soldering flux is soluble in most organic solvents, such as gasoline, acetone, and white spirit. Solubility increases greatly with increasing temperature. Heated solder fat becomes more fluid and pliable, which allows it to penetrate into surface unevenness.

Composition of solder fat, physical and chemical properties

Neutral flux is an alloy of rosin and stearin. Active solder fat is a complex composition. This is paraffin, petroleum jelly, zinc chloride and ammonium mixed with dielectric water.

Soldering gun

The gel applied to the contacts of radio components becomes like a form that the molten solder takes. The properties of the PG provide an ideal flat surface of the applied metal. The solder spreads in an even layer without bumps or depressions.

The viscous structure of the flux allows you to initially outline the contours of future soldering. When the soldering iron tip is heated, the flux liquefies, which helps the solder softly and quickly take the desired shape.

Important! The properties of solder gel make it possible to create connections between metal parts of complex configurations.

Types of solder fat

There are two varieties on the market today:

• Neutral. A substance based on rosin and stearin. It removes oxide films and other types of contaminants well from the surface. Suitable for soldering copper parts with low-temperature solders. Universal in use, it has gained popularity both in industry and in home workshops. The thick paste allows you to very accurately measure the amount of flux required for each operation.
• Active. It has a complicated composition, to which, in addition to the stearin-paraffin base, chemically active substances are added. Ideal for soldering visibly oxidized parts made of a wide variety of metals and alloys. Not recommended for desoldering microcircuits, since active components can destroy the terminals.

Active fat flux

Active chemical components perfectly corrode and remove oxide films on parts being soldered. They also make it easier to work with materials that are difficult to solder. After finishing the work, it is necessary to remove all flux residues from the soldering zone and adjacent areas - otherwise secondary corrosion may begin, initiated by the constituent parts of the flux.

Active solder fat

Active flux is also not suitable for soldering microcircuits and other miniature parts - the leads can simply corrode. The workplace of a solder using active soldering oil must be equipped with exhaust ventilation, since chloride vapors are poisonous.

Flux can be removed either by washing with a warm soapy solution or with a specially developed Flux-Off composition.

Neutral fat flux

The combined effect of heated stearin and rosin, which are the basis of neutral solder fat, dissolves the film of oxides on the surface of the parts being processed. This guarantees convenient, high-quality and fast operation. The neutral composition increases the fluidity of the tin-lead melt, allowing it to fill the gaps and roughness of the workpieces. After sintering at high temperatures, the flux forms a coating on the surface of the material that prevents corrosion.

Neutral solder fat

Neutral solder fat is suitable for most materials except aluminum alloys. Used together with low-melting solders of the POS family. Excellent compatibility with temperature-sensitive components such as microcircuits and printed circuit boards. It is washed off with both organic solvents and warm soapy water.

Making solder fat with your own hands

Soldering station - operating principle and types

On the Internet you can find a lot of recipes for making homemade solder fat. The product contains various chemical ingredients.

All recipes have one goal in common - to achieve maximum adhesion of the lead-tin alloy and displacement of oxides from the soldering process. Fat compounds are divided into passive and active compounds.

Making neutral fat

Neutral flux is a rosin-stearic mixture. Both reagents are commercially available. The manufacturing process consists of the following stages:

1. Rosin is ground to a fine powder and placed in a glass jar.
2. Stearin is also poured there. The mixture is made up in a 1:1 ratio.
3. The jar with the contents is heated in the microwave.
4. The oven is set to medium power mode and turned on for 4 minutes.
5. The mixture turns into a homogeneous viscous mass.

Rosin for soldering
The resulting neutral solder fat may have an insufficient degree of viscosity. Some experts advise adding palm kernel oil (cooking fat). In this case, the proportion of the composition of the pancreas will be as follows:

• rosin - 3 hours;
• stearin – 2 hours;
• cooking oil – 1 tsp.

The addition of palm kernel oil gives the product a density that makes the gel convenient for loading it into a syringe.

Production of active solder fat

To make active flux you will need the following components:

• paraffin;
• zinc chloride;
• deionized water;
• petrolatum;
• ammonium chloride.

Paraffin

The substance is a by-product of oil refining. It is a white plastic fusible material. You can buy paraffin at household chemical stores.

Zinc chloride

The chemical is a white crystalline powder. Its melting point is 3200 C. Easily dissolves in water, alcohol, glycerin and acetone. The average price of zinc chloride is 220 rubles/kg.

Petrolatum

The purified petroleum product is sold in pharmacies and cosmetics stores. It is inexpensive - from 40 rubles. for the tuba.

Ammonium chloride

Ammonium chloride, or ammonia, is an odorless, white crystalline powder. Finding it on sale is not difficult. Half a kilo of the product can be bought for 150 rubles.

There are no exact instructions for preparing active solder fat. Usually all components are mixed in approximate proportions:

• Vaseline – 10%;
• zinc chloride – 10%;
• ammonia – 10%;
• paraffin – 28%;
• deionized water – 2%.

The resulting product is stored in a closed container (a glass jar with a lid), which is kept in a dark and cool place.

Homemade solder fat

How to use soldering oil correctly

The technological process is very similar to conventional soldering using, say, rosin.

In the same way, it is important to properly prepare the soldering area: clean and degrease.

Next, the tip should be tinned to the parts being connected. The soldering pad is covered with a thin layer of fat. The tip of the electric soldering iron is immersed in flux, after which a little solder is picked up on it. The tin melt spreads over the surface of the material in an even layer and protects it from the formation of an oxide film. After tinning, you can solder the parts together. To do this, solder is added in slightly larger portions than with tinning.

The quantity should be sufficient to fill all gaps and uneven areas.

After the soldering has cooled, excess flux is removed with gasoline, isopropyl alcohol or Flux-off washing liquid.

Soldering fat and features of its use

In the Radio-sale.ru catalog, many visitors interested in technical chemistry have probably already noticed the presence of such a product as “soldering fat”. But if almost everyone who has encountered soldering at least once in their life knows about rosin as a flux, not everyone has thought about such an option as soldering fat, and not even everyone knows about it. Let's together try to understand the essence of the subject and understand why and how solder fat is used, and whether it has advantages and disadvantages.

Let's say right away that solder fat as a type of flux occupies a special place and therefore, in part, amateurs, especially beginners, have little or almost no knowledge of this substance. But real professionals know well about soldering fat and actively use it, since thanks to it the quality of soldering is significantly improved. Solder fat has, as you may have guessed, a special chemical composition and consistency, which makes it look very similar to fatty deposits of animal origin. This is what led to such an unusual name.

Composition and properties of solder fat

Although outwardly, as already mentioned, solder fat is indeed similar to ordinary animal fat, however, this similarity is deceptive. Let's look at what solder fat consists of, but first, let's note that today two types of this substance are used in practice: active and neutral solder fat. Each of them has its own characteristics of chemical composition and, as a consequence, characteristics of application.

Neutral solder fat

Thus, neutral solder fat is created from a mixture of rosin and stearin (as we see, rosin with all its advantages and disadvantages could not be avoided here). It is this chemical composition that explains why, due to neutral solder fat, it is possible to dissolve the oxide film that forms on the surfaces of the parts being joined. In addition, the neutral type of fat helps make the soldering process easy and soft. The solder becomes more fluid, distributed evenly and penetrates into any irregularities and crevices. Also, a clear advantage of neutral solder grease is its good solubility, thanks to which the user can easily wash off the residue using ordinary water or any organic solvent.

Active solder fat

Now about active solder fat. Its composition contains petroleum jelly, ammonium and zinc chlorides, deionized water and paraffin. In general, an explosive mixture, which, by the way, can be dangerous to your health, which is why when working with active solder fat you should always take care of good ventilation of the workplace.

The characteristics of the composition also determine the scope of application of active solder fat, however, we will talk about the features of using both types of solder fat in the next article.

Advantages and disadvantages

Active flux has the following advantages:

• superior in soldering quality to other fluxes;
• residues are washed off with water or solvents;
• capable of providing soldering of heavily oxidized parts and surfaces;
• affordable;
• long shelf life.

The disadvantages of active fat include harmful fumes when heated and the possibility of corrosion of the joint.

Neutral soldering flux has its advantages:

• provides a high-quality compound, second only to active fat;
• easily removable residues;
• is a dielectric;
• cheapness;
• does not contain hazardous and harmful substances;
• there is no risk of corrosion at the soldering site;
• shelf-life Unlimited.

The disadvantages of a neutral composition include:

• inapplicability to heavily oxidized surfaces;
• generation of solid waste that must be flushed away.

Despite the pronounced dielectric properties, the substance has a finite resistivity. Its remains must be removed, as they can distort the parameters of low-current electrical circuits.

Features of choice

The choice of a specific composition is determined by the list of works, materials and sizes of parts to be soldered.

For soldering ordinary, not overly oxidized parts, you can safely choose a neutral soldering flux. It is less harmful and its residues are easier to remove. In addition, there is no risk of secondary corrosion processes caused by fat residues.

If parts and structures that are heavily corroded and contaminated are used, then active fat takes advantage.

It makes sense to evaluate the packaging of the formulations. If you do not have practical experience in using this flux, or the amount of work to be done is limited, then it is better to purchase small jars.

Soldering with neutral fat

After you are convinced of the high quality of the fat and its compliance with the intended list and scope of work, you can take large packages - per unit of weight they will cost significantly less.