In order to fix the elements by soldering, it is necessary to use special materials that have a lower temperature of the beginning of melting. Many radio amateurs use the old approach - solder. Together with it, you must use a flux or acid.

Modern compounds - pastes - help to speed up the soldering process. They initially include all the necessary components and do not require any additives.

What are the features of this material and how to apply solder paste correctly, we will try to figure it out.

Solder paste and its properties

Initially, these formulations were used in technologies such as SMT. Currently, their scope of distribution has expanded significantly. The paste includes the following main components:

• Solder in the form of a powder with varying degrees of crushing. As a rule, the selected alloys include tin, lead, silver. Lead-free pastes are especially popular.
• Degreasing flux.
• Required binding additives. They simplify the mounting and fastening of smd components on boards. For larger board sizes, a more viscous paste is required.
• Activators and additional components.

High-quality soldering is ensured if the storage period and conditions are met. Most components have a shelf life of less than six months. For storage and transportation, it is necessary to provide a mode from +2 to + 10оС.

In the photo of the solder paste, you can see their typical modifications. However, when choosing, you need to pay attention to the compliance of the material with such requirements:

• a high level of soldering work with the strength of the joints obtained, the prevention of splashing and the formation of balls;
• the necessary adhesive parameters, thanks to which the elements are held before soldering;
• resistance to spreading during initial heating;
• absence or minimal amount of easily removable flux remaining after work;
• applicability of dispensing technology or screen printing;
• storage tolerance for a long time.

Varieties

Products of the best manufacturers of solder paste under the brands Qualitek, UNIVERSAL, Felder, HERAEUS, ALPHA, etc. are widely represented on the market. The entire assortment line can be divided into groups by type:

• The chemical composition of the flux is halogen-containing and halogen-free.
• According to the need for laundering - requiring processing and not requiring. Pastes of the first type can be washed with water (water-soluble) or special liquids.
• Lead-free and lead-free depending on the solder.
• By temperature - low, medium and high temperature.

If the paste is not washed off with water, then rosin is present in its composition. In this case, the parts must be washed with solvents.

It is important to take into account this feature - an increase in the degree of solderability of elements and smd components is accompanied by a drop in the reliability of fastening. And, for example, halogen-containing compositions improve the processability parameter, but are characterized by somewhat low reliability.

Important specifications

If you are interested in the question of which solder paste to choose, then you need to pay attention to the physicochemical properties of the mixture. They depend on the presence of binding components that affect the consistency, adhesive parameters, and the level of adhesion.

These properties include:

• the composition of the elements - the presence or absence of lead, the presence of alloying additions;
• solder particle size according to IliS;
• the shape of the particles, which affects the dosage possibilities;
• viscosity affecting the application technology - the need for a dispenser or stencil;
• the level of solderability, determined by the oxidation and contamination of the solder particles.

If no-clean pastes do not cause corrosion, then water-wash ones are capable of causing such processes at the soldering site, since they include some organic components.

Paste technology

If you have not used this composition yet, then our instructions for working with solder paste will help you:

• first you need to clean the board, degrease and dry thoroughly;
• install the board horizontally and fix it in this position;
• at the specified connecting points, the paste is evenly applied without gaps;
• small and smd elements are placed on the board;
• in some cases, for greater reliability, paste processing of the legs of the microcircuits is required;
• in the case of bottom heating of the board, it is necessary to start the hairdryer and warm up the upper section with the fastening element with a warm stream;
• after the evaporation of the flux, the temperature should be increased to the level of the solder melting;
• it is necessary to solder by constantly monitoring the process;
• let cool and rinse the board.

To manipulate microcircuits, you need to use a soldering iron at +250 - +300 Co. The 20-30 W and 12-36 V models can be used.

Soldering irons with conical tips should not be used. An increase in the efficiency of manipulations is provided by the use of a very thin wire for contact of the tip with the paste.

You can solder SMD components like this:

• place them on the contact pad;
• apply the paste to the legs;
• under the influence of a soldering iron with a given temperature, the paste spreads over the contact area;
• leave the items to cool.

Note!

To solder the wires, solder mass is applied to the wires in the connection area. Then a soldering iron is applied to the paste.

Making at home

Often there is no ready-made soldering material at hand, so it is advisable to know how to make solder paste with your own hands. To do this, you need to prepare a rod of tin-lead solder and fat for soldering. If you do not have the second component, then ordinary petroleum jelly plus LTI-120 flux can replace it.

The solder must be thoroughly grinded with a file, a file and a mechanical attachment with a drill. The crumb should be small. It is collected in a container and petroleum jelly is added in a 1: 1 ratio, as well as a little flux.

The ingredients are mixed. For good mixing, the mixture should be heated in a water bath. You can store it in a large medical syringe. With the help of it, the paste will then be applied to the required areas.

Photo of solder paste

Note!

Note!

Any kind of electronic equipment is a collection of printed circuit boards and circuits, without which the functioning of electronics is impossible. The strength and reliability of soldering joints on these surfaces depend not only on the professionalism of the worker, the serviceability of the machine, but also on the substance used for soldering, compliance with the rules of its operation and storage conditions.

General information

Solder paste is a paste-like mass that consists of many small spherical solder particles, flux and various additives. Why is it needed and what to do with it?

Soldering pastes are used for surface mounting of electronic components by soldering on printed circuit boards, hybrid integrated circuits, and ceramic substrates. After application to the surface, the composition remains active for several hours. Scope of application - industry.

What should be

Solder paste must meet certain requirements:

• not oxidize;
• do not quickly disintegrate into layers;
• maintain the properties of viscosity and stickiness;
• leave exclusively removable waste after soldering;
• do not splash when exposed to a heat source with a high concentration;
• not to negatively affect the board from a technical point of view;
• succumb to traditional solvents.

Specifications

Shape and dimensions of solder particles

How the solder paste is applied to the surface depends on the characteristics of the solder particles. Compositions with small particles are much less prone to oxidation. In addition, if the soldering agent has large particles of irregular shape, it threatens to block the stencil, therefore, the application procedure will fail.

Specific gravity of metal in the composition

This indicator determines the thickness of the fused solder, the degree of settlement and spreading of the substance for soldering depends on it. The thickness of the joint after reflow is in direct proportion to the specific gravity of the metal in the composition of the paste: the higher its percentage, the greater the thickness of the joint after reflow of the solder paste. The choice of the application method also depends on the concentration of the metal. So, if the solder paste contains 80% of it, it should be applied using a stencil method, if 90% - by dosing.

Type of flux in the composition of the paste

Affects the level of activity of the substance, the presence of the need for cleaning. Depending on the method of removing flux residues, there are three groups of fluxes:

• Rosin. The main component is purified natural resin, which is extracted from pine wood. Rosin fluxes are divided into non-activated, medium-activated and activated, slightly corrosive. The former are characterized by minimal activity indices, the latter are quite easy to clean, provide good wetting and spreading of the solder, the third are characterized by the highest activity indices and a low level of demand.
• Water washable. Contains organic acids. The use of a water-washable active flux is a guarantee of a good soldering result, while there is a need for cleaning with deionized water having a temperature of 55-65 degrees.
• No-wash. Do not need cleaning. Produced on the basis of natural and synthetic resins. The specific gravity of the resin in the composition of such fluxes is 35-45%. They show moderate activity, their residues after soldering are not corrosive and conductive, and the concentration of solid deposits can reach a maximum of 2%.

Properties

Viscosity

This is nothing more than the density of the solder paste. The paste is endowed with the ability to change the degree of its viscosity when exposed to a load of a mechanical type. It can be determined using special devices: Brookfield and Malcolm viscometers. As a rule, this indicator is indicated by the marking method.

Draft

Solder pastes have the ability to grow in size after the print is applied to the surface. The indicator in question should be at a low level, since a significant increase in the size of the solder paste print is the cause of the formation of bridges.

Time to save properties

It is reflected in such indicators as the longest residence time of the substance on the stencil before application or after application, which does not entail degradation of properties. In most cases, the value of the first parameter is within 8-48 hours, the second - 72 hours. These indicators are recorded by the manufacturer on the packaging. Moreover, one parameter (either of the two), or both, can be specified.

Adhesion

Identifies the solder paste's ability to hold SMD components in place after surface installation and prior to soldering. The degree of stickiness indicates the "pot life" of the paste and determines its shelf life. It is calculated through the implementation of a special test, in which a traditional tester is used, which is able to measure the force required to move an element of certain weight parameters from the area of ​​a pasty substance of certain sizes.

The presence of adhesiveness and its level depend on the type of solder paste. On average, the retention time is in the range of 4-8 hours, while the maximum indicator, which is typical for a number of pastes, can reach 24 hours or more.

Solder paste: how to use

The operating rules can be conditionally divided into three blocks:

1. General conditions of use:

• the room where the soldering work is carried out must be clean, not a source or place of concentration of dust or any other contamination;
• use protective goggles for the eyes and gloves for the hands for personal protection;
• use isopropyl alcohol or other solvent substances to clean the already applied paste from the board surface.

2. Before opening the packaging:

• place the paste in a room in which the temperature regime is in the range of 22-28 degrees, and the humidity is 30-60%;
• before opening the package, keep the paste at room temperature for at least a couple of hours, while resorting to the use of artificial methods of heating the substance is strictly prohibited;
• during operation, the soldering agent should be regularly stirred.

3. After opening the packaging:

Application methods

Solder pastes can be applied in two ways: ink jet and stencil. The first is based on the use of dispensers, and the second is based on the use of stencil printers.

Continuous jet method

Dispenser printing is a method of applying solder by "firing" it at almost room temperature (about 30 degrees) from the cartridge through the ejector onto the printed circuit board exactly to the place where the paste should be applied, based on the circuit board. The cartridge is in constant motion following the ordinate and abscissa above the surface of the printed circuit board. The correctness of the application of the solder layer depends on it. The cartridge stops exactly where it needs to and exactly when it needs to, thanks to a well-functioning drive system. At home, not an ejector and a cartridge can be used, but another solder paste dispenser - a syringe.

Stencil method

It is the most popular, it involves applying the paste to the soldering surface by forcing it through the apertures in the stencil canvas with a specially designed tool - a squeegee. In this case, the squeegee makes displacement movements along the surface of the stencil in a horizontal position.

Step-by-step instructions for the stencil method:

• Step 1. Fix the soldering surface (board) in the work area.
• Step 2. Align the soldering board and the stencil with absolute precision.
• Step 3. Squeeze out or apply the required amount of solder paste onto the stencil canvas.
• Step 4. Apply the paste through the stencil using a squeegee.

• Step 5. Check the quality characteristics of the soldering agent application.
• Step 6. Remove the soldering surface.
• Step 7. Clean the stencil.

Storage conditions

Solder pastes require not only compliance with the operating rules, but also special storage conditions, the main ones among them are the following:

Temperature regime

Solder pastes are sensitive to significantly low and high temperatures. Considering that the base contains two materials of different densities (flux and solder), it is considered possible that the natural process of stratification of the flux and other components of the soldering substance, as well as the appearance of a thin layer of flux above the surface, is possible. Exposure of the paste to high temperatures for a long time leads to significant delamination of the flux and the remaining paste, and is the reason for the formation of a thick near-surface layer of the flux. What is the result? But it turns out that the solder paste loses its properties, and, therefore, its application to the surface will be defective. The temperature regime, the indicators of which are higher than 30 ° C, will completely provoke the chemical decomposition of the soldering substance.

When exposed to low temperature indicators, the paste loses its wetting ability, since the flux activators partially or completely pass into the sediment. Some manufacturers' formulations can still be stored at temperatures from -20 to + 5 ° C.

Exposure to moisture

The most detrimental effect on solder paste is not low and high temperatures, but moisture. If the moisture level is increased, the solder balls in the paste begin to oxidize at a rapid rate, which leads to the waste of flux activators in order to clean the balls, and not on the brazed surfaces, as it should be. When moisture gets in, the paste spreads, bridges and solder balls are formed, flux / solder is sprayed, electronic components are displaced during the soldering process, and the retention time of electronic components decreases.

Can I do it at home

Can DIY solder paste be made at home? Of course yes!

Recipe 1

Ingredients: palm kernel oil, ammonium chloride (5-10%), aniline hydrochloric acid.

Method of preparation: mix ammonium chloride and aniline hydrochloric acid with palm kernel oil until a homogeneous pasty mass is obtained.

Recipe 2

Ingredients: vegetable oil (100 g), beef fat (300 g), natural rosin (500 g), ammonium chloride (100 g).

Method of preparation: melt oil, fat and rosin in a wide porcelain cup in a water bath. Grind the ammonium into powder and add to the mixture. Mix thoroughly until a paste is obtained.

Recipe 3

Ingredients: ammonium chloride (100 g), mineral oil (900 g).

Method of preparation: grind the ingredients in a porcelain mortar. Store in a closed glass container.

Requirements for solder pastes

• should not oxidize, strongly and quickly exfoliate;
• it is desirable to maintain its rheological properties for a long time (that is, the ability to viscous flow and deformation);
• should not spread far beyond the originally applied dose;
• should not leave solid, permanent residues after soldering;
• must have adhesive properties;
• should not be splashed when exposed to a sufficiently concentrated heating source;
• should not degrade the technical characteristics of the board;
• must be washed in standard solvents.

Solder paste characteristics

The main physicochemical properties of solder pastes are determined by introducing 4 - 15% of binders into the solder powder. It is they (sometimes with the addition of a solvent) that give the paste the desired consistency, prevent its delamination and spreading, give adhesive properties, adhesion to the substrate. The binder is neutral with respect to the solder during storage and brazing, and when heated, it volatilizes or melts without the formation of hard-to-remove solid residues. Organic resins or mixtures thereof, diluents and other substances are used as binders. To them are added plasticizers, thixotropic substances. The latter prevent the settling of solder powder particles during storage and provide a predetermined range of viscosity.

Solder paste application

The standard application of solder pastes is done by screen printing. An alternative to this process is the dot-by-dot application of the paste with a dispenser, but this is less productive. Screen printing machines, according to the principle of operation, differ little from similar machines for printing works, but the stencil forms themselves are necessarily made of metal sheets. These machines are equipped with a stencil cleaning system that prevents solder paste from contaminating the board surface.

Notes (edit)

Sources of

• V. Kuzmin "Materials for soldering electronic components in the production of modern electronic equipment", Electronic components, No. 6, 2001
• A. Medvedev "Updating technologies in the Russian electronics industry", Technologies in the electronics industry, No. 1, 2006
• A. Bolshakov “Is your paste suitable for dispensing? Factors affecting the right choice ", Technologies in the electronics industry, No. 2, 2005

Wikimedia Foundation. 2010.

• Payalpan
• Pwani

See what "Solder paste" is in other dictionaries:

solder paste- Paste mixture of powdered solder with flux and a binder or with one of them. Note A binder is a substance that is included in a solder paste to form a bond between solder particles. [GOST 17325 79] Topics ... ... Technical translator's guide

Solder paste- 117. Soldering paste D. Lötpaste E. Brazing (soldering) paste Paste mixture of powdered solder with flux and a binder or one of them. Note. The binder is understood as the substance included in the solder paste for ... ... Dictionary-reference book of terms of normative and technical documentation

SOLDERING PASTE- a pasty mixture of solder and flux powders ... Big Encyclopedic Polytechnic Dictionary

Printed circuit board- with electronic components mounted on it ... Wikipedia

Radio amateurs have long taken a fancy to such an innovation as solder paste. It was originally invented for soldering SMD components in machine board assembly. But now many people use such a paste for ordinary manual soldering of parts, wires, metals, etc. It is understandable - all in one at hand. After all, almost in fact, solder paste is a mixture of flux and solder.

In fact, it doesn't take much effort, time and ingredients to make solder paste for the needs of radio amateurs.
To make solder paste, we need:

1. Vaseline is medical. Used as a thickener;
2. Flux LTI-120 or other liquid.

I will make from these components. And ideally it is better to take:

1. Tin-lead solder bar;
2. Soldering fat. And if you find "active fat", then it's beauty in general.

How to make solder paste?

The whole process is incredibly simple.
We start by grinding the solder. I took a thick tubular piece and began to grind it with a file, a file and a mechanical drill attachment. What you use is up to you. But I am in favor of mechanics, since manual labor is too long and painstaking.

The smaller the crumb, the better. Small amount required.

Then add petroleum jelly in a 1: 1 ratio and a little LTI flux (these two ingredients can be replaced with brazing fat).

Mix everything thoroughly.

For better mixing, the mixture can be heated in a water bath or with an ordinary soldering iron, reducing its heating to 90 degrees Celsius.
Next, for storage, we transfer the resulting paste into a syringe with a thick specialized needle. Or no needles at all.
At this point, the paste is ready to use.

Soldering paste test

Apply some paste to the soldering area and solder it with a soldering iron.

My relationship with radio and microelectronics can be described with a wonderful anecdote about Leo Tolstoy, who loved to play the balalaika, but could not. Sometimes he writes the next chapter of War and Peace, and he thinks "trendy-brandy trendy-brandy ...". After courses in electrical engineering and microelectronics at my beloved Moscow Aviation Institute, plus the endless explanations of my brother, which I forget almost immediately, in principle, I manage to assemble simple circuits and even come up with my own, good now, if I don't feel like messing around with analog signals, amplifications, pickups, etc. you can find a ready-made micro-assembly and stay in the more or less understandable world of digital microelectronics.

To the point. Today we will talk about soldering. I know that many beginners who want to play with microcontrollers are intimidated by this. But, firstly, you can use
So, we are almost there. I write everything in such detail, because, honestly, for me it was a breakthrough. As I accidentally discovered, all that is needed for soldering simple components is a soldering iron, the most common one with a sting in the form of an awl:

And solder with flux inside:

It's all about the process. You need to do this:

• The part is inserted into the board and must be secured (you will not have a second hand to hold).
• A soldering iron is taken in one hand, and a solder wire in the other (it is convenient if it is in a special dispenser, as in the picture).
• Take solder on a soldering iron NO NEED.
• Touch the soldering iron with the tip of the soldering iron and heat it. Usually, it is 3-4 seconds.
• Then, without removing the soldering iron, with the other hand touch the tip of the solder wire with flux to the soldering point. In reality, all three parts touch at this place at once: the soldering element and its hole on the board, the soldering iron and the solder. A second later, "pshshshshsh" occurs, the tip of the solder wire melts (and a little flux flows out of it) and the required amount goes to the place of soldering. After a second, you can remove the soldering iron and blow.

The key point here, as you already understood, is the supply of solder and flux directly to the soldering point. And the flux "built-in" in the solder gives it the required minimum amount, reducing clogging of the board to a minimum.

It is clear that the waiting time in each phase requires at least minimal practice, but no more. I am sure that any beginner using this technique will solder Maximite himself in an hour.

Let me remind you the main signs of good soldering:

• A lot of solder does not mean quality contact. A droplet of solder at the point of contact should cover it from all sides, without gouging, but not be an excessively huge bulb.
• The color of the solder should be closer to shiny, not matte.
• If the board is double-sided and the holes are not plated, it is necessary to solder using the specified technology on both sides.

It is worth noting that all of the above refers to the soldering of elements that are inserted into the holes on the board. For soldering planar parts, the process is a little more complicated, but real. Planar elements take up less space, but require more precise positioning of "spots" for them.

Planar elements (of course, not the smallest ones) are even easier for soldering in some way, although for self-made devices you will already have to etch the board, since there will be no special convenience from using planar elements on the breadboard.

So, a small, almost theoretical bonus about soldering planar elements. These can be microcircuits, transistors, resistors, capacitors, etc. I repeat, at home there are objective restrictions on the size of elements that can be soldered with an ordinary soldering iron. Below I will give a list of what I personally soldered with an ordinary 220V soldering iron-awl.

For soldering a planar element, it will no longer be possible to use solder on the go, since it can "come off" too much, "pouring" several legs at once. Therefore, it is necessary to preliminarily tin the spots where the component is planned to be installed. Here, alas, it is no longer possible to do without liquid flux (at least I did not succeed).

You drip a little liquid flux onto a patch (or patch), take quite a bit of solder onto the soldering iron (you can do it without flux). For planar solder elements, very little is generally needed. Then lightly touch the tip of the soldering iron to each patch. Some solder should come off it. More than necessary, each patch will not "take".

Take the element with tweezers. Firstly, it is more convenient, and secondly, the tweezers will remove heat, which is very important for planar elements. Attach the element to the soldering point, holding it with tweezers. If this is a microcircuit, then you need to hold it by the leg that you are soldering. For microcircuits, the heat sink is especially important, so two tweezers can be used. You hold the part with one, and attach the other to the soldered leg (there are such tweezers with a clip that you do not need to hold with your hands). With the other hand, you again apply a drop of liquid flux to the soldering point (it may get a little on the microcircuit), with the same hand you take the soldering iron and touch the soldering point for a second. Since the solder and flux are already there, the leg to be soldered will be "immersed" in the solder applied at the tinning stage. Then the procedure is repeated for all legs. If necessary, you can drip in liquid flux.

When you buy a liquid gumboil, buy a liquid for cleaning the boards. Alas, with liquid flux, it is better to wash the board after soldering.

I must say right away that I am never a professional, and not even an advanced amateur in soldering. I did all this with an ordinary soldering iron. The pros have their own methods and equipment.

Of course, soldering a planar element requires a lot more skill. But it's still quite possible at home. And if you do not solder the microcircuits, but only the simplest elements, then everything is still simplified. Microcircuits can be bought already soldered into pads or in the form of ready-made assemblies.

Here are pictures of what I personally successfully soldered after a little workout.

This is the simplest type of enclosure. These can be put in pads, which are the same in terms of soldering complexity. These are simply soldered according to the first instruction.

The next two are harder. Here it is already necessary to solder according to the second instruction with a neat heat sink and liquid flux.

Elementary planar components, such as the resistors below, are quite easy to solder:

But there is, of course, a limit. This good is already beyond my abilities.

As a curtain, a couple of cheap but very useful things to buy in addition to a soldering iron, solder, tweezers and wire cutters:

Good luck in soldering! The smell of rosin is cool!