Any type 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 solder joints on these surfaces depend not only on the professionalism of the worker, the serviceability of the machine, but also on the soldering substance used, compliance with the rules of its operation and storage conditions.

General information

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

Solder 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 it be

Solder paste must meet certain requirements:

• do not oxidize;
• do not quickly disintegrate into layers;
• maintain viscosity and stickiness properties;
• leave only removable waste after soldering;
• do not splash when exposed to a high concentration heating source;
• do not have a negative impact on the board from a technical point of view;
• susceptible to traditional solvents.

Characteristics

Shape and dimensions of solder particles

The characteristics of the solder particles determine how solder paste will be applied to the surface. Compositions with small particles are much less prone to oxidation. In addition, if the soldering substance has large particles of irregular shape, this threatens to clog the stencil, and therefore the application procedure will fail.

Specific gravity of metal in the composition

This indicator determines the thickness of the melted solder; the degree of precipitation and spreading of the soldering substance depends on it. The thickness of the connection after reflow is directly dependent on the specific gravity of the metal in the paste: the higher its percentage, the greater the thickness of the connection after the solder paste has been reflowed. The choice of application method also depends on the metal concentration. So, if the solder paste contains it in a volume of 80%, it should be applied using a stencil method, if it contains 90%, it should be applied by dosing.

Type of flux in the paste

Affects the level of activity of the substance and the need for washing. Depending on the method of removing flux residues, three groups of fluxes are distinguished:

• Rosin. The main component is purified natural resin, which is extracted from pine wood. Rosin fluxes are divided into non-activated, moderately activated and activated slightly corrosive. The former are characterized by minimal activity indicators, the latter are quite easy to clean, provide good wetting and spreadability of the solder, and the third are characterized by the highest activity indicators and a low level of demand.
• Water-washable. Contains organic acids. The use of water-washable active flux guarantees a good soldering result, but there is a need for washing with deionized water at a temperature of 55-65 degrees.
• No laundering. Does not require washing. Manufactured from natural and synthetic resins. The specific gravity of the resin in the composition of such fluxes is 35-45%. They exhibit moderate activity, their solder residues are non-corrosive and non-conductive, and the concentration of solid residues can reach a maximum of 2%.

Properties

Viscosity

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

Draft

Solder pastes have the ability to expand in size after the imprint is applied to the surface. The considered indicator should be at a low level, since a significant increase in the size of the solder paste print causes the formation of jumpers.

Properties saving time

This is reflected in indicators such as the longest residence time of the substance on the stencil before 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, either one parameter (either of the two) or both can be specified.

Stickiness

Identifies the ability of solder paste to hold SMD components in place after installing them on the surface and before the soldering procedure. The degree of stickiness indicates the “viability” of the paste and determines its shelf life. It is calculated by implementing a special test, which uses a traditional tester capable of measuring the force required to move an element of certain weight parameters from an area of ​​a paste-like substance of certain dimensions.

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 value, which is typical for a number of pastes, can reach 24 hours or more.

Solder paste: how to use

The operating rules can be divided into three blocks:

1. General terms of use:

• the room where soldering work is carried out must be clean and not be a source or place of concentration of dust or any other contaminants;
• For personal protection, use eye protection and hand gloves;
• To clean the already applied paste from the surface of the board, use isopropyl alcohol or other solvents.

2. Before opening the packaging:

• place the paste in a room where the temperature is between 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 artificial methods of heating the substance is strictly prohibited;
• During operation, the soldering agent should be stirred regularly.

3. After opening the packaging:

Application methods

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

Drop-jet method

Dispenser printing is a method of applying a soldering agent by “shooting” it at almost room temperature (about 30 degrees) from a cartridge through an ejector onto a printed circuit board exactly in the place where the paste should be applied, based on the board diagram. The cartridge is in constant motion, following the ordinate and abscissa above the surface of the printed circuit board. The correct application of the solder layer depends on it. The cartridge stops exactly where you want it, exactly when you want it, 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 most popular and involves applying paste to the soldering surface by pressing it through apertures in the stencil with a specially designed tool - a squeegee. In this case, the squeegee makes moving 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 or apply the required amount of solder paste onto the stencil fabric.
• 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 operating rules, but also special storage conditions, the main ones being the following:

Temperature

Solder pastes are sensitive to significantly low and high temperatures. Considering that the base contains two materials of different densities (flux and solder), the natural process of delamination 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 considered possible. Exposing the paste to high temperatures for a long time leads to significant separation of the flux and the remaining paste, causing the formation of a thick surface layer of 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. Temperatures above 30°C will completely provoke chemical decomposition of the soldering agent.

When exposed to low temperatures, the paste loses its wetting ability, since the flux activators partially or completely turn into sediment. Compositions from some manufacturers 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 humidity levels are elevated, the solder balls in the paste begin to oxidize at a rapid rate, which results in flux activators being wasted on the balls instead of on the solder surfaces as they should be. When moisture enters, 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 is reduced.

Can it be done at home?

Can you create your own solder paste at home? Of course yes!

Recipe 1

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

Method of preparation: mix ammonium chloride and aniline hydrochloride with palm kernel oil until a homogeneous paste 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 the oil, fat and rosin in a wide porcelain cup in a water bath. Grind ammonium into powder and add to the mixture. Mix thoroughly to form a paste.

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.

The vast expanses of the country and difficult climatic conditions mean that sometimes it is easier to make soldering consumables yourself than to go to the nearest market or a specialized store.

Not everything can be done at home, but in this regard there is an exception. Having the most affordable components, it is quite possible to make it yourself.

There are many recommendations from craftsmen, each of which is based on their own experience and capabilities. The final product, after implementing any advice, must have basic qualities, without which the soldering paste will not be able to perform the required functions.

The following properties are important:

• oxidation resistance;
• homogeneous state;
• lack of tendency to delamination;
• acceptable viscosity;
• sufficient stickiness;
• ease of removal of residues;
• elimination of spattering during soldering;
• no negative impact on parts;
• good solubility in traditionally used liquids.

As the experience of craftsmen shows, solder paste that meets all the above criteria can be made with your own hands at home.

With vegetable oils

Many people recommend using palm kernel oil for solder flux paste. It itself already has a suitable consistency and allows for the thinnest soldering when carrying out electrical work.

The activity of such solder paste can be increased by adding ammonium chloride. The concentration of the additive varies from 5% to 10%. Some home craftsmen consider it necessary to add aniline hydrochloride to the soldering mixture.

It is advisable to use a refined product. It is free of impurities and will not foam the solder paste when the temperature rises. You will need another 300 g of pure beef fat. It is better to take melted fat that does not contain any fiber or muscle tissue.

The main component of homemade solder paste is rosin. You will need 500 g of it. All this must be combined in a porcelain cup, mixed carefully, heating until completely melted.

Pour 100 g of finely ground ammonium chloride into a homogeneous mixture, stirring until dissolved. Hot DIY solder paste should be immediately placed in a jar for later storage. It is not recommended to leave the composition in the cup.

On mineral oil

It is convenient to solder small parts using homemade flux paste consisting of two components. To prepare it yourself, you should take any mineral oil (a petroleum product) in the amount of 900 g.

It should not contain acidic impurities. Gradually add 100 g of ammonium chloride into the oil, rubbing the mixture until smooth. Immediately place the finished product into a sealed container.

Some craftsmen like viscous solutions to work with. For such situations, it is recommended to dissolve ammonium chloride in the specified proportion in kerosene.

For tinning

When working with car bodies and soldering wires, you need tinning paste. There are good ready-made products available for sale. You can make a similar one with your own hands.

It is recommended to take finely ground tin powder without any large particles, tertiary solder and dilute the mixture with glycerin. By thoroughly mixing and adjusting the amount of glycerin, you can obtain a paste-like mass of the required consistency.

Sometimes, instead of glycerin and solder, ready-made glycerin flux is added to pulverized tin.

Having the desire and minimal work skills, you can prepare easy-to-use soldering material without any problems.

Any type 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 solder joints on these surfaces depend not only on the professionalism of the worker, the serviceability of the machine, but also on the soldering substance used, compliance with the rules of its operation and storage conditions.

Solder 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.

• do not oxidize;

Type of flux in the paste

Properties saving time

• place the paste in a room where the temperature is between 22-28 degrees and the humidity is 30-60%;

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

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

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

Solder pastes: how to use? DIY solder paste

Any type 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 solder joints on these surfaces depend not only on the professionalism of the worker, the serviceability of the machine, but also on the soldering substance used, compliance with the rules of its operation and storage conditions.

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

Solder 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.

Solder paste must meet certain requirements:

• do not oxidize;
• do not quickly disintegrate into layers;
• maintain viscosity and stickiness properties;
• leave only removable waste after soldering;
• do not splash when exposed to a high concentration heating source;
• do not have a negative impact on the board from a technical point of view;
• susceptible to traditional solvents.

Shape and dimensions of solder particles

The characteristics of the solder particles determine how solder paste will be applied to the surface. Compositions with small particles are much less prone to oxidation. In addition, if the soldering substance has large particles of irregular shape, this threatens to clog the stencil, and therefore the application procedure will fail.

Specific gravity of metal in the composition

This indicator determines the thickness of the melted solder; the degree of precipitation and spreading of the soldering substance depends on it. The thickness of the connection after reflow is directly dependent on the specific gravity of the metal in the paste: the higher its percentage, the greater the thickness of the connection after the solder paste has been reflowed. The choice of application method also depends on the metal concentration. So, if the solder paste contains it in a volume of 80%, it should be applied using a stencil method, if it contains 90%, it should be applied by dosing.

Type of flux in the paste

Affects the level of activity of the substance and the need for washing. Depending on the method of removing flux residues, three groups of fluxes are distinguished:

• Rosin. The main component is purified natural resin, which is extracted from pine wood. Rosin fluxes are divided into non-activated, moderately activated and activated slightly corrosive. The former are characterized by minimal activity indicators, the latter are quite easy to clean, provide good wetting and spreadability of the solder, and the third are characterized by the highest activity indicators and a low level of demand.
• Water-washable. Contains organic acids. The use of water-washable active flux guarantees a good soldering result, but there is a need for washing with deionized water at a temperature of 55-65 degrees.
• No laundering. Does not require washing. Manufactured from natural and synthetic resins. The specific gravity of the resin in the composition of such fluxes is 35-45%. They exhibit moderate activity, their solder residues are non-corrosive and non-conductive, and the concentration of solid residues can reach a maximum of 2%.

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

Solder pastes have the ability to expand in size after the imprint is applied to the surface. The considered indicator should be at a low level, since a significant increase in the size of the solder paste print causes the formation of jumpers.

Properties saving time

This is reflected in indicators such as the longest residence time of the substance on the stencil before 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, either one parameter (either of the two) or both can be specified.

Identifies the ability of solder paste to hold SMD components in place after installing them on the surface and before the soldering procedure. The degree of stickiness indicates the “viability” of the paste and determines its shelf life. It is calculated by implementing a special test, which uses a traditional tester capable of measuring the force required to move an element of certain weight parameters from an area of ​​a paste-like substance of certain dimensions.

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 value, which is typical for a number of pastes, can reach 24 hours or more.

Solder paste: how to use

The operating rules can be divided into three blocks:

1. General terms of use:

• the room where soldering work is carried out must be clean and not be a source or place of concentration of dust or any other contaminants;
• For personal protection, use eye protection and hand gloves;
• To clean the already applied paste from the surface of the board, use isopropyl alcohol or other solvents.

2. Before opening the packaging:

• place the paste in a room where the temperature is between 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 artificial methods of heating the substance is strictly prohibited;
• During operation, the soldering agent should be stirred regularly.

3. After opening the packaging:

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

Dispenser printing is a method of applying a soldering agent by “shooting” it at almost room temperature (about 30 degrees) from a cartridge through an ejector onto a printed circuit board exactly in the place where the paste should be applied, based on the board diagram. The cartridge is in constant motion, following the ordinate and abscissa above the surface of the printed circuit board. The correct application of the solder layer depends on it. The cartridge stops exactly where you want it, exactly when you want it, 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.

It is most popular and involves applying paste to the soldering surface by pressing it through apertures in the stencil with a specially designed tool - a squeegee. In this case, the squeegee makes moving 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 or apply the required amount of solder paste onto the stencil fabric.
• 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.

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

Solder pastes are sensitive to significantly low and high temperatures. Considering that the base contains two materials of different densities (flux and solder), the natural process of delamination 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 considered possible. Exposing the paste to high temperatures for a long time leads to significant separation of the flux and the remaining paste, causing the formation of a thick surface layer of 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. Temperatures above 30°C will completely provoke chemical decomposition of the soldering agent.

When exposed to low temperatures, the paste loses its wetting ability, since the flux activators partially or completely turn into sediment. Compositions from some manufacturers can still be stored at temperatures from -20 to +5°C.

The most detrimental effect on solder paste is not low and high temperatures, but moisture. If humidity levels are elevated, the solder balls in the paste begin to oxidize at a rapid rate, which results in flux activators being wasted on the balls instead of on the solder surfaces as they should be. When moisture enters, 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 is reduced.

Can it be done at home?

Can you create your own solder paste at home? Of course yes!

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

Method of preparation: mix ammonium chloride and aniline hydrochloride with palm kernel oil until a homogeneous paste is obtained.

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

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

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.

DIY solder paste

Finally we did it! I’ve been planning this for a long time, my subscribers have been asking for it for a long time. We still made this same solder paste. In fact, the task turned out to be not as difficult as I initially imagined it.

To make solder paste with your own hands, we will need:

1. A rod of tin-lead solder (solder paste base);

2. Medical vaziline (thickener);

3. A little flux LTI-120 or some other liquid.

The whole process of preparing solder paste with your own is very simple: grind a tin-lead rod to a powder, add Vasiline, add a little flux.

I note that if you wish, you can try to prepare the paste a little differently, namely without using Vasiline. However, in this case, it is most likely unlikely to be possible to apply such solder paste with a syringe.

Friends, write down your options for making solder paste yourself! Perhaps you have much better recipes. No vice needed! Do-it-yourself clamp for a drilling machine. Flux made from alcohol and citric acid with all the details online. FLUX PASTE for SMD soldering + test. 'Life hack': Making solder paste with your own hands. A formidable DIY subwoofer. The banned static BTG generator has been producing 750 kW of electricity since 1980. How to make flux at home (we make flux paste from Sal). Highly sensitive hidden wiring detector using one transistor. How to quickly desolder microcircuits from boards! We make flux with our own hands.

Radio amateurs have long chosen such an innovation as solder paste. It was originally invented for soldering SMD components during machine assembly of boards. But now many people use this paste for ordinary manual soldering of parts, wires, metals, etc. It’s understandable - everything in one is at hand. After all, solder paste is almost actually a mixture of flux and solder.

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

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

I will make from these components. Ideally, it’s better to take:

1. Tin-lead solder rod;
2. Soldering fat. And if you find “active fat,” it’s absolutely beautiful.

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 chop it up with a file, a needle file and a mechanical drill attachment. What you use is up to you. But I am for mechanics, since manual labor is too long and painstaking.

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

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

Mix everything thoroughly.

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

Soldering paste test

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

I was looking for some way to prepare my homemade PCBs. One of the solutions that came to my mind was reflow with solder paste. Another really cool use for solder paste is in repairing brass parts - like pipes, trombones and tubas - because all you have to do is heat the joint with the paste and at the right temperature it will bond.

Show 11 more images

If you've looked for solder paste on the Internet, you know that it costs a lot. I was wondering if it was possible to make some entry level DIY solder paste at home. After looking at several forums, I found a dialogue in which someone used solder shavings mixed with flux and was able to replace the solder paste.

I decided to try to make a composition, and in the process it turned out that it was much easier than I thought. The whole point is that working with pre-processed boards becomes much easier and soldering time is significantly reduced.

Warning: This project contains lead shavings. Work in a well-ventilated area and wear a mask and gloves. Also ensure that materials do not get into food.

What you will need:

1. Brazing solder - 50-50 or 60-40. You can use flux-based solder, but not acid-based solder as it will corrode your components.
2. File - fine or medium. With smaller ones you will have to spend more effort, but the paste will be of better quality.
3. Solder Flux - Also called solder paste, but not to be confused with actual solder paste. Make sure the paste is not acidic! Unscrupulous stores sell such things.
4. Stove, fire source or oven.

This instruction includes 12 steps.

Step 1: Prepare solder pieces for melting

1. Cut the solder into strips or pieces
2. Make a melting pot out of aluminum foil. Layer the foil in multiple layers to prevent lead from seeping through and ruining your oven.
3. Make a “boat” or “bowl”

Step 2: Temper the Solder

You need to get a solid piece of solder down to a large blob. I used the oven on the highest heat setting for 40 minutes.

You can also place the aluminum boat on a metal baking sheet on top of a wire rack. Warning: Do not place the container directly on a heat source as this will cause a hole in the aluminum and lead will leak out. Once the solder has melted, remove it and cool. The output form doesn't matter.

Step 3: Cooling and Pre-Preparation

Remove aluminum foil.

Note: Make sure you remove all traces of aluminum so that it does not end up in the tin solder paste.

Step 4: Grinding a piece of solder

It's simple: use a file to grind the lead into a fine powder. Note that if you rub too hard, the sand will be too coarse and the solder will start to heat up, so you may need to turn the solder from time to time.

Be sure to wear a protective mask and gloves!

Step 5: Mix the powder with flux

Step 6: First Test

After several tests on boards, I decided to try the mixture in a real project. For this purpose, I took a classic basic preamp and decided to transplant it into an RCA Varacoustic ribbon microphone; the preamp will improve the sound of the microphone, give it phantom power, and allow it to actually be used.

I was in a hurry to show off, so unfortunately I didn't clean all the photoresist (blue residue on some panels and traces). The solder will not seat properly in these areas. Next time I'll soak the board in baking soda instead of giving it a quick clean.

Step 7: Add a thin layer of paste

I covered the board with what seemed to me to be a thin layer of paste. It turns out later that I should have used less paste and spread it out. It doesn't matter where the solder is. Once the flux and solder are melted, the solder will magically coat the copper traces.

Tip: For best etching, exposure and tinning results, it will be effective to clean the board with a kitchen cleaner like Comet, it is better, safer and faster than using acetone.

Step 8: Heat the board - part 1

For the demonstration I used a soldering iron. If your hair dryer heats up to 260 degrees, you can use the reflow soldering-welding method.

Step 9: Heat the board - part 2

Here I took a photo of the process halfway through, just to show how the paste flows along the paths.

Step 10: Almost done

After the solder has completely spread over the board, there will be a layer of flux on top that will need to be cleaned using Comet or soap and water. You can use abrasives to get rid of the flux.

Step 11: Final Board

As you can see, it turned out quite well for a first attempt - no interruptions in the tracks! Assembling the board becomes very simple. You can attach SMD parts to the board in the same way (I tried it, there are several SMD parts on the board that attached easily).

Step 12: Final Result

The result is an economical and labor-intensive way to replace rosin, which will last for a long time.