The soldering process is familiar not only to electronics enthusiasts, but also to ordinary residents who at home are faced with various problems associated with electrical appliances. In this material we will look at a method for making solder paste at home. Let us note right away that it is not recommended to use homemade paste for making microcircuits, since it is intended to facilitate soldering of wires and the like, when it is not very convenient to supply tin.
As always, first of all, we suggest you watch the video on how to make pasta
What we need:
- a piece of tin;
- glycerin flux;
- needle file or file.
Before we start making our solder paste, we note that the author advises using a needle file, as this allows you to get smaller chips, which is a plus for the paste. Why do we advise making solder paste, and not just buying it in specialized stores? Because high-quality paste costs a lot of money and is not accessible to everyone.
We take a piece of tin and a file and begin to clean the tin into crumbs.
To bind the shavings we need thick flux or soldering fat. Care must be taken to mix the shavings with a small amount of flux, otherwise the paste may be damaged.
We put the thick flux into the container along with the shavings and begin to mix it like dough. Mix thoroughly until a thick and homogeneous consistency is obtained.
At the end, we need to add glycerin flux to the resulting workpiece. Again, do not use flux in large quantities. Just add a couple of drops.
Mix thoroughly again.
Our solder paste is ready. It can be stored in an airtight jar or syringe. This will allow you to use the paste for a long time. This storage method is especially useful if you make a large quantity of solder paste and plan to use it repeatedly.
Soldering wires with this paste is very easy. It is enough to apply a small amount of paste to the wires, turn on the soldering iron and simply apply it to the paste.
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:
- Medical Vaseline. Used as a thickener;
- Flux LTI-120 or other liquid.
- Tin-lead solder rod;
- 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.Somehow it turned out that, having experience with a soldering iron for more than 35 years, I have never used soldering pastes, although I have heard a lot about them. And so I decided to fill this gap by taking for review a tube of one of the representatives of this large family, Best BS-706 paste.
Anyone interested in my first attempts at working with solder paste and my impressions after that, please come and visit me.
In general, I really want to try different pastes in comparison. And as for me, such a version of the review would be more interesting to the reader and educational for me. And this will be possible someday, but for now I only have one tube in my hands and I will experiment with it.
They sent the paste in a regular bag, with a tube in the form of a syringe inside. 
For obvious reasons, weighing the paste separately from the tube is problematic, so I had to weigh everything together. Total weight 35.6 grams, tube length about 100mm. 
The sizes are indicated on the store page, in general, everything is the same. 
The hole for the pusher is covered with a cap, but the pusher itself is not included in the kit, I had to use a cap from a marker, the diameter fits just perfectly, with a little friction, but the length is a little short, however, at the end of the review there will be a photo of what it looks like :) 
Declared composition of the paste:
Tin - 99%
Copper - 0.7%
Silver - 0.3%
Melting point - 138 degrees Celsius
Volume - 10 cc
The sticker also contains a list of precautions, in short - do not eat, do not poke into eyes, wash hands after work. 
Unfortunately, the needle is not included in the kit; if you unscrew the cap, you can see a rather thick tube. The paste is very fluid, I squeezed it out a little and after a while it just flowed onto the table. 
In general, the essence of solder paste is quite simple: a large number of microscopic solder balls are located in a special flux, representing a single mass. When heated, the flux helps to wet the soldered surfaces, and the solder actually solders them.
The melting point is affected by the composition of the solder, in this case it is stated to be 138 degrees and the solder consists of tin (99%), copper (0.7%) and silver (0.3%), BST328 paste from the same company has a melting point of 183 degrees and the composition is Tin (63%) + lead (37%).
As for me, there is too much flux here, which is why the paste seems very liquid. The flux is transparent and can be clearly seen in the photo. 
For the test, we used an Aoyue-2738 compressor soldering station, which I have been using for many years, and factory-made printed circuit boards. 
At first I decided to just experiment, or, as one might put it, “get my hands on it.” To put it simply, try what it is, solder paste.
To do this, I first applied a little paste to the contact pads of the board; I applied the paste in different quantities to evaluate the difference. The air temperature was set to about 250 degrees.
The first impression is that the paste is still very fluid, the air flow should be set as low as possible or the components will be blown off the board. In addition, according to the idea, the components themselves should have aligned themselves exactly due to surface tension forces, but for some reason this did not happen. 
I tried it a little differently, I just put some paste on the board, by the way, you can see the “sand” structure of the layer here.
After warming up, the component installed quite smoothly, and the excess paste collected into larger balls of solder. I didn’t really like the fact that under the resistor the solder also tends to collect into balls. 
But then the tests come.
To begin, I applied paste to four pads of the PCB. 
I set the temperature to 140 degrees. 
Unfortunately, the temperature fluctuates quite a bit, from about 137 to 170 degrees. This happens due to the very low air flow and high heater power. When the temperature drops, the controller turns on the heating, the temperature quickly drops to 165-170 degrees, then smoothly drops to 135-140. 
In general, of course, it would be more correct to measure the temperature at the soldering point since it will be lower than the temperature of the air leaving the station nozzle. But it will also be difficult to catch the moment correctly, so I decided to limit myself to comparing the air temperature set in the settings of the soldering station and the result obtained. I tried to heat the sites so as not to affect the neighboring ones.
And so, from left to right - 140-150-160-170-180-200-210-220 degrees.
At a temperature of 140-170 degrees the paste simply spreads, at 180 it tries to melt, at 200-220 it melts confidently. 
As a second test, I simply applied a lot of paste to several contact pads and saw how it behaved after warming up, i.e. the pads will stick together or separate as they should.
In principle, everything is quite good, most of the solder ended up where it should be, the smaller part gathered into large balls. 
The next test was soldering a pair of resistors of size 1206, this is also good, except that again, due to the high fluidity of the paste, the resistors are moved by the air flow.
The flux is almost transparent, but after washing with alcohol, whitish traces remain and the solder itself is a little matte. 
For example, soldering the same resistor with a regular soldering iron with the solder that I usually use. The procedure is as follows - I hold the component with tweezers, touch one pad with the tip and solder and fix it, then touch the second contact with the tip and solder, soldering it, after that I put the first contact in order. From the description it seems that the process is long and inconvenient, but in reality everything is simpler, I first fix all the SMD components this way, and then solder them all. Sometimes I use regular flux, we call it F-3.
In the photo you can see the correct soldering, when it turns out to be a mirror, in the reflection you can even see a little of my hand that was holding the camera. 
An alternative and more correct option for applying the paste is through a stencil. To do this, I used a piece of plastic in which I cut holes.
Initially, the idea was to make a normal stencil using a laser engraver, but I didn’t really need it, and just for the sake of review it would take quite a long time, so I decided to limit myself to this option. 
We apply the stencil. throw the paste on top, remove the excess using something flat, and get the paste applied to the board.
The film is a little uneven, because it seems that there is not enough paste, but in fact it turned out to be even with the thickness of the plastic, about 0.5mm. 
We install the components, and the thickness of the paste is approximately the same as the thickness of the component. The components hold up well, I turned the board upside down without any problems, nothing fell or moved.
Warm it up with a hairdryer.
As a result, two components were soldered almost perfectly, and one was turned 90 degrees :(
After that, I washed the board and only then removed the soldered components from the board, underneath them it was almost clean, and if it weren’t for the unwrapped component, I would have said that the test was passed. 
Video of soldering attempts.
In the second test, the hair dryer was slightly not perpendicular to the surface of the board, so the components began to blow away. Since filming and heating was not very convenient, I noticed it already during filming, but decided not to delete the video.
During the tests, several printed circuit boards and a bunch of SMD resistors were used. It’s not very convenient to experiment further, since each time I had to take a new board, but I think that it worked out clearly.
By the way, in this photo you can see the marker acting as a pusher for the syringe. 
I foresee a logical question: what are the identical boards in the photo? A long time ago I made custom power supplies, and since they were ordered often and with different characteristics, I developed a universal board.
One example can be seen. 
But the same board made it possible to build more powerful power supplies, up to about 70-100 Watts, as I did. 
At one time there was even an idea to make such kits for assembling power supplies, but experienced people are not interested in this, and I would be afraid to give beginners a kit where there is a danger of getting into the mains voltage. 
It’s difficult to say anything as a conclusion; I can’t judge objectively, since I have no experience working with solder pastes, so I’ll have to judge subjectively.
In some situations, the paste can be useful, for example, to facilitate the desoldering of “complex” components by diluting the solder on the board.
Personally, I didn’t like the high fluidity because of which you either have to keep the hair dryer far from the board and then you have to heat a large area, or use a very low compressor power.
But I liked the fact that the paste holds the components well on the board before soldering, does not contaminate the board much after soldering, and generally behaves quite well
Perhaps one of the more experienced readers will suggest good pastes and explain, perhaps I just did something wrong.
That's all for me, I hope that the review was useful, as always, I will be glad to have questions, advice and just comments.
The product was provided for writing a review by the store. The review was published in accordance with clause 18 of the Site Rules.
I'm planning to buy +23 Add to favorites I liked the review +103 +154The quality of electronic equipment largely depends on the strength of the connection between circuit components and printed circuit boards. Good soldering is ensured by solder paste. This mixture serves several functions.
The paste-like mass contains solder, fixing agents and flux. To create consistency, solvents, stabilizers, substances to maintain stable viscosity, and activators are added to the paste.
The solder component can be represented by eutectic alloys of lead and tin, the content of which is 62-63%, with or without the addition of silver. Sometimes solder is represented by lead-free alloys of tin (95.5-96.5%) and silver with or without copper additives.
The size of the particles of the viscous mass is of great importance, depending on which a stencil or solder paste dispenser should be used for application. Both methods can be implemented without a soldering iron.
If the particles are round in shape, you can use both a stencil and a dispenser. Spherical grains are usually obtained due to the atomization of the solder component during the production of solder paste.
The size and shape of the particles cause possible difficulties in application.
Solder paste with very small particles due to the large surface area in contact with air can oxidize quickly. Small grains can form solder balls. Very large round particles and grains of irregular shape tend to clog the stencil.
According to the size and shape of the particles, solder pastes are divided into 6 types. The choice must be made taking into account the output step and the size of the stencil windows.
Flux as a component of solder
Flux components are also subject to classification. There are 3 types of fluxes in solder pastes:
- rosin;
- water-washable;
- no-wash.
The rosin group of fluxes is represented by activated, moderately activated and completely non-activated compositions. Soldering fluxes that have not been activated show the least activity.
The most widely used fluxes are those with medium activity. They clean the surface well, spread over it, and wet the parts to be joined. However, they can cause corrosion. Therefore, after soldering, the working area must be washed with special solvents or hot aqueous solutions.
Soldering fluxes that have undergone significant activation are used for heavily oxidized parts. After soldering, the workplace is washed with organic mixtures with alcohol.
Water-washable flux compositions are based on organic acids. They are highly active and contribute to the formation of a good seam, but require mandatory washing with purified hot water.
No laundering is required when working with fluxes made from synthetic or natural resins. Even if there are residues on the surface after soldering, this will not harm the product.
The residue does not conduct current and is resistant to oxidation. It does not need to be washed. If desired, washing can be done with special solvents or hot aqueous solutions.
Rheological features
Important characteristics of surface mount solder pastes are viscosity, adhesiveness, duration of the properties retention period, and the ability to create a volumetric connection on the board.
Knowledge of quantitative indicators of rheological properties allows you to choose the right printer for applying solder paste, which can rationally dispense portions.
The paste is applied taking into account the tendency to increase the viscosity of the paste mass. A decrease in viscosity occurs with increasing temperature. To successfully solder with solder paste, you need to periodically add new portions to the mass and monitor the temperature readings in the working area. This can be easily done using screen printing machines equipped with thermal sensors.
Many packages of imported pastes indicate “lifetime”. The value determines the time interval from the moment the can is unsealed until the end of soldering, during which the rheological properties will remain unchanged.
If the indicator is low, you will have to work quickly to obtain a high-quality connection. Now there are mixtures on sale with a “lifetime” of 72 hours. You can work slowly with such tools.
An important characteristic is the stickiness of the solder paste, which reflects the ability of the part to be held on the board before starting work.
Some pastes can fix electronic components for more than a day, which is convenient when installing large boards. Compositions with low adhesiveness are capable of holding the element for 4 hours.
There is a large assortment of solder pastes on sale, some of which are sold in a syringe for manual or automatic dispensing, others in cans or cartridges.
Products in cans are intended for screen printing machines. They are made of metal sheets with great scrupulousness, which allows cells to be cut out on the board for applying solder paste with an accuracy of 0.1 mm.
Special types of stencils can regulate the thickness of the paste-like mass. The machines can operate in both manual and automatic modes. Expensive models are additionally equipped with a stencil cleaning system, which significantly increases productivity.
Storage conditions
Multi-component solder mixtures are influenced by external factors. The conditions required for proper storage are indicated on the packaging. They should be read and strictly followed.
Be sure to indicate not only the temperature suitable for storage, but also the range of its possible deviations.
Usually, when the storage temperature exceeds 30℃, the mixture will deteriorate irreversibly. Very cold environments may impair the performance of activators contained in solder or thermal paste.
The time it takes for the paste to reach room temperature is of great importance. It is important to know:
- how long it needs to be stirred;
- what temperature and air humidity should be maintained when using the paste;
- how long it can be stored under the specified conditions.
When the air is humid, solder balls may appear in the solder mass due to water absorption. The shelf life and storage conditions of solder pastes differ and depend on the composition. If you follow the manufacturers' instructions, the quality of soldering will meet your expectations.
For plumbing systems
A completely separate group consists of paste-like compositions intended for installation of fittings made of copper and its alloys in water supply systems with a soldering iron. These compositions are subject to special requirements, which are strictly regulated by GOST.
None of the paste components can be toxic. The flux must completely prevent oxidation of the seam and the penetration of corrosion products into the water.
Water supply pastes are completely unsuitable for working with electronic circuits for many reasons, in particular because copper or silver is often added to them to increase the strength of the connection. Such compositions are not used in electronics.
Soldering of parts to the surface of a printed circuit board is carried out mainly using solder paste. The composition of pastes can vary greatly, but basically the main components are solder, flux and binder. Any soldering paste looks like a thick and viscous mixture of chemicals.
Special qualities of materials for soldering
It is known that connecting elements by soldering is possible when using a material with a lower melting point. For simple amateur circuits, solder is still used together with flux or acid. The paste, which contains both components, as well as various additives, significantly speeds up the process of soldering complex printed circuit boards with SMD elements. Widely used in electronics production.
Let's look at the main components of soldering paste:
- powdered solder of different crushing qualities;
- flux;
- binding components;
- various additives and activators.
Various alloys with tin, lead and silver are chosen as solder materials. Recently, lead-free solder pastes have become the most popular.
Each solder paste contains flux, which acts as a degreaser. In addition, an adhesive binder is required, which facilitates the installation and fixation of SMD components on printed circuit boards. The larger the board size and the higher the elemental density, the more important it is to use more viscous solder pastes.
The shelf life of the paste has a big impact on the quality of soldering of SMD components. Since the composition usually contains active chemical components, its use and storage period is very short, no more than 6 months. During storage and transportation, it is necessary to maintain the temperature from +2 to +10. Only if all conditions are met, high-quality soldering is possible.
Variety of solder pastes
Depending on the use of various components, there are several types of solder pastes:
- washing;
- without washing;
- water soluble;
- halogen-containing;
- halogen-free.
The properties vary depending on the use of the flux included in its composition. Any paste that is not washed off with water contains rosin. To wash products from such a paste, you must use a solvent.
The general rule for contained elements and SMD components is that the better the solderability, the lower the reliability. Maintaining a compromise between these important properties is the key to effective functioning. The use of halogen-containing pastes significantly increases manufacturability, but somewhat reduces reliability.
Methods of using soldering pastes
In order to obtain a high-quality and reliable connection of SMD elements on a printed circuit board, you must perform certain actions:
- high-quality cleaning and degreasing of the printed circuit board followed by drying;
- fixing the board in a horizontal position;
- uniform and thorough application of solder paste to joints;
- installation of small and SMD elements on the surface of the board; for more reliable soldering, it is recommended to additionally apply paste to the legs of the microcircuits;
- when the board is heated from the bottom, the hair dryer is turned on and the upper part with the installed elements is heated with a gentle flow of warm air;
- after the flux has evaporated, the temperature of the hair dryer increases to the melting temperature of the solder;
- the soldering process is visually controlled;
- After cooling, the final washing of the printed circuit board is performed.
Basic tricks of high-quality soldering
In order to efficiently connect elements using soldering paste, you should take care of some points. First of all, it is important to clean and degrease the board, especially if oxides are noticeable, or the board has been lying unused for a long time. In this case, it is advisable to tin all the contact pads with low-melting solder.
Solder paste should have a convenient consistency. That is, it should not be too liquid or too thick. A “sour cream” structure is most suitable, as it will wet the surface well. Wettability plays a huge role in the reliability and quality of the solder joint.
When soldering SMD elements, it is important to apply a thin layer of paste. A thick layer can short-circuit the pins of the microcircuits. Soldering simple elements does not imply such subtlety.
If the printed circuit board is of significant size, it is advisable to use bottom heating with a hairdryer, iron or special means at a temperature of 150 degrees Celsius. If this is not provided for, the board may warp.
Excess and remnants of solder can be easily removed with a soldering iron with a variety of attachments. For example, to remove residues of substances used for soldering between the legs of microcircuits, it is convenient to use a “wave” tip.
