What is solder paste for? Solder paste with your own hands. Union Soltek lead-free solder pastes

In the production of modern electronic boards that underlie many devices (from a mobile phone to a GPS satellite), surface mount technology (SMT, from English - Surface Mount Technology) is used.

Solder paste for SMD mounting is a viscous substance based on solder powder and flux with the addition of a binder and other components. In industrial production, the application of pastes is carried out using a special dispenser or by screen printing. After that, the board with fixed electronic components is sent to a special convection oven. At home, in addition to solder paste, an infrared soldering iron or a hot air station is used for SMD mounting. The substance itself is applied using improvised tools (for example, a medical syringe).

Solder paste Metaux Blancs Ouvres (France)

The TOPTRADECO company sells high-quality solder pastes, solders and fluxes of the well-known European manufacturer MBO (Metaux Blancs Ouvres). Similar products do not have a long shelf life, but the products of the French brand do not lose their properties for 12 months, which is a unique offer on the market.

Materials for SMD mounting are manufactured in compliance with the European standard ISO 9001/2000. It is customary to separate the following types of MBO solder pastes:

• lead;
• lead-free;
• low temperature;
• high temperature;
• for dosing.

If you decide to buy MBO (Metaux Blancs Ouvres) solder paste for surface mounting of electronic components on boards from TOPTRADECO, you can be sure of the high quality of the solder joints. Also, our customers can take advantage of a wide range of services, including maintenance, diagnostics and repair of equipment for SMD installation.

Main solder alloys:

brand	Approximate composition,%	T melt, 0 C	Strength, kg/mm	Application
POS-18	Tin (18%), antimony (2.5%), lead (79.5%)	277	2,8	For soldering with reduced strength requirements seam, as well as for tinning before soldering
POS - 30	Tin (30%), lead (60%)	256	3,3	For tinning and soldering parts made of copper, copper alloys and steel
POS - 40	Tin (40%), antimony (2%), lead (58%)	235	3,2	For soldering in electrical equipment and soldering parts made of galvanized steel
POS - 46	Tin (4%), antimony (6%), lead (everything else)	265	5,8	For soldering with immersion in a bath of molten solder
POS-50	Tin (50%), antimony (0.8%), lead (49.2%)	222	3,6	For soldering critical parts, when we allow more high heat
POS-60	Tin (60%), antimony (0.8%), lead (39.2%)	190	4,1	For soldering highly critical joints, including number and in radio engineering
POS-61	Tin (40%), lead (60%)	190	4,3	For tinning and soldering in equipment where overheating is unacceptable
POS-61M	Tin (60%), copper (1-2%), lead (38-39%)	192	4,5	For tinning and soldering thin copper electric soldering irons wires, printed conductors and foil
POS-90	Tin (90%), lead (10%)	222	4,9	For soldering food utensils and medical instruments, parts or assemblies with subsequent silvering or gilding
POSK50-18	Tin (50%), cadmium (018%), lead (31%)	145	6,7	For soldering heat sensitive parts
POSSR-15	Tin (15%), zinc (0.6%), lead (83%), silver (1.25%)	276	8,1	For soldering parts made of zinc and galvanized steel

Send your orders through the form on the site or call the managers directly.

SMD components are small electronic components that are mounted on the surface of a printed circuit board. "SMD" (in transcription "SMD") is an abbreviation of the phrase from the English language "Surface Mounted Device", which translates as "a device mounted on a surface."

Another meaning of the word “surface” is that soldering is not done in the traditional way, when the leads of the components are inserted into the hole of the printed circuit board and soldered to the conductive tracks on the reverse side. SMD components are mounted on the front side, where all the tracks are located. This type of fit is called surface mounting.

SMD components, thanks to the latest technology, have a small size and weight. Any small element that functionally contains tens or even hundreds of resistors, capacitors and transistors will be several times smaller than an ordinary semiconductor diode.

As a result, radio-electronic devices made from surface-mounted components are very compact and lightweight.

The small size of SMD components does not create conditions for the occurrence of induced currents in the elements themselves. For this case, they are too small and do not affect performance. As a result, devices assembled on such parts work better, without creating interference and not reacting to interference from other devices.

SMD components can be placed very close to each other on the board. Modern parts are so small that most of the space began to be occupied by conductive paths, and not by radio components. This prompted manufacturers to make circuit boards multi-layered. They are like a sandwich of several boards, only the contacts from all the tracks are brought to the surface of the topmost of them. These contacts are called mounting patches. Such multilayer boards are very compact. They are used in the manufacture of mobile phones, smartphones, tablet computers. The details on them are so small that they can often be seen only under a microscope.

Soldering technology

As mentioned above, the soldering of SMD components is carried out directly on the surface of the mounting patches. Very often, the conclusions of the parts after installation are not even visible. Therefore, the use of a traditional soldering iron is not possible.

Soldering SMD components is carried out in one of several ways:

• heating the entire board in the oven;
• using an infrared soldering iron;
• using a hot air soldering iron or hair dryer.

When devices using SMD components are manufactured by industrial methods, special automatic robots are used. In this case, solder has already been pre-applied on the mounting patches in an amount sufficient for mounting. In other cases, during preparation, solder paste for SMD components is applied over the stencil. The robot arm puts the parts in place and securely fixes them. After that, the boards with installed SMD components are sent to the furnace.

The temperature in the furnace is gradually increased to a certain value, at which the solder is melted. For the material from which boards and radio components are made, this temperature is not dangerous. After all the solder is melted, the temperature is lowered. The decrease is carried out smoothly according to a certain program determined by the thermal profile. It is with this cooling, and not with sudden cooling, that the soldering will be the most durable.

Board preparation at home

To solder SMD components with high quality in a home workshop, you will need an infrared soldering iron or a hot air station. Before soldering, be sure to prepare the board. To do this, it must be cleaned and irradiated patches. If the board is new and has never been used anywhere, you can clean it with an ordinary eraser. After that, it is necessary to degrease the surface by applying flux. If it is old, and there is dirt and remnants of the old solder on it, you can prepare it with fine-grained sandpaper, also degreasing after cleaning with flux.

Soldering SMD components with a conventional soldering iron is not very convenient due to the small size of the pads. But if there is no soldering station, then you can also use a soldering iron with a thin tip, working with it carefully, picking up solder on a heated tip and quickly touching the contact.

Paste application

To solder microcircuits with high quality, it is better to use not solder, but solder paste. To do this, the element must be placed on the board and fixed. Of the tools, tweezers, plastic clamps, small clamps are used. When the leads of the SMD component are exactly on the mounting patches, solder paste is applied to them. To do this, you can use a toothpick, a thin brush or a medical syringe.

You can apply the composition without worrying that it covers the surface of the board around the mounting patches. During heating, surface tension forces will collect it into drops and localize it at the places of future contacts of the SMD component with the tracks.

warming up

After application, it is necessary to heat the installation area with an infrared soldering iron or a hair dryer (temperature approx. 250 °C). The soldering composition should melt and spread over the contacts of the mounted component and the patch. The power of the blow dryer must be adjusted so that it does not blow away drops of solder paste from the board. If the characteristics of the device used for soldering allow, the temperature should be reduced gradually. It is not allowed to accelerate cooling by blowing air over the contacts of SMD components.

The same technology is used for soldering LEDs, in case of replacing burned-out elements in any lamp or, for example, in instrument lighting. The only difference is that during soldering, the board must be heated from the side opposite to the one on which the components are installed.

Types of solder pastes

Solder paste is the best tool for automated soldering of SMD components. It is a viscous low-flowing flux substance, in which the smallest particles of solder are contained in suspension.

To be able to use it successfully, the paste must meet certain requirements:

• should not oxidize and exfoliate into components;
• must have a certain viscosity, that is, be liquid enough to melt from heating, and at the same time thick enough not to spread over the entire board;
• should not leave dirt and slag at the place of soldering;
• the paste should be well washed with common solvents.

According to the method of use, the compositions are divided into washable and non-washable. As the name implies, the remaining cleaning paste must be removed from the soldering area after completion, otherwise the components included in it can attack the traces and leads of the parts. No-clean compounds can remain after soldering, as they are completely neutral to the materials of boards and SMD components.

Washing agents, in turn, can be water-soluble and halogen-containing. Water soluble cleaners can be washed off the boards with deionized water.

Washing pastes sometimes contain halogens. They are introduced into the composition to improve performance properties. Halogen-containing pastes can be used for high speed printing or, conversely, where a very long setting time is required. Soldering properties are also improved by the introduction of halogens. Halogen-containing pastes are washed off with solvents.

DIY soldering paste

There are many brands and types of solder pastes on the market that meet all the conditions and requirements necessary for high-quality installation.

At home, you can make such a composition, having a hard solder bar, solder fat and flux on hand.

Solder must be crushed into a very fine fraction. This can be done with a file or sandpaper. The resulting dust from the tin-lead rod must be collected in a small container and mechanically mixed with soldering fat. If soldering fat is not at hand, you can use any liquid flux, and use ordinary petroleum jelly as a binder and thickener.

The consistency of the paste can be determined by eye, roughly calculating the proportions. The finished composition can be kept in a small plastic container with a tight-fitting lid. It is even better to load it into a regular medical syringe with a thick needle.

If you squeeze out the paste in a dosed manner at the place of future soldering, it will be very convenient to use such a paste, and the result will be durable and reliable.

The quality of the work of electronic equipment to a large extent depends on the strength of the connection of circuit components with printed circuit boards. Solder paste provides good soldering. This mixture performs several functions.

The paste-like mass contains solder, fixatives and flux. To create a consistency, solvents, stabilizers, substances to maintain a stable viscosity, activators are introduced into 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.

Of great importance are the particle sizes of the viscous mass, depending on which a stencil or solder paste dispenser should be used for application. Both methods are implemented without a soldering iron.

If the particles are round, both a stencil and a dispenser can be used. Spherical nuggets are typically produced by pulverizing the solder component in the preparation of the solder paste.

The size and shape of the particles cause possible difficulties in the application.

Solder paste with very small particles, due to the large air contact surface, can quickly oxidize. Small grains can form balls from the solder mass. Very large round particles, irregularly shaped grains 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;
• non-washable.

The rosin group of fluxes is represented by activated, moderately activated and completely non-activated compositions. Solder fluxes that have not been activated show the least activity.

The most widespread fluxes with medium activity. They clean the surface well, spread over it, 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, contribute to the formation of a good seam, but require mandatory washing with purified hot water.

No cleaning 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 remainder is non-conductive, resistant to oxidation. It may not be washed. If desired, rinsing can be done with special solvents or hot aqueous solutions.

Rheological features

Important characteristics of surface mount solder pastes are viscosity, tackiness, retention time, and the ability to create bulk joints on the board.

Knowing the 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-like mass. The decrease in viscosity occurs as the temperature rises. To successfully solder with solder paste, you need to periodically add new portions to the mass and control the temperature readings in the working area. This can be easily done using screen printing machines equipped with thermal sensors.

Many packages with imported pastes indicate "life time". The value determines the time interval from the moment the can is opened 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. Mixes are now on sale, with a “life time” of 72 hours. With such tools, you can work slowly.

An important characteristic is the adhesiveness of the solder paste, which reflects the ability of the part to be held on the board before work begins.

Some pastes can fix electronic components for more than a day, which is convenient when mounting large boards. Compounds with low tack are able to hold the element for 4 hours.

There is a wide range of solder pastes on sale, some of which are sold in a syringe for manual or automatic dosing, others in jars, cartridges.

Products in jars are intended for screen printing machines. They are made of metal sheets with great scrupulousness, which allows cutting cells on the board for applying solder paste with an accuracy of 0.1 mm.

Special types of stencils can adjust the thickness of the pasty mass. Machines can work both in manual, and in automatic modes. Expensive models are additionally equipped with a stencil cleaning system, which significantly increases work productivity.

Storage conditions

Multi-component solder mixtures are affected by external factors. The conditions that must be met for proper storage are indicated on the packaging. They should be read and strictly observed.

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 deteriorates irreversibly. Very cold environments can degrade the performance of activators contained in solder or thermal paste.

Of great importance is the time after which the paste reaches room temperature. It is important to know:

• how long should it be stirred;
• what temperature and humidity must be maintained when using the paste;
• how long can it be stored under the specified conditions.

When the air is humid, solder balls can appear in the solder mass due to the absorption of water. The term, storage conditions of solder pastes differ, depending on the composition. If you follow the manufacturer's instructions, the soldering quality will meet expectations.

For plumbing systems

A completely separate group is made up of pasty compositions intended for soldering fittings made of copper and its alloys in water supply systems. These compositions are subject to special requirements, which are strictly regulated by GOST.

None of the components of the paste can be toxic. The flux must completely exclude the oxidation of the seam, the ingress of corrosion products into the water.

Water supply pastes are absolutely 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.

Even if you never have to deal with chip parts on your own, you need to understand that 99% of all modern electronics are created on their basis. Therefore, every self-respecting radio amateur should, at least in general terms, represent the SMD process technology.
In the previous lesson, we already got acquainted with the so-called SMD components (chip components). Now it's time to learn how they are mounted and soldered.
You can solder an SMD part using the most common solder and a soldering iron with a thin tip. The process consists of three steps:

We apply solder to one contact pad;
- using tweezers, set the chip component to the desired position and, holding the part with tweezers, warm up one of its outputs. The part is fixed, the tweezers can be removed;
- solder the second output of the component.

Manual soldering of SMD components

In approximately the same way, you can solder SMD transistors and microcircuits.

But manual soldering is a very long and painstaking process, therefore it is used only by radio amateurs to create single designs. At large radio factories, they are trying to automate everything. Therefore, there no one solderes each part individually with a soldering iron, the process is completely different.

You already know what solder is: a flexible tin-lead wire that melts when heated with a soldering iron, and after cooling it solidifies and securely fixes the output of the radio component, while providing electrical contact. But solder can be not only in the form of a tin-lead rod. You can create solder in the form of a paste, which is called solder paste. The paste contains in its composition both flux and the smallest particles of tin. When heated, the paste melts, and after cooling it solidifies, providing electrical and mechanical contact.

Solder paste is applied to all pads. In the production of prototypes and small batches, the paste is applied using manual dispensers: with a syringe, for example, or even with a toothpick. But in large-scale production, a different paste application technology is used. First, a stencil is made: a thin sheet of stainless steel, which has holes that exactly match the contact pads of the printed circuit board. The stencil is pressed against the printed circuit board, a layer of solder paste is applied on top and leveled with a special spatula. Then the stencil rises, and thus, in just a couple of seconds, the solder paste is applied to all contacts of the printed circuit board.

Printed circuit board with solder paste applied to the contact pads

You can now install components on the board. The SMD component can be neatly installed on the desired pads. In amateur radio, the installation of components is done manually using conventional or vacuum tweezers, and in large industries this operation is performed by robots that can install up to several hundred parts per minute! Due to the fact that the solder paste is viscous, the component seems to be fixed in place, and this is very convenient.

After installing all the SMD components, the board is soldered. The board is placed in a special oven, where it heats up to about 300C in a few minutes. The solder paste melts, and after cooling, provides mechanical and electrical contact between the components. In order to avoid thermal shocks, it is important to adjust the thermal profile, that is, the rate of heating and cooling of the printed circuit board. In industry, special multi-zone furnaces are used, in each chamber of which a strictly specified temperature is maintained. The printed circuit board, moving along the conveyor, sequentially passes through all zones of the furnace.

Soldering ovens: industrial (left) and for small-scale soldering (right)

In small-scale and pilot production, compact ovens are used, in which the boards are “baked” one at a time. Radio amateurs sometimes even adapt household ovens for this purpose, or heat the printed circuit board with hot air using an industrial hair dryer. Of course, the quality of soldering with such artisanal methods is very unstable, but the requirements for the reliability of amateur radio structures are usually not high.

After soldering is completed, the board is washed from the flux residues that are part of the solder paste, dried and checked. If there are DIP components in the design, they are soldered last, and even in large radio factories, this process is usually done manually. The fact is that it is very difficult and expensive to automate the DIP process, which is why modern radio electronics are mainly designed on SMD components.

When solder paste was brought to the only normal store in the city, almost to order, I was the first in line for it :)
I have long wanted to completely switch to SMD, as the laziest technology - I was too lazy to drill holes and there was a LINKO 850 soldering station, a Chinese clone I don’t know what (Well, judging by the style of writing the logo, they mow everything under HAKKO =) A kind of Adibas =) approx. DI HALT), so far used only for dismantling. Picking out mosfets from motherboards is a sweet thing. I had pasta BAKU BK-30G(I have the same mud. Nasty thing, but it's fun to solder. approx. DI HALT)

We develop the payment as usual.

Wiring Tips for SMD Mounting

• Two sites side by side - never merge them! On the contrary, stretch and connect with a thin conductor, so they do not stick together (which makes the board sloppy) and allows you to visually check the presence of a track between them (just because there are two resistors nearby, or there is a conductor).
• Don't chase the size! Make the pads slightly larger than the component, and leave enough space between them. If you are limited in size, take a larger case, or make a double-sided board. At first he suffered such garbage. While the resolution is enough - I put it as close to each other as possible, now there are a bunch of small boards with 1206 components stuck in a checkerboard pattern - the board and conductors are not visible behind them.

After that, we poison as usual, but there are problems with tinning:
I puddle with a rose alloy, followed by removing the excess layer with a hot rubber scraper (right in the same pan / jar where the board was tinned) - it turns out flat conductors with almost a mirror shine :)

If you don’t have it, you can apply the following hint - we wind a braid for removing solder on a low-power soldering iron, tin it, and draw it along the tracks pre-coated with flux. If this does not work out, but tin with a sting, leave as thin a layer of tin as possible on the contact pads.
On flat tracks, parts are practically “glued” to solder paste, and they are installed worse on a convex tin layer. Well, if this is still a resistor, it will still be dragged into place by the surface tension of the solder (the main air pressure is at a minimum so as not to be blown away).

But mikruha (for example, the notorious FT232RL) on a convex surface, oh, how difficult it is to install evenly, everything strives to fall into the hole between the tracks, and if it gets up, the air flow, even at a small degree, will blow it into that very hole, after which the solder will spoil the legs , and contacts, turning the conclusions into a monolith ;-), and the flux will almost completely evaporate in a minute, after which it will be almost impossible to move it normally without first spoiling the conclusions with some kind of rosin-gel.

In short, as a result, we should get a board with FLAT contact pads (the flux there is weak, it clings to pink copper and alloy with a bang, but not so much to crap copper).

After that, having thoroughly mixed the paste, carefully, avoiding air bubbles, we tighten the semi-liquid paste (this paste, by the way, tends to dry out even when tightly closed. You can soak it by adding alcohol to it approx. DI HALT) into a regular insulin syringe, we put it on and break it off (it’s convenient for anyone, I first broke off the needle, leaving a centimeter, then spat and broke off at the root) the needle.

Now, having washed it well and dried it even more well (: the board, we smear a little paste on each platform. How much, you can see in the photo, but after two or three times you will understand for yourself, after which we seat the crumble with tweezers.

Installation Tips

• Install tall and large components last. First capacitors 0603, then resistors 1206, high LEDs, and then mikruhi.
• Each size has its own tweezers. (or is it already bourgeois?) Usually two are enough - a trifle and mikruha. You can’t take the same 2313 with small tweezers, and large ones don’t work so neatly to plant resistors as small ones - hands are shaking, chtoli. (And I always had enough. Approx. DI HALT)

Due to the fact that the temperature of the station floats a little, I had to learn how to determine the degree of frying by ... the smell ^_^ When the flux heats up to the operating temperature, it starts to smell something like vanilla ;-), and when it starts to smell like burnt hair, it means again I turned the temperature knob with my elbow and I had to go and buy 5 LEDs instead of the fried ones. (I prefer to fry at about 290 degrees at the exit temperature of the hair dryer. The board will have 10 degrees less, just right. And the air flow to a minimum. approx. DI HALT).