SMD mounting: basics of soldering, PCB soldering and technology. Installation of SMD at home. Installation and soldering of SMD elements

Good soldering, although not as important as the correct placement of radio elements, but it also plays a significant role. Therefore, we will consider SMD installation - what is needed for it and how it should be done at home.

Stocking up and preparing

For quality work, we need to have:

1. Solder.
2. Tweezers or pliers.
3. Soldering iron.
4. A small sponge.
5. Side cutters.

First you need to plug in the soldering iron. Then dampen the sponge with water. When the soldering iron is heated to such an extent that it can melt the solder, then it is necessary to cover the tip with it (solder). Then wipe it with a damp sponge. At the same time, too long contact should be avoided, as it is fraught with hypothermia. To remove the remnants of old solder, you can wipe the tip on a sponge (and also to keep it clean). Preparation is also carried out in relation to the radio component. Everything is done with tweezers or pliers. To do this, it is necessary to bend the leads of the radio component so that they can easily enter the holes in the board. Now let's talk about how SMD components are mounted.

Getting Started with Parts

Initially, you need to insert the components into the holes on the board that are intended for them. When doing this, make sure that the polarity is observed. This is especially important for elements such as electrolytic capacitors and diodes. Then you should slightly spread the leads so that the part does not fall out of the established place (but do not overdo it). Just before you start soldering, do not forget to wipe the tip with a sponge again. Now let's look at how SMD is installed at home at the soldering stage.

Fixing details

It is necessary to place the tip of the soldering iron between the board and the output in order to warm up the place where the soldering will be carried out. In order not to disable the part, this time should not exceed 1-2 seconds. Then you can bring solder to the place of soldering. Keep in mind that at this stage flux can splash on a person, so be careful. After the moment when the required amount of solder has time to melt, it is necessary to take the wire away from the place where the part is soldered. For its uniform distribution, it is necessary to hold the soldering iron tip for a second. Then, without moving the part, it is necessary to remove the device. It will take a few moments, and the place of soldering will cool down. All this time it is necessary to ensure that the part does not change its location. Excess can be cut off using side cutters. But make sure that the soldering point is not damaged.

Checking the quality of work

Look at the resulting SMD surface mount:

1. Ideally, the contact area and part lead should be connected. In this case, the soldering itself should have a smooth and shiny surface.
2. If a spherical shape is obtained or if there is a connection with neighboring pads, it is necessary to heat up the solder and remove its excess. Keep in mind that after working with it, there is always a certain amount of it on the soldering iron tip.
3. If there is a matte surface and scratches, melt the solder again and, without moving the parts, let it cool. If necessary, you can add it in a small amount.

A suitable solvent can be used to remove flux residue from the board. But this operation is not mandatory, because its presence does not interfere and does not affect the functioning of the circuit. And now let's pay attention to soldering theory. Then we will go through the features of each individual option.

Theory

Soldering is understood as the connection of certain metals with the use of other, more fusible ones. In electronics, solder is used for this, in which 40% lead and 60% tin. This alloy becomes liquid already at 180 degrees. Modern solders are produced as thin tubes that are already filled with a special resin that acts as a flux. Heated solder can create an internal connection if the following conditions are met:

1. It is necessary that the surfaces of the parts to be soldered be cleaned. To do this, it is important to remove all oxide films that form over time.
2. The part must be heated at the place of soldering to a temperature that is sufficient to melt the solder. Certain difficulties arise here when there is a large area with good thermal conductivity. After all, elementary power of the soldering iron may not be enough to heat the place.
3. Care must be taken to protect against oxygen. This task can be performed by colophonium, which forms a protective film.

Most Common Mistakes

Now let's look at the three most common mistakes, as well as how to fix them:

1. The soldering points are touched with the tip of the soldering iron tip. In this case, too little heat is supplied. It is necessary to apply the tip in such a way that the largest contact area is created between the tip and the soldering point. Then SMD installation will turn out to be of high quality.
2. Too little solder is used and long periods of time are maintained. When the process itself begins, part of the flux has already evaporated. The solder does not receive a protective layer, as a result - an oxide film. And how to properly install SMD at home? To do this, soldering professionals pump both the soldering iron and the solder at the same time.
3. Too early retraction of the tip from the soldering point. Heat up intensely and quickly.

You can take a capacitor for SMD mounting and fill your hand on it.

Soldering loose wires

Now we are going to practice. Let's say we have an LED and a resistor. You need to solder a cable to them. It does not use mounting plates, pins and other auxiliary elements. To achieve this goal, you need to perform the following operations:

1. Remove the insulation from the ends of the wire. They must be clean as they have been protected from moisture and oxygen.
2. We twist the individual wires of the core. This prevents their subsequent loosening.
3. We tin the ends of the wires. During this process, it is necessary to bring the heated tip to the wire along with the solder (which should be evenly distributed over the surface).
4. We shorten the leads of the resistor and LED. Then you need to tin them (regardless of whether old or new parts are used).
5. Hold the leads parallel and apply a small amount of solder. As soon as the gaps are evenly filled with it, it is necessary to quickly withdraw the soldering iron. Until the solder hardens completely, the part does not need to be touched. If this nevertheless happened, then microcracks appear, which adversely affect the mechanical and electrical properties of the connection.

PCB Soldering

In this case, it is necessary to apply less effort than in the previous one, since here the board holes play a good role as a retainer for parts. But experience is also important here. Often the result of the work of beginners is that the circuit begins to look like one large and solid conductor. But this is a simple matter, so after a little training, the result will be at a decent level.

Now let's figure out how SMD mounting works in this case. Initially, the tip of the soldering iron and solder are simultaneously brought to the place of soldering. Moreover, both the processed conclusions and the board should heat up. It is necessary to hold the sting until the solder evenly covers the entire contact point. Then it can be circled in a semicircle around the treated area. In this case, the solder should move in the opposite direction. We observe that it is evenly distributed over the entire contact area. After that, remove the solder. And the last step is to quickly remove the tip from the place of soldering. We are waiting for the solder to acquire its final shape and harden. This is how the SMD is mounted in this case. at the first attempts it will not look so hot, but over time you can learn how to do it at such a level that you can’t distinguish it from the factory version.

Everyone understands how it is possible with the help of a conventional soldering iron EPSN, with a power of 40 watts, and a multimeter, various electronic equipment, with output parts. But such details are now found, mainly only in power supplies of various equipment, and similar power boards, where significant currents flow and high voltage is present, and all control boards now go to the SMD element base.

On board SMD radio components

So what if we don’t know how to dismantle and solder back, because then at least 70% of the possible repairs of equipment, we won’t be able to do it on our own ... Someone who is not very deeply familiar with the topic of installation and dismantling may say, for this requires a soldering station and a soldering dryer, various nozzles and tips for them, no-clean flux, such as RMA-223, and the like, which usually does not happen in a home master's workshop.

Soldering Station

I have at home available, a soldering station and a hair dryer, nozzles and tips, fluxes, and solder with flux of various diameters. But what if you suddenly need to fix the equipment, on the road to order, or visiting friends? But is it inconvenient to disassemble and bring a defective board home, or to a workshop where appropriate soldering equipment is available, for one reason or another? It turns out there is a way out, and quite simple. What do we need for this?

What you need for good soldering

• 1. Soldering iron EPSN 25 watts, with a tip sharpened into a needle, for mounting a new microcircuit.

• 2. Soldering iron EPSN 40-65 watts with a tip sharpened under a sharp cone, for dismantling a microcircuit, using Rose or Wood alloy. A soldering iron with a power of 40-65 watts must be turned on necessarily through a Dimmer, a device for adjusting the power of the soldering iron. It is possible such as in the photo below, very convenient.

• 3. Alloy Rose or Wood. We bite off a piece of solder with side cutters from a droplet, and put it directly on the contacts of the microcircuit on both sides, if we have it, for example, in the Soic-8 package.

• 4. Dismantling braid. It is required in order to remove solder residues from the contacts on the board, as well as on the microcircuit itself, after dismantling.

• 5. SCF flux (alcohol rosin flux, crushed into powder, dissolved in 97% alcohol, rosin), or RMA-223, or similar fluxes, preferably based on rosin.

• 6. Flux Off, or 646 thinner, and a small, medium-hard bristle brush, usually used in school, for painting in art classes.

• 7. Tubular solder with flux, with a diameter of 0.5 mm, (preferably, but not necessarily this diameter).

• 8. Tweezers, preferably curved, L-shaped.

Unsoldering planar parts

So how does the process itself take place? Something . We bite off small pieces of solder (alloy) Rose or Wood. We apply our flux, abundantly, to all contacts of the microcircuit. We put a drop of solder to Rose, on both sides of the microcircuit, where the contacts are located. We turn on the soldering iron, and set it with a dimmer, the power is approximately 30-35 watts, I don’t recommend it anymore, there is a risk of overheating the microcircuit during dismantling. We carry out the sting of a heated soldering iron, along all the legs of the microcircuit, on both sides.

At the same time, the contacts of the microcircuit will close with us, but this is not scary, after we dismantle the microcircuit, we can easily remove excess solder from the contacts on the board, and from the contacts on the microcircuit, using a dismantling braid.

So, we took up our chip with tweezers, along the edges, where there are no legs. Usually the length of the microcircuit, where we hold it with tweezers, allows you to simultaneously drive the soldering iron tip, between the tips of the tweezers, alternately from both sides of the microcircuit, where the contacts are located, and slightly pull it up with tweezers. Due to the fact that during the melting of the Rose or Wood alloy, which have a very low melting point (about 100 degrees), relative to the lead-free solder, and even the usual POS-61, and moving with the solder on the contacts, it thereby reduces the overall melting point of the solder .

Dismantling chips using a braid

And in this way, the microcircuit is dismantled with us, without overheating dangerous for it. On the board, we have solder residues, Rose alloy and lead-free, in the form of sticky contacts. To bring the board back to normal, we take a dismantling braid, if the flux is liquid, you can even dip its tip into it, and put it on the solder “snot” formed on the board. Then we warm up from above, pressing down with a soldering iron tip, and draw a braid along the contacts.

Soldering braided radio components

Thus, all the solder from the contacts is absorbed into the braid, passes to it, and the contacts on the board are completely cleaned of solder. Then the same procedure must be done with all the contacts of the microcircuit, if we are going to solder the microcircuit to another board, or to the same one, for example, after flashing with a programmer, if it is a Flash memory chip containing the BIOS firmware of the motherboard, or monitor, or which or other technology. This procedure must be performed to clean the contacts of the microcircuit from excess solder. After that, we apply the flux again, put the microcircuit on the board, position it so that the contacts on the board strictly correspond to the contacts of the microcircuit, and there is still some space left on the contacts on the board, along the edges of the legs. Why are we leaving this place? So that you can lightly touch the contacts, with a soldering iron tip, solder them to the board. Then we take a 25 watt EPSN soldering iron, or a similar low-power one, and touch the two legs of the microcircuit located diagonally.

As a result, the microcircuit turns out to be “stuck” with us, and will no longer budge, since the melted solder on the contact pads will hold the microcircuit. Then we take solder with a diameter of 0.5 mm, with a flux inside, bring it to each contact of the microcircuit, and simultaneously touch the tip of the soldering iron, solder, and each contact of the microcircuit. I do not recommend using solder of a larger diameter, there is a risk of hanging “snot”. Thus, we have solder “deposited” on each contact. We repeat this procedure with all contacts, and the microcircuit is soldered into place. With experience, all these procedures can really be completed in 15-20 minutes, or even in less time. We only need to wash off the flux residues from the board, using solvent 646, or Flux Off cleaning agent, and the board is ready for tests after drying, and this happens very quickly, since the substances used for washing are very volatile. 646 solvent, in particular, is based on acetone. The inscriptions, silk-screen printing on the board, and the solder mask are not washed off or dissolved.

The only thing is that it will be problematic to dismantle a microcircuit in a Soic-16 package and more multi-output in this way, due to the difficulties with simultaneous heating, a large number of legs. Good soldering everyone, and less overheated microcircuits! Specially for Radio circuits - AKV.

Discuss the article SOLDERING SMD PARTS WITHOUT A HAIRDRYER

Many people wonder how to solder SMD components correctly. But before dealing with this problem, it is necessary to clarify what these elements are. Surface Mounted Devices - translated from English, this expression means surface mount components. Their main advantage is a greater mounting density than conventional parts. This aspect affects the use of SMD elements in the mass production of printed circuit boards, as well as their cost-effectiveness and manufacturability of installation. Conventional parts with wire-type leads have fallen out of favor along with the rapidly growing popularity of SMD components.

Errors and the basic principle of soldering

Some craftsmen claim that soldering such elements with their own hands is very difficult and rather inconvenient. In fact, similar work with HP components is much more difficult to carry out. In general, these two types of parts are used in various areas of electronics. However, many people make certain mistakes when soldering SMD components at home.

The main problem that amateurs face is the choice of a thin tip for a soldering iron. This is due to the existence of the opinion that when soldering with an ordinary soldering iron, you can smear the legs of SMD contacts with tin. As a result, the soldering process is long and painful. Such a judgment cannot be considered correct, since the capillary effect, surface tension, and wetting force play an important role in these processes. Ignoring these additional tricks makes it difficult to do the job yourself.

In order to properly solder SMD components, certain steps must be followed. To begin with, apply the soldering iron tip to the legs of the element taken. As a result, the temperature begins to rise and the tin melts, which eventually completely flows around the leg of this component. This process is called wetting force. At the same instant, the tin flows under the leg, which is explained by the capillary effect. Together with wetting the legs, a similar action occurs on the board itself. The result is a uniformly filled bundle of boards with legs.

Solder contact with neighboring legs does not occur due to the fact that a tension force begins to act, forming individual tin drops. It is obvious that the described processes proceed on their own, with only a small participation of the solderer, who only warms up the legs of the part with a soldering iron. When working with very small elements, they may stick to the tip of the soldering iron. To prevent this from happening, both sides are soldered separately.

Soldering in the factory

This process takes place on the basis of the group method. Soldering SMD components is carried out using a special solder paste, which is evenly distributed in a thin layer on the prepared printed circuit board, where there are already contact pads. This method of application is called screen printing. The material used in its appearance and consistency resembles toothpaste. This powder consists of solder to which flux has been added and mixed. The application process is carried out automatically as the printed circuit board passes through the conveyor.

Factory soldering of SMD parts

Further, the robots installed along the movement tape lay out all the necessary elements in the right order. Parts in the process of moving the board are firmly held in place due to the sufficient stickiness of the solder paste. The next step is heating the structure in a special furnace to a temperature that is slightly higher than that at which the solder melts. As a result of this heating, the solder melts and flows around the legs of the components, and the flux evaporates. This process makes the parts soldered into place. After the stove, the board is allowed to cool, and everything is ready.

Necessary materials and tools

In order to do the soldering of SMD components with your own hands, you will need certain tools and consumables, which include the following:

• soldering iron for soldering SMD contacts;
• tweezers and side cutters;
• an awl or needle with a sharp end;
• solder;
• a magnifying glass or magnifying glass, which are necessary when working with very small details;
• neutral liquid flux no-clean type;
• a syringe with which you can apply the flux;
• in the absence of the latter material, an alcohol solution of rosin can be dispensed with;
• for the convenience of soldering, the masters use a special soldering dryer.

Tweezers for installing and removing SMD components

The use of flux is essential and must be liquid. In this state, this material degreases the working surface, and also removes the oxides formed on the soldered metal. As a result, an optimal wetting force appears on the solder, and the soldering drop retains its shape better, which facilitates the entire work process and eliminates the formation of “snot”. The use of an alcohol solution of rosin will not allow you to achieve a significant result, and the resulting white coating is unlikely to be removed.

The choice of soldering iron is very important. The best tool is one that can be adjusted in temperature. This allows you not to worry about the possibility of damage to parts by overheating, but this nuance does not apply to the moments when you need to desolder SMD components. Any soldered part is able to withstand temperatures of about 250-300 ° C, which provides an adjustable soldering iron. In the absence of such a device, you can use a similar tool with a power of 20 to 30 W, designed for a voltage of 12-36 V.

Using a 220 V soldering iron will not lead to the best results. This is due to the high heating temperature of its tip, under the influence of which the liquid flux quickly evaporates and does not allow the parts to be effectively wetted with solder.

Experts do not advise using a soldering iron with a conical tip, since the solder is difficult to apply to parts and a lot of time is wasted. The most effective is considered a sting called "Microwave". Its obvious advantage is a small hole in the cut for a more convenient grip of the solder in the right amount. Even with such a sting on a soldering iron, it is convenient to collect excess soldering.

Tip for soldering iron "Microwave"

You can use any solder, but it is better to use a thin wire, with which it is comfortable to dose the amount of material used. The soldered part with the help of such a wire will be better processed due to more convenient access to it.

How to solder SMD components?

Work order

The process of soldering, with a careful approach to theory and gaining some experience, is not difficult. So, the whole procedure can be divided into several points:

1. It is necessary to place SMD components on special pads located on the board.
2. A liquid flux is applied to the legs of the part and the component is heated with a soldering iron tip.
3. Under the action of temperature, the contact pads and the legs of the part are flooded.
4. After pouring, the soldering iron is removed and time is given for the component to cool. When the solder has cooled, the job is done.

The process of soldering SMD components

When performing similar actions with a microcircuit, the soldering process is slightly different from the above. The technology will look like this:

1. The feet of the SMD components fit exactly into their contact points.
2. In places of contact pads, wetting with flux is performed.
3. To accurately hit the part on the seat, you must first solder one of its extreme legs, after which the component is easily exposed.
4. Further soldering is carried out with the utmost care, and the solder is applied to all legs. Excess solder is removed with a soldering iron tip.

Soldering iron with a sharp tip 24 V.

How to solder with a hair dryer?

With this method of soldering, it is necessary to lubricate the seats with a special paste. Then the necessary part is placed on the contact pad - in addition to components, these can be resistors, transistors, capacitors, etc. For convenience, you can use tweezers. After that, the part is heated with hot air supplied from a hair dryer at a temperature of about 250º C. As in the previous soldering examples, the flux evaporates under the action of temperature and melts the solder, thereby flooding the contact tracks and legs of the parts. Then the hair dryer is removed, and the board begins to cool. When completely cooled, the soldering can be considered finished.

Hair dryer for soldering small parts

lampagid.ru

Soldering SMD parts at home

SMD - Surface Mounted Devices - Surface Mount Components - this is how this English abbreviation stands for. They provide a higher mounting density than traditional parts. In addition, the assembly of these elements, the manufacture of a printed circuit board, turn out to be more technologically advanced and cheaper in mass production, so these elements are becoming more widespread and are gradually replacing the classic parts with wire leads.

A lot of articles on the Internet and in printed publications are devoted to the installation of such details; in my article on the choice of the main tool, I already wrote a little on this topic. Now I want to add it.

I hope my opus will be useful for beginners and for those who have not dealt with such components yet.

The release of the article is timed to coincide with the release of the first Datagor constructor, where there are 4 such elements, and the PCM2702 processor itself has super-small legs. The supplied printed circuit board has a solder mask, which facilitates soldering, but does not eliminate the requirements for accuracy, lack of overheating and static.

A few words about the tools and consumables necessary for this purpose. First of all, it is tweezers, a sharp needle or an awl, wire cutters, solder, a syringe with a fairly thick needle for applying flux is very useful. Since the details themselves are very small, it can also be very problematic to do without a magnifying glass. You will also need a liquid flux, preferably a neutral non-cleaning one. In extreme cases, an alcohol solution of rosin is also suitable, but it is still better to use a specialized flux, since their choice is now quite wide on sale. In amateur conditions, it is most convenient to solder such parts using a special soldering dryer or, in other words, a hot air soldering station. The choice of them now on sale is quite large and the prices, thanks to our Chinese friends, are also very affordable and affordable for most radio amateurs. Here, for example, is such a sample of Chinese production with an unpronounceable name. I have been using this station for three years now. While the flight is normal. And of course, you will need a soldering iron with a thin sting. It is better if this sting is made using the Microwave technology developed by the German company Ersa. It differs from the usual sting in that it has a small recess in which a drop of solder accumulates. Such a tip makes less sticking when soldering closely spaced leads and tracks. I strongly recommend finding and using it. But if there is no such miracle sting, then a soldering iron with an ordinary thin tip will do. In the factory, soldering SMD parts is carried out by a group method using solder paste. A thin layer of special solder paste is applied to the pads on the prepared printed circuit board. This is usually done by screen printing. Solder paste is a fine powder of solder mixed with flux. It has a consistency similar to toothpaste. After applying the solder paste, the robot lays out the necessary elements in the right places. The solder paste is sticky enough to hold the parts. Then the board is loaded into the oven and heated to a temperature just above the melting point of the solder. The flux evaporates, the solder melts and the parts are soldered into place. It remains only to wait for the board to cool down. Here you can try to repeat this technology at home. Such solder paste can be purchased from cell phone repair companies. In stores selling radio components, it is also now usually in stock, along with conventional solder. As a dispenser for the paste, I used a thin needle. Of course, this is not as accurate as, for example, Asus does when it manufactures its motherboards, but here it is as good as it could. It will be better if this solder paste is drawn into a syringe and gently squeezed through the needle onto the contact pads. You can see in the photo that I overdid it by sloshing too much pasta, especially on the left. Let's see what happens. We lay the parts on the contact pads greased with paste. In this case, these are resistors and capacitors. This is where thin tweezers come in handy. It is more convenient, in my opinion, to use tweezers with curved legs. Instead of tweezers, some use a toothpick, the tip of which is slightly smeared with flux for stickiness. There is complete freedom - to whom it is more convenient. After the parts have taken their position, you can start heating with hot air. The melting temperature of the solder (Sn 63%, Pb 35%, Ag 2%) is 178c*. I set the hot air temperature to 250c* and from a distance of ten centimeters I begin to warm up the board, gradually lowering the tip of the hair dryer lower and lower. Be careful with air pressure - if it is very strong, it will simply blow the parts off the board. As it warms up, the flux will begin to evaporate, and the dark gray solder will begin to lighten and eventually melt, spread and become shiny. Approximately as seen in the next picture. After the solder has melted, the tip of the hair dryer is slowly removed away from the board, allowing it to gradually cool down. Here's what happened to me. By large drops of solder at the ends of the elements, you can see where I put too much paste, and where I was greedy. Solder paste, generally speaking, can be quite scarce and expensive. If it is not available, then you can try to do without it. How to do this, consider the example of soldering a microcircuit. To begin with, all contact pads must be carefully and thickly irradiated. In the photo, I hope you can see that the solder on the contact pads lies in such a low hill. The main thing is that it should be distributed evenly and its amount on all sites should be the same. After that, we wet all the contact pads with flux and let it dry for some time so that it becomes thicker and stickier and the parts stick to it. Carefully place the chip in its intended place. We carefully combine the findings of the microcircuit with the contact pads. Next to the microcircuit, I placed several passive components - ceramic and electrolytic capacitors. So that the parts are not blown away by the pressure of air, we begin to heat up. There is no need to rush here. If it is rather difficult to blow off a large one, then small resistors and capacitors easily scatter in all directions. Here's what happened as a result. The photo shows that the capacitors are soldered as expected, but some of the legs of the microcircuit (24, 25 and 22 for example) are hanging in the air. The problem may be either uneven solder application on the pads or insufficient quantity or quality of flux. You can correct the situation with an ordinary soldering iron with a thin tip, carefully soldering the suspicious legs. A magnifying glass is needed to notice such soldering defects. A hot air soldering station is good, you say, but what about those who don’t have one, but only have a soldering iron? With the proper degree of accuracy, SMD elements can also be soldered with a conventional soldering iron. To illustrate this possibility, let's solder resistors and a couple of microcircuits without the help of a hair dryer with just a soldering iron. Let's start with the resistor. We install a resistor on the contact pads pre-tinned and moistened with flux. So that it does not budge during soldering and does not stick to the tip of the soldering iron, it must be pressed against the board with a needle at the time of soldering. Then it is enough to touch the tip of the soldering iron to the end of the part and the contact pad, and the part on one side will be soldered. On the other hand, solder in the same way. Solder on the tip of the soldering iron should be the minimum amount, otherwise it may turn out sticky. Here's what I got with soldering the resistor. The quality is not very good, but the contact is reliable. The quality suffers due to the fact that it is difficult to fix the resistor with a needle with one hand, hold the soldering iron with the other hand, and take pictures with the third hand. Transistors and stabilizer microcircuits are soldered in the same way. I first solder the heat sink of a powerful transistor to the board. Here solder I do not regret. A drop of solder should flow under the base of the transistor and provide not only reliable electrical contact, but also reliable thermal contact between the base of the transistor and the board, which plays the role of a radiator. During soldering, you can slightly move the transistor with a needle to make sure that all the solder under the base has melted and the transistor seems to be floating on a drop of solder. In addition, excess solder from under the base will be squeezed out, improving thermal contact. This is how the soldered integrated stabilizer chip on the board looks like. Now we need to move on to a more difficult task - soldering the microcircuit. First of all, we again make an accurate positioning of it on the contact pads. Then we slightly “grab” one of the extreme conclusions. After that, you need to check again the correctness of the coincidence of the legs of the microcircuit and the contact pads. After that, in the same way we grab the rest of the extreme conclusions. Now the chip will not go anywhere from the board. Carefully, one by one, we solder all the other conclusions, trying not to put a jumper between the legs of the microcircuit. This is where the “microwave” sting, which I mentioned at the beginning, is very useful to us. With it, you can solder multi-pin microcircuits by simply running the tip along the pins. There are practically no sticky spots, and it takes only a minute to solder one side with fifty pins in 0.5 mm increments. If you don’t have such a magical sting, then just try to do everything as carefully as possible. What to do if several legs of the microcircuit were flooded with one drop of solder and it was not possible to remove this sticking with a soldering iron? Here a piece of braid from a shielded cable will come to the rescue. We impregnate the braid with flux. Then we apply it to the zalyapuha and heat it with a soldering iron. The braid, like a sponge, absorbs excess solder and releases the legs of the microcircuit from shorting. It can be seen that a minimum of solder remained on the terminals, which evenly filled the legs of the microcircuit. I hope I did not tire you with my writings, and did not greatly upset the quality of the photographs and the soldering results obtained. Maybe someone will find this material useful. Good luck!

Sincerely, Timoshkin Alexander (TANk)

Alexander (TANk)

Russian Federation, Izhevsk

With a soldering iron since childhood. For this reason, I ended up in a special school, where instead of labor lessons in high school there were radio electronics lessons. Then the physics department of the university. Work as a technologist in the microelectronics workshop at a defense plant until the plant was destroyed.

Then he taught all kinds of physics at the university. And now for twenty years - I've been soldering a puddle, fixing computers.

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datagor.ru

Soldering technologies for SMD components and their implementation at home

Over the past few years, surface mount radio technology has become very popular and is used in the manufacture of most modern electronic devices. The abbreviation SMD stands for - surface mounted device, which in turn can be translated as "surface mounted device". The very name of this technology fully reveals its essence - radio components are mounted directly on the surface of the board, but unlike hinged components, SMD components do not need special mounting holes.

The absence of special holes for installing radio components made it possible to make printed circuit boards more compact. The use of surface mount technology allows you to significantly save space on the board, which in turn allows you to increase the density of radio components and make more complex devices.

In addition, most SMD components are miniature in size because they do not require large pins, as with pin components. But many people mistakenly believe that all SMD components without exception are very small. Among them, large radio components are quite common, which differ from their “output” counterparts only in the type of conclusions (which is logical).

But let's move on to the essence of the article, namely the question - how is the soldering of SMD components carried out and is it possible to implement it at home.

SMD and regular electric soldering iron

Quite often, in small-scale production or the production of prototype devices, specialists use conventional electric soldering irons. How to solder SMD components using a contact soldering iron?

1. First, flux is applied to the place where the component is to be installed.

3. Apply a little solder to the soldering iron tip. The main thing is not to overdo it and not apply too much.

4. A drop of solder is applied to the contacts of the component. Thanks to the flux, the solder spreads well and securely fastens the component to the contact on the board.

If there is too much solder, the soldering place will come out sloppy. Excess solder can be easily lulled with a special tape, or simply with a soldering iron tip.

For soldering SMD components with a conventional soldering iron, it is better to replace the standard tip with a thin one. If this is not the case, you can use the standard one, but before you start serious work, you need a little training.

The advantage of this method is its simplicity. If you have an ordinary soldering iron, then apart from it, nothing is actually required. The disadvantages are also obvious - the speed of work will be quite low (especially if you do not have SMD soldering skills).

Soldering with a hot air soldering station (hair dryer)

This method is also often used in small-scale production and repair. At the same time, the soldering quality will be much higher than when using a conventional soldering iron. Soldering with a hot air soldering station, or a hair dryer, proceeds as follows:

1. A special solder paste is applied to the board.

2. An SMD component is installed that needs to be soldered.

3. The component and the place to be soldered are warmed up with a hair dryer. At the same time, the flux evaporates from the solder paste, and the smallest grains of solder melt and spread, soldering the component to the board contacts.

The advantages of this method are a neat place to solder the component to the board and the simplicity of the whole process. The main thing is not to apply too much paste. This does not always require the application of an additional portion of the flux, since it is already contained in the paste.

There is only one disadvantage of this method - a hot air soldering station can be quite expensive. Also, the air flow does not act pointwise, but on a certain area. If you do not install a tip for working with miniature SMD components, there is a high probability of warming up and melting solder on already soldered components.

Soldering with an infrared soldering station

Implementing this type of soldering at home can be difficult as the entire process is done with an infrared soldering station. As the name implies, the flux is heated using infrared radiation. At the same time, it is important to control the heating temperature, and it is also impossible to do without heating the board itself. This is necessary to prevent its deformation when heated with an infrared soldering iron.

There are many types of infrared soldering stations, among which you can find both amateur and professional, designed to work in small-scale production and service centers. The only drawback of such soldering stations is the high cost, in comparison even with good hot air stations.

How is the soldering process using such equipment?

1. First, solder paste is applied to the board.

3. The component together with the soldering point is heated by infrared radiation, as a result of which the component is reliably soldered to the soldering point.

There are complex, programmable soldering stations that are able to independently solder elements to the board. All you need to do is apply paste and components to the soldering points, and the soldering station will do the rest. At the same time, you can monitor the process from the monitor screen, tracking the progress of work and temperature indicators.

The advantage of this method is obvious - with a good soldering station, the process of manufacturing boards can be made semi-automatic. At the same time, the quality of the work performed will always be on top. But there are some drawbacks - a soldering station is quite expensive, and using semi-automatic stations requires certain skills and knowledge.

Some craftsmen assemble their own soldering stations. Their cost is much lower than that of the factory ones, but the assembly and programming process itself is quite complicated.

Soldering in an induction furnace

This process is used in the industrial production of printed circuit boards. It allows you to produce tens or even hundreds of printed circuit boards per hour, while the entire process can be fully automated. How is the process of induction soldering and preparation for it?

1. A special stencil is applied to the board.

2. Through a stencil, a layer of solder paste is applied to the board.

4. The board is sent to the induction furnace, where the entire soldering process takes place.

The advantages of induction soldering are high production speed, the possibility of complete automation of the process. Cons - such a mini-production is difficult to implement at home. And for the most part, it's still not profitable.

So what's the bottom line?

Despite the complexity of some soldering methods, all of them can be implemented at home:

• Soldering with a conventional electric soldering iron is the most affordable way to mount SMD components. With a little practice, you will be able to solder even complex components with a large number of pins.
• Soldering with a hot air soldering station gives optimal soldering quality and will not cause much difficulty even for beginners, but such a station is much more expensive than a conventional soldering iron. But if you are a true radio amateur and often work with SMD components, such costs will be justified.
• The infrared soldering station provides excellent soldering quality. If a branded station is not affordable, you can try to assemble your own, on your own. There are many hobbyist projects out there that even have lists of all the necessary components, and you can also download open source firmware. But remember that assembling your own soldering station requires certain skills and knowledge.
• Induction soldering is the most difficult, as it requires knowledge, skills and rare components. Nevertheless, all this can be implemented at home, but think about whether it is worth it and whether you need to produce device boards on an industrial scale.

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Manual soldering of miniature SMD elements

Surface-mounted components in their name provide for installation on the surface of the board, and not in holes, like the old elements. SMDs (Surface Mounted Elements) are lighter, cheaper, smaller, and can be placed closer together. These factors, and others, have contributed to the widespread use of definitive components today.

There are many relatively inexpensive tools and simple methods for soldering and desoldering SMDs.

SMD soldering tools

1. Temperature controlled soldering iron. A 10 bucks tool with no temperature control isn't really the best trainer to learn how to solder SMT. You don't need an expensive soldering station, but you should be able to control the temperature.

A relatively inexpensive $50 adjustable soldering iron has a temperature control knob from 0 to 5. It comes with the usual wedge-shaped ST3 tip, which may be too wide for chip components, but is still used quite often for soldering. Many people will be more comfortable with ST7 or ST8 tapered tips. The ST5 miniwave nozzle is convenient for soldering parts in QFP, QFN, PLCC, SOIC packages. A small depression in its cut surface allows you to keep the solder in an amount sufficient to distribute it over the entire row of microcircuit pins.

1. Solder. For hand-soldering surface-mounted components, we need a 60/40 tin-lead alloy in the form of a wire with a diameter of 0.015 inches (0.4 mm). There may be more lead in the alloy and thicker wire if you need to secure the connector to the board.

1. Unsoldering tape. This is one of the things that is simply indispensable for hand soldering. Also known as a solder scraper, it helps remove solder. It is woven from thin copper wires into a long pigtail, and sometimes has a flux inside.

1. Tweezers. Flat tip grippers are essential for handling and holding miniature chip components. Very comfortable with curved ends. You can get these for about $5.

Some people use vacuum tweezers to pick up and replace small components.

1. Flux. It is not always used when hand soldering SMD boards, but some people cannot do without it. Flux can be used even with ready-made solder wires, since the thinner the wire, the less of this solvent it contains. During soldering, the legs of the elements are heated more than once, so it is important to add a little flux from the outside.

1. Magnifying glass with a flashlight. You will need plenty of light and a magnifying glass anyway when soldering miniature items. There are good head lenses like OptiVisors, magnifying 2.5 times, they have built-in lighting lamps.

You will need a 10x magnifying glass to check your work. These magnifiers also have a built-in flashlight.

Braid desoldering technique

To desolder, put a copper pigtail on the legs of the element and run a hot soldering iron over it. The heat and flux will draw the tin onto it. Use the other end of the pigtail if it seems that nothing is working (a small piece of it is cut off from the spool).

Depending on the circumstances, the pigtail must be raised higher, while the heat will be removed along it up from the area where the soldering iron touches.

To clean the braid, you need to add more flux.

Soldering two-pin elements

Elements such as resistors and capacitors often crack due to uneven heating. Solder two opposite ends at the same time. Use tweezers to hold the part on the board. Apply some solder to one side to form a neat fillet between the end of the element and the pad. Ideally, you should get exactly a smooth jumper, and not a huge ball of tin at the end.

If not, use copper tape to remove excess solder.

Soldering SOIC and other chips with multiple pins

Use tweezers or a suction cup to hold the SOIC (Small Loop Integrated Circuit) on the board. Solder one of the pins of the microcircuit, it is desirable that it be a power leg. Then grab the other power lead from the opposite side. Make sure all the other legs are lined up over their pads.

Connect the rest of the legs - starting with the extreme, not soldered contacts, draw a wave of solder, feeding tin wire to the soldering iron tip if necessary. Do this operation as quickly as possible without overheating the chip.

Removing sagging

When you are done soldering, inspect the legs of the chip elements. Small bridges between them can be easily removed by quickly heating them with a soldering iron dipped in flux. Thick jumpers are removed in a familiar way - with the help of a soldering tape.

High-quality soldering of the surface of microcircuit boards is ensured by special components, where solder paste for SMD plays a significant role. According to the generally accepted classification, the industry uses several subspecies of materials used for effective connection, in particular:

• Washout group.
• Cleanup group.
• Soluble based on aqueous liquid.
• Halogen-containing.
• Halogen free.

What is SMD and basic principles

The use of flux for soldering SMD components has its own characteristics, which can improve the connection of the surface of microcircuits and boards. The general recommendation for the use of flux for SMD soldering is effective for chip resistors, as well as SOIC, LQFP, QFN and others. The application of the thinnest layer of material allows for industrial soldering without compromising quality. By the way, literally from English, the meaning of SMD soldering paste is translated as “the use of components for surface soldering” (Surface Mounted Devices). As you can see from the working name of the paste, it allows you to provide a sufficient assembly tightness of the joint compared to conventional technologies.

Most craftsmen mistakenly believe that the use of SMD components is impractical at home. Most craftsmen believe that only TH technology can be needed at home, although the main problem is choosing the right soldering tip diameter. Inexperienced craftsmen really do not know the intricacies of using SMD soldering with solder paste, since the result of the work is “smearing” SMD tin with printed circuit board contacts. To avoid typical mistakes, some parameters should be taken into account: the capillary effect, which must have a fine structure of the structure, as well as surface tension and proper wetting of the treated surface. Ignoring the tasks at hand will not be able to fully answer the difficult question of which flux is best for SMD soldering at home or on an industrial scale.

High-quality contact with the legs of the microcircuit board with SMD components occurs for one simple reason, the effect begins to have a general tension force, which forms separate independent droplets of formation on the surface of the tin board.

As can be seen from the general description, the wizard's actions are minimized and the flux for soldering SMD components only heats up the legs of the applied parts of the micro-details. Remember, when working with very small components and parts, technological elements may seize (unforeseen connection) to the tip of a working hot soldering iron, which negatively affects the further operation of the microcircuit.

Features of technology in the factory

For industrial production, the paste for soldering SMD components is adapted to a group system, where an electronic flux application system is used on the surface of the microcircuit. On the surface of the contact working areas, a thin application technology is used using silk-screen printing. Thus, in terms of technology and consistency, the material is somewhat reminiscent of our usual toothpaste. The substance includes solder powder as well as flux components. The entire substance is mixed and conveyorized onto the surface of the microcircuit.

The automated system carefully turns over the boards that need to be soldered, then the microcircuits are moved to a temperature cabinet, where the mass spreads, followed by soldering. In the furnace, under the influence of the required temperature, a conditional flow around the technological contact legs of the SMD components occurs, and as a result, a fairly strong connection is obtained. After the temperature cabinet, the microcircuit is again transferred to the natural environment, where cooling takes place.

Can I solder with SMD paste myself?

Theoretically, yes, but in practice, quite a lot of experience is needed to carry out this technological operation. For work, we need the following tools and preparations:

• Special soldering iron with a thin tip for SMD components.
• Side cutters are tool.
• Industrial tweezers.
• An awl or a special thin needle.
• Solder material.
• A magnifying glass, you can use a magnifying glass (it will be necessary to constantly monitor the thin legs of the SMD components).
• Flux with neutral non-cleaning properties (additional preparation).
• The syringe with which we will apply the flux.
• If there is no non-washing preparation, we use alcohol infusion and rosin.
• Soldering dryer of medium load and power.

The flux must always be in a liquid state, so you completely disinfect the surface of the microcircuit. In addition, the preparation removes the formation of oxides on the surface of the board during operation. Remember that an alcohol solution together with rosin cannot ensure the quality of soldering, and their use is only permissible if there is no suitable soldering compound at hand.

Soldering iron selection

For work, you need to pick up a special soldering iron, which has an adjustable heating range. A soldering iron is suitable for working with a microcircuit, which has a working heating temperature of no more than + 250 ... + 300 C. If such a soldering iron is not at hand, it is allowed to use a device with a power of 20 to 30 W and no more than 12-36 Volts.

A soldering iron with a voltage of 220 volts will not be able to provide soldering quality, where it is very difficult to regulate the required flux heating temperature.

We do not recommend using a soldering iron with a cone-type tip, as this will damage the surface to be treated. The most optimal sting is the "microwave" type. A soldering iron with a voltage of 220 volts not only heats up quickly, but also leads to the fact that the components volatilize during the soldering process. For the efficient operation of the soldering iron, we recommend using the thinnest wire to ensure the interaction of the tip, flux and solder.

• We place the SMD components on a special contact working platform.
• We apply the liquid preparation to the legs of the components involved very carefully.
• Under the action of the operating temperature, the flux and solder spread over the contact area.
• We give the time necessary for the contacts and the preparation to cool down on the surface of the board.

But, for a microcircuit, the soldering procedure is slightly different from the above:

• We install SMD contacts on precisely installed contact points.
• Wet the joints with flux in the joints.
• For high-quality solder, we make reliable contact on one side, after which we solder the other leg.
• Extremely carefully solder other working components, do not forget to remove formations with a soldering iron tip.

In some cases, it is possible to use a special soldering gun for soldering, but for this it is necessary to create suitable working conditions. Remember that the hair dryer can only be heated to a temperature of +250 C, no more (in rare cases, up to +300 C).

Video: how to make a do-it-yourself flux for SMD soldering

All the best! This rating contains the best fluxes for soldering and is compiled from personal preferences and feedback from electronics repairmen. Many readers will now think - “Well, finally! Master Soldering has started to write something about soldering!” and they will be right - for almost 4 years, not a single decent article about the soldering process has been written on the blog, although the name of the blog seems to oblige. I admit, I confess, I will correct the situation.

I plan to publish reviews of soldering processes, soldering tools, soldering videos and new technologies in the soldering world. And today I will give my rating of the 10 best fluxes for soldering. This rating is based on personal preferences and all kinds of feedback from familiar electronics repairmen of various levels and does not claim to be exclusive. Let's go - fluxes for soldering.

Rating of the most popular soldering fluxes

What should we know about flux?

The flux is designed to improve the quality of the process of soldering two metal surfaces by soldering and, when heated, cleans the surfaces from oxide and greasy films. A good flux should have a low melting point and low specific gravity. Before the solder melts, it must have time to dissolve the oxides and not penetrate deep into the solder joint during the soldering process. The flux should spread well and wet the surface of the solder and the metal at the place of soldering.

In fifth place is the most popular flux of all time, the muse of musicians, gift of nature, her majesty rosin. Rosin is gum (from the resin of coniferous trees, has almost no fatty acids), extraction (extraction of coniferous sawdust with gasoline, contains more fatty acids than gum) and tall (residues after sulfate-cellulose production of soap).

In fourth place is the beloved alcohol-rosin flux SKF or FKSp (soldering alcohol-rosin flux). It consists of 60-80% alcohol and 20-40% rosin. Such a mixture can be prepared at home with your own hands. For example, many simply crumble rosin into alcohol in a ratio of about 1 to 3. It is convenient to use in a syringe with a needle. But when stored in a loosely closed syringe, it begins to dry out on the needle and stops flowing.

Advantages:

affordable and popular inactive flux, easy to apply, does not smoke much.

Disadvantages:

when heated, the alcohol begins to rapidly evaporate and hiss.

What to solder: copper wires, gold-plated and silver-plated contacts of microcircuits and radioelements, brass, zinc.

How to rinse: alcohol, solvents, gasoline, alcohol-gasoline mixture.

So we got to the Top 3 best soldering fluxes. On the prizes, I placed professional fluxes, which in ordinary life may not be useful. But in the craft - they are very necessary.

Fluxes Amtech RMA-223 and Kingbo RMA-218

The third bronze place is occupied by Amtech RMA-223 - it is a gel flux - a mixture of crushed rosin and solvent.

I also suspect that there may be activators and fragrance in the composition. - the biggest sign of a fake- on the sticker there is an inscription in small print “Coliformia” instead of “California”, however, oddly enough, the Chinese fake flux is very good in operation, and many services just sit on it. Although the masters from mysku do not advise to take this flux for Ali, but it is better to take an analogue.

Advantages:

it is convenient to apply the gel, good solderability, you can not wash it, a fake is cheap (about 200 rubles), but it soldered very well with it and smelled of perfume.

Expensive (a 10 g tube can cost 1,500 rubles), smelly, fakes come across. The price is a limiting factor, for example, a 30 g tube can cost from 2,000 rubles.

What to solder: mainly responsible lead-free and lead soldering.

How to rinse: most can not be washed off, alcohol, solvent, there is a proprietary solvent T2005M.

This concludes the Top 10 best soldering fluxes. Of course, there are a lot of other fluxes, including good Chinese and top German and Japanese ones. But I haven't used them, so I can't adequately describe them.

If you, dear readers, use any other flux and consider it the best in the world, then be sure to write to me about it in the comments. Perhaps it will appear in the rating after testing.

Soldering Master tried for you.