How to properly solder smd components. How to quickly desolder SMD components

One trouble happened here the other day - I burned the power track on the UART-USB converter board (on ATtiny2313). I had to replace the burnt track with a jumper wire. Everything seems to be working as it should, but this posting began to annoy me. I decided to upgrade the converter board for this case, so to speak, upgrade to version No. 2. And since the microcontroller is intact, it can be unsoldered and rearranged to a new board. Since I promised to show how to solder them, then, at the same time, I will fulfill my promise.

Desoldering SMD components.
Of course, the best tool for desoldering SMD components is a hair dryer, but in the absence of a hair dryer, you have to get out with improvised means. There are many ways, ranging from the manufacture of special attachments for a soldering iron (to heat all the legs at the same time), the use of mica, chemical etching, and ending with exotic methods, such as heating the board closely with a powerful spotlight. For the most part, these methods are not particularly humane to the board and tracks. They shamelessly overheat and become ill-suited for reuse.
For myself, I chose a method that is as gentle as possible for both the board and tracks, and for the soldered components. In addition, this method does not require any special materials or technologies.

Materials tools:
1 Special "braid" for solder removal. Getting it is not a problem - it is not a shortage. Can be replaced with a bundle of thin wires (of course, not oxidized);
2 Liquid flux. I buy a flux called F5. Can be replaced with alcohol-rosin, but the effect will be worse;
3 Needle or thin awl, tweezers.

The desoldering technology is as follows:
1 We moisten abundantly with flux, both the soldered legs and the “braid” itself;
2 With the help of a “braid” and a soldering iron, we remove the solder as much as possible. This will require several passes. Don't skimp on the braid!
3 After the solder is removed as much as possible, we proceed to tear off the legs from the tracks. This is done in the following way: wielding the needle as a lever, slightly pry the leg, leaning on the next one. Great effort is not needed - the legs lag behind very easily with a characteristic click. We do this procedure with all legs. If any leg does not lend itself - we do not force it, we leave it as it is;
4 After all the legs are torn off, the microcircuit will no longer hold anything - just pick it up from the board. If several legs have not come off the tracks, it’s okay to grab the case with tweezers (or pry it with an awl) and carefully tear it off with a little effort.

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054-Unsoldering SMD components.: 29 comments

1. hryam

   Of course, it is much easier to solder with a hairdryer, if there are additional nozzles, then in general a song. You play - you shoot. Your method is slightly vandal, it is quite possible to tear off the track under it along with the leg of the microcircuit, it’s good if you only need a microcircuit, but what if it’s the other way around? ...

2. GetChiper Post author

   In this I agree. But this is a less vandalistic way than, for example, pouring rosin or heating it with a kilowatt spotlight or an industrial hair dryer.
   We must understand that this method is only suitable for single desoldering if this happens to you often - a blow dryer is a must!

3. SemLeik

   And also, are SMD elements found only on computer boards ??

4. GetChiper Post author

   Why only on computer boards? They are used very widely. It is more profitable for manufacturers to make electronic equipment on SMD components for the following reasons:
   - SMD are cheaper
   - under SMD, you do not need to drill holes in the boards (this greatly simplifies and reduces the cost of production)
   - SMD take up less space and are stored in convenient automatic mounting ribbons
   - SMD is easier to mount automatically

   For the same reasons, except for the last point, for radio amateurs, it is also more profitable to use SMD components.

5. cosmogon

   Greetings. What hair dryer do you recommend? What brand, type. Not only soldering, but also soldering. Fan in the handle, in the block? What is better than one or the other? What is the price, and within what range?

6. GetChiper Post author

   I won’t say anything on the hair dryer’s bill - I don’t have it myself. I use a soldering iron.

7. anatoliy

   
   Fan rulez!!
   And even cooler technological convection oven 😀
   It's just no words, just emotions! Moreover, positive
   I tried to unsolder the motherboard somehow for the sake of fun. I put the thermostat on 290, it warmed up and beeped. He quickly took out the board and right in the frame about the edge of the open cardboard box. Bang!! All the details are there 🙂
   And soldering is just a fairy tale. Smeared with paste. put the details. shoved the fee. Selected a profile. Enabled. 30 sec. Biknulo took out. cooled, washed ready. All parts are strictly in the center of the sites. all at the same height.
   With a certain skill, you can assemble it from a household electric oven 🙂

8. aui2002

   Rumor has it that instead of an oven, you can take some powerful halogen spotlights. Nothing is fried either.

9. anatoliy

   It turns out ik. Still need to control the temperature. Our men made from a household oven. Microcontroller 4 thermocouples. And how is it??? Well, the IR sensor is from the motion detector.
   Differences from the industrial did not notice. Except for the price!

10. GetChiper Post author

    Wow - this is industrial technology! Although I already see the advantages of the stove (even for small boards).

11. aui2002

    Well, then it’s easier to buy a cheap autoclave stove (used in chemical laboratories) a new low-temperature or old high-temperature one (high-temperature ones heat up to about 1000 Celsius, but over time they “lose their grip” and do not warm up above 400-500. They are usually written off or sold for next to nothing.)

    Advantage over oven small size(30x20x40cm) and a built-in heating rate control system.

12. anatoliy

    
    Logically 🙂
    But it's not available everywhere! I would get one like this. Apply a conductive coating to the glass. It just needs 400C.

    Moreover, when soldering, it is not the speed that matters, but the so-called temperature profile. which must be strictly adhered to.
    Another important detail is the frame. In which the fee is fixed. It should be possible to remove it from the oven both in a cold state and in a hot one. Moreover, no shocks. Otherwise, the details will crumble.

13. aui2002

    
    In them, as a rule, there are 1-2 pairs of guides (sled) under them, the frame is quite easy to bungle.
    And as for the temperature profile, such furnaces are just “sharpened” for uniform heating of the entire volume.

14. anatoliy

    
    Well, what do you need to try 🙂 As I understand it, do you have a volunteer for the experiment? A powerful trinistor MK and 4 thermocouples and you will be happy 🙂 You can also organize blowing through the intake air for a sharp drop in temperature. And suitability is easy to determine. Set the thermocouple to heat at maximum power up to 300 degrees, then turn it off abruptly and build a heating-cooling profile in seconds. Then compare with the recommended for soldering. There are almost any datasheet on SMD parts. And realize suitability for alteration.
    IMHO, when soldering, it is necessary to heat up relatively sharply and cool it down smoothly

15. ZagZag

    Here I was looking for information about the definition of SMD components.
    Well, with resistors, everything is clear. 3 digits: 2 - face value, last - degree.
    Examples:
    102 = 10 * 10^2 = 1000 ohm = 1 ohm
    103 = 10 * 10^3 = 10 com
    Topic article.

Soldering chips from the board is not a trivial task, regardless of the type of controller. You unsolder one leg, but while you are doing the other, it freezes. You can bend the legs after soldering, but the problem of breaking off the contacts again arises. The question arises, how to solder the microcircuit from the board with a soldering iron? The answer is quite simple: use the knowledge of physics and improvised items. There are a number of options for carefully removing microchips from the board. But first, some theory.

Chip types

Currently, there are a number of cases, but only two are the most widespread, and in fact all other varieties are variants of two main types:

• DIP - roughly speaking, this case option for internal installation, the legs of this controller are placed in the holes on the board;
• SMD - this type of microchip is designed for surface mounting, in this case, "patch" is placed on the board, to which the legs of the microcircuit are soldered.

Each option has its own advantages and disadvantages. But within the framework of the article, their features in terms of desoldering are interesting. How to solder a microcircuit in a particular case, we will analyze a little lower.

Removing the DIP package

As already noted, this type of microcircuit is distinguished by mounting into holes on the circuit board. This imposes certain restrictions on the process of its dismantling. In order to carefully remove its legs from the holes, you need to remove the solder from the junction, almost completely freeing the legs. It should be noted that alternate heating and dismantling of a separate contact will not work here, since, as it cools, the solder remaining in place will again fix the microchip in place. Therefore, the desolderingDIPcase is optimal by the following methods:

1. Using improvised means - for this purpose, needles from medical syringes or special hollow tubes that are now sold in electrical stores are suitable. But the option of using a medical needle is the cheapest and most affordable. To do this, you need to pick up a needle with a diameter slightly smaller than the landing sockets for the microchip leg. Then cut off its pointed part with a file or just bite off, after which file off the flattened part with a file. After that, having installed the resulting hollow tube with an even cut on the seat, simply heat it with a soldering iron, thereby releasing the leg of the chip;
2. The second option is to drag the solder from the place of soldering onto copper wires moistened with flux, such as, for example, alcohol rosin. The wire with flux heated by the soldering iron gradually pulls the solder onto itself from the place of soldering. This option takes more time, but is also quite effective;
3. Using a soldering iron with solder suction - in this case, special difficulties in dismantling are not expected. The main thing is to control the heating temperature in the contact zone so as not to damage the board and the part itself.

These options will allow you to quickly and efficiently desolder DIP packages from the board.

Important! The main requirements for using a soldering iron in this case will be constant control over the pressure and temperature in the soldering zone. Overheating and excessive pressure can damage the part.

Important! When using a needle of a medical syringe, you can simplify the task of cutting it, for this, before cutting, it is enough to ignite the place of the cut red-hot.

SMD controllers

The surface mount housing is more easily dismantled. In this case, you can use a wide soldering iron tip and copper wire with flux and solder several contacts at once. But there is more interesting methods desoldering:

1. Using a metal strip or half of a razor blade to distribute the heat of the soldering iron to one row of chip legs. In this case, a steel strip is installed on a number of contacts on one side and heated with a tip until the solder melts, after which this side rises slightly above the board. The solder on the other side of the chip is then melted in the same way;
2. Using a long piece of copper braid with flux applied to it. The segment is placed on the legs of the microcircuit on one side and heated with a soldering iron; pulling the solder onto the braid, lift the part with tweezers. Then, in the same way, remove the solder on the other side of the controller;
3. Technically interesting option is the use of Rose or Wood alloys. Drops of this solder are applied to the contacts and heated, thereby lowering the melting point of the solder. Further, the solder gradually warms up, and the microcircuit is dismantled;
4. Using a hair dryer or blowtorch. To use this tool, flux is applied to the soldering points. After that, the surface and the part are heated, and the microcircuit is removed from the mounting patches with tweezers.

It should be noted that each dismantling option is used in specific conditions, the main task in this case is to choose the most optimal option from the point of view of safety and, when using it, not damage the part itself or the board tracks.

Important! When dismantling the microcircuit, it is important to remember that any parts or components on the board have their own temperature minimum, exceeding it will lead to the failure of the microcircuit.

The use of improvised tools and a soldering iron when mounting or dismantling microcontrollers is quite justified, but requires at least the skills to work with a soldering iron. In their absence, you should first practice on unnecessary details. This process will allow you to gain the necessary experience on how to desolder the microchip without damage, in addition to choosing the most best option work with a specific board and type of chip package.

Video

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.

Many articles on the Internet and in print publications are devoted to the installation of such parts. 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, where there are 4 such elements, and the PCM2702 processor itself has super-small legs. Supplied in a kit PCB has a solder mask, which facilitates soldering, but does not cancel the requirements for accuracy, lack of overheating and static.

Tools and materials

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 depression 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. For prepared printed circuit board a thin layer of special solder paste is applied to the pads. This is usually done by screen printing. Solder paste is a fine powder of solder mixed with flux. Its consistency is 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 cooling of the board.

This technology can be tried to repeat at home. Such solder paste can be purchased from repair companies. cell phones. 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. Here full freedom- whoever is more comfortable.

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. 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 stickiness may result.

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 float 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 more challenging 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.

How to solder SMD? Sooner or later, all electronics engineers had to deal with such a question.

There are times when a simple soldering iron cannot get close to SMD elements. In this case, it is best to use a soldering iron and thin metal tweezers.

In this article, we will talk about how to properly solder and desolder SMD. We will train on the corpse of the phone. I showed with a red rectangle that we will solder and solder back.

AOYUE INT 768 Soldering Station takes over

The hair dryer needs the right attachment. We choose the smallest one, since it will be a small smd-shku to solder and solder.

And here is the whole assembly.

Using a toothpick, apply the fluxplus to the smd-shku.

This is how we smeared it.

We set the temperature of the hair dryer at the soldering station to 300-330 degrees and begin to fry our part. If the solder does not melt, it can be thinned with Wood's or Rose's alloy using a thin soldering iron tip. As we will see that the solder begins to melt, with the help of a picent, we carefully remove the part without hitting the smd-shki that are nearby.

And here is our detail under the microscope

Now solder it back. To do this, we clean the patches (if you have not forgotten, these are contact pads) using a copper braid.

After we cleaned them of excess solder, we need to make bumps with new solder. To do this, we take quite a bit of solder on the tip of the soldering iron tip.

And we make tubercles on each contact pad.

Put the smd-detail there

And we warm it with a hairdryer until the solder spreads along the walls of the part. Do not forget about the flux, but you need very little of it.

Ready!

In conclusion, I would like to add that this procedure requires the ability to work with small details. Everything will not work out right away, but whoever needs it will eventually learn how to solder and desolder SMD components. Some craftsmen solder smd-shki with solder paste. The solder paste I used when soldering the BGA chips in this article.

There was a desire and a need to switch to more compact circuits than those assembled on a conventional breadboard. Before thoroughly purchasing textolite, elements and microcircuits for surface mounting, I decided to try and see if I could assemble such a trifle. In the vastness of Aliexpress, there was an excellent “simulator” for very reasonable money. If you have soldering experience, it makes little sense to read the review

The set is a light effect running lights, the speed is regulated by a variable resistor.
Everything arrived in a standard pimply envelope, in a zip package.

Appearance of the set

Consumables

soldering iron

I ended up using these healthy stings ... It turned out to be very convenient for them to correct crooked elements, since its size is enough to heat both soldering points, and then I was too lazy to change it.

Holders

the third hand, heat shrink is put on the crocodiles so as not to scratch the textolite, and the board at the same time keeps many times better


PCB Holder

A couple more photos