Designations of smd components on the diagrams. SMD marking. Guide for practitioners. What gives the use of SMD components

Modern radio equipment is built mainly only on the so-called chip components, these are chip resistors, capacitors, microcircuits, and so on. The output radio components that we used to solder from old TVs and tape recorders and that radio amateurs usually use to assemble their circuits and devices are less and less used in modern radio equipment.

What are the advantages of using such chip elements? Let's figure it out.

The advantages of this type of installation

Firstly, the use of chip components significantly reduces the size of finished printed circuit boards, their weight is reduced, as a result, this device will require a small compact case. So you can assemble very compact and miniature devices. The use of chip elements makes it possible to save a printed circuit board (fiberglass), as well as ferric chloride for etching them, in addition, you do not have to spend time drilling holes, in any case, it does not take much time and money.
Boards made in this way are easier to repair and easier to replace the radio elements on the board. You can make double-sided boards, and place elements on both sides of the board. Well, and saving money, because the chip components are cheap, and it is very profitable to buy them in bulk.

First, let's define the term surface mount, what does it mean? Surface mounting is a technology for the production of printed circuit boards, when radio components are placed on the side of the printed tracks, it is not necessary to drill holes to place them on the board, in short, this means "surface mounting". This technology is the most common today.

In addition to the pros, there are of course also cons. Boards assembled on a chip components are afraid of bends and bumps, because. after that, radio components, especially resistors with capacitors, simply crack. Chip components do not tolerate overheating when soldering. From overheating, they often crack and microcracks appear. The defect does not manifest itself immediately, but only during operation.

Types and types of chip radio components

Resistors and Capacitors

Chip components (resistors and capacitors) are primarily divided by size, there are 0402 - these are the smallest radio components, very small, such are used, for example, in cell phones, 0603 - also miniature, but slightly larger than the previous ones, 0805 - are used, for example, in motherboards boards, the most popular, then 1008, 1206 and so on.

Resistors:

Capacitors:

Below is a more table showing the dimensions of some elements:
- 1.0×0.5mm
- 1.6×0.8mm
- 2.0×1.25mm
- 3.2×1.6mm
- 4.5×3.2mm

All chip resistors are marked with a code, although a method for decoding these codes is given, many still do not know how to decipher the values of these resistors, in connection with this I painted the codes of some resistors, take a look at the table.

Note: There is an error in the table: 221 "Ohm" should be read as "220 Ohm".

As for capacitors, they are not labeled or labeled in any way, so when you buy them, ask the seller to sign the tapes, otherwise you will need an accurate multimeter with a capacitance detection function.

transistors

Basically, radio amateurs use transistors of the SOT-23 type, I won’t talk about the rest. The dimensions of these transistors are as follows: 3 × 1.75 × 1.3 mm.

As you can see, they are very small, you need to solder them very carefully and quickly. Below is the pinout of the conclusions of such transistors:

The pinout for most transistors in such a package is exactly the same, but there are exceptions, so before soldering the transistor, check the pinout by downloading the datasheet for it. Such transistors in most cases are designated with one letter and 1 number.

Diodes and zener diodes

Diodes, like resistors with capacitors, come in different sizes, larger diodes are marked with a strip on one side - this is the cathode, but miniature diodes can differ in labels and pinouts. Such diodes are usually designated by 1-2 letters and 1 or 2 numbers.

Zener diodes, like diodes, are indicated by a strip on the edge of the case. By the way, because of their shape, they like to run away from the workplace, they are very nimble, and if they fall, you won’t find them, so put them, for example, in the lid of a rosin jar.

Microcircuits and microcontrollers

Microcircuits come in different cases, the main and commonly used types of cases are shown below in the photo. The worst case type is SSOP - the legs of these microcircuits are located so close that it is almost impossible to solder without snot, the nearest outputs stick together all the time. Such microcircuits need to be soldered with a soldering iron with a very thin tip, and preferably with a soldering dryer, if there is one, I described the method of working with a hairdryer and solder paste in this one.

The next case type is TQFP, the photo shows a case with 32 legs (ATmega32 microcontroller), as you can see, the case is square, and the legs are located on each side of it, the main disadvantage of such cases is that they are difficult to solder with a conventional soldering iron, but you can. As for the other types of cases, it is much easier with them.

How and with what to solder the chip components?

It is best to solder the radio component chip with a soldering station with a stabilized temperature, but if there is none, then it remains only a soldering iron, which must be turned on through the regulator! (without a regulator, most ordinary soldering irons have a tip temperature of 350-400*C). The soldering temperature should be around 240-280*C. For example, when working with lead-free solders having a melting point of 217-227*C, the temperature of the soldering tip should be 280-300°C. During the soldering process, excessively high tip temperature and excessive soldering time must be avoided. The tip of the soldering iron should be sharply sharpened, in the form of a cone or a flat screwdriver.

The printed tracks on the board must be irradiated and coated with an alcohol-rosin flux. It is convenient to support the chip component during soldering with tweezers or a fingernail, you need to solder quickly, no more than 0.5-1.5 seconds. First, one lead of the component is soldered, then the tweezers are removed and the second lead is soldered. The microcircuits must be very accurately aligned, then the extreme outputs are soldered and they are checked again to see if all the outputs exactly fall on the tracks, after which the remaining outputs of the microcircuit are soldered.

If adjacent pins stick together when soldering chips, use a toothpick, put it between the pins of the chip and then touch one of the pins with a soldering iron, it is recommended to use more flux. You can go the other way, remove the screen from the shielded wire and collect solder from the microcircuit pins.

Some photos from personal archive

Conclusion

Surface mounting allows you to save money and make very compact, miniature devices. With all its disadvantages that take place, the resulting effect undoubtedly speaks of the prospects and relevance of this technology.

For the manufacture of printed circuit boards, surface mount technology is most often used. This method is also called SMD (surface mount technology), as well as SMD technology. Accordingly, the parts used in TMP are called chip or smd components.

Surface Mount Technology

This method lies in the fact that the elements are not inserted into pre-prepared holes, as is the case with traditional technology. They are installed on the contact pads of the board, where solder paste has already been previously applied. Then the prepared product is placed in an oven for group soldering of components. The finished board is cleaned and covered with a protective layer.

Benefits of using smd parts

The production of boards in this way has a number of advantages compared to the traditional through-hole technology:

faster installation;
production efficiency increases;
is a cheaper way to manufacture;
allows the use of smaller parts, which reduces the size and weight of finished products.

Smd marking of electrical elements

Radio components used for surface mounting are subject to this marking. The brand is applied to the case and characterizes its geometric dimensions, as well as the electrical characteristics of the chip components.

Conventionally, chip components are classified by the number of pins and by size.

According to the classification, electronic parts are divided into the following groups:

Two-contact, which include passive elements (capacitors, resistors and diodes) of a square or cylindrical shape, tantalum types of capacitors and diodes. Cases that belong to this type are abbreviated as SOD (SOD323, SOD128, etc.) and WLCSP2;
Three-pin – contain designations DPAK, D2PAK, D3PAK. The cases have the same design, but differ in size. The most dimensional – D3PAK. Designed for semiconductor parts with high heat generation. The developer of this case is Motorola. Also, this type is marked SOT (SOT883B, SOT23, etc.);
More than four contacts – contacts are placed on two sides. These include WLCSP(N) (where N is the number of pins), SOT, SOIC, SSOP, CLCC, LQFP, DFN, DIP / DIL, Flat Pack, TSOP, ZIP;
Having more than four conclusions located on four sides: LCC, PLCC, QFN, QFP, QUIP;
With pins arranged in a grid: BGA, uBGA.

The industry produces cases with and without leads. If the model does not provide for the presence of leads, then contact pads or solder balls are placed in their place (for example, type μBGA, LFBGA, etc.).

The industry produces the following types of chip components: resistors, transistors, capacitors, diodes, inductors and chokes, LEDs, microcircuits and zener diodes.

Chip Capacitors

Electrolytic capacitors are produced in the form of a barrel, while tantalum and ceramic are mainly – in the form of a parallelepiped.

The marking of the ceramic component does not always indicate the capacitance and operating voltage, but the electrolytic ones do. The strip on the hat is located on the side of the negative terminal.

marking smd resistors

Designations for resistances are applied to the body and consist of several numbers or numbers and a letter.

If the brand of the resistor consists of four or three digits, then the latter indicates the number of zeros after the number that is formed from the first digits. For example, the number 223 means 22000 ohms or 22k ohms, and the number 8202 means 82000 or 82k ohms.

If the symbol R is present in the brand, then this symbol indicates the separator of the integer and fractional parts of the number, for example, if 4R7 is indicated on the resistor, then this corresponds to 4.7 Ohm, and 0R22 - 0.22 Ohm.

Jumper resistors or chip components with zero resistance are also available. In the diagrams, they are used in the same way as fuses.

There are sizing standards for enclosures. For example, for size 0805 rectangular resistors and ceramic capacitors, the parts would be 0.6 inches long, 0.8 inches wide, and 0.23 inches high.

smd inductance

SMD inductors and chokes are available in the same package sizes as the resistors.

They are also marked with four digits. First two – denote the length, the next two denote the width. The parameters are set in inches. That is, if there is a coil with a brand of 0805, then this means that the part has a length of 0.08 inches and a width of 0.05.

Diodes smd

Cases for diodes and zener diodes can be in the form of a cylinder or parallelepiped. They are also defined by the sizes that match the resistor packages.

The polarity must be indicated on the part body. The output of the cathode is most often indicated by a strip located at the corresponding edge.

smd transistors

Available in low, medium or high power. They are also code marked, since the small size of the part does not allow the full name to be placed on them.

Attention! The lack of an international marking standard means that the same code can designate different types of transistors. Therefore, the decoding of the type of semiconductor device on the board can be performed practically only from the corresponding documentation for the board.

Cases are available in two types: SOT, DPAK. They can also contain diode assemblies.

Repair of boards with surface mount parts can be done both at home and in service centers, however, size 0805 is considered convenient for soldering. Smaller parts are mounted using an oven.

Thus, the selection of a burned-out smd radio component can cause certain difficulties for a radio amateur. Therefore, before starting the repair, it is imperative to have the documentation for the board available.

Video

SMD components - the path to miniaturization

Currently, there are increasing trends towards miniaturization and complication of almost all radio equipment. To reduce the overall dimensions of equipment, various microcircuits for specialized purposes are used. General-purpose microcircuits are used less frequently (they have worse parameters than specialized ones). Single-chip microprocessors are also widely used. All of the above does not exclude the use of additional "hinged" elements in structures. If, for example, in the scheme of a digital camera or a mobile phone, parts in "classic" cases are used as additional hanging elements, this will lead to a significant (several times!) increase in the dimensions of the device. It is specifically for such cases that unpackaged surface mount components (SMD components) were developed.

Currently, the industry produces transistors, resistors, capacitors, diodes, and even miniature coils. The use of such elements allows to significantly (several times) reduce the dimensions and weight of the structure, compared to those assembled on case elements ... According to SMD standards, components are produced in several standard sizes. For our purpose, elements of type 1206 are more suitable. A standard element (resistor or capacitor) in this design has external dimensions (in terms of) 3.2 by 1.6 mm, the thickness can reach up to 3 mm. With such dimensions, manual assembly of the structure is still possible. The use of elements of smaller sizes in amateur practice can present certain difficulties due to excessively small sizes (such components are soldered on automatic lines). It goes without saying that mounting SMD components requires the appropriate equipment - an illuminated lens, miniature tools and a soldering iron, and of course - an eagle eye and jewelry hands. Weigh carefully your abilities! If you doubt your abilities - it's better not to start working with unpackaged parts!

Several drawings of the execution of unpackaged components:

Resistors

ceramic capacitors

transistors

Each manufacturer has its own labeling of unpackaged components! On capacitors, there is often no marking at all, and if there is, then some kind of "gibberish". All this is due to very small sizes, so if you plan to manufacture structures from frameless elements, be sure to store each denomination separately and in a signed bag after purchase!!!

A practical example of using SMD components is shown below:

The figure shows the board of a three-stage amplifier (the scale is arbitrary). The calculated cascade with emitter stabilization, considered by us on one of the pages, is taken as a basis. As you can see in the figure, the dimensions of the board, thanks to the use of miniature parts, were reduced to 13 * 39 millimeters. If you modify the board a little, the size can be further reduced ...

Photo of the finished scarf (for size comparison - next to an ordinary match). As you can see, the dimensions of the board (especially the multivibrator) can be further reduced, but I don’t see the point in this ...

External and internal view of the structure:

We connect the cable wire to the cogs, and instead of the antenna, a piece of MGTF wire about 2 meters long is used. The external dimensions of the case are 60 * 38 * 15 millimeters. The power switch is visible at the top left...

A further improvement of this device can be considered the use of a PIR sensor (instead of a cable) and a solar battery to charge the battery. The solar battery can be used from a flashlight (there is everything on the same site!). These changes will minimize the cost of maintaining such a security system.

You can buy SMD components through Chip-Dip (Moscow) or Megachip (Peter) online stores.

Tools and materials

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 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. 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. 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 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. 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 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.

In our turbulent age of electronics, the main advantages of an electronic product are small dimensions, reliability, ease of installation and dismantling (equipment disassembly), low energy consumption and convenient usability ( from English- the convenience of use). All these advantages are by no means possible without surface mount technology - SMT technology ( S face M ount T echnology), and of course, without SMD components.

What are SMD components

SMD components are used in absolutely all modern electronics. SMD ( S face M ounted D evice), which is translated from English as “surface-mounted device”. In our case, the surface is a printed circuit board, without through holes for radio elements:

In this case, SMD components are not inserted into the board holes. They are soldered onto the contact tracks, which are located directly on the surface of the printed circuit board. In the photo below, there are tin-colored contact pads on the board of a mobile phone that used to have SMD components.

Advantages of SMD components

The biggest advantage of SMD components is their small size. In the photo below, simple resistors and:

Due to the small dimensions of SMD components, developers have the opportunity to place a larger number of components per unit area than simple output radio elements. Consequently, the mounting density increases and, as a result, the dimensions of electronic devices are reduced. Since the weight of the SMD component is several times lighter than the weight of the same simple output radio element, the mass of the radio equipment will also be many times lighter.

SMD components are much easier to desolder. For this we need a hair dryer. How to solder and solder SMD components, you can read in the article how to solder SMD correctly. Soldering them is much more difficult. In factories, they are placed on a printed circuit board by special robots. No one welds them manually in production, except for radio amateurs and radio equipment repairmen.

Multilayer boards

Since in equipment with SMD components there is a very dense installation, there should be more tracks in the board. Not all tracks fit on the same surface, so printed circuit boards make multilayer. If the equipment is complex and has a lot of SMD components, then there will be more layers in the board. It's like a layered cake. The printed tracks connecting the SMD components are located right inside the board and cannot be seen in any way. An example of multilayer boards is mobile phone boards, computer or laptop boards (motherboard, video card, RAM, etc.).

In the photo below, the blue board is Iphone 3g, the green board is the computer motherboard.

All radio repairers know that if you overheat a multilayer board, it will swell up with a bubble. In this case, the interlayer connections are torn and the board becomes unusable. Therefore, the main trump card when replacing SMD components is the right temperature.

On some boards, both sides of the printed circuit board are used, while the mounting density, as you understand, is doubled. This is another plus of SMT technology. Oh yes, it is also worth considering the fact that the material for the production of SMD components takes many times less, and their cost in mass production in millions of pieces costs, literally, a penny.

Main types of SMD components

Let's look at the main SMD elements used in our modern devices. Resistors, capacitors, low-value inductors, and other components look like ordinary small rectangles, or rather, parallelepipeds))

On boards without a circuit, it is impossible to know whether it is a resistor, or a capacitor, or even a coil. The Chinese mark as they want. On large SMD elements, they still put a code or numbers to determine their belonging and denomination. In the photo below, these elements are marked in a red rectangle. Without a diagram, it is impossible to say what type of radio elements they belong to, as well as their denomination.

Sizes of SMD components can be different. Here is a description of the sizes for resistors and capacitors. Here, for example, is a rectangular yellow SMD capacitor. They are also called tantalum or simply tantalum:

And this is what SMD looks like:

There are also these types of SMD transistors:

Which have a large denomination, in the SMD version they look like this:

And of course, how could it be without microcircuits in our age of microelectronics! There are a lot of SMD chip package types, but I mainly divide them into two groups:

1) Microcircuits, in which the leads are parallel to the printed circuit board and are located on both sides or along the perimeter.

2) Microcircuits, in which the conclusions are located under the microcircuit itself. This is a special class of microcircuits called BGA (from English ball grid array- an array of balls). The conclusions of such microcircuits are simple solder balls of the same size.

In the photo below, the BGA microcircuit and its reverse side, consisting of ball leads.

BGA chips are convenient for manufacturers in that they greatly save space on the printed circuit board, because there can be thousands of such balls under any BGA chip. This greatly simplifies the life of manufacturers, but does not make life easier for repairmen.

Summary

What do you use in your designs? If your hands are not shaking, and you want to make a small radio bug, then the choice is obvious. But still, in amateur radio designs, dimensions do not particularly play a big role, and soldering massive radio elements is much easier and more convenient. Some radio amateurs use both. Every day more and more new chips and SMD components are being developed. Smaller, thinner, more reliable. The future, unambiguously, belongs to microelectronics.

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