SMD marking. What are SMD components and why are they needed 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.

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.

Surface mounting- technology for the manufacture of electronic products on printed circuit boards, as well as methods for designing printed circuit assemblies related to this technology.

Surface mount technology for printed circuit boards is also called SMT (surface mount technology), SMT (surface mount technology) and SMD technology (from surface mounted device - a device mounted on a surface). It is the most common method of designing and assembling electronic assemblies on printed circuit boards today. Its main difference from the "traditional" hole-mounting technology is that the components are mounted on the surface of the printed circuit board, however, the advantages of surface-mounted printed circuit board technology are manifested due to a complex of features of the element base, design methods and technological methods for manufacturing printed circuit assemblies. (Cm.

A typical workflow in surface mount technology includes:

• Application of solder paste on contact pads (dosing in single and small batch production, screen printing in series and mass production)
• Installing components
• Group soldering by reflow paste in an oven (mainly by convection, but also by infrared heating or in the vapor phase See Vapor phase soldering. Retrieved February 05, 2008.)

In one-off production, in the repair of products and in the assembly of components that require special precision, as a rule, in small-scale production, individual soldering with a stream of heated air or nitrogen is also used.

One of the most important technological materials used in surface mounting is solder paste (also sometimes called solder paste), which is a mixture of powdered solder with organic fillers, including flux. In addition to supporting the soldering process and preparing surfaces, solder paste also performs the task of fixing components prior to soldering due to its adhesive properties. For more information about solder pastes, see Properties, application and storage of solder pastes. Retrieved February 05, 2008.

When soldering in surface mount, it is very important to ensure the correct temperature change over time (thermal profile) in order to avoid thermal shocks, to ensure good activation and wetting of the surface. See Reflow soldering modes for more information on thermal profiles. Retrieved February 05, 2008.

The development of thermal profiles (thermal profiling) is now of particular importance due to the spread of lead-free technology, in which the process window (the difference between the minimum required and maximum permissible temperature of the thermal profile) is significantly narrower due to the increased melting temperature of the solder.

Components that are used for surface mounting are called SMD components or SMD (Surface Mounted Component).

Story

Surface mount technology began its development in the 1960s and was widely used by the end of the 1980s. One of the pioneers in this technology was

disadvantages

• Increased demands on the accuracy of the soldering temperature and its dependence on time, since the entire component is subjected to heating during group soldering.
• High initial costs associated with installation and configuration of equipment, as well as with more complex prototyping.
• The need for special equipment (tools) even with a single and pilot production.
• High requirements for the quality and storage conditions of technological materials.

Housing sizes and types

SMD capacitors (left), versus two "regular" capacitors (right)

Links

• Encyclopedia of Surface Mount Defects
• Fundamentals of technology and equipment for surface mounting

Wikimedia Foundation. 2010 .

See what "SMD" is in other dictionaries:

smd- Saltar a navegación, búsqueda Las siglas SMD pueden referirse a: Santiago Martínez Delgado, artista colombiano cuyas iniciales eran SMD; Sega Mega Drive, una consola de juegos; Surface Mounted Device, que en inglés significa dispositivo de… … Wikipedia Español

smd- Definition: East Semitic, to grind (groats). semolina, simnel, from Latin simila, ultimately (perhaps via Greek semidālis, fine wheaten flour) from a Semitic source akin to Aramaic sǝmidā, fine flour, Arabic samīd, semolina, both probably from… … The American Heritage dictionary of the English language

.smd- In computing the .smd filename extension is used for:*The .smd filename extension is used for Sega Mega Drive ROM images for use with emulators. *The .smd a file used to create a .mdl file for Half Life and Half Life 2 . A .qc file is required to … Wikipedia

smd- I SMD, Elektronik: auf Oberflächen von Leiterplatten montierbare Bauelemente. SMD benötigen für die Montage keine Leiterplattenlöcher, sondern werden mit ihren… … Universal-Lexikon

smd- Cette page d'homonymie répertorie les différents sujets et articles partageant un même nom. SMD, sigle composé des trois lettres S, M et D, peut faire référence à : Syndrome myélodysplasique, une maladie de la moëlle osseuse, Storage Module… … Wikipédia en Français

smd- Die Abkürzung SMD steht für: Sauterdurchmesser (englisch: Sauter Mean Diameter), Kenngröße einer Partikelgrößenverteilung Schiffsmeldedienst, Hamburg Schweizer Mediendatenbank Sheet Metal Design, ein Programm modul von gängigen Anwenderprogrammen ... Deutsch Wikipedia

smd- Die Abkürzung SMD steht für: Sauterdurchmesser (englisch: Sauter Mean Diameter), Kenngröße einer Partikelgrößenverteilung Schiffsmeldedienst, Hamburg Schweizer Mediendatenbank Sheet Metal Design, ein Programmmodul von gängigen Anwenderprogrammen… … Deutsch Wikipedia

smd- senile macular degeneration. * * * SMD (electronics) abbrev Surface mounted device … Useful english dictionary

smd- strategic missile defense ... Military dictionary

smd- senile macular degeneration. * * * … Universalium

1. Introduction
2. SMD Component Enclosures
3. Sizes of SMD components
   • SMD resistors
   • SMD Capacitors
   • SMD coils and chokes
4. SMD transistors
5. Marking SMD components
6. Soldering SMD components

Introduction

Not only ordinary components with leads are now available to a modern radio amateur, but also such small, dark ones, on which one cannot understand what is written, details. They are called "SMD". In Russian it means "surface mount components". Their main advantage is that they allow the industry to assemble boards using robots that place SMD components at great speed in their places on printed circuit boards, and then massively “bake” and receive assembled printed circuit boards as a result. On the part of the person are those operations that the robot cannot perform. Not yet.

The use of chip components in amateur radio practice is also possible, even necessary, as it allows to reduce the weight, size and cost of the finished product. Plus, you don't have to drill at all.

For those who first encountered SMD components, confusion is natural. How to understand their diversity: where is the resistor, and where is the capacitor or transistor, what sizes do they come in, what cases of smd parts exist? You will find answers to all these questions below. Read on, it's useful!

Chip component housings

Rather conventionally, all surface-mounted components can be divided into groups according to the number of pins and package size:

Of course, not all cases are listed in the table, since the real industry releases components in new cases faster than the standardization bodies keep up with them.

Cases of SMD components can be either with or without leads. If there are no leads, then there are contact pads or small solder balls (BGA) on the case. Also, depending on the manufacturer, parts may vary in marking and dimensions. For example, capacitors can vary in height.

Most SMD component cases are designed to be mounted with special hardware that hams don't have and probably won't ever have. This is due to the technology of soldering such components. Of course, with a certain perseverance and fanaticism, you can solder at home.

Types of SMD packages by name

From all this zoo of chip components for amateur use, chip resistors, chip capacitors, chip inductors, chip diodes and transistors, LEDs, zener diodes, some microcircuits in SOIC packages can fit. Capacitors usually look like simple boxes or small barrels. The barrels are electrolytic, while the boxes are likely to be tantalum or ceramic capacitors.

Sizes of SMD components

Chip components of the same denomination can have different dimensions. The dimensions of an SMD component are determined by its "size". For example, chip resistors have sizes from "0201" to "2512". These four digits encode the width and length of the chip resistor in inches. Below in the tables you can see the sizes in millimeters.

smd resistors

smd capacitors

Ceramic chip capacitors are the same size as chip resistors, but tantalum chip capacitors have their own size system:

smd inductors and chokes

Inductances are found in many types of cases, but cases still obey the same sizing law. This facilitates automatic assembly. Yes, and for us, radio amateurs, it makes it easier to navigate.

Any coils, chokes and transformers are called "winding products". Usually we wind them ourselves, but sometimes you can buy finished products. Especially if SMD options are required, which are available with many bonuses: magnetic shielding of the case, compactness, closed or open case, high quality factor, electromagnetic shielding, wide operating temperature range.

It is better to select the required coil according to the catalogs and the required size. Sizes, as for chip resistors, are specified using a four-number code (0805). In this case, "08" indicates the length, and "05" the width in inches. The actual size of such an SMD component will be 0.08x0.05 inches.

smd diodes and zener diodes

Diodes can be both in cylindrical cases and in cases in the form of small parallelepipeds. Cylindrical diode packages are most often represented by MiniMELF (SOD80 / DO213AA / LL34) or MELF (DO213AB / LL41) packages. Their sizes are set in the same way as for coils, resistors, capacitors.

smd transistors

Surface mount transistors are also available in low, medium and high power. They also have matching cases. Transistor cases can be conditionally divided into two groups: SOT, DPAK.

I want to note that in such cases there can also be assemblies of several components, and not just transistors. For example, diode assemblies.

Marking SMD components

It sometimes seems to me that the marking of modern electronic components has turned into a whole science, similar to history or archeology, because in order to figure out which component is installed on the board, sometimes you have to conduct a whole analysis of the elements surrounding it. In this regard, the Soviet output components, on which the denomination and model were written in text, were just a dream for an amateur, since it was not necessary to turn over piles of reference books to figure out what kind of details they were.

The reason lies in the automation of the build process. The SMD components are installed by robots that have special spools (similar to the former magnetic tape spools) in which the chip components are located. The robot does not care what is in the reel and whether the parts have markings. A person needs a label.

Soldering chip components

At home, chip components can only be soldered to a certain size; size 0805 is considered more or less comfortable for manual installation. More miniature components are already soldered using an oven. At the same time, for high-quality soldering at home, a whole range of measures should be observed.

SMD components (chip components)- these are electronic circuit components printed on a printed circuit board (motherboard of a computer, laptop, tablet, smartphone, hard drive, etc.) using surface mount technology - SMT technology (English surface mount technology). That is, all electronic elements that are “fixed” on the board in this way are called SMD components (surface mounted device).

For this type of installation, it is characteristic that, unlike the older through-hole technology (when a hole is drilled in the textolite for an electronic component: a transistor, resistor, capacitor), SMD components are located much more compactly on the printed circuit board. The components themselves are much smaller.

If you pay attention to a modern laptop motherboard, you can see that it is SMD components that make up the bulk of the parts on the board - there are a lot of them and they are very heaped (small multi-colored squares and rectangles of gray, black), and on both sides of the textolite. In the following figure, the SMD components are marked in red.

The motherboard of a tablet or smartphone is made exclusively using SMT (surface mount) technology and SMD elements, since there is no place and need for through mounting.

In desktop motherboards, both mounting technologies are most often used. In the figure below, through-hole elements are marked in green. The contacts of the components (electrolytic capacitors in this case) are inserted into special holes in the motherboard and soldered on the reverse side.

Benefits of SMD Components and Surface Mount

• Smaller SMD components compared to through-hole elements;
• Significantly higher board density;
• Higher density of tracks (connections) on textolite;
• Components can be located on both sides of the board;
• Small errors during SMT mounting (soldering) are corrected automatically by the surface tension of molten tin (lead);
• Better resistance to mechanical failure due to vibration;
• Lower resistance and inductance;
• There is no need to drill holes and, as a result, a lower initial cost of production (economic effect);
• More adapted to automated assembly. Some automatic lines are capable of placing more than 136,000 components per hour;
• Many SMD components cost less than their through-hole counterparts;
• Suitable for devices with a very low profile (height). The printed circuit board can be used in an enclosure that is only a few millimeters thick

disadvantages

• Higher requirements for the production base and equipment;
• Low maintainability and higher requirements for repair specialists;
• Not suitable for mounting connectors and connectors, especially when used in the case of frequent disconnections and connections;
• Not suitable for use in high power and high load equipment

Using materials: Surface-mount technology,