Smd diode marked with one letter. Marking of SMD radio components

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

Surface Mount Technology

This method consists 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.

Advantages of using SMD parts

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

  • faster installation;
  • production efficiency increases;
  • is a cheaper manufacturing method;
  • 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 mark 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 square or cylindrical shape, tantalum types of capacitors and diodes. Cases that belong to this type, denoted by the abbreviation SOD (SOD323, SOD128, etc.) and WLCSP2;
  • Three-pin contain the designations DPAK, D2PAK, D3PAK. The cases have the same design, but differ in size. The largest D3PAK. Designed for semiconductor parts with high heat generation. The developer of this case is Motorola. This type is also marked SOT (SOT883B, SOT23, etc.);
  • Having more than four contacts contacts are placed on both 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 pins located on four sides: LCC, PLCC, QFN, QFP, QUIP;
  • With pins arranged in a lattice: BGA, uBGA.

The industry produces housings with and without leads. If the model does not provide for pins, 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 capacitors are mainly in the shape of a parallelepiped.

The marking of a ceramic component does not always indicate the capacity and operating voltage, and on electrolytic ones they are indicated. The strip on the cap is located on the negative terminal side.

Marking of smd resistors

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

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

If the brand contains the symbol R, then this symbol denotes 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 Ohms, and 0R22 - 0.22 Ohms.

There are also jumper resistors or zero-resistance chip components. In diagrams they are used in the same way as fuses.

There are standard sizes for housings. For example, for size 0805 rectangular resistors and ceramic capacitors, the parts will be 0.6 inches long, 0.8 inches wide, and 0.23 inches high.

Smd inductance

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

They are also marked with four numbers. First two indicate the length, the next two indicate the width. Parameters are specified in inches. That is, if there is a coil with the 0805 brand, this means that the part has a length of 0.08 inches and a width of 0.05.

SMD diodes

Housings for diodes and zener diodes can be cylindrical or parallelepiped-shaped. They are also determined by standard sizes that correspond to resistor housings.

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

Smd transistors

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

Attention! Absence international standard markings leads to the fact that the same code can mean different types transistors. Therefore, deciphering the type of semiconductor device on the board can be done almost only from the corresponding documentation for the board.

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

Repairing circuit boards with surface-mounted parts can be done both at home and in service centers, but size 0805 is considered convenient for soldering. Smaller parts are mounted using a stove.

Thus, selecting a burnt SMD radio component can cause certain difficulties for a radio amateur. Therefore, before starting repairs, you must have the documentation for the board available.

Video

Diode marking

Marking of output diodes:

The most common coding systems are:

  • JEDEC(USA)— Standardized EIA370 N-series numbering system.

Code type: <цифра><буква><серийный номер>[suffix].

The first digit is a number reflecting the number of transitions in the element (1 for diodes).

The letter is always the letter “N”.

The serial number is a two-, three-, or four-digit number that reflects the EIA registration number of the semiconductor device.

Suffix - reflects the breakdown of devices of the same type into different standard ratings according to characteristic parameters. A suffix can consist of one or more letters.

For example: 1N34A/1N270 (germanium diode), 1N914/1N4148 (silicon diode), 1N4001-1N4007 (1A silicon rectifier diode) and 1N54xx (3A power silicon rectifier diode).

  • PRO ELECTRON (Europe);

The designation consists of four elements.

The first element is a letter indicating the type of semiconductor material used in the device:

  • A - germanium;
  • B - silicon;
  • C - gallium arsenide;
  • R - other semiconductor materials.

The second element is a letter indicating the type of semiconductor device:

  • A - low-power pulsed and universal diodes;
  • B - varicaps;
  • E - tunnel diodes;
  • G - special-purpose devices (for example, generators), as well as complex devices containing several different components in one housing;
  • H - magnetically sensitive diodes;
  • P - photosensitive devices (photodiodes, phototransistors, etc.);
  • Q - light-emitting devices (LEDs, IR diodes, etc.);
  • X - multiplying diodes;
  • Y - rectifier diodes, boosters;

The third element is a letter, which is placed only for devices intended for use in special-purpose equipment (industrial, professional, military, etc.). Typically the letters “Z”, “Y”, “X” or “W” are used. This element is absent in the designations of general-purpose devices.

The fourth element is the two-, three-, or four-digit serial number of the device.

The designation may also contain some additional elements. For example, the suffix is ​​the same as in the JEDEC system, which reflects the breakdown of devices of the same type into different standard ratings according to characteristic parameters.

For some types of devices (such as zener diodes), additional classification may apply. In this case, an additional code is added to the main designation (may also be separated by a hyphen or fraction). For example, an additional code is often used containing information about the stabilization voltage and its possible spread (“A” – 1%, “B” – 2%, “C” – 5%, “D” – 10%, “E” – 15 %). If the stabilization voltage is not an integer, then the letter V is placed instead of a comma. In the additional code for rectifier diodes, the maximum amplitude of the reverse voltage is indicated.

For example, BZY88C4V7 is a special-purpose silicon zener diode with registration number 88, a stabilization voltage of 4.7 V with a maximum deviation of this voltage from the nominal value of ±5%.

Table 1 - Color coding of diodes (PRO ELECTRON).

  • JIS (Japan, Asia);

The designation consists of five elements.

The first element is a number reflecting the number of transitions in the element (0 – photodiodes; 1 – diodes).

The second element is the letter “S”, which stands for semiconductors.

The third element is a letter indicating the type of semiconductor device:

  • E - diodes;
  • G - Gunn diodes;
  • Q - light emitting diodes;
  • R - rectifier diodes;
  • S - low-current diodes;
  • T - avalanche diodes;
  • V - varicaps, p-i-n diodes, charge storage diodes;
  • Z - zener diodes, limiters.

The fourth element is the serial (registration) number of the device.

The fifth element is a modification of the device (“A” is the first, “B” is the second, etc.).

The standard marking may be followed by an additional index (“N”, “M”, “S”), reflecting some special properties of the device.


Table 2 - Diode Color Coding (JIS-C-7012 and JEDEC).

Marking of SMD diodes:

SMD diodes are usually marked using an alphanumeric code. Depending on the type of case (i.e. its size) and manufacturer, one or another coding system is used. It is quite obvious that it is not possible to consider all types of coding. Therefore, below we will consider some codes for the most commonly used diode packages. More full version You can look at SMD diode coding systems.

For SOD80 (MiniMELF) housings:

Table 3 - Coding of SMD diodes in the SOD80 package.

Example: BZV87-1V4 – silicon zener diode for stabilization voltage 1.4 V.

The remaining values ​​of the zener diodes are coded in a similar way.

Color coding:


Table 4 - Color coding of SMD diodes in the SOD80 package.

Often the manufacturer codes only the type of diode:

Table 5 - Color coding of SMD diode type.

For casesSOT89:


Table 6 - Coding of SMD diodes in the SOT89 package.

For SOD123, SOD323 housings:


Table 7 - Color coding of SMD diodes in SOD123 and SOD32 packages.

Symbol for diodes in diagrams

Figure 7 - Designation of diode terminals.
Figure 8 - UGO diodes.

Next to symbol the element type (VD) and serial number are indicated.

If you have looked into the insides of a modern electronic device, you have probably noticed that the radio elements look completely different from those of equipment produced 25-30 years ago. Conventional transistors, diodes and microcircuits have replaced pinhead-sized parts soldered directly on top of the board. Such parts, called SMD, are often as similar as two peas in a pod. How to distinguish one from the other and find out its type and purpose? Today we will talk about SMD diodes, zener diodes and their markings, and at the same time we will learn to distinguish one type of device from another.

What is SMD

First of all, what does “SMD” mean and where does this strange name come from? It's very simple: it's an abbreviation for English expression Surface Mounted Device, meaning a device mounted on a surface. SMD diode (left), transistor and surface mount LED

That is, unlike a conventional radio component, the legs of which are inserted into holes in printed circuit board and soldered on its other side, the smd device is simply placed on the contact pads provided on the board and soldered on the same side.
Fragments of boards assembled using SMD technology

Surface mount technology not only made it possible to reduce the dimensions of elements and the density of elements on the board, but also significantly simplified the installation itself, which today is easily handled by robots. The machine places the electronic component at the desired location on the board, heats this location with IR light or a laser to the melting temperature of the solder paste applied to the pads, and the installation of the element is completed.


Robot for SMD installation

SMD element housings

Semiconductor devices intended for surface mounting are produced in packages various types. For diodes and zener diodes, the main ones are: metal-glass cylindrical and plastic (ceramic) rectangular.


SMD semiconductors in various types of packages

Below I give standard sizes SMD cases semiconductor devices depending on the type.

Standard sizes of metal-glass imported SMD semiconductors

Housing type

Total length, mm

Width of contact pads, mm

Diameter, mm

DO-213AA (SOD80)3.5 0.48 1.65
DO-213AB (MELF)5.0 0.48 2.52
DO-213AC3.45 0.42 1.4
ERD03LL1.6 0.2 1.0
ERO21L2.0 0.3 1.25
ERSM5.9 0.6 2.2
MELF5.0 0.5 2.5
SOD80 (miniMELF)3.5 0.3 1.6
SOD80C3.6 0.3 1.52
SOD873.5 0.3 2.05

Standard sizes of imported SMD semiconductors in plastic and ceramic cases

Housing type

Length with leads, mm

Length withoutpins, mm

Width, mm

Height, mm

Output width, mm

DO-215AA6.2 4.3 3.6 2.3 2.05
DO-215AB9.9 6.85 5.9 2.3 3.0
DO-215AC6.1 4.3 2.6 2.4 1.4
DO-215BA6.2 4.45 2.6 2.95 1.3
ESC1.6 1.2 0.8 0.6 0.3
SOD-1233.7 2.7 1.55 1.35 0.6
SOD-1232.5 1.7 1.25 1.0 0.3
SSC2.1 1.3 0.8 0.8 0.3
SMA5.2 4.1 2.6 1.7
SMB5.4 4.3 3.6 2.3
SMC7.95 6.8 5.9 3.3

Expert opinion

Alexey Bartosh

Ask a question to an expert

In fact, there are many more brands and types of SMD diodes and zener diodes. New ones are appearing faster than I can type, and each reputable manufacturing company is trying to introduce a new standard and call it in its own way. The same can be said about labeling.

As for light-emitting SMD diodes (LEDs), everything is simpler. The actual dimensions of these devices correspond to their standard size. For example, it looks like a rectangle with dimensions of 2.8 x 3.5 mm, and 5050 – 5 x 5 mm.


The actual dimensions of light-emitting SMD diodes correspond to their designation

SMD semiconductor markings

We've dealt with the cases, but a case of the same standard size can contain devices with completely different characteristics. How to determine what you have in your hands? For this purpose, one or another marking is used, which is applied to the body of the device.

Diodes

SMD diodes in cylindrical packages are usually color-coded - marked with one or two colored stripes located at the cathode terminal.

Table color coding importedSMD diodes in a cylindrical housing

Similar markings are used for diodes in a rectangular case:

Color codingSMD diodes in SOD-123 packages

* — the marking strip is located closer to the cathode terminal

Some manufacturers put symbolic or numerical markings on their devices.

Symbolic markingSMD diodes, including Schottky diodes

Diode type

Marking

BAS16JU/A6
BAS21JS
BAV70JJ/A4
BAV99JK; JE; A
BAW56JD; A1
BAT54S1L44
BAT54C1L43
BAV23SL31

Semiconductor assemblies

Manufacturers often integrate several diodes into one housing. This not only reduces the dimensions of the entire structure, but also simplifies installation. Such devices are called SMD assemblies. Depending on the type and purpose of the SMD assembly, it can consist of a very different number of semiconductors: from two to several dozen, and they can be connected to each other in one way or another within the SMD assembly itself.

For example, a very common connection of two Schottky diodes used in pulsed rectifiers is anodes or cathodes. No less popular are ready-made SMD rectifier bridges consisting of four semiconductors. Like regular diodes, the assemblies are marked accordingly.


BAV70 dual-diode SMD assembly and bridge DB107GS appearance and their electrical diagram

Such SMD devices are produced in SOT, TSOP SSOP packages and can have a different number of pins, which depends on the number of semiconductors and the internal circuit of their connections. I provide the markings of the most popular assemblies below.

Marking of semiconductor SMD assemblies from Hewlett Packard

#

Tsokolevka

Assembly composition

Housing type
2 D1i2 diodes in seriesSOT23
3 D1j2 diodes common anodeSOT23
4 D1h2 diodes common cathodeSOT23
5 D6d2 diodesSOT143
7 D6c4 diodes connected by ringSOT143
8 D6adiode bridgeSOT143
WITHD2b2 diodesSOT323
ED2c2 diodes common anodeSOT323
FD2d2 diodes common cathodeSOT323
KD7b2 diodesSOT363
LD7f3 diodesSOT363
MD7g4 diodes common cathodeSOT363
ND7h4 diodes common anodeSOT363
PD7idiode bridgeSOT363
RD7j4 diodes connected in a ringSOT363

Marking of semiconductor SMD assemblies in SOT23 and SOT323 packages

Device type

Marking Assembly composition

Frame

BAV70JJ/A42 diodesSOT23
BAV99JK, JE, A7
BAW56JD, A1
BAT54SL442 Schottky
BAT54CL43
BAV70WA42 diodesSOT323
BAV99WA7
BAW56WA1
BAT54AW42 2 Schottky
BAT54CW43
BAT54SW44

According to the markings on the device body, we have a BAT54S assembly with Schottky semiconductors

Zener diodes

Zener diodes and diodes can have both color and symbol markings:

Color codingSMD zener diodes in a glass cylindrical case

* — marking strips are located closer to the cathode terminal

Symbolic markingSMD zener diodes BZX84 in a rectangular package

Device type

Marking

Stabilization voltage, V

BZX84C2V7W42.7
BZX84C3V0W53.0
BZX84C3V3W63.3
BZX84C3V9W83.9
BZX84C4V3Z04.3
BZX84C4V7Z14.7
BZX84C5V1Z25.1
BZX84C5V6Z35.6
BZX84C6V2Z46.2
BZX84C6V8Z56.8
BZX84C7V5Z67.5
BZX84C8V2Z78.2
BZX84C9V1Z89.1
BZX84C10Z910.0
BZX84C12Y212.0
BZX84C15Y415.0
BZX84C18Y618.0
BZX84C20Y820.0

Symbolic markingSMD zener diodes BZT52 in a rectangular package

LEDs

SMD LEDs are usually not marked (an exception may be counterfeits - they are often marked to make them more convincing), and their digital designation only indicates the size of the device. All other information can be found in the documentation included with the SMD LEDs, or from the plate that I give below:

Main FeaturesSMD LEDs of various types

Device type

Power, W

Luminous flux, lm

Dimensions, mm

2828 0.5 50 2.8 x2.8
2835(a)0.2 29 2.8 x3.5
2835(b);0.5 63 2.8 x3.5
2835(c)1 130 2.8 x3.5
3014 0.1 9-12 3.0 x 1.4
3020 0.06 5.4 3.0 x 2.0
3020(b)0.5 3.0 x 2.0
3020(c)1 125 3.0 x 2.0
3030 0.9 110-120 3.0 x 3.0;
3228 1 110 3.2 x 2.8
3258 0.2 6 3.2 x 5.8
3528(a)0.06 7 3.5 x 2.8
3528(b)1 110 3.5 x 2.8
3535(a)0.5 35-42 3.5 x 3.5
3535(b)1 110 3.5 x 3.5
3535(c)2 3.5 x 3.5
4014 0.2 22-32 4.0 x 1.4
4020 0.5 55 4.0 x 2.0
5050 0.2 14-22 5.0 x 5.0
5060 0.2 26 5.0 x 6.0
5630 0.5 30-45 5.6 x 3.0
5730 0.5 30-45 5.7 x 3.0
5733 0.5 35-50 5.7 x 3.3
5736 0.5 40-55 5.7 x 3.6
7014(a)0.5 35-49 7.0 x 1.4
7014(b)1 110 7.0 x 1.4
7020 1 110 7.0 x 2.0
7020 0.5 40-55 7.0 x 2.0
7030 1 110 7.0 x 3.0
8520(a)0.5 55-60 8.5 x 2.0
8520(b)1 110 8.5 x 2.0

As can be seen from the plate, the 2835 device can be produced in three modifications - 0.2, 0.5 and 1 W. Moreover, there are many fakes when craftsmen build a crystal of any power into a case of standard size 2835 - from 0.1 W and below. And to make the fake look more convincing, as I wrote above, scammers can even put a mark on it! It is impossible to determine either visually or by size what you really have in your hands. This can only be done using the accompanying documentation and an approximate price - the lower it is, the lower the power of the LED.

Expert opinion

Alexey Bartosh

Specialist in repair and maintenance of electrical equipment and industrial electronics.

Ask a question to an expert

In fact, with some experience, you can determine the approximate power of an LED visually without markings. The crystal is often visible through the compound with which it is filled. The larger the crystal size, the more powerful the device.

But that's not all. An LED of the same size may have different color temperature and even color. For the same 2835, the light can be warm, daytime and cold, and, for example, SMD 3020 can be of any color.

The 5050 product is equipped with three crystals placed in one housing, and each of them can also have its own glow color. All this information is found only in the accompanying documentation.


5050 LED with three crystals and led strip, assembled on three-color SMD 5050

So our conversation about SMD semiconductors and their markings has ended. Now you know what they are, and if necessary, you can determine by the marking the type of SMD diode, zener diode or LED that you are holding in your hands.

Marking of SMD components

Surface mount components are too small to bear standard markings on their housings. Therefore, there is a special system for designating such components: a code consisting of two or three characters is applied to the body of the device. The reference material provides information on more than 1500 codes.

Housing types and pinouts

The most common miniature package for low-power diodes, diode assemblies and transistors is probably the three-terminal SOT23, made of plastic. For diodes, two-terminal packages SOD123, SOD323 and subminiature ceramic SOD110 are often used; Sometimes alphanumeric markings are not applied to them, then the type of device can be determined by the color of the strip at the cathode terminal. Transistors, diode and varicap assemblies are placed in three-lead packages SOT323, SOT346, SOT416, SOT490, subminiature SOT663, as well as in four-terminal packages SOT223, SOT143, SOT343 and SOT103. Five-pin packages are also used, for example, SOT551A and SOT680-1, in which the collector and/or emitter pins are duplicated for ease of wiring of printed circuit boards. Miniature six-pin packages, for example SOT26A, house transistor assemblies and diode matrices. Drawings of the most common SMD housings are shown in the figure.

Some devices have a variety with a reverse pinout and, accordingly, the letter “R” (Reveres) in the marking. Their conclusions correspond to the conclusions of a conventional device turned upside down, i.e. mirror image. Identification is usually done by code, but some manufacturers use the same code. In this case, you will need a strong magnifying glass. Typically, the terminals of housings (for example, such as SC 59, SC-70, SOT-323) come out closer to the front surface, and for inverted type devices, the terminals are located closer to the bottom side of the device housing. The exceptions are the SO-8, SOT-23, SOT-143 and SOT-223 cases, for them everything is the other way around.



How to use the information provided

To identify an SMD component, you need to determine the type of case and read the identification code printed on it. Next, you should find the designation in the alphabetical list of codes. Unfortunately, some codes are not unique. For example, a component labeled 1A could be either BC846A or FMMT3904. Even the same manufacturer may use the same codes to designate different components. In such cases, the housing type should be taken into account for more accurate identification.

Various options encodings

Many manufacturers use additional characters as their own identification code. For example, components from Philips usually (but unfortunately not always) have a lowercase "p" in addition to the code; components from Siemens usually have an additional lowercase

the letter "s". For example, if a component has code 1 Ap, you should look in the table for code 1 A. According to Table 1, there are four different options.

But since the component has the suffix “p”, it is manufactured by Philips, which means it is BC846A.

Many new Motorola components have a superscript after the code - small letters, for example SAC. These letters are just the month the device was manufactured. Many devices from Rohm Semiconductors starting with the letter G are equivalent to devices with markings equal to the rest of the code. For example, GD1 is the same as 01, that is, BCW31.

Some devices have a single colored letter (usually diodes in miniature packages). The color, if it has a meaning, is indicated in the table in brackets after the code or separately - instead of the code. It can be somewhat difficult to identify different types of housings for the same device. For example, 1K in a SOT23 package is BC848B (power 250 mW), and 1K in a SOT323 package is BC848BW (power 200 mW). In the tables presented, such devices are usually considered to be equivalent.

The suffix "L" usually indicates a low-profile case, such as the SOT323 or SC70, while the "W" indicates a smaller version of the case, such as the SOT343.

Analogue devices and additional information

Where possible, the listing indicates a type of conventional (non-SMD) device that has equivalent characteristics. If such a device is generally known, then no other information is given. For less common devices, additional information is provided. If a similar device does not exist, it is given brief description device, which may be important when choosing a replacement.

When describing the properties of a component, some parameters specific to a particular device are used. Thus, the voltage specified for a rectifying diode is most often the maximum peak reverse voltage of the diode, and for zener diodes the stabilization voltage is given. Usually, if voltages, currents or powers are indicated, these are limit values. For transistors, the area of ​​application, operating range or cutoff frequency is indicated. For pulse diodes - switching time. For varicaps - the operating range and/or limits of capacitance change.

Some types of transistors (so-called “digital”) have built-in resistors. In this case, the “+” sign indicates a resistor connected in series with the base; without the “+” sign - a resistor that shunts the base-emitter junction. When two resistances are specified (separated by a slash), then the first of them is the resistance of the base resistor, the second is the resistance of the resistor between the base and emitter.

Table 1. Various encoding options

Description and/or analogue

p-MOS,20V,0.9A

Codes SMD components starting with the number - 1

In our turbulent age of electronics, the main advantages of an electronic product are small size, reliability, ease of installation and dismantling (disassembling equipment), low energy consumption and convenient usability ( from English– ease of use). All these advantages are by no means possible without surface mount technology - SMT technology ( S urface 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 urface M mounted D evice), which translated from English means “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 holes of the boards. They are soldered onto contact tracks, which are located directly on the surface of the printed circuit board. The photo below shows tin-colored contact pads on a mobile phone board that previously had SMD components.


Pros of SMD components

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



Thanks 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 installation density increases and, as a result, the dimensions of electronic devices decrease. Since the weight of an SMD component is many times lighter than the weight of the same simple output radio element, the weight of the radio equipment will also be many times lighter.

SMD components are much easier to desolder. For this we need a hairdryer. You can read how to desolder and solder SMD components in the article on how to solder SMDs correctly. It's much more difficult to seal them. In factories, special robots place them on a printed circuit board. No one solders them manually in production, except for radio amateurs and radio equipment repairmen.

Multilayer boards

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

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



All radio equipment repairers know that if a multilayer board is overheated, it will swell with a bubble. In this case, the interlayer connections break and the board becomes unusable. Therefore, the main trump card when replacing SMD components is the correct temperature.

Some boards use both sides of the printed circuit board, and the mounting density, as you understand, doubles. This is another advantage of SMT technology. Oh yes, it’s also worth taking into account the fact that the material required for the production of SMD components is much less, and their cost during mass production of millions of pieces literally costs pennies.

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, a capacitor, or even a coil. The Chinese mark as they please. On large SMD elements, they still put a code or numbers to determine their identity and value. 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 rating.


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


And this is what SMDs look like:



There are also these types of SMD transistors:


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



And of course, how can we live without microcircuits in our age of microelectronics! There are many SMD types of chip packages, but I divide them mainly into two groups:

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


2) Microcircuits in which the pins 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 terminals of such microcircuits are simple solder balls of the same size.

The photo below shows a BGA chip and its reverse side, consisting of ball pins.


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

Resume

What should you use in your designs? If your hands don’t shake and you want to make a small radio bug, then the choice is obvious. But still, in amateur radio designs, dimensions do not 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 microcircuits and SMD components are being developed. Smaller, thinner, more reliable. The future definitely belongs to microelectronics.