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.
First of all, what does “SMD” mean and where does this strange name come from? It's very simple: this is an abbreviation for the 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 the printed circuit board and soldered on the 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 Semiconductor devices intended for surface mounting are available in various types of packages. 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 present the standard sizes of SMD semiconductor device packages depending on the type.
Standard sizes of metal-glass imported SMD semiconductors
Type of shell | 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-213AC | 3.45 | 0.42 | 1.4 |
| ERD03LL | 1.6 | 0.2 | 1.0 |
| ERO21L | 2.0 | 0.3 | 1.25 |
| ERSM | 5.9 | 0.6 | 2.2 |
| MELF | 5.0 | 0.5 | 2.5 |
| SOD80 (miniMELF) | 3.5 | 0.3 | 1.6 |
| SOD80C | 3.6 | 0.3 | 1.52 |
| SOD87 | 3.5 | 0.3 | 2.05 |
Standard sizes of imported SMD semiconductors in plastic and ceramic cases
Type of shell | Length with leads, mm | Length withoutpins, mm | Width, mm | Height, mm | Output width, mm |
| DO-215AA | 6.2 | 4.3 | 3.6 | 2.3 | 2.05 |
| DO-215AB | 9.9 | 6.85 | 5.9 | 2.3 | 3.0 |
| DO-215AC | 6.1 | 4.3 | 2.6 | 2.4 | 1.4 |
| DO-215BA | 6.2 | 4.45 | 2.6 | 2.95 | 1.3 |
| ESC | 1.6 | 1.2 | 0.8 | 0.6 | 0.3 |
| SOD-123 | 3.7 | 2.7 | 1.55 | 1.35 | 0.6 |
| SOD-123 | 2.5 | 1.7 | 1.25 | 1.0 | 0.3 |
| SSC | 2.1 | 1.3 | 0.8 | 0.8 | 0.3 |
| SMA | 5.2 | 4.1 | 2.6 | — | 1.7 |
| SMB | 5.4 | 4.3 | 3.6 | — | 2.3 |
| SMC | 7.95 | 6.8 | 5.9 | — | 3.3 |
Expert opinion
Alexey Bartosh
Ask a question to an expertIn 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 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.
SMD diodes in cylindrical packages are usually color-coded - marked with one or two colored stripes located at the cathode terminal.
Imported color coding tableSMD 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 |
| BAS16 | JU/A6 |
| BAS21 | JS |
| BAV70 | JJ/A4 |
| BAV99 | JK; JE; A |
| BAW56 | JD; A1 |
| BAT54S1 | L44 |
| BAT54C1 | L43 |
| BAV23S | L31 |
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 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 | Type of shell |
| 2 | D1i | 2 diodes in series | SOT23 |
| 3 | D1j | 2 diodes common anode | SOT23 |
| 4 | D1h | 2 diodes common cathode | SOT23 |
| 5 | D6d | 2 diodes | SOT143 |
| 7 | D6c | 4 diodes connected by ring | SOT143 |
| 8 | D6a | diode bridge | SOT143 |
| WITH | D2b | 2 diodes | SOT323 |
| E | D2c | 2 diodes common anode | SOT323 |
| F | D2d | 2 diodes common cathode | SOT323 |
| K | D7b | 2 diodes | SOT363 |
| L | D7f | 3 diodes | SOT363 |
| M | D7g | 4 diodes common cathode | SOT363 |
| N | D7h | 4 diodes common anode | SOT363 |
| P | D7i | diode bridge | SOT363 |
| R | D7j | 4 diodes connected in a ring | SOT363 |
Marking of semiconductor SMD assemblies in SOT23 and SOT323 packages
Device type | Marking | Assembly composition | Frame |
| BAV70 | JJ/A4 | 2 diodes | SOT23 |
| BAV99 | JK, JE, A7 | ||
| BAW56 | JD, A1 | ||
| BAT54S | L44 | 2 Schottky | |
| BAT54C | L43 | ||
| BAV70W | A4 | 2 diodes | SOT323 |
| BAV99W | A7 | ||
| BAW56W | A1 | ||
| BAT54AW | 42 | 2 Schottky | |
| BAT54CW | 43 | ||
| BAT54SW | 44 |
According to the markings on the device body, we have a BAT54S assembly with Schottky semiconductors 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 |
| BZX84C2V7 | W4 | 2.7 |
| BZX84C3V0 | W5 | 3.0 |
| BZX84C3V3 | W6 | 3.3 |
| BZX84C3V9 | W8 | 3.9 |
| BZX84C4V3 | Z0 | 4.3 |
| BZX84C4V7 | Z1 | 4.7 |
| BZX84C5V1 | Z2 | 5.1 |
| BZX84C5V6 | Z3 | 5.6 |
| BZX84C6V2 | Z4 | 6.2 |
| BZX84C6V8 | Z5 | 6.8 |
| BZX84C7V5 | Z6 | 7.5 |
| BZX84C8V2 | Z7 | 8.2 |
| BZX84C9V1 | Z8 | 9.1 |
| BZX84C10 | Z9 | 10.0 |
| BZX84C12 | Y2 | 12.0 |
| BZX84C15 | Y4 | 15.0 |
| BZX84C18 | Y6 | 18.0 |
| BZX84C20 | Y8 | 20.0 |
Symbolic markingSMD zener diodes BZT52 in a rectangular package
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 supplied with the SMD LEDs, or from the plate that I provide below:
Main characteristicsSMD 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 expertIn 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 can have different color temperatures and even colors. 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.
The modern radio amateur now has access to not only ordinary components with leads, but also such small, dark parts that you can’t understand what’s written on them. They are called "SMD". In Russian this means "surface mount components". Their main advantage is that they allow the industry to assemble boards using robots that quickly place SMD components in their places on the printed circuit boards, and then mass bake them to produce assembled printed circuit boards. The human share remains with 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 you to reduce the weight, size and cost of the finished product. Moreover, you practically won’t have to drill.
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 types of SMD parts are there? You will find answers to all these questions below. Read it, it will come in handy!
Quite conventionally, all surface-mount components can be divided into groups according to the number of pins and housing size:
| pins/size | Very very small | Very small | Little ones | Average |
| 2 outputs | SOD962 (DSN0603-2) , WLCSP2*, SOD882 (DFN1106-2) , SOD882D (DFN1106D-2) , SOD523, SOD1608 (DFN1608D-2) | SOD323, SOD328 | SOD123F, SOD123W | SOD128 |
| 3 pins | SOT883B (DFN1006B-3) , SOT883, SOT663, SOT416 | SOT323, SOT1061 (DFN2020-3) | SOT23 | SOT89, DPAK (TO-252), D2PAK (TO-263), D3PAK (TO-268) |
| 4-5 pins | WLCSP4*, SOT1194, WLCSP5*, SOT665 | SOT353 | SOT143B, SOT753 | SOT223, POWER-SO8 |
| 6-8 pins | SOT1202, SOT891, SOT886, SOT666, WLCSP6* | SOT363, SOT1220 (DFN2020MD-6), SOT1118 (DFN2020-6) | SOT457, SOT505 | SOT873-1 (DFN3333-8), SOT96 |
| > 8 pins | WLCSP9*, SOT1157 (DFN17-12-8) , SOT983 (DFN1714U-8) | WLCSP16*, SOT1178 (DFN2110-9) , WLCSP24* | SOT1176 (DFN2510A-10) , SOT1158 (DFN2512-12) , SOT1156 (DFN2521-12) | SOT552, SOT617 (DFN5050-32), SOT510 |
Of course, not all packages are listed in the table, since the real industry produces components in new packages faster than the standardization bodies can keep up with them.
The housings of SMD components can be either with or without leads. If there are no leads, then there are contact pads or small balls of solder (BGA) on the case. Also, depending on the manufacturer, parts may differ in markings and dimensions. For example, capacitors may vary in height.
Most SMD component housings are designed for installation using special equipment that radio amateurs do not have and are unlikely to ever have. This is due to the technology of soldering such components. Of course, with a certain persistence and fanaticism, you can solder at home.
Types of SMD housings by name
| Name | Decoding | number of pins |
| SOT | small outline transistor | 3 |
| SOD | small outline diode | 2 |
| SOIC | small outline integrated circuit | >4, in two lines on the sides |
| TSOP | thin outline package (thin SOIC) | >4, in two lines on the sides |
| SSOP | seated SOIC | >4, in two lines on the sides |
| TSSOP | thin seated SOIC | >4, in two lines on the sides |
| QSOP | Quarter size SOIC | >4, in two lines on the sides |
| VSOP | Even smaller QSOPs | >4, in two lines on the sides |
| PLCC | IC in a plastic case with leads bent to form a letter-shaped case J | >4, in four lines on the sides |
| CLCC | IC in a ceramic package with leads bent to form a letter-shaped package J | >4, in four lines on the sides |
| QFP | square flat case | >4, in four lines on the sides |
| LQFP | low profile QFP | >4, in four lines on the sides |
| PQFP | plastic QFP | >4, in four lines on the sides |
| CQFP | ceramic QFP | >4, in four lines on the sides |
| TQFP | thinner than QFP | >4, in four lines on the sides |
| PQFN | power QFP without leads with a pad for a radiator | >4, in four lines on the sides |
| BGA | Ball grid array. Array of balls instead of pins | pin array |
| LFBGA | low profile FBGA | pin array |
| C.G.A. | housing with input and output terminals made of refractory solder | pin array |
| CCGA | CGA in ceramic case | pin array |
| μBGA | micro BGA | pin array |
| FCBGA | Flip-chip ball grid array. Man array of balls on a substrate to which a crystal with a heat sink is soldered | pin array |
| LLP | leadless housing |
From this whole zoo of chip components that can be used for amateur purposes: chip resistors, chip capacitors, chip inductors, chip diodes and transistors, LEDs, zener diodes, some microcircuits in SOIC packages. Capacitors usually look like simple parallelipipeds or small barrels. The barrels are electrolytic, and the parallelepipeds will most likely be tantalum or ceramic capacitors.
Chip components of the same denomination may have different dimensions. The dimensions of an SMD component are determined by its “standard size”. For example, chip resistors have standard sizes from “0201” to “2512”. These four digits encode the width and length of the chip resistor in inches. In the tables below you can see the standard sizes in millimeters.
| Rectangular chip resistors and ceramic capacitors | |||||
| Standard size | L, mm (inch) | W, mm (inch) | H, mm (inch) | A, mm | W |
| 0201 | 0.6 (0.02) | 0.3 (0.01) | 0.23 (0.01) | 0.13 | 1/20 |
| 0402 | 1.0 (0.04) | 0.5 (0.01) | 0.35 (0.014) | 0.25 | 1/16 |
| 0603 | 1.6 (0.06) | 0.8 (0.03) | 0.45 (0.018) | 0.3 | 1/10 |
| 0805 | 2.0 (0.08) | 1.2 (0.05) | 0.4 (0.018) | 0.4 | 1/8 |
| 1206 | 3.2 (0.12) | 1.6 (0.06) | 0.5 (0.022) | 0.5 | 1/4 |
| 1210 | 5.0 (0.12) | 2.5 (0.10) | 0.55 (0.022) | 0.5 | 1/2 |
| 1218 | 5.0 (0.12) | 2.5 (0.18) | 0.55 (0.022) | 0.5 | 1 |
| 2010 | 5.0 (0.20) | 2.5 (0.10) | 0.55 (0.024) | 0.5 | 3/4 |
| 2512 | 6.35 (0.25) | 3.2 (0.12) | 0.55 (0.024) | 0.5 | 1 |
| Cylindrical chip resistors and diodes | |||||
| Standard size | Ø, mm (inch) | L, mm (inch) | W | ||
| 0102 | 1.1 (0.01) | 2.2 (0.02) | 1/4 | ||
| 0204 | 1.4 (0.02) | 3.6 (0.04) | 1/2 | ||
| 0207 | 2.2 (0.02) | 5.8 (0.07) | 1 | ||
Ceramic chip capacitors are the same size as chip resistors, but tantalum chip capacitors have their own size system:
| Tantalum capacitors | |||||
| Standard size | L, mm (inch) | W, mm (inch) | T, mm (inch) | B, mm | A, mm |
| A | 3.2 (0.126) | 1.6 (0.063) | 1.6 (0.063) | 1.2 | 0.8 |
| B | 3.5 (0.138) | 2.8 (0.110) | 1.9 (0.075) | 2.2 | 0.8 |
| C | 6.0 (0.236) | 3.2 (0.126) | 2.5 (0.098) | 2.2 | 1.3 |
| D | 7.3 (0.287) | 4.3 (0.170) | 2.8 (0.110) | 2.4 | 1.3 |
| E | 7.3 (0.287) | 4.3 (0.170) | 4.0 (0.158) | 2.4 | 1.2 |
Inductors are found in many types of housings, but the housings are subject to the same size law. This makes automatic installation easier. And it makes it easier for us, radio amateurs, to navigate.
All kinds of coils, chokes and transformers are called “winding products”. Usually we wind them ourselves, but sometimes you can buy ready-made products. Moreover, if SMD options are required, which come with many bonuses: magnetic shielding of the housing, compactness, closed or open housing, high quality factor, electromagnetic shielding, wide range of operating temperatures.
It is better to select the required coil according to catalogs and the required standard size. Standard 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.
Diodes can be either in cylindrical cases or in cases in the form of small parallelipipeds. Cylindrical diode packages are most often represented by MiniMELF (SOD80 / DO213AA / LL34) or MELF (DO213AB / LL41) packages. Their standard sizes are set in the same way as for coils, resistors, and capacitors.
| Diodes, Zener diodes, capacitors, resistors | |||||
| Type of shell | L* (mm) | D* (mm) | F* (mm) | S* (mm) | Note |
| DO-213AA (SOD80) | 3.5 | 1.65 | 048 | 0.03 | JEDEC |
| DO-213AB (MELF) | 5.0 | 2.52 | 0.48 | 0.03 | JEDEC |
| DO-213AC | 3.45 | 1.4 | 0.42 | - | JEDEC |
| ERD03LL | 1.6 | 1.0 | 0.2 | 0.05 | PANASONIC |
| ER021L | 2.0 | 1.25 | 0.3 | 0.07 | PANASONIC |
| ERSM | 5.9 | 2.2 | 0.6 | 0.15 | PANASONIC, GOST R1-11 |
| MELF | 5.0 | 2.5 | 0.5 | 0.1 | CENTS |
| SOD80 (miniMELF) | 3.5 | 1.6 | 0.3 | 0.075 | PHILIPS |
| SOD80C | 3.6 | 1.52 | 0.3 | 0.075 | PHILIPS |
| SOD87 | 3.5 | 2.05 | 0.3 | 0.075 | PHILIPS |
Surface mount transistors can also be of low, medium and high power. They also have matching housings. Transistor cases can be divided into two groups: SOT, DPAK.
I would like to draw your attention to the fact that such packages may also contain assemblies of several components, not just transistors. For example, diode assemblies.
Sometimes it seems to me that the labeling of modern electronic components has turned into a whole science, similar to history or archeology, since 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 simply a dream for an amateur, since there was no need to rummage through piles of reference books to figure out what these parts were.
The reason lies in the automation of the assembly process. SMD components are installed by robots, in which special reels are installed (similar to the reels with magnetic tapes) in which chip components are located. The robot doesn’t care what’s in the bag or whether the parts are marked. Humans need labeling.
At home, chip components can only be soldered up to a certain size; size 0805 is considered more or less comfortable for manual installation. Smaller components are soldered using a stove. At the same time, for high-quality soldering at home, a whole range of measures should be observed.
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.
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.
Manufacturing boards in this way has a number of advantages compared to traditional through-hole technology:
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:
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.
Electrolytic capacitors are produced in the form of a barrel, while tantalum and ceramic capacitors are mainly – in the shape of a parallelepiped.
The markings of a ceramic component do not always indicate the capacitance and operating voltage, while electrolytic ones do. The strip on the cap is located on the negative terminal side.
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.
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.
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.
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! The lack of an international marking standard leads to the fact that the same code can indicate different types of 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.
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 encoding options
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, a brief description of the device is provided that may be helpful in selecting 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
