Dimensions of chip components. SMD resistors. Marking SMD resistors, sizes, online calculator. What are SMD components
In our turbulent age of electronics, the main advantages of an electronic product are small dimensions, reliability, ease of installation and dismantling (disassembly of equipment), 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 ( Surface Mount Technology), and of course, without SMD components.
What are SMD components
SMD components are used in absolutely all modern electronics. SMD ( Surface Mounted Device), 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, the SMD components are not inserted into the holes of the boards. They are soldered to the contact tracks, which are located directly on the surface of the printed circuit board. In the photo below, the pewter pads on the mobile phone board, which 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:
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 many 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 solder. To do this, we need a hairdryer. 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 equipped with special robots on a printed circuit board. Nobody solders them manually in production, except for radio amateurs and repairmen of radio equipment.
Layered Boards
Since the equipment with SMD components has a very tight installation, there should be more tracks in the board. Not all tracks fit on one surface, so printed circuit boards do layered. 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 cake. The printed tracks connecting the SMD components are located directly inside the board and cannot be seen at all. An example of multilayer motherboards is mobile phone, computer or laptop boards (motherboard, graphics card, RAM, etc.).
In the photo below, the blue board is Iphone 3g, the green board is the computer motherboard.
All repairmen of radio equipment know that if the multilayer board is overheated, then it swells with a bubble. At the same time, interlayer communications are broken 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, and the installation density, as you understand, doubles. 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 several times less, and their cost in serial production in millions of pieces costs, literally, a penny.
The main types of SMD components
Let's look at the main SMD elements used in our modern devices. Resistors, capacitors, inductors with a small nominal value, and other components look like ordinary small rectangles, or rather, parallelepipeds))
On boards without a circuit, it is impossible to find out 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 affiliation and face value. In the photo below, these elements are marked in a red rectangle. Without a circuit, it is impossible to say what type of radioelements they belong to, as well as their face value.
Sizes of SMD components may vary. Here is a description of the sizes for resistors and capacitors. For example, a rectangular SMD capacitor is yellow. They are also called tantalum or simply tantalum:
And this is what SMD looks like:
There are also such types of SMD transistors:
Which have a large denomination, in the SMD version they look like this:
And of course, how can microelectronics be without microchips in our century! There are a lot of SMD types of microcircuit cases, but I mainly divide them into two groups:
1) Chips in which the findings are parallel to the printed circuit board and are located on both sides or around the perimeter.
2) Microcircuits in which the findings are located under the microcircuit itself. This is a special class of chips 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 chip and its reverse side, consisting of ball terminals.
BGA microcircuits are convenient for manufacturers in that they save a lot of space on the printed circuit board, because there can be thousands of such balls under any BGA microcircuit. This greatly simplifies the life of manufacturers, but does not make life easier for repairmen.
Summary
What is nevertheless used in their designs? If your hands are not shaking and you want to make a little radio bug, then the choice is obvious. But still, in amateur radio designs, the dimensions do not particularly play a big role, and soldering massive radio elements is much easier and more convenient. Some hams use both. Every day more and more microchips and SMD components are developed. Smaller, thinner, more reliable. The future is definitely for microelectronics.
In general, the term SMD (from the English Surface Mounted Device) can be attributed to any small-sized electronic component intended for mounting on the surface of a board using SMT technology (surface mount technology).
SMT technology (from the English Surface Mount Technology) was developed to reduce the cost of production, increase the efficiency of manufacturing printed circuit boards using smaller electronic components: resistors, capacitors, transistors, etc. Today we will consider one of these - SMD resistor.
SMD resistors
SMD resistors - These are miniature ones designed for surface mounting. SMD resistors are significantly smaller than their traditional counterpart. They are often square, rectangular or oval in shape, with a very low profile.
Instead of the wire leads of conventional resistors, which are inserted into the holes of the printed circuit board, SMD resistors have small contacts that are soldered to the surface of the resistor housing. This eliminates the need to make holes in the printed circuit board, and thereby allows more efficient use of its entire surface.
Sizes of SMD Resistors
Basically, the term size includes the size, shape and configuration of the terminals (type of housing) of any electronic component. For example, the configuration of a conventional microcircuit, which has a flat case with a two-sided arrangement of terminals (perpendicular to the plane of the base), is called DIP.
SMD Resistors standardized, and most manufacturers use the JEDEC standard. The size of the SMD resistors is indicated by a numerical code, for example, 0603. The code contains information about the length and width of the resistor. Thus, in our example, code 0603 (in inches) the length of the case is 0.060 inches, width 0.030 inches.
The code size 1608 (in millimeters) will have the same size of the resistor in the metric system, respectively, the length is 1.6 mm, the width is 0.8 mm. To translate the dimensions in millimeters, it is enough to multiply the size in inches by 2.54.
Sizes of SMD resistors and their power
The size of the SMD resistor depends mainly on the required dissipation power. The following table lists the sizes and specifications of the most commonly used SMD resistors.
Marking SMD Resistors
Due to the small size of SMD resistors, it is almost impossible to apply traditional color marking of resistors to them.
In this regard, a special marking method was developed. The most common markings contain three or four digits, or two digits and a letter called EIA-96.
3 and 4 digit markings
In this system, the first two or three digits indicate the numerical value of the resistance of the resistor, and the last digit is an indicator of the multiplier. This last digit indicates the degree to which 10 must be raised to get the final multiplier.
A few more examples of determining the resistances in the framework of this system:
- 450 \u003d 45 x 10 0 equals 45 ohms
- 273 \u003d 27 x 10 3 equals 27000 Ohm (27 kOhm)
- 7992 \u003d 799 x 10 2 equals 79900 Ohm (79.9 kOhm)
- 1733 \u003d 173 x 10 3 is equal to 173000 Ohms (173 kOhm)
The letter “R” is used to indicate the position of the decimal point for resistance values \u200b\u200bbelow 10 ohms. Thus, 0R5 \u003d 0.5 Ohms and 0R01 \u003d 0.01 Ohms.
SMD resistors of increased accuracy (precision), combined with small sizes, created the need for a new, more compact labeling. In this regard, the EIA-96 standard was created. This standard is for resistors with a tolerance of 1%.
This marking system consists of three elements: two digits indicate the code, and the letter following them determines the multiplier. Two digits are a code that gives a three-digit resistance number (see table)
For example, code 04 means 107 ohms, and 60 corresponds to 412 ohms. The multiplier gives the final value of the resistor, for example:
- 01A \u003d 100 Ohm ± 1%
- 38С \u003d 24300 Ohm ± 1%
- 92Z \u003d 0.887 Ohm ± 1%
Online SMD Resistor Calculator
This calculator will help you find the resistance value of SMD resistors. Just enter the code written on the resistor and its resistance will be reflected below.
The calculator can be used to determine the resistance of SMD resistors, which are marked with 3 or 4 digits, as well as the standard EIA-96 (2 digits + letter).
Although we did our best to test the function of this calculator, we cannot guarantee that it calculates the correct values \u200b\u200bfor all resistors, because sometimes manufacturers can use their custom codes.
Therefore, in order to be absolutely sure of the resistance value, it is best to additionally measure the resistance with a multimeter.
We have already met with the main radio components: resistors, capacitors, diodes, transistors, microcircuits, etc., and also studied how they are mounted on a printed circuit board. Once again, we recall the main stages of this process: the outputs of all components are passed into the holes in the printed circuit board. After that, the conclusions are cut off, and then soldering is performed on the reverse side of the board (see Fig. 1).
This process we already know is called DIP-editing. This installation is very convenient for beginner hams: the components are large, they can be soldered even with a large "Soviet" soldering iron without the aid of a magnifier or a microscope. That is why all Master Kit kits for independent soldering involve DIP-mounting.
Fig. 1. DIP mounting
But DIP editing has very significant drawbacks:
Large radio components are not suitable for creating modern miniature electronic devices;
- output radio components are more expensive to manufacture;
- a printed circuit board for DIP-mounting is also more expensive due to the need to drill many holes;
- DIP installation is difficult to automate: in most cases, even in large factories for the production of electronics, the installation and soldering of DIP parts has to be done manually. It is very expensive and long.
Therefore, DIP-mounting is practically not used in the production of modern electronics, and it has been replaced by the so-called SMD process, which is the standard today. Therefore, any radio amateur should have at least a general idea of \u200b\u200bhim.
SMD installation
SMD components (chip components) are electronic circuit components applied to a printed circuit board using surface mount technology - SMT technology surface mount technology). That is, all electronic elements that are “fixed” to the board in this way are called SMD components (eng. surface mounted device). The process of mounting and soldering chip components is correctly called the SMT process. Saying "SMD-installation" is not entirely correct, but in Russia this is exactly the variant of the name of the process technology that has taken root, and therefore we will say the same.
In fig. 2. shows the portion of the SMD-board. The same board, made on DIP-elements, will have several times large dimensions.
Fig. 2. SMD installation
SMD installation has undeniable advantages:
Radio components are cheap to manufacture and can be arbitrarily miniature;
- printed circuit boards are also cheaper due to the lack of multiple drilling;
- Installation is easy to automate: special robots install and solder components. There is also no such technological operation as pruning.
SMD resistors
Getting to know the chip components is most logical to start with resistors, as with the simplest and most massive radio components.
The SMD resistor in its physical properties is similar to the “usual” output version that we have already studied. All its physical parameters (resistance, accuracy, power) are exactly the same, only the case is different. The same rule applies to all other SMD components.
Fig. 3. Chip resistors
Sizes of SMD Resistors
We already know that output resistors have a certain grid of standard sizes, depending on their power: 0.125W, 0.25W, 0.5W, 1W, etc.
Chip resistors also have a standard grid of sizes, only in this case the size is indicated by a four-digit code: 0402, 0603, 0805, 1206, etc.
The main sizes of resistors and their technical characteristics are shown in Fig. 4.
Fig. 4 Basic sizes and parameters of chip resistors
Marking SMD Resistors
Resistors are marked with a code on the case.
If there are three or four digits in the code, then the last digit means the number of zeros. 5. The resistor with the code “223” has the following resistance: 22 (and three zeros on the right) Ohm \u003d 22000 Ohm \u003d 22 kOhm. The resistor with the code "8202" has a resistance of 820 (and two zeros on the right) Ohm \u003d 82000 Ohm \u003d 82 kOhm.
In some cases, the marking is alphanumeric. For example, a resistor with a code of 4R7 has a resistance of 4.7 Ohms, and a resistor with a code 0R22 has a resistance of 0.22 Ohms (here the letter R is a separator).
There are also zero resistance resistors, or jumper resistors. Often they are used as fuses.
Of course, you can not remember the code system, but simply measure the resistance of the resistor with a multimeter.
Fig. 5 Marking chip resistors
Ceramic SMD Capacitors
Externally, SMD capacitors are very similar to resistors (see Fig. 6.). There is only one problem: the capacity code is not applied to them, so the only way to determine it is to measure using a multimeter that has a capacity measurement mode.
SMD capacitors are also available in standard sizes, usually similar to the sizes of resistors (see above).
Fig. 6. Ceramic SMD Capacitors
Electrolytic SMS Capacitors
Fig. 7. Electrolytic SMS Capacitors
These capacitors are similar to their output brethren, and the markings on them are usually explicit: capacity and operating voltage. The strip on the “cap” of the capacitor is marked with its negative output.
SMD Transistors
Fig. 8. SMD Transistor
The transistors are small, so writing their full name on them does not work. They are limited to code marking, and there is no designation of any international standard. For example, the code 1E may indicate the type of transistor BC847A, or maybe some other. But this fact absolutely does not bother either manufacturers or ordinary consumers of electronics. Difficulties can arise only during repair. It is sometimes very difficult to determine the type of transistor mounted on a printed circuit board without manufacturer documentation on this board.
SMD diodes and SMD LEDs
Photos of some diodes are shown in the figure below:
Fig. 9. SMD diodes and SMD LEDs
The polarity in the form of a strip closer to one of the edges is necessarily indicated on the diode case. Typically, the cathode pin is marked with a strip.
The SMD LED also has a polarity, which is indicated either by a point near one of the terminals, or in some other way (for more details, see the documentation of the component manufacturer).
It is difficult to determine the type of SMD diode or LED, as in the case of a transistor: a low-informative code is stamped on the diode case, and most often there are no labels at all on the LED case, except for the polarity mark. Developers and manufacturers of modern electronics care little about its maintainability. It is understood that the PCB will be repaired by a service engineer who has full documentation for a particular product. Such documentation clearly describes where a component is installed on the printed circuit board.
Installation and soldering of SMD components
SMD-installation is optimized primarily for automatic assembly by special industrial robots. But amateur amateur radio designs can also be performed on chip components: with sufficient accuracy and care, soldering parts the size of a rice grain can be done with the most ordinary soldering iron, you only need to know some subtleties.
But this is a topic for a separate big lesson, so more about automatic and manual SMD installation will be discussed separately.
A resistor is an element that has some kind of resistance, it is used in electronics and electrical engineering to limit the current or obtain the necessary voltages (for example, the use of a resistive divider). SMD resistors are surface mount resistors, in other words, surface mount PCBs.
The main characteristics for resistors are the nominal resistance, measured in Ohms and depends on the thickness, length and materials of the resistive layer, as well as the power dissipation.
SMD electronic components are small due to the fact that they either do not have conclusions for connection in the classical sense. Elements for surround mounting have long leads.
Previously, when assembling REA, they connected the circuit components to each other (wall mounting) or threaded them through the printed circuit board into the corresponding holes. Structurally, the conclusions or contacts are made in the form of metallized pads on the housing of elements. In the case of microcircuits and surface-mounted transistors, the elements have short rigid “legs”.
One of the main characteristics of SMD resistors is the size. This is the length and width of the case; according to these parameters, elements are selected that correspond to the board layout. Usually, the dimensions in the documentation are written in abbreviated four-digit number, where the first two digits indicate the length of the element in mm, and the second pair of characters - the width in mm. However, in fact, the dimensions may differ from the marking depending on the types and series of elements.
Typical dimensions of SMD resistors and their parameters
Figure 1 - designations for the interpretation of sizes.
1. SMD resistors 0201 :
L \u003d 0.6 mm; W \u003d 0.3 mm; H \u003d 0.23 mm; L1 \u003d 0.13 m.
Rated Power: 0.05 W
Operating voltage: 15 V
Maximum allowable voltage: 50 V
2. SMD resistors 0402 :
L \u003d 1.0 mm; W \u003d 0.5 mm; H \u003d 0.35 mm; L1 \u003d 0.25 mm.
Nominal value range: 0 Ohm, 1 Ohm - 30 MΩ
Permissible deviation from the nominal value: 1% (F); 5% (J)
Rated Power: 0.062 W
Operating voltage: 50 V
Operating temperature range: –55 - +125 ° С
3. SMD resistors 0603 :
L \u003d 1.6 mm; W \u003d 0.8 mm; H \u003d 0.45 mm; L1 \u003d 0.3 mm.
Nominal value range: 0 Ohm, 1 Ohm - 30 MΩ
Permissible deviation from the nominal value: 1% (F); 5% (J)
Rated power: 0.1W
Operating voltage: 50 V
Maximum allowable voltage: 100 V
Operating temperature range: –55 - +125 ° С
4. SMD resistors 0805 :
L \u003d 2.0 mm; W \u003d 1.2 mm; H \u003d 0.4 mm; L1 \u003d 0.4 mm.
Nominal value range: 0 Ohm, 1 Ohm - 30 MΩ
Permissible deviation from the nominal value: 1% (F); 5% (J)
Rated Power: 0.125 W
Operating voltage: 150 V
Maximum allowable voltage: 200 V
Operating temperature range: –55 - +125 ° С
5. SMD resistors 1206 :
L \u003d 3.2 mm; W \u003d 1.6 mm; H \u003d 0.5 mm; L1 \u003d 0.5 mm.
Nominal value range: 0 Ohm, 1 Ohm - 30 MΩ
Permissible deviation from the nominal value: 1% (F); 5% (J)
Rated Power: 0.25 W
Operating voltage: 200 V
Operating temperature range: –55 - +125 ° С
6. SMD resistors 2010 :
L \u003d 5.0 mm; W \u003d 2.5 mm; H \u003d 0.55 mm; L1 \u003d 0.5 mm.
Nominal value range: 0 Ohm, 1 Ohm - 30 MΩ
Permissible deviation from the nominal value: 1% (F); 5% (J)
Rated Power: 0.75 W
Operating voltage: 200 V
Maximum allowable voltage: 400 V
Operating temperature range: –55 - +125 ° С
7. SMD resistors 2512 :
L \u003d 6.35 mm; W \u003d 3.2 mm; H \u003d 0.55 mm; L1 \u003d 0.5 mm.
Nominal value range: 0 Ohm, 1 Ohm - 30 MΩ
Permissible deviation from the nominal value: 1% (F); 5% (J)
Rated power: 1w
Operating voltage: 200 V
Maximum allowable voltage: 400 V
Operating temperature range: –55 - +125 ° С
As you can see, with an increase in the size of the chip resistor, the nominal power dissipation also increases in the table below, this dependence is more clearly shown, as well as the geometric dimensions of other types of resistors:
Table 1 - Marking of SMD Resistors
Depending on the size, one of three types of resistor rating markings can be used. There are three types of marking:
1. Using 3 digits. In this case, the first two indicate the number of ohms, and the last number of zeros. So mark resistors from the E-24 series, with a deviation from the nominal value (tolerance) of 1 or 5%. The size of resistors with this marking is 0603, 0805 and 1206. An example of such a marking: 101 \u003d 100 \u003d 100 Ohms
Figure 2 - image of an SMD resistor with a nominal value of 10,000 Ohms, it is 10 kOhm.
2. Using 4 characters. In this case, the first 3 digits indicate the number of Ohms, and the last - the number of zeros. This describes resistors from the E-96 series of sizes 0805, 1206. If the letter R is present in the marking, it plays the role of a comma that separates integers from fractions. Thus, the 4402 marking stands for 44,000 ohms or 44 kOhms.
Figure 3 - Image of a 44 kΩ SMD resistor
3. Marking with a combination of 3 characters - numbers and letters. In this case, the first 2 characters are numbers, indicate the encoded resistance value in Ohms. The third character is the multiplier. In this way, resistors of standard size 0603 are marked from a series of resistances E-96, with a tolerance of 1%. The translation of letters into a factor is performed according to the series: S \u003d 10 ^ -2; R \u003d 10 ^ -1; B \u003d 10; C \u003d 10 ^ 2; D \u003d 10 ^ 3; E \u003d 104; F \u003d 10 ^ 5.
The codes (the first two characters) are decrypted according to the table below.
Table 2 - Interpretation of SMD Resistor Labeling Codes
Figure 4 is a resistor with a three-character marking 10C, if you use the table and the given series of factors, then 10 is 124 Ohms, and C is a factor of 10 ^ 2, which equals 12,400 Ohms or 12.4 kOhm.
The main parameters of the resistors
Figure 5 - Equivalent resistor circuit
So, inductance and capacitance are elements that affect the impedance and the fronts of currents and voltages depending on the frequency. The best in frequency characteristics are elements for surface mounting, due to their very small size.
Figure 6 - The graph shows the ratio of the impedance of the resistor to active at different frequencies
Resistor design
Surface mount resistors are cheap and convenient for pipelined automated assembly of electronic devices. However, they are not as simple as they might seem.
Figure 7 - The internal structure of the SMD resistor
The basis of the resistor is a substrate of Al2O3 - alumina. It is a good dielectric and a material with good thermal conductivity, which is no less important, since in the process of operation all the power of the resistor is released into the heat.
A thin metal or oxide film is used as the resistive layer, for example, chromium, ruthenium dioxide (as shown in the figure above). The characteristics of the resistors depend on the material of which this film consists. The resistive layer of individual resistors is a film up to 10 μm thick, made of a material with low TCR (temperature coefficient of resistance), which gives high temperature stability of parameters and the ability to create high-precision elements, an example of such a material is constantan, however, the values \u200b\u200bof such resistors rarely exceed 100 Ohms.
The pads of the resistor are formed from a set of layers. The inner contact layer is made of expensive materials such as silver or palladium. Intermediate - nickel. And the outer one is lead tin. This design is due to the need to provide high adhesion (cohesion) of the layers. The reliability of contacts and noise depends on them.
Figure 8 - the shape of the resistive layer
The installation of such elements takes place in furnaces, and in amateur radio workshops using a blow dryer, that is, a stream of hot air. Therefore, in their manufacture, attention is paid to the temperature curve of heating and cooling.
Figure 9 - Curve of heating and cooling when soldering SMD resistors
conclusions
The use of surface mount components positively affected the overall dimensions of electronic equipment, as well as the frequency characteristics of the element. Modern industry produces most of the common elements in the SMD version. Including: resistors, capacitors, diodes, LEDs, transistors, thyristors, integrated circuits.
