LED lamp based on cob diode. Lighting equipment based on COB and SMD LED matrices. Distinctive characteristics of COB

In the last decade, lighting companies have gained great popularity COB LEDs. This is because COB technology allows high-power directional white light LEDs to be designed and mass-produced from conventional light-emitting crystals in high volume, mass production. COB is an abbreviation, i.e., a reduction to the first letters of the English phrase chip-on-board. Translated into Russian as a crystal or element on a board.

The idea of this method is simple and as old as the Egyptian pyramids: if the strength of one person or the light of one LED is not enough, then attract a hundred people to pull the stone for the pyramid. Or place a dozen light-emitting crystals in one housing. COB LED This is a rectangular or round plate of yellow color, housed in a housing with a transparent cover or covered with a lens of secondary LED optics. The lens forms the desired directional pattern for the light flow and protects the COB structure from dust, water, mechanical impact, etc.

The essence of COB technology

Finished LED chips without housings are glued onto a heat-conducting artificial sapphire substrate or soldered onto a semiconductor silicon wafer. Depending on the operating voltage, the chips are connected in series circuits. For 9 V – 3 pcs., 12 V – 4 pcs. etc. The chain is powered by a current of one magnitude - the nominal operating current for crystals of this type, for example, 20 mA. Serial chains are connected in parallel, gaining power or luminous flux. Then the blue light LED crystals are coated with a yellow phosphor. This is how you dial heavy duty LEDs COB.

What does the phrase mean SMD COB LEDs? This is a COB matrix housed in an SMD package. These cases are designed for automated installation of ERE (electro-radio elements) directly onto the surface of a printed circuit board. COB is a set of technological operations for the production of high-power and ultra-high-power LEDs in the form of a single matrix. The matrix consists of tens or hundreds of crystals.

COB (Chip On Board) technology has reached LEDs. The method in which the chip is mounted directly on the board has long been used in the stamping of unified electronic boards and has proven itself to be extremely reliable and miniature. Its appearance brought novelty to the developing LED world and allowed us to look beyond the horizon of possibilities of semiconductor components.

The essence of technology

The idea of placing multiple LED chips on a board in one package arose as a result of unsuccessful attempts to increase light output and simultaneously obtain diffuse light from a group of powerful light-emitting SMD elements. Powerful SMD LEDs require a complex cooling system, which entails a significant increase in the cost of the final product.

Scientists abandoned increasing the power of a single crystal and began experiments on increasing and minimizing LED chips in one package. The result of the experiments was COB technology, which involves installing many tiny chips connected in series and parallel on a common base. A printed circuit board is usually made on a metal base (Metal Core Printed Circuit Board, MCPCB) and consists of three main layers - the metal base itself, the dielectric and the conductive layer. The base is made of metal alloys with high thermal conductivity. Thus, MCPCB not only serves as a motherboard, but is also a good heat conductor. On MCPCB, LED chips are attached using adhesive, then connected to each other and covered with a single layer of phosphor.

The resulting COB matrix emits evenly diffused light, does not overheat (with proper heat dissipation) and does not require complex optical systems. Using COB technology, it is possible to produce matrices of absolutely any geometric shape at low cost, which could not be achieved using previously known methods.

A few more words about production

The production of a COB matrix begins with preparing the substrate, onto the working surface of which a thin layer of adhesive is applied. The requirements for the thickness of the adhesive layer are very high. On the one hand, it must ensure reliable contact with microscopic LED crystals, and on the other, guarantee uniform heat dissipation.

Scientists managed to achieve a uniform distribution of a substance with high adhesion over the surface of the base using the magnetron sputtering method. As a result, the thermal contact between the chip and the base became more perfect, and the technology began to be called MCOB (Multi Chip-on-Board).

In the scientific literature, the concepts COB and MCOB often have the same general meaning.

Chips are installed on the prepared base of the future COB LED and the smallest particles of debris are removed using plasma cleaning. Then the LEDs are electrically connected and, finally, a layer of liquid phosphor is applied. After hardening, it not only does not transmit ultraviolet radiation, but also protects the board elements from external influences.

Distinctive characteristics of COB

Along with other types of LEDs, COB matrices have their “light and dark sides” that are worth mentioning. The first plus in favor of COB is the shape of the matrix, which can be made round, square, with technological holes... In general, any. This allows you to duplicate the dimensions of almost any artificial light source and adapt to the desired shape. The second positive aspect is the quality of the emitted light. Objects illuminated by COB lamps have a clear shadow boundary due to the uniform distribution of the light flux. SMD LED lamps cannot boast such contrast due to separately located crystals and reflectors.

You can’t ignore energy indicators. The power of one COB matrix depends on its geometry, the number of crystals and the perfection of the manufacturing technology used. It is worth noting the high light output of COB matrices. For example, the most technologically advanced, mass-produced COB matrix CXB1820 from Cree has a light output of 166 lm/W.

The disadvantage of COB technology is the non-repairability of the matrix in the event of partial or complete failure of individual chips.

About products

In economically developed countries, COB luminaires are already proving their superiority in practice. Without waiting to improve the technological process and reduce the cost of COB matrices, the Swiss are actively converting street lamps and advertising signs to the new technology. In large department stores and small shops, LEDs have replaced fluorescent lamps. This active implementation of energy-saving technologies is explained by the desire of wealthy Switzerland to completely abandon nuclear power plants in the next 20 years.

In other Eurozone countries, LED light sources are also prevailing over fluorescent ones, due to government support and promotions. The Optogan company has launched the production of high-power COB light-emitting diodes on the Russian market. Today, the Optogan company presents the most advanced line of COB LED matrices with the OCC series. Each COB matrix can have a specific color temperature (warm, normal, daytime or cool) with a clear indication of the brightness bin. More detailed information can be found in the specification.

Filament LED and lamps based on them

LED filaments are a modified version of COB matrices. Although COB and filament share a common technology base, they have distinct design differences. In LED filaments, crystals are not applied to a metal plate, but, as a rule, around the circumference of a glass rod. Therefore, the technology is often abbreviated as COG (Chip-on-Glass).

The practical use of LED filaments is dictated by the need to create economical lighting devices that are as similar as possible to incandescent lamps. Instead of a filament, several filament rods are built into a standard E14, E27 housing with a glass bulb, and a miniature driver is mounted in the base. The function of a radiator is performed by the thin glass of the flask and the gas with which it is filled. Of course, the conical arrangement of filaments inside the bulb does not allow one to completely imitate a filament, but the entire design as a whole retains the aesthetic properties of its predecessor. In addition, this type of COB technology gave birth to a new subspecies of LED lamps.

Ready-made LED lamps, spotlights and simply lamps designed using COB technology are just taking off in the race, while similar SMD products are already racing at high speed. This fact is clearly visible in the retail trade, where cheap SMD LED light bulbs still predominate. But this is just the beginning. It won't be long before people appreciate the benefits of COB technology, which will certainly affect the demand for products based on Chip On Board technology.

What are LEDs?

Before considering common types of LEDs, let's study general information about the corresponding devices. An LED is a semiconductor that is capable of converting electrical current into light. In this case, the semiconductor crystal, which is its main component, consists of several layers characterized by 2 types of conductivity. Namely - hole and electronic.

Conduction of the first type involves the transfer of an electron from one atom to another, which has a free place. In turn, another electron comes to the first atom, another electron comes to the previous one, etc. This mechanism operates due to covalent bonds between atoms. In this case, they do not move. In fact, a positive charge moves, which physicists conventionally call a hole. In this case, when an electron passes to holes, light is released.

The structure of an LED is generally similar to a rectifier diode. That is, it has 2 terminals - anode and cathode. This feature predetermines the need to maintain polarity when connecting the LED to a source of electric current.

The corresponding products are generally designed for a forward current of 20 milliamps. In principle, this value can be reduced, although in this case the color may change and the brightness of the LED may decrease. In turn, it is undesirable to increase the corresponding parameter. If the current exceeds the optimal value, a limiting resistor is used to reduce it to the required level.

There are quite a few nuances that should be kept in mind when installing LEDs. This is predetermined by their internal structure and form of execution. In some cases, it may be necessary to use a stabilizer for LEDs and other electronic components to ensure the functioning of the device in which the product in question is installed.

Depending on the composition of the semiconductors in the LED, it can be red, yellow, green or blue. For example, if the structure of the corresponding electronic component contains gallium nitride, the LED will glow blue. Actually, one of the criteria based on which certain types of LEDs are distinguished may be their color.

Application

The first LEDs supplied to the market were produced in metal housings. Gradually it began to be replaced by plastic. In this case, the color is usually selected taking into account the color of the LED glow. However, transparent plastic cases are also quite common.

The electronic devices under consideration are widely used in a variety of fields. This is due to the fact that almost everyone is characterized by:

Energy efficiency;

Long service life;

The ability to determine the color of the glow, as well as adjust its power;

Security;

Environmentally friendly.

If we talk about energy efficiency, LEDs with the same luminous efficiency can have significantly less power than conventional lamps. Lower LED power reduces the overall load on the building's energy system. The service life of devices can be several tens of times longer than that of conventional lamps. At the same time, in terms of functions, LEDs can be completely on par with them.

As mass demand for such products develops, as well as their cost, LEDs are increasingly used for the same purposes as conventional lamps. There are no difficulties in installing the corresponding solutions in comparison with traditional lighting devices. It is only important to make sure whether a particular LED is suitable for installation in the electrical network of the room. To do this, it may be necessary to identify its main parameters in advance - before purchasing LEDs.

What other benefits might the solutions under consideration have?

Thus, it can be noted that the color temperature of the LED can be almost any - including a combination of the above colors. In addition, the devices can be supplemented with various light filters, which can significantly expand the scope of LEDs in terms of selecting the required color temperature.

The ability to control the glow power is another advantage of the devices in question. This option goes well with their high energy efficiency. The LED power can be adjusted automatically - based on the actual conditions of use of the lighting fixtures. And this practically does not affect their service life.

LEDs are environmentally friendly because they do not emit types of radiation harmful to humans. This characteristic, again, expands the application possibilities of the devices in question.

Classification: indicator and lighting solutions

Experts distinguish 2 main categories of LEDs - indicator and lighting. The former are intended mainly to create a decorative lighting effect and are used as an element of decoration of a building, room, or vehicle. Or as a tool for text stylization - for example, on an advertising banner.

In turn, there are lighting LEDs. They are designed to increase the brightness of lighting in a room or in a certain area of the territory - for example, if we consider LEDs for cars. This type of solution is an alternative to the use of conventional lamps and, in many cases, more beneficial in terms of energy efficiency and environmental friendliness.

Types of execution

But let's return to the classification of LEDs. It is possible to define a wide range of reasons for their classification into certain categories. A common approach among experts involves identifying the following main types of LEDs:

Fiber;

Let's take a closer look at them.

What are the specifics of DIP LEDs?

If we study in more detail how these types of LEDs appeared on the market, then DIP class devices can be attributed to the first that began to be sold en masse. These solutions are crystals that are placed in housings with optical components, in particular a lens that creates a light beam.

DIP LEDs belong to the indicator category. They have another name - DIL. They are installed on a board on which holes must first be made. It can be noted that within the category under consideration, various types of LEDs can be distinguished, which differ in the diameter of the bulb, color, and material of manufacture. In this case, the corresponding parameters can be presented in the widest range. The shape of the solutions under consideration is cylindrical. Among the corresponding LEDs there are both monochrome and multicolor devices.

Spider LED

This type of LED is generally very similar to previous devices. But they have twice as many outputs - 4. While DIP LEDs have 2. The fact that the presented type of solution has more outputs optimizes heat dissipation and increases the reliability of the corresponding components. In practice, they are used in various fields, in particular as LEDs for cars.

SMD LEDs

These solutions are produced using the surface mounting concept. That is, they are LEDs installed on any surface, while other solutions can be installed through through-hole mounting.

The dimensions of LEDs of this type can be significantly smaller than those of alternative solutions, as well as the structures on which they are installed. Again, in this case it is legitimate to talk about more optimal heat removal. Using SMD LEDs in many cases it allows you to expand the variability of lighting designs.

SMD LEDs belong to the lighting category. They are characterized by a rather complex structure. So, the LED itself consists of a metal substrate. A crystal is fixed on it, which is soldered directly to the contacts of the substrate body. A lens is placed above the crystal. In this case, 1-3 LEDs can be installed on one substrate. SMD includes common types of ultra-bright LEDs, such as 3528. These solutions have a high level of demand.

COB LEDs

The next popular type of LED is COB. It is made using technology that involves installing the crystal directly on the board. This solution has many advantages:

Protection of the compound from oxidation;

Small design dimensions;

Heat dissipation efficiency;

Reducing the installation cost of LEDs - in comparison, in particular, with SMD-type devices.

If we consider the above types of LEDs, it can be noted that COB brand solutions can be classified as the most innovative. This technology was first implemented by Japanese engineers in the late 2000s. Now these types of LEDs continue to gain popularity.

According to experts, the solutions under consideration may even become the most popular on the market, especially if we talk about the commercial segment and the field of household lighting. It is worth noting that there are areas where the use of COB LEDs may be difficult. Among these is the production of professional lighting equipment. The fact is that the LEDs in question are not very optimal from the point of view of adapting to the organization of lighting with an established luminous intensity curve. In such cases, SMD type devices may be more suitable.

The diodes described are classified as lighting diodes. As experts note, they can be classified as the best based on the characteristics of the luminous flux. They are available in the market in different colors such as red, green, blue and also white. The luminous flux of these models has a dispersion angle of 40-120 degrees.

More than 9 COB LEDs can be installed on one substrate. They are coated with a phosphor, as a result of which they acquire high brightness. It can be noted that the luminous flux of these solutions is higher than that of SMD devices. Thus, if we consider which type of LEDs is better, then according to the specified criterion, a COB class solution may have an advantage.

COB LEDs are also used in the automotive industry. They can be used as a component of headlights, rear lights, and turn signals. The main thing is to install the purchased devices correctly. To do this, it makes sense to turn to experienced specialists.

Fiber LEDs

Fiber LEDs can be considered innovative. They appeared on the market recently, in 2015. The solutions in question were developed by engineers from South Korea.

These types of LEDs can be used in the production of clothing. That is, it is quite possible to make a shirt or T-shirt from them that can glow. The production of clothing based on fiber LEDs also involves the use of various polymers, as well as aluminum compounds.

Filament LEDs

Another example of innovative LEDs is Filament solutions. Their main advantage is high energy efficiency. For the same power, with LEDs such as COB, for example, Filament solutions can provide higher levels of illumination.

The one in question is most often used in the manufacture of one. Among the notable characteristics of the production of the corresponding LEDs is installation directly on a substrate made of glass. This approach makes it possible to distribute the light emitted by the LED over 360 degrees.

How to choose the best option?

How to determine the type of LED that is optimal for a particular design? There are a large number of criteria that you can focus on in this matter. In principle, it is quite legitimate to determine the scope of application of an LED based on its classification according to the characteristics that we discussed above. Let's study the specifics of choosing the appropriate electronic components, taking into account the characteristics of the devices:

Selecting LEDs: features of DIP solutions

As we noted above, DIP LEDs are among the earliest products to hit the market. Thus, they involve quite old, but still in demand technologies. Their main advantages are ease of installation, convenient form, low energy consumption, low heating, and a fairly high degree of protection from external influences.

Most often, the LEDs in question are available in diameters of 3 and 5 mm. If we compare LEDs by type, we can come to the conclusion that the solutions under consideration are the most optimal for use:

As elements of car tuning;

As decorative components;

As part of low-power - as an option for homemade - flashlights.

The LEDs in question have a relatively low cost and availability on the market. It can be noted that among the most common modifications are 12 volt LEDs. They can be present in various online catalogs, as well as specialized stores in a wide range. Actually, any 12 volt LEDs are characterized by a fairly high demand on the market.

Selecting LEDs: features of SMD type solutions

The corresponding type of solution is fundamentally different in appearance from others in that it has a flat shape. These electronic components are mounted without the use of feet. The current for SMD type LEDs is supplied to the terminals that are located on their reverse side.

Thus, the installation of these devices is carried out without the use of holes. The placement of LEDs can be done very compactly. As a result, the structure on which the corresponding devices are located may also become smaller.

The main ways of using the devices in question are the same auto-tuning, various types of interior lighting. Among the most significant advantages of these options are high brightness and light output. Combined with their small size, these solutions offer significant advantages over alternative product models.

Among the most common on the modern market is the 3528 LED type. These products are widely used in the production of LED strips. The design of the corresponding products allows the production of three-color LEDs - with red, blue, and green glow colors. Many other electronic components are manufactured based on the 3528 type solutions, such as the SMD 5050 type LED.

The products in question are also characterized by their affordability. They are usually presented on the market in a wide range.

Selecting LEDs: Features of COB Solutions

First of all, it is worth noting that a significant part of the LEDs of the corresponding type are very powerful designs. Their characteristic feature is the rapid dispersion of light, thanks to the placement of crystals on the surface, which provides dynamic heat dissipation.

The LEDs in question are very bright. This makes them in demand specifically for use in the design of car headlights. It is worth noting that these products should be installed taking into account a number of significant nuances - only experienced specialists can know these. Therefore, it is recommended to contact competent service personnel to install appropriate solutions.

COBLEDs- These are usually structures in the form of a matrix containing from several tens to several hundred light-emitting crystals. An example of an LED assembled using COB technology is the popular SMD 2835 LED, about which there is information in the article.

The development of LED devices is moving along the path of increasing their brightness, or rather obtaining an ever-increasing luminous flux. The flow can be increased in several ways:

increase the power of a single LED;
combine several tens or hundreds of low-power light-emitting crystals in one LED housing.

The first attempts were in the form of “Piranha” type LEDs. In them, three or four low-power crystals were placed in one case. Another example of this approach was the three-chip SMD 5050 LED.

In Piranha, the crystals are soldered to the end of a lead wire, which is a passive heat sink that transfers heat to the board and conductive copper traces.

In SMD packages, the chip(s) are mounted on a thin package bottom or ceramic substrate. Heat is dissipated through several thermal junctions: crystal - substrate - inner bottom of the case, outer bottom of the case - printed circuit board or heatsink surface. These junctions have solid thermal resistances that prevent heat from escaping from the crystal. Therefore, the crystals in such cases are not cooled very well.

SMD cases, when installing a large number of LEDs, take up a lot of space, “pushing apart” the luminous points of the LEDs. Therefore, to equalize the luminescence density of the lamp, matte or microprismatic light diffusers are introduced into its design. This solution reduces the luminous flux. Even transparent “screens” absorb up to 10% of the flow. And matte ones - up to 20 - 25%.

An excellent solution to this problem was found at the beginning of this century. Engineers proposed placing LED crystals on a large substrate. If in an SMD diode its dimensions range from 1.4 to 6 mm, then the new substrates were 10 - 30 mm in diameter or rectangular - up to 120 × 30 mm. The substrates are made of heat-conducting ceramics, artificial sapphire, or simply semiconductor silicon. The crystals were first glued, but the thickness of the glue was large and its thermal resistance was also high.

The glued crystals were connected in series chains operating at a voltage of 9, 12, 24 V or more. The chains were connected in parallel to obtain the required power and/or luminous flux. The connected and tested chains were coated with a phosphor based on silicone or epoxy resins. This method of manufacturing LED matrices is called COB technology. COB stands for Chip-on-Board or “chips on board”.

In 2009, the Chinese Academy of Sciences came up with a method for spraying a thin layer of adhesive (“glue”). The technology is called Multi Chip on Board or MCOV.

In SOV matrices, the cost of one lumen of light flux ranges from 0.07 rubles. up to 0.2 rub. In this case, the crystal density reaches 70 per square meter. cm. The luminous dots in the matrix are located much more densely than on a board with SMD diodes. The phosphor can be made in the form of a lens, which will form the desired luminous flux diagram. So the dimensions of the COB matrix have become much smaller than the SMD “matrix” similar in flow.

The power of the COB matrix can reach hundreds of watts, the light output is 120 – 160 Lm/W. Service life – up to 50 – 60 thousand hours. The high degree of automation of production has brought the average cost of a not very powerful COB matrix to the equivalent of several dollars. Therefore, repairing a lamp by replacing the matrix may be cheaper than buying a new lamp.

What is the difference between COB and SMD LEDs?

SMD is a method of mounting electronic components on a printed circuit board. SMD packages contain resistors, capacitors, transistors, inductors, etc.

COB LEDs is a technology for producing a usually high-power or very high-power LED. COB LEDs can be housed in SMD type housing. For example, SMD 2835 is manufactured using COB technology.

Difference between SMD and COB LEDs is that SMD is a type of LED housing designed for mounting on the surface of a board, and COB is a technology for manufacturing an LED or at the cost of a matrix.

Let's express our point of view on this dilemma, which is beginning to resemble a debate about which is better, iOS or Android. There is no clear answer to this question. It is necessary to clearly understand the purpose of the lamp, which uses a diode matrix. For some, COB will be better, for others - SMD.

COB for low power downlights

For example, COB clearly wins in commercial directional lighting fixtures. Such as track lights, downlights and other types of accent lighting.

For diffuse commercial lighting, a conventional LED strip or ruler mounted around the perimeter of the lamp body under the diffuser is more suitable. COB matrices also behave quite well in street floodlights with a power of up to 50 watts.

SMD for industrial dome lights over 50W

As for the lighting of industrial enterprises, for example, in industrial LED lamps the bell
It is almost impossible to find a COB matrix (see figure on the right) from world-famous advanced manufacturers, although a few years ago everyone loved such experiments.

Industrial LED dome lamps with a COB matrix are much cheaper than a lamp with an SMD diode board, such as industrial dome lamps.

This is due to the fact that a COB matrix with diodes from the same manufacturer costs 30-50% less, which reduces the cost of the lamp. The downside, according to reviews from most well-known manufacturers of industrial and street lighting, is the frequent replacement of COB matrices under warranty if the lamp power is more than 50 W.

At one of the factories with which we cooperate, we were told a story about how an industrial LED bell lamp with a high-quality heat dissipation system and a high-quality COB diode was left turned on with the chip down on the table, and within 2 hours the table caught fire.

Real experience

From our personal practice, we know the story of how a power engineer at a large enterprise, in order to save money at the expense of quality, bought industrial dome lamps with COB diodes and now he has to pay for his wrong decision: every year to change the diode boards in 15-20% of the lamps .

In order not to get scolded by his superiors for making the wrong choice at one time, he asks to be billed for fluorescent lamps and various electrical consumables instead of COB matrices, in order to hide real expenses.

COB Diode Degradation

We should also not forget about the real degradation of diodes in high-power industrial luminaires, which, according to user observations, is higher for high-power luminaires with COB elements. But very rarely does anyone carry out annual measurements of room illumination.

Diode counterfeiting: How to identify unscrupulous manufacturers of industrial lighting fixtures?

Glare effect of COB diodes

Another observation from users is the fact that industrial LED dome lights with COB matrix in warehouses and workshops give a stronger glare effect, which makes it difficult for personnel to work at heights.

Expert opinion: “Our opinion: COB LED luminaires are the best solution for accent lighting and moderate power luminaires up to 50W. The only exceptions are multi-module systems, in which each module is a separate COB matrix of moderate power. For lighting of more than 50 watts, it is better to use industrial bell lamps with an SMD matrix. Moreover, the greater the number of diodes per 1 watt of power, the better,” says Alexey Frolov, lighting engineer at Grandenergoproekt.