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, conventional lighting is more suitable. LED Strip Light or a ruler mounted around the perimeter of the lamp body under the diffuser. 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 receive a scolding from your superiors for what you did not do at one time right choice, he asks to be billed for fluorescent lamps and various electrical consumables instead of COB matrices, in order to hide the real costs.
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 COB LED dome lights in warehouses and workshops produce a stronger glare effect, which makes it difficult for personnel to work at heights.
Expert opinion: “Our opinion: LED lights with a COB matrix is The best decision for accent light 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.
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 stamping standardized 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 the MCPCB plays a role not only 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 new technology. In large department stores and small shops on shift fluorescent lamps LEDs have arrived. 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 also prevail over fluorescent ones, due to government support and promotions. On Russian market The production of powerful COB light-emitting diodes was launched by the Optogan company. 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.
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In the last decade, lighting companies have gained great popularity COB LEDs. This happened because COB technology allows the creation and mass production of high-power directional LEDs. white light based on conventional light-emitting crystals of large-scale 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 is it a rectangular or round plate yellow color, housed in a housing with a transparent lid 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 and so on.
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 housings are designed for automated installation of ERE (electro-radio elements) directly onto the surface 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.
The main direction of lighting technology is the introduction of LEDs into lamps of all kinds and types. But it should be noted that a single direction this development No. Today, in addition to well-known LED lamps, so-called COB lamps, which are based on more powerful LEDs, are also entering the market. LED bulbs COB( Chip-on-Board)- these are essentially the same LED light sources with which everyone wants to save energy consumption. But disputes are still raging among experts, in which the parties cannot agree on how to choose the right one.
It is believed that in modern lighting technology until 2009 there was only one direction of development - an increase in the glow power of diodes. Both then and today this direction is called Power LED ( powerful LED). Scientists managed to achieve significant results - LEDs with a power of up to 10 W were born. Although 3-6 watt devices remain in demand.
What is the essence of the Power LED concept? In principle, everything is quite simple - reduce the cost of light sources. It was believed that increasing power, and therefore brightness, would reduce the number of LEDs. But in reality none of this happened. The cost of Power LED lamps has not decreased, and the light output has not increased much. Why did it happen?
- The first reason is that the LED is and has always been a point source of light. But for the basic operating conditions of any lamp, diffused light is required. Therefore, diode lamps for the home were provided with special optical systems. Without them, the light source would emit brightness high power, besides, the stream was blinding. But there are two more factors here: firstly, the optical systems were expensive, and secondly, through them the lamp itself lost a certain amount of brightness (up to 35%).
- The second reason is that the assembly of LED lamps using COB diodes involves a fairly large amount of manual labor. So here, too, expenses greatly influenced the cost of the product.
Breakthrough
Since 2009, SMD diodes have appeared, the power of which is 0.01-0.2 watts. LEDs consist of this type of 1-3 crystals, which were glued to a ceramic square base with dimensions from 1.4 to 6 mm. And each point diode is coated on top with a phosphor. The most important thing is that the LEDs are connected to the plateau using the soldering method. And that means all technological process can be fully automated, eliminating expensive manual labor.
But that's not all.
- SMD diodes are low-power; for one lamp you have to install them in large quantities (up to 700 pieces). And this is one hundred percent scattering light. That is, there is no need to use expensive and complex optical systems. The best option is a lampshade made of ordinary glass, whose light loss is only 8%.
- The LEDs are located on the plateau at certain intervals, which are several times larger than the size of the crystals themselves. That is why the diodes themselves are so clearly visible individually, and not in the total mass. In addition, it is possible to increase the optimal glow in rooms where there is a computer. You can simply install lamps with milky LEDs.
The only disadvantage of SMD lamps is their low maintainability. It is almost impossible to disassemble and re-solder a burnt-out diode manually. So it is better if you completely replace the lamp with a new one. It won't cost much.
The breakthrough continues
So, back to the COB LED lamp topic. No one was going to give up these LEDs, it was just necessary to modify the lamp itself, making it inexpensive. There were several options for changing the design, but one turned out to be optimal.
- Firstly, they abandoned ceramic substrates. That is, the crystals began to be installed directly on the plateau.
- Secondly, all crystals were covered with a single layer of phosphor. Therefore, the lamp glows evenly without visible individual luminous points.
And here COB matrices began to win over SMD matrices. In the circuits of 220 V LED lamps there are up to 70 crystals per square centimeter. That is, the lamp becomes several times smaller, but its brightness was not inferior to other models. Eventually, it became possible to use both reflectors and diffusers in light sources of this type, which are installed on traditional lamps.
Production process
COB dies are manufactured in several automated steps.
- An adhesive composition is applied to the substrate, which will provide high adhesive properties.
- Installation of crystals.
- Hardening of the glue.
- Cleaning the matrix with plasma technology.
- Soldering crystals from the plateau.
- Application of phosphor.
Attention! In this technology, the phosphor is mixed with silicone. The latter ensures complete tightness of the light structure.
The most difficult technological operation, which until recently was impossible to implement, is the application of a thin adhesive layer. The thing is that the glue layer must be of a certain thickness. If it is thin, the crystals will begin to peel off during use. If it is too thick, the thermal transfer of the crystals to the substrate will decrease. This problem was solved by the Chinese, who proposed using the magnetron sputtering method. Therefore, the new matrices are now called MCOB, that is, Multi Chip-on-Board, which translated means “numerous crystals on the board.” True, this did not change the design of the LED lamp. It is this technology that currently allows the production of high-power LED lamps.
Parameters and characteristics
So, specifications. Modern COB luminaires can reach 100 Watts. At the same time, the brightness of the glow reaches up to 150 Lm/W, which is even a very decent indicator.
The dimensions of the matrix (it can be square or round) are from 1 to 3 cm. This is for internal use. For outdoor LED lamps, diodes with a matrix size of 3x12 cm are used. The service life of LED lamps with COB diodes is 300,000 hours, more powerful analogues last up to 500,000 hours.
Some experts, given the short service life, talk about the low ability of this type of lamps. But there is one caveat. Lamp life was tested under extreme conditions. After that, using mathematical calculations, they summed up that they would work continuously for 6 years. And during this time, new lighting devices will probably appear, more economical, reliable and bright.
Attention! Almost all manufacturers provide a warranty period of 200,000 hours, during which they are ready to carry out repairs.
In principle, the technical characteristics indicate that LED lamps are by far the most economical option for a lighting system in the house. Of course, it is also the most expensive in terms of the down payment (price). But it’s worth paying attention to them if the consumer is faced with the problem of saving.
Conclusion on the topic
It is probably no longer a secret for many that many European countries want to abandon electricity generated from the fission of uranium. Nuclear power plants are unreliable. For example, Switzerland will close all nuclear power plants by 2036, although they account for up to 41% of electricity generation. Therefore, Europeans are investing a lot of money in the development of new energy-intensive technologies, where LED lighting is a priority.
And the last thing on this topic. Many consumers are wondering which LED lamps are better, and how to choose the right one? If you have read the article, then you should understand that this question makes no sense.
As the power of LEDs increased, manufacturers began to look for ways to improve heat dissipation. As a result, COB LED technology emerged, which makes it possible to create compact and powerful light sources with high optical density, from which the excess heat is removed by the housing. These LEDs are built into lamps and spotlights for lighting industrial and residential premises, and architectural lighting.
In COB LEDs, crystals without a housing or substrate are located close to each other, connected in series in parallel and covered with a single layer of phosphor. Up to 70 chips can be placed on 1 cm2 of board, as a result the optical density is significantly increased (the glow is uniform, without dots). The board can have different sizes; excess heat is lost through the case, regardless of the number of diodes.
The shape of the module can be rectangular, square, round, oval, which allows it to be installed in almost any lighting fixture. Power depends on the area; high brightness can be achieved with minimal module dimensions. This design does not create shadows, the surface is illuminated evenly. These LED sources work well with all ballasts, brightness and color dimmers, and automatic lighting control systems.
Attention! To get more power, you can use a miniature COB LED matrix instead of a bulk SMD matrix.
Production process
The COB LED manufacturing process consists of many steps:
- manufacturing of substrates;
- applying a composition to them that ensures adhesion;
- crystal installations;
- hardening of the adhesive coating;
- plasma cleaning from contaminants;
- electrical connection of LEDs;
- coating the crystals with a phosphor, providing sealing.
The printed circuit board has three layers: a metal base, a dielectric, a layer that conducts current.
For a long time, the implementation of SOV technology was prevented by the lack of a method for uniformly applying an adhesive composition to substrates. It must be of a certain thickness; neither increase nor decrease is allowed. In the first option, the thermal contact with the body is broken, in the second, the crystals come off.
In 2009, the magnetron sputtering method was proposed, which makes it possible to create thermal contact of a quality superior to that created on SMD printed circuit boards. New method called MCOB (Multi Chip-onBoard). At the moment, all the best manufacturers use it.
Attention! Even in scientific publications, COB and MCOB have the same meaning.
SOV technology allows you to create matrices of any shape without additional optical elements.
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