Led cob lamps. Types and types of LEDs: classification, characteristics, purpose. I handed over the object and forgot

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. The new method was 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.

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 serves not only as a motherboard, but also as 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 also prevail 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.

Read also

The main direction of lighting technology is the introduction of LEDs into lamps of all kinds and types. But it should be noted that there is no single direction for this development. 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 COB lamps ( 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 emitted high-power brightness, and the flow was blinding. But there are two more factors: firstly, the optical systems themselves 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 of this type consist of 1-3 crystals, which are 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. This means that the entire technological process can be fully automated, avoiding 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, technical 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 home. 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.

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 onto 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 contacts-transitions: 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 was named 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”, which is 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 manufacturing 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.