SMD LEDs. Types and types of LEDs: classification, characteristics, purpose Packless LEDs

The luminous flux of the second generation of multi-chip LED assemblies of the Luxeon S family is 8000 lm. In addition, Philips Lumileds has resumed supply of blue LEDs in bulk and CSP (chip-scale package) sizes, which provide maximum flexibility for the manufacture of complex and densely packaged assemblies.

Thin Film Inverted Crystals

Lumileds has stopped supplying bulk blue LED chips, switching to a thin-film flip-chip architecture that eliminates the need to remove the sapphire substrate before packaging. With the advent of Flip-Chip LED components, the company developed an architecture in which a transparent substrate provides a stable position for the bare chip that manufacturers integrate directly into products.

The main advantage of the Flip-Chip architecture is the elimination of the use of thermocompression welding wire. Not only is this wire a possible cause of failure, but it also limits the placement of the LED chip and the driving current density of the LED. However, before the new design, Flip-Chip chips were too fragile to be sold in this form.

LED Flip-Chip from Lumiled

Now, luminaire manufacturers have the opportunity not only to install packaged LEDs in luminaires in the traditional way, but also to independently select the phosphor and housing for LED crystals in accordance with the requirements of the application.

Lumileds is the first manufacturer to develop and supply LEDs in CSP packages, which are essentially the same dimensions as the chips. Lumileds' Flip-Chip LED has a nearly identical footprint to the die. The only difference is the presence of pads at the base of the chip, which are optimized for standard reflow soldering processes. The degree of conversion of electrical energy into optical energy for a 1x1 mm crystal is 56-61%, depending on the wavelength. Lumileds traditionally does not specify the lumen output or efficiency of these LEDs, since emission at these wavelengths is in the reduced sensitivity range of the human eye.

Luxeon S multi-chip assemblies

Lumileds announced the second generation Luxeon S family of multi-chip components. The luminous flux density of these products reaches 50 lm/sq.mm, and their total luminous flux is 1000-1800 lm, depending on the design.

Second generation Luxeon S family of LED components

While the first generation Luxeon S products were designed as standard single light source assemblies in a small square package, the new products are essentially COB (chip-on-substrate) designs. Lumileds did not use COB labeling for these components, in part because these are LEDs with a phosphor that converts the light to white light, rather than an array of blue LEDs with a phosphor coating.

Rahul Bammi, vice president of Lumileds, clarified that the layout of the LEDs on the circuit board is designed in such a way as to provide the required beam angle. Among other applications, these assemblies are designed to replace 75- and 100-watt metal halide spotlights for retail stores.

The luminous flux density of the new assemblies is twice as high as the solutions offered on the market. The luminous flux of Luxeon S components reaches 8,000 lumens with half the size of the optical system, allowing these LEDs to be used to replace obsolete ceramic metal halide lamps (CMHA) for directional lighting and architectural applications. At the same time, Luxeon S assemblies provide comparable light output of 90 lm/W, but, unlike KMGLs, they turn on instantly, have greater color saturation, and their service life is four times higher than that of KMGLs, amounting to 60 thousand hours.

The company claims that thanks to the LEDs used and their arrangement, the light intensity in the central part of the beam is 50 thousand cd. This solution is also color optimized across the entire emission angle. Lumileds offers LEDs with color temperatures of 2700 or 3000 K with a color rendering index of 80 or 90, and 3500-5000 K with a CRI of 80.

LEDs are becoming increasingly popular in modern lighting systems. They are actively used in design, decoration, and other areas. LED sources emit pure light, are economical and safe. Nowadays, SMD LEDs are increasingly used, known as surface mounted devices, which means a surface-mounted device. Their power and luminous flux are constantly increasing, just like traditional light bulbs with long stems and a round plastic lens.

General structure and principle of operation of SMD LEDs

The main advantage of such LEDs is their maximum proximity of the crystal relative to the heat sink. This factor is important when emitting a powerful light flux with the release of a large amount of heat. The power of one SMD LED is in the range of 0.01-0.2 W, and from 1 to 3 crystals can be installed on a separate ceramic substrate.

Due to its design, the contact pads of the LED substrate are directly connected to the circuit board. A wide lighting angle and other parameters are possible with a standard base. These LEDs are widely used in various displays and scoreboards due to their small housing sizes. They are easily mounted on boards, combined into strips and rulers, convenient for subsequent separation and installation. A wide range of housing sizes significantly expands the scope of use of SMD LEDs.

To grow crystals, a standard technology is used, which is metal-organic epitaxy. The thickness of each grown layer is constantly measured and strictly controlled. Special impurities are added to individual layers - acceptors or donors, which ensure the formation of a p-n transition, when electrons are concentrated in the n-region and holes in the p-region.

At a certain stage, the films are etched, contacts are created to the transition layers, and the contact leads are covered with a metal film. Such a film is grown on a common substrate, after which it is cut into many chips with an area of ​​0.06-1.0 mm. These chips are later used to make LEDs.

Finished crystals are installed in special cases. Then contacts are made to them, and at the end an optical coating is mounted on the crystal to reflect radiation or, conversely, to brighten the surface. For example, when producing a white LED, phosphor is applied uniformly. At the next stage, heat is removed from the housing with the crystal, and then it is covered with a plastic dome to focus the light at the desired angle. Manufacturing LEDs in this way involves the use of new technologies, which account for about half the cost of the entire light source.

There is a special technology for placing SMD LEDs on a single substrate. In short, it is called COB, which means chip-on-board or chip on a board. When using this technology, several crystals are placed on the board at once, which do not have ceramic substrates and cases. The installed crystals are subsequently covered with a common layer of phosphor, which can significantly improve the characteristics and reduce the overall cost of the entire matrix.

Regardless of the manufacturing technology, all SMD LEDs are mounted on a common metal substrate, which often performs a cooling function. If the LED assembly has increased power, additional cooling is arranged using a radiator and fan.

Thus, low-power SMD LEDs, installed in large quantities in the lamp, make it possible to obtain high-quality diffused light without using any special optical systems. In this case, only protective glass is installed, absorbing only 8% of the light flux.

Pros and cons of SMD LEDs

Despite their lower power compared to fluorescent lamps, LEDs of this type are among the most promising. Due to white radiation, high accuracy of color and shade reproduction is ensured. SMD LEDs, due to their excellent luminous efficiency, reaching 146 lumens per W, are suitable for use in lighting systems.

The designs of these LED light sources are characterized by increased resistance to vibration and mechanical stress. Therefore, they are actively used in industrial and street lighting. The service life of such LEDs is about 30 thousand hours, with daily operation of at least 8 hours. All types of devices, including SMD 3528, SMD 5050 and others, can withstand any number of on and off cycles.

SMD lamps are distinguished by a wide range of colors, which includes not only radiation intensity, but also shades. In this regard, there is no need to use light filters. Many LEDs, for example, SMD 5630 and SMD 5730, have low inertia, that is, they immediately begin to work at full power. There is no need to wait for heating and subsequent glow, as is the case with conventional lamps.

LEDs SMD 3014, SMD 2835 and other similar elements have different emission angles. During operation, a directed light flux is generated, illuminating a specific area, and not the entire surrounding space. The undoubted advantage of such lamps is their absolute insensitivity to cold weather.

Disadvantages include intolerance to high temperatures, which requires additional measures for ventilation and heat removal. It should be noted the high cost of these devices, which fully pays off during further operation.

Characteristics of SMD elements

LEDs of this type differ from other products due to their own specific characteristics. First of all, their entire design is designed for surface mounting, eliminating the need for soldering, fastening and assembly. Most SMD LEDs have low thermal resistance, that is, they do not heat up and can be placed on any surface - ceilings, plastic panels, near tension fabrics, etc.

Depending on the brand, the sizes of SMD LEDs can be very different, and therefore they are successfully used in any place. During operation, the radiation power of these elements remains unchanged.

Many LEDs have a silicone coating to promote sealing and improved heat dissipation. In order to correctly select the right product, special markings of SMD LEDs are used, which display all the main parameters.

The technical characteristics are displayed more clearly in the table:

The constant increase in LED power to increase the luminous flux (brightness) has led to a change in the traditional cylindrical shape of the plastic LED housing. This is due to the fact that this design no longer satisfies manufacturers due to insufficient heat removal from the crystal. Therefore, in order to bring the SMD chip as close as possible to the heat-conducting surface, the traditional technology is being replaced by a more advanced SMD.

The name is an abbreviation for surface montage details. Although this technology has been used for a long time in the backlighting of mobile phone keyboards, the power of the first samples was not enough for lighting. Currently, SMD LEDs have crossed the threshold of a hundred watts and continue to increase it every month. An LED manufactured using SMD technology is shown schematically in the figure.

Along with a significant increase in the power and brightness of an SMD LED relative to its packaged counterparts, we also get a wider lighting angle. Thanks to this, it has become easier to produce LED lamps, since the luminous flux is not as narrowly concentrated as in conventional LEDs.

Some basic models of low-power packageless SMD LEDs and their technical characteristics are shown in the table:

LEDs made using SMD technology are mounted directly on a common substrate, which often acts as a radiator (cooling). This is how entire LED modules and plates are created, which can have a rectangular or round shape, be rigid or flexible - for example, LED strips. For powerful lamps and spotlights, SMD LED assemblies are manufactured on a massive metal radiator. In some cases, for LEDs over 100 watts, even forced cooling is used - blowing with a cooler.

The variety of SMD LEDs is expanding every day. SMD LEDs 3528, 2835, 5050, 3014, 5630 and 5730 are just the main sizes that have already gained worldwide popularity. In parallel with them, planar LEDs of various sizes with unpredictable parameters are being stamped under the “Made in China” sign.

If the time-tested characteristics of SMD 3528 and SMD 5050 LEDs, for the most part, correspond to the declared parameters, then there are many questions about light-emitting diodes of the new form factor. The Chinese have famously learned to counterfeit everything that is in demand in the consumer market, including LED products. Considering that LED lamps and strips from famous European companies are also assembled in China, what quality is included in them?

To clarify and see the differences among the most commonly used surface-mount LED chips today, we propose to compare their electrical, optical and structural parameters. But first, a few phrases about the scope of their application.

Application area

SMD LED is used wherever something needs to be illuminated, illuminated or simply decorated. They have become a basic element in general lighting bulbs, in indicator panels and LCD TVs, and in emergency lighting systems. The most popular product assembled using SMD LEDs is still the LED strip, as well as its modifications in the form of rulers and modules.

In the new variation, multi-color strips are constructed on groups that consist of four powerful LEDs of different colors “R+G+B+W”. In total, their light output is much greater than that of conventional SMD 5050 LEDs, and the presence of an independent white LED expands the light shades.

Brief technical specifications

Now we will consider each of the most popular standard sizes individually. Using numbers, we will try to give an objective assessment of each type and reveal its strengths and weaknesses.

The manufacturing company has the right to change the opto-electrical parameters of SMD LEDs, indicating this in the passport data. For example, SMD 5730 from Samsung and Sanan will have slightly different luminous output.

Planar light-emitting diodes of this type can easily be called pioneers, thanks to them surface-mount technology has reached its current heights and continues to progress. LED SMD 3528 has a rectangular shape with an aspect ratio of 3.5 by 2.8 mm and a height of 1.4 mm. On each of the opposite sides of a shorter length, two contacts are visible. A cut (key) is visible on the casing from the cathode side. The working surface has a round shape, coated with phosphor.

The voltage drop at a nominal current of 20 mA depends on the color of the radiation. For white LEDs it can be in the range of 2.8-3.4V, and the luminous flux is 7.0-7.5 lm. The brightness of SMD 3528 is highly dependent on temperature and at 80°C it decreases by 25%.

This type of LED can be called an improved version of SMD 3528. The design of SMD 5050 made it possible to implement multi-color LEDs based on blue, red and green crystals with the ability to control each color separately. Inside the 5.0 by 5.0 mm case there are three crystals with technical parameters identical to SMD 3528.

Accordingly, the manufacturer does not recommend exceeding the operating current value more than 60 mA. In this case, the forward voltage will be 3.3V, and the luminous flux will be 18 lm. The total power consumption of one SMD 5050 is 200 mW in the operating temperature range -40/+65°C.

With LEDs, lighting devices have stepped into a new stage of development. In a case measuring 5.6 by 3.0 mm, scientists created not only a new form factor, but also a semiconductor device with some design features, made using new materials. Unlike its predecessors, SMD 5630 is characterized by greater power and light output.

The luminous flux can reach 58 lm, measured at a forward current of 150 mA. Through proprietary SMD 5630 it is allowed to pass up to 200 mA DC and up to 400 mA pulsed current with a duty cycle of 25%. The magnitude of the forward voltage depends on the shade of white light and can range from 3.0 to 3.6V.

The SMD 5630 LED has 4 pins with a key near the first pin. Of these, only two terminals are used: 2 – cathode (-) and 4 – anode (+). Like many modern LED SMD chips, there is a substrate on the bottom that helps improve heat dissipation.

SMD 5730

Light-emitting diodes of this modification appeared almost simultaneously with the 5630 case and are their analogues. In turn, they are divided into two types: SMD 5730-05 and SMD 5730-1 with power consumption of 0.5 and 1.0 W, respectively. Both types are classified as highly efficient LEDs with a thermal resistance of only 4°C/W. Unlike SMD 5630, 5.7 by 3.0 mm LEDs are visually higher (by 0.5 mm) and, instead of four, have two contacts.

SMD 5730-05 can withstand currents up to 180 mA while dissipating 0.5 W of active power. It also works perfectly in pulse mode with a pulse amplitude of up to 400 mA, the duration of which is no more than 10% of the period. Operating at rated DC current, the SMD 5730-05 provides brightness up to 45 lm.

SMD 5730-1 can be operated at direct current up to 350 mA and pulsed current with a duty cycle of no more than 10% up to 800 mA. The typical voltage drop in the operating position is 3.2V with a power of up to 1.1 W. The crystal can withstand a p-n junction temperature of 130°C and functions normally in the range from -40 to +65°C. Compared to SMD 5050, it has lower thermal resistance and 6 times greater luminous flux, which in the proprietary version reaches 110 lm.

SMD 3014

SMD 3014 is a relatively new standard size belonging to the class of low-current LEDs. The maximum forward crystal current should not exceed 30 mA. Forward voltage zone 3.0–3.6V. White LEDs in warm shades have a minimum luminous output (8 lm), while cold LEDs have a maximum luminous output (13 lm). The dimensions of SMD 3014 are 3.0x1.4x0.75 mm. The anode and cathode leads are not limited to soldering at the ends. They go to the bottom of the case, which must be taken into account during the manufacture of the printed circuit board. The increased size of the contact pads improves heat dissipation and LED mounting. The anode lead is 2 times longer than the cathode.

The developers of SMD 2835 provided it with the best qualities that its predecessors had. The standard size 28 by 35 mm follows the shape of SMD 3528. But the new SMD 2835 has a much larger effective radiation area, which has a rectangular shape covered with phosphor. The element height is no more than 0.8 mm. Despite such small dimensions, the declared luminous flux can reach 50 lm.

In terms of other electrical characteristics, SMD 2835 is very similar to SMD 5730-05. In turn, the design of the element is identical to the SMD 3014 LED, when the anode and cathode terminals serve as a heat-sinking substrate.

Peculiarities

As we explore new Chinese SMD LED formats, this section can be expanded endlessly. For now, the most questions are about power consumption. By purchasing, for example, several SMD 5730 to assemble a lamp with your own hands or a ruler based on SMD 3014, the user expects to receive the luminous flux given in the data sheet. However, often a simple measurement of the load current and simple calculations show that the real power of one LED is 3–4 times lower. Why is that?

Because the size of 5.7 by 3.0 mm does not mean that the corresponding crystal is mounted inside. In this skillful way, the Chinese mislead buyers. The most interesting thing is that the buyer has practically no choice. Finding a branded product with the right parameters is difficult.

When designing a power supply with your own hands, you need to strive to ensure that the actual current in the load is approximately 95% of that specified in the technical specifications. By slightly underloading the LED, you can achieve an increase in operating life even in the case of low-quality Chinese LEDs.

For all LED models, luminous flux values ​​are indicated for a color temperature of 5000–5500°K. Warmer tones will have 10% less light output, and cooler tones will have 10% more light output. In addition, it is worth remembering the error during testing, which can reach 7%. So don’t be surprised if instead of the stated 50 lumens, the chip produces no more than 43 lumens.

Before turning it on for the first time, always check the LED with a multimeter, since the pinout, in the case of a fake, may not match. Near the key there can be both the anode and the cathode of the chip.

In cheap monochromatic SMD 5050 LED strips you can see how all three chips of one LED are connected in parallel and powered by one resistor. This approach simplifies the layout of current-carrying tracks of a flexible printed circuit board, reduces the number of resistors used, and therefore reduces production costs. Of course, the service life of such a tape is also reduced.

Chinese craftsmen have learned to create SMD LEDs of any arbitrary shape, which can be easily verified. It is enough to remove the protective lens from several light bulbs from different companies (base E14, E27) and read the type of LED installed on the board. There seems to be no limit to the variety. It is impossible to predict the technical characteristics of such chips.

Read also

The design features and overall dimensions of unpackaged diodes, diode matrices and transistors are shown in Figs. 11 and 12.

Examples of recording diode matrices and unpackaged transistors in design documentation:

Diode matrix KD908 3.362.015 TU.

Diode matrix KD917A 362.015 TU.

Transistor KT319A XX3.365.144 TU.

Figure 11. Dimensional drawings of packageless diodes and diode matrices A– KD901A-G: b- KD902A-I; V– KD904A-E; G– KD907A-G; d– KD911A, e- KD913A, and-KD918A-G, h- AL109A; And – AL3011A-B.

V

A

End of Fig. eleven.

Figure 12. Dimensional drawings of open-frame transistors of the following types: A- KT119A , b - KT120A, c - KT202A-G, d - KT-317A-B, d - KT318A-E, f - KT324-E, g - KT331A-G, h - KT333A-E, i - KT336A-E, j - KT354A-V, l - KT360A-V, m - KT369A-G, n - KT364A-V.

INTEGRATED CIRCUIT CASESAND

MICROPROCESSORS

Integrated circuit packages are classified according to the shape and location of the pins and are divided into 6 types in accordance with GOST 17467-88. Based on the shape and location of the pins, these types of housings are divided into subtypes. Subtypes are designated by two-digit numbers, for example: for type 1 housings, subtypes are designated by numbers 11, 12, 13, 14, 15 (the first digit indicates the housing type). Each type of housing is assigned a code consisting of a designation of the housing type (two-digit number) and a serial number of the standard size (two-digit number), for example: 1209, 4130, 5202.

When choosing a housing design, it is necessary to take into account that it should:

protect integrated circuits from environmental influences and mechanical damage, as well as ensure the cleanliness of the environment surrounding the elements and components of integrated circuits;

ensure the convenience and reliability of mounting semiconductor integrated circuit chips and hybrid integrated circuit boards in the housing;

remove heat from the microcircuit located inside the case;

ensure reliable electrical connection of circuit elements and at the same time provide electrical insulation between conductive elements;

ensure reliable fastening of the housing, be simple and cheap to manufacture and have high reliability.

All types of cases, depending on the materials used for their manufacture, are divided into the following types: metal-glass, metal-ceramic, metal-polymer, plastic and ceramic. Cases of the 1st type are made in metal-glass, metal-polymer and, much less often, in metal-ceramic design. For the manufacture of type 2 cases, plastic and ceramics are most often used. Cases of the 3rd type are made only in metal-glass version, 4-, 5-, and 6th types in metal-glass, metal-polymer and metal-ceramic versions.

Rice. 13. Type I subtype 1 hull design.

Rice. 14. Housing design type 1 subtype 2.

Rice. 15. Housing design type 1 subtype 3.

Rice. 16. Housing design of type 1 subtype 4.

Rice. 17. Hull design of type 1 subtype 5, options 1 and 2.

Rice. 18. Hull design type 1 subtype 5, option 3.

Rice. 19. Hull design of type 2 subtype I.

Rice. 20 Housing design type 2 subtype 2.

Rice. 21. Housing design type 3 subtype 1.

Rice. 2 2. Housing design type 3 subtype 2.

Rice. 23. Housing design type 4 subtype 1.

Figure 24. Design of housing type 4 subtype 2.

Rice. 25. Housing design 4 subtype 3.

Rice. 26. Hull design of type 4 subtype 4.

Rice. 27. Housing design of type 4 subtype 5.

Rice. 28. Hull design of type 5 subtype 1.

Fig.29. Hull design type 5 subtype 2.

Rice. 30. Hull design of type 6 subtype 1.

Fig. 31. Hull design type 6 subtype 2.

Metal-glass and metal-ceramic cases have the greatest mechanical strength. Reliable sealing of microcircuits is ensured by metal-glass cases in which the lid is attached to the base by welding, carried out in a vacuum or in an inert gas environment under pressure slightly higher than atmospheric.

Metal-ceramic cases also have high tightness. The lid in them is attached to the base by soldering. Plastic and metal-polymer cases are the least airtight.

To seal hybrid integrated circuits, you should mainly use metal-glass, metal-ceramic and plastic cases of types 1, 4, and 5.

Drawings and standard sizes of housings are shown in the figures and tables:

Type 1: Fig. 13-18; table 19-25;

Type 2: Fig. 19, 20; table 26-28;

Type 3: Fig. 21, 22; table 29-32;

Type 4: Fig. 23-27; table 33-43;

Type 5: Fig. 28-29; table 44-49;

Type 6: Fig. 30-31; table 50-52.

The chip key is located in the shaded area of ​​the case.

The designation of the body in the design documentation must consist of the word “Body”; standard size, including the housing subtype number and a two-digit number indicating the serial number of the standard size; a digital index that determines the actual number of pins; serial registration number and designation of the standard. Designation example: Housing 2105.14-5 GOST 17467-88.

Table 19

Dimensions, mm

Table 20

Dimensions, mm

Table 21

Dimensions, mm

Table 22

Dimensions, mm

Table 23

Dimensions, mm