LED lighting is based on the ability of semiconductors to convert electrical current into luminous flux. According to the purpose of the device are divided into two groups: indication and lighting. The first type has low power and is used to indicate instruments. The second type is installed in lighting fixtures. SMD LEDs are the most common variant of lighting elements.
What are SMD LEDs
Semiconductors made using surface mount technology are called smd LEDs. They differ from other devices in design features. The electronic chip is assembled on a printed circuit board made of copper or aluminum. A chip is used as a chip. The surface mount method simplifies production and reduces the cost of LEDs.
SMD electronic components are characterized by the maximum approximation of the semiconductor to the substrate, which removes heat. To create white light, the crystal is coated with a layer of phosphor. Key features of the device:
- high brightness;
- monochrome crystal emits one color - white, red, blue, yellow;
- consists of one or more crystals;
- modules are able to create lighting with a scattering angle from 100 to 160 °;
- smd diodes operate on direct current.
All semiconductor devices are characterized by a high working resource.
Marking manufacturers
All LED manufacturers apply standard marking of LEDs, the decoding of which gives information about the linear dimensions of the device. The digital designation shows the length and width of the LED chip in fractions of a millimeter. In some cases, in addition to the frame size, other parameters are applied - color and power. For example: SMD 2835 UWC 5 - matrix size 2.8 × 3.5 mm, color - white (Ultra White Color), power 0.5 W. For surface mount electronic components, there is a special smd 2l code.
LED characteristics
Device parameters affect the ability to use them in various fields. The main characteristics of the products include: voltage, power, glow angle, color temperature, light flux.
Consumption current
The average current strength on a chip is 0.02 A. For chips with several crystals, the characteristic increases by a multiple of their number. Fluctuations in the parameter negatively affect the intensity of the glow and the service life. Increasing the current increases the color temperature of the chip, changes the hue of the glow. To ensure the stability of the characteristics, current-limiting resistors are connected.
Luminous efficiency, angle of illumination, power
The luminous flux of the LED matrix is different from the light generated by an incandescent lamp. It is directional, therefore brighter in the central part. Typically, the scattering angle is in the range of 100-120 °. To change the parameter, lenses are used. By power, the devices are divided into 3 groups:
- low power - up to 0.5 W;
- average - 0.5-3 W;
- large - from 3 watts.
The characteristic is necessary when calculating the power supply. It is calculated by the formula - current strength times voltage.
The nominal voltage of the diodes is low, it is 1.1-4 V. The value varies due to the difference in colors and materials of electronic components. The white device has the highest voltage.
Colour temperature
The radiation intensity or color temperature is important for the comfortable perception of lighting by the human eye. There are several categories of white light:
- 2700-3500 - warm;
- 3500-5000 - neutral or daily;
- above 5000 - cold.
Color temperature is indicated in Kelvin (K), it is indicated in the marking.
Dimensions and their influence on the properties of LED sources
The size of the smd LEDs varies depending on the type. The brightness of the elements increases with the dimensions. The area of the glow can be round or rectangular. The larger the parameter, the brighter the lighting. Light flow also depends on the number of crystals. In various models, there are from 1 to 4 pieces. The power of the device depends on the size of the crystal. The characteristic is indicated by the manufacturer in "mil", 1 mil = 0.0254 mm. For example: a chip measuring 45 × 45 mil - power 1 W, 24 × 24 mil - 0.5 W.
Color range
The color of the LED depends on the material of the semiconductor and dopants. Primary colors: red, blue, green and yellow. White color is obtained by applying a layer of a phosphor to a crystal of blue glow. Two-color devices are used for indication. Tri-color is used in displays.
Description of main smd leds
The number of sizes of LED lighting sources is constantly increasing. The most widespread are several species.
SMD 2835
A 2.8 × 3.5 mm model demonstrates high light output. Its parameters:
- current - 60, 150, 300 mA;
- power - 0.2, 0.5, 1 W;
- light flow - 20-100 Lm.
The housing is made of heat-resistant polymer, designed to heat up to 240-260 °. A radiating area of a rectangular shape, covered with a phosphor.
SMD 5050
The LED matrix consists of three crystals placed in one housing. Its dimensions are 5.0 × 5.0 mm. Technical characteristics of LED components are similar to those of the smd 3528 diode:
- the total current is - 0.02 × 3 = 0.06 A;
- power - 3 × 0.7 = 0.21 W;
- Luminous flux - 18-20 Lm.
The chip is capable of emitting all shades of white, blue, red, yellow, green or tri-color RGB. It is used in flexible tapes, lamps. It is possible to adjust the glow mode.
SMD 5630
A new class of surface mounted devices, its dimensions are 5.6 × 3.0 mm. SMD 5630 models have improved brightness characteristics:
- rated current - 0.1-0.15 A;
- luminous flux - 32-57 Lm;
- voltage - 3-3.6 V.
To prevent overheating of the crystal, the chip is mounted on an aluminum substrate. The device is used in street and industrial lighting.
SMD 5730
The geometric parameters of the body are 5.7 × 3.0 mm. A large device is one of the super-bright diodes. The semiconductor is made from new materials that increase power. Characteristics:
- rated current - 0.15.0.18 A;
- power - 0.5-1 W;
- luminous flux - 45 Lm.
The angle of illumination is 120 °. The device is resistant to vibration, moisture, has a long service life.
SMD 3014
The diode in the 3.0 × 1.4 mm housing is one of the new options. Medium power model with good heat dissipation. Parameters:
- voltage - 2.7-3.3 V;
- current - up to 0.3 A;
- glow - 9-11 Lm.
Devices give all shades of white light.
SMD 3528
One of the most popular and inexpensive chips. The length of its sides is 3.5 × 2.8 mm. The working platform is round, a phosphor layer is applied to it. Characteristics:
- working current - 0.2-0.25 A;
- voltage - 3-3.2 V;
- luminous flux - up to 7 Lm.
The brightness of the model depends on temperature, an increase in the parameter leads to accelerated degradation of the crystal. At 75-80 ° the device shines weaker by 25%.
Application and connection requirements
The scope of LED devices includes domestic, commercial and street lighting. Depending on the size of the SMD, the LEDs are placed in lamps or in a ribbon backlight. Several chips placed on the board replace standard incandescent and energy-saving fluorescent lamps. Devices with a wide angle of illumination are used in spotlights. LED matrices replaced lamps in flashlights, headlights, indicators, traffic lights and signboards.
When connecting LEDs, the polarity must be observed. For stable and continuous operation, a separate resistor is connected to each chain of series-connected LEDs.The power source must give a voltage exceeding the total indicator of all chips.
Advantages and disadvantages
The use of SMD LEDs in various models of lighting devices is explained by their numerous advantages:
- wide scope of application;
- long service life;
- resistance to vibration;
- economical energy consumption;
- low temperature operation;
- instant start of the lighting device.
The disadvantages of electronic components include:
- sensitivity to heat;
- high cost of quality products;
SMD LEDs are effective sources of basic lighting and decorative lighting. A variety of elements allows you to choose the best option for power, brightness and color.
