Professor Yan: 11 key technologies for LED filament design, how much?

In the past three years, the LED filament lamp has rapidly heated up from the market demand. The international market has quickly recognized the LED filament lamp with technological innovation, and the market demand has doubled. Due to the low technical threshold for the production of led filament lamps, the current production of LED filament lamps has sprung up, and the quality of LED filament lamps is uneven. The LED filaments and LED filament lamps are easy to make but it is difficult to do well!

LED filament lamps are like the traditional incandescent lamps when their slender LED filaments shine, and they are loved and sought after by nostalgic people. The brightness, efficiency and shape of the LED filament lamp are equivalent to ordinary incandescent lamps, and people use it to retrieve the incandescent lighting environment that is about to be lost.

LED filament lamp adopts innovative technology of HVLEDs

LED filament lamp adopts high voltage and low current HVLEDs innovation technology. When the filament lamp is lit, it can only be driven by a small current of 10-15mA to drive, and the traditional low voltage, high current led bulb 300-700mA drive current In comparison, the instantaneous heat generation of the LED die of the same unit area is greatly reduced, and the illumination light source designed by the HVLEDs technology can be made bright and not hot. The temperature of the lamp head bottleneck of the traditional 5W led bulb is up to 75-95 ° C, while the LED filament lamp of the same power is illuminated for 8 hours, and the temperature of the A60 glass bulb is below 36 ° C. LED filament lamps are truly safe to use. The derating design of electronic products is an effective means of extending the life of electronic products.

At present, the technical design and production of 4W LED filament lamp lumens up to 400LM-520LM, equivalent to 40W-50W incandescent lamp brightness, light efficiency up to 100-130LM / W.

LED filament lamp products are used in A60 bulbs and C35 candle bulbs and tail-blown bulbs. The space inside them is very small. It needs heat and heat dissipation of special gas and glass bulb with limited capacity. The current frame structure and glass bubble space are only It is suitable to make a low-power bulb below 5W to ensure that the LED filament lamp will illuminate for a long time without being hot. Its products are shown in Figure 1. If you want to increase the power, you need to use A80 and A100 glass bubbles with more space.

Key technology for LED filament design

The key technologies of LED filament lamps are: LED filament design and manufacturing technology, filament lamp glass bubble sealing technology, and stroboscopic constant current driving power technology. These key design and manufacturing technologies are of the concern and concern of filament manufacturers.

The key technologies of LED filament design involve the following:

1. Filament shape design (thin and long);

2. Filament working voltage design (considering the efficiency of the whole lamp system);

3, filament working current design (A604W whole lamp lighting 8 hours glass bubble is not hot);

4, the area and power of the led chip (small area, low power);

5, led light angle chip (the chip can be achieved without back-plated 360 emission);

6, the working state of the filament design (HVLEDs, VF high voltage, small current, full string);

7, the substrate material (transparent and rigid, such as sapphire, transparent ceramics, glass);

8, color temperature adjustment (yellow phosphorescent powder + red powder);

9, blue light escaping (yellow phosphorescent phosphor powder);

10, pin design (to prevent soldering, pin using occlusion technology);

11, in line with the technical needs of glass bubble sealing (suitable for instant high temperature).

LED filament is one of the core technologies of filament lamp. The technical parameters and quality of LED filament involve the brightness, color temperature, index and service life of LED filament lamp, and the lumen ratio of cold and hot.

LED filament manufacturing technology currently has "solid crystal technology" for traditional packaging and "cladding technology". The solid crystal technology needs to be used for gold wire. The flip chip technology uses flip chip LED chips, which are like the ordinary electronic components, and can be reflow soldered. The production process is different and the production cost is different. This article takes the solid crystal technology as an example.

Blu-ray discharge

LED lighting sources and luminaires are not allowed to bleed out. Ensuring that LED light sources and lamps do not emit blue light is the responsibility and responsibility of every conscience entrepreneur and engineer; eliminating the LED light source and the blue light leakage of the lamps is also the basic guarantee for product quality.

The cross section of the LED filament is shown in Figure 2. 1 is a sapphire base strip, 2 is a blue-free LED chip without back plating, 5 is a gold wire, and 6 is a yellow phosphor phosphor. From Fig. 2, the yellow phosphor powder has been used to remove the entire sapphire. The base strip is coated and the blue light of the LED does not leak out.

If the LED filament is coated with yellow phosphor phosphor only on the upper and lower sides, there will be blue light leakage from the left and right sides. Some filaments are produced by spraying yellow phosphor powder in a row and then cutting the base strip by laser. The yellow strip phosphor is not coated on both sides of the transparent strip, and the blue light will leak out along the edge of the transparent strip. Figure 3 shows. This unreasonable production process needs to be corrected.

The LED filament with blue light leakage is normally observed and identified by the naked eye. As shown in Figure 4, the LED filament is covered with yellow phosphor powder on both the upper and lower sides of the sapphire strip, and the sapphire strip is visible on both sides. When the LED filament is lit, the blue light will leak out and can be detected by optical instruments.

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