PCB News - PCB manufacturer, discussion on high-power LED lighting technology

PCB manufacturer, discussion on high-power LED lighting technology

High-brightness light-emitting diodes (LEDs) are becoming a new generation of light sources for upgrading the traditional lighting industry due to their low power consumption, long life, fast response speed, no flicker, small size, no pollution, and easy integration. Today, when energy conservation, emission reduction, and environmental protection are increasingly concerned, semiconductor lighting has become a new economic growth point in PCBA processing, and it has been highly valued by governments, science and technology circles and industries around the world. So far, the United States, Japan, Europe, China and Taiwan have all launched their own semiconductor lighting plans, and the high-power LED lighting industry has become one of the most eye-catching industries.
It is worth noting that the upstream epitaxial chip technology has been basically mature and finalized so far, and low-cost and high-quality LED chips can meet the needs of lighting. Now the pricing power is shifting and developing to the midstream packaging and downstream application terminal markets. This means that whoever can apply the chip well, manufacture long-life, high-efficiency high-power LED lighting products, who is likely to become the ultimate winner of the LED industry. The problems of high-power LED lighting packaging and application have been highlighted. The most important thing is how to solve the heat dissipation problem of high-power LED lighting. This is not only a technical problem in structural design and engineering applications, but also involves thermal management modes. And fluid mechanics and other scientific issues. It is completely different from the existing "chip-aluminum substrate-a heat dissipation three-layer structure" high-power LED series lighting technology. The "chip-heat dissipation integration (two-layer structure) integrated high-power LED lighting series lamp" developed by us is in the technical route This aspect may have revolutionary and subversive significance, and it will become a new development direction for the high-power LED lighting industry.

1. Current status of high-power LED lighting products
At present, the luminous efficiency of the LED can convert about 30% of the electric energy into light, and almost all the other 70% of the electric energy is converted into heat, which increases the temperature of the LED. Because of its very small heat generation, low-power LEDs can be used well without heat dissipation measures, such as instrument lights, signal lights, and small-size LCD screen backlights. But for high-power LEDs, when used in commercial buildings, roads, tunnels, industrial and mining and other lighting fields, its heat dissipation is a big problem. If the heat of the LED chip cannot be dissipated, it will accelerate the chip's aging, light decay, color shift, and shorten the life of the LED. Therefore, the structural mode and thermal management design of high-power LED lighting systems are very important.
At present, all high-power LED lighting fixtures on the market adopt the "chip-aluminum substrate-heat sink three-layer structure model", that is, the chip is packaged on the aluminum substrate to form an LED light source module, and then the light source module is placed on the heat sink to make it High-power LED lighting fixtures.
It should be pointed out that the current thermal management system of high-power LEDs still uses the way that LEDs were used for indicator lights and display lights in the early days, which belongs to the thermal management mode of low-power LEDs. Using the "chip-aluminum substrate-heat sink three-layer structure mode" to prepare high-power LED lighting, there are obvious unreasonable places in the system structure, such as high contact resistance between the structures, high junction temperature, and low heat dissipation efficiency, so the chip The released heat cannot be effectively discharged and dissipated, resulting in low light efficiency, large light decay, and short life of LED lighting lamps, which cannot meet the lighting needs.
How to improve the heat dissipation capacity of the package is one of the key technologies that need to be solved urgently for high-power LEDs at this stage. The development direction and focus of LED lighting products are: high power, low thermal resistance, high light output, low light attenuation, small size, and light weight, which makes the requirements for LED heat dissipation efficiency higher and higher.
However, due to the limitation of many factors such as structure, cost and power consumption, it is difficult for high-power LED lighting to adopt an active heat dissipation mechanism, but can only use a passive heat dissipation mechanism. However, passive heat dissipation has greater limitations; and the energy conversion efficiency of LEDs is relatively high. Low, currently about 70% is still converted into heat, even if the light efficiency is doubled, 40% of the energy is converted into heat. That is to say, it is difficult to improve to the extent that heat dissipation is not considered, so in the long run, the heat dissipation problem of high-power LED lighting will be a long-standing problem.
Now that the time for high-power LEDs to be used in lighting is ripe, the development of an efficient thermal management system with natural heat dissipation has become a prerequisite and key factor for the industrialization of high-power LED lighting. Therefore, a new technical route and system structure are needed to completely solve the heat dissipation problem of high-power LED lighting.

2. New technical route for high-power LED lighting industry
In view of the existing high-power LED lighting heat dissipation technology, there are multiple thermal resistances and low heat dissipation problems. We try to solve the problem of low light efficiency, serious light decay, and cost through the "chip-heat dissipation integration (two-layer structure) mode". Higher series of questions.
2.1 Technical route
The "chip-heat dissipation integration (two-layer structure) mode" not only removes the aluminum substrate structure, but also places multiple chips directly on the heat sink to form a multi-chip module and a single light source, which is prepared into an integrated high-power LED Lamps and lanterns, the light source is a single light source, which is a surface light source or a cluster light source.
2.2 Technical key
How to enhance the thermal conductivity of the chip and reduce the thermal resistance interface layer involves issues such as the structural model of the thermal management system, fluid mechanics, and the engineering application of super thermal conductive materials; how to effectively control the heat storage of the heat dissipation substrate, plan the convective heat dissipation path, and establish high efficiency The natural convection heat dissipation system mainly starts from the design of the lamp structure.
2.3 Technical solution
Reduce the thermal resistance layer by changing the LED light source packaging structure, heat dissipation structure and lamp structure mode; apply super thermal conductivity materials to increase the thermal conductivity of the chip heat source; optimize the thermal management system based on the "chip-heat dissipation integrated two-layer structure" and increase The flow of air forms natural convection to dissipate heat.
2.4 Design ideas
A modular approach is adopted to prepare high-power LED lamps. The light source, heat dissipation, shape structure, etc. are packaged into a whole module, and the modules are independent of each other. Any module can be replaced separately. When a part fails, only the faulty module needs to be replaced. Replace other modules or replace the whole to continue normal operation. All module parts of the lamp can be disassembled and assembled by bare hands, realizing convenient, fast and low-cost maintenance.
2.5 Design points
For the modularization of the system, in addition to meeting the heat dissipation and replacement requirements of the lamps, it must also meet the optical (optical efficiency) requirements and styling (market) requirements of LED lighting lamps.
3. Introduction to the integrated structure of chip and heat dissipation
"Chip-heat dissipation integration (two-layer structure) mode" is a new type of LED light source packaging mode, structure mode and thermal management system mode. The high-power LED lighting lamps prepared by using this technology model not only completely solve the heat dissipation problem, but also effectively solve the problems such as light distribution, light efficiency, life and maintenance, and have developed a long life and high light efficiency. Of high-power LED products, such as street lights, downlights, tunnel lights, high bay lights, automobile headlights, landscape lights and other lighting equipment.

3.1 Technical characteristics
3.1.1 Connect the chip and the aluminum alloy + super thermal conductive material composite matrix (heat sink) as a whole, apply unique high-power LED packaging technology, and encapsulate multiple chips directly on the heat dissipation substrate, so that the chip and the heat dissipation substrate are The thermal resistance is smaller, and the entire heat dissipation substrate is a complete lamp, forming an integrated high-power LED lighting component.
3.1.2 The thermal management system is designed based on the principle of bionics, and the thermal resistance model of the two-layer structure with integrated chip and heat dissipation is established, and the junction temperature calculation and life prediction are carried out on it.
The characteristic of the integrated two-layer structure of chip-heat dissipation is that the heat source chip is directly encapsulated on the heat sink. As the temperature of the heat source rises, air flows in the porous heat sink. The holes provide a flow channel for air convection, and the heat is It is automatically emitted to ensure that the chip works normally within the safe use temperature range. The advanced heat conduction and heat convection system ensure a good heat dissipation effect and further improve the luminous efficiency of the chip.
3.1.3 The chip (45mil*45mi1) is packaged in an integrated manner (the chip is concentrated in a small area) to obtain a surface light source with higher luminous efficiency, which has the characteristics of high luminous flux density, high total luminous flux, and low glare.
At present, high-power LED lighting fixtures such as street lights, tunnel lights, downlights, spotlights, etc. have been prepared using the above-mentioned technology. In addition, the current high-power LED automotive headlights require electric fans to enhance heat dissipation, which is difficult to meet the needs of market applications. The clustered high-power LED automotive headlights made of two-layer structure solve the problem of using LED light sources in the automotive lighting industry. Limitations of manufacturing car headlights
3.2 Product technical indicators and advantages
(1) Efficient heat dissipation: Use natural heat dissipation methods to completely solve the heat dissipation problem of high-power LEDs (temperature difference <4 degree Celsius, radiator temperature <60 degree Celsius, measured under the condition of ambient temperature>35 degree Celsius);
(2) High current: the rated current supplied to the chip is 400-450mA each;
(3) High light efficiency: the whole light effect reaches 90.9 lm/W;
(4) Long life: >50 000h;
(5) Low light decay: The test result of the National Luminaire Quality Supervision and Inspection Center is: There is no light decay in the 1,000h life test;
(6) Integrated type: The integrated type is COR (Chip On Radiator), that is, the chip is integrated directly on the radiator, which is completely different from the COB (Chip On Board) integrated type that is integrated and bonded on the aluminum substrate. The integrated chip is a single chip, which is a surface light source, a single light source or a cluster type
The light source (installed with glass lens) emits;
(7) The lighting effect is the same as the traditional non-LED light source, and does not change the light consumption habits of human beings;
(8) Simple structure: easy to maintain, no need for overall replacement.
4. Technology development direction of high-power LED lighting industry
At present, for the technical route of the high-power LED lighting industry, we think there are two options: one is to continue to develop along the technical route of "chip-aluminum substrate-radiator (three-layer structure) mode"; the other is Develop the "chip-heat dissipation integration (two-layer structure) mode" technical route. "Chip-heat dissipation integrated structure" is an emerging technology. In this structure, except for the chip, everything else is brand new, including chip-heat dissipation integration, packaging, power supply, complete equipment, testing, and even standards, etc., It makes high-power LED lighting products have obvious advantages in terms of life, light efficiency, quality, design, controllability, cost, etc., compared with the "chip-aluminum substrate-radiator three-layer structure model", which is China's high-power and high-efficiency Semiconductor solid-state lighting research, application and industrialization can be a new field that can do a lot.