LED thermal substrate technology trend analysis – 915nm Diode Laser K91S02F-10.0
1 Introduction
With the rising awareness of global environmental protection, energy saving has become the trend. LED industry is one of the industries most attention in recent years. Development so far, LED product has energy saving, energy saving, high efficiency, fast response time, long cycle life, and do not contain mercury, environmental benefit … and so on. However, high-power LED products are usually about 20% of the input power can be converted into light, the remaining 80% are converted into heat energy.
In general, LED light when the heat if it can not be exported, will enable LED junction surface temperature is too high, thereby affecting the product life cycle, luminous efficiency, stability, and the LED junction surface temperature, luminous efficiency and life span between , the following diagram will be used for further explanation.
Figure 1 Results for the LED luminous efficiency of surface temperature and the diagram, when the junction surface temperature increased from 25 to 100 , the luminous efficiency will decline 20% to 75% range, among which 75% decline most yellow light serious. In addition, when the LED's operating environment, the higher the temperature, the lower the lifetime of their products (as shown in Figure 2), when the operating temperature from 63 74 when the rose, LED average life expectancy will be reduced 3 / 4. Therefore, to enhance the luminous efficiency of LED, LED heat dissipation system management and design has become an important issue, in the understanding of LED heat problem, you must first understand the cooling channels, thus the bottleneck for cooling improvements.
2, LED cooling channels
According to different packaging technology, the thermal methods are also different, the LED heat means all kinds of methods can roughly indicate the following figure 3:
Cooling channel description:
1. From the air cooling
2. Heat derived directly from the Systemcircuitboard
3. Derived by the gold wire to heat
4. The case of eutectic and Flipchip process, heat will be through the hole to the system board and Export)
Generally speaking, LED die (Die) to play gold, eutectic or flip chip connections between its substrate (SubstrateofLEDDie) to form an LED chip (chip), then then LED chip fixed on the system board (Systemcircuitboard). Therefore, LED cooling channels may be directly from the air cooling (as shown in Figure 1, three channels), or through the LED die substrate to the system board and then to atmosphere. The heat from the system board to the atmosphere depends on the rate of light-emitting lamp or system design.
However, the current bottleneck of the whole cooling system, most occur in the heat conduction from the LED die to the substrate and then to the main system board. This part of the possible cooling channels: one for direct heat to the substrate through the grain system circuit board (as shown in Figure 2, three channels), in which cooling channels, the grain of its LED heat dissipation ability of the substrate material shall be fairly important parameters. On the other hand, LED heat will be generated by the electrode metal wire and to the system board, in general, the use of gold as electrode bonding method, the cooling by the thin metal wire itself is limited by the geometric shapes (such as Figure 3 shows three ways); Therefore, recently that is eutectic (Eutectic) or flip chip (Flipchip) bonding mode, this design significantly reduce wire length, and a substantial increase in wire cross-sectional area, this way, through the LED electrode wire to the system board will effectively improve the thermal efficiency (as shown in Figure 3 channel 4).
Thermal path through the above explanation of the choice of substrate material that Cooling grain packages with LED LED heat dissipation in the management accounts for a very important part, after the segment will do for LED Thermal outline the substrate.
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