Parsing the LED heat dissipation substrate and the technology development trend
LED industry is one of the most high-profile industry in recent years. Development up to now, the LED products are energy saving, power saving, high efficiency, fast response time, long life cycle, and do not contain mercury, have environmental benefits; Wait for an advantage. However often LED high power products the input power, about 20% can be turned into light and the remaining 80% of the electricity are converted into heat energy.
In general, the heat energy produced during the LED if unable to export, will make the LED junction surface temperature is too high, thus affecting the product life cycle, luminous efficiency, stability, and the LED junction temperature, the relationship between the luminous efficiency and life, will use the diagram below for further instructions.
1, LED cooling way
According to different packaging technology, the cooling method is also different, and the LED signal under various cooling approach we can:
The cooling ways:
(1). Heat from the air
(2). Direct heat by Systemcircuitboard export
(3). Through the gold thread to heat the export
(4). If the eutectic and Flipchip process, the heat through the hole to the system circuit board and the export
In general, the LED grain (Die) with gold thread, eutectic or flip chip way links in the substrate (SubstrateofLEDDie) and form a LED chip (chip), then the LED chip is fixed on the system of the circuit board (Systemcircuitboard). Leds may, therefore, the cooling way for direct heat from the air, or through LED grain base board to the system circuit board to the atmospheric environment. And the cooling rate depends on the circuit board to the atmospheric environment by the system the whole light lamps and lanterns, or system design.
At this stage, however, the heat dissipation of the whole system bottlenecks, most occurred in the heat from LED grain to the substrate to the system circuit board give priority to. This section may be cooling way: one is directly borrow from grain base plate heat to the system circuit board, in the cooling way, its LED crystal substrate material thermal dispersion ability is the important parameter. On the other hand, the heat produced in the LED also can through electrode metal wire to the circuit board system, in general, use a gold wire method for electrode under the joint, heat dissipation of metal wire itself is relatively thin geometry and limited; Therefore, has the Eutectic (Eutectic) or flip chip (Flipchip) joint way, this design greatly reduce wire length, and significantly increase the cross-sectional area, as a result, LED by electrode wire to the system circuit board of the cooling efficiency will improve.
Through above the cooling way to explain, but learned that heat the choice of substrate materials and its LED grain encapsulation mode on the LED heat dispersion management accounts for the extremely important link, after a period of general outline for the LED heat dissipation substrate do.
2, LED heat dissipation substrate
LED heat dissipation base webmaster if use its heat dissipation substrate material itself has better thermal conductivity, heat from the LED grain exports. Therefore, we from the LED heat dissipation way narratives, LED heat dissipation substrate can be subdivided two major categories, respectively LED grain base board and system board, the two kinds of different cooling substrate respectively by carrying grain LED and LED chips will LED the heat energy produced during the grain luminescence, via LED grain cooling substrate to system circuit board, and then absorbed by the atmosphere, in order to achieve the effect of heat dispersion.
2.1 system circuit boards
System circuit board mainly as the LED heat dissipation system, the thermal conductivity to the cooling fins, shells or material from the atmosphere.
Printed circuit board (PCB) production technology in recent years has been very strong, the early system circuit board is given priority to with PCB LED products, but with the increase of the demand of the high power LED, PCB material of heat dissipation ability is limited, make its cannot be applied to the high power products, in order to improve the high power LED heat dissipation problem, has recently developed high heat conductivity coefficient of aluminum base board (MCPCB), the use of metal materials heat dissipation characteristics better features, has been to achieve the purpose of high power products. However, with the sustainable development of the LED brightness and performance requirements, although the system circuit board to the heat produced in the LED chip effective cooling to the atmospheric environment, but LED grain produced by heat cannot effectively from circuit boards, grain to system of dissenting word, when the LED to more efficient power, the LED heat dissipation bottleneck will appear in the LED grain cooling substrate.
2.2 the LED crystal substrate
If LED grain base webmaster as LED grain export and the system circuit board between heat medium, borrow consists line, eutectic or flip chip process combined with LED grain. And based on the heat dissipation, currently on the market the LED crystal substrate mainly ceramic substrates, with lines prepare different methods can be divided into: instead of thick film ceramic substrate, low temperature co-firing multilayer ceramic, and thin film ceramic substrates are three, in the traditional high power LED components, with thick film or low temperature co-firing ceramic substrates as grain cooling base board, and will be LED in gold grain combine with ceramic substrates.
As mentioned in introduction, the gold thread connections limit the effectiveness of heat along the electrode contact lost. Therefore, in recent years, domestic and foreign companies strive toward the solution to this problem. The solution has two, one is to look for the substrate material of high coefficient of heat transfer, to replace the alumina, contains a silicon substrate, silicon carbide substrate, anodized aluminum plate or aluminum nitride substrates, including semiconductor silicon and silicon carbide substrate material properties, make its meet more stringent tests at present stage, and anodized aluminum plate is easily due to lack of the anodized oxidation layer strength caused by fracture conductivity, make its limited in practical application, therefore, at this stage is relatively mature and ordinary higher acceptance is to aluminum nitride as the radiating substrate; Now, however, limited by aluminum nitride substrate shall not apply to the traditional thick film process (material must be approved by 850 after silver glue printing atmosphere heat treatment, the material reliability problems), as a result, aluminum nitride substrate Cheng Bei system circuit with thin film system.
----------Archled Technology Co.,Limited