For a long time, in the case that the heat dissipation requirement for LED is not very high, the LED is mostly packaged by using a conventional resin substrate. However, as the market application field continues to expand and the level of demand continues to increase, the traditional resin substrate has gradually become insufficient after the arrival of the high-power LED generation. Therefore, it is a hot topic in the industry to explore and forecast high-power LED packaging materials.
The principle of led heat dissipation
Studies have shown that high-power LED can only convert 20% of electrical energy into light energy, and the rest will be lost in the form of thermal energy. If up to 80% of the heat is not lost in time, the life of the led will be greatly reduced. How is the heat of led lost?
The heat dissipation capability of led is usually affected by the package mode and the thermal conductivity of the package material. The heat dissipation path is not limited to conduction, convection or radiation. Since the heat energy accumulated in the LED package material is mostly lost in conduction, the selection of the package material becomes more important.
Traditional materials can not meet the high-power LED cooling needs
With the emergence of more and more high-power LED applications on the market, while considering how to dissipate thermal energy, it is also necessary to take into account the stability and sustainability of LED illumination. If the heat of LED can't be lost as soon as possible, its brightness and life will drop very quickly. Therefore, for high-power LEDs, the traditional epoxy resin is limited by its characteristics, which does not meet its heat dissipation requirements.
Under the conditions of low power or general power of LED, the disadvantages of low thermal conductivity and poor heat resistance of epoxy resin have not been fully revealed. However, if epoxy resin is used as the material for packaging high-power LED, it is very likely that the life of the LED chip itself has not been reached before, and the epoxy resin is no longer sustainable.
In addition, not only the heat dissipation phenomenon will change the epoxy resin, but even the short wavelength will cause trouble to the epoxy resin. This is because short-wavelength light is also included in the white light LED luminescence spectrum, and the epoxy resin is easily damaged by short-wavelength light in white light LEDs. Even low-power white LEDs can make the epoxy resin damage worse, not to mention the high-power white LEDs emit more short-wavelength light, and the deterioration is naturally faster and more serious. Therefore, it is extremely urgent to find a new material to replace the epoxy package high power led.
Led heat sink type
At present, common types of led heat sink substrates include: hard printed circuit boards, high thermal conductivity aluminum substrates, ceramic substrates, flexible printed circuit boards, metal composite materials, and the like.
• Hard printed circuit boards (PCBs) are mostly used for various electronic substrates, but LED controllers cannot withstand the heat energy lost by high-power LEDs . Therefore, applications are limited to low-power and general-power LEDs , and do not have high power. Led extended application possibilities.
• High thermal conductivity aluminum substrate (metalcorepcb;mcpcb) is to change the substrate under the pcb to aluminum alloy. Generally speaking, although the heat dissipation coefficient of pure aluminum is higher than that of aluminum alloy, the use of pure aluminum is not high. Difficult, so only the aluminum alloy is used as the material of the substrate.
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