A bustling city cannot do without the decoration of LED lights. I believe everyone has seen LED, and its figure has appeared in every place of our life and also illuminates our life.
As the carrier of heat and air convection, the thermal conductivity of power-type LED encapsulated PCB plays a decisive role in the heat dissipation of LED. With its excellent performance and gradually decreasing price, DPC ceramic PCB shows strong competitiveness among many electronic packaging materials. It is the development trend of power LED packaging in the future. With the development of science and technology, the emergence of new preparation technology, high thermal conductivity ceramic materials as a new type of electronic packaging PCB materials, application prospects are very broad.
LED packaging technology is mostly developed and evolved on the basis of discrete device packaging technology, but it has great particularity. In general, the tube core of the discrete device is sealed in the body of the package, and the function of the package is mainly to protect the tube core and complete the electrical interconnection. While LED packaging is to complete the output of electrical signals, the normal work of the protection tube core, output: visible light function, both electrical parameters and optical parameters of the design and technical requirements, can not simply be used for the discrete device packaging LED.
With the continuous increase of input power of LED chips, the large amount of heat generated by high power dissipation puts forward higher requirements for LED packaging materials. In LED heat dissipation channel, encapsulated PCB is the key link connecting the internal and external heat dissipation channel, it has the function of heat dissipation channel, circuit connection, and chip physical support. For high-power LED products, the packaging PCB needs high electrical insulation, high thermal conductivity and the thermal expansion coefficient matching the chip.
The existing solution is to attach the chip directly to the copper radiator, but the copper radiator itself is a conductive channel. As far as the light source is concerned, no thermoelectric separation is achieved. Finally, the light source is encapsulated on the PCB board, and the insulation layer is still needed to achieve thermoelectric separation. At this point, the heat is not concentrated on the chip, but near the insulation layer beneath the light source. Once the power is increased, there is a heat problem. DPC ceramic substrate can solve this problem. It can fix the chip directly on the ceramic, and form vertical interconnect holes in the ceramic, to form an internal independent conductive channel. Ceramics themselves are insulators and can dissipate heat. This is thermoelectric separation at the light source level.
Smoldled stents that have emerged in recent years usually use high-temperature modified engineering plastic materials, using PPA (polyphthalamide) resin as raw material, and adding modified fillers to enhance some physical and chemical properties of PPA raw material. Therefore, PPA materials are more suitable for injection molding and using Smolded stents. PPA plastic has a very low thermal conductivity, and its heat dissipation is mainly carried out through the metal lead frame. Its heat dissipation capacity is limited, and it is only suitable for low-power LED packaging.
In order to solve the problem of thermoelectric separation at the level of the light source, the ceramic substrate should have the following characteristics:
first, it must have a very high thermal conductivity, several orders of magnitude higher than resin;
Second, it must have a high insulation strength;
Third, the circuit has high resolution and can be connected or flipped vertically with the chip without problems.
Fourth, the surface flatness is high, there will be no gap when welding.
Fifth, ceramics and metals should have high adhesion;
The sixth is a vertical interconnect through-hole, so SMD encapsulation can be implemented to guide the circuit from the back to the front.
The only substrate that meets these conditions is a DPC ceramic substrate.
The ceramic substrate with high thermal conductivity can significantly improve the heat dissipation efficiency, which is the most suitable product for the development of LED with high power and small size. Ceramic PCB has new thermal conductivity material and a new internal structure, which makes up for the defect of aluminum PCB, thus improving the overall heat dissipation effect of PCB. Among the current ceramic materials used to heat PCBs, BEO has high thermal conductivity, but its linear expansion coefficient is very different from that of silicon, and its toxicity in the manufacturing process limits its own application. The BN has good overall performance but is used as a PCB. The material has no outstanding advantages and is expensive. It is currently being studied and promoted; Silicon carbide has high strength and high thermal conductivity, but its resistance and insulation voltage resistance are low, and the combination of metallization is not stable, which will lead to the change of thermal conductivity and dielectric constant is not suitable for PCB insulation packaging material.
It is believed that when science and technology become more developed in the future, LED will bring more convenience to our life in more kinds of ways, which requires our researchers to work harder to learn knowledge, so as to contribute their strength to the development of science and technology.
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