Prosperous cities are inseparable from the decoration of LED lights. I believe we have all seen LED. Its figure has appeared in every place of our lives and illuminates our lives.
As the carrier of heat and air convection, the thermal conductivity of Power LED packaged PCB plays a decisive role in LED heat dissipation. DPC ceramic PCB with its excellent performance and gradually reduced price, in many electronic packaging materials show a strong competitiveness, is the future power LED packaging development trend. With the development of science and technology and the emergence of new preparation technology, high thermal conductivity ceramic material as a new electronic packaging PCB material has a very broad application prospect.
LED packaging technology is mostly developed and evolved on the basis of discrete device packaging technology, but it has great particularity. Generally, the core of a discrete device is sealed in a package body. The main function of the package is to protect the core and complete electrical interconnection. And LED packaging is to complete the output electrical signals, protect the normal work of the tube core, output: visible light function, both electrical parameters, and optical parameters of the design and technical requirements, can not simply be discrete device packaging for LED.
With the continuous improvement of LED chip input power, the large amount of heat generated by high power dissipation puts forward higher requirements for LED packaging materials. In LED heat dissipation channel, packaged PCB is the key link connecting internal and external heat dissipation channel, it has the functions of heat dissipation channel, circuit connection and chip physical support. For high-power LED products, packaging PCBS requires high electrical insulation, high thermal conductivity and a thermal expansion coefficient matching the chip.
The existing solution is to attach the chip directly to the copper radiator, but the copper radiator is itself a conductive channel. As far as light sources are concerned, thermoelectric separation is not achieved. Ultimately, the light source is packaged on a PCB board, and an insulating layer is still needed to achieve thermoelectric separation. At this point, although the heat is not concentrated on the chip, it is concentrated near the insulating layer beneath the light source. As power increases, heat problems arise. DPC ceramic substrate can solve this problem. It can fix the chip directly to the ceramic and form a vertical interconnect hole in the ceramic to form an independent internal conductive channel. Ceramics themselves are insulators, which dissipate heat. This is thermoelectric separation at the light source level.
In recent years, SMD LED supports 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 the use of SMD LED brackets. PPA plastic thermal conductivity is very low, its heat dissipation is mainly through the metal lead frame, heat dissipation capacity is limited, only suitable for low-power LED packaging.
In order to solve the problem of thermoelectric separation at the light source level, ceramic substrates should have the following characteristics: first, it must have high thermal conductivity, several orders of magnitude higher than resin; Second, it must have high insulation strength; Third, the circuit has high resolution and can be connected or flipped vertically with the chip without problems. The fourth is the high surface flatness, there will be no gap when welding. Fifth, ceramics and metals should have high adhesion; The sixth is the vertical interconnect through-hole, thus enabling SMD encapsulation to guide the circuit from the back to the front. The only substrate that meets these conditions is a DPC ceramic substrate.
Ceramic substrate with high thermal conductivity can significantly improve the heat dissipation efficiency, is the most suitable product for the development of high power, small size LED. Ceramic PCB has new thermal conductivity material and new internal structure, which makes up for the defects of aluminum PCB and improves the overall cooling effect of PCB. Among the ceramic materials currently used for cooling PCBS, BeO has high thermal conductivity, but its linear expansion coefficient is very different from that of silicon, and its toxicity during manufacturing limits its own application. BN has good overall performance, but is used as a PCB. The material has no outstanding advantages and is expensive. Currently being studied and promoted; Silicon carbide has high strength and high thermal conductivity, but its resistance and insulation resistance is low, and the combination after metallization is not stable, which will lead to changes in thermal conductivity and dielectric constant is not suitable for use as insulating packaging PCB material.
I believe that in the future, when science and technology are more developed, LED will bring greater convenience to our life in more kinds of ways, which requires our researchers to study harder, so as to contribute their own strength to the development of science and technology.