The power LED package PCB acts as a carrier of heat and air convection,and its thermal conductivity plays a decisive role in the heat dissipation of the LED.DPC ceramic PCB shows strong competitiveness in many electronic packaging materials due to its excellent performance and gradually decreasing price,which is the development trend of power LED packaging in the future.With the development of science and technology and the emergence of new manufacturing processes,high thermal conductivity ceramic materials have broad application prospects as new electronic packaging PCB materials.
LED packaging technology is mostly based on the development and evolution of discrete device packaging technology,but it has great particularity.Generally speaking,the die of the discrete device is sealed in the package,and the function of the package is mainly to protect the die and complete the electrical connection.The LED package completes the output of electrical signals,protects the normal operation of the die,and outputs:the function of visible light,the design and technical requirements of electrical parameters,and optical parameters.The packaging of discrete devices cannot be simply used for LEDs.
With the increase of the input power of the LED chip,the large amount of heat generated by the high power consumption puts forward higher requirements on the LED packaging materials.In the LED heat dissipation channel,the package PCB is an important link connecting the internal and external heat dissipation channels,and has the functions of heat dissipation channels,circuit connections and chip physical support.For high-power LED products,the package PCB requires high electrical insulation,high thermal conductivity,and a thermal expansion coefficient matching the chip.
The existing solution is to directly fix the chip on the copper radiator,but the copper radiator itself is the conductive channel.As far as the light source is concerned,no thermoelectric separation is achieved.To package the light source on the PCB board,an insulating layer needs to be introduced to achieve thermoelectric separation.At this time,the heat is not concentrated on the chip,but concentrated near the insulating layer under the light source.Once the power increases,there will be heat problems.DPC ceramic substrate can solve this problem.The chip can be directly fixed on the ceramic,and a vertical connection hole is formed on the ceramic to form an internal independent conductive channel.The ceramic itself is an insulator and can dissipate heat.This is the thermoelectric separation achieved at the light source level.
The SMDLED stents that have appeared in recent years usually use high-temperature modified engineering plastic materials,using PPA(polyphthalamide)resin as the raw material,adding modified fillers to improve the physical and chemical properties of the PPA material.Therefore,PPA material is suitable for injection and SMDLED stents.The thermal conductivity of PPA plastic is very low,its heat dissipation is mainly carried out through the metal lead frame,and the heat dissipation capacity is limited,which is only suitable for low-power LED packaging.
In order to solve the problem of thermoelectric separation at the light source level,the ceramic substrate must have the following characteristics:first,it must have a higher thermal conductivity,which is several levels higher than that of resin,second,it must have a higher insulation strength,and third,the circuit resolution must be high,Vertically connected to the chip or flipped fourth,the surface has high flatness,and there is no gap when soldering.Fifth,ceramic and metal should have high adhesion,and sixth is the vertical connection hole,which can realize SMD packaging and guide the circuit from the back to the front.The basis for satisfying these conditions is the DPC ceramic foundation.
The ceramic substrate with high thermal conductivity can significantly improve the heat dissipation efficiency and is a good product for the development of high-power,small-size LEDs.Ceramic PCB has a new thermal conductivity material and a new internal structure,which compensates for the defects of aluminum PCB and improves the overall heat dissipation effect of the PCB.The current ceramic material used for heat dissipation PCB,BeO has high thermal conductivity,but its linear expansion coefficient is very different from the linear expansion coefficient of silicon,and it is toxic during the manufacturing process,which limits its application.BN has good overall performance,but it is used as a PCB.This material has no outstanding advantages and is expensive.Silicon carbide,which is being researched and popularized at present,has high strength and high thermal conductivity,but its resistance and insulation withstand voltage are low,the bonding after metallization is unstable,and the change of thermal conductivity and dielectric constant is not suitable for PCB materials for insulating packaging.