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Future power LEDs will use DPC ceramic substrates

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As LED packaging is becoming thinner and less expensive, chip-on-board (COB) packaging technology is emerging. At present, COB package substrates mostly use metal core printed circuit boards, and high-power LED packages mostly use such substrates, and the price is between medium and high price.
The high-power LED heat-dissipating substrate commonly used in current consumption has extremely low thermal conductivity of the insulating layer, and due to the existence of the insulating layer, it cannot accept high-temperature welding, which limits the optimization of the package structure and is not conducive to LED heat dissipation.
How to improve the thermal conductivity of the epoxy insulation layer has become a hot topic in the current stage of aluminum substrates. At present, a modified epoxy resin or epoxy glass cloth bonded with a highly thermally conductive inorganic filler (such as a ceramic powder) is bonded, and the copper foil, the insulator and the aluminum plate are bonded by heat pressing. At present, a "all-glue aluminum substrate" has been developed in the world, and the thermal resistance of the fully-coated aluminum substrate can be 0.05K/W. In addition, a company in Taiwan recently developed a DLC for drilling carbon materials and applied it to the insulating layer of high-brightness LED package aluminum substrates. DLC has many superior data characteristics: high thermal conductivity, thermal average and high data intensity. Therefore, replacing the epoxy resin insulation layer of traditional metal-based printed circuit board (MCPCB) with DLC is expected to greatly improve the thermal conductivity of MCPCB, but its practical application effect has yet to be tested in the market.

A better performance aluminum substrate is to directly form an insulating layer on the aluminum plate and then print the circuit. The biggest advantage of this approach is the high separation force and thermal conductivity of up to 2.1 W / (m · K). However, the processing and manufacturing process of the aluminum substrate is complicated and costly. Moreover, the thermal shrinkage coefficient of the metal aluminum is greatly different from the chip data, and the thermal cycle often generates a large stress during the operation of the device, which may eventually cause failure, and thus is in practice. Less used.


DPC <a href='/' style='color:blue;'>ceramic substrate</a>s



Silicon-based package substrate: face a good rate of less than 60%
The silicon substrate is faced with a battle in the preparation of the insulating layer, the metal layer and the via hole, and the yield rate does not exceed 60%.
Silicon-based materials have been introduced into the LED industry from the semiconductor industry in recent years. The thermal conductivity and thermal shrinkage of the silicon substrate indicate that the silicon is a package that matches the LED. The thermal conductivity of silicon is 140W/m·K. When applied to LED package, the thermal resistance formed is only 0.66K/W. Moreover, silicon-based materials have been widely used in semiconductor manufacturing and related packaging, and related equipment and materials have been touched. It is quite mature. Therefore, if silicon is fabricated into an LED package substrate, mass production is likely to occur.
However, LED silicon substrate packages still have many technical problems. For example, in terms of data, silicon is prone to chipping and the strength of the mechanism is also problematic. In terms of construction, although silicon is an excellent thermal conductor, it has poor insulation and must be treated with oxidative insulation. In addition, the metal layer needs to be prepared by sputtering and separation plating, and the conductive holes are required to be corroded. Generally speaking, the preparation of insulating layer, metal layer and via hole are faced with the challenge, and the yield rate is not high. At present, although some Taiwanese companies have developed LED silicon substrates and mass production, the yield rate does not exceed 60%.
Ceramic package substrate: Improve heat dissipation efficiency to meet high power LED requirements
With the high thermal conductivity ceramic substrate, DPC significantly improves the heat dissipation efficiency, and is the most suitable product for high-power, small-size LED development.
The ceramic heat sink substrate has new heat conduction materials and a new internal structure, which compensates for the defects of the aluminum metal substrate, thereby improving the overall heat dissipation effect of the substrate. Among the ceramic materials currently used as heat-dissipating substrates, BeO has a high thermal conductivity, but its linear shrinkage coefficient is very different from silicon (Si), and it is toxic during manufacturing, which limits its application; BN has better comprehensive performance. However, as the substrate material, there are no outstanding advantages, and the price is expensive. Currently, it is only in the discussion and implementation; silicon carbide (SiC) has high strength and high thermal conductivity, but its resistance and insulation withstand voltage are low, and the metallized key Unstable, it will cause changes in thermal conductivity and dielectric constant, and should not be used as insulating package substrate. Although Al2O3 ceramic substrate is the most widely used and widely used ceramic substrate, its thermal shrinkage coefficient is higher than that of Si single crystal, which makes the Al2O3 ceramic substrate not suitable for high frequency, high power and large scale integration. Used in the circuit. A1N crystals have high thermal conductivity and are considered ideal for next-generation semiconductor substrates and packages.
AlN ceramic materials have been widely discussed since the beginning of the 1990s, and are currently widely expected to be promising electronic ceramic packaging materials. The heat dissipation efficiency of the AlN ceramic substrate is 7 times that of the Al2O3 substrate, and the heat dissipation effect of the AlN substrate applied to the high-power LED is remarkable, thereby greatly improving the service life of the LED. The defect of the AlN substrate is that even if the surface has a very thin oxide layer, it will have a great influence on the thermal conductivity. As long as the data and the process are strictly controlled, the AlN substrate with better bifurcation can be manufactured. At present, the large-scale consumption of AlN is still immature. Compared with the currently used Al2O3 substrate, the cost of the AlN substrate is about 3 to 5 times that of the Al2O3 substrate. However, if energy is produced in the future, the cost of the AlN substrate can be quickly dropped. At that time, the AlN substrate with strong heat dissipation will sometimes replace the Al2O3 substrate.
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