Nowadays, the commonly used high-power LED heat dissipation substrate structure in production is generally aluminum substrate: the lowest layer is aluminum metal layer, with a thickness of about 1.3mm; Above the aluminum layer is a polymer insulation layer, with a thickness of approximately 0.1mm; The top layer consists of copper wires and welding circuits. Although the thermal conductivity of aluminum is relatively high, the thermal conductivity of the insulation layer is extremely low, so the insulation layer becomes the heat dissipation bottleneck of the structural substrate, affecting the overall heat dissipation effect of the substrate; Meanwhile, due to the presence of the insulation layer, it cannot withstand high-temperature welding, which affects the implementation of the packaging process and limits the optimization of the packaging structure, thus hindering LED heat dissipation.

　　Due to the low thermal conductivity and poor heat resistance of polymer insulation materials, it is necessary to replace the insulation material to improve the overall thermal conductivity and heat resistance of the aluminum metal substrate. However, the use of insulation materials makes it impossible for the same line to be arranged on top of the aluminum metal substrate. Therefore, it is currently impossible to directly increase the thermal conductivity of the aluminum metal substrate. The ceramic heat dissipation substrate has new thermal conductivity materials and new internal structure to eliminate the defects of aluminum metal substrate and improve the overall heat dissipation effect of the substrate.

Comparison of various ceramic materials:

Type of ceramic material: Al2O3; 3Al2O3 · 2SiO2 mullite; 2Al2O3 · 2MgO · 5SiO2 cordierite; MgO · SiO2 block talc; 2MgO · SiO2 magnesium olivine; AlN; SiC; BeO

① Al2O3: Up to now, aluminum oxide substrate is the most commonly used substrate material in the LED field, due to its high strength and chemical stability compared to most other oxide ceramics in terms of mechanical, thermal, and electrical properties, as well as a rich source of raw materials, suitable for various technology manufacturing and different shapes.

② BeO: It has a higher thermal conductivity than metallic aluminum and is used in situations where high thermal conductivity is required. However, it rapidly decreases after the temperature exceeds 300 ℃, and most importantly, its toxicity limits its own development.

③ AlN: AlN has two very important performance values, one is high thermal conductivity, and the other is the expansion coefficient that matches Si. The disadvantage is that even with a very thin oxide layer on the surface, it can affect the thermal conductivity. Only by strictly controlling the material and process can a consistent AlN substrate be produced. At present, only Sliton is relatively mature in large-scale AlN production technology in China. Compared to Al2O3, the price of AlN is relatively higher, which is also a bottleneck restricting its development.

④ The ceramic substrate materials used in actual production and development include SiC, BN multiphase ceramics, AZ zirconia ceramics, and glass ceramics. Among them, BeO and SiC have high thermal conductivity (250W/m.K), while SiC has a small volume resistance (<1013W · cm), high dielectric constant (40), and high dielectric loss (50), which is not conducive to signal transmission. Moreover, the molding process is complex and the equipment is expensive, so the application range is also very small.

AlN ceramic substrate is a new generation of high-performance ceramic substrate, with high thermal conductivity (theoretical value of 319W/m.K, commercial AlN substrate thermal conductivity greater than 160W/m.k), low dielectric constant (8.8), and dielectric loss (<5 × 10-4), and the thermal expansion coefficient (4.4) in proportion to silicon × 10-4/℃), but due to its high cost, it has not been widely applied; Although Al2O3 ceramic substrate has a low thermal conductivity (20W/m.K), it has become the most widely used ceramic substrate due to its relatively simple production process, low cost, and low price.

Based on the above reasons, it can be seen that alumina ceramics are widely used in fields such as microelectronics, power electronics, LED electronics, and power modules due to their superior comprehensive performance.

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