The Best Choice For LED Packaging - Ceramic Substrate
As an important component of LED, the packaging substrate is not only a carrier, but also one of the important channels for heat dissipation. Its structure and material play a key role in the heat dissipation process.
At present, LED heat dissipation substrates mainly use metal (aluminum, copper) substrates and ceramic substrates. Metal substrates mainly include aluminum substrates, copper substrates, etc., and ceramic substrates mainly include aluminum oxide, aluminum nitride, silicon nitride, etc.
1. Aluminum substrate
Aluminum substrate is a metal-based copper clad laminate with good heat dissipation function. Generally, a single-sided board consists of three-layer structure, which are circuit layer (copper foil), insulating layer and metal base layer. For high-end use, there are also double-sided designs with a structure of circuit layer, insulating layer, aluminum base, insulating layer, and circuit layer. Very few applications are multi-layer boards, which can be made by laminating ordinary multi-layer boards with insulating layers and aluminum bases.
Aluminum substrates are widely used in LED lamps. Generally, the material of the circuit board is glass fiber, but because the LED generates a large amount of heat, the aluminum substrate is generally used for the LED lamp, which can conduct heat quickly.
2. Ceramic substrate
The ceramic substrate is made of ceramic material, generally made of alumina, aluminum nitride, silicon nitride, etc. Good heat dissipation performance can avoid short-circuit damage caused by insufficient heat dissipation.
The thermal conductivity of the alumina ceramic substrate is 30-50W/m.K. If it is an aluminum nitride substrate, the thermal conductivity can be removed by 170 W/m.K. It has the following properties:
① Strong mechanical stress, stable shape; high strength, high thermal conductivity, high insulation; strong bonding force, anti-corrosion.
② Good thermal cycle performance, the number of cycles is up to 50,000 times, and the reliability is high.
③ Like the PCB board (or IMS substrate), it can etch the structure of various patterns; no pollution and no pollution.
④ The operating temperature is -55℃～850℃; the thermal expansion coefficient is close to that of silicon, which simplifies the production process of the power module.
In terms of heat dissipation data, the heat dissipation of ceramic substrates is more than 7 times that of aluminum substrates. Among them, ceramic substrates are divided into alumina ceramic substrates and aluminum nitride ceramic substrates. Aluminum nitride ceramic substrates are 5 times more efficient than alumina ceramic substrates.
3. Aluminum substrate & ceramic substrate LED application comparison
The aluminum nitride ceramic material itself is an insulator, and there is no need to make an insulating layer on the PCB like a metal substrate. Conductive channels are formed through vertical interconnection holes, and the thermal expansion coefficient of the ceramic also matches that of most chips.
The aluminum base insulation layer is the largest thermal barrier in the power module structure. The better the thermal conductivity of the insulating layer, the more conducive to the diffusion of heat generated during the operation of the device, and the more conducive to reducing the operating temperature of the device, so as to achieve the purpose of increasing the power load of the module, reducing the volume, prolonging the life, and improving the power output.
That is, the aluminum substrate is subject to the insulating layer. The ceramic substrate does not have an insulating layer, so there will be no such trouble.
If high-power LED modules are involved, which requires extremely strong heat dissipation capability, ceramic substrates are required to replace them. Ceramic substrate has high circuit alignment accuracy and is recognized by the industry as a material with excellent thermal conductivity and heat dissipation performance. It is currently the most suitable solution for high-power LED heat dissipation. Although the cost is higher than that of metal substrates, the heat dissipation and stability required by lighting are higher than metal substrate.
