Most of the LED PCB bases are aluminum-substrate, but as LED lighting requires more and more brightness and longer shelf life, ceramic PCB base plates for LED merge. Which type of LED PCB plate is better? We will introduce different LED base PCBs and make comparison of them.
LED chips are sensitive to temperatures. When LEDs illuminate, a great amount of heat is generated. The larger current, the brighter the LED light. If the thermal is not dissipated immediately, the temperature rises. In turn, the elevating temperatures reduce the LED power and brightness. So the LED lamps have to solve the thermal dissipation problem, and choosing the PCB base plates is vital.
Chart 1 Aluminum LED PCB Base Plate
Aluminum has good thermal dissipation of 237W/mK but no electrical insulation at all. To make aluminum into an LED base plate, an insulation layer is added. However, the insulation layer has poor thermal dissipation. As a result, the aluminum LED PCB base plate has overall thermal dissipation only a little better than plastic.
When it works, the thermal transfers from the LED chips quickly to the aluminum layer then to the insulation layer. But due to the poor thermal dissipation, the thermal accumulates in the insulation layer. Though the thermal is not accumulated in the LED chips, when the LED lamp has higher power or works for a longer period, the chips are affected by thermal eventually.
Meanwhile, due to the insulation layer, the metal base plate can’t be welded at high temperatures, and there leave insufficient possibilities for the LED package optimization.
Besides, the aluminum LED base plate requires a fan to dissipate thermal, which takes up quite some space. And the aluminum price is high in recent years.
Chart2 Alumina LED PCB Base Plate
Alumina is currently the most used ceramic LED base plate material. The ceramic material alumina has thermal conductivity from 15W/mK to 50W/mK and good electrical insulation. When alumina is made into an LED PCB base, it has a thermal conductivity 10 times of the aluminum LED base plate. For traditional LED lamps for cars, the alumina base plate has enough thermal dissipation.
Besides, alumina is a cheap ceramic material. And there is no need to add an insulation layer and a fan.
However, the alumina LED PCB base plate has a higher thermal expansion coefficient than semiconductors. At 20°C to 300°C, the thermal expansion coefficient of 96% alumina is 6~7.5×10ˆ-6°C. For 99% alumina, it is 8~10×10ˆ-6°C. As for Si, the most used semiconductor, its thermal expansion coefficient is 3.5~4×10ˆ-6°C for Si. For this reason, the alumina LED PCB base plate is not appropriate for LED packaging used for high-frequency, high-power, and large-scale integrated circuits.
LED lamps for cars, ships, photography, and so are developing to higher powers for brighter light now and in the future. Traditional LED lamps are gradually replaced by high-power LEDs. Alumina LED base plates will also lose their majority in ceramic LED PCB base plates.
Chart3 Aluminum Nitride LED PCB Base Plate
Finally, we get to the aluminum nitride (AlN) LED PCB base plate. AlN is a promising electronic ceramic packaging material and AlN PCB is considered to be the most ideal LED PCB base.
The thermal conductivity of the AlN LED PCB base is 7 times higher than the alumina LED PCB base and 100 times higher than the aluminum base plate. For the high-power LEDs for car, ship, photography, spotlight, and so on, AlN is the most excellent PCB base plate option.
Besides, aluminum nitride has a greater hardness than alumina. And unlike normal ceramic, an AlN PCB base plate has good strength.
We have made an analysis of different LED base plates and listed their pros and cons. Here let’s sort them by different aspects.
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