Electrical engineering, Electronics
– Lighting systems
ELECTRICAL ENGINEERING, ELECTRONICS // KILN AND FURNACE ENGINEERING// ON- AND OFFSHORE ENGINEERING // POWER ELECTRONICS // MEASURING SYSTEMS // CONTROL SYSTEMS // WAFER PRODUCTION // ELECTRIC MOTORS // TELECOMMUNICATIONS // LIGHTING SYSTEMS // PHYSICAL RESEARCH // ELECTRONICS – GENERAL
The leading argument for using ceramic materials as substrate or casing materials for LED systems is the reliably high durability in operation over long periods. For applications with these requirements, the focus is on Al2O3 and AlN ceramics, the technical properties of which are listed in the following.
- Purity: ≥95 %
- Density: >98 % of the theoretical value
- Mean bending strength: >300 MPa
- Mean compressive strength: >2 000 MPa
- Thermal stability: > 1 000 °C
- Thermal conductivity: >180 W/m/K
- High thermal shock resistance
- Linear thermal expansion coefficient:
- Al2O3: 5.5 ppm/K (20 – 100 °C), 8.0 ppm/K (20 – 1000 °C)
- AlN: 3.5 ppm/K (20 – 250 °C), 5.5 ppm/K (20 – 1000 °C)
- High corrosion resistance
- Specific electrical resistance
- Al2O3: >1014 Ω*cm
- AlN: >1012 Ω*cm
- Geometric precision to the tolerance range of 0.001 mm
In an advanced stage of development today are ceramic-based LEDs, which will be introduced into applications thanks to their high efficiency in applications. They are sometimes already in applications that demand high light output combined with small size.
A central component of a high-pressure sodium vapour lamp is a tube made of transparent, coarse-crystalline ceramic that has generally been sintered between 1800 and 1900 °C in H2 atmosphere.
With the use of ceramic, at operating temperatures around 1000 °C, a light output of 150 lm/W can be achieved. Such lamps generally reach a usable lifetime of 30 000 operating hours.