Beryllium Oxide (Beryllia) Substrates can be substituted with Aluminum Nitride (AlN) Substrates for many applications.
Beryllium Oxide (Beryllia) substrates have thermal conductivity of 260 W/mk - that makes it the desirable material for high power microelectronic applications. Until fairly recently, this has been the case but now there is a controversy! Is BeO safe? Judge for yourself.
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Because of the safety controversy and also the cost, Beryllium Oxide has lost its popularity and Aluminum Nitride is replacing BeO in numerous applications. As the only other ceramic with high thermal conductivity, up to 200 W/mK, Aluminum Nitride substrates are available from Valley Design in a wide variety of sizes and thicknesses, many from stock. Aluminum Nitride (AlN) substrates come as-fired, and may be lapped to 25u" Ra, or polished to .5u" - 2u" Ra depending on the material quality.
Hybrid circuit designers sometimes choose Aluminum Nitride because they are not sure if alumina has the required thermal conductivity. Other times it is, of course, an absolute necessity. Beryllium Oxide substrates are being chosen less and less frequently in favor of non toxic AlN. Aluminum Nitride substrates can be used wherever thermo-mechanical or power dissipation properties are important such as highly integrated thick film and thin film components, water cooled power converters, and transmitter and HF diode substrates for use in satellite systems.
Typical Applications for AlN Substrates instead of BeO Substrates:
- Power Electronics
- Naval and Defense Systems
- Railway Systems
- Aeronautical, Telecommunication and Satellite Systems
- Environmental Systems including Emissions Control
Thermal management substrate related Web sites: