Direct copper bonded (DCB) alumina substrates are among sophisticated technical materials suitable for application in electronics, automotive and engineering industries. DCB substrates resist very severe operational conditions and assure high reliability. This technology provides alumina substrates which are very strongly bonded to copper foil, due to the solidified eutectic alloy Cu2O-Al2O3 or a suitable vitreous solder. Such substrates are ideal for the construction of elements in microelectronics hybrid circuits, power circuits and devices. As the bonding layer of a solidified eutectic or vitreous solder is very thin, the thermal resistivity stays sufficiently low; in addition, the dilatation properties of DCB substrates are close to those of silicon. This enables soldering of large silicon chips without the risk of creating mechanical stress and allows for the production of devices with very high construction effectivity. Examples of such applications are potential-free modules, bridge circuits, automotive ignition modules and Peltier elements. The vitreous bonding layers are advantageous for certain applications. State-of-the-art DCB bonding technology was developed for DCB aluminium nitride substrates, which have even better thermal qualities.