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Wire bonding is the manufacturing process for creating metallurgical bond connections between a thin wire (12.5 – 50 µm for gold fine-wires and 150 – 500 µm for aluminum thick-wires) and a suitably coated circuit carrier through friction welding. In principle, this method consists of pressure welding with the help of ultrasound. The metallurgical bond is mainly caused by frictional heat, created through the relative movement between the two bonding partner materials. To achieve high reliability over longer time and under difficult environmental conditions, high quality requirements regarding material and mechanical strength properties must be met by the surfaces of the bonding partners.
Multiple silicon chips are combined to a functional unit on a circuit carrier (for example PCB board, DCB substrate, thick film ceramic) which is mostly encased in a hybrid housing for environmental protection. The metallic conductors mounted attached inside the housing then serve as connections the connection to the outside. If a higher current carrying capacity is neededrequired, such as for example in power electronics, the Al thick-wire bonding connection is employed used <xr id="fig:Bond_connection_Al_thick_wire_on_clad_AlSi"/><!--(Fig. 9.1)-->.
<figure id="fig:Bond_connection_Al_thick_wire_on_clad_AlSi">
[[File:Bond connection Al thick wire on clad AlSi.jpg|right|thumb|Bond connection: Al thick-wire on clad AlSi; (a) Macro photograph, b) micro structure with ruptured wire]]