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 process consists of pressure welding with the aid 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.

Besides electroplated or chemically deposited gold coatings AlSi clad semi- finished materials are used for layered systems on circuit carriers and in hybrid housings (or for lead frames). These strip materials are manufactured by cold roll cladding of an AlSi1 alloy material onto Cu or Cu alloy strip (see chapter 3.2.1).

Printed circuit boards are also used as circuit carriers. Since many of the conductive structures are not electrically connected on the circuit board electroless processes are applied to create the final surface coatings (see chapter 7.1.2). Besides bonding to Nickel/Gold surfaces soldering is the most widely used process to create conductive connections. This can also be performed on electroless deposited tin surface coatings.

Kaspar, F.: Drahtbonden zur Kontaktierung auf elektronischen Baugruppen. VDE-Fachbericht 55 (1999) 97-103