Applications

Ultrasonic Wedge Bonding or US Bonding is used for bonding gold or aluminum wire. For power applications, copper wire can also be used. There are three different kinds of wire bonding: Thin wire bonding or just wire bonding with wires from 17 µm up to 75 µm. Heavy wire bonding with wires from 100 µm up to 500 µm. And ribbon bonding with flat-band ribbons of different sizes.

Thermosonic Ball Wedge Bonding or TS Bonding uses a combination of heat, pressure, and ultrasonic energy to create a weld between a gold, copper or silver ball and the surface of a chip. A gold, copper or silver wire is threaded through a capillary made from ultra-fine ceramics on which tip a high-voltage electric charge is applied to the wire. This melts the wire into a ball, called flame off. With pressure (bond force) and ultrasonic energy the capillary connects this ball now to the surface of the substrate. After that a loop is formed and a second bond applied in the form of a wedge bond, also called stitch bond.

Ribbon connections are low in impedance and have a considerable heat dissipation. Due to these characteristics ribbons are frequently used in radio frequency (RF) technology.

Bump bonding is used for flip-chip applications: mounting a chip up-side-down directly onto a substrate or second chip. No additional wire is used, and the contact is established solely by beforehand applied bumps. This method is very compact and low in inductance, due to the short conductor lengths. Furthermore, it is possible to stack multiple chips on top of each other.

Heavy wire bonding with wire diameters of 100μm to 500μm is used in power electronics such as used for LEDs, batteries and in the automotive sector.

Preparing mass production or facing a special application, it may be necessary to switch from the common materials gold and aluminum to copper. The advantages of copper wire are a cheaper wire price, better electrical conductivity and better thermal conductivity.

When bonding with copper wire, the copper has to be protected from oxidation by using a special antioxidation gas. This complicates the work process. An alternative could be bonding copper wire with aluminum coating. It can be easily wedge bonded and is well storable.

Insulated wires are short circuit proof due to the full insulation of the wire. Insulated wires are usually soldered. In some cases connecting the wire with a bonder can be a viable alternative.