Energy saving power management of high-current electric motors and battery-operated portable devices has led to more efficient power semiconductor silicon designs, primarily to accommodate higher currents coupled with lower resistance. To meet these stringent requirements, semiconductor manufacturers have utilized wire bonding processes that have increased the number of large aluminum wires per device to support higher current demands. This exacting process combines vibration and force to increase the surface temperatures of each component, resulting in enhanced molecular cohesion through the formation of intermetallic compounds between the wire and chip pad metals.

Wirebonding interconnects (via wire or wire ribbon) components and conducting paths. The most frequently used method of joining wires is ultrasonic welding, either with (thermosonic) or without (ultrasonic) heating of the bonding system. Wirebonds are found in a multitude of components, including automotive systems, computers, guidance systems, and medical instruments. The wire bond connections are inspected optically, using either a wire bond pull tester or micro-sectioning.

Two terms commonly associated with the process of wire bonding are wedge and ball, each of which defines the subsequent profile of the wire being welded to the device surface. In each case, the selection and condition of materials is vital to the success of the wire bonding process. Aluminum wire, for example, is always wedge bonded, as the aluminum is not conducive to forming the "ball" used in ball bonding. Gold wire, on the other hand, is commonly ball bonded, and the ball can be formed by melting the end of the gold wire in air, since gold will not oxidize and forms a molten ball easily on flame-off. In special cases, copper wire is used in ball bonding, but it requires a reducing atmosphere to form a ball without oxidizing significantly. In addition, gold ribbon is an excellent substitute for gold wire, due to its compatibility with high frequencies, which makes it an ideal choice for fine pitch applications in the manufacturing of telecommunication systems and peripheral equipment.

Equipment selection for wire bonding should be based on the requirements of the component, such as current, voltage, and environmental stress; the selection of wire bond materials (usually aluminum or gold); and, most importantly, the vendors' technological capacity. For example, bonding equipment for heavy aluminum wire wedge bonding is configured to apply higher bonding loads to meet the requirements of high current levels. Furthermore, procedures that eliminate stress during handling, fabrication, and assembly are critical to achieving success in the manufacturing process. This requires developing, implementing, and constantly monitoring vendors, in-coming inspection, in-house storage, and handling procedures to achieve successful, repeatable manufacturing results.

Orthodyne's PowerRibbon™ is industry recognized as a leading technology designed to work with current package design standards for heavy aluminum wire. An environmentally friendly ultrasonic interconnect process similar to aluminum wedge fine wire bonding, PowerRibbon™ Technology combines the flexibility and ruggedness of the large aluminum wire bonding process with the higher productivity and product performance of copper clip bonding. PowerRibbon™ can be retrofitted to the Orthodyne M360C wire bonder and supports ribbon sizes ranging from 30 mil x 3 mil to 80 mil x 8 mil. Additional ribbon sizes, predicated on requirements, are available.

For additional information, or to arrange for a demonstration of the Orthodyne PowerRibbon™ wire bonder located within the factory of the EMPF, please contact Bob Berta at 610-362-1200 ext 253 or via e-mail at rberta@aciusa.org.