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Fine-wire bonding is an important technology used for making electrical connections inside microelectronic device packages. In this method of interconnection, wire leads carry power and signals between semiconductor active circuits and leadframe or substrate metallization. Wire bonding technology is reviewed from a practical point of view. The thermocompression (T/C), thermosonic (T/S), and ultrasonic (U/S) bonding methods are briefly explained, and the advantages of each are considered. Proven practices for enhancing bond reliability are discussed. Suggestions are given for developing effective break strength and the elongation specifications for bonding wire. Wire inspection and quality assurance procedures are also reviewed. A major section deals with Al + 1% Si wire for U/S bonding, including Si dispersion, wire microstructure, mechanical properties, and bond heel cracking. Also discussed is Au wire for T/C and T/S bonding, including controlled metal doping, spooling, and the future trends in Au wire development. The advantages of Al/Mg wire for U/S bonding and the possible materials for Au-wire substitutes are additional subjects that are briefly addressed. This review is intended to serve as an up-to-date guide to wire bonding technology. It also points out areas in which additional material development work is required to maximize the utility of the new high-speed automated wire bonding equipment.