There are several kinds of semiconductor chip bonding methods--wire bonding, TAB, and flip chip bonding--and each is used in applications in ways which utilize its individual characteristics. Wire bonding is inexpensive and imposes fewer restrictions on wiring, but when used with conventional technology, it has been difficult to narrow the bonding pitch. The authors challenged themselves to develop a 40µm pitch wire bonding technology for use in development of a 600 DPI (dots per inch) LED print head. To accomplish this, a high strength ultra fine wire with a diameter of 10 µm was developed and a suitable wire bonding technology using that wire was determined. Finally, the targeted 40 µm pitch wire bonding technology was established.