Casio premieres chip-on-film

has developed a next-generation chip-on-film (COF), a film substrate for mounting liquid crystal driver chips on large-screen LCD panels. The newly developed sample has an inner lead pitch of 25 microns.

The company has collaborated with materials makers to change the compositions of polyimide film and solder resist in order to improve the reliability of the COF, which has copper wires laid on polyimide film.

The company has also worked with materials partner companies to change the expansion coefficients of the materials so that they become closer to that of liquid crystal glass in order to minimise the misalignment of wires when the COF and the LCD panel are connected.

Other technologies Casio Micronics has developed to commercialise the new COF include a new etching process that enables vertical etching of the sides of a wire, a chip bonding process that uses a highly insulating sealing resin co-developed with another company, and a new chip bonder and tester.