1968 Riston® Dry Film Photoresists
Riston dry film photoresists have helped keep the company at the leading edge of the electronics industry since their introduction in 1968. Innovations in photopolymer imaging in the early 1960s had prompted DuPont researchers to explore new possibilities for making electronic circuits.
Soon they developed solid photoresists, which take advantage of photopolymers' resistance to light (negative photoresists) or, in some cases, their sensitivity to light (positive photoresists). When an intricate pattern of circuitry is imprinted on a photomask, laid over a photopolymer template or photoresist and exposed to light, a precise reproduction of the superimposed pattern is created on the photoresist. The photoresist is laminated to a copper surface and a chemical, physical or laser process removes the exposed copper, leaving a neatly printed wiring board.
The immediate success of Riston stemmed in part from its dry film, which was more convenient and accurate than the wet film used by competitors, and from the efficient processor that came with it, making it more attractive to customers like IBM. In 1970 DuPont increased the capacity of its Riston plant in Towanda, Pa., and by 1977 was the industry leader in photoresists. It maintains that position today, with production facilities and joint ventures in Europe, Asia and the Americas. In 1999 DuPont introduced Riston photoresists that work with direct laser imaging, as well as photoresists adapted for the exotic materials and extremely small dimensions — less than 8/100,000 inches — of advanced electronic microcircuits. DuPont's YieldMaster 2000 system for processing Riston photoresists, installed for the customer at no cost, has improved the quality, speed and yield of production.