Pad printer

Additive processes for the manufacture of electronic circuits are very attractive. They offer a minimum number of process steps, a wide latitude in materials and function, few waste products, and have low fixed (capital) costs. They have been severely constrained by the intrinsically poor resolution and accuracy of their printing technology-an evolutionary derivative of silk-screen printing. Recognizing that this limitation was inherent in the screens themselves, we have developed an alternative printer that uses no screen. Rather, the image to be printed is formed by engraving a pattern plate or "cliche", filling the engraving with ink and scraping or "skiving" the excess away, then transferring the ink image from the cliche to the workpiece with a "pad" of carefully selected chemical and mechanical properties. We have developed: 1) the machine with the necessary precision; 2) a range of cliches offering useful trade-offs between cost, availability, and useful life; 3) pads which are highly compliant in their own thickness direction but adequately "rigid" in the image plane; and 4) a family of inks that combine familiar inorganic chemistry (and hence electrical functionality) but with fine-particle pigments for high resolution printing and with novel organics optimized for transfer printing. This printing system is readily capable of printing 1 mil, 25 /spl mu/ lines and spaces in an extensive array of familiar conductor, resistor, and dielectric formulations. It represents, therefore, a 5/spl times/ improvement in feature density relative to silk-screen.