Photoimaging resists

Photoimageable polyimides, 20 278-281 Photoimageable resists, 20 280. See also Photoresists... 

Circuit complexity Dry film, photoimageable resist, and a clean room are needed. 

Manufacture of Printed Wiring Boards. Printed wiring boards, or printed circuit boards, are usually thin flat panels than contain one or multiple layers of thin copper patterns that interconnect the various electronic components (e.g. integrated circuit chips, connectors, resistors) that are attached to the boards. These panels are present in almost every consumer electronic product and automobile sold today. The various photopolymer products used to manufacture the printed wiring boards include film resists, electroless plating resists (23), liquid resists, electrodeposited resists (24), solder masks (25), laser exposed photoresists (26), flexible photoimageable permanent coatings (27) and polyimide interlayer insulator films (28). Another new use of photopolymer chemistry is the selective formation of conductive patterns in polymers (29). 

Yako, Y. Photoimaging materials, patterning thereof, and solvent-resistant colorless patterns with good profile therefrom. Jpn. Kokai Tokkyo Koho JP 2004139070, 2004 Chem. Abstr. 2004,140, 397363. 

The third process technique used in these applications involves photounaging a permanent dielectric material in order to form the microvias. These photoimageable dielectrics resemble plating resists but must be able to be catalyzed for subsequent plating operations that will form the external circuit image, and must adhere sufficiently to the rest of the multilayer circuit to provide long-term reliability. 

Photoimageable Discrete. In a photoimageable discrete process, resistive compositions have been dispersed in traditional solder mask-like materials, which are applied to the surface of an etched layer. Imaging and development leave the desired geometry resistor after the development step. 

Image transfer Photoimageable, dry film, or screening of plating resists will depend on board complexity, volume, and labor skills. 

Photoimageable masks are available in either liquid or dry-film forms. Liquids account for more than 98 percent of the products used, due to their lower cost, greater availability, ease of use, and acceptability in assembly processing. Dry-film masks require spedal apphcation equipment, are expensive, are often not robust when used as a resist for final finishes snch as ENIG or immersion tin, and are too thick for use in some assembly processes. 

FIGURE 63.28 An example of a manufacturing process for photoimageable coverlay (a) A schematic flowchart of a generic process using either dry film or liquid resist, (b)... 

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