The PCB industry is a fast moving world, with demanding requirements. The trend towards miniaturization of electronic components continues, and the width of the tracks is following. Lines and spaces of 175 ¦Ìm (7 mil) were common in the mid nineties. Today widths of 75 ¦Ìm (3 mil) are entering volume production. We expect the lines and spaces to narrow down to 40 ¦Ìm. HDI (High Density Interconnect) has now become a reality. The finer the lines, the better the line width control has to be. For impedance controlled boards a good line width control is mandatory. The line width tolerances can be as tight as +/- 2 %. Line sharpness is losing its cosmetic aspect. Fringed lines means uncontrolled line width and may even cause shorts or opens. The exposure and development latitude have to be wide to absorb variable production volumes, fluctuations in the environment, the equipment and the materials used. Also changes due to seasoning and aging are to be absorbed by the system. There is no need to say that the film and chemistry must have a consistent quality. Beside all these technical requirements, the total cost to generate and use phototools must also be justified.
Traditional technologies have a problem fulfilling all these needs. Due to the nature of the technology used, a compromise is to be made between line sharpness or line width control and between fine line capability or latitude. In normal production circumstances with the traditional technology it is not possible to have them both.
Agfa has developed a new silver halide phototooling technology that makes it possible to produce phototools with very fine lines and excellent sharpness. The new Agfa technology is able to generate phototools with excellent line sharpness while one can very precisely control the line width. This technology also makes it possible to generate reproducible lines only 10 ¦Ìm wide, without any loss of sharpness and without having to compromise in latitude.
