The evolution of imaging technology

 First came the Carbon Arc source      for transferring an image from one medium to another. The primary market being  Graphic arts, with limited use in  printed circuit board fabrication.  The technology was unreliable and slow. Carbon Arc soon gave way to a more reliable source Collimated Short Arc

   made available with the advent of the semi-conductors. This was the technology for hi-technology imaging, and still very much in demand today. Although considered ideal for printed circuit boards and chemical milling products, the cost for a system was high, leaving only those with deep pockets to acquire. Here again market dynamics made it possible for a third technology to make its mark in the industries. High Pressure Metal  halide         systems. Much lower in cost and environmentally more friendly. With each step in the evolution of imaging systems came certain draw backs. The early metal halide systems enlisted the aid of large reflector        systems in order to enhance the amount of energy. These systems became know as "Flood" exposure systems, ideal for slow to expose resists, unfortunately lacking the ability to resolve fine lines.

Making it possible for  a new improved metal halide lamp  "Point Source"       to make it`s entrance as an affordable option to the "Flood system"  "point Source" became the work horse for imaging printed circuit boards. With its capability to resolve lines to 75 microns it soon took center stage and became the number one system in the markets.   As the demand for hi density packaging became more the norm, demanding line widths of 50 microns and in some cases smaller, point Source lost market share to the more traditional collimated systems.  Here again collimated systems too had restrictions of substrate size. As the trend for larger substrates became prevalent use of collimation also became an issue. The technologies used to collimate the light source are very expensive mirrors. Now the limitation is mirror size. there comes a point where it`s no longer becomes economical to keep making the mirrors larger.With all technologies there are always limitations, both the Flood and Point source systems; lamp life was always an issue. Lamp life is limited to an average of 600 hours. The greatest limitation was that of substrate size. Although both systems where designed to expose common sizes substrates. The larger the substrate the further away the lamp had to be positioned.This was not too much of an issue with the exception that; the further away the lamp, the longer the exposure time. In addition, the further away the lamp from the substrate, the greater the angle of collimation. Making it extremely difficult to maintain high resolution images. Adding to the problem, when using high intensity lamps, the longer the exposure time, the hotter the substrates became, again limiting substrate size, leaving the door wide open for a new technology "Light Emitting Diodes"   as the prime source for the illumination.