Laser Exposure Equipment For PCB With Large-area By The Way Of Scanning And Projection

As advances in electronic products with increasing demands for higher resolution and larger area of imaging, there are greater demands on printed circuit board design and fabrication. These are also driving the need for exposure equipment for the PCB production. Simultaneously, the continued pressure on manufacturing costs requires the advances in equipment performance be coupled with lower cost of ownership through such key factors as throughput, yield and use of conventional photoresists.With the gradually exposed various shortcomings in the conventional exposure tools for PCB, including limited substrate size, low throughput, common stitching errors, limited resolution, poor yield, high production cost and so on, a novel Laser Projection Imaging (LPI) exposure has been developed to take the place of the conventional Hg lamp exposure, using 351nm XeF excimer laser as its light source. And the exposures are made using conventional, dry -film and conventional fused silica glass masks and conventional processes.Based on the theory of LPI system, we set up a laser lithography equipment which is able to achieve 10μm resolution over large exposure area of 460mm×610mm on substrate materials as long as we adjust parameters. The equipment eliminates limitations of current lithography tools and all the benefits of it are immediately available to PCB manufacture without requiring any change to be made in current photoresists or processes.This equipment is available by the combination of four main parts:An XeF excimer laser with a wavelength of 351nm and single pulse energy of 120mJ, an illumination system with numerical aperture (NA) value of 0.02, a double telecentric optical projection lens with NA value of 0.025 and a X-Y precision stage which is controlled to move to make the mask and substrate can be scanned together, and the process be repeated until the entire substrate is imaged.In this paper, the configuration, optical design parameters, and manufacturing process are described. It is analyzed for the existing problem and useful technical solutions in the optics and machinery. At last, it is also discussed the optimum exposure parameters for the processes about lithography via the results of experiments under different conditions on laser projection imaging equipment.