Laser processing for microelectronics packaging applications

The microelectronics industry is moving toward smaller feature sizes. The main driving forces are to improve performance and to lower cost. From the performance point of view the small distances between chips together with the short interconnection routes have of great importance in order to achieve faster operation. Laser processing applied for via generation, direct pattern processing, image transfer, contour cutting, trimming, e tc. has proved to be efficient method for making rapid progress in this direction. On the other hand, smaller spaces between conductive patterns increase the risk of short circuits (caused by pattern faults, solder bridges, migration, etc.), that emphasizes the reliability aspects of applied process technologies. The paper describes the results of research projects that aimed at the application of CO2 and frequency-multiplied Nd:YAG lasers for drilling and direct patterning of copper clad glass fiber reinforced epoxy laminates, polyester foils and a couple of other structures. The physics of processing using five wavelengths, i.e. 10 600, 1064, 532, 355 and 266 nm, were modeled, examined and evaluated. Laser processing was combined with other - mainly metal coating processes, e.g, the through contacting of the generated vias were carried out by screen printing with polymer thick films, by wet chemical direct plating and by evaporation of thin metal layers, but the details of metallization are not given here. The conclusion summarizes the results and refers to the possibilities of laser processing of metal layers and polymeric materials in microelectronics packaging applications. (C) 2001 Elsevier Science Ltd. All rights reserved.