Laser Direct Ablation for Patterning Printed Wiring Boards Using Ultra-fast Lasers and High Speed Beam Delivery Architectures

Laser Direct Ablation (LDA) for patterning printed wiring boards (PWB) is a new technology in the industry. Unlike the Laser Direct Imaging (LDI) method, this unique approach to remove the dielectric material by laser and embed the signal trace lines into the PWB allows the formation of recessed signals to below 10 mu am (4 mu m demonstrated) and the creation of near padless vias to facilitate a reduction in both package size and format [4, 5]. We have developed a vector scanning based laser system for this application using a unique beam steering technology combined with a high repetition rate ultrafast laser [1 - 3]. One requirement for this application is to control the width and depth of the signal lines at the micron level. The system takes advantage of a proprietary tertiary beam positioning system that uses Acousto-Optic Deflectors (AODs) in addition to the conventional galvanometers and linear stages, and the scheme allows not only the accurate and high speed beam delivery but also precise material removal. This paper will introduce this new technology in fabricating high density interconnect circuit patterns, the laser application requirement, and system architecture for the application.