Via formation in green ceramic dielectrics using a YAG laser

A high-speed laser drilling process has been developed for producing fine-pitch vias of dimensions equivalent to fine-line screen printed conductors. Drilling speeds as high as 150-220 vias per second have been demonstrated on thick film and Green Tape dielectrics using an Nd:YAG laser. Throughputs greater than 300 vias/s could be achieved when multiple layers of Green Tape were drilled at once. There are a number of laser parameters which are critical to achieving high via formation rates while maintaining the accuracy of the via positioning. In addition, the electric composition and its thickness determine the beam power and number of pulses needed to drill each via. The quality of the drilled vias was improved by including a laser absorbing pigment in the dielectric formulation. Overall speed was also dependent upon design parameters such as via pitch, the symmetry of the circuit design, and the drilling sequence