Micromachining of vias through thermal-sprayed multilayer structures using ultrafast lasers

Thermal spray is an economical, safe, and efficient technology for material processing and fabrication in which finely divided metallic or nonmetallic surfacing materials are deposited in a molten or semi-molten condition onto a substrate to form a spray deposit pattern. One of the major strengths of thermal spray is its ability to fabricate multilayer structures rapidly, which makes it a promising tool to fabricate multilayer circuits for electronic components. However, to compliment the additive nature of thermal spray, an efficient technique for material removal and modification of the multiplayer circuits is highly desired, which is difficult or impossible by using traditional manufacturing techniques. Laser ablation provides a practical alternative for precise micromachining of thermal-sprayed multilayer samples, especially using femtosecond lasers where materials can be removed through a melting-free mechanism with negligible thermal damage. In the present work, ultrafast laser micromachining is used to fabricate a via to electrically connect the top and bottom conductors in an inductor, which consists of eight thermal-sprayed layers. A 750 μm square via is machined with a femtosecond laser system, and then backfilled with more silver material to connect different conductor layers. This work demonstrates that femtosecond lasers are a promising tool for micromachining and modification of thermal sprayed multilayer structures.