Product Code: ICAL06_1801

Development of Laser-based Techniques for Rapid Prototyping of Printed Wiring Boards
Authors:
Brock Golesich, Kuchera Defense Industries; PA USA
Kenneth Meinert, Applied Research Laboratory, Pennsylvania State University; State College PA USA
Nicholas Dellas, Department of Materials Science and Engineering, The Pnnsylvania State University; State College PA USA
Suzanne Mohney, Department of Materials Science and Engineering, The Pennsylvania State University; State College PA USA
Presented at ICALEO 2006

When small numbers of printed wiring boards are needed for any application, conventional fabrication methods may not be suitable. Laser processing methods are being developed as an alternate method to the conventional etch and plate technology currently in use. Lasers are being employed in several different techniques to further the ability to manufacture printed wiring boards, including direct write technology from liquid precursor solutions, direct patterning of resists, and laser-enhanced electroless plating. Techniques for laser direct writing of patterned copper and silver lines for electronics packaging are researched. Typically, copper is patterned using traditional lithography techniques involving masks. Laser direct writing provides a maskless process capable of rapid prototyping and circuit repair. Various techniques are compared including direct writing of photoresist, laser enhanced electroless plating, and direct writing from metallo-organic films, the latter two as techniques for depositing a silver seed to catalyze electroless copper deposition. Common seed layers for electroless deposition include platinum, palladium, and silver. Silver is selected as it is a lower cost alternative to the other precious metals and metallic copper can effectively deposit on it. The mechanism responsible for deposition is photothermal in laser enhanced electroless plating and pyrolytic for direct writing from metallo-organic films. Effects of laser wavelength [Nd:YAG (1.06 µm), frequency tripled Nd:YVO4 (355 nm), and CO2 (10.6 µm)], beam scan speeds, and solution concentrations on deposit resistivity are compared. We conclude laser direct writing can effectively deposit a patterned seed layer of a catalyst for subsequent electroless plating.