Machining metallized PVDF films

Hermann, MO -When Measurement Specialties Inc. (Norristown, PA) was looking for an efficient method of patterning speaker electrodes on a roll of PVDF film up to 600 feet long it turned to Laser Light Technologies Inc.

Hermann, MO -When Measurement Specialties Inc. (Norristown, PA) was looking for an efficient method of patterning speaker electrodes on a roll of PVDF film up to 600 feet long it turned to Laser Light Technologies Inc. (LLTI). Patterning electrodes includes removing a copper-nickel coating 0.07 in wide from both sides of a roll of 28 µm thick PVDF film with continuous metal coating on both sides. Laser machining is a cost-efficient method compared to alternative chemical etching.

LLTI uses a KrF excimer laser to remove the metal coating on the border of a 6- x 10-in area. Each speaker electrode also has a mark for the positive electrode and set of fiducials for skewing prior to automated cutting of electrodes from the roll. A dedicated LLTI laser machining system is required.

The motion portion of this system includes a 6-axes controller for material handling stages with 16 in. of travel in X and Y. A reel-to-reel system on top of the material handling stages has a closed-loop material feed and adjustable web tensioner. A motorized mask stage enables switching between the different masks required to machine a complete electrode pattern. Also a motorized Z stage for the projection lens simplifies system setup.

The combination of energy density and synchronization between material handling stage travel and repetition rate of the laser are the most important parameters. Applying too high an energy density to the PVDF film or overexposure can deteriorate the crystalline structure of the film and initiate optical absorption, which results in increased surface and bulk conductivity. Further, overexposure can severely damage chemical bonds in PVDF molecules, and the formation of burned intercrystallite areas is visible with optical inspection. It was determined that measuring electrical resistivity between the machined electrode and the surrounding metal coating provides an efficient method for monitoring metal ablation. LLTI can be contacted at www.laserusa.com

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