Use of Programmed Piezo Crystal Flexures for Economic Vapor Deposition of Parylene HT® on Unlimited Lengths of Magnet Wire

Abstract

The electronics industry recognizes the need for high-temperature electronics (HTE) particularly for aerospace and geothermal applications. HTE is generally defined as robust operation in temperatures up to 300°C. A major constraint to HTE is high temperature magnet wire which is pervasive in electronic component windings and signal wire for sensors. The magnet wire constraint is caused by the temperature limits of the thin Polytetrafluoroethylene (PTFE) and Fluorinated Ethylene Propylene (FEP) coatings applied to HT magnet wire that limits the operating temperature to 220°C. [1], [2] There are coatings, particularly parylene-based coatings such as parylene HT®, that would greatly improve HT magnet wire, signal wire, and create the potential for subminiature thermocouple (TC) sensors; however, the slow vapor deposition process required to apply parylene is generally thought impractical for use in pore-free coating of long lengths of small diameter wire. For this research, experiments were first performed coating small diameter, wire product prototypes in standard batch vacuum chambers utilizing static fixtures. Finding this approach impractical we devised a new process utilizing a piezo-crystal electrodynamically actuated fixture of 14” diameter by 18” height that supports a web of one 24,500’ long, continuous small-diameter wire. A prototype dynamic fixture was built and a trial run successfully coated a 1500’ length of 0.005” diameter copper wire with Parylene HT®. This successful demonstration was the basis for a DOL Phase I SBIR to explore the feasibility of electrodynamically actuated devises that would synchronize horizontal and vertical actuation to drive horizontal motion to the wire web to enable a continuous reel-to-reel operation for parylene vapor deposition. This is discussed in future work.