A wiper arm assembly and method of construction thereof includes a mounting head and a wiper arm configured for relative rotation during assembly from a disassembled position to a shipping position, wherein the wiper arm and mounting head are locked against rotation toward the disassembled position once in the shipping position. The first gate electrode has a three-layer structure in which a silicon nitride film is held between silicon oxide films, and the silicon nitride film includes triple coordinate nitrogen bonds. The shunt and pole structure are stacked such that the combined magnetic assembly has an opening extending centrally therethrough.