Patent ID: 6568068
Filing Date: 2003-05-27
Classification: H05B,Y10T

Abstract:
A method of fabricating a positive temperature coefficient (PTC) thermistor electrical heating device, comprising the steps of:assembling a PTC electrical heating device by enclosing one or more planar PTC heating elements having generally parallel, flat, contact surfaces between generally parallel, flat, contact surfaces of a pair of radiator members, thereby defining contact interfaces between the contact surfaces of the heating elements and the contact surfaces of the radiator members; applying a pressure across the interfaces; measuring the electrical resistance across the heating device; exposing the heating device to a first temperature for a first predetermined time period; determining whether a change occurs in the electrical resistance across the heating device when exposed to the first temperature during said first predetermined time period; exposing the heating device to a second temperature for a second predetermined time period; determining whether a change occurs in the electrical resistance across the heating device when exposed to the second temperature during said second predetermined time period; and during said steps of determining, in the event that the electrical resistance across the heating device is determined to have changed by more than a predetermined amount during one of said predetermined time periods, adjusting the pressure across the interfaces in the respective time period, thereby to stabilize the electrical resistance across the heating device in the respective time period.