SCREEN PRINTED THICK FILM METAL HEATER WITH PROTECTIVE TOP DIELECTRIC LAYER
A thick film high temperature thermoplastic insulated resistive heating element including one or more base dielectric layers screen printed on a metal substrate having a composition one or more melt-flowable thermoplastic polymers, inorganic filler particles, a transition dielectric layer on top of the uppermost based dielectric layer containing inorganic additives in addition to one or more melt-flowable thermoplastic polymers and inorganic filler particles. A heater layer is coated on top of the top dielectric layer where the topmost dielectric layer acts as a transition layer between the uppermost dielectric to protect the adjacent resistor layer from the development of hot spots and cracking arising from the propagation of microcracks due to, amongst other things, residual stresses transmitted to the resistive layer from the sub-layers due to the thermal history of the resistive heater and substrate. The topmost transition dielectric layer is comprised of a ternary or higher mixture of the thermoplastic material such as, but not limited to, polyether ether ketone (PEEK), the inorganic filler such as alumina and other additives such as aluminum nitride.