Patent ID: 7271369

Claim:
A method of manufacturing a PTC device, comprising: (a) placing an ohmic layer on each side of a first PTC material layer; (b) firing the first PTC material layer and the ohmic layers in accordance with a predefined temperature profile; (c) placing external metal layers over each ohmic layer on both sides of the first PTC layer; (d) firing the resulting structure comprising a PTC material layer, two ohmic layers and two metal layers, in accordance with a second temperature profile, to provide a first PTC structure, wherein the ohmic layer and metal layer on each side of the PTC material layer form corresponding first and second electrodes of the first PTC structure disposed on a top and bottom surface of the first PTC structure, respectively; (e) repeating steps (a)-(d) above with a second set of layers comprising a PTC material layer, two ohmic layers, and two external metal layers, to form a second PTC structure having third and fourth electrodes disposed on top and bottom surfaces, respectively, of the second PTC structure, wherein the third and fourth electrodes each comprise an ohmic layer and a metal layer; (f) stacking the first and second PTC structures on top of one another such that the second electrode of the first PTC structure is in electrical contact with the third electrode of the second PTC structure; (g) soldering or bonding the second electrode to the third electrode; and (h) electrically connecting the first and fourth electrodes to a first contact lead of the device and electrically connecting the second and third electrodes to a second contact lead of the device.