PPTC material with low percolation threshold for conductive filler

A polymeric positive temperature coefficient (PPTC) device, comprising:

• a first PPTC body and a second PPTC body;
• first and second metallic foil layers disposed on opposing sides of the first PPTC body, respectively, and extending from first and second metallic traces at opposing ends of the first PPTC body, respectively, wherein the first metallic foil layer extends toward, but does not contact, the second metallic trace, and wherein the second metallic foil layer extends toward, but does not contact, the first metallic trace;
• third and fourth metallic foil layers disposed on opposing sides of the second PPTC body, respectively, and extending from first and second metallic traces at opposing ends of the second PPTC body, respectively, wherein the third metallic foil layer extends toward, but does not contact, the second metallic trace, and wherein the fourth metallic foil layer extends toward, but does not contact, the first metallic trace;
• an electrically insulating first insulation layer covering the first metallic foil layer;
• an electrically insulating second insulation layer covering the second metallic foil layer;
• a first metallic electrode disposed on the electrically insulating first insulation layer in electrical contact with the first metallic trace;
• and
• a second metallic electrode disposed on the electrically insulating first insulation layer in electrical contact with the second metallic trace;
• wherein the PPTC body is formed of a PPTC material that includes a polymer matrix and a conductive filler consisting of tungsten carbide, wherein the conductive filler defines 20%-39% by volume of the PPTC material.