Surface-mounted over-current protection device

Abstract

A surface-mounted over-current protection device with positive temperature coefficient (PTC) behavior is disclosed. The surface-mounted over-current protection device comprises a first metal foil, a second metal foil corresponding to the first metal foil, a PTC material layer stacked between the first metal foil and the second metal foil, a first metal electrode, a first metal conductor electrically connecting the first metal foil to the first metal electrode, a second metal electrode corresponding to the first metal electrode, a second metal conductor electrically connecting the second metal foil to the second metal electrode, and at least one insulated layer to electrically insulate the first metal electrode from the second metal electrode. The surface-mounted over-current protection device, at 25° C., indicates that a hold current thereof divided by the product of a covered area thereof and the number of the conductive composite module is at least 0.16 A/mm 2 .

What is claimed is: 
     
       1. A surface-mounted over-current protection device, comprising: at least one conductive composite module, comprising:
 a first metal foil; 
 a second metal foil; and 
 a PTC material layer stacked between the first metal foil and the second metal foil, exhibiting a resistivity below 0.2 Ω-cm, comprising 
 at least one crystalline polymer and at least one conductive filler distributed in the at least one crystalline polymer and exhibiting a resistivity below 500 μΩ-cm; 
 a first metal electrode electrically connected to the first metal foil; 
 a second metal electrode electrically connected to the second metal foil; and 
 at least one first insulated layer disposed between the first metal electrode and the second metal electrode to electrically insulate the first metal electrode from the second metal electrode; wherein the surface-mounted over-current protection device, at 25° C., indicates that the value of a hold current thereof divided by the product of a covered area thereof and the number of the conductive composite module is from 0.16 0.215 A/mm 2  to 1 A/mm 2 . 
 
     
     
       2. The surface-mounted over-current protection device of  claim 1 , further comprising a first metal conductor electrically connecting the first metal foil to the first metal electrode. 
     
     
       3. The surface-mounted over-current protection device of  claim 1 , further comprising a second metal conductor electrically connecting the second metal foil to the second metal electrode. 
     
     
       4. The surface-mounted over-current protection device of  claim 1 , wherein the at least one crystalline polymer comprises polyethylene. 
     
     
       5. The surface-mounted over-current protection device of  claim 1 , wherein the conductive filler is a metal powder or a conductive ceramic powder. 
     
     
       6. The surface-mounted over-current protection device of  claim 5 , wherein the metal powder is nickel, copper, iron, tin, lead, silver, gold, platinum, or an alloy thereof. 
     
     
       7. The surface-mounted over-current protection device of  claim 5 , wherein the conductive ceramic powder is selected from the group consisting of titanium carbide, tungsten carbide, vanadium carbide, zirconium carbide, niobium carbide, tantalum carbide, molybdenum carbide, hafnium carbide, titanium boride, vanadium boride, zirconium boride, niobium boride, molybdenum boride, hafnium boride, and zirconium nitride. 
     
     
       8. The surface-mounted over-current protection device of  claim 1 , wherein the particle size distribution of the at least one conductive filler consisting essentially of 0.1 μm to 10 μm. 
     
     
       9. The surface mounted over-current protection device of claim 1, wherein the PTC material layer has a thickness of greater than 0.2 mm. 
     
     
       10. The surface mounted over-current protection device of claim 1, wherein the first metal electrode and the second metal electrode are disposed on one surface of the conductive composite module. 
     
     
       11. The surface mounted over-current protection device of claim 1, wherein the first metal electrode and the second metal electrode are disposed on opposite surfaces of the conductive composite module. 
     
     
       12. The surface mounted over-current protection device of claim 1, wherein the at least one crystalline polymer comprises high density polyethylene, low density polyethylene, polyvinylidene fluoride, polyvinyl fluoride, polytetrafluoroethylene, polychlorotrifluoroethylene, or the mixture thereof. 
     
     
       13. The surface-mounted over-current protection device of claim 1, further comprising non-conductive filler selected from the group consisting of zinc oxide, antimony oxide, aluminum oxide, silicon oxide, calcium carbonate, boron nitride, aluminum nitride, magnesium sulfate, barium sulfate, magnesium hydroxide, aluminum hydroxide, calcium hydroxide, and barium hydroxide. 
     
     
       14. The surface mounted over-current protection device of claim 13, wherein the PTC material layer is capable of withstanding a voltage over 12 volts. 
     
     
       15. A surface-mounted over-current protection device, comprising:
 a first conductive composite module, comprising:
 a first metal foil; 
 a second metal foil; and 
 a PTC material layer stacked between the first metal foil and the second metal foil, exhibiting a resistivity below 0.2 Ω-cm, comprising at least one crystalline polymer and at least one conductive filler distributed in the at least one crystalline polymer and exhibiting a resistivity below 500 μΩ-cm; 
   a second conductive composite module of the same structure and material of the first conductive composite module and being superimposed on the first conductive composite module;   a first metal electrode electrically connected to the first metal foil; and   a second metal electrode electrically connected to the second metal foil;   wherein the first metal electrode is insulated from the second metal electrode;   wherein the surface-mounted over-current protection device, at 25° C. indicates that the value of a hold current thereof divided by the product of two and a covered area thereof is from 0.215 A/mm 2  to 1 A/mm 2 .   
     
     
       16. The surface-mounted over-current protection device of claim 15, wherein a pair of first insulated layers are disposed on the first and second conductive composite modules and between the first metal electrode and the second metal electrode to electrically insulate the first metal electrode from the second metal electrode. 
     
     
       17. The surface-mounted over-current protection device of claim 16, wherein a second insulated layer is disposed between the first conductive composite module and the second conductive composite module. 
     
     
       18. The surface-mounted over-current protection device of claim 15, wherein the conductive filler is nickel, copper, iron, tin, lead, silver, gold, platinum, or an alloy thereof. 
     
     
       19. The surface-mounted over-current protection device of claim 15, wherein the conductive filler is selected from the group consisting of titanium carbide, tungsten carbide, vanadium carbide, zirconium carbide, niobium carbide, tantalum carbide, molybdenum carbide, hafnium carbide, titanium boride, vanadium boride, zirconium boride, niobium boride, molybdenum boride, hafnium boride, and zirconium nitride.