Conductive polymer device and method of manufacturing same

Abstract

An electronic device has three conductive polymer layers sandwiched between two external electrodes and two internal electrodes. The electrodes are staggered to create a first set of electrodes, in contact with a first terminal, alternating with a second set of electrodes in contact with a second terminal. The device is manufactured by: (1) providing (a) a first laminated substructure comprising a first polymer layer between first and second metal layers, (b) a second polymer layer, and (c) a second laminated substructure comprising a third polymer layer between third and fourth metal layers; (2) isolating selected areas of the second and third metal layers to form, respectively, first and second arrays of internal metal strips; (3) laminating the first and second laminated substructures to opposite surfaces of the second conductive polymer layer to form a laminated structure; (4) isolating selected areas of the first and fourth metal layers to form, respectively, first and second arrays of external metal strips; (5) forming insulation areas on the exterior surfaces of the external metal strips; and (6) forming a plurality of first terminals, each electrically connecting a metal strip in the first internal array to a metal strip in the second external array, and a plurality of second terminals, each electrically connecting a metal strip in the first external array to a metal strip in the second internal array; and (7) singulating the laminated structure into a plurality of devices, each having three polymer layers connected in parallel between first and second terminals.

What is claimed is:  
     
         1 . A method of fabricating an electronic device, comprising the steps of: 
 (1) providing (a) a first laminated substructure comprising a first conductive polymer layer sandwiched between first and second metal layers, (b) a second conductive polymer layer, and (c) a second laminated substructure comprising a third conductive polymer layer sandwiched between third and fourth metal layers;    (2) isolating selected areas of the second and third metal layers to form, respectively, first and second internal arrays of internal metal strips;    (3) laminating the first and second laminated substructures to opposite surfaces of the second conductive polymer layer to form a laminated structure;    (4) isolating selected areas of the first and fourth metal layers to form, respectively, first and second external arrays of external metal strips;    (5) forming a plurality of insulation areas on the exterior surfaces of each of the external metal strips; and    (6) forming a plurality of first terminals, each electrically connecting one of the internal metal strips in the first internal array to one of the external metal strips in the second external array, and a plurality of second terminals, each electrically connecting one of the external metal strips in the first external array to one of the internal metal strips in the second internal array.    
     
     
         2 . The method of    claim 1   , wherein the conductive polymer exhibits PTC behavior.  
     
     
         3 . The method of    claim 1   , wherein the metal layers are made of a material selected from the group consisting of nickel foil and nickel-coated copper foil.  
     
     
         4 . The method of claims  1 ,  2 , or  3 , further comprising the step of: 
 (7) separating the laminated structure into a plurality of devices, each comprising:    a first conductive polymer layer sandwiched between a first external electrode formed from one of the external metal strips in the first external array and a first internal electrode formed from one of the internal metal strips in the first internal array;    a second conductive polymer layer sandwiched between the first internal electrode and a second internal electrode formed from one of the internal metal strips in the second internal array; and    a third conductive polymer layer sandwiched between the second internal electrode and a second external electrode formed from one of the external metal strips in the second external array;    wherein the first terminal is in electrical contact only with the first internal electrode and the second external electrode, and the second terminal is in electrical contact only with the first external electrode and the second internal electrode.    
     
     
         5 . The method of claims  1 ,  2 , or  3 , wherein the step of isolating selected areas of the second and third metal layers comprises the step of etching a series of substantially parallel linear isolation gaps in each of the second and third metal layers to form the first and second internal arrays of internal metal strips.  
     
     
         6 . The method of    claim 5   , wherein the isolation gaps in the second and third metal layers are staggered relative to each other so that the internal metal strips in the first internal array are staggered with respect to the internal metal strips in the second internal array.  
     
     
         7 . The method of    claim 6   , wherein the step of isolating selected areas of the first and fourth metal layers comprises the steps of: 
 (4)(a) forming a series of substantially parallel linear slots through the laminated structure, each of the slots passing through one of the interior isolation gaps in either the second or third metal layer;    (4)(b) plating the internal side walls of the slots and the exterior surfaces of the first and fourth metal layers with a conductive metal plating layer; and    (4)(c) etching a series of substantially linear external isolation gaps in each of the first and fourth metal layers, including the metal plating layer applied thereto.    
     
     
         8 . The method of    claim 7   , wherein the step of etching a series of external isolation gaps is performed so that the external isolation gaps that are formed in the first metal layer are adjacent a first set of the slots, and the external isolation gaps that are formed in the fourth metal layer are adjacent a second set of the slots that alternate with the first set.  
     
     
         9 . The method of    claim 7   , wherein the step of forming the plurality of insulation areas comprises the step of depositing a layer of insulation material over the conductive metal plating layer on the exterior surfaces of the first and fourth metal layers so as to fill in the external isolation gaps with the insulation material, and so as to leave portions of the first and fourth metal layers adjacent each of the slots with exposed metal plating from the plating step.  
     
     
         10 . The method of    claim 9   , wherein the step of forming the pluralities of first and second terminals comprises the step of depositing a solder layer on the plated internal walls of the slots and on the portions of the first and fourth metal layers with exposed metal plating.  
     
     
         11 . The method of    claim 10   , wherein the step of depositing the solder layer is performed so that the portion of the solder layer that is deposited on the first and fourth metal layers is substantially flush with the layer of insulation material.  
     
     
         12 . An electronic device having first and second opposed end surfaces, the device comprising: 
 first, second, and third conductive polymer layers, each having first and second opposed surfaces;    the first and second conductive polymer layers being separated by a first internal electrode that is in electrical contact with the second surface of the first conductive polymer layer and with the first surface of the second conductive polymer layer;    the second and third conductive polymer layers being separated by a second internal electrode that is in electrical contact with the second surface of the second conductive polymer layer and with the first surface of the third conductive polymer layer;    a first external electrode having an internal surface in electrical contact with the first surface of the first conductive polymer layer and an external surface;    a second external electrode having an internal surface in electrical contact with the second surface of the third conductive polymer layer and an external surface;    a conductive metal layer having a first and second end portions respectively covering the first and second end surfaces of the device so as to be in electrical contact with the first and second internal electrodes, respectively, and top and bottom portions respectively covering the external surfaces of the first and second external electrodes;    a first terminal formed over the first end portion and part of the bottom portion of the conductive metal layer so as to be in electrical contact with the first internal electrode and with the second external electrode; and    a second terminal formed over the second end portion and part of the top portion of the metal layer so as to be in electrical contact with the second internal electrode and the first external electrode.    
     
     
         13 . The electronic device of    claim 12   , wherein the electrode elements are made of a metal foil.  
     
     
         14 . The electronic device of    claim 13   , wherein the metal foil is made of a material selected from the group consisting of nickel and nickel-coated copper.  
     
     
         15 . The electronic device of    claim 12   , wherein the first, second, and third conductive polymer layers are made of a material that exhibits PTC behavior.  
     
     
         16 . The electronic device of    claim 12   , wherein the first and second terminals are formed by a solder layer applied over the conductive metal layer.  
     
     
         17 . The electronic device of claims  12 ,  13 ,  14 ,  15 , or  16 , further comprising: 
 an insulative layer on each of the top and bottom portions of the conductive metal layer and located so as to insulate the first and second terminals from each other.    
     
     
         18 . The electronic device of    claim 17   , wherein the first and second terminals and the top and bottom portions of the conductive metal layer define substantially flush top and bottom surfaces of the device.  
     
     
         19 . The electronic device of claims  12 ,  13 ,  14 ,  15 , or  16 , wherein the first, second, and third conductive polymer layers are connected in parallel between the first and second terminals by the first and second internal electrodes and the first and second external electrodes.  
     
     
         20 . A method of fabricating an electronic device, comprising the steps of: 
 (1) providing a laminated structure comprising a first conductive polymer layer sandwiched between first and second metal layers;    (2) isolating selected areas of the first and second metal layers to form, respectively, first and second arrays of metal strips;    (3) forming a first plurality of insulation areas on the exterior surface of each of the first array of metal strips and a second plurality of insulation areas on the exterior surface of each of the second array of metal strips; and    (4) forming a plurality of first terminals, each electrically connected to one of the metal strips in the first array, and a plurality of corresponding second terminals, each electrically connected to one of the metal strips in the second array, each of the first terminals being isolated from a corresponding second terminal by one of the first plurality of insulation areas and one of the second plurality of insulation areas.    
     
     
         21 . The method of    claim 20   , wherein the conductive polymer exhibits PTC behavior.  
     
     
         22 . The method of    claim 20   , wherein the metal layers are made of a material selected from the group consisting of nickel foil and nickel-coated copper foil.  
     
     
         23 . The method of claims  20 ,  21 , or  22 , further comprising the step of: 
 (5) separating the laminated structure into a plurality of devices, each comprising:    a conductive polymer layer sandwiched between a first electrode formed from one of the metal strips in the first array and a second electrode formed from one of the metal strips in the second array;    a first terminal in electrical contact only with the first electrode; and    a second terminal in electrical contact only with the second electrode.    
     
     
         24 . The method of claims  20 ,  21 , or  22 , wherein the step of isolating selected areas of the first and second metal layers comprises the steps of: 
 (2)(a) forming a series of substantially parallel linear slots through the laminated structure;    (2)(b) plating the internal side walls of the slots and the exterior surfaces of the first and second metal layers with a conductive metal plating layer; and    (2)(c) etching a series of substantially linear isolation gaps in each of the first and second metal layers, including the metal plating layer applied thereto.    
     
     
         25 . The method of    claim 24   , wherein the step of etching a series of isolation gaps is performed so that the isolation gaps that are formed in the first metal layer are adjacent a first set of the slots, and the isolation gaps that are formed in the second metal layer are adjacent a second set of the slots that alternate with the first set.  
     
     
         26 . The method of    claim 24   , wherein the step of forming the first and second pluralities of insulation areas comprises the step of depositing first and second layers of insulation material over the conductive metal plating layer on the exterior surface of the first and second metal layers, respectively, so as to fill in the isolation gaps with the insulation material, and so as to leave portions of the first and second metal layers adjacent each of the slots with exposed metal plating from the plating step.  
     
     
         27 . The method of    claim 26   , wherein the step of forming the pluralities of first and second terminals comprises the step of depositing a solder layer on the plated internal walls of the slots and on the portions of the first and second metal layers with exposed metal plating.  
     
     
         28 . The method of    claim 27   , wherein the step of depositing the solder layer is performed so that the portion of the solder layer that is deposited on the first and second metal layers is substantially flush with the layer of insulation material.  
     
     
         29 . An electronic device having first and second opposed end surfaces, the device comprising: 
 a conductive polymer layer having first and second opposed surfaces;    a first electrode having an internal surface in electrical contact with the first surface of the conductive polymer layer and an external surface;    a second electrode having an internal surface in electrical contact with the second surface of the conductive polymer layer and an external surface;    a conductive metal layer having a first and second end portions respectively covering the first and second end surfaces of the device, and top and bottom portions respectively covering the external surfaces of the first and second electrodes;    a first terminal formed over the first end portion and part of the bottom portion of the conductive metal layer so as to be in electrical contact with the second electrode; and    a second terminal formed over the second end portion and part of the top portion of the metal layer so as to be in electrical contact with the first electrode.    
     
     
         30 . The electronic device of    claim 29   , wherein the electrode elements are made of a metal foil.  
     
     
         31 . The electronic device of    claim 30   , wherein the metal foil is made of a material selected from the group consisting of nickel and nickel-coated copper.  
     
     
         32 . The electronic device of    claim 29   , wherein the conductive polymer layer is made of a material that exhibits PTC behavior.  
     
     
         33 . The electronic device of    claim 29   , wherein the first and second terminals are formed by a solder layer applied over the conductive metal layer.  
     
     
         34 . The electronic device of claims  29 ,  30 ,  31 ,  32 , or  33 , further comprising: 
 an insulative layer on each of the top and bottom portions of the conductive metal layer and located so as to insulate the first and second terminals from each other.    
     
     
         35 . The electronic device of    claim 34   , wherein the first and second terminals and the top and bottom portions of the conductive metal layer define substantially flush top and bottom surfaces of the device.