Multilayered ceramic capacitor with improved lead frame attachment

Abstract

A capacitor with improved lead frame attachment is described wherein the improved lead frame attachment mitigates defects. The capacitor comprises parallel conductive internal electrodes of alternating polarity with a dielectric between the conductive internal electrodes. A first copper undercoat is in electrical contact with the conductive internal electrodes of a first polarity and a second copper undercoat is in electrical contact with conductive internal electrodes of a second polarity. A first lead is in electrical contact with the first copper undercoat with a first solder between the first lead and the first copper undercoat. A second lead is in electrical contact with the second copper undercoat with a second solder between the second lead and the second copper undercoat.

Claimed is: 
     
         1 . A capacitor comprising:
 parallel conductive internal electrodes of alternating polarity with a dielectric between said conductive internal electrodes;   a first copper undercoat in electrical contact with conductive internal electrodes of a first polarity;   a second copper undercoat in electrical contact with conductive internal electrodes of a second polarity;   a first lead in electrical contact with said first copper undercoat with a first solder between said first lead and said first copper undercoat;   a second lead in electrical contact with said second copper undercoat with a second solder between said second lead and said second copper undercoat;   a solderable silver layer between said first copper undercoat and said first lead; and   a flexible layer between said solderable silver layer and said first copper undercoat   
     
     
         2 . The capacitor of  claim 1  wherein said first copper undercoat has a surface oxide content of less than 1 percent. 
     
     
         3 . The capacitor of  claim 1  wherein said first copper undercoat has a glass frit content of less than 20 wt %. 
     
     
         4 . The capacitor of  claim 3  wherein said first copper undercoat has a glass frit content of at least about 5 wt % to no more than about 8 wt %. 
     
     
         5 . The capacitor of  claim 1  wherein said first copper undercoat has a film thickness of at least about 1 micron to no more than about 100 microns. 
     
     
         6 . The capacitor of  claim 5  wherein said first copper undercoat has a film thickness of at least about 10 micron to no more than about 100 microns. 
     
     
         7 . The capacitor of  claim 1  wherein said internal electrodes comprise a base metal. 
     
     
         8 . The capacitor of  claim 7  wherein said base metal is selected from nickel, copper, titanium, tungsten and molybdenum. 
     
     
         9 . The capacitor of  claim 8  wherein said internal electrodes comprises an alloy of nickel. 
     
     
         10 . The capacitor of  claim 9  wherein said alloy comprises at least one material selected from the group consisting of Cu, Si, Ba, Ti, Mn, Cr, Co, and Al. 
     
     
         11 . The capacitor of  claim 10  wherein said alloy comprises at least 95 wt % nickel. 
     
     
         12 . The capacitor of  claim 1  which does not have a plating layer comprising nickel or tin between said first copper undercoat and said first lead. 
     
     
         13 . A capacitor comprising:
 parallel conductive internal electrodes of alternating polarity with a dielectric between said conductive internal electrodes;   a first copper undercoat in electrical contact with conductive internal electrodes of a first polarity;   a second copper undercoat in electrical contact with conductive internal electrodes of a second polarity;   a first lead in electrical contact with said first copper undercoat with a first solder between said first lead and said first copper undercoat; and   a second lead in electrical contact with said second copper undercoat with a second solder between said second lead and said second copper undercoat.   
     
     
         14 . The capacitor of  claim 13  wherein said first copper undercoat is in direct electrical contact with said conductive internal electrodes. 
     
     
         15 . The capacitor of  claim 14  wherein said first lead is soldered directly to said first copper undercoat. 
     
     
         16 . The capacitor of  claim 13  wherein said first copper undercoat has a surface oxide content of less than 1 percent. 
     
     
         17 . The capacitor of  claim 13  wherein said first copper undercoat has a glass frit content of less than 20 wt %. 
     
     
         18 . The capacitor of  claim 17  wherein said first copper undercoat has a glass frit content of at least about 5 wt % to no more than about 8 wt %. 
     
     
         19 . The capacitor of  claim 13  wherein said first copper undercoat has a film thickness of at least about 1 micron to no more than about 100 microns. 
     
     
         20 . The capacitor of  claim 19  wherein said first copper undercoat has a film thickness of at least about 10 micron to no more than about 100 microns. 
     
     
         21 . The capacitor of  claim 13  wherein said internal electrodes comprise a base metal. 
     
     
         22 . The capacitor of  claim 21  wherein said base metal is selected from nickel, copper, titanium, tungsten and molybdenum. 
     
     
         23 . The capacitor of  claim 22  wherein said internal electrodes comprises an alloy of nickel. 
     
     
         24 . The capacitor of  claim 23  wherein said alloy comprises at least one material selected from the group consisting of Cu, Si, Ba, Ti, Mn, Cr, Co, and Al. 
     
     
         25 . The capacitor of  claim 24  wherein said alloy comprises at least 95 wt % nickel. 
     
     
         26 . The capacitor of  claim 13  which does not have a plating layer comprising nickel or tin between said first copper undercoat and said first lead. 
     
     
         27 . A capacitor comprising:
 parallel conductive internal electrodes of alternating polarity with a dielectric between said conductive internal electrodes wherein said conductive internal electrodes comprise a precious metal;   a first silver undercoat in electrical contact with conductive internal electrodes of a first polarity;   a second silver undercoat in electrical contact with conductive internal electrodes of a second polarity;   a first solderable silver layer in contact with said first silver undercoat;   a second solderable silver layer in contact with said second silver undercoat layers;   a first lead in electrical contact with said first silver undercoat with said first solderable silver layer between said first lead and said first silver undercoat; and   a second lead in electrical contact with said second silver undercoat with said second solderable silver layer between said second lead and said second silver undercoat.   
     
     
         28 . The capacitor of  claim 27  further comprising a flexible layer between said solderable silver layer and said first silver undercoat. 
     
     
         29 . The capacitor of  claim 27  wherein said first silver undercoat is in direct electrical contact with said conductive internal electrodes. 
     
     
         30 . The capacitor of  claim 27  wherein said conductive internal electrodes comprise a material selected from silver, palladium, gold, platinum and alloys thereof. 
     
     
         31 . The capacitor of  claim 30  wherein said conductive internal electrodes comprises silver-palladium alloy or silver-palladium-platinum alloy. 
     
     
         32 . The capacitor of  claim 27  which does not have a plating layer comprising nickel or tin between said first silver undercoat and said first lead. 
     
     
         33 . A method for forming a capacitor comprising the steps of:
 providing a monolith comprising parallel conductive internal electrodes of alternating polarity with a dielectric between said conductive internal electrodes;   applying a first copper undercoat in direct electrical contact with said conductive internal electrodes having a first polarity;   applying a second copper undercoat in direct electrical contact with said conductive internal electrodes having a second polarity;   soldering a first lead frame in electrical contact with said first copper undercoat; and   soldering a second lead frame in electrical contact with said second copper undercoat.   
     
     
         34 . The method for forming a capacitor of  claim 33  further comprising:
 forming a flexible termination prior to said soldering a first lead frame. 
 
     
     
         35 . The method of forming a capacitor of  claim 34  wherein said flexible termination comprises silver particles in a polymeric matrix. 
     
     
         36 . The method of forming a capacitor of  claim 34  wherein said flexible termination is formed by applying a paste and drying said paste. 
     
     
         37 . The method of forming a capacitor of  claim 36  wherein said paste comprises 77-79 wt % silver particles and 10-15 wt % organic resin in an organic solvent. 
     
     
         38 . The method of forming a capacitor of  claim 36  wherein said paste has a viscosity of at least 5 Pa-S to no more than about 50 Pa-S at 25° C. 
     
     
         39 . The method of forming a capacitor of  claim 36  wherein said paste has a viscosity of at least 7 Pa-S to no more than about 15 Pa-S at 25° C. 
     
     
         40 . The method for forming a capacitor of  claim 34  further comprising forming a solderable silver layer after said forming a flexible termination and prior to said soldering a first lead frame. 
     
     
         41 . The method for forming a capacitor of  claim 40  wherein said forming a solderable silver layer comprises applying a solution with a viscosity of 1-10 Pa-S at 25° C. 
     
     
         42 . The method for forming a capacitor of  claim 40  wherein said forming a solderable silver layer comprises applying a solution with a solids content of 30-60 wt %. 
     
     
         43 . The method for forming a capacitor of  claim 33  wherein said first lead is soldered directly to said copper undercoat. 
     
     
         44 . The method for forming a capacitor of  claim 33  wherein said first copper undercoat or said second copper undercoat has an surface oxide content of less than 1 percent. 
     
     
         45 . The method for forming a capacitor of  claim 33  wherein said first copper undercoat or said second copper undercoat has a surface glass content of about 5 to about 20 wt. percent. 
     
     
         46 . The method for forming a capacitor of  claim 45  wherein said first copper undercoat or said second copper undercoat has a surface glass content of about 5 to about 8 wt. percent. 
     
     
         47 . The method for forming a capacitor of  claim 33  wherein said first copper undercoat or said second copper undercoat has a total copper film thickness of at least 1 microns to no more than 100 microns. 
     
     
         48 . The method for forming a capacitor of  claim 47  wherein said first copper undercoat or said second copper undercoat has a total copper film thickness of at least 10 microns to no more than 100 microns. 
     
     
         49 . The method for forming a capacitor of  claim 33  further comprising surface treating of said copper. 
     
     
         50 . The method for forming a capacitor of  claim 49  further wherein said surface treating is acid cleaning or plasma cleaning. 
     
     
         51 . The method for forming a capacitor of  claim 33  wherein said applying a first copper undercoat comprises applying a solution with a viscosity of 20-50 Pa-S at 25° C. 
     
     
         52 . The method for forming a capacitor of  claim 33  wherein said applying a first copper undercoat comprises applying a paste comprising about 75-90 wt % copper and about 5-20 wt % glass frit. 
     
     
         53 . The method for forming a capacitor of  claim 52  wherein said applying a first copper undercoat comprises applying a paste comprises about 5-8 wt % glass frit. 
     
     
         54 . The method for forming a capacitor of  claim 52  wherein said glass frit is cadmium and bismuth free. 
     
     
         55 . The method for forming a capacitor of  claim 33  wherein said internal electrodes comprise a base metal. 
     
     
         56 . The method for forming a capacitor of  claim 55  wherein said base metal is selected from nickel, copper, titanium, tungsten and molybdenum. 
     
     
         57 . The method of forming a capacitor of  claim 56  wherein said internal electrodes comprise an alloy of nickel. 
     
     
         58 . The method of forming a capacitor of  claim 57  wherein said alloy comprises at least one material selected from the group consisting of Cu, Si, Ba, Ti, Mn, Cr, Co, and Al. 
     
     
         59 . The method of forming a capacitor of  claim 58  wherein said alloy comprises at least 95 wt % nickel. 
     
     
         60 . The method of forming a capacitor of  claim 33  wherein said lead frame comprises a material selected from phosphor bronze alloy 510, nickel iron alloy 42 copper iron alloy 194. 
     
     
         61 . The method of forming a capacitor of  claim 33  wherein said lead frame has a thickness of 76-500 microns. 
     
     
         62 . The method of forming a capacitor of  claim 33  wherein said soldering a first lead frame comprises soldering with a material which is lead free. 
     
     
         63 . The method of forming a capacitor of  claim 62  wherein said solder comprises 5-30 wt % antimony. 
     
     
         64 . A method for forming a capacitor comprising the steps of:
 providing a monolith comprising parallel conductive internal electrodes of alternating polarity with a dielectric between said conductive internal electrodes wherein said conductive internal electrodes comprise a precious metal;   applying a first silver undercoat in direct electrical contact with said conductive internal electrodes having a first polarity;   applying a second silver undercoat in direct electrical contact with said conductive internal electrodes having a second polarity;   applying a first flexible layer on said first silver undercoat;   applying a first solderable silver layer on said first flexible layer;   applying a second flexible layer on said second silver undercoat;   applying a second solderable silver layer on said second flexible layer;   soldering a first lead frame in electrical contact with said first silver solderable silver layer; and   soldering a second lead frame in electrical contact with said second silver solderable layer.   
     
     
         65 . The method of forming a capacitor of  claim 64  wherein said first flexible layer comprises silver particles in a polymeric matrix. 
     
     
         66 . The method of forming a capacitor of  claim 64  wherein said first flexible layer is formed by applying a paste and drying said paste. 
     
     
         67 . The method of forming a capacitor of  claim 66  wherein said paste comprises 77-79 wt % silver particles and 10-15 wt % organic resin in an organic solvent. 
     
     
         68 . The method of forming a capacitor of  claim 66  wherein said paste has a viscosity of at least 5 Pa-S to no more than about 50 Pa-S at 25° C. 
     
     
         69 . The method of forming a capacitor of  claim 68  wherein said paste has a viscosity of at least 7 Pa-S to no more than about 15 Pa-S at 25° C. 
     
     
         70 . The method for forming a capacitor of  claim 64  further comprising forming a solderable silver layer after said forming a flexible layer and prior to said soldering a first lead frame. 
     
     
         71 . The method for forming a capacitor of  claim 70  wherein said forming a solderable silver layer comprises applying a solution with a viscosity of 1-10 Pa-S at 25° C. 
     
     
         72 . The method for forming a capacitor of  claim 70  wherein said forming a solderable silver layer comprises applying a solution with a solids content of 30-60 wt %. 
     
     
         73 . The method for forming a capacitor of  claim 64  wherein said first silver undercoat or said second silver undercoat has a total silver film thickness of at least 1 micron to no more than 100 microns. 
     
     
         74 . The method for forming a capacitor of  claim 73  wherein said first silver undercoat or said second silver undercoat has a total silver film thickness of at least 10 micron to no more than 100 microns. 
     
     
         75 . The method for forming a capacitor of  claim 64  wherein said applying said first silver undercoat comprises applying a paste and drying said paste. 
     
     
         76 . The method for forming a capacitor of  claim 75  wherein said paste comprises at least about 75 wt % to no more than about 90 wt % silver and at least about 5 wt % to no more than about 20 wt % glass frit. 
     
     
         77 . The method for forming a capacitor of  claim 76  wherein said paste comprises about 5-8 wt % glass frit. 
     
     
         78 . The method for forming a capacitor of  claim 76  wherein said glass frit is cadmium and bismuth free. 
     
     
         79 . The method for forming a capacitor of  claim 64  wherein conductive internal electrodes comprises a material selected from silver, palladium, gold, platinum and alloys thereof. 
     
     
         80 . The method for forming a capacitor of  claim 79  wherein said conductive internal electrodes comprise silver-palladium or silver-palladium-platinum. 
     
     
         81 . The method of forming a capacitor of  claim 64  wherein said lead frame comprises a material selected from phosphor bronze alloy 510, nickel iron alloy 42 copper iron alloy 194. 
     
     
         82 . The method of forming a capacitor of  claim 64  wherein said lead frame has a thickness of 76-500 microns. 
     
     
         83 . The method of forming a capacitor of  claim 64  wherein said soldering a first lead frame comprises soldering with a material which is lead free. 
     
     
         84 . The method of forming a capacitor of  claim 83  wherein said solder comprises 5-30 wt % antimony.