Capacitor containing aluminum anode foil anodized in low water content glycerine-phosphate electrolyte

Abstract

A capacitor comprising an aluminum anode and a dielectric layer comprising phosphate doped aluminum oxide and process for making the capacitor. Furthermore, the capacitor is formed by the process of: forming an aluminum plate; pre-hydrating the aluminum; contacting the plate with an anodizing solution comprising glycerine, 0.1 to 1.0%, by weight, water and 0.01 to 0.5%, by weight, orthophosphate; applying a voltage to the aluminum plate and determining an initial current; maintaining the first voltage until a first measured current is no more than 50% of the initial current; increasing the voltage and redetermining the initial current; maintaining the increased voltage until a second measured current is no more than 50% of the redetermined initial current, and continuing the increasing of the voltage and maintaining the increased voltage until a final voltage is achieved.

Claimed is:  
     
         1 . A process for preparing a capacitor comprising: 
 fabricating an aluminum plate;    pre-hydrating said aluminium plate;    contacting said plate with an anodizing solution comprising glycerine, about 0.1 to about 2.0%, by weight, water and about 0.01 to about 0.5%, by weight, orthophosphate;    applying a voltage to said aluminum plate of at least about 220 volts.    
     
     
         2 . The process for preparing a capacitor of  claim 1  further comprising the step of: 
 etching said aluminum plate prior to said pre-hydrating of said aluminum plate.  
 
     
     
         3 . The process for preparing a capacitor of  claim 1  wherein said voltage is applied in increasing increments with an age time between each said increment.  
     
     
         4 . The process for preparing a capacitor of  claim 3  wherein said increments are less than about 75 volts.  
     
     
         5 . The process for preparing a capacitor of  claim 4  wherein said increments are at least about 20 V to no more than about 50 V.  
     
     
         6 . The process for preparing a capacitor of  claim 5  wherein said age time is sufficient for the current to decrease to from about 1 to about 50% of an initial current.  
     
     
         7 . The process for preparing a capacitor of  claim 6  wherein said age time is sufficient for the current to decrease to from about 10 to about 30% of said initial current.  
     
     
         8 . The process for preparing a capacitor of  claim 7  wherein said age time is sufficient for the current to decrease to about 20% of said initial current.  
     
     
         9 . The process for preparing a capacitor of  claim 1  wherein said anodizing solution is at a temperature of about 25° C. to about 125° C.  
     
     
         10 . The process for preparing a capacitor of  claim 9  wherein said anodizing solution is at a temperature of about 80° C. to about 105° C.  
     
     
         11 . The process for forming a capacitor of  claim 1  wherein said anodizing solution comprises about 0.01 to about 0.1%, by weight, soluble orthophosphate.  
     
     
         12 . The process for forming a capacitor of  claim 1  wherein said soluble orthophosphate is selected from a group consisting of ammonium phosphate, alkali metal phosphate, amine phosphate or mixtures thereof.  
     
     
         13 . The process for forming a capacitor of  claim 1  wherein said soluble orthophosphate is selected from a group consisting of mono-sodium phosphate, di-potassium phosphate, and sodium potassium phosphate.  
     
     
         14 . The process for forming a capacitor of  claim 1  wherein said soluble orthophosphate is selected from a group consisting of mono-ammonium phosphate and di-ammonium phosphate.  
     
     
         15 . The process for forming a capacitor of  claim 1  wherein said anodising solution comprises about 0.1 to about 1%, by weight, water.  
     
     
         16 . A capacitor prepared by the process of  claim 1 .  
     
     
         17 . A device comprising a capacitor of  claim 16 .  
     
     
         18 . The device of  claim 17  wherein said device is an implantable medical device.  
     
     
         19 . A process for preparing a capacitor comprising: 
 fabricating an aluminum plate;    pre-hydrating said aluminium plate;    contacting said plate with an anodizing solution comprising glycerine, about 0.1 to about 2.0%, by weight, water and about 0.01 to about 0.5%, by weight, orthophosphate;    applying a voltage to said aluminum plate and determining an initial current;    maintaining said first voltage until a first measured current is no more than 50% of said initial current;    increasing said voltage and redetermining said initial current;    maintaining said increased voltage until a second measured current is no more than about 50% of said redetermined initial current, and    continuing said increasing said voltage and said maintaining said increased voltage until a final voltage is achieved.    
     
     
         20 . The process for preparing a capacitor of  claim 19  further comprising the step of: 
 etching said aluminum plate prior to said pre-hydrating of said aluminum plate.  
 
     
     
         21 . The process for preparing a capacitor of  claim 19  wherein said final voltage is above 220 volts.  
     
     
         22 . The process for preparing a capacitor of  claim 19  wherein said voltage is increased by no more than about 75 volts.  
     
     
         23 . The process for preparing a capacitor of  claim 22  wherein said voltage is increased by at least about 20 V to no more than about 50 V.  
     
     
         24 . The process for preparing a capacitor of  claim 23  wherein said first measured current or said second measured current is from about 1 to about 50% of said initial current.  
     
     
         25 . The process for preparing a capacitor of  claim 24  wherein said first measured current or said second measured current is from about 10 to about 30% of said initial current.  
     
     
         26 . The process for preparing a capacitor of  claim 25  wherein said first measured current or said second measured current is about 20% of said initial current.  
     
     
         27 . The process for preparing a capacitor of  claim 19  wherein said anodizing solution is at a temperature of about 25° C. to about 125° C.  
     
     
         28 . The process for preparing a capacitor of  claim 27  wherein said anodizing solution is at a temperature of about 80° C. to about 105° C.  
     
     
         29 . The process for forming a capacitor of  claim 19  wherein said anodizing solution comprises about 0.01 to about 0.1%, by weight, soluble orthophosphate.  
     
     
         30 . The process for forming a capacitor of  claim 19  wherein said soluble orthophosphate is selected from a group consisting of ammonium phosphate, alkali metal phosphate, amine phosphate and mixtures thereof.  
     
     
         31 . The process for forming a capacitor of  claim 19  wherein said soluble orthophosphate is selected from a group consisting of mono-sodium phosphate, di-potassium phosphate, and sodium potassium phosphate.  
     
     
         32 . The process for forming a capacitor of  claim 19  wherein said soluble orthophosphate is selected from a group consisting of mono-ammonium phosphate and di-ammonium phosphate.  
     
     
         33 . A capacitor prepared by the process of  claim 19 .  
     
     
         34 . A device comprising a capacitor of  claim 33 .  
     
     
         35 . The device of  claim 34  wherein said device is an implantable medical device.  
     
     
         36 . A capacitor comprising: 
 an etched aluminum anode and a dielectric layer comprising phosphate doped aluminum oxide;    prepared by the process of:    forming an aluminum plate;    pre-hydrating said aluminium plate;    contacting said plate with an anodizing solution comprising glycerine, about 0.1 to about 2.0%, by weight, water and about 0.01 to about 0.5%, by weight, orthophosphate;    applying a voltage to said aluminum plate and determining an initial current;    maintaining said first voltage until a first measured current is no more than about 50% of said initial current;    increasing said voltage and redetermining said initial current;    maintaining said increased voltage until a second measured current is no more than 50% of said redetermined initial current, and    continuing said increasing said voltage and said maintaining said increased voltage until a final voltage is achieved.