Tantalum Wire Used for Anode Lead of Tantalum Capacitor and Manufacturing Method Thereof

Abstract

The present invention relates to a tantalum wire for anode lead of tantalum capacitors, characterized in that the cross section of the tantalum wire is approximate rectangular or regular rectangular. The present invention also relates to a process for manufacturing the tantalum wire, comprising the steps of: providing feedstock tantalum wire; subjecting the feedstock tantalum wire to heat treatment; subjecting the heat treated tantalum wire to surface pretreatment to form an oxide membrane on the surface-pretreated tantalum wire; rolling the surface-pretreated tantalum wire by lubricating with lubricant oil to make the cross section of the rolled tantalum wire being approximate rectangular or regular rectangular; subjecting the tantalum wire to final annealing.

1 . A tantalum wire for anode lead of tantalum capacitors, characterized in that the cross section of the tantalum wire is approximate rectangular or regular rectangular. 
     
     
         2 . The tantalum wire according to  claim 1 , wherein the leakage current of the tantalum wire is not more than 0.95 μA/cm 2 , preferably not more than 0.90 μA/cm 2 , more preferably not more than 0.80 μA/cm 2 , further preferably not more than 0.60 μA/cm 2 , furthermore preferably not more than 0.50 μA/cm 2 , particularly preferably not more than 0.30 μA/cm 2 , more particularly preferably not more than 0.20 μA/cm 2 , most preferably not more than 0.15 μA/cm 2 , and also preferably not more than 0.13 μA/cm 2 . 
     
     
         3 . The tantalum wire according to  claim 1 , wherein the pullout strength of the tantalum wire is 150 MPa or more, preferably 160 MPa or more, more preferably 170 MPa or more, more preferably 175 MPa or more, further preferably 180 MPa or more, particularly preferably 185 MPa or more. 
     
     
         4 . A process for manufacturing the tantalum wire according to  claim 1 , comprising the steps of:
 (1) providing feedstock tantalum wire;   (2) subjecting the feedstock tantalum wire to heat treatment;   (3) subjecting the heat treated tantalum wire to surface pretreatment to form an oxide membrane on the surface-pretreated tantalum wire;   (4) rolling the surface-pretreated tantalum wire while lubricating with lubricant oil to make the cross section of the rolled tantalum wire being approximate rectangular or regular rectangular;   (5) subject the tantalum wire to final annealing.   
     
     
         5 . The process according to  claim 4 , wherein the heat treatment step is vacuum annealing at a temperature of 1000-1450° C., preferably 1200-1400° C., and holding for 30-60 minutes, preferably 40-60 minutes. 
     
     
         6 . The process according to  claim 4 , wherein the surface pretreatment step is carried out at high temperature in oxygen atmosphere, preferably at a temperature of 500-700° C. in 99% pure oxygen for from 1 minute to 1 hour, preferably from 5 minutes to 30 minutes. 
     
     
         7 . The process according to  claim 4 , wherein the rolling step is multiple passes rolling, and the reduction rate of each pass is 20-95%, preferably 20-90%, more preferably 22-85%. 
     
     
         8 . The process according to  claim 4 , wherein annealing step is intervened during the rolling step to eliminate stress. 
     
     
         9 . The process according to  claim 4 , wherein the annealing step is vacuum annealing at a temperature of 1000-1450° C., preferably 1200-1400° C., and holding for 30-60 minutes, preferably 40-60 minutes. 
     
     
         10 . The process according to  claim 4 , wherein the tantalum wire is cleaned after the rolling step and before the final annealing step. 
     
     
         11 . The process according to  claim 4 , wherein the final annealing step is continuous wire drawing annealing with annealing temperature of 1600-2000° C., preferably 1700-1800° C. and wire drawing rate of 5-10 m/min. 
     
     
         12 . The process according to  claim 4 , wherein the lubricant oil is organic fluoro-chloro lubricant oil. 
     
     
         13 . The tantalum wire according to  claim 2 , wherein the pullout strength of the tantalum wire is 150 MPa or more, preferably 160 MPa or more, more preferably 170 MPa or more, more preferably 175 MPa or more, further preferably 180 MPa or more, particularly preferably 185 MPa or more.