U.S. patent application number 13/145209 was filed with the patent office on 2012-11-29 for tantalum wire used for anode lead of tantalum capacitor and manufacturing method thereof.
This patent application is currently assigned to Ningxia Orient Tantalum Industry Co., Ltd.. Invention is credited to Linghui Du, Guohua Qiu, Quinfeng Wan, Huifeng Wang, Yongxu Xie, Bing Zhao.
Application Number | 20120300362 13/145209 |
Document ID | / |
Family ID | 40838582 |
Filed Date | 2012-11-29 |
United States Patent
Application |
20120300362 |
Kind Code |
A1 |
Zhao; Bing ; et al. |
November 29, 2012 |
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.
Inventors: |
Zhao; Bing; (Shizuishan
City, CN) ; Du; Linghui; (Shizuishan City, CN)
; Xie; Yongxu; (Shizuishan City, CN) ; Wan;
Quinfeng; (Shizuishan City, CN) ; Wang; Huifeng;
(Shizuishan City, CN) ; Qiu; Guohua; (Shizuishan
City, CN) |
Assignee: |
Ningxia Orient Tantalum Industry
Co., Ltd.
Shizuishaan City
CN
|
Family ID: |
40838582 |
Appl. No.: |
13/145209 |
Filed: |
May 21, 2009 |
PCT Filed: |
May 21, 2009 |
PCT NO: |
PCT/CN09/00556 |
371 Date: |
September 23, 2011 |
Current U.S.
Class: |
361/302 ;
29/874 |
Current CPC
Class: |
B22F 2999/00 20130101;
B22F 2998/10 20130101; H01G 9/0029 20130101; C22C 1/045 20130101;
B22F 2998/10 20130101; B22F 2999/00 20130101; B21B 1/16 20130101;
Y10T 29/49204 20150115; B21B 1/18 20130101; B22F 5/12 20130101;
B22F 2003/248 20130101; B22F 3/24 20130101; B22F 2003/248 20130101;
B22F 3/02 20130101; B22F 2201/03 20130101; B22F 3/18 20130101; B22F
2003/248 20130101; H01G 9/048 20130101; H01G 9/012 20130101; H01G
9/052 20130101 |
Class at
Publication: |
361/302 ;
29/874 |
International
Class: |
H01G 4/35 20060101
H01G004/35; H01R 43/16 20060101 H01R043/16 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 20, 2009 |
CN |
200910000894.3 |
Claims
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 .mu.A/cm.sup.2,
preferably not more than 0.90 .mu.A/cm.sup.2, more preferably not
more than 0.80 .mu.A/cm.sup.2, further preferably not more than
0.60 .mu.A/cm.sup.2, furthermore preferably not more than 0.50
.mu.A/cm.sup.2, particularly preferably not more than 0.30
.mu.A/cm.sup.2, more particularly preferably not more than 0.20
.mu.A/cm.sup.2, most preferably not more than 0.15 .mu.A/cm.sup.2,
and also preferably not more than 0.13 .mu.A/cm.sup.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.degree. C.,
preferably 1200-1400.degree. 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.degree. 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.degree. C.,
preferably 1200-1400.degree. 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.degree. C., preferably 1700-1800.degree.
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.
Description
TECHNICAL FIELD
[0001] The present invention relates to tantalum wire used for
tantalum capacitor and manufacturing method thereof.
BACKGROUND ART
[0002] Tantalum capacitors have been widely used in fields of
telecommunication, computer, automobile, household appliance,
aerospace et al. Tantalum electrolytic capacitors manufactured with
tantalum powder as an anode and tantalum wire as anode lead have
the advantages of small volume, large electric capacity, high
degree of chip type, good reliability, and long service life, and
therefore can operate normally under extreme conditions under which
many other capacitors (such as ceramic, aluminum sheet capacitors,
etc.) cannot operate.
[0003] As to tantalum wire for anode lead of tantalum capacitors,
it is required to have high chemical purity, good surface finish
and precise dimensions, with its mechanical properties and
electronic properties satisfying the strict demands on capacitors.
For example, the specific demands on surface finish of tantalum
wire are as follows, the surface has no obvious defects such as
grooves, burrs, and sand holes, if observed under microscope of 60
magnification or more, and the specific requirement on electronic
properties is leakage current, which the smaller the better.
[0004] With the development on electronic techniques, the
requirements on the tantalum capacitors have been become
increasingly strict. Tantalum capacitors have been developed, step
by step, towards miniaturization, chip-type, and high capacity,
with the tantalum powder used having higher and higher specific
capacity. The above correspondingly restricts the sintering
temperature of anode pellet of tantalum capacitors. If the
sintering temperature is too high, the porosity of tantalum powder
is reduced largely, and thereby decreasing the specific capacity of
tantalum capacitors.
[0005] However, if conventional circular anode lead is used on
low-temperature sintered tantalum capacitors, the following
problems will arise, the anode lead made with circular tantalum
wire has small contact area with tantalum anode pellet due to its
relative small surface area, thereby leading to low contact
strength and excessive leakage current of tantalum capacitor, even
leading to the shedding of the tantalum wire from the anode pellet
which will result the failure of the tantalum capacitor. With
further development of miniaturization of tantalum capacitors, the
problem of low pullout strength of lead wire of tantalum capacitors
has more and more disadvantageous effect on the electronic
properties and reliability of tantalum capacitors.
[0006] Although it was suggested in the early 21.sup.th century
that tantalum wire of non-circular cross section was used to
replace present tantalum wire of circular cross section to solve
this problem. However, until now, among the tantalum capacitor
manufacturing techniques, almost all the tantalum wires are of
circular cross section. The reasons are as follows, none of the
manufacturers can produce special-shaped tantalum wires whose
chemical purity, surface finish, mechanical properties and
electronic properties can meet the requirements of tantalum
capacitors. In many cases, it is the surface finish, mechanical
properties and/or electronic properties cannot meet the strict
requirements of tantalum capacitors.
SUMMARY OF THE INVENTION
[0007] As to one or more problems existing in the prior art, the
present invention provides a special-shaped tantalum wire which
meets the strict requirements of anode lead of tantalum capacitors
and the manufacturing method thereof.
[0008] Particularly, the present invention provides tantalum wire
for anode lead of tantalum capacitors, characterized in that the
cross section of the tantalum wire is approximate rectangular or
regular rectangular.
[0009] The present invention also provides a process for
manufacturing tantalum wire, comprises the steps of: [0010] (1)
providing the feedstock tantalum wire; [0011] (2) subjecting the
feedstock tantalum wire to heat treatment; [0012] (3) subjecting
the heat treated tantalum wire to surface pretreatment to form an
oxide membrane on the treated tantalum wire; [0013] (4) rolling the
surface-pretreated tantalum wire which lubricated by lubrication to
make the cross section of the rolled tantalum wire being
approximate rectangular or regular rectangular; [0014] (5)
subjecting the tantalum wire to final annealing.
DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1: Photographs of the cross-section of tantalum wire
according to the present invention (100 times magnification);
[0016] FIG. 2: Schematic diagram of rolling the tantalum wire
according to the present invention.
EMBODIMENTS
[0017] It can be understood that above descriptions and following
embodiments are only demonstrative explanations. Those skilled in
the art can make various improvements, modifications or changes to
these embodiments, without deviating from the spirit and scope of
the invention.
[0018] In the present invention, the measurement of electronic
properties was conducted based on the method of GB3463-1995
tantalum wire, the National Standard of PRC; the property of
pullout strength was tested by the method of testing mechanical
property according to GB3463-1995 tantalum wire, after molded in
terms of following parameters: [0019] 1. Molding equipment:
automatic molding machine for tantalum electrolytic capacitor
[0020] 2. Shell type: E [0021] 3. Powder amount: 381-392 mg [0022]
4. Anode pellet size: 5.7.times.4.1.times.2.9 mm [0023] 5. Tantalum
wire embedment quantity: 1.6-1.9 mm [0024] 6. Density after
molding: 5.5-5.6 g/cm.sup.3:
[0025] In a preferred embodiment of the present invention, as to
electronic property, the leakage current of the tantalum wire
according to the invention is not more than 0.95 .mu.A/cm.sup.2,
preferably not more than 0.90 .mu.A/cm.sup.2, more preferably not
more than 0.80 .mu.A/cm.sup.2, further preferably not more than
0.60 .mu.A/cm.sup.2, furthermore preferably not more than 0.50
.mu.A/cm.sup.2, particularly preferably not more than 0.30
.mu.A/cm.sup.2, more particularly preferably not more than 0.20
.mu.A/cm.sup.2, more particularly preferably not more than 0.15
.mu.A/cm.sup.2, especially not more than 0.10 .mu.A/cm.sup.2.
[0026] In another preferred embodiment of the present invention, as
to mechanical property, the pullout strength of the tantalum wire
according to the present invention is 150 MPa or more, preferably
160 MPa or more, more preferably 170 MPa or more, further
preferably 175 MPa or more, furthermore preferably 180 MPa or more,
particularly preferably 185 MPa or more, more particularly
preferably 190 MPa or more, most preferably 195 MPa or more.
[0027] In another preferred embodiment of the present invention,
when the cross section of the tantalum wire is approximate
rectangular, the cross section size of the cross section is 0.5-4
mm long, preferably 1-3 mm long, with 0.015-1 mm wide, preferably
0.02-0.5 mm wide, and the two sides on the width direction are
curved
[0028] In another preferred embodiment of the present invention,
when the cross section of the tantalum wire is regular rectangular,
the cross section size of the cross section is 0.5-4 mm long,
preferably 1-3 mm long, 0.015-1 mm wide, preferably 0.02-0.5 mm
wide.
[0029] In a preferred embodiment of the present invention, the heat
treatment of feedstock tantalum wire is carried out by heating at
the recrystallization temperature or higher, preferably
1000-1450.degree. C., preferably 1200-1400.degree. C., and holding
for 30-60 minutes, preferably 40-60 minutes.
[0030] In an embodiment of the invention, the cross section of
feedstock tantalum wire is circular.
[0031] At the same time, in a preferred embodiment of the present
invention, in order to prevent the oxidation of wire material and
benefit the impurity evolution from the feedstock tantalum wire,
vacuum annealing can be employed. In a preferred embodiment of the
present invention, the vacuum degree of the vacuum annealing step
is greater than 5.0.times.10.sup.-2 Pa with leakage less than 0.5
Pa/min.
[0032] In a preferred embodiment of the present invention, in order
to prevent roll sticking during rolling of tantalum metal thereby
affecting the surface quality of special-shaped tantalum wire
product, circular tantalum wire is subjected to surface
pretreatment at high temperature in oxygen atmosphere.
[0033] In a preferred embodiment of the present invention, circular
tantalum wire is rolled using precision rolling mill. In further
preferred embodiment, pass reduction is 30-95% (thickness
reduction), and one or more pass(es) can be performed to the
desired size.
[0034] In a preferred embodiment of the present invention, in order
to prevent non-uniform lubrication during rolling thereby affecting
the surface quality of special-shaped tantalum wire product,
lubricant oil is employed for lubrication during rolling.
[0035] In a preferred embodiment of the present invention, the
lubricant oil is organic fluoro-chloro lubricant oil. In a
preferred embodiment of the present invention, working roll can be
grooved roller or flat roller.
[0036] In a preferred embodiment of the present invention, to
enhance rolling effect, special-shaped roll can be employed, such
as arc-shaped roll and convex roll.
[0037] In a preferred embodiment of the present invention, the
rolled special-shaped tantalum wire product is cleaned with
degreasing agent, and washed with clear water. At the meantime, if
desired, ultrasonic wave can be applied.
[0038] In a preferred embodiment of the present invention, the
rolled special-shaped tantalum wire product is annealed by heating
at the temperature of the recrystallization temperature or above,
using continuous wire drawing annealing. In further preferred
embodiment, to prevent the oxidation of wire, the operation is
carried out under the protection of inert gas, such argon.
[0039] In a preferred embodiment of the present invention, the
annealing temperature of the rolled special-shaped tantalum wire
product is 1600-2000.degree. C., and the rate is 5-10 m/min.
[0040] According to the present invention, the curvature of wire
reel should not be too large, otherwise, special-shaped tantalum
wire product will bend in a large extend, and therefore cannot meet
the requirements. In a preferred embodiment of the present
invention, the wire reel used has a diameter from .phi.200 mm to
.phi.300 mm.
Example 1
[0041] Circular tantalum wire having a diameter of 0.97 mm was
wound in a spool with the diameter of 300 mm, and placed into
annealing furnace. The furnace was evacuated with vacuum pump. When
the vacuum degree in the furnace reached to 5.0.times.10.sup.-2 Pa,
the furnace was electrically heated to a temperature of
1380.degree. C., hold for 60 minutes. After the heating was
stopped, the furnace was naturally cooled. When the furnace was
cooled to 180.degree. C., in order to accelerate cooling and
increase efficiency, inert gas such as argon could be introduced
into the furnace.
[0042] The annealed circular tantalum wire was subjected to surface
pretreatment in a muffle furnace. The annealed circular tantalum
wire was placed in a muffle furnace. After 99% high purity oxygen
was introduced into the furnace, the furnace was heated to
600.degree. C. and hold for 10 minutes, so that the circular
tantalum wire was subjected to surface pretreatment. The pretreated
circular tantalum wire was straightened and wound on a tray. The
whole tantalum wire should not be bended.
[0043] The tantalum wire wound on the tray was placed on
wire-releasing apparatus with tension, and was rolled using 12
rolls precision rolling machine. Organic fluoro-chloro lubricant
oil was used for lubrication during rolling.
[0044] During rolling, first pass was carried out with reduction
rate of 38%, with the size after rolling being 0.60.times.1.11 mm.
Second pass was carried out with reduction rate of 43%, with the
size after rolling being 0.34.times.1.36 mm. The surface of rolled
tantalum wire was with good surface finish, has no defects such as
rolling impressions, edge cracks, grooves or sand holes.
[0045] The rolled special-shaped tantalum wire was placed on a
wire-releasing apparatus with tension. The oil stains and other
impurities on the surface of the special-shaped tantalum wire was
washed with degreasing agent which was diluted to suitable
concentration and water, under the action of ultrasonic wave. The
tantalum wire was wound on wire-receiving apparatus. The cleaned
special-shaped tantalum wire was placed on a wire-releasing
apparatus with tension, subjected to continuous wire drawing
annealing. The annealing was 1750.degree. C., and the drawing rate
was 5 m/min. The tantalum wire was wound on wire-receiving
apparatus until the whole special-shaped tantalum wire on the
wire-releasing apparatus was all wound on the wire-receiving
apparatus, and thus the manufacture of special-shaped tantalum wire
is completed
Example 2
[0046] Feedstock (circular tantalum wire) has the diameter of 0.78
mm, and three passes rolling was conducted. The rest steps were the
same as described in Example 1. The dimension of each pass was
changed as follows:
.phi.0.78-0.43.times.1.19-0.27.times.1.22-0.23.times.1.24
Example 3
[0047] Feedstock (circular tantalum wire) has the diameter of 0.65
mm, and three passes rolling was conducted. The rest steps were the
same as described in Example 1. The dimension of each pass was
changed as follows:
.phi.0.65-0.37.times.1.09-0.20.times.1.11-0.15.times.1.12
Comparative Example 1
[0048] Feedstock (circular tantalum wire) has the diameter of 0.97
mm. Surface pretreatment was not carried out. White oil for rolling
was employed during rolling course to lubricate and cool. The rest
steps were the same as described in Example 1.
Comparative Example 2
[0049] Feedstock (circular tantalum wire) has the diameter of 0.78
mm. Surface pretreatment was not carried out. White oil for rolling
was employed during rolling course to lubricate and cool. The rest
steps were the same as described in Example 2.
Comparative Example 3
[0050] Feedstock (circular tantalum wire) has the diameter of 0.65
mm. Surface pretreatment was not carried out. White oil for rolling
was employed during rolling course to lubricate and cool. The rest
steps were the same as described in Example 3.
Comparative Example 4
[0051] Qualified circular tantalum wires for anode lead of tantalum
capacitors with same cross section area as the special-shaped
tantalum wire of 0.34.times.1.36 mm, 0.23.times.1.24 mm and
0.15.times.1.12 mm were employed, with their diameters being
.phi.0.767 mm, .phi.0.603 mm and .phi.0.463 mm, respectively.
[0052] The properties of circular tantalum wires and special-shaped
tantalum wires in the examples were tested as follows:
TABLE-US-00001 TABLE 1 Pullout strength of circular tantalum wires
and special-shaped tantalum wire in the examples Cross- Pullout
Dimension section Pullout strength No. (mm) area (mm.sup.2) force
(N) (MPa) Notes 1 0.34 .times. 1.36 0.462 86.5 187.3 Example 1 2
.phi.0.767 0.462 65.1 140.9 Comparative Example 4 3 0.23 .times.
1.24 0.285 55.6 195.0 Example 2 4 .phi.0.603 0.285 40.6 142.5
Comparative Example 4 5 0.15 .times. 1.12 0.168 33.9 201.6 Example
3 6 .phi.0.463 0.168 24.4 145.3 Comparative Example 4
TABLE-US-00002 TABLE 2 Electronic properties of circular tantalum
wires and special-shaped tantalum wire in the examples Leakage
current No. Dimension (mm) (.mu.A/cm.sup.2) Notes 1 0.34 .times.
1.26 0.10 Example 1 2 0.34 .times. 1.26 1.26 Comparative Example 1
3 0.23 .times. 1.24 0.09 Example 2 4 0.23 .times. 1.24 0.98
Comparative Example 2 5 0.15 .times. 1.12 0.11 Example 3 6 0.15
.times. 1.12 1.26 Comparative Example 3
* * * * *