U.S. patent application number 11/164682 was filed with the patent office on 2006-08-31 for anodizing valve metals by controlled power.
This patent application is currently assigned to Greatbatch, Inc.. Invention is credited to David Goad, Monica Kaforey, Yanming Liu, Barry Muffoletto, Neal Nesselbeck, Christina Scheuer, Ashish Shah, Joseph Spaulding.
Application Number | 20060191796 11/164682 |
Document ID | / |
Family ID | 35722394 |
Filed Date | 2006-08-31 |
United States Patent
Application |
20060191796 |
Kind Code |
A1 |
Muffoletto; Barry ; et
al. |
August 31, 2006 |
Anodizing Valve Metals By Controlled Power
Abstract
The present invention is directed to a method for anodizing
valve metal structures to a target formation voltage with a
controlled power source.
Inventors: |
Muffoletto; Barry; (Alden,
NY) ; Goad; David; (Buffalo, NY) ; Nesselbeck;
Neal; (Lockport, NY) ; Shah; Ashish; (East
Amherst, NY) ; Spaulding; Joseph; (Williamsville,
NY) ; Kaforey; Monica; (Orchard Park, NY) ;
Scheuer; Christina; (Amherst, NY) ; Liu; Yanming;
(Clarence Center, NY) |
Correspondence
Address: |
WILSON GREATBATCH TECHNOLOGIES, INC.
10,000 WEHRLE DRIVE
CLARENCE
NY
14031
US
|
Assignee: |
Greatbatch, Inc.
9645 Wehrle Drive
Clarence
NY
|
Family ID: |
35722394 |
Appl. No.: |
11/164682 |
Filed: |
December 1, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60633624 |
Dec 6, 2004 |
|
|
|
Current U.S.
Class: |
205/102 |
Current CPC
Class: |
C25D 11/04 20130101;
C25D 11/12 20130101; C25D 11/06 20130101; C25D 11/024 20130101;
H01G 9/0032 20130101; C25D 11/26 20130101 |
Class at
Publication: |
205/102 |
International
Class: |
C25D 5/18 20060101
C25D005/18 |
Claims
1. A method for anodizing a valve metal anode to a target formation
voltage, comprising the steps of: a) providing the valve metal
anode in an anodizing electrolyte; b) interconnecting a power
supply that generates an output from a source voltage and a source
current to provide an output power; c) subjecting the anode to the
output power; and d) regulating the power output so that the
difference between the output power and a desired power value is
adjusted toward zero until the target formation voltage is
reached.
2. The method of claim 1 including turning off the power supply for
a predetermined time between successive intervals of the anode
being subjected to the output power.
3. The method of claim 1 including providing the output power
applied to the anode based on one of the group consisting of
constant power, an increasing linear power, a decreasing linear
power, a linearly varied power within each pulse and between
pulses--increasingly and/or decreasingly, a non-linearly varied
power within each pulse and between pulses--increasingly and/or
decreasingly, a varied increasing power and a varied decreasing
power.
4. The method of claim 1 further comprising the step of turning off
the current and holding the voltage for a period of time sufficient
to allow the anodizing electrolyte to diffuse from the anode.
5. The method of claim 1 including providing the electrolyte having
a conductivity of about 10 .mu.S/cm to about 50,000 .mu.S/cm at
40.degree. C.
6. The method of claim 1 wherein the anodizing electrolyte
comprises an aqueous solution of ethylene glycol or an aqueous
solution of polyethylene glycol and H.sub.3PO.sub.4.
7. The method of claim 1 wherein the anode is a valve metal
selected from the group consisting of tantalum, aluminum, niobium,
titanium, zirconium, hafnium, and alloys thereof.
8. The method of claim 1 including pulsing the output power.
9. The method of claim 1 including forming the anode to over 200
volts.
10. The method of claim 1 including providing the output power at
below 50 Watts.
11. The method of claim 1 including providing the output power at
below 30 Watts.
12. The method of claim 1 including providing the output power at
below 10 Watts.
13. The method of claim 1 including agitating the anodizing
electrolyte.
14. The method of claim 1 further including the step of limiting
the current applied to the anode.
15. The method of claim 1 including adjusting the output power by
(a) measuring the source voltage and the source current to
calculate a measured power level, (b) comparing the measured power
level to a desired power level and (c) adjusting the source voltage
and the source current so the measured output power is at or near
the desired power level.
16. An anodized valve metal structure characterized as having been
anodized in an electrolyte to a target formation voltage by an
anodization protocol that subjects the valve metal structure to an
adjustable output power from a power supply, wherein the output
power was constantly adjusted so that the difference between the
output power and a desired power value approached zero until a
target formation voltage was reached.
17. The valve metal structure of claim 16 wherein the valve metal
structure was not subjected to a current for a predetermined time
frame.
18. The valve metal structure of claim 16 wherein the output power
is based on one of the group consisting of a constant power, an
increasing linear power, a decreasing linear power, a linearly
varied power within each pulse and between pulses--increasingly
and/or decreasingly, a non-linearly varied power within each pulse
and between pulses--increasingly and/or decreasingly, a varied
increasing power and a varied decreasing power.
19. The valve metal structure of claim 16 wherein the electrolyte
had a conductivity of about 10 .mu.S/cm to about 50,000 .mu.S/cm at
40.degree. C.
20. The valve metal structure of claim 16 wherein the valve metal
is selected from one of the group consisting of tantalum, aluminum,
niobium, titanium, zirconium, hafnium, and alloys thereof.
21. The valve metal structure of claim 16 wherein the output power
was pulsed.
22. The valve metal structure of claim 16 characterized as being
anodized to over 200 V.
23. The valve metal structure of claim 16 wherein the anodizing
electrolyte was agitated.
24. The valve metal structure of claim 16 wherein the output power
was obtained by (a) measuring the source voltage and the source
current to calculate a measure output power, (b) comparing the
measured output power to a desired power level and (c) adjusting
the source voltage and the source current so the measured output
power is at or near the desired power level.
Description
BACKGROUND OF THE INVENTION
[0001] In general, an electrolytic capacitor comprises an anode, a
cathode and a separator material. The separator material separates
the anode and the cathode. Impregnated in the separator material is
an ionically conductive electrolyte. The electrolyte typically
comprises water, organic solvent(s), and salt(s) of weak inorganic
and/or organic acids.
[0002] The anode is a valve metal. Valve metals include and are not
limited to aluminum, tantalum, niobium, titanium, zirconium,
hafnium and alloys thereof. The valve metals can be in any
conventional form. Examples of such forms include and are not
limited to etched foil, sintered powders, or other porous structure
forms. As an anode, the valve metal has its exterior surface coated
with a film of its corresponding oxide to serve as a
dielectric.
[0003] The oxide film is formed by anodizing the valve metals in an
appropriate anodizing electrolyte. The oxide film thickness
increases in accordance with the anodizing voltage applied to it
during the anodization process. The desired oxide film thickness is
determined by numerous factors. Some of those factors include and
are not limited to the capacitor working voltage, operating
temperature and other performance requirements.
[0004] The maximum anodizing voltage and the quality of the oxide
formed depend on the valve metal material, the anodizing
electrolyte composition, and the anodizing protocol. The anodizing
protocol refers to a series of voltage/current sequences and
profiles.
[0005] It is believed the anodization protocols that promote
locally excessive heating and insufficient material transport in
porous valve metal anode bodies cause breakdown during anodization
or poor anode electrical properties. The poor anode electrical
properties include high DC leakage. There have been numerous
attempts to solve these problems by altering the anodization
protocol. Some of the prior anodization protocols that have been
historically used and disclosed in recent patents include:
controlling the anodizing current density; mechanical, sonic, or
ultrasonic agitation of the electrolyte; anodizing by combining
control of voltage/current and controlled rest steps (U.S. Pat. No.
6,231,993 to Stephenson et al.); and controlled pulses of the
voltage/current (U.S. Pat. No. 6,802,951 to Hossick-Schott).
[0006] FIG. 1 illustrates an example of a prior anodization
protocol that is disclosed in U.S. Pat. No. 6,802,951. In FIG. 1,
the current (2) is maintained and the power (4) increases over
time. The anodizing protocol described in the '951 patent is
adequate for low voltage anodization because there are few oxide
defects, gray-outs, and early anodizing breakdown is generally not
a problem. The same results are not always obtainable for high
voltage anodization protocols. High voltage anodization is when the
anodizing voltage increases to over 200 volts during the course of
the anodization protocol. During a high voltage anodization
protocol, temperature in the porous valve metal anode increases.
The locally excessive temperature promotes oxide defects, gray-out,
and early anodizing breakdown in the anodes. Such results are
undesirable.
[0007] Another anodization protocol that is an obvious variation of
FIG. 1 is also disclosed in the '951 patent. In the '951 patent,
Hossick-Schott disclosed and claimed an anodization protocol having
(1) the voltage rise to a predetermined level; (2) when the voltage
rises the current remains constant, (3) when the voltage reaches a
predetermined level the current decreases; and (4) when the current
and/or voltage are rising, being maintained or decreasing, the
electrolyte composition is agitated.
[0008] What has been needed is another method for manufacturing a
valve metal anode such as the kind typically used in an
electrolytic capacitor. Particularly, it is desirable to provide
valve metal anodes with dielectric coatings having improved oxide
quality and high breakdown voltages.
[0009] An alternative anodization (formation) protocol for high
voltage sintered tantalum anodes is disclosed by Stephenson et al.
in U.S. Pat. No. 6,231,993. The '993 patent is assigned to Wilson
Greatbatch Ltd., the assignee for this application. Stephenson et
al. disclose (bracketed material added for clarity) the following
anodization protocol, which is partially illustrated in FIG. 2:
[0010] An exemplary formation protocol for a sodium reduced
tantalum powder pellet is as follows. Exemplary sodium reduction
tantalum pellets are available from H.C. Starck Inc., Newton, Mass.
under the "NH" family designation. In this exemplary protocol, the
pellet has a weight of about eight grams and the desired target
formation voltage is 231 volts. The formation electrolyte is of
polyethylene glycol, de-ionized water and H.sub.3PO.sub.4 having a
conductivity of about 2,500 .mu.S[/cm] to about 2,600 .mu.S[/cm] at
40.degree. C. The formation protocol is as follows:
[0011] 1. The power supply is turned on at an initial current [2a]
of 80 mA until the voltage [4a] reached 75 volts. The power supply
is then turned off [5a] for about three hours.
[0012] 2. The power supply is turned back on [with the current 2b
set] at 80 mA, [and the voltage 4b which is initially at] 75 volts
and [rises] to 115 volts. The power supply is then turned off [5b]
for about three hours.
[0013] 3. The power supply is turned back on [with the current 2c
set] at 49 mA, [and the voltage 4c which is initially at] 115 volts
and [rises] to 145 [volts]. The power supply is then turned off
[5c] for about three hours.
[0014] 4. The power supply is turned back on [with the current 2d
set] at 49 mA, [and the voltage 4d which is initially set at] 145
volts and [rises] to 175 [volts]. The power supply is then turned
off [5d] for about three hours.
[0015] 5. The power supply is turned back on [with the current 2e
set] at 40 mA, [and the voltage 4e which is initially set at] 175
volts and [rises] to 205 [volts]. The power supply is then turned
off [5e] for about three hours.
[0016] 6. The power supply is turned back on [with the current 2f
set] at 36 mA, [and the voltage 4f which is initially set at] 205
volts and [rises] to 225 [volts]. The power supply is then turned
off [5f] for three hours.
[0017] 7. The power supply is turned back on [with the current 2g
set] at 36 mA, [and the voltage 4g is which is initially set] at
205 volts and [rises] to 231 [volts]. The pellet is held at 231
volts for about one hour to complete the formation process. The
anodized pellet is then rinsed and dried.
[0018] If desired, the formation process is periodically
interrupted and the anodized pellet is subjected to a heat
treatment step. This consists of removing the anode pellet from the
anodization electrolyte bath. The anode pellet is then rinsed and
dried followed by heat treatment according to the procedure
described by D. M. Smyth et al., "Heat-Treatment of Anodic Oxide
Films on Tantalum", Journal of the Electrochemical Society, vol.
110, No. 12, pp. 1264-1271, December 1963.
[0019] The anodization protocol illustrated in FIG. 2 controls the
current and decreases the heat generated in comparison to the
protocol illustrated in FIG. 1. By decreasing the heat, the FIG. 2
anodization protocol obtains an anode having decreased DC
leakage.
[0020] However, there is a desire to find alternative anodization
protocols to obtain similar results in relation to the FIG. 2
protocol, but that can be obtained at a faster rate.
SUMMARY OF THE INVENTION
[0021] The present invention is directed to an anodization protocol
for valve metal structures. The anodization protocol calls for
valve metal structures to be positioned in an anodizing
electrolyte, and a supply system is electrically interconnected to
the valve metal structures. The supply system provides a source
voltage, a source current, and a controlled power. The supply
system can be any device that provides the controlled power. The
anodizing protocol subjects the valve metal structure to (a) the
source current, (b) the formation (source) voltage and (c) the
controlled power level. The power is controlled to decrease
excessive heating in the structure during anodization. The present
invention also includes the components for performing the
method.
[0022] The anodization protocol of the present invention provides
acceptable anodizing voltage and oxide quality at a desired rate in
relation to the prior art protocols.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 illustrates a representative sample of the anodizing
protocol disclosed in many prior art references.
[0024] FIG. 2 illustrates a representative sample of the anodizing
protocol disclosed in U.S. Pat. No. 6,231,993 to Stephenson et
al.
[0025] FIG. 3a illustrates an electrical schematic of the present
invention.
[0026] FIG. 3b illustrates a flow chart of the supply system of the
present invention.
[0027] FIGS. 4 to 13 illustrate different controlled power
protocols of the present invention.
[0028] FIG. 14 illustrates the source voltage and the source
current during the anodization on-time period.
DETAILED DESCRIPTION OF THE INVENTION
[0029] The present invention is directed to an anodization protocol
for valve metals 14. FIG. 3a illustrates some of the components
used for the anodization protocol. The first component is a supply
system 10. The supply system 10 provides controlled power, a source
current and a source voltage. The controlled power, the source
current and the source voltage are collectively referred to as
"output". The supply system's 10 output traverses a first
electrical conduit 202 to current limiting devices 12A, 12B and
12C. Each current limiting device can alter a portion of the supply
system's 10 output if the current exceeds a predetermined current
level. Each current limiting device 12A, 12B and 12C delivers an
altered output, which may or may not be altered in relation to the
output, through a second electrical conduit 203 to the anode(s) 14
associated with the respective current limiting device 12A, 12B and
12C. The anode(s) 14 are submerged in an anodizing electrolyte
within a formation tank(s) 16. A cathode 18 is positioned in each
formation tank 16 and receives a resulting output from the anode
and/or the electrolyte. The cathode 18 directs the resulting output
through a third electrical conduit 204 to the supply system 10.
[0030] This anodization protocol controls the power and current
with or without brief interruptions. The anodization protocol
offers the following advantages over the prior art: 1) controlled
power throughout the course of anodizing to decrease and/or avoid
excessive heating of the anode; 2) short anodizing time; and 3)
smooth change in current and power that avoids disruptive changes
in the current and voltage. The claimed anodization protocol also
results in desired anode electrical properties. Those desired
electrical properties include and are not limited to desired DC
leakage, a stable shelf life, desired charge/discharge energy
efficiency and capacitance, and desired stability during the
anode's operating life. These properties are desired for critical
applications. One such critical application is implantable
cardioverter defibrillators.
[0031] The Supply System 10 and the Output
[0032] The voltage 30 applied to an anode increases with anodizing
time, and the current 32 decreases at the same time, as illustrated
in FIG. 14. The power 34 (illustrated in FIGS. 4 to 13) received by
an anode is controlled for a desired power level(s) at specific
times. The desired power level(s) is designed not to overheat the
valve metal 14 (illustrated in FIGS. 3a and 3b) and simultaneously
obtain a desired DC leakage for the anode. This output control is
smooth and does not interrupt the anodizing process. The control is
accomplished through electronics that one of ordinary skill in the
power fields can manufacture and conforms to the flow chart
illustrated in FIG. 3b.
[0033] The supply system 10 has a power control unit 100, a
voltmeter 200, an ampmeter 240, a multiplier 206, and a difference
unit 212. The voltmeter 200 measures the output's voltage that
traverses the first conduit 202. The voltmeter 200 transmits the
voltage measurement 208 to the multiplier 206.
[0034] The ampmeter 240 measures the current that traverses the
first conduit 202. The ampmeter 240 transmits the current
measurement 205 to the multiplier 206.
[0035] The multiplier 206 computes the measured power value 210.
For example, the multiplier 206 may multiply the current
measurement 205 and the voltage measurement 208 to obtain a
measured power value 210. The multiplier 206 transmits the measured
power value 210 to a difference unit 212.
[0036] The difference unit 212 (which could also be a part of the
multiplier 206) also receives a desired power value 214. The
desired power value 214 can be pre-programmed into the difference
unit 212 or alternatively inputted by the user or any third party
who desires to input the desired power value 214 for the anode
14.
[0037] The difference unit 212 compares the desired power value 214
to the measured power value 210. If the difference unit 212
calculates that the difference between the desired power value 214
and the measured power value 210 is not zero, the difference unit
212 transmits a first signal 216 to the power control unit 100. In
response to the first signal 216, the power control unit 100
adjusts the power control unit's output 202 by adjusting the
current and/or the voltage so the difference between the desired
power value 214 and the measured power value 210 equals or is
adjusted toward zero.
[0038] Alternatively if the difference unit 212 calculates that the
difference between the desired power value 214 and the measured
power value 210 is zero, the difference unit 212 transmits a second
signal 218 to the power control unit 100. The second signal 218
instructs the power control unit not to alter the power supply
output in conduit 202. It is doubtful the second signal 218 will
ever be used since the power supply output in conduit 202 is
normally constantly changing to obtain the desired power value.
Additionally, the second signal 218 may not even be a transmitted
signal.
[0039] Other Components
[0040] The current limiting devices 12A, 12B and 12C receive the
output from the electrical conduit 202. The current limiting
devices are designed to ensure the current that is eventually
transmitted to the anodes does not exceed a predetermined value.
The current limiting devices can be a resistor, a fuse, or any
other type of device that can limit the current. If the current
limiting device limits the current passing through it or allows the
current to pass through it without altering the current, the
current limiting device 12A, 12B and 12C transmits what is referred
to as the altered output through the second conduit 203. The
specific limitation of the current varies depending on the desired
anode properties.
[0041] The valve metal material 14 receives the altered output from
the second conduit 203. As illustrated in FIG. 3a, there can be one
or more (preferably one) valve metal anode(s) interconnected to the
second conduit 203 extending from each current limiting device 12A,
12B and 12C. Each valve metal anode 14 and/or set of anodes 14 is
positioned within the formation tank (16). There can be one or more
formation tanks 16 in the anodization protocol. Each tank 16
contains an anodizing electrolyte.
[0042] The anodizing (formation) electrolyte can be any
conventional anodizing electrolyte. Examples of effective anodizing
electrolytes are disclosed in commonly assigned U.S. Pat. No.
6,231,993 to Stephenson et al., which is incorporated herein by
reference. In particular, the electrolyte can be an aqueous
solution of ethylene glycol or an aqueous solution of polyethylene
glycol and H.sub.3PO.sub.4. An exemplary formation electrolyte can
comprise 10-80 volume percent polyethylene glycol (PEG400) plus
0.1-10 volume percent H.sub.3PO.sub.4 and de-ionized water having a
conductivity of about 10 .mu.S/cm to about 50,000 .mu.S/cm at
40.degree. C. Alternatively, other electrolyte compositions can be
used that are designed to obtain desired anode properties.
[0043] The cathode 18 is positioned in each tank 16. The cathode 18
returns the resulting output to the supply system 10. The resulting
output is the current, voltage and power applied to the anode
and/or the electrolyte.
[0044] For better oxide quality, the anodization protocol may
incorporate a timing mechanism 98 within a circuitry area 99. The
circuitry area 99 is the area between and/or including the supply
system 10 and the valve metal 14--but not including the valve metal
itself. The timing mechanism 98 provides a rest time 50 during the
anodization protocol in which the anode 14 is not subject to any
controlled power, current or voltage, as illustrated in FIGS. 4 to
13. The rest time 50 can be obtained by the timing mechanism
turning on and off a switch, not shown, along the conduit(s) that
transports the current, voltage and power to the anodes 14.
[0045] The "on-times" (when the anode 14 receives the desired
power, current and voltage) and "off-times" can range from seconds
to hours. The on-times and off-times can be the same or different,
preferably the off-times are shorter than the on-times. The
on-times and the off-times can be fixed or varied during the course
of anodizing.
[0046] Alternatively, the anodes can be anodized continuously. That
means the anodizing protocol has no rest or off-time throughout the
entire anodization protocol.
[0047] The anodizing methods of the present invention apply to all
valve metals for electrolytic capacitor anodes. The valve metal
anodes include and are not limited to etched foils, pressed and
sintered powder bodies, or other forms of porous structures. The
anodizing methods of the present invention are particularly useful
for anodizing large and high voltage sintered powder anodes. Such
anodes are used in tantalum electrolytic capacitors.
[0048] FIGS. 4 to 13 illustrate some examples of the anodizing
protocols of the present invention. The x-axis in the figures can
be time or voltage. The controlled power 34 can also be applied to
the anode within the following protocol to obtain the desired
decreased DC leakage:
[0049] a) Constant power 34 anodizing with constant on-times and
off-times 50 at a set power value, as illustrated in FIG. 4.
[0050] b) Constant power 34 anodizing with varied on-time and
constant off-times 50, as shown in FIG. 5.
[0051] c) Constant power 34 within each pulse, varied power between
pulses with constant on-times and off-times 50, as exemplified in
FIG. 6.
[0052] d) Constant power 34 within each pulse, varied power between
pulses, varied on-time and constant off-times 50, as illustrated in
FIG. 7.
[0053] e) Linearly varied power 34 within each pulse and between
pulses, and constant on-times and off-times 50, as shown in FIG.
8.
[0054] f) Linearly varied power 34 with each pulse and between
pulses, varied on-time, and constant off-times 50, as illustrated
in FIG. 9.
[0055] g) Non-linearly varied power 34 within each pulse and
between pulses, constant on-times and off-times 50, as illustrated
in FIG. 10.
[0056] h) Non-linearly varied power 34 within each pulse and
between pulses, varied on-time, and constant off-times 50, as shown
in FIG. 11.
[0057] i) Varied (increased) power 34 within each pulse, constant
peak power, and constant on-time and off-times 50, as exemplified
in FIG. 12.
[0058] j) Varied (increased) power 34 within each pulse, varied
(increased) peak power, and constant on-time and off-times 50, as
shown in FIG. 13.
[0059] The valve metals formed in accordance to the present
invention are for anodes able to handle more than 200 volts without
"gray-out" or significant breakdown during anodization, and
acceptable anode electrical properties.
[0060] To improve electrolyte and heat transport from the anode to
the bulk electrolyte, the electrolyte can be agitated during the
anodizing. The agitation can be created by any conventional
agitation device 400. Examples of agitation devices 400 include:
mechanical stirrers, ultrasonic agitation devices or subsonic
agitation devices, and moving the anodes. All of these agitation
devices and methods are known to those of ordinary skill in the
art.
EXAMPLE
[0061] The anodization protocol of the present invention was
compared to a variation of the anodization protocol described by
Stephenson et al. in U.S. Pat. No. 6,231,993. The valve metal
pellets were taken from the same lot of Greatbatch, Inc.'s regular
production line and had similar weights--averaged 7.3 grams. The
electrolyte was 15% PEG400 and 85% water with a sufficient amount
of phosphoric acid added to provide a conductivity of 2550 .mu.S/cm
at 40.degree. C. Each pellet was positioned within a formation tank
that could contain 300 ml of electrolyte, and were maintained at
40.degree. C.
[0062] For this example, the anodes were formed to 240 volts in
accordance to the two protocols.
[0063] Prior Art Anodization Protocol:
[0064] A. 150 mA to 75 volts, then 1 hour rest;
[0065] B. 150 mA to 115 volts, then 1 hour rest;
[0066] C. 94 mA to 145 volts, then 1 hour rest;
[0067] D. 94 mA to 175 volts, then 1 hour rest;
[0068] E. 74 mA to 205 volts, then 1 hour rest;
[0069] F. 66 mA to 225 volts, then 1 hour rest;
[0070] G. 66 mA to 235 volts, then 1 hour rest; and
[0071] H. 66 mA to 240 volts.
[0072] The prior art anodization protocol took 28.25 hours, and the
anode's DC leakage was 0.91 nA/.mu.FV.
[0073] Present Invention Anodization Protocol
[0074] The anodization protocol used in this example is referred to
as the 17 watt constant power pulse protocol. That protocol has a
pulse limited to a maximum power of 17 watts and a maximum current
of 150 mA. The power-on period was for 50 seconds, and the
power-off period was for 10 seconds. No additional rests were
taken.
[0075] The resulting anode was formed in 22.8 hours and the anode's
DC leakage was 0.92 nA/.mu.FV.
[0076] It is appreciated that various modifications to the present
inventive concepts described herein may be apparent to those of
ordinary skill in the art without departing from the spirit and
scope of the present invention as defined by the herein appended
claims.
* * * * *