US3321389A - Method of anodically etching aluminum foils at elevated temperatures in an electrolyte including chloride and sulfate ions - Google Patents
Method of anodically etching aluminum foils at elevated temperatures in an electrolyte including chloride and sulfate ions Download PDFInfo
- Publication number
- US3321389A US3321389A US383960A US38396064A US3321389A US 3321389 A US3321389 A US 3321389A US 383960 A US383960 A US 383960A US 38396064 A US38396064 A US 38396064A US 3321389 A US3321389 A US 3321389A
- Authority
- US
- United States
- Prior art keywords
- etching
- aluminum foil
- percent
- aqueous
- metal
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
- 229910052782 aluminium Inorganic materials 0.000 title claims description 40
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 title claims description 38
- 238000005530 etching Methods 0.000 title claims description 32
- 239000011888 foil Substances 0.000 title claims description 29
- 238000000034 method Methods 0.000 title claims description 13
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 title description 9
- 239000003792 electrolyte Substances 0.000 title description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 title 1
- 229910052751 metal Inorganic materials 0.000 claims description 20
- 239000002184 metal Substances 0.000 claims description 20
- 230000015572 biosynthetic process Effects 0.000 claims description 8
- 239000003990 capacitor Substances 0.000 claims description 7
- 229910001514 alkali metal chloride Inorganic materials 0.000 claims description 4
- 229910052936 alkali metal sulfate Inorganic materials 0.000 claims description 4
- 239000000126 substance Substances 0.000 claims description 4
- 235000010210 aluminium Nutrition 0.000 description 32
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 4
- 239000000243 solution Substances 0.000 description 4
- 229910045601 alloy Inorganic materials 0.000 description 2
- 239000000956 alloy Substances 0.000 description 2
- 239000002585 base Substances 0.000 description 2
- 239000011780 sodium chloride Substances 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 1
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
- 239000012267 brine Substances 0.000 description 1
- 238000003486 chemical etching Methods 0.000 description 1
- 230000000295 complement effect Effects 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000000866 electrolytic etching Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 230000035515 penetration Effects 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- OTYBMLCTZGSZBG-UHFFFAOYSA-L potassium sulfate Chemical class [K+].[K+].[O-]S([O-])(=O)=O OTYBMLCTZGSZBG-UHFFFAOYSA-L 0.000 description 1
- 235000011151 potassium sulphates Nutrition 0.000 description 1
- 230000001932 seasonal effect Effects 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
- 235000011152 sodium sulphate Nutrition 0.000 description 1
- HPALAKNZSZLMCH-UHFFFAOYSA-M sodium;chloride;hydrate Chemical compound O.[Na+].[Cl-] HPALAKNZSZLMCH-UHFFFAOYSA-M 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25F—PROCESSES FOR THE ELECTROLYTIC REMOVAL OF MATERIALS FROM OBJECTS; APPARATUS THEREFOR
- C25F3/00—Electrolytic etching or polishing
- C25F3/02—Etching
- C25F3/04—Etching of light metals
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/12—All metal or with adjacent metals
- Y10T428/12431—Foil or filament smaller than 6 mils
Definitions
- Aluminum, and in particular aluminum foil so treated is of particular value in the construction of electrolytic capacitors which include an aluminum electrode having an electrically formed dielectric oxide film thereon.
- the capacitance of such a capacitor depends upon the area of filmed electrode surface in contact with the electrolyte between it and the complementary electrode.
- the present invention in another of its aspects, relates to novel features of the instrumentalities of the present invention described therein for teaching the principal object of the present invention and to the novel principles employed in the instrumentalities Whether or not these features and principles may be used in the said object or in the said field.
- the present invention provides a method of etching aluminum foil to be formed at low voltages to obtain increased capacitance so that capacitor sizes may be reduced.
- the invention consists of the addition of small amounts of a soluble sulfate to the etching bath which is composed of an aqueous sodium chloride solution containing 16-24% sodium chloride by weight. Both sodium and potassium sulfates have been used, however, any soluble sulfate is suitable.
- the sulfate is mixed with the etching solution prior to the etching, and additional sulfate is added thereafter if necessary.
- the addition of the sulfate ion increases the electrical capacitance of the etched aluminum foil and particularly increases the 3,321,389 Patented May 23, 1967 capacitance of etched aluminum foil processed especially for low formation voltages.
- sulfate serves to increase the penetration powers of the etching solution thereby increasing the eifective surface area of the etched foil which, in turn, increases the capacitance.
- the etching process is carried out between 100 C. Current densities of 1 ampere per square inch and up and a cycle of 4-15 ampere minutes per square inch are utilized. The specific current density and time cycle depends upon the size of the foil. A unidirectional current is used throughout the operation.
- the method of treating the surfaces of substantially oxide free aluminum foil having a purity of at least 99.93 percent used in a capacitor electro-formed between about 30 and 100 volts to increase the effective surface thereof by etching thereon a fine etch pattern comprising the steps of immersing a substantially oxide free aluminum foil having a purity of at least 99.93 percent in an aqueous etching bath containing about 16 to 24 percent by weight of an alkali metal chloride and about 0.1 to 10 percent by weight of a soluble alkali metal sulfate, maintaining said aqueous etching bath at a temperature of about 70 to 100C, conducting between said substantially oxide free aluminum foil which is made anodic and cooperating cathode a unidirectional current having a density of about one ampere per square inch or higher of said metal surface and having a time cycle duration of about 4 to 15 ampere minutes per square inch of said metal surface thereby causing etching of said metal surfaces of said aluminum foil by a combined chemical and electrolytic action, continuing said etching
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- ing And Chemical Polishing (AREA)
Description
United States Patent 3,321,389 METHOD OF ANODICALLY ETCHING ALUMI- NUM FOlLS AT ELEVATED TEMPERATURES IN AN ELECTRGLYTE INCLUDENG CHLO- RIDE AND SULFATE IONS Daniel J. Anderson, Indianapolis, Ind., assignor to P. R. Mallory & Co., Inc., Indianapolis, Ind., a corporation of Delaware No Drawing. Filed July 20, 1964, Ser. No. 383,960 3 Claims. (Cl. 204-141) The present invention relates to improvements in the etching of aluminum and aluminum-base alloys and more particularly relates to the treatment of aluminum and aluminum-base alloys to increase the effective surface area thereof.
Aluminum, and in particular aluminum foil so treated is of particular value in the construction of electrolytic capacitors which include an aluminum electrode having an electrically formed dielectric oxide film thereon. The capacitance of such a capacitor depends upon the area of filmed electrode surface in contact with the electrolyte between it and the complementary electrode.
It is known in the art to increase the efiective surface area of aluminum, and in particular aluminum foil, by both a chemical etching process and by an anodic electrolytic etching process in which a smooth direct current is employed or in which unidirectional uninterrupted current of fluctuating magnitude is employed. The increase in the effective surface area of aluminum so treated is largely due to the production of very fine and relatively deep pores. However, it has been found that the addition of sulfate to the etching solution produces an increase in capacitance and is particularly applicable for increasing the effective surface area of aluminum processed for low voltage formation.
Therefore, it is an object of the present invention to provide an improved process for etching aluminum to increase the effective surface area thereof.
It is an object of the present invention to provide an improved process for etching aluminum to increase the average capacity of etched aluminum foil processed especially for low formation voltages of 100 volts and less.
It is an object of the present invention to provide an improved process for etching aluminum which reduces capacity variations of a seasonal nature which occur in low voltage foil, due to variations in the temperature at which the etching brine is made up.
The present invention, in another of its aspects, relates to novel features of the instrumentalities of the present invention described therein for teaching the principal object of the present invention and to the novel principles employed in the instrumentalities Whether or not these features and principles may be used in the said object or in the said field.
With the aforementioned objects enumerated, other objects will be apparent to those possessing ordinary skill in the art. Other objects will appear in the following description and the appended claims.
Generally speaking the present invention provides a method of etching aluminum foil to be formed at low voltages to obtain increased capacitance so that capacitor sizes may be reduced. The invention consists of the addition of small amounts of a soluble sulfate to the etching bath which is composed of an aqueous sodium chloride solution containing 16-24% sodium chloride by weight. Both sodium and potassium sulfates have been used, however, any soluble sulfate is suitable. The sulfate is mixed with the etching solution prior to the etching, and additional sulfate is added thereafter if necessary. The addition of the sulfate ion increases the electrical capacitance of the etched aluminum foil and particularly increases the 3,321,389 Patented May 23, 1967 capacitance of etched aluminum foil processed especially for low formation voltages.
The following table shows typical results obtained utilizing the aforementioned invention. Figures are given in microfarads per square inch at 30 volts formation.
Foil Purity Gms. NaSOr per 100 gms. N 2:01
99.93% Al 99.99% Al The addition of sulfate serves to increase the penetration powers of the etching solution thereby increasing the eifective surface area of the etched foil which, in turn, increases the capacitance. The etching process is carried out between 100 C. Current densities of 1 ampere per square inch and up and a cycle of 4-15 ampere minutes per square inch are utilized. The specific current density and time cycle depends upon the size of the foil. A unidirectional current is used throughout the operation.
It will be understood that the present invention as hereinbefore described is merely illustrative and not exhaustive in scope. Since many Widely different embodiments of the invention may be made Without departing from the scope thereof, it is intended that all matter contained in the above description shall be interposed as illustrative and not in a limiting sense. Having thus described my invention,
I claim:
1. The method of treating the surfaces of substantially oxide free aluminum foil having a purity of at least 99.93 percent used in a capacitor electro-formed at up to volts to increase the effective surface thereof by etching thereon a fine etch pattern comprising the steps of immersing a substantially oxide free aluminum foil having a purity of at least 99.93 percent in an aqueous bath containing about 16 to 24 percent by weight of an alkali metal chloride and about 0.1 to 10 percent by weight of a soluble alkali metal sulfate, maintaining said aqueous etching bath at a temperature of about 70 to 100 C., conducting between said substantially oxide free aluminum foil which is made anodic and a cooperating cathode a unidirectional current having a density of about one ampere per square inch of said metal surface and having a time cycle duration of about 4 to 15 ampere minutes per square inch of said metal surface thereby causing etching of said metal surface of said aluminum foil by a combined chemical and electrolytic action, continuing said etching of said metal surfaces until the capacity value of said metal surfaces is effectively increased by the formation of a fine etch pattern therein, and cleansing said aluminum foil of said aqueous etch bath.
2. The method of treating the surfaces of substantially oxide free aluminum foil having a purity of at least 99.93 percent used in a capacitor electro-formed at up to 100 volts to increase the effective surface thereof by etching thereon a fine etch pattern comprising the steps or immersing a substantially oxide free aluminum foil having a purity of at least 99.93 percent in an aqueous etching bath containing an alkali metal chloride and a soluble alkali metal sulfate, maintaining said aqueous etching bath at a temperature of about 70 to 100 C., conducting between said substantially oxide free aluminum foil which is made anodic and a cooperating cathode a unidirectional current having a density of about one ampere per square inch of said metal surface and having a time cycle duration of about 4 to 15 ampere minutes per square inch of said metal surface thereby causing etching of said metal surfaces of said aluminum foil by a combined chemical and electrolytic action, continuing said etching of said metal surfaces until the capacity value of said metal surfaces is effectively increased by the formation of a fine etch pattern therein, and cleansing said aluminum foil of said aqueous etch bath.
3. The method of treating the surfaces of substantially oxide free aluminum foil having a purity of at least 99.93 percent used in a capacitor electro-formed between about 30 and 100 volts to increase the effective surface thereof by etching thereon a fine etch pattern comprising the steps of immersing a substantially oxide free aluminum foil having a purity of at least 99.93 percent in an aqueous etching bath containing about 16 to 24 percent by weight of an alkali metal chloride and about 0.1 to 10 percent by weight of a soluble alkali metal sulfate, maintaining said aqueous etching bath at a temperature of about 70 to 100C, conducting between said substantially oxide free aluminum foil which is made anodic and cooperating cathode a unidirectional current having a density of about one ampere per square inch or higher of said metal surface and having a time cycle duration of about 4 to 15 ampere minutes per square inch of said metal surface thereby causing etching of said metal surfaces of said aluminum foil by a combined chemical and electrolytic action, continuing said etching of said metal surfaces until the capacity value of said metal surfaces is effectively increased by the formation of a fine etch pattern therein, and cleansing said aluminum foil of said aqueous etch bath.
References Cited by the Examiner UNITED STATES PATENTS 2,336,846 12/1943 Clark 204141 2,598,043 5/1952 Eichner 204-141 3,085,950 4/1963 Thomas et al. 204-141 FOREIGN PATENTS 467,024 9/ 1937 Great Britain.
JOHN H. MACK, Primary Examiner.
R. K. MIHALEK, Assistant Examiner.
Claims (1)
1. THE METHOD OF TREATING THE SURFACES OF SUBSTANTIALLY OXIDE FREE ALUMINUM FOIL HAVING A PURITY OF AT LEAST 99.93 PERCENT USED IN A CAPACITOR ELECTRO-FORMED AT UP TO 100 VOLTS TO INCREASE THE EFFECTIVE SURFACE THEREOF BY ETCHING THEREON A FINE ETCH PATTERN COMPRISING THE STEPS OF IMMERSING A SUBSTANTIALLY OXIDE FREE ALUMINUM FOIL HAVING A PURITY OF AT LEAST 99.93 PERCENT IN AN AQUEOUS BATH CONTAINING ABOUT 16 TO 24 PERCENT BY WEIGHT OF AN ALKALI METAL CHLORIDE AND ABOUT 0.1 TO 10 PERCENT BY WEIGHT OF A SOLUBLE ALKALI METAL SULFATE, MAINTAINING SAID AQUEOUS ETCHING BATH AT A TEMPERATURE OF ABOUT 70 TO 100%C., CONDUCTING BETWEEN SAID SUBSTANTIALLY OXIDE FREE ALUMINUM FOIL WHICH IS MADE ANODIC AND A COOPERATING CATHODE A UNIDIRECTIONAL CURRENT HAVING A DENSITY OF ABOUT ONE AMPERE PER SQUARE INCH OF SAID METAL SURFACE AND HAVING A TIME CYCLE DURATION OF ABOUT 4 TO 15 AMPERE MINUTES PER SQUARE INCH OF SAID METAL SURFACE THEREBY CAUSING ETCHING OF SAID METAL SURFACE OF SAID ALUMINUM FOIL BY A COMBINED CHEMICAL AND ELECTROLYTIC ACTION, CONTINUING SAID ETCHING OF SAID METAL SURFACES UNTIL THE CAPACITY VALUE OF SAID METAL SURFACES IS EFFECTIVELY INCREASED BY THE FORMATION OF A FINE ETCH PATERN THEREIN, AND CLEANSING SAID ALUMINUM FOIL OF SAID AQUEOUS ETCH BATH.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US383960A US3321389A (en) | 1964-07-20 | 1964-07-20 | Method of anodically etching aluminum foils at elevated temperatures in an electrolyte including chloride and sulfate ions |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US383960A US3321389A (en) | 1964-07-20 | 1964-07-20 | Method of anodically etching aluminum foils at elevated temperatures in an electrolyte including chloride and sulfate ions |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| US3321389A true US3321389A (en) | 1967-05-23 |
Family
ID=23515477
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| US383960A Expired - Lifetime US3321389A (en) | 1964-07-20 | 1964-07-20 | Method of anodically etching aluminum foils at elevated temperatures in an electrolyte including chloride and sulfate ions |
Country Status (1)
| Country | Link |
|---|---|
| US (1) | US3321389A (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3477929A (en) * | 1966-04-18 | 1969-11-11 | Fujitsu Ltd | Method of etching aluminum foil in the manufacturing of aluminum electrolytic condensers |
| US3884783A (en) * | 1972-08-30 | 1975-05-20 | Nat Steel Corp | Direct current electrolytic etching of aluminum foil without the use of contact rolls |
| US3957553A (en) * | 1972-08-09 | 1976-05-18 | Pennwalt Corporation | Non-chromated alkaline etching bath and etching process for aluminum |
| US4395305A (en) * | 1982-08-23 | 1983-07-26 | Sprague Electric Company | Chemical etching of aluminum capacitor foil |
| US4427506A (en) | 1982-09-24 | 1984-01-24 | Sprague Electric Company | AC Etching of aluminum capacitor foil |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB467024A (en) * | 1935-12-09 | 1937-06-09 | Dubilier Condenser Co 1925 Ltd | Improvements in or relating to electrolytic condensers and other electrolytic devices |
| US2336846A (en) * | 1938-01-03 | 1943-12-14 | Gen Electric | Etching of capacitor armatures |
| US2598043A (en) * | 1947-02-20 | 1952-05-27 | Reynolds Metals Co | Process of preparing planographic printing plates |
| US3085950A (en) * | 1959-02-20 | 1963-04-16 | British Aluminium Co Ltd | Electrolytic etching of aluminum foil |
-
1964
- 1964-07-20 US US383960A patent/US3321389A/en not_active Expired - Lifetime
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB467024A (en) * | 1935-12-09 | 1937-06-09 | Dubilier Condenser Co 1925 Ltd | Improvements in or relating to electrolytic condensers and other electrolytic devices |
| US2336846A (en) * | 1938-01-03 | 1943-12-14 | Gen Electric | Etching of capacitor armatures |
| US2598043A (en) * | 1947-02-20 | 1952-05-27 | Reynolds Metals Co | Process of preparing planographic printing plates |
| US3085950A (en) * | 1959-02-20 | 1963-04-16 | British Aluminium Co Ltd | Electrolytic etching of aluminum foil |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3477929A (en) * | 1966-04-18 | 1969-11-11 | Fujitsu Ltd | Method of etching aluminum foil in the manufacturing of aluminum electrolytic condensers |
| US3957553A (en) * | 1972-08-09 | 1976-05-18 | Pennwalt Corporation | Non-chromated alkaline etching bath and etching process for aluminum |
| US3884783A (en) * | 1972-08-30 | 1975-05-20 | Nat Steel Corp | Direct current electrolytic etching of aluminum foil without the use of contact rolls |
| US4395305A (en) * | 1982-08-23 | 1983-07-26 | Sprague Electric Company | Chemical etching of aluminum capacitor foil |
| US4427506A (en) | 1982-09-24 | 1984-01-24 | Sprague Electric Company | AC Etching of aluminum capacitor foil |
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