Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
  • H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
  • H01G9/004—Details
  • H01G9/04—Electrodes or formation of dielectric layers thereon
  • H01G9/048—Electrodes or formation of dielectric layers thereon characterised by their structure
  • H01G9/055—Etched foil electrodes
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
  • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
  • C22F1/04—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon

Definitions

• the invention relates to refined aluminum sheets intended to serve as an anode in an electrolytic capacitor and more specifically to aluminum sheets for anodes of medium and high voltage electrolytic capacitors.
• the refined aluminum sheets intended to serve as an anode in an electrolytic capacitor are obtained from ingots which have a thickness of the order of a few hundred millimeters. These ingots are successively hot and cold rolled with intermediate annealing to the final thickness of the order of 0.1 mm. The strip finally undergoes a recrystallization heat treatment-
• an electrochemical etching is carried out on the strip intended to increase the apparent surface and an anodization intended to form the barrier oxide layer (formation).
• the electrical capacity of the strip is all the higher as, before etching and formation, the metallurgical structure comprises a high percentage of grains having the orientation • - 001 - ⁇ 100> (cube texture, also called dice texture).
• French patent FR 2113782 thus teaches a process comprising: 1. cold rolling with a work hardening rate (defined as the ratio of the variation in thickness to the final thickness) greater than 1000%,
• Japanese patent application JP-60-63360 / 85 teaches a process characterized by hot rolling in two parts: the first in the direction perpendicular to the ingot pouring direction, the second in the ingot pouring direction.
• the measurement methods used to determine the percentage of dice texture are based on the following principle: the sample undergoes a chemical attack, a mirror is placed parallel to the sheet and it is determined either by eye or with a image the percentage of the sample area that is shiny. Such a method is described in Japanese patent application JP-6063360/85.
• the applicant has set itself the objective of developing a refined aluminum sheet which makes it possible to obtain, after etching, a high, constant and reproducible level of capacity.
• the object of the invention is a refined aluminum sheet intended to serve as an anode in an electrolytic capacitor characterized in that less than 20% of the grains have an orientation offset by 10 ° to 20 ° relative to the orientation d ideal.
• a grain has an ideal orientation when a crystallographic plane of Miller indices (100) is parallel to the plane of the sheet and its crystallographic direction of Miller indices I 010 l remains parallel to the rolling direction of the sheet .
• the grain orientation is shifted from the ideal orientation when the crystallographic plane of Miller indices (100) and the crystallographic direction of Miller indices I 0101 are not entirely parallel to the plane of the grain, respectively. sheet and rolling direction. This offset is quantified by the angle which measures the rotation of the crystal lattice of the grain with respect to the ideal orientation (see f g - 1) -
• the individual orientation of the grains on the surface of the capacitor sheet can be measured in a scanning electron microscope using the EBSD (Electron Back Scattering Diffraction) technique.
• EBSD Electro Back Scattering Diffraction
• the observation of many samples of the usual production showed that there are very few grains shifted from 20 ° to 40 °. Above 40 ° offset, the grain has retained a rolling type deformation orientation. Below 10 °, the rotations occur around random directions, while beyond 10 °, they are systematically exercised around axes close to the rolling direction or the transverse direction.
• Example 1 The very numerous tests carried out by the applicant (see Example 1) have shown that the presence of grains shifted by 10 ° to 20 ° relative to the orientation d was much more harmful for obtaining a good capacity than its weak implying shift. The tests also showed that the relationship between decreased capacity and percentage of shifted grains was not linear. The capacity decreases much more quickly beyond 20% of shifted grains.
• Figure 1 shows schematically the rotation of a grain relative to the ideal die orientation.
• Samples (500 mm x 1000 mm) of refined aluminum sheet with a thickness of 100 ⁇ m and a purity of 99.99% were prepared under the following conditions:
• Samples of the 8 samples were then examined using the ESBD technique. We determined on each of them the distribution of the disorientations compared to the orientation d and in particular the percentage of grains shifted from 10 ° to 20 ° compared to the orientation d ideal.
• Each sheet was immersed in an aqueous solution containing 5% hydrochloric acid HCl and 9% aluminum chloride AlCl . ⁇ hLO at a temperature of 85 ° C.
• the etching was applied directly by a direct current having a current density of 10 A / dm for 800 sec.
• the oxide formation was then carried out at 400 V in a 7% aqueous solution of boric acid H BO-, and of ammonia NH.0H at 90 ° C.
• Table I The results obtained are collated in Table I.
• samples A3 A3 A4 while having a percentage of texture in die have a lower capacity than those of samples B.
• This defect in capacity is due to the high volume fraction ( greater than 20%) of the orientation grains offset by 10 ° to 20 ° relative to the ideal orientation.

Landscapes

• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Power Engineering (AREA)
• Crystallography & Structural Chemistry (AREA)
• Physics & Mathematics (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Thermal Sciences (AREA)
• Microelectronics & Electronic Packaging (AREA)
• ing And Chemical Polishing (AREA)
• Metal Rolling (AREA)
• Analysing Materials By The Use Of Radiation (AREA)

Priority Applications (4)

Applications Claiming Priority (2)

Publications (1)

Family

ID=9453616

Family Applications (1)

Country Status (8)

Families Citing this family (4)

Citations (2)

• 1993
  • 1993-12-01 FR FR9314620A patent/FR2713390B1/fr not_active Expired - Fee Related
• 1994
  • 1994-11-11 TW TW083110462A patent/TW289117B/zh not_active IP Right Cessation
  • 1994-11-29 JP JP51543995A patent/JP3366008B2/ja not_active Expired - Fee Related
  • 1994-11-29 EP EP95902801A patent/EP0731976B1/fr not_active Expired - Lifetime
  • 1994-11-29 WO PCT/FR1994/001383 patent/WO1995015573A1/fr not_active Ceased
  • 1994-11-29 KR KR1019960701629A patent/KR100300645B1/ko not_active Expired - Fee Related
  • 1994-11-29 CN CN94194250A patent/CN1046370C/zh not_active Expired - Fee Related
  • 1994-11-29 DE DE69412855T patent/DE69412855T2/de not_active Expired - Lifetime

Patent Citations (2)

Non-Patent Citations (2)

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