JPS6280298A - Anode used in electrochemical treatment at low ph and high current density - Google Patents

Abstract

An anode for use in electroforming copper foil is formed by depositing a multilayer coating on a substrate of a film forming metal. At least one interior layer consists essentially of substantially pore free platinum which is applied electrolytically to a thickness of at least about 5 micrometers (about 200 microinches), and then densified by heat treating in an oxygen containing atmosphere at from 600 to 775 DEG C. At least one of the exterior layers consists essentially of at least 97% iridium oxide and up to about 3% rhodium oxide, which is applied by thermal decomposition of thermally decomposable platinum group metal compounds in an oxygen containing atmosphere at a temperature of not more than about 600 DEG C.

Description

DETAILED DESCRIPTION OF THE INVENTION Electrically manufactured copper foil forms the backbone of modern "child devices. As the number of integrated circuit products increases,
Although the amount of foil required has increased correspondingly,
Even the most dimensionally stable anodes available today cannot withstand the conditions required for optimal foil production.
There are limits to the speed at which these foils can be manufactured. The anode of the present invention withstands high acid concentrations, current densities, and temperatures that rapidly destroy conventionally known anodes, allowing the production of high-purity, pore-free copper foils at high speeds and at low cost under harsh conditions. Particularly suitable for manufacturing. In particular, the anode of the present invention is made by a three step process which, although very sensitive in terms of detail, provides an extremely robust and durable anode when properly implemented.

In the first step of the method of the invention, platinum is electrodeposited onto a completely descaled, degreased and clean device substrate. It is important to coat the platinum to a thickness of at least about 150 microinches and up to about 400 microinches, preferably at least about 225 microinches, and most preferably at least about 250 microinches.

The second step of the method of the invention involves a heat treatment called "densification", which is essential to obtain the anode of the invention. In the "densification" step, the platinum-coated anode is heated in air to a temperature of 800-775 °C,
The temperature is maintained for about 1/4 to 2 hours, or until the stress in the electrodeposited film is relaxed and the pores obtained from the electrodeposition process are closed.

The final step of the invention is to coat a ``densified'' platinum-coated substrate with a thermally decomposable compound of iridium and rhodium, and then heat it in air to decompose the compound into an oxide. Approximately 97% 0) I
A catalytic oxide outer coating consisting of rO2 and up to about 3% Rh2 [13] is applied. In the present invention, it has been found that it is important to carry out the decomposition below about 600° C., since the use of higher temperatures (eg, about 690° C.) makes the product much less durable. Ff of thermally decomposable compounds
fffi is at least about 15 yr2/g of iridium
(calculated with respect to the weight of the metal), preferably 20
The amount should be sufficient to fill 27 g rrr, more preferably 25 ra2/g.

The coating substrate can be any known film-forming metal that, when uncoated, rapidly decomposes by forming an adhesive protective oxide film in the electrolyte into which the anode is inserted. Be dynamic. Typical substrates are titanium, tantalum, vanadium, tungsten, aluminum, zirconium, niobium and molybdenum in tubes, rods, sheets, mesh, expanded metal or other special shapes for special applications. 'When making electrically produced copper foils, the anode is used in the form of a cylinder or a section of a cylinder that fits the shape of a mandrel or drum so that the electrically produced foil has a uniform thickness. It is particularly advantageous if the cathode can be easily removed from the drum. The anode core is often copper or other highly electrically conductive metal, such as aluminum or a highly electrically conductive iron alloy, with an outer layer of a film-forming metal such as titanium.

Before applying the electrolyte layer, the substrate is cleaned and descaled by methods such as spraying particles of aluminum oxide in an air jet, followed by chemical cleaning and degreasing. Usually, the anode is coated immediately after degreasing, but the anode can be stored and there are no adverse effects if several devices are present between degreasing and coating.

Platinum electrolyte coatings are applied to conventional dimensionally stable counter electrodes by immersing the substrate in an aqueous platinum electroplating bath for at least 15 min.
A current of about 7 to about 70 amperes per square foot can be applied to the substrate until 0, preferably 225, and more preferably 250 microinches of platinum are coated. Any conventional platinum electroplating bath can be used. Typically such baths contain platinum compounds such as ammines, nitrides or hydroxy complexes as well as various known additives such as brighteners, auxiliaries to improve the toughness of the deposited film and remove impurities, and baths. is an aqueous dispersion, solution or mixture containing additives that improve the electrical conductivity of Typical platinum compounds include H2PtCl6, K
2Pt(OHh), H2Pt(NO2)2S04 and diammine dinitroplatinum(II). Useful compositions for platinum electroplating baths are described by F. Lowenheim (F.
, Lowenheim), ``Modern Electroblating''
ing) J 3rd edition, 1874, pp. 355-357, and McGraw-Fist Hill (M.
cGraw Hill), published in 1978, Electroblating, pages 1298-299. Concentrates prepared to create and replenish platinum electroplating baths are sold in Ichisaka. To obtain a high quality platinum layer, the temperature of the bath is preferably between about 150 and about 200''.
Must be kept at 85-930C.

Once the platinum coating has reached the desired thickness, the anode can be removed from the bath and subjected to a heat treatment called densification to relieve stress in the coating and the pores contained within it.

If the "densification" step is omitted or not performed properly, the resulting anode will have poor durability due to immature passivation. Thermal densification is accomplished by heating the platinum-coated anode in air, nitrogen, helium, vacuum, or any convenient atmosphere to about 550-850° C. depending on the nature of the platinum film, for about 150 to about 150 minutes. I can do it. The thermal densification process is complete when the coating is visually observed and the pores are closed and the coating is highly reflective.

After thermal densification is completed, the anode is cooled and the iridium-containing compound is thermally decomposed in an oxygen-containing atmosphere to coat the anode with an outer layer of iridium oxide. Among the iridium compounds that can be used are hexachloroiridic acid, (NH4)2Ir
Included are C16, rrc14 and iridium resinates, as well as other halogen-containing compounds. These compounds are typically dispersed in any conventional carrier, such as inbutanol and other aliphatic alcohols, and then applied to a substrate by any conventional method, such as dipping, brushing or spraying. In most cases (calculated as metal) from about 0.5 to about 3.0 g/l112. Preferably, 1 to 2 g/112 of iridium is coated on a support containing sufficient iridium to coat the substrate, and then this is applied at a concentration of about 400 to about 550
C.1, preferably at a temperature of 450 to about 500.degree. C., to drive off the carrier and convert the iridium compound to an oxide. (
total of at least approximately 15 g/m2 (calculated as metal)
The process is repeated until at least about 20 g/112, more preferably at least about 25 g/l112 of iridium is coated. The temperature of the pyrolysis step is extremely important. As shown in the examples below, if a decomposition temperature of about 600°C or higher is used to decompose an iridium compound, the durability of the resulting anode will be significantly deteriorated.
The anode obtained by decomposing the iridium compound at a temperature below, preferably about 400 to about 550°C, more preferably 450 to 500°C, is surprisingly durable, and can quickly destroy the anode of the conventional method. It exhibits a long life even when oxygen is generated in a bath at a temperature of about 85° C. or higher.

R of up to about 3z is often present in iridium oxide films.
It is advantageous to include h2O3 to promote adhesion. This can be accomplished by including any conventional rhodium compound in the iridium-containing coating composition. Rhodium resinates are particularly useful.

The anode of the present invention is immersed in a bath containing a suitable copper compound, such as copper sulfate, copper chloride, and other soluble platinum compounds, at a pH of about -2 to 3, and is made of stainless steel or other corrosion-resistant alloy. Used as a counterelectrode, the anode has a current of about 400 to about 2,000 amperes (4,300 to 21,00 amps) per square foot of anode.
Copper foils can be electrically produced using the anode of the present invention by passing a current of 100 amperes (10') into the bath and generating oxygen at the anode. Quite surprisingly, the anodes of the present invention exhibit a high degree of durability when used at bath temperatures above 85°C up to about 90°C. It is also surprising that the anodes of the present invention have an anode of from about 500 to up to about 3 per square foot.
000 amperes (5,400~32,000 amperes/
Even when operating at a current density of
50g/Jl! Suitable for use at sulfuric acid concentrations of

Under these conditions, conventional anodes will fail rapidly, unless the anode of the present invention is used, or even if an anode similar to the present anode is used but not made in strict accordance with the present invention. deteriorates to. The ability to use these harsh conditions is highly desirable to copper foil manufacturers because they allow foils to be manufactured more efficiently, quickly, and economically under these harsh conditions. Accordingly, there is a long-held but unmet need that the anodes of the present invention can be used under conditions suitable for the rapid and energy-efficient production of high-purity, pore-free electrolytic copper foil films. The anode of the present invention, which satisfies the above requirements, is also highly suitable for applications where porous foils are desired, and applications involving oxygen generation, such as batteries, electrical manufacturing, and electrosynthesis.

Example 1 This example illustrates the production of an anode of the present invention. Dimensions are 4
The X8 Xo, 0.62 inch titanium substrate was descaled, tempered, degreased, and coated with platinum to a thickness of 250 microinches. The platinum coating is then heated in air to 690° C. for 374 hours to densify it. After cooling, a solution of hexachloroiridic acid and rhodium resinate dispersed in butanol is applied to the substrate for approximately 90 minutes.
After coating a coating consisting of 8% rro 2 and 2z Rh2O3, it is calcined in air at 450° C. and the process is repeated until the coating contains 15 g (as metal) of iridium per m2, pH approximately O1. Current density of about 188OASF (20,00OA/112), 4,0 when used in copper foil electrical manufacturing at about 60℃
After 00 hours, the anode could still be operated with a substantially constant overvoltage of 2.83 volts.

Example 2 Example 1 was repeated but with iridium oxide (third step)
was made at 690°C. Conditions similar to Example 1 (pHO
, current density 1860, temperature 60° C.), the anode became unusable after 620 hours.

Claims (1)

Claims: 1. An anode for oxygen evolution consisting essentially of a film-formable metal matrix having a multilayer coating, wherein at least one inner layer of the coating is at least about 200 microinches thick. The at least one outer layer of the coating consists essentially of substantially pore-free platinum that has been electroplated and then heat treated at 600 DEG to 775 DEG C. in an oxygen-containing atmosphere to densify it, the at least one outer layer of the coating having at least about consisting essentially of 97% iridium oxide and up to about 3% rhodium oxide; An anode characterized by being made of 2. The anode of claim 1, wherein said outer layer is formed by pyrolysis at about 400 DEG to about 550 DEG C. 3. The anode of claim 1, wherein said inner layer has a thickness of at least about 225 microinches. 4. The anode of claim 1, wherein said inner layer has a thickness of at least about 250 microinches. 5. The anode of claim 4, wherein said outer layer is formed by pyrolysis at about 450 to about 500C. 6. In an aqueous bath containing 100 g/l or more of sulfuric acid,
A method of electrically manufacturing copper foil using the anode of claims 1-5 at a current density of at least about 500 amperes per square foot and a temperature of 85°C or above.