US3689417A - Powderless etching bath - Google Patents

Powderless etching bath Download PDF

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Publication number
US3689417A
US3689417A US43195A US3689417DA US3689417A US 3689417 A US3689417 A US 3689417A US 43195 A US43195 A US 43195A US 3689417D A US3689417D A US 3689417DA US 3689417 A US3689417 A US 3689417A
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Prior art keywords
aluminum
etching
acid
bath
ingredient
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Expired - Lifetime
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US43195A
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English (en)
Inventor
Takashi Oikawa
Takeshi Fujimoto
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Resonac Holdings Corp
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Showa Denko KK
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Classifications

    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
    • C23F1/00—Etching metallic material by chemical means
    • C23F1/10—Etching compositions
    • C23F1/14—Aqueous compositions
    • C23F1/42—Aqueous compositions containing a dispersed water-immiscible liquid

Definitions

  • This invention relates to an improved powderless etching bath for etching aluminum or an aluminum-base alloy.
  • Powderless etching technique has been well known per se.
  • a fiat or cylindrical plate of an acid-soluble metal is coated with a light-sensitive coating or enamel.
  • the coated surface is exposed to light through a negative having an image thereon so as to produce a corresponding image on the coating.
  • the exposed coating surface is developed, forming an acid-resistant coating in the form of the image produced by the exposure.
  • This acid resistant coating is further hardened by heating and the final acid-resistant image is called the resist.
  • the image-bearing surface of the plate is then subjected to etching by an acid to produce the image in relief.
  • the etching bath employed usually consists of a major amount of an aqueous solution of an acid as the etching agent and a minor amount each of a water-immiscible organic liquid and a filming agent.
  • the filming agent is composed of an anionic surface active material having both hydrophobic and hydrophilic properties, such as sulfated or sulfonated organic compounds or phosphate esters.
  • etch factor is defined as the ratio of the depth of the etch adjacent to a line of resist divided by one-half of the total loss in width, i.e. side-etch, of metal immediately beneath the resist.
  • Powderless etching of zinc, magnesium or their respective metal-base alloys and various etching baths used in such etching are known, for instance, by U.S. Pats. 2,640,763, 2,640,764, 2,763,536, 2,979,387, 3,023,138, and 3,337,462. It is currently a wide practice to etch the zinc, magnesium, or their alloys using etching baths containing an aqueous solution of nitric acid as an etching agent. Aluminum or an aluminum-base alloy cannot be etched with such nitric acid aqueous solution. In our copending application Ser. No. 783,717 filed Dec. 13, 1968, now U.S. Pat. No. 3,607,484.
  • aluminum or an aluminum-base alloy is etched with advantage by using an etching bath comprising an aqueous solution of sulfuric acid containing metal ions of a metal having an ionization tendency less than that of aluminum and halogen ions, a water-immiscible organic liquid and a phosphate ester surface active agent.
  • an etching bath comprising an aqueous solution of sulfuric acid containing metal ions of a metal having an ionization tendency less than that of aluminum and halogen ions, a water-immiscible organic liquid and a phosphate ester surface active agent.
  • the etching bath to be used should not corrode an acid resistant coating and should have a practical rate of etching aluminum and a high etch factor. It is also desired that the etching bath should be easily handled, not evolve noxious gases such as nitrous oxide and should be readily emulsified.
  • the etching bath for aluminum or its alloy used in the present invention meets all of these requirements.
  • an object of the present invention is to provide an improved bath for powderless etching of aluminum or an aluminum-base alloy.
  • the powderless etching bath for etching aluminum or aluminum-base alloy comprises:
  • the proportion of the ingredients in the bath being one liter of (a), 0.01-7 gram ion (b) as the metal, 10-100 milliliters of (c), 0.5- grams of (d), and 0.05-24 grams of (e) where the amount of (e) is in the range of 10-30% by weight of (d).
  • the etching method of the present invention comprises providing the etching bath described in claim 1, bringing the etching bath to a well emulsified condition, and impinging the etching bath upon the metal surface to be etched.
  • Metals to be etched by the etching bath of the present invention are pure aluminum, industrially pure aluminum and aluminum-base alloys.
  • the aluminum-base alloy used herein, is meant an alloy containing at least 80% by weight of aluminum.
  • an alloy containing at least by weight of aluminum and the balance being zinc and/or tin is usually used and the etching bath of the present invention is suitable for application to such alloys.
  • the aluminum and aluminum-base alloys will hereinafter be referred to simply as aluminum.
  • the acid aqueous solution employed as ingredient (a) is a predominant component for etching aluminum, and the acid consists mainly of sulfuric acid.
  • An aqueous nitric acid solution conventionally employed to etch zinc or magnesium does not etch aluminum at all, but an aqueous solution of sulfuric acid etches aluminum at a practical rate.
  • Aqueous sulfuric acid solutions of 0.8-10 N (corresponding to about 38-38% by weight of H SO are used. Good results are obtained with the normality of 1.5 N to 3 N. Together with sulfuric acid, a minor amount of an aqueous solution containing other inorganic acids can be used.
  • As the inorganic acids hydrochloric acid, hydrofluoric acid, nitric acid and phosphoric acid are used with especially favorable results.
  • the other inorganic acids to be mixed act to accelerate the rate of etching aluminum with sulfuric acid.
  • the ratio of such inorganic acid to be mixed should not exceed onehalf of the normality of the acid aqueous solution (0.8- N). For example, when the acid aqueous solution has a normality of 2 N, it is necessary that at least one N should be based on the sulfuric acid.
  • Ingredient (b) is a metal or its compound soluble in ingredient (a), an acid aqueous solution, said metal having an ionization tendency less than that of aluminum.
  • the ingredient (b) is dissolved in ingredient (a) to become metal ions, and acts to accelerate the rate of etching aluminum.
  • Metals having an ionization tendency less than that of aluminum are well known, and included within such metals are zinc, chromium, iron, cadmium, cobalt, nickel, tin, copper, mercury, and antimony. Of these, ions of Cu, Ni, Co and Fe have proved to have an especially marked effect of promoting the rate of etching aluminum.
  • the ions of Cu and Ni not only contribute to an increased etching rate, but also ensure the formation of a smooth etched surface and the achievement of a high etch factor.
  • the elemental metals themselves may be used as component (b) if they are soluble in component (a).
  • the metal compounds more readily soluble in ingredient (a) are used with preference. Examples of such compounds include inorganic acid salts of metals, such as the sulfates, nitrate, halides, phosphates and carbonates; organic acid salts of the metals, such as the formates, acetates and salts of higher fatty acids, and oxides and hydroxides of the metals.
  • the amount of the ingredient (b) is 0.01-7 gram-ions, preferably 0.05-1 gram-ion, calculated as the metallic ion based on one liter of the ingredient (a).
  • the water-immiscible organic liquid used as ingredient (c) acts to reduce the side etch of a metal substrate to be etched.
  • This is an essential component of all of the powderless etching baths heretofore known, and the various usable organic liquids are known. All of such known compounds are applicable in the present invention.
  • the examples of these compounds include aliphatic, aromatic or naphthenic hydrocarbons (for instance, xylene, cumene, kerosene); hydrocarbon-type lubricant oils; aromatic solvents (for instance, Solvesso of Esso, U.S.A.
  • the amount of ingredient (c) is usually 10100 milliliters, preferably -70 milliliters, per liter of ingredient (a).
  • the phosphate ester anionic surface active agent used as ingredient (d) has both hydrophobic and hydrophilic properties, and has an action of emulsifying and dispersing the ingredient (c), organic liquid, in ingredient (a), acid aqueous solution, forming a film on relief side-walls of the metal to be etched in cooperation with the organic liquid, and thus reducing the side-etch.
  • Such surfactants are usually called filming agents.
  • Typical examples of the known filming agents are sulfated or sulfonated organic compounds and phosphate ester compounds. The latter compounds are disclosed in US. Pat. No. 3,337,462. It has now been found that in etching aluminum, phosphate ester surfactants give especially good results as filming agents.
  • the phosphate ester compounds used in the invention are phosphate esters or polyphosphate esters expressed by the general formula wherein n is 0, l or an integer of usually up to 10, and R is a group A-O-(C H O),, (C H O) in which A is a hydrogen atom or a hydrocarbon radical, and a and b are 0, l, or an integer of usually up to 9; the Rs may be the same or different and A in at least one R is hydrocarbon radical.
  • A saturated or unsaturated alkyl groups, aryl groups, alkaryl groups and aralkyl groups.
  • Preferred are hydrocarbon radicals having 6-18 carbon atoms.
  • hydrocarbon radicals examples include octyl group, nonyl group, decyl group, dodecyl group, oleyl group, myristyl group, naphthyl group, nonyl phenyl group and dodecyl phenyl group.
  • A represents hydrogen, it may be in the form of a salt or adduct.
  • these phosphate ester compounds may be in the form of a mixture.
  • the amount of ingredient (d) is O.58O grams, preferably 1-10 grams, per liter of the ingredient (a).
  • the nonionic surface active agent as ingredient (e) is not used in the conventional etching baths. This is one of the characteristic ingredients used for the first time in the present invention. It has been found that the addition of a small amount of the nonionic surface active agent to an etching bath results in a marked reduction in the side-etch of the resist. This is more surprising in view of the fact that unlike anionic surfactans, nonionic surfactans are hardly capable of forming a film of the organic liquid when used singly.
  • the nonionic surfactant used in the invention assists the emulsifying capability of the phosphate ester anionic surfactant to produce a well emulsified etching bath with ease, and ensures a stable and smooth etching operation. Accordingly, the
  • nonionic surfactant has the advantage of replacing a part of the phosphate ester surfactant which is relatively expensive. This makes it possible to save about 10-20% of the amount of phosphate ester to be used which is required when the nonionic surfactant is not added. Thus, the nonionic surfactant and the phosphate ester are considered to exhibit a synergistic effect.
  • the amount of the nonionic surfactant is chosen within the range of 0.05-24 grams, preferably 0.07-16 grams, per liter of ingredient (a), and it is proper that the amount is 1030%, preferably 14-20%, based on the weight of ingredient (d).
  • nonionic surface active agents have been known heretofore. All of such known compounds can be used in the invention if they are substantially stable in the presence of the acid in the bath.
  • nonionic surfactants used with good results in the present invention are ethers such as polyoxyethylene cetyl ether, and polyoxyethylene nonyl phenyl ether, esters such as sorbitan monolaurate, sorbitan trioleate, polyoxyethylene sorbitan monostearate, polyethylene glycol distearate and saccharose ester, pluronic types such as an oxyethylene-oxypropylene block copolymer, condensed amines or amides such as polyoxyethylene lauryl amine, and polyoxyethylene stearylamide, and polyethylene imines such as polyethylene imine oleyl ether.
  • the anionic phosphate ester surfactants as ingredient (d) are prepared from nonionic surfactants. In this case, it is possible to leave some of the nonionic surfactant in the product without completing the esterification reaction. If such phosphate ester surfactants containing unreacted nonionic surfactant are used, the nonionic surfactant contained there can be utilized as ingredient (e) and it is not necessary to add ingredient (e) separately. In any case, the requirement is that the ingredients (d) and (e) should be contained in the etching bath in the proportions specified above. A combined amount of ingredients (d) and (e) may be as small as less than one gram per milliliter of the organic liquid employed as ingredient (c).
  • the etching bath of the present invention consists of the above-mentioned ingredients.
  • a concentrated mixture of ingredients (a) and (b) and a mixture of ingredients (c), (d) and (e) separately and mix and dilute them prior to use.
  • the method of etching aluminum or an aluminum-base alloy of the present invention is practised by using the above-described etching bath.
  • the operation of etching may be the same as the conventional powderless etching process.
  • impinging the etching bath upon the metal surface to be etched can be effected by spray jetting the bath or tion of name plates, templates, print-wiring and the like.
  • test piece was mounted in a small-sized paddle-type etching machine, and etched at a temperature of 28 C. with the number of rotation of the paddle maintained at 1,500 r.p.m. for the time indicated in Table 1.
  • the etched piece was withdrawn, washed with water, and dried.
  • the etch factor and the etch depth were measured with respect to each test piece. The results are shown in Table 1.
  • a 2S Alcoa standards.
  • B 17S Alcoa standards.
  • C 72S Alcoa standards).
  • D 0.5% Zn, the balance Al.
  • E 0.5 Zn, 0.1% Sn, the balance Al.
  • F 1% Zn, 0.2% Sn, the balance Al.
  • G 1.5% Zn, the balance Al.
  • Fepowder (5.) phatezsxgguryl oxyethylene e er 8 H1804 (3), H01 Zn(OH)z (100), Polyphosphate ester of the Solvesso-IOO (25), C 8 28 0. 50
  • a powderless etching bath for etching aluminum or an aluminum-base alloy which comprises:
  • said acid being selected from the group consisting of sulfuric acid and a mixture of sulfuric acid and at least one inorganic acid selected from hydrochloric acid, hydrofluoric acid, nitric acid and phosphoric acid, more than one-half of said normality value being based on the sulfuric acid present,
  • (e) a nonionic surface active agent a nonionic surface active agent, the proportions being 0.01-7 gram-ions of (b), 10-100 milliliters of (0), 0.5-80 grams of (d), and 0.05-24 grams of (e) where the amount of (e) is in the range of 10- 30% by weight of (d) per one liter of (a).
  • said water-immiscible organic liquid (c) is selected from the group consisting of aliphatic hydrocarbons, aromatic hydrocarbons, naphthenic hydrocarbons, hydrocarbon lubricant oils, terpene, liquid paraflin, chlorinated hydrocarbons, unsaturated higher fatty acids, and natural fats, said organic liquid having a boiling point higher than 80 C.
  • n 0 to 10
  • each R is a group UNITED STATES PATENTS 3,330,743 7/1967 Jestl et a1.
  • 156-22 X 3,402,083 9/ 1968 Patsko et al 156-14 3,490,968 1/ 1970 Brown 252-79.4 X

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  • Chemical & Material Sciences (AREA)
  • Dispersion Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • ing And Chemical Polishing (AREA)
  • Photosensitive Polymer And Photoresist Processing (AREA)
US43195A 1969-06-11 1970-06-03 Powderless etching bath Expired - Lifetime US3689417A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP44045399A JPS4931187B1 (enExample) 1969-06-11 1969-06-11

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JP (1) JPS4931187B1 (enExample)
DE (1) DE2028827A1 (enExample)
FR (1) FR2051075A5 (enExample)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4032379A (en) * 1974-02-11 1977-06-28 Philip A. Hunt Chemical Corporation Nitric acid system for etching magnesium plates
US4059481A (en) * 1975-07-14 1977-11-22 Dai Nippon Insatsu Kabushiki Kaisha Method of making an intaglio halftone gravure printing plate
US4089736A (en) * 1976-04-27 1978-05-16 Rolls-Royce Limited Method of removing Al-Cr-Co coatings from nickel alloy substrates
US6355121B1 (en) 1996-11-25 2002-03-12 Alcoa Inc. Modified etching bath for the deposition of a protective surface chemistry that eliminates hydrogen absorption at elevated temperatures
US20220145474A1 (en) * 2020-11-12 2022-05-12 Tech Met, Inc. Compositions and methods for creating nanoscale surface geometries on metals of an implantable device

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS63184141U (enExample) * 1987-05-21 1988-11-28
CN100419122C (zh) * 2004-11-24 2008-09-17 鸿富锦精密工业（深圳）有限公司 喷淋型铝合金化学蚀刻液

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4032379A (en) * 1974-02-11 1977-06-28 Philip A. Hunt Chemical Corporation Nitric acid system for etching magnesium plates
US4059481A (en) * 1975-07-14 1977-11-22 Dai Nippon Insatsu Kabushiki Kaisha Method of making an intaglio halftone gravure printing plate
US4089736A (en) * 1976-04-27 1978-05-16 Rolls-Royce Limited Method of removing Al-Cr-Co coatings from nickel alloy substrates
US6355121B1 (en) 1996-11-25 2002-03-12 Alcoa Inc. Modified etching bath for the deposition of a protective surface chemistry that eliminates hydrogen absorption at elevated temperatures
US20220145474A1 (en) * 2020-11-12 2022-05-12 Tech Met, Inc. Compositions and methods for creating nanoscale surface geometries on metals of an implantable device
US11952669B2 (en) * 2020-11-12 2024-04-09 Tech Met, Inc. Compositions and methods for creating nanoscale surface geometries on metals of an implantable device

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JPS4931187B1 (enExample) 1974-08-20
DE2028827A1 (de) 1971-01-28
FR2051075A5 (enExample) 1971-04-02

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