Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D3/00—Electroplating: Baths therefor
  • C25D3/02—Electroplating: Baths therefor from solutions
  • C25D3/46—Electroplating: Baths therefor from solutions of silver
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D17/00—Constructional parts, or assemblies thereof, of cells for electrolytic coating
  • C25D17/002—Cell separation, e.g. membranes, diaphragms
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D3/00—Electroplating: Baths therefor
  • C25D3/02—Electroplating: Baths therefor from solutions
  • C25D3/38—Electroplating: Baths therefor from solutions of copper
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
  • C25D5/02—Electroplating of selected surface areas
  • C25D5/022—Electroplating of selected surface areas using masking means
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
  • C25D5/10—Electroplating with more than one layer of the same or of different metals
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
  • C25D5/34—Pretreatment of metallic surfaces to be electroplated
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
  • H05K3/00—Apparatus or processes for manufacturing printed circuits
  • H05K3/22—Secondary treatment of printed circuits
  • H05K3/24—Reinforcing the conductive pattern
  • H05K3/244—Finish plating of conductors, especially of copper conductors, e.g. for pads or lands

Definitions

• the present invention relates to a method for silver electroplating with a non-cyanide bath, and in particular to a method for forming a silver plating film using an acid plating bath, exhibiting good adhesiveness while suppressing dissolution of resist in pattern plating.
• Silver is widely used not only for functional plating as it is excellent in properties such as electric conductivity and solderability, but also for decorative plating as it is also excellent in aesthetic appearance. In the current industrial practices, almost all the silver plating processes are operated with a cyanide bath.
• JP H02-290993A discloses a bath using potassium iodide as a complexing agent and teaches that the pH is in the range of 1 to 11, preferably 3 to 6.
• JP H07-166391A discloses a silver-plating solution using succinimide as a complexing agent at a pH of 4 to 10.
• Plating solutions using hydantoin as a complexing agent are also disclosed.
• hydantoin is generally used in alkaline baths at a pH of 7 or more as disclosed in JP H08-104993A
• hydantoin-containing silver-plating solutions and strike plating solutions used at a pH of 3.0 to 10.0 are described in JP H07-180085A.
• JP2000-34593A discloses “a phosphine-containing aqueous solution for reduction-deposition of metal”.
• a silver electroplating solution at a pH of 0.98 is disclosed in the same.
• 3365866 discloses a silver-plating solution containing at least one of alkane sulfonic acid ion and alkanol sulfonic acid ion, and a non-ionic surfactant. Though there is no description about pH, it is deemed to be a strong acid bath judging from the disclosed composition.
• Acid baths are more suitable to partial plating and pattern plating than alkaline baths as the former are less likely to attack resist than the latter.
• strong acid silver-plating baths made with simple salt at pH of less than 3 are advantageous as they can be stable without using a complexing agent and thereby can be formed and operated at lower cost.
• Silver exhibits noble potential and thus has a problem of readily causing displacement deposition.
• some literature references have disclosed baths that can reduce or prevent deposition by adding additives or using other methods, such baths cannot prevent it in an industrially applicable way.
• the subject matter of the present invention is a method for silver plating onto a substrate using a non-cyanide acid silver plating bath (A), comprising conducting strike plating onto the substrate using a non-cyanide acid strike plating bath (B) prior to the silver plating.
• both the non-cyanide acid silver plating bath (A) and the non-cyanide acid strike plating bath (B) have a pH of less than 3.
• the non-cyanide acid strike plating bath (B) is an acid silver strike plating bath (B1) or an acid copper strike plating bath (B2).
• either or both of the non-cyanide acid silver plating bath (A) and the non-cyanide acid strike plating bath (B) contain at least a sulfonate ion.
• either or both of the non-cyanide acid silver plating bath (A) and the non-cyanide acid strike plating bath (B) contain at least an aliphatic phosphine.
• the acid copper strike plating bath (B2) contains at least a sulfate ion.
• either or both of the non-cyanide acid silver plating bath (A) and the non-cyanide acid strike plating bath (B) further contain an azole compound and/or a thiophene compound.
• either or both of the non-cyanide acid silver plating bath (A) and the non-cyanide acid strike plating bath (B) further contain a surfactant and/or a surface-active polymer compound.
• the method further comprises the step of conducting displacement deposition prevention treatment to the substrate between the strike plating and the silver plating and wherein the strike plating is conducted using the acid copper strike plating bath (B2).
• the method further comprises the step of conducting pretreatment using an acid degreasing bath prior to the strike plating.
• either or both of the non-cyanide acid silver plating bath (A) and the non-cyanide acid strike plating bath (B) comprise an ion-exchange membrane therein to separate an anode and a cathode.
• the method for non-cyanide silver plating according to the present invention uses an acid bath for both the strike plating step and the main silver plating step, it can solve the following two problems:
• the present invention can provide a method for forming a silver plating film exhibiting good adhesiveness suitable for partial or pattern plating using resist.
• the present invention can provide a method that can be carried out at lower cost despite using a non-cyanide bath.
• the method can be applied not only to functional plating to form a plating film excellent in properties such as solderability but also to decorative plating.
• an alkaline strike plating bath is used in the previous step.
• an alkaline strike plating bath is used before an acid silver plating bath, since alkaline components in the alkaline strike plating bath may remain on the metal surface to be plated after completion of the strike plating, good plating film may not be formed in the subsequent silver plating process.
• the present inventors have determined that one or more improvements can be made by strike plating using a strong acid bath prior to silver plating using a strong acid silver plating bath.
• the present invention may have one or more advantages including, but not limited to, suppressing dissolution of resist in pattern plating, preventing alkaline components from remaining on the metal surface to be plated, and forming a dense plating film with good adhesiveness.
• One embodiment of the invention provides a method for silver plating onto a substrate using a non-cyanide acid silver plating bath (A), comprising conducting strike plating onto the substrate using a non-cyanide acid strike plating bath (B) prior to the silver plating.
• A non-cyanide acid silver plating bath
• B non-cyanide acid strike plating bath
• Both the silver plating bath (A) and the strike plating bath (B) are required to be acidic.
• both baths have a pH of less than 3.
• the bath (A) having a pH of less than 3 eliminates the need for a complexing agent for stability, allowing the plating process to be operated at lower cost. Accordingly, in one type of embodiment of the invention, the silver plating bath is essentially free of or completely free of a complexing agent. Further, by adjusting the acidity of the both baths to the pH of less than 3, adhesion of alkaline components onto the substrate possibly occurring in the previous strike plating step, which may affect the adhesiveness, can be avoided.
• the pH is preferably less than 3 and more preferably less than 2.
• Silver strike plating is preferably adopted as the strike plating step. Copper strike plating is also adopted as the strike plating bath. In such case, depending on the desired properties of the plating film, displacement prevention treatment or silver strike plating may be preferably conducted between the copper strike plating step and the silver plating step.
• any or all of the silver plating bath (A), the copper strike plating bath (B1) and the silver strike plating bath (B2) may contain any known acid alone or in combination as the acid component for keeping the bath acidic.
• Sulfonic acids are preferably used in terms of appearance of the plating film and electric properties such as surface resistivity of the plating film, etc.
• aliphatic and aromatic sulfonic acids may be preferably used and aliphatic sulfonic acids may be more preferably used.
• Preferable aliphatic sulfonic acids include alkane sulfonic acids and alkanol sulfonic acids.
• alkane sulfonic acids include methanesulfonic acid, ethanesulfonic acid, 1-propanesulfonic acid, 2-propanesulfonic acid, 1-butanesulfonic acid, 2-butanesulfonic acid and pentanesulfonic acid, etc.
• alkanol sulfonic acids examples include 2-hydroxyethane-1-sulfonic acid (isethionic acid), 2-hydroxypropane-1-sulfonic acid (2-propanolsulfonic acid), 2-hydroxybutane-1-sulfonic acid and 2-hydroxypentane-1-sulfonic acid, as well as 1-hydroxypropane-2-sulfonic acid, 3-hydroxypropane-1-sulfonic acid, 4-hydroxybutane-1-sulfonic acid and 2-hydroxyhexane-1-sulfonic acid, etc.
• either or both of the silver plating bath (A) and the strike plating bath (B) may at least contain one or more aliphatic or aromatic phosphines represented by the Formula (1):
• X 1 , X 2 and X 3 which may be the same or different, each represent a hydrogen atom, a substituted or unsubstituted C 1 to C 10 alkyl group, or a substituted or unsubstituted benzene ring, one or more substituents for the substituted alkyl or the substituted benzene ring being selected from the group consisting of a hydroxyl group, a carboxyl group, a sulfonic group and an amino group, provided that all of X 1 , X 2 and X 3 are not hydrogen atoms at the same time.
• Y 1 , Y 2 and Y 3 which may be the same or different, each represent an unsubstituted C 1 to C 3 alkyl group or a C 1 to C 3 alkyl group substituted with one or more substituents selected from the group consisting of a hydroxyl group, a carboxyl group, a sulfonic group and an amino group,
• the phosphines include unsubstituted alkyl phophines in which each alkyl group is a methyl group, an ethyl group or a propyl group; and substituted alkyl phosphines in which each alkyl group is substituted by one or more substituents selected from the group consisting of a hydroxyl group, a carboxyl group, a sulfonic group and an amino group.
• the substituted alkyl phosphines include hydroxy lower alkyl phophines having a hydroxymethyl group, a hydroxyethyl group or a hydroxypropyl group; carboxy lower alkyl phophines having a carboxymethyl group, a carboxyethyl group or a carboxypropyl group; sulfo lower alkyl phophines having a sulfomethyl group, a sulfoethyl group or a sulfopropyl group; and amino lower alkyl phophines having an aminomethyl group, an aminoethyl group or an aminopropyl group.
• Tris(hydroxy lower alkyl)phophines in which one hydrogen atom on each lower alkyl group is substituted by a hydroxyl group to form each hydroxy lower alkyl selected from the group consisting of a hydroxymethyl group, a hydroxyethyl group and a hydroxypropyl group, may be more preferably used among these phosphines from the viewpoints of cost and stability. Tris(3-hydroxypropyl)phophine may be most preferably used.
• the copper strike plating bath (B1) of the present invention preferably contains at least a sulfate ion as one of the bath components.
• any or all of the silver plating bath (A), the copper strike plating bath (B1) and the silver strike plating bath (B2) of the present invention may further contain an azole and/or thiophene compound.
• azole compounds tetrazoles, imidazoles, benzimidazoles, pyrazoles, indazoles, thiazoles, benzothiazoles, oxazoles, benzoxazoles, triazoles and derivatives thereof may be preferably used.
• imidazoles, pyrazoles, indazoles and triazoles may be more preferably used, and triazoles may be most preferably used. Examples of these compounds are listed below.
• Preferred imidazoles include imidazole, 1-methylimidazole, 1-phenylimidazole, 2-methylimidazole, 2-ethylimidazole, 2-propylimidazole, 2-butylimidazole, 2-phenylimidazole, 4-methylimidazole, 4-phenylimidazole, 2-aminoimidazole, 2-mercaptoimidazole, imidazole-4-carboxylic acid, benzimidazole, 1-methylbenzimidazole, 2-methylbenzimidazole, 2-ethylbenzimidazole, 2-butylbenzimidazole, 2-octylbenzimidazole, 2-phenylbenzimidazole, 2-trifluoromethylbenzimidazole, 4-methylbenzimidazole, 2-chlorobenzimidazole, 2-hydroxybenzimidazole, 2-aminobenzimidazole, 2-mercaptobenzimidazole, 2-methylthiobenzimidazole, 5-nitrobenzimi
• Preferred pyrazoles or indazoles include pyrazole, 3-methylpyrazole, 4-methylpyrazole, 3,5-dimethylpyrazole, 3-trifluoromethylpyrazole, 3-aminopyrazole, pyrazole-4-carboxylic acid, 4-bromopyrazole, 4-iodopyrazole, indazole, 5-aminoindazole, 6-aminoindazole, 5-nitroindazole, 6-nitroindazole, etc. More preferred pyrazoles include pyrazole and 3-aminopyrazole.
• Examples of compounds other than imidazoles, pyrazoles and indazoles include tetrazoles, thiazoles, benzothiazoles, oxazoles, benzoxazoles and triazoles.
• Preferred tetrazoles and derivatives thereof include tetrazole, 5-aminotetrazole, 5-mercapto-1-methyltetrazole and 5-mercapto-1-phenyltetrazole, etc.
• Preferred thiazoles or benzothiazoles and derivatives thereof include thiazole, 4-methylthiazole, 5-methylthiazole, 4,5-dimethylthiazole, 2,4,5-trimethylthiazole, 2-bromothiazole, 2-aminothiazole, benzothiazole, 2-methylbenzothiazole, 2,5-dimethylbenzothiazole, 2-phenylbenzothiazole, 2-chlorobenzothiazole, 2-hydroxybenzothiazole, 2-aminobenzothiazole, 2-mercaptobenzothiazole and 2-methylthiobenzothiazole, etc.
• Preferred oxazoles or benzoxazoles and derivatives thereof include isoxazole, anthranil, benzoxazole, 2-methylbenzoxazole, 2-phenylbenzoxazole, 2-chlorobenzoxazole, 2-benzooxazolinone and 2-mercaptobenzoxazole, etc.
• Preferred triazoles and derivatives thereof include 2H-1,2,3-triazole-2-ethanol, N-trimethylsilyl-1,2,4-triazole, 3-amino-5-methyl-1,2,4-triazole, 5,5′-diamino-3,3′-bis-1,2,4-triazole, 4H-1,2,4-triazole-4-propanol, 1,2-dihydroxy-5-(phenylmethyl)-3H-1,2,4-triazole-3-thione, 1,2,4-triazole-1-acetic acid, 1,2,3-triazole, 1,2,4-triazole, 1H-1,2,4-triazole-1-ethanol, 1,5-dimethyl-1H-1,2,3-triazole-4-carboxylic acids, 5-amino-1,2,4-triazole-3-carboxylic acids, 2H-1,2,3-triazole-2-acetic acid, 1,2,4-triazole-3-carboxylic acids, 1-methyl-1,2,4-triazole-3-
• Preferred thiophenes and derivatives thereof include thiophene, 2-bromothiophene, 2-thiophenenitrile, 3-dodecylthiophene, 4-dibenzothiophene-4-boric acid, tetrahydrothiophene, benzothiophene-3-boric acid, tetrahydrothiophene-1,1-dioxide, 2-(acetylamino)thiophene, 2-benzoylthiophene, 3-thiopheneacetonitrile, 2-amino-5-methylthiophene-3-nitrile, 4-methyl-2-thiophenecarboxylic acids, 2-chloro3-methylthiophene, 3-[(chloroacetyl)amino]-2-thiophenemethylcarboxylates, 3-acetylthiophene, 5-chlorothiophene-2-boric acid, 5-methylthiophene-2-boric acid, 2-thiophenesul
• the above-stated compounds may be used preferably in the range of 0.01 to 50 g/L and more preferably in the range of 0.05 to 10 g/L.
• any or all of the silver plating bath (A) and the strike plating bath (B) may further contain a surfactant and/or surface-active polymer compound.
• the addition of the surfactant and/or surface-active polymer compound may improve one or more properties including throwing power, refinement and uniformity in grain size, and adhesiveness, etc.
• Preferred surfactants include known cationic surfactants, anionic surfactants, nonionic surfactants and amphoteric surfactants, which may be used alone or in combination as necessary.
• Preferred cationic surfactants include tetra(lower alkyl)ammonium halides, alkyl trimethylammonium halides, hydroxyethylalkylimidazolines, polyoxyethylenealkylmethylammonium halides, alkylbenzalkonium halides, dialkyldimethylammonium halides, alkyldimethyl benzilammonium halides, alkylamine hydrochlorides, alkylamine acetates, alkylamine oleates, alkylaminoethylglycins, alkylpyridinium halides, etc.
• Preferred anionic surfactants include alkyl(or formalin condensate)- ⁇ -naphthalene sulfonic acid(or salt thereof), fatty acid soaps, alkylsulfonates, ⁇ -olefinsulfonates, alkyl benzene sulfonates, alkyl(or alkoxy)naphthalenesulfonates, alkyldiphenylether disulfonates, alkylethersulfonates, alkylsulfate salts, polyoxyethylenealkylethersulfate salts, polyoxyethylene alkylphenol ether sulfate salts, higher-alcohol monophosphate salts, polyoxyalkylene alkylether phosphates, polyoxyalkylenealkylphenylether phosphates, polyoxyalkylene phenylether phosphates, polyoxyethylene alkylether acetates, alkyloyl sarcosines, alkyloyl s
• Preferred nonionic surfactants or surface-active polymer compounds include polyoxyalkylene alkyl ethers(or esters), polyoxyalkylene phenyl(or alkyl phenyl)ethers, polyoxyalkylene naphthyl(or alkyl naphthyl)ethers, polyoxyalkylene styrenated phenyl ethers(or derivatives thereof having a polyoxyalkylene chain added to the phenyl group), polyoxyalkylene bisphenol ethers, polyoxyethylene polyoxypropylene block polymers, polyoxyalkylene sorbitan fatty acid esters, polyoxyalkylene sorbitan fatty acid esters, polyethylene glycol fatty acid esters, polyoxyalkylene glycerine fatty acid esters, polyoxyalkylene alkyl amines, condensation adducts of ethylenediamine and polyoxyalkylene, polyoxyalkylene fatty acid amides, polyoxyalkylene castor (or/and hardened
• Preferred amphoteric surfactants include 2-alkyl-N-carboxymethyl (or ethyl)-N-hydroxyethyl(or methyl)imidazolinium betaines, 2-alkyl-N-carboxymethyl(or ethyl)-N-carboxymethyloxyethylimidazolinium betaines, dimethyl alkyl betaines, N-alkyl- ⁇ -aminopropionic acids (or salts thereof), alkyl(poly)aminoethyl glycines, N-alkyl-N-methyl- ⁇ -alanines (or salts thereof), fatty acid amido propyldimethyl aminoacetic acid betaines, etc.
• the content of these surfactants is generally in the range of 0.001 g/L to 50 g/L and preferably in the range of 0.01 g/L to 50 g/L.
• the acid strike plating bath and the silver plating bath used in the silver plating method of the invention may contain a grain refiner, a smoother and a brightener, etc., alone or in combination, in addition to the above-stated surfactants.
• the content thereof is generally in the range of 0.01 to 50 g/L and preferably in the range of 0.1 to 30 g/L.
• any or all of the silver plating bath (A) and the strike plating bath (B) used in the invention may further contain a displacement deposition prevention agent.
• Any known displacement deposition prevention agents may be used.
• the agent include heterocyclic thione compounds, amide or imide compounds, amino acids, open chain secondary amines having a sulfur atom and a double bond, cyclic thiol compounds having a sulfur atom with a double bond, amino or thiol compounds having a pyridine, pyrimidine, piperidine, piperazine or triazine skelton, etc.
• agent examples include 3-amino rhodanine, 3-thiourazole, 2-thiouramil, 4-thiouramil, 2,5-dioxo-4-thio-hexahydropyrimidine, 4,6-dioxo-2-thio-hexahydropyrimidine, 2,6-dioxo-4-thio-hexahydropyrimidine, glutamic acid imide, succinimide, glutamic acid, arginine, valine, diethylthiourea, dimethylthiourea, thioacetamide, allylthiourea, thiosemicarbazide, dimercaptothiadiazole, thiosalicylic acid, benzoxazole, thiobenzamide, 2-aminopyridine, 3-aminopyridine, 4-aminopyridine, aminopyrimidine, N-aminopyrrolidine, N-aminomethylpyrrolidine, N-aminoethylpyrrolidine,
• the invention may further comprise a displacement deposition prevention treatment step after the strike plating in case where the copper strike plating bath (B2) is used for the strike plating.
• the displacement deposition prevention agents as mentioned above that may be contained in the silver plating bath (A) and/or the strike plating bath (B) may be contained in the solution used for this step.
• an acid degreasing bath may be preferably used in the degreasing step, which is conducted prior to the silver or copper strike plating.
• the degreasing step though it is not limited to using the acid bath and an alkaline bath may be also used, it is recommendable to use the acid degreasing bath in the degreasing step if the resist or masking agent used for patterning has a weak resistance to alkali.
• either or both of the silver plating bath (A) and the strike plating bath (B) include an ion-exchange membrane to conduct the silver plating and/or the silver strike plating with an anode being separated from a cathode.
• the ion-exchange membrane may be preferably applied to any of the silver plating bath (A) and the strike plating bath (B), it may be more preferably applied to the strike plating bath (B). Furthermore, it may be still more preferably applied to the strike plating bath that is stabilized by a complexing agent. It can bring a remarkable effect to the strike plating bath using a phosphine compound as the complexing agent.
• the anion-exchange membrane may be preferably used.
• the ion-exchange membrane By separating the cathode and the anode with the ion-exchange membrane, the disintegration of the complexing agent, smoother, and brightener, etc., added in the plating bath or the strike plating bath may be prevented. The adverse effect on the plating film of compounds generated by consumption or disintegration of these additives may be also prevented.
• the ion-exchange membrane may also prevent an increase in silver concentration in the bath when a silver anode is used, facilitating the control of metal concentration in the bath.
• an insoluble anode By separating the cathode and the anode, accordingly the cathode chamber and the anode chamber (i.e. catholyte and anolyte), an insoluble anode may be used.
• the insoluble anode that made of any known materials such as a carbon anode, a platinum anode, a platinum-coated titanium anode, a ruthenium oxide-coated electrode and iridium oxide-coated electrode, etc. may be used. Accordingly, the silver anode and the insoluble anode as stated above may be used alone or in combination as the anode.
• the method of silver plating using the acid bath according to the invention generally comprises the successive steps of, but not limited to, degreasing, acid activation, strike plating and silver plating. Water washing is usually conducted between each step.
• the acid silver strike plating is generally conducted under the following conditions.
• the bath temperature is preferably 10 to 50 degrees C. and more preferably 20 to 35 degrees C.
• the electric current density is preferably 0.5 to 5 A/dm 2 and more preferably 2 to 3 A/dm 2 .
• the plating time is preferably 10 to 300 seconds and more preferably 20 to 100 seconds.
• the acid copper strike plating is generally conducted under the following conditions.
• the bath temperature is preferably 20 to 40 degrees C. and more preferably 25 to 35 degrees C.
• the electric current density is preferably 0.2 to 10 A/dm 2 and more preferably 1 to 5 A/dm 2 .
• the plating time is preferably 10 to 300 seconds and more preferably 20 to 100 seconds.
• the silver plating is generally conducted under the following conditions.
• the bath temperature is preferably 10 to 50 degrees C. and more preferably 15 to 40 degrees C.
• the electric current density is preferably 0.1 to 10 A/dm 2 and more preferably 0.5 to 5 A/dm 2 .
• the plating time changes as appropriate in accordance with the desired thickness of plating film.
• Each plating process was evaluated from the aspects of both adhesiveness of plating film and existence of dissolution of resist.
• Adhesiveness of plating film was evaluated by a bending test. In the bending test, each test piece was bent 90 degrees twice in accordance with JIS-H8504 standards before checking whether peeling of plating film occurred or not. The dissolution of resist was checked during or after conducting each plating process onto a test piece having a simulated pattern formed with a plating resist.
• As for the plating resist developer and resist stripper, PHOTO FINER PER-2000 series (Taiyo Ink MFG, Co., Ltd) was applied for the formation of the simulated pattern under the standard conditions.
• Acid degreasing, silver cyanide strike plating, acid silver plating and drying were applied to a copper substrate in this order. Washing was conducted between each step.
• the composition of the treatment bath used in each step is as follows.
• Silver plating bath silver methanesulfonate (as silver) 30 g/L methanesulfonic acid 80 g/L 3-amino-1,2,4-triazole 5 g/L 1,2,4-triazole 3 g/L 2-mercaptobenzimidazole 0.1 g/L temperature 25 degrees C. electric current density 1 A/dm 2 plating time 5 min
• Acid degreasing, alkaline pyrophosphate copper strike plating, displacement prevention treatment, 5% methanesulfonic acid dipping, acid silver plating, and drying were applied to a 42 alloy substrate in this order. Washing was conducted between each step.
• the composition of the treatment bath used in each step is as follows.
• Alkaline copper pyrophosphate strike plating bath copper pyrophosphate (as copper) 25 g/L pyrophosphoric acid 200 g/L ammonium nitrate 7 g/L temperature 55 degrees C. electric current density 4 A/dm 2 plating time 60 sec
• Silver plating bath silver methanesulfonate (as silver) 30 g/L methanesulfonic acid 80 g/L 3-amino-1,2,4-triazole 5 g/L 1,2,4-triazole 3 g/L 2-mercaptobenzimidazole 0.1 g/L temperature 25 degrees C. electric current density 1 A/dm 2 plating time 5 min
• Acid degreasing, acid silver strike plating, acid silver plating and drying were applied to a copper substrate in this order. Washing was conducted between each step.
• the composition of the treatment bath used in each step is as follows.
• Silver strike plating bath silver methanesulfonate (as silver) 3 g/L tris(3-hydroxypropyl)phosphine 15 g/L methanesulfonic acid 40 g/L temperature 25 degrees C. electric current density 2.5 A/dm 2 plating time 60 sec
• Silver plating bath silver methanesulfonate (as silver) 30 g/L methanesulfonic acid 80 g/L 3-amino-1,2,4-triazole 5 g/L 1,2,4-triazole 3 g/L 2-mercaptobenzimidazole 0.1 g/L temperature 25 degrees C. electric current density 1 A/dm 2 plating time 5 min
• Acid degreasing, acid activation, silver strike plating, silver plating and drying were applied to a copper substrate in this order. Washing was conducted between each step.
• the composition of the treatment bath used in each step is as follows. In Example 2, the anode and the cathode were separated by an anionic exchange membrane in the silver strike plating bath. Iridium oxide was used as the anode. 5% methanesulfonic acid solution was used as anolyte.
• Silver strike plating bath silver methanesulfonate (as silver) 3 g/L tris(3-hydroxypropyl)phosphine 15 g/L methanesulfonic acid 40 g/L temperature 25 degrees C. electric current density 2.5 A/dm 2 plating time 60 sec
• Silver plating bath silver methanesulfonate (as silver) 30 g/L methanesulfonic acid 80 g/L polyvinyl pyrrolidone 1 g/L 2-(2′-hydroxy-5′-methylphenyl) 0.1 g/L benzotriazole 2-aminothiazole 0.5 g/L temperature 25 degrees C. electric current density 1 A/dm 2 plating time 5 min
• Acid degreasing, silver strike plating, silver plating and drying were applied to a 42 alloy substrate in this order. Washing was conducted between each step.
• the composition of the treatment bath used in each step is as follows.
• Silver strike plating bath silver isethionate (as silver) 3 g/L tris(3-hydroxypropyl)phosphine 15 g/L isethionic acid 40 g/L temperature 25 degrees C. electric current density 2.5 A/dm 2 plating time 60 sec
• Acid degreasing, silver strike plating, silver plating and drying were applied to a 42 alloy substrate in this order. Washing was conducted between each step.
• the silver plating bath contained displacement prevention agent.
• the composition of the treatment bath used in each step is as follows.
• Silver strike plating bath silver methanesulfonate (as silver) 3 g/L tris(3-hydroxypropyl)phosphine 15 g/L methanesulfonic acid 40 g/L 3-amino rhodanine 0.05 g/L temperature 25 degrees C. electric current density 2.5 A/dm 2 plating time 60 sec
• Silver plating bath silver methanesulfonate (as silver) 30 g/L methanesulfonic acid 80 g/L alkylamineoxide-based surfactant 0.1 g/L thiophene-2-carboxylic acid 0.5 g/L temperature 25 degrees C. electric current density 1 A/dm 2 plating time 5 min
• Acid degreasing, copper strike plating, displacement prevention treatment, acid dipping, silver plating and drying were applied to a 42 alloy substrate in this order. Washing was conducted between each step.
• the composition of the treatment bath used in each step is as follows.
• Copper strike plating bath copper methanesulfonate (as copper) 10 g/L tris(3-hydroxypropyl)phosphine 15 g/L methanesulfonic acid 10 g/L sulfuric acid 50 g/L temperature 50 degrees C. electric current density 5 A/dm 2 plating time 10 sec
• Displacement prevention treatment bath dipotassium hydrogenphosphate 5 g/L 2-mercaptobenzimidazole 0.03 g/L amino piperazine 1 ml/L temperature 20 degrees C. dipping time 10 sec
• Silver plating bath silver methanesulfonate (as silver) 30 g/L methanesulfonic acid 80 g/L tris(3-hydroxypropyl)phosphine 150 g/L 1,2,4-triazole 4 g/L 2-mercapto-benzothiazole 0.05 g/L 4-amino-1,2,4-triazole 3 g/L temperature 25 degrees C. electric current density 1 A/dm 2 plating time 5 min
• Acid degreasing, copper strike plating, silver strike plating, silver plating and drying were applied to a 42 alloy substrate in this order. Washing was conducted between each step.
• the composition of the treatment bath used in each step is as follows.
• Copper strike plating bath copper methanesulfonate (as copper) 10 g/L tris(3-hydroxypropyl)phosphine 15 g/L methanesulfonic acid 10 g/L sulfuric acid 50 g/L temperature 50 degrees C. electric current density 5 A/dm 2 plating time 10 sec
• Silver strike plating bath silver methanesulfonate (as silver) 3 g/L tris(3-hydroxypropyl)phosphine 15 g/L methanesulfonic acid 40 g/L aminopiperazine 1 ml/L temperature 25 degrees C. electric current density 2.5 A/dm 2 plating time 60 sec
• Silver plating bath silver methanesulfonate (as silver) 30 g/L methanesulfonic acid 80 g/L 3-mercapto-1,2,4-triazole 10 g/L 1,2,4-triazole 1 g/L 2-mercapto-benzothiazole 0.05 g/L temperature 25 degrees C. electric current density 1 A/dm 2 plating time 5 min

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• 2006
  • 2006-06-09 JP JP2006161049A patent/JP2007327127A/ja active Pending
• 2007
  • 2007-06-07 US US11/759,417 patent/US20070284258A1/en not_active Abandoned

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