JP5380593B2 - Copper plating method - Google Patents

Description

  The present invention generally relates to a copper plating method. More specifically, the present invention relates to an electrolytic copper plating pretreatment liquid suitable for forming a copper plating layer having a thickness of up to about 20 μm on a metal and a copper plating method using the same.

  Electro copper plating is used in various industrial applications. For example, it is also used for decorative plating films and corrosion protection films. It is also used in the electronics industry such as printed circuit boards and semiconductor manufacturing. In the production of a circuit board, copper plating is applied to a wiring layer formed on the surface of a printed circuit board or a conductive layer on a wall surface of a through hole penetrating between the surfaces of the board.

  Electroplating methods for forming metal films on articles such as copper-clad laminates, printed wiring boards, and wafers generally include a degreasing process for removing oil and fat components adhering to the substrate surface, and washing with acid after sulfuric acid. An active process, optionally water washing, is performed for the electroplating process. In the degreasing step, the object to be plated is treated with an acidic solution containing an acid component such as phosphoric acid and an additive such as a surfactant in order to remove the oil and fat component adhering to the surface of the object to be plated. In the acid activation step, the object to be plated is treated with an acidic solution containing sulfuric acid as a main component, and the oxide remaining on the metal surface on the object to be plated is removed. The acidic solution used for this acid activation process may be called a pre-dip bath. Common acidic copper plating solutions improve the uniformity and quality of copper ions that dissolve from copper sulfate salts, electrolytes such as sulfuric acid in sufficient quantities to impart conductivity to the plating bath, and plating films. Brightener or copper deposition accelerator (Brightener), hyperpolarizer (leveler), surfactant, copper deposition inhibitor, and the like.

  In electrolytic copper plating solutions used in the manufacture of printed circuit boards, it is known that bright and uniformly deposited copper plating films can be obtained on substrates by using brighteners, leveling agents, and surfactants. It has been. As an additive for a copper sulfate plating solution composition containing copper sulfate and sulfuric acid, a plating solution for adding polyalkylene oxide and chloride ions (for example, Patent Document 1) is known. This patent publication discloses that chloride ions and bromide ions have equivalent actions, and that chloride ions and bromide ions can be added to the copper plating solution. In addition, as a copper sulfate plating solution, a compound containing at least one heteroatom of sulfur, nitrogen, or a plating solution containing bromine ions or iodine ions (for example, Patent Document 2) without containing organic additives and chloride ions, A plating solution containing a reaction product of an alkylene oxide compound and epichlorohydrin (for example, Patent Document 3) is known.

US Pat. No. 2,931,760 Japanese Unexamined Patent Publication No. 63-186893 JP 2004-250777 A

  However, in recent years, when manufacturing a flexible printed circuit board based on a polyimide resin or the like, the conductive circuit layer formed on the board should be thickened because the folding resistance and flexibility of the board may be impaired. There are certain restrictions on. However, generally, when a copper plating layer having a relatively thin thickness of up to about 20 μm is deposited using a conventionally known electrolytic copper plating solution, the obtained copper plating layer has a good appearance and physical properties. It wasn't. That is, when the thickness of the copper plating layer is thinner than about 20 μm, the surface of the copper plating film has a uniform and good gloss depending on the surface roughness of the underlying metal and the size of the copper plating particles to be deposited. It was difficult to obtain a copper plating film.

  The present invention provides a copper plating method capable of depositing a copper plating film having a uniform surface, a smooth surface, and a specular gloss even when the copper plating film is relatively thin. Objective. In particular, the present invention has a uniform and smooth surface when forming thin copper plating in copper plating on a copper clad laminate or copper plating for forming a conductor circuit of a printed circuit board, An object of the present invention is to provide an electrolytic copper plating method capable of forming a glossy copper plating film.

  In order to solve the above-mentioned problems, the present inventor has intensively studied a copper plating method and a pretreatment liquid. As a result, before performing an electrolytic copper plating process in the copper plating method, the object to be plated is treated with a solution containing bromide ions. By doing so, it was found that even a relatively thin copper plating film can deposit a copper plating film having excellent gloss and uniform precipitation, and having a smooth surface. It came.

  In one aspect of the present invention, after a pretreatment liquid containing at least 0.75 mg / L bromide ions and an object to be plated are brought into contact with each other, copper plating is deposited by electrolytic copper plating using the copper plating liquid. A copper plating method characterized by the above.

  In another aspect, the present invention is characterized in that an object to be plated is brought into contact with a pre-dip acidic solution containing at least 0.75 mg / L bromide ions, and copper plating is deposited by electrolytic copper plating using a copper plating solution. A copper plating method is provided.

  In the present invention, the pre-dip acidic solution containing at least 0.75 mg / L bromide ions and the object to be plated are contacted, washed with water, and then copper plating is deposited by electrolytic copper plating using a copper plating solution. A copper plating method characterized by the above.

  Furthermore, as another aspect of the present invention, after bringing a pretreatment liquid containing at least 0.75 mg / L bromide ions into contact with an object to be plated, copper plating is deposited by electrolytic copper plating using the copper plating liquid. In the copper plating method, the copper plating solution contains copper ions, an electrolyte and chloride ions and bromide ions, and the contents of chloride ions and bromide ions in the copper plating solution are represented by the following formulas (1) and (2 And a copper plating method characterized by satisfying the relationship of (3);

(In the formula, Cl is a chloride ion concentration (mg / L) in the copper plating solution composition, and Br is a bromide ion (mg / L) in the copper plating solution composition).
I will provide a.

  Another aspect of the present invention provides a pretreatment solution for electrolytic copper plating containing at least 0.75 mg / L of bromide ions.

  By using the copper plating method of the present invention, even when a copper plating film having a relatively thin thickness is deposited, copper having an excellent plating appearance and depositing uniformly and having a smooth surface It is possible to deposit a plating film. A thin copper plating film having a specular gloss is useful for forming a circuit of a flexible printed circuit board.

Hereinafter, the present invention will be described in detail.
Abbreviations used throughout this specification have the following meanings unless otherwise indicated.
g = grams; mg = milligram; ° C. = degrees centigrade; min = minute; m = meters; cm = centimeters; [mu] m = micron (micrometer); L = liter; mL = milliliter; A = amperes; mA / cm ² = Milliamperes per square centimeter; ASD = amperes per square decimeter; dm ² = square decimeter. All numerical ranges include boundary values unless otherwise specified, and can be combined in any order. All amounts are percent by weight, unless otherwise specified, and all ratios are by weight.
Throughout this specification, the terms “plating solution” and “plating bath” have the same meaning and are used interchangeably. The term “brightener” means an organic compound additive that acts to increase the plating deposition rate of an electroplating bath, and has the same meaning as the terms “precipitation accelerator” and “brightener”, and is interchangeable. Used for. The term “precipitation inhibitor” means the same meaning as the term “carrier” and means an organic compound additive having an action of suppressing the plating deposition rate of metal in electroplating. The term “leveler” or “leveling agent” means an organic compound that acts in electroplating to form a substantially flat deposited metal layer. The term “alkane”, “alkanol” or “alkylene” refers to a linear or branched alkane, alkanol or alkylene, respectively.

  In the present invention, for example, an object to be plated such as a build-up printed circuit board, a flexible printed circuit board, or a wafer is brought into contact with a treatment liquid containing at least 0.75 mg / L bromide ions, and then the copper plating solution is used to electrically It is a copper plating method characterized by depositing copper plating by copper plating.

The treatment liquid containing bromide ions of the present invention may be a pretreatment liquid that is brought into contact with the object to be plated immediately before the electrolytic copper plating treatment, or may be a pre-dip acidic solution used in the acid activation step. good. That is,
(I) a step of degreasing the object to be plated;
(Ii) performing an acid activity treatment;
(Iii) a step of bringing a pretreatment liquid containing bromide ions into contact with an object to be plated;
(Iv) a step of electrolytic copper plating;
An electrolytic copper plating method including Washing the object to be plated between the steps does not affect the effect obtained by the method of the present invention, and can be washed between the steps as needed.

  Moreover, the said process (ii) and (iii) can also be performed simultaneously by adding a bromide ion in the pre-dip acidic solution used by an acid activation process. It is also possible to treat the object to be plated with a pre-dip acidic solution to which bromide ions have been added, and then treat the object to be plated with a pretreatment liquid containing bromide ions.

  In the present invention, the pretreatment liquid containing bromide ions is preferably an aqueous solution containing bromide ions. Bromide ions in the aqueous solution are added in an amount of at least 0.75 mg / L or more, preferably at least 1 mg / L or more, more preferably at least 2 mg / L or more. The bromide ions can be added to the pretreatment liquid up to 1000 mg / L, preferably up to 100 mg / L. The pretreatment liquid containing bromide ions can contain other compounds, surfactants, acids, corrosion inhibitors, and the like, but is preferably an aqueous solution composed of bromide ions and water. As water, deionized water, tap water, distilled water, or the like can be used.

  In the present invention, bromide ions are preferably supplied from a bromide ion source that is soluble in a pretreatment aqueous solution or a pre-dip acidic solution and can supply bromide ions (bromine ions). Such bromide ion sources include hydrogen bromide, potassium bromide, sodium bromide, magnesium bromide, copper (II) bromide, silver bromide, bromoform, carbon tetrabromide, ammonium bromide, tetraethylammonium bromide, Examples thereof include bromide compounds such as 1-ethyl-3-methylimidazolium bromide that do not adversely affect the pretreatment liquid and the copper plating bath. These bromide ion sources can be used alone or in combination of two or more.

  In the present invention, the pre-dip acidic solution is a solution mainly used to remove oxides remaining on the metal surface on the object to be plated, which is used for the acid activation treatment. The pre-dip acidic solution is preferably an aqueous solution containing an acid. Specific examples include aqueous solutions of sulfuric acid, methanesulfonic acid, fluoroboric acid, and the like. The acid can be used alone or in combination of two or more. The pre-dip acidic solution is an aqueous solution containing the acid at a concentration of 1 to 50% by weight, preferably 5 to 20% by weight. The pre-dip acidic solution of the present invention may contain an arbitrary surfactant, a halogen ion other than bromide ions, a nitrogen atom-containing organic compound, a sulfur atom-containing organic compound, and the like.

  Examples of the surfactant include anionic, cationic, nonionic and amphoteric surfactants, and nonionic surfactants are particularly preferable. A preferred nonionic surfactant is a polyether containing an ether oxygen atom in one molecule. For example, polyoxyethylene lauryl ether, polyethylene glycol, polypropylene glycol, polyoxyethylene alkyl ether, polyoxyethylene polyoxypropylene glycol, polyoxyethylene nonylphenyl ether, polyoxyethylene polyoxypropylene alkylamine, polyoxyalkylene addition of ethylenediamine Preferably, polyoxyethylene monoalkyl ether such as polyoxyethylene monobutyl ether, polyoxypropylene monobutyl ether, polyoxyethylene polyoxypropylene glycol monobutyl ether, polyethylene glycol or phenol ethoxy having a repetition number of 5 to 500 Rate. Such surfactants can be used alone or in combination of two or more.

  Examples of halogen ions other than bromide ions that can be contained in the pre-dip acidic solution include chloride ions (chlorine ions) and iodine ions. Chloride ions are preferably supplied from a chloride ion source that is soluble in the pre-dip acidic solution and can supply chloride ions (chlorine ions). Such chloride ion sources include hydrogen chloride, sodium chloride, copper chloride, ammonium chloride, lithium chloride, potassium chloride, and other chloride compounds that do not adversely affect the pre-dip acidic solution and the copper plating bath. Similarly, iodine ions are soluble in the pre-dip acidic solution and are preferably supplied from an iodine ion source capable of supplying iodine ions. These chloride ion source and iodine ion source can be used alone or in combination of two or more.

  The nitrogen atom-containing organic compound that can be contained in the pre-dip acidic solution includes amine compounds, amide compounds, thioamide compounds, compounds having an aniline or pyridine ring, other heterocyclic compounds or condensed heterocyclic compounds, aminocarboxylic acids, and the like. For example, alkylamine, dialkylamine, trialkylamine, arylalkylamine, imidazole, triazole, tetrazole, benzimidazole, benzotriazole, piperidine, morpholine, piperazine, pyridine, oxazole, benzoxazole, pyrimidine, quinoline, Isoquinoline, thiourea, dimethylthiourea, glycine, diaminomethyleneaminoacetic acid, N-methylglycine, dimethylglycine, β-alanine, cysteine, glutamic acid, asparagi Acid, and the like reaction products disclosed imidazole and diethylene glycol with epichlorohydrin in JP 2004-250777. Such nitrogen atom-containing organic compounds can be used alone or in combination of two or more.

Examples of the sulfur atom-containing organic compound that can be contained in the pre-dip acidic solution include organic compounds having one or more sulfur atoms and having a sulfide or sulfonic acid group, thiourea compounds, and benzothiazole compounds. Examples of the organic compound having a sulfido or sulfonic acid group include a compound having a —S—CH ₂ O—R—SO ₃ M structure or a compound having a —S—R—SO ₃ M structure in the molecule (in the formula, M is hydrogen or an alkali metal atom, and R is an alkylene group containing 3 to 8 carbon atoms). Specifically, for example, N, N-dimethyl-dithiocarbamic acid- (3-sulfopropyl) ester; 3-mercapto-propylsulfonic acid- (3-sulfopropyl) ester; 3-mercapto-propylsulfonic acid sodium salt; 3-mercapto-1-propanesulfonic acid potassium salt; carbonic acid-dithio-o-ethyl ester; bissulfopropyl disulfide; bis- (3-sulfopropyl) -disulfide disodium salt; 3- (benzothiazolyl-s-thio) Propylsulfonic acid sodium salt; pyridinium propyl sulfobetaine; 1-sodium-3-mercaptopropane-1-sulfonate; N, N-dimethyl-dithiocarbamic acid- (3-sulfoethyl) ester; 3-mercapto-ethylpropylsulfonic acid- ( 3-sulfoe 3-mercapto-ethylsulfonic acid sodium salt; 3-mercapto-1-ethanesulfonic acid potassium salt; carbonic acid-dithio-o-ethyl ester-s-ester; bissulfoethyl disulfide; 3- (benzothiazolyl-s) -Thio) ethyl sulfonic acid sodium salt; pyridinium ethyl sulfobetaine; 1-sodium-3-mercaptoethane-1-sulfonate; thiourea such as thiourea, 1,3-dimethylthiourea, trimethylthiourea, diethylthiourea, allylthiourea Compound etc. are mentioned.

  The compound that can be optionally added to the pre-dip acidic solution of the present invention can be optionally added in an amount within a range that does not adversely affect the effect of the pre-dip acidic solution. For example, the surfactant is 0 ppm to 200 ppm, preferably 1 ppm to 150 ppm, the halogen ion is 0 ppm to 200 ppm, preferably 100 ppm or less, and the nitrogen atom-containing organic compound is 0 ppm to 300 ppm with respect to the entire pre-dip acidic solution. The sulfur atom-containing organic compound may be added in an amount of 0 ppm to 150 ppm, preferably 0 ppm to 10 ppm, preferably 7 ppm or less.

  As the copper plating method of the present invention, by adding bromide ions to the pre-dip acidic solution, (ii) a step of performing an acid activation treatment, and (iii) a step of bringing the pretreatment liquid containing bromide ions into contact with the object to be plated; Can be performed simultaneously. The bromide ion is added to the pre-dip acidic solution in an amount of at least 0.75 mg / L, preferably at least 1 mg / L, more preferably at least 2 mg / L. The bromide ions can be added to the pre-dip acidic solution up to 1000 mg / L, preferably up to 100 mg / L.

The copper plating method of this invention can enjoy the effect of this invention by adding a bromide ion to the well-known degreasing solution used for the process of (i) degreasing the to-be-plated thing. The copper plating method in such a case includes a step of bringing a degreasing solution containing bromide ions into contact with an object to be plated in a degreasing treatment step, and a step of performing electroplating using an acid activation treatment step and a copper plating solution.
When bromide ions are added to the degreasing solution, the concentration of bromide ions in the solution of the degreasing step is at least 50 mg / L, preferably 100 mg / L or more, more preferably 200 mg / L or more.

  The copper plating method of the present invention is a degreasing step in which an object to be plated and a degreasing solution are contacted at a liquid temperature of 10 ° C. to 70 ° C., preferably room temperature to 50 ° C. for 10 seconds to 30 minutes, preferably 1 minute to 5 minutes. The step of contacting the pre-dip acidic solution and the object to be plated at a liquid temperature of 10 ° C. to 70 ° C., preferably 20 to 30 ° C. for 10 seconds to 10 minutes, preferably 30 seconds to 5 minutes, A step of treating a copper plating solution with a pretreatment solution containing bromide ions at a liquid temperature of 10 ° C. to 70 ° C., preferably 20 ° C. to 30 ° C. for 10 seconds to 10 minutes, preferably 30 seconds to 5 minutes. And using electroplating. The copper plating method in which bromide ions are added to the pre-dip acidic solution or degreasing solution can also be performed at the same liquid temperature and time as described above.

  When a pre-dip acidic solution containing bromide ions is used in the acid activation treatment step, the copper plating method of the present invention is a step of (iii) bringing the pretreatment liquid containing bromide ions into contact with the object to be plated after the acid activation treatment step. May or may not be included. Moreover, it may replace with this (iii) process and may perform water washing, and may perform an electrolytic copper plating process following an acid activation process process.

  In the present invention, a known copper plating solution can be used as the copper plating solution. The copper plating solution may contain copper ions, an electrolyte, and optional additives.

  The copper ions are preferably at least partially soluble in the electroplating bath and are supplied from a copper ion source capable of supplying copper ions. As such a copper ion source, a copper salt is preferable, and examples thereof include copper sulfate, copper chloride, copper acetate, copper nitrate, copper fluoroborate, copper methanesulfonate, copper phenylsulfonate, and copper p-toluenesulfonate. . In particular, copper sulfate or copper methanesulfonate is preferable. The copper ion source can be used alone or in combination of two or more. Such metal salts are generally commercially available and can be used without purification.

  The copper ions are present in the copper plating solution as copper ions in an amount ranging from 10 g / L to 200 g / L, preferably from 15 g / L to 100 g / L, more preferably from 20 g / L to 75 g / L. To be supplied.

  The electrolyte is preferably an acid, sulfuric acid; acetic acid; alkylsulfonic acids such as fluoroboric acid, methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, and trifluoromethanesulfonic acid: phenylsulfonic acid, phenolsulfonic acid, and toluenesulfone. Aryl sulfonic acids such as acids; sulfamic acid; hydrochloric acid; phosphoric acid and the like. In particular, sulfuric acid or methanesulfonic acid is preferable. These acids can be supplied in the form of a metal salt or halide, and can be used alone or in combination of two or more. Such an electrolyte is generally commercially available and can be used without purification.

  The electrolyte is usually present in the copper plating solution in an amount ranging from 1 g / L to 300 g / L, preferably from 5 g / L to 250 g / L, more preferably from 10 g / L to 200 g / L.

  As optional additives that can be contained in the copper plating solution, the above-described halogen ions such as bromide ions, chloride ions or iodine ions, surfactants, nitrogen atom-containing organic compounds, sulfur atom-containing organic compounds, and the like are used. it can.

  As the halogen ions, it is preferable that the copper plating solution contains chloride ions and bromide ions. The chloride ion and bromide ion concentrations are as follows when the chloride ion concentration (mg / L) in the copper plating solution composition is Cl and the bromide ion (mg / L) in the copper plating solution composition is Br: It is preferable that the concentration satisfy the relationships of the formulas (1) to (3).

  More preferably, the relationship of the following formulas (4) and (5) is satisfied.

  More preferably, the concentration satisfies the relationship of the following formulas (6) and (7).

  When a soluble anode is used in electroplating, bromide ions are 2 to 8 mg / L (mg / L) when the chloride ion concentration in the copper plating bath is in the range of more than 10 mg / L and 30 mg / L. When the chloride ion concentration in the copper plating bath is in the range of more than 30 mg / L to 70 mg / L, the bromide ion is 1 to 10 mg / L, and the chloride ion concentration in the copper plating bath is 70 mg / L to 100 mg / L. In the range up to L, the bromide ion is preferably 2 to 10 mg / L. It is particularly preferred that the chloride ion concentration in the copper plating bath is in the range of more than 30 mg / L to 70 mg / L and the bromide ion concentration is in the range of 2 to 8 g / L.

The copper plating solution may contain a known precipitation accelerator. The precipitation accelerator is selected from the above nitrogen atom-containing organic compounds.
Such precipitation accelerators may be used in various amounts and may generally be used in an amount of at least 1 mg, preferably at least 1.2 mg, more preferably at least 1.5 mg per liter of plating bath. . For example, the deposition accelerator is present in the copper plating bath in an amount ranging from 1 mg / L to 200 mg / L. The amount of precipitation accelerator particularly useful in the copper plating bath of the present invention is from 0 mg / L to 50 mg / L.

  When a surfactant is used for the copper plating solution, in the plating bath, for example, 0 g / L or more and 50 g / L or less, preferably 0.05 g / L or more and 20 g / L or less, more preferably 0.1 g / L or more. The concentration is preferably 15 g / L or less.

  The copper plating solution composition can be prepared by adding the above components in any order. For example, it is preferable to add a copper ion source and an electrolyte to water, then add a chloride ion source and a bromide ion source, and if necessary, add a leveling agent, a precipitation accelerator, a surfactant, and the like.

  The electroplating method of the present invention is carried out by bringing an object to be plated into contact with a copper plating solution and performing electroplating using the object to be plated as a cathode. As the electroplating method, a known method can be adopted. Corresponding to plating methods such as barrel plating, through-hole plating, rack plating, and high-speed continuous plating, the concentration of each component of the plating solution is arbitrarily selected.

The electroplating method can be performed, for example, at a plating bath temperature of 10 to 65 ° C., preferably room temperature to 50 ° C.
The cathode current density, for example, 0.01 to 100 A / dm ^2, and preferably suitably selected in the range of 0.05~20A / dm ^2.

  During the electroplating process, the plating bath may be unstirred, but it is also possible to select a method such as workpiece swinging, stirring with a stirrer, liquid flow with a pump, air stirring, and the like.

  The copper plating method of the present invention is useful for any object to be plated that can be electroplated with copper. Examples of such an object to be plated include a printed wiring board, an integrated circuit, a semiconductor package, a lead frame, and an interconnect. In particular, it is useful for lead frames, flexible printed wiring boards, and the like on which copper having a relatively thin thickness is deposited.

  The copper plating method of the present invention has excellent gloss without dimple-like pits even when the deposited copper plating film has a thickness of 20 microns or less, preferably 15 microns or less, more preferably 12 microns or less. A copper plating film that is uniformly deposited and has a smooth surface can be deposited.

  The following examples illustrate the invention, but such examples are illustrative only and do not limit the scope of the invention.

Example 1
20 mg / L sodium bromide was added to deionized water to prepare a pretreatment solution.
A 10 cm × 5 cm rolled copper foil that has been degreased using Acid Cleaner 1022B acid degreasing (Rohm and Haas Electronic Materials Co., Ltd.) by a known method is washed with deionized water at room temperature for 1 minute, and the liquid temperature After dipping for 1 minute in a pre-dip acidic solution consisting of a 10% strength sulfuric acid aqueous solution at 25 ° C. and for 1 minute in a prepared pretreatment solution at a liquid temperature of 25 ° C., using a copper plating solution having the following composition, Copper was deposited by plating. Electroplating was performed using a phosphorous copper-containing soluble anode so that a copper plating film having a thickness of 8 microns was deposited while stirring with air under the conditions of a liquid temperature of 25 ° C. and a current density of 3 ASD. .
The obtained copper plating film was observed visually and with a metal microscope PME3 (manufactured by Olympus Corporation). The copper plating film was uniformly deposited, had a smooth surface, and had a good specular gloss appearance with no dimple-like pits.

Example 2
A copper plating film was deposited on the rolled copper foil in the same manner as in Example 1 except that the amount of sodium bromide was 1 mg / L. The obtained copper plating film was uniformly deposited, had a smooth surface, and had a good specular gloss appearance without dimple-like pits.

Example 3
A copper plating film was deposited on the rolled copper foil in the same manner as in Example 1 except that the amount of sodium bromide was 50 mg / L. The obtained copper plating film was uniformly deposited, had a smooth surface, and had a good specular gloss appearance without dimple-like pits.

Comparative Example 1
A copper plating film was deposited on the rolled copper foil in the same manner as in Example 1 except that sodium bromide was not added and deionized water was used as a pretreatment solution. The obtained copper plating film was uniformly deposited and had a smooth surface, but had a glossy appearance with a large number of dimple-like pits.

Example 4
10 mg / L sodium bromide was added to a 10% by weight aqueous sulfuric acid solution to prepare a pre-dip acidic solution.
A 10 cm × 5 cm rolled copper foil that has been degreased using Acid Cleaner 1022B acid degreasing (manufactured by Rohm and Haas Electronic Materials Co., Ltd.) by a known method is placed in a pre-dip acidic solution at a liquid temperature of 25 ° C. for 1 minute. After immersion, copper was deposited by electroplating using the copper plating solution of Example 1. Electroplating was performed using a phosphorous copper-containing soluble anode so that a copper plating film having a thickness of 8 microns was deposited while stirring with air under the conditions of a liquid temperature of 25 ° C. and a current density of 3 ASD. .
The obtained copper plating film was observed visually and with a metal microscope PME3 (manufactured by Olympus Corporation). The copper plating film was uniformly deposited, had a smooth surface, and had a good specular gloss appearance with no dimple-like pits.

Comparative Example 2
A copper plating film was deposited in the same manner as in Example 1 except that sodium bromide was not added to the pre-dip acidic solution.
Although the obtained copper plating film was uniformly deposited, dimple-like pits were present and mirror gloss could not be obtained.

Examples 5-9 and Comparative Examples 3-4
Using the pre-dip acidic solution prepared by adjusting the bromide ion concentration in the pre-dip acidic solution as shown in Table 1, a copper plating film was deposited and observed in the same manner as in Example 4.
These results are shown in Table 1. In the table, the evaluation of uniformity is evaluated by the ratio of the thickness of the plating film at the end of the copper foil to the thickness of the plating film at the center of the copper foil, and the difference of less than 5 = 20%, 4 = 20% or more A difference of less than 40%, 3 = a difference of 40% or more and less than 60%, 2 = a difference of 60 or more and less than 80%, and 1 = a difference of 80% or more. Evaluation of dimple-like pits on the surface of the copper plating film is 5 = cannot be confirmed, 4 = can confirm pits with a shallow depth, 3 = can confirm pits with a certain number of depths, 2 = has depth Many pits can be confirmed, 1 = pits with a depth on the entire surface can be confirmed. NA means that no pretreatment liquid is used.

Example 10
A copper plating film was deposited in the same manner as in Example 2 except that 1 mg / L sodium bromide was added to the pre-dip acidic solution, and the obtained copper film was observed. The results are shown in Table 1.

A pre-dip acidic solution was prepared using a bromide compound shown in Table 2 instead of sodium bromide, and a copper plating film was deposited and observed in the same manner as in Example 4.
The results are shown in Table 2.

Example 12
Copper plating treatment was performed in the same manner as in Example 4 except that a copper plating solution having the following composition was used.
The obtained copper plating film was uniformly deposited, had a smooth surface, and had a good specular gloss appearance without dimple-like pits.

Example 13
Copper plating treatment was performed in the same manner as in Example 4 except that 100 ppm of polyoxyethylene polyoxypropylene glycol monobutyl ether was further added as a surfactant to the pre-dip acidic solution.
The obtained copper plating film was uniformly deposited, had a smooth surface, and had a good specular gloss appearance without dimple-like pits.

Example 14
The copper plating treatment was performed in the same manner as in Example 4 except that 50 ppm of hydrogen chloride was further added as chloride ions to the pre-dip acidic solution, and washing was performed immediately before the copper plating treatment.
The obtained copper plating film was uniformly deposited, had a smooth surface, and had a good specular gloss appearance without dimple-like pits.

Example 15
The copper plating treatment was performed in the same manner as in Example 4 except that the time of the copper plating treatment was adjusted so that the deposited copper plating film had a thickness shown in Table 3. Table 3 shows the results regarding the obtained copper plating film as in Example 4.

Claims (5)

A copper plating method comprising a step of treating an object to be plated with a solution containing bromide ions before performing an electrolytic copper plating treatment, wherein the solution containing bromide ions contains at least 0.75 mg / L of bromide ions. The copper plating solution contains copper ions, electrolytes, chloride ions, and bromide ions, and the content of chloride ions and bromide ions in the copper plating solution is represented by the following formulas (1), (2) and (3):

To meet the relationship. A copper plating method comprising a step of treating an object to be plated with a solution containing bromide ions before performing an electrolytic copper plating treatment, wherein the solution containing bromide ions contains at least 0.75 mg / L of bromide ions. It is an acidic solution, and the copper plating solution contains copper ions, electrolytes, chloride ions, and bromide ions, and the content of chloride ions and bromide ions in the copper plating solution is represented by the following formulas (1), (2) And (3):

To meet the relationship.   The method according to claim 1 or 2, wherein the solution containing bromide ions used in the treatment step before the electrolytic copper plating treatment further contains a surfactant.   The method according to claim 1, wherein the copper plating solution further contains a precipitation accelerator.   The printed circuit board which has a copper plating film formed by the method in any one of Claims 1-4.