Patent Application
20250215597
The present invention relates to a copper plating solution for PR pulse electrolysis and a copper plating method by a PR pulse electrolysis method.
PTL 1 is a technique disclosed by the present Applicant and discloses the following:
When copper plating is performed by a PR pulse electrolysis method using an electrolytic copper plating solution comprising the additive of the technique disclosed by the present Applicant, the appearance of the resulting plating film, film physical properties, filling performance, etc. can be improved while maintaining excellent throwing power of the PR electrolytic copper plating solution. The PR electrolytic copper plating solution comprising the additive is particularly useful for performing via filling, through-hole filling, through-hole plating, etc. by an electrolytic copper plating method.
PTL 2 discloses
An object of the present invention is to newly provide a copper plating solution for PR pulse electrolysis and a copper plating method by a PR pulse electrolysis method.
As a result of extensive research, the present inventors have developed a technique for producing a copper film by pulse electrolysis by using a polyvalent metal ion, such as an iron (II) ion, and an unsaturated fatty acid in combination, and further using an aqueous copper (II) ion solution comprising copper sulfate etc.
Specifically, the present invention encompasses the following copper plating solution for periodic reverse (PR) pulse electrolysis and the following copper plating method by a PR pulse electrolysis method.
A copper plating solution for PR pulse electrolysis, comprising:
The copper plating solution for PR pulse electrolysis according to Item 1, wherein the polyvalent metal ion is an ion of at least one polyvalent metal selected from the group consisting of cobalt, iron, and cerium.
The copper plating solution for PR pulse electrolysis according to Item 1 or 2, wherein the polyvalent metal ion is at least one polyvalent metal ion selected from the group consisting of cobalt (II), iron (II), and cerium (III).
The copper plating solution for PR pulse electrolysis according to any one of Items 1 to 3, wherein the copper plating solution for PR pulse electrolysis comprises 0.3 g/L to 3.0 g/L of the polyvalent metal ion.
The copper plating solution for PR pulse electrolysis according to any one of Items 1 to 4, wherein the unsaturated fatty acid is at least one unsaturated fatty acid selected from the group consisting of alkenes and alkynes.
The copper plating solution for PR pulse electrolysis according to any one of Items 1 to 5, wherein the unsaturated fatty acid is at least one unsaturated fatty acid selected from the group consisting of alkenes and alkynes having two or three carboxyl groups.
The copper plating solution for PR pulse electrolysis according to any one of Items 1 to 6, wherein the copper plating solution for PR pulse electrolysis comprises 0.5 g/L to 10 g/L of the unsaturated fatty acid.
The copper plating solution for PR pulse electrolysis according to any one of Items 1 to 7, wherein the copper plating solution for PR pulse electrolysis further comprises an acid component and is an acidic aqueous solution.
The copper plating solution for PR pulse electrolysis according to any one of Items 1 to 8, further comprising a halide ion.
The copper plating solution for PR pulse electrolysis according to any one of Items 1 to 9, further comprising a sulfur-containing organic compound.
The copper plating solution for PR pulse electrolysis according to any one of Items 1 to 10, wherein the copper plating solution for PR pulse electrolysis has a total content of at least one amine compound selected from the group consisting of tertiary amine compounds and quaternary amine compounds of less than 1 mg/L.
A copper plating method by a PR pulse electrolysis method, comprising:
The copper plating method by a PR pulse electrolysis method according to Item 12, wherein step (1) is performed under PR pulse electrolysis conditions of a current density ratio of anode to cathode (anode current density/cathode current density) of 0.2 to 0.85.
The copper plating method by a PR pulse electrolysis method according to Item 12 or 13, wherein step (1) is performed under PR pulse electrolysis conditions of a positive current application time of 5 milliseconds to 200 milliseconds, and an application time ratio of positive to negative currents (positive current application time/negative current application time) of 5 or more and less than 50.
Conventionally, when plating treatment is performed on a substrate in which portions with densely packed through-holes and vias are scattered, the surface film thickness after plating treatment would be non-uniform since the surface area per unit area greatly varies.
The copper plating solution for PR pulse electrolysis of the present invention comprises a polyvalent metal ion, such as an iron (II) ion, and an unsaturated fatty acid in combination, and further comprises a copper (II) ion, such as a copper sulfate aqueous solution. The use of the copper plating solution for PR pulse electrolysis of the present invention enables the formation of a copper film with a uniform surface thickness in an excellent manner by pulse electrolysis.
The use of the copper plating solution for PR pulse electrolysis of the present invention can make the surface film thickness distribution of the resulting copper film uniform.
The copper plating solution for PR pulse electrolysis of the present invention preferably does not comprise a tertiary amine compound and a quaternary amine compound.
The present invention can newly provide a copper plating solution for PR pulse electrolysis and a copper plating method by a PR pulse electrolysis method.
The present invention is described in detail below.
Embodiments representing the present invention are intended to provide a better understanding of the purpose of the invention and do not limit the scope of the invention, unless otherwise specified.
In the present specification, the terms “comprise” and “contain” include the concepts of “comprise,” “contain,” “consist essentially of,” and “consist of.”
In the present specification, the numerical range represented by “A to B” means A or more and B or less.
The copper plating solution for PR pulse electrolysis of the present invention comprises:
The copper plating solution for PR pulse electrolysis of the present invention comprises a polyvalent metal ion, such as an iron (II) ion, and an unsaturated fatty acid in combination, and further comprises a copper (II) ion, such as a copper sulfate aqueous solution. The use of the copper plating solution for PR pulse electrolysis of the present invention enables the formation of a copper film with a uniform surface thickness in an excellent manner by pulse electrolysis.
The use of the copper plating solution for PR pulse electrolysis of the present invention can make the surface film thickness distribution of the resulting copper film uniform.
The use of the copper plating solution for PR pulse electrolysis of the present invention in electrolytic copper plating by a PR pulse electrolysis method achieves excellent appearance of the resulting plating film and excellent physical properties of the plating film, as well as, for example, excellent via filling performance and through-hole filling performance.
The PR pulse electrolytic copper plating method of the present invention is useful as a plating method for via filling, through-hole filling, through-hole plating, and the like.
Excellent film thickness uniformity cannot be obtained with the use of conventional copper plating solutions that are used under direct current electrolysis conditions when such copper plating solutions comprise a polymer, a sulfur-based additive (a brightener), a tertiary amine compound, and a quaternary amine compound (a leveler) as additives.
Sufficient film thickness uniformity or excellent film physical properties cannot be obtained with the use of conventional copper plating solutions that are used under PR pulse current conditions when such copper plating solutions comprise a polymer, a sulfur-based additive (a brightener), a tertiary amine compound, and a quaternary amine compound (a leveler) as additives.
Under PR pulse current conditions with the use of conventional copper plating solutions that are used, when such copper plating solutions comprise a polyvalent metal ion, an unsaturated fatty acid, a polymer, a sulfur-based additive (a brightener), a tertiary amine compound, and a quaternary amine compound (a leveler) as additives, and have a total content of the tertiary amine compound and quaternary amine compound (leveler) of 1 mg/L or more, sufficient film thickness uniformity or excellent film physical properties cannot be obtained.
Excellent film thickness uniformity and excellent film physical properties are obtained with the use of the copper plating solution of the present invention, which is used under PR pulse current conditions, when the copper plating solution comprises a polyvalent metal ion, an unsaturated fatty acid, a polymer, and optionally a sulfur-based additive (a brightener) as additives.
Excellent film thickness uniformity and excellent film physical properties are obtained with the use of the copper plating solution of the present invention, which is used under PR pulse current conditions, when the copper plating solution comprises a polyvalent metal ion, an unsaturated fatty acid, a polymer, and optionally a sulfur-based additive (a brightener) as additives, and preferably has a total content of a tertiary amine compound and a quaternary amine compound (leveler) of less than 1 mg/L.
The copper plating solution for PR pulse electrolysis of the present invention comprises a copper (II) ion.
The copper (II) ion source for use is not particularly limited as long as it is a copper compound that is soluble in a plating solution.
The copper compound that provides the copper ion (II) source is preferably copper (II) sulfate, copper (II) oxide, copper (II) chloride, copper (II) carbonate, copper (II) pyrophosphate, copper (II) alkanesulfonates, such as copper (II) methanesulfonate, copper (II) alkanolsulfonates, such as copper (II) propanol sulfonate, organic acid copper (II), such as copper (II) caprylate, copper (II) laurate, copper (II) stearate, and copper (II) naphthenate, and the like.
The copper (II) ion source and the copper compound for use may be at least one compound selected from the group consisting of the compounds mentioned above. These copper (II) ion sources and copper compounds may be used alone or as a mixture (blend) of two or more.
The copper (II) ion concentration in the copper plating solution for PR pulse electrolysis may be any range without particular limitation. The copper (II) ion concentration in the copper plating solution for PR pulse electrolysis is preferably in the range of 10 g/L to 300 g/L.
The copper plating solution for PR pulse electrolysis of the present invention comprises a polyvalent metal ion. In the copper plating solution for PR pulse electrolysis, the polyvalent metal ion is a polyvalent metal ion, excluding copper (II) ions.
In the copper plating solution for PR pulse electrolysis, the polyvalent metal ion functions as an agent for averaging the film thickness and can improve film thickness uniformity.
A polyvalent metal compound that provides the polyvalent metal ion source is preferably a sulfate or nitrate of cobalt, iron, cerium, or the like.
The polyvalent metal ion is preferably an ion of at least one polyvalent metal selected from the group consisting of cobalt, iron, and cerium. The polyvalent metal ion is more preferably at least one polyvalent metal ion selected from the group consisting of cobalt (II), iron (II), and cerium (III).
The polyvalent metal ion source and the polyvalent metal for use may be at least one compound selected from the group consisting of the compounds mentioned above. These polyvalent metal ion sources and polyvalent metals may be used alone or as a mixture (blend) of two or more.
The polyvalent metal ion concentration in the copper plating solution for PR pulse electrolysis may be any range without particular limitation. The polyvalent metal ion concentration in the copper plating solution for PR pulse electrolysis is preferably in the range of 0.3 g/L to 3.0 g/L.
Through holes (also referred to below as “THs”) are formed in electronic components of printed circuit substrates and IC substrates to impart electrical and thermal conductivity. This structure in electronic components is becoming smaller and smaller, and in copper electroplating as well, THs (holes) are becoming smaller in diameter and more densely packed.
Electronic components are becoming more multi-layered, increasing the plate thickness and increasing the aspect ratio representing the ratio of the hole diameter to the plate thickness. When a substrate with a high aspect ratio has many portions with densely packed holes and many portions with non-densely packed holes, the surface area of the substrate varies.
A portion in which through holes (THs) are not densely packed (also referred to below as a “sparse TH portion”) has a small surface area and thus allows electricity to flow relatively easily. On the other hand, a portion in which through holes (THs) are densely packed (also referred to below as a “dense TH portion”) has a large surface area and thus serves as resistance and does not allow electric current to flow easily.
In the case of a treatment method in which a direct current is applied, a large amount of electricity flows through the sparse TH portion, resulting in thick deposition of copper on the substrate surface. On the other hand, in the dense TH portion, electricity does not flow easily, resulting in thin deposition of copper on the substrate surface.
Typically, in order to prevent a difference in current distribution due to a difference in the surface area of a printed circuit substrate, a copper plating solution for PR pulse electrolysis comprises a nitrogen-based compound that suppresses the electrodeposition of copper.
The nitrogen-based compound is usually composed of a tertiary amine compound and a quaternary amine compound, and is positively charged in an aqueous solution. When negative current is applied to a substrate, the tertiary amine compound and the quaternary amine compound, which are positively charged, are adsorbed to the substrate and become a resistor, suppressing the electrodeposition of copper.
When the entire substrate is treated under high resistance, the current distribution can be made uniform even with a difference in surface area, and a film can be formed with a uniform film thickness distribution. However, when the ratio of the number of THs per unit area between the sparse TH portion and the dense TH portion is 4 or more, the thickness of the copper surface film is no longer uniform.
For printed circuit substrates, if the copper surface film is thick, forming a fine circuit is difficult. If the copper film thickness is too thin inside the THs, the connection reliability deteriorates.
In the dense TH portion, the film on the surface and the film inside the through-holes are both thin since current does not flow easily. In order to obtain connection reliability, adjusting the time for plating treatment and the amount of current is required so that the film thickness is equal to or greater than the specified thickness. However, this will result in an increase in the thickness of the copper surface film in the sparse TH portion on the same substrate in which electricity flows easily.
The thickness of the copper surface film inside the through-holes also increases to excessively reduce the hole diameter, which will cause the treatment liquid to remain in the subsequent substrate production step, resulting in the occurrence of deficiencies.
When present in the sparse TH portions, vias will form convex shapes due to overfilling of copper. If convex shapes are formed, an additional polishing or etching step must be provided to smooth the surface shape, which causes problems in terms of economy and in terms of performing steps.
In PR pulse electrolysis, positive pulse electrolysis for electrodepositing copper and negative pulse electrolysis for dissolving copper are combined, and a cycle of switching between positive and negative is repeated in a very short period of time. PR pulse electrolysis is a technique for efficiently filling vias and through-holes with copper as a technique for improving deposition efficiency.
The copper plating solution for PR pulse electrolysis of the present invention comprises a polyvalent metal ion.
Due to sacrificial oxidation during negative pulse application, copper dissolution is less likely to occur.
The copper plating solution for PR pulse electrolysis of the present invention preferably comprises at least one unsaturated fatty acid selected from the group consisting of alkenes and alkynes having at least two carboxyl groups, or at least one unsaturated fatty acid selected from the group consisting of alkenes and alkynes having less than four carboxyl groups. The efficiency of copper deposition can improve.
The polyvalent metal ion and unsaturated fatty acid exert their effects when low current is applied.
For this reason, in the dense TH portion, sacrificial oxidation of polyvalent metal ions becomes effective, and the dissolution current is moderately suppressed, reducing copper dissolution. Accordingly, at lower positive pulses, the unsaturated fatty acid can improve the copper deposition efficiency.
On the other hand, since a higher pulse current is applied in the sparse TH portion, the effects of the polyvalent metal ion and the unsaturated fatty acid are not easily produced, and dissolution and deposition occur repeatedly; thus, a copper film is gradually formed.
As a result, the thickness of the copper film on the substrate surface in the dense TH portion and the sparse TH portion become uniform, and the copper film inside the through-holes in the dense TH portion also has a thickness that does not impair connection reliability. In the sparse TH portion, unless excessive current is applied, treatment can be performed without an increase in thickness of the copper film inside the THs.
The copper plating solution for PR pulse electrolysis of the present invention comprises an unsaturated fatty acid. In the copper plating solution for PR pulse electrolysis, the unsaturated fatty acid functions as an appearance improver and can improve film physical properties.
The unsaturated fatty acid is preferably at least one unsaturated fatty acid selected from the group consisting of alkenes and alkynes. The unsaturated fatty acid is more preferably at least one unsaturated fatty acid selected from the group consisting of alkenes and alkynes having two or three carboxyl groups. The unsaturated fatty acid is more preferably fumaric acid, maleic acid, acetylenedicarboxylic acid, aconitic acid, or the like.
The unsaturated fatty acid for use may be at least one compound selected from the group consisting of the compounds mentioned above. These unsaturated fatty acids may be used alone or as a mixture (blend) of two or more.
The content of the unsaturated fatty acid in the copper plating solution for PR pulse electrolysis may be any range without particular limitation. The content of the unsaturated fatty acid in the copper plating solution for PR pulse electrolysis is preferably in the range of 0.5 g/L to 10 g/L.
Preferably, the copper plating solution for PR pulse electrolysis of the present invention further comprises an acid component and is an acidic aqueous solution.
The acid component is preferably at least one acid component selected from the group consisting of organic acids and inorganic acids. The copper plating solution for PR pulse electrolysis can be formed into an acidic copper plating solution.
The organic acid is preferably an alkane sulfonic acid, such as methanesulfonic acid, ethanesulfonic acid, 1-propanesulfonic acid, or 2-propanesulfonic acid; an alkanol sulfonic acid, such as 2-hydroxyethane-1-sulfonic acid, 2-hydroxypropane-1-sulfonic acid, 1-hydroxypropane-2-sulfonic acid, or 3-hydroxypropane-1-sulfonic acid; or the like.
The inorganic acid is preferably sulfuric acid, hydrochloric acid, or the like.
The acid component for use may be at least one compound selected from the group consisting of the compounds mentioned above. These acid components may be used alone or as a mixture (blend) of two or more.
The acid component content in the copper plating solution for PR pulse electrolysis may be any range without particular limitation. The acid component content in the copper plating solution for PR pulse electrolysis is preferably in the range of 20 g/L to 300 g/L.
The copper plating solution for PR pulse electrolysis of the present invention preferably further comprises a halide ion.
The halide ion is preferably a chloride ion (Cl−), a bromide ion (Br−), or the like.
The halide ion for use may be at least one compound selected from the group consisting of the compounds mentioned above. These halide ions may be used alone or as a mixture (blend) of two or more.
The halide ion content in the copper plating solution for PR pulse electrolysis may be any range without particular limitation. The halide ion content in the copper plating solution for PR pulse electrolysis is preferably in the range of 5 mg/L to 200 mg/L.
The halide ion content is adjusted, if necessary, by adjusting the halide ion concentration in the copper plating solution for PR pulse electrolysis by using hydrochloric acid, sodium chloride, or the like.
The copper plating solution for PR pulse electrolysis of the present invention preferably further comprises a sulfur-containing organic compound.
The sulfur-containing organic compound is one referred to as a “brightener.” The sulfur-containing organic compound for use is preferably, for example, an additive that is blended in a copper sulfate plating solution for through-hole plating, or an additive that is blended in a copper sulfate plating solution for blind via holes.
The sulfur-containing organic compound for use is preferably a sulfur compound, such as 3-mercaptopropanesulfonic acid, a sodium salt thereof, bis(3-sulfopropyl) disulfide, a disodium salt thereof, N, N-dimethyldithiocarbamic acid (3-sulfopropyl) ester, or a sodium salt thereof.
The sulfur-containing organic compound for use may be at least one compound selected from the group consisting of the compounds mentioned above. These sulfur-containing organic compounds may be used alone or as a mixture (blend) of two or more.
The content of the sulfur-containing organic compound in the copper plating solution for PR pulse electrolysis may be any range without particular limitation. The content of the sulfur-containing organic compound in the copper plating solution for PR pulse electrolysis is preferably in the range of 0.1 mg/L to 50 mg/L.
The copper plating solution for PR pulse electrolysis of the present invention preferably has a total content of at least one amine compound (nitrogen-based compound) selected from the group consisting of tertiary amine compounds and quaternary amine compounds of less than 1 mg/L.
Technology for Reducing the Concentration of Nitrogen-based Compound
The presence of a large amount of a tertiary amine compound and a quaternary amine compound in the copper plating solution for PR pulse electrolysis inhibits the electrodeposition of copper and makes it difficult to obtain the effects of the polyvalent metal ion and unsaturated fatty acid.
Therefore, the copper plating solution for PR pulse electrolysis preferably comprises less than 1 mg/L of a tertiary amine compound and a quaternary amine compound, and preferably does not comprise a tertiary amine compound and a quaternary amine compound.
Pulse electrolysis treatment not only dissolves copper during negative pulse application, but also strips away sulfur-based additives, which are factors that improve film physical properties, at the same time. If a film is formed with sulfur-based additives being not adsorbed, and nitrogen-based compound being adsorbed on the copper surface, the ductility of the film deteriorates.
Epoxy resin used for substrates has a thermal expansion coefficient greatly different from that of copper. Thus, a copper plating film with poor ductility, if formed, cannot follow resin expansion when thermal expansion occurs in the substrate, causing the formation of cracks in the copper plating film and resulting in electrical disconnection.
The copper plating solution for PR pulse electrolysis of the present invention preferably does not require a large amount of a nitrogen-based compound that is typically used in acidic copper sulfate plating. For this reason, although PR pulse electrolysis is used, there are no systematic concerns about film physical properties, making it possible to obtain a copper film with excellent physical properties.
The nitrogen-containing organic compound is usually one referred to as a “leveler.” The tertiary amine compound and the quaternary amine compound for use are preferably, for example, an additive that is blended in a copper sulfate plating solution for through-hole plating, or an additive that is blended in a copper sulfate plating solution for blind via holes.
The tertiary amine compound and quaternary amine compound for use are preferably, for example, a nitrogen compound, such as a phenazine compound, a safranine compound, polyalkyleneimine, a thiourea derivative, or polyacrylic acid amide.
The tertiary amine compound and the quaternary amine compound (nitrogen-containing organic compound) for use may be at least one compound selected from the group consisting of the compounds mentioned above. These tertiary amine compounds and quaternary amine compounds (nitrogen-containing organic compounds) may be used alone or as a mixture (blend) of two or more.
The total content of the tertiary amine compound and the quaternary amine compound (nitrogen-containing organic compound) in the copper plating solution for PR pulse electrolysis may be any range without particular limitation. The total content of the tertiary amine compound and the quaternary amine compound (nitrogen-containing organic compound) in the copper plating solution for PR pulse electrolysis is preferably in the range of less than 1 mg/L.
The copper plating solution for PR pulse electrolysis of the present invention preferably further comprises a nonionic polyether polymer surfactant.
The nonionic polyether polymer surfactant is one referred to as a “polymer component.” The nonionic polyether polymer surfactant for use is preferably, for example, an additive that is blended in a copper sulfate plating solution for through-hole plating, or an additive that is blended in a copper sulfate plating solution for blind via holes.
The nonionic polyether polymer surfactant is preferably, for example, a polyether compound, such as polyethylene glycol, polypropylene glycol, polyethylene oxide, or polyoxyalkylene glycol.
The nonionic polyether polymer surfactant for use may be at least one compound selected from the group consisting of the compounds mentioned above. These nonionic polyether polymer surfactants may be used alone or as a mixture (blend) of two or more.
The content of the nonionic polyether polymer surfactant in the copper plating solution for PR pulse electrolysis may be any range without particular limitation. The content of the nonionic polyether polymer surfactant in the PR pulse electrolytic copper plating solution is preferably in the range of 0.01 g/L to 10 g/L.
The copper plating solution for PR pulse electrolysis of the present invention can produce excellent effects, in particular, when a copper sulfate plating solution is used as the base bath. Specific examples of the composition of the copper sulfate plating solution are described below.
Copper (II) ion: Copper sulfate pentahydrate is contained in an amount of 20 g/L to 300 g/L.
Polyvalent metal ion: An iron ion (Fe2+) is contained in an amount of 0.3 g/L to 3 g/L.
Unsaturated fatty acid: Fumaric acid, maleic acid, acetylenedicarboxylic acid, aconitic acid, etc. are contained in an amount of 0.5 g/L to 10 g/L.
Sulfuric acid: The amount contained is 20 g/L to 300 g/L.
Chloride ion: The amount contained is 5 mg/L to 200 mg/L.
The copper plating solution for PR pulse electrolysis of the present invention is an electrolytic copper plating solution used for electrolytic copper plating by allowing a PR pulse current to pass through.
The copper plating method by a PR pulse electrolysis method of the present invention comprises
(1) allowing a PR pulse current to pass through a copper plating solution for PR pulse electrolysis to perform electrolytic copper plating by using an object to be plated as a cathode,
The copper plating solution for PR pulse electrolysis of the present invention is an electrolytic copper plating solution used for electrolytic copper plating by allowing a PR pulse current to pass through.
For the conditions for applying a PR pulse current when the electrolytic copper plating solution is used, the current density in positive electrolysis for depositing a copper plating film is preferably 0.1 A/dm2 (ASD) to 10 A/dm2 (ASD), and more preferably about 1 A/dm2 (ASD) to 5 A/dm2 (ASD).
For the conditions for applying a PR pulse current when the electrolytic copper plating solution is used, the current density in negative (reverse) electrolysis for dissolving a copper plating film is preferably 0.1 A/dm2 (ASD) to 100 A/dm2 (ASD), and more preferably 1 A/dm2 (ASD) to 80 A/dm2 (ASD).
In the copper plating method by a PR pulse electrolysis method, step (1) is preferably performed under PR pulse electrolysis conditions of a current density ratio of anode to cathode (anode current density/cathode current density) of 0.2 to 0.85.
Positive current application time: the current flow time required to deposit copper on an objected to be plated. The positive electrolysis time is preferably 5 milliseconds (msec) to 200 milliseconds (msec), and more preferably 10 milliseconds (msec) to 100 milliseconds (msec).
Negative current application time: the current flow time required to elute copper from an object to be plated. The negative (reverse) electrolysis time is preferably 0.1 milliseconds (msec) to 10 milliseconds (msec).
In the copper plating method by a PR pulse electrolysis method of the present invention, step (1) is preferably performed under PR pulse electrolysis conditions of a positive current application time of 5 milliseconds to 200 milliseconds, and an application time ratio of the positive current to negative current (positive current application time/negative current application time) of 5 or more and less than 50.
The liquid temperature of the plating solution is preferably 10° C. to 40° C.
The plating solution is preferably stirred, for example, by air stirring, jet stirring, or the like. It is also possible to use any of these stirring methods in combination.
In performing plating treatment, the anode for use is preferably a soluble or insoluble anode. The soluble anode for use is preferably phosphorus-containing copper with a phosphorus content of 0.02% to 0.06% by mass.
The insoluble anode for use is preferably titanium coated with iridium oxide, titanium plated with platinum, or the like. The anode for use may have any shape and the shape is preferably, for example, a rod-like, a spherical, or a plate-like shape.
The type of the object to be plated (cathode) for the copper plating solution for PR pulse electrolysis is not particularly limited. When the object to be plated is a substrate having microscopic holes, such as through-holes and via holes, a plating film can be uniformly formed even inside the microscopic holes due to excellent throwing power.
The formed plating film has an excellent appearance and also has excellent physical properties, such as elongation and tensile strength.
When plating treatment is performed, the pretreatment method is not particularly limited.
In the pretreatment method, when the object to be plated is a printed wiring board having through-holes and via holes,
Conventionally, when plating treatment is performed on a substrate in which portions with densely packed through-holes and vias are scattered, the surface film thickness after plating treatment would be non-uniform since the surface area per unit area greatly varies.
The copper plating solution for PR pulse electrolysis of the present invention comprises a polyvalent metal ion, such as an iron (II) ion, and an unsaturated fatty acid in combination, and further comprises a copper (II) ion, such as a copper sulfate aqueous solution. The use of the copper plating solution for PR pulse electrolysis of the present invention enables the formation of a copper film with a uniform surface thickness in an excellent manner by pulse electrolysis.
The use of the copper plating solution for PR pulse electrolysis of the present invention can make the surface film thickness distribution uniform.
The copper plating solution for PR pulse electrolysis of the present invention preferably does not comprise a tertiary amine compound and a quaternary amine compound.
The use of the copper plating solution for PR pulse electrolysis of the present invention to perform copper plating by a PR pulse electrolysis method achieves excellent throwing power and improves the appearance of the resulting plating film, film physical properties, filling performance, etc.
The copper plating solution for PR pulse electrolysis of the present invention is useful for performing via filling, through-hole filling, through-hole plating, etc. by an electrolytic copper plating method.
The present invention is described in detail below with reference to Examples.
The present invention is not limited to the following specific Examples.
A copper plating solution for PR pulse electrolysis (a copper sulfate plating solution) shown in Table 1 was prepared.
The plating time was adjusted so that the surface film thickness at the sparse TH portion was 40 μm.
A substrate with numerous through-holes each having a diameter of 0.3 mm and a depth of 1.6 mm, and with a 1 μm-thick electroless copper plating film formed on its entire surface was used as an object to be plated. The object to be plated was immersed in a degreasing solution (trade name: DP-320 Clean, manufactured by Okuno Chemical Industries Co., Ltd., 100 mL/L aqueous solution) at 45° C. for 5 minutes, washed with water for 1 minute, and immersed in 100 g/L dilute sulfuric acid for 1 minute for pretreatment.
Next, electrolytic copper plating was performed by a PR pulse electrolysis method under each of the following plating conditions by using the copper plating solution for PR pulse electrolysis to thus form a copper plating film with a film thickness of 40 μm.
After electrolytic copper plating was performed by allowing a PR pulse current to pass through, the through-hole portions of the plated object were evaluated for the difference in film thickness between the dense and sparse portions (throwing power).
Plating conditions (Tables 3, 4, and 6 to 8)
When the copper plating solutions for PR pulse electrolysis of the present invention were used, the resulting plating films had a difference in film thickness between the dense and sparse portions of less than 10 μm, indicating that copper plating films with excellent throwing power, excellent appearance, and excellent film physical properties were formed.
In contrast, when the copper plating solutions for PR pulse electrolysis of the Comparative Examples were used, the resulting plating films had a difference in film thickness between the dense and sparse portions of more than 10 μm, indicating that the throwing power was not excellent.
The copper plating solution for PR pulse electrolysis of the present invention comprises a polyvalent metal ion, such as an iron (II) ion, and an unsaturated fatty acid in combination, and further comprises a copper (II) ion, such as a copper sulfate aqueous solution. The use of the copper plating solution for PR pulse electrolysis of the present invention enables the formation of a copper film with a uniform surface thickness in an excellent manner by pulse electrolysis. The use of the copper plating solution for PR pulse electrolysis of the present invention can make the surface film thickness distribution of the resulting copper film uniform.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022-060520 | Mar 2022 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2023/013050 | 3/30/2023 | WO |
