JP7538579B2 - Copper plating solution for PR pulse electrolysis and copper plating method by PR pulse electrolysis - Google Patents

Description

The present invention relates to a copper plating solution for PR pulse electrolysis and a copper plating method using the PR pulse electrolysis method.

Patent Document 1 is a technology disclosed by the present applicant, and discloses: (1) an additive for a copper plating solution used in a PR pulse electrolysis method, comprising at least one component selected from alkenes; (2) an acidic copper plating solution for plating by a PR pulse electrolysis method, comprising the additive, and using an acidic aqueous solution containing copper ions and at least one acid component selected from organic acids and inorganic acids as a basic plating bath; and (3) a copper plating method by a PR pulse electrolysis method, comprising passing a PR pulse current through the acidic copper plating solution, with an object to be plated as a cathode, to perform electrolytic copper plating.

When copper plating is performed by the PR pulse electrolysis method using an electrolytic copper plating solution containing the additive of the technology disclosed by the present applicant, the excellent uniform electrodeposition of the PR electrolytic copper plating solution is maintained, while the appearance, film properties, filling properties, etc. of the plating film formed can be improved. Furthermore, the PR electrolytic copper plating solution containing this additive is particularly useful when performing via filling, through-hole filling, through-hole plating, etc. by the electrolytic copper plating method.

Patent Document 2 discloses (1) an additive for a pulse copper plating bath, which contains as an active ingredient a tertiary amine compound obtained by reacting a polyol selected from a polyether polyol or a polyalkylene glycol in which an alkylene oxide has been added to a polyhydric alcohol having a hydroxyl group on an adjacent carbon atom with epihalohydrin to epoxidize the polyol, and then reacting with an amine; and (2) an additive for a pulse copper plating bath, which contains as an active ingredient a quaternary ammonium compound obtained by reacting a polyol selected from a polyether polyol or a polyalkylene glycol in which an alkylene oxide has been added to a polyhydric alcohol having a hydroxyl group on an adjacent carbon atom with epihalohydrin to epoxidize the polyol, and then reacting with an amine to obtain a tertiary amine compound, and then reacting the tertiary amine compound with a compound.

Patent No. 5636633 JP 2008-266722 A

The present invention aims to provide a new copper plating solution for PR pulse electrolysis and a copper plating method using the PR pulse electrolysis method.

After extensive research, the inventors have developed a technology for producing a copper film by pulse electrolysis using a combination of polyvalent metal ions such as iron (II) ions and unsaturated fatty acids, and an aqueous solution of copper (II) ions using copper sulfate or the like.

That is, the present invention includes the following copper plating solution for PR (Periodic Reverse) pulse electrolysis and a copper plating method using the PR pulse electrolysis method.

Item 1.
A copper plating solution for PR pulse electrolysis,
Copper(II) ions,
A copper plating solution for PR pulse electrolysis, comprising polyvalent metal ions (excluding copper (II) ions) and unsaturated fatty acids.

Item 2.
2. 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.

Item 3.
3. 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).

Item 4.
4. 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 contains 0.3 g/L to 3.0 g/L of the polyvalent metal ion.

Item 5.
5. 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.

Item 6.
6. 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.

Item 7.
7. 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 contains the unsaturated fatty acid in an amount of 0.5 g/L to 10 g/L.

Item 8.
8. The copper plating solution for PR pulse electrolysis according to any one of items 1 to 7, further comprising an acid component and being an acidic aqueous solution.

Item 9.
9. The copper plating solution for PR pulse electrolysis according to any one of items 1 to 8, further comprising a halide ion.

Item 10.
10. The copper plating solution for PR pulse electrolysis according to any one of items 1 to 9, further comprising a sulfur-containing organic compound.

Item 11.
11. The copper plating solution for PR pulse electrolysis according to any one of items 1 to 10, wherein the total content of at least one amine compound selected from the group consisting of a tertiary amine compound and a quaternary amine compound in the copper plating solution for PR pulse electrolysis is less than 1 mg/L.

Item 12.
A copper plating method by PR pulse electrolysis, comprising:
(1) A process of performing electrolytic copper plating in a PR pulse electrolytic copper plating solution by passing a PR pulse current through a workpiece as a cathode;
Including,
The copper plating solution for PR pulse electrolysis is
Copper(II) ions,
Contains polyvalent metal ions (excluding copper (II) ions) and unsaturated fatty acids,
A copper plating method using the PR pulse electrolysis method.

Item 13.
13. A copper plating method by PR pulse electrolysis according to item 12, wherein the step (1) is carried out under PR pulse electrolysis conditions of an anode/cathode current density ratio (anode current density/cathode current density) of 0.2 to 0.85.

Item 14.
14. The copper plating method by PR pulse electrolysis according to item 12 or 13, wherein the step (1) is performed under PR pulse electrolysis conditions of a positive current application time of 5 milliseconds to 200 milliseconds and a positive current/negative current application time ratio (positive current application time/negative current application time) of 5 or more and less than 50.

Conventionally, when plating a board that has densely-spaced through holes and vias, the change in surface area per unit area is large, resulting in uneven surface film thickness after plating.

The copper plating solution for PR pulse electrolysis of the present invention uses polyvalent metal ions such as iron (II) ions and unsaturated fatty acids in combination, and contains copper (II) ions such as an aqueous solution of copper sulfate. By using the copper plating solution for PR pulse electrolysis of the present invention, it is possible to produce a copper film with a uniform surface thickness by pulse electrolysis. By using the copper plating solution for PR pulse electrolysis of the present invention, it is possible to make the surface thickness distribution of the copper film uniform.

The copper plating solution for PR pulse electrolysis of the present invention preferably does not contain tertiary amine compounds or quaternary amine compounds.

The present invention can provide a new copper plating solution for PR pulse electrolysis and a copper plating method using the PR pulse electrolysis method.

The present invention is described in detail below.

The embodiments illustrating the present invention are intended to provide a better understanding of the spirit of the invention and, unless otherwise specified, do not limit the content of the invention.

In this specification, the terms "comprise" and "containing" are concepts that encompass all of "comprise," "consist essentially of," and "consist of."

In this specification, when a numerical range is indicated as "A to B," it means A or more and B or less.

[1] Copper plating solution for PR pulse electrolysis The copper plating solution for PR pulse electrolysis of the present invention is
Copper(II) ions,
Contains polyvalent metal ions (excluding copper (II) ions) and unsaturated fatty acids.

The copper plating solution for PR pulse electrolysis of the present invention uses polyvalent metal ions such as iron (II) ions and unsaturated fatty acids in combination, and contains copper (II) ions such as an aqueous solution of copper sulfate. By using the copper plating solution for PR pulse electrolysis of the present invention, it is possible to produce a copper film with a uniform surface thickness by pulse electrolysis. By using the copper plating solution for PR pulse electrolysis of the present invention, it is possible to make the surface thickness distribution of the copper film uniform.

By using the copper plating solution for PR pulse electrolysis of the present invention, when electrolytic copper plating is performed by the PR pulse electrolysis method, the plating appearance formed is good, the physical properties of the plating film are good, and the via filling and through-hole filling properties are also good. 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, etc.

In conventional copper plating solutions used under direct current electrolysis, the uniformity of the film thickness is not good when using copper plating solutions containing additives such as polymers, sulfur-based additives (brighteners), tertiary amine compounds, and quaternary amine compounds (levelers).

In the conventional copper plating solution used under PR pulse current conditions, when using copper plating solution containing additives such as polymers, sulfur-based additives (brighteners), tertiary amine compounds, and quaternary amine compounds (levelers), the uniformity of the film thickness is insufficient and the film properties are also poor.

In the copper plating solution used under conventional current conditions of PR pulse, when additives such as polyvalent metal ions, unsaturated fatty acids, polymers, sulfur-based additives (brighteners), tertiary amine compounds, and quaternary amine compounds (levelers) are used, if the content of tertiary amine compounds and quaternary amine compounds (levelers) is 1 mg/L or more, the uniformity of the film thickness is insufficient and the film properties are also poor.

In the copper plating solution used in the present invention under the current conditions of PR pulse, when a copper plating solution containing polyvalent metal ions, unsaturated fatty acids, polymers, and optionally sulfur-based additives (brighteners) is used as additives, the uniformity of the film thickness is good and the film properties are also good.

In the copper plating solution used under the current conditions of the present invention, PR pulse current conditions include additives such as polyvalent metal ions, unsaturated fatty acids, polymers, and optionally sulfur-based additives (brighteners). When the content of tertiary amine compounds and quaternary amine compounds (levellers) is less than 1 mg/L, the uniformity of the film thickness is good and the film properties are also good.

[1-1] Copper (II) ions The copper plating solution for PR pulse electrolysis of the present invention contains copper (II) ions.

The copper ion (II) source can be any copper compound that is soluble in the plating solution. The copper compound that provides the copper ion (II) source is preferably copper sulfate (II), copper oxide (II), copper chloride (II), copper carbonate (II), copper pyrophosphate, copper (II) methanesulfonate or other alkanesulfonates, copper (II) propanolsulfonate or other alkanolsulfonates, copper (II) caprylate, copper (II) laurate, copper (II) stearate, copper (II) naphthenate or other organic acids, etc.

The copper ion (II) source and the copper compound may be at least one compound selected from the group consisting of the above compounds, and these copper ion (II) sources and copper compounds may be used alone or in a mixture (blend) of two or more types.

The copper (II) ion concentration in the copper plating solution for PR pulse electrolysis can be within a range without particular limitations. The copper (II) ion concentration in the copper plating solution for PR pulse electrolysis is preferably within a range of 10 g/L to 300 g/L.

[1-2] Polyvalent metal ions (excluding copper (II) ions)
The copper plating solution for PR pulse electrolysis of the present invention contains polyvalent metal ions. In the copper plating solution for PR pulse electrolysis, the polyvalent metal ions are polyvalent metal ions other than copper (II) ions. In the copper plating solution for PR pulse electrolysis, the polyvalent metal ions function as a film thickness leveling agent and can improve the uniformity of the film thickness.

The polyvalent metal compound providing the source of polyvalent metal ions is preferably a sulfate or nitrate of cobalt, iron, cerium, etc.

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 an ion of at least one polyvalent metal selected from the group consisting of cobalt (II), iron (II), and cerium (III).

The polyvalent metal ion source and the polyvalent metal may be at least one compound selected from the group consisting of the above compounds, and these polyvalent metal ion sources and polyvalent metals may be used alone or in a mixture (blend) of two or more types.

The polyvalent metal ion concentration in the copper plating solution for PR pulse electrolysis can be within a range without any particular limitation. The polyvalent metal ion concentration in the copper plating solution for PR pulse electrolysis is preferably within the range of 0.3 g/L to 3.0 g/L.

Use of polyvalent metal ions such as iron (II) ions in combination with unsaturated fatty acids In electronic components of printed circuit boards and IC boards, through-holes (hereinafter also referred to as "TH") are formed to provide electrical and thermal conductivity. This structure in electronic components is becoming smaller, and in copper electroplating, THs (holes) are becoming smaller and more densely packed. Electronic components are becoming multi-layered, the board thickness is increasing, and the aspect ratio, which indicates the hole diameter relative to the board thickness, is increasing. When there are many "densely packed" and "undensely packed" holes in a high aspect ratio board, a difference in surface area occurs even within the board.

Areas where the through holes (TH) are not densely packed (hereinafter also referred to as "sparse TH areas") have a small surface area, so electricity flows relatively easily. However, areas where the through holes (TH) are densely packed (hereinafter also referred to as "dense TH areas") have a high surface area, so they act as a resistance and current does not flow easily. When processing by applying a direct current, more electricity flows through sparse TH areas, so copper deposits thickly on the board surface. On the other hand, electricity does not flow easily through dense TH areas, so copper deposits thinly on the board surface.

Technology for making copper film thickness uniform In general, in order to prevent current distribution due to surface area differences in a printed circuit board, a nitrogen-based compound that suppresses copper electrodeposition is used in the copper plating solution for PR pulse electrolysis. Nitrogen-based compounds are usually composed of tertiary amine compounds and quaternary amine compounds, and are positively charged in aqueous solution. When a negative current is applied to the board, the tertiary amine compounds and quaternary amine compounds are positively charged, so they are adsorbed to the board and become resistors, suppressing copper electrodeposition.

When the entire board is processed under high resistance, the current distribution can be made uniform even if there are differences 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 sparse TH areas and dense TH areas becomes 4 or more, there is a limit to how uniform the copper surface film thickness can be. For printed circuit boards, if the copper surface film thickness is too thick, it becomes difficult to form fine circuits. Also, if the copper film thickness within the TH is too thin, connection reliability deteriorates.

Because it is difficult for current to flow in dense TH areas, the thickness of both the surface film and the film inside the through-hole becomes thin. To ensure connection reliability, it is necessary to adjust the plating process time and current amount to achieve a film thickness greater than the specified value, but in sparse TH areas on the same board where electricity flows easily, the thickness of the copper surface film thickens. The copper film inside the through-hole also thickens, causing the hole diameter to become excessively small, resulting in residues of processing liquid remaining in the subsequent board manufacturing process, causing defects.

When a via is present in a sparse TH area, it will become convex due to overfilling of copper. This will require additional polishing or etching processes to smooth out the surface shape, which will cause problems both economically and in terms of process.

Usefulness of the copper plating method by the PR pulse electrolysis method of the present invention : PR pulse electrolysis combines "positive pulse electrolysis for electrodepositing copper" and "negative pulse electrolysis for dissolving copper" and cycles positive and negative in a very short time. PR pulse electrolysis is a method for efficiently bath-filling vias and through-holes with copper as a method for improving deposition efficiency.

The copper plating solution for PR pulse electrolysis of the present invention contains polyvalent metal ions, which undergo sacrificial oxidation during negative pulse application, making copper dissolution less likely to occur, and preferably contains 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, thereby improving the efficiency of copper precipitation.

Polyvalent metal ions and unsaturated fatty acids exert their effects when a low current is applied.

For this reason, in the dense TH area, sacrificial oxidation of polyvalent metal ions becomes effective, the dissolution current is moderately suppressed, reducing copper dissolution, and unsaturated fatty acids can improve the copper precipitation efficiency at low positive pulses.

On the other hand, in the sparse TH area, a high pulse current is applied, so the effect of polyvalent metal ions and unsaturated fatty acids is less likely to occur, and dissolution and precipitation occur repeatedly, gradually forming a copper film. As a result, the copper film thickness on the board surface in the dense TH area and the sparse TH area becomes uniform, and the through-hole copper film in the dense TH area can also be processed with a film thickness that does not impair connection reliability. In the sparse TH area, by not processing with excess current, the TH copper film can be processed without swelling.

[1-3] Unsaturated fatty acid The copper plating solution for PR pulse electrolysis of the present invention contains 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 the physical properties of the film.

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 having two or three carboxyl groups and selected from the group consisting of alkenes and alkynes. The unsaturated fatty acid is more preferably fumaric acid, maleic acid, acetylenedicarboxylic acid, aconitic acid, etc.

The unsaturated fatty acid may be at least one compound selected from the group consisting of the above compounds, and these unsaturated fatty acids may be used alone or in a mixture (blend) of two or more types.

The content of unsaturated fatty acids in the copper plating solution for PR pulse electrolysis can be within a range without particular limitations. The content of unsaturated fatty acids in the copper plating solution for PR pulse electrolysis is preferably within the range of 0.5 g/L to 10 g/L.

[1-4] Acid Component The copper plating solution for PR pulse electrolysis of the present invention preferably further contains 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, and the copper plating solution for PR pulse electrolysis can be made 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, or 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.

The inorganic acid is preferably sulfuric acid, hydrochloric acid, etc.

The acid component may be at least one compound selected from the group consisting of the above compounds, and these acid components may be used alone or in a mixture (blend) of two or more.

The acid content in the copper plating solution for PR pulse electrolysis can be within a range without any particular limitation. The acid content in the copper plating solution for PR pulse electrolysis is preferably within the range of 20 g/L to 300 g/L.

[1-5] Halide ions The copper plating solution for PR pulse electrolysis of the present invention preferably further contains halide ions.

The halide ion is preferably a chloride ion (Cl ⁻ ), a bromide ion (Br ⁻ ), or the like.

The halide ion may be at least one compound selected from the group consisting of the above compounds, and these halide ions may be used alone or in a mixture (blend) of two or more types.

The halide ion content in the copper plating solution for PR pulse electrolysis can be within a range without any particular limitation. The halide ion content in the copper plating solution for PR pulse electrolysis is preferably within the range of 5 mg/L to 200 mg/L. The halide ion content is adjusted as necessary using hydrochloric acid, sodium chloride, etc. to adjust the halide ion concentration in the copper plating solution for PR pulse electrolysis.

[1-6] Sulfur-containing organic compound The copper plating solution for PR pulse electrolysis of the present invention preferably further contains a sulfur-containing organic compound.

The sulfur-containing organic compound is known as a brightener. The sulfur-containing organic compound is preferably an additive contained in a copper sulfate plating solution for through-hole plating or an additive contained in a copper sulfate plating solution for blind via holes.

The sulfur-containing organic compound is preferably a sulfur compound such as 3-mercaptopropanesulfonic acid, its sodium salt, bis(3-sulfopropyl)disulfide, its disodium salt, or N,N-dimethyldithiocarbamic acid (3-sulfopropyl) ester, its sodium salt.

The sulfur-containing organic compound may be at least one compound selected from the group consisting of the above compounds, and these sulfur-containing organic compounds may be used alone or in combination (blend) of two or more.

The content of sulfur-containing organic compounds in the copper plating solution for PR pulse electrolysis can be within a range without any particular limitation. The content of sulfur-containing organic compounds in the copper plating solution for PR pulse electrolysis is preferably within a range of 0.1 mg/L to 50 mg/L.

[1-7] Tertiary amine compound and quaternary amine compound In the copper plating solution for PR pulse electrolysis of the present invention, the total content of at least one amine compound (nitrogen-based compound) selected from the group consisting of tertiary amine compounds and quaternary amine compounds in the copper plating solution for PR pulse electrolysis of the present invention is preferably less than 1 mg/L.

Technology for reducing the concentration of nitrogen-based compounds: If the PR pulse electrolytic copper plating solution contains a large amount of tertiary amine compounds and quaternary amine compounds, the electrodeposition of copper is inhibited, making it difficult to obtain the effects of the polyvalent metal ions and unsaturated fatty acids. Therefore, the tertiary amine compounds and quaternary amine compounds are preferably contained in an amount of less than 1 mg/L or are not contained at all.

Pulse electrolysis not only dissolves copper during negative pulses, but also strips away sulfur-based additives, which are a factor in improving the physical properties of the film. If the sulfur-based additives do not adsorb and nitrogen-based compounds adsorb to the copper surface and a film is formed, the ductility of the film deteriorates.

The epoxy resin used in the circuit board has a thermal expansion coefficient that is significantly different from that of copper, so if a copper plating film with poor ductility is formed, when thermal expansion occurs in the circuit board, it will not be able to keep up with the expansion of the resin, causing cracks in the copper plating film and resulting in electrical disconnections.

The copper plating solution for PR pulse electrolysis of the present invention preferably does not require a large amount of nitrogen-based compounds that are generally used in acid copper sulfate plating. Therefore, although PR pulse electrolysis is used, there is no systematic concern about the film properties, and a copper film with good physical properties can be obtained.

The nitrogen-containing organic compound is usually called a leveller. The tertiary amine compound and quaternary amine compound are preferably additives contained in copper sulfate plating solutions for through-hole plating or additives contained in copper sulfate plating solutions for blind via holes.

The tertiary amine compounds and quaternary amine compounds preferably used are nitrogen compounds such as phenazine compounds, safranine compounds, polyalkyleneimines, thiourea derivatives, and polyacrylic acid amides.

The tertiary amine compound and quaternary amine compound (nitrogen-containing organic compound) may be at least one compound selected from the group consisting of the above-mentioned compounds, and these tertiary amine compounds and quaternary amine compounds (nitrogen-containing organic compounds) may be used alone or in a mixture (blend) of two or more types.

The content of tertiary amine compounds and quaternary amine compounds (nitrogen-containing organic compounds) in the copper plating solution for PR pulse electrolysis can be within a range without any particular limitation. The content of tertiary amine compounds and quaternary amine compounds (nitrogen-containing organic compounds) in the copper plating solution for PR pulse electrolysis is preferably within a range of less than 1 mg/L.

[1-8] Nonionic polyether polymer surfactant The copper plating solution for PR pulse electrolysis of the present invention preferably further contains a nonionic polyether polymer surfactant.

The non-ionic polyether polymer surfactant is what is called a polymer component. The non-ionic polyether polymer surfactant is preferably an additive that is blended into copper sulfate plating solutions for through-hole plating or an additive that is blended into copper sulfate plating solutions for blind via holes.

The nonionic polyether polymer surfactant is preferably a polyether compound such as polyethylene glycol, polypropylene glycol, polyethylene oxide, or polyoxyalkylene glycol.

The nonionic polyether polymer surfactant may be at least one compound selected from the group consisting of the above compounds, and these nonionic polyether polymer surfactants may be used alone or in combination (blend) of two or more types.

The content of the non-ionic polyether polymer surfactant in the copper plating solution for PR pulse electrolysis can be within a range without any particular limitation. The content of the non-ionic polyether polymer surfactant in the copper plating solution for PR pulse electrolysis is preferably within a range of 0.01 g/L to 10 g/L.

[1-9] Preferred copper plating solution for PR pulse electrolysis The copper plating solution for PR pulse electrolysis of the present invention can provide good effects, particularly when the base bath is a copper sulfate plating solution. Specific examples of the composition of the copper sulfate plating solution are shown below.

PR pulse electrolytic copper sulfate plating solution Copper (II) ions: Contains 20 g/L to 300 g/L of copper sulfate pentahydrate.

Polyvalent metal ions: Contains 0.3g/L to 3g/L of iron ions (Fe2 ⁺ ).

Unsaturated fatty acids: Contains fumaric acid, maleic acid, acetylenedicarboxylic acid, aconitic acid, etc. at 0.5g/L to 10g/L.

Sulfuric acid: Contains 20g/L to 300g/L.

Chloride ions: Contains 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 when performing electrolytic copper plating by passing a PR pulse current.

[2] Copper plating method by PR pulse electrolysis The copper plating method by the PR pulse electrolysis of the present invention is as follows:
(1) A process for performing electrolytic copper plating by passing a PR pulse current through a workpiece as a cathode in a PR pulse electrolytic copper plating solution;
The copper plating solution for PR pulse electrolysis is
Copper(II) ions,
Contains polyvalent metal ions (excluding copper (II) ions) and unsaturated fatty acids.

The copper plating solution for PR pulse electrolysis of the present invention is an electrolytic copper plating solution used when performing electrolytic copper plating by passing a PR pulse current.

[2-1] Anode/cathode current density ratio When using an electrolytic copper plating solution, the conditions for applying a PR pulse current are such that the current density of the 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).

When using an electrolytic copper plating solution, the conditions for applying a PR pulse current are such that the current density of the negative (reverse) electrolysis to dissolve the 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 a copper plating method using PR pulse electrolysis, step (1) is preferably carried out under PR pulse electrolysis conditions with an anode/cathode current density ratio (anode current density/cathode current density) of 0.2 to 0.85.

[2-2] Positive current/negative current application time ratio Positive current application time: current time for depositing copper on the plated object. 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 time required to dissolve copper from the object to be plated. The negative (reverse) electrolysis time is preferably 0.1 milliseconds (msec) to 10 milliseconds (msec).

In the copper plating method using the PR pulse electrolysis method of the present invention, step (1) is preferably carried out under PR pulse electrolysis conditions in which the positive current application time is 5 milliseconds to 200 milliseconds and the positive current/negative current application time ratio (positive current application time/negative current application time) is 5 or more and less than 50.

[2-3] Electrolytic copper plating The temperature of the plating solution is preferably 10°C to 40°C.

The plating solution is preferably stirred by air stirring or jet stirring, or a combination of both may be used.

When performing plating, the anode is preferably either a soluble anode or an insoluble anode. The soluble anode is preferably phosphorus-containing copper with a phosphorus content of 0.02% to 0.06% by mass. The insoluble anode is preferably titanium coated with iridium oxide, titanium plated with platinum, or the like. The anode is preferably in the shape of a rod, sphere, plate, or other shape.

There are no particular limitations on the type of substrate (cathode) to be plated with the PR pulse electrolytic copper plating solution. When the substrate is a board having micropores such as through holes and via holes, the excellent uniform electrodeposition allows a uniform plating film to be formed even inside the micropores. The plating film formed has a good appearance, and the physical properties of the plating film, such as elongation and tensile strength, are also good.

When plating is performed, the pretreatment method is not particularly limited. In the pretreatment method, when the object to be plated is a printed wiring board with through holes and via holes formed therein, (1) the object to be plated that has been subjected to electroless copper plating used in the manufacture of printed circuit boards is degreased to remove any dirt that may have adhered in the previous process, (2) pickled to remove the oxide film and activated, and (3) immersed in the PR pulse electrolytic copper plating solution of the present invention and electrolytic plating is performed by passing a PR pulse current through it.

Conventionally, when plating a board that has densely-spaced through holes and vias, the change in surface area per unit area is large, resulting in uneven surface film thickness after plating.

The copper plating solution for PR pulse electrolysis of the present invention uses polyvalent metal ions such as iron (II) ions and unsaturated fatty acids in combination, and contains copper (II) ions such as an aqueous solution of copper sulfate. By using the copper plating solution for PR pulse electrolysis of the present invention, it is possible to produce a copper film with a uniform surface thickness by pulse electrolysis. By using the copper plating solution for PR pulse electrolysis of the present invention, it is possible to make the surface film thickness distribution uniform.

The copper plating solution for PR pulse electrolysis of the present invention is preferably an embodiment that does not contain tertiary amine compounds or quaternary amine compounds.

By using the copper plating solution for PR pulse electrolysis of the present invention to perform copper plating using the PR pulse electrolysis method, it is possible to achieve good uniform electrodeposition and improve the appearance, film properties, filling properties, etc. of the plating film formed.

The PR pulse electrolytic copper plating solution of the present invention is useful for performing via filling, through-hole filling, through-hole plating, etc. by electrolytic copper plating.

The present invention is explained in detail below with reference to examples.

The present invention is not limited to the specific examples below.

[1] Copper sulfate plating solution Composition A copper plating solution for PR pulse electrolysis (copper sulfate plating solution) shown in Table 1 was prepared.

The plating time was adjusted so that the surface film thickness of the TH sparse area was 40 μm.

[2] Copper sulfate plating process

A substrate with numerous through-holes, each 0.3 mm in diameter and 1.6 mm deep, and a 1 μm-thick electroless copper plating film formed over the entire surface, was used as the substrate. This was immersed in a degreasing solution (product name: DP-320 Clean, manufactured by Okuno Chemical Industries Co., Ltd., 100 mL/L aqueous solution) at 45°C for 5 minutes, then rinsed with water for 1 minute and pretreated by immersing in 100 g/L dilute sulfuric acid for 1 minute.

Next, using a copper plating solution for PR pulse electrolysis, electrolytic copper plating was performed using the PR pulse electrolysis method under each plating condition to form a copper plating film with a thickness of 40 μm.

After electrolytic copper plating was performed by passing a PR pulse current, the through-hole portion of the plated object was evaluated for density-dense film thickness difference (uniform electrodeposition).

Plating conditions (Tables 3, 4, and 6-8)
Positive current density: 3.6A/ ^dm2
Negative current density: 7.2A/ ^dm2
Positive electrolysis time: 10msec
Negative electrolysis time: 0.6msec
Bath temperature: 25℃
Agitation: Jet agitation Plating conditions (Table 5)
Positive current density: 3.6A/ ^dm2
Negative current density: 7.2A/dm ² , 10.8A/dm ² , 18.0A/dm ²
Positive electrolysis time: 10msec
Negative electrolysis time: 0.3msec, 0.6msec, 1.0msec
Bath temperature: 25℃
Mixing: Jet mixing

When the PR pulse electrolytic copper plating solution of the present invention was used, the density difference of the formed plating film was less than 10 μm, and a copper plating film with excellent uniform electrodeposition, good appearance and film properties was formed.

In contrast, when the comparative example PR pulse electrolytic copper plating solution was used, the difference in thickness between the dense and thin plating films formed exceeded 10 μm, and the uniform electrodeposition was not good.

[3] Industrial Applicability The copper plating solution for PR pulse electrolysis of the present invention uses polyvalent metal ions such as iron (II) ions and unsaturated fatty acids in combination, and contains copper (II) ions such as copper sulfate aqueous solution. By using the copper plating solution for PR pulse electrolysis of the present invention, a copper film can be produced with good uniformity in surface thickness by pulse electrolysis. By using the copper plating solution for PR pulse electrolysis of the present invention, it is possible to make the surface thickness distribution of the copper film uniform.

Claims (11)

A copper plating solution for PR pulse electrolysis,
Copper(II) ions,
Contains polyvalent metal ions (excluding copper (II) ions) and unsaturated fatty acids,
In the PR pulse electrolytic copper plating solution,
The polyvalent metal ion is contained in an amount of 0.3 g/L to 3.0 g/L.
Contains 0.5 g/L to 10 g/L of the unsaturated fatty acid,
The total content of at least one amine compound selected from the group consisting of tertiary amine compounds and quaternary amine compounds is less than 1 mg/L.
PR pulse electrolytic copper plating solution. The copper plating solution for PR pulse electrolysis according to claim 1, wherein the polyvalent metal ions are ions 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 claim 1, wherein the polyvalent metal ion is at least one type of 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 claim 1, 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 claim 1, 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 claim 1 further contains an acid component and is an acidic aqueous solution. The copper plating solution for PR pulse electrolysis according to claim 1 further contains halide ions. The copper plating solution for PR pulse electrolysis according to claim 1, further comprising a sulfur-containing organic compound. A copper plating method by PR pulse electrolysis, comprising:
(1) A process of performing electrolytic copper plating in a PR pulse electrolytic copper plating solution by passing a PR pulse current through a workpiece as a cathode;
Including,
The copper plating solution for PR pulse electrolysis is
Copper(II) ions,
Contains polyvalent metal ions (excluding copper (II) ions) and unsaturated fatty acids,
In the PR pulse electrolytic copper plating solution,
The polyvalent metal ion is contained in an amount of 0.3 g/L to 3.0 g/L.
Contains 0.5 g/L to 10 g/L of the unsaturated fatty acid,
The total content of at least one amine compound selected from the group consisting of tertiary amine compounds and quaternary amine compounds is less than 1 mg/L.
A copper plating method using the PR pulse electrolysis method. 10. The copper plating method by PR pulse electrolysis according to claim 9 , wherein the step (1) is carried out under PR pulse electrolysis conditions of an anode/cathode current density ratio (anode current density/cathode current density) of 0.2 to 0.85. 10. The copper plating method by PR pulse electrolysis according to claim 9, wherein the step (1) is performed under PR pulse electrolysis conditions of a positive current application time of 5 milliseconds to 200 milliseconds and a positive current/negative current application time ratio (positive current application time/negative current application time) of 5 or more and less than 50 .