JP6814845B2 - Electroless Copper Plating Compositions and Methods for Electrolessly Plating Copper on Substrates - Google Patents

Description

The present invention is a method for electroless plating copper on an electroless copper plating composition and a base material, in which electroless copper plating has a high electroless copper plating rate at low temperatures and is electroless. Compositions for copper plating relate to compositions and methods for electroless copper plating that are stable. More specifically, the present invention is a method for electroless plating copper on a composition for electroless copper plating and a substrate, and electroless copper plating has a high electroless copper plating rate at a low temperature. And the composition for electroless copper plating is stable, and the composition for electroless copper plating relates to the composition and method for electroless copper plating containing a pyridinium compound or a salt thereof.

Electroless copper plating baths are widely used in the metal coating industry to deposit copper on various types of substrates. For example, in the production of printed circuit boards, electroless copper baths are used to deposit copper on the walls of through holes and on the line path as a base for subsequent electrolysis copper plating. Electroless copper plating is also used in the decorative plastics industry to deposit copper on non-conductive surfaces as a base for further plating copper, nickel, gold, silver and other metals as needed. To. Electrolytic copper baths in commercial use today include: water-soluble divalent copper compounds, chelating or complexing agents for chelating divalent copper ions, For example to improve the stability of roschel salts and sodium salts of ethylenediaminetetraacetic acid, reducing agents such as formaldehyde and precursors or derivatives of formaldehyde, and baths, to regulate plating rates and to improve the gloss of copper precipitates Various additional additives.

However, it is understood that each component in the electroless copper bath affects the plating performance and therefore the concentration must be adjusted to obtain the most desirable plating performance under the particular constituents and operating conditions. Should be. Other factors that affect the internal plating potential difference, the quality of the precipitate and the rate of precipitation include temperature, degree of agitation, type and concentration of the basic constituents described above.

In the electroless copper plating bath, those components are continuously consumed and the changing state of the bath becomes constant, so that the consumed components must be replenished regularly. It is extremely difficult to adjust the bath to maintain a high plating rate while precipitating copper substantially evenly over a long period of time. In general, electroless copper plating rates of 0.6 μm / 5 min and above are highly desirable (preferably desired in current horizontal plating applications), but are achieved especially at low electroless plating temperatures such as below 40 ° C. That is rare. Repeated consumption and replenishment of bath components with several metal turnovers (MTOs) can lead to bath instability, for example due to the accumulation of side reaction products. Therefore, such baths, especially those with high plating performance, that is, baths with high activity, become unstable and naturally tend to deteriorate as they are used. The instability of such electroless copper baths can result in heterogeneous or discontinuous copper plating along the surface. For example, in the production of printed circuit boards, copper is electrolessly plated on the wall surface of a through hole, and the copper deposited on the wall surface is substantially continuous and homogeneous, and the copper precipitate is formed. It is important that the crevices or gaps inside are minimal and preferably absent. Such discontinuities in copper deposits can ultimately lead to malfunctions of various electronic devices, including printed circuit boards with such defects.

In order to deal with the above-mentioned stability problem, various compounds classified by the name of "stabilizer" have been introduced into electroless copper plating baths. Examples of stabilizers that have been used in electroless copper plating baths include sulfur-containing compounds such as disulfides and thiols. However, many stabilizers reduce the electroless copper plating rate and, at higher concentrations, become catalytic poisons, which can reduce the plating rate or make plating impossible, impairing the performance of the plating bath. There is sex. A decrease in plating speed is not preferable for electroless copper plating performance. The electroless copper plating rate is also temperature dependent, so if the rate decreases due to a high stabilizer concentration, it can be increased by increasing the plating temperature. However, when the operating temperature is raised, the stability of the electroless copper bath decreases due to the increase in the accumulation of by-products, and the rate of production of by-products by side reactions also increases. Therefore, the effect of increasing the concentration of the stabilizer is increased. There is a risk that part of the As a result, in most cases the amount of stabilizer used must be a careful compromise between maintaining a high plating rate and maintaining an electroless bath stable for extended periods of time.

Alternatively, it is possible to incorporate "accelerator" additives in the formulation of the electroless bath. Ideally, the accelerator additive does not adversely affect the stability of the electroless bath so that higher plating rates can be achieved or at lower temperatures while maintaining sufficient bath stability. The same plating rate is achieved (which typically also improves bath stability). Lowering the temperature of the electroless bath also reduces the cost of the electroless bath, for example, because the passivation rate of plating chemicals is reduced. Further, by lowering the working temperature, a more stable formulation can be obtained, so that the need for maintenance is reduced. Finally, lowering the plating temperature also makes it possible to suppress the generation of internal stresses in the precipitates due to the electroless method, which makes the metal coating process more suitable for high adhesion applications. Therefore, speed acceleration in electroless copper plating is an important strategy for lowering the working temperature, for example, lowering the internal stress of copper deposited on flexible substrates and lowering the overall running cost of the metal coating. Is.

Therefore, there is a need for additives for electroless copper plating baths that allow high electroless copper plating rates at low temperatures and provide glossy, homogeneous copper precipitates on the substrate.

The present invention is a composition for electroless copper plating, wherein one or more copper ion sources, one or more pyridinium compounds, one or more complexing agents, one or more reducing agents and optionally. It relates to an electroless copper plating composition comprising one or more pH adjusters selectively and having an electroless copper plating composition having a pH greater than 7.

The present invention is an electroless copper plating method.
a) Step of providing a base material containing a dielectric,
b) A step of applying a catalyst to a substrate containing a dielectric,
c) A step of applying an electroless copper plating composition to a substrate containing a dielectric, wherein the electroless copper plating composition is one or more copper ion sources, one or more pyridinium compounds, The pH of the composition for electroless copper plating, which comprises one or more complexing agents, one or more reducing agents and optionally one or more pH adjusting agents, is greater than 7. And d) It also relates to a method including a step of electrolessly plating copper on a substrate containing a dielectric using an electroless copper plating composition.

The pyridinium compound can increase the electroless copper plating rate at a low plating temperature of 40 ° C. or lower. The composition and method for electroless copper plating of the present invention further enable good wall coating of through holes even at low plating temperatures. By lowering the plating temperature, the consumption of additives in the electroless copper plating composition caused by undesired side reactions or decomposition is suppressed, whereby a more stable electroless copper plating composition is obtained. And the operating cost of the electroless copper plating process is reduced.

The composition for electroless copper plating of the present invention is stable over a wide concentration range of pyridinium compounds. The wide range of operations for the concentration of the pyridinium compound means that the performance of the electroless copper plating composition does not substantially change regardless of how the components of the composition are replenished and consumed. Means that you do not need to monitor carefully.

Throughout this specification, the abbreviations below have the following meanings unless explicitly stated to be contextually different: g = grams; mg = milligrams; mL = milliliters; L = liters; cm = centimeters; mm = millimeters; μm = micron; ppm = number of copies per million = mg / L; ° C. = temperature per liter; g / L = number of grams per liter; DI = deionization; C = elemental carbon; Pd = palladium; Pd ( II) = +2 oxidized state of palladium ions; Pd ° = palladium reduced to its metallic state compared to the ionic state;% by weight = weight percent; and Tg = glass transition temperature.

Unless otherwise noted, all quantities are weight percent. All numerical ranges include both ends and can be combined in any order, with the exception of the case where it is logical that the sum of such numerical ranges is 100%.

The terms "plating" and "precipitation" are used interchangeably throughout this specification. The terms "composition" and "bath" are used interchangeably throughout this specification. The term "alkyl" means an organic chemical group consisting only of carbon and hydrogen and having the general formula: C _n H _{2n + 1} , unless otherwise described herein as having a substituent. The term "mean" is even with the mean of the sample. Unless otherwise noted, all quantities are weight percent. All numerical ranges include both ends and can be combined in any order, with the exception of the case where it is logical that the sum of such numerical ranges is 100%.

The composition for electroless copper plating of the present invention comprises one or more copper ion sources, one or more pyridinium compounds, one or more complexing agents, one or more reducing agents, water and optionally. The pH of the composition for electroless copper plating, which comprises one or more pH adjusters, is greater than 7.

Preferably, the one or more pyridinium compounds are of the formula:

(In the formula, R ₁ is a linear or branched substituted or unsubstituted (C _1- C ₁₀ ) alkyl, substituted or unsubstituted (C _6- C ₁₀ ) aryl, substituted or unsubstituted (C _6- C). ₁₀ ) Selected from the group consisting of heterocyclic aromatic groups and substituted or unsubstituted benzyls (where the substituents are selected from the group consisting of hydroxyl, sulfate, amino, amide, carbonyl and carboxyl), and R ₂ has (selected from the group consisting of hydrogen, hydroxyl, sulfate, carbonyl, carboxyl, vinyl, amino and amide). More preferably, R ₁ is a linear or branched substituted and unsubstituted (C _2- C ₄ ) alkyl and substituted or unsubstituted C ₆ -heterocyclic aromatic group (where the substituent is hydroxyl). And is selected from the group consisting of sulfate), and more preferably R ₂ is selected from the group consisting of hydrogen, hydroxyl and sulfate, and most preferably R ₁ is linear. Selected from the group consisting of substituted or unsubstituted (C _2- C ₄ ) alkyl, where the preferred substituent is sulfate, and most preferably R ₂ is hydrogen. The pyridinium compound of formula (I) preferably contains a counter anion for neutralizing the positive charge of the pyridinium compound.

The pyridinium compounds mentioned above are hydroxide salts, sulfates, tetrafluoroborates, hexafluorophosphates, nitrates, formates, acetates, tartrates or halogen salts (where the halide is chloride). It is preferably selected from the group consisting of substances, bromides, fluorides and iodides). More preferably, the salt is a halide selected from the group consisting of chlorides and bromides, and most preferably the halide is chloride. To give three examples of preferred pyridinium compounds of the invention, internal salts of 1-butylpyridinium chloride and 1- (3-sulfopropyl) pyridinium hydroxide (also known as 1- (3-sulfopropyl) pyridinium). Is a salt of 1- (4-pyridyl) pyridinium chloride.

The pyridinium compound of the present invention is contained in an amount of 0.5 ppm or more, preferably 1 ppm to 50 ppm, more preferably 2 ppm to 30 ppm, still more preferably 2.5 ppm to 20 ppm, and most preferably 5 ppm to 20 ppm.

Sources of copper ions and counter anions include, but are not limited to, water-soluble halides, nitrates, acetates, sulfates and other organic and inorganic salts of copper. Copper ions can also be obtained using one or a mixture of such copper salts. Examples are copper sulphate, such as copper sulphate pentahydrate, copper chloride, copper nitrate, copper hydroxide and copper sulfamate. The one or more copper ion sources in the composition for electroless copper plating of the present invention are preferably 0.5 g / L to 30 g / L, more preferably 1 g / L to 25 g / L, and even more preferably. It is in the range of 5 g / L to 20 g / L, even more preferably 5 g / L to 15 g / L, and most preferably 10 g / L to 15 g / L.

Complexing agents include, but are not limited to: sodium potassium tartrate, sodium tartrate, sodium salicylate, sodium salt of ethylenediaminetetraacetic acid (EDTA), nitriloacetate and its alkali metal salts, gluconic acid, Gluconate, triethanolamine, modified ethylenediaminetetraacetic acid, S, S-ethylenediamine disuccinic acid, hydantine and hydantin derivatives. Hydantoin derivatives include, but are not limited to, 1-methyl hydantoin, 1,3-dimethyl hydantoin and 5,5-dimethyl hydantoin. The complexing agent is preferably selected from one or more of potassium sodium tartrate, sodium tartrate, nitriloacetic acid and alkali metal salts thereof, such as sodium and potassium salts of nitriloacetate, hydantoin and hydantoin derivatives. It is preferable to exclude EDTA and salts thereof from the electroless copper plating composition of the present invention. The complexing agent is more preferably selected from potassium sodium tartrate, sodium tartrate, nitriloacetic acid, sodium salts of nitriloacetic acid and hydantoin derivatives. It is even more preferred to select the complexing agent from potassium sodium tartrate, sodium tartrate, 1-methylhydantoin, 1,3-dimethylhydantoin and 5,5-dimethylhydantoin. It is more preferred to select the complexing agent from potassium sodium tartrate and sodium tartrate. The complexing agent is most preferably sodium potassium tartrate (Rochelle salt).

The complexing agent is 10 g / L to 150 g / L, preferably 20 g / L to 150 g / L, more preferably 30 g / L to 100 g / L, still more preferably, in the composition for electroless copper plating of the present invention. It is contained in an amount of 35 g / L to 80 g / L, most preferably 35 g / L to 55 g / L.

Reducing agents include, but are not limited to: aldehydes such as formaldehyde, formaldehyde precursors, formaldehyde derivatives such as paraformaldehyde, bohydrides such as sodium bohydride, substituted bohydrides. , Bolan, eg dimethylamine borane (DMAB), saccharides such as glucose (glucose), glucose, sorbitol, cellulose, sucrose, mannitol and gluconolactone, hypophosphate and salts thereof, eg sodium hypophosphate, hydroquinone. , Catecol, resorcinol, quinol, pyrogallol, hydroxyquinol, fluoroglusinol, guaiacol, gallic acid, glyoxylic acid, 3,4-dihydroxybenzoic acid, phenolsulfonic acid, cresolsulfonic acid, hydroquinonesulfonic acid, catecholsulfonicic acid, Tyrone and All salts of the reducing agents mentioned above. The reducing agent is preferably selected from formaldehyde, formaldehyde derivatives, formaldehyde precursors, borohydrides and hypophosphorous acids and salts thereof, hydroquinone, catechols, resorcinol and gallic acid. The reducing agent is more preferably selected from formaldehyde, formaldehyde derivatives, formaldehyde precursors and sodium hypophosphite. The reducing agent is most preferably formaldehyde.

The reducing agent is 0.5 g / L to 100 g / L, preferably 0.5 g / L to 60 g / L, more preferably 1 g / L to 50 g / L, and further, in the composition for electroless copper plating of the present invention. It is more preferably contained in an amount of 1 g / L to 20 g / L, even more preferably 1 g / L to 10 g / L, and most preferably 1 g / L to 5 g / L.

The pH of the electroless copper plating composition of the present invention is greater than 7. The pH of the electroless copper plating composition of the present invention is preferably higher than 7.5. The pH of the electroless copper plating composition is more preferably 8 to 14, even more preferably 10 to 14, even more preferably 11 to 13, and most preferably 12 to 13.

Optionally, but preferably, one or more pH adjusters are included in the electroless copper plating composition of the present invention to adjust the pH of the electroless copper plating composition to an alkaline pH. It can be. Acids and bases, including organic and inorganic acids and bases, can be used to regulate their pH. It is preferable to use an inorganic acid or an inorganic base or a mixture thereof to adjust the pH of the electroless copper plating composition of the present invention. Examples of inorganic acids suitable for adjusting the pH of the electroless copper plating composition include phosphoric acid, nitric acid, sulfuric acid and hydrochloric acid. Inorganic bases suitable for adjusting the pH of the electroless copper plating composition include, for example, ammonium hydroxide, sodium hydroxide, potassium hydroxide and lithium hydroxide. It is preferable to use sodium hydroxide, potassium hydroxide or a mixture thereof to adjust the pH of the electroless copper plating composition, and sodium hydroxide is used to adjust the pH of the electroless copper plating composition of the present invention. It is most preferable to adjust.

Optionally, but preferably, one or more stabilizers may be included in the electroless copper plating compositions of the present invention. Stabilizers include, but are not limited to: 2,2'-dipyridyl and derivatives, 4,4'-dipyridyl, phenanthroline and phenanthroline derivatives, thiophosphoric acid, 2,2'dithiodichonic acid. , Mercaptosuccinic acid, cysteine, methionine, thionin, thiourea, benzothiazole, mercaptobenzothiazole, 2,2'-thiodiacetic acid, 3,3'-thiodipropionic acid, 3,3'-dithiodipropionic acid, Thiousulfates and glycols such as polypropylene glycol and polyethylene glycol.

Such an optional stabilizer is 0.1 ppm to 20 ppm, preferably 0.5 ppm to 10 ppm, more preferably 0.5 ppm to 5 ppm, and most preferably 0, in the composition for electroless copper plating of the present invention. Included in an amount of .5 ppm to 2 ppm.

Optionally, but preferably, one or more secondary accelerators may be included in the electroless copper plating compositions of the present invention. Such accelerators include, but are not limited to: some free nitrogen bases such as guanidine, guanidine derivatives such as guanidine hydrochloride, pyridine and pyridine derivatives such as aminopyridine, di-. And tri-alkylamines such as trimethylamine and triethylamine, N, N, N', N'-tetrax (2-hydroxypropyl) ethylenediamine and ethylenediamine tetraacetic acid and nickel (II) salts such as nickel sulfate (II). An example of a preferred secondary accelerator is guanidine hydrochloride.

Such accelerators may be included in an amount of 0.1 ppm to 500 ppm, preferably 0.2 to 15 ppm, more preferably 0.3 ppm to 10 ppm, most preferably 0.3 ppm to 5 ppm.

Optionally, one or more surfactants may be included in the electroless copper plating compositions of the present invention. Such surfactants include ionic, eg, cationic and anionic surfactants, nonionic surfactants and amphoteric surfactants. It is also possible to use a mixture of surfactants. The surfactant may be included in the composition in an amount of 0.001 g / L to 50 g / L, preferably 0.01 g / L to 50 g / L.

Cationic surfactants include, but are not limited to: tetra-alkylammonium halides, alkyltrimethylammonium halides, hydroxyethylalkylimidazolins, alkylimidazoliums, alkylbenzalconium halides, alkylamine acetates. , Alkylamine oleate and alkylaminoethylglycine.

Anionic surfactants include, but are not limited to: alkylbenzene sulfonates, alkyl or alkoxynaphthalene sulfonates, alkyldiphenyl ether sulfonates, alkyl ether sulfonates, alkyl sulphates, polyoxyethylene alkyl ether sulphates, Polyoxyethylene alkylphenol ether sulfate ester, higher alcohol phosphoric acid monoester, polyoxyalkylene alkyl ether phosphoric acid (phosphate ester) and alkylsulfosuccinate.

Amphoteric surfactants include, but are not limited to: 2-alkyl-N-carboxymethyl or ethyl-N-hydroxyethyl or methylimidazolium betaine, 2-alkyl-N-carboxymethyl or Ethyl-N-carboxymethyloxyethyl imidazolium betaine, dimethylalkyl betaine, N-alkyl-β-aminopropionic acid or salts thereof and fatty acid amide propyldimethylaminoacetate betaine.

It is preferable that the surfactant is nonionic. Nonionic surfactants include, but are not limited to: alkylphenoxypolyethoxyethanol, polyoxyethylene polymers with 20 to 150 repeating units, and polyoxyethylene with polyoxypropylene. Random and block copolymers and polyamines such as polyallylamine.

Optionally, one or more crystal growth inhibitors may be included in the electroless copper plating compositions of the present invention. Crystal growth inhibitors include, but are not limited to: cyanide and cyanide-containing inorganic salts such as potassium hexacyanoferrate, 2-mercaptobenazol, 2,2'-bipyridine and 2,2'. -Bipyridine derivatives, 1,10-phenanthroline and 1,10-phenanthroline derivatives, vanadium oxide, such as sodium metavanadate and nickel salts, such as nickel sulfate (II). The crystal growth inhibitor is added in an amount well known to those skilled in the art.

Preferably, the composition for electroless copper plating of the present invention comprises one or more copper ion sources (including corresponding anions), one or more pyridinium compounds having the formula (I) or salts thereof. Or multiple complexing agents, one or more reducing agents, water, optionally one or more pH adjusters, optionally one or more stabilizers, optionally one or more. The pH of the composition for electroless copper plating is 10 to 14, which is composed of a secondary accelerator, optionally one or more surfactants, and optionally one or more crystal growth inhibitors. is there.

More preferably, the composition for electroless copper plating of the present invention comprises one or more copper ion sources (including corresponding anions), one or more pyridinium compounds having the formula (I) or salts thereof (here). The salt is selected from the group consisting of salts of hydroxides, chlorides and bromides), one or more complexing agents, one or more reducing agents, water, one or more pH adjustments. Agents, one or more stabilizers, optionally one or more secondary accelerators, optionally one or more surfactants and optionally one or more crystal growth inhibitors The composition for electroless copper plating comprises 11 to 13.

Most preferably, the composition for electroless copper plating of the present invention comprises one or more copper ion sources (including corresponding anions), 1-butylpyridinium chloride, 1- (3-sulfopropyl) pyridinium hydroxide. And one or more pyridinium compounds selected from the group consisting of 1- (4-pyridyl) pyridinium chloride, one or more complexing agents, one or more reducing agents, water, one or more pH. Regulators, one or more stabilizers, optionally one or more secondary accelerators, optionally one or more surfactants and optionally one or more suppression of crystal growth The pH of the composition for electroless copper plating, which comprises an agent, is 12 to 13.

The electroless copper compositions and methods of the present invention can be used for electroless plating copper on various substrates such as dielectrics, semiconductors, metal clad and non-clad substrates such as printed circuit boards. it can. Such metal clad and non-clad printed circuit boards can include thermosetting resins containing fibers such as fiberglass, thermoplastic resins and combinations thereof, and embodiments impregnated with them. The substrate is preferably a metal clad printed circuit or a distribution frame having a plurality of through holes, vias or a combination thereof. The electroless copper plating composition and method of the present invention can be used in either a horizontal process or a vertical process for producing a printed circuit board, and the electroless copper plating composition and method of the present invention can be used in the horizontal process. It is preferable to use the method.

Thermoplastic resins include, but are not limited to: acetal resins, acrylic resins such as methyl acrylate, cellulose-based resins such as ethyl acetate, cellulose propionate, cellulose acetate butyrate and nitrocellulose. , Polyether, nylon, polyethylene, polystyrene, styrene blends such as acrylonitrile-styrene copolymer and acrylonitrile-butadiene-styrene copolymer, polycarbonate, polychlorotrifluoroethylene and vinyl polymers and copolymers such as vinyl acetate, vinyl alcohol, vinyl butyral, Vinyl chloride, vinyl chloride-acetate copolymer, vinylidene chloride and vinylformal.

Thermosetting resins include, but are not limited to: allylphthalate, furan, melamine-formaldehyde, phenol-formaldehyde and phenol-furfural copolymers alone or butadiene-acrylonitrile copolymers or acrylonitrile-butadiene-styrene. Compounded with copolymers, polyacrylic esters, silicones, ureaformaldehyde, epoxy resins, allyl resins, glyceryl phthalates and polyesters.

Using the composition and method for electroless copper plating of the present invention, a substrate containing both low T _g and high T _g resins can be electroless copper plated. Low _{T g} resins have a _{T g} of less than 160 ° C., the resin of the high The _{T g} has a 160 ° C. or more _{T g.} Typically, resins of high The _{T g} has a _{T g} of 160 ° C. to 280 ° C., or such as 170 ° C. to 240 ° C.. High _Tg polymer resins include, but are not limited to: a blend of polytetrafluoroethylene (PTFE) and polytetrafluoroethylene. Such blends include, for example, PTFE with polyphenylene oxide and cyanate esters. Other types of polymer resins which include resins with a high T _g, but the following may be mentioned, but not limited to: epoxy resin, for example, difunctional and multifunctional epoxy resins, bimaleimide / triazine and epoxy resins ( BT epoxy), epoxy / polyphenylene oxide resin, acrylonitrile-butadiene-styrene, polycarbonate (PC), polyphenylene oxide (PPO), polyphenylene ether (PPE), polyphenylene sulfide (PPS), polysulfone (PS), polyamide, polyester, eg polyethylene Terephthalate (PET) and polyethylene terephthalate (PBT), polyetherketone (PEEK), liquid crystal polymer, polyurethane, polyetherimide, epoxy and their composite materials.

In the electroless copper plating method using the electroless copper composition of the present invention, the base material is optionally cleaned or degreased, optionally roughened or micro-roughened, and optionally the base material. Can be optionally etched or micro-etched to optionally swell the substrate with solvent to remove dirt from the through holes, and optionally use various cleaning and anti-fog treatments.

The base material for electroless copper plating using the composition and method for electroless copper plating of the present invention is preferably a dielectric material and a metal clad base material having a plurality of through holes, for example, a printed circuit board. Optionally, the substrate is rinsed with water to clean and degreas, and then the walls of the through holes are cleaned. Dielectric prepping or softening or decontamination of through holes can be initiated by applying a solvent swelling agent. Although the electroless copper plating method is preferably for plating the wall surface of the through hole, it is also assumed that the electroless copper plating method can also be used for electroless copper plating the wall surface of the via. To.

Conventional solvent swelling agents can be used. The specific type can be changed according to the type of the dielectric material. Small-scale experiments can be performed to determine which solvent swelling agent is suitable for a particular dielectric material. In many cases, the T _g of the dielectric determines the type of solvent swelling agent used. Solvent swelling agents include, but are not limited to, glycol ethers and their associated ether acetates. Glycol ethers known to those of skill in the art and their associated ether acetates can be used in conventional doses. Examples of commercially available solvent swelling agents include: CIRCUPOSIT ™ Conditioner 3302A, CIRCUPOSIT ™ Hole Prep 3303 and CIRCUPOSIT ™ Hole Prep 4120 solutions (Dow Electronic Mate). ).

It is also possible to optionally add the promoter after the solvent swelling. A commonly used promoter can be used. Such promoters include sulfuric acid, chromic acid, alkaline permanganate or plasma etching. It is preferable to use alkaline permanganate as a promoter. Examples of commercially available promoters include: CIRCUPOSIT ™ Promoter 4130 and CIRCUPOSIT ™ MLB Promoter 3308 solutions (available from Dow Electrical Materials). Optionally, wash the substrate and through holes with water.

If a promoter is used, then a neutralizing agent is applied to neutralize any residue remaining after the promoter. Conventional neutralizers can be used. The neutralizing agent is preferably an acidic aqueous solution containing one or more amines, or a solution of 3% by weight hydrogen peroxide and 3% by weight sulfuric acid. An example of a commercially available neutralizer is CIRCUPOSIT ™ MLB Neutralizer 216-5. Optionally, the substrate and through holes are washed with water and then dried.

After neutralization, apply an acid or alkaline conditioner. Conventional conditioners can be used. Such conditioners may include one or more cationic surfactants, nonionic surfactants, complexing agents and pH regulators or buffers. Examples of commercially available acid conditioners include: CIRCUPOSIT ™ Conditioner 3320A and 3327 solutions (available from Dow Advanced Materials). Suitable alkaline conditioners include, but are not limited to, alkaline aqueous solutions of surfactants containing one or more quaternary amines and polyamines. Examples of commercially available alkaline surfactants are CIRCUPOSIT ™ Conditioners 231, 3325, 813 and 860 formulations (available from Dow Electrical Materials). Optionally, wash the substrate and through holes with water.

Optionally, it can also be microetched after conditioning. Conventional micro-etching compositions can be used. Microetching is intended to clean and provide a finely roughened metal surface on the exposed metal (eg, inner layer and surface etching), thereby plating electroless copper and The adhesiveness of the subsequent electroplating is improved. Microetching agents include, but are not limited to: 60 g / L to 120 g / L of sodium persulfate or sodium oxymonosulfate or a mixture of potassium oxymonosulfate and sulfuric acid (2%) or Common sulfuric acid / hydrogen peroxide. Examples of commercially available micro-etching compositions are CIRCUPOSIT ™ Microetch 3330 Etch solution and PREPOSIT ™ 748 Etch solution (both available from Dow Electrical Materials). Optionally, wash the substrate with water.

It is also possible to optionally apply the predip to the micro-etched substrate and through holes. Examples of predip agents include, but are not limited to: organic salts such as sodium potassium tartrate or sodium citrate, 0.5% to 3% sulfuric acid, nitric acid or 25 g / L to 75 g. An acidic solution of / L sodium chloride. An example of a commercially available predip is an acidic predip CIRCUPOSIT ™ 6520 solution.

The catalyst is then applied to the substrate. Although it is assumed that various commonly used catalysts suitable for electroless metal plating, including catalytic metals, can be used, it is preferable to use a palladium catalyst in the method of the present invention. The catalyst can be a nonionic palladium catalyst, eg, a colloidal palladium-tin catalyst, or the catalyst can be ionic palladium. If the catalyst is a colloidal palladium-tin catalyst, an acceleration step is performed to remove tin from the catalyst and expose the palladium metal for electroless copper plating. If the catalyst is a colloidal palladium-tin catalyst, the acceleration step may be carried out after adsorbing the catalyst, for example by using hydrochloric acid, sulfuric acid or tetrafluoroboric acid as accelerators in 0.5% to 10% water. This is done to remove tin from the catalyst to expose the palladium metal for electrolytic copper plating. If the catalyst is an ionic catalyst, the method excludes the acceleration step and instead applies a reducing agent to the substrate after applying the ionic catalyst to reduce the metal ions of the ionic catalyst. , Those metal states (eg, Pd (II) ions are Pd ° metals). Examples of suitable commercially available colloidal palladium-tin catalysts are the CIRCUPOSIT ™ 3340 catalyst and the CATAPOSIT ™ 44 catalyst (available from Dow Electrical Materials). An example of a commercially available palladium ionic catalyst is CIRCUPOSIT ™ 6530 Catalyst. The catalyst is applied by immersing the substrate in a solution of the catalyst, spraying the catalyst solution onto the substrate, or atomizing the catalyst solution onto the substrate using a conventional device. be able to. The catalyst can be applied at room temperature to 80 ° C., preferably 30 ° C. to 60 ° C. After applying the catalyst, the substrate and through holes are optionally washed with water.

It is possible to reduce the metal ions of a catalyst to its metallic state using a commonly used reducing agent known to reduce metal ions to metal. Such reducing agents include, but are not limited to: dimethylamine borane (DMAB), sodium borohydride, ascorbic acid, iso-ascorbic acid, sodium hypophosphite, hydrazine hydrate. , Formic acid and formaldehyde. The reducing agent is added in an amount that reduces substantially all of the metal ions to the metal. Such amounts are well known to those of skill in the art. If the catalyst is an ionic catalyst, the reducing agent is applied after the catalyst is applied to the substrate and before the metal coating is applied.

Next, the base material and the wall surface of the through hole are copper-plated using the composition for electroless copper plating of the present invention. The electroless copper plating method of the present invention can be carried out at a temperature of 40 ° C. or lower. The electroless copper plating method of the present invention is preferably carried out at a temperature of room temperature to 40 ° C., but the electroless copper plating is more preferably room temperature to 35 ° C., even more preferably 30 ° C. to 35 ° C., most preferably. Is carried out at 30 ° C. to 34 ° C. The base material can be immersed in the electroless copper plating composition of the present invention, or the electroless copper plating composition can be sprayed on the base material. The electroless copper plating method of the present invention using the electroless copper plating composition of the present invention is carried out in an alkaline environment having a pH higher than 7. Preferably, the electroless copper plating method of the present invention is preferably carried out at a pH higher than 7.5, and electroless copper plating is more preferably 8 to 14, even more preferably 10 to 14, even more preferably. It is carried out at a pH of 11 to 13, most preferably 12 to 13.

Preferably, the electroless copper plating rate of the present invention is 0.6 μm / 5 minutes or more at a temperature of 40 ° C. or lower, and more preferably, the electroless copper plating rate of the present invention is a temperature of 35 ° C. or lower. 0.65 μm / 5 minutes or more, for example 0.65 μm / 5 minutes to 1 μm / 5 minutes, and even more preferably 0.7 μm / 5 minutes or more, for example 0.75 μm / 5 minutes to 1 μm / 5 minutes or for example 0. It is 75 μm / 5 min to 0.8 μm / 5 min, and most preferably, electroless plating is performed at a temperature of 30 ° C. to 34 ° C.

The electroless copper plating method using the electroless copper plating composition of the present invention makes it possible to obtain a good average backlight value for electroless copper plating of through holes of a printed circuit board. Such an average backlight value is preferably 4.5 or more, more preferably 4.6 to 5, even more preferably 4.7 to 5, and most preferably 4.8 to 5. Since such a high average backlight value can be obtained, the electroless copper plating method of the present invention using the composition for electroless copper plating of the present invention can be used in commercial electroless copper plating. (The printed circuit board industry actually requires a backlight value of 4.5 or higher). The electroless copper metal plating composition and method of the present invention have made it possible to obtain a uniform, high-brightness copper precipitate over a wide concentration range of a pyridinium compound or a salt thereof even at a high plating rate.

The following examples are for further explaining the present invention and are not intended to limit the scope of the present invention.

Example 1
Electroless copper plating rate of electroless copper plating bath containing pyridinium compound Prepare 10 kinds of electroless copper plating baths. All 10 baths contain the following ingredients:
1.10 g / L copper sulfate pentahydrate 2.40 g / L Rochelle salt 3.8 g / L sodium hydroxide 4.4 g / L formaldehyde 5.0.5 ppm 2,2'-dithionisuccinate Acid 6. Water (balance amount)

The pH of each bath is 13. To the nine electroless plating compositions, one of the following pyridinium compounds is added in the amounts shown in Table 1. Bath 10 is a control and no pyridinium compound is added.

Each bath is used to copper-plat on a solid epoxy substrate of NP140 material (Nanya, Taiwan).

First, each epoxy substrate is treated according to the following process, and then electroless copper plating is performed.
(1) Conditioner 231 was applied at 40 ° C. for 1.5 minutes;
(2) Wash with DI water at room temperature for 2 minutes;
(3) Pre-dip at room temperature for 0.5 minutes using nitric acid with pH = 2;
(4) Wash with DI water at room temperature for 2 minutes;
(5) 100 ppm CIRCUPOSIT ™ 6530 catalyst was added at 40 ° C. for 1 minute;
(6) Wash with DI water at room temperature for 1 minute;
(7) An aqueous solution of 5 g / L boric acid and 0.6 g / L dimethylamine borane is added at 32 ° C. for 1 minute; and (8) DI water is used for washing at room temperature for 1 minute.

Electroless copper plating is performed at 34 ° C. for 5 minutes. The plating rate is determined by weighing each substrate before electroless copper plating using a conventional laboratory chemical balance, and then weighing each substrate after plating. Then, using the difference in weight between the respective substrates, the thickness of the precipitate was calculated using the surface area of the laminate (= 25 cm ² ) and the density of the copper precipitate (8.92 g / cm ³ ), and the value was calculated. Is divided by the length of the plating time to convert to the plating rate. Table 2 shows the plating rates in each bath.

The inclusion of 1-butylpyridinium chloride, 1- (3-sulfopropyl) pyridinium hydroxide or 1- (4-pyridyl) pyridinium chloride in the electroless copper plating bath increases the plating rate. Copper precipitates from the bath containing 1-butylpyridinium chloride and 1- (3-sulfopropyl) pyridinium hydroxide on substantially the entire surface of the epoxy substrate at concentrations of 2.5 ppm, 10 ppm and 20 ppm. Gives a glossy and homogeneous appearance. Copper precipitates plated from a bath containing 1- (4-pyridyl) pyridinium chloride show a glossy homogeneous surface with fine spots of coarse precipitates. Copper precipitates plated from a control bath show inhomogeneous, coarse and dark precipitates in large areas and microscopic areas of glossy precipitates.

Example 2 (Comparative Example)
Electroless copper plating rate of electroless copper plating bath containing pyridine (free nitrogen base) Prepare three types of electroless copper plating baths. All three baths contain the following ingredients:
1.10 g / L copper sulfate pentahydrate 2.40 g / L Rochelle salt 3.8 g / L sodium hydroxide 4.4 g / L formaldehyde 5.0.5 ppm 2,2'-dithionisuccinate Acid 6. Water (balance amount)

The pH of each bath is 13. Pyridine is added to the bath in an amount of 2.5 ppm (comparative bath 1), 10 ppm (comparative bath 2) or 20 ppm (comparative bath 3).

Each bath is used to plate copper on an epoxy substrate. The epoxy substrate is treated in the same manner as described in Example 1 to prepare electroless copper plating. Electroless copper plating is performed at 34 ° C. for 5 minutes. Next, the plating rate is determined as described in Example 1. Table 3 shows the plating rates in each bath.

The plating rate of pyridine at 2.5 ppm is higher than that of the control in Example 1, but is lower than the plating rate of the control at higher concentrations of 10 ppm and 20 ppm. The plating rate of pyridine is lower than that of the control electroless copper bath in Example 1. In the copper precipitate, a glossy homogeneous region and a coarse and dull colored region are mixed.

Example 3
Electroless copper plating rate of electroless copper plating bath containing pyridinium compound and guanidine hydrochloride 14 kinds of electroless copper plating baths are prepared. All 14 baths contain the following ingredients:
1.10 g / L copper sulfate pentahydrate 2.40 g / L Rochelle salt 3.8 g / L sodium hydroxide 4.4 g / L formaldehyde 5.0.5 ppm 2,2'-dithionisuccinate Acid 6.0.36 ppm guanidine hydrochloride 7. Water (balance amount)

The pH of each bath is 13. To 13 kinds of electroless plating compositions, one kind of the following pyridinium compound is added in the amount shown in Table 4. The bath 24 is a control and no pyridinium compound is added.

Each bath is used to plate copper on a solid epoxy substrate. After treating each epoxy base material, electroless copper plating is performed as described in Example 1. Electroless copper plating is performed at 34 ° C. for 5 minutes. The plating rate is determined as described in Example 1. Table 5 shows the plating rates in each bath.

Including 1-butylpyridinium chloride, 1- (3-sulfopropyl) pyridinium hydroxide or 1- (4-pyridyl) pyridinium chloride in an electroless copper plating bath results in faster plating rates than controls containing guanidine hydrochloride. It gets higher. Copper precipitates from baths containing 1-butylpyridinium chloride and 1- (3-sulfopropyl) pyridinium hydroxide have a glossy, homogeneous appearance across all epoxy substrates. Copper precipitates plated from a bath containing 1- (4-pyridyl) pyridinium chloride show a glossy homogeneous surface with fine spots of coarse precipitates. Copper precipitates plated from a control bath show glossy precipitates in small regions mixed with inhomogeneous, coarse precipitates in large regions.

Example 4 (Comparative Example)
Electroless copper plating rate of electroless copper plating bath containing pyridine (free nitrogen base) and guanidine hydrochloride Five types of electroless copper plating baths are prepared. All five baths contain the following ingredients:
1.10 g / L copper sulfate pentahydrate 2.40 g / L Rochelle salt 3.8 g / L sodium hydroxide 4.4 g / L formaldehyde 5.0.5 ppm 2,2'-dithionisuccinate Acid 6.0.36 ppm guanidine hydrochloride 7. Water (balance amount)

The pH of each bath is 13. Pyridine is added to the bath in an amount of 2.5 ppm (comparative bath 4), 5 ppm (comparative bath 5), 10 ppm (comparative bath 6), 15 ppm (comparative bath 7) or 20 ppm (comparative bath 8).

Each bath is used to plate copper on an epoxy substrate. The epoxy substrate is treated in the same manner as described in Example 1, and then electroless copper plating is performed. Electroless copper plating is performed at 34 ° C. for 5 minutes. The plating rate is determined as described in Example 1. Table 6 shows the plating rates in each bath.

Despite the combination with the accelerator guanidine hydrochloride, the maximum plating rate in an electroless copper bath containing the base pyridine is just over 0.60 μm / 5 min. Generally, when the concentration of pyridine in the electroless bath is increased, the electroless copper plating rate tends to decrease. In the copper precipitate, the shiny, homogeneous region is mixed with the coarse, dull colored region.

Example 5
Backlight experiment using the alkaline electroless copper aqueous composition of the present invention containing a pyridinium compound The following alkaline electroless copper aqueous composition of the present invention having the components and amounts disclosed in Table 7 below is prepared.

The pH of the alkaline electroless copper aqueous composition is pH = 13 as measured at room temperature using a conventional pH meter (available from Fisher Scientific).

Six different FR / 4 glass epoxy panels with multiple through holes are prepared: TUC-662, SY-1141, IT-180, 370HR, EM825 and NPGN. The panel is an 8-layer copper clad panel. TUC-662 is obtained from Taiwan Union Technology, and SY-1141 is obtained from Shengyi. IT-180 is available from ICT Corp. Obtained from, NPGN is obtained from Nanya, 370HR is obtained from Isola, and EM825 is obtained from the Elite Materials Corporation. The T _g value of the panel is in the range of 140 ° C to 180 ° C. Each panel is 5 cm x 10 cm.

The through holes of each panel are processed as follows.
1. 1. Clean the through holes in each panel at 80 ° C. for 6 minutes using CIRCUPOSIT ™ Hole Prep 3303 solution;
2. 2. The through holes in each panel were then washed with running tap water for 2 minutes;
3. 3. The through holes were then treated with an aqueous permanganate solution of CIRCUPOSIT ™ MLB Promoter 3308 at 80 ° C. for 8 minutes;
4. The through holes are then washed with running tap water for 4 minutes;
5. The through holes are then treated with 3 wt% sulfuric acid / 3 wt% hydrogen peroxide neutralizer at room temperature for 2 minutes;
6. The through holes in each panel were then washed with running tap water for 2 minutes;
7. The through-holes in each panel were then treated with CIRCUPOSIT ™ Conditioner 231 alkaline solution at 60 ° C. for 1.5 minutes;
8. The through holes are then washed with running tap water for 2 minutes;
9. Through holes are then treated with sodium persulfate / sulfuric acid etching solution at room temperature for 1 minute;
10. The through holes in each panel were then washed with running DI water for 1 minute;
11. The panel was then immersed in acidic Pre-Dip CIRCUPOSIT ™ 6520 for 0.5 minutes at room temperature and then in CIRCUPOSIT ™ 6530 Catalyst, which is an aqueous concentrate of an ionic alkaline palladium catalyst. The catalyst was buffered with sufficient amounts of sodium carbonate, sodium hydroxide or nitric acid to achieve a catalytic pH of 9-9.5. Shi;
12. The through holes in each panel were then washed with running DI water for 1 minute at room temperature;
13. The panel was then immersed in a solution of 0.6 g / L dimethylamine borane and 5 g / L boric acid at 32 ° C. for 1 minute to reduce the palladium ions to a palladium metal;
14. The through holes in each panel were then washed with running DI water for 1 minute;
15. Next, the panel was immersed in the electroless copper plating composition shown in Table 7, copper was plated at 34 ° C. and pH 13, and copper was deposited on the wall surface of the through hole for 5 minutes;
16. The copper-plated panel was then washed with running tap water for 4 minutes;
17. Each copper-plated panel is then dried using compressed air; and 18. The wall surface of the through-hole of the panel is examined for the plating coverage using the backlight method described below.

For each panel, cut as close as possible to the center of the through hole to expose the copper-plated walls. Its cross section, within 3 mm thick from the center of the through hole, is removed from each panel and placed under a conventional light microscope with a light source under the sample at 50x magnification. The quality of the copper precipitate is determined by the amount of light that can be seen under a microscope through the sample. Inside the plated through holes, transmitted light can be observed only in the region where the electroless coating is incomplete. If no light is transmitted, the section is completely dark and is rated 5 on the backlight scale, which indicates that the walls of the through holes are completely covered with copper. If the light passes through all sections without any dark areas, this means that there is very little or no deposition of copper metal on the walls of the through holes, so 0 in that section. Give a score of. If the section has some dark areas along with bright areas, rate them 0-5. At least 10 through holes are inspected and each board is evaluated. A backlight value greater than 4.5 indicates a commercially acceptable catalyst in the plating industry.

The average backlight values for each type of FR / 4 glass epoxy panel are disclosed in the following table.

Both of these baths show very good backlight values overall.

Claims (10)

A composition for electroless copper plating, wherein one or more copper ion sources, one or more pyridinium compounds, one or more complexing agents, one or more reducing agents and optionally one. includes a species or more pH adjusting agents, the pH of the electroless copper plating compositions is much larger than 7, the one or more pyridinium compounds, formula:
(In the formula, R ₁ is a linear or branched substituted or unsubstituted (C _1- C ₁₀ ) alkyl, substituted or unsubstituted (C _6- C ₁₀ ) aryl, substituted or unsubstituted (C _6- C). ₁₀ ) Selected from the group consisting of heterocyclic aromatic groups and substituted or unsubstituted benzyls, the substituents selected from the group consisting of hydroxyl, sulfate, amino and carboxyl, and R ₂ is hydrogen, hydroxyl, sulfate, (Selected from the group consisting of amino, carboxyl and vinyl)
A composition for electroless copper plating having. The composition for electroless copper plating according to claim 1, wherein the one or more pyridinium compounds or salts thereof are in an amount of at least 0.5 ppm. The one or more complexing agents include potassium sodium tartrate, sodium tartrate, sodium salicylate, sodium salt of ethylenediaminetetraacetic acid, nitriloacetic acid and its alkali metal salts, gluconic acid, gluconate, triethanolamine, modified ethylenediaminetetraacetic acid. The composition for electroless copper plating according to claim 1, which is selected from acetic acid, S, S-ethylenediaminediamine disuccinic acid, hydantin and a hydantin derivative. The composition for electroless copper plating according to claim 1, wherein the one or more reducing agents are selected from aldehydes, borohydrides, substituted borohydrides, boranes, saccharides and hypophosphates. .. The composition for electroless copper plating according to claim 1, further comprising one or more compounds selected from a secondary accelerator, a crystal growth inhibitor and a stabilizer. It is an electroless copper plating method.
a) Step of providing a base material containing a dielectric,
b) A step of applying a catalyst to the substrate containing the dielectric,
c) A step of applying an electroless copper plating composition to the base material containing the dielectric, wherein the electroless copper plating composition is one or more copper ion sources, one or more. The pH of the composition for electroless copper plating, which comprises a pyridinium compound, one or more complexing agents, one or more reducing agents and optionally one or more pH adjusting agents, is greater than 7. the size rather, the one or more pyridinium compounds, formula:
(In the formula, R ₁ is a linear or branched substituted or unsubstituted (C _1- C ₁₀ ) alkyl, substituted or unsubstituted (C _6- C ₁₀ ) aryl, substituted or unsubstituted (C _6- C). ₁₀ ) Selected from the group consisting of heterocyclic aromatic groups and substituted or unsubstituted benzyls, the substituents selected from the group consisting of hydroxyl, sulfate, amino and carboxyl, and R ₂ is hydrogen, hydroxyl, sulfate, (Selected from the group consisting of amino, carboxyl and vinyl)
Having a step, and d) using said electroless copper plating compositions, which comprises the step of electroless plating of copper onto said substrate comprising said dielectric. The method according to claim 6 , wherein the amount of the one or more pyridinium compounds or salts thereof is at least 0.5 ppm. The method of claim 6 , wherein the electroless copper plating composition further comprises one or more compounds selected from stabilizers and secondary accelerators. The method according to claim 6 , wherein the composition for electroless copper plating is 40 ° C. or lower. The method according to claim 6 , wherein the catalyst is a palladium catalyst.