US3615735A - Electroless copper plating - Google Patents

Electroless copper plating Download PDF

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Publication number
US3615735A
US3615735A US752250A US3615735DA US3615735A US 3615735 A US3615735 A US 3615735A US 752250 A US752250 A US 752250A US 3615735D A US3615735D A US 3615735DA US 3615735 A US3615735 A US 3615735A
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solution
copper
formaldehyde
moles
group
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US752250A
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Charles R Shipley Jr
Lucia Shipley
Michael Gulla
Oleh B Dutkewych
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Shipley Co Inc
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Shipley Co Inc
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    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
    • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
    • C23C18/31—Coating with metals
    • C23C18/38—Coating with copper
    • C23C18/40—Coating with copper using reducing agents
    • C23C18/405—Formaldehyde

Definitions

  • Hayes Atlorney Roberts, Cushman & Grover ABSTRACT An electroless copper-plating solution comprising a source of cupric ions, hydroxyl radicals, formaldehyde or a formaldehyde precursor preferably paraformaldehyde and a complexing agent for copper; said solution characterized by the addition of a member selected from the group consisting of a formaldehyde addition agent, a solution soluble salt of a Group Vlll metal of the Periodic Chart of the elements, preferably a combination thereof and most preferably, the two in combination with an organic silicon compound.
  • the copper plate deposited from the preferred solution is alloyed with the Group VIII metal cation and is distinguishable from prior art electroless copper deposits by substantially improved bending or tensile properties and a smoother, more highly reflecting surface appearance.
  • the electroless copper-plating solution is capable of providing a rapid rate of copper deposition dependent upon the selection of the complexing agent and the stability of its chelate with copper without sacrifice in tensile or bending properties of the copper deposit.
  • This invention relates to a metal-depositing composition and more particularly, to an electroless copper-plating solution capable of providing an electroless copper deposit of improved appearance and bending or tensile properties.
  • Electroless copper deposition refers to the chemical plating of copper over clean catalytically active surfaces by chemical reduction in the absence of an external electric current. Such processes and compositions useful therefor are known and are in substantial commercial use. They are disclosed in a number of prior art patents, for example, U.S. Pat. Nos. 2,938,805; 3,01 1,920; 3,310,430; and 3,383,224.
  • Known electroless copper deposition solutions generally comprise four ingredients dissolved in water. They are (1) a source of cupric ions, usually a copper salt, such as copper sulfate (2) a reducing agent such as formaldehyde, or preferably, a formaldehyde precursor such as paraformaldehyde, (3) hydroxide, generally an alkali metal hydroxide and usually sodium hydroxide, sufficient to provide the required alkaline solution in which said compositions are effective, and (4) a complexing agent for copper sufficient to prevent its precipitation in alkaline solution.
  • a source of cupric ions usually a copper salt, such as copper sulfate
  • a reducing agent such as formaldehyde, or preferably, a formaldehyde precursor such as paraformaldehyde
  • hydroxide generally an alkali metal hydroxide and usually sodium hydroxide
  • the subject invention is an improvement over that described in the above-noted patents and provides an electroless copper solution capable of depositing an electroless copper plate of improved bending or tensile properties.
  • the copper solution is characterized by the addition of a member selected from the group consisting of a formaldehyde addition agent, a Group VIII metal salt of the Periodic Chart of the elements, preferably mixtures thereof, and most preferably, mixtures thereof with a solution-soluble organic silicon compound.
  • a formaldehyde addition agent or a Group VIII metal salt provides some improvement in tensile properties. Combination of the two provides an additive improvement in tensile properties.
  • electroless copper deposits from the solutions of this invention provide the advantages of excellent laydown properties, excellent solderability and improved smoothness, brightness, and overall appearance.
  • Preferred Copper salt 0.0 02 moles to satura- 0.02 to 0.12 moles.
  • complexing agent Minimum necessary About 1 to 3 times to maintain copper the moles of cupric in solution. ion. Sufficient to provide 0.1 to 0.8 moles.
  • pH 10 pH 10 or greater. Greater than 1 p.p.rn. 5 to 250 p.p.m. Up to that amount 0.1 to 1 times the that retards deposimoles of formaltion. dehyde. 5 to 2,500 p.p.m 30 to 1,000 p.p.m. To 1 liter of solution. To 1 liter of solution.
  • any water-soluble copper salt heretofore used for preparing electroless copper deposition solutions may be used.
  • acetate, sulfate and other organic and inorganic acid salts of copper are generally suitable as is known in the art. Copper sulfate is preferred.
  • Suitable complexing agents for the copper ions are well known in the art and include Rochelle salts, the sodium salts (mono-, di-, tri-, and tetrasodium salts) of ethylene diaminetetraacetic acid, nitrilotriacetic acid and its alkali metal salts, triethanolamine, modified ethylene diaminetetraacetic acids such as N-hydroxyethylenediaminetriacetate, hydroxyalkyl substituted dialkylene triamines such as pentahydroxypropyl diethylenetriamine, sodium salicylate, and sodium tartrate.
  • Other complexing agents for copper ions are disclosed in U.S. Pat. Nos. 2,996,408; 3,075,855; 3,075,856; and 2,938,805.
  • the preferred class of complexing agents are those described in U.S. Pat. No. 3,329,512 noted above. They include hydroxyalkyl-substituted tertiary amines corresponding to one of the following structures:
  • R is an alkyl group having from two to four carbon atomsjR is a lower alkylene radical and n is a positive integer.
  • these complexing agents include tetrahydroxypropyl ethylene diamine, pentahydroxypropyl diethylene trihydroxypropylamine (tripropanolamine), trihydroxypropyl hydroxyethyl ethylene diamine, etc.
  • the aforesaid amines are preferably used in small amounts in combination with other complexing agents and with certain polymers dispersed in solution such as cellulose ethers, hydroxyethyl starch, polyvinyl alcohol, polyvinylpyrrolidone, peptones, gelatin, polyamides and polyacrylamides.
  • the rate of copper deposition is, to some extent, dependent upon the selection of the complexing agent.
  • Complexing agents such as pentahydroxypropyl diethylene triamine provide a fast rate of copper deposition, usually in excess of 1.0 mil per hour.
  • the copper solutions of this invention provide copper deposits from solutions containing any of the known complexing agents for copper ions, they are particularly well adapted for copper solutions having complexing agents that provide a rapid rate of copper deposition.
  • the silicon additive is one that is soluble in the copper solutions and comprises the organic silicon compounds disclosed in the above-noted copending U.S. Pat. No. 3,475,186. It should be noted that many silicon compounds are not fully soluble in aqueous alkaline solutions and many are considered insoluble. However, the silicon, for purposes of the present invention, is required in solution in parts per million and silicon compounds termed insoluble in aqueous solution usually are soluble to the extent ofa few parts per million and suitable for purposes of the present invention. For these silicon compounds considered insoluble in water, it is desirable to dissolve the compound in a solvent, such as alcohol, and add the solution to the electroless copper solution with agitation to form a dispersion or an emulsion. An excess of the silicon compound will be required to provide the necessary concentration of silicon compound in solution.
  • a solvent such as alcohol
  • Exemplary of the silicon compounds within the scope of the invention are the silanes, such as silane itself, disilane, tetramethylsilane, trimethylethylsilane, tetraethylsilane, tetraphenylsilane, dimethyldichlorosilane, etc., and low to intermediate molecular weight polysiloxanes, such as silicone fluids, gums, and resins substituted with methyl-, ethyl-, vinyl-, phenyl-, chloro-, bromo-, methoxy-, hydroxy-, etc.
  • Other suitable organic silicon compounds are disclosed in the abovenoted U.S. Pat. No. 3,475,186.
  • the polysiloxanes are the least soluble silicon compounds in basic copper solutions, but are preferred because they provide the greatest increase in ductility and also enhance appearance by yielding a finer grained, more highly reflecting copper deposit. Of the polysiloxanes, the silicon fluids are most preferred.
  • the solid polysiloxanes are preferably dissolved in a solvent such as alcohol and added to the copper solution.
  • the formaldehyde addition agent for purposes of this invention is one that may be added to solution in amounts sufficient to undergo reaction with formaldehyde to form a relatively unstable formaldehyde adduct without poisoning the solution.
  • Reactions of this nature and formaldehyde addition agents are well known in the art and described in various publications, such as Formaldehyde" by .1. Frederick Walker, Reinhold Publishing Company, Third Edition 1964, pgs. 219-221, included herein by reference.
  • Preferred formaldehyde addition agents are sulfites, bisulfites and phosphites of a metal cation that does not codeposit with copper and preferably, an alkali metal cation.
  • Preferred formaldehyde addition agents are sodium sulfite, potassium bisulfite, and sodium phosphite.
  • the formaldehyde addition agent and formaldehyde or preferably, paraformaldehyde are reacted with each other to form the adduct prior to addition to the remaining components of the copper solution.
  • the Group VIII metal salts are preferably water-soluble inorganic salts of iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium, and platinum; salts of iron, nickel,
  • Suitable salts include phosphates, nitrates, halides and acetates of the above metals. lron, nickel and platinum to a greater extent and the remaining Group VIII metals to a lesser extent codeposit with copper to form a copper alloy. The Group VIII metal codeposits in a smaller proportion relative to copper present in the original electroless solution.
  • a wetting agent may be added to solution in accordance with art-recognized procedure.
  • the baths may be used at widely varying temperatures, e.g., at least room temperature and preferably up to about 140F. As temperature is increased, it is customary to find an increase in the rate of plating. Temperature is not highly critical, and within the usual operating range, excellent, bright deposits of electroless copper having excellent tensile properties are obtained. Preferably, the bath is used without agitation.
  • the surface to be plated should be catalytically active and free of grease and contaminating material.
  • the surface area to receive the deposit must first be sensitized to render it catalytically active as by the well-known treatment with an acidic aqueous solution of stannous chloride followed by treatment with a dilute aqueous acidic solution of palladium chloride.
  • an acidic colloidal formulation formed by the admixture of stannous chloride and a precious metal chloride, preferably palladium chloride, the stannous chloride being present in stoichiometric excess based upon the amount of precious metal chloride.
  • (l) F-l-35 14 A silicone fluid believed to be a dimethylpolysiloxane-ethylene glycol copolymer available from the General Electric Co.
  • SF-l I38 A silicone fluid believed to be a dimethylpolysiloxane-polyalkylene oxide copolymer available from the General Electric Company.
  • a deposit was considered poor if it was dark in color and powdery in appearance.
  • a fair deposit was one lighter in color though powdery in appearance.
  • a good deposit was one having a fine-grained metallic copper appearance.
  • Examples 2 to 6 illustrate copper containing only a Group VIII metal salt.
  • Examples 7 to 9 illustrate copper solutions containing only a formaldehyde addition agent. No recordable improvement in properties is apparent using either of these additives in the above copper solution.
  • Examples 10 to 12 illustrate the use of a silicon compound and show some improvement in both appearance and tensile properties.
  • the combination of a silicon compound with either a Group VIII metal salt or a formaldehyde addition agent (examples 13 to 16) provides a somewhat greater improvement.
  • Combination of the silicon compound with both a formaldehyde addition agent and a Group VIII metal salt provides substantial improvement in tensile properties as evidenced by the ductility in all cases in excess oftwo bends and in some cases, as high as five bends.
  • Additive composition and deposit properties are set forth in the following table:
  • Example 28 using an electroless copper composition containing a silicon compound, a formaldehyde addition agent and a Group VIII metal salt provides a copper deposit having a significant improvement in tensile properties. Formulations having one additive only show some improvement.
  • EXAMPLE 29 a) cuso.-sH.o 8.0 g. b) Patuformaldehyde 7.5 g. c) NaOH (25% solution by weight) 50.0 ml. d) trihydroxypropylhydroxyethyl ethylene diumine 20.0 g. e) SF-l 138" 200 p.p.m. 0 M50. 300 p.p.m. g) NaHSO 20 g. h) Water [0 1 liter of solution Electroless copper deposited from the above solution was bright and withstood three and one-half bends. Copper deposited from a control solution free of additives e, f, and g had a poor appearance and was brittle.
  • Copper deposited from the above solution was bright in color and capable of withstanding in excess of five bends. Copper deposited from a solution free of additives e, f, and g was found to be brittle.
  • each additive alone or in combinations of two, increased ductility substantially.
  • the combination of the three additives provided a substantially greater increase in ductility.
  • Additive compositions and deposit properties are set forth in the following table:
  • FIG. 4 shows the cross section of the copper deposited from i the formulation of example 59.
  • FIGS. 3 and 4 show substantially smoother deposits than those of FIGS. 1 and 2. The rough deposit in FIGS. 1 and 2 are believed to be more readily fractured by bending due to the troughs in the deposit which act as the weakest point of the deposit.
  • Copper solutions of this invention find utility for all purposes for which electroless copper solutions have heretofore been used including both decorative and industrial applications. They are especially useful for the formation of printed circuit boards where the deposits act as ductile conductors and as ductile connectors plated onto the walls of throughholes.
  • the formation of a printed circuit board having conductive through-holes is illustrated in the following example.
  • EXAMPLE 60 a Sandblast one side of a phenolic substrate leaving the second surface smooth.
  • an aqueous electroless copper-plating solution comprising a source of cupric ions, hydroxyl radicals, a source of formaldehyde and sufficient complexing agent to render said cupric ions soluble in alkaline solution
  • the improvement comprising an additive in the solution of at least two members selected from the group consisting of a formaldehyde addition agent in an amount of from at least 0.] moles times the moles of formaldehyde to that amount that restricts copper deposition, a solution soluble salt of a Group VIII metal of the Periodic Chart of the elements in an amount of from 5 to 2,5000 parts per million parts of solution and an organic silicon compound in solution in an amount of from 1 part silicon per million parts of solution to that amount that restricts deposition of copper from solution,
  • an electroless copper-plating solution comprising a source of cupric ions, hydroxyl radicals, formaldehyde and sufficient complexing agent to render said cupric ions soluble in alkaline solution, the improvement comprising an additive an amount of from 5 to 250 parts of silicon in solution per million parts of solution, (b) a formaldehyde addition agent selected from the group of alkali metal sulfites, bisulfites and phosphites in an amount of from 0.1 to 1 times the moles of formaldehyde in solution and (c) a solution-soluble salt of a member selected from the group of iron, nickel andplatinum salts in an amount offrom 5 to 2,500 parts per million parts of solution, said solution soluble salt having an anionic portion noninterfering with the plating solution.
  • the copper-plating solution of claim 2 having as additives an organic silicon compound and a formaldehyde addition agent.
  • the copper-plating solution of claim 2 having as additives an organic silicon compound, a formaldehyde addition agent and a solution soluble salt of a Group VIII metal of the Periodic Chart of the elements.
  • an aqueous electroless copper-plating solution comprising a source of cupric ions, hydroxyl radicals formal dehyde and sufficient complexing agent to render said cupric ions soluble in alkaline solution
  • the improvement comprising an additive in the solution of a small but effective amount of an organic silicon compound in an amount of from I part silicon in solution per million parts of solution to that amount that restricts deposition of copper from solution and at least one member selected from the group consisting of a formaldehyde addition agent selected from the group consisting of alkali metal sulfites, bisulfites and phosphites in an amount of from 0.1 moles times the moles of formaldehyde to that amount that restricts copper deposition and a solution soluble salt of a Group VIII metal selected from the group of iron, nickel and platinum in an amount from 5 to 2,500 parts per million parts of solution.

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  • Chemical & Material Sciences (AREA)
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  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
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US752250A 1968-08-13 1968-08-13 Electroless copper plating Expired - Lifetime US3615735A (en)

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Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3765936A (en) * 1968-08-13 1973-10-16 Shipley Co Electroless copper plate
US4167601A (en) * 1976-11-15 1979-09-11 Western Electric Company, Inc. Method of depositing a stress-free electroless copper deposit
US4228213A (en) * 1979-08-13 1980-10-14 Western Electric Company, Inc. Method of depositing a stress-free electroless copper deposit
US4265943A (en) * 1978-11-27 1981-05-05 Macdermid Incorporated Method and composition for continuous electroless copper deposition using a hypophosphite reducing agent in the presence of cobalt or nickel ions
US4720404A (en) * 1984-02-04 1988-01-19 Josif Culjkovic Aqueous alkaline bath for the chemical deposition of copper, nickel, cobalt and their alloys
US5077099A (en) * 1990-03-14 1991-12-31 Macdermid, Incorporated Electroless copper plating process and apparatus
US5256441A (en) * 1992-08-04 1993-10-26 Amp-Akzo Corporation Ductile copper
US5258200A (en) * 1992-08-04 1993-11-02 Amp-Akzo Corporation Electroless copper deposition
US5269838A (en) * 1992-04-20 1993-12-14 Dipsol Chemicals Co., Ltd. Electroless plating solution and plating method with it
US5810913A (en) * 1995-10-18 1998-09-22 Murata Manufacturing Co., Ltd. Activating catalytic solution for electroless plating and method of electroless plating
US6398855B1 (en) * 1999-01-15 2002-06-04 Imec Vzw Method for depositing copper or a copper alloy
US20040226407A1 (en) * 2003-05-14 2004-11-18 David Ericson Method and apparatus for converting metal ion in solution to the metal state
US20050067297A1 (en) * 2003-09-26 2005-03-31 Innovative Technology Licensing, Llc Copper bath for electroplating fine circuitry on semiconductor chips
US9153449B2 (en) 2012-03-19 2015-10-06 Lam Research Corporation Electroless gap fill

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3093509A (en) * 1959-09-28 1963-06-11 Wein Samuel Process for making copper films
US3134690A (en) * 1960-02-09 1964-05-26 Eriksson Lars Erik Method for deposition of a copper layer on a non-conductive material
US3329512A (en) * 1966-04-04 1967-07-04 Shipley Co Chemical deposition of copper and solutions therefor
US3436233A (en) * 1964-05-27 1969-04-01 Ibm Method and composition for autocatalytically depositing copper
US3475186A (en) * 1968-01-05 1969-10-28 Shipley Co Electroless copper plating

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3093509A (en) * 1959-09-28 1963-06-11 Wein Samuel Process for making copper films
US3134690A (en) * 1960-02-09 1964-05-26 Eriksson Lars Erik Method for deposition of a copper layer on a non-conductive material
US3436233A (en) * 1964-05-27 1969-04-01 Ibm Method and composition for autocatalytically depositing copper
US3329512A (en) * 1966-04-04 1967-07-04 Shipley Co Chemical deposition of copper and solutions therefor
US3475186A (en) * 1968-01-05 1969-10-28 Shipley Co Electroless copper plating

Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3765936A (en) * 1968-08-13 1973-10-16 Shipley Co Electroless copper plate
US4167601A (en) * 1976-11-15 1979-09-11 Western Electric Company, Inc. Method of depositing a stress-free electroless copper deposit
US4265943A (en) * 1978-11-27 1981-05-05 Macdermid Incorporated Method and composition for continuous electroless copper deposition using a hypophosphite reducing agent in the presence of cobalt or nickel ions
US4228213A (en) * 1979-08-13 1980-10-14 Western Electric Company, Inc. Method of depositing a stress-free electroless copper deposit
US4720404A (en) * 1984-02-04 1988-01-19 Josif Culjkovic Aqueous alkaline bath for the chemical deposition of copper, nickel, cobalt and their alloys
US5077099A (en) * 1990-03-14 1991-12-31 Macdermid, Incorporated Electroless copper plating process and apparatus
US5269838A (en) * 1992-04-20 1993-12-14 Dipsol Chemicals Co., Ltd. Electroless plating solution and plating method with it
US5258200A (en) * 1992-08-04 1993-11-02 Amp-Akzo Corporation Electroless copper deposition
US5256441A (en) * 1992-08-04 1993-10-26 Amp-Akzo Corporation Ductile copper
US5429861A (en) * 1992-08-04 1995-07-04 Amp-Akzo Corporation Electroless copper deposited on a printed circuit board capable of withstanding thermal cycling
US5810913A (en) * 1995-10-18 1998-09-22 Murata Manufacturing Co., Ltd. Activating catalytic solution for electroless plating and method of electroless plating
US6398855B1 (en) * 1999-01-15 2002-06-04 Imec Vzw Method for depositing copper or a copper alloy
US6585811B2 (en) * 1999-01-15 2003-07-01 Imec Vzw Method for depositing copper or a copper alloy
US20040226407A1 (en) * 2003-05-14 2004-11-18 David Ericson Method and apparatus for converting metal ion in solution to the metal state
US20050067297A1 (en) * 2003-09-26 2005-03-31 Innovative Technology Licensing, Llc Copper bath for electroplating fine circuitry on semiconductor chips
US9153449B2 (en) 2012-03-19 2015-10-06 Lam Research Corporation Electroless gap fill

Also Published As

Publication number Publication date
DE1966198B2 (de) 1978-07-13
JPS5129701B1 (enrdf_load_stackoverflow) 1976-08-27
DE1966198C3 (de) 1979-03-15
DE1966198A1 (de) 1971-11-11

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