Classifications

• • 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
  • C23C18/32—Coating with nickel, cobalt or mixtures thereof with phosphorus or boron
  • C23C18/34—Coating with nickel, cobalt or mixtures thereof with phosphorus or boron using reducing agents
• • 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

Definitions

• the invention relates to an aqueous alkaline bath for the chemical deposition of copper, nickel, cobalt or their alloys according to the preamble of claim 1 and a method for the adhesive chemical deposition of these metals and alloys according to the preamble of claim 11.
• Baths of the type described in the introduction are generally known. They usually contain considerable amounts of complexing agents to prevent the precipitation of metal hydroxides. This inevitably leads to an unsatisfactory quality of the coatings deposited from these baths, which, depending on the bath type, contain considerable amounts of impurities such as carbon, nitrogen, hydrogen and others. can contain, which have a decisive influence on the crystal structure and thus on technologically important properties, such as specific electrical conductivity, internal tension, adhesive strength and ductility. For example, this has a particularly disruptive effect in the production of printed circuit boards in which undesired bubbles, lifts and cracks can form, and the more so the thicker the deposited metal layer.
• the concentrates or rinsing water produced during the operation of the known baths are moreover usually obtained in the form of solutions which can only be disposed of with great technical effort since their direct return to the working process is not readily possible.
• the object of the present invention is to provide a bath and a method which permit a highly adhesive chemical deposition of copper, nickel, cobalt and their alloys with the greatest purity and at the same time technically problem-free recovery of the metals used.
• metal coatings of the highest purity can be deposited from the bath according to the invention, which is not possible with the known chemical baths.
• the sum of impurities in carbon, hydrogen and nitrogen in copper coatings deposited according to the invention is 0.03%, while in conventional coatings, impurities are in the order of 0.07 to 0.37%.
• the quality of the metal coatings deposited according to the invention therefore corresponds to that which is otherwise only achieved with electrolytic metal deposition. Purity and the properties of the coatings deposited according to the invention, such as average residual stress, average lattice distortion and the crystallite size, are therefore equal to the electroplated coatings.
• the bath according to the invention therefore enables in particular the production of printed circuit boards with adhesive layers which are extremely ductile and easy to solder and which are characterized by the lowest internal stresses, which means a breakthrough in technology.
• the complexing agents to be scrapped according to the invention also have the particular advantage of being readily biodegradable and thus, in contrast to the known complexing agents, to be particularly environmentally friendly.
• the glycerol to be used according to the invention has not been shown to have any damaging effect on organisms, so that, taking further account of its classification as a highly biodegradable substance, it exhibits favorable ecological properties.
• metals copper, nickel and cobalt their sulfates, nitrates, chlorides, bromides, rhodanides, oxides, hydroxides, carbonates, basic carbonates, acetates and others can be used, specifically in metal concentrations of 10 -4 to 2 mol / liter, preferably of 10 - 2 to 1 mole / liter.
• These metal compounds form complex compounds with the complexing agents according to the invention in the bath solution, which develop the desired effect.
• these complex compounds can also be prepared per se in a manner known per se and can only be added to the bath solution before they are used.
• the complex compound Schiff's potassium cupri biuret according to the invention can be prepared by adding 1 mol of copper acetate to an aqueous solution of 1 mol of biuret and 4 mol of potassium hydroxide by precipitation with a 2% alcoholic potassium hydroxide solution.
• the molar ratio of metal to complexing agent is at least -1: 0.8, preferably from 1: 1 to 1: 6.
• the labeled polyols which also have the general formula, are suitable as complexing agents according to the invention with R in the meaning of hydrogen or C 1 -C 6 alkyl and n the numbers 2 to 8 can be described.
• Biuret-type compounds are understood to mean those which have at least two in the molecule Contain groups that are connected in an open chain and directly to one another or by a C or N atom.
• the stability of the metal complexes formed from these complexing agents is extremely high, but can, if desired, be influenced immediately if the pH changes by acidification, which leads to the complete precipitation of the metal hydroxide, which can then be returned to the working process.
• the pH of the bath according to the invention should be greater than 10, preferably from 12 to 14, and is kept at the desired value by adding customary pH-regulating substances or mixtures of substances.
• Particularly suitable reducing agents are formaldehyde, sodium borohydride, dimethylaminoborane, diethylaminoborane, sodium hypophosphite, hydrazine, glyceraldehyde, dihydroxyacetone and other customary reducing agents.
• the bath is operated at temperatures from 5 ° C to the boiling point, preferably from 20 ° to 80 ° C.
• the bath can additionally contain stabilizers known per se based on polyamines, N-containing compounds, reaction products of N-containing compounds with epihalohydrins, sulfur or selenium compounds with the oxidation state minus one or minus two, mercury compounds or lead compounds, to ensure a sufficient lifespan of the bath.
• the basic composition of the bath according to the invention is as follows:
• the bath according to the invention is suitable for the full and partial metallization of conductors and non-conductors after corresponding customary pretreatment, such as degreasing, pickling, cleaning, conditioning, activating and reducing.
• customary pretreatment such as degreasing, pickling, cleaning, conditioning, activating and reducing.
• a preferred field of application is the production of printed circuits.
• the conductors that had been plated through in this bath were, according to the transmitted light method, flawless.
• the deposition rate was approx. 2 fm / h, so that a treatment time of 15-20 minutes is completely sufficient.
• This bath deposits ductile copper coatings at a speed of approx. 5 ⁇ m / h, which are particularly suitable for semi or additive technology.
• Copper-phosphorus alloys with 0.3 to 0.5% phosphorus were deposited from this bath.
• the deposition rate was 1.2 ⁇ m / h.
• Adhesive layers of Cu 2 O on Al 2 0 3 ceramic could be deposited from this bath. After an annealing process at 400 to 600 ° C, within 10 minutes the layers were strengthened to 30 ⁇ m / in an acidic galvanic copper bath. Tempering and spinel formation resulted in an increase in adhesive strength of up to 2 N / mm in a peel test. With conventional techniques, without spinel formation, an adhesive strength of only 0.7 N / mm is achieved.
• Ductile nickel coatings with a boron content of approximately 0.2 to 0.4% could be deposited from this bath.

Landscapes

• Chemical & Material Sciences (AREA)
• General Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Electroplating And Plating Baths Therefor (AREA)
• Chemically Coating (AREA)
• Manufacturing Of Printed Wiring (AREA)
• Treatment Of Water By Oxidation Or Reduction (AREA)

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Publications (2)

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Citations (3)

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• 1984
  • 1984-02-04 DE DE19843404270 patent/DE3404270A1/de not_active Withdrawn
  • 1984-12-15 DE DE8484115513T patent/DE3475535D1/de not_active Expired
  • 1984-12-15 EP EP84115513A patent/EP0152601B1/fr not_active Expired
• 1985
  • 1985-01-31 AT AT0027385A patent/AT384829B/de not_active IP Right Cessation
  • 1985-02-01 CA CA000473446A patent/CA1254353A/fr not_active Expired
  • 1985-02-04 JP JP60018815A patent/JPS60204885A/ja active Pending
• 1986
  • 1986-08-07 US US06/896,741 patent/US4720404A/en not_active Expired - Fee Related

Patent Citations (3)

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