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
  • C23C18/38—Coating with copper
  • C23C18/40—Coating with copper using reducing agents
  • C23C18/405—Formaldehyde

Definitions

• Electroless copper deposition refers to the chemical plating of copper over active surfaces by chemical means and in the absence of external electric current. Such processes and compositions useful therewith are known and are in substantial commercial use. They are disclosed in a number of prior art patents, for example United States Patent 3,011,920, issued Dec. 16, 1961.
• Known electroless copper deposition solutions compries basically four ingredients dissolved in water. These are (1) a source of cupric ions usually copper sulphate, (2) formaldehyde as reducing agent therefor, (3) alkali, generally an alkali metal hydroxide and usually sodium hydroxide, suflicient to provide the required alkaline solution in which said compositions are effective, and (4) a complexing agent for the copper sufiicient to prevent its precipitation in alkaline solution.
• a new complexing agent has been discovered which when used alone or in admixture with other complexing agents provides substantial advantages.
• These new additives are hydroxyalkyl substituted dialkylene triamines having the following structure.
• R groups taken individually, are -(CH OH, CH COOH, -C H COOH or inert organic radicals such as lower alkyl or lower dialkyl ethers having from 1 to 4 carbon, inclusive.
• inert as used above means that the radicals do not react in the copper solution and neither contribute to nor detract from the ice complexing activity of the molecule.
• the product is useful for an extremely wide range of plating applications for copper and provides thicknesses of up to 70 millionths of an inch readily.
• the copper deposite is of excellent quality, both analytically and by appearance.
• the deposited copper has an extraordinarily high electrical conductivity greatly simplifying the usual operation of increasing the copper thickness by electroplating. Coatings of 40 millionths of an inch or more can be immediately electroplated with current densities of as high as 100 amps per square foot without harm or burning of the electroless copper plating. With most prior electroless compositions, initial electric plating had to be stated below current densities of 40 amperes and slowly increased to the desired density. Good copper to copper bonds are obtained.
• Example 1 is currently preferred.
• Copper sulfate is the source of copper ions and the NaOH provides the desired alkalinity, generally a pH of 10 or preferably higher.
• Other soluble copper salts and other alkali metal hydroxides can be employed.
• concentration is not critical and usuable amounts are withinthe limits generally known in the art.
• Sufficient copper must be employed to provide a useful deposit and sufiicient alkali to provide the high pH required.
• Sufiicient formaldehyde must be employed to serve as a reducing agent for the copper in the presence of a catalytic surface and sufficient complexing agent used to prevent precipitation of copper in alkaline solution.
• concentration is not critical and usuable amounts are withinthe limits generally known in the art.
• Sufficient copper must be employed to provide a useful deposit and sufiicient alkali to provide the high pH required.
• Sufiicient formaldehyde must be employed to serve as a reducing agent for the copper in the presence of a catalytic surface and sufficient complexing agent used to prevent precipitation of copper in alkaline solution.
• the limits of concentration of these ingredients is given in the following Table I.
• compositions according to this invention are stable for extended deposition at temperatures of up to about 65 F. Above this temperature the stability without treatment may be less than desirable. If so, they can be stabilized by the addition of chemical stabilizers or by aerating them in accordance with the disclosure of US. Patent No. 2,938,805.
• the novel solution herein disclosed can be applied to the surfaces to be plated in any suitable way.
• the sufaces are immersed in a tank containing the solution which can be heated or cooled to provide the desired temperature and to which aeration or stabilizers can be applied if desired.
• the solutions will plate onto a large variety of known catalytic metals or onto noncatalytic surfaces such as dielectrics pre-treated with known sensitizing substances.
• an improved basic aqueous bath containing a source of cupric ions, hydroxyl radicals, formaldehyde and sufficient com-plexing agent to render said ions soluble in alkaline solution wherein the improvement comprises using at least one complexing agent of the following substituted triamine wherein at least three of said R R R R and R radicals are (CH OH and no more than two are -(CH OH, CH COOH, C H COOH or lower alkyl or lower dialkyl ethers having from 1 to 4 carbons, at least 0.15 mols of said triamine being present per mol of copper was.
• a bath according to claim 1 wherein said triamine is pentahydroxypropyl diethylene triamine.

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• 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)
• Chemically Coating (AREA)

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Cited By (3)

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Citations (1)

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• 1965
  • 1965-11-09 US US507049A patent/US3383224A/en not_active Expired - Lifetime
• 1966
  • 1966-11-08 GB GB50015/66A patent/GB1097848A/en not_active Expired
  • 1966-11-08 DE DE19661521512 patent/DE1521512B1/de not_active Withdrawn
  • 1966-11-09 FR FR83163A patent/FR1498966A/fr not_active Expired
  • 1966-11-09 CH CH1612366A patent/CH458874A/fr unknown
  • 1966-11-09 BE BE689534D patent/BE689534A/xx unknown
  • 1966-11-09 NL NL666615822A patent/NL148947B/xx not_active IP Right Cessation

Patent Citations (1)

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