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

• the invention is directed to an electroless co 1 pper so uuon [58] Field of Search ..l06/l, 1 17/47 A, IRE/ 1 6 2)? .characterized by inclusion of a polyether adduct of an alkine alcohol and an alkylene oxide for improved solution stability and deposit appearance.
• Electroless copper deposition refers to the chemical plating of copper over active surfaces 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. No. 3,011,920 and 3,457,089.
• Known electroless copper deposition solutions comprise 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, sufficient to provide the required alkaline solution in which said compositions are effective, and (4) a complexing agent for the copper sufficient to prevent its precipitation in alkaline solution.
• a source of cupric ions usually copper sulphate
• formaldehyde as reducing agent therefor
• alkali generally an alkali metal hydroxide and usually sodium hydroxide
• compositions containing both an oxidizing and a reducing agent present in the same solution have limited stability and tend to trigger (spontaneously decompose) with reduction of substantially all of the copper in the solution not only on the part to be plated, but on the walls of containers, stirring elements and the like. Consequently, it is customary to include stabilizers in the composition which provide resistance against triggering and which increase the range of useable concentration and temperature without destroying the capacity of the solutions to deposit copper by reduction at catalytic surfaces in contact therewith.
• the stabilizer used for the electroless copper depositing solution is a polyether adduct of an alkine alcohol and an alkylene oxide.
• the alkine alcohols contemplated for formation of the adduct are those of the above mentioned U.S. Pat. No: 3,457,089 as well as higher molecular weight homologues thereof and aryl substituted alkine alcohols. It has been found that the adducts have greater solubility in solution than alkine alcohols from which they are formed and therefore, higher molecular weight alcohols can be used. This is believed to be responsible for increased stabilization. Improved deposit appearance is believed to be due to the surfactant affect of the non-ionic hydrophobes of the polyether resulting from the epoxidation of the alkylene oxide.
• the components of the polymeric adduct in accordance with the invention comprise an alkine alcohol and an alkylene oxide.
• the alkine alcohols useful in forming the adduct correspond to one of the following formulas:
• R,R' and R" individually are divalent alkylene, cycloalkylene, alkylene ether, and arylene radicals, said radicals having from one to 12 carbon atoms.
• alkine alcohols corresponding to the above formulas include the following:
• Lower molecular weight alkylene oxides having from two to five carbon atoms are contemplated for formation of the adducts.
• examples of such oxides include ethylene oxide, propylene oxide, isobutylene oxide and 1,2-epoxy butane.
• the adducts are formed by an epoxidation reaction with cleavage of the epoxide group of the alkylene oxide by the -OH group of the alcohol to form the polyether.
• the adducts can be represented by the following formulas:
• A is an alkylene radical having from two to five carbon atoms
• n is a whole in teger ranging from 1 to 100 and preferably from 5 to 50.
• the adducts are formed using conventional epoxidation reactions for alcohols and alkylene oxides. Generally, elevated temperatures, e.g., 50 to 150 C, and elevated pressures, e.g., in excessof l and preferably above 2 atmospheres, are used. Typically, an epoxidation catalyst such as BC] or a tertiary amine is also used.
• the ratio of the alkylene oxide to the alcohol is dependent upon the number of OH groups on the alcohol and the desired chain length of the polyether in accordance with art recognized procedure. Details for formation of polyether adducts of alcohols and alkylene oxides can be found in .lelinek, GE.
• the above polyether adducts are used in quantities which are efi'ective to improve stability and deposit appearance or otherwise improve the performance of the solution, but in quantities that are not so great as to prevent deposition.
• useful quantities are between 2.0 and 2000 parts per million parts of solution by weight though the preferred range is from about to 200 parts per million parts.
• the maximum quantity of any given adduct that can be put into solution is dependent upon the degree of ethoxylationi.e., the chain length of the polyether. Generally, the higher the degree of ethoxylation, the larger the quantity of adduct that can be dissolved in solution.
• Example 1 was repeated without the addition of the adduct.
• a phenolic substrate was prepared for plating using the conventional pre-treatment steps of cleaning, conditioning and catalyzing with Cuposit 6F, a one step palladium-stannic acid catalyst.
• the part was plated by immersionin the formulation of Example 1. The part so plated had a bright surface appearance.
• a phenolic part was plated with the formulation of Example 1 where ethyloctynol was substituted for the adduct and a shiny deposit was obtained, though the deposit was not as bright as that obtained from the solution containing the adduct.
• Example 2 The procedure of Example 1 was repeated substituting for the adduct of Example I, the following compound in an amount of 100 parts per million parts of solution:
• the bath did not trigger within 30 hours.
• Example 1 EXAMPLES Using the formulation and procedure of Example 1, the adduct of Example 1 was substituted with the following com- With the palladium drop test, the bath did not trigger within 36 hours.
• concentrations of the above ingredients are not critical and are generally in the ranges previously known to be useful in electroless coppering solutions.
• Sufiicient copper must be employed to provide a useful deposit and sufficient alkali to provide the high pH required, generally from 10 to 14.
• sufficient 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 the alkali solution during storage. and use.
• polyether adducts of this invention are considered to be new compounds, an example is set forth below illustrating a process for their synthesis.
• EXAMPLE 5 Charge 2 moles of ethyl octynol and a tertiary amine catalyst into a stainless steel pressure vessel equipped with agitator, temperature gauge, inlet tubes for ethylene oxide and nitrogen, and connection for a vacuum system. Flush with nitrogen until all oxygen has been removed from the system. Pull 28 inch vacuum and then start addition of moles of ethylene oxide while maintaining the temperature in the system within the range of 50l20 C. The vessel is maintained at a pressure of 20 to 40 psi. The ethylene oxide is added over a period of 10 hours. Thereafter, the system is cooled to 40 C, flushed with nitrogen and the product is discharged from the vessel. The yield is about 98 percent.
• an aqueous, alkaline electroless copper plating solution comprising a source of cupric ions, formaldehyde as a reducing agent, a complexing agent to maintain said cupric ions in solution and hydroxide to provide required solution pH
• the improvement comprising an polyether stabilizer selected from the group of where each ofR, R and R" are individually selected from the group of divalent alkylene, cycloalkylene, alkylene ether and arylene radicals, said radicals having from one to 12 carbon atoms, A is an alkylene radical having from two to five carbon atoms and n is a whole integer ranging between 1 and 100.
• polyether is the reaction product of an alkine alcohol and an alkylene oxide.
• alkylene oxide is selected from the group of ethylene oxide, propylene oxide, isobutylene oxide and 1,2-epoxy butane.
• an aqueous, alkaline electroless copper plating solution comprising a source of cupric ions, formaldehyde as a reducing agent, a complexing agent to maintain said cupric ions in solution and hydroxide to provide required solution pH, the improvement comprising a stabilizing quantity of a polyether of the formula JICECRI OAI L .11-
• R is selected from the group of divalent alkylene, cycloalkylene, alkylene ether and arylene radicals, said radicals having from one-l2 carbon atoms.
• A is an alkylene radical having from two-five carbon atoms and n is a whole integer ranging between 1 and 100.
• a method for stabilizing an electroless copper plating solution comprising a source of cupric ions, formaldehyde as a reducing agent, a complexing agent to maintain said cupric ions in solution and hydroxide to provide required solution pH, said method comprising addition to said solution of a stabilizing quantity of a polyether adduct corresponding to the where each R,R' and R are individually selected from the group of divalent alkylene, cycloalkylene, alkylene ether and arylene radicals, said radicals having from one to 12 carbon atoms, A is an alkylene radical having from two to five carbon atoms and n is a whole integer ranging between 1 and 100.
• alkylene oxide is selected from the group of ethylene oxide, propylene oxide, isobutylene oxide and 1,2-epoxy butane.

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• Organic Chemistry (AREA)
• Chemically Coating (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

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Citations (2)

• 1971
  • 1971-05-20 US US145508A patent/US3661597A/en not_active Expired - Lifetime
• 1972
  • 1972-01-21 IT IT19688/72A patent/IT946822B/it active
  • 1972-02-09 CA CA134,344A patent/CA979603A/en not_active Expired
  • 1972-02-29 GB GB930472A patent/GB1352087A/en not_active Expired
  • 1972-05-04 JP JP47043801A patent/JPS5236089B1/ja active Pending

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