GB1597519A

GB1597519A - Electrodeposition of copper

Info

Publication number: GB1597519A
Application number: GB1677478A
Authority: GB
Original assignee: Oxy Metal Industries Corp
Current assignee: Oxy Metal Industries Corp
Priority date: 1977-05-04
Filing date: 1978-04-27
Publication date: 1981-09-09
Also published as: DE2818725A1; AR224861A1; FR2389689A1; CA1105045A; FR2389689B1; NL7804874A; JPS5448646A

Description

(54) ELECTRODEPOSITION OF COPPER (71) We, OXY METAL INDUSTRIES CORPORATION, a Corporation organised under the laws of the State of California, United States of America, of 21441 Hoover Road, Warren, Michigan 48089, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to the electrodeposition of copper from aqueous acidic plating baths, especially from copper sulphate and fluoroborate baths, and more particularly it relates to the use of certain organic compounds in the baths to give bright, highly ductile, low stress, good leveling copper deposits over a wider range of bath concentration and operating current densities.

In U.S. Patent No. 3,770,598, assigned to the assignee of the present invention, there has been proposed the addition of certain reaction products to acidic copper plating baths to yield generally the above recited benefits. These prior art additives are formed by the reaction of polyethylenimine with an alkylating agent, such as benzyl chloride. While these reaction products are efficacious in improving the copper deposit, often they may be found to be relatively insoluble in the aqueous acidic plating baths.

We have found that improved copper deposits can be obtained from aqueous acidic copper plating baths by the addition thereto of poly (alkanol quaternary ammonium salts). Such salts are more soluble in and more compatible with the aqueous acidic baths as compared with the previously utilized alkylated polyethylenimines of the prior art.

The composition and method of this invention broadly comprises acidic copper -plating baths of either the acidic copper sulphate or acidic copper fluoroborate type. As is known in the art, such acidic copper sulphate baths typically contain from 180 to 250 grams per liter of copper sulphate and 30 to 80 grams per liter of sulphuric acid; while the acidic copper fluoroborate baths typically contain from 200 to 600 grams per liter of copper fluoroborate and 0 to 60 grams per liter of fluoroboric acid. Additionally, it is found that with the additives of the present invention, these acid copper plating baths may be operated under conditions of high acid and low metal content.Thus, even with plating baths which contain as little as 7.5 grams per litre copper and as much as 350 grams per litre sulphuric acid or 350 grams per litre of fluoroboric acid, excellent plating results are still obtained.

Desirably, these plating baths are operated at current densities within the range of 10 to 100 amps per square foot, although, in many instances, current densities as low as 0.5 amps per square foot may also be used. Typically, with low copper and high acid baths, current densities within the range of. about 10 to 50 amps/ft2 are used. Additionally, in high agitation baths, such as those used in plating rotogravure cylinders, current densities up to as high as 400 amps/ft2 may be used. The baths may be operated with air agitation, cathode-rod agitation, or solution agitation and cathode-rod agitation, depending upon the particular bath and plating conditions which are used.Typical bath temperatures are within the range of 25 to 350C., although both lower and higher temperatures, e.g., 500 C. or more, may also be used. In this regard, it is to be noted that the plating baths of the present invention may also be used in copper electrorefining processes. In such processes, temperatures up to about 60"--70"C may be used.

Although it has been found to be desirable that the content of chloride and/or bromide anions in the bath is below 0.1 gram per liter, appreciably greater amounts of many inorganic cations, e.g. ferrous iron, nickel, cobalt, zinc, and cadmium, may be present in the bath, for example, in amounts at least as high as 25 grams per litre, without detrimental effect. It has further been found that not only do the acid copper plating baths of the present invention give excellent results when used under conditions of high acid and low copper metal content, but, additionally the baths have been found to be particularly well adapted for throughhole plating, and thus, find appreciable utilization in the manufacture of printed circuit board.

The poly (alkanol quaternary ammonium salt) of the present invention are used in an amount of 0.04 to 1000 mgfl of the plating bath. They may be prepared bv the following reaction sequence. The first step involves the reaction of a mixture of a polyalkylenamine with an alkylene oxide to form a polyalkanolamine. The second step involves the reaction of the polyalkanolamine with an alkylating or quaternization agent to yield a poly (alkanol quaternary ammonium salt).This reaction sequence may be represented as follows:

+ p (alkylating agent)

wherein: R1=alkylene group of 1--6 carbon atoms; R2=alkylene group of 1--6 carbon atoms;

R5=alkyl group of 1--4 carbon atoms; aralkyl; alkenyl group of 2--4 carbon atoms; alkynyl group of 2--4 carbon atoms alkylene sulphonate group of 1--4 carbon atoms (e.g.

CH2CH2CH2SO3e); and

R8=H, -CH3,-CH2OH; R7=alkyl group of 1--4 carbon atoms; m=l to 2; XO=CIO, Bro, CH3SO4s; p=l to 2; n=from above 17,000 to 23,500.

The values of m and p selected must be such that the final product contains some alkanol quaternary ammonium groups. If the value of p is less than 2, it is to be understood that the number of R5 groups (and quaternary ammonium groups) in the above formula has a corresponding value. When the alkylating agent is an alkanesultone, it is to be understood that Xs of the formula is the sulphonate group (SO39) attached to the alkylene group.

Specific polyalkylamines that can be utilized are polyalkylenimines which may be expressed as the polymerization product of:

wherein R8 and R9 may be hydrogen, or alkyl of from one to three carbon atoms, and R10 may be hydrogen, alkyl, aralkyl, or hydroxy alkyl of from one to three carbon atoms. The preferred polyalkylenimine is unsubstituted polyethylenimine, ranging in molecular weight up to 1,000,000.

Specific alkylene oxides which can be utilized are ethylene oxide, propylene oxide and glycidol which are reacted with polyethylenimines to yield products ranging in molecular weight up to 1,000,000, such that in the structural formula set forth above, "n" has a value of from above 17,000 to 23,500. The polyalkylenimine alkylene oxide reaction products or polyalkanolamines when reacted with an alkylating agent give products which are soluble in the acidic copper plating bath, the reaction products from ethylene oxide and glycidol being more soluble than those from propylene oxide.

Various organic compounds can be reacted with the polyalkanolamines to alkylate the nitrogen thereof and to form the reaction products added to the baths of the present invention.

Specific compounds which have been found to give particularly good results are benzyl chloride, allyl bromide, dimethyl sulphate, propanesultone, and (3chloro-2 hydroxypropyl) trimethyl ammonium chloride i.e. [Cl-CH2-CllOH- CH2-N(CH3)3i+Cl-.

The formation of the reaction product is relatively simple. It is only necessary to dissolve the requisite amount of polyalkanolamine in hot water, add the desired amount of alkylating agent, and heat the reaction mixture to a temperature from 500 C. to approximately 1000C. The ratio of the polyalkanolamine to alkylating agent may be varied, so that not all of the amino groups of the polyalkanolamine are alkylated. To illustrate the invention further, and taking N - (2 - hydroxy ethyl)polyethylenimine and benzyl chloride as the reaction ingredients, the following reaction is believed to take place:

In addition to the above described brightening agent, the aqueous acid copper plating baths of the present invention also desirably contain at least one bath soluble polyether compound.Various polyether compounds which are soluble in the plating bath may be used. For example, particularly in high sulphuric acid and low copper metal baths, non-ionic polyether wetting agents, eg. polyglycols having carbon chains greater than 6 in length, may be useful. In general, however, the most preferred polyethers are those containing at least six ether oxygen atoms and being free from alkyl chains having more than six carbon atoms in a straight or branched chain. Of the various polyether compounds which may be used, excellent results have been obtained with the polypropylene propanols and glycols of average molecular weight of from 360 to 1,000, i.e., polyethers which contain a group (C3H6O)y where y is an integer of from 6 to 20. Excellent results have also been obtained with polyethers containing the group (C2H4O)x where x is an integer of at least 6.Exemplary of the various preferred polyether compounds which may be used are those set forth in Table II appearing in Columns 5 and 6 of U.S. Patent No. 3,328,273. Desirably, the plating baths of the present invention contain these polyether compounds in arnounts within the range of 0.01 to 5 grams per litre, with the lower concentrations generally being used with the higher molecular weight polyethers.

In addition to the polyethylenimine reaction product and the polyether compound, the aqueous acidic copper plating baths of the present invention also desirably contain an organic divalent sulphur compound. Typical of the suitable organic divalent sulphur compounds which may be used are sulphonated organic sulphides, i.e., organic sulphide compounds carrying at least one sulphonic group.

These organic sulphide sulphonic compounds may also contain various substituting groups, e.g. methyl, chloro, bromo, methoxy, ethoxy, carboxy and hydroxy, on the molecules, especially on the aromatic and heterocyclic sulphide sulphonic acids.

The organic sulphide sulphonic acids may be used as the free acids, or as salts eg.

the alkali metal salts, or organic amine salts. Exemplary of specific sulphonate organic sulphides which may be used are those set forth in Table I in Columns 5 and 6 and Columns 7 and 8 of U.S. Patent No. 3,267,010. Other suitable organic divalent sulphur compounds which may be used are mercaptans, thiocarbamates, thiolcarbamates, thioxanthates, and thiocarbonates which contain at least one sulphonic group. Additionally, organic polysulphide compounds may also be used.

Such organic polysulphide compounds may have the formula XR1HS)nR2SO3H, wherein R' and R2 are the same or different alkylene group containing from I to 6 carbon atoms, X is hydrogen or SO3H and n is a number from 2 to 5. These organic divalent sulphur compounds are aliphatic polysulphides wherein at least two divalent sulphur atoms are vicinal and wherein the molecule has one or two terminal sulphonic acid groups. The alkylene portion of the molecule may be substituted eg with methyl, ethyl, chloro, bromo, ethoxy, or hydroxy groups. These compounds may be added as the free acids or as salts eg the alkali metal or amine salts. Exemplary of specific organic polysulphide compounds which may be used are set forth in Table I of Column 2 of U.S. Patent No. 3,328,273. Desirably, these organic sulphide compounds are present in the plating baths of the present invention in amounts within the range of 0.0005 to 1.0 grams per litre.

WHAT WE CLAIM IS: 1. A bath for electrodepositing copper comprising an aqueous acidic copper plating bath having dissolved therein 0.04 to 1000 mg/l of a reaction product of an alkoxylated polyalkylenamine with an alkylating agent, the reaction product having a formula as defined below:

wherein: R1 is an alkylene group of 1-6 carbon atoms; R2 is an alkylene group of ld carbon atoms;

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. In addition to the above described brightening agent, the aqueous acid copper plating baths of the present invention also desirably contain at least one bath soluble polyether compound. Various polyether compounds which are soluble in the plating bath may be used. For example, particularly in high sulphuric acid and low copper metal baths, non-ionic polyether wetting agents, eg. polyglycols having carbon chains greater than 6 in length, may be useful. In general, however, the most preferred polyethers are those containing at least six ether oxygen atoms and being free from alkyl chains having more than six carbon atoms in a straight or branched chain.Of the various polyether compounds which may be used, excellent results have been obtained with the polypropylene propanols and glycols of average molecular weight of from 360 to 1,000, i.e., polyethers which contain a group (C3H6O)y where y is an integer of from 6 to 20. Excellent results have also been obtained with polyethers containing the group (C2H4O)x where x is an integer of at least 6. Exemplary of the various preferred polyether compounds which may be used are those set forth in Table II appearing in Columns 5 and 6 of U.S. Patent No. 3,328,273. Desirably, the plating baths of the present invention contain these polyether compounds in arnounts within the range of 0.01 to 5 grams per litre, with the lower concentrations generally being used with the higher molecular weight polyethers. In addition to the polyethylenimine reaction product and the polyether compound, the aqueous acidic copper plating baths of the present invention also desirably contain an organic divalent sulphur compound. Typical of the suitable organic divalent sulphur compounds which may be used are sulphonated organic sulphides, i.e., organic sulphide compounds carrying at least one sulphonic group. These organic sulphide sulphonic compounds may also contain various substituting groups, e.g. methyl, chloro, bromo, methoxy, ethoxy, carboxy and hydroxy, on the molecules, especially on the aromatic and heterocyclic sulphide sulphonic acids. The organic sulphide sulphonic acids may be used as the free acids, or as salts eg. the alkali metal salts, or organic amine salts. Exemplary of specific sulphonate organic sulphides which may be used are those set forth in Table I in Columns 5 and 6 and Columns 7 and 8 of U.S. Patent No. 3,267,010. Other suitable organic divalent sulphur compounds which may be used are mercaptans, thiocarbamates, thiolcarbamates, thioxanthates, and thiocarbonates which contain at least one sulphonic group. Additionally, organic polysulphide compounds may also be used. Such organic polysulphide compounds may have the formula XR1HS)nR2SO3H, wherein R' and R2 are the same or different alkylene group containing from I to 6 carbon atoms, X is hydrogen or SO3H and n is a number from 2 to 5. These organic divalent sulphur compounds are aliphatic polysulphides wherein at least two divalent sulphur atoms are vicinal and wherein the molecule has one or two terminal sulphonic acid groups. The alkylene portion of the molecule may be substituted eg with methyl, ethyl, chloro, bromo, ethoxy, or hydroxy groups. These compounds may be added as the free acids or as salts eg the alkali metal or amine salts. Exemplary of specific organic polysulphide compounds which may be used are set forth in Table I of Column 2 of U.S. Patent No. 3,328,273.Desirably, these organic sulphide compounds are present in the plating baths of the present invention in amounts within the range of 0.0005 to 1.0 grams per litre. WHAT WE CLAIM IS:

1. A bath for electrodepositing copper comprising an aqueous acidic copper plating bath having dissolved therein 0.04 to 1000 mg/l of a reaction product of an alkoxylated polyalkylenamine with an alkylating agent, the reaction product having a formula as defined below:

R5 is an alkyl group of 1 carbon atoms; an aralkyl group; an alkenyl group of 2-4 carbon atoms; an alkynyl group of 2-4 carbon atoms; an alkylene sulphonate group of 14 carbon atoms, or is

Rs is H, -CH3, -CH2OH; R7 is alkyl group of 1A carbon atoms; X- is Clue, Byre, or CH3SO4e; p is 1 to 2; n is from above 17,000 to 23,500.

2. A bath as claimed in Claim 1, in which the reaction product is the reaction product of an alkoxylated polyalkylenamine with benzyl chloride, allyl bromide, propanesultone, dimethyl sulphate or (3-chloro-2 hydroxypropyl) trimethyl ammonium chloride.

3. A bath as claimed in Claim 2, in which the alkoxylated polyalkylenamine is made from the reaction of ethylene oxide, propylene oxide or glycidol, with a polyalkylenamine.

4. A bath as claimed in Claim 1, 2 or 3 in which R1 and R2 are ethylene groups.

5. A bath as claimed in any one of Claims 1 to 4 in which there is also present 0.01 to 5.0 gfl of a bath soluble polyether compound and 0.0005 to 1.0 gfl of an organic divalent sulphur compound selected from aliphatic polysulphides and organic sulphides carrying at least one sulphonic group.

6. A bath as claimed in any one of claims 1 to 4 in which the bath contains a polyether compound present in an amount of 0.01 to 5.0 gfl and 0.0005 to 1.0 gfl of an organic divalent sulphate compound.

7. A method for preparing a poly (alkanol quaternary ammonium salt) represented by the following steps:

+ p (alkylating agent

wherein: R1 is an alkylene group of la carbon atoms; R2 is an alkylene group of 16 carbon atoms;

R5 is an alkyl group of 1 4 carbon atoms; an aralkyl group; an alkenyl group of 2-4 carbon atoms; an alkynyl group of 2-4 carbon atoms; an alkylene sulphonate group of 1--4 carbon atoms, or is

R6 is H, -CH3, or -CH2OH; R7 is an alkyl group of 1--4 carbon atoms; m is 1 to 2;; XQ is Clue, Byre, or CH3SO4S; p is 1 to 2; n is from above 17,000 to 23,500.

8. A method as claimed in Claim 7 in which the polyalkylenamine is polyethyleneimine.

9. A poly (alkanol quaternary ammonium salt) whenever made by a method as claimed in Claim 7 or claim 8.

10. A bath as claimed in any one of Claims 1 to 6 in which the poly (alkanol quaternary ammonium salt) is as claimed in Claim 9.

11. A method of electrodepositing copper on a substrate which comprises making the substrate the cathode and immersing it in a bath as claimed in any one of Claims 1 to 6 or 10 and providing a copper anode and passing an electric current through the bath from the cathode to the anode whereby to deposit copper on the cathode.

12. An article bearing copper whenever deposited by a method as claimed in Claim 13 or Claim 14.