CA1050924A

CA1050924A - Electrodeposition of copper

Info

Publication number: CA1050924A
Application number: CA235,687A
Authority: CA
Inventors: Hans-Gerhard Creutz; Roy W. Herr
Original assignee: Oxy Metal Industries Corp
Current assignee: Oxy Metal Industries Corp
Priority date: 1975-03-11
Filing date: 1975-09-12
Publication date: 1979-03-20
Also published as: BR7506841A; FR2303871A1; BE833384A; ES440918A1; GB1526076A; SE444822B; JPS5821035B2; DE2541897C2; JPS51104442A; DE2541897A1; SE7510192L; NL7510771A; AU496780B2; US4110176A; IT1046971B; FR2303871B1; AU8478375A

Abstract

ABSTRACT OF THE DISCLOSURE
A composition and method for electrodepositing ductile, bright, well leveled copper deposits from an aqueous acidic copper plating bath having dissolved therein from about 0.04 to about 1000 milligrams per liter of a poly (alkanol quaternary ammonium salt) formed as the reaction product of a polyalkanol-amine with an alkylating or quaternization agent. The polyalkan-olamine constituent typically is formed as the reaction product of a polyalkylenimine (e.g. polyethylenimine) with an alkylene oxide.

Description

~s~z~
This invention relates to the electrodeposition of copper from aqueous acidic plating baths, especially from cop-per sulfate 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 cop-per deposits over a wider range of bath concentration and operat-ing 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 polyethy:lenimine with :: an alkylating agent, such as benzyl chloride. While these re-action products were eficacious in improving the copper deposit, these materials are often relatively insoluble in the aqueous acidic plating baths.
, It has been found that improved copper deposits can be obtained from aqueous acidic copper plating baths by the additlon thereto of poly (alkanol quaterna~y a~nonium salts).
Such salts are more soluble in and more compatible with the aqueous acidic baths than were the previously utilized alk~
ated polyethylenimines of the prior.art.
The composition and method of this invention broadly : comprises acidic copper plating baths of either the acidic copper sulfate or acidic copper fluoroborate type. As is known in the art, such acidic copper sulfate baths typically contain rom about 180 to 250 grams per liter of copper sulfate and 30 to 80 grams per liter of sulfuric acid, while the acidic copper fluoroborate baths typically contain from about 200 to 600 grams per liter of copper fluoroborate and about 0 to 60 ~rams per liter of fluoroboric acid. Additionally, it is found that with the additives of the present invention, these acid copper plat-9~
ing baths may be operated under conditions of high acid and lowmetal content. Thus, even with plating baths ~hich contain as little as about 7.5 grams per liter of copper and as much as 350 grams per liter of sulfuric acid or 350 grams per liter of fluoroboric acid, excellent plating results are still obtained.
Desirably, these plating baths are operated at current densities within the range of about 10 to 100 amps per square foot, although, in many instances, current densities as low as about 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/ft are used. Additionally, in high agitation baths, such as those used in plating rotogravure cylin-ders, current densitites up to as high as about ~00 amps~ft2 may be used. The baths may be operated with air agitation, cathode-rod agitation, or solution agitation and cathode-rod agitation, de-pending upon the particular bath and plating conditions which are used. Typical bath temperatures are within the range of about 25 to 35C., although both lower and higher temperatures, e.g., 50C. 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 60C - 70C. may be used.
Although it has been found to be desirable that chlorine and/or bromide anions in the bath are below about 0.1 gram per liter, appreciably greater amounts of many inorganic cations, ; such as ferrous iron, nickel, cobalt, zinc, cadmium, and the like, may be present in the bath, as for example, amounts at least as high as about 25 grams per liter, without detrimental effec-t.
It has further been found that no-t 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 parti-cularly well adapted for throughhole plating, and thus, findappreciable utilization in the manufacture of printed circuit board.
The poly (alkanol quaternary ammonium salt) of the pre-sent invention may be prepared in a reaction sequence. One step involves the reaction of a mixture of a polyalkylenimine with an alkylene oxide to form a polyalkanolamine. Another step involves the reaction of the polyalkanolamine with an alkylating or quaternization agent to yield a poly (alkanol quaternary am-10 monium salt). This reaction sequence may be represented as follows: O
-~ Rl - NH - R2 ~ I ~n + m CH2- - OEI - R6 R~ R2 - I ~n R3 R4 :

+ p (alkylating agent) IR5 IR$
> ~-Rl - ~ - R2 ~ ~n P~

wherein: .
Rl = alkylene group of 1-6 carbon atoms;
R2 = alkylene group of 1-6 carbon atoms, OH

R3= -CH2 - CH R6 fH
R4 = -CH2 ~ C~ - R6 or H ;
R5 = alkyl group of 1~4 carbon atoms;
aralkyl:
alkenyl group of 1-4 carbon atoms, alkynyl group of 1-4 carbon atoms;

;

... . . . .

~!S~2~
alkylene sulfonate group of~l-4 carbon atoms (e.g. - CH~CH2CH2SO3 ), and OEI
-CH2 - ~H -- CH2 N~\ ( R7 ) 3 OH
, (e.g. - CH2- 1H - CH2 ~ (CH3)3 R6 = H ~ C~3, C 2 R7 = alkyl group of 1-4 carbon atoms , m = 1 to 2 ; :
~ = Cl , Br~, ~H3SO4~ , ::
". p = 1 to 2 , Tne values of m and p selected must be such that the ', final product contains some alkanol quaternary a~nonium groups.

'i If the value of p is less than 2, it is understood that the num~
, ber of R5 groups (and quaternary ammonium groups) in the above ' formula has a corresponding value. When the alkylating agent ' is an aLkanesultone, it is understood that ~ of the formula is ,:
the sulfona-te group (SO3~) attached to the alky.Lene group. ' : Specific polyalkylenimines which can be utilized may :' be expressed as the polymerization product of:

R8 ~ C \ ~CH - Rg ~' wherein R8 and Rg may be hydrogen, alkyl of from one to three carbon atoms, and Rlo may be hydrogen, alkyl, aralkyl, or hydroxy ', alkyl of from one to three carbon atoms. The preferred poly-., alkylenimine is unsubstituted polyethylenimine, ranging in mole-l,'cular weight from about 300 to about 1,000,000.

`~ Specific alkylene oxides which can be u-tilized are ., 30 ethylene oxide, propylene o~ide and glyc.idol which are reacted .; .
~ with polyethyle,nimines to yield products ranging in molecular _ ~ -~15~
weight from about 300 to about 1,000,000. The polyalkylenimine alkylene oxide reaction products or polyalkanolamines when re-acted 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 thar~ those from propylene oxide.
Various organic compounds can be reacted with the poly-alkanolamines to alkylate the nitrogen thereof and to form the reaction products added to the baths of the present invention~ :
10Specific compounds which have been found to give par-ticularly good results are benzyl chloride, allyl bromide, dimethyl sulfate, propanesultone, and (3-chloro-2 hydroxypropyl) trimethyl ammonium chloride or [Cl-CH2-CHOH-CH2-N(CH3)3] 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 alkyl-ating agent, and heat the reaction mixture to a temperature from about 50C. to about approximately 100C. The ratio of the poly-alkanolamine to alkylating agent may be varied, so that not all of the amino groups of the polyalkanolamine are al]cylated. To illustrate the invention further, and assuming N-(2-hydroxyethyl) polyethylenimine and benzyl chloride as the reaction ingredients, the following is believed to take place:

CH2 - CH2 - lj~ ~ ~C6H5 - CH2 Cl >
. ~H2 - CH20H
_ _ CH2 - C6H5 +
. -CH2 - CH2 - ~ ~ - n C13 In addition to the above described brighten.ing agent~ :

30 the aqueous acid copper plating baths of the present invention also de,sirably contain at least one bath soluble polyether com-pound. Various polyether compounds which are soluble in the plat-

2~
ing bath may be used. For example, particularly in high sulfuric ; acid and low copper metal baths, non-ionic polyether wetting agents, such as 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 cha:Lns having more than six carbon atoms in a straight or branched chain. Of the vari-ous polyether compounds which may be used, excellent results have been obtained with the polypropylene propanols and glycols of average molecular weight of from about 360 to 1,000, i.e., poly-ethers which contain a group ~C3H60)y where y is an integer of from about 6 to 20. Excellent results have also been obtained with polyethers containing the group (C2H~0)x where x is an in-teger of at least 6. Exemplary of the various preferred poly-ether compounds which may be used are those set forth in Table II appearing in Columns 5 and 6 of UOS. Patent No. 3,328,273.
Desirably, the plating baths of the present invention contain these polyether compounds in amounts within the range of about 0.01 to 5 grams per liter, with the lower concentrationsgenerally being used with the higher molecular weight polyethers.
~ n 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 sulfur compound. Typical of the suitable organic di-` valent sulfur compounds which may be used are sulfonated organic sulfides, i.e., organic sulfide compounds carrying at least one sulfonic group. These organic sulfide sulfonic compounds may also contain various substituting groups, such as methyl, chloro, bromo, methoxy, ethoxy, carboxy and hydroxy, on the molecules, especially on the aromatic and heterocyclic sulfide sulfonicacids. The organic sul~ide sulfonic acids may be used as the free acids, the alkali metal salts, organic amine salts, or the li]ce.
I

:

~L~S~g2~
Exemplary oE specific sulfonate organic sulfides which may be used are those set forth in Table I in Columns 5 and 6 and Col-umns 7 and 8 of U.S. Patent ~o. 3,267,010. Other suitable or-ganic divalent sulfur compounds which may be used are mercaptans, thiocarbamates,thiolcarbamates, thioxanthates, and thiocarbonates which contain at least one sulfonic group. Additionally, organic polysulfide compounds may also be used. Such organic polysulfide compounds may have the formula XRl -(S)nR2SO3H, wherein Rl and R2 are the same or different alkylene group containing from about l to 6 carbon atoms, X is hydrogen or SO3H and n is a number from about 2 to 5. These organic divalent sulfur compounds are aliphati.c polysulfides wherein at least two divalent sulfur atoms are vicin-al and wherein the molecule has one or two terminal sul:~onic acid cJroups. The alkylene portion of the molecule may be substituted with groups such as methyl, ethyl, chloro, bromo, ethoxy, hydroxy, and khe like. These compounds may be added as the free acids or as the alkali metal or amine salts. Exemplary of specific organic polysulfide 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 sulfide compounds are present in the plating baths ,~ of the present invention in amounts within the range of about 0.005 to 1.0 grams per liter.
The following specific examples of reaction products and their manner of preparation and of specific plating baths and their operation are presented as exemplary of the present i.nvention, and not by way of limitation.

PE~EP~ TI~U OF uEACTION PRODUCTS

(a~ A mixture of:

109 parts oE ethoxylated polyethylen-.imine (mol. wt. about 1,200 prepared with a l:l mole ratio of ethylene oxide to polyethylenimine polymer repeat unit) .. . , . . . ; , . . , ~ .. . .

~5~
was dissolved in 500 parts of water, to this solution was added 64 parts of benzyl chloride at 80 - 90C.
This reaction mixture was heated at 90C. for 5 hours and heat-ing was continued at 70C. for 19 hours. The reaction product was cooled and diluted to one liter.
(b) The identical mixture and procedure of (a) above was repeated, but with ethoxylated polyethylen-imine of about 3600 molecular weight.
10 (c) The identical mixture and procedure of ~a) above was repeated, but with ethoxylated polyethylen-imine of about 120,000 molecular weight.
(d) A mixture of:
146 parts of propoxylated polyethylen-imine (mol. wt. about 1,000 prepared wi-th a 1:2 mole ratio of propylene oxide to polyethylenimine polymer repeat unit) was dissolved in 500 parts of water, to this solution was added 64 parts of benzyl chloride at 80 - 90C.
. This reaction mixture was heated at 90C. for 5 hours and heat-ing was continued at 70C. for 19 hours. The reaction product was cooled and diluted to one liter.
(e) A mixture of:
109 parts of propoxylated polyethylen-imine (mol. wt 4 about 3,000 prepared with a 1:1 mole ratio of propylene oxide to polyethylenimine polymer repeat unit) was dissolved and reacted with benzyl chloride as defined in (d) a~ove to obtain a reaction product.
' :"
- ELECTROPLATING EXAMPLES
. . _. ._, . . . _ . _ _ EXAMPLE I
A "J" shaped polished steeL panel was cleaned and plated with a thin cyanide copper coating. The coated panel was rinsed and then plated in an acid plating bath having the composition:

~5~9~ :
220 g/l C 04 5H20 60 g/l H2S0 10 mg/l HCl 15 mg/l HS03 - (cH2)3 -S-S (CH2)3 3 10 mg/l Polyethylene glycol M.W. 9,000 The panel was plated for 20 minutes at 40 amps per square foot using air agitation and a temperature of about 25C.
The resultant plated panel was uneven and generally dull.

EXAMPLE II

A second "J" shaped polished steel panel was cleaned, coated and then plated in a bath having the composition of Exam- :.
ple I, except for the addition thereto of:

0.5 my/l of the reaction product of example (c) above.
The resultant panel was mirror bright, even and had improved leveling characteristics.

EXAMPLE III
A "J" shaped polished steel panel was cleaned and coated as .in Example I, and then was electroplated in an acidic copper bath having the composition:

3~L~ 0unces/Gal.
Copper metal [from Cu ~BF4)2] 2 HBF4 ( 100%) 29 Parts/Million CH3~c6H4-s-s-c6H3-cH3 S03~ 20 i :

Polyethylene glycol (mol. wt.
.. about 6,000~ 10 Reaction product of Example (d~
: above ~ :

The plated panel was brlght and even with good leveling _ g _ :
:.

EXAMPLE IV

A "J" shaped polished steel panel was cleaned and coated as in Example I, and then was electroplated in a bath having the composition:

Inqredient Ounces/Gal.

H2SO4 (100o/o) 20 Parts/Million Dithio Carbamate-S-Propane sulfonic acid 15 ! Ethoxylated Lauryl A:Lcohol with 15 moles Ethylene oxide 50 Reaction product of example (a) above 0.4 ~, The plated panel had a full bright, well leveled copper plate evenly deposited thereon.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:-

1. A bath for electrodepositing copper comprising an aqueous acidic copper plating bath having dissolved therein a reaction product of an alkoxylated polyalkylenimine with an alkylating agent as defined below:
+ p (alkylating agent) p x?
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 1-4 carbon atoms;
alkynyl group of 1-4 carbon atoms;
alkylene sulfonate group of 1-4 carbon atoms (e.g. - CH2CH2CH2SO3?); and R6 = H, -CH3, -CH2OH ;
R7 = alkyl group of 1-4 carbon atoms ;
m = 1 to 2 ;
X? = Cl-, Br?, CH3SO4? ;
p = 1 to 2.

2. A bath as defined in Claim 1, in which the reaction product of an alkoxylated polyalkylenimine with an alkylating agent selected from the group consisting of benzyl chloride, allyl bromide, propanesultone, dimethyl sulfate and (3-chloro-2 hydroxypropyl) trimethyl ammonium chloride.

3. A bath as defined in Claim 1, wherein the alkylene oxide used to synthesize the alkoxylated polyalkylenimine is selected from the group consisting of ethylene oxide, propyl-ene oxide and glycidol.

4. A bath as defined in Claim 1, wherein R1 and R2 are defined as ethylene.

5. The bath as claimed in Claim 2, wherein there is also present a bath soluble polyether compound and an organic divalent sulfur compound selected from aliphatic polysulfides and or-ganic sulfides carrying at least one sulfonic group.

6. The bath as claimed in claim 2, wherein the polyether compound is present in an amount within the range of about 0.01 to 5 grams per liter and the organic divalent sulfur compound is present in an amount within the range of about 0.00005 to 0.1 grams per liter.