Acid bath for the galvanic deposition of copper, and the use of

Details Acid bath for the galvanic deposition of copper, and the use of Acid bath for the galvanic deposition of copper, and the use of

1994-04-06

1995-07-18

Niebling, John

Electrolysis: processes, compositions used therein, and methods

Electrolytic coating

Depositing predominantly single metal coating

205297, 205298, 106126, C25D 338

Patent

active

054338409

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
The invention is directed to an acid bath for the galvanic deposition of bright, ductile and smooth copper coats and to the use of this combination. The bath according to the invention can be used for strengthening the conductors of printed circuits as well as for decorative applications.
2. Description of the Prior Art
The addition of organic substances to galvanic copper baths to achieve bright depositions has been known for a long time. However, the numerous compounds which are already known for this purpose, e.g. thiourea, gelatins, molasses, coffee extract, "basic" dyestuffs and thiophosphoric acid esters, no longer have any practical significance, since the quality of the copper coats obtained by their use--in particular with respect to homogeneous appearance, hardness and breaking elongation--do not meet current requirements.
Baths containing a mixture of high-molecular compounds containing oxygen with organic, especially aromatic, thio compounds are known from the prior art (DE-AS 1521062). However, these baths yield unsatisfactory results with respect to control of metal and/or levelling or smoothing.
By way of improvement, DE-AS 2039831 describes an acid copper bath containing at least one dye from the polymeric phenazonium compound series in addition to a polymeric oxygen-containing compound and a thio compound with a water-soluble group. Other efforts describe the combination of organic thio compounds and polymeric oxygen-containing compounds with other dyes such as Crystal Violet (EP-PS 71512) or phthalocyanine derivatives with aposafranene (DE-PS 3420999) or a combination with amides (DE-PS 2746938).
A disadvantage in the use of conventional oxygen-containing high-molecular compounds is the stability in the electrolyte. In normal use, these compounds slowly decompose during the electrolysis into water-insoluble polymers which continue to build up in the electrolyte, form a jelly-like border around the walls, and are finally deposited on the goods themselves so that these goods are marred by defects which render them unusable. This decomposition is extremely intensified when the bath temperature rises above 28.degree. C.


SUMMARY AND DESCRIPTION OF THE INVENTION

The present invention has the object of preventing these disadvantages.
This object is met according to the invention by an acid bath containing at least one polyalkylene glycol ether of the general formula ##STR1## where n=8-800, preferably 14-90, and m=0-50, preferably 0-20, R.sup.1 is a low alkyl C.sub.1 to C.sub.4, R.sup.2 is an aliphatic chain or an aromatic group, and a is either 1 or 2.
The amount of polyalkylene glycol ether which can be added to achieve a significant improvement of the copper deposition is approximately 0,005 to 30 g/liter, preferably 0.02 to 8.0 g/liter. The relative molecular mass can be between 500 and 35000 g/mole, preferably between 800 and 4000 g/mole.
The polyalkylene glycol ethers are known per se or can be produced according to processes which are known per se by converting polyalkylene glycols with an alkylating agent such as dimethyl sulfate or tert.butene.
Examples of the polyalkylene glycol ethers used according to the invention and the preferred concentrations in which they are used are listed in Table 1:


TABLE 1 ______________________________________ preferred concentration polyalkylene glycol ether g/liter ______________________________________ dimethyl polyethylene glycol ether 0.1-5.0 dimethyl polypropylene glycol ether 0.05-1.0 di-tert.-butyl polyethylene glycol ether 0.1-2.0 stearyl monomethyl polyethylene glycol ether 0.5-8.0 nonylphenol monomethyl polyethylene 0.5-6.0 glycol ether polyethylene polypropylene dimethyl ether 0.02-5.0 (mixed or block polymer) octyl monomethyl polyalkylene ether 0.05-0.5 (mixed or block polymer) dimethyl-bis(polyalkyleneglycol)octylene ether 0.02-0.5 (mixed or block polymer) .beta.-naphthol monomethyl polyethylene glycol 0.03-4.0 ether _________

REFERENCES:
patent: 3743584 (1973-07-01), Todt et al.
patent: 4820388 (1989-04-01), Kurze et al.
patent: 5328589 (1994-07-01), Martin

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