JPH0218387B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Field of Application] Broadly speaking, the present invention is applicable to substrates, particularly various plastics which are non-conductive substrates that have undergone various pre-treatments and are easily copper-plated. The present invention relates to an improved composition for producing an electroless copper plated film and a method of using the same. Conventionally known electroless copper plating baths typically contain copper ions, a complexing agent for preventing precipitation of copper ions, a reducing agent for copper ions to metal ions, a PH control agent, a stabilizer, a rate control agent and optional ingredients. However, a preferred component is a wetting agent to improve the coverage and distribution of the copper coating.

[Technical background] Due to the increasing use of decorative plating trim in automobiles, it is necessary to reduce the cost of conventional electroless copper plating solutions, simplify maintenance and management, and improve stability. Further research efforts have been made to produce uniform copper plating with good adhesion at a plating rate that is industrially satisfactory.

[Object of the Invention] The object of the present invention is to improve the electroless copper plating bath in such a manner that the amount of complexing agent required can be significantly reduced as a result of the synergistic action of a certain combination of complexing agents. The object of the present invention is to provide a bath composition and a method of using the same, which can significantly reduce the cost of new preparation and replenishment of the bath, and achieve the above-mentioned benefits and objectives.

[Benefits from the invention] In addition, the present invention enables industrial operation at lower pH than previously possible, thereby reducing the amount of alkaline PH control agent required, while reducing the need for alkaline agents such as caustic and formalin. This makes it possible to reduce the deterioration reaction of the reducing agent and to significantly reduce the consumption amount of the reducing agent. Another advantage of the bath of the present invention is that it can be operated at bath temperatures above room temperature, allowing bath temperatures below about 66°C (150°C), which is a desirable bath for autocatalytic copper deposition. It is possible to ensure activity. The ability to operate at such high temperatures means, in turn, that the bath can be cooled down to room temperature during outages for several weeks, and this cooling reduces the activity of the bath, making it possible to maintain the bath during the outage. This means that it has the effect of improving stability and preventing autocatalytic decomposition. Also, operating at such high temperatures usually causes evaporation of the bath.
An advantage is that a space is created in the plating tank, and this space can be used to add replenishment chemicals as necessary. Because conventional electroless plating baths operate at room temperature, it is often necessary to remove some of the operating bath to create space for the addition of make-up chemicals, resulting in a loss of valuable plating solution. There was a problem with waste liquid treatment. The improved bath composition of the present invention significantly reduces, or in some cases eliminates, the need for the addition of rate control agents, such as cyanide and iodide, commonly used in conventional electroless copper baths. bath control and replenishment is further simplified and the cost of required materials is reduced.

DESCRIPTION OF THE INVENTION The benefits and advantages of the present invention include the use of a sufficient amount of copper to autocatalytically deposit copper, typically about
copper ions in a concentration range of 0.5 to about 30 g/concentration and a reducing agent in an amount sufficient to reduce the copper ions to a metallic state;
That is, preferably formaldehyde in an amount of from about 0.1 to about 40 g/m and an amount sufficient to complex the copper ions in the bath such that the molar ratio of complexing agent to copper ions is from about 1:1 to about 5:1. This is achieved by using an electroless copper plating bath consisting of an alkaline aqueous solution containing a certain amount of complexing agent. The complexing agent is ethylenediaminetetraacetic acid (EDTA) and N,N,
One type of amine compound selected from the group consisting of N',N'-tetrakis-(2-hydroxypropyl)ethylenediamine (THPEDA), gluconic acid, glucoheptonic acid and their bath-soluble
and a hydroxy acid selected from the group consisting of compatible salts as well as mixtures thereof. The hydroxy acid in the mixture is present in a molar ratio of 0.1 to 3:1 to the amine compound. The bath further includes a stabilizer, preferably about 2.5
g/Heterogeneous cyclic organic sulfide compound, bath PH
hydroxyl ions in an amount of from about 9 to 14, optionally up to about 1 g/rate of a rate control agent such as cyanide, iodide, and derivatives thereof, and up to about 10 g/optional of a bath solubility/compatibility. It may contain a wetting agent.

According to the proposal of the method of the present invention, the substrate to be copper plated is stirred in a bath at a temperature of 21°C (70°C).
〓) to about 66°C (150〓) and is immersed in this electroless copper solution to deposit a dense copper film with a uniform thickness and good adhesion on the surface. Perform plating for a sufficient period of time. If desired, the electroless copper plated substrate is further subjected to conventional electroplating, and one to several electroplated films are deposited on the surface to achieve the desired physical properties and appearance. It can be made to have.

[Preferred Embodiment] According to the proposal regarding the composition of the present invention, the plating bath of the present invention contains copper ions in an amount sufficient to deposit metallic copper on the substrate as an essential component, and copper ions in a metallic state. a sufficient amount of complexing agent to maintain the copper ions in an alkaline medium, hydroxyl ions to bring the pH to the alkaline side, as well as stabilize the bath and provide suitable Optional stabilizers, rate control agents, and wetting agents are included in amounts sufficient to provide deposition activity and achieve good wetting agent uniformity of the resulting copper film.

Copper ions can be introduced into the bath in any form as long as they are bath-soluble and compatible copper salts, but the anions introduced at this time do not have any adverse effect on the plating properties of the method of the present invention. do not have. Typical sources of copper ions are cupric chloride dihydrate and copper sulfate pentahydrate. The copper ion concentration is generally about 0.5 g/ to about 30 g/, preferably about 5 g/. Higher concentrations of copper ions are required to obtain adequate copper deposition rates when the bath is operated at room temperature, but at approximately 60-66°C.
Approximately 0.5 during high temperature operation such as (140゜~150〓)
Concentrations as low as g/g/g can be used.

In addition to copper ions, the alkaline aqueous solution contains a sufficient amount of a reducing agent to reduce the copper ions and deposit metallic copper on the coated article. For this purpose, formaldehyde is preferably used, and of course paraformaldehyde can also be used. Additionally, phosphites, hydrazine and their derivatives have also been used or proposed to be used as reducing agents, but generally are not as effective as formaldehyde. The reducing agent concentration varies in relation to the copper ion concentration in the bath, but it is approximately
0.1 to about 40g/, preferably about 1 to about 5g/
is within the range of

In addition to the copper ions and reducing agent, the alkaline aqueous solution further includes an amount of an organic complexing agent mixture to maintain the copper ions in solution;
Efforts have been made to prevent copper hydroxide from precipitating in the alkaline medium. Preferably, the total complexing agent concentration is at least about 1 mole per mole ratio of copper ions, with a mole ratio of complexing agent to copper ions of about 5:1. The complexing agent molar ratio is from about 1.3:1 to about 3.5:1, typically about 1.7:
Control to 1.

The complexing agent is ethylenediaminetetraacetic acid (EDTA) and N,N,N',N'-tetrakis-
an amine compound selected from the group consisting of (2-hydroxypropyl)ethylenediamine (THPEDA); and an organic hydroxy acid selected from the group consisting of gluconic acid, glucoheptonic acid, bath-soluble and compatible salts thereof, and mixtures thereof. It has now been discovered that there is a kind of synergistic effect on the complexing properties and on the activity and stability of the bath. Hydroxy acid pair
The molar ratio of EDTA is from 0.1 to about 3:1. The molar ratio depends on the type of amine compound used relative to the hydroxy acid. For example, when THPEDA is used as the amine compound, the molar ratio of gluconic acid and/or glucoheptonic acid to the amine compound ranges from about 0.11:1 to about 2.45:1, preferably from about 0.2:1 to about 1:1. most preferably about
The molar ratio is 0.26:1. On the other hand, amine compounds
When EDTA, the gluconic acid and/or glucoheptonic acid is about 0.25:1 to about 3:1, preferably about 0.6:1 to about 2:1, most preferably
Contained in a molar ratio of 1.3:1. Advantageously, the complexing agent mixture is introduced as an alkali metal salt to prevent acidification of the bath. Sodium salts are preferred for this purpose.

The amount of complexing agent added can be significantly reduced by using a mixture of the two complexing agents in the above proportions, but in this case each of the two complexing agents individually complexes all the copper ions in the bath. present in insufficient quantities to do so.

This electroless copper plating solution is alkaline and
It contains hydroxyl ions in an amount such that the pH is between about 9 and about 14. More preferably, this PH range is from 10.5 to about 12.5. Typically a PH of 11.5 gives favorable results; this PH level produces industrially acceptable copper plating while reducing hydroxyl ion concentrations, resulting in less formaldehyde reaction and degradation tendency. Over time, the amount of supplies will be reduced and it will become more economical. The PH of the bath can be maintained by adding an alkali metal hydroxide, preferably sodium hydroxide.

In addition to the aforementioned components, the electroless copper plating bath may also contain various stabilizers known in the art, which enhance the co-deposition of copper onto the catalyst particles formed in the bath. This can prevent the copper ions in the bath from being rapidly lost. Although various compounds have been used or proposed, 2-mercaptobenzothiazole is widely used for this purpose. Other stabilizers used or proposed as an alternative include 2,5-dimercapto-1,
3,4-thiodazole, 8-mercaptopurine,
0-phenanthroline, 1-phenyl-5-mercaptotetrazole, 2,2-dipyridyl, 2-
(2-pyridyl)-benzimidazole, benzothiazole-thioether polyethylene glycol, thiazole, isothiazole, thiodine, benzotriazole, diazole, imidazole,
guanidine, pyrimidine, 2,2'-biquinoline,
2,9-dimethylphenanthroline and 4,7-
Diphenyl-1,10-phenanthroline.
Such stabilizers can optionally be used at a concentration of up to about 2.5 g/g, preferably from about 0.0001 to about 0.5 g/g.

Although it has been found that such clever combinations of complexing agents eliminate the need for the normally required rate control agents, under certain circumstances it may be possible to use rate control agents such as cyanides, iodides or their compounds. Approximately 1
It can be used in the electroless copper plating bath in amounts up to 100 g/g/g. Such rate control agents synchronize with the stabilizer by reducing the bathing rate. It has also been found that the use of relatively small amounts of such rate control agents improves the shine and ductility of copper coatings. When used, it is used in an amount of about 1 g or less, preferably 1 ppm to about 200 ppm.

The electroless copper plating bath further contains a controlled amount of a bath-soluble, compatible wetting agent as an optional but preferred ingredient to produce a more uniform copper coating on the substrate. Common types of wetting agents that can be used satisfactorily are those used in conventional electroless copper plating baths, e.g.
A nonionic block copolymer of ethylene oxide and propylene oxide, commercially available as "Pluronic P85" (trade name) from BASF; a nonionic phosphate, commercially available as "Gafac RE610" (trade name) from GAF. Esters and others are typical. The preferred amount for use is about 10 g/or less, typically about 0.1 to about 3 g/.

The proposal for the method of the present invention is to prepare an alkaline aqueous solution having the composition as described above, and then to heat it from about room temperature (16°C, 60°) to below about 71°C (160°), preferably about 27°C to 60°C. 66℃ (80~150〓)
Bring the bath temperature to The substrate to be copper plated is cleaned to remove surface contaminants as necessary. In the case of non-conductive substrates such as plastics, active sites are formed on the surface by first treatment with a tin-palladium complex treatment solution, followed by an acceleration treatment to form autocatalytic copper Make it easier to form a film. Generally, the plating rate of the solution is adjusted to a desired rate by adjusting the copper ion concentration, reducing agent concentration, bath temperature, pH, and complexing agent concentration. Increasing copper ion concentration, increasing reducing agent concentration, increasing bath temperature and PH, and decreasing complexing agent concentration all contribute to increasing copper precipitation rate. Generally, a copper film deposition rate of at least 0.508 microns (20 microinches) in 10 minutes is commercially preferred. Alternatively, the plating speed of the agitation may be reduced and air agitation, cathode rod agitation or other mechanical agitation means employed.

[Example] In order to further explain the present invention, an example will be described next. These examples are for illustrative purposes only and are not intended to limit the scope of the claims herein described and appended hereto.

Example 1 About 9 g/(0.023 mol) of cupric chloride was added in an amount such that the copper ion concentration was about 2 g/(0.032 mol).
EDTA tetrasodium salt, approximately 9g/(0.032
mol) of sodium glucoheptonate dihydrate, formaldehyde as a reducing agent in an amount to provide a formaldehyde concentration of about 3 g/mole, sodium hydroxide to adjust the pH of the solution to about 11.6, and about 0.05 to An alkaline electroless copper plating aqueous solution was prepared by dissolving a sulfur-containing stabilizer such as 2-mercaptobenzothiazole in water in an amount of about 10 ppm.

The initial copper concentration and other bath components were replenished to allow the bath to age so that the copper ion concentration corresponded to about 5 to 10 rotations. The aging bath had a glucoheptonate to EDTA molar ratio of about 1.4:1 and a total complexing agent to copper ion molar ratio of about 1.7:1.

Copper was deposited on the test panel under air agitation at a bath temperature of approximately 60°C (140°C), resulting in a glossy, smooth, uniform pink color with a plating rate of approximately 1.143μ (45 microinches) per 10 minutes. Copper plating was deposited. The bath was stable.

Comparative Example 1 An alkaline aged electroless copper plating aqueous solution was prepared in the same manner as in Example 1 except that no complexing agent was added. Bath stability under typical kinetic conditions for the addition of fixed amounts of EDTA and glucoheptonate, as well as a fixed amount of both, to a fraction of this complexing agent-free aging solution. observed. 0.032 mol for sample A
Upon addition of EDTA, the bath was observed to be unstable. 0.023 for other fraction sample B
Glucoheptonate vs. EDTA Added in combination with 0.014 moles of glucoheptonate and 0.014 moles of EDTA
The molar ratio was approximately 0.6:1. The deposited copper film is semi-bright and the plating speed is approximately 0.152μ in 10 minutes.
(6 microinches). For sample C
0.021 mol glucoheptonate and 0.016 mol
Glucoheptonate vs. EDTA with the addition of EDTA
in a relative molar ratio of approximately 1.3:1. This electroless copper plating bath produces approximately 1.42μ (56μ) in 10 minutes.
A pink copper film was deposited at a deposition rate of 10 microinches.

To Sample D, a mixture of 0.028 moles glucoheptonate and 0.008 moles EDTA was added to give a molar ratio of glucoheptonate to EDTA of approximately 3.5:1.
I made it so that The bath was unstable with a copper deposition rate of approximately 34 microinches per 10 minutes.

For sample E, 0.035 mole glucoheptonate was added without EDTA. The copper precipitation rate is
It was approximately 0.405μ (16 microinches) for 10 minutes.
The bath was unstable and showed a tendency to decompose.

These results indicate that the use of substantially equimolar amounts of EDTA alone or glucoheptonate alone does not provide a stable aqueous alkaline electroless copper plating solution.

When glucoheptonate and EDTA are used together within the above molar ratio, i.e., the molar ratio of glucoheptonate to EDTA is about 0.1:1 to 3:1, preferably about 0.6:1 to 2:1. It can be seen that the bath stability is good and a satisfactory copper-plated film can be obtained only in this case.

Example 3 Approximately 2 g/(0.032 mol) copper ion, approximately 9 g/
We prepared an aged alkaline electroless copper plating aqueous solution containing (0.023 mol) EDTA, approximately 5.3 g/(0.021 mol) gluconate, but gluconate
The molar ratio of EDTA was about 0.9:1, the formaldehyde concentration was about 3 g/ml, and there was enough sodium hydroxide to provide a pH of about 11.6. The bath also contained up to about 0.25 ppm of 2-mercaptothiazole as a sulfur-containing stabilizer compound.

When the bath temperature of the solution was set to 60℃ and it was plated on a test panel under air agitation, approximately
A light pink copper film was deposited at a plating rate of 0.939μ (37 microinches).

Example 4 2g/(0.032mol) copper ion, approximately 8g/
(0.027 mol) THPEDA, consisting of about 2 g/(0.007 mol) sodium glucoheptonate dihydrate, a molar ratio of glucoheptonate to THPEDA of about 0.26:1, about 3 g formaldehyde/(0.007 mol), and a pH of about 12.2. An aged aqueous alkaline electroless copper plating solution was prepared consisting of sufficient sodium hydroxide to provide a solution.

The bath temperature was approximately 60°C, and air was stirred.
A bright, smooth, pink-toned copper plating film was formed on the test panel at a plating rate of approximately 3.556 microns (140 microinches) in 10 minutes.

Example 5 Approximately 5 g/(0.08 mol) copper ion, approximately 15 g/
(0.05 mol) THPEDA, approx. 7.5 g/(0.02 mol)
EDTA, consisting of approximately 3.75 g/(0.013 mol) sodium glucoheptonate dihydrate, with a molar ratio of glucoheptonate to two amine compounds of approximately
0.18:1, formaldehyde concentration approx. 5g/, approx.
An aged alkaline electroless copper plating aqueous solution containing sufficient sodium hydroxide to a pH of 12.2 was prepared. The bath temperature was approximately 60°C, and air was stirred. A light pink-toned copper plating film was formed on the test panel at a rate of approximately 3.124 microns (123 microinches) in 10 minutes.

Claims (1)

[Claims] 1. In an electroless copper plating bath containing a sufficient amount of copper ions to deposit copper, a reducing agent, and a sufficient amount of hydroxyl ions to make the pH alkaline, ethylenediaminetetra acetic acid or N,
an amine compound consisting of N,N',N'-tetrakis-(2-hydroxypropyl)ethylenediamine; and a hydroxy acid selected from the group consisting of gluconic acid, glucoheptonic acid, bath-soluble and compatible salts thereof, and mixtures thereof. an electroless copper plating bath containing a complexing agent consisting of a mixture of compounds in an amount sufficient to complex copper ions in the bath, wherein the hydroxyl acid compound and the amine compound are in a molar ratio of 0.1. An improved electroless copper plating bath comprising a ~3:1 mixture. 2. The electroless copper plating bath according to claim 1, wherein said hydroxyl ions are contained in an amount such that the pH of the bath is from 9 to 14. 3 The hydroxyl ions raise the pH of the bath from 10.5 to 12.5.
An electroless copper plating bath according to claim 1, wherein the electroless copper plating bath is contained in an amount such that the electroless copper plating bath comprises: 4 The amine compound is ethylenediaminetetraacetic acid, and the hydroxy acid compound has a molar ratio of hydroxy acid compound to amine compound of 0.25:1 to 1.
An electroless copper plating bath according to claim 1, wherein the bath is present in an amount of 3:1. 5 The amine compound is ethylenediaminetetraacetic acid, and the hydroxy acid compound has a molar ratio of hydroxy acid compound to amine compound of 0.6:1 to 1.
2. An electroless copper plating bath according to claim 1, wherein the electroless copper plating bath is present in an amount of 2:1. 6. The compound according to claim 1, wherein the amine compound is ethylenediaminetetraacetic acid and the hydroxy acid compound is present in an amount such that the molar ratio of hydroxy acid compound to amine compound is 1.3:1. Electrolytic copper plating bath. 7. The amine compound is N,N,N',N'-tetrakis-(2-hydroxypropyl)ethylenediamine, and the hydroxy acid compound has a molar ratio of hydroxy acid compound to amine compound of 0.11:1 to 1.
An electroless copper plating bath according to claim 1, wherein the electroless copper plating bath is present in an amount of 2.45:1. 8. The amine compound is N,N,N',N'-tetrakis-(2-hydroxypropyl)ethylenediamine, and the hydroxy acid compound has a molar ratio of hydroxy acid compound to amine compound of 0.2:1 to 1.
An electroless copper plating bath according to claim 1, wherein the electroless copper plating bath is present in an amount of 1:1. 9. The amine compound is N,N,N',N'-tetrakis-(2-hydroxypropyl)ethylenediamine, and the hydroxy acid compound is such that the molar ratio of hydroxy acid compound to amine compound is 0.26:1. Claim 1 comprising:
Electroless copper plating bath as described in . 10 The molar ratio of complexing agent to copper ion is 1:1 to 5:
1. The electroless copper plating bath according to claim 1, wherein the complexing agent and the copper ions are present in such a manner that the complexing agent and the copper ion are present in such a manner that the complexing agent and the copper ion are present in such a manner that the complexing agent and the copper ion are present in such a manner that the complexing agent and the copper ion are present in such a manner that the complexing agent and the copper ion are present. 11. The electroless copper plating bath of claim 1 further comprising 2.5 g/l of a rate controlling agent. 12. The electroless copper plating bath of claim 1 further comprising 1 g/g of rate controlling agent. 13. The electroless copper plating bath according to claim 1, further comprising 10 g/wetting agent. 14 Copper ions in an amount sufficient to precipitate copper,
In an electroless copper plating bath containing a reducing agent and sufficient hydroxyl ions to make the pH alkaline, ethylenediaminetetraacetic acid or N,N,N',N'-tetrakis-(2-hydroxypropyl) ) an amine compound consisting of ethylenediamine; and a hydroxy acid compound selected from the group consisting of gluconic acid, glucoheptonic acid and bath-soluble/compatible salts thereof, and mixtures thereof; An improved electroless copper plating bath containing an amount sufficient to complex ions, wherein the hydroxyl acid compound and the amine compound are present as a mixture in a molar ratio of 0.1 to 3:1. It consists of the steps of immersing the substrate in an electroless copper plating bath, controlling the bath temperature at 15 to 71°C, and continuing to immerse the substrate until copper plating of the desired thickness is deposited. Electroless copper plating method on a substrate.