JPS6141774A - Modified aqueous bath for nickel plating and method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Related Applications] This invention is disclosed in U.S. Patent Application No. 503,881 (1983
(dated June 17, 2017) Partial continuation application for K (GIP)
This corresponds to

[Industrial application field]

The present invention relates generally to autocatalytic chemical plating of nickel, and more particularly to electroless aqueous nickel plating baths and methods for plating nickel onto substrates.

[Background of the invention]

[Prior Art] Various nickel-containing solutions have been used or proposed for chemically depositing nickel on a substrate. Various additive compounds are included to promote bath stability after extended use. These compositions include
For example, U.S. Patent No. 2,762,723;
There are disclosures in Japanese Patent No. 822,293; and Japanese Patent No. 3,489,576. In addition to a certain amount of nickel ions, such known electroless nickel baths contain hypophosphite anions for reducing nickel cations to metallic nickel. It is oxidized to phosphate anions and other degradation products, some of which combine with other nickel ions in the bath to form a fine particulate dispersion that oxidises other nickel ions present in the bath. The disadvantage is that as a result of the uneven chemical reduction of nickel ions, the nickel film deposited on the substrate is extremely rough, coarse, and even porous in some cases. Such particulate dispersed materials tend to destabilize the chemical balance of the bath, eventually causing the bath to decompose and having to be discarded and replaced.

For these and other reasons, various additives, such as those described in the aforementioned U.S. patents, have been proposed for use in the past to stabilize the bath and at the same time improve the rate of nickel deposition on the substrate. Efforts are being made to control the In electroless nickel plating baths that use hypophosphite ions as the reducing agent, the nickel film is actually composed of a nickel-υ alloy containing about 2% to about 15% phosphorus by weight. It's normal. While the physical and chemical properties of such a nickel-phosphorus alloy depend on the phosphorus content, the change in υ in the film depends on the bath temperature - pH.
It is influenced by a series of factors including primary hypophosphite ion concentration, nickel ion concentration, phosphite ion and hypophosphite degradation product concentrations, and the overall chemical composition of the bath, including additives.

In end-use areas for electroless nickel-plated articles, relatively high phosphorus content of 9% by weight or higher may be used for applications requiring maximum hardness or where a non-magnetic nickel film is desired. It is usually necessary to produce a high nickel alloy film.

However, there are many applications for electroless nickel-phosphorus alloys for which it is desirable to have a low phosphorus content, and the Aerospace Material Standard (Aerospace Material 5)
pe-clfication), AMS 2405
In A, standards have been established for nickel-phosphorus alloy films in which the υ content is kept to a minimum so that it does not exceed 8wt% in any case.

Conventional compositions and methods that produce a nickel-phosphorus alloy film with a low amount of public phosphorus metal tend to result in unstable bath pressure;
It has been found that there are drawbacks such as short bath life and/or relatively narrow usable concentration ranges for certain cypress bath components, making bath control more difficult. For example, the addition of thiourea to certain electroless nickel baths has been found to be effective in reducing phosphorous in deposited nickel films. However, 2.5 and 3 ppm (33-40 micromol/1
) Thiourea stops the precipitation of the plating. Because the concentration range of thiourea in the bath that allows for satisfactory bath operation is extremely narrow, this additive makes analysis and replenishment operations difficult and time-consuming to maintain proper composition parameters. , cannot be put to practical use in actual industrial equipment due to high cost.

U.S. Patent No. 2,762,723 and U.S. Patent No. 3,48
No. 9,576 proposes other sulfur-containing organic additives to stabilize the bath and/or increase the rate of nickel deposition from electroless nickel plating baths.

It has been found that such alternative additive materials also have a narrow usable concentration range and cannot be put to practical use industrially, and furthermore, many of these sulfur-containing organic compounds have a concentration of about 8 Fc%.
A nickel-phosphorus alloy film with a phosphorus content below cannot be formed.

Known compositions and methods for producing relatively phosphorus-rich nickel-phosphorus alloy films also suffer from difficulties in controlling the concentration of bath components, and in requiring control, maintenance, and replenishment to maintain the bath at peak performance. The disadvantage is that it is difficult. Although the use of stabilizers to increase bath stability has been proposed, excessive stabilization can occur in known compositions, resulting in failure of the plating to deposit. In such a case, the bath must be discarded and a new bath prepared, which is uneconomical and time consuming.

[Purpose of the invention]

The object of the invention is to provide a relatively low phosphorus solution containing additives which can be used satisfactorily over a relatively wide usable concentration range and at the same time increase the rate of nickel precipitation by 30% or more. An object of the present invention is to provide an improved electroless nickel plating bath and method for depositing a nickel-phosphorous alloy. It is also an object of the present invention to provide a relatively phosphorus-rich nickel phosphorus solution, which has a wide tolerance to variations in bath composition, so that the bath is easy to control and easy to maintain and replenish. An object of the present invention is to provide an improved electroless nickel plating bath and method for use in depositing nickel. Furthermore, it is an object of the present invention to add the additives of the present invention to electroless nickel plating baths that contain excessive amounts of organic and/or inorganic stabilizers, thereby causing excessive stabilization and rendering them inoperable. VC6 provides a method for regenerating a bath so that satisfactory bath operation can be resumed.

[Summary of the invention]

The benefits of this invention include an aqueous solution containing nickel ions, hypophosphite ions, and a sulfonium betaine compound in an amount sufficient to control the rate of nickel precipitation and the phosphorous concentration in the nickel film in accordance with the compositional proposals of this invention. This is accomplished by preparing an electroless nickel plating bath. This sulfonium betaine compound generally refers to compounds represented by the general formula and mixtures thereof.

[Structure of the invention]

Generally, the nickel ion concentration is about 1 to about 151/l
, hyponite ion from about 2 to about 4011/l, and sulfonium betaine compound concentration from about 1 to @20 micromoles/l. In order to extend the period of satisfactory commercial operation, the bath also contains about 200 JI/- to complex K, nickel ions and at the same time to solubilize hypophosphite degradation products formed after long-term use. Contains complexing agents. This electroless plating bath also contains about 30,117 below buffering agents to control the surface bits to a minimum of about 1
97 preferably contains a wetting agent and hydrogen or hydroxide ions to make the bath acidic or alkaline. Although optional, the bath preferably further includes at least one auxiliary various known organic or inorganic stabilizer along with the sulfonium betaine compound, which component undesirably degrades the rate of nickel precipitation. Can be used in substandard amounts.

[Means for solving problems]

According to a related proposal, a cleaned and suitably treated substrate is exposed to this electroless nickel plating bath at a bath temperature of about 40'C to boiling point for 1 minute to several hours, and even for several days. A phosphorous-nickel alloy with a low phosphorus content is deposited on the optical surface of the metal or non-metallic substrate by contacting it to produce a nickel-phosphorus alloy of a desired thickness. Stirring is desirable during precipitation, in which case air agitation or other types of mechanical agitation are employed. The bath is also preferably periodically or continuously filtered to remove solid contaminants. The bath is also periodically and/or continuously replenished to maintain optimum concentrations of bath components and pH at appropriate levels.

Furthermore, this invention makes it possible to make an electroless nickel bath that has become inoperable due to excessive stabilization by organic and/or inorganic stabilizers, operable by adding a certain effective amount of a sulfonium betaine compound. We provide an effective method for regenerating baths.

[Description of preferred embodiments]

The electroless, aqueous plating baths of this invention can be operated in a wide pH range on the acidic and alkaline sides, such as from about pH 4 to about 10, with typical pH ranges for acidic baths being from about 4 to about 7. Preferably it is about 4.3 to about 5.2. The pH of the alkaline bath is about 7 to about 10. Preferably it ranges from about 8 to about 9. Since hydrogen ions are generated during operation and the bath tends to become acidic, alkali metal and ammonium hydroxides, carbonates, and bicarbonates are periodically or continuously added to the bath.
I will prepare H. In order to stabilize the pH of the bath, the bath also contains about 3017 K or less, preferably about 4 to 12 F/K.
L of acetic acid, propionic acid, boric acid, and various other buffer compounds are added.

Nickel ions can be found in various bath-soluble forms such as nickel sulfate hexahydrate, nickel chloride, nickel acetate, and others.
Compatible nickel salts are used to introduce into the bath an operating nickel ion concentration of about 1 to about 1511/l, preferably about 3 to about 91/l, with concentrations of about 5 to about 8 g/l being introduced into the bath. Most preferred. Hypophosphorous acid reducing ion is hypophosphorous acid 1
Using sodium hypophosphite, potassium hypophosphite and other bath-soluble/compatible salts, the hypophosphite ion concentration is from 2 to about 401/l, preferably from about 12 to 251/l,
Most preferably, it is introduced into the bath at about 15 to about 20 p/l - 8 degrees. The concentrations of nickel ions and hypophosphite ions used at that time are varied within the ranges described below depending on the relative concentrations of these two components in the bath, the types and concentrations of other components in the bath, and the operating conditions at that time. .

In order to prepare an industrial plating bath with satisfactory bath life and operating performance, it is necessary to complex the nickel ions in the bath and to further reduce the degradation products of hypophosphite formed during bath operation. Preferably, a sufficient amount of complexing agent or complexing agent mixture is present in the bath to dissolve the complexing agent or complexing agent mixture. Complexation of nickel ions in the bath, inhibiting the formation of nickel phosphite, which has a relatively low solubility and tends to form insoluble suspensions that promote bath decomposition. This produces a coarse nickel plating film that cannot function as a catalytic nucleus and is also undesirable.

Generally the complexing agent is about 2001/l, preferably about 15 to
about 759/l, most preferably about 20 to about 4011/l
Use in the amount of The various complexing or chelating agents described in the above-mentioned US patent are suitable for the purpose and their selection #-i is made in part by the PHK of the bath;
K to provide the most stable complex under H.

Typical complexing agents are acids such as glycolic acid, butyric acid, malic acid, glycine, citric acid, acetic acid, tartaric acid, succinic acid and others, as well as the alkali metal and ammonium salts of these acids. Although alkaline earth metals can also be used to some extent,
Kagaru alkaline earth gold F4F! They are less desirable because of their tendency to form insoluble precipitates with bath components, and it is preferred to exclude them for that reason.

Additionally, some complexing agents such as acetic acid also act as buffers, so bath compositions can be optimized taking into account the dual function of these acids.

In addition to the components listed above, this bath contains one essential component that is effective in slowing the rate of precipitation of nickel-phosphorus alloys and in producing alloy films that generally contain less than about 8% phosphorus by weight. Plating rate and phosphorus content control agents present in appropriate amounts are included. The additive consists of a sulfonium betaine compound selected from the group consisting of compounds of the general formula as well as mixtures thereof.

A sulfonium betaine compound that generally fits the above structural formula and has been found to be particularly preferred is 3-5-isothiuronium propane sulfonate.

This is generally applicable when R1, R1, R, and R4 in the above formula are hydrogen and n is 3.

Among other preferred sulfonium betaine compounds Kl'j,
N,N'-dimethyl-3-8-isothiuronium propanesulfonate.

N,N'-diethyl-3-5-isothiuronium propanesulfonate.

N,N'-dihydroxymethyl-3-S-isothiuronium propanesulfonate.

N,N'-diisopropyl-3-8-inchuronium propanesulfonate.

N, N, N', N'-tetramethyl-3-S
-isothiuronium propane sulfonate.

N,N,N'-trimethyl-3-8-inchuronium propanesulfonate.

2-8-isothiuronium ethanesulfonate.

Included are 3-3-inchuronium propan-2-ol sulfonate and others.

These additive compounds are effective in very small amounts, from concentrations as low as about 1 micromol/l to concentrations of about 200 micromol/l. This wide range of usable operating concentrations simplifies bath analysis and control during process operations, which is a significant advantage over known types of additive compounds. . In a preferred embodiment, the sulfonium betaine compound has a molecular weight of about 10 to about 15
A concentration of 0 micromol/l is used, preferably from about 20 to about 120 micromol/l. In the case of an alkaline bath,
about 1 to about 50 micromoles/1. Preferably about 2 to about 2
It is 5 micromol/l.

According to a ninth preferred embodiment of the invention, the sulfonium betaine compound contains lead ions, cadmium ions,
Used in combination with other inorganic and/or organic stabilizers of known types, including tin, bismuth, antimony, and zinc ions, these ions can be used in baths containing halides, acetates, sulfates, etc. It is preferable to introduce them into the bath in the form of soluble and compatible salts. Alternatively, cyanide ions, thiophanate ions, and other stabilizers may be used, 8 at concentrations from about 1 to about 20 pp.
It is m. Typically, lead ions are used at concentrations of about 2 ppm or less; cadmium ions at about 10 ppm or less; and antimony and tin ions at about 1100 ppm or less.

The upper concentration limit for such co-stabilizers or mixtures thereof is such that the rate of nickel precipitation is inhibited to such an extent that the bath becomes inoperable.

Additionally, the bath may contain various known wetting agents or mixtures thereof that are soluble and compatible with the other bath components. The presence of a wetting agent prevents the formation of foci in the two-ring alloy film, and typically about 197 is used below.

In the proposed method of the invention, the article to be plated is brought into contact. In the case of acidic form, about 70° to about 95°C.

The bath temperature in the case of a calcifier, which preferably operates at a bath temperature of from about 80 DEG to about 90 DEG C., can generally be operated within a wide operating range, but at relatively low temperatures compared to acid baths. The reason is that with respect to bath pH and bath temperature, as the pH increases, the precipitation rate of nickel increases, but as the bath pH decreases, the bath stability increases, while the precipitation rate of nickel increases as the bath temperature increases. This is because there is a mutual relationship in which the stability of the bath decreases as the temperature increases.

The contact time between the electroless nickel solution and the substrate to be plated depends on the desired thickness of the nickel-phosphorus alloy.

Typically, the contact time ranges from about 1 minute to several hours, or even days.

Typical film thicknesses for many industrial applications are from about 0.2 to about 1.
5 mils (5-38μ). Approximately 3 to 5 when abrasion resistance is required such as pulp, pipes, dies, etc.
A film thickness of mil (76 to 127 μm) may be used. If desired,
Approximately 0.25 inches (0,642
) is also possible.

It is recommended to perform gentle stirring during the plating period. For example, air and mechanical agitation, bath circulation and barrel rotation are applied. The bath may also be periodically or continuously K-filtered to reduce contaminant levels. By periodically or continuously replenishing bath components, the concentrations of nickel ions and hypophosphite ions in particular are maintained within preferred ranges, and pi (
It is also done to maintain the desired level.

The substrate to be plated is preliminarily surface-treated according to a known method to provide a clean, catalytically active surface. For substrates that do not have catalytic activity and cannot be coated directly with an electroless nickel bath, preliminary electroplating of nickel or another metal with catalytic activity can be used to trap the surface of the substrate in an electroless nickel bath. It is also possible to make it possible to accept target precipitation.

According to another proposal regarding the method of the present invention, the use of excessive amounts of inorganic and/or organic stabilizers inhibits the deposition of a phosphorus alloy film on the substrate, resulting in inoperability. Effective operation of an electrolytic nickel plating bath can be reproduced by adding to the bath the aforementioned sulfonium betaine compounds, as well as mixtures thereof, in amounts sufficient to restore the bath to satisfactory operation. The concentration of the sulfonium betaine compound used to effectively regenerate the bath is within the limits set forth above, and for acidic baths is about 20 to about 120 micromol/1.
．． Concentrations of about 2 to 25 micromoles/l are typical for alkaline baths.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to examples, but the present invention is not limited to these examples without departing from the gist of the present invention.

Example 1 271/l nickel sulfate hexahydrate (equivalent to 61/l nickel ions); 241/l sodium hypophosphite hydrate (14,79/l hypophosphite ions) 149/l malic acid: 91/l acetic acid;
and three 500 d electroless nickel plating baths containing ammonium hydroxide to bring the pH of each bath to approximately 5.
Bath, prepared. Separate stabilizers of the type described above were added to each bath as described in Table IK.

Table 1 Thiourea 3.0 1.1 6.
2thiodipropionic acid 3.0 1.3
Within 9.60: μ/hr The lead ion concentration shown in Table 1 is 2.4 micromol/l;
The thiourea concentration corresponds to 39.4 micromol/l; the thiodipropion rR concentration corresponds to 16.8 micromol/lK.

The temperature of each bath was controlled at about 88° to about 90°C. A cleaned stainless steel test piece (39a+I) was immersed in each bath,
Using this as a cathode, electroplating was preliminarily performed for 30 seconds to promote chemical plating on the stainless steel surface. Next, electroless deposition of a nickel-phosphorus alloy was carried out for a total of 60 minutes. The resulting nickel-phosphorus alloy film was peeled off from the stainless steel surface, and the wall thickness of the coil was measured.
The inclusion content was analyzed. Table 1 shows the precipitation rate in mil/hr (μ/hr) and the weight percent of phosphorus in the nickel alloy film.

The results in Table 1 show that both thiourea and thiodipropionic acid are effective in increasing the deposition rate of nickel alloy films compared to baths where lead ions are the only stabilizer. However, even though both thiourea and thiodipropionic acid are thio compounds, only the thiourea stabilizer reduces the fraction in the alloy plated film. The phosphorus content in the nickel alloy coating exceeds 9% by weight when lead ions or thiodipropionic acid stabilizers are used.

Example 2 279/l of nickel sulphate I hexahydrate; 3011/l
of sodium hypophosphite monohydrate (equivalent to 18,417 L of hypophosphite ion); 2611/L of butyric acid;
A series of 500-electroless nickel plating baths were prepared containing 911/l of acetic acid; and ammonium hydroxide to bring the pH of the bath to about 4.9. A certain amount of a thiourea stabilizer or a sulfonium betaine compound consisting of 3-5-inchuronium propane sulfonate was added to each bath sample according to the concentrations shown in Table 2.

As a control sample, one sample without added stabilizer was prepared.

Table 2 S 0.80
(20) 9.90 Thiourea 13.
1 1.00 (25) 6.67 Thiourea 26.3 1.25 (32) 0.76
Thiourea 39.4 1.10 (28)
6.83 Thioclea 52.6 1.02 (2
6) 6.49 Thiourea 65.7 1
．． 03(27) 6.46 Thiourea 78.
9 zero -3-8-iso
6.3 1.10 (28)
8.22 Thiuronium propane 31.6 1.10 (28
) 7.36 Sulfonate 63.2 1.23(31) 6.36
94.9 1.00 (25) 6.2
9110.7 1.12 (28) 5.
95126.5 1.02 (26) 5
．． 42142.4 1.05 (27)
5.34158・2 zero
Within -0: μ/hr Clean stainless steel specimens were first electroplated for 30 seconds in accordance with the method described in Example 1 to start plating deposition on each specimen, and then the bath temperature was approximately 88° ~ 6 at about 90℃
Contact with the bath was made for 0 minutes. The nickel-phosphorus alloy film produced from each bath sample was peeled off as a foil, and the foil was measured with a dial micrometer to determine the deposition rate, and the phosphorus content in the film was analyzed. The results are shown in Table 2.

The results in Table 2 show that both the thiourea stabilizer and the sulfonium betaine compound additive increase the deposition rate of the nickel-phosphorus alloy film compared to the same bath without added stabilizer. However, since the useful operating range of sulfonium betaine compounds is more than twice that of thiourea stabilizers, it can be seen that they offer the advantage of substantially simplifying the maintenance and control of the plated film during industrial operations. Moreover,
According to the method of the present invention, phosphorus analysis in membranes from baths using sulfonium betaine compounds yields values that are more than 17% lower than those obtained using thiourea stabilizers.

Example 3 27 g/l nickel sulfate hexahydrate; 309/l sodium hypophosphite i 359/l butyric acid; x-s
tz/L of succinic acid; 0.511/l of tartaric acid; lda/l of lead ions and 1 we/l of cadmium ions to 60-130 micro%/1f) 3-8-'f A 6 ton electroless nickel plating bath was prepared vI4 containing a sulfonium betaine compound consisting of nium propane sulfonate. The pH of the bath was adjusted and maintained at about 4.2 to about 5.2 using ammonium hydroxide, and the bath temperature during the test was controlled at about 85° to about 95°C. This bath is replenished periodically to bring the nickel and hypophosphite ion concentration up to 8.
It was held substantially constant over the turnover. The term bath "turnover" or bath cycle is defined as the period of plating in which all of the initial nickel content in the bath is depleted and replenished by the next addition. Generally, the useful operating life of electroless nickel plating baths according to known techniques ranges from about 6 to about 10 turnovers before the bath is discarded.

At various times during the operational life of the bath, specimens were plated in the bath according to the method described in Example IK, and the phosphorus content in the resulting film was analyzed as well as the rate of deposition of the nickel alloy film was measured. The results are shown in Table 3.

Table 3 6.4 4.695℃0.50 (13) 3.57.
8 4.895℃0.48(12) 2.88.1
4.285°C 0.22 (5, 6) Within 3.20: μ/hr From the results in Table 3, it is clear that the phosphorus content in the nickel alloy film obtained using the electroless nickel plating bath prepared according to the method of the present invention is It is clear that the content i% is very low,
The concentrations and operating conditions at this time are typical of those used in industrial cases.

These tests have shown that if lead and cadmium ions alone are used as stabilizers without sulfonium betaine compounds, nickel alloy membranes have a It is predicted that phosphorus will be included.

In contrast, when a sulfonium betaine compound is used, a nickel alloy with a phosphorus content of less than 4% f1 is precipitated. Additionally, the bath of Example 3 was found to be easy to control because of the 3-8-isothiuronium propane sulfonate additive compound, which had a relatively wide effective operational concentration range.

Example 4 279/l nickel sulfate hexahydrate (equivalent to 69/l nickel ions); 309/l sodium hypophosphite monohydrate (18,41/l hypophosphorous acid) ions) ; 3111/l of butyric acid; 211/l of malic acid; 0.6 pit of citric acid; 0.002379/
A 500-C electroless nickel plating bath was prepared using 1 liter of cadmium acetate dihydrate (equivalent to cadmium ion in IQ/L) and ammonium hydroxide in an amount sufficient to bring the pH to approximately 5.0. . Then 0.176117t in the bath
potassium antimony tartrate I trihydrate (5bzKtc
aH<O+z·3H, corresponding to 0.64 w/L of antimony ion) was added. When this bath was heated to 90°C and a cleaned steel specimen (80 - surface area) was immersed in the bath, nickel precipitation did not occur because the bath was excessively stabilized by antimony and cadmium. I found out.

In the bath mentioned above, 8 μ/l (40.4 micromol/A
) of 3-S-isothiuronium propanesulfonate was added. When this bath was heated to 90° C. and a steel specimen (surface area 80 ci) was immersed in the bath, a very good nickel film was obtained. This nickel precipitation rate is about 30
1.3 mil/hr (33
μ/hr). The phosphorus content was analyzed to be 7.951i%.

This example shows that the sulfonium betaine compounds of this invention can also regenerate over-stabilized electroless nickel plating baths back to satisfactory operating conditions.

Example 5 271/l nickel sulfate hexahydrate, 301/l sodium hypophosphite, 311 I/l butyric acid, 29/l
l of malic acid and the pH of the bath to about 5. Four samples of 5QO+aj electroless nickel plating baths were prepared using ammonium hydroxide in an amount sufficient to achieve OK. Furthermore, 2IIP/4 lead ions and 3 so/L cadmium ions were added to each bath to stabilize the bath and brighten the nickel alloy film. Lead and cadmium ions were added as acetate. For these four sample baths, three
-5-inchuronium propanesulfonate was added and the bath temperature was then maintained between 85° and 95°C. after that,
A stainless steel test piece (surface area 80cj), which had been preliminarily subjected to Wattnickel strike for 15 seconds to make it easier to plate the stainless steel and to make it easier to peel off the plating film for analysis, was tested for 30 minutes. , plated.

The plating results are summarized in Table 4K.

Table 4 2θro Precipitation Ses Precipitation Ses 20.
2 1.0 (25) 7.04
0.4 1.0 (25) 5:
260.6 0.9 (23)
Within 3.80: μ/hr Baths that did not contain the sulfonium betaine compound were overly stabilized by lead and cadmium, so no electroless nickel film was formed.

Addition of sulfonium betaine eliminated the excessive concentration of metal stabilizer, and a satisfactory plated film was obtained with a good deposition rate. This example further shows that increasing the concentration of sulfonium betaine decreases the phosphorus content in the membrane, so controlling the concentration of sulfonium betaine in the bath can thereby obtain the desired value of phosphorus content in the membrane. It shows that it is possible.

Example 6 Four samples of a 5001 Lt electroless nickel bath were prepared according to the bath formulation described in Example 5. However, the price of lead pK
, 16 w/l of antimony (added as antimony potassium tartrate) was used as metal stabilizer, while the cadmium ion (added as acetate) concentration was set at 1 q/l. The four samples also contained varying concentrations of 3-8-isothiuronium propane sulfonate. Example 5
A nickel-phosphorus alloy film was obtained by the method described in , and the precipitation rate and phosphorus content were measured. The results are shown in Table 5.

Table 5 zero 1.0 (25) 10.620.2
1.0(25) 7.1640.4. 1.0
(25) 6.6960.6 1゜0 (25)
6.8280.8 Precipitation Sez
Precipitated cement within 0: μ/hr According to these results, when antimony rather than lead is used together with 3-8-isothiuronium propane sulfonate as a metallic stabilizer, It has been found that the phosphorus content does not continue to decrease with increasing pressure of sulfonium betaine, but rather maintains a fairly constant value at about 7'M content. This feature is an advantage in industrial implementation, and means that even if the sulfonium betaine concentration changes significantly, the phosphorus content of the nickel alloy film does not change much. Excessive amounts of sulfonium betaine compounds over-stabilize the bath and should generally be avoided. The actual concentration at which nickel will no longer precipitate depends on the basic bath composition as well as the concentration and type of other metal ions in the bath.

Example 7 An aqueous acidic electroless plating bath containing the following components was prepared.

Ingredients 11/1NiSO4-
6I(,027 NaH2P02m H2O30 Malic acid 15 Butyric acid 10 Citric acid
0.5 Sb” 0.010Pb++0
．． 0005 0(1++0.001 NH40H (amount to adjust pH 4,6-5,2K) Bath temperature approx. 75
It was operated at a temperature of 95°C to about 95°C. The concentrations of the various bath components were varied up or down by at least 25 degrees without appreciably decreasing the efficiency of the system. Substitution of bath components is also possible. For example, if an ammonium-free bath is desired for environmental reasons, sodium hydroxide can be used. Potassium hypophosphite can also be used in place of sodium hypophosphite. Sodium, potassium, ammonium and other salts of complexing acids can also be used in place of the acid itself. Similarly, metallic stabilizers can be added as salts of mildly soluble anions such as acetic acid, tartaric acid, propionic acid.

Example 8 Nickel ion 6 in 269/l nickel chloride hexahydrate
．． 491L K equivalent), 1! M'/l of sodium hypophosphite (equivalent to 9.29/l of hypophosphite ion), 50
II/l ammonium chloride, 6011/l diammonium hydrogen citrate, and 0.00311/l 3
A 500 ILt alkaline electroless nickel plating bath containing -3-thiuronium propane sulfonate (equivalent to 15 micromol 1tVc) was prepared. Adjust the pH of the bath to 8.5
It was operated at a bath temperature of 80° to 85°C.

Test specimens made of non-conductive polymeric material were pretreated in known manner to render their surfaces receptive to electroless plating. As is well known, this method involves cleaning, etching, neutralization, and activation using an aqueous/acidic solution containing a tin-palladium complex to form active sites on the base surface, followed by an acceleration treatment. It consists of various processes. The pretreated polymer specimens were immersed in this alkaline bath for 30 minutes.

When the plated test piece was observed, a nickel alloy film containing about 3% by weight of phosphorus was deposited.

Deposition rate is approximately 0.2 mil/hr (5,1μ/hr)
It came out.

Although this deposition rate is relatively low compared to common acidic electroless nickel plating baths, it is still common for many applications such as plating on plastics, glass, and other non-metallic substrates. Appropriate speed.

It has also been found that when a sulfonium betaine compound is further added to this alkaline bath, the precipitation of the nickel alloy film stops when the concentration reaches about 25 micromol/l. The maximum permissible concentration of sulfonium betaine compounds in such alkaline baths will vary depending on the current chemistry of the bath and the types and concentrations of other components. Generally, useful operating concentrations of sulfonium betaine compounds are lower in alkaline electroless nickel plating baths than in acidic electroless nickel plating baths.

Examples About 1 to about 15 JI/A nickel ions; about 2 to about 40
97L hypophosphite ion; glycolic acid, butyric acid.

Malic acid, glycine, citric acid, acetic acid, tartaric acid.

about 20,097 selected from succinic acid and bath-soluble/compatible salts thereof and mixtures thereof;
Mildly soluble wetting agents of up to about g/l; lead, cadmium, tin, bismuth, antimony.

about 14) Opp selected from zinc and mixtures thereof;
a concentration of stabilizing metal ions of up to about 20 ppm; cyanide, thiocyanate and other known stabilizing ions of up to about 20 ppm; and 3-8-1 sotiuronium pronosulfonate.

N,N'-dimethyl-3-3-isothiuronium propanesulfonate.

N,N'-diethyl-3-3-isothiuronium propanesulfonate.

N,N'-dihydroxymethyl-3-S-isothiuronium propanesulfonate.

N,N'-diisopropyl-3-S-isothiuronium propanesulfonate.

N, N, N', N'-tetramethyl-3-8
-inchuronium propane sulfonate, {N,N,N'-)dimethyl-3-S-isothiuronium propane sulfonate.

2-3-isothiuronium ethanesulfonate.

from about 1 to about 200 micromoles of a sulfonium betaine compound selected from the group consisting of 3-3-isothiuronium propan-2-ol sulfonate and mixtures thereof and an acidic 1m pH of from about 4 to about 7 and about 7~
A series of electroless nickel plating baths were prepared containing the necessary hydrogen or hydroxide ions to achieve an alkaline pH of about 10. The bath components were varied within the above ranges to ensure that the optimum nickel-phosphorus alloy was precipitated.

The test piece was plated in a series of baths ranging from 1 hour to about 1 minute to several days at a bath temperature of 40° to below the boiling point to obtain a desired film thickness. Most of them were mild-mannered.

A satisfactory nickel alloy was obtained.

Claims (20)

[Claims] (1) A sufficient amount of nickel ions, hypophosphite ions to chemically precipitate nickel, and a sufficient amount of a sulfonium betaine compound to control the rate of nickel precipitation and the phosphorus concentration in the nickel film. It is a bath that consists of
The sulfonium betaine compound has the general formula ▲ mathematical formula, chemical formula, table, etc.
-C_6 hydroxyalkyl group, R is the same or different, is H or OH, and n is an integer from 1 to 5] and mixtures thereof.・Electroless nickel plating bath. (2) further containing a complexing agent in an amount sufficient to complex the nickel ions in the bath and dissolve all of the degradation products of hypophosphite in the bath; A bath according to claim 1. (3) The bath according to claim 1, which has a pH of 4 to 10. (4) The bath according to claim 1, further comprising a buffer. (5) The sulfonium betaine compound is at least 1-
2. Bath according to claim 1, characterized in that it is contained in an amount of 200 micromol/l. (6) Bath according to claim 1, characterized in that it has a pH of 4 to 7 and contains the sulfonium betaine compound in an amount of 20 to 120 micromol/l. (7) Bath according to claim 1, characterized in that it has a pH of 7 to 10 and that the sulfonium betaine compound is contained in an amount of 2 to 25 micromol/l. (8) The bath according to claim 1, characterized in that the nickel ions are contained in an amount of 1 to 15 g/l. (9) The bath according to claim 1, characterized in that the hypophosphite ion is contained in an amount of 2 to 40 g/l. (10) The nickel ion is contained in an amount of 1 to 15 g/l, the hypophosphorous ion is contained in an amount of 2 to 40 g/l, and the sulfonium betaine compound is contained in an amount of at least 1 to 15 g/l.
2. Bath according to claim 1, characterized in that it is contained in an amount of 200 micromol/l. (11) The bath according to claim 10, further containing 200 g/l or less of a complexing agent. (12) Bath according to claim 11, characterized in that it further contains a complexing agent in an amount of 20 to 40 g/l. (13) The bath according to claim 10, further comprising a buffer in an amount of 30 g/l or less. (14) The bath according to claim 1, wherein the sulfonium betaine compound consists of 3-S-isothiuronium propane sulfonate. (15) The sulfonium betaine compound is N,N'-
Dimethyl-3-S-isothiuroniumpropanesulfonate, N,N'-diethyl-3-S-isothiuroniumpropanesulfonate, N,N'-dihydroxymethyl-3-S-isothiuroniumpropanesulfonate, N,N '-diisopropyl-3-S-isothiuroniumpropanesulfonate, N,N,N',N'-tetramethyl-3-S-isothiuroniumpropanesulfonate, N,N,N'-trimethyl-3-S- Isothiuronium propanesulfonate, 2-S-isothiuronium ethanesulfonate, 3-S
2. Bath according to claim 1, characterized in that the bath is selected from the group consisting of -isothiuronium propan-2-ol sulfonate and mixtures thereof. (16) In combination with the sulfonium betaine compound, a costabilizer further selected from the group consisting of lead ions, cadmium ions, tin ions, bismuth ions, antimony ions, zinc ions, cyanide ions, thiocyanate ions, and mixtures thereof. 2. A bath according to claim 1, characterized in that it contains nickel in an amount below a level such that it undesirably reduces the rate of nickel precipitation. (17) 1 to 15 g/l of the nickel ion, 2 to 40 g/l of the hypophosphite ion, at least 1 to 200 micromol/l of the sulfonium betaine compound, and 200 g/l of a complexing agent; 2. Bath according to claim 1, characterized in that it contains an amount of 30 g/l of agent and 1 g/l of wetting agent. (18) a sufficient amount of nickel ions, hypophosphite ions to chemically precipitate nickel, and a sufficient amount of a sulfonium betaine compound to control the rate of nickel precipitation and the phosphorus concentration in the nickel film; The sulfonium betaine compound has a general formula ▲ has a mathematical formula, a chemical formula, a table, etc. ▼ where R_1, R_2, R_3 and R_4 are the same or different types, H, C_1 to C_6 alkyl group, C_1~
C_6 hydroxyalkyl group, R is the same or different, is H or OH, and n is an integer of 1 to 5, and aqueous/non-aqueous compounds selected from the group consisting of mixtures thereof; A method for chemically depositing nickel on a substrate, which comprises the step of bringing an electrolytic nickel plating bath into contact with the substrate to be plated for a sufficient time to deposit a desired thickness of nickel on the substrate. (19) In combination with the sulfonium betaine compound, the electroless nickel bath further comprises lead ions, cadmium ions, tin ions, bismuth ions, antimony ions, zinc ions, cyanide ions, thiocyanate ions, and mixtures thereof. 19. A method according to claim 18, characterized in that the co-stabilizer selected from the group is contained in an amount below such a level as to undesirably reduce the rate of nickel precipitation. (20) A method for regenerating an aqueous electroless nickel bath that has become inoperable due to the presence of an excessive concentration of co-stabilizer, comprising:
General formula▲There are mathematical formulas, chemical formulas, tables, etc.▼ [In the formula, R_1, R_2, R_3 and R_4 are the same or different, H, C_1 to C_6 alkyl group, C_1
-C_6 hydroxyalkyl group, R is the same or different, is H or OH, and n is an integer from 1 to 5] and mixtures thereof. A method comprising adding a compound to the bath in an amount sufficient to restore the plating activity of the bath.