JPH0913175A - Electroless nickel plating bath using diamine type biodegradable chelating agent - Google Patents

Abstract

PURPOSE: To obtain an electroless Ni plating bath capable of performing Ni plating excellent in stability and high in P content at a high speed by incorporating a specific diamine type biodegradable chelating agent as an active ingredient. CONSTITUTION: At least one kind of the diamine type degradable chelating agent expressed by the formula (in the formula, each of A<1> -A<4> is H, COOM, SO3 M or RO3 M2 , A<5> is a 1-8C linear, branched or cyclic alkylene group, M is H, an alkali metal or an ammonium group and each of (n) and (m) is an integer of 1-8) is incorporated in the electroless Ni plating bath as the active ingredient. The bath is preferably controlled to the alkaline by NaOH, KOH or NH4 OH. The Ni plating high in P content can be performed at a high speed further by using sodium hypophosphite as a reducing agent.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an electroless Ni plating bath using a diamine type biodegradable chelating agent as a complexing agent.

An electroless Ni plating bath containing a diamine-type biodegradable chelating agent has advantages such as reduced environmental load, improved bath stability, faster plating speed, and higher P content in Ni coating. It is used as a plating bath. Especially high P
The content of electroless Ni plating is widely used for hard disks, transistor packages in the electronic component industry, optical components in the aircraft and automobile industries, etc. by utilizing the non-magnetic property, uniformity, corrosion resistance and gloss of the resulting coating. .

[0003]

2. Description of the Related Art As complexing agents used in electroless Ni plating baths, nitrogen-free types such as citric acid, tartaric acid, gluconic acid, malic acid, lactic acid, succinic acid, ethylenediamine, bipyridyl, glycine, aspartic acid, Nitrogen-containing types such as ethylenediaminetetraacetic acid (EDTA) are conventionally known.

However, an electroless Ni plating bath mainly using a nitrogen-free type complexing agent typified by citric acid is excellent in bath stability, but under alkaline conditions where the plating rate is high, the Ni coating film is P content tends to decrease, which is not suitable for efficiently producing a Ni film having a high P content. In addition, tartaric acid, gluconic acid and the like, when used in a large amount in the bath composition, may form an insoluble salt and precipitate depending on the pH condition, and there is a limit to their use as the first complexing agent.

On the other hand, the Ni plating bath mainly using a nitrogen-containing complexing agent has a too complexing force and the plating rate remarkably decreases, and a complexing force is too weak and the bath stability is remarkably poor. In most cases, few compounds have the appropriate complexing power. Further, ethylenediamine, EDTA and the like are non-biodegradable and should be avoided from the viewpoint of environmental problems in the future. Especially since 1995, London
Immediate alternatives are desirable as dumping treaties prohibit ocean dumping.

[0006]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the problems of the prior art, and is excellent in stability and contains at least one selected from diamine-type biodegradable chelating agents as an active ingredient. Another object is to provide an electroless Ni plating bath.

Another object of the present invention is to provide a plating bath which realizes Ni plating with a high P content and at a high speed which could not be realized by a conventional complexing agent such as citric acid.

[0008]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that a diamine-type biodegradable chelating agent having succinic acid, glutaric acid or the like as a basic skeleton is electroless Ni plated. It has been found to have a suitable chelating power as a bath complexing agent.

Furthermore, the present inventors have found that an electroless Ni plating bath using a diamine-type biodegradable chelating agent as a complexing agent has stability of the bath, plating rate, properties of the Ni coating formed, and coating. The present invention has been achieved by finding that it is an excellent bath from the viewpoint of the P content in the inside.

That is, the present invention relates to an electroless Ni plating bath containing at least one selected from the diamine type biodegradable chelating agents represented by the following general formula [1] as an active ingredient.

General formula [1] (In the formula, A ¹ , A ² , A ³ and A ⁴ are hydrogen, COO
M, SO ₃ M, PO ₃ M ₂ , A ⁵ has 1 to 8 carbon atoms
Represents an alkylene group which may form a straight chain, a branched chain or a ring, and may include an ether bond —O—, an ester bond —COO—, and an amide bond —CONH— in the chain. M represents hydrogen, an alkali metal, or an ammonium group, and n and m each represent an integer of 1-8. )

The present invention will be described in detail below. Specific examples of the compound of the general formula [1] of the present invention include the compounds represented by the following structural formulas and alkali metal salts or ammonium salts thereof.

(1) Ethylenediaminedisuccinic acid (ED
DS)

(2) 1,3-propanediaminedisuccinic acid (PDDS)

(3) Ethylenediamine diglutaric acid (E
DDG)

(4) 1,3-Propanediamine diglutaric acid (PDDG)

(5) 2-hydroxy-1,3-propanediamine disuccinic acid (PDDS-OH)

(6) 2-Hydroxy-1,3-propanediamine diglutaric acid (PDDG-OH)

(7) 1,2-propanediaminedisuccinic acid

(8) 2-Methyl-1,3-propanediaminedisuccinic acid

(9) 1,3-Butanediaminedisuccinic acid

(10)

(11)

(12)

(13)

(14)

(15) 1,2-Cyclohexanediaminedisuccinic acid

(16) 1,3-Cyclohexanediaminedisuccinic acid

(17)

(18)

(19)

(20)

Preferred compounds of the general formula [1] of the present invention from the viewpoint of biodegradability are ethylenediaminedisuccinic acid, 1,3-propanediaminedisuccinic acid, (S, S).
-Ethylenediamine diglutaric acid, 1,3-propanediamine diglutaric acid, 2-hydroxy-1,3-propanediamine disuccinic acid, 2-hydroxy-1,3-propanediamine diglutaric acid or alkali metal salts thereof or An ammonium salt may be mentioned.

From the viewpoint of biodegradability, more preferred compounds of the general formula [1] of the present invention are (S, S) -ethylenediaminedisuccinic acid and (S, S) -1,3-propanediaminedisuccinic acid. , (S, S) -ethylenediamine diglutaric acid, (S, S) -1,3-propanediamine diglutaric acid, (S, S) -2-hydroxy-1,3-propanediamine disuccinic acid, (S , S) -2-Hydroxy-1,3-propanediamine diglutaric acid or their alkali metal salts or ammonium salts.

Various metals and non-metals can be used for the material to be plated of the present invention. Catalytically active materials such as rolled steel for general structure, carbon steel for machine structure, and nickel can be directly plated after degreasing and etching. For special metals such as stainless steel, molybdenum steel, titanium, tungsten, molybdenum, tantalum, copper, silver, gold, aluminum, magnesium, lead, solder, bismuth, antimony and ITO, or non-metals such as plastics and ceramics. However, Ni plating can be performed by performing pretreatment and activation according to each characteristic.

The plating bath of the present invention has a basic composition of three components: Ni ⁺⁺ ion supplier, reducing agent, and complexing agent.
As the Ni ⁺⁺ ion supplier, nickel sulfate, nickel chloride, nickel nitrate or the like is used, and nickel sulfate is preferable. As the reducing agent, phosphinates such as sodium hypophosphite and boron hydrides such as sodium borohydride are used. For the purpose of Ni-P alloy plating, phosphinate is used,
Sodium hypophosphite is preferred.

The complexing agent used in the present invention is selected from various diamine-type biodegradable chelating agents. Even if one kind of compound is used alone, a plurality of compounds are mixed. You may use.

The amount of the diamine-type biodegradable chelating agent used as a complexing agent in the present invention varies depending on the complexing power, but with respect to Ni ⁺⁺ ions at a concentration of 5 to 500 mM,
It is used in an amount of 0.2 to 30 times, preferably 0.5 to 2.0 times, and particularly preferably 0.7 to 1.2 times.

Further, the diamine type biodegradable chelating agent used as the complexing agent in the present invention has a strong buffering power, and therefore, itself functions as a buffering agent to control the pH. Mineral acids such as sulfuric acid, hydrochloric acid and nitric acid, and organic acids having a low complexing power such as acetic acid and succinic acid can be used for pH adjustment in an acidic bath. Further, for adjusting the pH in an alkaline bath, it is preferable to use an inorganic base such as sodium hydroxide, potassium hydroxide, potassium carbonate or sodium carbonate or a nitrogen-containing base having a low complexing power such as ammonia, ethylenediamine or triethanolamine. it can.

A wide pH range of 3 to 12 is adopted for the bath, and the plating is preferably carried out within the range of pH 4 to 10. When a phosphinate is used as the reducing agent, N
Although i-P alloy plating is possible, in order to obtain a Ni coating having a high P content at a high speed, it is carried out in the range of pH 4 to 10, preferably in the range of pH 5 to 9.

The temperature of the bath is in the range of 60 to 98 ° C, preferably 80 to 95 ° C.

The electroless Ni plating bath using the diamine-type biodegradable chelating agent as a complexing agent according to the present invention usually has a coating excellent in uniformity, adhesion, gloss and wettability under high bath stability. Although it is applied with a high number of turns, it is also an effective means to add a trace amount of a surfactant, thiourea, lead salts or the like in order to further improve the film properties, bath stability and liquid life.

In the electroless Ni plating bath using the diamine type biodegradable chelating agent as a complexing agent in the present invention, it is necessary to remove heavy metals and hypophosphite in the waste liquid treatment. The contained waste liquid can be treated as general waste water because it is rapidly decomposed in the natural environment.

The diamine type biodegradable chelating agent in the present invention is selected in consideration of the complexing power according to the purpose. For example, EDDS, which has a relatively strong chelating power, is selected as a very advantageous chelating agent from the viewpoint of maintaining bath stability. On the other hand, chelating power is relatively soft PDDS, P
DDS-OH is selected as a very advantageous chelating agent from the standpoint of plating rate.

The most characteristic feature of the diamine type biodegradable chelating agent in the present invention is that it is possible to form a Ni coating film having a high P content at a high speed regardless of which complexing agent is used. For example, in the high plating rate region of pH 8 to 10 (alkaline bath with ammonia), the P content in the Ni plating film obtained when citric acid is used as a complexing agent is
It is about 4 to 5%, but when any of the diamine-type biodegradable chelating agents according to the present invention is used under the same conditions, 10
% Or higher high P plating is possible. This fact indicates that the Ni plating bath in the present invention has extremely great industrial importance. That is, the Ni-P alloy is
When the P content is 8% or more, it becomes an amorphous glossy amorphous, and when it is 10% or more, it becomes a non-magnetic film regardless of the precipitation state.
Plating opens the way to the manufacture of hard disks in the electronics industry, transistor packages, optical components in the aircraft and automotive industries, and more.

[0046]

EXAMPLES The present invention will now be described in detail with reference to examples, but the present invention is not limited to the following examples.

Example 1 Table 1 shows the maximum plating rate when the diamine type biodegradable chelating agent of the present invention is used as a complexing agent. Also,
Bath pH and buffer strength (pH change) at the maximum plating speed, P
The content and bath stability are also shown in Table 1. (Measurement Conditions) Ni ⁺⁺ ion supply _{concentration: NiSO 4 · 6 (H 2} 0) as 0.10M reducing agent _{concentration: NaH 2 PO 2 · (H} 2 0) as 0.2
0M Complexing agent concentration: 0.07M Plating temperature: 80 ° C pH adjustment: with H ₂ SO ₄ and NH ₄ OH

[0048]

[Table 1]

However, the analysis conditions and symbols in Table 1 are as follows. (Analysis conditions) -Velocity: Increase mass of plating film per 60 minutes of 10 cm ² test plate mg-pH change: Maximum plating rate when the pH of the plating bath was measured in 0.5 increments in the range of pH 4-10 Give p
H value and pH after measurement. P content: P weight% in the formed Ni-P alloy coating (symbol) ◎: Extremely stable ○: Stable △: Slightly unstable ×: Unstable, bath decomposition

Comparative Examples 1 to 5 Table 2 shows the maximum plating rate when a complexing agent other than the diamine-type biodegradable chelating agent was used under the same conditions as in Examples 1 to 20. Table 2 also shows the pH and buffering power (pH change) of the bath at the maximum plating speed, the P content, and the stability of the bath.

[0051]

[Table 2]

[0052]

According to the present invention, a diamine type biodegradable chelating agent having aspartic acid, glutaric acid or the like as a basic skeleton is used as a complexing agent having an appropriate chelating power in an electroless Ni plating bath. can do. The present invention also has the following effects. 1) Ni plating with a high P content and a high P content, which cannot be realized by a conventional complexing agent such as citric acid, can be prepared. 2) The formed Ni film is non-magnetic, uniform, corrosion resistant,
It has excellent glossiness and is widely used for hard disks in the electronic component industry, transistor packages, and optical components in the aircraft and automobile industries. 3) The stability of the bath is extremely good,
High turn number plating can be performed.

Claims (5)

[Claims] 1. An electroless Ni plating bath containing, as an active ingredient, at least one selected from diamine-type biodegradable chelating agents represented by the following general formula [1]. General formula [1] (In the formula, A ¹ , A ² , A ³ and A ⁴ are hydrogen, COO
M, SO ₃ M, PO ₃ M ₂ , A ⁵ has 1 to 8 carbon atoms
Represents a alkylene group which may form a straight chain, a branched chain or a ring, and may include an ether bond —O—, an ester bond —COO—, and an amide bond —CONH— in the chain. M represents hydrogen, an alkali metal, or an ammonium group, and n and m each represent an integer of 1-8. ) 2. A diamine-type biodegradable chelating agent represented by the general formula [1] is ethylenediaminedisuccinic acid, 1,
3-propanediamine disuccinic acid, ethylenediamine diglutaric acid, 1,3-propanediamine diglutaric acid,
The electroless Ni plating bath according to claim 1, which is 2-hydroxy-1,3-propanediamine disuccinic acid, 2-hydroxy-1,3-propanediamine diglutaric acid, or an alkali metal salt or ammonium salt thereof. 3. The diamine-type biodegradable chelating agent represented by the general formula [1] is (S, S) -ethylenediaminedisuccinic acid, (S, S) -1,3-propanediaminedisuccinic acid, (S, S) -ethylenediamine diglutaric acid,
(S, S) -1,3-propanediamine diglutaric acid,
(S, S) -2-Hydroxy-1,3-propanediaminedisuccinic acid, (S, S) -2-Hydroxy-1,3-
The electroless Ni plating bath according to claim 1, which is propanediamine diglutaric acid or an alkali metal salt or ammonium salt thereof. 4. The electroless Ni plating bath according to claim 1, which is made alkaline with NaOH, KOH, and NH ₄ OH. 5. The electroless Ni plating bath according to claim 4, wherein a Ni coating having a high P content using sodium hypophosphite as a reducing agent is applied at a high rate.