JP4139347B2 - Electroless nickel plating bath and electroless nickel alloy plating bath - Google Patents

Description

  The present invention relates to an electroless nickel plating bath and an electroless nickel alloy plating bath (hereinafter abbreviated as “electroless nickel (alloy) plating bath”) having a low environmental load, and more particularly, mercury and arsenic. The present invention relates to an electroless nickel plating bath and an electroless nickel alloy plating bath which do not contain elements having a large environmental load such as cadmium and lead, and have excellent bath stability and plating deposition rate.

  Electroless plating is a technique for obtaining a metal film by reducing metal ions by a chemical reaction from a solution containing metal ions and a reducing agent. Among them, electroless nickel plating or electroless nickel alloy plating (hereinafter collectively referred to as “electroless nickel (alloy) plating”) is not only rust prevention, decoration, and hardness improvement, but also solderability. It has effects such as improvement and improvement in solder wettability, and is widely used industrially for resistors, magnetic disks, electromagnetic wave shields, as well as base plating for gold plating on printed circuit boards and ITO substrates. Further, it is also used as a metal matrix for obtaining a composite plating film in which fine particles such as polytetrafluoroethylene are uniformly dispersed in a metal film.

  Conventionally, in order to maintain the stability of the plating bath, electroless nickel (alloy) plating solutions contain water-soluble salts or ions of elements that have a significant environmental impact, such as mercury, arsenic, cadmium, and lead. Have been added. The presence of these stabilizers suppresses the random reduction of nickel ions at the temperature required for the reduction reaction of nickel ions to metal, that is, a reaction generally referred to as self-decomposition, and the nickel (alloy) plating film Good production and good continuous use of the plating bath were possible.

  However, since these stabilizers are also present as ions in the electroless nickel (alloy) plating bath, these stabilizer ions are produced when a nickel (alloy) plating film is formed by a reduction reaction from the electroless nickel plating bath. At the same time, it has been known that it is reduced to a metal and taken into the nickel film or co-deposited into the nickel (alloy) film.

  On the other hand, it has been pointed out that elements such as mercury, arsenic, cadmium, lead, etc. present in the plating film may affect the environment and the human body. Regulations such as restriction directive (RoHS), used automobile directive (ELV), and law regarding the procurement of environmental goods in Japan (Green Purchasing Law) in Japan have been established. The use of hazardous substances is prohibited. Among these harmful substances, stabilizer elements such as mercury, arsenic, cadmium, and lead, which have been conventionally used as stabilizers in electroless plating baths, are also included.

  Among these stabilizer elements, mercury, arsenic, and cadmium have been used less early because they are particularly harmful and environmental impacts, but lead is used as a stabilizer for electroless nickel plating baths. It has become common to use. However, lead is a substance that has been confirmed to affect the human body and the environment, and a stabilizer element in place of lead has been desired.

  To date, tellurium, thallium and the like have been published as alternative stabilizer elements (Non-Patent Document 1 and Non-Patent Document 2). However, it was not as good as lead.

In addition, metal salts such as iron, copper, tin, cobalt, tungsten, rhenium, manganese, palladium, vanadium, zinc, chromium, gold, silver, and platinum are added to these electroless nickel plating baths, and electroless nickel alloy plating is performed. It is known to be a bath. However, these metals are intended to be alloyed with nickel, and improve physical properties such as hardness and wear resistance of the electroless nickel film, and have little effect as stabilizers.
Ibaraki Prefectural Industrial Technology Center Research Report No. 21 76-77 (1993) Abstracts of the 88th Lecture Meeting of the Surface Technology Association 185-186 (1993)

  The present invention has been made in view of such a technical background, and its problem is to achieve good production of a plating film and good continuous use of a plating bath without substantially containing lead, which is a harmful substance. The object is to provide an electroless nickel (alloy) plating bath.

  As a result of intensive studies to solve the above problems, the present inventors have found that such problems can be solved by adding a specific element to the electroless plating bath, and the present invention has been completed.

  That is, the present invention provides an electroless nickel plating bath containing a water-soluble nickel salt, a reducing agent, molybdenum and antimony.

  The present invention also provides an electroless nickel plating bath containing a water-soluble nickel salt, an alloyed metal salt, a reducing agent, molybdenum and antimony.

  According to the present invention, it is possible to provide an electroless nickel (alloy) plating bath that is excellent in plating film appearance, plating deposition rate, and plating bath stability without substantially containing harmful substances such as lead. it can. In addition, the electroless nickel (alloy) plating bath is less likely to deteriorate the performance even during continuous use of the plating bath, so that the plating bath needs to be renewed and the working efficiency can be improved. .

  The present invention is an electroless nickel plating bath containing at least a water-soluble nickel salt, a reducing agent, molybdenum and antimony, and an electroless nickel alloy plating bath in which an alloying metal salt is further added to the electroless nickel plating bath.

  The water-soluble nickel salt in the electroless nickel (alloy) plating bath of the present invention is not particularly limited, and commonly used water-soluble nickel salts such as nickel sulfate, nickel chloride, nickel acetate, nickel nitrate, hypophosphorous acid It is blended in the plating bath as nickel or the like. These can be used individually by 1 type or in combination of 2 or more types.

  The amount of these water-soluble nickel salts in the electroless nickel (alloy) plating bath is not particularly limited, but the nickel ion concentration is preferably 0.1 g / L to 100 g / L, It is particularly preferably 1 to 50 g / L. If it is less than 0.1 g / L, it may be unreacted, and if it is more than 100 g / L, decomposition due to overreaction may occur.

  Further, the reducing agent that can be used in the electroless nickel (alloy) plating bath of the present invention is not particularly limited. Preferred examples include hypophosphorous acid, sodium hypophosphite, and potassium hypophosphite. Hypophosphorous acid (salt) such as dimethylamine borane, amine borane such as trimethylamine borane; hydrazine (salt) such as hydrazine; sodium borohydride and the like. These can be used individually by 1 type or in combination of 2 or more types.

  The concentration of this reducing agent in the electroless nickel (alloy) plating bath varies depending on the type of reducing agent used and the required deposition rate, but is 1 g / L to 100 g / L for the entire plating bath. 2g / L to 50g / L is particularly preferable. If it is less than 1 g / L, it may be unreacted, and if it is more than 100 g / L, decomposition due to overreaction may occur.

  A feature of the electroless nickel (alloy) plating of the present invention is that it contains both molybdenum and antimony in its composition.

  Although there is no particular limitation on the form of molybdenum in the electroless nickel (alloy) plating bath, it is preferable to take the form of molybdate or molybdenum ions. The molybdenum may be added to the electroless nickel (alloy) plating bath in the form of molybdate such as sodium molybdate, potassium molybdate, and ammonium molybdate; These can be used singly or in combination of two or more.

  The content of the molybdenum with respect to the entire plating bath is not particularly limited, but is preferably 0.1 mg / L to 1 g / L in terms of molybdenum metal, and particularly preferably 10 mg / L to 500 mg / L. preferable. Further, it is more preferably 20 mg / L to 200 mg / L. If it is less than 0.1 mg / L, it may self-decompose, and if it is more than 1 g / L, it may cause poor plating appearance or stop the reaction.

  On the other hand, the form of antimony in the plating bath is not particularly limited, but it is preferably in the form of antimonate ions or antimony ions. This antimony includes, for example, antimonic acid salts such as sodium antimonate, potassium antimonate, and ammonium antimonate; their antimonate hydrates; antimonic acid; antimonyl-L-tartaric acid, and antimonyl potassium tartrate. (Alloy) It can be added to the plating bath, and these can be used alone or in combination of two or more.

  The content of antimony with respect to the entire plating bath is not particularly limited, but in terms of antimony metal, it is preferably 0.1 mg / L to 1 g / L, and preferably 0.5 mg / L to 200 mg / L. Particularly preferred. Further, it is more preferably 1 mg / L to 100 mg / L. If it is less than 0.1 mg / L, it may self-decompose, and if it is more than 1 g / L, it may cause poor plating appearance or stop the reaction.

  Further, the mixing ratio of molybdenum and antimony is not particularly limited, but 0.5 to 20 parts by weight of antimony is preferable with respect to 100 parts by weight of molybdenum. Particularly preferred is 1 to 10 parts by weight. If it is less than 0.5 part by weight, it may be self-decomposed. If it is more than 20 part by weight, the plating appearance may be poor or the reaction may be stopped. Further, the content of the total of molybdenum and antimony with respect to the entire plating bath is not particularly limited, but is preferably 25 mg / L to 1 g / L, and particularly preferably 50 mg / L to 200 mg / L.

  When the electroless nickel (alloy) plating bath of the present invention is an electroless nickel alloy plating bath, it is necessary to further contain an alloying metal salt. This alloyed metal salt is added to improve physical properties such as hardness, magnetism, spreadability, electrical resistance, and toughness of the plating film, and is not particularly limited. Examples thereof include iron, copper, tin, cobalt, tungsten, rhenium, manganese, palladium, vanadium, zinc, chromium, gold, silver, platinum, and the like. These alloyed metal salts can be used singly or in combination of two or more.

  The content of the alloyed metal salt with respect to the entire electroless nickel alloy plating bath is preferably 0.1 g / L to 100 g / L as a water-soluble alloyed metal salt, and preferably 1 g / L to 50 g / L. It is particularly preferred.

  In the electroless nickel (alloy) plating bath of the present invention, various components can be blended as necessary in addition to the above-described essential components. Of these, various inorganic acids and organic acids are preferably used as complexing agents. Specifically, but not limited to, boron compounds such as boric acid and borax; acetic acid, propionic acid, malic acid, lactic acid, succinic acid, malonic acid, adipic acid, citric acid, gluconic acid, Examples thereof include monocarboxylic acid compounds such as glycolic acid, dicarboxylic acid compounds or hydroxycarboxylic acid compounds; amino acids such as glycine. These can be used individually by 1 type or in combination of 2 or more types.

  The content of the complexing agent is not particularly limited as long as it does not impair the effects of the present invention, but is preferably 1 g / L to 100 g / L with respect to the entire electroless nickel (alloy) plating bath. / L to 40 g / L is particularly preferable. If it is less than 1 g / L, it may undergo autolysis or nickel phosphite may be produced when hypophosphite is used as a reducing agent. Moreover, when more than 100 g / L, unreacted and sufficient reaction rate may not be obtained.

  The electroless nickel (alloy) plating bath of the present invention may further contain a reaction accelerator. The reaction accelerator is not particularly limited, but an organic sulfur compound or an inorganic sulfur compound is preferably used. Specifically, thiosulfate, thionate, polythionate, thiourea, thiocyanate, thiosulfonate, thiocarbonate, thiocarbamate, thiosemicarbazide, sulfide, disulfide, thiol, mercaptan, etc. These can be used singly or in combination of two or more.

  The content of the reaction accelerator is not particularly limited as long as the effect of the present invention is not impaired, but is preferably 0.001 mg / L to 1000 mg / L with respect to the entire electroless nickel (alloy) plating bath. 0.01 mg / L to 100 mg / L is particularly preferable. When the amount is less than 0.001 mg / L, the reaction promoting effect may not be obtained. When the amount is more than 1000 mg / L, the plating appearance may be poor or the reaction may be stopped.

  The electroless nickel (alloy) plating bath of the present invention may further contain a film property improving agent. Although there is no limitation in particular as a film physical property improving agent, Polytetrafluoroethylene (PTFE), Tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), Fluorine resin or fluoride compound such as fluoride pitch; Nylon, polyethylene Organic polymers such as: graphite, fluorinated graphite, molybdenum disulfide, boron nitride, silicon carbide, titanium oxide, diamond and other inorganic materials; carbon nanotubes, etc., water-insoluble fine particles and short fibers generally used in electroless composite plating baths These can be used singly or in combination of two or more.

  The content of the film physical property improving agent is not particularly limited as long as the effect of the present invention is not impaired, but is preferably 0 to 500 g / L with respect to the entire electroless nickel (alloy) plating bath, and 1 g / L. 10 g / L is particularly preferred. When the amount is more than 500 g / L, good deposition of the plating film cannot be obtained, and uniform dispersion of the film property improving agent in the film may not be obtained.

  The electroless nickel (alloy) plating bath of the present invention does not substantially contain mercury, arsenic, cadmium or lead, but the present invention has little possibility of affecting the environment and the human body, and regulations, guidelines, etc. It does not exclude the inclusion of such trace amounts of metals that are not subject to the above.

  The method of using the electroless nickel (alloy) plating bath of the present invention obtained as described above is not particularly limited as long as it is the same as the method of using a normal electroless plating bath. The use of the following conditions is mentioned.

  That is, the electroless nickel (alloy) plating bath of the present invention is constructed, and the object to be plated that has been degreased, washed with water, activated, etc. may be immersed therein. The pH of the electroless nickel (alloy) plating bath is not particularly limited, but is preferably 3 to 10, and particularly preferably 4 to 9 during plating. By setting the pH of the electroless plating bath to this range, an efficient reduction reaction of metal ions proceeds, and the effect of improving the deposition rate of the electroless plating film can be obtained. For adjusting the pH of the plating bath, an acid such as hydrochloric acid, sulfuric acid or sulfamic acid, or an alkali such as sodium hydroxide or ammonium hydroxide, preferably diluted with water, can be added as appropriate.

  Further, the temperature of the bath during plating of the electroless nickel (alloy) plating bath of the present invention is not particularly limited as long as it is a temperature at which nickel ion reduction reaction is carried out, but in order to cause an efficient reduction reaction. 15-98 degreeC is preferable and 25-90 degreeC is especially preferable.

  Furthermore, in performing electroless nickel (alloy) plating using the electroless nickel (alloy) plating bath of the present invention, as a result of the progress of plating, metal ions are reduced to metal by a reducing agent, The metal ion concentration and the reducing agent concentration are lowered, and the pH is also lowered. Therefore, water-soluble nickel salt, reducing agent, complexing agent, molybdenum, antimony, pH adjusting agent, etc. are replenished continuously or at appropriate times in an electroless nickel (alloy) plating bath. It is preferable to return the concentration to the original concentration. It is also preferable to measure the metal ion concentration, the reducing agent concentration and the pH in the plating solution continuously or at appropriate time intervals, and replenish them according to the measurement results.

  EXAMPLES Next, although an Example is given and this invention is further demonstrated, this invention is not limited to these Examples.

Example 1
[Evaluation of initial performance of electroless nickel plating bath]
An electroless nickel plating bath of the present invention having the following composition and containing molybdenum and antimony as stabilizers was prepared according to a conventional method. For comparison, a material containing only one of molybdenum and antimony and a material containing lead were used. In Table 1, the contents of molybdenum, antimony, and lead are the contents as metals.

<Electroless nickel plating bath composition>
Nickel sulfate heptahydrate 25g / L
Sodium hypophosphite monohydrate 20g / L
DL-malic acid 25g / L
Lactic acid 10g / L
Acetic acid 5g / L
Stabilizer Amounts listed in Table 1 Surfactant as appropriate

  An SPCC-SB iron plate (size: 0.3 mm x 50 mm x 50 mm) was used as the specimen to be plated, and immersed in each electroless nickel plating bath 1L under the following plating conditions, and electroless nickel plated Went.

<Plating conditions>
PH of plating solution 4.9
Bath temperature 90 ° C
Agitation Air agitation Plating time 20 minutes

  About the obtained electroless nickel plating film | membrane, the plating film external appearance was evaluated on condition of the following. Further, the deposition rate was measured to evaluate the plating bath stability. The results are shown in Table 2.

<Evaluation method of plating film appearance>
Judgment Appearance of plating film ◎: Uniform appearance with gloss ○: Uniform appearance with low gloss
△: Non-glossy and whitish appearance ×: Non-uniform appearance with undeposited parts

<Evaluation method of precipitation rate>
Judgment Deposition rate ◎: 15 μm / hr or more ○: 15-12 μm / hr
Δ: 12 to 10 μm / hr
×: 10 μm / hr or less

<Method for evaluating plating bath stability>
The deposit on the bottom of the plating tank during plating was visually confirmed.
Judgment Preliminary confirmation of precipitates ◎: No dotted precipitate with a diameter of 1 mm or less
○: 1 to 5 spot-like precipitates having a diameter of 1 mm or less were confirmed. Δ: 6 to 20 spot-like precipitates having a diameter of 1 mm or less were confirmed. More than 21 deposits were confirmed.

  From the results of Table 2, it was confirmed that in the case of the plating bath (1) of the present invention containing 100 mg / L of molybdenum and 5 mg / L of antimony, the effect is equal to or better than that of lead. Furthermore, it was confirmed that molybdenum has a concentration of 10 to 100 mg / L and exhibits extremely excellent effects for the above evaluation items.

Example 2
[Continuous use test of electroless nickel plating bath]
From the results of Tables 1 and 2, the plating bath of the present invention (1), comparative plating bath (2), and comparisons in which the performance equal to or higher than that of lead was confirmed in all aspects of plating film appearance, deposition rate, and plating bath stability. A continuous use test was performed on the plating bath (3) and the comparative plating bath (7). In the continuous use test, an electroless nickel plating bath was used continuously for 1, 2, 3, 4, 5, 6 turns, and electroless plating was performed. Evaluation was carried out in the same manner as above.

Moreover, the relative precipitation rate was evaluated using the following judgment conditions.
<Relative precipitation rate>
The deposition rate at the time of continuous use for each turn was measured by the same method as in Example 1, and the measured value was measured for each turn with respect to the initial deposition rate obtained in Example 1 using the following criteria. The reduction rate of the deposition rate was evaluated.
Judgment Precipitation rate ◎: Decreased by 0-10% ○: Decreased by 10-20% △: Decreased by 20-50% ×: Decreased by 50% or more

  Here, the one-turn continuous use means that plating is continuously performed until an amount of nickel metal corresponding to the initial nickel ion concentration in the electroless nickel plating bath is plated. For example, if the initial nickel ion concentration in the electroless nickel plating bath is M [g / L], the time when nickel of M [g / L] is deposited by plating is one turn. Therefore, in this case, continuous use of 5 turns means continuous plating until nickel plating of 5 × M [g / L] is performed.

  Since the comparative plating bath (2) self-decomposed soon after the start of the continuous use test, the continuous use test was stopped. Since the comparative plating bath (3) also self-decomposed after 2 turns, the continuous use test was stopped.

  Among the plating baths evaluated in Example 2, the present plating bath (1) was the best. That is, the plating bath (1) of the present invention can continue electroless nickel plating well up to 6 turns, and even when continuously used, there is little decrease in the appearance of the plating film and decrease in the deposition rate, and the bath stability. It was also excellent. In addition, not only molybdenum but also antimony was used together, the results of the continuous use test were remarkably improved.

  Furthermore, the plating bath (1) of the present invention was excellent in the appearance of the plating film when the turn proceeded, as compared with the comparative plating bath (7) using lead. In addition, it was confirmed that the decrease in the deposition rate was small, and in the plating bath stability, the generation of precipitates in the plating bath was small, and it was confirmed that the performance was comparable to lead.

  According to the present invention, an electroless nickel (alloy) plating bath excellent in plating film appearance, deposition rate, and plating bath stability can be provided without substantially containing harmful substances such as lead. . The electroless nickel (alloy) plating bath is less likely to deteriorate the excellent performance even during continuous use, so that the plating bath needs to be renewed and work efficiency can be improved.

Therefore, the electroless nickel (alloy) plating bath of the present invention can be suitably used in a wide range of applications such as resistors, magnetic disks, electromagnetic wave shields, gold plating base plating, and fine metal-containing composite plating films. is there.
more than

Claims (12)

An electroless nickel plating bath containing a water-soluble nickel salt, a reducing agent, molybdenum in the range of 0.1 mg / L to 1 g / L, and antimony in the range of 0.1 mg / L to 1 g / L.   The electroless nickel plating bath according to claim 1, further comprising a complexing agent.   The electroless nickel plating bath according to claim 1 or 2, further comprising a reaction accelerator.   The electroless nickel plating bath according to any one of claims 1 to 3, further comprising a film physical property improving agent. The electroless nickel plating bath according to any one of claims 1 to 4, which contains a water-soluble nickel salt in a range of 0.1 g / L to 100 g / L. The electroless nickel plating bath according to any one of claims 1 to 5 , wherein the antimony is contained in an amount of 0.5 to 20 parts by weight with respect to 100 parts by weight of molybdenum .   The electroless nickel plating bath according to any one of claims 1 to 6, wherein molybdenum is added as sodium molybdate, potassium molybdate, ammonium molybdate or molybdic acid.   The electroless device according to any one of claims 1 to 7, wherein antimony is added as sodium antimonate, potassium antimonate, ammonium antimonate, antimonic acid, antimonyl-L-tartaric acid or potassium antimonyl tartrate. Nickel plating bath. Electroless nickel alloy plating bath containing water-soluble nickel salt, alloyed metal salt, reducing agent, molybdenum in the range of 0.1 mg / L to 1 g / L, and antimony in the range of 0.1 mg / L to 1 g / L .   The electroless nickel alloy plating bath according to claim 9, wherein the metal of the alloyed metal salt is iron, copper, tin, cobalt, tungsten, rhenium, manganese, palladium, vanadium, zinc, chromium, gold, silver or platinum.   The electroless nickel plating bath or electroless nickel alloy plating bath according to any one of claims 1 to 10, which contains substantially no mercury, arsenic, cadmium or lead. An electroless nickel plating method or an electroless nickel alloy plating method using the electroless nickel plating bath or electroless nickel alloy plating bath according to any one of claims 1 to 11.