JP4063655B2 - Conductive electroless plating powder and manufacturing method thereof - Google Patents

Description

【００８９】
【表２】

【００９０】
【表３】

【００９１】
表２、表３に示す結果から明らかなように、各実施例のめっき粉末（本発明品）は電気抵抗が十分に低い上に、高温で長時間保存しても電気抵抗の増加が小さく耐熱性が十分に高いことが判る。これに対して比較例のめっき粉末は、電気抵抗は低いものの、長時間の保存によって電気抵抗が増加し耐熱性が低いものであったり、電気抵抗は低いものの、めっき皮膜が剥がれやすいものであることが判る。
【００９２】
【発明の効果】
以上、詳述した通り、本発明によれば、導電性無電解めっき粉体におけるめっき皮膜と芯材粉体との密着性が向上し、且つ導電性無電解めっき粉体の耐熱性が向上し、高温で長時間保存しても電気抵抗の増加が小さくなる。
【図面の簡単な説明】
【図１】本発明の導電性無電解めっき粉体の第１の実施形態におけるめっき皮膜の断面の一例を示す走査型電子顕微鏡写真である。
【図２】本発明の導電性無電解めっき粉体の第２の実施形態におけるめっき皮膜の断面の一例を示す走査型電子顕微鏡写真である。
【図３】従来の導電性無電解めっき粉体のめっき皮膜の断面の一例を示す走査型電子顕微鏡写真である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a conductive electroless plating powder and a method for producing the same, and more specifically, a conductive electroless plating powder having a nickel film with improved adhesion and heat resistance to a core powder, and the method thereof. It relates to a manufacturing method.
[0002]
[Prior art and problems to be solved by the invention]
As a method of performing electroless plating on a synthetic resin core material powder, the present applicant previously carried a precious metal ion on a synthetic resin core powder using a noble metal-trapping surface treatment agent, and then plated. A method has been proposed in which the electroless plating process is performed by putting it in a liquid (see Patent Document 1). This method is called a so-called bathing method, and the plating solution contains a metal salt, a reducing agent, a complexing agent, a buffering agent, a stabilizer and the like. This method has the advantage that the adhesion between the plating film and the core powder is improved. In order to further improve the adhesion, the present applicant has also proposed a method in which the electroless plating method is further improved (see Patent Document 2).
[0003]
However, various performances required for electroless plating powders are becoming stricter every day, and the requirements for the adhesion between the plating film and the core powder are becoming stricter, especially at high temperatures (heat resistance). It is requested.
[0004]
[Patent Document 1]
JP 61-64882 A
[Patent Document 2]
Japanese Unexamined Patent Publication No. 1-224282
[0005]
Accordingly, an object of the present invention is to provide a conductive electroless plating powder having improved adhesion and heat resistance between the plating film and the core material powder, and a method for producing the same.
[0006]
[Means for Solving the Problems]
As a result of intensive studies, the inventors of the present invention are different from the structure of the plating film described in Patent Document 1, that is, the structure in which fine metal particles are dense and exhibit a substantially continuous film. It has also been found that the object is achieved by forming a two-layered film having different crystal orientations.
[0007]
The present invention relates to a conductive electroless plating powder in which a nickel film is formed on the surface of core material particles by an electroless plating method, wherein the nickel film is formed on the surface of the core material particles and the first layer. And a second layer formed adjacent to the first layer, wherein the first layer and the second layer have different grain boundary orientation directions, respectively. The object is achieved by providing an electrolytic plating powder.
[0008]
In addition, the present invention provides a preferable production method of one embodiment of the conductive electroless plating powder,
After capturing the noble metal ions on the core material powder having the ability to capture noble metal ions or imparting the ability to capture noble metal ions by surface treatment, this is reduced and supported on the surface of the core material powder. Then, the core powder is dispersed in an aqueous medium containing a complexing agent composed of an organic carboxylic acid or a salt thereof to prepare a first aqueous suspension, which has the same kind as the complexing agent. Two liquids, a first nickel ion-containing liquid containing a complexing agent and a first reducing agent-containing liquid, are added individually and simultaneously to cause an electroless plating reaction to form a first layer. The core material powder in which the first layer is formed is dispersed in an aqueous medium containing a complexing agent composed of an amine compound to prepare a second aqueous suspension, and the second aqueous suspension is A second nickel ion-containing liquid containing a complexing agent of the same type as the complexing agent contained therein, and Conductive electroless plating powder characterized in that two liquids of two reducing agent-containing liquids are added individually and simultaneously to cause an electroless plating reaction to form a second layer on the first layer. The above object is achieved by providing the manufacturing method.
[0009]
Furthermore, the present invention provides a preferable production method of another embodiment of the conductive electroless plating powder as described above.
After capturing the noble metal ions on the core material powder having the ability to capture noble metal ions or imparting the ability to capture noble metal ions by surface treatment, this is reduced and supported on the surface of the core material powder. Then, the core powder is dispersed in an aqueous medium containing a complexing agent composed of an amine compound to prepare a first aqueous suspension, to which a complexing agent of the same type as the complexing agent is added. Two liquids, a first nickel ion-containing liquid and a first reducing agent-containing liquid, are added individually and simultaneously to cause an electroless plating reaction to form a first layer, and then the first layer The formed core material powder is dispersed in an aqueous medium containing a complexing agent composed of an organic carboxylic acid or a salt thereof to prepare a second aqueous suspension, and the second aqueous suspension is A second nickel ion-containing liquid containing a complexing agent of the same type as the complexing agent contained therein, and Conductive electroless plating powder characterized in that two liquids of two reducing agent-containing liquids are added individually and simultaneously to cause an electroless plating reaction to form a second layer on the first layer. The above object is achieved by providing the manufacturing method.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described below based on preferred embodiments with reference to the drawings. The conductive electroless plating powder (hereinafter also simply referred to as plating powder) of the first embodiment of the present invention is obtained by forming a nickel film on the surface of a core material powder by an electroless plating method. . The nickel coating includes at least two layers of a first layer formed on the surface of the core particle and a second layer formed adjacent to the first layer.
[0011]
In the first layer formed on the surface of the core material powder, no crystal grain boundary is observed in the cross section in the thickness direction of the layer. The absence of a crystal grain boundary includes both the case where the crystal grain boundary does not exist and the case where the crystal grain boundary exists but is too small to be observed. Whether or not a crystal grain boundary is observed in the cross section in the thickness direction of the first layer can be visually grasped by observation with a scanning electron microscope (hereinafter also referred to as SEM). Specifically, when a cross section in the thickness direction of the first layer is observed with a magnification of up to 100000 times by SEM, if no crystal grain boundary is observed, it can be said that no crystal grain boundary is recognized. it can.
[0012]
In the second layer formed on the first layer, grain boundaries in the layer are oriented mainly in the thickness direction of the layer. That is, the crystal in the second layer has a columnar structure mainly extending in the thickness direction of the layer. Whether or not the grain boundaries of the second layer are oriented in the thickness direction of the layer can be visually grasped by SEM observation as in the case of the first layer. Specifically, when a columnar structure extending in the thickness direction of the second layer is observed when an SEM is used to observe a cross section in the thickness direction of the second layer at a magnification of up to 100000 times, the grain boundary is It can be said that is mainly oriented in the thickness direction.
[0013]
FIG. 1 shows an SEM photograph showing the first embodiment of the plating powder of the present invention. The magnification is 50000 times. As is clear from FIG. 1, the nickel coating on the plating powder is composed of a first layer formed on the surface of the core material particles and a second layer formed adjacent to the first layer. Yes. In the first layer, no crystal grain boundary is observed in the cross section in the thickness direction. The second layer is composed of a number of columnar structures extending in the thickness direction. In FIG. 1, the height of each columnar structure in the second layer is larger than the width, but depending on the method of forming the second layer, the height and width of the columnar structure are almost the same. In some cases, the width is larger than the height. Furthermore, it may be a truncated cone shape or its inverted shape. On the other hand, in the SEM photograph of the electroless nickel plating powder shown in FIG. 3 which is a conventional product (magnification is the same as in FIG. 1), the nickel film does not have a clear two-layer structure, and its thickness direction In the cross section, only the grain-like grain boundary is observed.
[0014]
As is clear from FIG. 1, the nickel film in the plating powder of the first embodiment has a clear two-layer structure, and is a dense, homogeneous and continuous film. On the other hand, the nickel film in the plating powder shown in FIG. 3 which is a conventional product has coarse crystal grains and is inhomogeneous. As will be apparent from the examples described later, a nickel film having a two-layer structure as shown in FIG. 1 (that is, no grain boundaries are observed in the first layer, and the second layer has a columnar structure in the thickness direction). The present inventors have found that the nickel film having a high adhesion to the surface of the core powder is extremely high. Furthermore, it has been found that the heat resistance is high and the conductivity of the plating powder is difficult to decrease even under high temperature conditions. The reason for this is not clear, but since the crystal particles are not present in the first layer, which is the layer existing on the surface of the core material powder, or if it is present, the first layer is very small. It is presumed that it becomes dense and homogeneous, and as a result, the adhesion to the surface of the core powder becomes high.
[0015]
An example of the procedure for SEM observation of the cross section of the nickel coating in the plating powder is as follows. 50 parts by weight of the plating powder, 100 parts by weight of Epicoat 815 (manufactured by Japan Epoxy Resin Co., Ltd.) and 5 parts by weight of EpiCure (manufactured by Japan Epoxy Resin Co., Ltd.) are kneaded and cured for 10 minutes with a dryer at 110 ° C. A sample of × 10 mm × 2 mm is molded. The obtained sample is bent and fractured, and the part where the fracture surface of the plating film appears is observed by SEM.
[0016]
As a result of the X-ray diffraction measurement performed by the present inventors, the first and second layers in the nickel film are not completely amorphous, but have a part of crystalline, crystalline and amorphous. It turns out that the state where quality is mixed is common. However, the crystal form in each layer is not critical in the present invention. If no grain boundary is observed in the first layer and the second layer has a columnar structure in the thickness direction, each layer is crystalline. Whether it is amorphous or not, the desired adhesion and heat resistance are exhibited.
[0017]
The thickness of the nickel film has a considerable influence on its adhesion, and if the film is too thick, it tends to fall from the core powder and the conductivity tends to decrease. On the contrary, even if the film is too thin, desired conductivity cannot be obtained. From these viewpoints, the thickness of the first layer is preferably about 0.0025 to 5 μm, particularly about 0.005 to 1 μm. The thickness of the second layer is also preferably in the same range. Furthermore, the thickness of the entire nickel film including the first and second layers is preferably about 0.005 to 10 μm, particularly about 0.01 to 2 μm.
[0018]
Depending on the type of reducing agent used when forming the nickel film by electroless plating, the nickel film may be an alloy of nickel and another element. For example, when sodium hypophosphite is used as the reducing agent, the resulting nickel film is a nickel-phosphorus alloy. However, in the present invention, such a nickel alloy film is also called a nickel film in a broad sense.
[0019]
The plated powder of the present invention is formed by forming the above-mentioned nickel film on the surface of the core powder. From the viewpoint of further improving the conductivity of the plated powder, a thin layer of gold is formed on the outermost surface. A plating layer may be formed. The thickness of the gold plating layer is generally about 0.001 to 0.5 μm. The thickness of the gold plating layer can be calculated from the amount of gold ions added and chemical analysis.
[0020]
There is no particular limitation on the type of core material powder on which the nickel film is formed, and both organic powder and inorganic powder are used. Considering the electroless plating method described later, the core material powder is preferably dispersible in water. Therefore, the core powder is preferably substantially insoluble in water, and more preferably does not dissolve or change in acid or alkali. "Dispersible in water" means that a suspension substantially dispersed in water can be formed to such an extent that a nickel coating can be formed on the surface of the core powder by a normal dispersing means such as stirring.
[0021]
There is no restriction | limiting in particular in the shape of core material powder. In general, the core material powder may be in the form of a powder, but may have other shapes, for example, a fiber shape, a hollow shape, a plate shape, a needle shape, or an indefinite shape. As the size of the core material powder, an appropriate size is selected according to the specific application of the plating powder of the present invention. For example, when the plating powder of the present invention is used as a conductive material for connecting an electronic circuit, the core powder is preferably spherical particles having an average particle diameter of about 0.5 to 1000 μm.
[0022]
Specific examples of the core powder include metal (including alloys), glass, ceramics, silica, carbon, metal or non-metal oxides (including hydrates), and metal silicates including aluminosilicates as inorganic materials. Metal carbide, metal nitride, metal carbonate, metal sulfate, metal phosphate, metal sulfide, metal acid salt, metal halide and carbon. Organic materials include natural fiber, natural resin, polyethylene, polypropylene, polyvinyl chloride, polystyrene, polybutene, polyamide, polyacrylate, polyacrylonitrile, polyacetal, ionomer, polyester and other thermoplastic resins, alkyd resin, phenol resin, urea Examples thereof include resins, melamine resins, benzoguanamine resins, melamine resins, xylene resins, silicone resins, epoxy resins, and diallyl phthalate resins. These may be used alone or in a mixture of two or more.
[0023]
It is preferable that the surface of the core material powder is modified so that the surface thereof has a precious metal ion capturing ability or a precious metal ion capturing ability. The noble metal ions are preferably palladium or silver ions. Having a precious metal ion scavenging ability means that the precious metal ion can be captured as a chelate or salt. For example, when an amino group, imino group, amide group, imide group, cyano group, hydroxyl group, nitrile group, carboxyl group, etc. are present on the surface of the core powder, the surface of the core powder is precious metal ion Has capture ability. In the case of modifying the surface so as to have the ability to trap noble metal ions, for example, a method described in JP-A-61-64882 can be used.
[0024]
Next, a second embodiment of the plating powder of the present invention will be described with reference to FIG. For these embodiments, only the points different from the first embodiment will be described, and for the points that are not particularly described, the description in detail regarding the first embodiment is applied as appropriate.
[0025]
FIG. 2 shows an SEM photograph showing a second embodiment of the plating powder of the present invention. The magnification is 50,000 times as in FIG. As is clear from FIG. 2, the nickel coating on the plating powder in the present embodiment is adjacent to the first layer and the first layer formed on the surface of the core material particles as in the first embodiment. The second layer is formed. However, this embodiment is different from the first embodiment in that the first layer is composed of a number of columnar structures extending in the thickness direction, and the second layer has a cross section in the thickness direction. No crystal grain boundary is observed. That is, the two-layer structure of the nickel film in the plating powder of the present embodiment is a structure in which that of the first embodiment is turned upside down.
[0026]
As is clear from FIG. 2, the nickel film of this embodiment has a clear two-layer structure similar to that of the first embodiment, and is a dense, homogeneous and continuous film. As will be apparent from the examples described later, a nickel film having a two-layer structure as shown in FIG. 2 (that is, the first layer has a columnar structure in the thickness direction, and crystal grain boundaries are present in the second layer. It was found that the nickel film (which is not recognized) has high heat resistance, and it is difficult to lower the conductivity of the plated powder even under high temperature conditions.
[0027]
The thickness of the first layer in the present embodiment can be the same as the thickness of the second layer in the first embodiment. The thickness of the second layer in the present embodiment can be the same as the thickness of the first layer in the first embodiment. Further, the thickness of the entire nickel film including the first and second layers can be the same as that of the first embodiment. These reasons are the same as those in the first embodiment.
[0028]
Next, a preferred method for producing the plating powder of the present invention will be described taking the production of the plating powder of the first and second embodiments as an example. First, manufacture of the plating powder of 1st Embodiment is demonstrated. The manufacturing method of the plating powder of 1st Embodiment is divided roughly into (A) formation process of a 1st layer, and (B) formation process of a 2nd layer. The first layer forming step (A) includes (A1) a catalytic treatment step, (A2) an initial thin film forming step, and (A3) an electroless plating step. Similarly, the second layer forming step (B) includes (B1) a catalytic treatment step, (B2) an initial thin film forming step, and (B3) an electroless plating step.
[0029]
In the catalyzing treatment step (A1), after capturing the noble metal ions in the core material powder having the ability to capture the noble metal ions or imparting the ability to capture the noble metal ions by the surface treatment, this is reduced and the A noble metal is supported on the surface of the core material powder. In the initial thin film forming step (A2), the core material powder carrying the noble metal is dispersed and mixed in an initial thin film forming liquid containing a complexing agent composed of nickel ions, a reducing agent and an organic carboxylic acid or a salt thereof. Then, nickel ions are reduced to form an initial nickel thin film on the surface of the core powder. In the electroless plating step (A3), a complex consisting of an organic carboxylic acid of the same kind as the complexing agent is added to an aqueous suspension containing the core material powder on which an initial thin film of nickel is formed and the complexing agent. Two liquids, a nickel ion-containing liquid containing an agent and a reducing agent-containing liquid, are added individually and simultaneously to cause an electroless plating reaction. Hereinafter, each process is explained in full detail.
[0030]
(A1) Catalytic treatment process
When the core powder itself has the ability to capture noble metal ions, a direct catalytic treatment is performed. If not, surface modification treatment is performed. In the surface modification treatment, the core material powder is added to water or an organic solvent in which the surface treatment agent is dissolved and sufficiently stirred and dispersed, and then the powder is separated and dried. The amount of the surface treatment agent depends on the type of the core powder, and the specific surface area of the powder is 1 m. ² A uniform reforming effect can be obtained by adjusting within the range of 0.3 to 100 mg / g.
[0031]
Next, the core powder is dispersed in a dilute acidic aqueous solution of a noble metal salt such as palladium chloride or silver nitrate. As a result, noble metal ions are trapped on the powder surface. Noble metal salt concentration is 1m of powder surface area ² 1 × 10 per ^-7 ~ 1x10 ^-2 A molar range is sufficient. The core powder with the precious metal ions captured is separated from the system and washed with water. Subsequently, the core material powder is suspended in water, and a reducing agent is added thereto to reduce the noble metal ions. As a result, the noble metal is supported on the surface of the core powder. Examples of the reducing agent include sodium hypophosphite, sodium boron hydroxide, potassium borohydride, dimethylamine borane, hydrazine, formalin and the like.
[0032]
Before capturing the noble metal ions on the surface of the core powder, a sensitization treatment for adsorbing tin ions on the powder surface may be performed. In order to adsorb tin ions on the powder surface, for example, the surface-modified core material powder may be put into an aqueous solution of stannous chloride and stirred for a predetermined time.
[0033]
(A2) Initial thin film formation process
The initial thin film forming step is performed for the purpose of uniformly depositing nickel on the core material powder and smoothing the surface of the core material powder. In the initial thin film forming step, first, the core material powder carrying the noble metal is sufficiently dispersed in water. For the dispersion, a shearing dispersion device such as a colloid mill or a homogenizer can be used. In dispersing the core powder, for example, a dispersant such as a surfactant can be used as necessary. The aqueous suspension thus obtained is dispersed and mixed in an initial thin film forming liquid containing a complexing agent comprising nickel ions, a reducing agent and an organic carboxylic acid or a salt thereof. Thereby, the reduction reaction of nickel ions is started, and an initial thin film of nickel is formed on the surface of the core material powder. As described above, the initial thin film formation step is performed for the purpose of uniform precipitation and smoothing the surface of the core powder, so that the formed initial thin film of nickel can smooth the surface of the core powder. As long as it is thin. From this viewpoint, the thickness of the initial thin film is preferably 0.001 to 2 μm, particularly preferably 0.005 to 1 μm. The thickness of the initial thin film can be calculated from the amount of nickel ions added and chemical analysis. The complexing agent is not consumed by the reduction of nickel ions.
[0034]
From the viewpoint of forming the initial thin film having the thickness described above, the concentration of nickel ions in the initial thin film forming liquid is 2.0 × 10. ^-Four ~ 1.0 mol / liter, especially 1.0 x 10 ^-3 It is preferable that it is -0.1 mol / liter. As the nickel ion source, a water-soluble nickel salt such as nickel sulfate or nickel chloride is used. From the same viewpoint, the concentration of the reducing agent in the initial thin film forming solution is 4 × 10. ^-Four ~ 2.0 mol / liter, especially 2.0 x 10 ^-3 It is preferable that it is -0.2 mol / liter. As the reducing agent, those similar to those used for the reduction of the noble metal ions described above can be used.
[0035]
It is important that the initial thin film forming liquid contains a complexing agent. By this, and by making the 1st nickel ion containing liquid mentioned later contain a complexing agent, the 1st layer in which a crystal grain boundary is not recognized can be formed easily. The complexing agent is a compound having a complex forming action on the metal ion to be plated. In the formation of the first layer, an organic carboxylic acid or a salt thereof such as citric acid, hydroxyacetic acid, tartaric acid, malic acid, lactic acid or gluconic acid, or an alkali metal salt or ammonium salt thereof is used as the complexing agent. These complexing agents can be used alone or in combination of two or more. Of these complexing agents, tartaric acid or a salt thereof is particularly preferable because the first layer in which no crystal grain boundary is observed can be formed more easily. The concentration of the complexing agent affects the formation of the first layer in which no grain boundary is observed. From this viewpoint and the solubility of the complexing agent, the amount of the complexing agent in the initial thin film forming liquid is preferably 0.005 to 6 mol / liter, particularly preferably 0.01 to 3 mol / liter.
[0036]
From the viewpoint that an initial thin film can be easily formed, the concentration of the core material powder in the aqueous suspension is preferably 0.1 to 500 g / liter, particularly preferably 0.5 to 300 g / liter.
[0037]
The aqueous suspension obtained by mixing the aqueous suspension containing the core powder and the initial thin film forming liquid is then subjected to an electroless plating process described later. In the aqueous suspension before being subjected to the electroless plating step, the ratio of the total surface area of the core powder contained in the aqueous suspension to the volume of the aqueous suspension (this ratio is generally a load). Is called 0.1-15m) ² / Liter, especially 1-10m ² / Liter is preferable from the viewpoint that the first layer in which no crystal grain boundary is observed can be easily formed. If the load is too high, the reduction of nickel ions in the liquid phase will be significant in the electroless plating process described later, and a large amount of nickel fine particles will be generated in the liquid phase, which will adhere to the surface of the core powder. Therefore, it becomes difficult to form a uniform first layer.
[0038]
(A3) Electroless plating process
In the electroless plating step, (a1) a core material powder on which an initial thin film is formed and a first aqueous suspension containing the complexing agent, (b1) a first nickel ion-containing liquid, and (c1) first 3 liquids of 1 reducing agent containing liquid are used. As the first aqueous suspension (a1), the one obtained in the above-described initial thin film formation step may be used as it is.
[0039]
Separately from the first aqueous suspension of (a1), two liquids of a first nickel ion-containing liquid (b1) and a first reducing agent-containing liquid (c1) are prepared. The first nickel ion-containing liquid is an aqueous solution of a water-soluble nickel salt such as nickel sulfate or nickel chloride, which is a nickel ion source. The concentration of nickel ions is 0.1 to 1.2 mol / liter, particularly 0.5 to 1.0 mol / liter, so that the first layer in which no crystal grain boundary is observed can be easily formed. Is preferable.
[0040]
It is important that the first nickel ion-containing liquid contains the same complexing agent as the complexing agent contained in the first aqueous suspension. That is, it is important that the same kind of complexing agent is contained in both the first aqueous suspension (a1) and the first nickel ion-containing liquid (b1). As a result, the first layer in which no crystal grain boundary is recognized can be easily formed. The reason for this is not clear, but by adding a complexing agent to both the first aqueous suspension of (a1) and the first nickel ion-containing liquid of (b1), nickel ions are stabilized. It is presumed that the reduction reaction is prevented from proceeding rapidly.
[0041]
The concentration of the complexing agent in the first nickel ion-containing liquid (b1) also affects the formation of the first layer in the same manner as the concentration of the complexing agent in the aqueous suspension (a1). From this viewpoint and the solubility viewpoint of the complexing agent, the amount of the complexing agent in the first nickel ion-containing liquid is preferably 0.01 to 12 mol / liter, particularly 0.02 to 6 mol / liter.
[0042]
The first reducing agent-containing liquid (c1) is generally an aqueous solution of a reducing agent. As the reducing agent, those similar to those used for the reduction of the noble metal ions described above can be used. It is particularly preferable to use sodium hypophosphite. Since the concentration of the reducing agent affects the reduction state of nickel ions, it is preferably adjusted to a range of 0.1 to 20 mol / liter, particularly 1 to 10 mol / liter.
[0043]
Two liquids, the first nickel ion-containing liquid (b1) and the first reducing agent-containing liquid (c1), are added individually and simultaneously to the first aqueous suspension (a1). As a result, nickel ions are reduced, and nickel is deposited on the surface of the core powder to form a film. The addition rate of the first nickel ion-containing liquid and the first reducing agent-containing liquid is effective for controlling the nickel deposition rate. The deposition rate of nickel affects the formation of the first layer in which no grain boundary is observed. Therefore, it is preferable to control the deposition rate of nickel by adjusting the addition rate of both solutions to 1 to 10,000 nanometers / hour, particularly 5 to 300 nanometers / hour. The deposition rate of nickel can be obtained by calculation from the addition rate of the first nickel ion-containing liquid.
[0044]
While the two liquids are added to the first aqueous suspension, the concentration of the complexing agent in the aqueous suspension is not constant, and the amount of the first aqueous suspension is increased by the addition of the two liquids. And, it is changed due to the addition of the complexing agent contained in the first nickel ion-containing liquid. In this production method, taking into consideration the solubility of the complexing agent, the concentration of the complexing agent in the first aqueous suspension is 0.005 to 6 mol / liter, particularly 0, in the addition process of the two liquids. It has been found by the present inventors that it is particularly advantageous to keep it in the range of 0.02 to 3 mol / liter. By keeping the concentration of the complexing agent in the first aqueous suspension in the addition process of the two liquids within the above range, the first layer in which no crystal grain boundary is observed can be formed more easily. In order to keep the concentration of the complexing agent in the first aqueous suspension within the above range, the addition rate (nickel deposition rate) of the first nickel ion-containing liquid and the first reducing agent-containing liquid, or The initial concentration of the complexing agent in the first aqueous suspension or the concentration of the complexing agent in the first nickel ion-containing liquid may be adjusted. These values are as described above.
[0045]
While the two liquids are being added to the first aqueous suspension, the load described above is 0.1-15 m. ² / Liter, especially 1-10m ² / Liter is preferable. This makes it possible to more easily form the first layer in which nickel is deposited uniformly and no grain boundary is observed. For the same reason, it is also preferable that the loading amount at the time when the addition of the two liquids is completed and the reduction of nickel ions is completed is within this range.
[0046]
Although depending on the type of reducing agent used, the pH of the first aqueous suspension is maintained in the range of 3 to 13, particularly 4 to 11, during the nickel ion reduction reaction. It is preferable from the point which prevents the production | generation of a thing. In order to adjust the pH, for example, a predetermined amount of a pH adjusting agent such as sodium hydroxide may be added to the first reducing agent-containing liquid.
[0047]
In this way, a plated powder is obtained in which the first layer made of a nickel film is formed on the surface of the core powder. In the first layer of the plating powder, no crystal grain boundary is observed in the cross section in the thickness direction.
[0048]
The plating powder in which the first layer is formed on the surface of the core powder is filtered off, and then the second layer is formed on the first layer. As described above, the formation process of the second layer includes (B1) a catalytic treatment process, (B2) an initial thin film formation process, and (B3) an electroless plating process. In particular, in order to form a desired second layer, a film having a crystal structure different from the crystal structure of nickel in the first layer is formed on the first layer by the initial thin film formation step of (B2). It is important to form crystal structural matching strain.
[0049]
Among the steps (B1) to (B3), the catalytic treatment step (B1) is the same as the catalytic treatment step (A1) described above. In the initial thin film forming step (B2), an amine compound is used as the complexing agent in place of the organic carboxylic acid or salt thereof which is the complexing agent used in the initial thin film forming step (A2) described above. . By using an amine compound as the complexing agent, the second layer having a columnar structure can be easily formed. As the amine compound, for example, a compound having an amino group such as glycine, alanine, ethylenediamine, diethylenetriamine, triethylenetetramine, pentaethylenehexamine is used. These complexing agents can be used alone or in combination of two or more. Among these complexing agents, it is preferable to use glycine or ethylenediamine in particular because the second layer having a columnar structure can be formed more easily. The concentration of the complexing agent affects the formation of the second layer having a columnar structure. From this viewpoint and the viewpoint of the solubility of the complexing agent, the amount of the complexing agent in the initial thin film-forming solution is preferably 0.003 to 10 mol / liter, particularly 0.006 to 4 mol / liter. Moreover, in the aqueous suspension before being subjected to the electroless plating step described below, the load is 0.1 to 15 m. ² / Liter, especially 1-10m ² / Liter is preferable from the viewpoint that the second layer having a columnar structure can be easily formed.
[0050]
In the electroless plating step (B3), (a2) a second powder containing a core material powder having an initial thin film formed on the first layer and the complexing agent (that is, a complexing agent comprising an amine compound). Three liquids are used: an aqueous suspension, (b2) a second nickel ion-containing liquid, and (c2) a reducing agent-containing liquid. As the second aqueous suspension (a2), the one obtained in the above-described initial thin film formation step (B2) may be used as it is. The second nickel ion-containing liquid (b2) and the second reducing agent-containing liquid (c2) should be the same as those used in the electroless plating step (A3) described above. Can do. However, the second nickel ion-containing liquid (b2) contains an amine compound instead of the complexing agent (that is, organic carboxylic acid or salt thereof) contained in the first nickel ion-containing liquid (b1). A complexing agent comprising: In this step, it is important that both the second aqueous suspension (a2) and the second nickel ion-containing liquid (b2) contain the same complexing agent (that is, an amine compound). is there. Thereby, the second layer having a columnar structure can be easily formed. In addition to the complexing agent comprising the amine compound described above, other types of complexing agents are added to the second aqueous suspension of (a2) and the second nickel ion-containing liquid of (b2). You may keep it. Examples of such a complexing agent include organic carboxylic acids or salts thereof such as citric acid, hydroxyacetic acid, tartaric acid, malic acid, lactic acid or gluconic acid, or alkali metal salts or ammonium salts thereof. When other types of complexing agents are used in combination, similar to the complexing agent composed of an amine compound, the same kind is used for the second aqueous suspension of (a2) and the second nickel ion-containing liquid of (b2). It is preferable to add those.
[0051]
In the process of adding the second nickel ion-containing liquid (b2) and the second reducing agent-containing liquid (c2) to the second aqueous suspension (a2), The inventors have found that it is particularly advantageous to keep the concentration of the complexing agent in the range of 0.003 to 10 mol / liter, in particular 0.006 to 4 mol / liter. . By maintaining the concentration of the complexing agent in the second aqueous suspension in the addition process of the two liquids within the above range, the second layer having a columnar structure can be formed more easily. In order to keep the concentration of the complexing agent in the second aqueous suspension within the above range, the addition rate (nickel deposition rate) of the second nickel ion-containing liquid and the second reducing agent-containing liquid, or The initial concentration of the complexing agent in the aqueous suspension or the concentration of the complexing agent in the second nickel ion-containing liquid may be adjusted.
[0052]
While adding the second nickel ion-containing liquid of (b2) and the second reducing agent-containing liquid of (c2) to the second aqueous suspension of (a2), the loading amount is 0.1 to 15 m. ² / Liter, especially 1-10m ² / Liter is preferable. As a result, the second layer having a columnar structure can be more easily formed while nickel is uniformly deposited. For the same reason, it is also preferable that the loading amount at the time when the addition of the two liquids is completed and the reduction of nickel ions is completed is within this range.
[0053]
During the reduction reaction of nickel ions, the pH of the second aqueous suspension is preferably kept in the range of 3 to 13, particularly 4 to 11, from the viewpoint of preventing the formation of a water-insoluble precipitate of nickel.
[0054]
In this way, a plating powder having a two-layer structure in which a second layer made of a nickel film is formed on the surface of the first layer is obtained. The grain boundaries of the second layer in the plating powder are mainly oriented in the thickness direction of the layer.
[0055]
The obtained plating powder is separated after filtration and water washing are repeated several times. Further, as an additional process, a gold plating layer as the uppermost layer may be formed on the nickel film. The gold plating layer can be formed according to a conventionally known electroless plating method. For example, by adding an electroless plating solution containing ethylenediaminetetraacetic acid tetrasodium, trisodium citrate and potassium gold cyanide, adjusted to pH with sodium hydroxide, to an aqueous suspension of plating powder, A gold plating layer is formed on the film.
[0056]
Next, manufacture of the plating powder of 2nd Embodiment is demonstrated. The method for producing a plated powder according to the second embodiment includes (A) the first layer forming step and (B) the second layer forming method in the plated powder producing method according to the first embodiment. The process is reversed, and the other points are the same as those in the method for producing the plating powder of the first embodiment. Therefore, regarding the production of the plating powder according to the second embodiment, the explanation in detail regarding the production of the plating powder according to the first embodiment is appropriately applied.
[0057]
The plating powder of the present invention thus obtained is, for example, conductive for connecting the electrodes of an anisotropic conductive film (ACF), heat seal connector (HSC), and liquid crystal display panel to the circuit board of the driving LSI chip. It is suitably used as a material.
[0058]
As mentioned above, although this invention was demonstrated based on the preferable embodiment, this invention is not restrict | limited to the said embodiment. For example, in the above embodiment, the nickel film has a two-layer structure, but instead of this, one or more further layers made of nickel may be formed on the second layer. One or more sets of the first layer and the second layer may be formed on the second layer.
[0059]
In the plating powder manufacturing method described above, the catalyzing treatment step (B1) is performed prior to forming the second layer on the first layer formed by the electroless plating step (A3). However, this catalytic treatment step is not performed, and after the core material powder on which the first layer is formed by the electroless plating step (A3) is filtered or dispersed, the initial stage of (B2) You may perform a thin film formation process (refer Example 9 and 11 mentioned later). Alternatively, if necessary, the initial thin film (B2) can be directly applied to the core powder without filtering or dispersing the core powder on which the first layer is formed by the electroless plating step (A3). You may perform a formation process.
[0060]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples. However, the scope of the present invention is not limited to such examples.
[0061]
[Examples 1 to 4]
(A1) Catalytic treatment step for forming the first layer
Spherical silica having an average particle size of 12 μm and a true specific gravity of 2.23 was used as the core material powder. 40 g of the solution was added to 400 ml of an aqueous conditioner solution (“Cleaner Conditioner 231” manufactured by Shipley) with stirring. The concentration of the aqueous conditioner solution was 40 ml / liter. Subsequently, the core material powder was subjected to surface modification and dispersion treatment by stirring for 30 minutes while applying ultrasonic waves at a liquid temperature of 60 ° C. The aqueous solution was filtered and the core powder washed once with repulp water was made into 200 ml slurry. 200 ml of stannous chloride aqueous solution was added to this slurry. The concentration of this aqueous solution is 5 × 10 ^-3 Mol / liter. The mixture was stirred at room temperature for 5 minutes, and sensitization treatment was performed to adsorb tin ions on the surface of the core material powder. Subsequently, the aqueous solution was filtered and washed once with repulp water. Next, the core powder was made into 400 ml slurry and maintained at 60 ° C. While stirring the slurry using ultrasonic waves, 2 ml of a 0.11 mol / liter palladium chloride aqueous solution was added. The state of stirring as it was was maintained for 5 minutes, and an activation treatment for trapping palladium ions on the surface of the core powder was performed. Next, the aqueous solution was filtered, and the core material powder washed once with repulp hot water was made into 200 ml of slurry. The slurry was stirred while using ultrasonic waves, and 20 ml of a mixed aqueous solution of 0.017 mol / liter dimethylamine borane and 0.16 mol / liter boric acid was added thereto. The mixture was stirred for 2 minutes while using ultrasonic waves at room temperature to reduce palladium ions.
[0062]
(A2) Initial thin film forming step for forming the first layer
200 ml of the slurry obtained in the step (A1) was added to the initial thin film forming solution (I-1) shown in Table 1 with stirring to form an aqueous suspension. The initial thin film forming liquid was heated to 75 ° C., and the liquid volume was 1.8 liters. Immediately after the slurry was introduced, hydrogen generation was observed, confirming the start of initial thin film formation. One minute later, 0.063 mol of sodium hypophosphite was added, and stirring was continued for another minute. The load of aqueous suspension is 4.5m ² / Liter.
[0063]
(A3) Electroless plating process for forming the first layer
The first aqueous suspension obtained in the step (A2) contains the first nickel ion-containing liquid (II-1) shown in Table 1 and 2.75 mol / liter sodium hypophosphite. Two liquids of the first reducing agent-containing liquid composed of 6 mol / liter sodium hydroxide were added at an addition rate of 7 ml / min. The amount added was 435 ml each. Generation of hydrogen was observed immediately after the addition of the two liquids, confirming the start of the plating reaction. Until the addition of the two liquids was completed, the concentration of the complexing agent in the first aqueous suspension was maintained at the concentration shown in Table 1. After the addition of the two liquids was completed, stirring was continued while maintaining the temperature at 75 ° C. until hydrogen bubbling stopped. The load after the addition of the two liquids is 3.1 m ² / Liter. The first aqueous suspension was then filtered and the filtrate was repulped three times.
[0064]
(B1) Catalytic treatment step for forming the second layer
The plating powder obtained in the step (A3) was subjected to palladium ion reduction treatment by the same catalytic treatment as in the step (A1).
[0065]
(B2) Initial thin film forming step for forming the second layer
Using the 200 ml slurry obtained in the step (B1) and the initial thin film forming liquid (I-2) shown in Table 1, an initial thin film was formed on the first layer under the same conditions as in the step (A2). Formed. The load amount of the second aqueous suspension containing the plated powder thus obtained is 4.5 m. ² / Liter.
[0066]
(B3) Electroless plating process for forming the second layer
In the second aqueous suspension obtained in the step (B2), a second nickel ion-containing liquid (II-2) shown in Table 1 and 2.75 mol / liter sodium hypophosphite and 2. Two liquids of a second reducing agent-containing liquid consisting of 6 mol / liter sodium hydroxide were added. The addition conditions are the same as in step (A3). Generation of hydrogen was observed immediately after the addition of the two liquids, confirming the start of the plating reaction. Until the addition of the two liquids was completed, the concentration of the complexing agent in the second aqueous suspension was maintained at the concentration shown in Table 1. After the addition of the two liquids was completed, stirring was continued while maintaining the temperature at 75 ° C. until hydrogen bubbling stopped. The load after the addition of the two liquids is 3.1 m ² / Liter. Next, the second aqueous suspension was filtered, and the filtrate was washed with repulp three times and then dried with a vacuum dryer at 110 ° C. Thereby, the plating powder which has a nickel- phosphorus alloy plating film was obtained. When the cross section of the plating film of the obtained plating powder was observed with an SEM at an enlargement magnification of 50000 times, it was confirmed that the cross sections of the first layer and the second layer had different grain boundary orientation directions. . The thickness of each plating layer calculated from the added amount of nickel ions was as shown in Table 1.
[0067]
[Examples 5 to 8]
1 liter of electroless plating solution for gold plating was prepared. The electroless plating solution contains 0.027 mol / liter tetrasodium ethylenediaminetetraacetate, 0.038 mol / liter trisodium citrate and 0.01 mol / liter potassium gold cyanide, The pH was adjusted to 6. While stirring the electroless plating solution at a liquid temperature of 60 ° C., 33 g of each of the plating powders obtained in Examples 1 to 4 was added to the plating solution, and gold plating was performed for 20 minutes. Next, the liquid was filtered, and the filtrate was washed with repulp three times and then dried with a dryer at 110 ° C. As a result, a plating powder in which a gold electroless plating layer was formed on the nickel film was obtained. The thickness of the gold plating layer calculated from the added amount of gold ions was 0.025 μm.
[0068]
Example 9
(A1) Catalytic treatment step for forming the first layer
Spherical benzoguanamine-melamine-formalin resin (trade name “Eposter” manufactured by Nippon Shokubai Co., Ltd.) having an average particle size of 14 μm and a true specific gravity of 1.39 was used as the core powder. 30 g of that was made into 400 ml slurry and maintained at 60 ° C. Thereafter, reduction treatment of palladium ions was performed in the same manner as in the step (A1) of Example 1. However, in this reduction treatment, unlike the step (A1) of Example 1, no sensitization treatment with stannous chloride was performed.
[0069]
(A2) Initial thin film forming step for forming the first layer
Using the 200 ml slurry obtained in the step (A1) and the initial thin film forming liquid (I-1) shown in Table 1, an initial thin film was formed under the same conditions as in the step (A2) of Example 1. . However, the number of moles of sodium hypophosphite added was 0.042 moles. The load of aqueous suspension is 4.6m ² / Liter.
[0070]
(A3) Electroless plating process for forming the first layer
The first aqueous suspension obtained in the step (A2) contains the first nickel ion-containing liquid (II-1) shown in Table 1 and 2.75 mol / liter sodium hypophosphite. Two liquids of the first reducing agent-containing liquid consisting of 6 mol / liter of sodium hydroxide were added at an addition rate of 3 ml / min. The amount added was 205 ml each. Generation of hydrogen was observed immediately after the addition of the two liquids, confirming the start of the plating reaction. Until the addition of the two liquids was completed, the concentration of the organic carboxylic acid (complexing agent) in the first aqueous suspension was kept at the concentration shown in Table 1. The load after the addition of the two liquids is 3.8 m ² / Liter. After the addition of the two liquids was completed, stirring was continued while maintaining the temperature at 75 ° C. until hydrogen bubbling stopped. Next, the aqueous suspension was filtered to obtain a plating powder on which the first layer was formed.
[0071]
(B2) Initial thin film forming step for forming the second layer
Using the 200 ml slurry obtained in the step (A3) and the initial thin film forming solution (I-2) shown in Table 1, on the first layer under the same conditions as in the step (B2) of Example 1 An initial thin film was formed. However, the number of moles of sodium hypophosphite added was 0.042 moles. The load amount of the second aqueous suspension containing the plating powder thus obtained is 4.6 m. ² / Liter.
[0072]
(B3) Electroless plating process for forming the second layer
In the second aqueous suspension obtained in the step (B2), a second nickel ion-containing liquid (II-2) shown in Table 1 and 2.75 mol / liter sodium hypophosphite and 2. Two liquids of a second reducing agent-containing liquid consisting of 6 mol / liter sodium hydroxide were added. The addition conditions are the same as in step (A3). Generation of hydrogen was observed immediately after the addition of the two liquids, confirming the start of the plating reaction. Until the addition of the two liquids was completed, the concentration of the amine compound (complexing agent) in the second aqueous suspension was maintained at the concentration shown in Table 1. The load after the addition of the two liquids is 3.8 m ² / Liter. After the addition of the two liquids was completed, stirring was continued while maintaining the temperature at 75 ° C. until hydrogen bubbling stopped. Next, the second aqueous suspension was filtered, and the filtrate was washed with repulp three times and then dried with a vacuum dryer at 110 ° C. Thereby, the plating powder which has a nickel- phosphorus alloy plating film was obtained. When the cross section of the plating film of the obtained plating powder was observed with an SEM with an enlargement magnification of 50000 times, the plating film had a two-layer structure of a first layer and a second layer, as in FIG. Grain boundaries were not observed in the first layer, and the second layer had a columnar structure in the thickness direction. The thickness of each plating layer calculated from the added amount of nickel ions was as shown in Table 1.
[0073]
Example 10
A plating powder in which a gold electroless plating layer was formed on a nickel film was obtained in the same manner as in Example 5 except that 18.1 g of the plating powder obtained in Example 9 was used. The thickness of the gold plating layer calculated from the added amount of gold ions was 0.025 μm.
[0074]
Example 11
(A1) Catalytic treatment step for forming the first layer
A spherical acrylic resin having an average particle size of 10 μm and a true specific gravity of 1.33 was used as the core material powder. 20 g of that was made into 200 ml of slurry, and 200 ml of stannous chloride aqueous solution was added to the slurry. The concentration of this aqueous solution is 5 × 10 ^-3 Mol / liter. The mixture was stirred at room temperature for 5 minutes, and sensitization treatment was performed to adsorb tin ions on the surface of the core material powder. Subsequently, the aqueous solution was filtered and washed once with repulp water. Next, the core powder was made into 400 ml slurry and maintained at 60 ° C. Thereafter, reduction treatment of palladium ions was performed in the same manner as in the step (A1) of Example 1.
[0075]
(A2) Initial thin film forming step for forming the first layer
Using the 200 ml slurry obtained in the step (A1) and the initial thin film forming liquid (I-1) shown in Table 1, an initial thin film was formed under the same conditions as in the step (A2) of Example 1. . However, the number of moles of sodium hypophosphite added was 0.042 moles. The load of aqueous suspension is 4.5m ² / Liter.
[0076]
(A3) Electroless plating process for forming the first layer
The first aqueous suspension obtained in the step (A2), the first nickel ion-containing liquid (II-1) shown in Table 1, 2.75 mol / liter sodium hypophosphite, Electroless plating was performed under the same conditions as in the step (A3) of Example 9 using a first reducing agent-containing liquid composed of 2.6 mol / liter sodium hydroxide. However, the addition amount of the first nickel ion-containing liquid and the first reducing agent-containing liquid was 202 ml, respectively. The load after the addition of these two liquids is 3.8 m ² / Liter. The first aqueous suspension was filtered to obtain a plating powder on which the first plating layer was formed.
[0077]
(B2) Initial film forming step for forming the second layer
Using the 200 ml slurry obtained in the step (A3) and the initial thin film forming solution (I-2) shown in Table 1, on the first layer under the same conditions as in the step (B2) of Example 1 An initial thin film was formed. However, the number of moles of sodium hypophosphite added was 0.042 moles. The load amount of the second aqueous suspension containing the plated powder thus obtained is 4.5 m. ² / Liter.
[0078]
(B3) Electroless plating step for forming second plating layer
In the second aqueous suspension obtained in the step (B2), the second nickel ion-containing liquid (II-2) shown in Table 1 and 2.75 mol / liter sodium hypophosphite and 2 Two liquids of a second reducing agent-containing liquid consisting of 0.6 mol / liter sodium hydroxide were added. The addition conditions are the same as in step (A3). Generation of hydrogen was observed immediately after the addition of the two liquids, confirming the start of the plating reaction. Until the addition of the two liquids was completed, the concentration of the amine compound (complexing agent) in the second aqueous suspension was maintained at the concentration shown in Table 1. After the addition of the two liquids was completed, stirring was continued while maintaining the temperature at 75 ° C. until hydrogen bubbling stopped. Next, the second aqueous suspension was filtered, and the filtrate was washed with repulp three times and then dried with a vacuum dryer at 110 ° C. The load after the addition of the two liquids is 3.8 m ² / Liter. Thereby, the plating powder which has a nickel- phosphorus alloy plating film was obtained. When the cross section of the plating film of the obtained plating powder was observed with an SEM with an enlargement magnification of 50000 times, the plating film had a two-layer structure of a first layer and a second layer, as in FIG. Grain boundaries were not observed in the first layer, and the second layer had a columnar structure in the thickness direction. The thickness of each plating layer calculated from the added amount of nickel ions was as shown in Table 1.
[0079]
Example 12
A plating powder having a gold electroless plating layer formed on a nickel film was obtained in the same manner as in Example 5 except that 13.8 g of the plating powder obtained in Example 11 was used. The thickness of the gold plating layer calculated from the added amount of gold ions was 0.025 μm.
[0080]
[Comparative Example 1]
In this comparative example, a conventional electroless plating bath method was adopted. The steps up to the catalyst treatment step were the same as in Example 1. As electroless plating solution, 0.11 mol / liter nickel sulfate, 0.24 mol / liter sodium hypophosphite, 0.26 mol / liter sodium malate, 0.18 mol / liter sodium acetate and 2 × 10 ^-6 A solution containing mol / liter of lead acetate and having a pH adjusted to 5 was used. A 6 liter electroless plating solution was heated to 75 ° C. to build a bath, and a core material powder subjected to a catalyst treatment was put into the bath and dispersed by stirring to initiate a nickel reduction reaction. Using an automatic pH adjuster, the pH of the solution during the reduction reaction was maintained at 5 by adding a 5 mol / liter aqueous sodium hydroxide solution. When the reaction stopped halfway, a 2 mol / liter sodium hypophosphite aqueous solution was added little by little to continue the reaction. When the liquid no longer foamed even when sodium hypophosphite aqueous solution was added, all additions were stopped, the liquid was filtered, and the filtrate was washed with repulp three times and then dried with a vacuum dryer at 110 ° C. Thereby, the powder which has a nickel- phosphorus alloy plating film was obtained. When the cross section of the plating film of the obtained plating powder was observed with an SEM at an enlargement magnification of 50000 times, a lump-shaped crystal grain boundary was observed in the cross section in the thickness direction of the film as in FIG. Since this plating powder was manufactured by a conventional electroless plating method, a fine nickel decomposition product was mixed therein and could not be put to practical use.
[0081]
[Comparative Examples 2 and 3]
(A2) Initial thin film formation process
200 ml of the catalyst-treated core material powder obtained in the same manner as (A1) in Example 1 was added to the initial thin film forming solution (I-1) shown in Table 1 with stirring. To an aqueous suspension. The initial thin film forming liquid was heated to 75 ° C., and the liquid volume was 1.8 liters. Immediately after the slurry was introduced, hydrogen generation was observed, confirming the start of initial thin film formation. One minute later, 0.063 mol of sodium hypophosphite was added, and stirring was continued for another minute. The load of aqueous suspension is 4.5m ² / Liter.
[0082]
(A3) Electroless plating process
In the aqueous suspension obtained in the initial thin film formation step, the nickel ion-containing liquid (II-1) shown in Table 1 and 2.75 mol / liter sodium hypophosphite and 2.6 mol / liter hydroxylated Two reducing agent-containing liquids consisting of sodium were added at an addition rate of 7 ml / min. The amount added was 870 ml each. Generation of hydrogen was observed immediately after the addition of the two liquids, confirming the start of the plating reaction. Until the addition of the two liquids was completed, the concentration of the complexing agent having an amino group in the aqueous suspension was maintained at the concentration shown in Table 1. After the addition of the two liquids was completed, stirring was continued while maintaining the temperature at 75 ° C. until hydrogen bubbling stopped. The load after the addition of the two liquids is 2.4m ² / Liter. Subsequently, the aqueous suspension was filtered, and the filtrate was washed with repulp three times and then dried with a vacuum dryer at 110 ° C. Thereby, the plating powder which has a nickel- phosphorus alloy plating film was obtained. When the cross section of the plating film of the obtained plating powder was observed with an SEM at an enlargement magnification of 50000 times, a film having a single structure was obtained. The thickness of the plating film calculated from the amount of nickel ion added was 0.54 μm.
[0083]
[Comparative Examples 4 and 5]
A plating powder in which a gold electroless plating layer was formed on a nickel film was obtained in the same manner as in Example 5 except that 33 g of the plating powder obtained in Comparative Examples 2 and 3 was used. The thickness of the gold plating layer calculated from the added amount of gold ions was 0.025 μm.
[0084]
[Performance evaluation]
About the plating powder obtained in Examples 1-12 and Comparative Examples 1-5, the volume specific resistance value was measured with the following method, and the adhesiveness of the plating film was evaluated. The results are shown in Table 2 below.
[0085]
[Measurement of volume resistivity]
In a resin cylinder with an inner diameter of 10 mm standing vertically, 1.0 g of plating powder was put, and the electric resistance between the upper and lower electrodes was measured in a state where a load of 10 kg was applied to determine the volume resistivity value.
[0086]
[Evaluation of heat resistance of plating film]
The plating powder was stored in an oxidizing atmosphere at 200 ° C. for 24 hours, 48 hours, 72 hours, 96 hours, and 120 hours, respectively. A volume specific resistance value of the plated powder after storage was measured by the above-described method, and the resistance value was used as a measure of heat resistance.
[0087]
[Evaluation of adhesion of plating film]
The plating powder 2.2g and the zirconia bead 90g of diameter 1mm were put into a 100 ml mayonnaise bottle. Further, 10 ml of toluene was added to the mayonnaise bottle using a whole pipette. The inside of the mayonnaise bottle was stirred for 10 minutes at 400 rpm using a stirrer (three one motor). After the completion, the plating powder and the zirconia beads were separated, the plating powder was observed with an SEM, and the degree of peeling of the plating film was evaluated according to the following criteria.
○: Peeling of the plating film was not observed.
Δ: Some peeling of the plating film was observed.
X: Peeling of the plating film was observed.
[0088]
[Table 1]

[0089]
[Table 2]

[0090]
[Table 3]

[0091]
As is apparent from the results shown in Tables 2 and 3, the plating powders of the examples (product of the present invention) have sufficiently low electrical resistance, and even when stored at high temperatures for a long time, the increase in electrical resistance is small and heat resistance It turns out that the nature is high enough. On the other hand, although the plating powder of the comparative example has low electrical resistance, the electrical resistance increases due to storage for a long time and heat resistance is low, or the electrical resistance is low, but the plating film is easily peeled off. I understand that.
[0092]
【The invention's effect】
As described above in detail, according to the present invention, the adhesion between the plating film and the core material powder in the conductive electroless plating powder is improved, and the heat resistance of the conductive electroless plating powder is improved. Even when stored at high temperature for a long time, the increase in electrical resistance is small.
[Brief description of the drawings]
FIG. 1 is a scanning electron micrograph showing an example of a cross-section of a plating film in a first embodiment of a conductive electroless plating powder of the present invention.
FIG. 2 is a scanning electron micrograph showing an example of a cross section of a plating film in a second embodiment of the electroless electroless plating powder of the present invention.
FIG. 3 is a scanning electron micrograph showing an example of a cross section of a plating film of a conventional conductive electroless plating powder.

Claims (10)

In a conductive electroless plating powder in which a nickel film is formed on the surface of a core material particle by an electroless plating method, the nickel film is formed on the surface of the core material particle and the first layer. And a second layer formed adjacent to each other, and the orientation directions of the grain boundaries in the first layer and the second layer are different from each other. . One of the first layer and the second layer has a grain boundary in the cross section when the cross section in the thickness direction of the layer is observed with a scanning electron microscope at a magnification of up to 100000 times. The conductive electroless plating powder according to claim 1, wherein the other layer is a layer in which the grain boundary in the layer is oriented mainly in the thickness direction of the layer. The first layer is a layer in which no crystal grain boundary is observed in the cross section when the cross section in the thickness direction of the layer is observed with a scanning electron microscope at a magnification of up to 100000 times. The conductive electroless plating powder according to claim 2, wherein the grain boundary in the layer is a layer in which grain boundaries in the layer are oriented mainly in a thickness direction of the layer. The first layer is a layer in which grain boundaries in the layer are oriented mainly in the thickness direction of the layer, and the second layer has a cross section in the thickness direction of the layer, which is a scanning electron. The electroless electroless plating powder according to claim 2, wherein the electroless plating powder is a layer in which no crystal grain boundary is observed in the cross section when observed under a magnification of up to 100,000 times with a microscope. The electroless electroless plating powder according to claim 1, wherein a gold electroless plating layer is formed on the outermost surface. A method for producing a conductive electroless plating powder according to claim 3,
After capturing the noble metal ions on the core material powder having the ability to capture noble metal ions or imparting the ability to capture noble metal ions by surface treatment, this is reduced and supported on the surface of the core material powder. Then, the core powder is dispersed in an aqueous medium containing a complexing agent composed of an organic carboxylic acid or a salt thereof to prepare a first aqueous suspension, which has the same kind as the complexing agent. Two liquids, a first nickel ion-containing liquid containing a complexing agent and a first reducing agent-containing liquid, are added individually and simultaneously to cause an electroless plating reaction to form a first layer. The core material powder in which the first layer is formed is dispersed in an aqueous medium containing a complexing agent composed of an amine compound to prepare a second aqueous suspension, and the second aqueous suspension is A second nickel ion-containing liquid containing a complexing agent of the same type as the complexing agent contained therein, and Conductive electroless plating powder characterized in that two liquids of two reducing agent-containing liquids are added individually and simultaneously to cause an electroless plating reaction to form a second layer on the first layer. Manufacturing method. In the process of adding the first nickel ion-containing liquid and the first reducing agent-containing liquid to the first aqueous suspension, the concentration of the complexing agent in the first aqueous suspension is 0. The addition amount of the first nickel ion-containing liquid and the first reducing agent-containing liquid, or the complex in the first aqueous suspension so as to be maintained in the range of 0.005 to 6 mol / liter. Adjusting the initial concentration of the agent or the concentration of the complexing agent in the first nickel ion-containing liquid, and adding the second nickel ion-containing liquid and the second reduction to the second aqueous suspension. In the process of adding the agent-containing liquid, the concentration of the complexing agent in the second aqueous suspension is maintained in the range of 0.003 to 10 mol / liter. Liquid and the amount of the second reducing agent-containing liquid added, or the initial amount of the complexing agent in the second aqueous suspension Degree or method for producing a conductive electrolessly plated powder according to claim 6, wherein adjusting the concentration of the complexing agent of the second nickel ion-containing solution. A method for producing a conductive electroless plating powder according to claim 4,
After capturing the noble metal ions on the core material powder having the ability to capture noble metal ions or imparting the ability to capture noble metal ions by surface treatment, this is reduced and supported on the surface of the core material powder. Then, the core powder is dispersed in an aqueous medium containing a complexing agent composed of an amine compound to prepare a first aqueous suspension, to which a complexing agent of the same type as the complexing agent is added. Two liquids, a first nickel ion-containing liquid and a first reducing agent-containing liquid, are added individually and simultaneously to cause an electroless plating reaction to form a first layer, and then the first layer The formed core material powder is dispersed in an aqueous medium containing a complexing agent composed of an organic carboxylic acid or a salt thereof to prepare a second aqueous suspension, and the second aqueous suspension is A second nickel ion-containing liquid containing a complexing agent of the same type as the complexing agent contained therein, and Conductive electroless plating powder characterized in that two liquids of two reducing agent-containing liquids are added individually and simultaneously to cause an electroless plating reaction to form a second layer on the first layer. Manufacturing method. In the process of adding the first nickel ion-containing liquid and the first reducing agent-containing liquid to the first aqueous suspension, the concentration of the complexing agent in the first aqueous suspension is 0. The amount of the first nickel ion-containing liquid and the first reducing agent-containing liquid added, or the complex in the first aqueous suspension so as to be maintained in the range of 0.003 to 10 mol / liter. Adjusting the initial concentration of the agent or the concentration of the complexing agent in the first nickel ion-containing liquid, and adding the second nickel ion-containing liquid and the second reduction to the second aqueous suspension. In the process of adding the agent-containing liquid, the concentration of the complexing agent in the second aqueous suspension is maintained in the range of 0.005 to 6 mol / liter. Liquid and the amount of the second reducing agent-containing liquid added, or the initial amount of the complexing agent in the second aqueous suspension Degree or method for producing a conductive electrolessly plated powder according to claim 8, wherein adjusting the concentration of the complexing agent of the second nickel ion-containing solution. The conductive electroless plating according to any one of claims 6 to 9, wherein the complexing agent comprising the organic carboxylic acid or a salt thereof is tartaric acid or a salt thereof, and the complexing agent comprising the amine compound is glycine or ethylenediamine. Powder manufacturing method.

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