JP2001131756A - Method of electroless plating surface of porous body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of electroless plating, which is capable of easily forming a plated film only on the surface of a porous body having many pores. SOLUTION: The surface of a porous body 1 having many pores 10 can be plated by this electroless plating method, which is comprised of the filling process of heating a filling material 2 to a temperature of not less than the melting point, then filling the molten filling material 2 into the fine pores 10 of the porous body 1 and solidifying the molten filling material, the treatment process for converting into a catalyst of subjecting the surface of the porous body 1 to sensitization treatment and activation treatment, the filling material removing process of removing the filling material 2 filled in the porous pores 10 and the plating process of dipping the porous body 1 into a plating bath and forming a plated film 4 on the surface of the porous body 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for performing electroless plating only on the surface of a porous body having pores.

[0002]

2. Description of the Related Art In a porous body having a large number of pores, it is sometimes desired to maintain the pores as they are and form a metal coating layer only on the surface. For example, an extremely excellent particulate filter (DPF) for a diesel engine can be formed by forming a metal coating layer only on the surface of a partition wall of a honeycomb structure described later and using this as an electrode.

[0003]

As a method of forming a metal coating layer on an insulator, electroless plating is widely used. However, electroless plating is only applied to the surface of a porous body. Not enough technology has been established. That is, when a normal electroless plating method is applied to a porous body, plating is performed not only on the surface of the porous body but also inside the pores. Therefore, it is not possible to utilize the characteristics of the pores maintaining the insulating state.

On the other hand, in JP-A-6-296876, a spot-shaped non-conductive portion is formed on the through hole wall surface of a porous honeycomb structure, and then electroplating is performed on the porous through hole wall surface. A method for forming a metal-coated honeycomb structure having a microporous metal coating layer is shown. However, in this method, it is difficult to cover all the through-holes on the honeycomb surface with non-conductive particles, and it is possible to avoid the presence of plating inside the through-holes (pores). Absent.

The present invention has been made in view of such conventional problems, and an object of the present invention is to provide an electroless plating method capable of easily forming a plating film only on the surface of a porous body having a large number of pores. Things.

[0006]

According to the first aspect of the present invention, there is provided a method for performing electroless plating on a surface of a porous body having a large number of pores,
A filling step of filling the pores of the porous body with the filler liquefied by heating to a temperature equal to or higher than the melting point, and a sensitizing treatment and an activating treatment on the surface of the porous body after the filler is solidified. Performing a catalyzing treatment step, and then performing a filler removing step of removing the filler filled in the pores, immersing the porous body in a plating bath, and plating the surface with a plating film. A method of electroless plating on the surface of a porous body, which comprises performing a plating step of forming

The most remarkable point in the present invention is that the above-mentioned filling step is performed, the above-mentioned catalyzing treatment step is performed, and then the above-mentioned filler removing step is performed, and then the above-mentioned plating step is performed.

In the filling step, a filler having a property of being liquefied by heating and solidified by cooling is used. Then, the filler is heated and liquefied to fill the pores of the porous body. As a filling method, for example, there is a method of immersing a porous body in a bath filled with the filler so that the filler enters the pores.

Next, after the filler penetrated into the pores is solidified by cooling, the above-mentioned catalyzing treatment step is performed. This catalyzing treatment step is performed in the same manner as the conventionally known catalyzing treatment method in the electroless plating method. As an example of a specific method, a porous body is immersed in a tin chloride solution and subjected to a sensitization treatment for adsorbing Sn ²⁺ on its surface, and further immersed in a palladium chloride solution to make Pd (catalyst fine particles) porous. The above-mentioned catalyzing step can be carried out by performing an activating treatment for precipitating on the surface of the body.

The above-described sensitizing and activating processes can be performed in one step. As the solution used for the sensitizing treatment and the activating treatment, those other than those described above can be used, and various metals other than Pd can be used as the catalyst fine particles. In the present invention, the degreasing step using an alkaline solution, which is usually performed in the conventional electroless plating method, can be omitted. In this case, the possibility that the filled filler is removed by the degreasing step can be eliminated.

Next, a filler removing step of removing the filler filling the pores of the porous body is performed. As a method of removing the filler, a method of liquefying the filler by applying heat and flowing it out, or a method of heating and burning out the filler can be employed.

Next, a plating step of immersing the porous body in a plating bath to form a plating film on its surface is performed. This plating step is the same as the method in the conventionally known electroless plating method. For example, when a Cu film is formed as a plating film, the above-described porous body is immersed in a plating bath mainly composed of copper sulfate.

Next, the function and effect of the present invention will be described.
In the present invention, the catalyzing treatment step is performed after the filling step. Thereby, catalyst fine particles (Pd or Au, Ag,
Pt) can be deposited only on the surface of the porous body without penetrating into the pores. Therefore, in the subsequent plating step, a plating film can be formed only on the surface of the porous body where the catalyst fine particles exist.

As described above, in the present invention, a plating film can be easily formed only on the surface of a porous body by adding the above-mentioned filling step and filler removing step to a conventional electroless plating method.

Next, a second aspect of the present invention is a method for performing electroless plating on the surface of a porous body having a large number of pores,
A filling step of filling the pores of the porous body with the filler liquefied by heating to a temperature equal to or higher than the melting point, and a sensitizing treatment and an activating treatment on the surface of the porous body after the filler is solidified. Performing a catalyzing treatment step, and then performing a plating step of immersing the porous body in a plating bath to form a plating film on the surface thereof, and removing the filler filling the pores. A method of electroless plating on the surface of a porous body, characterized by performing a filler removing step.

According to the present invention, the order of the filler removing step and the plating step is reversed from that of the first aspect. In this case, the same operation and effect as described above can be obtained.

Next, before performing the filling step, a masking step of applying a masking material having a viscosity that does not penetrate into the pores is performed on the surface of the porous body. After performing the filling step, it is preferable to perform a mask removing step of removing the masking material.

In this case, the filling step can be performed in a state where only the surface of the porous body is covered with the masking material, and the adhesion of the filler to the surface of the porous body can be reliably prevented. . Therefore, in the catalyzing treatment step after the subsequent mask removing step, the catalyzed particles can be very uniformly deposited on the porous material surface, and the subsequent plating film can be formed uniformly and firmly. Can be.

As the above masking material, there are both a water-soluble type and a type soluble in an organic solvent. As the water-soluble type, for example, a methylcellulose-based binder, starch paste, arabic rubber paste, or the like can be used. Examples of the type that can be dissolved in an organic solvent include commercially available synthetic rubber-based adhesives (synthetic rubbers such as chloroprene rubber and styrene-butadiene diluted with a solvent) and cellulose-based adhesives.

Further, it is preferable that the filler has a melting point in the range of 50 to 300 ° C. If the melting point is lower than 50 ° C., the filler may be melted in a step after the filling step. On the other hand, if it exceeds 300 ° C., it becomes difficult to remove the filler in the filler removing step. There is a problem.

In the case where a filler removing step is performed before the plating step (the invention of claim 1), it is most preferable to use a filler having a melting point of 50 to 100 ° C. In this case, in the filler removing step, the filler can be easily removed by washing with hot water or the like.

In the case where the filler removing step is performed after the plating step (the invention of claim 2), it is preferable that the melting point of the filler is higher than the processing temperature in the plating step. This is because when the melting point of the filler is significantly lower than the plating temperature, most of the filler melts out, and a plating film is formed inside the wall due to diffusion of the catalyst fine particles adhering to the filler surface described later. It is possible that On the other hand, when the processing temperature in the plating step is close to the melting point of the filler, the filler near the surface may be melted, and a part of the melted filler may promote plating. That is, the catalyst fine particles adhering to the filler surface may flow out into the plating solution, and this may become a nucleus for forming a plating film on the porous body surface. Therefore, it is preferable that the processing temperature of the plating step and the melting point of the filler are close to each other.

When the masking step is performed, the melting point of the filler is preferably set to 50 to 100 ° C. This is because the work in the filler removing step is easily performed as in the above. However, when the masking material is removed by heat treatment in the mask removal step, the melting point of the filler needs to be higher than the treatment temperature. When the masking material is removed by a solvent or the like, it is necessary to select a filler that does not dissolve in the solvent.

Further, as in the invention of claim 5, the filler is preferably paraffin. In this case,
The above-described filling step and filler removing step can be easily performed.

According to a sixth aspect of the present invention, in the filling step, the porous body is immersed in a bath of the filler liquefied by heating to a temperature higher than the melting point of the filler by at least 20 ° C. Then, it is preferable to remove the filler from the bath of the filler, and drop and remove extra filler attached thereto. The heating temperature of the filler is its melting point + 20 ° C
If it is lower than the above range, sufficient fluidity may not be obtained when the porous body is pulled up from the above-mentioned filler bath to remove excess filler. Therefore, there is a problem that a large amount of excess filler remains on the surface of the porous body, making it difficult to perform the subsequent catalyzing treatment process normally.

Further, as in the invention of claim 7, the porous body may be a honeycomb structure in which partition walls having a large number of pores are provided in a honeycomb shape. In this case, for example, an excellent particulate filter of a diesel engine can be easily configured.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment A method for electroless plating a porous body surface according to an embodiment of the present invention will be described with reference to FIGS. In the present example, a honeycomb structure made of cordierite was used as the porous body 1. Then, five examples (E1 to E5) in which the porous body was subjected to electroless plating by the method according to the present invention and two comparative examples (C1, C2) were performed. The performance was evaluated by measuring the plating adhesion rate and the electrical resistance value. Note that a paraffin as a filler described later used had a melting point of about 70 ° C.

(Embodiment E1) In this embodiment E1,
As shown in FIG. 1, the filling step (a) and the catalyzing step (b) are performed, then the filler removing step (c) is performed, and then the electroless plating is performed by the plating step (d). did. Such a method of performing the filler removing step before the plating step is referred to as a “pre-cutting method” in this example.

The steps in Example E1 will be described more specifically with reference to FIG. First, in the filling step, paraffin was used as a filler and liquefied by heating it to 90 ° C. Then, the porous body 1 made of the honeycomb structure was immersed in a paraffin bath provided with paraffin in a bathtub. Next, the porous body was taken out of the paraffin bath, and extra paraffin attached was dropped and removed. As a result, as shown in FIG. 1A, the pores 10 of the porous body 1 were filled with the filler 2 made of paraffin.

Next, in the catalyzing treatment step, first, an alkali degreasing step was performed at room temperature using an aqueous solution containing sodium carbonate and sodium hydroxide as main components, followed by a sensitizing treatment and a catalyzing treatment. The sensitization treatment was performed by immersing the porous body 1 in a sensitizer containing tin chloride solution (manufactured by Okuno Pharmaceutical) for 3 minutes. The catalyzing treatment was performed by immersing the porous body 1 in an activator (manufactured by Okuno Pharmaceutical) containing palladium chloride for 1 minute.
In this example, the sensitization process and the catalysis process were performed again. As a result, as shown in FIG.
The catalyst fine particles 3 made of Pd were deposited on the surface of.

Next, the filler removal step was performed by hot water washing. That is, the porous body 1 was immersed in a bath containing boiling water to dissolve the filler 2. As a result, as shown in FIG. 1 (c), most of the filler 2 was removed. However,
As shown in the figure, the filler 2 was not completely removed, and a part remained in the pores 10.

Next, the plating step was performed by immersing the porous body 1 in a plating bath filled with an electroless Ni-P plating solution (manufactured by Okuno Pharmaceutical Co., Ltd.) heated to 80 ° C. for 8 minutes. As a result, a Ni plating film 4 was formed on the surface of the porous body 1 as shown in FIG.

Next, in this example, a heat treatment step of maintaining the temperature at 500 ° C. for 4 hours was performed. Thus, as shown in FIG. 1E, the filler 2 slightly remaining in the pores 10 could be burned off. Then, as shown in the figure, a porous body 1 having the plating film 4 formed only on the surface was obtained.

Example E2 In Example E2, the heating temperature of paraffin as the filler 2 was changed to 110 ° C. in the filling step in Example E1. Others were the same as Example E1.

Example E3 In Example E3, the heating temperature of paraffin as the filler 2 was changed to 150 ° C. in the filling step of Example E1. Others were the same as Example E1.

Example E4 In Example E4, as shown in FIG. 2, a filling step and a catalyzing step were performed.
Next, after performing the above-described plating step, electroless plating was performed by a method of performing a filler removing step. The method in which the filler removing step is performed after the plating step in this manner is referred to as a “post punching method” in this example.

The steps in Example E4 will be described more specifically with reference to FIG. First, the filling step was performed basically in the same manner as in Example E1, and only the heating temperature of paraffin was 110 ° C. as in Example E2. As a result, as shown in FIG. 2A, the pores 10 of the porous body 1 were filled with the filler 2 made of paraffin.

Next, the catalyzing step was performed in the same manner as in Example E1. As a result, as shown in FIG. 2B, the fine catalyst particles 3 made of Pd are
Was precipitated. Next, a plating step was performed before the filler removing step. The processing conditions in the plating step were the same as in Example E1. As a result, as shown in FIG. 2C, the plating film 4 was formed on the surface of the porous body 1 while the filler 2 in the pores 10 was left as it was.

Next, a heat treatment step of maintaining the temperature at 500 ° C. for 4 hours was performed. This is the filler removal step in this embodiment. As a result, as shown in FIG.
Filler 2 remaining in 0 could be burned off. Then, as shown in FIG.
Was obtained.

(Embodiment E5) In this embodiment E5,
A masking step and a mask removing step (masking method) were performed in addition to the above pre-cutting method. Specifically, as shown in FIG. 3A, a mask step was performed before the filling step. As the masking material 5, methyl cellulose as a water-soluble binder was used. That is, a solution obtained by dissolving the binder in water was injected and applied to the inside and the outer wall of the honeycomb cell, whereby the surface was covered with the masking material 5. At this time, the outer peripheral surface and the end surface of the honeycomb were not covered with the masking material 5.

Next, a filling step was performed in the same manner as in Example E1 (E2). The heating temperature of the paraffin was determined in Example E.
110 ° C. in the same manner as in Example 2. As a result, as shown in FIG. 3B, the pores 10 of the porous body 1 were filled with the filler 2 made of paraffin. In this case, the infiltration of the filler 2 into the pores 10 is performed through the path from the outer peripheral surface and the end face, and sufficient filling is performed regardless of the presence of the masking material 5.

Next, a mask removing step was performed before the catalyzing step was performed. Specifically, since the masking material 5 is water-soluble, it was removed by washing with water. Thus, as shown in FIG. 3C, the masking material 5 covering the surface of the porous body 1 was removed cleanly.

Next, a catalyzing treatment step was performed in the same manner as in Example E1. The conditions were the same as in Example E1. As a result, as shown in FIG. 3D, catalyst fine particles 3 made of Pd were deposited on the surface of the porous body 1. Next, a filler removing step was performed in the same manner as in Example E1. As a result, FIG.
Most of the filler 2 was removed as shown in FIG.

Next, a plating step was performed in the same manner as in Example E1. As a result, as shown in FIG.
A Ni plating film 4 was formed on the surface of. Next, as in Example E1, a heat treatment step of maintaining the temperature at 500 ° C. for 4 hours was performed. As a result, as shown in FIG. 3 (g), the filler 2 slightly remaining in the pores 10 was burned off.

Comparative Example C1 In Comparative Example C1, the respective steps of the electroless plating method were within the scope of the present invention, but the heating temperature when the filler 2 was particularly paraffin was lowered to 70 ° C. This is a comparative example. Others are Example E1
Same as. The one obtained by the present comparative example C1 had almost no plating film formed on the surface of the porous body 1 (not shown).

(Comparative Example C2) This Comparative Example C2 is a comparative example of Example E.
1 omits a filling step and a filler removing step. In the one obtained in Comparative Example C2, the plating film was formed not only on the surface of the porous body but also on the inner surface of the pores 10.

(Measurement of Plating Adhesion Rate) Next, in this example, the plating adhesion rate was measured for the porous bodies obtained by the above five examples and two comparative examples. Specifically, the difference between the weight before and after the electroless plating was applied to the porous body 1 was defined as the amount of plating, and the value obtained by dividing the weight by the weight of the porous body 1 before the electroless plating was defined as the plating adhesion rate.

The measurement results are shown in Table 1 and FIG. FIG.
This shows only Examples E1 to E3 and Comparative Example C1, in which the horizontal axis represents the temperature of paraffin (° C.), and the vertical axis represents the plating adhesion rate (wt%) and the electric resistance value (Ω) described later. Things.

As can be seen from Table 1 and FIG. 4, from the comparison between Examples E1 to E3 and Comparative Example C1, when paraffin was used as the filler 2, the plating temperature increased as the heating temperature increased in this filling step. It can be seen that the rate increases. And 90 ° C. higher than the melting point of paraffin.
It was found that when the temperature was higher than or equal to ° C., an almost satisfactory plating adhesion rate was obtained. Also, from the comparison between Example E2 and Example E4, it is understood that the difference between the above-described pre-punching method and the post-punching method has little effect on the plating adhesion rate. In Comparative Example C2, the plating film was formed even in the pores 10,
Very high plating adhesion was shown.

(Measurement of Electric Resistance Value) Next, in the present example, the electric resistance value was measured for the porous bodies obtained in the above five examples and two comparative examples. Specifically, the electric resistance between both ends of the same cell was measured by a two-terminal method using a tester. Table 1 and FIG. 4 show the measurement results.
Shown in

As can be seen from Table 1 and FIG. 4, a comparison between Examples E1 to E3 and Comparative Example C1 shows that when paraffin is filled near the melting point, the paraffin covers the surface as well, and the plating adhesion rate is low. It was found to be significantly lower. Therefore, it was found that the paraffin filling is preferably performed at a temperature higher than the melting point by 20 ° C. or more, in this case, at a temperature of 90 ° C. or more.

[0052]

[Table 1]

[0053]

As described above, according to the present invention, it is possible to provide an electroless plating method capable of easily forming a plating film only on the surface of a porous body having many pores.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing the processing steps of Example E1 in the embodiment.

FIG. 2 is an explanatory view showing a processing step of Example E4 in the embodiment.

FIG. 3 is an explanatory view showing a processing step of Example E5 in the embodiment.

FIG. 4 is an explanatory diagram showing a relationship between a paraffin temperature, a plating adhesion rate, and an electric resistance value in the embodiment.

[Explanation of symbols]

 1. . . 9. porous body, . . Pores, 2. . . Filler, 3. . . Catalyst fine particles, 4. . . 4. plating film; . . Masking material,

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C04B 41/88 C04B 41/88 S C23C 18/20 C23C 18/20 Z (72) Inventor Noriko Uojima Aichi No. 41, Toyota Chuo Research Institute, Nagakute-machi, Aichi-gun, Toyoda Central Research Institute Co., Ltd. (72) Inventor Nobuo Kamiya 41, Toyota Chuo Research Institute, Inc. Inventor Toshio Jintori 41-cho, Chuchu-ji, Yokomichi, Nagakute-cho, Aichi-gun, Aichi Prefecture F-term in Toyota Central R & D Laboratories Co., Ltd. FA03 FB14 FB17 FB19 FB20 4K022 AA04 AA37 BA14 BA16 BA35 CA05 CA06 CA07 CA08 CA18 CA20 CA21 DA01 EA01

Claims (7)

[Claims] 1. A method for applying electroless plating to a surface of a porous body having a large number of pores, wherein a filler liquefied by heating to a temperature higher than the melting point is filled in the pores of the porous body. And a catalyzing step of subjecting the surface of the porous body to a sensitization treatment and an activation treatment after solidifying the filler, and then removing the filler filled in the pores. An electroless plating method for a surface of a porous body, which comprises a step of immersing the porous body in a plating bath and forming a plating film on the surface after performing a filler removing step of removing the filler. 2. A method for performing electroless plating on a surface of a porous body having a large number of pores, wherein a filler liquefied by heating to a temperature higher than the melting point is filled in the pores of the porous body. And a catalyzing step of subjecting the surface of the porous body to a sensitizing treatment and an activating treatment after solidifying the filler, and then immersing the porous body in a plating bath so as to cover the surface of the porous body. An electroless plating method for a porous body surface, comprising: performing a plating step of forming a plating film; and then performing a filler removing step of removing the filler filling the pores. 3. The masking step according to claim 1, wherein a masking step of applying a masking material having a viscosity that does not penetrate into the pores is performed on the surface of the porous body before performing the filling step. Performing a step of removing a mask for removing the masking material after the step (a). 4. The method according to claim 1, wherein:
A method for electroless plating a porous material surface, wherein the filler has a melting point in the range of 50 to 300 ° C. 5. The method according to claim 1, wherein:
A method for electrolessly plating a porous body surface, wherein the filler is paraffin. 6. The method according to claim 1, wherein:
In the filling step, the porous body is immersed in a bath of the filler liquefied by heating to a temperature higher than the melting point of the filler by 20 ° C. or more, and then the porous body is pulled out of the bath of the filler and extraly added. An electroless plating method on a surface of a porous body, which is performed by dropping and removing an attached filler. 7. The method according to claim 1, wherein:
An electroless plating method on a surface of a porous body, wherein the porous body is a honeycomb structure in which partition walls having a large number of pores are provided in a honeycomb shape.