JP4012968B2 - Electroless plating method and product on smooth substrate - Google Patents

Description

  The present invention relates to an electroless plating method and a product on a smooth substrate.

In the method of electroless plating on a ceramic substrate, as a pretreatment for performing electroless plating, the ceramic substrate is treated with a silane coupling solution to perform a silane coupling treatment, and the ceramic substrate further contains palladium chloride or the like. It is known that an electroless plating film having good adhesion (for example, about 9 Kgfmm ⁻² (about 26 MPa)) can be formed by treating the plating catalyst solution and performing the plating catalyst treatment step ( For example, refer nonpatent literature 1.).

  By the way, in recent years, due to the development of the electronics industry, there is a demand for higher quality in various electronic devices that support this. For this reason, it is required to use a substrate (smooth substrate) having a smoother surface as various substrates used in these various electronic devices. As a result, an electroless plating method capable of forming an electroless plating film having good adhesion even on such a smooth substrate has become necessary.

However, when electroless plating is applied to a smooth substrate, the surface of the substrate does not have unevenness that exhibits an anchor effect, so the adhesion of the formed electroless plating film is low. For this reason, even with the electroless plating method described in Non-Patent Document 1 described above, there is a problem that it is not easy to form an electroless plating film on a smooth substrate with good adhesion.
Research Results Report, Research Center for Area Development, University of Yamanashi 1998 No. 6, pp. 55-60 “Basic research on advanced precision plating technology on ceramics”

  Then, this invention was made in order to solve the above-mentioned problem, and it aims at providing the electroless-plating method which can form the electroless-plating film which has favorable adhesiveness also in a smooth substrate. To do.

  As a result of intensive efforts to achieve the above-mentioned object, the present inventor performed a coupling treatment using a coupling solution having a concentration lower than that of a conventional substrate as a pretreatment for performing electroless plating, thereby obtaining a smooth substrate. The inventors have found that it is possible to form an electroless plating film having good adhesion, and have completed the present invention.

  That is, the method of electroless plating on a smooth substrate according to the present invention includes a coupling treatment step in which a smoothing substrate is contacted with a coupling solution containing a coupling agent, and a plating catalyst solution containing a plating catalyst on the smooth substrate. In the electroless plating method for a smooth substrate including a plating catalyst treatment step for contact and an electroless plating step for performing electroless plating on the smooth substrate in this order, the coupling solution is 0.001 to 0.00. It contains 3% by volume of a coupling agent.

For this reason, according to the electroless plating method on the smooth substrate according to the present invention, the coupling agent is bonded to the smooth substrate in the coupling treatment step. In the plating catalyst treatment step, the plating catalyst is supported on the coupling agent bonded to the smooth substrate. In the electroless plating step, the electroless plating reaction is started by the supported plating catalyst to form an electroless plating film.
At this time, in the coupling treatment step, a coupling solution having a concentration of 0.001 to 0.3% by volume, which is considerably lower than the conventional one, is used. To do.

By the way, when the coupling agent is bonded to the smooth substrate as a multimolecular film, the multimolecular film has a portion having a low binding force (bonding portion between coupling agent molecules). The bond is broken, and as a result, the electroless plating film is easily peeled off from the smooth substrate. That is, the adhesion of electroless plating is weak.
On the other hand, according to the electroless plating method on the smooth substrate according to the present invention, this monomolecular film does not have a portion having a small binding force, so that the coupling agent molecule itself is destroyed even when an external force is applied. It is speculated that the monomolecular film will not be destroyed until this is done. For this reason, it is estimated that the electroless plating film does not easily peel off from the smooth substrate, and as a result, good adhesion is exhibited.
That is, according to the electroless plating method on the smooth substrate according to the present invention, it is possible to form an electroless plating film having good adhesion even on the smooth substrate.

  In the electroless plating method on the smooth substrate according to the present invention, the concentration of the coupling solution is set to 0.3% by volume or less. This is because when the concentration of the coupling solution exceeds 0.3% by volume, formation of a polymolecular film by polymerization of coupling agents begins, and the adhesion of the formed electroless plating film may decrease. It is. From this viewpoint, the concentration of the coupling solution is preferably 0.1% by volume or less, and more preferably 0.075% by volume or less.

  In the electroless plating method on the smooth substrate according to the present invention, the concentration of the coupling solution is set to 0.001% by volume or more. This is because when the concentration of the coupling solution is less than 0.001% by volume, the time required for the coupling process becomes longer and the productivity may decrease, and the film formation of the coupling agent becomes non-uniform and electroless This is because uneven plating may occur. From that viewpoint, the concentration of the coupling solution is preferably 0.01% by volume or more, and more preferably 0.02% by volume or more.

  In the electroless plating method on the smooth substrate according to the present invention, it is preferable to adopt the coupling treatment conditions so that the coverage of the monomolecular film on the smooth substrate is 50% or more. This is because when the coverage is less than 50%, the amount of the plating catalyst supported on the smooth substrate becomes too small in the plating catalyst treatment step, and the electroless plating formation reaction becomes slow, or the electroless plating film This is because there is a case where the film is formed unevenly.

In the electroless plating method on the smooth substrate according to the present invention, a silane coupling agent and a titanium coupling agent can be preferably used as the coupling agent. Of these, a silane coupling agent can be more preferably used.
As the silane coupling agent, a silane coupling agent having an amino group at the terminal, among them, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyl Trimethoxysilane, N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane, N, N-bis [3- (trimethoxysilyl) propyl] ethylenediamine, p- [N- (2-aminoethyl) amino Methyl] phenethyltrimethoxysilane and the like can be preferably used.

In the electroless plating method on the smooth substrate according to the present invention, the method of bringing the coupling solution into contact with the smooth substrate in the coupling treatment step is preferably performed by immersing the smooth substrate in the coupling solution. Thereby, a uniform coupling process can be performed easily.
However, the electroless plating method for the smooth substrate according to the present invention is not limited to this, and the coupling solution can be brought into contact with the smooth substrate by, for example, applying the coupling solution to the smooth substrate. .

In the electroless plating method on the smooth substrate according to the present invention, the time for bringing the coupling solution into contact with the smooth substrate in the coupling treatment step includes the type of coupling agent, the concentration of the coupling solution, the treatment temperature, and the contact temperature. Depending on the method and the like, the time may be about 2 to 30 minutes. This is because if this time is shortened, uniform coupling processing may not be performed, and if this time is long, productivity may be reduced.
In addition, when the density | concentration of a coupling solution is thin, it is also preferable to set it as 30 minutes or more.

  In the electroless plating method on the smooth substrate according to the present invention, it is preferable to use a mixed solvent of water and an organic solvent as the solvent containing the coupling agent. In this case, it is more preferable to use a mixed solvent of water and alcohol, and it is more preferable to use a mixed solvent of water and ethanol. As the ratio of water and ethanol, when the total volume of the solvent is 100% and the conditions are such that the ethanol volume is 20% or less, good adhesion can be obtained.

  In the method of electroless plating on a smooth substrate according to the present invention, the measurement of adhesion strength can be performed using a thin film adhesion tester, or can be performed according to a JIS standard tape test method. Among these, when evaluating the electroless-plating film | membrane which uses an electronic device, the former is especially preferable among these.

  In the electroless plating method on the smooth substrate according to the present invention, various substrates can be used depending on the application. For example, in the case of non-magnetic undercoating of a glass substrate for magnetic disks or in the case of soft magnetic undercoating of a glass substrate for perpendicular magnetic recording, a precision polished ceramic substrate is used in the case of forming a wiring circuit on a ceramic substrate. In the case of forming a wiring circuit on an insulating thin film of an integrated circuit, a substrate on which an insulating thin film is formed, and in the case of forming a blind electrode of a SAW filter, a piezoelectric substrate or the like can be preferably used.

In the electroless plating method on the smooth substrate according to the present invention, it is preferable to use a smooth substrate having an average surface roughness Ra of 1.0 nm or less as the smooth substrate.
By adopting such a method, it becomes possible to manufacture a high-quality electronic device as required in the electronics industry.

  In the electroless plating method on the smooth substrate according to the present invention, the average surface roughness Ra of the smooth substrate is set to 1.0 nm or less when the average surface roughness Ra is set to a value exceeding 1.0 nm. This is because the performance (for example, recording density, holding power, wiring width, frequency characteristics, etc.) of the manufactured electronic device may be lower than a predetermined value. From this viewpoint, the average surface roughness Ra of the smooth substrate is preferably 0.5 nm or less, and more preferably 0.3 nm or less.

  In the electroless plating method for a smooth substrate according to the present invention, the average surface roughness Ra can be measured using a commercially available surface roughness meter.

  The electroless plating method for a smooth substrate according to the present invention aims to form an electroless plating film having good adhesion even on a smooth substrate. Is preferably not subjected to a treatment such as a hydrofluoric acid treatment or an alkali treatment which roughens the substrate surface and increases the average surface roughness Ra.

In the electroless plating method on the smooth substrate according to the present invention, the plating catalyst solution used in the plating catalyst treatment step is preferably a solution containing palladium and gold.
By setting it as such a method, the adhesiveness of electroless plating can be improved.

In that case, it is preferable to select the ratio of gold and palladium so that the numerical value of the ratio of palladium to the total amount of palladium and gold expressed in terms of the atomic ratio is 0.25 to 0.70.
In this case, a palladium compound such as palladium chloride (PdCl ₂ ) or sodium palladium (II) chloride (2NaCl · PdCl ₂ ) can be preferably used as the palladium. Gold is a gold compound such as tetrachlorogold (III) acid tetrahydrate (HAuCl ₄ · 4H ₂ O) or sodium tetrachloroaurate (III) sodium dihydrate (NaAuCl ₄ · 2H ₂ O). It can be preferably used.

  These palladium compounds and gold compounds are dissolved in an acidic aqueous solution such as hydrochloric acid (HCl), adjusted to pH with an alkaline aqueous solution such as sodium hydroxide, and then immersed in a smooth substrate that has been subjected to a coupling treatment, thereby treating the plating catalyst. A process is performed and a plating catalyst made of palladium and gold is supported on a smooth substrate.

In the electroless plating method on the smooth substrate according to the present invention, it is preferable to perform the plating catalyst treatment step under the condition of pH 3-5.
Generally, an acidic aqueous solution such as hydrochloric acid is used to dissolve a palladium compound, a gold compound, and the like, so that the pH of the plating catalyst solution is 2 or lower. In this case, it is estimated that the metal used as a plating catalyst exists as a complex anion in the plating catalyst solution. For this reason, in the plating catalyst treatment step, only a complex amount of the stoichiometric ratio of the complex anion is supported with respect to the coupling agent, so that the amount of the finely divided plating catalyst generated in the subsequent reduction step is small. In addition, when the fine particle plating catalyst is generated, it aggregates and segregation occurs at a mesoscopic level, and as a result, it is not easy to increase the catalytic activity.
On the other hand, in the electroless plating method on the smooth substrate according to the present invention, the pH value is set to a value within the above range, so that the metal serving as the plating catalyst is fine (average particle size in the plating catalyst solution). Is 30 nm or smaller (preferably with an average particle size of 20 μm or less, more preferably with an average particle size of 10 nm or less) in a dispersed state (colloidal state or clustered state). It is presumed that the surface area of the plating catalyst metal is increased thereby increasing the catalytic activity.

In the electroless plating method on the smooth substrate according to the present invention, the plating catalyst treatment step dissolves the palladium compound and the gold compound in an acidic aqueous solution having a pH of 2.5 or less, and then adjusts the pH of the aqueous solution to 3 to 5. It is preferable to carry out using a solution obtained by adjusting to the above.
For this reason, palladium and gold are once dissolved uniformly in an acidic aqueous solution, and then converted into ultrafine particles in the process of adjusting the pH to 3 to 5. Therefore, the ultrafine particles contain palladium and gold extremely uniformly. Therefore, it is speculated that the catalytic activity is also increased from this viewpoint.

In the electroless plating method on the smooth substrate according to the present invention, the method of bringing the plating catalyst solution into contact with the smooth substrate in the plating catalyst treatment step is preferably performed by immersing the smooth substrate in the plating catalyst solution. Thereby, a uniform plating catalyst process can be performed easily.
However, the electroless plating method on the smooth substrate according to the present invention is not limited to this, and the plating catalyst solution can be brought into contact with the smooth substrate by, for example, applying the plating catalyst solution to the smooth substrate. .

  In the electroless plating method on the smooth substrate according to the present invention, the time for bringing the plating catalyst solution into contact with the smooth substrate in the plating catalyst treatment step includes the type of plating catalyst, the concentration of the plating catalyst solution, the treatment temperature, and the contact method. Depending on the above, the time can be set to about 2 to 30 minutes. This is because if this time is shortened, uniform plating catalyst treatment may not be performed, and if this time is long, productivity may be reduced.

In the electroless plating method on the smooth substrate according to the present invention, it is preferable to perform the electroless plating step without performing the treatment for reducing the plating catalyst, that is, the reduction treatment after the plating catalyst treatment step.
In the conventional electroless plating method, since the plating catalyst treatment process is performed under conditions where the pH is relatively low (for example, 2 or less), the metal serving as the plating catalyst is supported on the coupling agent as a complex anion. Yes. For this reason, it is necessary to reduce this complex anion in advance before the electroless plating process. However, as described above, the metal as the plating catalyst aggregates and segregation at a mesoscopic level occurs as a result. It is presumed that the catalyst activity is lowered and the adhesiveness is lowered.
On the other hand, according to the electroless plating method on the smooth substrate according to the present invention, since the plating catalyst treatment process is performed under the condition of pH 3 to 5, the metal used as the plating catalyst has a very small particle size. (The average particle size is 30 nm or smaller) The ultrafine particles such as hydroxide are supported on the coupling agent. For this reason, the ultra fine particles are easily reduced without being subjected to a reduction treatment and function as a plating catalyst made of ultra fine particles. Therefore, the metal serving as the plating catalyst does not aggregate on the coupling agent, and the adhesion is not reduced.

In the electroless plating method on the smooth substrate according to the present invention, an electroless plating step can be performed according to a conventional method. As the electroless plating solution, an autocatalytic electroless plating solution such as an electroless Ni-P plating solution, an electroless Ni-B plating solution, an electroless Ni-PB plating solution, and an electroless Ni-Cu- P plating solution, electroless copper plating solution and the like can be preferably used.
There are no particular limitations on the electroless plating conditions, and suitable conditions can be adopted in accordance with conventional methods according to the type of the smooth substrate and the type of the electroless plating solution.

In the electroless-plating method to the smooth substrate which concerns on this invention, it is preferable to further include the heat processing process which heat-processes a smooth substrate on 200-350 degreeC conditions after an electroless-plating process.
By setting it as such a method, the adhesiveness of the electroless plating film with respect to a smooth substrate can be made favorable.

  According to the method of electroless plating on a smooth substrate according to the present invention, an electroless plating film having good adhesion can be formed even on a smooth substrate. For example, magnetic disks, perpendicular magnetic recording magnetic disks, ceramics, etc. It is possible to improve the performance of electronic devices such as a substrate in which a wiring circuit is formed on a substrate, a substrate in which a wiring circuit is formed on an insulating thin film, and a SAW filter.

The product according to the present invention is a product manufactured using a smooth substrate on which an electroless plating film is formed by the electroless plating method on the smooth substrate according to the present invention.
For this reason, the product according to the present invention is manufactured using a substrate on which an electroless plating film having good adhesion is formed on a smooth substrate as described above. Product.

  An electroless plating structure according to the present invention is an electroless plating structure including a smooth substrate and an electroless plating film formed on the smooth substrate by an electroless plating method, wherein the coupling is formed on the smooth substrate. The electroless plating film is formed on a monomolecular film of the agent.

  Therefore, according to the electroless plating structure according to the present invention, as described above, even when an external force is applied, it is presumed that the monomolecular film is not destroyed until the coupling agent molecule itself is destroyed. The For this reason, it is estimated that the electroless plating film is not easily peeled off from the smooth substrate, and as a result, it has good adhesion. That is, the electroless plating structure on the smooth substrate according to the present invention is an electroless plating structure having good adhesion even on the smooth substrate.

In the electroless plating structure according to the present invention, the coverage of the monomolecular film on the smooth substrate is preferably 50% or more.
If this coverage is less than 50%, in the plating catalyst treatment step, the amount of the plating catalyst supported on the smooth substrate becomes too small, and the electroless plating film may be formed unevenly. Because there is.

In the electroless plating structure according to the present invention, the electroless plating film is an electroless plating film formed by using a plating catalyst containing ultrafine particles having an average particle diameter of 30 nm or less and containing palladium and gold. It is preferable.
By comprising in this way, the surface area of the plating catalyst metal containing palladium and gold is increased, the catalytic activity is increased, and as a result, high adhesion strength of the electroless plating film to the smooth substrate is obtained. From this point of view, the electroless plating film is preferably formed using a plating catalyst composed of ultrafine particles having an average particle diameter of 20 nm or less, and a plating catalyst composed of ultrafine particles having an average particle diameter of 10 nm or less is used. More preferably, the electroless plating film is formed.

In the electroless plating structure according to the present invention, the smooth substrate has an average surface roughness Ra of 1.0 nm or less, and is measured using a thin film adhesion tester of the electroless plating film on the smooth substrate. The tensile strength to be applied is preferably 24 MPa or more.
Such a configuration makes it possible to manufacture high-quality electronic devices as required in the electronics industry.

  The tensile strength is measured by using a Sebastian V-type strength tester manufactured by QUAD GROUP as a thin film adhesion tester, and soldering a φ1.8 mm copper stud pin to the electroless plating film (280 ° C. It can be performed with good reproducibility by preheating for 6 minutes and then heating on a hot plate at 280 ° C. for 2 minutes, and then pulling it vertically and measuring its tensile strength.

The product of the present invention is a product provided with the above electroless plating structure.
For this reason, since the product according to the present invention has an electroless plating structure in which an electroless plating film having good adhesion is formed on a smooth substrate as described above, the product has high reliability and high quality. Product.

[Embodiment 1]
FIG. 1 is a diagram showing a flowchart of an electroless plating method on a smooth substrate according to Embodiment 1 of the present invention. As shown in FIG. 1, the electroless plating method on a smooth substrate according to Embodiment 1 includes a coupling treatment step in which a coupling solution containing a coupling agent is brought into contact with the smooth substrate, and a plating catalyst on the smooth substrate. An electroless plating method for a smooth substrate, which includes a plating catalyst treatment step for contacting a contained plating catalyst solution and an electroless plating step for subjecting the smooth substrate to electroless plating in this order. The electroless plating method on the smooth substrate according to Embodiment 1 will be described for each manufacturing process.

1. Preparation of Smooth Substrate A sapphire substrate (manufactured by Shinko Co., Ltd., diameter 30 mm, thickness 1 mm, average surface roughness Ra = 0.18 nm) was prepared and washed with isopropyl alcohol as the smooth substrate of the first embodiment. Instead of washing with isopropyl alcohol, degreasing using a weak alkaline degreasing solution, washing with hydrochloric acid, and washing with pure water may be used.

2. Coupling treatment step 3-aminopropyltriethoxysilane is dissolved in a mixed solvent of 20% ethanol and 80% water by volume, and a silane coupling solution containing 0.005% by volume of this 3-aminopropyltriethoxysilane is prepared. did.
Thereafter, the above 1. The sapphire substrate prepared in (1) was immersed in this silane coupling solution for 15 minutes to perform silane coupling treatment. Then, it air-dried at room temperature and heat-processed at 80 degreeC for 1 hour.

3. Plating catalyst treatment step After sodium palladium chloride (II) and sodium tetrachloroaurate (III) dihydrate were dissolved in hydrochloric acid, the pH of these aqueous solutions was adjusted to 4 using an aqueous sodium hydroxide solution. Then, these solutions were mixed and the metal-plating catalyst solution whose ratio of palladium is 0.5 by atomic ratio was created. This plating catalyst solution contains hydroxide ultrafine particles having an average particle diameter of about 10 nm.
After that, 2. The sapphire substrate subjected to the silane coupling treatment was immersed in this plating catalyst solution for 15 minutes to perform the plating catalyst treatment.

4). Electroless plating step Electroless Ni-P plating bath consisting of nickel sulfate (hexahydrate) 26.3 g / l, sodium hypophosphite (monohydrate) 21.0 g / l, glycine 15.0 g / l It was created. The pH was 4 and the bath temperature was 68 ° C.
Thereafter, the above 3. The sapphire substrate subjected to the plating catalyst treatment was immersed in this plating bath for 15 minutes and subjected to electroless plating to form an electroless plating film having a thickness of about 0.5 μm.

5). Heat treatment step 4. The sapphire substrate on which the electroless plating film was formed was placed in a dryer and heat-treated at 280 ° C. for 30 minutes.

  Through the above steps, an electroless plating structure in which an electroless plating film was formed on a smooth substrate was obtained. FIG. 2 is a schematic diagram for explaining the electroless plating. As shown in FIG. 2, the electroless plating structure 100 according to the first embodiment includes a smooth substrate 10 on which a monomolecular film of a silane coupling agent 20 is formed, and a plating catalyst is formed on the monomolecular film of the silane coupling agent 20. 30 is supported, and the electroless plating film 40 is formed using the plating catalyst 30 as a catalyst.

6). Evaluation of Electroless Plating Film on Smooth Substrate In the method of electroless plating on a smooth substrate according to Embodiment 1, the adhesion strength of the obtained electroless plating structure is measured by a thin film adhesion tester (QUAD GROUP Sebastian V A mold strength tester). Specifically, a φ1.8 mm copper stud pin for measurement is soldered to the electroless plating film (preheating at 280 ° C. for 6 minutes and then heating on a hot plate at 280 ° C. for 2 minutes), and then pulled vertically, This was done by measuring the strength.
As a result, an extremely excellent value of 36 MPa was obtained as the tensile strength.

[Embodiment 2]
In Embodiment 2, electroless plating was performed by the same method as in Embodiment 1 except that “3. Plating catalyst treatment step” in Embodiment 1 was replaced with the following “3A. Plating catalyst treatment step”. .

3A. Plating catalyst treatment process Palladium (II) sodium chloride and sodium tetrachloroaurate (III) dihydrate are dissolved in hydrochloric acid to create an acidic aqueous solution containing both palladium and gold. The pH of this acidic aqueous solution was adjusted to 4 to prepare a plating catalyst solution in which the proportion of palladium contained in the plating catalyst solution was 0.5 in atomic ratio.
After that, 2. The sapphire substrate subjected to the silane coupling treatment was immersed in this plating catalyst solution for 15 minutes to perform the plating catalyst treatment.

As a result, an extremely excellent value of 45 MPa was obtained as the tensile strength.
Thus, in the case of Embodiment 2, palladium and gold are well dispersed in each of the fine particles contained in the plating catalyst solution because the adhesion strength superior to that of Embodiment 1 was obtained. This is presumably because the catalytic activity of the plating catalyst was increased.

[Comparative Experiment 1]
In Comparative Experiment 1, the adhesion strength of the electroless plating film to the smooth substrate was evaluated by changing the concentration of the silane coupling agent contained in the silane coupling solution.
Each step of the electroless plating method according to Comparative Experiment 1 is basically the same as each step of the electroless plating method according to Embodiment 1 described above, but in Comparative Experiment 1, in the coupling process step The concentration of the silane coupling agent contained in the sila coupling solution is varied from 0.001 to 0.5% by volume.

  FIG. 3 is a diagram showing a relationship between the silane coupling agent concentration and the adhesion strength, that is, a diagram showing a result of evaluating the adhesion strength of the electroless plating film to the smooth substrate by changing the silane coupling agent concentration. . The horizontal axis indicates the concentration of the silane coupling agent contained in the silane coupling solution, and the vertical axis indicates the adhesion strength (MPa).

  As is clear from FIG. 3, it was found that the highest adhesion strength (36 Mpa) was obtained when the concentration of the silane coupling agent was 0.05% by volume. It was also found that good adhesion strength (about 28 MPa or more) was obtained when the concentration of the silane coupling agent was 0.001 to 0.3% by volume.

[Comparative Experiment 2]
In Comparative Experiment 2, the adhesion strength of the electroless plating film to the smooth substrate was evaluated by changing the ratio of palladium contained in the plating catalyst solution.
Each process of the electroless plating method according to Comparative Experiment 2 is basically the same as each process of the electroless plating method according to Comparative Experiment 1. The electroless plating method according to Comparative Experiment 2 is different from the electroless plating method according to Comparative Experiment 1 in the following two points. That is, (1) In the electroless plating method according to Comparative Experiment 1, the concentration of the silane coupling agent is changed (0.001 to 0.5% by volume). (2) In the electroless plating method according to Comparative Experiment 1, the proportion of palladium contained in the plating catalyst solution is fixed (0.5). Experiment 2 differs in that this ratio is changed (0.1 to 1).

  FIG. 4 is a diagram showing the relationship between the composition of the plating catalyst solution and the adhesion strength, that is, the result of evaluating the adhesion strength of the electroless plating film to the smooth substrate by changing the proportion of palladium contained in the plating catalyst solution. FIG. The horizontal axis represents the composition ratio of palladium contained in the plating catalyst solution (the ratio of palladium to the total amount of palladium and gold expressed in terms of atomic ratio), and the vertical axis represents the adhesion strength (MPa).

  As is apparent from FIG. 4, it was found that the highest adhesion strength (36 MPa) was obtained when the composition ratio of palladium contained in the plating catalyst solution was 0.5. It was also found that good adhesion strength (24 MPa or more) was obtained when the composition ratio of palladium contained in the plating catalyst solution was 0.25 to 0.7.

[Comparative Experiment 3]
In Comparative Experiment 3, the adhesion strength of the electroless plating film to the smooth substrate was evaluated by changing the pH of the plating catalyst solution.
Each process of the electroless plating method according to Comparative Experiment 3 is basically the same as each process of the electroless plating method according to Comparative Experiment 1. The electroless plating method according to comparative experiment 3 is different from the electroless plating method according to comparative experiment 1 in the following two points. That is, (1) In the electroless plating method according to Comparative Experiment 1, the concentration of the silane coupling agent is changed (0.001 to 0.5% by volume). (2) In the electroless plating method according to Comparative Experiment 1, the pH value of the plating catalyst solution is fixed at 4, but in Comparative Experiment 3, The pH value is changed (1.5 to 6).

  FIG. 5 is a diagram showing the relationship between the pH of the plating catalyst solution and the adhesion strength, that is, a diagram showing the results of evaluating the adhesion strength of the electroless plating film to the smooth substrate by changing the pH value of the plating catalyst solution. It is. The horizontal axis indicates the pH value of the plating catalyst solution, and the vertical axis indicates the adhesion strength (MPa).

  As is clear from FIG. 5, it was found that when the pH value of the plating catalyst solution was 4, the greatest adhesion strength (36 MPa) was obtained. It was also found that good adhesion strength (26 MPa or more) was obtained when the pH value of the plating catalyst solution was 3-5.

  As described above, according to the electroless plating method for a smooth substrate according to the present invention, an electroless plating film having good adhesion can be formed even on the smooth substrate.

It is a figure which shows the flowchart of the electroless-plating method to the smooth substrate which concerns on Embodiment 1. FIG. 3 is a schematic diagram for explaining an electroless plating structure according to Embodiment 1. FIG. It is a figure which shows the relationship between the silane coupling agent density | concentration and the adhesive strength in the comparative experiment 1. It is a figure which shows the relationship between the composition of the plating catalyst solution in Comparative Experiment 2, and adhesive strength. It is a figure which shows the relationship between the pH of the metal-plating catalyst solution in Comparative Experiment 3, and adhesive strength.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Smooth substrate, 20 ... Silane coupling agent, 30 ... Plating catalyst, 40 ... Electroless plating film, 100 ... Electroless plating structure

Claims (7)

A smooth substrate for forming an electroless plating film having a tensile strength of 24 MPa or more measured on a smooth substrate having an average surface roughness Ra of 1.0 nm or less using a thin film adhesion tester. An electroless plating method for
A coupling treatment step of contacting the smooth substrate with a coupling solution containing 0.001 to 0.1% by volume of a coupling agent;
A plating catalyst treatment step of bringing the plating catalyst solution containing palladium and gold into contact with the smooth substrate;
An electroless plating method for a smooth substrate, comprising: an electroless plating step for applying electroless plating to the smooth substrate in this order. In the electroless-plating method to the smooth substrate of Claim 1,
The method for electroless plating on a smooth substrate, wherein the coupling solution contains 0.001 to 0.075% by volume of a coupling agent. In the electroless-plating method to the smooth substrate of Claim 1 or 2,
The electroless plating method for a smooth substrate, wherein the plating catalyst treatment step is performed under conditions of pH 3-5. In the electroless-plating method to the smooth substrate of Claim 1 or 2,
The plating catalyst treatment step is performed using a solution obtained by dissolving a palladium compound and a gold compound in an acidic aqueous solution having a pH of 2.5 or less, and then adjusting the pH of the aqueous solution to 3 to 5. An electroless plating method on a smooth substrate. In the electroless-plating method to the smooth substrate in any one of Claims 1-4,
An electroless plating method for a smooth substrate, wherein the electroless plating step is performed without performing a treatment for reducing the plating catalyst after the plating catalyst treatment step. In the electroless-plating method to the smooth substrate in any one of Claims 1-5,
An electroless plating method for a smooth substrate, further comprising a heat treatment step of performing a heat treatment of the smooth substrate at 200 to 350 ° C. after the electroless plating step.   The product manufactured using the smooth substrate in which the electroless-plating film was formed with the electroless-plating method to the smooth substrate in any one of Claims 1-6.

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