JP4658634B2 - Electroless plating catalyst solution and electroless plating method using the same - Google Patents

Description

  The present invention relates to an electroless plating catalyst solution used for electroless plating and an electroless plating method using the same.

For example, non-conductive substances such as glass, ceramics, and plastics have no catalytic activity for electroless plating, and an electroless plating film cannot be directly formed thereon. Therefore, when electroless plating is applied to an object to be plated that does not have catalytic activity, electroless plating is generally performed after applying a catalyst such as palladium (Pd) with a catalyst solution to activate the surface of the object to be plated. It has been done. However, the conventional electroless plating catalyst solution has a problem that the adhesion of the plating film to the object to be plated is insufficient (see, for example, Patent Document 1). For this reason, for example, although the concentration and pH of palladium in the electroless plating catalyst solution are controlled, it has been difficult to stably obtain a plating film having excellent adhesion.
Japanese Patent Laid-Open No. 10-30188

  The present invention has been made in view of such problems, and an object thereof is to provide an electroless plating catalyst solution capable of stably obtaining a plating film having excellent adhesion and an electroless plating method using the same. There is.

In order to achieve this object, the electroless plating catalyst solution of the present invention comprises an aqueous solution containing at least a palladium salt and chloride ions, and the concentration of hydrogen ions [H ⁺ ] and chloride in the aqueous solution. The product of the product ion concentration [Cl ⁻ ] is in the range of 10 ⁻¹³ <[H ⁺ ] ² · [Cl ⁻ ] ⁴ <10 ⁻⁸ . Here, the hydrogen ion concentration [H ⁺ ] and the chloride ion concentration [Cl ⁻ ] are each expressed in mol / L.
In the present invention, the product of the hydrogen ion concentration [H ⁺ ] and the chloride ion concentration [Cl ⁻ ] in the aqueous solution is 10 ^−11.8 <[H ⁺ ] ² · [Cl ⁻ ] ⁴ <10. It can be in the range of ^-8 .
In the electroless plating catalyst solution of the present invention, the palladium salt is at least one or more selected from palladium (II) chloride, sodium palladium (II) chloride, and ammonium palladium (II) chloride. It is characterized by that.
In addition, the electroless plating catalyst solution of the present invention further includes a gold salt.
Further, in the electroless plating catalyst solution of the present invention, the gold salt is tetrachlorogold (III) acid, sodium tetrachlorogold (III), potassium tetrachlorogold (III), tetrachlorogold (III). It is at least one or more kinds selected from ammonium acid.
In the electroless plating catalyst solution of the present invention, the chloride ion is derived from at least one or more selected from palladium salt, gold salt, hydrochloric acid, sodium chloride, and potassium chloride. It is characterized by.
The electroless plating catalyst solution of the present invention is characterized in that sodium hydroxide or potassium hydroxide is used for pH adjustment of the aqueous solution.
In the present invention, the palladium salt is at least one kind selected from palladium chloride (II), palladium chloride (II) sodium and palladium chloride (II) ammonium, and the chloride ion is a palladium salt. Electroless plating derived from at least one or more selected from gold salt, hydrochloric acid, sodium chloride, and potassium chloride, and using sodium hydroxide or potassium hydroxide to adjust the pH of the aqueous solution. Catalyst solution.
Further, the electroless plating method of the present invention is characterized in that after any of the above electroless plating catalyst solutions is applied to the object to be plated, electroless plating is performed on the object to be plated. .
Moreover, the electroless plating method of the present invention is characterized in that electroless nickel plating is applied to the object to be plated.

As described above, in the electroless plating catalyst solution of the present invention, the concentration of hydrogen ions [H ⁺ ] and the concentration of chloride ions [Cl ⁻ ] in an aqueous solution containing at least a palladium salt and chloride ions. By setting the product to a range of 10 ⁻¹³ <[H ⁺ ] ² · [Cl ⁻ ] ⁴ <10 ⁻⁸ , a catalyst having excellent plating film adhesion can be imparted to the object to be plated. Therefore, in the electroless plating method of the present invention, a plating film having excellent adhesion to the object to be plated by applying the electroless plating after applying the catalyst to the object to be plated using the electroless plating catalyst solution. Can be formed stably.

Hereinafter, the electroless plating catalyst solution to which the present invention is applied and the electroless plating method using the same will be described in detail.
First, the electroless plating catalyst solution to which the present invention is applied will be described.
The electroless plating catalyst solution to which the present invention is applied is composed of an aqueous solution containing at least palladium (Pd) salt and chloride ions. As a result of investigating the influence on adhesion, it was found that the product of the concentration of hydrogen ions [H ⁺ ] and the concentration of chloride ions [Cl ⁻ ] in this aqueous solution has a great influence on the adhesion of the plating film. .

したがって、この場合の平衡定数Ｋは、下記数１で表される。

また、この場合の水素イオンの濃度［Ｈ^＋］と塩化物イオンの濃度［Ｃｌ⁻］との積は、下記数２で表すことができる。

Specifically, palladium (II) chloride generally used in the electroless plating catalyst solution is in an equilibrium state shown in the following chemical formula 1 in an aqueous solution.

Therefore, the equilibrium constant K in this case is expressed by the following formula 1.

In this case, the product of the hydrogen ion concentration [H ⁺ ] and the chloride ion concentration [Cl ⁻ ] can be expressed by the following formula 2.

In the electroless plating catalyst solution to which the present invention is applied, the product of the hydrogen ion concentration [H ⁺ ] and the chloride ion concentration [Cl ⁻ ] represented by the above formula 2 is 10 ⁻¹³ <[H ⁺ ] ² · [Cl ⁻ ] ⁴ <10 ⁻⁸ is preferable. That is, when this product is smaller than 10 ⁻¹³ , palladium hydroxide in the chemical formula 1 is precipitated, so that the metal palladium fine particles adhering to the surface of the object to be plated become coarse, and the adhesion of the plating film is increased. Sexuality gets worse. On the other hand, when this product is larger than 10 ⁻⁸ , the pH value is lowered and the chloride ions are increased, the palladium complex is stabilized and does not adhere to the object to be plated, and the adhesion of the plating film is also deteriorated.

Therefore, in this electroless plating catalyst solution, the product of the hydrogen ion concentration [H ⁺ ] and the chloride ion concentration [Cl ⁻ ] contained in the aqueous solution is 10 ⁻¹³ <[H ⁺ ] ^2. The concentration of hydrogen ions [H ⁺ ] and the concentration of chloride ions [Cl ⁻ ] are adjusted so as to be in the range of [Cl ⁻ ] ⁴ <10 ⁻⁸ . Specifically, in this electroless plating catalyst solution, palladium (II) sodium chloride, palladium (II) ammonium chloride, and the like can be used as the palladium salt in addition to the above-described palladium (II) chloride. At least one or more selected from among the above can be used. The electroless plating catalyst solution may contain a gold (Au) salt in the aqueous solution. Examples of the gold salt include tetrachlorogold (III) acid, sodium tetrachlorogold (III), potassium tetrachlorogold (III), ammonium tetrachlorogold (III), and the like. At least one or more selected from among the above can be used.

Further, in this electroless plating catalyst solution, in addition to the above-described palladium salt and gold salt, hydrochloric acid (HCl), sodium chloride (NaCl), or potassium chloride (KCl) is added to the aqueous solution. The concentration [H ⁺ ] of contained hydrogen ions and the concentration [Cl ⁻ ] of chloride ions can be easily adjusted. That is, hydrogen ions and chloride ions in this aqueous solution may be derived from hydrochloric acid, sodium chloride, or potassium chloride introduced into this aqueous solution in addition to the palladium salt and gold salt described above. Furthermore, sodium hydroxide (NaOH) or potassium hydroxide (KOH) can be used to adjust the pH of the electroless plating catalyst solution.

As described above, in this electroless plating catalyst solution, the product of the hydrogen ion concentration [H ⁺ ] and the chloride ion concentration [Cl ⁻ ] contained in the aqueous solution is 10 ⁻¹³ <[H ⁺ ] By keeping it in the range of ² · [Cl ⁻ ] ⁴ <10 ⁻⁸ , a catalyst excellent in adhesion of the plating film can be imparted to the object to be plated. Furthermore, in the present invention, such a catalyst solution for electroless plating can be easily managed.

Next, an electroless plating method using the electroless plating catalyst solution will be described.
The electroless plating method of the present invention can be applied to the case where a nickel (Ni) plating film 2 is formed on the surface of a substrate 1 which is an object to be plated, for example, as shown in FIG. For example, a glass substrate, a ceramic substrate, a silicon substrate, a resin substrate on which a metal film is formed, or the like can be used. Before applying electroless nickel plating to the substrate 1, acid (sulfuric acid / hydrogen peroxide), alkali, warm water (pure water), or the like was used as a treatment for disposing a large amount of OH groups on the surface of the substrate 1. It is desirable to perform ultrasonic cleaning or cleaning using ultraviolet rays on the substrate 1 in advance. This removes oils and fats that impede adhesion from the surface of the substrate 1 and forms a substrate on which a silane coupling agent to be described later can firmly adhere to and bind to the surface of the substrate 1. As such a substrate 1, for example, a ceramic substrate mainly composed of alumina (Al ₂ O ₃ ) is ultrasonically cleaned with acetone and then cleaned with sulfuric acid / hydrogen peroxide, or a glass substrate is purified after being cleaned with ultraviolet rays. Examples include those obtained by ultrasonic cleaning with water and those obtained by cleaning a silicon substrate with sulfuric acid / hydrogen peroxide. The object to be plated is not necessarily limited to such a substrate shape, and may be processed into a predetermined shape.

  When electroless nickel plating is performed on the surface of the substrate 1, first, silane coupling treatment is performed on the surface of the substrate 1. For this silane coupling treatment, it is desirable to use an aminosilane-based coupling agent. For example, a dilute solution such as 3-aminopropyltriethoxysilane or N-2 (aminoethyl) 3-aminopropylmethyldimethoxysilane is used. Can be used. Thereby, the silane coupling agent which becomes the key of adhesiveness can be firmly bonded to the surface of the substrate 1.

  Next, the substrate 1 is immersed in the electroless plating catalyst solution, whereby the surface of the substrate 1 that has been subjected to the silane coupling treatment is subjected to a catalyst treatment. Thereby, the catalyst of palladium and gold | metal | money can be provided to the surface by which the silane coupling process of the board | substrate 1 was performed.

  Next, electroless nickel plating is performed on the surface of the substrate 1 that has been subjected to the catalyst treatment by immersing the substrate 1 in a nickel plating bath. For the nickel plating bath, for example, a plating solution containing nickel sulfate, sodium phosphinate, glycine, or the like can be used. As described above, the Ni plating film 2 can be formed on the substrate 1.

  In the electroless plating method to which the present invention is applied, since the electroless nickel plating is performed after applying the catalyst to the substrate 1 using the above-described electroless plating catalyst solution, the Ni plating having excellent adhesion to the substrate 1 is applied. The film 2 can be formed stably.

  In addition, the electroless plating method of the present invention is not necessarily limited to the case where electroless nickel plating is applied to an object to be plated, and for example, when electroless plating such as electroless copper plating is applied to an object to be plated. Applicable. In the electroless plating method of the present invention, it is also possible to perform different electroless plating such as electroless copper plating after the electroless nickel plating is applied to the object to be plated.

Hereinafter, the effects of the present invention will be clarified by examples. However, the following examples do not limit the technical scope of the present invention.
Example 1
In Example 1, first, a ceramic substrate mainly composed of alumina was prepared as an object to be plated, and this substrate was ultrasonically washed with acetone and then washed with sulfuric acid / hydrogen peroxide. Next, the substrate was immersed in a dilute solution of 3-aminopropyltriethoxysilane and rinsed, and the substrate surface was subjected to silane coupling treatment. Next, the substrate was immersed in an electroless plating catalyst solution in which HAuCl ₄ and PdCl ₂ were mixed and rinsed, and the substrate surface was subjected to a catalyst treatment. Further, the electroless plating catalyst solution has a pH value, a molar concentration of Pd salt, a molar concentration of Au salt such that −log ([H ⁺ ] ^2. [Cl ⁻ ] ⁴ ) = 8.05, What adjusted the molar concentration of Cl < ^- > ion was used, respectively. Next, electroless nickel plating was performed by immersing the substrate in a commercially available nickel plating bath containing nickel sulfate, sodium phosphinate, glycine and the like. The Ni plating film was formed in the board | substrate through the above processes.
(Example 2)
In Example 2, the pH value, the molar concentration of the Pd salt, the molar concentration of the Au salt, and the molar concentration of the Cl ⁻ ion are set so that −log ([H ⁺ ] ² · [Cl ⁻ ] ⁴ ) = 10.05. The substrate was subjected to electroless nickel plating in the same manner as in Example 1 except that each adjusted electroless plating catalyst solution was used.
(Example 3)
In Example 3, the pH value, the molar concentration of the Pd salt, the molar concentration of the Au salt, and the molar concentration of the Cl ⁻ ion were set so that −log ([H ⁺ ] ^2. [Cl ⁻ ] ⁴ ) = 11.05. The substrate was subjected to electroless nickel plating in the same manner as in Example 1 except that each adjusted electroless plating catalyst solution was used.
Example 4
In Example 4, the pH value, the molar concentration of the Pd salt, the molar concentration of the Au salt, and the molar concentration of the Cl ⁻ ion were set so that −log ([H ⁺ ] ² · [Cl ⁻ ] ⁴ ) = 11.83. The substrate was subjected to electroless nickel plating in the same manner as in Example 1 except that each adjusted electroless plating catalyst solution was used.
(Example 5)
In Example 5, the pH value, the molar concentration of the Pd salt, the molar concentration of the Au salt, and the molar concentration of the Cl ⁻ ion were set so that −log ([H ⁺ ] ² · [Cl ⁻ ] ⁴ ) = 12.68. The substrate was subjected to electroless nickel plating in the same manner as in Example 1 except that each adjusted electroless plating catalyst solution was used.
(Comparative Example 1)
In Comparative Example 1, the pH value, the molar concentration of the Pd salt, the molar concentration of the Au salt, and the molar concentration of the Cl ⁻ ion were such that −log ([H ⁺ ] ² · [Cl ⁻ ] ⁴ ) = 7.05. The substrate was subjected to electroless nickel plating in the same manner as in Example 1 except that each adjusted electroless plating catalyst solution was used.
(Comparative Example 2)
In Comparative Example 2, the pH value, the molar concentration of Pd salt, the molar concentration of Au salt, and the molar concentration of Cl ⁻ ion were set so that −log ([H ⁺ ] ^2. [Cl ⁻ ] ⁴ ) = 13.83. The substrate was subjected to electroless nickel plating in the same manner as in Example 1 except that each adjusted electroless plating catalyst solution was used.
(Comparative Example 3)
In Comparative Example 3, the pH value, the molar concentration of the Pd salt, the molar concentration of the Au salt, and the molar concentration of the Cl ⁻ ion were such that −log ([H ⁺ ] ² · [Cl ⁻ ] ⁴ ) = 16.83. The substrate was subjected to electroless nickel plating in the same manner as in Example 1 except that each adjusted electroless plating catalyst solution was used.

And it measured about the adhesive force of the Ni plating film with respect to each board | substrate of these Examples 1 thru | or Example 5 and Comparative Examples 1 thru | or Comparative Example 3. In addition, the measurement of this adhesion force was performed by using a Sebastian IV type manufactured by QUAD GROUP and contacting a standard stud pin. Table 1 below summarizes these. The results of measurement shown in Table 1 are summarized with the product of the hydrogen ion concentration [H ⁺ ] and the chloride ion concentration [Cl ⁻ ] as the vertical axis and the adhesion of the Ni plating film to the substrate as the horizontal axis. The graph is shown in FIG.

  As shown in Table 1 and the graph of FIG. 1, in Examples 1 to 5, compared with Comparative Example 1 and Comparative Example 3, the adhesion is 20 MPa or more, and the Ni plating film is against the substrate. It can be seen that sufficient adhesion is obtained.

Next, instead of the electroless plating catalyst solution in which HAuCl ₄ and PdCl ₂ were mixed, the adhesion of the Ni plating film to the substrate was investigated when the electroless plating catalyst solution made of PdCl ₂ was used. . That is,
(Example 6)
In Example 6, PdCl ₂ in which the pH value, the molar concentration of the Pd salt, and the molar concentration of the Cl ⁻ ion were adjusted so that −log ([H ⁺ ] ^2. [Cl ⁻ ] ⁴ ) = 10.68 was obtained. The substrate was subjected to electroless nickel plating in the same manner as in Example 1 except that the electroless plating catalyst solution made of was used.
(Comparative Example 4)
In Comparative Example 4, PdCl ₂ in which the pH value, the molar concentration of the Pd salt, and the molar concentration of the Cl ⁻ ion were adjusted so that −log ([H ⁺ ] ^2. [Cl ⁻ ] ⁴ ) = 7.05 was obtained. The substrate was subjected to electroless nickel plating in the same manner as in Example 1 except that the electroless plating catalyst solution made of was used.
(Comparative Example 5)
In Comparative Example 5, PdCl ₂ in which the pH value, the molar concentration of the Pd salt, and the molar concentration of the Cl ⁻ ion were adjusted so that −log ([H ⁺ ] ^2. [Cl ⁻ ] ⁴ ) = 14.83. The substrate was subjected to electroless nickel plating in the same manner as in Example 1 except that the electroless plating catalyst solution made of was used.

  And the same measurement as the case shown in the said Table 1 was performed about the adhesive force of the Ni plating film with respect to each board | substrate of these Example 6, the comparative example 4, and the comparative example 5. FIG. A summary of these is shown in Table 2 below. The measurement results shown in Table 2 are collectively shown in the graph of FIG.

  As shown in Table 2 and FIG. 1, in Example 5, compared with Comparative Example 4, the adhesion force is 20 MPa or more, and the Ni plating film has obtained sufficient adhesion force to the substrate. Recognize. In Comparative Example 5, a Ni plating film could not be deposited on the substrate.

From the above, the product of the hydrogen ion concentration [H ⁺ ] and the chloride ion concentration [Cl ⁻ ] in the electroless plating catalyst solution is 10 ⁻¹³ <[H ⁺ ] ² · [Cl ⁻ ] ^4. It became clear that the electroless nickel plating excellent in adhesiveness can be stably formed on a board | substrate by being in the range of <10 < ^-8 >.

FIG. 1 is a cross-sectional view showing a substrate on which electroless nickel plating has been applied by an electroless plating method to which the present invention is applied. FIG. 2 is a graph showing the relationship between the product of the hydrogen ion concentration and the chloride ion concentration and the adhesion of the Ni plating film to the substrate.

Explanation of symbols

  1 ... Substrate (to be plated), 2 ... Ni plating film

Claims (10)

The product of an aqueous solution containing at least a palladium salt and chloride ions, and the product of the hydrogen ion concentration [H ⁺ ] and the chloride ion concentration [Cl ⁻ ] in the aqueous solution,
10 ⁻¹³ <[H ⁺ ] ^2. [Cl ⁻ ] ⁴ <10 ⁻⁸
A catalyst solution for electroless plating characterized by being in the range. Hydrogen ion concentration in the aqueous solution [H ⁺ ] And chloride ion concentration [Cl ⁻ ] Product with
10 ^-11.8 <[H ⁺ ] ² ・ [Cl ⁻ ] ⁴ <10 ^-8 The catalyst solution for electroless plating according to claim 1, wherein the catalyst solution is in the range. 3. The palladium salt according to claim 1 or 2 , wherein the palladium salt is at least one or more selected from palladium (II) chloride, sodium palladium (II) chloride, and ammonium palladium (II) chloride. Catalyst solution for electroless plating. The catalyst solution for electroless plating according to any one of claims 1 to 3 , wherein the aqueous solution further contains a gold salt. The gold salt is at least one or more selected from tetrachlorogold (III) acid, sodium tetrachlorogold (III), potassium tetrachlorogold (III), and ammonium tetrachlorogold (III). The catalyst solution for electroless plating according to claim 4 , wherein The said chloride ion originates in at least 1 sort (s) or multiple types chosen from palladium salt, gold salt, hydrochloric acid, sodium chloride, and potassium chloride, The thing of Claim 1 or 5 characterized by the above-mentioned. Electrolytic plating catalyst solution.   The catalyst solution for electroless plating according to claim 1, wherein sodium hydroxide or potassium hydroxide is used for pH adjustment of the aqueous solution. The palladium salt is at least one or more selected from palladium (II) chloride, sodium palladium (II) chloride, and ammonium palladium (II) chloride, and the chloride ion includes a palladium salt, a gold salt, It originates in at least 1 sort (s) chosen from hydrochloric acid, sodium chloride, and potassium chloride, and sodium hydroxide or potassium hydroxide is used for pH adjustment of the said aqueous solution. The catalyst solution for electroless plating according to any one of the above. An electroless plating process comprising: applying a catalyst to an object to be plated using the electroless plating catalyst solution according to any one of claims 1 to 8; Plating method. Electroless plating can Way Method according to claim 9, characterized by applying electroless nickel plating on the object to be plated.

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