JP2005120407A - Method for electroless-plating article to be plated having polyimide resin - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for electroless-plating an article to be plated having a polyimide resin, which is superior in safety during a plating operation, does not cause the blister and peeling of the plating film from the polyimide resin at all, and rapidly and uniformly grows a plating film having adequate adhesiveness. <P>SOLUTION: The method for electroless-plating the article to be plated having the polyimide resin comprises a pretreatment step of immersing the article to be plated in an aqueous solution containing one or more alkali metal compounds and one or more primary amino alcohols; a degreasing and cleaning step; a catalyst-imparting step; and a catalyst-activating step. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an electroless plating method for an object to be plated having a polyimide resin. More specifically, for example, the present invention relates to an electroless plating method on a through hole or a via hole of a multilayer printed wiring board in which the whole or a part of an insulating layer of the printed wiring board is made of a polyimide resin as an object to be plated.

  Polyimide resin is a plastic having excellent heat resistance and electrical insulation, and is used as an insulating material for various electronic devices. For example, it is widely used as an insulating material for flexible printed circuit boards and tape automatic bonding (TAB) mounting substrates. Further, with the recent popularization of portable electronic devices, there is an increasing demand for rigid flex wiring boards in which a flexible printed wiring board is used as a core layer and multilayered.

  In addition to the polyimide resin used as the core layer, the rigid flex wiring board includes a conductive layer mainly made of metallic copper, an insulating layer made of glass cloth, epoxy resin, and the like. When a through hole is formed in this wiring board and electroless plating for imparting conductivity is performed, a plating layer must be formed quickly and uniformly on all the constituent layers. Also, the plating film should not swell or peel off after electroless plating or after electroplating.

  However, the electroless plating method used for the conventional printed wiring board has a problem in the adhesion between the polyimide resin and the plating film. Further, if the adhesion of the film is weak, the plating film is peeled off during electroless plating, and the film falls to the plating bath, so that the decomposition of the plating bath is accelerated.

  As a method of performing electroless plating on a polyimide resin, it is difficult to perform electroless plating after performing etching which has been conventionally performed with ABS resin or the like. For example, amides, pyrrolidones and complex compounds can be used before etching. Perform pre-etching to swell the resin using a mixed solution or aqueous solution containing cyclic carbonates as the main component, then etch with chromic acid / sulfuric acid mixed solution, and then immerse in autocatalytic electroless plating solution A method has been proposed (for example, Patent Document 1).

  In the present specification, the “self-catalyzed electroless plating solution” is a solution used in “chemical reduction plating” using a reducing agent for plating reaction in electroless plating, The metal ion which becomes the raw material of the metal (metal which forms a plating layer) which has a catalytic action is shown. That is, the above-mentioned metal is a catalytic action (autocatalyst) with respect to the reaction between the reducing agent and the metal ion when the raw material metal ion is reduced by the reducing agent and deposited as metal on the surface of the object to be plated. It has an action).

  As another method, an electroless plating method including a step of applying a catalyst after a step of treating with an aqueous solution containing hydrazine hydrate and an alkali metal hydroxide has been proposed (Patent Documents 2 and 3). .

Japanese Patent Laid-Open No. 5-112872 Japanese Patent No. 3166868 Japanese Patent Laid-Open No. 5-112873

  In these methods, the former is a method using a mixed solution of chromic acid and sulfuric acid, and it is necessary to consider the working environment and environmental pollution, and the latter is a method using a large amount of explosive hydrazine, Safety must be considered.

  The present invention has been made in view of the above problems, and when performing electroless plating on an object to be plated having a polyimide resin, there is no swelling or peeling of the plating film from the polyimide resin, and the adhesion is good. An object is to provide an electroless plating method in which a plating film grows rapidly and uniformly. Moreover, it aims at providing the electroless-plating method which considered the safety | security at the time of plating operation.

As a result of intensive studies, the present inventors have found that the above object can be achieved by an electroless plating method that satisfies the following specific conditions, and have reached the present invention.
That is, the invention according to claim 1 of the present invention includes at least one alkali metal compound and at least one primary amino alcohol as a pretreatment for performing electroless plating on an object to be plated having a polyimide resin. An electroless plating method characterized by performing electroless plating including a step of immersing an object to be plated in an aqueous solution containing, a step of degreasing and washing, a catalyst application step, and a catalyst activation step.
The invention according to claim 2 immerses the object to be plated in an aqueous solution containing at least one alkyl alcohol in addition to the at least one alkali metal compound and the at least one primary amino alcohol. The electroless plating method according to claim 1, wherein:
The invention according to claim 3 is characterized in that the one or more alkali metal compounds are lithium hydroxide, sodium hydroxide, potassium hydroxide, lithium carbonate, sodium carbonate, potassium carbonate, trilithium phosphate, tribasic phosphate. The electroless plating method according to claim 1 or 2, wherein the electroless plating method is selected from the group consisting of sodium, tripotassium phosphate, lithium silicate, sodium silicate, and potassium silicate.
The invention according to claim 3 is characterized in that the one or more primary amino alcohols are 2-aminoethanol, 1-amino-2-propanol, 2-amino-1-propanol, 3-amino-1- The electroless plating method according to any one of claims 1 to 3, which is selected from the group consisting of propanol and 2-amino-1-butanol.

The present invention provides an aqueous solution containing one or more alkali metal compounds and one or more primary amino alcohols as a pretreatment for performing electroless plating on an object having a polyimide resin. The present invention provides an electroless plating method characterized by performing degreasing and cleaning, and then performing electroless plating including a catalyst application step and a catalyst activation step.
In the electroless plating method of the present invention, since the polyimide resin is hydrophilized by the above pretreatment, the subsequent degreasing, catalyst application and activation, and the electroless plating reaction should be performed quickly and uniformly on the polyimide resin surface. Can do.

  Further, in the electroless plating method of the present invention, the object to be plated is immersed in an aqueous solution containing one or more kinds of alkyl alcohols in addition to one or more kinds of alkali metal compounds and one or more kinds of primary amino alcohols. It is characterized by. As a result, the polyimide resin is hydrophilized more effectively, so that the subsequent degreasing and cleaning, catalyst application and activation, and electroless plating reaction can be performed quickly and uniformly on the polyimide resin.

  By using the object to be plated that has been pretreated by the method of the present invention, there is no problem that undeposited portions are generated on the surface of the polyimide resin in the object to be plated, or the plating film is not formed with a uniform thickness. Generation | occurrence | production of the problem of the swelling and peeling of the plating film after electrolytic plating is fully prevented, and the plating film with favorable adhesiveness can be deposited rapidly and uniformly. Further, according to the present invention, since a treatment solution using chromic acid or hydrazine having a safety problem is not used, it is possible to provide an electroless plating method that is easy to handle during a plating operation.

Hereinafter, preferred embodiments of the electroless plating method of the present invention will be described in detail.
In the electroless plating method of the present invention, the object to be plated is immersed in an aqueous solution containing one or more alkali metal compounds and one or more primary amino alcohols, and then degreased and washed, and then provided with a catalyst. Electroless plating including a process and a catalyst activation process is performed.
The concentration of the alkali metal compound is preferably 0.05 to 10 mol / L. When the concentration of the alkali metal compound is less than 0.05 mol / L, the hydrophilicity of the polyimide resin in the object to be plated becomes insufficient, and when the concentration of the alkali metal compound exceeds 10 mol / L, the polyimide resin Will dissolve and contaminate the object to be plated, so that the effects of the present invention described above cannot be obtained.

  The concentration of the primary amino alcohol is preferably 0.005 to 5 mol / L. When the amino alcohol concentration is less than 0.005 mol / L, the hydrophilicity of the polyimide resin in the object to be plated is insufficient, and when the amino alcohol concentration exceeds 5 mol / L, the polyimide resin is dissolved. Since the object to be plated is contaminated, the effects of the present invention described above cannot be obtained.

  In addition, the electroless plating method of the present invention is a method in which an object to be plated is immersed in an aqueous solution containing at least one alkyl alcohol in addition to at least one alkali metal compound and at least one primary amino alcohol. , Degreasing and cleaning, and then performing electroless plating including a catalyst application step and a catalyst activation step.

  The concentration of the alkyl alcohol is preferably 10 mol / L or less. When the concentration of the alkyl alcohol exceeds 10 mol / L, the volatility of the treatment liquid increases, and the polyimide resin in the object to be plated dissolves and contaminates the object to be plated. The effect of cannot be obtained.

  Examples of the alkali metal compound contained in the pretreatment aqueous solution include lithium hydroxide, sodium hydroxide, potassium hydroxide, lithium carbonate, sodium carbonate, potassium carbonate, trilithium phosphate, trisodium phosphate, tripotassium phosphate, silica It is preferably at least one selected from the group consisting of lithium acid, sodium silicate, and potassium silicate.

  The primary amino alcohol contained in the pretreatment aqueous solution is 2-aminoethanol, 1-amino-2-propanol, 2-amino-1-propanol, 3-amino-1-propanol, 2-amino-1 -It is preferably at least one selected from the group consisting of butanol.

  The alkyl alcohol contained in the pretreatment aqueous solution is preferably at least one selected from the group consisting of methanol, ethanol, 1-propanol, and 2-propanol.

  The temperature of the pretreatment aqueous solution is preferably 5 to 70 ° C. Moreover, in order to perform hydrophilicization of a polyimide resin more efficiently, it is preferable that it is 30-60 degreeC. If the temperature of the aqueous solution is less than 5 ° C., the hydrophilicity of the polyimide resin in the object to be plated becomes insufficient, and if the temperature of the aqueous solution exceeds 70 ° C., the polyimide resin dissolves and contaminates the object to be plated. Therefore, the effect of the present invention described above cannot be obtained.

  The time for immersing the object to be plated in the pretreatment aqueous solution is preferably between 30 seconds and 20 minutes. Moreover, in order to hydrophilize polyimide resin more efficiently, it is preferable that it is between 1 minute and 10 minutes. If the immersion time is less than 30 seconds, the hydrophilicity of the polyimide resin in the object to be plated becomes insufficient, and if the immersion time exceeds 20 minutes, the polyimide resin dissolves and contaminates the object to be plated. Therefore, the effect of the present invention described above cannot be obtained.

  Further, the object to be plated obtained after being immersed in the pretreatment aqueous solution may be further washed with water. This operation is for removing an excess amount of the pretreatment liquid adhering to the surface of the object to be plated. By optimizing the cleaning conditions, it is possible to remove excess pretreatment liquid adhering to the surface of the object to be plated. The water used for washing is more preferably ion exchange water.

  As a result, when the object to be plated is immersed in an electroless plating solution in the subsequent plating step, the plating reaction can be efficiently advanced on the surface of the object to be plated, and the surface of the object to be plated can be efficiently processed. A plating film can be deposited uniformly.

  In addition, in said pre-processing, you may employ | adopt the method of drying, after apply | coating a pre-processing liquid to a to-be-plated thing.

  In the plating step, after the pretreatment, the object to be plated obtained after the degreasing cleaning, the catalyst application and the activation treatment is immersed in an autocatalytic electroless plating solution. As the autocatalytic electroless plating solution to be used, a known autocatalytic electroless plating solution can be used. For example, electroless copper plating solution, electroless nickel-phosphorous plating solution, electroless nickel-boron plating solution, electroless palladium plating solution, electroless silver plating solution, electroless gold plating solution and the like.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples.

(Example 1)
A 50 × 50 mm, 25 μm thick polyimide film “Kapton V” (trade name, manufactured by Toray DuPont Co., Ltd.) was used as an object to be plated, and electroless copper plating was performed in the following steps.

  First, as a pretreatment, an aqueous solution containing 0.5 mol / L of sodium hydroxide as an alkali metal compound and 0.2 mol / L of 2-aminoethanol as a primary amino alcohol was adjusted to 50 ° C. The polyimide film of the object to be plated was immersed for 5 minutes to make the polyimide film hydrophilic. Next, it was washed with water at room temperature (25 ° C.) for 5 minutes.

  Next, as a process of degreasing, the liquid temperature of “CLC-601” (trade name, manufactured by Hitachi Chemical Co., Ltd.), which is a cleaner conditioner (liquid), is adjusted to 60 ° C., and a polyimide film is placed in this liquid. It was immersed for 5 minutes, washed and conditioned for the polyimide film, and then washed with water for 2 minutes at room temperature.

  Next, the polyimide film obtained as a catalyst provision process and a catalyst activation process was immersed in "PD-301" (Hitachi Chemical Industry Co., Ltd., a brand name) which is an acidic process liquid for 2 minutes at room temperature. And it immersed for 5 minutes at room temperature in "HS-202B" (made by Hitachi Chemical Co., Ltd., brand name) which is a catalyst solution for electroless plating. The obtained polyimide film was washed with water at room temperature for 2 minutes.

  Next, the polyimide film obtained above was immersed in “ADP-202” (trade name, manufactured by Hitachi Chemical Co., Ltd.), which is an acidic treatment solution, at room temperature for 5 minutes. In this way, a palladium catalyst for electroless plating was deposited on the surface of the polyimide film. And the polyimide film obtained here was washed with water for 2 minutes at room temperature.

  The polyimide film obtained above was immersed in “CUST-201” (trade name, manufactured by Hitachi Chemical Co., Ltd.), an autocatalytic electroless copper plating solution, at a liquid temperature of 25 ° C. for 15 minutes (plating step). . And it washed with water for 5 minutes at room temperature, and dried for 10 minutes at 80 degreeC. In this manner, an electroless copper plating film (film thickness: 0.22 μm) was formed on the surface of the polyimide film.

  In order to evaluate the adhesion between the object to be plated and the electroless copper plating film, a rectangular cellophane adhesive tape (made by Nichiban Co., Ltd., trade name: “Cero tape” (size: 18 mm × 50 mm) was strongly attached, and a peeling test was performed. This test was performed at room temperature (25 ° C.) and 55% relative humidity. The results are shown in Table 1 below.

(Example 2)
Using a polyimide film “UPILEX S” (trade name, manufactured by Ube Industries Co., Ltd.) having a size of 50 × 50 mm and a thickness of 50 μm, an electroless copper plating film ( (Film thickness: 0.21 μm).
Next, in order to evaluate the adhesion between the object to be plated and the electroless plating film, a peeling test was conducted by the same method as in Example 1, and the results are shown in Table 1 below.

(Example 3)
As the pretreatment, Examples were used except that an aqueous solution containing 2.0 mol / L of ethanol as an alkyl alcohol in addition to 0.5 mol / L of sodium hydroxide and 0.2 mol / L of 2-aminoethanol was used as the pretreatment liquid. 1 was used to form an electroless copper plating film (film thickness: 0.24 μm) on the surface of the polyimide film.
Next, in order to evaluate the adhesion between the object to be plated and the electroless plating film, a peeling test was conducted by the same method as in Example 1, and the results are shown in Table 1 below.

Example 4
As the pretreatment, Examples were used except that an aqueous solution containing ethanol 2.0 mol / L in addition to sodium hydroxide 0.5 mol / L and 2-aminoethanol 0.2 mol / L was used as the pretreatment liquid. By the same procedure and conditions as in No. 2, an electroless copper plating film (film thickness: 0.20 μm) was formed on the surface of the polyimide film.
Next, in order to evaluate the adhesion between the object to be plated and the electroless plating film, a peeling test was conducted by the same method as in Example 1, and the results are shown in Table 1 below.

(Comparative Example 1)
A 50 × 50 mm, 25 μm thick polyimide film “Kapton V” (trade name, manufactured by Toray DuPont Co., Ltd.) was used as an object to be plated, and electroless copper plating was performed in the following steps.
Adjust the liquid temperature of “CLC-601”, a cleaner conditioner (liquid), to 60 ° C., immerse the polyimide film in this liquid for 5 minutes, wash and condition the polyimide film, and then at room temperature (25 ° C.). Washed with water for 2 minutes.
Then, it was immersed for 2 minutes at room temperature in “PD-301” which is an acidic treatment solution, and was immersed for 5 minutes in “HS-202B” which is a catalyst solution for electroless plating at room temperature. Next, it was washed with water at room temperature for 2 minutes and immersed in “ADP-202”, which is an acidic treatment solution, for 5 minutes at room temperature. In this way, a palladium catalyst for electroless plating was deposited on the surface of the polyimide film. The polyimide film obtained above was washed with water at room temperature for 2 minutes and immersed in “CUST-201” which is an autocatalytic electroless copper plating solution at a liquid temperature of 25 ° C. for 15 minutes. It was washed with water at room temperature for 5 minutes and dried at 80 ° C. for 10 minutes. In this way, an electroless copper plating film (film thickness: 0.24 μm) was formed on the surface of the polyimide film.
In order to evaluate the adhesion between the object to be plated and the electroless plating film, a peeling test was conducted by the same method as in Example 1, and the results are shown in Table 1 below.

(Comparative Example 2)
Using a polyimide film “UPILEX S” (trade name, manufactured by Ube Industries Co., Ltd.) having a size of 50 × 50 mm and a thickness of 50 μm, an electroless copper plating film ( (Film thickness: 0.23 μm). In order to evaluate the adhesion between the object to be plated and the electroless plating film, a peeling test was conducted by the same method as in Example 1, and the results are shown in Table 1 below.

  As is apparent from the results in Table 1, the electroless plating method (Examples 1 to 4) of the present invention is superior in adhesion compared to the conventional electroless plating methods (Comparative Examples 1 and 2). Was confirmed. In Comparative Examples 1 and 2, swelling of the plating film was visually observed after electroless copper plating.

(Example 5)
Each aqueous solution having the composition shown in Table 2 was adjusted to 50 ° C., and a polyimide film (Kapton V, Upilex S) as an object to be plated was immersed in this solution for 5 minutes to hydrophilize the polyimide film. Washed with water for a minute. Water droplets remaining on the obtained polyimide film were removed by CO ₂ blow, and then dried at 80 ° C. for 10 minutes. And as shown in FIG. 1, 1 microliters pure water was dripped slowly at the polyimide film, and the contact angle x (degree) of the water on a polyimide film was measured. The results (average values) are shown in Table 2.

  As is clear from the results in Table 2, it was confirmed that the polyimide surface was hydrophilized by the pretreatment of the electroless plating method of the present invention.

The figure explaining the contact angle used in Example 5 of this invention.

Claims (4)

A step of immersing the object to be plated in an aqueous solution containing one or more kinds of alkali metal compounds and one or more kinds of primary amino alcohol as a pretreatment for performing electroless plating on the object to be plated having a polyimide resin, degreasing cleaning An electroless plating method comprising performing electroless plating including a step of performing a catalyst, a catalyst applying step, and a catalyst activation step. The object to be plated is immersed in an aqueous solution containing one or more alkyl alcohols in addition to the one or more alkali metal compounds and the one or more primary amino alcohols. Electroless plating method. The one or more alkali metal compounds are lithium hydroxide, sodium hydroxide, potassium hydroxide, lithium carbonate, sodium carbonate, potassium carbonate, trilithium phosphate, trisodium phosphate, tripotassium phosphate, lithium silicate, The electroless plating method according to claim 1 or 2, wherein the electroless plating method is selected from the group consisting of sodium silicate and potassium silicate. The one or more primary amino alcohols comprise 2-aminoethanol, 1-amino-2-propanol, 2-amino-1-propanol, 3-amino-1-propanol, 2-amino-1-butanol. The electroless plating method according to any one of claims 1 to 3, wherein the electroless plating method is selected from the group.

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