JP2006219715A - Method for plating metal on heat-resistant and insulative resin - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for forming a metallic layer in a desired portion of a heat-resistant and insulative resin such as a polyimide resin, which gives little load to the environment, needs few production steps and can reduce a treatment cost. <P>SOLUTION: The method for plating a metal on the desired portion of the heat-resistant and insulative resin comprises the steps of: (a) irradiating the desired portion of the heat-resistant and insulative resin with ultra-violet rays having wavelengths of 300 nm or shorter; (b) immersing the resin in an alkaline solution containing nonionic and/or anionic surfactants; (c) immersing the resin in a catalyst solution of an acidic colloid; and (d) plating a metal on the resin. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a metal plating method for a heat resistant insulating resin, and more particularly to a metal plating method capable of performing metal plating on a desired portion of the heat resistant insulating resin.

  In recent years, due to the downsizing and speeding up of electronic devices, polyimide resin films having a low dielectric constant, high insulation resistance, and good heat resistance have been widely used as flexible printed circuit board materials.

  Generally, a flexible printed circuit board is used in which at least one surface of a polyimide resin film is mainly coated with copper as a conductive layer. Conventionally, such a flexible printed circuit board has been used a three-layer base material by a laminate method in which a polyimide resin film and a copper foil are bonded via an adhesive. However, the adhesive makes the insulating and heat resistant of the substrate. In order to give an adverse effect, recently, a two-layer base material in which a metal layer is directly formed on a polyimide resin film has been used. And the dry method and the wet method are used for preparation of the two-layer base material which formed the metal layer on such a polyimide resin film.

  Examples of the dry method for producing the two-layer base material include a sputtering method for forming a metal layer on a polyimide resin film, a vacuum deposition method, an ion plating method, and a casting method for forming a polyimide resin film on a metal foil.

  On the other hand, examples of the wet method include a method using electroless plating and electroplating. Specifically, the polyimide resin film surface is hydrophilized using a mixed aqueous solution of hydrazine and alkali metal hydroxide, then electrolessly plated with nickel, cobalt, etc., and heat treated at a high temperature of about 450 ° C. A method of plating has been reported (Patent Document 1).

  Prior to plating by wet method, after the polyimide resin film surface is treated with short wavelength ultraviolet rays, the treated surface is activated with an alkali metal hydroxide to enhance the adhesive strength of copper, etc. Has also been reported (Patent Document 2).

  However, when forming a two-layer base material by forming a metal layer on a polyimide resin film by a conventional dry method or wet method, there are the following problems in forming a metal layer only on one side. For example, when the dry method is used, it is easy to form a metal layer on one side, but the apparatus becomes large and expensive. On the other hand, the wet method as described above uses a highly toxic hydrazine and requires high temperature treatment, so the environmental load is high. Furthermore, in order to form a metal layer only on one side, plating is unnecessary. In order to prevent metal deposition on the side, a masking step and a mask removing step are required, and the number of steps is increased.

Japanese Patent Application Laid-Open No. 5-114779 JP 2004-186661 A

  Therefore, the present invention can solve the above-mentioned technical problems, has a small environmental load, has a short number of steps, and can reduce costs. It is in providing the method of forming.

  As a result of intensive studies to achieve the above-mentioned problems, the inventors have irradiated a desired portion of the heat-resistant insulating resin with ultraviolet rays having a wavelength of 300 nm or less, and then applied a nonionic and / or anionic surfactant. It has been found that metal plating can be performed on a desired portion of the heat-resistant insulating resin by immersing in an alkaline solution contained and further immersing in an acidic colloid catalyst solution.

That is, the present invention provides the following steps (a) to (d)
(A) A step of irradiating a desired part of the heat-resistant insulating resin with ultraviolet rays having a wavelength of 300 nm or less (b) A step of immersing in an alkaline solution containing a nonionic and / or anionic surfactant (c) An acidic colloid catalyst solution (D) The metal plating method to the desired site | part of the heat resistant insulating resin characterized by including the process of performing metal plating is provided.

  Moreover, this invention provides the heat resistant insulating resin by which metal plating was given to the desired site | part of the surface obtained by the said metal plating method.

  According to the metal plating method of the present invention, metal plating can be performed only on a desired portion of the heat-resistant insulating resin. For example, flexible printing that requires plating on only one side or a predetermined pattern on the surface is possible. It can use suitably for manufacture of a wiring board etc.

  In addition, the metal plating method of the present invention does not require masking or high-temperature heat treatment as compared with the conventional method, and does not use a substance having a high environmental load, so that the cost for metal plating can be reduced. it can.

  The heat-resistant insulating resin to be plated by the metal plating method of the present invention is not particularly limited, and for example, UV irradiation such as polyamide, polyarylate, polyimide, polyetherketone, polyetherimide, polyphenylene sulfide, etc. Resins in which a part of the resin is destroyed by the process and a hydrophilic group such as a hydroxyl group, a carbonyl group, or a carboxyl group is generated. Among these heat resistant insulating resins, a polyimide resin excellent in heat resistance, electrical, mechanical and chemical properties is preferable. Moreover, although the form of these resin is not specifically limited, the film-like thing used for manufacture of a flexible printed wiring board is preferable.

The heat-resistant insulating resin can be subjected to metal plating on a desired site by processing in the following steps (a) to (d). Below, each process is demonstrated in detail.
(A) A step of irradiating a desired part of the heat-resistant insulating resin with ultraviolet rays having a wavelength of 300 nm or less (b) A step of immersing in an alkaline solution containing a nonionic and / or anionic surfactant
(C) Step of immersing in acidic colloid catalyst solution (d) Step of applying metal plating

In the step (a) of irradiating a desired part of the heat-resistant insulating resin with ultraviolet rays having a wavelength of 300 nm or less (hereinafter referred to as “ultraviolet ray irradiation step”), a low-pressure mercury lamp or excimer lamp is used as the ultraviolet light source. This is performed by irradiating a desired part of the heat-resistant insulating resin. By this ultraviolet irradiation process, the surface molecules of the heat-resistant insulating resin are cleaved to generate hydrophilic groups such as hydroxyl groups, carbonyl groups, and carboxyl groups. In the ultraviolet irradiation step, it is preferable to irradiate ultraviolet rays having a wavelength of 180 to 290 nm and an intensity of 5 mW / cm ² or more, and particularly irradiating ultraviolet rays having a wavelength of 254 nm and an intensity of 10 mW / cm ² or more. Is preferred.

  The heat resistant insulating resin subjected to the step (a) is then immersed in an alkaline solution containing a nonionic and / or anionic surfactant in the step (b) (hereinafter referred to as “alkali treatment step”). ) Examples of the nonionic and / or anionic surfactant include anionic surfactants such as sodium dodecyl sulfate, sodium laurate, sodium dodecylbenzenesulfonate, and nonionic surfactants such as polyethylene glycol and polyoxyethylene dodecyl ether. These may be used alone or in combination of two or more. Among these surfactants, anionic surfactants are preferable. The reason why cationic surfactants are not preferred as surfactants is that if they are used, the catalyst will be easily adsorbed even on the non-irradiated surface of the insulating resin and electroless plating will be performed on both sides. This is because it is difficult to plate only the side.

  The alkaline solution containing the surfactant is preferably an alkaline component such as sodium hydroxide, potassium hydroxide, lithium hydroxide, etc., adjusted to pH 8 or more, preferably pH 10-14. When the pH of the alkaline solution is less than 8, it is not preferable because the amount of catalyst adsorption is lowered and subsequent electroless plating may be difficult.

  As described above, the surface roughness (Ra) of the heat-resistant insulating resin that has undergone the alkali treatment step is increased by 2 times or more, preferably 3 to 10 times that before the ultraviolet irradiation, so that the catalyst adsorption amount and the adhesion of the copper plating layer are increased. Improves. In the present invention, the surface roughness means the arithmetic average roughness described in JIS B0601.

  The heat-resistant insulating resin treated in the step (b) is further subjected to a step of immersing in the acidic colloid catalyst solution in the step (c) (hereinafter referred to as “catalyst adsorption step”). Examples of the acidic colloid catalyst solution include tin-palladium, tin-rhodium, tin-ruthenium, tin-platinum, tin-silver, tin-nickel, tin-copper, tin-cobalt and the like. When an alkaline catalyst solution is used as the catalyst, it is not preferable because the catalyst is adsorbed and plated other than the ultraviolet irradiation surface (desired portion). The adsorption of the catalyst in this catalyst adsorption step may be performed under conditions of a treatment temperature of 20 to 40 ° C. and a treatment time of 1 to 10 minutes.

  The heat-resistant insulating resin subjected to the step (c) is subjected to an activation treatment, if necessary, and then subjected to metal plating as a step (d). The activation treatment liquid used in this activation treatment is not particularly limited, and examples thereof include a hydrochloric acid solution and a sulfuric acid solution used for normal activation treatment. In addition, hydrazine, tin chloride, formalin, sodium hypophosphite, a boron hydroxide compound, or an amine borane compound may be used for activation.

  In the metal plating step (hereinafter referred to as “metal plating step”) in the step (d), it is preferable to first perform electroless plating and then perform electroplating, but only electroless plating may be used. The metal to be plated is not particularly limited and includes nickel, cobalt, copper and the like. Also, the plating conditions may be appropriately determined according to the metal to be plated and the film thickness. For example, in the case of a metal plating process for manufacturing a flexible printed wiring, the electroless nickel plating may be performed under such a condition that the film thickness is about 0.05 to 0.3 μm and the electrolytic copper plating is about 5 to 35 μm. .

  In the metal plating method of the present invention, a process such as drying can be appropriately added as long as the effect is not impaired.

  Hereinafter, the present invention will be specifically described by way of examples and comparative examples of the present invention, but the present invention is not limited thereto.

Example 1
A 10 × 10 cm polyimide resin film (Kapton 100EN: manufactured by Toray DuPont) is set in an ultraviolet irradiation device (manufactured by Sen Engineering Co., Ltd.). ² ) was irradiated for 60 seconds.

  Next, a mixed aqueous solution (pH 13) containing 0.5 g / L of sodium dodecyl sulfate and 50 g / L of sodium hydroxide was heated to 50 ° C., and the polyimide resin film irradiated with ultraviolet rays was immersed therein for 3 minutes. Washed with water. With these treatments, the surface roughness (Ra) of the polyimide resin film increased from 0.99692 nm before UV irradiation to 3.282 nm. The surface roughness was measured using a probe microscope (SPA-400: manufactured by SSI Nano Technology).

  Subsequently, this was subjected to a catalytic treatment for 5 minutes with a 25 ° C. tin-palladium mixed catalyst solution (PB-318: manufactured by Ebara Eugleite Co., Ltd.), and then an activation treatment solution (PB-445: Ebara, also at 25 ° C.). The activation treatment was performed for 5 minutes.

Further, this was treated at 35 ° C. for 2 minutes with an electroless nickel plating bath (Enilex NI-100: manufactured by Ebara Eugene Corporation) to form a nickel layer having a thickness of 0.1 μm. Subsequently, after drying at 80 ° C. for 15 minutes using a dryer, copper sulfate 75 g / L, sulfuric acid 180 g / L, hydrochloric acid 40 mg / L, brightener (Cubelight 21MU: manufactured by Ebara Eugene Corporation) 5 ml / L Was electroplated at 25 ° C. and 2 A / dm ² for 50 minutes to form a 20 μm copper layer on the nickel layer, and a flexible printed circuit board was produced.

Example 2
A flexible printed circuit board was produced in the same manner as in Example 1 except that ultraviolet irradiation was performed with the ultraviolet intensity at a wavelength of 254 nm set to 10 mW / cm ^{2 in} Example 1.

Example 3
A flexible printed circuit board was produced in the same manner as in Example 1 except that in Example 1 above, ultraviolet irradiation was performed with an ultraviolet intensity of 254 nm at a wavelength of 5 mW / cm ² .

Example 4
A flexible printed circuit board was produced in the same manner as in Example 1 except that the same amount of sodium glycol dodecyl sulfate (molecular weight 1000) as nonionic surfactant was used.

Comparative Example 1
A polyimide resin film was treated in the same manner as in Example 1 except that ultraviolet irradiation was not performed in Example 1 above.
However, in this comparative example, film formation of electroless nickel plating was not recognized, and therefore, electrolytic copper plating could not be performed.

Comparative Example 2
A polyimide resin film was treated in the same manner as in Example 1 except that the same amount of sodium dodecyl sulfate and dodecyltrimethylammonium chloride as a cationic surfactant was used in Example 1 above.
However, in this comparative example, electroless nickel plating was observed on both sides of the polyimide resin film, that is, on the non-irradiated surface.

Comparative Example 3
A polyimide resin film was treated in the same manner as in Example 1 except that only 0.5 g / L of sodium dodecyl sulfate was used in the above example and an aqueous solution (pH 6) containing no alkali component was used.
However, in this comparative example, film formation of electroless nickel plating was not recognized, and thus it was not electrolytic copper plating.

Comparative Example 4
In Example 1 above, instead of the tin-palladium mixed catalyst solution, an alkali ion catalyst (Activator PC-65H (treatment conditions: 50 ° C., 5 minutes): manufactured by Ebara Eugilite) was used, and the activation treatment liquid (PB- 445: Example except that the activation treatment was carried out with a reduction treatment solution (Accelerator PC-66H (treatment conditions: 35 ° C., 5 minutes): produced by Ebara Eugelite) instead of the activation treatment with Ebara Eugene Light). The polyimide resin film was processed in the same manner as in 1.
However, in this comparative example, electroless nickel plating was observed on both sides of the polyimide resin film, that is, on the non-irradiated surface.

Test example 1
Adhesion strength test:
About the flexible printed circuit board of Examples 1-4 and Comparative Examples 1-4, the depositing state of plating was evaluated on the following evaluation criteria. Moreover, about what the plating deposited, the notch which reaches to a heat resistant insulating resin was made into the copper plating layer by 1 cm width, and the adhesive force of the copper plating layer was measured with the tension tester. These results are shown in Table 1.

<Evaluation criteria for plating deposition state>
(Evaluation) (Content)
○: Plated on one side only △: Plated on both sides ×: Not plated

Since the metal plating method of the present invention can perform metal plating on a desired portion of the heat-resistant insulating resin, it is particularly suitable for manufacturing a flexible printed wiring board.
more than

Claims (5)

Next steps (a) to (d)
(A) A step of irradiating a desired part of the heat-resistant insulating resin with ultraviolet rays having a wavelength of 300 nm or less (b) A step of immersing in an alkaline solution containing a nonionic and / or anionic surfactant
(C) The process of immersing in an acidic colloid catalyst solution (d) The metal plating method to the desired site | part of the heat resistant insulating resin characterized by including the process of performing metal plating. The metal plating method according to claim 1, wherein the ultraviolet ray having a wavelength of 300 nm or less described in step (a) is an ultraviolet ray having a wavelength of 180 to 290 nm and an intensity of 5 mW / cm ² or more.   The metal plating method according to claim 1 or 2, wherein the pH of the alkaline solution described in step (b) is 8 or more.   The metal plating method according to any one of claims 1 to 3, wherein the heat-resistant insulating resin is a polyimide resin. A heat-resistant insulating resin obtained by applying metal plating to a desired portion of a surface obtained by the metal plating method according to any one of claims 1 to 4.