JPH09111472A - Formation of metallic conductive layer on fluororesin body surface - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily form a metallic conductive layer on the surface of a fluororesin body with a small number of stages by making the surface of a fluororesin body to be plated hydrophilic and then successively forming a substrate silver conductive layer and a copper electroplating layer on the surface. SOLUTION: A fluororesin body (tetrafluoroethylene resin, etc.) to be plated is passed through alcohol to remove the contaminant such as grease depositing on the surface and then passed through a metallic sodium-naphthalene complex soln. to make its surface hydrophilic. The body is washed with water and passed through a reducing agent contg. silver-mirror plating soln. to form a substrate silver plating layer on the surface by the autocatalytic reaction. The body is washed with water, then electroplated in a copper electroplating soln. to form a copper electroplating layer on the substrate silver plating layer and then washed with water. Consequently, the production cost is reduced, and a fluororesin body stabilized in quality is produced in good yield.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a metal conductive layer on the surface of a fluororesin body, and particularly to a surface of a fluororesin composition used for members such as coaxial cables and electric circuit boards for high frequency applications. The present invention relates to a method of forming a highly conductive metal layer.

[0002]

2. Description of the Related Art Fluororesins having a low dielectric constant are used for insulating members such as coaxial cables and electric circuit boards which require excellent high-frequency performance. However, since the fluororesin has chemically stable characteristics, it is considerably difficult to form a metal conductive layer having strong adhesion on the surface, and the essential point is to modify the surface of the fluororesin body. The selection of the means for forming the underlying metal conductive layer can be mentioned. As the means for modifying the surface of the fluororesin body, a method of chemically modifying the surface of the fluororesin body with an etching treatment liquid or a method of physically modifying the surface of the fluororesin body with plasma or excimer laser is used. Etc. However, the means for modifying the surface of the fluororesin body using plasma or excimer laser has a drawback that the equipment cost is high, and therefore chemical modifying means is generally used. Further, as a means for forming the underlying metal conductive layer, a forming means by electroless plating is mainly adopted. In addition to this, since it is difficult to modify the surface of the fluororesin body, glass fiber or metal filler is added to the fluororesin material to roughen the fluororesin, and the anchor effect of this additive is used. A method of adhering a metal foil to the surface of the fluororesin body has also been proposed. However, this method is not sufficient in terms of the adhesive strength between the fluororesin and the metal body, and has the drawback that the high-frequency transmission characteristics are hindered by the interposition of an additive filler or an adhesive. Therefore, conventionally, a combination of a chemical surface modification method and a metal plating method has been generally adopted as a method for forming a metal conductive layer on the surface of a fluororesin.

A conventional technique of forming a metal conductive layer on the surface of a fluororesin by a chemical surface modification method and a metal plating method will be described below with reference to FIG. FIG. 4 shows a flowchart of the manufacturing process, which will be described along with each process.
(1) First, by degreasing treatment, dirt such as oil and fat and dust adhering to the surface of the plated fluororesin body is removed with a cleaning liquid such as alcohol. (2) Next, in the surface modification treatment, the surface of the fluororesin body is micro-etched using an etching solution to make the surface hydrophilic. This treatment step has an important influence on the success or failure of quality formation such as adhesion and appearance of the metal plating layer in the subsequent plating step, and it has been difficult to modify the surface of chemically stable fluororesin until now. But recently
With the use of metal sodium naphthalene complex solution, surface modification became relatively easy. (3) Next, the surface of the modified fluororesin body is negatively (-) charged by a conditioner treatment. A surfactant and a sodium hydroxide solution are used as the treatment liquid. (4) Next, in the pre-depping treatment, a 35% hydrochloric acid solution is used to prevent the alkaline liquid or water adhering to the surface of the fluororesin body from the previous step from mixing in the catalyzed treatment solution in the next step. Remove this.

Next, a catalytic process for depositing a catalytic metal on the surface of the fluororesin body before plating is started. (5) First, by activating, Pd ⁺⁺ and Sn ⁺⁺ are adsorbed in a colloidal state on the surface of the fluororesin body. The catalyst liquid contains palladium chloride (PdCl ₂ ) and tin chloride (Sn
A mixture of Cl ₂ ) and 35% hydrochloric acid is used. (6) Next, in an accelerator treatment, Pd ⁺⁺ is reduced as metal Pd to the surface of the fluororesin body by an oxidation-reduction reaction [Sn ⁺⁺ + Pd ⁺⁺ → Sn ⁺⁺⁺⁺ + Pd ⁰ ] between SnCl ₂ and PdCl _2. Is deposited.

Through the above pretreatment steps, the plated fluororesin body is introduced into the plating step. (7) First, the surface of the fluororesin body on which the metal Pd is deposited is nickel-plated by electroless nickel plating as the base metal plating. (8) Next, by electroplating,
An electrolytic copper plating layer is applied on the electroless nickel plating layer on the surface of the fluororesin body. Through the above steps, the step of forming the metal-plated conductive layer on the surface of the fluororesin body is completed.

[0006]

As described above, in the conventional method, many steps are required to form the metal plating layer on the surface of the fluororesin body. In particular, the pretreatment step of the electroless nickel plating treatment involves a chemisorption reaction step of depositing a catalytic metal on the surface of the fluororesin body before plating, so the number of series of steps involved in this increases and the treatment time also increases. Become longer,
Also, it was difficult to manage the liquid under stable conditions in each process. For this reason, there has been a problem that the production cost increases and the product yield decreases due to the occurrence of defects.

Therefore, an object of the present invention is to provide a method for forming a metal plating layer on the surface of a fluororesin body which has a small number of steps and is easy to manage.

[0008]

In order to achieve the above object, the method for forming a metal conductive layer on the surface of a fluororesin body of the present invention comprises:
A surface modification step of hydrophilizing the surface of the plated fluororesin body; a step of forming an underlying silver conductive layer on the surface-modified plated fluororesin body surface by a silver mirror reaction method; The constitutional feature is that it comprises a step of forming a copper plating layer on the base silver conductive layer by an electroplating method.

[0009]

In the method for forming a metal conductive layer on the surface of a fluororesin according to the present invention, the surface of the fluororesin to be plated is made hydrophilic, and the surface of the modified fluororesin is first subjected to silver mirror reaction by a silver base reaction. It forms a layer. In the step of forming the underlying silver conductive layer by the silver mirror reaction method, a series of pretreatment steps such as the chemical adsorption reaction step of the conventional method are not required, and only a silver mirror plating step is necessary, so the process management is easy. Becomes As a result, the manufacturing cost is gradually reduced, the product quality is stable, and the yield is improved. Further, since the obtained base silver plating layer has extremely strong adhesion to the surface of the fluororesin body, it is possible to form a copper plating layer having a thickness of several tens to several hundreds of microns by the electroplating step of the next step. .
Further, since the underlying silver conductive layer having excellent conductivity is interposed between the surface of the fluororesin body and the copper-plated conductive layer, excellent high frequency transmission characteristics can be provided.

[0010]

Embodiments of the present invention will be described in detail below with reference to the flow chart of the manufacturing process of FIG.

The fluororesin to be plated is first subjected to (1) a degreasing treatment step through an alcohol liquid to remove dirt such as oil on the surface, and then (2) a hydrophilic treatment step, for example, a treatment liquid. After passing through the metal sodium naphthalene complex solution, the surface is modified to be a hydrophilic surface, and the carry-in solution is removed in the (3) water washing step. The steps up to this point are the same as those of the above-described conventional technique, and thus detailed description thereof will be omitted. Next, the fluororesin to be plated enters (4) a silver mirror plating step, passes through a silver mirror plating solution containing a reducing agent, forms a base silver plating layer on the surface by an autocatalytic reaction, and (5) is washed with water. It As the silver mirror plating solution, for example, (a) a composition bath solution using ammonia as a reducing agent; AgNO ₃ = 7.5 g / dm ³ , NH ₄ OH =
75 g / dm ³ , NH ₄ NO ₃ = 100 g / dm ³ , or (b) a composition bath solution using Rochelle salt as a reducing agent; AgNO
₃ = 0.02 mol / dm ³ , NH ₃ = 0.17 mol
/ Dm ³ , Rochelle salt = 0.02 mol / dm ³ , KO
H = 0.1 mol / dm ³ ; and the like. Then
The fluororesin to be plated enters (6) the electroplating process, an electrocopper plating layer is formed on the base silver plating layer in the electrolytic copper plating solution, and (7) the surface is subjected to a water washing treatment to form a metal conductive layer on the surface. To finish. It should be noted that the above-mentioned hydrophilic treatment of the surface of the fluororesin to be plated does not depart from the object and effect of the present invention even if excimer laser irradiation treatment or plasma treatment is used in place of the metal sodium naphthalene complex solution treatment.

Next, examples of the high frequency coaxial line of FIG. 2 and the low dielectric constant printed circuit board of FIG. 3 to which the method of the present invention is applied will be described.

Example 1 A PTFE-insulated electric wire 1 having an outer diameter of 0.66 mm obtained by extrusion-coating a tetrafluoroethylene resin (PTFE) 3 on a silver-plated copper-coated steel wire 2 having a wire diameter of 0.203 mm is plated. It was a wire rod. After the wire to be plated 1 is passed through an alcohol liquid to remove oils and fats on the surface, 1 in a metal sodium naphthalene complex solution at a liquid temperature of 10 ° C (for example, Tetra Etch manufactured by Junkosha Co., Ltd.) The surface was made hydrophilic by dipping and passing it for a minute, and washed with water. Then, the plated wire 1
0.05 μm on the surface by dipping and passing it in a silver mirror plating composition liquid using the ammonia (a) above at a liquid temperature of 25 ° C as a reducing agent.
A base silver plating layer 4 having a thickness was formed. The required processing time at this time was 0.2 minutes. After that, it is washed with water to remove the carry-in solution, subsequently introduced into a copper sulfate plating solution having a solution temperature of 25 ° C., and electroplated with copper at a current density condition of 4 A / dm ² for 120 minutes to give a thickness of 100 μm. The copper electroplating layer 5 was formed and washed with water to obtain a high frequency coaxial wire 6.

--Example 2-- In the silver mirror plating step, the same wire material 1 to be plated as in Example 1 was used.
A high-frequency coaxial cable 6 was obtained under exactly the same processing conditions as in Example 1 except that the base silver plating layer 4 having a thickness of 1 μm was formed and the required processing time at this time was 0.4 minutes.

-Example 3-In the silver mirror plating step, the same wire material 1 to be plated as in Example 1 was used.
A high-frequency coaxial wire 6 was obtained under exactly the same processing conditions as in Example 1 except that a base silver plating layer 4 having a thickness of 5 μm was formed and the processing time required at this time was 2 minutes.

Example 4 In the silver mirror plating step, the same plated wire 1 as in Example 1 was used.
A high-frequency coaxial wire 6 was obtained under exactly the same processing conditions as in Example 1 except that the base silver plating layer 4 having a thickness of 0 μm was formed and the processing time required at this time was 4 minutes.

Example 5 A PTFE substrate having a length of 150 mm × a width of 150 mm × a thickness of 1 mm was used as the material 11 to be plated. After removing oils and fats on the surface of the material 11 to be plated in an alcohol liquid, the liquid temperature is 10 ° C.
It was immersed for 1 minute in the metal sodium naphthalene complex solution described above to make the surface hydrophilic, and then washed with water. Then, the material 11 to be plated is immersed for 24 seconds in a silver mirror plating composition solution using the Rochelle salt of (b) above at a liquid temperature of 25 ° C. as a reducing agent, and the surface of the underlying silver plating layer 12 having a thickness of 0.1 μm is formed. After removing the carry-in liquid by washing with water, the liquid temperature is continuously adjusted to 25
Copper electroplating was performed in a copper sulfate plating solution at a temperature of 5 ° C. under a current density condition of 5 A / dm ² for 45 minutes to form an electrolytic copper plating layer 13 having a thickness of 15 μm and washed with water. Next, a known wiring pattern forming method, resist coating-pre-baking-exposure-developing-cleaning-post-baking-etching-
A wiring pattern was formed on both surfaces of the plated substrate 11 and the through holes 14 by a photofabrication method including a resist peeling process, and a low dielectric constant printed circuit board 15 was obtained.

-Comparative Examples 1 to 3- Using the wire to be plated having the same structure as in Example 1 above, the thickness of the electroless nickel plating layer of the underlayer was set to (1) Comparative Example 1 by the conventional process shown in FIG. : 0.05 μm, (2) Comparative Example 2:
Table 3 shows the processing time from the surface hydrophilicity-imparting treatment to the formation of the electroless nickel undercoat layer in each comparative example. The degreasing step, the surface hydrophilizing step and the electrolytic copper plating step were made into high frequency coaxial wires under the same processing conditions as in Example 1 above.

Regarding the high-frequency coaxial wires of Examples 1 to 4 and Comparative Examples 1 to 3, the processing time from the surface hydrophilization treatment to the formation of the underlying plating layer, the manageability of the processing liquid, and the attenuation characteristics of the high-frequency coaxial wire. Table 1 shows the results of comparison.

[0020]

[Table 1] Note) ◎: Excellent ○: Good △: Poor

As is clear from the comparison results in Table 1 above,
According to the present invention, compared with the conventional method, the time for forming the metal conductive layer on the surface of the fluororesin body is shortened, and the manageability of the treatment liquid is excellent. Further, the high frequency coaxial line based on the method of the present invention has excellent attenuation characteristics in the high frequency region.

[0022]

According to the method for forming a metal conductive layer on the surface of a fluororesin according to the present invention, a series of pretreatment steps such as the chemisorption reaction step of the conventional method are unnecessary in the step of forming the underlying silver conductive layer, Since an extremely simple process is sufficient, the process time can be shortened to a few hundredths to a few tenths and the burden of liquid management can be reduced. As a result, the manufacturing cost is gradually reduced, the product quality is stable, and the yield is improved. In addition, since an underlying silver conductive layer having excellent conductivity is interposed between the surface of the fluororesin body and the copper-plated conductive layer, it is possible to provide excellent high frequency transmission characteristics, and to manufacture coaxial lines and printed circuit boards for high frequency applications. It is extremely effective for the method.

[Brief description of the drawings]

FIG. 1 is a process drawing of a method for forming a metal conductive layer on a surface of a fluororesin body of the present invention.

FIG. 2 is a sectional view of a high frequency coaxial line based on the method of the present invention.

FIG. 3 is a cross-sectional view of a low dielectric constant printed circuit board based on the method of the present invention.

FIG. 4 is a process drawing of a conventional method for forming a metal conductive layer on the surface of a fluororesin body.

[Explanation of symbols]

 1 plated fluororesin wire 2 conductive wire 3 fluororesin insulator 4,12 base silver plating layer 5,13 electrolytic copper plating layer 6 high frequency coaxial wire 11 plated fluororesin substrate 14 through hole 15 low dielectric constant printed circuit board

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location C23C 18/44 C23C 18/44 C23F 1/00 C23F 1/00 A 4/00 4/00 A ( 72) Inventor Shunichi Yoshimura 300 Oya, Oita, Ueda, Nagano Tokyo Special Electric Cable Co., Ltd.

Claims (2)

[Claims] 1. A surface modification step of hydrophilizing the surface of a plated fluororesin body, and a step of forming a base silver conductive layer on the surface-modified plated fluororesin surface by a silver mirror reaction method. A method of forming a metal conductive layer on the surface of a fluororesin body, which comprises the step of forming a copper plating layer on the formed base silver conductive layer by an electroplating method. 2. The fluororesin is tetrafluoroethylene resin (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin (PFA), tetrafluoroethylene-hexafluoropropylene copolymer resin ( 2. A method for forming a metal conductive layer on the surface of a fluororesin body according to claim 1, which is a simple substance fluororesin of either FEP) or a tetrafluoroethylene-ethylene copolymer resin (ETFE).