JP2008071802A - High corrosion resistant electromagnetic wave shield molding and its production process - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high corrosion resistant electrocmagnetic wave shield molding, and to provide its production process. <P>SOLUTION: An electrocmagnetic wave shield molding film consists of a metal shield layer of copper, and a protective layer on the metal shield layer wherein the protective layer is composed of an Sn-Cu-Cr alloy and the thickness of the protective layer is in the range of 40-120% that of the metal shield layer. In the Sn-Cu-Cr alloy, the mass ratio Cu/Sn of Cu for Sn is 0.05-0.20 and the mass ratio Cr/Sn of Cr for Sn is 0.15-0.40. The metal shield layer and the protective layer are formed by vacuum film deposition. Preferably, the thickness of the metal shield layer is set in the range of 0.5-1.5 μm and the thickness of the protective layer is set in the range of 0.5-1.0 μm. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electromagnetic wave shielding molded body, and more particularly, to an electromagnetic wave shielding molded body that is covered with an electromagnetic wave shielding film composed of a metal shield layer and a protective layer and has excellent corrosion resistance.

  Devices that transmit and receive radio waves, such as electric / electronic devices and mobile phones, are often subjected to electromagnetic wave shielding treatment in order to avoid malfunction of the devices. As electromagnetic wave shielding treatment, a method of producing a molded product using plastic mixed with a conductive metal, a method of applying a conductive paint to the surface of the molded product, or a wet plating method or a vacuum film formation on the surface of the molded product A method of forming an electromagnetic wave shielding film made of a metal thin film by a method is known. In electric / electronic devices and mobile phones, an electromagnetic wave shielding film is often formed inside the casing.

  As the wet plating method, an electroless plating method is used. In the electroless plating method, since the chromic acid etching or the addition of a palladium catalyst is performed, the adhesion between the molded product and the thin film is strong. However, there is a problem that it is necessary to treat the waste liquid, the treatment time is long, and both surfaces of the molded product are plated.

  On the other hand, in the formation of an electromagnetic wave shielding film by a vacuum film forming method, a primer layer is provided on a base material of a molded product, a copper layer is formed thereon as an electromagnetic wave shielding film, and a nickel layer is formed as a protective layer. . Alternatively, an aluminum film having a thickness of 1 μm to 2 μm is formed as an electromagnetic wave shielding film on the base material of the molded product.

  However, when used in the sea or in a corrosive environment, the electromagnetic wave shielding film has insufficient corrosion resistance. For example, in the salt spray test, discoloration and dissolution start in 2 to 6 hours. Can not pass the standard of “no discoloration or dissolution in the result of 24 h salt spray test” required by the manufacturer.

  In contrast, JP 2004-169091 A discloses a copper layer having a thickness of 0.2 μm or more and a thickness of 0.01 μm to 0.15 μm by plating, vapor deposition, or thermal spraying on the surface of a steel plate. A plated steel sheet is described in which the nickel layer is formed sequentially and does not corrode as a result of the salt spray test for 16 hours. However, the base material is a steel plate and cannot be applied to a resin base material such as a casing of a mobile phone.

  Japanese Patent Application Laid-Open No. 2003-293192 discloses a Ni plating layer having a thickness of 0.05 μm or more as a first layer and a Cu plating layer having a thickness of 0.2 μm or more on both surfaces as a second layer on both surfaces of a base steel plate. In addition, there is described a steel sheet excellent in corrosion resistance by forming a chemical treatment layer with benzotriazole on both sides as a third layer and a resin film layer having a thickness of 3 μm or less on both sides or one side as a fourth layer. However, the base material is a steel plate and cannot be applied to a resin base material such as a casing of a mobile phone. In addition, forming the chemical treatment layer on the plating layer is not a general method because it complicates the process and increases the cost.

  Japanese Patent Application Laid-Open No. 2000-200990 discloses a highly corrosion-resistant absorber in which a soft magnetic powder made of an Fe-based alloy containing 5 to 35% by mass of Cr is contained in rubber or resin in a proportion of 5 to 65% by volume. Are listed. The method described in Japanese Patent Application Laid-Open No. 2000-200990 includes a base material containing a corrosion-resistant conductive powder, and the already molded product cannot be processed.

  In JP 2000-059086 A, a DC magnetic field of 80 A / m is applied in the rolling direction, and the magnetic flux density in the rolling direction is excellent in corrosion resistance for forming a coating containing zinc as a main component on a steel sheet having a magnetic flux density of 1.2 T. An electrical steel sheet is described. However, the base material is a steel plate and cannot be applied to a resin base material such as a casing of a mobile phone.

  On the other hand, as a method of obtaining a molded body having an electromagnetic wave shielding film by forming a protective layer on an electromagnetic wave shielding layer formed on a resin base material, Japanese Patent Application Laid-Open No. 5-345987 discloses that A metal layer is formed by vapor deposition, sputtering, or ion plating, an electroless copper plating film is formed on the obtained metal layer, and the electroless copper plating film is further formed. Describes an electromagnetic wave shielding treatment method having excellent corrosion resistance by forming an electroless nickel plating film. However, although electroless nickel plating has higher corrosion resistance than vapor deposited nickel, the color changes to green as a result of the 24 h salt spray test.

Japanese Patent Laid-Open No. 2001-251084 discloses that electroless copper plating and electroless nickel plating are sequentially formed on a plastic, and then at least one selected from the group consisting of electroless gold plating and electroless silver plating. A method of forming an electromagnetic wave shielding film having excellent corrosion resistance by forming a plating film is described. However, this is a method of forming an electroless gold plating film or an electroless silver plating film on the electroless nickel plating, which increases the number of steps and costs, and is not a general method.
JP 2004-169091 A JP 2003-293192 A JP 2000-200990 A JP 2000-059086 A JP-A-5-345987 JP 2001-251084 A

  An object of this invention is to provide the electromagnetic wave shield molded object which has high corrosion resistance, and its manufacturing method.

  The electromagnetic wave shielding film of the present invention is an electromagnetic wave shielding film made of a metal shield layer made of copper and a protective layer on the metal shield layer, the protective layer made of an Sn-Cu-Cr alloy, and The thickness of the protective layer is 40% to 120% of the thickness of the metal shield layer.

  The Sn—Cu—Cr alloy has a Cu to Sn mass ratio Cu / Sn of 0.05 to 0.20, and a Cr to Sn mass ratio Cr / Sn of 0.15 to 0.40. It is desirable.

  The electromagnetic wave shielding molded body of the present invention is an electromagnetic wave shielding molded body that covers the electromagnetic wave shielding film, wherein the metal shield layer has a thickness of 0.5 μm to 1.5 μm, and the protective layer has a thickness of 0.5 μm to 1.0 μm.

  When manufacturing the electromagnetic wave shielding film and the electromagnetic wave shielding molded body according to the present invention, the metal shield layer and the protective layer are formed by a vacuum film forming method.

  According to the present invention, it is possible to provide an electromagnetic wave shield molded article having high corrosion resistance, high productivity, and low cost.

  Currently used as the base material for forming the electromagnetic wave shielding film are ABS resin (acrylonitrile-butadiene-styrene copolymer resin), PC resin (polycarbonate resin), and mixed resin of ABS resin and PC resin. The molded product made is common.

  In recent years, especially in mobile phones, in order to meet the demand for weight reduction and thinning, a thin and strong thermoplastic resin such as ABS / PC (mixed resin of ABS resin and PC resin), polyamide resin, polyphenylene sulfide. Engineering plastics such as resins, fluororesins, liquid crystal polymers, or resins containing glass fibers in them are often used as substrates.

  Since the molded body made of these has high solvent properties and almost no surface functional groups, an electromagnetic wave shielding film is formed on the surface of the substrate in the film formation using only the wet plating method or the vacuum film formation method. It is difficult.

  Therefore, in this case, in order to obtain adhesion between the base material and the metal shield layer made of copper, an undercoat is applied on the molded body or a functional group is added to the base material with oxygen ions. A shield layer is formed to a thickness of 0.5 μm to 1.5 μm.

  The metal shield layer is preferably formed by a vacuum film forming method that can be formed uniformly and can be a film having excellent environmental resistance. Examples of the vacuum film forming method include a vacuum deposition method, an ion plating method, and a sputtering film forming method.

  Copper as a film forming material can be evaporated by means such as resistance heating, induction heating, electron beam irradiation, holocathode discharge. The evaporated particles obtained by these means can be deposited on the surface of a plastic molded article by high-frequency excitation and ionization.

  In particular, an ion plating method in which a high melting point target is dissolved with an electron gun, a metal is evaporated, and a film is formed on a substrate is preferable, and a high-quality film can be formed at a high film formation speed over a large area. it can.

  When the thickness of the metal shield layer is less than 0.5 μm, sufficient electromagnetic wave shielding characteristics are not exhibited. In addition, the original structure of the film becomes rough and the corrosion resistance is significantly reduced. On the other hand, even when the thickness of the metal shield layer is thicker than 1.5 μm, the electromagnetic wave shielding characteristics hardly change. On the contrary, the film stress becomes strong, the adhesive force with the base material is lowered, or the adhesive force with the second layer is lowered, and it is easy to spontaneously peel off after film formation.

  In the present invention, a protective layer made of a Sn—Cu—Cr alloy is formed on a metal shield layer capable of obtaining electromagnetic wave shielding characteristics. The metal shield layer is also preferably formed by a vacuum film formation method that can be formed uniformly and can be a film having excellent environmental resistance. Similarly, it is preferable to use an ion plating method as the vacuum film forming method.

  Due to the difference in melting point and boiling point of these metals, films are formed mainly in the order of Sn, Cu, and Cr in a vacuum.

  Of these metals, Sn is a metal that is a main component of the protective layer, has a low melting point, and has relatively high corrosion resistance.

  Since Cu has a low resistance value and is the same metal as the underlying Cu, it has a function of improving adhesion with the metal shield layer.

  Cr has a function of forming a dense oxide film on the Sn alloy and thereby improving the corrosion resistance of the protective layer.

  In the electromagnetic wave shielding film of the present invention, the protective layer made of an Sn—Cu—Cr alloy has a Cu to Sn mass ratio of Cu / Sn of 0.05 to 0.20, and a Cr to Sn mass ratio of Cr / Sn. 0.15 to 0.40.

  In addition to improving conductivity and adhesion, Cu has the role of reducing crystal grains and prevents the generation of whiskers that are likely to occur in Sn films. In order to obtain these effects, it is necessary that the mass ratio Cu / Sn of Sn to Sn is 0.05 or more. On the other hand, if it exceeds 0.20, the effect of preventing the generation of whiskers is not changed, the film formation time is prolonged, and the color of the film is slightly reddish.

  Cr is incorporated into the film to form a Cr oxide film and improve the corrosion resistance of the protective layer. When the mass ratio of Cr to Sn, Cr / Sn, is less than 0.15, discoloration occurs as a result of the 24 h salt spray test. On the other hand, if it exceeds 0.40, Cr does not fly completely in the vacuum film formation method, and remains on the target, affecting the subsequent film formation.

  The thickness of the protective layer made of the Sn—Cu—Cr alloy is 40% to 120% of the thickness of the metal shield layer. Since the Sn—Cu—Cr alloy used in the present invention is mainly composed of Sn as described above, it is a flexible film and does not easily crack even if the protective layer is thickened.

  In order to cover the underlying metal shield layer deposited on the corners and vertical walls of the product, and to reduce pinholes, the thickness of the protective layer is at least 40% of the thickness of the metal shield layer. is required. Therefore, the thickness of the protective layer is determined in proportion to the thickness of the metal shield layer to be formed.

  In order to eliminate pinholes, it is desirable that the protective layer is thicker. However, if the thickness of the protective layer exceeds 120% of the thickness of the metal shield layer, the productivity decreases and the cost increases. There is a possibility that delamination occurs between the metal shield layer and the stress.

  Specifically, when the thickness of the metal shield layer is 0.5 μm, the thickness of the protective layer is 40% to 120%, which is 0.2 μm to 0.6 μm, and the viewpoint of eliminating pinholes To 0.4 μm to 0.6 μm is desirable. When the thickness of the metal shield layer is 1 μm, the thickness of the protective layer is 0.4 μm to 1.2 μm, which is 40% to 120%, and 0.4 μm to 1.m from the viewpoint of productivity. 0 μm is desirable. When the thickness of the metal shield layer is 1.5 μm, the thickness of the protective layer is set to 0.6 μm to 1.8 μm which is 40% to 120%, and 0.6 μm to 1. 0 μm is desirable.

(Example 1)
As a substrate, a substrate having a size of 50 mm × 50 mm and a thickness of 2 mm made of Reny (registered trademark) 1022H (manufactured by Mitsubishi Engineering Plastics Co., Ltd.) in which 50% by mass of polyamide resin and glass fiber was blended was used.

  An undercoat made of epoxy and urethane was applied to the substrate by 0.5 μm and dried at 85 ° C. for 30 minutes.

  After that, it was attached to an ion plating apparatus (AAIH-W36200SBT, manufactured by Shinko Seiki Co., Ltd.), evacuated to 1 × 10 −2 Pa, first, argon gas was flowed at 150 cc / min, high frequency output of 1 kW was applied, and argon was supplied. The substrate was cleaned and activated with ions for 5 minutes.

  In the first layer, copper was formed to a thickness of 0.8 μm, and in the second layer, a Sn—Cu—Cr alloy having a mass ratio of Sn: Cu: Cr = 1: 0.15: 0.30 was added to argon in 0%. An electromagnetic wave shielding molded body coated with an electromagnetic wave shielding film was obtained by forming a film with a thickness of 6 μm.

  The following tests were carried out on the obtained electromagnetic wave shield moldings, respectively.

[Initial adhesion confirmation test]
Initial adhesion was confirmed by a cross-cut tape test. Specifically, cellophane tape (CT1835, manufactured by Nichiban Co., Ltd.) is used for 100 squares obtained by cutting a 1 mm × 1 mm cut with a knife on the surface of the electromagnetic wave shielding film formed on the electromagnetic wave shielding molded body. After the cellophane tape was attached, when the cellophane tape was peeled off, the adhesiveness to the base material was evaluated by examining whether or not peeling occurred with the base material.

  As a result, no peeling occurred in 100 squares.

[Moisture resistance test]
The effect of humidity on the adhesion to the substrate was investigated. Specifically, after maintaining for 240 hours and 600 hours in an environment of a temperature of 60 ° C. and a humidity of 95%, changes in appearance were observed, and the same cross-cut tape test as described above was performed for each.

  As a result, there was no change in the appearance, and no peeling occurred in one square out of 100 squares.

[Heat resistance test]
The effect of temperature on the adhesion to the substrate was investigated. Specifically, after maintaining in an environment of temperature 85 ° C. and humidity 0% for 240 hours, the appearance change was observed, and the same cross-cut tape test as described above was performed.

  As a result, there was no change in appearance, and no peeling occurred in 1 square out of 100 squares.

[Measurement of sheet resistance]
The electromagnetic wave shielding characteristics were evaluated by measuring the sheet resistance. Specifically, the sheet resistance of the metal shield layer formed on the base material was measured by using a surface resistance meter (manufactured by Mitsubishi Chemical Corporation, Loresta, MP, MCP-T350) according to the principle of a four-terminal measurement method.

  As a result, the sheet resistance was 0.30 × 10 −2 Ω / □ or less. With this value of sheet resistance, it was confirmed that an electromagnetic wave shielding characteristic of 30 dB was obtained.

[Corrosion resistance test]
After performing a salt spray test (JIS-Z-2371) at a temperature of 35 ° C. for 24 hours, the change in appearance was observed, and the same cross tape test as described above was performed for each.

  As a result, there was no change in appearance, and no peeling occurred in 1 square out of 100 squares.

(Example 2)
An electromagnetic wave shield molded article was obtained in the same manner as in Example 1 except that the first layer was formed with a copper film of 0.5 μm.

  About the obtained electromagnetic wave shield molded object, the test similar to Example 1 was implemented. As a result, the same result as in Example 1 was obtained.

(Example 3)
In the first layer, a copper film of 1.0 μm was formed, and in the second layer, a Sn—Cu—Cr alloy having a mass ratio of Sn: Cu: Cr = 1: 0.15: 0.30 was added in argon. An electromagnetic wave shield molded body was obtained in the same manner as in Example 1 except that the film thickness was 1.0 μm.

  About the obtained electromagnetic wave shield molded object, the test similar to Example 1 was implemented. As a result, the same result as in Example 1 was obtained.

Example 4
In the first layer, copper was formed to a thickness of 1.5 μm, and in the second layer, a Sn—Cu—Cr alloy having a mass ratio of Sn: Cu: Cr = 1: 0.15: 0.30 was added in argon, An electromagnetic wave shield molded body was obtained in the same manner as in Example 1 except that the film thickness was 1.0 μm.

  About the obtained electromagnetic wave shield molded object, the test similar to Example 1 was implemented. As a result, the same result as in Example 1 was obtained.

(Example 5)
In the first layer, a copper film of 1.0 μm was formed, and in the second layer, a Sn—Cu—Cr alloy having a mass ratio of Sn: Cu: Cr = 1: 0.20: 0.40 was added in argon. An electromagnetic wave shield molded body was obtained in the same manner as in Example 1 except that the film thickness was 1.0 μm.

  About the obtained electromagnetic wave shield molded object, the test similar to Example 1 was implemented. As a result, the same result as in Example 1 was obtained.

(Example 6)
In the first layer, copper was formed to a thickness of 1.0 μm, and in the second layer, an Sn—Cu—Cr alloy having a mass ratio of Sn: Cu: Cr = 1: 0.05: 0.15 was added in argon, An electromagnetic wave shield molded body was obtained in the same manner as in Example 1 except that the film thickness was 1.0 μm.

  About the obtained electromagnetic wave shield molded object, the test similar to Example 1 was implemented. As a result, the same result as in Example 1 was obtained.

(Example 7)
An ABS / PC resin (manufactured by Toyobo Co., Ltd.) is used as a base material, and a rubber bond (manufactured by Konishi Co., Ltd., G103), an undercoat composed of MEK and xylene is applied to a thickness of 0.5 μm, 60 ° C., 30 An electromagnetic wave shield molded article was obtained in the same manner as in Example 1 except that it was dried.

  About the obtained electromagnetic wave shield molded object, the test similar to Example 1 was implemented. As a result, the same result as in Example 1 was obtained.

(Comparative Example 1)
In the first layer, a copper film having a thickness of 1.0 μm was formed, and in the second layer, a Sn—Cu—Cr alloy having a mass ratio of Sn: Cu: Cr = 1: 0.15: 0.30 was added to argon in 0%. An electromagnetic wave shield molded article was obtained in the same manner as in Example 1 except that the film thickness was 3 μm (30% with respect to the first layer).

  About the obtained electromagnetic wave shield molded object, the test similar to Example 1 was implemented. As a result of a salt spray test (JIS-Z-2371) at a temperature of 35 ° C. for 24 hours, a part of the membrane was dissolved.

(Comparative Example 2)
In the first layer, a film of copper of 1.0 μm was formed, and in the second layer, a Sn—Cu—Cr alloy having a mass ratio of Sn: Cu: Cr = 1: 0.05: 0.125 was added in argon, An electromagnetic wave shield molded body was obtained in the same manner as in Example 1 except that the film thickness was 1.0 μm.

  About the obtained electromagnetic wave shield molded object, the test similar to Example 1 was implemented. As a result of a salt spray test (JIS-Z-2371) at a temperature of 35 ° C. for 24 hours, a part of the membrane was dissolved.

(Comparative Example 3)
In the first layer, a copper film having a thickness of 1.5 μm was formed, and in the second layer, an Sn—Cu—Cr alloy having a mass ratio of Sn: Cu: Cr = 1: 0.15: 0.45 was placed in argon under 1 An electromagnetic wave shield molded article was obtained in the same manner as in Example 1 except that a film thickness of 0.0 μm was formed.

  About the obtained electromagnetic wave shield molded object, the test similar to Example 1 was implemented. As a result, the same result as in Example 1 was obtained. However, 3 g of Cr target grains remained without evaporating.

(Comparative Example 4)
In the first layer, a copper film having a thickness of 1.5 μm was formed, and in the second layer, an Sn—Cu—Cr alloy having a mass ratio of Sn: Cu: Cr = 1: 0.25: 0.15 was added in argon under 1 A molded electromagnetic wave shield was obtained in the same manner as in Example 1 except that a film thickness of 0.0 μm was formed.

  About the obtained electromagnetic wave shield molded object, the test similar to Example 1 was implemented.

  As a result, the same result as in Example 1 was obtained. However, when the film was observed well, the thick part was reddish.

(Conventional example)
Although an attempt was made to obtain an electromagnetic wave shield molding in the same manner as in Example 1 except that the first layer was formed with a copper thickness of 1.5 μm and the second layer was formed with Ni as a protective film, The film had high stress, and cracks occurred when the film was formed to a thickness of 0.3 μm or more. Even when the occurrence of cracks was not visually confirmed, a large crack occurred in the 80 ° C. heat resistance test 48 h.

  On the other hand, the test similar to Example 1 was implemented about the electromagnetic wave shield molded object obtained when the Ni film | membrane which does not enter a crack is 0.2 micrometer.

  As a result, in the corrosion resistance test, after 16 hours of the salt spray test, corrosion of the underlying copper began and turned green. As a result of enlarging the surface 100 times, microcracks were generated.

Claims (5)

  An electromagnetic wave shielding film comprising a metal shield layer made of copper and a protective layer on the metal shield layer, the protective layer is made of an Sn-Cu-Cr alloy, and the thickness of the protective layer is An electromagnetic wave shielding film comprising 40% to 120% of the thickness of the metal shield layer.   The Sn—Cu—Cr alloy has a Cu to Sn mass ratio Cu / Sn of 0.05 to 0.20, and a Cr to Sn mass ratio Cr / Sn of 0.15 to 0.40. The electromagnetic wave shielding film according to claim 1.   3. A method for forming an electromagnetic wave shielding film according to claim 1, wherein the metal shielding layer and the protective layer are formed by a vacuum film forming method.   It is an electromagnetic wave shielding molded object which coat | covered the electromagnetic wave shielding film of Claim 1 or 2, The thickness of the said metal shielding layer is 0.5 micrometer-1.5 micrometers, and the thickness of the said protective layer is 0.00. An electromagnetic wave shield molded product, characterized by being 5 μm to 1.0 μm.   It is a manufacturing method of the electromagnetic wave shield molded object of Claim 4, Comprising: The said metal shield layer and the said protective layer are formed into a film by the vacuum film-forming method, The manufacturing method of the electromagnetic wave shield molded object characterized by the above-mentioned.