KR20010073610A - Method for forming an EMI Shielding film - Google Patents

Abstract

PURPOSE: A method for manufacturing an EMI Shielding film is provided to form an EMI shielding film on a non-conductive plate using an electroplating technique. CONSTITUTION: A first metal layer is formed on a non-conductive plate by using a PVD(Physical Vapor Deposition). A second metal layer is electroplated on the first metal layer by using the first metal layer as a cathode. A third metal layer is electro-plated on the second metal layer by using the second metal layer as a cathode. Preferably the first metal layer and the second metal layer are copper and a third metal layer is nickel and the PVD is a sputtering method. The non-conductive plate is one of plastic, glass and ceramic.

Description

Method for forming an EMI Shielding film

The present invention relates to a method of forming an electromagnetic interference (EMI) shielding film on a non-conductive material, and in particular, a method of forming an EMI shielding film on a non-conductive material by using electroplating. It is about.

Electromagnetic interference emissions are harmful energy emissions in the frequency range from as low as 60 Hz to as high as 1000 MHz. Radio frequency interference (RFI) is a portion of EMI radiation within about 0.01 to 1000 MHz.

EMI radiation is generated by many different forms of operation of electronic devices, from microwave devices to home computers. The cause of the radiation is that electronic devices generate noise picked up by conduction through power lines serving as other devices or antennas in the frequency range.

EMI emissions are well known for affecting such various problems as disturbing other devices and disturbing police car radio networks, communication systems, precision test equipment and cardiac pacemakers.

Most industrial countries have established rules on the minimum allowable EMI emissions for electronic devices. For example, in the United States, the minimum allowable EMI emission rules for all digital electronic products that generate or use frequencies between 10 KHz and 1000 MHz. It has been in operation since 1983.

The metals are provided in a housing for the electronic device as a shield for accommodating the radiation. With regard to non-conductive materials, often used methods, including the arc spray method, painting with paints containing metal, the cathode sputtering method and the vacuum metal coating method, are involved in forming the metallic coating. Suitable metals to be used as EMI shields are copper, silver, chromium, nickel, gold, and zinc.

Cathodic sputtering and vacuum metal cladding can produce coatings that exhibit good conductivity and adhesion, while cathode sputtering and vacuum metal cladding tend to be microscopic cracking, require high power and crush thermoplastic substrates. Can be. A technique called electroless plating has been used to solve these problems, and in general, US patent No. 4,514,486 mentioning that a double layer of electroless copper coated with electroless nickel is used as an EMI shield. Can be seen from

Forming a coating film on the opposite conductive substrate by the non-electrolytic plating involves dipping in a series of aqueous solution baths for pretreatment, dipping in a noble metal catalyst solution, and then adhering to the catalyst absorbed by the substrate and dissolving it on the substrate. There is a need for a process of dipping the dissolved metal in a non-electrolytic plating solution to deposit the metal.

One important problem associated with such non-electrolytic plating is that it is non-selective. The coating is formed by locking the entire substrate in solution. As a result, metal is plated on the entire surface of the substrate. Additional coatings are applied because non-electrolytic plating is covered on the surface of any unwanted portion. This is a waste of time and process waste. Selective non-electrolytic plating attempts for EMI protection have been described in US patent 4,670,306 and U.K patent application serial No. 2169925 A is shown.

It is an object of the present invention to provide a method of forming an EMI shield on a non-conductive substrate using conventional electroplating techniques.

Another object of the present invention is to provide a method for selectively forming an EMI shielding film on a non-conductive substrate using conventional electroplating techniques.

In order to achieve the object of the present invention, the method for manufacturing an EMI shielding film proposed by the present inventors includes forming a first metal layer on a non-conductive substrate by physical vapor deposition and using the first metal layer as a cathode. It is characterized by including the step of electroplating the second metal layer thereon.

Preferably, the second metal layer is used as a cathode and the substrate is immersed in a second electroplating bath to electroplate the third metal layer over the second metal layer.

Preferably, the first, second and third metal layers are copper (Cu), silver (Ag), nickel (Ni), zinc (Zn), gold (Au), platinum (Pt), chromium (Cr), aluminum It is characterized by being independently selected from the group having (Al), cadmium (Cd), tungsten (W) and their alloys.

Most preferably, the first metal layer and the second metal layer are copper, and the third metal layer is nickel.

Preferably, the physical vapor deposition method is a sputtering method.

The non-conductive substrate usable in the method of the present invention may be plastic, glass or ceramic. Progressively, plastic substrates are used in the present invention.

Detailed description of the preferred embodiment of the present invention is as follows.

Electroplating techniques are an economical means to form metal coatings on conductive substrates at room temperatures with much higher deposition rates compared to those formed by physical vapor deposition (PVD) and electroless plating.

For most of the housing of electrical elements made of non-conductive plastics, electroplating techniques are not applied to forming EMI shields thereon. In the present invention, a thin metal layer on a non-conductive housing or a non-conductive substrate is formed by physical vapor deposition (PVD) so that one or more metal layers to be electroplated on the thin metal layer can be used to adequately provide EMI shielding and additional protection. First is deposited.

The thin metal layer may in principle have a thick thickness sufficient to act as a cathode in electroplating. Preferably, the lower temperature in the chamber and the PVD process should be as thin as possible so as not to deform the plastic housing during PVD. Suitable thicknesses of the thin metal layer range from 0.1 μm to 1.0 μm. The present invention can further use the anisotropic tool of the PVD to selectively deposit a thin metal layer on the plastic housing, and a mask is used to cover a portion of the plastic housing surface where the metal layer is not required to be deposited. Sputtering is advantageous among the well known PVD techniques, including sputtering and evaporation methods. In the present invention, a suitable state for performing sputtering in a sputtering chamber is as follows.

Chamber pressure: 10 ⁻² to 10 ⁻⁵ torr;

Chamber temperature: 30-200 ℃

Voltage: 300-700 V; And

Residual time of substrate: 1 to 10 minutes

One or more metal layers may now be electroplated exclusively on the thin metal layer in a conventional electroplating system, which may be utilized as a cathode and continuously immersed in one or more electroplating baths. Preferably, two electroplating steps are performed to form a copper layer or a metal layer having superconductivity, and then to form a nickel layer or a metal layer having corrosion resistance (non-corrosive property). Suitable electroplating baths for copper electroplating can be CuSO ₄ aqueous solutions. For example, a suitable electroplating bath for nickel electroplating is an aqueous solution comprising NiSO ₄ , NiCl ₂ and H ₃ BO ₃ .

Example

In one suitable embodiment, a copper layer of about 0.2 μm is deposited on a polymer substrate made of ABS and PC by sputtering at a condition of 10 −2 torr, 50 ° C. in a 450 V argon plasma for 4 minutes. ABS stands for acrylonitrile-butadiene copolymer, and PC stands for polycarbonate. About 0.5 micrometer copper layer is electroplated on the said 0.2 micrometer copper layer, and about 1.0 micrometer nickel layer is electroplated on it.

The EMI shielding film of the present invention has the following effects.

That is, the EMI shielding layer of the present invention thus formed shows good adhesion to the ABS and PC substrate and does not break.

Claims (9)

Forming a first metal layer on the non-conductive substrate by physical vapor deposition; And electroplating a second metal layer on the first metal layer using the first metal layer as a cathode. The method of claim 1, And electroplating a third metal layer on the second metal layer using the second metal layer as a cathode. The method according to claim 1 or 2, In the physical vapor deposition method, a mask is used so that the first metal layer is formed on a predetermined portion of the non-conductive substrate not covered with the mask. The method according to claim 1, 2 or 3, The method of claim 1, wherein the first metal layer and the second metal layer are copper. The method according to claim 2, 3 or 4, EMI shielding film manufacturing method characterized in that the third metal layer is nickel. The method of claim 1, The physical vapor deposition method is a sputtering method EMI shielding film production method characterized in that. The method according to claim 1, 2 or 3, The first metal layer and the second metal layer may include copper (Cu), silver (Ag), nickel (Ni), zinc (Zn), gold (Au), platinum (Pt), chromium (Cr), aluminum (Al), and cadmium. (Cd), tungsten (W) and a method of manufacturing an EMI shield, characterized in that independently selected from the group having their alloys. The method according to claim 2 or 7, The third metal layer is copper (Cu), silver (Ag), nickel (Ni), zinc (Zn), gold (Au), platinum (Pt), chromium (Cr), aluminum (Al), cadmium (Cd), EMI shielding film production method characterized in that the selected from the group comprising tungsten (W) and their alloys. The method according to claim 1, 2 or 3, EMI shielding film manufacturing method characterized in that the non-conductive substrate is a plastic substrate.