JPH04180699A - Manufacture of enclosure for electromagnetic shielding use - Google Patents

Abstract

PURPOSE:To make this enclosure lightweight without the exfoliation of a conductive layer and without damaging the outward appearance and the mechanical characteristic of a molded product and to use it as a common component by a method wherein, after a porous plastic molded body has been plated with a metal, a seal is put on a part required to reveal the plated part and a painting operation is executed. CONSTITUTION:A metal mold 1 for molding use is filled with a mixture 2 which is formed of plastic ponders or of the plastic powders and a reinforcing agent; the metal mold is heated; the plastic powders are melted and bonded or the plastic powders and the reinforcing agent are melted and bonded; and a porous plastic molded body 3 is manufactured. Then, the molded body 3 is plated with a metal 4; a seal 5 is put on a part required to reveal the plated metal 4; a painting operation 6 is executed; after that, the seal is stripped and an enclosure for electromagnetic shielding use is manufactured. Since the bonding property of the plated metal is a conductive layer to the plastic is high, it is possible to prevent the conductive layer from chipping off during its use. As a result, there is no damage that circuits in an apparatus are short-circuited, and reliability can be enhanced. Since the enclosure is formed of the porous plastic molded body, it is lightweight, and it can be used as a common component when it is subjected to a secondary working operation.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method of manufacturing an electromagnetic shielding case.

[Conventional technology]

BACKGROUND OF THE INVENTION There is a remarkable trend toward miniaturization and weight reduction of electronic and electrical equipment, and as a result, how to eliminate the influence of electromagnetic waves that can lead to erroneous operation has become a major problem.

For this purpose, a metal casing is used and the electronic equipment is housed inside it, but e? There is a high demand for plastic products as housings for electronic devices due to their durability, aesthetics, and corrosion resistance. However, plastic does not have the ability to shield electromagnetic waves, and attempts have been made to shield electromagnetic waves by making plastic conductive using various methods.

This method involves molding the plastic into the required shape and then spraying a low-melting point metal using metal spraying to form a metal film on the plastic surface, or applying metal plating or conductive paint to the molded product. How to apply conductive light such as metal powder, short metal fibers or carbon in plastic #I
The plastic molded product is made conductive by molding the housing using a material mixed with L agent, and is used as a shield for electromagnetic waves.

[Problem to be solved by the invention]

The formation of a conductive layer on the surface of a molded product using thermal spraying, plating, or conductive paint is viewed as a major problem because the conductive layer tends to peel off from the molded product, and peeled pieces of the conductive layer can cause short circuits in equipment circuits. has been done. Also, if a conductive filler is mixed in, the conductivity will not be imparted unless it is filled in a large amount.
When filled in a large amount, the appearance of the molded product surface tends to deteriorate and the mechanical properties tend to be impaired. Furthermore, with the recent trend toward lighter weight, smaller size, and greater variety of electronic devices, there has been a desire for parts that are lightweight, have excellent electromagnetic shielding properties, and can be used commonly in a wide variety of devices. No suitable molding method has been found, and the currently attempted manufacturing methods for electromagnetic shielding casings have some problems.

[Means to solve the problem]

As a result of various studies, the inventors of the present invention discovered that in the manufacture of a housing used for the purpose of shielding electromagnetic waves, plastic powder or a mixture of plastic powder and reinforcing agent is fused in a mold used to mold the housing. After metal plating is applied to the porous plastic molded product obtained by the process, the areas where the metal plating needs to be exposed are sealed and painted, making it lightweight and common without peeling off the conductive layer or impairing the appearance or mechanical properties of the molded product. The inventors have discovered that it is possible to manufacture an electromagnetic shielding casing that can be used as a component, leading to the present invention.

A method of manufacturing an electromagnetic shielding casing will be explained with reference to FIG. The molding mold (i) is filled with plastic powder or a mixture of plastic powder and reinforcing agent (2), and the mold is heated to fuse the plastic powders together or the plastic powder and the reinforcing agent to form a porous plastic molded body ( 3). Next, metal plating (4) is applied to the porous plastic molded body, and after sealing (5) and painting (6) the parts where the metal plating needs to be exposed, the seal is peeled off to form the electromagnetic shielding casing. Manufacture.

The plastic powder is a thermoplastic or thermosetting resin powder, and the plastic powder or the plastic powder is mixed with a reinforcing agent and filled into a mold. In order to fill the mold uniformly, it is best to tilt the mold or apply vibration. Then, the molding die is heated to fuse the plastic powders together or the plastic powder and the reinforcing agent to create a porous plastic molded body. This porous plastic molded article may partially contain closed cells, but preferably has open cells. The higher the heating temperature and the longer the heating time, the more the fusion progresses and the number of closed cells. Therefore, adjust the heating temperature and heating time to change the degree of fusion and choose appropriate conditions.
The density of the porous plastic molded body is preferably 10 to 80% of the true density of the plastic powder. Two or more types of plastic powder may be mixed.

Glass fibers, organic fibers, carbon fibers, ceramic fibers, whiskers, inorganic particles, etc. are used as reinforcing agents, and these are added mainly to increase the strength of the porous plastic molded body. For mixing with plastic powder, the powder and reinforcing agent are mixed uniformly using a V blender, ribbon blender, Henschel mixer, etc.

For metal plating on porous plastic molded bodies, we use conventional electroless plating, and if necessary, we use electroplating in combination to adjust the plating thickness and ensure that it has the ability to shield the necessary electromagnetic waves. Make it. Metals to be plated include copper, nickel, chromium, gold, silver, tin, copper-zinc alloy, nickel-phosphorus alloy, etc.

The portions of the metal-plated porous plastic castle that require exposed metal plating are then sealed. The locations of this seal are (1) the part where the conductive layer of the electromagnetic shielding case needs to be connected to the electronic device, or the part where the transmission line such as a coaxial line exits from the case and connects to the shield jacket of the transmission line, (2) ventilation These include a part for attaching a wire mesh or a perforated metal plate to a hole or a drawer of a shaft of a movable mechanism, and (3) a part for connecting a waveguide using solder, screws, etc. Sealing is generally done using adhesive tape, but there are also methods of applying a release agent, wax, etc.

The coating is carried out by a commonly used method using paint, such as brush, roller, dip, spraying, electrostatic, powder coating, etc. Preferably, dip painting, spray painting, etc. can be easily performed. Paints consist of film-forming elements, solvents, pigments, etc.The film-forming elements include alkyd resins, aminoalkyd resins, vinyl resins, acrylic resins,
Epoxy resin system, urethane resin system, unsaturated polyester resin system, chlorinated rubber system, emulsion resin system, water-soluble resin system,
There are solvent-free types, and epoxy resin types and urethane resin types are good because they have excellent heat resistance, durability, and electrical properties.

[Effect]

In a porous plastic molded body, plastic particles are fused to each other, and voids between the particles continue from the surface to the inside of the molded body, so the surface area is large. When metal plating is applied to this, the contact area is larger than that of a smooth flat surface, and the inner layer of the porous plastic molded body is plated, so their anchoring effect increases the adhesion between the plastic and metal plating. For example, when electroless metal plating is applied to PE, blisters (
blistering) occurs, and there is no adhesion between the plated metal and PE.

To improve this, after adding a soluble substance to PE and molding it, the surface is made uneven by dissolving the soluble substances on the surface of the molded product or by dissolving the amorphous portion of the PE with a sulfuric acid-chromic acid mixture. P by forming or by oxidation reaction.
It has become common practice to introduce a polar group into F and perform plating.

However, when plating is performed using a porous material with PE powder fused to it, the above treatment is not performed (but no blisters occur, and the adhesion is good due to the increased surface area and anchoring effect). If a coating is applied on top of the metal plating that reflects the surface shape of the porous plastic molded body, the adhesion between the plated metal and the paint will be good for the same reason that the adhesion between the porous plastic molded body and the metal plating is good. Since the paint is plated and seals the metal, the metal-plated conductive layer and paint will not peel off from the porous plastic molded body.Therefore, unlike conventional methods, the conductive layer is coated on the surface of the injection molded product by thermal spraying, plating, or conductive paint. In the method of forming
Although there was a risk that the conductive layer pieces would peel off and short-circuit the circuit of the device, the manufacturing method of the present invention eliminates this possibility. Of course, even without painting, the adhesiveness between the plastic and the metal plate is good, so the effect is sufficient. However, it is necessary to cover the conductive layer with a paint film to prevent electric shock and rust. On the other hand, when a conductive filler such as short metal fibers is mixed, the surface appearance of the molded product is poor and the mechanical properties tend to deteriorate. As a result, the surface of the metal-plated porous plastic molded body is smoothed by painting, resulting in a good appearance. Also, since the metal plating only covers the surface of the porous plastic molded body, there is no deterioration in mechanical properties. Furthermore, depending on the paint, metallic, camp-tone, hammer tone, flake tone, pearl tone, etc.
It is possible to create a painted surface with an appearance such as iris burl or cracking, thereby increasing the commercial value.

Furthermore, since the material is porous plastic, the size, position, number, etc. of the through holes can be easily secondary-processed using drills, punches, etc., so the casing can be created using one mold and then processed later. This allows it to be used as a common component in a wide variety of equipment. At this time, if you change the color or appearance by painting, you can avoid using the parts incorrectly.

〔Example〕

Length 10an, width 5CI11, height 3cm, R thickness 0.3■
Ultra high molecular weight PE Miperon XM-
220 (average particle size 0.03 mm, melting point 136°C, Mitsui Petrochemical Industries, Ltd.) and short glass fiber FE as a reinforcing agent.
A mixture of 30 parts by weight of SS-010 (average fiber length 1°0 mm, Fuji Fiberglass Co., Ltd.) in a Henschel mixer was vibrated with a vibrator and filled so that the molding space was sufficiently filled. 18
A porous plastic molded body was obtained by heating at 0° C. for 15 minutes to fuse PE powder and short glass fibers. Next, this porous plastic molded body was subjected to electroless copper plating and electrolytic copper plating by the following method. Conditioner for porous plastic molded bodiesHitachi Conditioner C0ND-201
(Hitachi Chemical Co., Ltd.) at room temperature (10-35℃)
After immersing for 2 minutes in a pre-dip PD-201 (Hitachi Chemical Co., Ltd.) bath at room temperature, it was further immersed in a sensitizer H3-201 (Hitachi Chemical Co., Ltd.) bath for 10 minutes at room temperature.
Soaked for minutes. and adhesion promoter A) Dp-301 (
Hitachi Chemical Co., Ltd.) bath for 3 minutes at room temperature, then immersed in an electroless steel plating solution CUST-201 (Hitachi Chemical Co., Ltd.) bath for 15 minutes at 24°C, resulting in a copper plating thickness of approximately 0.3
μm was formed. Next, 200 g/J of copper sulfate, 50 g/J of sulfuric acid
Electrical steel plating was performed under the conditions of 2.8 A/dm'' in an electrolytic copper plating bath containing an appropriate amount of additives to form a conductive layer with a copper plating thickness of 20 μm. After washing with water, this was heated at 80°C. It was left to dry for 2 hours.Then, the bottom of the four side surfaces on the side where the bottom was open and both inclined surfaces at a height of 5 mm from the bottom were sealed with adhesive tape of a polyethylene terephthalate substrate.Next, this was done. The main agent and curing agent of epoxy resin paint Atom #8000 (
Atom Chemical Paint Co., Ltd.) was poured into a paint mixture and cured at 80° C. for 4 hours to obtain a coated surface with a good appearance. Then, peel off the seal along with the paint adhered to the seal, place the seal on a double-sided copper-clad epoxy laminate board with a thickness of 1.6 mm, and place the exposed bottom part of the metal foil on a 1.6 mm thick double-sided copper-clad epoxy laminated board. I soldered the copper foil to the four sides of the casing and the board.

Comparative Example PH powder HIZEX 33 was placed in the same mold as in the example.
00FP (Mitsui Petrochemical Industries, Ltd.) was mixed with 30 parts by weight of glass short edge mFEss-010 as a reinforcing agent in a Henschel mixer, and heated and pressed at 180°C for 15 minutes with a compression molding press to form a shape with vertical loam, width of 5 cm, and height. Sa3
A box with a wall thickness of 0.3 cm and an open bottom and ribs everywhere was molded.

This was subjected to electroless copper plating in the same manner as in the example, but blisters occurred. After removing the copper plating, 800
The surface was roughened with abrasive paper, electroless copper plating was performed, and then electroplating was performed. When the surface was roughened with abrasive paper, no blisters were observed and copper plating could be performed in the same manner as in the example. Then, it was sealed and then painted in the same manner as in the example.

To easily compare the adhesion between plastic and conductive layer,
When the electromagnetic shielding casings obtained in Examples and Comparative Examples were dropped onto concrete from a height of 1 m 100 times,
In the example, no significant peeling was observed, whereas in the comparative example, although there was no missing part as the coating was supported, peeling at the interface between the PE surface and the plated metal was observed.

〔Effect of the invention〕

According to the present invention, since the plating metal that is the conductive layer has high adhesion to the plastic, the conductive layer is prevented from being chipped during use. Furthermore, since the surface of the plated metal is coated, the effect of preventing the conductive layer from missing is greater, and there is no risk of short-circuiting of the device's circuit that would occur if the conductive layer is missing, improving reliability. Furthermore, since it is a porous plastic molded body, it is lightweight, and the parts of the housing that require metal plating are masked.
Since this part is not painted, connection with other components is easy and shielding performance is improved. By performing secondary processing on the housing, it can be used as a common component, and by changing the color and appearance through painting, it is possible to avoid accidentally attaching the housing to a different device.

[Brief explanation of drawings]

FIGS. 1(a) to 1(f) are conceptual diagrams showing the manufacturing process of the electromagnetic shielding case. Explanation of symbols (1) Molding mold (2) Plastic powder (3) Porous plastic molded body (4) Metal plating (5) Seal (6) Coating film formed by painting (a) (b) (c ) Figure 1 (d) (e) (f) Figure 1

Claims (1)

[Claims] 1. In manufacturing a housing used for the purpose of shielding electromagnetic waves, metal is added to a porous plastic molded body obtained by fusing plastic powder or a mixture of plastic powder and a reinforcing agent in a mold used to mold the housing. A method for producing an electromagnetic shielding casing, which comprises plating and then sealing and painting the parts where the metal plating needs to be exposed.