JPH05160594A - Manufacture of shielding case - Google Patents

Abstract

PURPOSE:To perform a mass production and to reduce a manufacturing cost by adhering metal powder to an adhering surface of a case and further heating it to form a shielding layer. CONSTITUTION:A molded resin plate 20 is coated with an adhesive 21 to form an adhesive layer. Then, a powder coating for adhering metal powder to the adhering surface is conducted to form a metal layer 23 on one side surface of the plate 20, and further a heating step may be provided. This is the step of forming a metal layer integrated by melting the powder for forming a metal powder layer by hot air. In this case, it is necessary to contain metal powder having a low melting point and containing, for example, lead in the metal powder. Thus, a metal layer 24 in which all metal powder is integrated is obtained. Accordingly, a shielding layer matched to required shielding characteristics can be easily manufactured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a shield case for obtaining an EMI shield effect, and more particularly,
The present invention relates to a method of manufacturing a shield case that can be manufactured quickly with simple steps.

[0002]

2. Description of the Related Art In recent years, LSIs and ICs have been widely used as elements of circuits in electric equipment. Further, in the case of the electric device, plastic has been used in place of metal in view of design and total cost, and in response to a demand for miniaturization and weight reduction. Therefore, most of the electromagnetic energy generated from this device easily passes through this case, and unnecessary radio waves become abnormal signals between devices, increasing the chances of adversely affecting data and commands. At present, various shielding techniques have been developed and are actually applied to products in order to reduce this adverse effect. Examples of the main technique include a conductive plastic molding method, a metal plate shielding method, a conductive coating method, a metal foil film coating method, and a plating method.

The conductive plastic molding method uses metal fibers,
This is a method in which flakes and powders are used as a filler, and they are mixed with a resin and molded, and since the filler is covered with a polymer, the conductivity is not so good. Increasing the content of the filler results in poor dispersibility of the filler, poor impact properties, damage to molds and molding machines, and decorative coating on the exterior. The metal plate shielding method is used in some cases because it is cheap in terms of cost, but for high-performance equipment, it is impossible to use a complex metal plate, and it is difficult to assemble and prevent electromagnetic waves from leaking. As a result, the use cases are limited. The conductive coating method is a method in which metal powder is mixed into a resin coating material for coating, but a coating film having a certain thickness is required because the resin serves as a binder. For this reason, variations easily occur depending on the quality of mixing of the paint, the spraying method, and the like. The metal foil film coating method is a method of attaching a metal foil film to the inner surface or the outer surface of a molded plastic case. Since this method requires a step of adhering the metal foil film, it is difficult to assemble and reduce electromagnetic wave leakage as in the metal shielding method. Finally, regarding the plating method, particularly the electroless method can obtain a uniform and dense continuous film of metal even in the case of a complicated shape, so that a very good shielding effect can be obtained.

[0004]

In the case of the conventional shield technique as described above, which is manufactured at a low cost through a relatively simple process, the productivity is satisfactory, but the reliability of the shield effect is high. In terms of sexuality, it is hard to say that he is always satisfied. On the other hand, in the case where the reliability is satisfied, the manufacturing process is complicated, it is not suitable for mass production, and it is expensive, so that the range of use is naturally limited. In short, it can be said that a considerable amount of work had to be done in order to manufacture a case with high shield reliability by the conventional technology. The present invention has been made in order to solve such contradictory problems of the conventional techniques, and it is possible to manufacture a shield case having a very high shield reliability in a relatively simple process. It is intended to provide a method for manufacturing a shield case.

[0005]

DISCLOSURE OF THE INVENTION The present invention for achieving the above object is a method of manufacturing a shield case for shielding unnecessary interference radio waves emitted from the inside of an electric device or entering from the outside, which is molded. A step of forming an adhesive layer on the surface of the plastic case that requires shielding,
A step of adhering metal powder to the adhesive adhering surface of the case. A method of manufacturing a shield case that shields unnecessary interference radio waves emitted from the inside of electric equipment or entering from the outside, the step of forming an adhesive layer on the surface of a molded plastic case that requires shielding And a step of adhering a metal powder containing at least a low melting point metal to the adhesive adhering surface of the case, and heating the metal powder adhering surface of the case to melt the low melting point metal to flatten the metal powder adhering surface. And a process.

Further, there is provided a method of manufacturing a shield case for shielding unnecessary interference radio waves emitted from the inside of electric equipment or entering from the outside, wherein an adhesive layer is formed on the surface of the molded plastic case which requires the shield. A step of forming, a step of adhering a metal powder containing at least a low melting point metal to the adhesive adhering surface of the case, a step of adhering a powder for controlling the thickness of the adhered metal powder, and a case of adhering the metal powder to the case Melting the low melting point metal by heating the surface to flatten the metal powder adhesion surface as a continuous metal layer.

[0007]

In the present invention thus constructed, the metal powder adheres only to the adhesive adhering surface of the case, and the metal powder can be adhered in a relatively short time. It can be manufactured very efficiently. Since the shield characteristics can be changed depending on the particle size of the metal powder used and the thickness of the metal powder layer to be formed, it is possible to manufacture a case having the required shield characteristics by appropriately changing these elements. it can. Further, if the metal powder mixed with the low-melting-point metal powder is adhered and then heated by hot air, by a heated mold, or by hot stamping, the low-melting metal is continuously melted by the hot air. Since the metal layer is formed, it is possible to improve the shield effect and manufacture a case that is good in appearance. Furthermore, when the step of attaching the powder for controlling the thickness of the attached metal powder is provided, the thickness of the metal powder layer can be adjusted according to the required shield characteristics, etc. A metal layer having a thickness of 1 can be obtained relatively easily.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1A is an external view of a shield case 11 according to the present invention, and FIG. 1B is an enlarged view of a section B of the case. As shown in the figure, the case 11 is formed of a thermoplastic or thermosetting general-purpose, engineering or super engineering plastic material. In this embodiment, ABS is used as the plastic material.
Uses resin. As a thermoplastic plastic material that can be used for molding the case 11, a crystalline material is
Examples thereof include polyethylene, polypropylene, polybutene-1, polymethylpentene-1, polyethylene terephthalate, polyacetal, nylon, and fluorine resin, and non-crystalline substances include polyvinyl chloride, polyvinylidene chloride, polystyrene, and polyphenylene sulfide. , ABS resin, acrylic resin, cellulosic resin,
Examples thereof include polycarbonate, phenoxy resin, polyphenylene oxide, polysulfone, ionomer, styrene butadiene, and thermoplastic elastomer. Polymer alloys, plastic compounds and the like can be mentioned in the same manner. Examples of the thermosetting plastic material include phenol resin, urea resin, melamine resin, epoxy resin, unsaturated polyester resin, alkyd resin, silicone resin, urethane resin, furan resin and polyimide. Besides,
Various reinforced plastic materials can be mentioned as well.

The formation of the case using the above plastic material is mainly performed by injection molding using a mold, vacuum molding,
It is performed by blow molding or the like. And this case 1
The inner surface of No. 1 is composed of a metal powder layer having a good shielding effect over the entire surface or a metal layer containing a metal powder having a melting point lower than the melting point of the ABS resin, and is adhered by an adhesive layer 13. The shield layer 12 is formed. The shield layer 12 protects the circuit located inside the shield case 10 from unwanted interference waves from the outside. On the contrary, the electromagnetic energy generated from this circuit is prevented from being emitted to the outside of the shield case 10. In addition, the metal powder layer in the present embodiment refers to a layer formed by uniformly adhering the metal powder to the bonding surface in the step described later, and the metal layer is formed after the heating step. The layer integrated by melting the low melting point metal is referred to. As a metal having a melting point lower than that of the plastic material, it is possible to use an alloy containing lead as a main component. The component ratio of lead to other metals in this alloy is determined by comprehensively considering the required melting point, shielding performance and the like. In the illustrated example, the shield layer 12 is formed only on the inner surface of the case, but it may be formed on the entire outer surface or the inner and outer surfaces thereof depending on manufacturing or required shield performance. ..

2 and 3 are views showing a method of manufacturing a shield case according to the present invention. In order to simplify the description, this method will be described on the assumption that a metal powder layer or a metal layer is formed on a plastic plate. First, in the first step, the adhesive 21 is applied to the molded resin plate 20. The adhesive layer 13 is formed by this step. As a method of forming this adhesive layer, various methods such as dipping, spraying, two-color molding, and printing can be applied. In the case where only a part of the case has a shielding property, for example, an unnecessary portion of plating may be masked and an adhesive may be applied to the required portion. Which of the above methods is to be adopted is selected in consideration of the application place and area of the adhesive. Any kind of adhesive can be used as long as it can bond the resin material and the metal. As an example of a specific example in this step, for example, masking is applied to an unnecessary plating portion of the exterior part (made of plastic), dipping or spraying this adhesive in a solvent-containing adhesive bath, and applying this at room temperature. If it is performed, the next step should be performed before the adhesive is dried or cured.If it is performed in an atmosphere having a temperature higher than the melting point of the adhesive, the adhesive should be dried before the next step. Conduct each.

Next, in the second step, when the adhesive is applied in a room temperature atmosphere, before the adhesive applied in the first step is dried, or the adhesive is three-dimensionally cross-linked. Before curing, and in the case where the booth is heated, at this temperature, the powder is applied with the metal powder adhered to the adhesive surface in a state of having the adhesive property. This powder coating is to spray a metal powder on the adhesive surface to form a metal powder layer, and is performed in the booth 22. The atmosphere condition in the booth 22 is preferably room temperature, or a temperature lower than the thermal deformation temperature of the exterior plastic parts, for example, in the case of ABS resin, a temperature of about 50 to 70 ° C. in a nitrogen atmosphere. The type of this metal powder is, for example,
Powders of any kind of metal such as copper, nickel, ferrite, etc., or alloys thereof can be used as long as the shielding effect can be obtained. It is preferable that the particle size of the metal powder is as small as possible, but an optimum particle size is used according to the required shield characteristics and cost. Also,
When the heating in the next step is performed by hot pressing or hot stamping, it is preferable to mix a powder having a melting point higher than the melting point of the metal powder with the above metal powder. This is because the thickness of the formed metal layer can be controlled by this mixing. For example, if the particle diameter of the mixed powder is 100 microns, the thickness of the metal layer formed will be 100 microns, and if the powder having the particle diameter of 500 microns is mixed, the thickness will be 500 microns. can do. By mixing this powder, the thickness of the metal layer can be controlled to a desired value.

Through the above steps, the metal powder layer 23 is formed on one surface of the resin plate 20. If you cannot obtain the desired shielding effect with this process,
The metal powder layer 23 may be formed on the opposite surface in the same process as this, or the thickness of the metal powder layer 23 may be increased by repeating the above process on the same surface. You can Which process is used is determined by the required shielding performance and the appearance required for the case. In other words, when a good appearance is required and high shielding performance is required, a process that can form a metal powder layer with a thickness that provides the required shielding performance only on the inner surface of the case is required. Will be adopted.

In addition to the above steps, a heating step may be provided as a third step. This heating step is a step of melting the metal powder forming the metal powder layer with hot air to form an integrated metal layer. Further, since it is only necessary to bring the metal powder into a molten state, hot pressing may be performed with a heated mold instead of hot air, or hot stamping may be performed. When this step is added, it is necessary that the metal powder that constitutes the metal powder layer contains a metal that melts at a temperature that does not adversely affect the resin or the adhesive. That is, it is necessary that at least the low-melting metal powder containing lead as a main component is contained in the metal powder used in the powder coating step. By providing this step, the metal powder having a low melting point is melted and integrated with other metal powders, so that the metal layer 24 in which all the metal powders are in a series can be obtained. This metal layer 2
Since No. 4 has almost the same quality as the metal layer obtained by plating or the like, the same shielding performance can be expected.

If the shield case is manufactured as in the above-described embodiments, it is possible to easily meet the further demands for weight reduction and downsizing, which are expected in the future, and the complicated shapes associated therewith. Becomes Also, it is possible to easily manufacture products that meet the required shield characteristics,
The manufacturing man-hour is surprisingly reduced as compared with the conventional plating. Therefore, it is possible to manufacture a shield case having a good shield performance in a short time, and it is possible to provide a low-cost shield case.

[0015]

As described above, according to the present invention, the metal powder is attached to the adhesive surface of the case, and the metal powder is further heated to form the shield layer. It becomes possible to manufacture a good product with a simple manufacturing process. Therefore, mass production becomes possible, and the production cost can be reduced.

[Brief description of drawings]

1 (A) and 1 (B) are an external view and a partially enlarged cross-sectional view of a shield case according to the present invention.

FIG. 2 is a diagram showing a method of manufacturing a shield case according to the present invention.

FIG. 3 is a diagram showing a manufacturing process of a shield case according to the present invention.

[Explanation of symbols]

 10 ... Shield case 11 ... Case 12 ... Shield layer 20 ... Resin plate 21 ... Adhesive 22 ... Booth 23 ... Metal powder layer 24 ... Metal layer

Claims (3)

[Claims] 1. A method of manufacturing a shield case for shielding unnecessary interference radio waves emitted from the inside of an electric device or entering from the outside, wherein an adhesive layer is provided on a surface of a molded plastic case that requires a shield. A method of manufacturing a shield case, comprising: a forming step; and a step of adhering a metal powder to an adhesive adhering surface of the case. 2. A method of manufacturing a shield case for shielding unnecessary interference radio waves emitted from the inside of an electric device or entering from the outside, wherein an adhesive layer is formed on a surface of a molded case made of plastic, which requires a shield. A step of forming, a step of adhering a metal powder containing at least a low melting point metal to the adhesive adhering surface of the case, melting the low melting point metal by heating the metal powder adhering surface of the case, And a step of flattening it as a continuous metal layer. 3. A method of manufacturing a shield case for shielding unnecessary interference radio waves emitted from the inside of an electric device or entering from the outside, wherein an adhesive layer is formed on a surface of the molded case made of plastic which requires the shield. A step of forming, a step of adhering a metal powder containing at least a low melting point metal to the adhesive adhering surface of the case, a step of adhering a powder for controlling the thickness of the adhered metal powder, and a step of adhering the metal powder on the case. A step of melting the low melting point metal on the surface by heating and flattening the metal powder adhesion surface as a continuous metal layer.