JPS62276900A - Electromagnetic shielding material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an electric wave shielding material, and particularly to a member for electromagnetically shielding various electronic devices from the outside. be.

[Conventional technology]

As the applications of electronic devices expand, countermeasures against electromagnetic interference have become necessary.

For this reason, powders, short fibers, flakes, etc. of copper, aluminum, nickel, iron, brass, etc. are mixed with synthetic resin to shield electronic devices and their surrounding parts from electromagnetic waves, and the mixture is shaped into the desired shape. A method of molding it to cover electronic equipment and shielding it from electromagnetic waves has been devised and applied.

However, since copper and aluminum are metals with good conductivity, they are effective in shielding electric fields, but are not very effective against magnetic fields. Further, since nickel and iron are magnetic materials, they have a shielding effect against a 6ff field, but are not very effective against an electric field.

Additionally, a method has been devised in which the amorphous alloy short fiber material is directly mixed into a synthetic resin, but this method was also insufficiently effective.

[Problem that the invention seeks to solve]

The present invention improves the electromagnetic wave shielding effect by improving the shortcoming of amorphous alloy short fibers, which is insufficient conductivity, and by specifying the composition, dimensions, amount of amorphous alloy, etc. The object of the present invention is to provide an electromagnetic wave shielding material that has a high shielding effect against both types of radiation.

[Means and actions for solving the problem] Currently, various electromagnetic wave shielding methods have been developed and applied, but no effective method for shielding both electric fields and magnetic fields in a wide frequency band has yet been developed.

Amorphous alloys are excellent magnetic materials, and in particular, their magnetic permeability exceeds that of supermalloy, which is said to be the highest in the past, and their saturation magnetization is also sufficiently high. In other words, it has long been noted that it is a material that has an extremely high magnetic field shielding effect.

On the other hand, the electric field shielding effect was insufficient compared to other metals. The reason is thought to be that the amorphous alloy has high specific resistance.

In order to increase the electrical conductivity of the Fe-based amorphous alloy short fibers that are mixed with the resin, the present inventors coated them with a highly conductive metal by plating, etc., and also changed the composition of the amorphous alloy material, the dimensions of the fibers, and the amount of the fibers mixed. By identifying this, we succeeded in obtaining an electromagnetic wave shielding material that has excellent shielding effects for both electric and magnetic fields.

The metal used as the coating material in the present invention has an electrical conductivity sufficiently higher than that of the amorphous alloy, that is, an electrical resistivity of less than 10 μΩcm, such as copper, silver, brass, zinc, nickel, aluminum, etc. At least one type or two or more types. Incidentally, the electrical resistivity of an amorphous alloy is 120 μΩcm. If the thickness of the coating is 0.1 μm or less, the shielding effect will be small;
Even if it is made more than m, the effect is saturated and no further improvement can be expected. Therefore, the coating thickness is set to 0.1 μm to 5 μm.

The method of plating as a coating, using copper as an example, is as follows.

(Activation process) Hydrochloric acid (35% solution) 12% by volume, sulfuric acid (85% solution) 7
Volume%, citric acid powder 5% by weight, nitric acid (68% solution) 7
3% by weight of amorphous alloy short fibers in an acidic activation bath containing 0.2% by weight of nonionic surfactant, 0.1% by weight of N-alkyl trimethylene diamine, and 0.05% by weight of amine corrosion inhibitor. The surface was activated by dipping for a minute.

(Copper plating method) The activated amorphous alloy short fibers described above were plated with copper using one of the following two copper plating methods.

(A) Sulfuric acid S (5%) (7 nights) 6% by volume, formalin (37% solution) 2% by volume, caustic soda 10 g/l,
The solution was set at a liquid temperature of 50° C. with a volume of 25 g/l of ethylenediamine-4-acetic acid-disodium, and treated for 3 minutes, resulting in copper plating of about 0.4 μm on the surface of the amorphous alloy short fibers.

(B) Copper pyrophosphate (metal content 36%) 80 g/f, potassium pyrophosphate 300 g/l, ammonia (20%
Solution) A solution of 0.2% by volume was heated to a temperature of 60°C, a voltage of 6 to 7V was applied to the amorphous short fibers, and electrolytic plating was performed for 3 minutes. Copper plated.

The dimensions of the amorphous short fibers used in the present invention are thickness 1
0/jm ~ 150/jm, width 0.1 mm ~ l Dragon,
The length should range from 1 to 30 doubles. The above-mentioned size range was determined in consideration of the electromagnetic wave shielding performance, the compatibility with the resin, the ease of manufacturing the fiber, etc. One example of a specific method for producing amorphous alloy short fibers is the method disclosed in Japanese Patent Application Laid-Open No. 59-150113. However, the present invention is not limited to short fibers produced by this method.

For example, long fibers may be cut into short fibers.

The alloy composition of the amorphous alloy short fiber used in the present invention is based on iron, contains small amounts of other metals, and is further composed of semimetals, and is represented by Fe1X and Mc.

Here, X is Cr or Mo.

One or more of W, Ni, Co, M is B, C.

Represents one or more of P and Si. Also, the content is a
: 60-90 (at%), more than boo and 15 or less, c: in the range of 10-35. However, a+b+c=l
o.

It is. The reason for adding the X element is to improve the amorphous formation ability, thermal stability, corrosion resistance, electromagnetic shielding properties, etc. Since addition of more than 15 at% may significantly reduce saturation magnetization depending on the element, the upper limit was set at 15 at%.

Metalloids have 10 to 3 elements necessary for amorphous formation.
The above range was specified because it is necessary to add 5at%.

Annealing is also effective in improving the electromagnetic shielding properties of amorphous short fibers. Annealing may be performed either before or after the plating process. The annealing conditions vary depending on the components, but can be determined experimentally based on the balance between improvement of magnetism and deterioration of mechanical properties due to embrittlement or crystallization. Annealing may be performed in a magnetic field. Static II: Includes both magnetic fields and rotating magnetic fields.

In addition, the synthetic resins used in the present invention include polyethylene, polyamide, nylon, polypropylene, polystyrene,
Thermoplastic resins such as ABS and polyvinyl chloride, and thermosetting resins such as epoxy, polyester, and phenol are used.

The method for producing the electromagnetic shielding material of the present invention involves blending a predetermined amount of the metal-plated and annealed amorphous alloy short fibers with a synthetic resin, kneading them, and producing pellets using a granulator. The blending amount of the amorphous alloy short fibers is 10 to 70%, preferably 20 to 60% by weight with respect to the synthetic resin.
% is good.

The above appropriate blending amount was determined by taking into consideration the moldability of the resin mixed with short fibers, electromagnetic wave shielding properties, etc.

〔Example] Next, an example will be given and explained.

Amorphous alloy short fibers having the composition, dimensions, plating material, and plating thickness shown in Table 1 are mixed with polystyrene resin at the filling rate shown in Table 1, and heated and pressure-formed in a mold to form a sheet of 150 dragon angles. And so.

Cut the sheet that has been formed once, heat it again in the same mold,
By pressure molding, a sheet with a high degree of short fiber dispersion was created.

The electromagnetic wave shielding properties of each sample were measured using an electric wave shielding effect measuring device manufactured by Atopan Test Co., Ltd.

The results were as shown in Table 1.

It is clear that compared to the short fibers produced by the chatter vibration method of the comparative example, even with a small amount mixed, the fibers have high shielding properties for both electric and magnetic fields.

〔Effect of the invention〕

The electromagnetic shielding material of the present invention, which is made by mixing Fe% amorphous alloy short fibers plated with a highly conductive metal into a synthetic resin, has better magnetic properties and electrical connectivity than metal powders or other metal short fibers, so it can withstand electromagnetic waves. has a high shielding effect. Therefore, the purpose can be achieved by mixing the amount of livelihood.

Claims (1)

[Claims] 1. An electromagnetic shielding material characterized by being molded from a synthetic resin mixed with Fe-based amorphous alloy short fibers coated with a highly conductive metal. 2. Copper or silver in which the metal coating has a thickness of 0.1 μm to 5 μm,
The electromagnetic wave shielding material according to claim 1, characterized in that it is made of at least one or two or more of brass, zinc, nickel, and aluminum. 3. The dimensions of the amorphous alloy short fibers to be mixed are 10 μm to 150 μm in thickness, 0.1 mm to 1 mm in width, and 2 in length.
The electromagnetic wave shielding material according to claim 1, wherein the electromagnetic wave shielding material has a thickness of mm to 30 mm. 4. The amount of the amorphous alloy short fibers mixed is 1 by weight.
Claim 1 characterized in that the ratio is 0 to 70%.
Electromagnetic wave shielding material described in section. 5. The chemical composition of the amorphous alloy short fiber is Fe_a
The electromagnetic wave shielding material according to claim 1, characterized in that it is X_bM_c. Here, X is Cr, Mo, W
, Ni, Co, M is B, C, P, S
One or more types of i, a: 60 to 90 (at%),
b: more than 0 and less than 15, c: 10-35, but a+b
+c=100. 6. The chemical composition of the amorphous alloy short fiber is Fe_a
The electromagnetic wave shielding material according to claim 1, characterized in that it is Cr_bB_cC_d. Here a: 70~
85 (at%) b: 1-12, c: 10-16, d: 1
~8, but a+b+c+d=100. 7. The electromagnetic wave shielding material according to claim 1, wherein the amorphous alloy short fibers are subjected to strain relief annealing or magnetic field annealing.