JPS62152199A - Electromagnetic wave 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 (Industrial Field of Application) The present invention is composed of a metal foam made of an aggregate of closed cells. This relates to 11-wave shielding material.

(Prior art) Recently, information processing devices and electronic office equipment have become rapidly popular as electronic equipment becomes more sophisticated and lower in price. The problem of radio wave interference to equipment is occurring, and measures to prevent it are desired. Conventionally, many methods have been adopted as electromagnetic shielding measures. For example, applying electrical conductivity to electronic equipment housings, etc. by coating plastics with conductive paint or plating, or adding conductive fillers such as metal fibers, carbon 11 navy blue, powder, etc. Although methods such as mixing of
This was unsatisfactory in terms of cost and other factors.

(Purpose of the Invention) This invention was made to solve these conventional problems, and has a wide electromagnetic wave shielding effect over a wide electromagnetic frequency range, is lightweight, and has a thermal and mechanical properties. The present invention provides an electromagnetic shielding material made of a metal foam made of an aggregate of closed cells with excellent properties.

(Structure of the Invention) The present invention is a foamed metal plate consisting of an aggregate of closed cells J, in which the diameter of four through holes extending between the surfaces of the metal plate is 5 mm or less.

Here, the concept that the hole diameter of the currency hole is 5 ml or more includes the case where the hole diameter is Qmm, that is, the case where the closed cells do not penetrate between the front and back surfaces of the foamed metal plate. If the through-hole diameter exceeds 5 mm, the electromagnetic shielding function will deteriorate. Further, although there may be a plurality of sets of through holes, it is necessary that all of the through holes have a hole diameter of 5 mm or less.

This foamed metal plate can be used alone as wall materials, ceiling materials, floor materials, etc. in electronic equipment rooms, or as electronic equipment casings, or it can be used by pasting it on board materials such as wood or plastic deck. It's okay. Furthermore, this foamed metal plate may be made into a composite material integrally molded with plastic.

(Example) Add a thickener and a molten aluminum to molten aluminum! Foamed aluminum consisting of a large number of closed cells was produced by stirring. For this production, a mold was used which was heated entirely to a temperature above the melting point of foamed aluminum.

After stirring the above materials in the mold, foaming begins, and as the bubbles grow, the mold is sealed with an air release port, and the foam material decomposes due to heat, resulting in a large number of bubbles. When the mold expanded, the air inside the mold was released to the outside of the mold. When the inside of the mold is completely filled with foamed aluminum, the discharge port is closed by the molten foamed aluminum and the mold is sealed, and the upper limit of the internal pressure of the many bubbles inside the sealed mold causes the bubbles to interact with each other. A uniform cell structure is formed under the pressure balance of . Then, heating of the vi type was stopped, and the aluminum foam was cooled and solidified. In addition, 0°2 to 8% by weight of calcium as a thickener was added and stirred to adjust the viscosity of aluminum, and then 1 to 3% by weight of titanium hydride was added and stirred.
Foamed. The foamed aluminum manufactured in this way has bubbles with a diameter of approximately 2 to 5 mm and is uniformly dispersed, and even when a foamed aluminum ingot is cut into a plate shape, the through holes penetrating both the front and back surfaces have a diameter of 5+ni. was rarely exceeded.

During the above foaming and cooling process, the film surface between the bubbles may be torn due to photographing of the mold, etc., and through holes with a diameter exceeding 5 mm may be scattered, but in that case, the foamed aluminum By inserting and filling small pieces of foamed aluminum plate, or by cutting the foamed aluminum plate into thin pieces so as to divide the thickness in half, stacking them on top of each other with their positions shifted so as to close the through hole, and bonding them with adhesive etc. It is also possible to make the hole diameter of the through hole 5 mm or less.

The cross-sectional structure of the aluminum foam produced as described above is shown in FIG. When this was cut into a plate shape with a thickness of 5IIIll and the electromagnetic wave shielding characteristics were measured and the characteristics of electromagnetic wave transmission loss and electromagnetic wave frequency were investigated, Figure 2 (A)
~(D>).

(A) is O~100KHz, (B) is 0~1MHz, (
C) is O~100Ml-1z, (D) is O~10010
Each electromagnetic wave transmission loss (d
B) is shown. Each sample had a large number of through holes with a diameter of 1 mm or less and some through holes with a diameter of 5a+m or less.
It has been shown that there is an electromagnetic shielding effect of approximately 80 dB at frequencies above B, particularly above 20 MH2. This is 1~
This is almost equivalent to the 1 m wave shielding effect of a 2 mm thick aluminum plate, and can be said to have a sufficient effect as the electromagnetic wave shielding material.

Figure 3 shows the measurement results of electromagnetic shielding characteristics when there are many through holes with a hole diameter of over 5 mm, and (A) is O~10
0Kt-1z, (B) is O~1MH21 (C) is 0~1
00MHz, (D) indicates each electromagnetic wave transmission loss (dB) in the frequency range of 0 to 100100O. Although it exhibits an electromagnetic shielding effect of approximately 60 dB in the high frequency range, the electromagnetic shielding properties deteriorate in the low frequency range. In other words, when a through hole exists, the electromagnetic shielding function is insufficient if the hole diameter is 5 mm or more, but if the hole diameter is 5 mm or more, the electromagnetic shielding function is insufficient.
By setting III to 11 or less, a high electromagnetic shielding function can be achieved over a wide frequency range.

Figure 4 shows the state of the through holes 10 in the aluminum foam plate 1, d
indicates the through hole diameter. There is almost no difference in electromagnetic shielding properties between the case where there are a plurality of through holes with a hole diameter d of 5 mm or less and the case where there are no through holes at all, and the electromagnetic wave shielding effect is almost equal to that of an aluminum plate.

Figure 5 shows a state in which foamed aluminum plate 1 is attached to plastic plate 2, Figure 6 shows a state in which foamed aluminum plate 1 is embedded in plastic plate 3, and Figure 7 shows a composite of foamed aluminum plate 1 and plastic plate 3. FIG. 8 shows the state in which the body is press-molded, and the state in which plastic 4 is baked or painted on the surface of the foamed aluminum plate 1. In this way, it can be used as a variety of composite materials or molded into various shapes depending on the purpose. Furthermore, when painting is applied, it is easy to adhere to the surface due to the large number of irregularities formed on the surface, and it is also possible to completely coat the inner surface of the bubbles by electrostatic painting.

(Effects of the Invention) As explained above, the present invention is a foamed metal plate made of an aggregate of closed cells, which is configured such that the diameter of the through hole passing through the front and back surfaces of the metal plate is 5IllIl or less. This foamed metal plate can be used alone as wall materials, ceiling materials, floor materials, etc. of electronic equipment rooms, or as electronic equipment casings, or it can be attached to board materials such as wood or plastic. It can be used as Furthermore, this foamed metal plate may be integrally molded with plastic to form a composite material. By applying it to these uses, it is possible to exhibit an excellent electromagnetic shielding function, and it is also possible to exhibit an effect that is lightweight and has excellent thermal and mechanical properties.

[Brief explanation of drawings]

Fig. 1 is a metallographic photograph showing an example of the present invention, Figs. 2 (A) to (D) are electromagnetic shielding characteristic diagrams of the foamed metal plate of this invention, and Figs. 3 (A) to (D). An electromagnetic wave shielding characteristic diagram of a foamed aluminum plate when there are many through holes with a hole diameter of over 3 mm+, FIG. 4 is a cross-sectional explanatory diagram of the through holes,
5 and 6 are cross-sectional explanatory views of a composite body with plastic, FIG. 7 is a cross-sectional explanatory view of this composite body in a press-molded state, and FIG. 8 is a cross-sectional explanatory view of a plastic covering material. 1... Foamed aluminum plate, 2, 3... Plastic plate, 4... Plastic coating. Patent applicant Zhou, Director of the Institute of Industrial Science and Technology, Shinko Wire Industry Co., Ltd.

Claims (1)

[Claims] 1. An electromagnetic wave shielding material, which is a foamed metal plate made of an aggregate of closed cells, and has a through hole penetrating between the front and back surfaces of the metal plate with a hole diameter of 5 mm or less.