WO2008026247A1 - Electromagnetic wave shield structure and formation method thereof - Google Patents

Abstract

To reduce the manufacturing cost of an electronic apparatus as much as possible by improving the structure and the formation method of an electromagnetic wave shield thereby reducing the cost of the electromagnetic wave shield of the electronic apparatus as much as possible. A wiring board to which a plurality of electronic components are fixed is covered with an electromagnetic wave shield sheet, and then the electromagnetic wave shield sheet is sucked through the wiring board by reducing pressure. The electromagnetic wave shield sheet consists of a basic layer composed of a thermoplastic sheet, and a metal layer laminated on the basic layer directly or through an other layer on the outside of the electromagnetic wave shield sheet. The electromagnetic wave shield sheet, sucked by reducing pressure, is deformed plastically along the profile of the electronic component, thus covering the electronic components individually.

Description

 Electromagnetic wave shield structure and formation method thereof

 Technical field

 The present invention relates to an electromagnetic wave shielding structure that shields each electronic component on a wiring board of an electronic device from unnecessary electromagnetic waves, and a method for forming the same.

 Background art

 An information terminal such as a mobile phone is equipped with an imaging module in which components such as an imaging device, a lens, and an IC that is a driver for driving the imaging device are integrated as a package. An electronic component such as a CCD is mounted on the wiring board. This electronic component generates electromagnetic waves, which may interfere with the communication function of the information terminal. For this reason, electromagnetic waves are shielded by covering the electronic components mounted on the wiring board with a shield case.

 In the conventional electromagnetic wave shielding structure shown in FIG. 11, for the purpose of shielding the electromagnetic wave of each electronic component 12 mounted on the wiring board 10, the wiring board 10 is made of metal in such a manner that the electronic parts 12 are accommodated. The shield case 14 is assembled.

 [0004] A continuous ground pattern 16 is formed on the surface of the wiring board 10 so as to surround the electronic component 12, and the lower edge of the shield case 14 assembled at a predetermined position of the wiring board 10 is ground pattern. Electromagnetic shielding is applied to each electronic component 12 by bringing it into contact with 16 to achieve conduction.

 [0005] Further, in another conventional electromagnetic wave shielding structure shown in FIG. 12, for the purpose of shielding the electromagnetic wave of each electronic component 12 mounted on the wiring substrate 10, the electronic component 12 is accommodated in the wiring substrate 10 so as to be accommodated. Shield case 18 is assembled.

 [0006] The shield case 18 is formed by, for example, applying a plating, vapor deposition, conductive coating or the like to the surface of a resin molded product, and has a housing 20 corresponding to each electronic component 12.

[0007] On the surface of the wiring board 10, a continuous ground pattern 16 is formed so as to go around each electronic component 12, and a shield case 18 assembled at a predetermined position of the wiring board 10 is formed. The lower edge of each of the electronic components 12 is brought into contact with the ground pattern 16 so as to conduct electricity, thereby shielding the electromagnetic wave from each electronic component 12.

 Patent Document 1: JP 2004-71629 A

 Patent Document 1: Japanese Patent Laid-Open No. 2002-232099

 Disclosure of the invention

 Problems to be solved by the invention

[0008] As described above, the conventional electromagnetic wave shield requires the shield cases 14 and 18, and the force of the shield cases 14 and 18 needs to be prepared in various types corresponding to the arrangement of the electronic components 12 on the wiring board 10. For this purpose, various types of molds for manufacturing the shield cases 14 and 18 are required. Therefore, there is a problem that the manufacturing cost of the electronic equipment is increased due to the mold cost. .

 [0009] Further, in the conventional electromagnetic wave shield, the shield cases 14, 18 must be soldered to the wiring board 10, but the soldering process is costly, and this process increases the manufacturing cost of the electronic equipment, Then there was a problem.

 [0010] The problem to be solved by the present invention is to reduce the cost of electromagnetic shielding of electronic equipment as much as possible by improving the structure and covering method of the electromagnetic shielding, and thus reduce the manufacturing cost of electronic equipment as much as possible. It is in the point to.

 Means for solving the problem

 [0011] In the electromagnetic wave shielding structure according to the present invention, an electromagnetic wave shielding sheet is coated on a wiring board on which a plurality of electronic components are attached in a state of being plastically deformed along the shape of the electronic parts, and the wiring board has a plurality of penetrating holes. The electromagnetic wave shielding sheet has a base layer made of a plastic sheet and an outer side of the base layer! And a metal layer laminated on the base layer directly or via another layer, wherein the ground pattern and the metal layer are electrically connected. .

[0012] Further, in the method for forming an electromagnetic wave shielding sheet structure according to the present invention, an electromagnetic wave shielding sheet is coated on a wiring board on which a plurality of electronic components are attached, and the electromagnetic wave shielding sheet is sucked under reduced pressure through the wiring board. The wiring board has a plurality of through holes, and the electromagnetic wave shielding sheet includes a base layer made of a plastic sheet and an outer side of the base layer. And a metal layer laminated on the base layer directly or via another layer, the plastic sheet is made of thermoplastic resin, and the vacuum suction is performed under heating. It is what.

 Here, a conductive plastic may be used as the other layer! As the conductive plastic, for example, polyacetylene, polypyrrole, polythiophene, or polyarine, or a composite material in which graphite or metal powder is dispersed in general-purpose plastic can be used.

 [0014] The thickness of the metal layer is preferably 1000 A to 3000 A. The metal layer has a thickness of 10

If it is less than 00 A, there is an inconvenience that leakage of electromagnetic waves due to pinholes, which makes it difficult to uniformly deposit the metal layer, cannot be ignored. If it exceeds 3000 A, the metal layer is steeply formed during vacuum forming. This is because there is no inconvenience that the metal layer is easily broken in the range of 1000 A to 3 oooA.

 [0015] The metal layer may be copper, aluminum, nickel, iron oxide (Fe 2 O 3), gold or silver.

 twenty three

 Can be mentioned. Examples of the plastic sheet include polycarbonate (PC) resin, polyethylene terephthalate (PET) resin, and polystyrene (PS) resin. The plastic sheet is also preferably flame retardant in terms of its ability to attach to the wiring board of electronic equipment.

[0016] The thickness of the base layer is preferably 50 to 2000 μm. When the thickness of the base layer is less than 50 μm, the handling of the electromagnetic wave shielding sheet in vacuum molding is too delicate, and when it exceeds 2000 m, the vacuum molding becomes difficult. This is because there is no inconvenient in the -2000 μm range.

 [0017] Further, it is preferable that a part of the through hole formed in the wiring board is formed in the vicinity of the electronic component. If the through hole is formed in the vicinity of the electronic component, the electromagnetic wave shielding sheet penetrates deeply between the electronic components, and each electronic component is well shielded against electromagnetic waves, thus improving the characteristics of the electronic device. is there.

[0018] Further, before the electromagnetic wave shielding sheet is sucked under reduced pressure, a molding material such as putty is added to the electronic component to correct the shape of the electronic component so that the wiring board is used as a mold. The electromagnetic shielding sheet may be sucked under reduced pressure. If you do this This is because the metal layer is less cracked at the portion corresponding to the corner of the electronic component. The invention's effect

 [0019] In the present invention, the electromagnetic shielding sheet is coated on the electronic component on the wiring board by utilizing the vacuum molding technique. Therefore, it is not necessary to mold the electromagnetic shielding with a mold. Only reducing the manufacturing cost of electronic equipment has the advantage.

 [0020] Further, the present invention does not require soldering to attach the electromagnetic wave shield to the wiring board, so that the mounting cost of the electromagnetic wave shield is reduced, and accordingly, the manufacturing cost of the electronic device is reduced by the amount not soldered. There is an advantage of reducing.

 [0021] Further, according to the present invention, since the electromagnetic shielding film is coated on the electronic component on the wiring board by using the vacuum forming technique, the electromagnetic shielding is buried between the electronic components, and the electronic components are mutually connected. It has the advantage that it is well shielded and therefore the characteristics of the electronic device are good.

 Brief Description of Drawings

FIG. 1 is an exploded explanatory view of an electromagnetic wave shielding structure according to the present invention.

 FIG. 2 is a cross-sectional view of an electromagnetic wave shielding structure according to the present invention.

 FIG. 3 is an enlarged view of part A in FIG.

 FIG. 4 is a graph showing the relationship between the shielding effect (dB) of the electromagnetic wave shielding sheet of sample number 1 and each frequency (MHz) of electromagnetic waves.

 FIG. 5 is a graph showing the relationship between the shielding effect (dB) of the electromagnetic wave shielding sheet of sample number 2 and each frequency (MHz) of electromagnetic waves.

 FIG. 6 is a graph showing the relationship between the shielding effect (dB) of the electromagnetic wave shielding sheet of sample number 3 and each frequency (MHz) of electromagnetic waves.

 FIG. 7 is a graph showing the relationship between the shielding effect (dB) of the electromagnetic wave shielding sheet of sample number 4 and each frequency (MHz) of the electromagnetic wave.

 FIG. 8 is a graph showing the relationship between the shielding effect (dB) of the electromagnetic wave shielding sheet of sample number 5 and each frequency (MHz) of electromagnetic waves.

FIG. 9 is a graph showing the relationship between the shielding effect (dB) of the electromagnetic wave shielding sheet of sample number 6 and each frequency (MHz) of electromagnetic waves. [FIG. 10] FIG. 10 is a graph showing the relationship between the shielding effect (dB) of the plastic sheet of Sample No. 7 and each frequency (MHz) of electromagnetic waves.

 FIG. 11 is an exploded explanatory view of an example of a conventional electromagnetic shielding structure.

 FIG. 12 is an exploded explanatory view of another example of a conventional electromagnetic shielding structure.

 Explanation of symbols

 10 Wiring board

 12 Electronic components

 14 Sino Red Case

 16 Ground pattern

 18 Sino Red Case

 20 containment

 22 Electromagnetic wave sheet

 24 Through hole

 26 Base

 28 Conductive layer

 30 metal layers

 32 holes

 34 Bali

 BEST MODE FOR CARRYING OUT THE INVENTION

 [0024] By reducing the cost of electromagnetic shielding of electronic equipment, the purpose was achieved by using vacuum forming technology without degrading the characteristics of electromagnetic shielding.

 1 is an exploded explanatory view of the electromagnetic wave shielding structure according to the present invention, FIG. 2 is a cross-sectional view of the electromagnetic wave shielding structure according to the present invention, and FIG. 3 is an enlarged view of a portion A in FIG.

 [0026] Reference numeral 10 denotes a wiring board. A plurality of electronic components 12 are attached on the wiring board 10, and a ground pattern 16 is formed on the upper surface of the wiring board 10. The upper surface side of the wiring board 10 is covered with an electromagnetic wave shielding sheet 22 that is plastically deformed along the shape of the electronic component 12.

[0027] The wiring substrate 10 is provided with a plurality of through holes 24 in a dispersed state. Through hole 24 It is also provided along the electronic component 12.

[0028] The electromagnetic wave shielding sheet 22 includes a base layer 26 made of a plastic sheet, and a metal layer 30 laminated on the outer side of the base layer 26 and on the side not in contact with the electronic component 12 with a conductive layer 28 interposed therebetween. The base layer 26 is composed of a polycarbonate (PC) resin sheet having a thickness of 0.1 mm, the conductive layer 28 is composed of polythiol, and the metal layer 30 is composed of a copper deposition layer (thickness: 100θΑ to 300θΑ).

 [0029] In the electromagnetic wave shielding sheet 22, a hole 32 is opened in advance so that the metal layer 30 side force is also directed toward the base layer 26, and the burr 34 at the edge of the hole 32 returns to the back side (wiring board 10 side). The metal layer 30 of 34 is in contact with the ground pattern 16, the hole 32 is filled with solder, and the metal layer 30 of the hole 32 and the burr 34 is electrically and mechanically connected to the ground pattern 16.

 [0030] Next, a method for forming the electromagnetic wave shielding sheet structure on the wiring board will be described.

 First, the electromagnetic wave shielding sheet 22 is coated on the wiring board 10. Here, the electromagnetic shielding sheet 22 is coated with the metal layer 30 facing outward and the base layer 26 facing inside, ie, the base layer 26 facing the electronic component 12 side.

 Next, the electromagnetic wave shielding sheet 22 is heated and softened. Here, the wiring board 10 may be heated in advance, or the electromagnetic wave shielding sheet 22 may be heated after coating.

 Next, the electromagnetic wave shielding sheet 22 is sucked under reduced pressure through the wiring board 10. The electromagnetic shielding sheet 22 is sucked to the wiring board 10 side by vacuum suction and is plastically deformed along the shape of the electronic component 12 on the wiring board 10 by heat to cover the electronic component 12.

 [0034] As shown in FIG. 3, the electromagnetic wave shielding sheet 22 has a hole 32 formed in advance so that the force on the metal layer 30 side also faces the base layer 26, and the burr 34 at the edge of the hole 32 returns to the back side. In this way, the metal layer 30 of the substrate 34 is in contact with the ground pattern 16. Then, by soldering the hole 32, the metal layer 30 of the hole 32 and the burr 34 is electrically and mechanically connected to the ground pattern 16.

 Example 1

[0035] As shown in Table 1 below, the thickness of the metal layer 30 is 1000 A, 1500 A, and 3000 A, and the metal layer 30 does not have the metal layer 30 and the electromagnetic wave shielding sheet that also has a copper deposition force. plastic Using a sheet (PC), the shielding ratio (dB) of electromagnetic waves was measured for each frequency of electromagnetic waves by the KEC method (Kansai Electronics Industry Promotion Center), and the results shown in Figs. 4 to 10 were obtained. It was.

[table 1]

図 4〜図 10に示す結果によれば、本発明に係る電磁波シールド構造は、電磁波の 周波数 10 1000MHzで 40dB以上のノイズ抑制効果を有していることがわかり、こ の電磁波シールド構造を用いた場合はシールド率 99%が達成できることがわかる。

According to the results shown in FIGS. 4 to 10, it can be seen that the electromagnetic wave shielding structure according to the present invention has a noise suppression effect of 40 dB or more at an electromagnetic wave frequency of 10 1000 MHz, and this electromagnetic wave shielding structure was used. It can be seen that a shield rate of 99% can be achieved.

Claims

The scope of the claims  [1] An electromagnetic wave shielding sheet is coated on a wiring board on which a plurality of electronic components are attached in a state of being plastically deformed along the shape of the electronic component, and the wiring board has a plurality of through holes and a ground pattern. The electromagnetic wave shielding sheet also has a force including a base layer made of a plastic sheet and a metal layer laminated on the base layer directly or via another layer over the outside of the base layer. An electromagnetic wave shielding structure characterized in that the metal layer is electrically connected.  2. The electromagnetic wave shielding structure according to claim 1, wherein the through hole is formed in the vicinity of an electronic component. [3] The electromagnetic shielding structure according to claim 1 or 2, wherein the other layer is made of a conductive material. 4. The electromagnetic shielding structure according to claim 3, wherein the conductive material is a conductive plastic. [5] The electromagnetic wave shielding structure according to any one of claims 1 to 4, wherein the metal layer has a thickness of 1000 A to 3000 A. [6] The metal layer may be copper, aluminum, nickel, iron oxide (Fe 2 O 3), gold or silver.  twenty three  The electromagnetic wave shielding structure according to any one of claims 1 to 5, wherein: [7] The electromagnetic wave shield according to any one of claims 1 to 6, wherein the plastic sheet is made of polycarbonate (PC) resin, polyethylene terephthalate (PET) resin or polystyrene (PS) resin. Construction. [8] The electromagnetic wave shielding structure according to any one of [1] to [7], wherein the base layer has a thickness of 50 to 2000 m. [9] The method includes a step of coating an electromagnetic wave shielding sheet on a wiring board on which a plurality of electronic components are attached, and vacuum-sucking the electromagnetic wave shielding sheet through the wiring board, and the wiring board has a plurality of through holes. The electromagnetic wave shielding sheet has a base layer made of a plastic sheet and an outer side of the base layer! And a metal layer laminated on the base layer directly or via another layer, the plastic sheet is made of thermoplastic resin, and the vacuum suction is performed under heating. A method for forming an electromagnetic wave shielding structure. 10. The method for forming an electromagnetic wave shield structure according to claim 9, wherein the through hole is formed in the vicinity of an electronic component. [11] The method for forming an electromagnetic wave shielding structure according to [9] or [10], wherein the other layer is made of a conductive material. 12. The method for forming an electromagnetic wave shielding structure according to claim 11, wherein the conductive material is a conductive plastic. [13] The method for forming an electromagnetic wave shielding structure according to any one of [9] to [12], wherein the metal layer has a thickness of 1000 A to 3000 A. [14] The metal layer is made of copper, aluminum, nickel, iron oxide (Fe 2 O 3), gold or silver.  twenty three  The method for forming an electromagnetic wave shielding structure according to claim 9, wherein: [15] The plastic sheet is made of polycarbonate (PC) resin, polyethylene terephthalate ( The method for forming an electromagnetic shielding structure according to any one of claims 9 to 14, wherein the electromagnetic shielding structure is made of PET) resin or polystyrene (PS) resin. [16] The method for forming an electromagnetic wave shielding structure according to any one of [9] to [15], wherein the base layer has a thickness of 50 to 2000 μm. 17. The method for forming an electromagnetic shielding structure according to any one of claims 9 to 16, wherein the electromagnetic shielding sheet is sucked under reduced pressure after a molding material is added to the electronic component to correct the shape. .