JP2005276943A - Radiating flexible printed circuit board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radiating FPC (Flexible printed circuit board) by which measures for heat radiation can be taken by coating a liquid ceramic paint with a superior heat radiation effect while its merits such as small in thickness, light in weight, bending property, etc. are demonstrated; and to improve thinning mounting, weight reduction and the degree of freedom in mounting design without failing the bending property. <P>SOLUTION: In the radiating flexible printed circuit board, a liquid ceramic paint is applied onto a heat generator, an FPC substrate, or a circuit pattern for forming a heat-radiating FPC the liquid ceramic paint is applied instead of a cover-lay layer to make a radiating cover-layer structure served as the cover-lay layer; and a through hole or a via hole is provided in the FPC substrate and the liquid ceramic paint is applied onto the surfaces of the circuit pattern, the FPC substrate and the heat generator, thus making a radiating FPC structure. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a heat-dissipating flexible printed wiring board coated with a liquid ceramic paint {hereinafter referred to as heat-dissipating flexible wiring board; referred to as a heat-dissipating FPC (Flexible printed circuit board)}. Heat dissipation measures can be taken while taking advantage of the advantages of thinness, lightness, bendability, etc., as well as thin mounting, lightening, and improved flexibility in mounting design, and heat dissipation without sacrificing bendability. Concerning FPC.

  At present, the heat generation density due to the high integration and high speed of electronic components tends to increase more and more, and heat countermeasures for electronic devices using these components are becoming more important. As a typical example of a conventional heat countermeasure, as shown in FIG. 2 (a), a method of attaching a heat radiating plate 13 'to a flexible wiring board (see, for example, Patent Document 1) or as shown in FIG. 2 (b). There is a method of attaching a heat sink 14 'to a flexible wiring board (for example, see Patent Document 2).

JP-A-10-229255 Japanese Patent Application Laid-Open No. 11-195736

  The problem to be solved is that the heat radiating parts such as the heat sink and heat sink must have a large surface area because of the method of dissipating heat by convection such as an air cooling fan, which is inevitably bulky and increases the mounting volume. In addition to this, there is a problem that the weight is increased and the bendability of the bent corner, which is an advantage of FPC, is impaired.

  The first of the heat dissipation FPC of the present invention is that a liquid ceramic paint is applied to a heat-generating component, FPC base material, or circuit pattern to form a heat dissipation FPC, and the second is a liquid ceramic instead of a coverlay layer. Third, by providing a heat dissipation coverlay structure that also serves as a coverlay layer by applying paint, a through hole or via hole is provided in the FPC base material, and the circuit pattern, the FPC base material, and the heat generating component are provided. This is a point that a liquid ceramic paint is applied to the surface of the surface to make a heat dissipation FPC structure.

The heat dissipation FPC of the present invention is applied with a liquid ceramic paint to take heat dissipation measures,
1. The film made of liquid ceramic paint dissipates heat by heat radiation, and its emissivity is as high as 0.96 (ideal value: 1), and its ability to dissipate heat is high.
2. A heat dissipation effect can be obtained with a thin film (≧ 50 μm).
3. Since it is a thin film, its thickness and weight are hardly increased, and the thickness and weight are reduced.
4). The heat radiation film has bendability (flexibility) and does not impair the bendability of the FPC.
5). Liquid ceramic paints are electrically insulating and can be applied directly onto circuit patterns.
Since 6.3 to 5 can be used as a substitute for the coverlay, it is possible to make a heat dissipation coverlay that also serves as a coverlay.
7). The shape and arrangement of the heat dissipation part are easy, and there is no need to customize heat dissipation parts for each product, increasing the degree of freedom in mounting design.
8). With the above items, the heat dissipation effect can be obtained while taking advantage of the characteristics of FPC such as thinness, lightness and bendability.
Therefore, its industrial value is great.

  Hereinafter, embodiments of the heat radiation FPC 1 of the present invention will be described in detail with reference to the accompanying drawings.

  First, the heat dissipation FPC 1 of the first embodiment of the present invention is a heat dissipation FPC in which a liquid ceramic paint is applied to a heat generating component of an FPC, an FPC base material, or a circuit pattern, although the drawings are omitted. Here, the heat radiation FPC of the present invention was performed by spraying, printing, roll coater or the like on a heat generating component, an FPC base material, or a circuit pattern.

  Next, the heat radiation FPC 1 of the second embodiment of the present invention is a heat radiation flexible wiring board in which a liquid ceramic paint is applied instead of the whole or part of the coverlay layer as shown in FIG. . Here, a polyimide film is usually used as the coverage layer, but by using the liquid ceramic paint 2 instead, a heat dissipation cover lay structure that also serves as a cover lay layer is obtained. As shown in the figure, the whole or part of the coverlay layer may be used.

  As the heat radiation FPC 1 of the third embodiment of the present invention, an undercoat was applied between the circuit pattern of the second embodiment and the liquid ceramic paint as shown in FIG. This is a heat dissipation FPC. Here, as the undercoat, thermocompression bonding with an adhesive typified by an epoxy or a bonding sheet was employed. In order to improve the adhesion to the undercoat, it is preferable to chemically and mechanically roughen the underlying circuit pattern as a pretreatment. In addition, you may apply | coat to the circuit pattern 4 and the FPC base material 3 of the structure shown to FIG.

  As shown in FIG. 1 (c), the heat radiation FPC 1 of the fourth embodiment of the present invention is overcoated on the surface of the liquid ceramic paint applied to the second embodiment in order to further improve the mechanical strength and moisture resistance. This is a heat dissipation FPC that has been subjected to Here, as a representative example of the overcoat, a polyester film is used, but it is not limited to this.

  As shown in FIG. 1 (d), the heat dissipation FPC 1 of the fifth embodiment of the present invention is an embodiment in the case of a special shape, and the FPC base material is provided with a through hole 7 and a via hole 8, and the circuit This is a heat dissipation FPC in which the liquid ceramic paint 2 is applied to the surface of the pattern 4, the FPC base material 3, and the heat generating component 5 and applied over the entire surface of the FPC. In this case, the heat of the heat generating component 5 is transmitted to the liquid ceramic paint 2 through the through hole 7 and the via hole 8, and heat can be radiated more effectively.

  As a sixth embodiment of the present invention, the liquid ceramic paints of the first to fifth embodiments radiate heat by converting it into infrared rays, and the heat radiation film having the infrared radiation effect comprises silicon dioxide / aluminum oxide. It consists of an emulsion composition containing a liquid and kaolin. Here, the liquid ceramic paint comprises an emulsion composition in which a metal oxide such as aluminum oxide or one or more nitrides such as aluminum nitride is contained in an emulsion containing a silicone resin, and kaolin is added to the metal oxide. enter.

  Next, Table 1 below shows the temperature reduction effect on the liquid ceramic paint application area of the heat dissipation FPC 1 having the entire structure of FIG. 1 (a) and applied with the liquid ceramic paint of the present invention.

From this table, it can be seen that the temperature reduction effect increases according to the application area of the liquid ceramic paint, but has a temperature reduction effect of about 10 ° C. for one side and about 20 ° C. for both sides.
Next, although not shown in the table, the thickness of the liquid ceramic paint was also verified. As a result, if the thickness was less than 50 μm, the heat dissipation effect was not sufficient. However, when the thickness was 50 μm or more, almost preferable results were obtained. It was found that when the coating was thicker than 50 μm, the heat dissipation effect did not change significantly and showed a gradual upward trend.

  Furthermore, Table 2 shows a comparison table between the heat dissipation FPC 1 and the heat sink to which the liquid ceramic paint of the present invention is applied.

  From this table, the heat radiation FPC coated with the liquid ceramic paint of the present invention was able to obtain a heat radiation effect equivalent to or better than that of the heat sink. In addition, when the coating film is 100 μm, it can be seen that the volume of the coated portion of the liquid ceramic paint of the present invention is about 1/8 of that of the heat sink component and is greatly reduced.

  So far, the heat dissipation FPC of the present invention has been described with reference to examples of typical heat dissipation FPC and through holes and via holes, but there may be some modifications, and it includes various modifications. Needless to say.

(A) is a second embodiment of the heat dissipation FPC 1A of the present invention in which the liquid ceramic paint 2 is applied instead of the entire cover lay layer 6 or a part thereof. (B) is a third embodiment of the heat dissipation FPC 1B of the present invention in which an undercoat 10 is applied between the circuit pattern 4 and the liquid ceramic coating 2 application of the second embodiment. (C) is a fourth embodiment of the heat dissipation FPC 1C of the present invention in which an overcoat 11 is further applied to the application surface of the liquid ceramic paint 2 of the second embodiment in order to further improve mechanical strength and moisture resistance. (D) of the present invention in which through holes 7 and via holes 8 are provided in the FPC base material 3 and the circuit pattern 4, and the liquid ceramic paint 2 is applied to the surfaces of the circuit pattern 4, the FPC base material 3 and the heat generating component 5. It is 5th Example of thermal radiation FPC1D. (A) is an embodiment in the case where heat is radiated by a conventional heat radiating plate 13 '. (B) is an embodiment in the case where heat is radiated by the conventional heat sink 14 '.

Explanation of symbols

1A, 1B, 1C, 1D
Heat dissipation flexible wiring board (heat dissipation FPC) of the present invention
2 Liquid ceramic paint 3 FPC base material 4 Circuit pattern 5 Heat-generating component 6 Coverlay layer 7 Through hole 8 Via hole 9 Plating
10 Undercoat
11 Overcoat 1 'Conventional heat dissipation flexible wiring board (heat dissipation FPC)
5 'heat generating parts
12 'FPC
13 'heat sink
14 ′ heat sink

Claims (6)

  In a flexible wiring board in which a circuit pattern is formed on an FPC substrate made of an insulator, a heat generating component is further mounted thereon, and a coverlay layer is provided on the circuit pattern, the heat generating component, the FPC substrate, and the circuit A heat-dissipating flexible wiring board characterized by applying a liquid ceramic paint to a pattern.   In a flexible wiring board in which a circuit pattern is formed on an FPC substrate made of an insulator, a heat generating component is further mounted thereon, and a coverlay layer is provided on the circuit pattern, the whole or one of the coverlay layers is provided. A heat-dissipating flexible wiring board, wherein a liquid ceramic paint is applied instead of the part.   A heat-dissipating flexible wiring board, wherein an undercoat is further applied between the circuit pattern of claim 1 and the liquid ceramic paint to further improve adhesion.   A heat-dissipating flexible wiring board, characterized in that an overcoat is further applied to the application surface of the liquid ceramic paint according to claims 1 to 3 in order to further improve mechanical strength and moisture resistance.   In a flexible wiring board in which a circuit pattern is formed on an FPC substrate made of an insulator, a heat generating component is further mounted thereon, and a coverlay layer is provided on the circuit pattern, a through hole or a hole is formed in the FPC substrate. A heat radiating flexible wiring board, wherein a via hole is provided and a liquid ceramic paint is applied to the surface of the circuit pattern, the FPC base material, and the heat generating component.   The liquid ceramic coating composition according to any one of claims 1 to 5, wherein the heat radiation film having an infrared radiation effect is radiated by converting heat into infrared rays, and the emulsion composition comprises a liquid containing silicon dioxide / aluminum oxide and kaolin. A heat-dissipating flexible wiring board characterized by comprising a thing.

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