JP2008177235A - Prepreg and printed wiring board using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a prepreg capable of efficiently suppressing radiation noise from a printed board having electronic components mounted thereon and electromagnetic interference generated in the board, and easily ensuring insulating characteristics between layers in a multilayer substrate, and to provide a printed circuit board using the prepreg. <P>SOLUTION: A ferrite plating layer 2 is formed on the surface of a warp-and weft-knitted glass cloth 1, and the layer 2 is coated with an insulating resin layer 3 such as epoxy to form a prepreg 4. After forming the ferrite plating layer 2, the epoxy resin, etc., is impregnated into the glass cloth, thereby obtaining the prepreg 4. In this case, the thickness of the ferrite plating film should be about 0.5 μm in order to obtain a noise suppressing effect, and it is preferably not more than 10 μm in consideration of the thickness of the glass cloth and the practical thickness of the prepreg. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a prepreg for a printed circuit board on which electronic components such as semiconductor elements are mounted, and a printed circuit board using the prepreg.

  Digital devices such as mobile phones, digital still cameras, and notebook computers have been improved in performance, such as being equipped with more functions than ever due to higher processing speed and communication speed. On the other hand, speeding up and high-density mounting have deteriorated the electromagnetic field environment, and the frequency region in which the problem of mutual interference and radiation noise has been gradually increased. Countermeasures against radiation noise have also been taken on printed circuit boards on which electronic components are mounted, but there are increasing cases where conventional designs and countermeasures alone are insufficient.

  Patent Document 1 discloses a multilayer printed wiring board having a power supply circuit and a ground circuit in an inner layer, and a magnetic layer is coated on at least one of the power supply circuit and the ground circuit. A multilayer printed circuit board including a ferrite-coated metal magnetic fine particle formed by coating a ferrite layer containing a polymer having a carboxyl group on a core made of magnetic fine particles is shown. It is described that a multilayer printed wiring board having stable characteristics can be obtained.

  Patent Document 2 discloses a magnetic prepreg constituted by impregnating a glass cloth with a magnetic paint composed of soft magnetic powder and a thermosetting resin as a prepreg constituting a printed wiring board. It is a substantially flat metal powder, and the main component of the thermosetting resin is a prepreg which is an epoxy resin, which describes that a printed wiring board having excellent noise characteristics can be obtained.

  FIG. 4 is a view showing an example of the cross-sectional structure of the prepreg shown in Patent Document 2, in which a glass cloth 1 knitted vertically and horizontally is covered with a thermosetting resin 12 in which soft magnetic powder is dispersed, and the prepreg 13 Is formed. FIG. 5 shows a cross-sectional view of an example of a multilayer printed circuit board using the prepreg. A circuit pattern 14 is formed by etching or the like on a single-layer substrate in which a prepreg 13 and a copper foil or the like are laminated, and the plurality of circuit patterns are stacked with the prepreg as an adhesive sheet and heated and pressed. The circuit patterns of the respective layers are connected through through holes 15 as necessary, and electronic components 16 such as LSI are mounted on the printed circuit board.

JP 2006-100608 A JP-A-10-79593

  However, the printed circuit board described in Patent Document 1 covers a power layer or a ground circuit with a magnetic layer formed by dispersing metal fine particles coated with a ferrite layer in a resin such as an epoxy resin or a phenol resin, The effect of removing noise and preventing mutual interference depends on the amount of dispersed metal fine particles, and if a greater effect is to be obtained, the amount of metal fine particles in the magnetic layer must be increased. However, if the amount of the metal fine particles is increased, the insulation performance of the circuit portion covered with the metal fines is deteriorated and the basic performance of the substrate is lowered. In addition, since this method coats the magnetic layer only on the power supply circuit and the ground circuit portion, when a general multilayer printed board is formed, a dedicated process is required. Can not provide.

  On the other hand, if the prepreg described in Patent Document 2 is used, a general-purpose multilayer printed board can be formed by laminating with a metal layer such as a copper foil. However, since this prepreg is formed by impregnating a glass cloth with a magnetic coating material in which soft magnetic powder is dispersed in a thermosetting resin, as in the case of Patent Document 1, an attempt is made to obtain a large noise removal effect. When the amount of the soft magnetic powder is increased, there is a problem that the insulation between the wiring patterns formed on the metal layer is deteriorated and the basic performance of the substrate is lowered.

  The present invention has been made in view of such problems, and the object of the present invention is to effectively suppress radiation noise from a printed circuit board on which electronic components are mounted, electromagnetic interference generated in the circuit board, and the like. An object of the present invention is to provide a prepreg in which insulation characteristics between layers are easily secured in a multilayer substrate and a printed circuit board using the prepreg.

  In order to solve the above-mentioned problems, the prepreg of the present invention is a prepreg for a printed circuit board, in which a soft magnetic layer is formed in close contact with at least a part of the surface of a glass cloth serving as a base material. An insulating resin layer is provided. The printed circuit board of the present invention uses the prepreg.

  The soft magnetic layer may be a ferrite thin film layer having a thickness of 10 microns or less.

  As described above, in the present invention, the prepreg is not provided by dispersing fine particles of a metal substance in a resin or the like as in the prior art, but a two-layer structure of a soft magnetic layer and an insulating resin layer is provided on the glass cloth surface. Therefore, it is easy to ensure insulation characteristics. Further, by using the prepreg according to the present invention, noise generated on the substrate can be effectively and stably suppressed by controlling the material and film thickness of the soft magnetic layer, and is distinguished from the soft magnetic layer. By providing the insulating resin layer, a printed circuit board having excellent insulating characteristics can be easily obtained.

  As described above, according to the present invention, radiation noise from a printed circuit board on which electronic components are mounted, electromagnetic interference generated in the circuit board, and the like can be effectively suppressed, and insulation characteristics between layers can be easily secured in a multilayer board. Prepreg and a printed circuit board using the same are obtained.

  Embodiments of a prepreg according to the present invention and a printed circuit board using the prepreg will be described below with reference to the drawings.

  FIG. 1 is a sectional view showing an embodiment of a prepreg according to the present invention. A ferrite plating layer 2 is formed on the surface of a glass cloth 1 knitted longitudinally and laterally, and this is covered with an insulating resin layer 3 such as epoxy to form a prepreg 4. Here, a spray method or the like is used for forming the ferrite plating layer 2 on the glass cloth 1. For example, by using a spin spray method in which a glass cloth is placed on a turntable and the turntable is rotated while supplying a plating solution from above with a nozzle, the ferrite concentration can be controlled by controlling the solution concentration, supply amount, rotation speed, coating time, etc. The thickness and quality of the plating film can be controlled, and a desired film can be obtained. The prepreg 4 is obtained by impregnating a glass cloth with an epoxy resin after forming the ferrite plating layer 2. Here, the thickness of the ferrite plating film is required to be about 0.5 μm or more in order to obtain a noise suppressing effect, and is preferably 10 μm or less in consideration of the thickness of the glass cloth and the practical thickness of the prepreg.

  FIG. 2 is a sectional view showing an embodiment of a printed circuit board according to the present invention formed using the prepreg 4 of the above embodiment. In FIG. 2, a circuit pattern 5 is formed by etching or the like on a single-layer substrate in which a prepreg 4 and copper foil are laminated, and the plurality of circuit patterns are stacked using the present prepreg as an adhesive sheet and heated and pressed. 1 shows a cross-sectional view of an example of a multilayer printed circuit board. The circuit patterns of the respective layers are connected by through holes which are omitted in the drawing as required, and electronic components such as LSI are mounted on the printed circuit board.

  In the printed circuit board according to the present embodiment, the noise generated by the circuit pattern 5 of each layer is absorbed or shielded by the ferrite plating layer 2 formed on the surface of the glass cloth 1, and the coupling to the circuit pattern of the adjacent layer is performed. It is suppressed.

  FIG. 3 is a diagram showing an example of a result of measuring the conduction noise suppression effect by arranging the prepreg of the present embodiment in the vicinity of a transmission line simulating a noise transmission path using a microstrip line. is there. This figure shows the frequency characteristics of the conductive noise suppression effect when using a prepreg in which a ferrite plating layer with a thickness of about 2 μm is formed on a glass cloth with a thickness of about 90 μm and coated with an epoxy resin layer. 7 is a characteristic of the prepreg of the present invention, and 8 and 9 are characteristics when a noise suppression sheet (registered trademark: film impeder) having a thickness of 25 μm and 50 μm, which is often used for noise suppression, is used for comparison. Show. From this measurement result, it was confirmed that the printed circuit board using the prepreg according to the present invention has almost the same suppression effect as the noise suppression sheet having a thickness of 25 μm even in the high frequency region.

  That is, according to the printed circuit board according to the present invention, noise generated on the board can be efficiently removed without using a noise suppression sheet or the like, and the time and cost related to noise countermeasures after circuit mounting can be reduced. Density mounting is possible. Further, since the circuit pattern of each layer is separated by an insulating resin layer that does not contain metal fine particles or the like, it is easy to ensure the insulating characteristics.

  As described above, according to the present invention, it is possible to effectively suppress noise generated in an electric circuit board mounted on a printed circuit board, and to easily secure the insulating characteristics of the electric circuit and a printed circuit board using the prepreg. can get.

  In addition, this invention is not limited to said embodiment, A change is possible according to a use and the objective. For example, as the soft magnetic layer, an amorphous or nano-granulated thin film, a composite thin film of ferrite and resin, or the like can be used instead of the ferrite plating layer.

Sectional drawing which shows one Embodiment of the prepreg by this invention. Sectional drawing which shows one Embodiment of the printed circuit board by this invention formed using the prepreg of this Embodiment. The figure which shows an example of the result of having measured the conduction noise suppression effect by the prepreg used for the printed circuit board of this Embodiment. The figure which shows an example of the cross-sectional structure of the conventional prepreg. Sectional drawing of an example of the multilayer printed circuit board using the conventional prepreg.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Glass cloth 2 Ferrite plating layer 3 Insulating resin layer 4, 13 Prepreg 5, 14 Circuit pattern 7 Characteristic 8 of the printed circuit board of the present invention Characteristic 9 when a noise suppression sheet having a thickness of 25 μm is pasted 9 Noise having a thickness of 50 μm Characteristics 12 when the suppression sheet is pasted Thermosetting resin 15 in which soft magnetic powder is dispersed Through hole 16 Electronic component

Claims (3)

  A prepreg for a printed circuit board, wherein a soft magnetic layer is formed in close contact with at least a part of a glass cloth surface as a base material, and an insulating resin layer is provided on the soft magnetic layer. .   The prepreg according to claim 1, wherein the soft magnetic layer is a ferrite thin film layer having a thickness of 10 μm or less.   A printed circuit board comprising the prepreg according to claim 1.

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