JP2006297628A - Metal foil with resin for printed wiring board, and printed wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a printed wiring board capable of suppressing resonance between a power source layer and a ground layer and enhanced in the degree of freedom of a design, and a metal foil with a resin for obtaining the printed wiring board. <P>SOLUTION: The metal foil 10 with the resin has a metal foil 11, the resin layer 12 provided on the metal foil 11 and the noise suppressing layer 13, which contains a magnetic metal material, formed on the surface of the resin layer 12. A plurality of the metal foils 10 with the resin are laminated so that each of the noise suppressing layers 3 is positioned between the power source layer and the ground layer on each of the metal foils 11. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a resin-coated metal foil for a printed wiring board and a printed wiring board using the same.

In recent years, electronic devices have been required to be smaller and lighter, and printed wiring boards have been multilayered. The printed wiring board can be obtained, for example, by laminating a plurality of “copper foils with resin” in which a prepreg obtained by impregnating a reinforcing material such as glass cloth with a resin such as an epoxy resin is provided on a copper foil.
However, in the multilayered printed wiring board, the copper foil constituting the power supply layer and the ground layer spreads over almost the entire surface of the printed wiring board, and these copper foils have a parallel plate structure with an open peripheral edge. Resonance (power supply-ground layer resonance) occurs between the power supply layer and the ground layer, and electromagnetic noise is generated from the peripheral edge of the substrate.

As a printed wiring board in which resonance between the power source and the ground layer is suppressed, an interlayer connection that electrically connects a ground region formed in the first ground layer and a ground region formed in the second ground layer. A member provided with a member and a power line wired to at least one of the first ground layer and the second ground layer has been proposed (Patent Document 1).
However, the printed wiring board has a problem that the degree of freedom in design is extremely low due to the necessity of providing an interlayer connection member and the positional relationship between each ground layer and the power line.

Patent Document 2 proposes that a solder resist layer in which plate-like magnetic particles, plate-like nonmagnetic particles, and a binder are arranged on both surfaces of a printed wiring board is proposed.
However, the solder resist layer in the printed wiring board prevents electromagnetic wave noise generated from the signal wiring from leaking to the outside of the printed wiring board, and does not suppress power-ground layer resonance. Therefore, the printed wiring board itself (for example, mounted electronic components, other signal wirings, etc.) is affected by electromagnetic noise generated from the signal wiring or electromagnetic noise generated by power supply-ground layer resonance.
JP 2003-163467 A JP-A-9-283939

  Accordingly, an object of the present invention is to provide a printed wiring board capable of suppressing power-ground layer resonance and having a high degree of design freedom, and a metal foil with a resin for obtaining the printed wiring board.

The metal foil with resin for printed wiring boards of the present invention has a metal foil, a resin layer provided on the metal foil, and a noise suppression layer including a magnetic metal material formed on the surface of the resin layer. It is characterized by that.
The noise suppression layer is preferably a layer formed by physically depositing a magnetic metal material on the surface of the resin layer by a sputtering method in a reactive gas atmosphere.
The magnetic metal material is preferably nickel or an alloy containing nickel.

The volume resistivity R1 (Ω · cm) converted from the measured value of the surface resistance of the noise suppression layer and the volume resistivity R0 (Ω · cm) of the magnetic metal material satisfy 0.5 ≦ logR1−logR0 ≦ 3. It is preferable to do.
A non-noise suppressing portion having no noise suppressing layer may be formed on the surface of the resin layer.
In the printed wiring board of the present invention, the noise suppression layer is positioned between the power supply layer and the ground layer made of the metal foil through the prepreg of the resin-coated metal foil of the present invention. A plurality of layers are laminated.

According to the metal foil with a printed wiring board resin of the present invention, it is possible to obtain a printed wiring board that can suppress power-ground layer resonance and has a high degree of design freedom.
The printed wiring board of the present invention can suppress power-ground layer resonance and has a high degree of design freedom.

<Metal foil with resin>
FIG. 1 is a schematic cross-sectional view showing an example of a metal foil with resin for printed wiring boards of the present invention (hereinafter simply referred to as “metal foil with resin”). The metal foil with resin 10 has a metal foil 11, a resin layer 12 provided on the metal foil 11, and a noise suppression layer 13 including a magnetic metal material formed on the surface of the resin layer 12. It is.

Examples of the metal foil 11 include copper foil, aluminum foil, nickel foil, and tin foil. Of these, copper foil is preferred. Examples of the copper foil include electrolytic copper foil and rolled copper foil.
The thickness of the metal foil 11 is preferably 3 to 50 μm.

  It is preferable that the resin layer 12 withstands the heating during the production of the printed wiring board and has the heat resistance required for the printed wiring board. In addition, it is preferable that the characteristic values required for the design of the printed wiring board, such as dielectric constant and dielectric loss tangent, are known. Therefore, the material of the resin layer 12 includes polyimide, epoxy resin; reinforced resin in which a reinforcing material such as glass cloth is impregnated with a resin such as epoxy resin, bismaleimide triazine resin, polytetrafluoroethylene, polyphenylene ether, or the like. preferable. The state of the reinforced resin may be a B-stage (semi-cured state) or a C-stage (cured state).

  The thickness of the resin layer 12 is preferably 0.5 to 125 μm. If the resin layer 12 is too thick, the printed wiring board becomes thick and the noise suppression effect may be insufficient. If the resin layer 12 is too thin, it may be difficult to maintain insulation between the metal foil 11 and the noise suppression layer 13.

  The noise suppression layer 13 is a layer containing a magnetic metal material. For example, on the resin layer 12, a plurality of independent nanometer level magnetic metal material microclusters and a magnetic metal material formed between them are formed. It is a layer composed of defects that do not exist.

  FIG. 2 is a schematic view of the metal foil with resin 10 as seen from the noise suppression layer 13 (upper surface) side, and FIG. 3 is a schematic perspective view of the metal foil with resin 10. The microcluster 14 is formed by physically thinly depositing a magnetic metal material on the resin layer 12 and is not a sufficient metal thin film. Although the microclusters 14 are grouped in contact with each other, there are many defects in which the magnetic metal material does not exist between the grouped microclusters 14, and the grouped microclusters 14 are independent of each other. Yes.

  Here, the microcluster of the magnetic metal material is a group formed by collecting several tens to several hundreds of thousands of magnetic metal atoms. When the aggregation of the microclusters proceeds, ultrafine particles, fine particles, and metal thin films are formed, but the microclusters are just before becoming ultrafine particles, and are clearly distinguished from ultrafine particles, fine particles, and metal thin films. is there.

  FIG. 4 is a field emission scanning electron microscope image obtained by observing the surface of the noise suppression layer 13 formed on the surface of the resin layer 12. FIG. 5 is a high-resolution transmission electron microscope image of a cross section in the film thickness direction of the noise suppression layer 13. FIG. 6 is an electron beam diffraction image of the noise suppression layer 13. From FIG. 4 to FIG. 6, a crystal lattice (microcluster) in which magnetic metal atoms arranged at intervals of several tens of millimeters are arranged as very small crystals and defects in which no magnetic metal material exists in a very small range are recognized. That is, the microclusters are spaced apart from each other, and no clear grain boundary is observed. The crystal orientation of each microcluster is recognized to be disordered, and has not grown into a homogeneous metal thin film, ultrafine particle, fine particle or the like made of a magnetic metal material.

  The thickness of the noise suppression layer 13 is preferably 5 to 200 nm. By setting the thickness of the noise suppression layer 13 to 5 nm or more, a sufficient noise suppression effect can be exhibited. On the other hand, when the thickness of the noise suppression layer 13 exceeds 200 nm, the microclusters 14 aggregate to form a homogeneous metal thin film made of a magnetic metal material and return to the bulk magnetic metal material, and the metal reflection becomes stronger. The noise suppression effect is also reduced and is not effective. Here, the thickness of the noise suppression layer 13 is an average thickness of the entire noise suppression layer 13 including defects.

  In the present invention, it is important that the noise suppression layer 13 does not exist as a mere metal thin film layer but exists in a state where the microclusters 14 are grouped. Such a state is based on the relationship between the volume resistivity R1 (Ω · cm) converted from the actual measurement value of the surface resistance of the noise suppression layer 13 and the volume resistivity R0 (Ω · cm) (reference value) of the magnetic metal material. Can be confirmed. That is, when the volume resistivity R1 and the volume resistivity R0 satisfy 0.5 ≦ logR1−logR0 ≦ 3, the microclusters 14 of the magnetic metal material are in close proximity and are individually independent. Therefore, an excellent noise suppression effect is exhibited.

The metal foil with resin 10 is manufactured by physically depositing a magnetic metal material on the surface of the resin layer 12 and forming the noise suppression layer 13 on the surface of the resin layer 12.
As a method of forming the noise suppression layer 13, a physical vapor deposition method (PVD) in which a magnetic metal material is vaporized by some method and deposited on the surface of the resin layer 12 placed in the vicinity can be applied.

  When physical vapor deposition is classified according to the vaporization method of magnetic metal material, it can be divided into an evaporation system and a sputtering system. Examples of the evaporation system include an EB vapor deposition method and an ion plating method. Examples of the sputtering system include sputtering methods such as a magnetron sputtering method and a counter target type magnetron sputtering method. Among these, the sputtering method is preferable from the viewpoints of thickness control of the noise suppression layer 13 and low thermal damage of the resin layer 12.

  Examples of magnetic metal materials include iron, nickel, cobalt, and alloys containing these. Examples of the alloy include Fe—Ni, Fe—Co, Fe—Cr, Fe—Si, Fe—Al, Fe—Cr—Si, Fe—Cr—Al, and Fe—Al—Si. These magnetic metal materials may be used individually by 1 type, and may be used in combination of 2 or more type. Nickel or an alloy containing nickel is preferred because it is resistant to oxidation.

  The vapor deposition mass of the magnetic metal material is preferably 5 to 200 nm in terms of film thickness. By setting the thickness to 5 nm or more, a sufficient mass for noise suppression can be secured, and by setting the thickness to 200 nm or less, a microcluster state can be maintained and a noise suppression effect can be obtained. The vapor deposition mass is obtained by vapor-depositing a magnetic metal material on a hard substrate such as glass or silicon under the same conditions, and measuring and averaging the deposited thickness.

  When the vapor deposition mass of the magnetic metal material is increased, it becomes difficult to obtain a microcluster state. Specifically, when it is about 20 nm or more, it tends to grow into a simple metal thin film layer by a normal sputtering method. Therefore, it is preferable to stabilize the microcluster state by introducing a reactive gas such as nitrogen, oxygen, hydrogen sulfide, silane or the like in addition to the normal argon gas when depositing the magnetic metal material. In particular, the use of nitrogen gas inhibits giant crystallization when the magnetic metal material is deposited, and can achieve a very stable microcluster state.

<Printed wiring board>
FIG. 7 is a schematic cross-sectional view showing an example of the printed wiring board of the present invention. The printed wiring board 20 includes a signal processing layer 21 subjected to pattern processing, a ground layer 22, a power source layer 23 subjected to pattern processing, a ground layer 24, a power source layer 25 subjected to pattern processing, and a ground layer 26. Are stacked via the insulating layer 27 or the insulating layer 28, between the ground layer 22 and the power supply layer 23, between the power supply layer 23 and the ground layer 24, and between the ground layer 24 and the power supply layer 25. In the meantime, the noise suppression layer 13 is provided between the power supply layer 25 and the ground layer 26.
In addition, a through hole 29 that electrically connects the power supply layers 23 and 25 and the signal wiring layer 21 is formed.

  The signal wiring layer 21, the ground layers 22, 24, and 26, and the power supply layers 23 and 25 are layers made of metal foil such as copper foil, and are conductive layers. In particular, the ground layers 24 and 26 and the power supply layers 23 and 25 are layers derived from the metal foil 11 of the metal foil 10 with resin.

  The insulating layers 27 and 28 are layers obtained by curing a prepreg obtained by impregnating a reinforcing material such as a glass cloth with a resin such as an epoxy resin. In particular, the insulating layer 28 is a layer derived from the resin layer 12 of the metal foil 10 with resin.

The printed wiring board 20 is obtained by laminating a plurality of resin-coated metal foils 10 through a prepreg so that the noise suppression layer 13 is located between the power supply layer made of the metal foil 11 and the ground layer. .
Specifically, (i) metal foil with resin 10, prepreg, metal foil with resin 10, prepreg, metal foil with resin 10, prepreg, metal foil with resin 10, prepreg, normal metal foil with resin without noise suppression layer , A method of laminating in the order of ordinary metal foil with resin without a noise suppression layer, and heating and pressing them together; (ii) laminating metal foil with resin 10, prepreg, metal foil with resin 10 in this order; After these are hot-pressed, the resin-coated metal foil 10 or a normal resin-coated metal foil without a noise suppression layer is further laminated thereon, and the method of sequentially repeating the heat-pressing step is manufactured.

  The through hole 29 or the via hole (not shown) is formed by drilling or the like in (a) the printed wiring board 20 obtained by the method (i) or the laminate obtained in the middle of the method (ii). (B) A metal foil 10 with resin, prepreg, and a normal metal foil with resin without a noise suppression layer are previously provided with holes corresponding to the through holes 29 or via holes. After forming these layers, the inner wall of the hole is plated with copper or the like. The size of the hole is preferably larger than the finally formed through hole 29 or via hole in order to secure insulation between the through hole 29 or via hole and the ground layer and the noise suppression layer 13.

  The metal foil 11 may be processed in advance into a pattern such as a signal wiring or a power supply wiring, or a hole corresponding to a through hole, a via hole, or the like may be formed in advance in the metal foil 11; The metal foil 11 on the surface of the laminate obtained in the course of processing may be processed into a pattern such as signal wiring or power supply wiring, or holes corresponding to through holes, via holes, etc. may be formed in the metal foil 11. .

  Moreover, the non-noise suppression part which does not have a noise suppression layer may be previously formed in the metal foil 10 with resin. The non-noise suppressing portion is preferably formed at a position corresponding to the through hole or the via hole, a position corresponding to the signal wiring of the signal wiring layer 21, and the like. When the noise suppression layer 13 is disposed in the vicinity of the signal wiring of the signal wiring layer 21, there is a possibility that the waveform of the signal current flowing through the signal wiring is distorted (the corner portion of the square wave is rounded).

  As a method of forming the non-noise suppression portion, a method of applying a laser to the noise suppression layer 13 to ablate and remove the noise suppression layer 13; masking the portion where the noise suppression layer 13 is left, and noise other than the portion that has been magked Examples include a method of removing the suppression layer 13 by etching; a method of masking the surface of the resin layer 12 corresponding to the non-noise suppression portion, and physically depositing a magnetic metal material on a portion other than the muked portion.

  In the printed wiring board 20 described above, since the noise suppression layer 13 including a magnetic metal material is provided between the power supply layer and the ground layer, the electromagnetic coupling between the power supply layer and the ground layer is performed. Can be suppressed, and power-ground layer resonance can be suppressed. As a result, generation of electromagnetic noise from the peripheral edge of the substrate can be suppressed. Further, since it is only necessary to provide the noise suppression layer 13 containing a magnetic metal material between the power supply layer and the ground layer, there is no need to provide an interlayer connection member, and there is no restriction on the positional relationship between the power supply layer and the ground layer. . Therefore, the design flexibility of the printed wiring board 20 is high.

Note that the printed wiring board of the present invention is not limited to the printed wiring board 20 of the illustrated example, and may be of any form as long as it is obtained using the metal foil with resin of the present invention. May be.
In addition, a noise suppression layer may be provided between the power supply layer or the ground layer and the signal wiring layer. However, when a noise suppression layer is provided in the vicinity of the signal wiring layer, the waveform of the signal current flowing through the signal wiring is not present. It is preferable not to provide a noise suppression layer in the vicinity of the signal wiring layer because there is a risk that the corner portion of the square wave will be rounded.

Examples are shown below.
[Example 1]
Resin layer of copper foil with resin (made by Mitsui Mining & Smelting Co., Ltd., trade name “MHCG100G”, 18 μm thick copper foil provided with a 50 μm thick prepreg impregnated with epoxy resin on a glass cloth) On top of this, nickel as a magnetic metal material was physically vapor-deposited under the following conditions by an opposed target magnetron sputtering method to form a noise suppression layer, and a resin-coated copper foil having a noise suppression layer was obtained.
(Conditions) Temperature of resin layer: normal temperature (25 ° C.), nickel deposition mass (film thickness conversion): 25 nm, reactive gas atmosphere: argon gas 60 sccm and nitrogen gas 20 sccm, power: 2 kW.

About the copper foil with resin which has a noise suppression layer, the surface resistance of a noise suppression layer is measured by DC 4 terminal method with a measurement voltage of 10 V by MCP-T600 manufactured by Dia Instruments, and an average value of 5 measurement points is obtained. Furthermore, volume resistivity R1 (Ω · cm) was calculated from the average value and the thickness of the noise suppression layer. The volume resistivity R1 was 4.75 × 10 ⁻⁴ Ω · cm. The volume resistivity R0 (document value) of nickel was 7.24 × 10 ⁻⁶ Ω · cm, logR1−logR0 was 1.80, and the relationship of 0.5 ≦ logR1−logR0 ≦ 3 was satisfied.

A printed wiring board 20 as shown in FIG. 7 was manufactured using a resin-coated copper foil having a noise suppression layer as the resin-coated metal foil 10.
A 1.2 mm non-noise suppression portion corresponding to the through hole 29 was formed in advance in the noise suppression layer 13 of the metal foil with resin 10 using a YAG laser processing machine. Further, the metal foil 11 to be the power supply layers 13 and 15 is processed into a power supply wiring pattern in advance by etching, and a 1.2 mm hole corresponding to the through hole 29 is formed in the metal foil 11 to be the ground layer 14 in advance. .

Separately, a copper foil with resin without a noise suppression layer (trade name “MHCG100G” manufactured by Mitsui Mining & Smelting Co., Ltd.) is prepared, and the copper foil to be the signal wiring layer 21 is processed into a signal wiring pattern in advance, and a ground layer A 1.2 mm hole corresponding to the through hole 29 was formed in advance in the copper foil 22.
The noise suppression layer 13 is positioned between the power supply layer and the ground layer made of the metal foil 11 through a prepreg having a thickness of 50 μm obtained by impregnating the metal foil with resin 10 with a glass cloth impregnated with epoxy resin. Then, a resin-coated copper foil serving as the ground layer 22 was laminated thereon, and a resin-coated copper foil serving as the ground layer 22 was laminated thereon, and these were heated and pressed to obtain a printed wiring board 20.

Next, a hole having a diameter of 1.0 mm was formed in the printed wiring board 20 using a drill, and the inner wall of the hole was plated with copper to form a through hole 29.
Next, a power supply, a signal generating IC, and an amplifier were mounted on the signal wiring layer 21 by soldering to obtain a printed wiring board 20 on which electronic components were mounted.

[Comparative Example 1]
A printed wiring board on which electronic components were mounted was obtained in the same manner as in Example 1 except that the noise suppression layer was not provided on the resin-coated copper foil.

[Evaluation]
In a small anechoic chamber, a high frequency current of 0.13 to 3 GHz was passed through the printed wiring board, and electromagnetic waves emitted from the peripheral edge of the printed wiring board were measured. A log periodic antenna was used as an antenna, and an EMC analyzer “HP8594EM” manufactured by Agilent Technologies was used as a measuring instrument.
At a frequency of 1 GHz, an electromagnetic wave of 51.16 dBμV was measured with the printed wiring board of Comparative Example 1, whereas it was only 36.23 dBμV with the printed wiring board of Example 1, and an attenuation effect of about 15 dB was recognized.

  The copper foil with resin of the present invention is useful as a printed wiring board through which a high-frequency current of 0.5 GHz or more flows so that generation of electromagnetic noise due to power-ground layer resonance becomes a problem.

It is a schematic sectional drawing which shows an example of the copper foil with resin of this invention. It is an upper surface schematic diagram of the copper foil with resin of this invention. It is a perspective schematic diagram of the copper foil with resin of this invention. It is a field emission scanning electron microscope image of the surface of a noise suppression layer. It is a high-resolution transmission electron microscope image of the cross section of a noise suppression layer. It is an electron beam diffraction image of a noise suppression layer. It is a schematic sectional drawing which shows an example of the printed wiring board of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Metal foil with resin 11 Metal foil 12 Resin layer 13 Noise suppression layer 14 Micro cluster 20 Printed wiring board 21 Signal wiring layer 22 Ground layer 23 Power source layer 24 Ground layer 25 Power source layer 26 Ground layer 27 Insulating layer 28 Insulating layer 29 Through hole

Claims (6)

Metal foil,
A resin layer provided on the metal foil;
A metal foil with a resin for a printed wiring board, comprising: a noise suppression layer including a magnetic metal material formed on a surface of the resin layer.   2. The print according to claim 1, wherein the noise suppression layer is a layer formed by physically depositing a magnetic metal material on the surface of the resin layer by a sputtering method in a reactive gas atmosphere. Metal foil with resin for wiring boards.   3. The metal foil with resin for printed wiring boards according to claim 1, wherein the magnetic metal material is nickel or an alloy containing nickel.   The volume resistivity R1 (Ω · cm) converted from the measured value of the surface resistance of the noise suppression layer and the volume resistivity R0 (Ω · cm) of the magnetic metal material satisfy 0.5 ≦ logR1−logR0 ≦ 3. The metal foil with resin for printed wiring boards as described in any one of Claims 1 thru | or 3 characterized by the above-mentioned.   The metal foil with resin for printed wiring boards according to any one of claims 1 to 4, wherein a non-noise suppressing portion having no noise suppressing layer is formed on a surface of the resin layer. The metal foil with resin for printed wiring boards according to any one of claims 1 to 5, wherein the noise suppression layer is located through a prepreg and between a power supply layer and a ground layer made of the metal foil. As described above, a printed wiring board comprising a plurality of stacked layers.

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