JP2006294967A - Printed wiring board and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a printed wiring board suppressing resonance between a power source and a ground layer, and having the high degree of freedom in design, and also to provide a manufacturing method thereof. <P>SOLUTION: The printed wiring board 10 has power source layers 13, 15 and ground layers 12, 14, 16. In the printed wiring board 10, a coupling shielding layer 22 including a magnetic metal material is provided between the power source layer and the ground layer. The method of manufacturing the printed wiring board 10 has a process in which a coupling shielding film 20 having the coupling shielding layer 22 formed on the surface of a resin film 21 is arranged between a plurality of metallic foils to be used as the power source layer and the ground layer. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a printed wiring board and a method for manufacturing the same.

In recent years, electronic devices have been required to be smaller and lighter, and printed wiring boards have been multilayered.
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

  Therefore, an object of the present invention is to manufacture a printed wiring board that can suppress power-ground layer resonance and has a high degree of design freedom, and a printed wiring board that can easily take measures to suppress power-ground layer resonance. It is to provide a method.

The printed wiring board of the present invention is a printed wiring board having a power supply layer and a ground layer, wherein a coupling shielding layer containing a magnetic metal material is provided between the power supply layer and the ground layer.
A layer made of a resin film is further provided between the power supply layer and the ground layer,
The bonding shielding layer is preferably a layer formed by physically depositing a magnetic metal material on the surface of the resin film by a sputtering method in a reactive gas atmosphere.
The magnetic metal material is preferably nickel or an alloy containing nickel.

The method for manufacturing a printed wiring board according to the present invention includes a step of disposing a coupling shielding film in which a coupling shielding layer containing a magnetic metal material is formed on the surface of a resin film between a plurality of metal foils serving as a power supply layer and a ground layer. It is characterized by having.
In the method for manufacturing a printed wiring board according to the present invention, a non-bonding shielding portion having no bonding shielding layer may be formed in advance on a part of the bonding shielding film.

The printed wiring board of the present invention can suppress power-ground layer resonance and has a high degree of design freedom.
According to the method for manufacturing a printed wiring board of the present invention, it is possible to easily take measures for suppressing power-ground layer resonance.

<Printed wiring board>
FIG. 1 is a schematic cross-sectional view showing an example of the printed wiring board of the present invention. The printed wiring board 10 includes a signal wiring layer 11 subjected to pattern processing, a ground layer 12, a power source layer 13 subjected to pattern processing, a ground layer 14, a power source layer 15 subjected to pattern processing, and a ground layer 16. Are stacked via an insulating layer 17, between the ground layer 12 and the power supply layer 13, between the power supply layer 13 and the ground layer 14, between the ground layer 14 and the power supply layer 15, Between the layer 15 and the ground layer 16, a layer made of the bonding shielding film 20 is provided.
In addition, a through hole 18 that electrically connects the power supply layers 13 and 15 and the signal wiring layer 11 is formed.

The signal wiring layer 11, the ground layers 12, 14, 16 and the power supply layers 13, 15 are layers made of a metal foil such as a copper foil, and are conductive layers.
The insulating layer 17 is a layer obtained by curing a prepreg in which a reinforcing material such as a glass cloth is impregnated with a resin such as an epoxy resin.

The bonding shielding film 20 includes a resin film 21 and a bonding shielding layer 22 formed on the surface of the resin film 21.
The coupling shielding layer 22 is a layer containing a magnetic metal material. For example, on the resin film 21, 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 bonding shielding film 20 as viewed from the bonding shielding layer 22 (upper surface) side, and FIG. 3 is a schematic perspective view of the bonding shielding film 20. The microcluster 23 is formed by physically thinly depositing a magnetic metal material on the resin film 21 and is not a sufficient metal thin film. Although the microclusters 23 are in contact with each other and are grouped, there are many defects in which the magnetic metal material does not exist between the grouped microclusters 23, and the grouped microclusters 23 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 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 bonding shielding layer 22 formed on the resin film 21. FIG. 5 is a high-resolution transmission electron microscope image of the cross section in the film thickness direction of the bonding shielding layer 22. FIG. 6 is an electron beam diffraction image of the coupling shielding layer 22. 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 bonding shielding layer 22 is preferably 5 to 200 nm. By setting the thickness of the coupling shielding layer 22 to 5 nm or more, a sufficient coupling shielding effect can be exhibited. On the other hand, when the thickness of the coupling shielding layer 22 exceeds 200 nm, the microclusters 23 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 coupling shielding effect is also reduced and is not effective. Here, the thickness of the coupling shielding layer 22 is an average thickness of the entire coupling shielding layer 22 including defects.

  In the present invention, it is important that the bonding shielding layer 22 does not exist as a mere metal thin film layer but exists in a state where the microclusters 23 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 bonding shielding layer 22 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 23 of the magnetic metal material are in very close proximity and are individually independent. Therefore, an excellent bonding shielding effect is exhibited.

It is preferable that the resin film 21 withstands the heating during the production of the printed wiring board 10 and has the heat resistance required for the printed wiring board 10. Further, it is preferable that the characteristic values required for the design of the printed wiring board 10 such as dielectric constant and dielectric loss tangent are known. Accordingly, the material of the resin film 21 is preferably polyimide; a reinforced resin in which a reinforcing material such as glass cloth is impregnated with a resin such as epoxy resin, bismaleimide triazine resin, polytetrafluoroethylene, or polyphenylene ether.
The thickness of the resin film 21 is preferably 2 to 125 μm. If the resin film 21 is too thick, the printed wiring board 10 becomes thick. When the resin film 21 is too thin, it becomes difficult to handle the bonding shielding film 20.

The bonding shielding film 20 is manufactured by physically depositing a magnetic metal material on the surface of the resin film 21 and forming the bonding shielding layer 22 on the surface of the resin film 21.
As a method of forming the bonding shielding layer 22, 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 film 21 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 bonding shielding layer 22 and low thermal damage of the resin film 21.

  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.

  In the printed wiring board 10 described above, since the coupling shielding layer 22 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 coupling shielding layer 22 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 degree of freedom in designing the printed wiring board 10 is high.

The printed wiring board of the present invention is not limited to the printed wiring board 10 in the illustrated example, and in a printed wiring board having a power supply layer and a ground layer, a magnetic metal material is provided between the power supply layer and the ground layer. Any form may be used as long as a coupling shielding layer containing is provided.
In addition, a coupling shielding layer may be provided between the power supply layer or the ground layer and the signal wiring layer. However, if a coupling shielding layer is provided in the vicinity of the signal wiring layer, the signal current is attenuated and adversely affects signal propagation. It is preferable not to provide a coupling shielding layer in the vicinity of the signal wiring layer.

<Method for manufacturing printed wiring board>
The printed wiring board 10 has the coupling shielding film 20 disposed between the plurality of metal foils serving as the power supply layers 13 and 15 and the ground layers 12, 14 and 16 via the prepreg serving as the insulating layer 17, and further to the signal wiring. The metal foil used as the layer 11 is piled up, and these are heated and pressed.

  Specifically, (i) metal foil, prepreg, bond shielding film 20, prepreg, metal foil, prepreg, bond shield film 20, prepreg, metal foil, prepreg, bond shield film 20, prepreg, metal foil, prepreg, bond shield A method of laminating film 20, prepreg, metal foil, prepreg, and metal foil in this order, and heating and pressing them together; (ii) laminating metal foil, prepreg, and bonded shielding film 20 in this order; After that, a method of sequentially repeating a step of laminating and heating and pressing the prepreg and the metal foil in this order, and a step of laminating and heating and pressing the prepreg and the bonding shielding film 20 in this order, Manufactured by etc.

  The through-hole 18 or the via hole (not shown) is formed by drilling or the like in (a) the printed wiring board 10 obtained by the method (i) or the laminate obtained in the middle of the method (ii). And (b) forming holes corresponding to the through holes 18 or via holes in advance in the metal foil, prepreg, and bonding shielding film 20 and laminating them. It is formed by a method of applying copper plating or the like to the inner wall of the hole. The size of the hole is preferably larger than the finally formed through hole 18 or via hole in order to ensure insulation between the through hole 18 or via hole and the ground layer and the coupling shielding film 20.

  The metal foil may be processed in advance into a pattern such as signal wiring or power wiring, or a hole corresponding to a through hole, a via hole, etc. may be formed in advance in the metal foil; The metal foil on the surface of the laminate obtained in step 1 may be processed into a pattern such as signal wiring or power supply wiring, or holes corresponding to through holes, via holes, or the like may be formed in the metal foil.

  Further, the bonding shielding film 20 may be previously formed with a non-bonding shielding portion having no bonding shielding layer. The non-bonding shielding portion is preferably formed at a position corresponding to the through hole or via hole, a position corresponding to the signal wiring of the signal wiring layer 11, and the like. When the coupling shielding layer 22 is disposed in the vicinity of the signal wiring of the signal wiring layer 11, the signal current is attenuated, which may adversely affect signal propagation.

  As a method for forming the non-bonding shielding portion, a method of applying a laser to the bonding shielding layer 22 to ablate and remove the bonding shielding layer 22; A method of removing the shielding layer 22 by etching; a method of masking the surface of the resin film 21 corresponding to the non-bonding shielding portion, and a physical vapor deposition of a magnetic metal material other than the portion that has been muked; Examples thereof include a method of punching with a punching die, laser processing, punching press, etc., and removing the bonding shielding layer 22 together with the resin film 21.

  In the method for manufacturing the printed wiring board 10 described above, the bonding shielding film 20 is disposed between the plurality of metal foils serving as the power supply layer and the ground layer via the prepreg serving as the insulating layer 17. Similarly to the conventional printed wiring board, the printed wiring board 10 can be manufactured simply by stacking and heating the materials of the respective layers. Therefore, it is possible to easily take measures to suppress the power-ground layer resonance.

Examples are shown below.
[Example 1]
On one side of a 25 μm thick polyimide film (trade name “Kapton” manufactured by Toray DuPont Co., Ltd.), which is a resin film 21, nickel, which is a magnetic metal material, is physically applied by the facing target type magnetron sputtering method under the following conditions. To form a bond shielding layer 22 to obtain a bond shielding film 20.
(Conditions) Temperature of resin film 21: normal temperature (25 ° C.), nickel deposition mass (film thickness conversion): 25 nm, reaction gas atmosphere: argon gas 60 sccm and nitrogen gas 20 sccm, power: 2 kW.

About the joint shielding film 20, the surface resistance of the joint shielding layer 22 is measured by DC 4 terminal method with a measurement voltage of 10V by MCP-T600 manufactured by Dia Instruments, and an average value of five measurement points is obtained. The volume resistivity R1 (Ω · cm) was calculated from the value and the thickness of the bonding shielding layer 22. The volume resistivity R1 was 4.8 × 10 ⁻⁴ Ω · cm. The volume resistivity R0 (document value) of nickel was 7.24 × 10 ⁻⁶ Ω · cm, logR1−logR0 was 1.82, and the relationship of 0.5 ≦ logR1−logR0 ≦ 3 was satisfied.

A printed wiring board 10 as shown in FIG. 1 was manufactured.
The copper foil to be the signal wiring layer 11 is processed into a signal wiring pattern in advance, the copper foil to be the power supply layers 13 and 15 is processed into a power supply wiring pattern in advance, and the through holes 18 are formed in the metal foil to be the ground layers 12 and 14. A 1.2 mm hole corresponding to was previously formed.
In addition, a 1.2 mm hole corresponding to the through hole 18 was previously formed in the bonding shielding film 20 using a carbon dioxide laser processing machine.
Between these copper foils, a bonding shielding film 20 was sandwiched through a prepreg having a thickness of 50 μm in which a glass cloth was impregnated with an epoxy resin, and these were heated and pressed to obtain a printed wiring board 10.

Next, a hole with a diameter of 1.0 mm was formed in the printed wiring board 10 using a drill, and the inner wall of the hole was plated with copper to form a through hole 18.
Next, a power supply, a signal generating IC, and an amplifier were mounted on the signal wiring layer 11 by soldering, and the printed wiring board 10 on which electronic components were mounted was obtained.

[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 bonding shielding film 20 was not provided.

[Evaluation]
In a small anechoic chamber, a high frequency current of 0.1 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 observed. It was.

  The printed wiring board of the present invention is useful as a printed wiring board through which a high-frequency current of 0.3 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 printed wiring board of this invention. It is an upper surface schematic diagram of a joint shielding film. It is a perspective schematic diagram of a joint shielding film. It is a field emission scanning electron microscope image of the surface of a joint shielding layer. It is a high-resolution transmission electron microscope image of the cross section of a joint shielding layer. It is an electron beam diffraction image of a joint shielding layer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Printed wiring board 11 Signal wiring layer 12 Ground layer 13 Power supply layer 14 Ground layer 15 Power supply layer 16 Ground layer 17 Insulating layer 18 Through hole 20 Bonding shielding film 21 Resin film 22 Bonding shielding layer 23 Microcluster

Claims (5)

In a printed wiring board having a power supply layer and a ground layer,
A printed wiring board characterized in that a coupling shielding layer containing a magnetic metal material is provided between a power supply layer and a ground layer. A layer made of a resin film is further provided between the power supply layer and the ground layer,
2. The print according to claim 1, wherein the bonding shielding layer is a layer formed by physically depositing a magnetic metal material on the surface of the resin film by a sputtering method in a reactive gas atmosphere. Wiring board.   3. The printed wiring board according to claim 1, wherein the magnetic metal material is nickel or an alloy containing nickel.   What is claimed is: 1. A printed wiring board comprising a step of disposing a bonding shielding film having a bonding shielding layer containing a magnetic metal material formed on a surface of a resin film between a plurality of metal foils serving as a power supply layer and a ground layer. Production method. 5. The method of manufacturing a printed wiring board according to claim 4, wherein a non-bonding shielding portion having no bonding shielding layer is formed in advance on a part of the bonding shielding film.

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