JP5567243B2 - Multilayer printed circuit board and manufacturing method thereof - Google Patents

Description

  The present invention relates to a noise suppression structure, a multilayer printed circuit board, and a manufacturing method thereof.

  In recent years, with the widespread use of the Internet, high clock frequencies in the quasi-microwave band (0.3 to 10 GHz) such as personal computers, information appliances, wireless LAN, Bluetooth, optical modules, mobile phones, personal digital assistants, intelligent road information systems, etc. CPUs, electronic devices using high-frequency buses, and information communication devices using radio waves have become widespread, and ubiquitous societies that require high-performance digital devices and high-performance devices through low-voltage driving have come. .

  However, with the widespread use of these devices, malfunctions to themselves or other electronic devices caused by radiation noise radiated from these devices and conduction noise conducted through conductors in the devices have become a problem. For example, in a multilayer printed circuit board, when a large number of transistors in a semiconductor element mounted on the board are driven at the same time, unnecessary high-frequency current flows into the power supply layer and the ground layer, causing potential fluctuations. Due to the potential fluctuation, simultaneous switching noise occurs in the power supply layer and the ground layer. Furthermore, since the power supply layer and the ground layer have a parallel plate structure in which the peripheral ends are open, resonance occurs between the power supply layer and the ground layer due to potential fluctuations, and radiation noise is generated from the peripheral ends. Is emitted.

  As a method for suppressing radiation noise, there are (i) a method using an electromagnetic wave shielding material that reflects electromagnetic waves, and (ii) a method using an electromagnetic wave absorbing material that absorbs electromagnetic waves propagating in space. As a method for suppressing conduction noise and radiation noise, there is (iii) a method for suppressing high-frequency current flowing in a conductor before becoming conduction noise and radiation noise.

However, in the case of the method (i), although the shielding effect of the radiation noise can be obtained, the radiation noise returns to itself due to unnecessary radiation or reflection of the radiation noise by the shielding material. In the case of the method (ii), the electromagnetic wave absorbing material (see, for example, Patent Documents 1 and 2) is heavy, thick, and brittle, so that it is unsuitable for devices that require reduction in size and weight. Further, the conduction noise cannot be suppressed by the methods (i) and (ii).
Therefore, recently, attention has been focused on the method (iii).

  Patent Document 3 discloses that a high-resistance metal film is formed on a copper foil constituting a power supply layer and a ground layer. The high resistance metal film is a single layer film or alloy film of nickel, cobalt, tin, tungsten or the like having a higher resistivity than copper formed by plating. Even if the semiconductor element is switched, the power supply layer and the ground layer In addition, since the high-frequency current is removed by the high-resistance metal film, unnecessary electromagnetic waves (radiated noise) radiated to the outside can be suppressed.

  However, for example, a metal with good workability such as nickel has a low resistance, so that a sufficient effect cannot be obtained. In addition, a metal having high resistance such as tungsten is very difficult to process, and cannot be used in a portion where a complicated and fine pattern needs to be formed, such as around a semiconductor element, and is not practical. Moreover, it cannot be said that suppression of radiation noise is sufficient.

Patent Document 4 discloses a multilayer printed circuit board in which a resistor such as carbon or graphite is provided between a power supply layer and a ground layer and at the peripheral end of the multilayer printed circuit board.
However, simply providing a resistor at the peripheral end only changes the impedance at the peripheral end and changes the resonance frequency, which increases the electric field strength and magnetic field strength at other locations on the multilayer printed circuit board. . Therefore, radiation noise or the like due to resonance still cannot be suppressed, and further measures are required.

Patent Document 5 discloses a capacitive printed wiring board that includes a capacitor laminate in which a dielectric sheet is sandwiched between two conductive foils and has a structure in which the two conductive foils are electrically connected to different devices. Has been.
However, since the capacitor laminate has a certain thickness, the capacitive printed wiring board must be thick, which is not suitable for high-density mounting. In addition, when the capacitive printed wiring board is thickened, resonance easily occurs between conductors having a parallel plate structure, and thus radiation noise cannot be sufficiently suppressed.
JP-A-9-93034 JP-A-9-181476 JP-A-11-97810 Japanese Patent No. 2867985 Japanese Patent No. 2738590

  Accordingly, an object of the present invention is to provide a noise suppressing structure, a multilayer printed circuit board, and a method capable of easily manufacturing the multilayer printed circuit board, in which generation of conduction noise and radiation noise is suppressed and the thickness can be reduced. is there.

The multilayer printed circuit board according to the present invention includes a first conductor, a noise suppression layer electromagnetically coupled to the first conductor via an insulating layer, and a second conductor facing the noise suppression layer via the insulating layer. has the door, noise suppressing layer, the metallic material comprises a noise suppressing structure is a layer having a thickness of 5~300nm formed by physically depositing on the insulating layer in an atmosphere containing a reactive gas One of the first conductor and the second conductor is a power supply layer, the other is a ground layer, and further has a signal transmission layer, and a power supply layer is provided between the signal transmission layer and the noise suppression layer. Alternatively, a ground layer is present .

In the multilayer printed circuit board of the present invention, the noise suppression layer and the first conductor are disposed so as to face each other, and the surface area of the noise suppression layer on the side facing the first conductor is equal to that of the first conductor. , 10% or more of the surface area facing the noise suppression layer, and the surface area of the noise suppression layer facing the second conductor is equal to the surface area of the second conductor facing the noise suppression layer. It is preferably 10% or more.

The noise suppression layer is preferably a layer composed of a plurality of independent clusters and a defect in which no cluster exists, or a layer in which a plurality of independent clusters and a part of the insulating layer are mixed.
The metal material is preferably nickel or a nickel alloy .
The reactive gas is preferably nitrogen gas.

The insulating layer between the first conductor and the noise suppression layer is preferably a layer made of polyimide.
The thickness of the insulating layer between the first conductor and the noise suppression layer is preferably 3 to 25 μm .

The multilayer printed circuit board of the present invention preferably further has a through hole or a via hole, and the through hole or the via hole and the noise suppression layer are electrically connected.

The method of manufacturing a multilayer printed circuit board according to the present invention includes a step of removing a part of the first conductor of the noise suppression structure according to the present invention by etching, and the first conductor and the noise suppression using the first conductor as a mask. leaving the insulating layer contact and the noise suppressing layer between layers, characterized by a step of removing the non This etching.

The noise suppression structure and the multilayer printed circuit board according to the present invention can suppress the generation of conduction noise and radiation noise and can be thinned.
According to the method for producing a multilayer printed circuit board of the present invention, it is possible to easily produce a multilayer printed circuit board in which generation of conduction noise and radiation noise is suppressed and the thickness is reduced.

<Noise suppression structure>
1 to 3 are schematic cross-sectional views showing examples of the noise suppression structure of the present invention. In the noise suppression structure 10, the first conductor 11 through which high-frequency current flows and the noise suppression layer 12 are electromagnetically coupled via the insulating layer 13, and the noise suppression layer 12 further connects the second conductor 14 and the insulating layer 13. It is a structure that is electromagnetically coupled via The electromagnetic coupling is a phenomenon in which a voltage is induced when a magnetic flux generated by a current flowing through the first conductor 11 is linked to the noise suppression layer 12. In the present invention, it is necessary that the noise suppression layer and the power supply layer or the ground layer are not electrically connected but are electromagnetically coupled via the insulating layer.

  As shown in FIG. 1, the noise suppression structure 10 may be on different planes in which the first conductor 11 and the second conductor 14 are parallel, and as shown in FIG. 2, the first conductor 11 and the second conductor 10. The conductors 14 may be in the same plane with the insulating layer 13 interposed therebetween. In addition, as shown in FIG. 3, two or more noise suppression layers 12 may be provided. In the case of the noise suppression structure 10 shown in FIG. 3, the conductor closer to each noise suppression layer 12 becomes the first conductor 11, and the conductor far from each noise suppression layer 12 becomes the second conductor 14. .

(conductor)
Examples of the material for each conductor include metal foils such as copper foil, aluminum foil, and nickel foil; metal particle dispersion films made of silver paste and the like.
Each conductor is a signal transmission layer, a power supply layer, or a ground layer in a multilayer printed circuit board.

  In order to exhibit a sufficient noise suppression effect, it is preferable that the second conductor is easily electromagnetically coupled to the noise suppression layer. Therefore, the width of the second conductor is preferably wider than that of the first conductor. In particular, as shown in FIG. 1, when the first conductor 11 and the second conductor 14 are in different parallel planes, and the first conductor 11 is a signal transmission layer, or a power supply layer When a high frequency current flows with a certain width in the case of a plane such as the like, a feedback current that is three times the width flows through the second conductor, so the width of the second conductor is at least It is preferably 3 times or more of the first conductor.

(Noise suppression layer)
The noise suppression layer is a layer having a thickness of 5 to 300 nm formed by physically depositing a metal material on the insulating layer.

Examples of the metal material include ferromagnetic metals and paramagnetic metals.
Ferromagnetic metals include iron, carbonyl iron; Fe-Ni, Fe-Co, Fe-Cr, Fe-Si, Fe-Al, Fe-Cr-Si, Fe-Cr-Al, Fe-Al-Si, Fe -Pt and other iron alloys; cobalt and nickel; and alloys thereof.
Examples of the paramagnetic metal include gold, silver, copper, tin, lead, tungsten, silicon, aluminum, titanium, chromium, molybdenum, alloys thereof, and alloys with ferromagnetic metals.
Of these, nickel, iron-chromium alloy, tungsten, and noble metals are preferable because they are resistant to oxidation. However, since noble metals are expensive, practically nickel, iron-chromium alloy, and tungsten are preferable, and nickel or nickel alloy is particularly preferable.

When the noise suppression layer is a layer formed by physically vapor-depositing a metal material on the insulating layer in an atmosphere containing a reactive gas, the metal material in the noise suppression layer exists in the state of a metal compound.
Examples of the metal compound include an alloy composed of a metal and one or more elements selected from the group consisting of boron, carbon, nitrogen, silicon, phosphorus, and sulfur, an intermetallic compound, a solid solution, and the like. Since the metal compound is slightly less metallic than metal and has a higher specific resistance, the noise suppression layer containing the metal compound does not have a resonance frequency, and the frequency that exhibits the noise suppression effect is broadened. It has advantages such as high stability. As the metal compound, a metal compound composed of a metal and nitrogen is particularly preferable because it can be easily obtained by using nitrogen gas as a reactive gas in a physical vapor deposition method described later.

  The noise suppression layer is a layer exhibiting paramagnetism. Even if the noise suppression layer is a layer containing a ferromagnetic metal, it does not exhibit the characteristics of a bulk ferromagnetic metal in the form of a single layer or a composite layer described later, and exhibits paramagnetism.

  Whether the noise suppression layer exhibits paramagnetism can be confirmed by measuring the magnetic field dependence of the magnetic susceptibility using a superconducting quantum interferometer (SQUID). This apparatus is an apparatus for measuring magnetization by changing the temperature while applying a magnetic field to a sample to be measured, and can measure a minute magnetization. For example, when the magnetic field dependence of magnetic susceptibility is confirmed using a superconducting quantum interferometer for a sample in which a noise suppression layer having a thickness of 80 nm is formed using nickel, which is a ferromagnetic metal, on a polymer film having a thickness of 25 μm. As shown in FIG. 4, there is no hysteresis due to the magnetic field sweep, and flat magnetic field dependence is exhibited even in the low magnetic field region. This result confirms that the sample does not exhibit ferromagnetism but exhibits paramagnetism.

  In the present invention, it is important that the noise suppression layer does not exist as a mere metal thin film layer but exists as a single layer or a composite layer described later. As a result, some resonance peaks observed in the transmission attenuation factor in the noise attenuation effect measurement using the microstrip line transmission line described later are observed in the normal metal thin film, whereas the noise suppression layer in the present invention is used. However, the transmission attenuation rate continues to increase.

The form of the single layer or the form of the composite layer is 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 metal material (reference value). Can be confirmed from the relationship. That is, when the volume resistivity R1 and the volume resistivity R0 satisfy 0.5 ≦ logR1−logR0 ≦ 3, the clusters of the metal materials are in very close proximity and each exist independently. As a result, an excellent noise suppression effect is exhibited.
When logR1-logR0 is less than 0.5, the metallicity is high, the metal reflection is increased, and the noise suppression effect is also reduced. When logR1-logR0 exceeds 3, the electromagnetic coupling between the conductor and the noise suppression layer is weakened. As a result, the noise suppression effect is reduced and becomes ineffective.

  The form of the noise suppression layer is a “single layer” consisting of a plurality of independent nanometer level clusters and defects in which no cluster exists; a plurality of independent nanometer level clusters and a part of the material of the insulating layer; A “composite layer” that is a mixture of and combined. Hereinafter, the single layer and the composite layer will be described.

Single layer:
The single layer is, for example, an aggregate of clusters composed of a plurality of independent clusters of nanometer level metal materials and defects in which the metal material formed therebetween does not exist. Even if the metal material is a ferromagnetic metal, the single layer form does not exhibit the properties of a bulk ferromagnetic metal and exhibits paramagnetism.

  FIG. 5 is a high-resolution scanning electron microscope image of the single layer formed on the insulating layer as viewed from the single layer (upper surface) side, and FIG. 6 is a schematic diagram thereof. A plurality of independent nanometer-level metal material clusters 15 formed on the insulating layer 13 and a single layer (noise suppression layer 12) consisting of defects existing therebetween are confirmed.

  FIG. 7 is a high-resolution scanning electron microscope image of a single layer in which the mass of the metal material is further increased as viewed from the single layer (upper surface) side, and FIG. 8 is a schematic diagram thereof. Although the clusters 15 are brought into contact with each other and are clustered to increase the size of the clusters, a large number of defects in which the metal material does not exist remain between the clustered clusters 15, thus forming a homogeneous metal thin film. Not.

  The clustered cluster 15 is in an independent state or in an electromagnetically coupled or contacted state. The growth of the cluster 15 is fractal, and it seems that a dendritic current path exists. In the present invention, the clusters 15 grouped in this way are treated as independent clusters as long as there are defects between the clusters 15 and each cluster 15 is independent.

  Here, the cluster is a group formed by aggregating hundreds to millions of atoms such as metals. As the cluster agglomerates, the particles and the metal thin film are formed. The clusters are clearly distinguished from the particles and the metal thin film as described below.

  FIG. 9 is a high-resolution transmission electron microscope image of the cross section of the single layer in the film thickness direction. FIG. 10 is an electron beam diffraction image of a single layer. From FIG. 5, FIG. 6, FIG. 9, and FIG. 10, a very small crystal lattice portion in which atoms such as metals are arranged at intervals of several tons and a defect portion in which atoms such as metals do not exist are recognized. That is, the clusters are spaced apart and no clear grain boundaries are observed. The crystal orientation of each cluster is recognized to be disordered, and it does not grow into a homogeneous metal thin film, ultrafine particle, fine particle, or the like made of a metal material. Therefore, the resistance of the surface is several times higher than the resistance as a homogeneous metal thin film.

  The reason for the noise suppression layer composed of such cluster aggregates is not clear, but is considered to exhibit a noise suppression effect for the following reasons (i) to (iv). (I) Since the clusters are in the nanometer level, are not integrated, and are in close proximity, energy is required for electrons to jump between the clusters, that is, the resistance is high. (Ii) Since the distance between the clusters is very small, the capacitance between the clusters varies in a complicated manner depending on the location, and constitutes a dielectric absorbing material. (iii) Due to the open stub effect that current paths branched in a dendritic shape are formed and the current paths have a plurality of various lengths.

  Or, (iv) the size of the cluster is the size that becomes atomic polarization, and shows a large dielectric loss tangent in the transition from dipole polarization to atomic polarization (that is, such material polarization follows the change in electric field) Therefore, the resonance condition is disturbed, and that amount is lost as thermal energy. As a result, even a thin layer is considered to exhibit a sufficient noise suppression effect.

  The average thickness of the single layer is preferably 5 to 300 nm, more preferably 5 to 100 nm, and particularly preferably 5 to 50 nm. By setting the average thickness of the single layer to 5 nm or more, a sufficient noise suppression effect can be exhibited. On the other hand, when the average thickness of the single layer exceeds 300 nm, clusters are aggregated and a homogeneous metal thin film made of a metal material is formed, returning to the characteristics of the bulk metal material, the metal reflection is strengthened, and the noise suppression effect Becomes smaller and is not effective. Here, the average thickness of the single layer is the average thickness of the entire single layer including defects, and a cluster formed on a smooth and hard insulating layer made of ceramic or the like is measured by an atomic force microscope (AFM) or It can be measured by observing the gap from the substrate surface using a scanning probe microscope.

  The average particle size of the cluster is preferably 5 to 100 nm, and more preferably 5 to 50 nm. If the average particle size of the clusters is less than 5 nm, the distance between the clusters is too far, there is no interaction between the clusters, and a sufficient noise suppression effect cannot be exhibited. On the other hand, when the average particle size of the clusters exceeds 100 nm, the clusters are aggregated to form a homogeneous metal thin film made of a metal material, returning to the characteristics of the bulk metal material, the metal reflection is strengthened, and the noise suppressing effect is also achieved. Smaller and less effective. Here, the average particle diameter of the clusters is an average diameter obtained by measuring the diameters of all the clusters in the high-resolution scanning electron microscope image when the single layer is viewed from the upper surface side on the electron microscope image. The diameter when the cluster is elliptical is ½ of the total of the major axis and the minor axis.

Composite layer:
For example, a composite layer is a set of clusters in which a plurality of independent nanometer level metal material clusters (microclusters) and a part of the material of the insulating layer are mixed, and the material of the insulating layer exists between the clusters. Is the body. Even if the metal material is a ferromagnetic metal, it does not exhibit the properties of a bulk ferromagnetic metal and exhibits paramagnetism in the form of a composite layer.

FIG. 11 is a high-resolution transmission electron microscope image of the cross section in the film thickness direction of the composite layer, and FIG. 12 is a schematic diagram thereof.
The composite layer (noise suppression layer 12) includes a portion where a crystal lattice 16 in which atoms such as metals having a few tens of intervals are arranged as very small crystals, and an insulating layer in which metal atoms or the like do not exist within a very small range. 13 consists of a part where only a part of 13 is observed and a part where atoms 17 such as metal are not crystallized but dispersed in the insulating layer 13. That is, a grain boundary indicating that the metal material is present as fine particles having a clear crystal structure is not observed, and a complex heterostructure in which the metal material and a part of the insulating layer 13 are integrated at a nanometer level (inhomogeneous / non-uniform). It has a homogeneous structure) and has not grown into a homogeneous metal thin film, ultrafine particle, fine particle, or the like made of a metal material.

The average thickness of the composite layer is preferably 5 to 300 nm, more preferably 8 to 300 nm. The thickness of the composite layer is the average depth at which atoms such as metals penetrated the surface of the insulating layer, and depends on the deposition mass of the metal, the material of the insulating layer, the conditions of physical vapor deposition, etc. The thickness is about 1.5 to 3.0 times. By setting the average thickness of the composite layer to 5 nm or more, a sufficient noise suppression effect can be exhibited. On the other hand, when the average thickness of the composite layer exceeds 300 nm, the crystal lattice 16 aggregates to form a homogeneous metal thin film made of a metal material, returning to the characteristics of the bulk metal material, increasing the metal reflection, and noise. The suppression effect is also reduced and is not effective. Here, the average thickness of the composite layer is calculated based on the high-resolution transmission electron microscope image of the cross section in the film thickness direction of the noise suppression layer as shown in FIG. The thickness of the dark portion is measured on an electron microscope image and averaged.
The reason for such a composite layer is not clear, but is considered to exhibit a noise suppressing effect for the same reason as the single layer.

(Method for forming noise suppression layer)
The noise suppression layer is formed by a physical vapor deposition method (PVD method).
When the insulating layer is a relatively hard material such as ceramics, the noise suppression layer is likely to be a single layer, and when the insulating layer is a relatively soft material such as a resin, the noise suppression layer is likely to be a composite layer. In addition, when the surface of the insulating layer has larger undulations and roughness than the cluster size, when it is porous, or when the bonding force between the polymer chains of the insulating layer is weak, a single layer on the insulating layer with low energy Even if formed, it may appear to be in a composite layer state.

PVD method:
The PVD method is a method in which a metal material (target) is vaporized by some method in a vacuumed container, and the vaporized metal material is deposited on an insulating layer placed nearby. The PVD method is divided into an evaporation system and a sputtering system depending on the vaporization method of the metal material. Examples of the evaporation system include an EB vapor deposition method and an ion plating method. Examples of the sputtering system include a high frequency sputtering method, a magnetron sputtering method, a counter target type magnetron sputtering method, and an ion implantation method.

  In the EB vapor deposition method, since the energy of the evaporated particles is as small as 1 eV, the insulating layer is hardly damaged. In addition, the noise suppression layer tends to be porous and the noise suppression layer tends to have insufficient strength, but the specific resistance of the noise suppression layer increases.

  According to the ion plating method, the argon gas and the ions of the evaporated particles are accelerated and collide with the insulating layer. Therefore, the energy is larger than that of the EB vapor deposition method, the particle energy is about 1 KeV, and the noise suppression layer with strong adhesion is formed. Can get. However, adhesion of micro-sized particles called droplets cannot be avoided, and there is a possibility that the discharge stops.

  The magnetron sputtering method is characterized in that although the target utilization efficiency is low, a strong plasma is generated under the influence of a magnetic field, so that the growth rate is fast and the particle energy is as high as several tens of eV. In high frequency sputtering, a target with low conductivity can be used.

  Among the magnetron sputtering methods, the facing target type magnetron sputtering method generates plasma between facing targets, encloses the plasma by a magnetic field, places an insulating layer between the facing targets, and does not receive plasma damage. It is a method of depositing a metal material on the top. Therefore, the metal material on the insulating layer is not re-sputtered, the growth rate is higher, and the sputtered metal atoms are not impact-relaxed, and the dense material has the same composition as the target composition. Cluster can be formed.

  In the present invention, in order to easily form an independent cluster without forming a homogeneous metal thin film of a metal material on an insulating layer, an ion plating method, a magnetron sputtering method, a counter target is used for the following reasons. The magnetron sputtering method and the ion implantation method are preferable.

  The covalent bond energy in an organic polymer is about 4 eV. Specifically, the bond energies of C—C, C—H, Si—O, and Si—C are 3.6 eV, 4.3 eV, and 4.6 eV, respectively. 3.3 eV. On the other hand, in the ion plating method, magnetron sputtering method, facing target type magnetron sputtering method, and ion implantation method, the evaporated particles have high energy. It is conceivable that some chemical bonds of the molecule are broken and collide. Therefore, when the shear modulus of the insulating layer made of an organic polymer is sufficiently small, when the metal material is deposited, the organic polymer vibrates and moves, and the local mixing action between the metal atoms and the organic polymer is caused. As a result, atoms such as metals enter from about 5 to 300 nm from the surface of the insulating layer, and not a metal thin film made of a homogeneous metal material but a composite layer having a nanometer-level heterostructure.

As the metal material (target), the above metal material may be used.
Note that when a metal material is deposited on the insulating layer, the metal material is deposited as plasma or ionized metal atoms. Therefore, the composition of the deposited metal material is not necessarily the same as the composition of the metal material used as the target. It is not necessarily the same.

  Since the metal deposition rate in the PVD method varies depending on the type of metal material, it is preferable to confirm these conditions in advance for each type of metal material. Further, it is preferable to form the clusters slowly so that the clusters are not grown on the metal thin film. In some cases, the forming operation may be temporarily stopped, the degree of growth may be confirmed, and the forming operation may be performed again.

The vapor deposition mass of the metal material is preferably 5 to 100 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 100 nm or less, the cluster state can be maintained and the noise suppression effect can be obtained.
When the vapor deposition mass of the metal material is reduced, the noise suppression effect is reduced. Therefore, the vapor deposition mass of the metal material may be increased by laminating a plurality of noise suppression layers via an insulating layer. The total deposition mass is preferably about 10 to 500 nm in terms of film thickness, although it depends on the level of noise suppression effect required.

  When the deposition mass of the metal material increases, it becomes difficult to obtain a cluster state. Specifically, when it is about 20 nm or more, a normal sputtering method tends to grow into a simple metal thin film. Therefore, it is preferable to stabilize the cluster by introducing a reactive gas such as nitrogen gas, oxygen gas, hydrogen sulfide gas, silane gas in addition to normal argon gas during the deposition of the metal material by sputtering. In particular, when nitrogen gas is used, huge crystallization at the time of deposition of the metal material is inhibited, and a highly stabilized cluster can be obtained.

  In addition, when the insulating layer is made of a hard material such as ceramics and has a low affinity with a metal material, the cluster can be stabilized by having the cluster and another material simultaneously exist on the insulating layer. Thus, it is possible to reliably prevent these from aggregating and crystallizing and growing into fine particles, a metal thin film or the like. Specifically, when a cluster is formed by the PVD method, a method (insulating vapor deposition method) in which a reactive gas is introduced and an inorganic substance or an organic substance partially reacts with the cluster surface or the like can be employed. Examples of the gas include methane gas, acetylene gas, silane gas, fluorocarbon gas, and paraxylylene. The noise suppression layer formed by the insulating vapor deposition method is a composite layer.

(Loss power ratio)
As a confirmation method of the noise suppression effect of the noise suppression layer, there is a method of measuring the S parameter reflection attenuation amount S11 and the transmission attenuation amount S21. The standardization of this method is under consideration in Working Group 10 and Technical Committee 51 of International Electrotechnical Commission (IEC).
FIG. 14 is a schematic configuration diagram showing an apparatus used for the measurement of the reflection attenuation S11 and the transmission attenuation S21 under consideration. A sample 23 (50 mm × 50 mm) in which a noise suppression layer is formed on an insulating layer is placed in close contact with a microstrip line 22 provided in the test fixture 21 and having a specified characteristic impedance (such as 50Ω). Changes in the S parameter before and after mounting the sample 23 (reflection attenuation amount S11 and transmission attenuation amount S21) are measured by a network analyzer 24 electrically connected to the microstrip line 22. The noise suppression effect can be measured by performing calibration only with the test fixture 21 in advance and reading the S parameter when the sample 23 is mounted.

In the present invention, this method is adopted, and the loss power ratio described in “Industrial Materials” (November 2002 issue, Nikkan Kogyo Shimbun) is obtained by the following formula. The loss power ratio takes a value of 0 to 1, and is represented by the following formula.
Loss power ratio (Ploss / Pin) = 1- (| Γ | ² + | Τ | ² )
Here, S11 = 20log | Γ |, S21 = 20log | Τ |, Γ is a reflection coefficient, and Τ is a transmission coefficient.

In order to sufficiently exhibit the noise suppression effect in the quasi-microwave band, the loss power ratio at 1 GHz is preferably 0.4 or more. If it is smaller than this, it cannot be said that there is a sufficient noise suppression effect. Furthermore, the loss power ratio is preferably 0.5 or more. If the loss power ratio is 0.5 or more, there is a sufficient noise suppression effect. The current technology cannot achieve a loss power ratio exceeding 0.9 at 1 GHz.
In order to set the loss power ratio of the noise suppression layer to 0.4 to 0.9, it is basically a structure in which paramagnetic clusters having an average particle diameter of 2 to 100 nm are densely dispersed on the insulating layer. In addition, the conditions for forming the cluster, the surface properties of the insulating layer, and the like may be controlled.

  The noise suppression layer has a characteristic that the noise suppression effect increases as the area covering the conductor increases. For example, as shown in FIG. 15, when the dimension in the L direction of the sample 23 in FIG. 14 is increased, the loss power ratio at 1 GHz increases. Moreover, as shown in FIG. 16, when the dimension in the W direction of the sample 23 in FIG. 14 is increased, the loss power ratio at 1 GHz increases.

When a sufficient area for forming the noise suppression layer cannot be secured, the area can be gained by stacking the noise suppression layer, and a large effect can be achieved with a small area. For example, as shown in FIG. 17, the laminated noise suppression layer is an isolation layer made of an insulating material on the noise suppression layer 12 formed on the insulating layer 13 by printing, coating, physical vapor deposition, chemical vapor deposition, or the like. 18 and the noise suppression layer 12 is further formed thereon. As the insulating material for the isolation layer 18, the same materials as those for the insulating layer described above can be used. An opening 19 may be formed in the isolation layer 18 as necessary. At this time, the two noise suppression layers 12 are integrated through the opening 19.
As described above, when the plurality of noise suppression layers 12 are arranged at intervals, the capacitance component increases and a stub structure is also generated, so that a further noise suppression effect is exhibited.

(Transmission attenuation factor)
The transmission attenuation rate indicates an attenuation amount per unit length at which conduction noise transmitted through the conductor is attenuated by the noise suppression layer. The transmission attenuation factor can be obtained from the reflection attenuation amount S11 and the transmission attenuation amount S21 by the following equation. The transmission attenuation rate is being standardized by IEC Working Group 10 and Technical Committee 51.
Transmission attenuation factor (Rtp) = − 10 × log {10 ^{S21 / 10} / (1-10 ^{S11 / 10} )} [dB]

In order to sufficiently exhibit the noise suppressing effect in the quasi-microwave band, the transmission attenuation factor at 1 GHz is preferably 10 dB or more. If it is smaller than this, it cannot be said that there is a sufficient noise suppression effect. Furthermore, it is preferable that the transmission attenuation rate is stabilized at 20 dB or more in a wide range of the quasi-microwave band. If the transmission attenuation factor is 20 dB or more, a sufficient noise suppression effect can be expected. In the conventional technique, it is not possible to obtain a transmission attenuation factor exceeding 10 dB at 1 GHz.
In order to stabilize the transmission attenuation rate of the noise suppression layer to 10 dB or more at 1 GHz and to stabilize the transmission attenuation rate to 20 dB or more in a wide range of the quasi-microwave band, a paramagnetic material having an average particle diameter of 2 to 100 nm on the insulating layer. Based on the structure in which the clusters are densely dispersed, the conditions for forming the clusters, the surface physical properties of the insulating layer, and the like may be controlled.

(Insulating layer)
The insulating layer is a layer made of a dielectric having a surface resistance of 10 ⁶ Ω / cm ² or more.
The material of the insulating layer may be an inorganic material or an organic material as long as it is a dielectric.

  Examples of the inorganic material include ceramics such as aluminum oxide, silicon oxide, and silicon nitride, and foamed ceramics. Note that when the insulating layer is a hard material such as ceramics, atoms such as metals are difficult to enter the insulating layer, clusters are aggregated, and it is easy to form a homogeneous metal thin film. By suppressing, an independent cluster is formed and the distance between the clusters is widened, so that it is difficult to aggregate.

  Examples of organic materials include polyolefins, polyamides, polyesters, polyethers, polyketones, polyimides, polyurethanes, polysiloxanes, phenolic resins, epoxy resins, acrylic resins, polyacrylates, vinyl chloride resins, and chlorinated polyethylene resins; Examples include diene rubbers such as natural rubber, isoprene rubber, butadiene rubber, and styrene butadiene rubber; non-diene rubbers such as butyl rubber, ethylene propylene rubber, urethane rubber, and silicone rubber. The organic material may be thermoplastic, thermosetting, or an uncured product thereof. Further, it may be a modified product such as the above-mentioned resin or rubber, a mixture, or a copolymer.

When the insulating layer is made of an organic material, the aggregation of the clusters is suppressed by the organic polymer chain, and the dispersibility can be maintained in a state where the clusters are close to each other. As a result, it is easy to maintain the structure of the cluster aggregate, and a noise suppression layer having a large noise suppression effect can be obtained.
As an insulating layer, elements such as oxygen, nitrogen, and sulfur that can be covalently bonded to a metal from the standpoint of adhesion to the cluster, and inhibiting cluster aggregation and growth and stabilizing cluster dispersion Those having a surface containing a group containing benzene and those having the surface activated by irradiating the surface with ultraviolet rays, plasma or the like are preferable. Examples of groups containing elements such as oxygen, nitrogen and sulfur include hydrophilic groups such as hydroxyl groups, carboxyl groups, ester groups, amino groups, amide groups, thiol groups, sulfone groups, carbonyl groups, epoxy groups, isocyanate groups, and alkoxy groups. Is mentioned.

As the insulating layer, a separation structure membrane having a vertically aligned hexagonal close-packed cylinder array type phase separation structure in which a hydrophilic polymer component is a cylinder portion and the other portion is a hydrophobic polymer component (Japanese Patent Application Laid-Open No. 2004-124088). No.), a support having a surface modified film having a lower affinity for metal than the substrate formed on the substrate, and exposing the substrate having a high affinity for metal in a desired pattern by lithography using electron beam A metal cluster is formed, such as a body (Japanese Patent Laid-Open No. 2004-111818), a mold having a small beam diameter of several nanometers and a support having a fine uneven pattern formed by nanoimprinting. A support having a portion that is easy to form and a portion in which a metal cluster is difficult to be formed (hereinafter referred to as a selective support) may be used.
By using the selective support, clusters can be arranged in a desired pattern, and the size, density, and distance between clusters can be controlled. As a result, the noise suppression effect can be exhibited efficiently. At this time, the arrangement pitch of the clusters is preferably 5 to 60 nm, and the average particle size of the clusters is preferably 4 to 55 nm.

The insulating layer preferably has a low shear elastic modulus when forming a cluster by the PVD method from the viewpoint of inhibiting cluster aggregation and growth and maintaining the dispersibility of the cluster. Specifically, those having a shear modulus of 1 × 10 ¹⁰ Pa or less are preferable. In order to obtain a desired shear modulus, the insulating layer may be heated to, for example, 100 to 300 ° C. as necessary. At this time, it is necessary to set the temperature so that the insulating layer does not decompose, evaporate, reduce viscosity, or the like. When performing PVD at room temperature (25 ° C.), the insulating layer is preferably an elastic body having a rubber hardness of about 80 ° (JIS-A) or less.

The following methods are known as methods for measuring the shear modulus.
(1) A tensile elastic modulus is obtained from the relationship between tensile stress and strain defined in JIS K7113, and a shear elastic modulus is obtained from the following formula based on this.
Shear modulus = Tensile modulus / (2 x (1 + Poisson's ratio))
Here, the value of 2 × (1 + Poisson's ratio) is approximately 2.6 to 3.0 from a rigid polymer to a rubbery elastic body.
(2) Using a viscoelasticity measuring device capable of grasping the temperature characteristics, the shear modulus is measured by setting the test mode to the shear mode.
(3) Using a viscoelasticity measuring device, setting the test mode to the tensile mode, measuring the storage elastic modulus G ′ and the loss elastic modulus G ″, obtaining the complex elastic modulus G * from the following formula, and calculating the complex elastic modulus as the tensile elasticity As the modulus, the shear modulus is obtained from the following formula.
G * = √ ((G ′) ² + (G ″) ² )
The shear modulus in the present invention is a value measured using a solid analyzer RSA-II manufactured by Rheometric Scientific as a viscoelastic modulus measuring apparatus in a shear mode under a measurement frequency of 1 Hz.

In addition, the insulating layer has a shear modulus higher than 1 × 10 ⁴ Pa after the formation of the cluster so that cluster aggregation, that is, homogenization, can be suppressed even when thermal and mechanical stress is applied. preferable. By increasing the shear modulus after the formation of the clusters, the movement of the resin can be suppressed, and the clusters at the nanometer level can be surely suppressed from agglomerating and crystallizing and growing into fine particles and metal thin films. More preferably, 1 × 10 ⁷ Pa or more is preferable in the temperature range in which the noise suppression structure is used.
In order to obtain a desired shear modulus, it is preferable that the insulating layer is fired and solidified or chemically crosslinked after the formation of the cluster. In this respect, it is particularly preferable to use an organic material that has a low shear modulus before formation of the cluster and can be cross-linked after formation to increase the shear modulus. A curable resin (such as an electron beam) is preferred.

In the case where the insulating layer is an organic polymer, gas permeability can be used as an index indicating the size of intermolecular voids in which atoms such as metals enter and can easily form independent clusters. Originally, it is preferable to check the intermolecular voids of the organic polymer by the permeability of argon gas and krypton gas equivalent to the size of atoms such as metals, but these gases are generally used for measuring gas permeability. Therefore, for example, carbon dioxide permeability data can be substituted. Examples of the organic polymer having a large carbon dioxide permeability at room temperature include polyphenylene oxide, polymethylpentene having a carbon dioxide permeability of 1 × 10 ⁻⁹ [cm ³ (STP) cm / (cm ² × s × cmHg)] or more. Nylon 11, a mixture or copolymer of rubber components such as high impact polystyrene and other components, polybutadiene or polyisoprene of 1 × 10 ⁻⁸ [cm ³ (STP) cm / (cm ² × s × cmHg)] or more Styrene butadiene rubber, silicone rubber and the like. Among these, rubbers such as silicone rubber are particularly preferable from the viewpoint of shear modulus.

From the viewpoint of preventing cluster oxidation, an organic material having low oxygen permeability is preferable. Examples of such an organic material include polyethylene, polytrifluorochloroethylene, polymethyl methacrylate, 1 × with an oxygen permeability of 1 × 10 ⁻¹⁰ [cm ³ (STP) cm / (cm ² × s × cmHg)] or less. 10 ⁻¹² [cm ³ (STP) cm / (cm ² × s × cmHg)] The following polyethylene terephthalate, polyacrylonitrile and the like can be mentioned.
Here, the oxygen permeability is a gas permeability coefficient measured and determined according to JIS K7126.

  Furthermore, a silane coupling agent, a titanate coupling agent, a nonionic surfactant, a polar resin oligomer, etc. may be mix | blended in an insulating layer, it may be made to react with a cluster, and a cluster may be stabilized. By blending such an additive, formation of a homogeneous metal thin film can be suppressed, and cluster oxidation can be prevented, which is advantageous. In addition, reinforcing fillers, flame retardants, antioxidants, antioxidants, colorants, thixotropic improvers, plasticizers, lubricants, heat improvers, and the like may be added as appropriate to the insulating layer.

  As the insulating layer, when the noise suppressing structure is mounted on the multilayer printed circuit board, polyimide, glass epoxy prepreg, and glass epoxy board are preferable from the viewpoint of heat resistance. In addition, the insulating layer between the first conductor and the noise suppression layer is preferably polyimide because it can be easily removed by etching in a method for manufacturing a multilayer printed circuit board described later.

Polyimide is a reaction product of diamine and tetracarboxylic dianhydride.
As a polyimide, from the viewpoint of etching processability, 1,3-bis (3-aminophenoxy) benzene, 4,4-bis (3-aminophenoxy) biphenyl, 3,3′-diaminobenzophenone, Those using at least one diamine selected from the group consisting of o-phenylenediamine, p-phenylenediamine, m-phenylenediamine, and 4,4′-diaminodiphenyl ether are preferred.
As tetracarboxylic dianhydride, 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride, pyromellitic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride Things are preferred.
As the polyimide, those in which an imide group is directly linked to an aromatic ring are preferable from the viewpoint of heat resistance.

  FIG. 18 is a graph for confirming how the loss power ratio at 1 GHz is affected by the distance from the microstrip line to the noise suppression layer. Specifically, a polyimide film is interposed between the microstrip line 22 and the sample 23 shown in FIG. 14, the thickness of the polyimide film is changed, the S parameter at 1 GHz is measured, and the loss power ratio is obtained. It is the graph which plotted the loss power ratio with respect to the thickness of a polyimide film.

As shown in FIG. 18, the noise suppression effect of the noise suppression layer increases as the distance from the conductor to be suppressed becomes shorter. Therefore, the thickness of the insulating layer between the first conductor and the noise suppression layer is preferably 50 μm or less, and preferably 25 μm or less, from the viewpoint of noise suppression effect and the thickness of the multilayer printed circuit board. More preferred. Moreover, in order to maintain the insulation between the noise suppression layer and the first conductor, the thickness of the insulating layer is preferably 3 μm or more.
When the insulating layer between the first conductor and the noise suppression layer is a layer made of polyimide, the thickness of the insulating layer is preferably 25 μm or less from the viewpoint of etching processability.

  The thickness of the insulating layer between the second conductor and the noise suppression layer is preferably 500 μm or less from the viewpoint of reducing the thickness of the multilayer printed circuit board. Moreover, in order to maintain the insulation between the noise suppression layer and the second conductor, the thickness of the insulating layer is preferably 3 μm or more.

In the noise suppression structure of the present invention described above, the noise suppression layer is a layer having a thickness of 5 to 300 nm formed by physically depositing a metal material on the insulating layer. The clusters of metal materials are in very close proximity and exist independently, and an excellent noise suppression effect is exhibited.
Moreover, since the noise suppression layer in this invention can fully exhibit a noise suppression effect even if it is 5-300 nm thin, the noise suppression structure can be thinned.

  Although the mechanism of the manifestation of the noise suppression effect by the noise suppression structure of the present invention is not clear, the noise suppression layer becomes a capacitive resistor by electromagnetically coupling with the second conductor, and is electromagnetically coupled to the noise suppression layer. The high-frequency current flowing in the first conductor is considered to be converted into thermal energy by this capacitive resistor.

  By incorporating the noise suppression structure of the present invention into an electronic component, high-frequency current flowing through the conductor of the electronic component that causes conduction noise can be suppressed, and radiation noise can also be suppressed. An electronic component includes a conductor used for signal transmission, a power source, a ground, and the like. Examples of the electronic component include a semiconductor element; a system in package (SIP) in which an electronic element such as the semiconductor element is mounted. And a printed circuit board. In particular, multilayer printed circuit boards mounted with semiconductor elements are required to maintain the waveform quality (SI, Signal Integrity) flowing in the signal transmission layer, while the power supply voltage decreases as power consumption decreases. Therefore, the S / N ratio of the transmission signal is getting worse. For this reason, it is necessary to stabilize the power supply (PI, Power Integrity), and suppression of high-frequency current is required.

<Multilayer printed circuit board>
The multilayer printed circuit board of the present invention comprises the noise suppression structure of the present invention. In the multilayer printed circuit board, the conductor in the noise suppression structure is a signal transmission layer, a power supply layer, or a ground layer. In order to sufficiently exhibit the noise suppressing effect, it is preferable that one of the first conductor and the second conductor is a power supply layer and the other is a ground layer. In order to suppress the adverse effect on the signal by the noise suppression layer, it is preferable that a power supply layer or a ground layer exists between the signal transmission layer and the noise suppression layer.

FIG. 19 is a schematic cross-sectional view showing an example of the multilayer printed circuit board of the present invention. The multilayer printed circuit board 30 includes a signal transmission layer 31, an insulating layer 13, a ground layer 32, an insulating layer 13, a noise suppression layer 12, an insulating layer 13, a power supply layer 33, an insulating layer 13, and a signal transmission layer 31 in order from the top. It is comprised. The upper signal transmission layer 31 and the ground layer 32 are connected via a via hole 34, and the lower signal transmission layer 31 and the power supply layer 33 are connected via a via hole 35. The via hole 35 is electrically connected to the noise suppression layer 12.
FIG. 19 shows an example in which the first conductor is a power supply layer and the second conductor is a ground layer.

FIG. 20 is a schematic sectional view showing another example of the multilayer printed circuit board of the present invention. The multilayer printed circuit board 30 includes a signal transmission layer 31, an insulating layer 13, a ground layer 32, an insulating layer 13, a noise suppression layer 12, an insulating layer 13, a power supply layer 33, an insulating layer 13, and a signal transmission layer 31 in order from the top. It is comprised. The upper signal transmission layer 31 and the ground layer 32 are connected via a via hole 34, and the lower signal transmission layer 31 and the power supply layer 33 are connected via a via hole 35. The via hole 34 is electrically connected to the noise suppression layer 12.
FIG. 20 is an example in which the first conductor is a ground layer and the second conductor is a power supply layer.

FIG. 21 is a schematic sectional view showing another example of the multilayer printed circuit board of the present invention. The multilayer printed circuit board 30 includes a signal transmission layer 31, an insulating layer 13, a ground layer 32, an insulating layer 13, a noise suppressing layer 12, an insulating layer 13, a noise suppressing layer 12, an insulating layer 13, and a power supply layer 33 in order from the top. , The insulating layer 13 and the signal transmission layer 31. The upper signal transmission layer 31 and the ground layer 32 are connected via a via hole 34, and the lower signal transmission layer 31 and the power supply layer 33 are connected via a via hole 35. The via hole 34 is electrically connected to the noise suppression layer 12.
FIG. 21 is an example in which there are two noise suppression layers, and the ground layer and the power supply layer are both the first conductor and the second conductor.

  In the multilayer printed circuit board of the present invention, it is preferable that the via hole (through hole) and the noise suppression layer are electrically connected. By electrically connecting the via hole and the noise suppression layer, conduction noise generated in the via hole can be suppressed. When the via hole and the noise suppression layer are electrically connected, it can be interpreted that the noise suppression layer and the power supply layer or the ground layer are electrically connected. However, in the present invention, the noise suppression layer and the power supply layer are Or, unless the ground layer is in direct contact, the noise suppression layer and the power supply layer or the ground layer are not electrically connected.

  In the multilayer printed circuit board, the copper foil constituting the power supply layer and the ground layer spreads over almost the entire surface of the multilayer printed circuit board, and feeds power to the semiconductor element. When a large number of transistors in the semiconductor element are driven at the same time, unnecessary high-frequency current flows into the power supply layer and the ground layer, and potential fluctuation occurs. Due to the potential fluctuation, simultaneous switching noise occurs in the power supply layer and the ground layer. Furthermore, since the power supply layer and the ground layer have a parallel plate structure in which the peripheral ends are open, resonance occurs between the power supply layer and the ground layer due to potential fluctuations, and radiation noise is generated from the peripheral ends. Is emitted. Therefore, by arranging the noise suppression layer between the power supply layer and the ground layer, the high frequency current is suppressed, the potential of the power supply layer is stabilized, and as a result, conduction noise such as simultaneous switching noise and radiated noise due to resonance are reduced. It can be suppressed.

<Manufacturing method of multilayer printed circuit board>
The multilayer printed circuit board of the present invention includes, for example, a metal foil such as a copper foil; a prepreg or an adhesive sheet; a wiring member (1) provided with a metal foil on a prepreg or an adhesive sheet; and a metal foil provided on one surface of the prepreg The wiring member (2) having a noise suppression layer formed on the other surface is sequentially laminated, and a resin such as a prepreg is cured.

When forming a via hole (through hole) in a multilayer printed circuit board, it is necessary to remove the portion where the via hole is formed in the noise suppression layer and the power supply layer or the ground layer that are not connected to the via hole.
In order to remove the power supply layer or the ground layer in the portion where the via hole is to be formed, a normal wet etching method using an acidic etchant may be used.

  As a method of removing the noise suppression layer in the portion where the via hole is formed, for example, (i) a dry etching method in which the noise suppression layer is removed with a laser or the like at the stage of the wiring member (2), or (ii) FIG. At the stage of the noise suppression structure shown in FIG. 3, after removing a part of the first conductor by a wet etching method using an acidic etchant, the first conductor and the noise suppression layer are formed using the first conductor as a mask. And a method of removing the insulating layer and the noise suppression layer between them by dry etching or wet etching.

  As a method for removing the noise suppression layer, the method (ii) is preferable because it is not necessary to align the portion where the via hole is formed between the noise suppression layer and the power supply layer or the ground layer. It is more preferable that all the etching in the method (ii) is performed by a wet etching method because an apparatus is unnecessary and easy. By making the insulating layer between the first conductor and the noise suppression layer a layer made of polyimide, using the first conductor as a mask, the insulating layer and the noise suppression layer are wet etched using an alkaline etching solution. Can be removed at the same time.

  As a method for producing the wiring member (1) having an insulating layer made of polyimide, for example, a method of depositing a metal such as copper on a polyimide film to form a metal thin film; polyimide as a solvent on a metal foil such as copper foil The method of apply | coating and dissolving the dissolved solution; The method of bonding a polyimide fill and metal foil with a polyimide-type adhesive agent etc. are mentioned.

Examples are shown below.
(Average thickness of single layer)
Measurement was performed using a scanning probe microscope (Nanopics 2000) manufactured by Seiko Instruments Inc.
(Average particle size of single layer cluster)
The surface of the single layer was observed and measured using a scanning electron microscope JSM-6700F manufactured by JEOL.
(Average thickness of composite layer)
The cross section of the composite layer was observed and measured using a transmission electron microscope H9000NAR manufactured by Hitachi, Ltd.
(Magnetic field dependence of magnetic susceptibility)
Measurement was performed using a superconducting quantum interferometer PPMS manufactured by Quantum Design.

Example 1
A multilayer printed circuit board 30 having the layer configuration shown in FIG. 19 was manufactured as follows.
A wiring member (1) was prepared in which a copper foil having a thickness of 18 μm and serving as an upper signal transmission layer 31 and a ground layer 32 was provided on both surfaces of a prepreg of a glass epoxy resin having a thickness of 100 μm serving as the insulating layer 13.
Subsequently, the pattern of the ground layer 32 was formed on the copper foil on one side of the wiring member (1) by a normal wet etching method.

An epoxy resin to be the insulating layer 13 was applied to a copper foil having a thickness of 12 μm serving as the power supply layer 33 so as to have a thickness of 5 μm and cured. On the insulating layer 13, a deposition mass (in terms of film thickness) of 20 nm is formed by the facing target type magnetron sputtering method under the conditions of an argon gas flow rate of 60 sccm, a nitrogen gas flow rate of 20 sccm, a pressure of 7.5 × 10 ⁻¹ Pa, and a power of 2 kW. Nickel metal was physically vapor-deposited to form a single layer (noise suppression layer 12) having a plurality of independent clusters and defects having no clusters, and a wiring member (2) was produced. The average thickness of the noise suppression layer 12 was 22 nm, and the cluster average particle size was 29 nm. It was confirmed by measuring the magnetic field dependence of the magnetic susceptibility using a superconducting quantum interferometer that the noise suppression layer 12 exhibits paramagnetism.

Of the noise suppression layer 12 of the wiring member (2), the noise suppression layer in the portion where the via hole is formed was eliminated with a carbon dioxide gas laser processing machine with a diameter 1 mm larger than the via diameter, and anti-via processing was performed. The area of the noise suppression layer 12 facing the power supply layer 33 was 74% of the area of the power supply layer 33. Further, the area of the noise suppression layer 12 facing the ground layer 32 was 78% of the area of the ground layer 32.
Next, the wiring member (1) and the wiring member (2) were laminated via a prepreg of a glass epoxy resin having a thickness of 100 μm to be the insulating layer 13 so that the noise suppression layer 12 and the ground layer 32 were inside. .
Next, the pattern of the power supply layer 33 was formed by a normal wet etching method.

Next, an 18 μm copper foil serving as the lower signal transmission layer 31 was laminated on the power supply layer 33 side via a prepreg of a 100 μm thick glass epoxy resin serving as the insulating layer 13.
Next, the wiring pattern of the upper and lower signal transmission layers 31 was formed by a normal wet etching method, and via holes 34 and 35 were formed by drilling and plating of via holes to obtain a multilayer printed circuit board 30 of 145 mm × 100 mm. In the multilayer printed circuit board 30, the noise suppression structure of the present invention is formed by the ground layer 32, the noise suppression layer 12, and the power supply layer 33.

  A noise generating FPGA (Field Programmable Gate Array) was mounted on the upper signal transmission layer 31, the FPGA power supply was connected to the power supply layer 33, and the FPGA ground was connected to the ground layer 32. The FPGA is a semiconductor element that simultaneously switches 6000 flip-flop circuits at a clock frequency of 120 MHz. Forty FPGA bypass capacitors were mounted in the main part of the FPGA power line and ground line so that the FPGA could be driven.

(Example 2)
A multilayer printed circuit board 30 having the layer configuration shown in FIG. 20 was manufactured as follows.
An epoxy resin to be the insulating layer 13 was applied to a copper foil having a thickness of 18 μm serving as the ground layer 32 so as to have a thickness of 10 μm and cured. On the epoxy resin, tungsten metal having a deposition mass (in terms of film thickness) of 8 nm is physically deposited by magnetron sputtering under the conditions of an argon gas flow rate of 50 sccm, a pressure of 7.1 × 10 ⁻¹ Pa, and a power of 1.8 kW. I let you. Next, a polyolefin thin film was formed by plasma polymerization of methane gas under conditions of methane gas flow rate of 1 sccm and argon gas flow rate of 0.2 sccm. This operation was repeated 30 times to form a composite layer (noise suppression layer 12) in which a plurality of independent clusters and a polyolefin thin film were mixed, and a wiring member (2) shown in FIG. The total deposition mass (in terms of film thickness) was 240 nm, the average thickness was 300 nm, and the cluster average particle size was 38 nm. It was confirmed by measuring the magnetic field dependence of the magnetic susceptibility using a superconducting quantum interferometer that the noise suppression layer 12 exhibits paramagnetism.

As shown in FIG. 22B, a 18 μm-thick copper foil serving as the power supply layer 33 is formed on the noise suppression layer 12 side of the wiring member (2), and a 500 μm-thick glass epoxy resin prepreg serving as the insulating layer 13. Laminated.
Next, as shown in FIG. 22C, the pattern of the ground layer 32 and the pattern of the power supply layer 33 were formed by a normal wet etching method.

Next, as shown in FIG. 22D, using the ground layer 32 as a mask, the insulating layer 13 between the ground layer 32 and the noise suppression layer 12 is plasma-etched using an oxygen gas of 100 sccm and tetrafluoride. While flowing carbon gas at 50 sccm, high frequency power of 13.56 MHz was supplied at 500 W and removed by dry etching.
Next, as shown in FIG. 22 (e), using the ground layer 32 as a mask, the noise suppression layer 12 is removed by wet etching using a 15% by mass sodium hydroxide aqueous solution at room temperature to form a via hole and Other insulating pattern portions were formed. The area of the noise suppression layer 12 facing the ground layer 32 was 78% of the area of the ground layer 32. Further, the area of the noise suppression layer 12 facing the power supply layer 33 was 74% of the area of the power supply layer 33.

Next, as shown in FIG. 23 (f), an 18 μm copper foil to be the upper and lower signal transmission layers 31 is applied to the ground layer 32 and the power source layer 33, and a 500 μm thick glass epoxy resin prepreg to be the insulating layer 13. Laminated.
Next, as shown in FIG. 23 (g), the wiring pattern of the upper and lower signal transmission layers 31 is formed by a normal wet etching method, and the via hole drilling shown in FIG. 23 (h) and the plating shown in FIG. 23 (i) are performed. Via holes 34 and 35 and the like were formed by processing to obtain a multilayer printed circuit board 30 of 145 mm × 100 mm. In the multilayer printed circuit board 30, the noise suppression structure of the present invention is formed by the ground layer 32, the noise suppression layer 12, and the power supply layer 33. In the same manner as in Example 1, an FPGA and a bypass capacitor were mounted.

(Example 3)
A multilayer printed circuit board 30 having the layer configuration shown in FIG. 21 was manufactured as follows.
A polyimide solution was applied to each of two copper foils having a thickness of 18 μm to be the ground layer 32 or the power supply layer 33 and cured so as to have a thickness of 15 μm. Thus, the insulating layer 13 was obtained. The insulating layer 13 made of polyimide is a layer formed by drying a varnish made of a reaction product of benzophenonetetracarboxylic dianhydride and diaminodiphenyl ether.

Next, a deposition mass (in terms of film thickness) of 5 nm is formed on the insulating layer 13 by a magnetron sputtering method under the conditions of an argon gas flow rate of 50 sccm, a nitrogen gas flow rate of 20 sccm, a pressure of 7.1 × 10 ⁻¹ Pa, and a power of 1.2 kW. Nickel metal was physically vapor-deposited to form a single layer (noise suppression layer 12) having a plurality of independent clusters and portions where no clusters exist, and a wiring member (2) shown in FIG. . The average thickness of the noise suppression layer 12 was 5 nm, and the cluster average particle size was 5 nm. It was confirmed by measuring the magnetic field dependence of the magnetic susceptibility using a superconducting quantum interferometer that the noise suppression layer 12 exhibits paramagnetism.

As shown in FIG. 24 (b), two wiring members (2) were laminated via a prepreg of a glass epoxy resin having a thickness of 75 μm to be the insulating layer 13 so that the noise suppression layer 12 was inside. .
Next, as shown in FIG. 24C, the pattern of the ground layer 32 and the pattern of the power supply layer 33 were formed by a normal wet etching method.

  Next, as shown in FIG. 24D, the ground layer 32 is used as a mask, the insulating layer 13 between the ground layer 32 and the noise suppression layer 12 is used, and the power supply layer 33 is used as a mask. The insulating layer 13 between the suppression layer 12 was removed by wet etching using a mixed aqueous solution (40 ° C.) of potassium hydroxide (14 mass%) and monoethanolamine (70 mass%). Subsequently, as shown in FIG. 24 (e), the noise suppression layer 12 was removed by wet etching using the same aqueous solution under the same conditions to form a portion for forming a via hole and other insulating pattern portions. The area of each noise suppression layer 12 facing the power supply layer 33 and the ground layer 32 was 42% and 57%, respectively.

Next, as shown in FIG. 25 (f), an 18 μm copper foil to be the upper and lower signal transmission layers 31 is applied to the ground layer 32 and the power supply layer 33, and a 75 μm thick glass epoxy resin prepreg to be the insulating layer 13. Laminated.
Next, as shown in FIG. 25 (g), the wiring pattern of the upper and lower signal transmission layers 31 is formed by a normal wet etching method, and the via hole drilling shown in FIG. 25 (h) and the plating shown in FIG. 25 (i) are performed. Via holes 34 and 35 and the like were formed by processing to obtain a multilayer printed circuit board 30 of 145 mm × 100 mm. In the multilayer printed circuit board 30, the noise suppression structure of the present invention is formed by the ground layer 32, the noise suppression layer 12, and the power supply layer 33. In the same manner as in Example 1, an FPGA and a bypass capacitor were mounted.

(Example 4)
Except for changing the deposition mass (in terms of film thickness) to 27 nm, nickel metal is physically vapor-deposited on the insulating layer 13 in the same manner as in Example 1 and has a plurality of independent clusters and portions where no clusters exist. A layer (noise suppression layer 12) was formed to produce a wiring member (2). The average thickness of the noise suppression layer 12 was 30 nm, and the cluster average particle size was 25 nm.
Further, the area of the noise suppression layer 12 that faces the power supply layer 33 is 10% of the area of the power supply layer 33, and the area of the noise suppression layer 12 that faces the ground layer 32 is the area of the ground layer 32. A multilayer printed circuit board 30 having the layer configuration shown in FIG. 19 was manufactured in the same manner as in Example 1 except that the content was changed to 10%. Further, an FPGA and a bypass capacitor were mounted in the same manner as in Example 1.

(Comparative Examples 1-4)
A comparative multilayer printed circuit board was manufactured in the same manner as in Examples 1 to 4, except that the noise suppression layer 12 was not provided and an insulating pattern such as an anti-via around the noise suppression layer 12 was not formed. Further, an FPGA and a bypass capacitor were mounted in the same manner as in Example 1.

(Comparative Example 5)
A comparative multilayer printed circuit board was produced in the same manner as in Example 3 except that the average thickness of the noise suppression layer 12 was 1 nm. Further, an FPGA and a bypass capacitor were mounted in the same manner as in Example 1.

(Comparative Example 6)
A comparative multilayer printed circuit board is manufactured in the same manner as in Example 2 except that the physical vapor deposition of tungsten metal and the plasma polymerization of methane gas are repeated 50 times, and the average thickness of the noise suppression layer 12 is 500 nm. did. Further, an FPGA and a bypass capacitor were mounted in the same manner as in Example 1.
Examples 1 to 4 and Comparative Examples 1 to 6 are summarized in Table 1.

( Reference Example 1 )
A multilayer printed circuit board 30 having the layer configuration shown in FIG. 20 was produced as follows.
A polyimide solution was applied to a copper foil having a thickness of 18 μm to be the ground layer 32 so as to have a thickness of 3 μm, and cured to obtain an insulating layer 13. The insulating layer 13 made of polyimide is a layer formed by drying a varnish made of a reaction product of benzophenonetetracarboxylic dianhydride and diaminodiphenyl ether.

Next, an iron metal having a deposition mass (in terms of film thickness) of 25 nm is physically deposited on the insulating layer 13 by ion implantation under the conditions of an argon gas flow rate of 50 sccm, a pressure of 5.2 × 10 ⁻¹ Pa, and a power of 2.2 kW. To form a composite layer (noise suppression layer 12) in which a plurality of independent clusters and polyimide are mixed to produce a wiring member (2) shown in FIG. The average thickness of the noise suppression layer 12 was 260 nm. It was confirmed by measuring the magnetic field dependence of the magnetic susceptibility using a superconducting quantum interferometer that the noise suppression layer 12 exhibits paramagnetism.

As shown in FIG. 22A, a prepreg of a glass epoxy resin having a thickness of 18 μm serving as the power supply layer 33 and a glass epoxy resin having a thickness of 200 μm serving as the insulating layer 13 is provided on the noise suppression layer 12 side of the wiring member 2. Laminated.
Next, as shown in FIG. 22C, the pattern of the ground layer 32 and the pattern of the power supply layer 33 were formed by a normal wet etching method.

  Next, as shown in FIG. 22D, using the ground layer 32 as a mask, the insulating layer 13 between the ground layer 32 and the noise suppression layer 12 is made of potassium hydroxide (14 mass%) and monoethanolamine (70 It was removed by a wet etching method using a mixed aqueous solution (40 ° C.). Subsequently, as shown in FIG. 22 (e), the noise suppression layer 12 was removed by wet etching under the same conditions using the same aqueous solution to form a portion for forming a via hole and other insulating pattern portions. The area of each noise suppression layer 12 facing the power supply layer 33 and the ground layer 32 was 35% and 44%, respectively.

Next, as shown in FIG. 23 (f), an 18 μm copper foil to be the upper and lower signal transmission layers 31 is applied to the ground layer 32 and the power supply layer 33, and a 200 μm thick glass epoxy resin prepreg to be the insulating layer 13. Laminated.
Next, as shown in FIG. 23 (g), the wiring pattern of the upper and lower signal transmission layers 31 is formed by a normal wet etching method, and the via hole drilling shown in FIG. 23 (h) and the plating shown in FIG. 23 (i) are performed. Via holes 34 and 35 and the like were formed by processing to obtain a multilayer printed circuit board 30 of 85 mm × 100 mm. In the multilayer printed circuit board 30, the noise suppression structure of the present invention is formed by the ground layer 32, the noise suppression layer 12, and the power supply layer 33. In the same manner as in Example 1, an FPGA and a bypass capacitor were mounted.

( Reference Example 2 )
A multilayer printed circuit board 30 was manufactured in the same manner as in Reference Example 1 except that the thickness of the insulating layer 13 made of polyimide was 25 μm. Further, an FPGA and a bypass capacitor were mounted in the same manner as in Example 1.

( Reference Example 3 )
A multilayer printed circuit board 30 was manufactured in the same manner as in Reference Example 2 except that the thickness of the insulating layer 13 made of polyimide was 1 μm. Further, an FPGA and a bypass capacitor were mounted in the same manner as in Example 1.

( Reference Example 4 )
A multilayer printed circuit board 30 was manufactured in the same manner as in Reference Example 2 , except that the thickness of the insulating layer 13 made of polyimide was 50 μm. Further, an FPGA and a bypass capacitor were mounted in the same manner as in Example 1.
Reference Examples 1 to 4 are summarized in Table 2.

(Evaluation 1)
Using a high-frequency probe (manufactured by Agilent, 85024A), the level of simultaneous switching noise in the power supply layer 33 was measured from 500 MHz to 1900 MHz to obtain spectrum data. The spectrum data of Example 1 is shown in FIG. 26, and the spectrum data of Comparative Example 1 is shown in FIG. Spike noise appeared at 600, 720, 840, 960, 1080, 1200, 1320, 1440, 1560, 1680, and 1800 MHz, which are harmonics of the clock frequency of the FPGA. In Examples 1 to 4 and Comparative Examples 1 to 6, voltage levels at the above frequencies were compared.

In Example 1, compared with Comparative Example 1, the noise was suppressed by about 12.6 dB on average, and the suppression was 23.3 dB at 960 MHz.
In Example 2, compared with Comparative Example 2, the noise was suppressed by about 10.8 dB on average, and 21.2 dB was suppressed at 960 MHz.
In Example 3, compared with Comparative Example 3, the noise was suppressed by about 13.4 dB on average, and the suppression was 20.6 dB at 960 MHz.
In Example 4, noise was suppressed by an average of 9.7 dB compared to Comparative Example 4, and 13.4 dB was suppressed at 960 MHz.
In Comparative Example 5, compared with Comparative Example 3, the noise was suppressed only by an average of about 0.1 dB, and the noise suppressing effect was not recognized.
In Comparative Example 6, compared with Comparative Example 2, the noise was suppressed only by an average of about 2.1 dB, and the noise suppressing effect was not recognized.

(Evaluation 2)
In a six-sided anechoic chamber, the intensity levels of the horizontal and vertical polarizations of noise radiated from the multilayer printed circuit board were measured. From 30 MHz to 1000 MHz was measured by the 3 m method (log periodic antenna), and from 1000 MHz to 2000 MHz was measured by the 1.5 m method (horn antenna), spectrum data of radiation noise caused by simultaneous switching noise in the power supply layer 33 was obtained.
28 and 29 show horizontal polarization spectrum data of Reference Example 1 , and FIGS. 30 and 31 show horizontal polarization spectrum data of Reference Example 3 , respectively. 32 and 33 show vertical polarization spectrum data of Reference Example 1 , and FIGS. 34 and 35 show vertical polarization spectrum data of Reference Example 3 , respectively.

Spike noise mainly appeared at 480, 1080, 1320, 1440, and 1920 MHz, which are harmonics of the clock frequency of the FPGA. In Reference Examples 1 to 4 , the noise levels at the above frequencies were compared.
In Reference Example 1 , compared with Reference Example 3 , the average noise was suppressed by about 4 to 7 dB. In Reference Example 3 , a short circuit through the noise suppression layer was confirmed.
In Reference Example 2 , the average noise was suppressed by 3 to 4 dB compared to Reference Example 4 . In Reference Example 4 , compared to Reference Example 2, it took 2.3 times longer to remove the insulating layer made of polyimide and the noise suppression layer.

  According to the noise suppression structure of the present invention, it is possible to take high-quality EMC countermeasures for an electronic device or the like while maintaining high performance, size reduction, and weight reduction of the electronic device or the like.

It is a schematic sectional drawing which shows an example of the noise suppression structure of this invention. It is a schematic sectional drawing which shows the other example of the noise suppression structure of this invention. It is a schematic sectional drawing which shows the other example of the noise suppression structure of this invention. It is a graph which shows the result of having measured the magnetic field dependence of the magnetic susceptibility about a noise suppression layer. It is the high-resolution scanning electron microscope image which looked at the single layer from the upper surface. It is a schematic diagram of the single layer of FIG. It is the high-resolution scanning electron microscope image which looked at the other single layer from the upper surface. It is a schematic diagram of the single layer of FIG. FIG. 6 is a high-resolution transmission electron microscope image of a cross section of a single layer in FIG. 5. FIG. 6 is an electron diffraction image of a single layer in FIG. 5. It is a high-resolution transmission electron microscope image of the cross section of a composite layer. It is a schematic diagram of the composite layer of FIG. It is a high-resolution transmission electron microscope image for demonstrating the measuring method of the thickness of a composite layer. It is a schematic block diagram which shows an example of the measuring apparatus of a noise suppression effect. It is a graph which shows the change of the loss power ratio of the noise suppression layer in 1 GHz with respect to the dimension of the L direction of the sample in FIG. It is a graph which shows the change of the loss power ratio of the noise suppression layer in 1 GHz with respect to the dimension of the W direction of the sample in FIG. It is a schematic sectional drawing which shows the other example of a noise suppression layer. It is a graph which shows the change of the loss power ratio of the noise suppression layer in 1 GHz with respect to the distance from a microstrip line to a noise suppression layer. It is a schematic sectional drawing which shows an example of the multilayer printed circuit board of this invention. It is a schematic sectional drawing which shows the other example of the multilayer printed circuit board of this invention. It is a schematic sectional drawing which shows the other example of the multilayer printed circuit board of this invention. It is a schematic sectional drawing explaining each process in the manufacturing method of the multilayer printed circuit board of this invention. It is a schematic sectional drawing explaining each process in the manufacturing method of the multilayer printed circuit board of this invention. It is a schematic sectional drawing explaining each process in the manufacturing method of the multilayer printed circuit board of this invention. It is a schematic sectional drawing explaining each process in the manufacturing method of the multilayer printed circuit board of this invention. 6 is spectrum data showing the level of simultaneous switching noise in the power supply layer of the multilayer printed circuit board of Example 1. FIG. 12 is spectrum data showing the level of simultaneous switching noise in the power supply layer of the multilayer printed circuit board of Comparative Example 6. It is spectrum data which shows the intensity level of the noise of the horizontal polarization in the reference example 1 . It is spectrum data which shows the intensity level of the noise of the horizontal polarization in the reference example 1 . It is spectrum data which shows the intensity level of the noise of the horizontal polarization in the reference example 3 . It is spectrum data which shows the intensity level of the noise of the horizontal polarization in the reference example 3 . It is spectrum data which shows the intensity level of the noise of the vertically polarized wave in the reference example 1 . It is spectrum data which shows the intensity level of the noise of the vertically polarized wave in the reference example 1 . It is spectrum data which shows the intensity level of the noise of the vertically polarized wave in the reference example 3 . It is spectrum data which shows the intensity level of the noise of the vertically polarized wave in the reference example 3 .

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Noise suppression structure 11 1st conductor 12 Noise suppression layer 13 Insulating layer 14 2nd conductor 15 Cluster 30 Multilayer printed circuit board 31 Signal transmission layer 32 Ground layer 33 Power supply layer 34 Via hole 35 Via hole

Claims (10)

A first conductor;
A noise suppression layer electromagnetically coupled to the first conductor via an insulating layer;
A second conductor facing the noise suppression layer via an insulating layer,
The noise suppression layer comprises a noise suppression structure, which is a layer having a thickness of 5 to 300 nm formed by physically depositing a metal material on an insulating layer in an atmosphere containing a reactive gas ,
Either one of the first conductor and the second conductor is a power supply layer, and the other is a ground layer,
Furthermore, it has a signal transmission layer,
A multilayer printed circuit board in which a power supply layer or a ground layer exists between a signal transmission layer and a noise suppression layer . The noise suppression layer and the first conductor are disposed so as to face each other, and the surface area of the noise suppression layer on the side facing the first conductor is the surface area of the first conductor on the side facing the noise suppression layer. 10% or more of
The multilayer printed circuit board according to claim 1, wherein a surface area of the noise suppression layer on the side facing the second conductor is 10% or more of a surface area of the second conductor on the side facing the noise suppression layer.   The multilayer printed circuit board according to claim 1 or 2, wherein the noise suppression layer is a layer composed of a plurality of independent clusters and a defect in which no cluster exists.   The multilayer printed circuit board according to claim 1 or 2, wherein the noise suppression layer is a layer in which a plurality of independent clusters and a part of the insulating layer are mixed.   The multilayer printed circuit board according to claim 1, wherein the metal material is nickel or a nickel alloy.   The multilayer printed circuit board according to claim 1, wherein the reactive gas is nitrogen gas.   The multilayer printed circuit board in any one of Claims 1-6 whose insulating layer between a 1st conductor and a noise suppression layer is a layer which consists of polyimides.   The multilayer printed circuit board in any one of Claims 1-7 whose thickness of the insulating layer between a 1st conductor and a noise suppression layer is 3-25 micrometers. In addition, it has through holes or via holes,
And a through hole or via hole and the noise suppressing layer is electrically connected, a multilayer printed circuit board according to any one of claims 1-8. Removing a part of the first conductor of the multilayer printed circuit board according to any one of claims 1 to 9 by etching;
And a step of leaving the insulating layer and the noise suppression layer between the first conductor and the noise suppression layer, and removing the other by etching, using the first conductor as a mask.

Images