JP4916803B2 - Multilayer printed circuit board - Google Patents

Description

  The present invention relates to a noise suppression structure and a multilayer printed circuit board.

  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, and intelligent road information systems 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 and a multilayer printed circuit board which can suppress the generation of conduction noise and radiation noise and can be thinned.

The multilayer printed circuit board according to the present invention includes a first conductor layer, a second conductor layer, a noise suppression layer provided between the first conductor layer and the second conductor layer, and a first conductor. A first insulating layer provided between the layer and the noise suppression layer, and a second insulating layer provided between the second conductor layer and the noise suppression layer, the noise suppression layer comprising: A region (I) which is a layer having a thickness of 5 to 300 nm containing a metal material or conductive ceramics which is electromagnetically coupled to the first conductor layer and in which the noise suppression layer and the first conductor layer are opposed to each other. And a region (II) in which the noise suppression layer and the first conductor layer are not opposed to each other, and the noise suppression layer and the second conductor layer are opposed to each other. A multilayer printed circuit board comprising (I) and a region (II) adjacent noise suppression structures,
Either 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. Between the signal transmission layer and the noise suppression layer, the power supply layer or A ground layer is present .

The area of the noise suppression layer is preferably substantially the same as the area of the second conductor layer.
The noise suppression structure in the present invention has a region (I) in the peripheral portion of the first conductor layer, is a region where the first conductor layer exists, and includes the first conductor layer, the noise suppression layer, It is preferable to have a region (III) that is a region that does not face each other.
The first conductor layer may be divided into a plurality of parts.
The thickness of the first insulating layer is preferably 0.05 to 25 μm.
The relative dielectric constant of the first insulating layer is preferably 2 or more.
The noise suppression layer preferably has a defect in which a metal material or conductive ceramic does not exist.

The average width of the region (I) obtained from the following formula (1) is preferably 0.1 mm or more.
Average width [mm] of area (I) = area [mm ² ] of area (I) / length of boundary line [mm] of area (I) and area (II) (1).
As for the average width | variety of area | region (II) calculated | required from following formula (2), 1-50 mm is preferable.
Average width [mm] of region (II) = area [mm ² ] of region (II) / length of boundary line [mm] (2) between region (I) and region (II).

In the multilayer printed circuit board of the present invention, it is preferable that the noise suppression structure functions also as a capacitive laminate.

  The noise suppression structure and multilayer printed circuit board of the present invention can suppress the generation of conduction noise and radiation noise and can be thinned.

<Noise suppression structure>
FIG. 1 is a cross-sectional view showing an example of the noise suppression structure of the present invention, and FIG. 2 is a top view. The noise suppression structure 10 includes a first conductor layer 11, a second conductor layer 12, a noise suppression layer 13 provided between the first conductor layer 11 and the second conductor layer 12, A first insulating layer 14 provided between the first conductor layer 11 and the noise suppressing layer 13, and a second insulating layer 15 provided between the second conductor layer 12 and the noise suppressing layer 13. Have

  In the noise suppression structure 10, the noise suppression layer 13 is electromagnetically coupled to the first conductor layer 11. The electromagnetic coupling is a phenomenon in which a voltage is induced by a magnetic flux generated by a current flowing through the first conductor layer 11 interlinking with the noise suppression layer 13. In the present invention, it is necessary that the noise suppression layer 13 is not electrically connected to the first conductor layer 11 but is electromagnetically coupled through the first insulating layer 14. In the noise suppression structure 10, the noise suppression layer 13 is preferably electromagnetically coupled to the second conductor layer 12.

  In the noise suppression structure 10, the region (I), which is a region where the noise suppression layer 13 and the first conductor layer 11 are opposed, and the noise suppression layer 13 and the first conductor layer 11 are opposed. A region (II) that is a region that is not formed and the noise suppression layer 13 and the second conductor layer 12 face each other, and the region (I) and the region (II) are adjacent to each other. Yes.

The noise suppression structure 10 exhibits the noise suppression effect by having the region (I) and the region (II) adjacent to each other. The reason is considered as follows.
The noise suppression layer 13 has a fine conductive path such as a microcluster described later. In the region (II), the conductive path has a plurality of fine and complicated open stub structures arranged on the second conductor layer 12. The open stub structure is considered to function as a transmission line filter by electromagnetically coupling with the first conductor layer 11 in the adjacent region (I).

  Therefore, in the region (II), it is necessary that the noise suppression layer 13 and the first conductor layer 11 do not face each other, and that the noise suppression layer 13 and the second conductor layer 12 face each other, In the region (I), the noise suppression layer 13 and the first conductor layer 11 face each other, and the noise suppression layer 13 needs to be electromagnetically coupled to the first conductor layer 11.

In the region (I), in order for the noise suppression layer 13 to be sufficiently electromagnetically coupled to the first conductor layer 11, the average width of the region (I) obtained from the following formula (1) is preferably 0.1 mm or more. .
Average width [mm] of area (I) = area [mm ² ] of area (I) / length of boundary line [mm] of area (I) and area (II) (1).
The upper limit of the average width of the region (I) depends on the size of the first conductor layer 11 and is an arbitrary value.

  When the noise suppression layer 13 and the second conductor layer 12 are present on the entire surface of the noise suppression structure 10, the length of the boundary line between the region (I) and the region (II) is as shown in FIG. The boundary line between the region (I) where the first conductor layer 11 is present and the region (II) where the first insulating layer 14 is exposed on the surface where the first conductor layer 11 is not present (indicated by the bold line 16 in the figure) ).

Further, the average width of the region (II) obtained from the following formula (2) is preferably 1 to 50 mm.
Average width [mm] of region (II) = area [mm ² ] of region (II) / length of boundary line [mm] (2) between region (I) and region (II).
If the average width of the region (II) is 1 mm or more, a sufficient noise suppression effect can be obtained. Moreover, the noise suppression effect in the low frequency of 100 MHz or less is exhibited. Even if the average width of the region (II) exceeds 50 mm, the area of the region (II) increases too much for the noise suppression effect, and the noise suppression structure 10 becomes larger than necessary, resulting in a high density. Affects implementation. In addition, the impedance of the first conductor layer 11 may increase.

  Even if only the noise suppression layer 13 or only the second conductor layer 12 is wide, the area of the region (II) cannot be sufficiently secured, and the noise suppression effect is small. In order to ensure a sufficient area of the region (II), it is preferable that both the noise suppression layer 13 and the second conductor layer 12 have a maximum area in the noise suppression structure 10. In order to sufficiently secure the area of the region (II), the area of the noise suppression layer 13 is substantially the same as the area of the second conductor layer 12 (80 to 80 of the area of the second conductor layer 12). 100%).

  The noise suppression structure 10 of FIG. 4 has a region (I) at the peripheral edge of the first conductor layer 11, is a region where the first conductor layer 11 exists, and the first conductor layer 11 It is an example which has area | region (III) which is an area | region which the noise suppression layer 13 does not oppose. Since the high-frequency current flowing through the first conductor layer 11 is concentrated at the peripheral edge due to the edge effect, the noise suppression layer 13 can be electromagnetically coupled efficiently at the peripheral edge of the first conductor layer 11. If the region (III) is provided, it is easy to form a through hole or a via hole insulated from the noise suppression layer 13. Further, the area of the region (I), that is, the noise suppression effect is not affected by the through hole or the via hole.

  The noise suppression structure 10 in FIG. 5 is an example in which the first conductor layer 11 is divided into two parts to become the first conductor layer 11a and the first conductor layer 11b. Thus, if the first conductor layer 11 is divided, even if the region (II) is narrow, the region of the first conductor layer 11b is defined as the region (II) in the first conductor layer 11a. Even when the region (II) is restricted, a sufficient noise suppression effect can be obtained. Similarly, in the first conductor layer 11b, the region of the first conductor layer 11a can be regarded as the region (II). The division of the first conductor layer 11 is performed due to a difference between a digital circuit and an analog circuit, a difference in frequency, a difference in voltage, a difference in function, and the like.

(Conductor layer)
Examples of each conductor layer include a metal foil; a conductive particle dispersion film in which metal particles are dispersed in a polymer binder, a glassy binder, or the like. Examples of the metal include copper, silver, gold, aluminum, nickel, and tungsten.
In the multilayer printed circuit board, each conductor layer is a layer serving as a signal transmission layer, a power supply layer, or a ground layer, and is usually a copper foil. The thickness of the copper foil is usually 3 to 35 μm. The copper foil may be subjected to a surface roughening treatment or a chemical conversion treatment with a silane coupling agent or the like in order to improve the adhesion with the insulating layer.

(Noise suppression layer)
The noise suppression layer 13 is a thin film having a thickness of 5 to 300 nm containing a metal material or conductive ceramics.
If the thickness of the noise suppression layer 13 is 5 nm or more, a sufficient noise suppression effect can be obtained. If the thickness of the noise suppression layer 13 is 300 nm or less, a micro cluster described later will not grow and a homogeneous thin film made of a metal material or the like will not be formed. When a homogeneous thin film is formed, the surface resistance is reduced, the metal reflection is increased, and the noise suppression effect is also reduced.
The thickness of the noise suppression layer 13 is determined based on the high-resolution transmission electron microscope image (for example, FIG. 8) of the cross section in the film thickness direction of the noise suppression layer. Thickness is determined by measuring on an electron microscope image and averaging.

The surface resistance of the noise suppression layer 13 is preferably 1 × 10 ⁰ to 1 × 10 ⁴ Ω. In the case where the noise suppression layer 13 is a homogeneous thin film, a limited material having a high volume resistivity is required. However, when the volume resistivity of the material is not so high, a metal material or conductive ceramic is formed on the noise suppression layer 13. The surface resistance can be increased by providing a physical defect that does not exist to form a heterogeneous thin film or a chain of microclusters described later. The surface resistance of the noise suppression layer 13 is measured as follows.
Using two thin film metal electrodes (length 10 mm, width 5 mm, distance 10 mm between electrodes) formed by depositing gold or the like on quartz glass, the object to be measured is placed on the electrodes, and the object to be measured is placed on the object to be measured. The size 10 mm × 20 mm is pressed with a load of 50 g, and the resistance between the electrodes is measured with a measurement current of 1 mA or less. This value is used as the surface resistance.

  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.

  Examples of the conductive ceramic include an alloy, an intermetallic compound, a solid solution, and the like including a metal and one or more elements selected from the group consisting of boron, carbon, nitrogen, silicon, phosphorus, and sulfur. Specifically, nickel nitride, titanium nitride, tantalum nitride, chromium nitride, zirconium nitride, titanium carbide, silicon carbide, chromium carbide, vanadium carbide, zirconium carbide, molybdenum carbide, tungsten carbide, chromium boride, molybdenum boride, silicidation Examples thereof include chromium and zirconium silicide.

  Since the conductive ceramic has a higher volume resistance than the metal, the noise suppression layer including the conductive ceramic does not excessively reduce the characteristic impedance. Therefore, metal reflection in the noise suppression layer is reduced. In addition, since conductive ceramics do not have a specific resonance frequency, the frequency at which the noise suppression effect is exerted is widened. Furthermore, it has advantages such as high chemical stability and high storage stability. As the conductive ceramic, a nitride or carbide that is easily obtained by using a reactive gas such as nitrogen gas or methane gas in the physical vapor deposition method described later is particularly preferable.

  Examples of a method for forming the noise suppression layer 13 include a normal wet plating method, a physical vapor deposition method, and a chemical vapor deposition method. In these methods, although it depends on the conditions and materials used, it is possible to form a heterogeneous thin film having fine physical defects by not growing a thin film by terminating the growth of the thin film at an early stage. . Alternatively, an inhomogeneous thin film can also be formed by a method of forming a defect by etching a homogeneous thin film with an acid or the like, or a method of forming a defect by a laser ablation.

  FIG. 6 is a field emission scanning electron microscope image obtained by observing the surface of the noise suppression layer made of a metal material formed on the surface of the insulating layer by physical vapor deposition, and FIG. 7 is a schematic diagram thereof. The noise suppression layer 13 is observed as an aggregate of a plurality of microclusters 17. The microcluster 17 is formed by physically depositing a metal material or the like on the first insulating layer 14 (or the second insulating layer 15) very thinly. There is a general defect and it is not a homogeneous thin film. Although the microclusters 17 are in contact with each other and collect to form a chain, there are many defects that do not exist in the metal material or the like between the aggregated microclusters 17.

FIG. 8 is a high-resolution transmission electron microscope image of a cross section in the film thickness direction of the noise suppression layer. From FIG. 6 and FIG. 8, a crystal lattice (microcluster) in which metal atoms spaced by several kilometers are arranged as very small crystals and defects in which a metal material or the like does not exist in a very small range are recognized. That is, the microclusters are spaced apart from each other and have not grown into a homogeneous thin film made of a metal material or the like. The state having such a physical defect is that the volume resistivity R ₁ (Ω · cm) converted from the measured value of the surface resistance of the noise suppression layer 13 and the volume resistivity R _{0 of the} metal material (or conductive ceramic). It can be confirmed from the relationship with (Ω · cm) (document value). That is, when the volume resistivity R ₁ and the volume resistivity R ₀ satisfy 0.5 ≦ logR ₁ −logR ₀ ≦ 3, an excellent noise suppression effect is exhibited.

  The noise suppression layer 13 may be patterned into a desired shape, and an anti-via such as a through hole may be formed. The noise suppression layer 13 can be processed into a desired pattern shape by a normal etching method, a laser ablation method, or the like.

(Insulating layer)
The insulating layer is a layer made of a dielectric having a surface resistance of 1 × 10 ⁶ Ω 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, aluminum nitride, silicon oxide, and silicon nitride, and foamed ceramics. When the insulating layer is a hard material such as ceramics, the microclusters are aggregated and it is easy to form a homogeneous thin film. However, by forming a thin film while keeping the mass of the metal material low, the microcluster Becomes difficult to agglomerate, resulting in a heterogeneous thin film having defects.

  Organic materials include polyolefin, polyamide, polyester, polyether, polyketone, polyimide, polyurethane, polysiloxane, polysilazane, phenolic resin, epoxy resin, acrylic resin, polyacrylate, vinyl chloride resin, chlorinated polyethylene, etc. Resins; diene rubbers such as natural rubber, isoprene rubber, butadiene rubber and styrene butadiene rubber; and 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, it has a complex surface structure at the nano level due to the morphology of the organic polymer, so that the aggregation of the microclusters is suppressed and the structure of the non-uniform microcluster aggregate is maintained. And a noise suppression layer having a large noise suppression effect can be obtained.
As an insulating layer, oxygen, nitrogen, sulfur, etc. that can be covalently bonded to metals from the point of adhesion to the cluster and the ability to stabilize the dispersion of the microcluster by inhibiting the aggregation and growth of the microcluster Those having a group containing the above element on the surface 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.

  The thickness of the first insulating layer 14 is preferably thinner than that of the second insulating layer 15 in order to make the first conductor layer 11 subject to noise suppression. Further, the thickness of the first insulating layer 14 is preferably 0.05 to 25 μm. If the thickness of the 1st insulating layer 14 is 0.05 micrometer or more, the insulation of the noise suppression layer 13 and the 1st conductor layer 11 will be ensured, and the noise suppression effect will fully be exhibited. Further, the divided first conductor layer 11 (for example, the first conductor layers 11a and 11b in FIG. 5) does not short-circuit. In addition, when the first conductor layer 11 is etched, the noise suppression layer 13 can be protected from an etching solution or the like. When the thickness of the first insulating layer 14 is 25 μm or less, the noise suppression layer 13 is sufficiently electromagnetically coupled to the first conductor layer 11. Moreover, the noise suppression structure 10 can be thinned.

The relative dielectric constant of the first insulating layer 14 is preferably 2 or more, and more preferably 2.5 or more. If the relative dielectric constant of the first insulating layer 14 is 2 or more, the dielectric constant of the first insulating layer 14 is increased, and the noise suppression layer 13 is sufficiently electromagnetically coupled to the first conductor layer 11. In currently available materials, the maximum dielectric constant is 100,000.
Further, when a material having a high dielectric constant is used for the second insulating layer 15, the noise suppression structure 10 is made of a capacitive laminate including the first conductor layer 11 and the second conductor layer 12. Can be considered. If it also has a function as a capacitive laminate, on the low frequency side such as 1 GHz or less, the same effect as the case where a conventional bypass capacitor is used together can be obtained. The noise suppression effect can be exhibited in a wide range from a low frequency to a high frequency of several tens of GHz. In order to increase the capacitance of the capacitive laminate by a method other than increasing the dielectric constant, the area of the first conductor layer 11 is increased, or the first conductor layer 11 and the second conductor layer 12 are The interval may be narrowed.

  As a method for forming the insulating layer, a normal method suitable for the material can be used. In the case of ceramics, sol-gel method, PVD method such as sputtering, CVD method and the like can be mentioned. In the case of organic materials, there are a method in which a resin solution is directly coated on a conductor layer by a spin coating method, a spray coating method, a method in which a gravure-coated insulating layer is transferred onto a conductor layer, etc. Can be mentioned.

In the noise suppression structure 10 described above, the noise suppression layer 13 is a layer having a thickness of 5 to 300 nm including a metal material or conductive ceramics that electromagnetically couples with the first conductor layer 11, and noise suppression. The region (I), which is a region where the layer 13 and the first conductor layer 11 face each other, and the region where the noise suppression layer 13 and the first conductor layer 11 do not face each other, and the noise suppression layer 13 And the second conductor layer 12 are opposed to each other, and the region (I) and the region (II) are adjacent to each other, so that an excellent noise suppression effect is exhibited.
Moreover, since the noise suppression layer 13 is very thin, the noise suppression structure 10 is not bulky, and the noise suppression structure 10 can be thinned.

  By incorporating the noise suppression structure of the present invention into an electronic component, high-frequency current flowing through the conductor layer of the electronic component that causes conduction noise can be suppressed, and as a result, radiation noise can also be suppressed. The electronic component includes a conductor used for signal transmission, a power source, a ground, and the like. As the electronic component, for example, a semiconductor element, a system in package (SIP) in which an electronic element such as the semiconductor element is mounted. Semiconductor packages, printed circuit boards, and the like. 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. It is useful to apply the present noise suppression structure to a multilayer printed circuit board.

<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 layer and the second conductor layer is a power supply layer and the other is a ground layer. Moreover, since the noise suppression layer suppresses high frequency components, there is a risk of degrading the high-speed pulse signal of the signal transmission layer. Therefore, it is preferable that a power supply layer or a ground layer exists between the signal transmission layer and the noise suppression layer.

  The thickness of the signal transmission layer, the power supply layer, and the ground layer is usually the thickness of the copper foil, and is 3 to 35 μm. The thickness of the prepreg or adhesive sheet serving as the second insulating layer is usually 3 μm to 1.6 mm. All the layers tend to be thinner due to the demand for thinner multilayer printed circuit boards.

A multilayer printed circuit board is manufactured as follows, for example.
An epoxy varnish or the like is applied onto the copper foil, dried and cured to obtain a power supply layer on which the first insulating layer is formed. A noise suppression layer is formed on the first insulating layer, and the noise suppression layer is etched to have a desired pattern shape.
Next, a prepreg made of glass fiber or the like impregnated with glass fiber or the like is laminated on the noise suppression layer, and the prepreg is cured to produce a core (noise suppression structure) having a power supply layer and a ground layer. To do.
Next, the power supply layer or the ground layer on the core is etched so as to have a desired pattern shape by photolithography or the like. Thereafter, copper foils are bonded to the outer surfaces of the power supply layer and the ground layer by prepregs to form signal transmission layers, respectively, thereby completing a four-layer printed circuit board.

  FIG. 9 is a cross-sectional view showing an example of the multilayer printed circuit board of the present invention. The multilayer printed circuit board 20 includes a signal transmission layer 21, an insulating layer 22, a ground layer 23 (second conductor layer 12), an insulating layer 24 (second insulating layer 15), a noise suppression layer 13, An insulating layer 25 (first insulating layer 14), a power source layer 26 (first conductor layer 11), an insulating layer 27, and a signal transmission layer 28 are configured. The signal transmission layer 21 and the signal transmission layer 28 are connected through a through hole 31, the power supply line 32 and the power supply layer 26 are connected through a via hole 33, and the ground line 34 and the ground layer 23 are connected to a via hole. 35 is connected. An electronic component 41 such as a semiconductor element and a bypass capacitor 42 are mounted on the power supply line 32 and the ground line 34.

  In the multilayer printed circuit board 20, since the noise suppression structure 10 is provided, a region where the noise suppression layer 13 and the power supply layer 26 (first conductor layer 11) face each other is a region (I). A region where the noise suppression layer 13 and the power supply layer 26 (first conductor layer 11) are not opposed to each other, and a region where the noise suppression layer 13 and the ground layer 23 (second conductor layer 12) are opposed to each other. Becomes region (II). Since the region (I) and the region (II) are adjacent to each other, the high-frequency current is suppressed and the potential of the power supply layer 26 is stabilized. As a result, conduction noise such as simultaneous switching noise and radiation noise due to resonance are suppressed. It is done.

Examples are shown below.
(Noise suppression layer thickness)
The cross section of the noise suppression layer was observed using a transmission electron microscope H9000NAR manufactured by Hitachi, Ltd., and the thicknesses of the five noise suppression layers were measured and averaged.

(S21 parameter measurement)
An S parameter between SMA connectors of the test piece was measured using a vector network analyzer 37247D manufactured by Anritsu Corporation.

(Voltage measurement)
The voltage of the power supply layer was measured using a spectrum analyzer R3132 with tracking generator manufactured by Advantest Corporation.

Example 1
An epoxy varnish was applied onto a copper foil (first conductor layer) having a thickness of 18 μm, dried and cured, and a first insulating layer having a thickness of 3 μm was formed. The surface resistance of the first insulating layer was 8 × 10 ¹² Ω.
Next, nickel metal was physically vapor-deposited by reactive sputtering in a nitrogen gas atmosphere on the entire surface of the first insulating layer to form a heterogeneous noise suppression layer having a thickness of 30 nm containing nickel nitride. The surface resistance of the noise suppression layer was 97Ω.

On the noise suppression layer, an epoxy prepreg having a thickness of 100 μm (second insulating layer, surface resistance 6 × 10 ¹⁴ Ω) and a copper foil having a thickness of 18 μm (second conductor layer) are laminated, and the prepreg is cured. A two-layer substrate was produced.
A test piece having a size of 74 mm × 160 mm is cut out from the two-layer substrate, and both side portions along the longitudinal direction of the copper foil of the first conductor layer of the test piece are etched to obtain a region (as shown in FIG. A noise suppression structure 10 having an average width (L) of II) of 1.5 mm was obtained.

  As shown in FIG. 11, SMA connectors 51 connected to the first conductor layer 11 and the second conductor layer 12 are mounted on both ends in the longitudinal direction of the noise suppression structure 10, and the vector network analyzer 52 is connected to the SMA connector 51. Were connected, and S parameters were measured at 400 points from a frequency of 50 MHz to 10 GHz to create a graph. A graph is shown in FIG. Further, the total of 400 measured values was obtained as a pseudo-integral value.

(Comparative Example 1)
A two-layer substrate was produced in the same manner as in Example 1 except that the noise suppression layer was not formed. A test piece was cut out from the two-layer substrate in the same manner as in Example 1, and the copper foil of the first conductor layer was etched in the same manner as in Example 1. In the same manner as in Example 1, the S parameter of the test piece was measured to prepare a graph. A graph is shown in FIG. Further, the total of 400 measured values was obtained as a pseudo-integral value. Table 1 shows the difference (absolute value) between the pseudo-integral value of Example 1 and the pseudo-integral value of Comparative Example 1. The larger the absolute value, the higher the noise suppression effect of the noise suppression structure 10 of the first embodiment.

(Example 2)
A noise suppression structure 10 was obtained in the same manner as in Example 1 except that the average width (L) of the region (II) shown in FIG. In the same manner as in Example 1, the S parameter of the noise suppression structure 10 was measured, and a graph was created. A graph is shown in FIG. Further, the total of 400 measured values was obtained as a pseudo-integral value.

(Comparative Example 2)
A two-layer substrate was produced in the same manner as in Example 1 except that the noise suppression layer was not formed. A test piece was cut out from the two-layer substrate in the same manner as in Example 1, and the copper foil of the first conductor layer was etched in the same manner as in Example 2. In the same manner as in Example 1, the S parameter of the test piece was measured to prepare a graph. A graph is shown in FIG. Further, the total of 400 measured values was obtained as a pseudo-integral value. Table 1 shows the difference (absolute value) between the pseudo-integral value of Example 2 and the pseudo-integral value of Comparative Example 2.

(Example 3)
A noise suppression structure 10 was obtained in the same manner as in Example 1 except that the average width (L) of the region (II) shown in FIG. In the same manner as in Example 1, the S parameter of the noise suppression structure 10 was measured, and a graph was created. A graph is shown in FIG. Further, the total of 400 measured values was obtained as a pseudo-integral value.

(Comparative Example 3)
A two-layer substrate was produced in the same manner as in Example 1 except that the noise suppression layer was not formed. A test piece was cut out from the two-layer substrate in the same manner as in Example 1, and the copper foil of the first conductor layer was etched in the same manner as in Example 3. In the same manner as in Example 1, the S parameter of the test piece was measured to prepare a graph. A graph is shown in FIG. Further, the total of 400 measured values was obtained as a pseudo-integral value. Table 1 shows the difference (absolute value) between the pseudo-integral value of Example 3 and the pseudo-integral value of Comparative Example 3.

(Comparative Example 4)
The copper foil of the first conductor layer of the test piece in Example 1 was not etched. About the test piece whose average width (L) of the area | region (II) shown in FIG. 10 is 0 mm, it carried out similarly to Example 1, measured the S parameter, and created the graph. A graph is shown in FIG. Further, the total of 400 measured values was obtained as a pseudo-integral value.

(Comparative Example 5)
A two-layer substrate was produced in the same manner as in Example 1 except that the noise suppression layer was not formed. A test piece was cut out from the two-layer substrate in the same manner as in Example 1. The copper foil of the first conductor layer of the test piece was not etched. In the same manner as in Example 1, the S parameter of the test piece was measured to prepare a graph. A graph is shown in FIG. Further, the total of 400 measured values was obtained as a pseudo-integral value. Table 1 shows the difference (absolute value) between the pseudo-integral value of Comparative Example 4 and the pseudo-integral value of Comparative Example 5.

  From the results of Table 1, it can be seen that the smaller the first conductor layer 11 and the larger the average width (L) of the region (II), the higher the noise suppression effect. In Comparative Example 4 where there is no region (II), no noise suppression effect is observed.

Example 4
A two-layer substrate was produced in the same manner as in Example 1 except that the thickness of the noise suppression layer was 20 nm. A test piece having a size of 100 mm × 200 mm was cut out from the two-layer substrate, and both side portions along the longitudinal direction of the copper foil of the first conductor layer of the test piece were etched to obtain a region (as shown in FIG. The noise suppression structure 10 having an average width (L) of II) of 30 mm was obtained. In addition, before laminating each layer, an anti-via for preventing contact with the through hole was previously formed in the first conductor layer, the second conductor layer, and the noise suppression layer.

The first conductor layer 11 of the noise suppression structure 10 is a power layer, and the second conductor layer 12 is a ground layer. A signal transmission layer is formed by bonding 18 μm-thick copper foil with 50 μm-thick epoxy prepreg on both outer surfaces of the power supply layer and the ground layer, respectively. As shown in FIG. 16 and FIG. Etching into a predetermined shape.
As shown in FIGS. 16 and 17, by forming a through hole 31 in the anti-via, the signal transmission layer 21 passes through the through hole 31 to the signal transmission layer 28, and again passes through the through hole 31 to the signal transmission layer 21. A signal line 60 with an impedance of 50Ω having a structure returning to the above was formed, and the multilayer printed circuit board 20 was obtained.
The input SMA connector was connected to the signal line 60 and the ground layer 23, and the output SMA connector was connected to the power supply layer 26 and the ground layer 23. Using a spectrum analyzer with a tracking generator, a signal of 50 MHz to 3 GHz was input to the signal line 60, and the voltage fluctuation of the power supply layer 26 at that time was measured. The measurement results are shown in FIG.

(Comparative Example 6)
A multilayer printed circuit board was obtained in the same manner as in Example 4 except that the average width (L) of the region (II) was 0 mm. In the same manner as in Example 4, the voltage fluctuation of the power supply layer was measured. The measurement results are shown in FIG.
When Example 4 and Comparative Example 6 were compared, when the power supply layer (first conductor layer) was small and the average width (L) of the region (II) was large, excitation of the power supply layer by the high-frequency signal could be suppressed. . In Comparative Example 6 having no region (II), no noise suppression effect was observed.

(Example 5)
As shown in the cross-sectional view of FIG. 19, a first conductor layer 11 having a width of 25 mm × a length of 60 mm × a thickness of 12 μm, a second conductor layer 12 of a width of 60 mm × a length of 60 mm × a thickness of 12 μm, and a width of 60 mm. × 60 mm long × 0.1 μm thick first insulating layer 14 (surface resistance 2 × 10 ⁹ Ω) and 60 mm wide × 60 mm long × 50 μm thick second insulating layer 15 (surface resistance 3 × 10 ¹⁴ Ω) was produced.
The noise suppression layer 13 has an average width (L) of the region (II) of 3 mm, an average width (M) of the region (III) of 0 mm, and a thickness of 15 nm. Silver was physically vapor-deposited by an electron beam (EB) vapor deposition method. The surface resistance of the noise suppression layer 13 was 55Ω.
In the same manner as in Example 1, the S parameter of the noise suppression structure 10 was measured, and a graph was created. A graph is shown in FIG. Further, the total of 400 measured values was obtained as a pseudo-integral value. Table 2 shows the difference (absolute value) between the pseudo-integral value and the pseudo-integral value when the noise suppression layer is not formed.

(Example 6)
A noise suppression structure 10 was obtained in the same manner as in Example 5 except that the noise suppression layer 13 was formed so that the average width (M) of the region (III) was 15 mm. The S parameter of the suppression structure 10 was measured and a graph was created. A graph is shown in FIG. Further, the total of 400 measured values was obtained as a pseudo-integral value. Table 2 shows the difference (absolute value) between the pseudo-integral value and the pseudo-integral value when the noise suppression layer is not formed.

(Example 7)
A noise suppression structure 10 was obtained in the same manner as in Example 5 except that the noise suppression layer 13 was formed so that the average width (M) of the region (III) was 23 mm. The S parameter of the suppression structure 10 was measured and a graph was created. A graph is shown in FIG. Further, the total of 400 measured values was obtained as a pseudo-integral value. Table 2 shows the difference (absolute value) between the pseudo-integral value and the pseudo-integral value when the noise suppression layer is not formed.

  From the results of Table 2, if there is a region (I) at least in the peripheral portion of the first conductor layer 11, the noise suppressing effect can be obtained without being affected by the size of the average width (N) of the region (I). I found it to work.

  The noise suppression structure and the multilayer printed circuit board of the present invention are useful as a semiconductor element such as an IC or LSI, a power supply layer in an electronic component, and a multilayer printed circuit board that supplies power or transmits signals to these electronic components.

It is sectional drawing which shows an example of the noise suppression structure of this invention. It is a top view of the noise suppression structure of FIG. It is a top view of the noise suppression structure for demonstrating the boundary line of area | region (I) and area | region (II). It is sectional drawing which shows the other example of the noise suppression structure of this invention. It is sectional drawing which shows the other example of the noise suppression structure of this invention. It is the field emission scanning electron microscope image which observed the surface of the noise suppression layer. It is a schematic diagram of FIG. 7 is a high-resolution transmission electron microscope image of a cross section of the noise suppression layer in FIG. 6. It is sectional drawing which shows an example of the multilayer printed circuit board of this invention. It is sectional drawing which shows the noise suppression structure in an Example. It is a block diagram which shows an S parameter measurement system. It is a graph which shows S21 (transmission attenuation amount) in Example 1 and Comparative Example 1. It is a graph which shows S21 (transmission attenuation amount) of the noise suppression structure in Example 2 and Comparative Example 2. It is a graph which shows S21 (transmission attenuation amount) in Example 3 and Comparative Example 3. It is a graph which shows S21 (transmission attenuation amount) in the comparative example 4 and the comparative example 5. FIG. It is sectional drawing which shows the multilayer printed circuit board in an Example. It is XVII-XVII sectional drawing in FIG. 6 is a graph showing voltage fluctuations in a power supply layer of Example 4 and Comparative Example 6. It is sectional drawing which shows the other example of the noise suppression structure in an Example. It is a graph which shows S21 (transmission attenuation amount) in Examples 5-7.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Noise suppression structure 11 1st conductor layer 12 2nd conductor layer 13 Noise suppression layer 14 1st insulating layer 15 2nd insulating layer 20 Multilayer printed circuit board 23 Ground layer 24 Insulating layer 25 Insulating layer 26 Power supply layer

Claims (10)

A first conductor layer;
A second conductor layer;
A noise suppression layer provided between the first conductor layer and the second conductor layer;
A first insulating layer provided between the first conductor layer and the noise suppression layer;
A second insulating layer provided between the second conductor layer and the noise suppression layer;
The noise suppression layer is a layer having a thickness of 5 to 300 nm containing a metal material or conductive ceramics that electromagnetically couples with the first conductor layer.
Region (I), which is a region where the noise suppression layer and the first conductor layer face each other, and a region where the noise suppression layer and the first conductor layer do not face each other, and the noise suppression layer and the second conductor layer and a conductive layer having a region (II) is a region facing the, and comprises a noise suppressing structure region (I) and region (II) is you adjacent to a multilayer printed circuit board ,
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 multilayer printed circuit board according to claim 1, wherein an area of the noise suppression layer is substantially the same as an area of the second conductor layer. Having a region (I) at the periphery of the first conductor layer ;
The multilayer printed circuit board according to claim 1, wherein the multilayer printed circuit board has a region (III) in which the first conductor layer is present and the first conductor layer and the noise suppression layer are not opposed to each other. The multilayer printed circuit board according to claim 1, wherein the first conductor layer is divided into a plurality of parts. The multilayer printed circuit board in any one of Claims 1-4 whose thickness of a 1st insulating layer is 0.05-25 micrometers. The multilayer printed circuit board according to claim 5, wherein the dielectric constant of the first insulating layer is 2 or more. The multilayer printed circuit board according to any one of claims 1 to 6, wherein the noise suppression layer has a defect in which a metal material or conductive ceramic does not exist. The multilayer printed circuit board in any one of Claims 1-7 whose average width | variety of area | region (I) calculated | required from following formula (1) is 0.1 mm or more.
Average width [mm] of area (I) = area [mm ² ] of area (I) / length of boundary line [mm] of area (I) and area (II) (1). The multilayer printed circuit board in any one of Claims 1-8 whose average width of area | region (II) calculated | required from following formula (2) is 1-50 mm.
Average width [mm] of region (II) = area [mm ² ] of region (II) / length of boundary line [mm] (2) between region (I) and region (II). The multilayer printed circuit board according to any one of claims 1 to 9 , wherein the noise suppression structure is a capacitive laminate.

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