JP4130883B2 - Circuit board - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a circuit board used as, for example, a high-frequency printed wiring board, and more particularly, to improve the quality of a signal propagating through a wiring with low current consumption, excellent crosstalk and radiation noise suppression function. It is related with the circuit board which can do.
[0002]
[Prior art]
Microstrip lines, strip lines, and the like that are widely used as high-frequency signal transmission lines are formed on circuit boards such as printed wiring boards, and are used in various electronic devices such as mobile phones.
[0003]
The characteristic impedance of the signal transmission line is generally 50Ω.
Further, in order to supply a sufficient signal from an active element such as LSI to the 50Ω wiring, for example, a buffer circuit is formed in the input / output unit of the LSI, and a large current is generated by the buffer circuit. This 50Ω wiring is driven.
[0004]
Since a signal transmission line formed on a circuit board such as a printed wiring board generally has a low characteristic impedance of 50Ω, it is necessary to flow a large current to propagate a signal on the transmission line. There has been a problem in that the buffer circuit becomes large and power consumption increases.
[0005]
For example, when a 1V signal is propagated through a transmission line, it is necessary to pass a current of I = V / Z = 20 mA (I: current, V: voltage, Z: characteristic impedance) according to Ohm's law. In particular, in portable devices such as mobile phones, flowing a large current has caused serious problems such as a decrease in battery life.
[0006]
As a technique for solving the above-mentioned problem, there is a technique for increasing the characteristic impedance of the transmission line and reducing the current flowing through the transmission line. However, the characteristic impedance of a normal transmission line is about 200 to 300Ω, and is sufficient. There was a problem that the effect of reducing power consumption could not be obtained.
[0007]
This will be described with reference to FIG. FIG. 16 is a characteristic diagram showing the relationship between the wiring width W and the characteristic impedance Z in the microstrip line. The relative dielectric constant εr of a dielectric having a thickness h = 100 μm existing between the wiring and the ground metal layer is a parameter. As a plot. The wiring thickness t is 10 μm.
[0008]
As shown in FIG. 16, the characteristic impedance increases as the wiring width W is reduced, but it is saturated at about 200Ω to 300Ω and does not increase. Characteristic impedance (specific impedance) Z when electromagnetic waves travel in a uniform medium is expressed by Z = √ (μ / ε) (μ: permeability, ε: dielectric constant), but it is common for resins, etc. In the case of a dielectric, the relative dielectric constant ε is about 2 to 4 and the relative magnetic permeability μ is about 1. Therefore, when the relative dielectric constant is 2, the characteristic impedance is 267Ω, and when the relative dielectric constant is 4, the characteristic impedance is 188Ω. It becomes the theoretical limit. Even if a resin having a relative dielectric constant of 1 is realized, the theoretical limit of characteristic impedance is 377Ω. Therefore, there has been a limit to simply increasing the characteristic impedance by conventional extension and reducing power consumption.
[0009]
If this is explained using a relative permittivity εr and a relative permeability μr, in a conventional dielectric that has been conventionally used, μr (about 1) <εr. It cannot be larger than the intrinsic impedance (377Ω).
[0010]
Furthermore, in order to reduce the size of the printed circuit board, the wiring formed on the above-described printed wiring board has a problem that crosstalk increases due to a decrease in the distance from the adjacent wiring.
[0011]
[Problems to be solved by the invention]
The present invention solves these problems and raises the characteristic impedance of the signal transmission line, which has conventionally been about 200 Ω, to 300 Ω or more, preferably 500 Ω or more, and improves the overall LSI system including a circuit board such as a printed wiring board. The purpose is to reduce power consumption. Furthermore, an object of the present invention is to suppress the crosstalk and radiation noise between adjacent wirings and improve the signal quality of signals propagating through the wirings.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, a circuit board according to the present invention comprises:
In a circuit board in which a conductor is embedded inside an insulator,
When the relative permittivity is εr and the relative permeability is μr, the conductor is substantially surrounded by a first insulator that satisfies μr ≧ εr (that is, the specific impedance Z is 377Ω or more). It is characterized by.
[0013]
In the present invention, the conductor may be substantially surrounded by a second insulator that does not satisfy μr ≧ εr, and the periphery of the second insulator may be substantially surrounded by the first insulator. Alternatively, at least a part of the conductor is substantially surrounded by a second insulator that does not satisfy μr ≧ εr, and the periphery of the second insulator is surrounded by the first insulator together with the periphery of the conductor. It may be substantially enclosed.
[0014]
In the present invention, the “insulator” refers to a material having a specific resistance measured by JISC3005 of 1 kΩcm or more. In the present invention, the term “conductor” refers to one having a specific resistance measured by JISC3005 of less than 1 kΩcm, and is used in a concept including wiring and circuits. The cross-sectional shape of the conductor is not limited to a rectangle, but may be a circle, an ellipse, or other shapes. Further, the cross-sectional shape of the insulator is not particularly limited.
In the present invention, “substantially enclose” means that the effective magnetic permeability and dielectric constant only have to satisfy desired values even if there is an unenclosed part.
[0015]
In the present invention, the relative dielectric constant εr and the relative magnetic permeability μr of the insulator are evaluated by an effective dielectric constant and an effective magnetic permeability that affect electromagnetic waves propagating through the conductor, regardless of the structure of the insulator surrounding the conductor. As a method for measuring the effective permittivity or the effective permeability, it is possible to measure by using a triplate line resonator method or the like that measures an electromagnetic wave actually propagating through the wiring and determines the permittivity and the permeability.
[0016]
According to the circuit board of the present invention, since the first insulator satisfying μr ≧ εr is used as the insulating material between the conductors, the specific impedance can be increased to about 377Ω or more. For this reason, it is possible to reduce the current consumption in each stage as compared with a circuit board using a conventional insulating material satisfying μr <εr. As a result, the power consumption of the entire LSI system including the LSI and the printed wiring board can be reduced.
[0017]
In the present invention, preferably, the first insulator that substantially surrounds each of the conductors is partitioned by a second insulator that does not satisfy μr ≧ εr for each of the conductors. In the case of the present invention, a magnetic field generated around a conductor such as a wiring can be confined in the first insulator surrounding the conductor, and crosstalk and radiation noise between conductors such as adjacent wirings can be suppressed, and the wiring The signal quality of the signal propagating through the conductor can be improved.
[0018]
In the present invention, preferably, the first insulator is formed by mixing a magnetic substance with an inorganic substance. By mixing a magnetic material (μr> 1) in the inorganic material, a first insulator that satisfies μr ≧ εr can be easily realized.
[0019]
Alternatively, in the present invention, the first insulator may include a synthetic resin and a magnetic material. Also in this case, the first insulator satisfying μr ≧ εr can be easily realized by including the magnetic material (μr> 1) in the synthetic resin.
[0020]
In addition to the magnetic material and the synthetic resin, the first insulator includes a curing agent, a curing accelerator, a flame retardant, a soft polymer, a heat stabilizer, a weather stabilizer, an antiaging agent, a leveling agent, and an antistatic agent. , Slip agents, antiblocking agents, antifogging agents, lubricants, dyes, pigments, natural oils, synthetic oils, waxes, emulsions, fillers, ultraviolet absorbers, and the like.
[0021]
In the present invention, the synthetic resin is not particularly limited. For example, epoxy resin, phenol resin, polyimide resin, polyester resin, fluorine resin, modified polyphenyl ether resin, bismaleimide / triazine resin, modified polyphenylene oxide resin, silicon resin And acrylic resin, benzocyclobutene resin, polyethylene naphthalate resin, polycycloolefin resin, polyolefin resin, cyanate ester resin, melamine resin, and acrylic resin.
[0022]
Since these resins have a lower dielectric constant than a ferrite material that is a typical magnetic material, the effect of increasing impedance can be exhibited without canceling the effect of increasing permeability. As a particularly preferable resin, a resin having a small dielectric loss (tan δ) and a small content of moisture and unnecessary organic substances is preferable, a relative dielectric constant is about 2 to 3, and tan δ = 2 × 10.^-4Polycycloolefin resin and polyolefin resin are particularly preferable.
In the present invention, the magnetic body preferably has electrical insulation. Although it does not specifically limit as an electrically insulating magnetic body, The metal oxide magnetic body containing Co, Ni, Mn, Zn, etc. is illustrated. By including an insulating magnetic material, the eddy current loss in the first insulator constituting the circuit board becomes negligibly small, which contributes only to increasing the magnetic permeability of the circuit board. In addition, since the eddy current loss of the circuit board can be reduced, the loss can be suppressed even at a high frequency of about several hundred MHz to 1 GHz.
[0023]
In the present invention, the amount of the magnetic material with respect to 100 parts by weight of the synthetic resin is not particularly limited, but is usually 1/10.⁶It is contained in the first insulator at a ratio of ˜300 parts by weight. The effect of this invention increases by making the content rate of a magnetic body into the said range. If the content of the magnetic material is too low, the amount of the magnetic material present in the first insulator is reduced, so that the effect of the present invention is reduced. Conversely, if the content is too high, uniform dispersibility cannot be obtained. There is a tendency for manufacturing difficulties to occur.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described based on embodiments shown in the drawings.
First embodiment
As shown in FIG. 1, a printed wiring board 100 as a circuit board according to an embodiment of the present invention is formed on a plate-like or film-like first insulator 101 and a lower surface of the first insulator 101. The first conductive film 102, the second conductive film 103 formed on the upper surface of the first insulator 101, and a plurality of wirings (conductors) 104 included in the first insulator 101 are included. The wiring substrate 100 of this embodiment is used as a substrate for a strip line, for example.
[0025]
The thickness T2 of the wiring 104 is not particularly limited. However, when the wiring substrate 100 is used as a strip line, the signal frequency is f, the conductivity of the wiring 104 is σ, and the magnetic permeability of the wiring 104 is μi. Infiltration skin depth {1 / (πfμiσ)}^1/2The above is preferable. The thickness T1 of the first insulator 101 surrounding the wiring 104 is not particularly limited, but T ′ ≧, where T ′ is the smaller one of the distances a and b between the wiring 104 and the first conductive film 102 and the second conductive film 103. {1 / (πfμiσ)}^1/2It is preferable that By doing in this way, the energy of a signal can be concentrated in an insulator and the loss in wiring can be reduced. The wiring 104 is preferably disposed at a substantially central portion in the thickness direction of the first insulator 101.
[0026]
The width W of the wiring 104 is not particularly limited, but {1 / (πfμiσ)}^1/2The above is preferable. The distance P between the wirings 104 may be uniform or non-uniform between the wirings, and is not particularly limited. However, the distance P is preferably equal to or greater than the T ′. Thus, crosstalk between adjacent wirings can be reduced. Note that the number of the wirings 104 embedded in the first insulator 101 is not particularly limited, and the wirings 104 may be formed in multiple layers in the thickness direction in the first insulator 101. A circuit board composed of 102, 103, and 104 may be formed in multiple layers.
[0027]
The thickness T3 of the conductive films 102 and 103 formed on both surfaces of the first insulator 101 is not particularly limited, but {1 / (πfμiσ)}^1/2The above is preferable.
[0028]
The first insulator 101 is obtained by mixing a minute magnetic powder with a synthetic resin having a low dielectric constant. The fine magnetic powder is sufficiently smaller than the magnetic domain size, for example, about several tens of nanometers or less. The magnetic powder is an insulator. For example, a metal oxide magnetic material containing Co, Ni, Mn, Zn, or the like is smaller than the magnetic domain size by a gas evaporation method, an atomizing method, a chemical synthesis method, etc. It is formed in a spherical shape, flat shape, or fiber shape of a moderate size. Alternatively, the magnetic powder may be obtained by forming a metal magnetic fine powder and oxidizing it.
[0029]
The first insulator 101 shown in FIG. 1 is obtained by mixing and molding the fine magnetic substance powder obtained as described above in a synthetic resin. The synthetic resin material is not particularly limited and includes those exemplified above.
[0030]
In general, the permeability of magnetic materials decreases as the frequency increases due to the Stoke limit. Therefore, when the circuit board of the present embodiment is used for high frequency applications, it is preferable that the dielectric constant of the first insulator 101 is low. Synthetic resin has a lower dielectric constant than a typical magnetic material, such as a ferrite material, and therefore can exhibit an effect of increasing specific impedance even in a high frequency region. From this viewpoint, as a preferable synthetic resin, the polycycloolefin resin and the polyolefin resin as described above are particularly preferable.
[0031]
The material of the conductive films 102 and 103 and the wiring 104 is not particularly limited as long as it is a conductive material, and a normal wiring material, for example, a material mainly composed of a metal material such as copper, gold, silver, or aluminum is used. .
[0032]
In order to embed the wiring 104 in the first insulator 101, for example, the following is performed.
[0033]
As shown in FIG. 2A, first, the lower insulating layer 101a of the first insulator 101 is formed into a sheet shape. The first conductive film 102 is formed on the lower surface of the lower insulating layer 101a, and the wiring layer 104a is formed on the upper surface of the lower insulating layer 101a. The first conductive film 102 and the wiring layer 104a can be formed, for example, by plating a Cu film, a sputtering method, an organic metal CVD method, a bonding method of a metal film such as Cu, or the like.
[0034]
Next, as shown in FIG. 2B, the wiring layer 104a is patterned by photolithography or the like to form a wiring 104 having a desired pattern. Subsequently, as shown in FIG. 2C, the upper insulating layer 101b is laminated on the lower insulating layer 101a on which the wiring 104 is formed. The upper insulating layer 101b is formed on a sheet in the same manner as the lower insulating layer 101a, for example, and is bonded onto the lower insulating layer 101a by, for example, a press method. Thereafter, as shown in FIG. 2D, a second conductive film 103 is formed on the upper insulating layer 101b in the same manner as the first conductive film 102.
[0035]
The upper insulating layer 101b may be formed by, for example, a spin coating method or a coating method. For example, a solution in which a resin material is contained in a solvent such as xylene and a fine magnetic material such as ferrite is uniformly dispersed by a surfactant or the like is applied onto the lower insulating layer 101a by a spin coating method or the like and baked. Alternatively, the upper insulating layer 101b that is solidified by evaporating the solvent may be formed.
As shown in FIG. 3, the circuit board obtained in this way comprises the first insulator 101 with a lower insulating layer 101a and an upper insulating layer 101b. The lower insulating layer 101a and the upper insulating layer 101b may be formed of the same material or different materials. However, it is preferable that both of these insulating layers 101a and 101b satisfy μr ≧ εr.
[0036]
Further, at least one of the insulating layers is coated and fired by mixing a minute magnetic material with an inorganic material such as inorganic SOG (Spin On Glass) hydrogenated silsesquiosan polymer (HSQ) used in the LSI manufacturing process. May be formed.
[0037]
According to the wiring substrate 100 of the present embodiment, since the first insulator 101 that satisfies μr ≧ εr is used as the insulating material between the conductors, the specific impedance is about 377Ω or more, preferably 300Ω or more, and further 500Ω. The power consumption of the entire LSI system including a circuit board such as a printed wiring board can be reduced.
[0038]
In the present embodiment, since the wiring 104 is embedded in the first insulator 101, the magnetic field generated around the wiring 104 can be confined in the first insulator 101 surrounding the wiring, and adjacent to each other. Crosstalk and radiation noise between the wirings 104 can be suppressed, and the signal quality of the signal propagating through the wirings 104 can be improved.
[0039]
Second embodiment
As shown in FIG. 4, in this embodiment, the periphery of the wiring 104 is surrounded by the second insulator 105, and the periphery thereof is further surrounded by the first insulator 101. The same function and effect can be expected.
Hereinafter, in each embodiment, the same code | symbol is attached | subjected to the member which is common in the said 1st Embodiment, the description is partially abbreviate | omitted, and only a difference is demonstrated in detail hereafter.
[0040]
In the present embodiment, the second insulator 105 surrounding the wiring 104 is made of a normal synthetic resin that does not contain a minute magnetic material. The second insulator 105 satisfies μr <εr and does not satisfy μr ≧ εr. The thickness of the second insulator 105 may be smaller than ½ of the distance P between the wirings 104 shown in FIG. 1, and is preferably １ ／ or less.
[0041]
Further, as shown in FIG. 5, the second insulator 105 does not necessarily need to cover the entire circumference of the wiring 104, and may cover only a part thereof.
Further, as shown in FIGS. 6A and 6B, the first insulator 101 does not cover the entire circumference of the wiring 104 and may be partially surrounded by the second insulator 105. good. Further, at the outlet of the wiring 104, there may be a portion where the wiring 104 is not surrounded by the first insulator 101 at a through-hole connection portion or the like. As shown in FIGS. 6A and 6B, the width W2min of the portion 106 that is not surrounded by the first insulator 101 around the wiring 104 is equal to that of the wiring 104 in a direction parallel to the width W2min. It is preferably narrower than the maximum width W1max.
[0042]
Third embodiment
As shown in FIG. 7, in this embodiment, the periphery of the wiring 104 is surrounded by a first insulator 205 in which spherical first insulators 201 (only different in shape from the first insulator 101) are dispersed. Except for this, it has the same configuration as that of the first embodiment, and the same effect can be expected.
[0043]
In this embodiment, the wiring 104 is surrounded by the first insulator 205 in which the spherical first insulators 201 are dispersed. This means that the wiring (conductor) 104 is substantially covered by the first insulator 201. It will be surrounded by.
[0044]
In the embodiment shown in FIG. 8, the wiring 104 is surrounded by the first insulator 305 in which the flat first insulator 301 is dispersed. This means that the wiring (conductor) 104 is the first. It is substantially surrounded by the insulator 301.
[0045]
Further, in the embodiment shown in FIG. 9, the wiring 104 is surrounded by the first insulator 405 in which the fiber-shaped first insulator 401 is dispersed. This means that the wiring (conductor) 104 is the first. It is substantially surrounded by the insulator 401.
[0046]
Fourth embodiment
As shown in FIG. 10, in this embodiment, the first insulators 501 that satisfy the plate-like or film-like μr ≧ εr formed between the first conductive film 102 and the second conductive film 103 are respectively provided. Each wiring 104 is partitioned by a second insulator 505 that does not satisfy μr ≧ εr.
[0047]
The first insulator 501 is made of the same material as the first insulator 101 in the wiring board 100 of the first embodiment, and is manufactured in the same manner. The second insulator 505 is a normal synthetic resin, and the magnetic powder is not dispersed therein.
[0048]
The width W4 of the first insulator 501 needs to be larger than the width W of the wiring 104, and it is sufficient that the wiring 104 is substantially surrounded by the first insulator 501. The wiring 104 is preferably arranged in the vicinity of the approximate center in the width direction of the first insulator 501. The width W <b> 3 of the second insulator 505 may be smaller than the width W <b> 4, specifically, 0 or more, and is determined so that the wiring 104 is substantially surrounded by the first insulator 501. That is, as shown in FIG. 11, the minimum width W3min of the second insulator 505 may be equal to or greater than the minimum width W2min of the portion 605 where the periphery of the wiring 104 is not surrounded by the first insulator 501.
[0049]
A wiring board formed by alternately repeating the first insulator 501 and the second insulator 505 can be manufactured as follows, for example.
That is, first, as shown in FIG. 12A, a substrate in which the wiring 104 is embedded in the first insulator 501 is formed in the same manner as in the step shown in FIG. Thereafter, as shown in FIG. 12B, the groove 505a is formed by a laser processing or the like in a pattern in which the second insulator 505 shown in FIG. 10 is formed. Thereafter, as shown in FIG. 12C, a resin to be the second insulator 505 is poured from above the groove 505a by spin coating or the like to form the second insulator 505, and then an extra insulator Part 505b is removed.
[0050]
According to the wiring board according to the present embodiment, the wiring 104 is embedded in each first insulator 501, and each first insulator 501 is partitioned by the second insulator 505. For this reason, according to this embodiment, the effect of the said 1st Embodiment can be further improved. That is, according to the present embodiment, the magnetic field generated around the wiring 104 can be more effectively confined in the first insulator 501 surrounding the wiring 104, and crosstalk and radiation noise between adjacent wirings 104 can be obtained. And the signal quality of the signal propagating through the wiring 104 can be improved.
[0051]
The present invention is not limited to the above-described embodiment, and can be variously modified within the scope of the present invention.
For example, the circuit board according to the present invention can be used for a circuit other than a strip line, for example, a microstrip line or a substrate for other circuits.
[0052]
【Example】
Hereinafter, although this invention is demonstrated based on a more detailed Example, this invention is not limited to these Examples.
[0053]
Example 1
[0054]
This fine magnetic powder was mixed with 100 parts of a polysilane olefin resin (norbornene cycloolefin ring-opening polymer modified product (Tg = 170 ° C.), 40 parts bisphenol curing agent, and 0.1 part imidazole effect accelerator. 1 is obtained by uniformly dispersing a ferrite material (manufactured by Toda Kogyo Co., Ltd.), which is a fine magnetic powder made of an insulator, in a varnish obtained by dissolving a varnish in a solvent, cast-molding, and heat-treating, and FIG. The relative dielectric constant ε of the first insulator 101 was 2.9, and the amount of magnetic powder dispersed was 100 parts by weight of the component other than the varnish solvent. The ratio was 100 parts by weight.
[0055]
In the first insulator 101, the wiring 104 made of copper metal having a cross-sectional width W of 10 μm and a cross-sectional thickness T2 of 10 μm is arranged at the approximate center in the thickness direction with a wiring interval P = 200 μm. Embedded in.
[0056]
Next, the same plating was performed on the lower surface and the upper surface of the first insulator 101 to form conductive films 102 and 103 having a thickness of 20 μm, whereby the wiring substrate 100 was obtained.
[0057]
The magnetic permeability μ of the first insulator 101 in this wiring board 100 was measured and found to be 25.
[0058]
The result of obtaining the relationship with the characteristic impedance by changing the width W of the wiring 104 between 1 and 100 μm is shown by a solid line in FIG.
[0059]
Comparative Example 1
Instead of the first insulator 101, a wiring board was manufactured in the same manner as in Example 1 except that the insulator was obtained without dispersing the fine magnetic powder in the varnish. The relative dielectric constant ε = 2 of the insulator and the magnetic permeability μ = 1 of the wiring board. The result of obtaining the relationship with the characteristic impedance by changing the width W of the wiring 104 between 1 and 100 μm is shown by a dotted line in FIG.
[0060]
Evaluation 1
As shown in FIG. 13, it was confirmed that the characteristic impedance was improved in the example compared to the comparative example (conventional stripline). That is, it has been confirmed that the characteristic impedance, which is conventionally limited to 100 to 200Ω, can be about 300 to 500Ω or more in this embodiment. Moreover, since it is not necessary to extremely reduce the wiring width in order to increase the wiring impedance, it is possible to reduce the loss due to the wiring resistance.
[0061]
Example 2
A wiring board is manufactured in the same manner as in Example 1 except that the dispersion amount of the magnetic powder in the first insulator 101 is changed and the permeability of the first insulator 101 at 100 MHz is changed in the range of 1 to 100. did. The relationship between the characteristic impedance of the transmission line formed on the wiring board 100 and the relative permeability of the first insulator 101 is shown in FIG. It was confirmed that a transmission line having a relative permeability of about 25, a characteristic impedance of 500Ω, a relative permeability of about 100, and a characteristic impedance of 1000Ω was obtained.
[0062]
Example 3
The wiring board in Example 1 having a characteristic impedance of 500Ω is selected, and the result of obtaining the relationship between frequency and power consumption is shown by a curve A in FIG.
[0063]
Comparative Example 2
The wiring board in Comparative Example 1 having a characteristic impedance of 50Ω is selected, and the result of obtaining the relationship between the frequency and the power consumption is shown by a curve B in FIG.
[0064]
Evaluation 2
As shown in FIG. 15, the loss of the magnetic material starts to increase near the rotational magnetization resonance frequency from above 1 GHz, but at a frequency smaller than about 1 GHz, the domain wall has a single magnetic domain structure that is a micromagnetic material. The movement is stopped and low loss can be realized. By forming a transmission line wiring in the first insulator of Example 3 adjusted to have a relative permeability of 25 and setting the characteristic impedance to 500Ω, it is 1/10 compared to the 50Ω characteristic impedance of Comparative Example 2 which is a conventional example. It was confirmed that low power consumption can be achieved.
[0065]
Furthermore, compared to the case of a characteristic impedance of 50Ω that is generally used conventionally, in Example 3, a characteristic impedance of about 500Ω or more can be easily formed, so that the current flowing through the wiring is reduced to about 1/10 or It was confirmed that the power consumption of the printed circuit board and the buffer circuit for driving the wiring would be 1/10 or less.
[0066]
Although the above embodiment shows the case where the present invention is applied to a printed wiring board, the present invention may be applied to the internal wiring of an LSI, and the same effect can be obtained.
[0067]
【The invention's effect】
As described above, according to the present invention, the characteristic impedance of the signal transmission line, which has conventionally been about 200Ω, is increased to 300Ω or more, preferably 500Ω or more, and includes an LSI system including a circuit board such as a printed wiring board. Overall power consumption can be reduced. In addition, according to the present invention, crosstalk and radiation noise with adjacent wirings can be suppressed, and the signal quality of signals propagating through the wirings can be improved.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a structure of a printed wiring board in an embodiment of the present invention.
FIG. 2 is a cross-sectional view showing the structure of a printed wiring board according to another embodiment of the present invention.
3A to FIG. 3D are cross-sectional views showing how to make the printed wiring board shown in FIG.
FIG. 4 is a cross-sectional view showing the structure of a printed wiring board according to another embodiment of the present invention.
FIG. 5 is a cross-sectional view showing the structure of a printed wiring board according to another embodiment of the present invention.
6 (a) and 6 (b) are cross-sectional views showing the structure of a printed wiring board according to another embodiment of the present invention.
FIG. 7 is a cross-sectional view showing the structure of a printed wiring board according to another embodiment of the present invention.
FIG. 8 is a cross-sectional view showing the structure of a printed wiring board according to another embodiment of the present invention.
FIG. 9 is a cross-sectional view showing the structure of a printed wiring board according to another embodiment of the present invention.
FIG. 10 is a cross-sectional view showing the structure of a printed wiring board according to another embodiment of the present invention.
FIG. 11 is a cross-sectional view showing the structure of a printed wiring board according to another embodiment of the present invention.
12 (a) to 12 (c) are cross-sectional views showing a manufacturing process of the printed wiring board according to the embodiment shown in FIG.
FIG. 13 is a characteristic diagram showing the relationship between the characteristic impedance and the wiring width when a strip line is formed on the printed wiring board in the example of the present invention and the comparative example.
FIG. 14 is a characteristic diagram showing the relationship between characteristic impedance and relative magnetic permeability when a strip line is formed on the printed wiring board in the embodiment of the present invention.
FIG. 15 is a characteristic diagram showing a relationship between characteristic impedance, power consumption, and frequency of a transmission line formed on a printed wiring board using the first insulator in the embodiment of the present invention.
FIG. 16 is a characteristic diagram showing the relationship between the wiring width and characteristic impedance of a conventional microstrip line.
[Explanation of symbols]
100 ... Printed wiring board (circuit board)
101, 101a, 101b, 201, 301, 401, 501 ... first insulator
105, 205, 305, 405, 505 ... second insulator
102, 103 ... conductive film
104 ... Wiring

Claims (8)

In a circuit board in which a conductor is embedded as a transmission line inside an insulator, when the relative permittivity is εr and the relative permeability is μr, the first insulator satisfies μr ≧ εr, and the conductor is A circuit board characterized by being substantially surrounded and having a characteristic impedance of 300Ω or more of the conductor as the transmission line . 2. The conductor according to claim 1, wherein the conductor is substantially surrounded by a second insulator that does not satisfy μr ≧ εr, and the second insulator is substantially surrounded by the first insulator. Circuit board. At least a portion of the conductor is substantially surrounded by a second insulator that does not satisfy μr ≧ εr, and the second insulator is substantially surrounded by the first insulator together with the periphery of the conductor. The circuit board according to claim 1, which is surrounded by A plurality of the conductors are embedded inside the circuit board,
The first insulator that substantially surrounds each of the conductors is partitioned by a second insulator that does not satisfy μr ≧ εr for each of the conductors. A circuit board according to any one of the above. The circuit board according to claim 1, wherein the first insulator is a magnetic substance mixed with an inorganic substance. The circuit board according to claim 1, wherein the first insulator contains a synthetic resin and a magnetic substance. The synthetic resins include epoxy resins, phenol resins, polyimide resins, polyester resins, fluororesins, modified polyphenyl ether resins, bismaleimide / triazine resins, modified polyphenylene oxide resins, silicon resins, acrylic resins, benzocyclobutene resins, polyethylene naphthalates. The circuit board according to claim 6, wherein the circuit board is at least one selected from the group consisting of a phthalate resin, a polycycloolefin resin, a polyflephine resin, a cyanate ester resin, a melamine resin, and an acrylic resin. The circuit board according to claim 5, wherein the magnetic body is an insulator.

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