JP2015056555A - High-speed transmission substrate and electronic component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-speed transmission substrate which responds to a request for thinning, has a low transmission loss, and has an excellent shield effect; and to provide an electronic component provided with the same.SOLUTION: A high-speed transmission substrate includes a first printed wiring board, and a second printed wiring board arranged so as to face the first printed wiring board. The first printed wiring board has a first dielectric layer, a conductive pattern laminated on the second printed wiring board side of the first dielectric layer, and a first conductive layer laminated on an opposite side to the second printed wiring board side of the first dielectric layer. The second printed wiring board has a second dielectric layer, and a second conductive layer laminated on an opposite side to the first printed wiring board side of the second dielectric layer. The first dielectric layer and the second dielectric layer are high-speed transmission substrates containing fluorine resins as main components. The conductive pattern may include a transmission section for a high frequency signal, and a shield portion surrounding the transmission section. The periphery of the transmission section may be surrounded by an insulating material containing a fluorine resin as a main component.

Description

  The present invention relates to a high-speed transmission board and an electronic component.

  High-speed transmission boards are used for transmitting high-frequency signals, digital signals, and the like. As such a high-speed transmission board, a high-speed transmission board with a shield function having a stripline structure, a microstrip structure, or the like is used for noise prevention, crosstalk prevention, and the like. The stripline structure and the microstrip structure are structures in which a signal line is disposed on one surface side of a dielectric layer and a ground layer is stacked on the other surface side.

  Such a high-speed transmission substrate with a shield function is desired to be thinned, and in order to realize such a thinning, a dielectric layer is thinned. When the dielectric layer is made thin, it is necessary to keep the parasitic capacitance constant for impedance matching. On the other hand, in order to keep the parasitic capacitance constant, it is necessary to narrow the width of the signal line. However, if the width of the signal line is reduced, the transmission loss in the signal line increases. For this reason, it has been proposed to keep the parasitic capacitance constant by providing an opening in the ground layer and reducing the area where the ground layer and the signal line face each other (see Japanese Patent Laid-Open No. 2000-77802).

JP 2000-77802 A

  However, when an opening is provided in the ground layer as described above, the presence of this opening may cause an insufficient shielding effect. Further, when the ground layer is solid to obtain a high shielding effect, it is necessary to increase the thickness of the dielectric layer in order to suppress an increase in transmission loss of the signal line. If the thickness of the dielectric layer is increased in this way, the shielding effect of the dielectric layer may be insufficient, and the shielding effect on the side surface of the dielectric layer is likely to be lowered. Further, increasing the thickness of the dielectric layer is contrary to the demand for thinning.

  The present invention has been made in view of the circumstances as described above, and provides a high-speed transmission board having a low transmission loss and an excellent shielding effect while responding to a request for thinning, and an electronic component including the same. Objective.

  The present invention, which has been made to solve the above problems, includes a first printed wiring board and a second printed wiring board disposed opposite to the first printed wiring board, wherein the first printed wiring board is a first printed wiring board. 1 dielectric layer, a conductive pattern laminated on the second printed wiring board side of the first dielectric layer, and a first conductive layer laminated on the opposite side of the first dielectric layer to the second printed wiring board side And the second printed wiring board has a second dielectric layer and a second conductive layer laminated on the opposite side of the second dielectric layer from the first printed wiring board side. The first dielectric layer and the second dielectric layer are high-speed transmission substrates mainly composed of a fluororesin.

  Another aspect of the present invention made to solve the above-described problems is an electronic component including the high-speed transmission board.

  According to the high-speed transmission board of the present invention, the transmission loss is low and the shielding effect can be enhanced while meeting the demand for thinning. Therefore, the high-speed transmission board can be suitably applied as a wiring board for transmitting high-frequency signals and a high-speed transmission board for electronic components.

It is a typical sectional view showing the high-speed transmission substrate concerning one embodiment of the present invention. It is another typical sectional drawing of the high-speed transmission board | substrate of FIG. It is typical sectional drawing which decomposes | disassembles and shows the high-speed transmission board | substrate of FIG. It is a schematic plan view of the 1st printed wiring board of the high-speed transmission board | substrate of FIG. It is a typical bottom view of the 1st printed wiring board of the high-speed transmission board | substrate of FIG. It is a schematic plan view of the 2nd printed wiring board of the high-speed transmission board | substrate of FIG.

[Description of Embodiment of the Present Invention]
A high-speed transmission board according to the present invention includes a first printed wiring board and a second printed wiring board disposed opposite to the first printed wiring board, wherein the first printed wiring board includes a first dielectric layer and And a conductive pattern laminated on the second printed wiring board side of the first dielectric layer, and a first conductive layer laminated on the opposite side of the first dielectric layer to the second printed wiring board side. The second printed wiring board has a second dielectric layer and a second conductive layer laminated on the opposite side of the second dielectric layer from the first printed wiring board side, and the first dielectric layer and The second dielectric layer is mainly composed of a fluororesin.

  The high-speed transmission substrate has a conductive pattern disposed between the first dielectric layer and the second dielectric layer. The first dielectric layer and the second dielectric layer are mainly composed of a fluororesin, and this fluororesin generally tends to have a low dielectric loss tangent (tan δ) and relative dielectric constant (εr). Therefore, when the first dielectric layer and the second dielectric layer are mainly made of fluororesin, the transmission loss of the conductive pattern can be sufficiently reduced and a sufficient transmission speed can be obtained. Accordingly, since it is not necessary to increase the thickness of the first dielectric layer and the second dielectric layer in order to improve transmission characteristics, the high-speed transmission substrate can reduce the thickness of the first dielectric layer and the second dielectric layer. .

  In the high-speed transmission substrate, the first conductive layer and the second conductive layer are laminated outside the first dielectric layer and the second dielectric layer. That is, the conductive pattern is disposed between the first conductive layer and the second conductive layer. Therefore, the first conductive layer and the second conductive layer can function as a shield against the conductive pattern. In particular, by reducing the distance between the first conductive layer and the second conductive layer by thinning the first dielectric layer and the second dielectric layer, an excellent shielding effect can be exhibited, and the first conductive layer and the second conductive layer Since the deterioration of the shielding property on the side surface can be suppressed, the high-speed transmission board can further improve the shielding effect.

  The conductive pattern may include a high-frequency signal transmission unit and a shield unit surrounding the transmission unit. Thus, since the conductive pattern includes the transmission part and the shield part surrounding the transmission part, the shield part can exert a higher shielding effect on the transmission part.

  The periphery of the transmission unit may be surrounded by an insulating material mainly composed of a fluororesin. In this way, the transmission part is surrounded by an insulating material mainly composed of a fluororesin, so that the transmission part is surrounded by an insulating material that tends to have a low dielectric loss tangent (tan δ) and relative dielectric constant (εr). Become. Therefore, transmission loss in the transmission unit can be further reduced and a higher transmission speed can be obtained.

  The high-speed transmission substrate may further include a through hole that conducts the first conductive layer and the second conductive layer. Thus, by having a through hole that conducts the first conductive layer and the second conductive layer, the potentials of the first conductive layer and the second conductive layer are equalized, and these conductive layers are used as a ground layer (shield). It can function suitably. As a result, the high-speed transmission board can exhibit a higher shielding effect. In addition, by making the potentials of the first conductive layer and the second conductive layer equal, the withstand voltage of the high-speed transmission substrate can be further increased.

  The ten-point average roughness (Rz) of at least one surface of the conductive pattern is preferably 4 μm or less. In this way, by setting the ten-point average roughness (Rz) of at least one surface of the conductive pattern to 4 μm or less, generation of transmission delay due to the skin effect on the surface of the conductive pattern is suppressed, and resistance attenuation and leakage attenuation are increased. Transmission loss due to can be suppressed. Therefore, the high-speed transmission board is excellent in high-frequency signal transmission characteristics and can support high-speed and large-capacity wireless communication.

  The high-speed transmission board may further include a first cover film laminated on the outside of the first printed wiring board and a second cover film laminated on the outside of the second printed wiring board. Thus, by further providing the first and second cover films laminated on the outside of the first and second printed wiring boards, the mechanical strength of the high-speed transmission board can be ensured and the shape maintainability can be improved. .

  A chemical bond may be provided between the fluororesin of the first dielectric layer and the conductive pattern. Thus, by having a chemical bond between the fluororesin of the first dielectric layer and the conductive pattern, the bondability between the first dielectric layer and the conductive pattern is increased, and the bonding strength can be improved.

  The chemical bond may be formed by ionizing radiation irradiation. According to such ionizing radiation irradiation, a chemical bond can be appropriately formed, so that the bondability between the conductive pattern and the first dielectric layer can be further improved.

  The chemical bond may be formed via a coupling agent present at the interface between the first dielectric layer and the conductive pattern. By interposing the coupling agent in this way, the chemical bond can be realized easily and reliably, and as a result, the bondability between the first dielectric layer and the conductive pattern can be improved easily and reliably.

  As the coupling agent, a silane coupling agent having a functional group containing an N atom or an S atom is preferable. Thus, by using a coupling agent as a silane coupling agent having a functional group containing an N atom or an S atom, the bondability between the first dielectric layer and the conductive pattern can be further improved. Although the reason for this is not clear, the hydrolyzable group of the silane coupling agent is fixed to the conductive pattern by a silane coupling reaction, while the N atom or S atom of the amino group, sulfide group, etc. of the silane coupling agent. It is presumed that the bondability is improved by the chemical group containing a chemical bond with a carbon radical site generated when the fluororesin that is the main component of the first dielectric layer is radicalized.

  It is preferable that at least one of the first dielectric layer and the second dielectric layer has a chemical bond formed by ionizing radiation irradiation between molecules. As described above, at least one of the first dielectric layer and the second dielectric layer has a chemical bond between the molecules, so that the mechanical strength of at least one of the first dielectric layer and the second dielectric layer is increased. It is possible to further improve the mechanical strength of the high-speed transmission board.

  Examples of the fluororesin for the first dielectric layer and the second dielectric layer include tetrafluoroethylene / hexapropylene copolymer (FEP), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), and polytetrafluoroethylene. (PTFE) or tetrafluoroethylene-perfluorodioxole copolymer (TFE / PDD) is preferred. Such a fluororesin is considered to be a compound that easily generates fluorine radicals by electron beam irradiation or heating. For this reason, the high-speed transmission substrate can appropriately form the chemical bond by including the first dielectric layer mainly composed of the illustrated fluororesin, so that the bondability between the first dielectric layer and the conductive pattern is more excellent. It will be a thing. Moreover, since the illustrated fluororesin is a material having a low dielectric loss tangent (tan δ) and relative dielectric constant (εr), the first dielectric layer and the second dielectric layer have such a fluororesin as a main component, The high-speed transmission board excellent in transmission characteristics such as transmission loss and transmission speed can be obtained more easily.

  The present invention is an electronic component including the high-speed transmission board. Since the electronic component includes the high-speed transmission substrate, the electronic component is excellent in transmission characteristics such as transmission loss and transmission speed and shielding effect.

  Here, the “fluororesin” refers to one in which at least one hydrogen atom bonded to the carbon atom constituting the repeating unit of the polymer chain is substituted with a fluorine atom or an organic group having a fluorine atom. The “main component” is a component having the largest content, for example, a component having a content of 50% by mass or more. The “ten-point average roughness (Rz)” is a value measured according to JIS B 0601: 1994, the evaluation length (l) is 3.2 mm, and the cut-off value (λc) is 0.00. The value is 8 mm. “Chemical bond” refers to a covalent bond or a hydrogen bond.

[Details of the embodiment of the present invention]
Hereinafter, an embodiment of a high-speed transmission board according to the present invention will be described in detail with reference to FIGS.

[High-speed transmission board]
The high-speed transmission substrate of FIGS. 1 to 3 can be suitably used as a wiring body for high-frequency transmission. The high-speed transmission board includes a first printed wiring board 1, a second printed wiring board 2 disposed opposite to the first printed wiring board 1, an adhesive layer 3 for bonding these printed wiring boards 1 and 2, a first Through holes 4 </ b> A and 4 </ b> B, a second through hole 5, a first coverlay 6 stacked on the first printed wiring board 1, and a second coverlay 7 stacked on the second printed wiring board 2 are provided.

  The high-speed transmission board is flat as a whole and has flexibility. Here, the flexibility of the high-speed transmission board can be evaluated by, for example, the folding resistance described below.

  The folding resistance of the high-speed transmission substrate can be evaluated as the number of times until the sample (high-speed transmission substrate) is bent at a rate of 170 times per minute with a tension of 4.9 N and the sample is disconnected. The number of times until the high-speed transmission substrate is disconnected is preferably 6 times or more, and more preferably 12 times or more. The number of disconnections until the high-speed transmission board is disconnected is the number of times measured in accordance with JIS C 5016 “Flexible Printed Circuit Board Test Method (8.7 Folding Resistance)”: 1994. It is defined as the average value of the measurement results.

  The lower limit of the thickness of the high-speed transmission substrate is preferably 100 μm, more preferably 180 μm, and even more preferably 246 μm. On the other hand, the upper limit of the thickness of the high-speed transmission substrate is preferably 600 μm, more preferably 500 μm, and still more preferably 400 μm. If the thickness of the high-speed transmission substrate is less than the lower limit, a sufficient transmission bandwidth may not be obtained. On the other hand, if the thickness of the high-speed transmission board exceeds the upper limit, desired flexibility may not be obtained.

[First printed wiring board]
The 1st printed wiring board 1 is comprised from the strip | belt-shaped sheet | seat body in planar view, as shown in FIG.4 and FIG.5. The first printed wiring board 1 includes a conductive pattern 10, a first conductive layer 11, and a first dielectric layer 12.

<Conductive pattern>
As shown in FIGS. 1 to 3, the conductive pattern 10 is laminated on the first dielectric layer 12 on the side where the second printed wiring board 2 is laminated (upper side in FIGS. 1 to 3). Part 13 and shield part 14. In this conductive pattern 10, it is preferable that at least the transmission part 13 includes a rust-proofing layer.

(Transmission part)
The transmission unit 13 functions as a signal line. As shown in FIG. 4, the transmission unit 13 is formed in a straight line extending in the longitudinal direction of the first dielectric layer 12, and is disposed at the center in the width direction of the first dielectric layer 12. The average width W1 of the transmission unit 13 is not particularly limited, but the lower limit of the average width W1 is preferably 10 μm, more preferably 50 μm, and even more preferably 70 μm. On the other hand, the upper limit of the average width W1 is preferably 300 μm, more preferably 240 μm, and further preferably 230 μm. If the average width W1 is less than the lower limit, the transmission loss in the transmission unit 13 may be too large. On the other hand, when the average width W1 exceeds the upper limit, the area where the transmission unit 13 and the shield unit 14 face each other is widened, and the parasitic capacitance between the transmission unit 13 and the shield unit 14 becomes too large, thereby matching impedance. There is a risk that it may not be possible to obtain.

(Shield part)
The shield part 14 is formed in a substantially U shape in plan view surrounding the transmission part 13. The shield part 14 has a pair of long side parts 14a and a connecting part 14b. The pair of long side portions 14 a are disposed on both sides of the transmission unit 13 so as to extend in the longitudinal direction along the long side of the first dielectric layer 12 with a gap from the transmission unit 13. Both ends of the long side portion 14 a are disposed outside the both ends of the transmission unit 13. The connection part 14b is arrange | positioned outside the one end of the transmission part 13, and has connected one end of a pair of long side part 14a. As a result, the shield part 14 has a U shape that opens near the other end of the transmission part 13.

  The average thickness T1 (see FIG. 1) of the transmission portion 13 and the shield portion 14 (conductive pattern 10) is not particularly limited, but the lower limit of the average thickness T1 is preferably 5 μm, more preferably 10 μm, and 12 μm. Is more preferable. On the other hand, the upper limit of the average thickness T1 is preferably 40 μm, more preferably 25 μm, and still more preferably 18 μm. If the average thickness T1 of the transmission unit 13 is less than the lower limit, the transmission loss in the transmission unit 13 may be too large. Further, if the average thickness T1 of the shield part 14 is less than the lower limit, the shield part 14 itself may not have sufficient conductivity, and the shield effect by the shield part 14 may not be sufficiently obtained. On the other hand, if the average thickness T1 of the transmission unit 13 and the shield unit 14 exceeds the above upper limit, the flexibility of the high-speed transmission board may be excessively lowered, and the shield unit 14 may affect the parasitic capacitance and Consistency may be difficult to obtain. In addition, the said average thickness T is a value including this rust prevention process layer, when forming a rust prevention process layer in the transmission part 13 and the shield part 14. FIG.

  The transmission unit 13 preferably has a substantially uniform thickness at any location in the plane direction. Similarly, the shield unit 14 preferably has a uniform thickness at any location in the plane direction. Here, “substantially uniform” means that the error is within 40% with respect to the average thickness T1, and “average thickness” is defined as an average value of measured values at arbitrary 10 points. . In the following, other elements are defined in the same manner when referred to as “average thickness”.

  The average interval W2 in the width direction between the transmission unit 13 and the long side portion 14a of the shield unit 14 is not particularly limited, but the lower limit of the average interval W2 is preferably 50 μm, more preferably 100 μm, and 200 μm. Is more preferable. On the other hand, the upper limit of the average interval W2 is preferably 1000 μm, more preferably 600 μm, and still more preferably 400 μm. If the average interval W2 is less than the lower limit, the shield part 14 may affect the parasitic capacitance, and impedance matching may be difficult to obtain. On the other hand, if the average interval W2 exceeds the upper limit, the high-speed transmission board may become too large in the width direction.

  The average width of the shield part 14 is not particularly limited, but the lower limit of the average width is preferably 100 μm, and more preferably 200 μm. On the other hand, the upper limit of the average width is preferably 500 μm, and more preferably 400 μm. If the average width is less than the above lower limit, the continuity of the shield part 14 itself cannot be obtained sufficiently, and the shield effect by the shield part 14 may not be sufficiently obtained. On the other hand, if the average width exceeds the upper limit, the high-speed transmission board may become too large in the width direction.

  Moreover, what is necessary is just to set the impedance of the circuit containing the conductive pattern 10 suitably according to the specification of the said high-speed transmission board | substrate. The lower limit of the impedance is usually 10Ω, and preferably 30Ω. The upper limit of the impedance is usually 100Ω, and preferably 80Ω.

  The transmission loss at a frequency of 10 GHz of the conductive pattern 10 is preferably 0.230 dB / cm or less, and more preferably 0.228 dB / cm or less. Thereby, the high-speed transmission substrate can be suitably used for transmission in a high-frequency region.

  The transmission loss at a frequency of 100 GHz of the conductive pattern 10 is preferably 3.10 dB / cm or less, more preferably 3.05 dB / cm or less, and further preferably 3.00 dB / cm or less. Thereby, the said high-speed transmission board | substrate can be used suitably also for transmission of a higher high frequency area | region of 100 GHz or more.

  The upper limit of the ten-point average roughness (Rz) of at least one surface of the conductive pattern 10 is preferably 4 μm, more preferably 3 μm, and even more preferably 2 μm. By setting the surface roughness of the conductive pattern 10 in this way, it is possible to ensure the bonding strength by chemical bonding or the like with the fluororesin of the first dielectric layer 12 described later while setting a suitable transmission speed and transmission loss. The lower limit of the ten-point average roughness (Rz) of the first dielectric layer 12 is not particularly limited and may be appropriately determined in consideration of manufacturability, cost, and the like. Typically, the conductive pattern 10 preferably has the ten-point average roughness (Rz) in the above range on the surface of the transmission unit 13 and the first dielectric layer 12 that is laminated.

  The conductive pattern 10 is formed, for example, by etching a metal layer stacked on one surface of the first dielectric layer 12. Although this metal layer can be formed of a conductive material, a pattern having a desired shape can be easily and reliably formed by using a copper foil.

(Anti-rust treatment layer)
As for the conductive pattern 10, it is preferable that the transmission part 13 contains the antirust process layer at least as mentioned above. This rust prevention treatment layer suppresses a decrease in bonding strength due to oxidation of the surface of the conductive pattern 10. The rust-proofing layer preferably contains cobalt, chromium or copper, and more preferably contains cobalt or a cobalt alloy as a main component. The antirust treatment layer may be formed as a single layer or a plurality of layers. The antirust treatment layer may be formed as a plating layer. This plating layer is formed as a single metal plating layer or an alloy plating layer. The metal constituting the single metal plating layer is preferably cobalt. Examples of the alloy constituting the alloy plating layer include cobalt alloys such as cobalt-molybdenum, cobalt-nickel-tungsten, and cobalt-nickel-germanium.

  The lower limit of the average thickness of the rust preventive layer is preferably 0.5 nm, more preferably 1 nm, and even more preferably 1.5 nm. There exists a possibility that the oxidation of the conductive pattern 10 cannot fully be suppressed as the average thickness of this antirust process layer is less than the said minimum. On the other hand, the upper limit of the average thickness is preferably 50 nm, more preferably 40 nm, and even more preferably 35 nm. If the average thickness of the rust-proofing layer exceeds the upper limit, it may not be possible to obtain an antioxidant effect commensurate with the increase in thickness.

<First conductive layer>
The first conductive layer 11 is laminated on the other surface (the surface on the first printed wiring board 1 side) of the first dielectric layer 12. It serves as a ground layer and a shield for the transmission unit 13. The first conductive layer 11 is located on both sides in the width direction of the transmission portion 13 in a plan view as shown in FIG. 5, and corresponds to the thickness direction of the shield portion 14 of the conductive pattern 10 in a sectional view as shown in FIG. It is provided at the position. The average thickness and average width of the first conductive layer 11 are not particularly limited, but can be the same as the average thickness and average width of the shield part 14.

<First dielectric layer>
The first dielectric layer 12 is formed by laminating the conductive pattern 10. The first dielectric layer 12 has a fluororesin as a main component. The first dielectric layer 12 may contain an optional component as necessary in addition to the fluororesin.

  The fluororesin of the first dielectric layer 12 preferably forms a chemical bond with one surface of the conductive pattern 10 (lamination surface with respect to the first dielectric layer 12). This chemical bond is formed by a form directly formed between the conductive pattern 10 and the fluororesin of the first dielectric layer 12, or by a coupling agent interposed between the conductive pattern 10 and the fluororesin of the first dielectric layer 12. And a form formed between the conductive pattern 10 and the fluororesin of the first dielectric layer 12 and a form in which these two forms are combined. The first dielectric layer 12 preferably has a chemical bond formed between the molecules of the fluororesin.

(Coupling agent)
The coupling agent is used to form a chemical bond between the conductive pattern 10 and the fluororesin of the first dielectric layer 12. As this coupling agent, a silane coupling agent is preferable, and among them, a silane coupling agent having a functional group containing an N atom or an S atom (hereinafter also referred to as “reactive functional group”) is more preferable. In the silane coupling agent having the reactive functional group, a hydrolyzable group (—OCH ₃ , —OC ₂ H ₅ , —OCOCH _3, etc.) is hydrolyzed to silane coupling on one surface of the conductive pattern 10. Fixed by reaction. On the other hand, the silane coupling agent is presumed to be chemically bonded to the first dielectric layer 12 at the reactive functional group as described later.

  Examples of the functional group containing an N atom include an amino group and a ureido group.

  Examples of the silane coupling agent having a functional group containing an N atom include aminoalkoxysilane, ureidoalkoxysilane, and derivatives thereof.

  Examples of the aminoalkoxysilane include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, and N-2- (aminoethyl) -3. -Aminopropyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane and the like.

  Examples of aminoethoxysilane derivatives include ketimines such as 3-triethoxysilyl-N- (1,3-dimethyl-butylidene) propylamine, and N- (vinylbenzyl) -2-aminoethyl-3-aminopropyltrimethoxy. Examples thereof include salts of silane coupling agents such as silane acetate.

  Examples of the ureidoalkoxysilane include 3-ureidopropyltriethoxysilane, 3-ureidopropyltrimethoxysilane, and γ- (2-ureidoethyl) aminopropyltrimethoxysilane.

  Examples of the functional group containing an S atom include a mercapto group and a sulfide group.

  Examples of the silane coupling agent having a functional group containing an S atom include mercaptoalkoxysilane, sulfide alkoxysilane, and derivatives thereof.

  Examples of mercaptoalkoxysilanes include 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyl (dimethoxy) methylsilane, mercaptoorganyl (alkoxysilane), and the like.

  Examples of the sulfide alkoxysilane include bis (3- (triethoxysilyl) propyl) tetrasulfide and bis (3- (triethoxysilyl) propyl) disulfide.

  As said silane coupling agent, what introduce | transduced the modification group may be used. As the modifying group, a phenyl group is preferable.

  Examples of the silane coupling agent include 3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, and bis ( 3- (Triethoxysilyl) propyl) tetrasulfide is preferred.

  As the coupling agent, another coupling agent can be used instead of or in addition to the silane coupling agent having a functional group containing an N atom or an S atom. The other coupling agent preferably includes a functional group reactive to the fluororesin of the first dielectric layer 12 or a radical thereof, and a functional group that can be chemically bonded to the conductive pattern 10. Coupling agents can be used.

  Examples of the titanium coupling agent include isopropyl triisostearoyl titanate, isopropyl tristearoyl titanate, isopropyl trioctanoyl titanate, isopropyl dimethacrylisostearoyl titanate, isopropyl tridodecylbenzenesulfonyl titanate, isopropyl isostearoyl diacryl titanate, isopropyl tri ( Dioctyl phosphate) titanate, isopropyl tricumyl phenyl titanate, isopropyl tris (dioctyl pyrophosphate) titanate, isopropyl tri (n-aminoethyl-aminoethyl) titanate, tetraisopropyl bis (dioctyl phosphite) titanate, tetraoctyl bis (ditridecyl phos) Fight) Titanate, Tetra (2 2-diallyloxymethyl-1-butyl) bis (ditridecyl) phosphite titanate, dicumylphenyloxyacetate titanate, bis (dioctylpyrophosphate) oxyacetate titanate, diisostearoylethylene titanate, bis (dioctylpaurophosphate) ethylene titanate, Bis (dioctyl paurophosphate) diisopropyl titanate, tetramethyl orthotitanate, tetraethyl orthotitanate, tetrapropyl orthotitanate, tetraisopropyl tetraethyl orthotitanate, tetrabutyl orthotitanate, butyl polytitanate, tetraisobutyl orthotitanate, 2-ethylhexyl titanate, stearyl titanate , Cresyl titanate monomer, cresyl titanate Terpolymer, diisopropoxy-bis- (2,4-pentadionate) titanium (IV), diisopropyl-bis-triethanolamino titanate, octylene glycol titanate, titanium lactate, acetoacetic estiltitanate, diisopropoxybis 8acetylacetonato) titanium, di-n-butoxybis (triethanolaluminate) titanium, dihydroxybis (lactato) titanium, titanium-isopropoxyoctylene glycolate, tetra-n-butoxytitanium polymer, tri-n-butoxytitanium Monostearate polymer, butyl titanate dimer, titanium acetylacetonate, polytitanium titanium acetylacetonate, titanium octylene glycolate, titanium lactate ammonium salt, Emissions lactate ethyl ester, titanium triethanolaminate, polyhydroxy titanium stearate.

  The upper limit of the relative dielectric constant (εr) of the first dielectric layer 12 is preferably 3, more preferably 2.7, even more preferably 2.5, and particularly preferably 2.3. If the relative dielectric constant (εr) exceeds the above upper limit, the dielectric loss tangent (tan δ) increases, and there is a possibility that the transmission loss cannot be sufficiently reduced, and there is a possibility that a sufficient transmission speed cannot be obtained. The lower limit of the relative dielectric constant (εr) of the first dielectric layer 12 is not particularly limited, but 1.2 is preferable. When the relative dielectric constant (εr) is less than the lower limit, it is difficult to ensure the dimensional stability of the first dielectric layer 12. In particular, when the relative dielectric constant is reduced by foaming, the elastic modulus is too low, which may make it difficult to process and convey.

  The upper limit of the dielectric loss tangent (tan δ) of the first dielectric layer 12 is preferably 0.004, more preferably 0.0035, and still more preferably 0.003. If this dielectric loss tangent (tan δ) exceeds the above upper limit, the transmission loss may not be sufficiently reduced, and a sufficient transmission rate may not be obtained. The dielectric loss tangent (tan δ) of the first dielectric layer 12 is not particularly limited, and the dielectric loss tangent (tan δ) is preferably as small as possible.

  The lower limit of the flexural modulus after the exposure test of the first dielectric layer 12 is preferably 20 GPa, more preferably 30 GPa, and even more preferably 40 GPa. If the bending strength of the first dielectric layer 12 after the exposure test is less than the lower limit, the strength as the high-speed transmission substrate may not be sufficient, and sufficient weather resistance may not be ensured. The upper limit of the bending strength after the exposure test of the first dielectric layer 12 is preferably 80 GPa, more preferably 70 GPa, and further preferably 60 GPa. If the bending strength of the first dielectric layer 12 after the exposure test exceeds the upper limit, the flexibility of the high-speed transmission substrate may not be sufficiently secured.

  As a minimum of average thickness of the 1st dielectric layer 12, 10 micrometers is preferred, 25 micrometers is more preferred, and 50 micrometers is still more preferred. If the average thickness of the first dielectric layer 12 is less than the above lower limit, the dielectric loss tangent becomes large and there is a possibility that the transmission loss cannot be sufficiently reduced, and there is a possibility that a sufficient transmission speed cannot be obtained. There is a possibility that the manufacturing operation of the substrate may be difficult. The upper limit of the average thickness of the first dielectric layer 12 is preferably 150 μm, more preferably 125 μm, and even more preferably 106 μm. If the average thickness of the first dielectric layer 12 exceeds the upper limit, the thickness of the first dielectric layer 12 and the high-speed transmission substrate may become unnecessarily large, and the material cost of the first dielectric layer 12 may increase. In addition, sufficient flexibility may not be obtained.

(Fluorine resin)
A fluororesin is one in which at least one hydrogen atom bonded to a carbon atom constituting a repeating unit of a polymer chain is substituted with a fluorine atom or an organic group having a fluorine atom (hereinafter also referred to as “fluorine atom-containing group”). Say. The fluorine atom-containing group is a group in which at least one hydrogen atom in a linear, branched or cyclic organic group is substituted with a fluorine atom. For example, a fluoroalkyl group, a fluoroalkoxy group, a fluoropolyether group, etc. Can be mentioned.

  The “fluoroalkyl group” means an alkyl group in which at least one hydrogen atom is substituted with a fluorine atom, and includes a “perfluoroalkyl group”. Specifically, a “fluoroalkyl group” is a group in which all hydrogen atoms of an alkyl group are substituted with fluorine atoms, and all hydrogen atoms other than one hydrogen atom at the end of the alkyl group are substituted with fluorine atoms. Group and the like.

  The “fluoroalkoxy group” means an alkoxy group in which at least one hydrogen atom is substituted with a fluorine atom, and includes a “perfluoroalkoxy group”. Specifically, a “fluoroalkoxy group” is a group in which all hydrogen atoms of an alkoxy group are substituted with fluorine atoms, and all hydrogen atoms other than one hydrogen atom at the end of the alkoxy group are substituted with fluorine atoms. Group and the like.

  The “fluoropolyether group” is a monovalent group having a plurality of alkylene oxide chains as repeating units and having an alkyl group or a hydrogen atom at the terminal, and the alkylene oxide chain and / or the terminal alkyl group or A monovalent group having a group in which at least one hydrogen atom in a hydrogen atom is substituted with a fluorine atom. “Fluoropolyether group” includes “perfluoropolyether group” having a plurality of perfluoroalkylene oxide chains as repeating units.

  Examples of fluororesins include tetrafluoroethylene / hexapropylene copolymer (FEP), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), polytetrafluoroethylene (PTFE), or tetrafluoroethylene-perfluorodiode. A xol copolymer (TFE / PDD) is preferred.

(Optional component)
Examples of optional components of the first dielectric layer 12 include engineering plastics, flame retardants, flame retardant aids, pigments, antioxidants, reflection-imparting agents, masking agents, lubricants, processing stabilizers, plasticizers, and foaming agents. It is done.

  As said engineering plastic, it can select and use from a well-known thing according to the characteristic calculated | required by the 1st dielectric layer 12, Typically, an aromatic polyether ketone resin can be used.

  This aromatic polyetherketone has a structure in which the benzene rings are bonded to the para position and the benzene rings are connected to each other by a rigid ketone bond (-C = O) or a flexible ether bond (-O-). Resin. As the aromatic polyether ketone, for example, ether ether ketone (PEEK) having a structural unit in which an ether bond, a benzene ring, an ether bond, a benzene ring, a ketone bond and a benzene ring are arranged in this order, an ether bond, a benzene ring, Examples include polyether ketone (PEK) having a structural unit in which a ketone bond and a benzene ring are arranged in this order. Among them, PEEK is preferable as the aromatic polyether ketone. Since such an aromatic polyether ketone is excellent in wear resistance, heat resistance, insulation, workability, etc., the first dielectric layer 12 containing the aromatic polyether ketone is bonded to the conductive pattern 10. Excellent in properties.

  A commercially available product can be used as the aromatic polyether ketone such as PEEK. As P aromatic polyether ketones, those of various grades are commercially available, and a single grade of aromatic polyether ketone that is commercially available may be used alone, or multiple grades of aromatic polyketone may be used. Ether ketone may be used in combination, or modified aromatic polyether ketone may be used.

  The content of the engineering plastic is not particularly limited. As a minimum of content of engineering plastics, it is 10 normally by a total mass ratio with a fluororesin, 20 is preferable and 35 is more preferable. The upper limit of the content is usually 50 and preferably 45 or less. If the content of the engineering plastic is less than the lower limit, the characteristics of the first dielectric layer 12 may not be sufficiently improved. On the other hand, if the content of the engineering plastic exceeds the above upper limit, the advantageous characteristics of the fluororesin may not be sufficiently exhibited.

  Various known flame retardants can be used, and examples thereof include halogen flame retardants such as bromine flame retardants and chlorine flame retardants.

  Various known flame retardant aids can be used, and examples include antimony trioxide.

  Various known pigments can be used as the pigment, and examples thereof include titanium oxide.

  Various known antioxidants can be used as the antioxidant, and examples thereof include phenolic antioxidants.

  As the reflection imparting agent, various known ones can be used, and examples thereof include titanium oxide.

  The first dielectric layer 12 is preferably irradiated with ionizing radiation. The ionizing radiation irradiation is preferably performed under heating. By irradiating the first dielectric layer 12 with ionizing radiation, the fluororesin is radicalized.

  Thus, when the above-mentioned coupling agent is used because the fluororesin is radicalized, it is considered that this coupling agent and the radical of the fluororesin are chemically bonded. Specifically, it is presumed that the coupling agent is chemically bonded to the fluororesin by chemically bonding the reactive functional group of the coupling agent to the radical portion. As described above, the coupling agent is chemically bonded to the radical portion of the fluororesin, and the coupling agent is chemically bonded to the conductive pattern 10 as described above, whereby the fluororesin of the first dielectric layer 12 and the conductive pattern 10 are A chemical bond with a coupling agent interposed between them is formed. As a result, a chemical bond is formed between the fluororesin and the conductive pattern 10, so that the bonding strength between the first dielectric layer 12 and the conductive pattern 10 can be increased.

  Here, it is presumed that the silane coupling agent is present between the conductive pattern 10 and the first dielectric layer 12 in the order of ridges. For this reason, the coupling agent hardly affects the surface properties of the conductive pattern 10 and the surface of the conductive pattern 10 is not roughened, so that the signal transmission performance is hardly deteriorated by the coupling agent. It is considered a thing.

  On the other hand, when the above coupling agent is not used, when the fluororesin is radicalized by ionizing radiation irradiation or the like, the radical portion of the fluororesin forms a chemical bond with the conductive pattern 10. Therefore, by forming a chemical bond between the fluororesin and the surface of the conductive pattern 10, the chemical bond between the first dielectric layer 12 and the conductive pattern 10 even when the coupling agent is not used. It is possible to increase the bonding strength.

  Further, when the fluororesin is radicalized, a chemical bond is formed between the molecules of the fluororesin, and when the first dielectric layer 12 includes an engineering plastic such as a PEEK resin, a chemical bond is formed between the fluororesin and the engineering plastic. A bond is formed. The bonds between the molecules of the fluororesin by chemical bonds and the bonds between the fluororesin and the engineering plastic are covalent bonds or hydrogen bonds, and these chemical bonds are stronger than the intermolecular bonds (FF bonds) of the fluororesin. Therefore, in the high-speed transmission substrate, a chemical bond is formed between the molecules of the fluororesin or a chemical bond is formed between the fluororesin and the engineering plastic, thereby improving the mechanical strength of the first dielectric layer 12. It becomes possible to make it.

  Here, examples of the ionizing radiation include charged particle beams such as electron beams and high-energy ion beams, high-energy electromagnetic waves such as γ-rays and X-rays, and neutral beams. Among these, electron beams are preferable. This is because the electron beam generator is relatively inexpensive, a high output electron beam can be obtained, and the degree of radical generation, that is, the degree of chemical bond formation, can be easily controlled.

  As the irradiation dose of the ionizing radiation, an effect can be obtained in a wide range, and any ionizing radiation may be selected, but about 50 KGy to 800 KGy is preferable. When the irradiation dose of ionizing radiation is less than the above lower limit, radicalization becomes insufficient, and the effect of improving the mechanical strength of the first dielectric layer 12, the effect of improving the bonding strength between the conductive pattern 10 and the first dielectric layer 12, and the like. May not be sufficiently obtained. On the other hand, when the irradiation dose of ionizing radiation exceeds the above upper limit, decomposition of the resin component (breaking of the polymer main chain) becomes excessive, and the mechanical strength of the first dielectric layer 12 may be reduced. On the other hand, if the irradiation dose is 50 KGy to 800 kGy, radicalization can be sufficiently advanced and the resin component is hardly decomposed, and sufficient mechanical strength, bonding strength, and the like can be obtained.

  The ionizing radiation irradiation is preferably performed in a state of heating the first dielectric layer 12 or the resin material immediately before forming the first dielectric layer 12 in a low oxygen or oxygen-free atmosphere.

  By performing ionizing radiation irradiation in a low-oxygen or oxygen-free atmosphere, the bonding strength of the first dielectric layer 12 to the conductive pattern 10 can be improved. Specifically, if the oxygen concentration is less than 1000 ppm, an effect of improving the bonding strength can be obtained. When the oxygen concentration is 500 ppm or less, a remarkable effect of improving the bonding strength is obtained, and when the oxygen concentration is 100 ppm or less, a more remarkable effect of improving the bonding strength is obtained. From the viewpoint of stability and ease of control of the oxygen concentration during ionizing radiation irradiation, the oxygen concentration is preferably 10 ppm or less.

  The heating temperature during irradiation with ionizing radiation is preferably equal to or higher than the melting point of the fluororesin that is the main component of the first dielectric layer 12. The heating temperature is preferably 80 ° C. or higher than the melting point, more preferably 40 ° C. or lower than the melting point. For example, when the main component of the first dielectric layer 12 is FEP, since the melting point of FEP is about 270 ° C., the heating temperature is preferably 270 ° C. to 350 ° C. By performing the heating temperature at a temperature higher than the melting point of the resin, radicalization of the fluororesin and formation of chemical bonds can be appropriately promoted. On the other hand, by making the upper limit of the heating temperature 80 ° C. or higher than the melting point of the fluororesin, thermal decomposition of the fluororesin (breaking of the polymer main chain) can be suppressed, and the mechanical strength of the first dielectric layer 12 And a decrease in bonding strength can be suppressed.

  In addition, when the 1st dielectric layer 12 contains engineering plastic, the heating temperature at the time of ionizing radiation irradiation has preferable melting | fusing point or more of a fluororesin and engineering plastic. By setting the heating temperature in this way, a chemical bond can be formed between the fluororesin and the engineering plastic, and the mechanical strength and the like of the first dielectric layer 12 can be further increased.

[Second printed wiring board]
As shown in FIGS. 1 and 2, the second printed wiring board 2 is disposed to face the first printed wiring board 1. The second printed wiring board 2 includes a second conductive layer 20 and a second dielectric layer 21.

<Second conductive layer>
The second conductive layer 20 serves as a ground layer and a shield for the transmission unit 13. The second conductive layer 20 is laminated on the second dielectric layer 21 on the side opposite to the first printed wiring board 1 side. The second conductive layer 20 can be composed of a metal layer. The metal layer constituting the second conductive layer 20 can be the same as the metal layer constituting the conductive pattern 10 or the like.

  As shown in FIG. 6, the second conductive layer 20 may be formed in a solid shape. Thereby, the high-speed transmission board has a higher shielding effect on the second printed wiring board 2 side. The “solid shape” means a state in which there is substantially no opening at least in a region overlapping with the transmission unit 13 in plan view. Note that “substantially having no opening” includes not only the case where the opening does not exist completely, but also the case where a minute hole such as bubble removal exists.

  When the second conductive layer 20 is formed as a solid as described above, the average distance H in the thickness direction between the transmission unit 13 and the second conductive layer 20 is preferably 25 μm or more and 200 μm or less. The average thickness of the second conductive layer 20 may be approximately the same as the average thickness T1 of the transmission unit 13. That is, the lower limit of the average thickness of the second conductive layer 20 is preferably 5 μm, more preferably 10 μm, and even more preferably 12 μm. On the other hand, the upper limit of the average thickness of the second conductive layer 20 is preferably 40 μm, more preferably 25 μm, and even more preferably 18 μm.

<Second dielectric layer>
The second dielectric layer 21 contains a fluororesin as a main component and may contain an optional component other than the fluororesin. The fluororesin and optional components in this case are the same as those of the first dielectric layer 12 of the first printed wiring board 1 described above.

  The second dielectric layer 21 preferably has chemical bonds formed between the molecules of the fluororesin by irradiation with ionizing radiation. Thus, the chemical bond is formed between the molecules of the fluororesin of the second dielectric layer 21, so that the mechanical strength of the second dielectric layer 21 can be improved. The second dielectric layer 21 may have a chemical bond with the second conductive layer 20 formed by ionizing radiation irradiation. As described above, since the second dielectric layer 21 has a chemical bond with the second conductive layer 20, the bonding property of the second conductive layer 20 to the second dielectric layer 21 can be improved. In addition, what is necessary is just to make the irradiation conditions of the said ionizing radiation irradiation the same as the case of the 1st printed wiring board 1 mentioned above.

  In addition, the second dielectric layer 21 also has the above-mentioned characteristics in terms of relative dielectric constant (εr), dielectric loss tangent (tan δ), bending strength after exposure test, light transmittance, light transmittance after exposure test, dimensions, and the like. The same as the first dielectric layer 12 of one printed wiring board 1 is preferable.

(Adhesive layer)
The adhesive layer 3 adheres the first printed wiring board 1 and the second printed wiring board 2. The adhesive layer 3 is disposed between the first printed wiring board 1 and the second printed wiring board 2.

  Moreover, although the dielectric constant of the contact bonding layer 3 is not specifically limited, As an upper limit of this dielectric constant, 4.0 is preferable, 3.0 is more preferable, 2.0 is further more preferable. If the relative dielectric constant exceeds the upper limit, the presence of the adhesive layer 3 may cause the transmission characteristics of the high-frequency signal in the transmission unit 13 to deteriorate.

  The material constituting the adhesive layer 3 is not particularly limited as long as it is an insulating and adhesive material, and can be selected from known materials, and a fluororesin or a liquid crystal polymer is preferable.

  Examples of the fluororesin used for the adhesive layer 3 include those similar to the fluororesin of the first dielectric layer 12 of the first printed wiring board 1 described above. By forming the adhesive layer 3 from a material mainly composed of a fluororesin, the periphery of the transmission unit 13 is surrounded by an insulating material mainly composed of the fluororesin. As described above, the transmission part 13 is made of an insulating material mainly composed of a fluororesin, that is, the transmission part 13 is surrounded by the adhesive layer 3 and the first dielectric layer 12, so that the transmission loss in the transmission part 13 can be sufficiently reduced. At the same time, a sufficient transmission rate can be obtained.

  Examples of the liquid crystal polymer used for the adhesive layer 3 include the same liquid crystal polymers as those of the cover films 60 and 70 of the coverlays 6 and 7 described later. By forming the adhesive layer 3 from a material containing a liquid crystal polymer as a main component, it is possible to ensure high adhesive strength between the first printed wiring board 1 and the second printed wiring board 2 and to improve shape maintainability. it can.

  The average thickness of the adhesive layer 3 (distance between the first dielectric layer 12 and the second dielectric layer 21) is not particularly limited as long as it is larger than the average thickness of the conductive pattern 10. The lower limit of the average thickness of the adhesive layer 3 is preferably 10 μm, more preferably 20 μm, and even more preferably 30 μm. The upper limit of the average thickness of the adhesive layer 3 is preferably 100 μm, more preferably 85 μm, and even more preferably 70 μm. If the average thickness of the adhesive layer 3 is less than the above lower limit, it is difficult to form the adhesive layer 3, and there is a possibility that a good adhesion state between the first printed wiring board 1 and the second printed wiring board 2 cannot be obtained. On the other hand, when the average thickness of the adhesive layer 3 exceeds the above upper limit, the flexibility of the high-speed transmission substrate may be excessively lowered, and the dielectric loss in the adhesive layer 3 may be increased.

[First through hole]
As shown in FIGS. 2, 4, and 5, the first through holes 4 </ b> A and 4 </ b> B constitute an input / output unit of the transmission unit 13. These first through holes 4 </ b> A and 4 </ b> B penetrate the second dielectric layer 21 in the thickness direction at both ends of the transmission unit 13 and are connected to the transmission unit 13.

  The first through holes 4A and 4B are further connected to a circuit, wiring, mounting connection pads, and the like formed on the first printed wiring board 1 side of the first dielectric layer 12 (not shown). The first through holes 4A and 4B can be formed by forming a through hole and then plating the inner wall of the through hole or filling the through hole with a conductor. The inner diameters of the first through holes 4A and 4B are not particularly limited, but are preferably 50 μm or more and 500 μm or less.

  As shown in FIG. 4, the upper limit of the angle γ formed by a pair of virtual lines connecting the center of the first through hole 4A and the end portion angle of the long side portion 14a of the shield portion 14 is preferably 45 °, 40 ° Is more preferable. As a result, the first through hole 4A and the end of the transmission unit 13 can be retracted by a certain distance inside the first dielectric layer 12, so that even if the shield unit 14 is open in a U shape, the shield The shielding effect by the part 14 can fully be exhibited.

[Second through hole]
As shown in FIGS. 1, 4 and 5, the second through hole 5 connects the first conductive layer 11 and the second conductive layer 20. The second through hole 5 continuously penetrates the first dielectric layer 12, the shield part 14, and the second dielectric layer 21, and is connected to the first conductive layer 11 and the second conductive layer 20 at the end. Thus, by having the 2nd through-hole 5 which conducts the 1st conductive layer 11 and the 2nd conductive layer 20, the electric potential of the 1st conductive layer 11 and the 2nd conductive layer 20 is made equal, These conductive layers 11 , 20 can function suitably as a ground layer (shield). As a result, the high-speed transmission board can exhibit a higher shielding effect. In addition, by making the potentials of the first conductive layer 11 and the second conductive layer 20 equal, the withstand voltage of the high-speed transmission substrate can be further increased.

  The distance L (see FIG. 5) between the second through holes 5 adjacent to each other in the longitudinal direction of the first dielectric layer 12 is not particularly limited, but is preferably within 1 cm. Thereby, the shielding effect by the shield part 14 can be improved more. The inner diameter of the second through hole 5 is not particularly limited, but is preferably 50 μm or more and 500 μm or less, for example, like the inner diameter of the second through hole 5.

  The second through hole 5 can be formed in the same manner as the first through holes 4A and 4B. The location, number, size and the like of the second through hole 5 are not particularly limited and can be appropriately designed.

[First coverlay]
The first coverlay 6 protects the first conductive layer 11 and enhances the shape maintainability of the high-speed transmission board. The first coverlay 6 is laminated on the outer side of the first printed wiring board 1 (on the opposite side to the second printed wiring board 2). The first coverlay 6 includes a cover film 60 and an adhesive layer 61.

<Cover film>
The cover film 60 constitutes the outermost layer of the high-speed transmission board. As a minimum of average thickness of this cover film 60, 3 micrometers is preferred and 7 micrometers is more preferred. On the other hand, the upper limit of the average thickness of the cover film 60 is preferably 25 μm, and more preferably 12 μm. When the average thickness of the cover film 60 is less than the above lower limit, the insulating property may be insufficient. On the other hand, when the average thickness of the cover film 60 exceeds the upper limit, the flexibility of the high-speed transmission substrate may be excessively lowered.

  The cover film 60 preferably has insulating properties, and more preferably has rigidity capable of imparting a predetermined shape maintaining property to the high-speed transmission substrate. Examples of the material constituting the cover film 60 include a liquid crystal polymer.

  The liquid crystal polymer includes a thermotropic type exhibiting liquid crystallinity in a molten state and a lyotropic type exhibiting liquid crystallinity in a solution state, and it is preferable to use a thermotropic liquid crystal polymer as the cover film 60.

  The liquid crystal polymer is, for example, an aromatic polyester obtained by synthesizing an aromatic dicarboxylic acid and a monomer such as an aromatic diol or an aromatic hydroxycarboxylic acid. A typical example is a polymer obtained by polymerizing monomers of the following formulas (1), (2) and (3) synthesized from parahydroxybenzoic acid (PHB), terephthalic acid and 4,4′-biphenol. , A polymer obtained by polymerizing monomers of the following formulas (3) and (4) synthesized from PHB, terephthalic acid and ethylene glycol, the following formula (2) synthesized from PHB and 2,6-hydroxynaphthoic acid, Examples thereof include a polymer obtained by polymerizing the monomers (3) and (5).

  The liquid crystal polymer is not particularly limited as long as it exhibits liquid crystallinity, and the above-mentioned polymers are the main components (in the liquid crystal polymer, 50 mol% or more), and other polymers or monomers may be copolymerized. . The liquid crystal polymer may be a liquid crystal polyester amide, a liquid crystal polyester ether, a liquid crystal polyester carbonate, or a liquid crystal polyester imide.

  The liquid crystal polyester amide is a liquid crystal polyester having an amide bond, and examples thereof include a polymer obtained by polymerizing monomers of the following formula (6) and the above formulas (2) and (4).

  The liquid crystal polymer is preferably produced by melt polymerization of raw material monomers corresponding to the constituent units constituting the liquid crystal polymer, and solid-phase polymerization of the obtained polymer (prepolymer). Thereby, a high molecular weight liquid crystal polymer having high heat resistance, strength and rigidity can be produced with good operability. Melt polymerization may be carried out in the presence of a catalyst. Examples of this catalyst include metal compounds such as magnesium acetate, stannous acetate, tetrabutyl titanate, lead acetate, sodium acetate, potassium acetate, and antimony trioxide, And nitrogen-containing heterocyclic compounds such as 4- (dimethylamino) pyridine and 1-methylimidazole, and nitrogen-containing heterocyclic compounds are preferably used.

  Note that the cover film 60 may include a filler, an additive, and the like in addition to the liquid crystal polymer. Further, the cover film 60 may be formed of a material other than the liquid crystal polymer. However, from the viewpoint of maintaining the shape of the high-speed transmission substrate, a material capable of forming a highly rigid film is preferable.

<Adhesive layer>
The adhesive layer 61 adheres the cover film 60 to the outside of the first printed wiring board 1. The material constituting the adhesive layer 61 is not particularly limited as long as it has adhesiveness and insulating properties, and examples thereof include nylon resin, epoxy resin, butyral resin, and acrylic resin.

  The average thickness of the adhesive layer 61 is not particularly limited, but the upper limit is preferably 10 μm and more preferably 20 μm. The upper limit of the average thickness of the adhesive layer 61 is preferably 50 μm and more preferably 30 μm. If the average thickness of the adhesive layer 61 is less than the above lower limit, the adhesiveness may be insufficient, and if it exceeds the upper limit, the flexibility of the high-speed transmission substrate may be excessively lowered.

[Second coverlay]
The second coverlay 7 protects the second conductive layer 20 and enhances the shape maintaining property of the high-speed transmission board. The second coverlay 7 is stacked on the outer side (opposite side of the first printed wiring board 1) with respect to the second printed wiring board 2. The second coverlay 7 includes a cover film 70 and an adhesive layer 71. Since the cover film 70 and the adhesive layer 71 of the second cover lay 7 are the same as the cover film 60 and the adhesive layer 61 of the first cover lay 6 described above, the following description is omitted.

[Method of manufacturing high-speed transmission board]
The high-speed transmission substrate is, for example, (1) a rust prevention treatment layer forming step,
(2) coating process,
(3) drying process,
(4) 1st adhesion process,
(5) Second bonding step,
(6) First printed wiring board forming step,
(7) First through hole forming step,
(8) Second printed wiring board forming step,
(9) Third adhesion step,
It is obtained from a manufacturing method including (10) a second through hole forming step and (11) a cover lay stacking step.

<(1) Rust prevention treatment layer formation process>
The antirust treatment layer forming step includes a first conductive film, a second conductive film, and a third conductive film (hereinafter simply referred to as “conductive film”) for forming the conductive pattern 10, the first conductive layer 11, and the second conductive layer 20. This is a step of forming a rust-proofing layer on at least the first conductive film. For example, a metal foil is used as the conductive film. This rust prevention treatment layer forming process is performed by applying a rust prevention solution containing metal ions to all or a part of at least one surface of the conductive film, and then drying the rust prevention solution. As metal ions, cobalt ions, chromium ions and copper ions are preferable, and cobalt ions are more preferable. As the coating method of the rust preventive solution, various known methods can be adopted, and examples thereof include a method of immersing the conductive film in the rust preventive solution and a method of applying the rust preventive solution to the conductive film. The drying of the rust preventive solution may be either natural drying or forced drying. By drying the rust preventive solution in this way, a rust preventive treatment layer of metal oxide derived from metal ions in the rust preventive solution is formed on all or part of at least one surface of the conductive film.

  The antirust treatment layer forming step may be performed by a plating method such as a water-soluble electrolytic plating method. When the plating method is employed, the rust prevention treatment layer is preferably formed as a single metal plating layer or an alloy plating layer and includes cobalt.

<(2) Coating process>
The coating process is performed in order to chemically bond the above-described coupling agent to the conductive film. This coating step is performed by applying a composition containing a silane coupling agent (hereinafter also referred to as “coupling agent-containing composition”) to at least a part of one surface of the conductive film.

  There is no restriction | limiting in particular as a coating method of the coupling agent containing composition in a coating process, For example, the method of immersing an electrically conductive film in a coupling agent containing composition, The method of apply | coating a coupling agent containing composition to an electrically conductive film And a method of immersing the conductive film in the coupling agent-containing composition is preferable.

  When employ | adopting the method of immersing an electrically conductive film in a coupling agent containing composition, the temperature of a coupling agent containing composition shall be 20 to 40 degreeC normally, and immersion time shall be 10 to 30 second.

(Coupling agent-containing composition)
The coupling agent-containing composition contains a coupling agent such as the above silane coupling agent and a solvent, and may contain other optional components as long as the effects of the present invention are not impaired.

  As a minimum of content of a coupling agent in a coupling agent content composition, 0.1 mass% is preferred and 0.5 mass% is more preferred. If the content of the coupling agent is less than the lower limit, the bondability between the first dielectric layer 12 and the conductive pattern 10 (transmission unit 13) may not be sufficiently improved. On the other hand, as an upper limit of content of a coupling agent, 5 mass% is preferable, 3 mass% is more preferable, and 1.5 mass% is further more preferable. When the content of the coupling agent exceeds the above upper limit, the coupling agent tends to aggregate and it may be difficult to prepare the coupling agent-containing composition.

(solvent)
The solvent is not particularly limited as long as it can dissolve the coupling agent, and examples thereof include alcohols such as methanol and ethanol, toluene, hexane, and water. However, as the solvent, ethanol is preferable for the ethoxysilane-based aminosilane coupling agent and methanol is preferable for the methoxysilane-based aminosilane coupling agent from the viewpoint of storage stability.

(Optional component)
Optional components include antioxidants, viscosity modifiers, surfactants, and the like. Examples of the antioxidant include iron, sugar, reductone, sodium sulfite, ascorbic acid (vitamin C) and the like.

<(3) Drying process>
A drying process is a process of drying the coupling containing composition applied to the electrically conductive film. Although this drying process may be performed by either natural drying or forced drying, natural drying is preferred. Moreover, it is preferable to heat-process a electrically conductive film after drying a coupling agent containing composition. By performing the heat treatment, the coupling agent can be more reliably fixed to all or a part of at least one surface of the conductive film. The heat treatment can be performed, for example, by heating at 100 to 130 ° C. for 1 to 10 minutes in a thermostatic bath.

<(4) 1st adhesion process>
The first bonding step is a step of bonding the first conductive film to one surface of the first dielectric layer 12 and bonding the second conductive film to the other surface. In this first bonding step, for example, the first conductive film (conductive pattern 10) is placed on one surface of the first dielectric layer 12, and the second conductive film (first conductive layer 11) is placed on the other surface. It is performed by pressurizing and heating in the state. The first bonding step can be performed using a known hot press machine. The first bonding step is preferably performed by vacuum pressing under a low oxygen concentration, for example, a nitrogen atmosphere. By performing the first adhesion step under a low oxygen concentration, oxidation of one surface (adhesion surface) of the first conductive film can be suppressed, and a decrease in bonding strength can be suppressed.

  Here, by appropriately selecting the pressure heating conditions in the bonding step, the terminal or side chain of the fluororesin that is the main component of the first dielectric layer 12 can be decomposed to radicalize part of the fluororesin. it can. The heating temperature is preferably at least the crystal melting point of the fluororesin that is the main component of the first dielectric layer 12, more preferably at least 30 ° C. above the crystal melting point, and even more preferably at least 50 ° C. above the crystal melting point. For example, when the main component of the first dielectric layer 12 is FEP, since the crystal melting point of this FEP is about 270 ° C., the heating temperature is preferably 270 ° C. or higher, more preferably 300 ° C. or higher, and further preferably 320 ° C. or higher. . By heating the first dielectric layer 12 at such a heating temperature, radicals of fluororesin can be generated effectively. However, since the fluororesin itself may be deteriorated when the heating temperature is too high, the upper limit of the heating temperature is preferably 600 ° C. or less, more preferably 500 ° C. or less.

  In this bonding step, other known radical generation methods such as ionizing radiation irradiation may be used in combination with the pressure heating. Examples of ionizing radiation irradiation include γ-ray irradiation treatment. By performing ionizing radiation irradiation under heating in this way, radicalization of the fluororesin can be generated more effectively while suppressing deterioration of the fluororesin. Therefore, irradiation with ionizing radiation under heating promotes the radicalization of the fluororesin and the formation of chemical bonds, and further improves the bondability between the first dielectric layer 12 and the conductive pattern 10 (particularly the transmission portion 13). Can be improved.

  Further, the ionizing radiation irradiation is not necessarily performed in the bonding process, and may be performed at the same time when the first dielectric layer 12 is formed, for example, or after the first dielectric layer 12 is formed and before the bonding process is performed. It may be performed after the bonding step. Further, the irradiation with ionizing radiation is not necessarily performed under heating, and radicalization of the fluororesin may be performed only by irradiation with ionizing radiation.

<(5) Second bonding step>
The second bonding step is a step of bonding the third conductive film to one surface of the second dielectric layer 21. This second bonding step is performed, for example, by applying pressure and heating with the third conductive film (second conductive layer 20) placed on one surface of the second dielectric layer 21. This second bonding step can be performed using a known hot press machine.

<(6) First printed wiring board forming step>
In the first printed wiring board forming step, the first conductive pattern 10 (the transmission unit 13 and the shield unit 14) is formed on one surface of the first dielectric layer 12 by patterning the conductive film, and the first conductive layer is formed on the other surface. 11 is a step of forming the first printed wiring board 1 by forming 11. Examples of this patterning include known etching techniques such as dry etching and wet etching. Among these, wet etching is preferable from the viewpoint of productivity in terms of etching speed. In this wet etching, for example, portions of the first conductive film and the second conductive film that are to be the conductive pattern 10 are masked, and desired portions (not masked) of the first conductive film and the second conductive film using an etchant. This is done by removing the part). As this etching solution, for example, sulfuric acid / hydrogen peroxide (mixed solution of sulfuric acid and hydrogen peroxide solution), sodium sulfate sulfate or the like can be used.

  The patterning may be performed before the first bonding step and the second bonding step. The patterning before the bonding step may be performed by, for example, a method of bonding the conductive film to the first dielectric layer 12 after patterning the conductive film formed on the surface of the release film, or a method of stacking the punched conductive film. it can.

<(7) First through hole forming step>
The first through hole forming step is a step of forming the first through holes 4A and 4B in the first printed wiring board 1. The first through holes 4A and 4B can be formed, for example, by forming a through hole and then plating the inner wall of the through hole or filling the through hole with a conductor. The through holes can be formed by etching using a photomask or laser processing, for example. The plating treatment on the inner wall of the through hole can be performed, for example, by electroless plating, and the filling of the conductor into the through hole can be performed using a conductor paste.

<(8) Second printed wiring board forming step>
The second printed wiring board forming step is a step of forming the second printed wiring board 2 by forming the second conductive layer 20 on one surface of the second dielectric layer 21 by patterning the conductive film. This patterning can be performed in the same manner as the patterning in the first printed wiring board forming step described above.

<(9) Third bonding step>
The third bonding step is a step of bonding the first printed wiring board 1 and the second printed wiring board 2. In this third bonding step, these printed wiring boards 1 and 2 are bonded by applying pressure and heating with an adhesive interposed between the first printed wiring board 1 and the second printed wiring board 2. Done in The adhesive is not particularly limited as long as it is a material having insulating properties and adhesive properties, and can be selected from known materials. As described above, a fluororesin and a liquid crystal polymer are preferable. In addition, you may adhere | attach the 1st dielectric layer 12 of the 1st printed wiring board 1 and the 2nd dielectric layer 21 of the 2nd printed wiring board 2 directly by melt | fusion etc., without using a cementing agent.

<(10) Second through hole forming step>
The second through hole forming step is a step of forming the second through hole 5 in the adhesive body between the first printed wiring board 1 and the second printed wiring board 2. This second through-hole forming step can be performed, for example, in the same manner as the first through-hole forming step.

<(11) Coverlay lamination process>
The cover lay stacking step is a step of obtaining the high-speed transmission substrate by stacking the first cover lay 6 and the second cover lay 7. In this cover lay stacking step, for example, the first cover lay 6 in which the adhesive layer 61 is formed in advance is placed on the cover film 60 so as to cover the first conductive layer 11, and the cover film is covered so as to cover the second conductive layer 20. The second cover lay 7 on which the adhesive layer 71 is formed in advance is placed on the plate 70 and then heated by pressure. Thereby, the cover film 60 is fixed to the first dielectric layer 12 via the adhesive layer 61, and the cover film 70 is fixed to the second dielectric layer 21 via the adhesive layer 71.

  The pressure heating conditions may be appropriately determined depending on the constituent materials of the adhesive layers 61 and 71 used for the coverlays 6 and 7.

<Advantages>
In the high-speed transmission substrate, the conductive pattern 10 (the transmission unit 13 and the shield unit 14) is disposed between the first dielectric layer 12 and the second dielectric layer 21. The first dielectric layer 12 and the second dielectric layer 21 are mainly composed of a fluororesin, but this fluororesin generally tends to have a low dielectric loss tangent (tan δ) and relative dielectric constant (εr). Therefore, when the first dielectric layer 12 and the second dielectric layer 21 are mainly composed of fluororesin, the transmission loss of the conductive pattern 10 (particularly the transmission unit 13) can be sufficiently reduced and a sufficient transmission speed can be obtained. Thereby, since it is not necessary to increase the thickness of the first dielectric layer 12 and the second dielectric layer 21 in order to improve the transmission characteristics, the first dielectric layer 12 and the second dielectric layer 21 can be made thinner.

  In the high-speed transmission substrate, the first conductive layer 11 and the second conductive layer 20 are laminated outside the first dielectric layer 12 and the second dielectric layer 21. That is, the conductive pattern 10 (transmission unit 13) is disposed between the first conductive layer 11 and the second conductive layer 20. Therefore, the 1st conductive layer 11 and the 2nd conductive layer 20 can be functioned as a shield with respect to the conductive pattern 10 (transmission part 13). In particular, by reducing the distance between the first conductive layer 11 and the second conductive layer 20 by reducing the thickness of the first dielectric layer 12 and the second dielectric layer 21, an excellent shielding effect can be exhibited, and the first conductive layer 11. And since the deterioration of the shield property in the side surface of the 2nd conductive layer 20 can be suppressed, a shield effect can be improved more.

[Other Embodiments]
The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is not limited to the configuration of the embodiment described above, but is defined by the scope of the claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of the claims. The

  For example, the adhesive layer between the first printed wiring board and the second printed wiring board may be omitted, and the first dielectric layer and the second dielectric layer may be fused. In this case, the transmission unit is embedded in the first dielectric layer and the second dielectric layer. As a result, the transmission part is surrounded by an insulating material mainly composed of a fluororesin.

  Further, the through hole connecting the first conductive layer and the second conductive layer does not necessarily have to penetrate the shield portion of the first printed wiring board, and can be omitted.

  Furthermore, instead of the coverlay, the first conductive layer and the second conductive layer may be covered with an insulating resin coating or the like.

  Further, the transmission unit is not limited to a straight line shape, but may be determined according to the shape of the first dielectric layer or the like, or may be another shape such as a curved shape or a bellows shape. Furthermore, the shield part can be omitted. The first conductor layer may have other shapes such as a belt shape or a mesh shape. The second conductor layer may have another shape such as a solid shape or a mesh shape.

  Furthermore, the present invention is also directed to an electronic component using a high-speed transmission board. Specifically, in the present invention, for example, an electronic component in which a circuit element such as a semiconductor device or a chip resistor is electrically connected to the high-speed transmission substrate as in the above embodiment is also within the intended range.

  ADVANTAGE OF THE INVENTION According to this invention, the high-speed transmission board | substrate which is low in transmission loss and excellent in the shielding effect can be provided, responding to the request for thickness reduction. Therefore, the high-speed transmission board can be suitably applied as a wiring board for transmitting high-frequency signals and a high-speed transmission board for electronic components.

DESCRIPTION OF SYMBOLS 1 1st printed wiring board 10 Conductive pattern 11 1st conductive layer 12 1st dielectric layer 13 Transmission part 14 Shield part 14a Long side part 14b Connection part 2 2nd printed wiring board 20 2nd conductive layer 21 2nd dielectric layer 3 Adhesion Layer 4A, 4B First through hole 5 Second through hole 6 First cover lay 60 Cover film 61 Adhesive layer 7 Second cover lay 70 Cover film 71 Adhesive layer W1 (transmission part) average width W2 (transmission part and shield part) Average distance (in the width direction) of the long side of the T1 average thickness H (of the transmission part and shield part) H (average of the distance in the thickness direction of the transmission part and the second conductive layer) L (interval of the second through holes) L
γ (first through hole on the non-go region side) angle

Claims (13)

A first printed wiring board, and a second printed wiring board disposed opposite to the first printed wiring board,
The first printed wiring board is opposite to the first dielectric layer, the conductive pattern laminated on the second printed wiring board side of the first dielectric layer, and the second printed wiring board side of the first dielectric layer. A first conductive layer laminated on the side,
The second printed wiring board has a second dielectric layer and a second conductive layer laminated on the opposite side of the second dielectric layer from the first printed wiring board side,
A high-speed transmission board in which the first dielectric layer and the second dielectric layer are mainly composed of a fluororesin.   The high-speed transmission board according to claim 1, wherein the conductive pattern includes a high-frequency signal transmission unit and a shield unit surrounding the transmission unit.   The high-speed transmission board according to claim 2, wherein the periphery of the transmission unit is surrounded by an insulating material mainly composed of a fluororesin.   The high-speed transmission board according to claim 1, 2, or 3, further comprising a through hole that conducts the first conductive layer and the second conductive layer.   5. The high-speed transmission substrate according to claim 1, wherein a ten-point average roughness Rz of at least one surface of the conductive pattern is 4 μm or less.   6. The apparatus according to claim 1, further comprising: a first cover film laminated on an outer side of the first printed wiring board; and a second cover film laminated on an outer side of the second printed wiring board. High-speed transmission board described in 1.   The high-speed transmission board according to any one of claims 1 to 6, wherein the high-speed transmission board has a chemical bond between the fluororesin of the first dielectric layer and the conductive pattern.   The high-speed transmission substrate according to claim 7, wherein the chemical bond is formed by ionizing radiation irradiation.   The high-speed transmission substrate according to claim 7 or 8, wherein the chemical bond is formed via a coupling agent present at an interface between the first dielectric layer and the conductive pattern.   The high-speed transmission substrate according to claim 9, wherein the coupling agent is a silane coupling agent having a functional group containing an N atom or an S atom.   11. The method according to claim 1, wherein at least one of the first dielectric layer and the second dielectric layer has a chemical bond formed by ionizing radiation irradiation between molecules. The high-speed transmission board described.   The fluororesin of the first dielectric layer and the second dielectric layer is tetrafluoroethylene / hexapropylene copolymer (FEP), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), polytetrafluoroethylene ( The high-speed transmission substrate according to any one of claims 1 to 11, which is PTFE) or tetrafluoroethylene-perfluorodioxole copolymer (TFE / PDD). An electronic component comprising the high-speed transmission board according to any one of claims 1 to 12.

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