WO2022211042A1

WO2022211042A1 - Laminate for printed circuit board and junction for multilayer printed circuit board

Info

Publication number: WO2022211042A1
Application number: PCT/JP2022/016605
Authority: WO
Inventors: 誠一善見; 順哉中坪; 茂樹今村
Original assignee: 大日本印刷株式会社
Priority date: 2021-03-31
Filing date: 2022-03-31
Publication date: 2022-10-06
Also published as: JPWO2022211042A1; TW202246053A; JP7298786B2

Abstract

The present disclosure provides a laminate for printed circuit boards, obtained by laminating a base material, an adhesive layer, and a metal foil in this order. The base material contains a low-dielectric resin material. The adhesive layer contains a thermosetting resin. The maximum height roughness (Rz) of the surface of the metal foil on the adhesive layer side is 10 μm or less. The maximum height roughness (Rz) of the surface of the base material on the adhesive layer side is 0.1 μm or more.

Description

Laminate for printed wiring board and joined body for multilayer printed wiring board

The present disclosure relates to a printed wiring board laminate and a multilayer printed wiring board assembly.

In recent years, the demand for various printed wiring boards has increased as electronic products have become lighter, smaller, and more dense. A printed wiring board generally uses a metal laminate in which a conductive layer made of metal foil is laminated on a base material, and the conductive layer of the metal laminate is patterned to form a circuit.

It is expected that mobile communication systems, typified by mobile phone terminals, will use higher frequency bands in the future than at present. As the frequency increases, the transmission loss in the high frequency circuit also increases. Therefore, the printed wiring board for the fifth generation mobile communication system is required to have excellent electrical characteristics corresponding to frequencies in the high frequency band.

Patent Document 1 can be cited as a technique related to laminated films used for rubber moldings. The aforementioned Patent Document 1 discloses a laminated film having an adhesive layer on one surface of a fluororesin film. The adhesive layer is a deposited film formed on the fluororesin film by a plasma chemical vapor deposition method using a vapor deposition gas composition containing an organic silicon compound.
In addition,

Patent Documents

2 and 3 disclose laminates with an adhesive layer suitable for manufacturing products related to printed wiring boards.

Patent No. 5895468 Patent No. 6485577 Patent No. 6718148

In recent years, the use of base materials containing low-dielectric resin materials such as liquid crystal polymers (LCP) and fluorine-based resins has been studied as base materials for printed wiring boards that handle high-frequency information signals. Such a base material may have poor adhesion to the metal foil. In addition, in order to suppress transmission loss, the metal foil is required to have a low roughness, but a metal foil with a low surface roughness tends to have insufficient adhesiveness to the base material.

The present disclosure is an invention made in view of the above problems, and a main object thereof is to provide a laminate for a printed wiring board in which a base material and a metal foil are strongly bonded and transmission loss is suppressed. .

In order to achieve the above object, the present disclosure provides a laminate for a printed wiring board in which a base material, an adhesive layer, and a metal foil are laminated in this order, wherein the base material contains a low dielectric resin material. , the adhesive layer contains a thermosetting resin, the maximum height roughness (Rz) of the adhesive layer side surface of the metal foil is 10 μm or less, and the adhesive layer side surface of the base material is Provided is a printed wiring board laminate having a maximum height roughness (Rz) of 0.1 μm or more.

Further, in the present disclosure, the first base material, the first adhesive layers disposed on both sides of the first base material, and the surface of each of the first adhesive layers opposite to the first base material A first printed wiring board laminate having a first metal foil disposed, a second base material, second adhesive layers disposed on both sides of the second base material, and one of the second a second printed wiring board laminate having a second metal foil disposed on the surface of the adhesive layer opposite to the second base material, the first printed wiring board laminate, and In the second printed wiring board laminate, the second adhesive layer on the side of the second printed wiring board laminate on which the second metal foil is not disposed is the second adhesive layer of the first printed wiring board laminate. 1. A bonded structure for a multilayer printed wiring board arranged to face a metal foil, wherein the first base material and the second base material contain a low dielectric resin material, and the first adhesive layer and the second base material contain a low dielectric resin material. The second adhesive layer contains a thermosetting resin, and the maximum height roughness (Rz) of the surfaces of the first metal foil and the second metal foil facing the first adhesive layer and the second adhesive layer is 10 μm or less. and the maximum height roughness (Rz) of the surfaces of the first base material and the second base material on the first adhesive layer and second adhesive layer sides is 0.1 μm or more, for a multilayer printed wiring board Provide a conjugate.

In the present disclosure, it is possible to provide a laminate for a printed wiring board in which the base material and the metal foil are firmly adhered and the transmission loss is suppressed.

1 is a schematic cross-sectional view illustrating a printed wiring board laminate of the present disclosure; FIG. 1 is a schematic cross-sectional view illustrating a printed wiring board laminate of the present disclosure; FIG. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic cross-sectional view illustrating a joined body for a multilayer printed wiring board of the present disclosure and a manufacturing process thereof; 1 is a schematic cross-sectional view illustrating a conventional joined body for a multilayer printed wiring board and a manufacturing process thereof; FIG. It is a schematic sectional drawing which illustrates the conventional laminated body for printed wiring boards.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings and the like. However, the present disclosure can be embodied in many different forms and should not be construed as limited to the description of the embodiments exemplified below. In addition, in order to clarify the description, the drawings may schematically represent the width, thickness, shape, etc. of each part compared to the embodiment, but this is only an example, and the interpretation in the present disclosure is limited. do not do. In addition, in this specification and each figure, the same reference numerals may be given to the same elements as those described above with respect to the existing figures, and detailed description thereof may be omitted as appropriate. Also, for convenience of explanation, the terms "upper" and "lower" may be used, but the up-down direction may be reversed.

Also, in this specification, there is no particular limitation when a configuration such as a member or a region is “above (or below)” another configuration such as another member or another region. So far, this includes not only when directly above (or directly below) other structures, but also when above (or below) other structures, i.e. above (or below) other structures and between other structures. Including cases where the constituent elements of are included.

A. Printed Wiring Board Laminate FIG. 1 is a schematic cross-sectional view illustrating a printed wiring board laminate in the present disclosure. The printed wiring board laminate 10 according to the present disclosure shown in FIG. It has an adhesive layer 3 and a metal foil 4 in this order. Further, as shown in FIG. 2, the printed wiring board laminate 10 according to the present disclosure includes a vapor deposition layer 2 and a thermosetting resin on both sides of a base material 1 containing a low dielectric resin material. and the metal foil 4 in this order.

Here, FIG. 5 shows a schematic cross-sectional view illustrating a conventional printed wiring board laminate. In the conventional printed wiring board laminate 20, the base material 11 containing the low dielectric resin material and the metal foil 14 are laminated by thermal welding. Adhesion to metal foil may be poor. Furthermore, metal foils with low surface roughness have poor adhesion to low dielectric substrates. Therefore, the conventional printed wiring board laminate 20 has insufficient adhesiveness between the base material 11 and the metal foil 14 .

The present inventors have studied the layer structure of a laminate for a printed wiring board that is strongly bonded while suppressing transmission loss. Further, by arranging an adhesive layer between the base material and the metal foil, it is possible to obtain a laminate for a printed wiring board in which the base material and the metal foil are firmly bonded while ensuring the smoothness of the metal foil. I found

Therefore, according to the present disclosure, high frequency bands, specifically 3-5 GHz, 25-30 GHz, 60-80 GHz, > A laminated body for a printed wiring board that is compatible with the fifth generation mobile communication system using 100 GHz or the like can be obtained.

1. Substrate (1) Surface Roughness The substrate in the present disclosure contains a low dielectric resin material and has a maximum height roughness (Rz) of 0.1 μm or more on the adhesive layer side surface. The maximum height roughness (Rz) may be 0.3 μm or more, 0.4 μm or more, 0.5 μm or more, or 0.6 μm or more, It may be 0.7 μm or more. On the other hand, the maximum height roughness (Rz) may be, for example, 20.0 μm or less, 10.0 μm or less, and preferably 5.0 μm or less.

By setting the maximum height roughness (Rz) of the adhesive layer side surface of the base material to a specific value or more, an anchor effect can be imparted to the adhesive layer, and adhesion to the adhesive layer can be improved.

Note that the maximum height roughness (Rz) in the present disclosure is a value obtained by a method conforming to JIS B 0601 (2001). That is, using a surface roughness measuring instrument (Kosaka Laboratory Surfcorder SE1700α), only the reference length described in JIS B 0601 is extracted from the roughness curve in the direction of the average line, and the peak line and valley bottom of this extracted portion Rz is the distance from the line measured in the direction of the longitudinal magnification of the roughness curve.

Further, in the present disclosure, in addition to the measurement using a surface roughness measuring instrument, the method described in JP-A-2020-95254 can be used to obtain the adhesive layer side of the substrate from a cross-sectional SEM image of the laminate for printed wiring boards. The maximum height roughness (Rz) of the surface can be determined. The cross section is exposed by known techniques such as ion beams and microtome.

Specifically, the laminate is cut so that the cross section of the base material in the lamination direction in the laminate can be observed, and the cross section is visually observed with a scanning transmission electron microscope (trade name: S-5500 manufactured by Hitachi High Technology). . After that, by performing image processing on the observed image, the maximum height roughness (Rz) of the adhesive layer side surface of the base material can be obtained.
As an image processing method, commercially available image processing software such as image Pro PLUS (manufactured by Media Cybernetics) can be used. As shown in Examples described later, the Rz measured by the surface roughness measuring instrument and the Rz measured from the cross-sectional SEM image of the laminate are almost the same.

A base material in the present disclosure includes a low dielectric resin material. The dielectric constant ε of such a substrate is, for example, 4.0 or less, may be 3.5 or less, or may be 3.0 or less.
Also, the dielectric loss tangent tan δ of the substrate is, for example, 0.01 or less, may be 0.006 or less, or may be 0.002 or less.

Here, the dielectric constant and dielectric loss tangent are the dielectric constant and dielectric loss tangent at 23°C and 28 GHz. Permittivity and dielectric loss tangent can be measured by a resonator method. Permittivity and loss tangent are measured with a microwave network analyzer, for example, equipped with a network analyzer (Keysight Technologies E8363B PNA series) and a split cylinder resonator 28 GHz (EM Lab split cylinder resonator 28 GHz CR-728). can be measured using the system.

(2) Materials Examples of low-dielectric resins contained in such base materials include fluorine-based resins, liquid crystal polymers, polyphenylene ether resins (PPE), syndiotactic polystyrene resins (SPS), cycloolefin copolymer resins (COC), cycloolefin copolymer resins (COC), Olefin polymer resin (COP) and the like are included.

Examples of fluorine-based resins include polytetrafluoroethylene (PTFE), perfluoroalkoxy resin (PFA) composed of a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether, tetrafluoroethylene and hexafluoropropylene copolymer (FEP), tetrafluoroethylene and hexafluoropropylene copolymer (FEP), Fluoroethylene, perfluoroalkyl vinyl ether and hexafluoropropylene copolymer (EPE), copolymer of tetrafluoroethylene and ethylene or propylene (ETFE), polychlorotrifluoroethylene resin (PCTFE), copolymer of ethylene and chlorotrifluoroethylene (ECTFE ), vinylidene fluoride resin (PVDF), or vinyl fluoride resin (PVF). The substrate may contain only one type of fluororesin, or may contain two or more types.

The above liquid crystal polymer is a polymer capable of forming a melt phase having optical anisotropy. Examples of liquid crystal polymers include polyarylate liquid crystal polymers, wholly aromatic polyesters, semi-rigid aromatic polyesters, and polyesteramides. In addition, liquid crystal polymers include (1) aromatic or aliphatic dihydroxy compounds, (2) aromatic or aliphatic dicarboxylic acids, (3) aromatic hydroxycarboxylic acids, (4) aromatic diamines, aromatic hydroxylamines or aromatic and copolymers made from group aminocarboxylic acids.

In addition, in terms of obtaining good heat resistance, the liquid crystal polymer has a polymer main chain composed of an aromatic group, and these aromatic groups are ester bonds (-C(O)O- or -OC(O)- ), amide bonds (-C(O)NH- or -NHC(O)-), liquid crystalline polyesters or liquid crystalline polyesteramides are preferred. The above-mentioned aromatic group means a monocyclic aromatic group, a condensed ring aromatic group, a monocyclic aromatic group or a condensed ring aromatic group directly bonded, an oxygen atom, a sulfur atom, a carbon number of 1 to The concept also includes a group of 6 linked via a linking group such as an alkylene group, a sulfonyl group and a carbonyl group. The substrate may contain only one type of liquid crystal polymer, or may contain two or more types.

The low dielectric resin material is preferably a thermoplastic resin.

The base material in the present disclosure may contain a reinforcing material as an optional component. The coefficient of thermal expansion can be reduced by containing the reinforcing material.
The reinforcing material is not particularly limited as long as it has a coefficient of thermal expansion smaller than that of the low dielectric resin material, and examples thereof include silica. Further, it is desirable to use a reinforcing material having insulating properties, heat resistance that does not melt and flow at the melting point of the low dielectric resin material, tensile strength equal to or greater than that of the low dielectric resin material, and corrosion resistance.

Such a reinforcing material can be composed of, for example, a glass cloth formed into a glass cloth, a fluororesin-containing glass cloth obtained by impregnating such a glass cloth with a fluororesin, a resin cloth, a heat-resistant film, or the like. is.
Examples of the resin cloth include those containing heat-resistant fibers made of metal, ceramics, polytetrafluoroethylene, polyetheretherketone, polyimide, aramid, or the like. As the heat-resistant film, liquid crystal polymer, polyimide, polyamideimide, polybenzimidazole, polyetheretherketone, polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, thermosetting resin, crosslinked resin, etc. What is used as a main component can be mentioned.

The resin cloth and the heat-resistant film preferably have a melting point (or heat distortion temperature) higher than the thermocompression bonding temperature in "6. Production method for printed wiring board laminate (4) Adhesion step" described later. . The weaving method of the resin cloth is preferably plain weave in order to make the base material thinner, but twill weave and satin weave are preferable in order to make the base material bendable. In addition, a known weaving method can be applied.

The content of the reinforcing material in the base material is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less.

The thickness of the substrate in the present disclosure is, for example, 10 μm or more, may be 20 μm or more, or may be 50 μm or more. On the other hand, the thickness of the substrate is, for example, 300 μm or less, and may be 200 μm or less.

(3) Others In the present disclosure, the surface of the adhesive layer side of the base material may have a vapor deposition film in order to improve adhesion with the adhesive layer, and the adhesive layer side of the base material may have a vapor deposition film. The surface may be subjected to surface treatment.
The surface of such a deposited film on the side opposite to the base material, or the surface of the base material subjected to surface treatment, usually reflects the surface shape of the adhesive layer side of the base material as it is. Therefore, the maximum height roughness (Rz) of these surfaces is equivalent to the maximum height roughness (Rz) of the adhesive layer side surface of the substrate.

a. Vapor-Deposited Film The vapor-deposited layer used in the present disclosure is preferably a vapor-deposited film containing carbon, silicon and oxygen. Furthermore, it is preferable that the vapor-deposited film is adhered to the substrate by a siloxane bond. The vapor-deposited film is preferably a layer formed by vapor-phase chemical vapor deposition (CVD) using a vapor deposition gas composition containing an organosilicon compound (hereinafter also referred to as "source gas").

The deposited film is preferably a dense and highly flexible continuous layer containing mainly carbon, silicon and oxygen. Moreover, it is preferable that at least one of a methyl (CH ₃ ) group and an ethyl (C ₂ H ₅ ) group is present on the surface of the deposited film. By forming at least one of the CH ₃ group and the C ₂ H ₅ group on the surface of the deposited film, the adhesion with the adhesive layer is improved.

Such a vapor deposition film uses an organosilicon compound monomer containing a methyl group directly bonded to a Si atom as a vapor deposition material, and a vapor deposition gas composition containing a vapor deposition monomer gas and optionally an oxygen supplying gas. can be used to form a film by a CVD method. There are several CVD methods, such as thermal CVD and optical CVD, but it is preferable to employ the plasma CVD method, which allows low-temperature film formation and is less prone to coloration of the base material. The amount of CH ₃ groups and C ₂ H ₅ groups present on the surface can be adjusted by changing the ratio of the vapor deposition monomer gas and the oxygen supplying gas in the vapor deposition gas composition during film formation.

The thickness of the deposited film is, for example, 5 nm or more, and may be 10 nm or more. On the other hand, the thickness of the deposited film is, for example, 100 nm or less, and may be 50 nm or less. The thickness of the deposited film can be measured using, for example, a fluorescent X-ray spectrometer (model name: RIX2000 type) manufactured by Rigaku Corporation.

　In order to form a vapor deposition film, for example, an object to be vapor deposited (base material) is introduced into a vacuum chamber. Then, a vapor deposition gas composition containing a vapor deposition monomer gas comprising an organosilicon compound and optionally an oxygen supplying gas is introduced into the vacuum chamber at a constant rate, and the surface of the object (substrate) to be vapor deposited is subjected to the CVD method. A deposition film is formed thereon.

Examples of organosilicon compounds include organosilicon compounds containing _CH3 directly bonded to silicon (Si) atoms. Specific examples include hexamethyldisiloxane (HMDSO), tetramethyldisiloxane (TMDSO), octamethyl Cyclotetrasiloxane, methylsilane, dimethylsilane, trimethylsilane, tetramethylsilane, ethylsilane.

Other organosilicon compounds may be any organic compound that has an appropriate vapor pressure at room temperature and can be subjected to CVD (particularly plasma CVD). Therefore, using a material having a functional group with 3 or more carbon atoms such as C ₃ H ₈ group, a deposited film containing at least one of CH ₃ group and C ₂ H ₅ group is formed by CVD (especially plasma CVD). method).

On the other hand, oxygen gas, for example, is used as the oxygen supply gas. Ozone gas or laughing gas (N ₂ O gas) can be used instead of oxygen gas, but oxygen gas is most preferable in terms of film formation efficiency and cost.

In addition, a gas (carrier gas) for efficiently introducing the vapor deposition monomer gas into the vacuum chamber and a gas for the purpose of generating or enhancing plasma are also introduced into the vapor deposition gas composition as necessary. you can

The most common plasma CVD method is to apply an electric field of 13.56 MHz between parallel plate electrodes. That is, a vapor deposition gas composition is introduced into the vacuum chamber to maintain a constant pressure, and 13. between a flat plate electrode placed in the vacuum chamber and a ground electrode placed facing the flat plate electrode in parallel. A 56 MHz RF alternating voltage is applied.

For example, by applying a power of 300 W, a glow discharge plasma is generated, and the plasma flow is used to chemically react the vapor deposition gas composition, thereby forming a vapor deposition film. The vapor-deposited film (substrate) is usually placed on the surface of the ground electrode, but may be placed on the side of the plate electrode to which the RF voltage is applied.

In the present disclosure, it is possible to apply a lower frequency (40 kHz, 50 kHz, etc.) or a higher frequency (2.45 GHz, etc.) instead of applying a 13.56 MHz RF AC voltage. Alternatively, a DC voltage may be applied. Instead of a flat plate electrode, it is possible to use a hollow cathode electrode that generates a plasma flow by blowing out gas, or to generate an induced plasma from an external coil. It is also possible to increase the plasma density by using a magnetic field or by using the ECR resonance phenomenon (a phenomenon in which electrons in the plasma undergo cyclotron resonance by appropriately adjusting the electric and magnetic fields).

Film formation by the plasma CVD method has various conditions such as input power, gas flow rate, film formation pressure, distance between electrodes, and film formation time, and these conditions can be adjusted as appropriate. The input power is, for example, 20 W or more, and may be 50 W or more. On the other hand, the input power is, for example, 1000 W or less, and may be 800 W or less.

Furthermore, in the present disclosure, plasma treatment is preferably performed after the CVD method. Examples of plasma treatment include electron beam treatment, corona treatment, atmospheric pressure plasma treatment, low pressure plasma treatment, and the like. From the viewpoint of productivity, corona treatment, atmospheric pressure plasma treatment, low-pressure plasma treatment, and the like are preferable, and oxygen plasma treatment under low pressure is particularly preferable because the plasma atmosphere can be easily controlled.

The contact angle of water on the surface of the deposited film is, for example, 10° or more, may be 30° or more, or may be 50° or more. On the other hand, the contact angle of water is, for example, 120° or less, may be 100° or less, or may be 80° or less. The contact angle of water is a value measured using a contact angle tester under conditions of 20° C. and 50% RH.

b. Surface Treatment of Substrate The substrate in the present disclosure may be one in which the surface on the adhesive layer side is subjected to surface treatment. This is because the adhesiveness with the adhesive layer is improved. Surface treatments include plasma treatment, corona treatment, flame treatment, flame treatment and chemical treatment.

The above surface treatment may form a surface treatment layer in which functional groups containing oxygen atoms are introduced on the substrate surface. The thickness of the surface treatment layer in this case is, for example, 1 nm or more, and may be 5 nm or more. On the other hand, the thickness of the surface treatment layer is, for example, 50 nm or less, and may be 30 nm or less. The thickness of the surface treatment layer can be measured, for example, using a fluorescent X-ray spectrometer (model name: RIX2000 type) manufactured by Rigaku Corporation.

Further, when the substrate in the present disclosure is a fluororesin containing no oxygen, the surface treatment layer appears as a layer containing oxygen on the surface of the fluororesin. Specifically, the atomic concentration of oxygen is preferably 1.0 atomic percent (at. %) or more.

In order to perform surface treatment, for example, the base material is degassed, and then the base material surface is subjected to vacuum discharge treatment. The degassing treatment and the vacuum discharge treatment are preferably performed continuously as a series of steps while maintaining a vacuum state.

The degassing treatment of the substrate includes, for example, a treatment of holding the substrate at a degree of vacuum of 1.0×10 ⁻¹ Pa or less in an inert gas stream having an oxygen concentration of 0.01% or less. Examples of inert gas include rare gas and nitrogen gas. Examples of rare gases include argon (Ar), helium (He), neon (Ne), krypton (Kr), and xenon (Xe). The oxygen concentration of the inert gas may be 0.001% or less. The degree of vacuum (gas pressure) in the inert gas stream may be 5.0×10 ⁻² Pa or less, or 1.0×10 ⁻² Pa or less. On the other hand, the degree of vacuum is, for example, 1.0×10 ⁻⁴ Pa or more.

The degassing treatment may be performed while the substrate is heated. The heating temperature is, for example, 30° C. or higher, may be 40° C. or higher, or may be 50° C. or higher. On the other hand, the heating temperature is, for example, 100° C. or lower, may be 90° C. or lower, or may be 80° C. or lower. The treatment time of the degassing treatment is, for example, 20 seconds or longer, may be 30 seconds or longer, or may be 40 seconds or longer. On the other hand, the treatment time of the degassing treatment is, for example, 90 seconds or less, may be 80 seconds or less, or may be 70 seconds or less.

Vacuum discharge treatment is a process that cleans and modifies the surface of the base material. Vacuum discharge treatment includes, for example, corona discharge treatment and glow discharge treatment, and glow discharge treatment under low pressure is particularly preferred. When vacuum discharge treatment is performed in the presence of an inert gas, the gas used is ionized to generate plasma in which gas ions and electrons coexist.

Vacuum discharge treatment is performed on the surface of the base material that has been subjected to degassing treatment in an inert gas stream with an oxygen concentration of 0.01% or less at 1.0 × 10 ^-3 Pa or more and 1.0 × 10 ^-2 Pa It is preferable to apply a DC electric field while maintaining the following degree of vacuum and simultaneously perform vacuum discharge treatment with an applied power of 0.2 W/cm ² or more for 10 seconds or more. The oxygen concentration of the inert gas may be 0.001% or less. The degree of vacuum (gas pressure) in the inert gas stream is, for example, 1.0×10 ⁻³ Pa or more, may be 3.0×10 ⁻³ Pa or more, and may be 5.0×10 ⁻³ Pa or more may be sufficient. On the other hand, the degree of vacuum (gas pressure) in the inert gas stream is, for example, 1.0×10 ⁻² Pa or less, and may be 9.0×10 ⁻³ Pa or less.

In the vacuum discharge treatment, an AC electric field is usually applied. The frequency of the alternating current is preferably 10 kHz or more and 900 MHz or less. The applied power of the AC electric field is, for example, 0.2 W/cm ² or more, may be 0.3 W/cm ² or more, or may be 0.4 W/cm ² or more. On the other hand, the applied power of the AC electric field is, for example, 1.0 W/cm ² or less, may be 0.9 W/cm ² or less, or may be 0.8 W/cm ² or less.

The processing time of the vacuum discharge treatment is, for example, 10 seconds or longer, may be 15 seconds or longer, or may be 20 seconds or longer. On the other hand, the processing time of the vacuum discharge treatment is, for example, 100 seconds or less, may be 70 seconds or less, or may be 50 seconds or less.

In the present disclosure, a DC electric field may be applied simultaneously with the vacuum discharge treatment in order to modify the surface of the substrate. A DC electric field is applied in a direction that forces the cationized inert gas atoms toward the surface of the substrate. In order to apply a DC electric field to the base material, it is preferable to apply a negative voltage to the electrode placed on the side opposite to the treated surface of the base material and a positive voltage to the electrode placed opposite to it.

The electric field intensity of the DC electric field is, for example, 10 V/cm or more, may be 30 V/cm or more, may be 50 V/cm or more, or may be 70 V/cm or more. On the other hand, the electric field intensity of the DC electric field is, for example, 200 V/cm or less, and may be 150 V/cm or less.

The contact angle of water on the surface of the substrate on the surface-treated side is, for example, 10° or more, may be 30° or more, or may be 50° or more. On the other hand, the contact angle of water is, for example, 120° or less, may be 100° or less, or may be 80° or less. The contact angle of water is a value measured using a contact angle tester under conditions of 20° C. and 50% RH.

2. Adhesive Layer The adhesive layer in the present disclosure contains a thermosetting resin. A thermosetting resin functions as an adhesive and is preferably in a semi-cured state or a cured state. In the present invention, "semi-cured" means a state in which the curing of the resin is stopped in the middle, and is a B-stage (thermosetting resin means the cured intermediate) state of the composition. Moreover, it is preferable that the adhesive layer is in contact with the substrate.

Examples of thermosetting resins include epoxy resins, silicone resins, unsaturated polyester resins, saturated polyester resins, melamine resins, phenol resins, polyamides, ketone resins, urethane resins, urea resins, acrylic resins, vinyl resins, alkyd resins, Examples include amino alkyd resins, hydrocarbon resins (aromatic and aliphatic), rubber resins, fluororesins, and polyimide resins. Moreover, the curing temperature of the thermosetting resin is, for example, 250° C. or lower, and may be 200° C. or lower. As the polyimide resin, for example, a polyimide adhesive described in Japanese Patent No. 6790816 can be used.

Furthermore, as the adhesive layer of the present disclosure, an adhesive composition containing a carboxyl group-containing styrene elastomer and an epoxy resin described in Japanese Patent No. 6485577, and a modified polyolefin resin described in Japanese Patent No. 671848, and an adhesive composition containing an epoxy resin can also be suitably used.

The adhesive layer in the present disclosure may further contain a low dielectric resin material. As such a low dielectric resin material, the materials described in "A. Laminate for printed wiring board 1. Base material" can be used.
Specific examples include polyolefin, polystyrene, polyphenylene ether (PPE), fluororesin, and liquid crystal polymer. Examples of the polyolefins include cycloolefin polymers (COP), cycloolefin copolymers (COC), α-olefin copolymers, and the like. Moreover, syndiotactic polystyrene (SPS) etc. can be mentioned as said polystyrene.

The dielectric constant ε of the adhesive layer is, for example, 4.0 or less, may be 3.5 or less, or may be 3.0 or less. The dielectric constant is a value obtained by using a dielectric constant measuring device for the adhesive layer (after curing) at a measurement temperature of 23° C. and a measurement frequency of 10 GHz. The dielectric loss tangent tan δ of the adhesive layer is, for example, 0.01 or less, may be 0.006 or less, or may be 0.002 or less. The dielectric loss tangent can be measured by the same method as the dielectric constant.

The thickness of the adhesive layer is, for example, 1 μm or more, and may be 5 μm or more. On the other hand, the thickness of the adhesive layer is, for example, 300 μm or less, and may be 200 μm or less. In the present disclosure, the thickness of the adhesive layer is preferably thinner than the thickness of the substrate. Since the dielectric constant of the base material is often lower than that of the adhesive layer, it is preferable in terms of electrical properties if the thickness of the adhesive layer is thinner than the thickness of the base material. The ratio of the thickness of the substrate to the thickness of the adhesive layer (thickness of substrate/thickness of adhesive layer) is preferably 1 or more, particularly preferably 3 or more.

3. Metal Foil The metal foil in the present disclosure is preferably located on the side of the adhesive layer opposite to the base material and is in contact with the adhesive layer.

In the present disclosure, the metal foil has a maximum height roughness (Rz) of 10.0 μm or less on the adhesive layer side surface. Electric current flows on the surface of the metal foil due to the skin effect caused by eddy currents, but if the surface roughness of the metal foil is large, the path becomes long and the loss tends to increase. Therefore, the loss can be suppressed when the maximum height roughness (Rz) of the metal foil is as smooth as the above value or less. In particular, in the case of printed wiring boards used in fifth-generation mobile communication systems, it is important to reduce conductor loss, so the surface of the metal foil is preferably smooth.

The maximum height roughness (Rz) of the adhesive layer side surface of the metal foil is preferably 5.0 μm or less, more preferably 2.0 μm or less. On the other hand, the maximum height roughness (Rz) is, for example, 0.1 μm or more, preferably 0.5 μm or more, and particularly preferably 1.0 or more.
The maximum height roughness (Rz) of the metal foil can be measured by the measurement method described above in "1. Base material".

According to the present disclosure, even if the surface roughness of the metal foil is within the range described above, due to the effect of the adhesive layer, a predetermined adhesive strength can be maintained and conductor loss can be reduced.

Examples of metal materials for metal foil include copper, aluminum, gold, silver, stainless steel, titanium, and nickel. Among these, copper (copper foil) is preferable from the viewpoint of workability and cost. Furthermore, the copper foil may be a rolled copper foil or an electrolytic copper foil.

The thickness of the metal foil is, for example, 1 μm or more, may be 5 μm or more, or may be 10 μm or more. On the other hand, the thickness of the metal foil is, for example, 200 μm or less, may be 100 μm or less, or may be 50 μm or less.

In the present disclosure, the metal foil is preferably patterned.

4. Others The printed wiring board laminate in the present disclosure has the base material, the adhesive layer, and the metal foil described above. For example, it may be a laminate having an adhesive layer and a metal foil on one side of the substrate (especially a single-sided copper-clad laminate), or a laminate having an adhesive layer and a metal foil on both sides of the substrate. It may also be a body (especially a double-sided copper-clad laminate).

The interlayer adhesive strength between the substrate and the metal foil may be, for example, 6.0 N/15 mm or more, or may be 10.5 N/15 mm or more. In accordance with JIS K 6854-2, the interlaminar bond strength was measured using a test piece cut to a width of 15 mm from the laminate (after curing) under the conditions of 23°C and 30% RH with a tensile tester (Inc. It is a value measured by pulling at a peeling angle of 180° at a tensile speed of 50 mm/min using a model number: STB-1225S manufactured by A&D.

The use of the laminate for printed wiring boards in the present disclosure is not particularly limited, but it has excellent electrical properties corresponding to frequencies in the high frequency band, so it is particularly used for producing printed wiring boards for 5th generation mobile communication systems. It is preferably used as a laminate for

6. Method for manufacturing printed wiring board laminate The method for manufacturing a printed wiring board laminate in the present disclosure is not particularly limited, but contains a low dielectric resin material, and at least one surface has the maximum height roughness (Rz) and a metal foil preparation step of preparing a metal foil in which at least one surface has the maximum height roughness (Rz), and the maximum height roughness of the substrate ( and a bonding step of bonding a metal foil to a surface having Rz) via an adhesive layer containing a thermosetting resin.

(1) Substrate Preparing Step This step is a step of preparing a substrate containing a low dielectric resin material and having a maximum height roughness (Rz) of 0.1 μm or more on at least one surface.
A method for obtaining such a surface state is not particularly limited, but may be, for example, either chemical treatment or physical treatment. The physical treatment is performed, for example, by blasting the surface of the film containing the low dielectric resin material.

In the present disclosure, wet blasting is particularly preferred. The maximum height roughness can be adjusted by adjusting the type, particle size, content in the slurry, etc. of the abrasive used in the blasting treatment and the treatment time. For example, the particle size of the abrasive may be 1 μm or more, or 10 μm or more. Moreover, it may be 200 μm or less, or may be 100 μm or less. The abrasive is not particularly limited, and examples thereof include alumina (Al ₂ O ₃ ), silicon carbide (SiC), stainless steel, zirconia (ZrO ₂ ), glass, chromium, melamine resin, and phenol resin.

Also, if it contains a low dielectric resin material and the maximum height roughness (Rz) of at least one surface is 0.1 μm or more, it can be used as a base material as it is.

(2) Metal Foil Preparing Step This step is a step of preparing a metal foil having a maximum height roughness (Rz) of 10 μm or less on at least one surface. As the metal foil having the maximum height roughness, a commercially available product may be used, or the surface of the metal foil may be smoothed. Methods for smoothing the surface of the metal foil include, for example, half-etching using wet etching and dry etching. Etching conditions are appropriately set according to the type of metal foil.

(3) Bonding step The bonding step is a step of bonding the substrate and the metal foil via an adhesive layer containing a thermosetting resin, and the smooth surface of the metal foil is arranged so that at least the adhesive layer side. be. As a result, a laminate is obtained in which the substrate, the adhesive layer and the metal foil are laminated in this order in the thickness direction.

Examples of methods for forming the adhesive layer include a method of applying a resin composition containing an uncured thermosetting resin, and then curing or semi-curing the uncured thermosetting resin with heat. The resin composition may be applied onto a substrate, may be applied onto a metal foil, or may be applied onto both of them. A coating method is not particularly limited, and a known method can be adopted. The heating temperature for curing the thermosetting resin is, for example, 250° C. or lower, and may be 200° C. or lower.

B. Bonded product for multilayer printed wiring board The bonded product for a multilayer printed wiring board according to the present disclosure includes a first base material, first adhesive layers disposed on both sides of the first base material, and the first adhesive layers. A first printed wiring board laminate having a first metal foil arranged on the surface opposite to the first base material, a second base material, and a second base material arranged on both sides of the second base material and a second printed wiring board laminate having a second adhesive layer and a second metal foil disposed on the surface of one of the second adhesive layers opposite to the second base material. , the first laminate for printed wiring board and the second laminate for printed wiring board, the second adhesive layer on the side of the second laminate for printed wiring board where the second metal foil is not arranged is , arranged to face the first metal foil of the first printed wiring board laminate, the first base material and the second base material containing a low dielectric resin material, the first adhesive layer and The second adhesive layer contains a thermosetting resin, and the maximum height roughness (Rz) of the surfaces of the first metal foil and the second metal foil facing the first adhesive layer and the second adhesive layer is 10 μm or less. and the maximum height roughness (Rz) of the surfaces of the first base material and the second base material on the first adhesive layer and second adhesive layer sides is 0.1 μm or more, for a multilayer printed wiring board It is a zygote.

FIG. 3(a) shows a process diagram for manufacturing a multilayer printed wiring board assembly according to the present disclosure, and FIG. 3(b) shows a multilayer printed wiring board assembly according to the present disclosure. In this example, the bonded body 100 for a multilayer printed wiring board shown in FIG. A first printed wiring board laminate 10A having a first metal foil pattern 4p disposed thereon, and a second deposited film 2, a second adhesive layer 3, and a second metal foil patterned on one side of a second substrate 1. The second printed wiring board laminate 10B having the second metal foil pattern 4p disposed on the second printed wiring board and the second vapor deposition film 2 and the second adhesive layer 3 on the other surface is the second printed wiring board laminate It is joined by the second adhesive layer 3 of the laminate 10B.

Since the base material, the adhesive layer, and the metal foil used for the bonded body for multilayer printed wiring board are the same as those in the above-described "A. Laminate for printed wiring board", descriptions thereof are omitted here. The adhesive layer in the assembly for multilayer printed wiring boards is usually in a cured state.
The number of the first printed wiring board laminate included in the joined body for a multilayer printed wiring board in the present disclosure is usually one, and one or more second laminates are provided on one side or both sides of the first printed wiring board laminate. 2 printed wiring board laminates are placed.

Conventionally, multilayer printed wiring boards having two or more layers of circuits have been widely used as circuit boards used inside electrical and electronic devices. Here, FIG. 4(a) shows a process diagram for manufacturing a conventional multilayer printed wiring board assembly, and FIG. 4(b) shows a conventional multilayer printed wiring board assembly. As shown in FIG. 4(a), conventional printed

wiring board laminates

20A and 20B using a low dielectric resin material (especially thermoplastic resin) such as liquid crystal polymer (LCP) and fluororesin for the base material 11. When manufacturing the multilayer printed wiring board bonded body 200 by bonding, the laminated bodies are bonded to each other by heat welding. A high temperature of about 400° C. is usually required for this heat welding. Therefore, as shown in FIG. 4(b), the thermoplastic resin may be melted and the metal foil pattern 14p may be displaced.

On the other hand, in the multilayer printed wiring board bonded body of the present disclosure, the laminated body is bonded at a relatively low temperature (for example, 200° C. or less) by using the adhesive layer containing the thermosetting resin described above. be able to.

It should be noted that the present disclosure is not limited to the above embodiments. The above embodiment is an example, and any device that has substantially the same configuration as the technical idea described in the claims of the present disclosure and achieves the same effect is the present invention. It is included in the technical scope of the disclosure.

Examples and comparative examples are shown below to describe the present disclosure in more detail.
[Manufacture of laminate for printed wiring board]
(Example 1-1)
Polytetrafluoroethylene (PTFE) film (TOMBO No. 9001 (manufactured by Nichias) Maximum height roughness (Rz) of both main surfaces 0.45 μm, arithmetic mean roughness (Ra) 0.08 μm, dielectric constant ε 2.0 , dielectric loss tangent 0.0002, thickness 50 μm) was prepared as a substrate. Both surfaces of this substrate were subjected to the following plasma treatment. A copper foil (CF-T49A-DS-HD2, thickness 12 μm, Rz 2.0 μm, manufactured by Fukuda Metal Foil & Powder Co., Ltd.) was also prepared. A thermosetting low dielectric adhesive film (epoxy resin, dielectric constant ε2.3, dielectric loss tangent 0.002, thickness 25 μm) is placed on both sides of the plasma-treated PTFE film. Copper foils were arranged and they were bonded together by thermocompression bonding (180° C., 1 MPa, 60 minutes) to obtain a laminate for a printed wiring board.
In addition, when the produced printed wiring board laminate was cut and the Rz of the adhesive layer side surface of the base material was measured from the cross-sectional SEM image by the measurement method described in the above "1. Base material", it was 0. It was 45 μm, and a value equivalent to the Rz of the PTFE film was obtained.

Plasma treatment conditions/Gas: Ar 600 sccm
・Pressure: 4Pa
・Processing time: 5 minutes

(Examples 1-2 to 1-9)
Both main surfaces of the polytetrafluoroethylene (PTFE) film used in Example 1-1 were subjected to wet blasting under the abrasive and air pressure conditions shown in Table 1, thereby achieving the maximum height shown in Table 1. A substrate with roughness (Rz) and arithmetic mean roughness (Ra) was obtained. A printed wiring board laminate was produced in the same manner as in Example 1-1, except that the obtained base material was used.

(Example 2-1)
Polytetrafluoroethylene (PTFE) film (V7900 (manufactured by Valqua) Maximum height roughness (Rz) of both main surfaces 0.34 μm, arithmetic mean roughness (Ra) 0.07 μm, dielectric constant ε2.0, dielectric loss tangent 0.0002, thickness 50 μm) was prepared. A printed wiring board laminate was produced in the same manner as in Example 1-1, except that this was used as the base material.

(Examples 2-2 to 2-19)
The polytetrafluoroethylene (PTFE) film used in Example 2-1 (maximum height roughness (Rz) of both main surfaces 0.34 μm, arithmetic mean roughness (Ra) 0.07 μm, dielectric constant ε 2.0 , dielectric loss tangent 0.0002, thickness 50 μm) were subjected to wet blasting under the abrasive and air pressure conditions shown in Tables 2 and 3, resulting in the maximum height shown in Tables 2 and 3. A substrate having a roughness (Rz) and an arithmetic mean roughness (Ra) was obtained. A printed wiring board laminate was produced in the same manner as in Example 2-1, except that the obtained base material was used.

[Peel strength test]
The peel strength (interlayer adhesive strength) of the laminates for printed wiring boards obtained in Examples 1-1 to 1-9 and Examples 2-1 to 2-19 was measured according to the above "5. Laminate for printed wiring boards Measured by the method described in . The results are shown in Tables 1, 2 and 3.
The evaluation results were judged according to the following criteria.
A: Adhesion strength was large.
B: Adhesion strength was at a practically acceptable level.
C: Adhesion strength was low, and there was a problem in practical use.

From Tables 1, 2, and 3, the printed wiring board laminates (Examples 1-1 to 1-9 and Examples 2-1 to 2-19) in the present disclosure consisted of a base material and a metal foil. It was confirmed that they were strongly adhered.

The polytetrafluoroethylene (PTFE) film (TOMBO No. 9001 (manufactured by Nichias)) used in Example 1, the polytetrafluoroethylene (PTFE) film (V7900 (manufactured by Valqua) used in Example 2, )), the dielectric constant at 28 GHz and The dissipation factor was measured and summarized in Table 4 below. Measurements were performed using Keysight Network Analyzer E8363B and EM Lab Split Cylinder Resonator CR-728.

(Examples 3-1 to 3-4, Comparative Example)
The substrate in Example 1-5 (Rz = 0.87 μm), the substrate in Example 1-7 (Rz = 1.71 μm), the substrate in Example 2-5 (Rz = 0.90 μm), and the implementation In the same manner as in Example 1-1, except that the substrate (Rz = 1.76 μm) in Example 2-7 was used and a copper foil having a surface height roughness (Rz) shown in Table 5 was used. A printed wiring board laminate was produced. As a comparative example, RF705T (trade name) manufactured by Panasonic Corporation was used. Note that RF705T (trade name) manufactured by Panasonic Corporation had a dielectric constant of 2.9 and a dielectric loss tangent of 0.002.

[Transmission loss measurement]
A copper foil on one surface of the obtained printed wiring board laminate was patterned to prepare a microstrip line having a wiring length of 100 mm and an impedance of 50Ω.
The transmission loss S21 parameter was measured with a network analyzer (E8363B PNA series manufactured by Keysight Technologies) at a measurement frequency of 1 GHz to 40 GHz. Moreover, it evaluated according to the following evaluation criteria. Table 6 shows the results.

[Evaluation criteria]
A: Transmission loss was small B: Transmission loss was at a level that did not pose a problem in practical use C: Transmission loss was large and there was a problem in practical use

From Table 5, it was confirmed that the transmission loss was suppressed in the printed wiring board laminate of the present disclosure as compared with the comparative example. This is considered to be due to the high dielectric constant and dielectric loss tangent of RF705T (trade name) manufactured by Panasonic Corporation used in the comparative example.
(The Rz of the base material and the Rz of the copper foil in the comparative example are included in the numerical values in claim 1, but they have a different structure and seem to have a high dielectric loss tangent. Structurally, there is no adhesive layer and the base material It seems to be the composition of the material (resin layer) and copper foil.Since the product name is disclosed, if it seems that there is no need to explain the structure of the comparative example, there is no need to provide any additional explanation. think.)

(Example 4)
Polytetrafluoroethylene (PTFE) film used in Example 1-1 (TOMBO No. 9001 (manufactured by Nichias) Maximum height roughness (Rz) of both main surfaces 0.45 μm, arithmetic mean roughness (Ra) 0 0.08 μm, dielectric constant ε2.0, dielectric loss tangent 0.0002, thickness 50 μm), silica deposition films were formed as follows.

(Silica deposition film formation method)
A PTFE film is introduced into a vacuum chamber, and a vapor deposition gas composition containing hexamethyldisiloxane (HMDSO) as a vapor deposition monomer gas, oxygen gas, and helium gas as a carrier gas is introduced into the vacuum chamber. Then, a 13.56 MHz RF AC voltage is applied between a flat plate electrode installed in a vacuum chamber and a ground electrode installed parallel to the flat plate electrode, and one side of the PTFE film is removed by plasma CVD. A vapor deposition film was formed on the surface. A vapor deposition film was also formed on the other surface in the same manner, and a vapor deposition film was formed on both sides of the PTFE film. Note that no plasma treatment was performed after the CVD treatment.

A laminate for a printed wiring board was produced in the same manner as in Example 1-1, except that a PTFE film having a deposited silica film formed thereon was used as the base material.
The composition of the deposited silica film was determined by XPS analysis. Table 6 shows the results. The composition of the PTFE film and the composition of the surface-treated layer obtained by the plasma treatment of Example 1-1 are also shown. In addition, the peel strength (interlayer adhesive strength) of the printed wiring board laminate obtained in Example 4 was measured by the peel strength test, and the result was 6.0 N / 15 mm, and the base material and the metal foil were strong. was adhered to.

DESCRIPTION OF SYMBOLS 1... Base material 2... Vapor-deposited film 3... Adhesive layer 4... Metal foil 10... Laminate for printed wiring board 100... Joined body for multilayer printed wiring board

Claims

A laminate for a printed wiring board in which a substrate, an adhesive layer, and a metal foil are laminated in this order,
The base material contains a low dielectric resin material,
The adhesive layer contains a thermosetting resin,
The maximum height roughness (Rz) of the adhesive layer side surface of the metal foil is 10 μm or less, and the maximum height roughness (Rz) of the adhesive layer side surface of the base material is 0.1 μm or more. A laminate for a printed wiring board.
The printed wiring board laminate according to claim 1, wherein the surface of the metal foil on the adhesive layer side has a maximum height roughness (Rz) of 0.1 µm or more.
The printed wiring board laminate according to claim 1 or 2, wherein the substrate has a dielectric constant of 4.0 or less and a dielectric loss tangent of 0.01 or less.
The laminate for a printed wiring board according to any one of claims 1 to 3, wherein the base material contains at least one kind of fluororesin and liquid crystal polymer as the low dielectric resin material.
The printed wiring board laminate according to any one of claims 1 to 4, wherein the adhesive layer is in a semi-cured state or a cured state.
6. The laminate for a printed wiring board according to any one of claims 1 to 5, wherein the adhesive layer has a dielectric constant of 4.0 or less and a dielectric loss tangent of 0.01 or less in a cured state. body.
The printed wiring board laminate according to any one of claims 1 to 6, wherein the thickness of the adhesive layer is thinner than the thickness of the base material.
The printed wiring board laminate according to any one of claims 1 to 7, wherein the metal foil is a copper foil.
The printed wiring board laminate according to any one of claims 1 to 8, wherein the metal foil is patterned.
10. The laminate for a printed wiring board according to any one of claims 1 to 9, wherein the maximum height roughness (Rz) of the adhesive layer side surface of the base material is 20.0 μm or less. body.
The printed wiring board laminate according to any one of claims 1 to 10, wherein the adhesive layer contains a low dielectric resin.
a first substrate, first adhesive layers disposed on both sides of the first substrate, and a first metal foil disposed on a surface of each of the first adhesive layers opposite to the first substrate and a first printed wiring board laminate, and
a second base material, second adhesive layers disposed on both sides of the second base material, and a second metal foil disposed on a surface of one of the second adhesive layers opposite to the second base material and a second printed wiring board laminate having
In the first printed wiring board laminate and the second printed wiring board laminate, the second adhesive layer on the side where the second metal foil of the second printed wiring board laminate is not arranged is A multilayer printed wiring board assembly arranged to face the first metal foil of the first printed wiring board laminate,
The first base material and the second base material contain a low dielectric resin material,
The first adhesive layer and the second adhesive layer contain a thermosetting resin,
The maximum height roughness (Rz) of the surfaces of the first metal foil and the second metal foil facing the first adhesive layer and the second adhesive layer is 10 μm or less,
A joined body for a multilayer printed wiring board, wherein the maximum height roughness (Rz) of the surfaces of the first base material and the second base material facing the first adhesive layer and the second adhesive layer is 0.1 μm or more.