TW202014064A - Low dielectric substrate material - Google Patents

Abstract

This low dielectric substrate material comprises, in the following order in the thickness direction, a porous resin layer, ah adhesive layer, and a metal layer. The thickness d1 of the adhesive layer and the thickness d2 of the porous resin layer satisfy formula (1). d1/d2 ≤ 0.5 (1).

Description

Low dielectric substrate

The present invention relates to a low-dielectric-based sheet, in particular, to a low-dielectric-based sheet that can be preferably used for manufacturing high-frequency antennas or high-speed transmission substrates.

Previously, the so-called "third generation (3G)" standard and "fourth generation (4G)" standard wireless communication have been widely used. However, in recent years, there has been a tendency for the communication capacity of image data and the like to further increase (the tendency to increase the capacity). In the above-mentioned standard wireless communication, it is impossible to transmit large-capacity data at a practical level.

Therefore, the development of so-called "fifth generation (5G)" standard wireless communication is constantly being promoted. If it is "fifth generation (5G)" standard wireless communication, it can transmit large-capacity data. Furthermore, in the "fifth generation (5G)" standard wireless communication, the above-mentioned data can also be transmitted at high speed. In recent years, the expectation of using the "fifth generation (5G)" standard has increased day by day.

Specifically, in the "Fifth Generation (5G)" standard wireless communication, high frequencies including millimeter waves are used. This millimeter wave is easily attenuated by moisture in the atmosphere. As a base plate for high-frequency antennas that release millimeter waves, a base plate with a low dielectric constant is required. If a low-dielectric substrate is used for the antenna, the millimeter wave electric wave can be efficiently released. In addition, if a base material for a low-dielectric antenna is used, the communication distance is extended, and the area of the antenna member can be reduced, which in turn reduces power consumption.

In addition, in recent years, as FPC (Flexible Print Circuit), high-speed transmission FPC that requires high-speed data transmission is required. As the base material of the high-speed transmission FPC, a low-dielectric base material is also required.

In response to the above requirements, that is, as an antenna for large-capacity data wireless communication or as a base material for high-speed transmission FPC, the development of low-dielectric substrates with low dielectric constants has been continuously promoted, and the use of polyacrylic acid has been developed. Substrates of low-dielectric resin materials such as amine resins and fluorine resins.

On the other hand, substrates made of porous materials have also been studied. Since the porous body contains air having the lowest dielectric constant of 1, the dielectric constant of the porous body is relatively low. As a metal foil laminate with such a porous body, for example, there is proposed a metal foil laminate with a resin porous layer as an insulating material and metal foils arranged on both sides in the thickness direction (for example, refer to the following patent documents 1). [Prior Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2004-82372

[Problems to be solved by the invention]

However, the previous porous body including the above-mentioned Patent Document 1 can be used for wireless communication of the "third generation (3G)" standard or the "fourth generation (4G)" standard, or used for transmission at the previous speed The base sheet of the FPC of the data, but because of its low porosity, the dielectric constant is not sufficiently low, and it does not have the "fifth generation (5G)" standard or the low dielectric constant of the level required for high-speed transmission FPC .

In addition, in the metal foil laminate of the above-mentioned Patent Document 1, in order to prevent the metal foil from falling off from the porous layer, an adhesive layer with a sufficient film thickness is arranged between them, and the resin porous body is bonded to the metal foil. However, in the "fifth generation (5G)" standard or the low dielectric constant of the level required for high-speed transmission FPC, the dielectric constant of the subsequent layer will have a greater impact, resulting in the disadvantage that the above-mentioned level cannot be achieved.

The invention provides a low-dielectric-based sheet material with a lower dielectric constant and good adhesion strength of a metal layer. [Technical means to solve the problem]

Therefore, the inventors have made intensive studies, and as a result have invented a low-dielectric-based sheet that can easily use a porous resin layer with a significantly higher porosity, which has a low level suitable for the fifth generation (5G) standard or high-speed transmission FPC The dielectric constant and the adhesion strength of the metal layer are good.

The present invention [1] includes a low-dielectric-based plate material, which is sequentially provided with a porous resin layer, an adhesive layer and a metal layer in the thickness direction, and the thickness d1 of the adhesive layer and the thickness d2 of the porous resin layer satisfy the following formula (1): d1/d2≦0.5 (1).

The present invention [2] includes the low-dielectric-based sheet as in [1], which satisfies the following formula (2): 2≦d2/d1≦150 (2). [Effect of invention]

When the low-dielectric-based plate material has a porous resin layer and the porous resin layer has a high porosity, it can have a sufficiently low low dielectric constant. Specifically, the low-dielectric-based sheet may have a relatively low dielectric constant sufficient for antennas of the fifth generation (5G) standard wireless communication or high-speed transmission FPC.

Since the low-dielectric-based plate material includes the porous resin layer, the adhesive layer and the metal layer in this order in the thickness direction, the adhesive strength between the metal layer and the porous resin layer is good.

In addition, in the low-dielectric-based sheet, the thickness d1 of the adhesive layer is thinner than the thickness d2 of the porous resin layer, so the amount of adhesive layer with higher dielectric constant is less than that of the porous resin layer with lower dielectric constant the amount. Therefore, the influence of the adhesive layer on the dielectric constant can be suppressed, so that the dielectric constant of the low-dielectric base plate becomes lower.

Therefore, it is possible to suppress the metal layer from falling off, and it can have a low dielectric constant sufficient for an antenna of the fifth generation (5G) standard wireless communication or a high-speed transmission FPC.

<First embodiment> One embodiment of the low dielectric substrate sheet of the present invention will be described with reference to FIGS. 1 and 2.

[Basic appearance] First, the layer configuration, manufacturing method, and usage method of the low-dielectric substrate sheet 1 as a basic aspect will be described in order.

〔Low dielectric substrate sheet and its layer structure〕 As shown in FIG. 1, the low-dielectric substrate sheet 1 has one surface and the other surface facing in the thickness direction, and has a shape extending in a plane direction orthogonal to the thickness direction.

The low-dielectric-based sheet 1 includes a first metal layer 3, a porous resin layer 4 disposed on one side in the thickness direction of the first metal layer 3, an adhesive layer 5 disposed on one side in the thickness direction of the porous resin layer 4, and the arrangement A second metal layer (an example of a metal layer) 6 on one side in the thickness direction of the adhesive layer 5. That is, the low-dielectric-based sheet material 1 includes the first metal layer 3, the porous resin layer 4, the adhesive layer 5, and the second metal layer 6 in this order from the other side to the side in the thickness direction. It is preferable that the low-dielectric-based sheet 1 includes only the first metal layer 3, the porous resin layer 4, the adhesive layer 5 and the second metal layer 6.

[1st metal layer] The first metal layer 3 has one surface and the other surface facing in the thickness direction, and has a sheet shape (plate shape) shape extending in the surface direction. The material of the first metal layer 3 is not particularly limited, and examples thereof include copper, iron, silver, gold, aluminum, nickel, alloys thereof (stainless steel, bronze), and the like. Preferably copper is cited. The thickness of the first metal layer 3 is, for example, 0.1 μm or more, preferably 1 μm or more, and for example, 100 μm or less, preferably 50 μm or less.

〔Porous resin layer〕 The porous resin layer 4 has one surface and the other surface facing in the thickness direction, and has a sheet shape extending in the surface direction. The other surface of the porous resin layer 4 is in contact with (adhering to) one surface of the first metal layer 3.

The porous resin layer 4 has a plurality of fine pores (pores) 10. The porous resin layer 4 has, for example, either an independent bubble structure or a continuous bubble structure. It is preferable to have an independent bubble structure mainly. In this case, the ratio of independent bubbles exceeds, for example, 50%, preferably 80% or more, more preferably 90% or more, and for example, less than 100%. If the ratio of independent bubbles is higher than the above lower limit, the decrease in pattern accuracy caused by the penetration of the etching solution used in the patterning of the first metal layer 3 and the second metal layer 6 into the porous resin layer 4 can be suppressed . That is, it is possible to suppress that the portion protected by the resist of the first metal layer 3 and the second metal layer 6 due to the penetration of the etching solution into the porous resin layer 4 is also removed by the etching solution.

Furthermore, in order to fabricate the antenna circuit board, when the low-dielectric base material of the present invention is subjected to hole processing and then plated using a drill or laser, the infiltration of the plating liquid is suppressed, so it can be used in the hole A metal layer with a uniform thickness is formed on the surface. Here, the soaking of the plating solution means that the plating solution penetrates from the porous portion exposed by the above-mentioned hole-forming process, thereby depositing metal in the porous resin layer 4; it will become a metal formed on the surface of the hole The thickness of the layer becomes non-uniform, or becomes discontinuous, which causes the exposed portion of the porous resin layer.

The porosity in the porous resin layer 4 is 60% or more, more preferably 70% or more, still more preferably 80% or more, and particularly preferably 85% or more. Furthermore, the porosity in the porous resin layer 4 is less than 100%, preferably less than 99%. The porosity is obtained, for example, by image analysis of a cross-sectional SEM (scanning electron microscope) photo of the porous resin layer 4. Alternatively, the porosity is obtained by calculation based on the following formula: Porosity (%)=(1-specific gravity of non-porous resin layer/specific gravity of porous resin layer)×100.

Furthermore, in the formula, the non-porous resin layer includes the material of the porous resin layer 4, but it is not a porous but a dense film.

If the porosity in the porous resin layer 4 is higher than the above lower limit, the porous resin layer 4 has a low dielectric constant sufficient to sufficiently meet the fifth-generation (5G) standard or high-speed transmission FPC. Specifically, the low-dielectric substrate sheet 1 is as described above, and is useful as a substrate sheet that is sufficiently compatible with the fifth-generation (5G) standard or high-speed transmission FPC.

The average diameter (ie, average pore diameter) of the pores 10 in the porous resin layer 4 is, for example, 10 μm or less, and, for example, 0.1 μm or more. The average pore diameter is obtained by image analysis of the cross-sectional SEM photograph of the porous resin layer 4. In the image analysis system, the SEM image is binarized, and after identifying the void 10, the pore size is calculated and the histogram is plotted. The analysis software uses ImageJ.

The dielectric constant of the porous resin layer 4 at a frequency of 10 GHz is appropriately adjusted according to the porosity and the type of resin described below. Specifically, it is, for example, 2.5 or less, preferably 2.0 or less, and, for example, more than 1.0. The dielectric constant is measured by the resonator method using a frequency of 10 GHz.

If the dielectric constant of the porous resin layer 4 is below the upper limit, the low-dielectric substrate sheet 1 has a low dielectric constant, so it can be effectively used as a fifth-generation (5G) standard or high-speed transmission FPC substrate sheet .

The material of the porous resin layer 4 is not particularly limited, and examples thereof include resins such as thermosetting resins and thermoplastic resins.

Examples of thermosetting resins include polycarbonate resins, thermosetting polyimide resins, thermosetting fluorinated polyimide resins, epoxy resins, phenol resins, urea resins, melamine resins, and o-phthalic acid. Diallyl formate resin, silicone resin, thermosetting urethane resin, fluororesin (fluoroolefin-containing polymer (specifically, polytetrafluoroethylene (PTFE), etc.)), liquid crystal polymer (LCP) etc. These can be used alone or in combination of two or more.

Examples of the thermoplastic resin include olefin resin, acrylic resin, polystyrene resin, polyester resin, polyacrylonitrile resin, maleimide resin, polyvinyl acetate resin, ethylene-vinyl acetate copolymer, and poly Vinyl alcohol resin, polyamide resin, polyvinyl chloride resin, polyacetal resin, polyphenylene ether resin, polyphenylene sulfide resin, polyphenol resin, polyether resin, polyether ether ketone resin, polyaromatic resin, Thermoplastic polyimide resin, thermoplastic fluorinated polyimide resin, thermoplastic urethane resin, polyether amide imide resin, polymethylpentene resin, cellulose resin, liquid crystal polymer, ionic polymer, etc. . These can be used alone or in combination of two or more.

Among the above resins, from the viewpoint of mechanical strength, polyimide resins (including thermosetting polyimide resins and thermoplastic polyimide resins) and fluorinated polyimide resins (thermosetting) are preferably exemplified. Fluorinated polyimide resin and thermoplastic fluorinated polyimide resin), polycarbonate resin, polyether amide imide resin. Particularly good examples are polyimide resins.

Polyimide resin is a material most suitable for lamination by pressurization, which is included in the production step of the low-dielectric base plate 1 including the porous resin layer 4 having an independent bubble structure. The details of the above-mentioned preferred resin properties and manufacturing methods are described in, for example, Japanese Patent Laid-Open No. 2018-021171 and Japanese Patent Laid-Open No. 2018-021172.

The porous resin layer 4 may have surface layers (not shown) formed on one surface and the other surface in the thickness direction.

The arithmetic mean roughness (Ra) of one side or the other side in the thickness direction of the porous resin layer 4 is, for example, 0.1 μm or more, preferably 0.2 μm or more, and for example, 1.0 μm or less, preferably 0.7 μm or less. Moreover, the maximum height (Rz) of one surface or the other surface in the thickness direction of the porous resin layer 4 is, for example, 1.0 μm or more, preferably 2.0 μm or more, and for example, 15.0 μm or less, preferably 10.0 μm or less.

The thickness of the porous resin layer 4 is, for example, 2 μm or more, preferably 5 μm or more, more preferably 25 μm or more, still more preferably 50 μm or more, and for example, 1,000 μm or less, preferably 500 μm or less.

In addition, layers other than the porous resin layer 4, specifically, the first metal layer 3, the adhesive layer 5 (described below), and the second metal layer 6 (described below) are different from the porous resin layer 4, for example Non-porous, that is, does not substantially have fine pores, dense.

[Next layer] Next, the layer 5 has a sheet shape along the surface direction of the porous resin layer 4 in the thickness direction.

The material of the adhesive layer 5 is not particularly limited, and various types of adhesives such as hot-melt adhesives and thermosetting adhesives may be mentioned, and specifically, acrylic adhesives, epoxy adhesives, silicon Ketone adhesives. Preferably, an acrylic adhesive is used.

The thickness of the next layer 5 is, for example, 2 μm or more, preferably 5 μm or more, and, for example, 50 μm or less, preferably 25 μm or less.

[2nd metal layer] The second metal layer 6 has one surface and the other surface facing in the thickness direction, and has a sheet shape extending in the surface direction. The other surface of the second metal layer 6 is adhered to one surface of the porous resin layer 4 via the adhesive layer 5. The material and thickness of the second metal layer 6 are the same as those of the first metal layer 3.

The thickness of the low dielectric substrate sheet 1 is the total thickness of the first metal layer 3, the porous resin layer 4, the adhesive layer 5 and the second metal layer 6, for example 10 μm or more, preferably 20 μm or more, and, for example It is 5,000 μm or less, preferably 2,000 μm or less.

[Manufacturing method of low dielectric substrate] Next, a method of manufacturing the low-dielectric substrate sheet 1 will be described.

In addition, in the manufacture of the low-dielectric substrate sheet 1 of one embodiment, for example, each member and one area layer are formed (formed) by the roll-to-roll method.

Specifically, first, the first metal layer 3 is prepared. For example, a foil (metal foil) containing the above-mentioned materials is prepared as the first metal layer 3.

Then, a porous resin layer 4 is formed on one surface of the first metal layer 3. For example, the porous resin layer 4 is formed (made into) on one surface of the first metal layer 3.

Specifically, first, a varnish containing the above-mentioned resin precursor, porous agent, nucleating agent, and solvent is prepared, and then the varnish is applied to one surface of the first metal layer 3 to form a coating film. The types and mixing ratios of the porosifying agent, nucleating agent and solvent in the varnish are described in, for example, Japanese Patent Laid-Open No. 2018-021171 and Japanese Patent Laid-Open No. 2018-021172.

In particular, the mass fraction (provision ratio) of the porous agent is, for example, 1 part by mass or more, preferably 3 parts by mass or more, more preferably 20 parts by mass or more, and even more preferably 50 parts by mass with respect to 100 parts by mass of the precursor. The mass part or more is, for example, 300 mass parts or less, preferably 250 mass parts or less.

The nucleus agent is a foaming nucleus agent (bubble regulator) that becomes a nucleus when the precursor is foamed (porous). In addition, as the nucleating agent, in addition to the nucleating agent (PTFE, etc.) described in the above-mentioned gazette, fluororesins (polymers of fluorinated olefins) such as poly(trifluorochloroethylene) and the like (a Group) Acrylic esters and copolymers containing the above-mentioned fluorine-containing olefins as monomer units.

The nucleating agent can be any one of solid, liquid, and semi-solid at room temperature (23°C), and is preferably solid. If the nucleus agent is solid at normal temperature, examples of the shape of the nucleus agent include a substantially spherical shape, a substantially plate shape, a substantially needle shape, and an indefinite shape (including a block shape), and preferably a substantially spherical shape.

If the nucleating agent is solid at normal temperature, the average value of the maximum length of the nucleating agent (average particle diameter if it is roughly spherical) is, for example, 2,000 nm or less, preferably 1,000 nm or less, more preferably 800 nm In the following, it is more preferably less than 500 nm, and, for example, 1 nm or more.

In addition, the core agent can also be prepared in the form of a slurry previously dispersed in a solvent (PTFE).

Then, the coating film is dried by heating, thereby promoting the removal of the solvent, and on the other hand, forming a phase separation structure in which the nucleus agent is the nucleus precursor and the porous agent.

Then, for example, by a supercritical extraction method using supercritical carbon dioxide as a solvent, the porous agent is extracted (extracted or removed) from the precursor.

Then, the precursor is hardened to form a porous resin layer 4, specifically, a porous resin.

Then, the adhesive layer 5 is arranged on one surface of the porous resin layer 4. For example, the adhesive agent is applied to one surface of the porous resin layer 4, or the adhesive layer 5 obtained by forming the adhesive agent into a sheet shape in advance is attached to one surface of the porous resin layer 4.

Then, the second metal layer 6 is arranged on one surface of the adhesive layer 5. For example, a foil (metal foil) containing the above materials is attached to one side of the adhesive layer 5.

With this, the low-dielectric-based sheet 1 is manufactured.

The low-dielectric-based sheet 1 can be used for various purposes, for example, and is preferably used for manufacturing a high-frequency antenna suitable for the fifth generation (5G) standard or a high-speed transmission substrate (high-speed transmission FPC, etc.). Specifically, the low-dielectric substrate 1 can be used as a substrate for high-frequency antennas or high-speed transmission FPC.

When the low-dielectric-based sheet 1 is used for the above-mentioned applications, the second metal layer 6 is patterned as shown in FIG. 2 by light lithography (for example, subtraction method), for example, to form signal wiring (differential Wiring etc.) or antenna wiring etc. side wiring 17. Then, the first metal layer 3 is patterned by photolithography, and the other-side wiring 18 such as a ground wiring is formed, for example.

With this, a pattern laminate 13 including the other side wiring 18, the porous resin layer 4, the adhesive layer 5 and the one side wiring 17 in order toward one side in the thickness direction is manufactured, and the pattern laminate 13 is provided to be suitable for the fifth generation ( 5G) Standard high-frequency antenna or high-speed transmission substrate.

Moreover, the low dielectric substrate sheet 1 has a porous resin layer 4, the porous resin layer 4 has 60% or more, more preferably 70% or more, further preferably 80% or more, particularly preferably 85% or more In the case of porosity, it can have a sufficiently low low dielectric constant. Specifically, the low dielectric constant is, for example, 2.5 or less, preferably 2.0 or less. Therefore, the low-dielectric-based board 1 can have a relatively low dielectric constant sufficient to cope with the fifth generation (5G) standard wireless communication antenna substrate or high-speed transmission FPC.

In addition, the low-dielectric substrate sheet 1 includes the first metal layer 3 and the second metal layer 6, so it can be patterned as a wiring supporting an antenna of the fifth generation (5G) standard or a substrate for high-speed transmission FPC. Specifically, even if the first metal layer 3 and the second metal layer 6 are patterned under industrial etching conditions, the substrate suitable for the fifth-generation (5G) antenna or high-speed transmission FPC can be formed with excellent accuracy Of wiring.

In addition, when the porous resin layer 4 has an independent bubble structure, and the ratio of independent bubbles is high, more than 50%, further 80% or more, and further 90% or more, the patterning can be suppressed. The accuracy of the pattern is reduced due to the penetration of the etching solution used in the process. Therefore, the low dielectric substrate 1 is useful as a substrate sufficient to fully and reliably deal with the fifth generation (5G) standard of wireless communication or high-speed transmission FPC.

<Significant feature points> Next, the significant features of the low-dielectric substrate sheet 1 will be described below.

The low-dielectric-based sheet 1 includes a porous resin layer 4, an adhesive layer 4, and a second layer 6 in this order in the thickness direction. Therefore, the adhesive strength between the porous resin layer 4 and the second metal layer 6 is good.

Specifically, the adhesive force between the porous resin layer 4 and the second metal layer 6 is, for example, 0.3 N/mm or more, preferably 0.6 N/mm or more, and for example, 3.0 N/mm or less.

The adhesive force between the porous resin layer 4 and the second metal layer 6 is the 90° peel strength when peeling the second metal layer 6 from the porous resin layer 4 at an angle of 90 degrees at 23°C. The details will be The details are described in the examples.

Therefore, it is possible to suppress the second metal layer 6 from falling off from the low-dielectric substrate 1. In particular, when the second metal layer 6 is formed on the wiring 17, it is possible to suppress the peeling of all or part of the wiring 17 from the porous resin layer 4, thereby suppressing the disconnection of the wiring 17.

In addition, the thickness d1 of the adhesive layer 5 and the thickness d2 of the porous resin layer 4 satisfy the following formula (1): d1/d2≦0.5 (1).

The ratio (d1/d2) of the thickness d1 of the subsequent layer 5 to the thickness d2 of the porous resin layer 4 is 0.5 or less. In other words, the thickness d1 of the adhesive layer 5 is half of the thickness d2 of the porous resin layer 4 or thinner than half of the thickness d2 of the porous resin layer 4.

That is, the thickness of the adhesive layer 5 having a higher dielectric constant than the porous resin layer 4 is sufficiently thinner than the thickness of the porous resin layer 4, so the influence of the adhesive layer 5 on the dielectric constant can be reduced. Therefore, the dielectric constant of the low-dielectric base plate 1 can be reduced. Therefore, it can be preferably used as a high-frequency antenna or high-speed transmission board suitable for the fifth generation (5G) standard.

In addition, in a low-dielectric-based plate material provided with a resin substrate and a metal layer, since there is no adhesive layer, the adhesive force is poor. On the other hand, if an adhesive layer is disposed between the resin substrate and the metal layer in order to improve the adhesive force, the dielectric constant of the low-dielectric base material will be affected by the dielectric constant of the adhesive layer. Moreover, in the previous resin substrates, there is no requirement for a low dielectric that can be used as a high-frequency antenna or a high-speed transmission board suitable for the fifth generation (5G) standard, so there is no performance other than the adhesion of the adhesive layer. Pay attention. However, based on the necessity of being suitable for the 5th generation (5G) standard, the base material has been required to be further low-dielectric, and the inventors found that this requirement can be satisfied by not only making the resin substrate low-dielectric but also the adhesive layer low-dielectric.

Specifically, the inventors found that by making the thickness of the adhesive layer thinner, the dielectric constant of the porous resin layer lower than that of the adhesive layer is dominant, and the dielectric constant of the entire base plate can be reduced. However, if the adhesive layer is too thin, the adhesive force between the resin substrate and the metal layer becomes insufficient. Therefore, the adhesive layer must be designed with a thickness that can achieve sufficient suppression of the adhesive force and the dielectric constant. Therefore, in the present invention, by making the adhesive layer 5 thinner than one-and-a-half of the porous resin layer 4, while ensuring the adhesive force, the dielectric constant increase is suppressed, and as a result, the second metal layer 6 is not peeled off (adhesive layer 4's adhesive force) and the low-dielectric base plate 1 low dielectric balance.

In the above formula (1), the above ratio (d1/d2) is 0.3 or less, more preferably 0.1 or less. In addition, the ratio (d1/d2) is, for example, 0.01 or more, preferably 0.03 or more.

In addition, in the low-dielectric-based sheet 1, it is preferable to satisfy the following formula (2): 2≦d2/d1≦150 (2).

Specifically, the ratio (d2/d1) of the thickness d2 of the porous resin layer 4 to the thickness d1 of the adhesive layer 5 is preferably 2 or more, more preferably 3 or more, and still more preferably 10 or more. It is 150 or less, more preferably 25 or less, and still more preferably 20 or less.

If the above ratio is equal to or greater than the above lower limit, the adhesive force between the porous resin layer 4 and the second metal layer 6 is more excellent. On the other hand, if the above ratio is equal to or lower than the above upper limit, the dielectric constant of the low-dielectric substrate sheet 1 becomes lower, which is extremely useful as a substrate sheet suitable for the fifth-generation (5G) standard or high-speed transmission FPC.

In addition, in the low-dielectric-based sheet 1, it is preferable to satisfy the following formula (3): 5 μm≦d2－d1≦115 μm (3).

Specifically, the difference (d2-d1) between the thickness d2 of the porous resin layer 4 and the thickness d1 of the adhesive layer 5 is preferably 5 μm or more, more preferably 20 μm or more, and still more preferably 50 μm or more, and, It is preferably 115 μm or less, and more preferably 100 μm or less.

If the difference is more than the lower limit, the dielectric constant of the low-dielectric substrate 1 further becomes lower. On the other hand, if the above ratio is equal to or lower than the above upper limit, the adhesive force between the porous resin layer 4 and the second metal layer 6 is more excellent.

Moreover, in the low-dielectric-based sheet 1, the thickness d1 of the adhesive layer 5 is, for example, 1 μm or more, preferably 4 μm or more, more preferably 5 μm or more, and for example, 50 μm or less, preferably 44 Below μm, more preferably below 10 μm.

When the thickness d1 of the adhesive layer 5 is equal to or greater than the above lower limit, the adhesive force between the porous resin layer 4 and the second metal layer 6 is more excellent. On the other hand, if the above ratio is equal to or lower than the above upper limit, the dielectric constant of the low-dielectric base material 1 further becomes lower.

The dielectric constant of the frequency of the next layer 5 at 10 GHz is appropriately adjusted according to the type of the adhesive, specifically, for example, 3.10 or less, preferably 2.80 or less, more preferably 2.50 or less, for example 1.00 or more. If the dielectric constant of the adhesive layer 5 is equal to or lower than the above upper limit, the dielectric constant of the low-dielectric base plate 1 further becomes lower.

The dielectric constant of the low-dielectric base plate 1 at a frequency of 10 GHz is, for example, 2.00 or less, preferably 1.80 or less, more preferably 1.60 or less, and for example, 1.00 or more.

<Change example> Next, a variation of an embodiment will be described. In the following modified examples, the same components and steps as those in the above-mentioned embodiment are denoted by the same reference symbols, and detailed descriptions thereof are omitted. Moreover, one embodiment and each modification can be combined as appropriate. Furthermore, unless specifically described, each modified example can exert the same effects as those of the first embodiment.

In the above description, the roll-to-roll method is used to manufacture the low-dielectric substrate sheet 1, but it is not limited to this, and the low-dielectric substrate sheet 1 may be produced by a batch method (single-sheet type), for example.

Furthermore, in one embodiment, the low-dielectric-based sheet material 1 includes the first metal layer 3, but for example, the low-dielectric-based sheet material 1 may not include the first metal layer 3, although this is not shown in this case. That is, in one embodiment, it is a low-dielectric-based sheet material with a double-sided metal laminate type, but in other embodiments, for example, it may be a low-dielectric-based sheet material with a single-sided metal laminate type.

Although not shown, the low-dielectric substrate sheet 1 may include a first release sheet disposed on the other side of the first metal layer 3 and a second release sheet disposed on one side of the second metal layer 6.

That is, the low-dielectric-based sheet 1 may include the first release sheet, the first metal layer 3, the porous resin layer 4, the adhesive layer 5, the second metal layer 6 and the 2 Peel off the sheet.

In addition, although not shown, the low-dielectric-based sheet 1 may further include a functional layer interposed between layers or formed on the surface. [Example]

Hereinafter, Examples and Comparative Examples are shown, and the present invention will be described more specifically. Furthermore, the present invention is not limited by the examples and comparative examples. In addition, the specific values of the blending ratio (content ratio), physical property values, parameters, etc. used in the following description may correspond to the blending ratio (content ratio), physical property values, parameters, etc. corresponding to their equivalents described in the above “embodiments”. The upper limit (defined as "below" and "not reached" values) or the lower limit (defined as "above" and "exceeded" values) instead.

Example 1 First, the first metal layer 3 containing copper and having a thickness of 12.5 μm is prepared.

Then, to 100 parts by mass of the polyimide precursor solution described in the reference example of Japanese Patent Laid-Open No. 2018-021172, 4.2 parts by mass of the imidate catalyst (2-imidazole) and 200 parts by mass were prepared A porosifying agent containing polyoxyethylene dimethyl ether (manufactured by NOF Corporation, grade: MM400, weight average molecular weight 400), 3 parts by mass of a nucleating agent containing PTFE and having an average particle diameter of 1000 nm, and NMP (N-methyl Pyrrolidone) while preparing a varnish. The nucleus agent is prepared by preparing the slurry pre-dispersed in NMP with respect to the polyimide precursor. In addition, the total blended parts of NMP in the varnish was adjusted so as to be 150 parts by mass with respect to 100 parts by mass of the polyimide precursor by adding those contained in the slurry.

The varnish was applied to one side of the first metal layer 3, and dried at 120°C for 30 minutes to remove NMP. Then, the supercritical extraction method was used to remove the porous agent, and then, under vacuum, at 380 It was heated at ℃ for 2 hours to amide imide, thereby producing a porous resin layer 4 containing polyimide embedded on one surface of the first metal layer 3.

The thickness of the porous resin layer 4 is 120 μm. The porosity in the porous resin layer 4 is 80%, and the average pore diameter is 7 μm. In addition, the dielectric constant of the porous resin layer 4 at a frequency of 10 GHz is 1.5.

Then, an adhesive layer 5 containing an acrylic adhesive and having a thickness of 5 μm was formed on one surface of the porous resin layer 4.

Then, the second metal layer 6 containing copper and having a thickness of 12 μm is attached to one side of the adhesive layer 5.

As a result, as shown in FIG. 1, a low-dielectric substrate sheet 1 including the first metal layer 3, the porous resin layer 4, the adhesive layer 5, and the second metal layer 6 in this order in the thickness direction is manufactured.

Examples 2 to 5 Except that the thickness d1 of the adhesive layer 5 and the thickness d2 of the porous resin layer were changed to the thicknesses d1 and d2 described in Table 1, the low dielectric substrate sheet 1 was produced in the same manner as in Example 1.

Comparative examples 1 to 3 Except that the thickness d1 of the adhesive layer 5 and the thickness d2 of the porous resin layer were changed to the thicknesses d1 and d2 described in Table 1, the low dielectric substrate sheet 1 was produced in the same manner as in Example 1.

Evaluation ＜Thickness＞ The thickness of each layer was measured using a dial gauge (manufactured by PEACOCK, "UPRIGHT DIAL GAUGE R1-205").

<adhesive force>

In each of the Examples and Comparative Examples, a tensile compression tester (manufactured by Imada Manufacturing Co., Ltd., "SUZ-50NT-2R2T") was used to measure by performing a 90-degree peel test at a peel speed of 50 mm/min. The adhesive force between the porous resin layer 4 and the second metal layer 6. Furthermore, at this time, the adhesive layer 5 and the porous resin layer 4, the second metal layer 6, or both are bonded at only a few points or the entire surface.

The case where the adhesive force was 0.6 N/mm or more was evaluated as 0.

The case where the adhesive force was 0.3 N/mm or more and less than 0.6 N/mm was evaluated as △.

The case where the adhesive force was less than 0.3 N/mm was evaluated as ×.

<Dielectric constant> In the low-dielectric-based plates of the examples and comparative examples, a PNA network analyzer (manufactured by Agilent Technologies, product name "5227A") and SPDR resonator were used to measure the specific dielectric constant at 10 GHz.

Table 1 shows the results of the above evaluation.

<Arithmetic average roughness (Ra), maximum height (Rz)>

Three test pieces obtained by cutting the porous resin layer 4 produced in Example 1 to a size of 50 mm×50 mm were measured using a scanning confocal laser microscope (manufactured by Olympus, “OLS3000”) Then the arithmetic average roughness (Ra) and maximum height (Rz) of the surface on the layer side.

Ra was 0.444 μm, 0.399 μm, 0.396 μm, and the average value of Ra was 0.41 μm. In addition, Rz is 4.767 μm, 8.62 μm, and 6.502 μm, respectively, and the average value of Rz is 6.63 μm.

[Table 1]

In addition, the above invention is provided as an exemplary embodiment of the present invention, but it is merely a mere illustration and should not be interpreted in a limited manner. Variations of the invention that are clear to those skilled in the art are included in the following patent applications. [Industry availability]

The low-dielectric-based sheet can be preferably used for manufacturing high-frequency antennas or high-speed transmission substrates.

1: Low dielectric substrate sheet 3: the first metal layer 4: porous resin layer 5: then layer 6: 2nd metal layer 13: Pattern laminate 17: Wiring on one side 18: Wiring on the other side d1: thickness of the next layer d2: Thickness of porous resin layer

FIG. 1 shows a cross-sectional view of an embodiment of a low-dielectric-based sheet material of the present invention. FIG. 2 shows a cross-sectional view of the pattern laminate obtained from the low dielectric substrate sheet shown in FIG. 1. FIG.

1: Low dielectric substrate sheet

3: the first metal layer

4: porous resin layer

5: then layer

6: 2nd metal layer

d1: thickness of the next layer

d2: Thickness of porous resin layer

Claims (2)

A low-dielectric-based sheet material, characterized in that a porous resin layer, an adhesive layer and a metal layer are sequentially provided in the thickness direction, and The thickness d1 of the adhesive layer and the thickness d2 of the porous resin layer satisfy the following formula (1): d1/d2≦0.5 (1). If the low-dielectric-based sheet of claim 1, it satisfies the following formula (2): 2≦d2/d1≦150 (2).

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