JP5186266B2 - Multilayer wiring circuit board and manufacturing method thereof - Google Patents

Description

  The present invention relates to a multilayer wiring circuit board, and more particularly to a multilayer wiring circuit board obtained by multilayering a wiring board having a liquid crystal polymer as a base material layer and a method for manufacturing the same.

  In recent years, as electronic devices have become lighter, thinner, and smaller, wiring circuits have been required to have higher density. As a technique for realizing this, a multilayer wiring circuit board in which a plurality of wiring boards are stacked and integrated is known. As an example, a multilayer flexible wiring circuit board obtained by multilayering a flexible wiring board having polyimide as a base layer using an interlayer adhesive may be used.

  Furthermore, as the performance of electronic devices has been improved and the transmission frequency has been increased, a multilayer wiring circuit board having a liquid crystal polymer as a base layer is suitably used as a representative substrate corresponding to the high frequency. Yes. Liquid crystal polymer is a resin characterized by a low dielectric constant and low dielectric loss tangent, and multilayer printed circuit boards using the same resin as an insulating layer have a higher transmission loss in the high frequency region than when other resins are used as an insulating layer. Has the effect of reducing.

  A multilayer wiring circuit board having a liquid crystal polymer as an insulating layer is manufactured by thermocompression bonding in a state where the liquid crystal polymer is heated to near the melting point of a liquid crystal polymer base material which is a thermoplastic resin. However, the heating temperature becomes 250 ° C. or more, and there is a problem that it cannot be manufactured by a general-purpose hot press. Furthermore, due to thermal deformation of the liquid crystal polymer base material, there is a concern that the circuit conductor is likely to be misaligned and the electrical characteristics such as impedance mismatching are adversely affected. In addition, the multilayer wiring circuit board using a liquid crystal polymer as a base layer has an anchor effect that is insufficient if the multilayer adhesive interface is smooth, and the interlayer adhesion is insufficient. There is also a problem that a roughening process is required and the manufacturing process is complicated (see Patent Document 1).

  In general, as an interlayer adhesive for producing a multilayer wiring circuit board, one obtained by semi-curing a thermosetting resin such as an epoxy resin and molding it into a sheet shape is widely known. However, these have a high dielectric constant and dielectric loss tangent, and do not have sufficient electrical characteristics to be used as a material for a high-frequency substrate.

On the other hand, it has been found that an adhesive sheet made of siloxane-modified polyimide has a characteristic that the dielectric constant is lower than that of a general-purpose epoxy adhesive and has excellent adhesive properties. However, these are often used for a wiring board based on polyimide (see Patent Document 2).
JP 2006-179609 A JP 2001-203467 A

  The present invention has been made in view of the above-mentioned problems of the prior art, and can reduce the manufacturing conditions in a multilayer wiring circuit board using a liquid crystal polymer, and transmission loss in a high frequency region, which is a feature of the liquid crystal polymer. An object of the present invention is to provide a multilayer wiring circuit board in which the above is reduced.

  In order to achieve the above object, the inventors of the present invention have provided a multilayer wiring circuit board using a liquid crystal polymer as a base layer, and a multilayer wiring using a conventional liquid crystal polymer by using an adhesive sheet made of siloxane-modified polyimide as an insulating layer. The present inventors have found that a multilayer wiring circuit board that can be manufactured under relaxed conditions as compared with a circuit board and that has excellent transmission characteristics in a high-frequency region can be obtained.

  That is, the multilayer wiring circuit board of the present invention is a resin comprising a liquid crystal polymer as a base layer, a plurality of wiring boards each having a circuit conductor layer provided on one or both sides thereof, and a siloxane-modified polyimide between the wiring boards. The multilayer wiring circuit board is characterized in that an insulating layer formed from is interposed, and has excellent transmission characteristics in a high frequency region.

Further, the relationship between the thermal deformation temperature Lt (° C.) of the liquid crystal polymer constituting the base material of the multilayer wiring circuit board of the present invention and the thermal deformation temperature St (° C.) of the resin containing the siloxane-modified polyimide of the insulating layer is expressed as Lt> St.
Furthermore, in the multilayer wiring circuit board of the present invention, the circuit conductor layer has a surface roughness Rz of 0.5 to 3 μm at the interface between the liquid crystal polymer of the wiring board and the resin containing the siloxane-modified polyimide of the insulating layer adjacent thereto. It is preferable to be in the range.

  According to the multilayer wiring circuit board of the present invention, since the insulating layer containing the siloxane-modified polyimide resin is disposed between the high-density multilayer wiring circuit boards, the manufacturing conditions at the time of production are relaxed, and the characteristics of the liquid crystal polymer It is possible to sufficiently reduce the transmission loss in the high-frequency region, which enables excellent high-density wiring.

Hereinafter, the present invention will be described in detail with reference to preferred embodiments thereof.
First, the multilayer wiring circuit board of the present invention will be described. That is, the multilayer wiring circuit board of the present invention has at least two liquid crystal polymer base layers and a wiring circuit layer formed from a resin containing siloxane-modified polyimide between the wiring boards.

  The liquid crystal polymer used in the present invention forms an optically anisotropic melt phase. The liquid crystal polymer is not particularly limited in its kind, but a so-called wholly aromatic liquid crystal polymer, that is, a liquid crystal polymer that does not contain an aliphatic long chain and is substantially composed only of an aromatic is preferable, and among them, A polyester represented by the structural formula (1) consisting of 6-hydroxy-2-naphthoic acid and p-hydroxybenzoic acid is more preferable (m and n are integers).

The liquid crystal polymer can be selected from various liquid crystal polymers such as a liquid crystal polymer used as an insulating layer for a commercially available liquid crystal polymer film or a copper clad laminate, or a liquid crystal polymer can be appropriately prepared and used. You can also. As the liquid crystal polymer film, Bexter (manufactured by Kuraray Co., Ltd.) or the like can be used, and as the copper-clad laminate, Espanesque L series (manufactured by Nippon Steel Chemical Co., Ltd.) can be used.
The liquid crystal polymer preferably has a linear expansion coefficient in the range of 1 × 10 ^{−6 to} 25 × 10 ⁻⁶ / ° C., for example, from the viewpoint of obtaining stable dimensional accuracy of the substrate.
Further, the heat distortion temperature Lt (° C.) of the liquid crystal polymer according to the present invention is preferably 180 ° C. or higher, particularly 210 to 330 ° C. If it exists in this range, manufacture mentioned later can be implemented easily and does not have a bad influence on a liquid crystal polymer at the time of heat adhesion.

The circuit conductor layer according to the present invention is such that the circuit conductor layer is provided on one or both sides of the liquid crystal polymer wiring circuit layer as described above. Such a circuit conductor layer is formed by subjecting a conductor layer such as a metal foil to a known circuit formation process.
Examples of such metal foils include conductive metals such as copper, aluminum, iron, silver, palladium, nickel, chromium, molybdenum, tungsten, zinc, and alloys thereof. Among these, stainless steel, copper An alloy copper foil containing 90% or more of foil or copper is preferable.
The thickness of the liquid crystal polymer can be, for example, about 5 to 100 μm, and preferably 10 to 50 μm. Moreover, the thickness of a wiring circuit layer and a conductor layer can be about 3-35 micrometers, for example, Preferably, it is 5-25 micrometers.
The surface roughness Rz of the circuit conductor layer serving as an interface between the liquid crystal polymer of the wiring board and the resin containing the siloxane-modified polyimide of the insulating layer adjacent thereto is preferably in the range of 0.5 to 3 μm, particularly 0.7 to 1 A range of 0.5 μm is preferred. If the surface roughness Rz is within such a range, sufficient interlayer adhesion strength is ensured without adversely affecting the transmission characteristics in the high-frequency region that may occur when the roughness of the boundary surface is significantly large. Can do.
Here, Rz refers to the 10-point average roughness defined by JIS B0601 (1994).

The insulating layer (adhesive layer) between the circuit boards in the present invention contains siloxane-modified polyimide as a main component, and an epoxy resin is introduced and / or blended into the siloxane-modified polyimide as necessary, and a curing agent or other A thermosetting resin composition containing an additive is preferably used, and more preferably, 70 to 99% by mass of siloxane-modified polyimide and 1 to 30% by mass of an epoxy resin are blended.
The thermal deformation temperature of the siloxane-modified polyimide in the present invention is preferably in the range of 60 to 170 ° C, more preferably 80 to 170 ° C. If the thermal deformation temperature of the siloxane-modified polyimide is within the above range, the heating adhesion temperature can be set without difficulty.

Examples of the siloxane-modified polyimide include those having a structural unit represented by the following general formula (1) having a silicon unit and a structural unit represented by the following general formula (2). In the general formula (2), at least 1 mol% of Ar ₂ may be a divalent aromatic group having a functional group having reactivity with the epoxy resin represented by the following general formula (3).

In general formula (1), Ar ₁ represents a tetravalent aromatic group. R ₁ and R ₂ represent a divalent hydrocarbon group, and R ₁ and R ₂ are a C 1-6 divalent alkylene group or phenylene group. R _{3 to} R ₆ represent a hydrocarbon group having 1 to ₆ carbon atoms, and those composed of a methyl group, an ethyl group, a propyl group, or a phenyl group are preferable. n is the average number of repetitions and represents a number of 1 to 20, preferably a number of 1 to 10.

In general formula (2), Ar ₁ represents a tetravalent aromatic group, and Ar ₂ represents a divalent aromatic group. A part of Ar ₂ may be replaced with a trivalent or tetravalent aromatic group represented by the following general formula (3).

一般式（３）中、Ａｒ_３は３価又は４価の芳香族基を表し、Ｘはエポキシ基と反応性を有する官能基であり、好ましくは、水酸基、アミノ基又はカルボキシル基であり、ｍは１又は２であるが、ｍが２の場合Ｘは同じであっても異なっていてもよい。

In General Formula (3), Ar ₃ represents a trivalent or tetravalent aromatic group, X is a functional group reactive with an epoxy group, preferably a hydroxyl group, an amino group, or a carboxyl group, m Is 1 or 2, but when m is 2, X may be the same or different.

  The structural ratio (molar ratio) of the structural units represented by the general formula (1) and the general formula (2) having the silicon unit is as follows: General formula (1) / general formula (2) = 10/90 to 70/30 The range is preferably, more preferably in the range of general formula (1) / general formula (2) = 10/90 to 45/55, and general formula (1) / general formula (2) = 10/90. Most preferably, it is in the range of ~ 40/60.

A polyimide having a silicon unit is obtained by reacting diaminosiloxane and aromatic diamine with tetracarboxylic dianhydride in an organic solvent.
As diaminosiloxane, diaminosiloxane represented by the following general formula (4) is used.

  In the above formula, the average n number of diaminosiloxane is 1 to 20, preferably 1 to 10, more preferably 1 to 8. If the value of n is larger than this value, the adhesiveness is lowered, which is not preferable. By introducing a siloxane structural unit into the polyimide using these diaminosiloxanes, the resin film is given flexibility and fluidity by thermocompression bonding, and the filling property to the pattern metal layer is also good.

  Examples of specific compounds of diaminosiloxane include ω, ω′-bis (2-aminoethyl) polydimethylsiloxane, ω, ω′-bis (3-aminopropyl) polydimethylsiloxane, ω, ω′-bis ( 4-aminophenyl) polydimethylsiloxane, ω, ω′-bis (3-aminopropyl) polydiphenylsiloxane, ω, ω′-bis (2-aminopropyl) polydimethylphenylsiloxane, and the like.

  As aromatic diamines, m-phenylenediamine, p-phenylenediamine, 4,4′-diaminodiphenyl ether, 4,4′-diaminodiphenylpropane, 4,4′-diaminodiphenylmethane, 2,2-bis (3-amino) Phenoxyphenyl) propane, 2,2-bis (4-aminophenoxyphenyl) propane, bis [4- (4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] sulfone, 1,4 Examples include -bis (4-aminophenoxy) benzene and 1,3-bis (4-aminophenoxy) benzene.

When replacing a part of Ar ₂ in the general formula (2) with a trivalent or tetravalent aromatic group represented by the general formula (3) in the present invention, an aromatic diamine having a functional group reactive with an epoxy group Can be used. Examples of the aromatic diamine having a functional group reactive with such an epoxy resin include 2,5-diaminophenol, 3,5-diaminophenol, 4,4 ′-(3,3′-dihydroxy) diaminobiphenyl, 4,4 ′-(2,2′-dihydroxy) diaminobiphenyl, 2,2′-bis (3-amino-4-hydroxyphenyl) hexafluoropropane, 3,3 ′, 4,4′-biphenyltetraamine, 3,3 ′, 4,4′-tetraaminodiphenyl ether, 4,4 ′-(3,3′-dicarboxy) diphenylamine, 3,3′-dicarboxy-4,4′-diaminodiphenyl ether, etc. 4,4 ′-(3,3′-dihydroxy) diphenylamine is one of the preferred ones.
By using these aromatic diamines, it reacts with the epoxy resin at the time of heat curing to form a cross-linking mechanism, so that the adhesive strength with the first resin layer, chemical resistance, etc. can be further improved. Although the aromatic diamine which has a reactive functional group with respect to the said epoxy resin can be used at least 1 mol% or more of all the diamines, Preferably it is the range of 1-10 mol%.

  Examples of tetracarboxylic dianhydrides include pyromellitic dianhydride, 3,3 ′, 4,4′-diphenyl ether tetracarboxylic dianhydride, 3,3 ′, 4,4′-diphenylsulfone tetracarboxylic acid dianhydride. Anhydride, 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 2,3,3 ′, 4′-biphenyl Examples thereof include tetracarboxylic dianhydride.

  The epoxy resin used in the present invention is not particularly limited as long as it can be mixed with polyimide, but is preferably a liquid or powdery epoxy resin having an epoxy equivalent of 500 or less. When epoxy equivalent exceeds 500, adhesive strength and heat resistance will fall. Specific examples of such epoxy resins include bisphenol A, bisphenol F, bisphenol S, fluorene bisphenol, phenols such as 4,4′-biphenol, 2,2′-biphenol, hydroquinone, resorcin, or tris- ( 4-hydroxyphenyl) methane, 1,1,2,2-tetrakis (4-hydroxyphenyl) ethane, phenol novolak, trivalent or higher phenols such as o-cresol novolak, or halogenation such as tetrabromobisphenol A There are glycidyl ethers derived from bisphenols. These epoxy resins can be used alone or in combination of two or more.

  In addition, if necessary, an epoxy resin curing agent may be used for the purpose of accelerating curing. Specific examples thereof include phenols such as phenol novolac and o-cresol novolac, acids such as pyromellitic anhydride and phthalic anhydride. And anhydrides.

When setting it as the resin composition which mix | blended the epoxy resin with the polyimide which has the said silicon unit, it is preferable to make the compounding ratio into the range of 70-99 mass% of siloxane modified polyimide, and 1-30 mass% of epoxy resins. By setting it as this range, heat resistance and adhesiveness can be further improved without deteriorating the original characteristics of polyimide. In addition, although the polyimide which has a silicon unit may have the effect | action which hardens an epoxy resin, even in that case, it treats as a polyimide in this invention, and is distinguished from a hardening | curing agent.
Examples of the additive appropriately blended in the resin composition include a coupling agent, a filler, a pigment, a thixotropic agent, and an antifoaming agent.

  Although the thickness range of the insulating layer formed from the resin containing the siloxane-modified polyimide in the present invention can be appropriately selected according to the plate thickness design value, the range of 10 to 100 μm is preferable, and the range of 35 to 50 μm is more preferable. preferable. As an insulating layer formed from a resin containing a siloxane-modified polyimide, a polyimide-based bonding sheet SPB (manufactured by Nippon Steel Chemical Co., Ltd.) can also be used.

  The multilayer wiring circuit board of the present invention has a plurality of liquid crystal polymer substrate layers and circuit conductor layers as described above. Specifically, it is preferably obtained by using a flexible wiring board having a circuit conductor layer laminated on at least one surface of the liquid crystal polymer base material layer.

  Next, a method of manufacturing the multilayer wiring circuit board of the present invention using the flexible wiring board and the insulating layer formed from the resin containing the siloxane-modified polyimide will be described with reference to the drawings.

FIG. 1 is a process schematic diagram showing a preferred embodiment of a method for producing a multilayer wiring circuit board of the present invention (FIG. 1A corresponds to a wiring board manufacturing process, and FIG. 1C corresponds to the outer layer forming step, FIG. 2A corresponds to the wiring board manufacturing step, and FIG. 2B corresponds to the stacking step.
The multilayer wiring circuit board of the present invention includes, for example, a process of manufacturing a wiring board using a double-sided flexible wiring board (wiring board manufacturing process), and an insulating layer formed of the wiring board and a resin containing siloxane-modified polyimide. And a step of forming a protective layer on the wiring circuit (outer layer forming step) after a circuit forming process is performed on the outer layer copper foil of the wiring board to form a wiring circuit. Can be produced.

In the wiring board manufacturing step, first, at least two double-sided flexible wiring boards using a liquid crystal polymer as a base material layer are prepared. Then, a circuit forming process is performed only on one side of the copper foil of the double-sided flexible wiring board to produce the wiring boards 10 and 11. As a method of the circuit formation process, a known method can be appropriately employed.
Thus, as shown in FIG. 1A, the liquid crystal polymer base layers 1 and 2 and the wiring circuits 3 ′ and 4 ′ formed on one side of the liquid crystal polymer base layers 1 and 2 are provided. The wiring boards 10 and 11 having the copper foils 5 and 6 on the opposite surface can be produced.

In the lamination step, first, the liquid crystal polymer base layers 1 and 2 and the wiring circuits 3 ′ and 4 ′ formed on one side of the liquid crystal polymer base layers 1 and 2 are respectively provided, and the copper foil 5 is provided on the opposite side. In addition, wiring boards 10 and 11 having 6 are prepared. Then, as shown in FIG. 1 (b), so that the copper foil 5 and 6 of the flexible wiring board 10, 11 on the outside, respectively, are opposed to the wiring substrate 10 and the second single-sided flexible laminated plate 11, Lamination is performed via an adhesive sheet (insulating layer) 7 made of a resin containing the siloxane-modified polyimide.

  In addition, the lamination is performed under heat and pressure in a temperature range not lower than the thermal deformation temperature St (° C.) of the resin containing the siloxane-modified polyimide and lower than the thermal deformation temperature Lt (° C.) of the liquid crystal polymer. For example, the temperature can be surely set to a temperature higher than the heat deformation temperature of the siloxane-modified polyimide, more preferably 180 ° C. or more, and less than the heat deformation temperature of the liquid crystal polymer of 235 ° C. Further, in terms of setting, the relationship between the thermal deformation temperature Lt (° C.) of the liquid crystal polymer and the thermal deformation temperature St (° C.) of the resin containing the siloxane-modified polyimide is Lt> St.

Furthermore, the pressure range in the heat and pressure treatment is preferably in the range of 1 MPa to 10 MPa, more preferably in the range of 4 to 6 MPa. Further, the holding time is not particularly limited, but is generally preferably in the range of 10 to 60 minutes.
Although not shown in FIG. 1, a coverlay film or a solder resist may be provided on both sides of the wiring boards 10 and 11 as necessary. As such a cover lay film, a cover lay film or a liquid crystal polymer film in which an epoxy resin adhesive, an acrylic resin adhesive, or a siloxane-modified polyimide adhesive is provided on a polyimide film is preferably used.

  In the outer layer forming step, as shown in FIG. 1C, a circuit forming process is performed on the copper foils 5 and 6 of the double-sided flexible wiring boards 10 and 11 to form the wiring circuits 5 ′ and 6 ′, and then the wiring circuit 5 ′. In addition, a coverlay film or solder resists 8 and 9 are laminated on 6 ′ as a protective layer. As a method of the circuit formation process, a known method can be appropriately employed. As the coverlay films 8 and 9, a coverlay film or a liquid crystal polymer film in which an epoxy resin adhesive, an acrylic resin adhesive, or a siloxane-modified polyimide adhesive is provided on a polyimide film is preferably used.

  The multilayer wiring circuit board 12 of the present invention can be manufactured by the method including the wiring board manufacturing process, the laminating process, and the outer layer forming process as described above. Further, in the method of manufacturing the multilayer wiring circuit board of the present invention, the method of manufacturing the multilayer wiring circuit board having four wiring circuit layers has been described as an example. Thus, for example, a multilayer wiring circuit board having 6 to 8 wiring circuit layers can be provided. In this case, the coverlay films 8 and 9 are preferably used only for protecting the outermost wiring circuit layer.

(Example)
EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example.

The following measurement evaluation was performed.
[Measurement of heat distortion temperature]
Using a thermomechanical analyzer (manufactured by Bruker, 4000SA), thermal expansion in the length direction of the test piece under conditions of a width of 2 mm, a length of 30 mm, a distance between chucks of 15 mm, a load of 2 g, and a heating rate of 5 ° C./min. The amount is measured and the inflection point is defined as the heat distortion temperature.
[Measurement of adhesive strength]
Using a tensile tester (manufactured by Toyo Seiki Co., Ltd., Strograph-M1), the force at the time of peeling a test piece having a width of 10 mm and a length of 100 mm in a 180 ° direction at a speed of 50 mm / min is defined as an adhesive strength.

[Measurement of transmission loss]
Circuit processing was applied to the copper foil of the double-sided flexible wiring board, and then laminated with an adhesive sheet to produce a transmission line (off-center strip line) consisting of three layers of conductors of signal lines on the top and bottom. The design of the transmission line was performed using high frequency circuit design software (manufactured by Agilent Technologies, Advanced Design System). At both ends of the transmission line, equidistant pads comprising a ground, a signal line, and three grounds were arranged for measurement. The transmission loss was calculated by measuring the S parameter using a pico probe for microwaves (manufactured by GGB) and a network analyzer (manufactured by Agilent Technologies, E8364B).

Preparation of siloxane-modified polyimide film (Synthesis example of siloxane-modified polyimide)
A reaction vessel was charged with 37.14 g (0.11 mol) of 3,3 ′, 4,4′-diphenyl ether tetracarboxylic dianhydride (ODPA), 200 g of N-methyl-2-pyrrolidone and 200 g of diethylene glycol dimethyl ether, Mix well at room temperature. Next, in the general formula (4), R ₁ , R ₂ : — (CH ₂ ) ₃ —, and R _{3 to} R ₆ : —CH ₃ , n = 8.4, average molecular weight 740 diaminosiloxane 31.56 g (0.035 mol) was added dropwise, the reaction solution was ice-cooled with stirring, and 30.25 g (0.07 mol) of 2,2′-bis (4-aminophenoxyphenyl) propane (BAPP). and 4,4 '- (3,3'-dihydroxy) was added diaminobiphenyl (HAB) 1.04 g (0.005 mol), stirred for 2 hours at room temperature to obtain a made of polyamide acid solution. This made of Polyamide acid solution heated to 190 ° C., 20 hours heated and stirred to obtain a polyimide solution of inherent viscosity 0.9 dl / g.

(Production example of resin film)
25 parts by mass of a bisphenol A type epoxy resin (manufactured by Japan Epoxy Resin Co., Ltd., Epicoat 828) is mixed with 75 parts by mass of the solid content of the polyimide solution obtained by the synthesis example of the siloxane-modified polyimide, and the mixture is kept at room temperature for 2 hours. And a resin solution of a siloxane-modified polyimide-containing resin composition was prepared. This resin solution was applied onto a PET film and dried to obtain a resin film with a PET film. The heat distortion temperature of the resin on the PET film was 80 ° C. In the following examples, this resin film (hereinafter abbreviated as SP-A) was used.

Example 1
A double-sided flexible wiring board having a 25 μm-thick liquid crystal polymer (thermal deformation temperature: 235 ° C.) as a base layer and a 9 μm-thick copper foil (surface roughness Rz: 2.0 μm) provided on both sides thereof is prepared. Then, circuit processing was performed on the copper foil on one side to obtain two wiring boards 10 and 11 as shown in FIG. 1A in which arbitrary wiring circuits 3 ′ and 4 ′ were formed.

  Next, the wiring boards 10 and 11 are made to face each other so that the copper foils 5 and 6 of the wiring boards 10 and 11 are outside, and the adhesive sheets 7 (SP-A) formed from a resin containing a siloxane-modified polyimide are interposed therebetween. The layers were laminated under the conditions of a temperature of 180 ° C., a pressure of 4 MPa, and a pressure holding time of 60 minutes (FIG. 1B). The thus obtained copper foil on both sides of the multilayer wiring circuit board shown in FIG. 1B was further subjected to circuit processing to provide a coverlay film (FIG. 1C).

The obtained multilayer printed circuit board was filled with no gaps between the wiring circuit and the insulating layer (adhesive sheet), and between the liquid crystal polymer base material layer and the insulating layer (adhesive sheet). The adhesive strength between the wiring circuit and the insulating layer (adhesive sheet) is as good as 0.71 kN / m, and the adhesive strength between the liquid crystal polymer substrate layer and the insulating layer (adhesive sheet) is as good as 0.67 kN / m. It was.

(Comparative Example 1)
The same procedure as in Example 1 was performed except that a liquid crystal polymer film having a thickness of 25 μm and a heat distortion temperature of 235 ° C. was used for the adhesive sheet. However, since the thermal deformation temperature of the liquid crystal polymer used as the adhesive sheet is high, it cannot be laminated at a low temperature of 200 ° C. or lower, and the lamination conditions need to be a temperature of 260 ° C., a pressure of 6 MPa, and a pressure holding time of 15 minutes. was there.
The obtained multilayer printed circuit board has an adhesive strength of 0.52 kN / m between the wiring circuit and the insulating layer (adhesive sheet), and an adhesive strength between the liquid crystal polymer substrate layer and the insulating layer (adhesive sheet) of 0.21. kN / m and inferior to that of Example 1 of the present invention.

(Example 2)
A double-sided flexible wiring board having the same liquid crystal polymer 13 as that used in Example 1 as a base layer is prepared, and circuit processing is performed on the copper foils on both sides to form arbitrary wiring circuits 3 ′ and 4 ′. A wiring board 14 as shown in FIG. Further, in the same manner as in Example 1, the copper foil on one side of the double-sided flexible wiring board having a liquid crystal polymer as a base layer was subjected to circuit processing to obtain two wiring boards 10 and 11 on which arbitrary wiring circuits were formed. It was. Next, on both sides of the wiring board 14, the wiring boards 10 and 11 are made of copper via adhesive sheets (SP-A) 15 and 16 formed from the same resin containing siloxane-modified polyimide as used in Example 1. The multilayer wiring board 17 was obtained by laminating the foils on the outside. The lamination conditions at this time were set to a temperature of 180 ° C., a pressure of 4 MPa, and a holding time of 60 minutes. The copper foil on both sides of the multilayer wiring circuit board obtained in this way shown in FIG. 2B was further subjected to circuit processing to provide a coverlay film.

(Example 3)
In the same manner as Example 1, high frequency transmission lines having three strip line structures (a) to (c) shown in FIG. 3 were prepared. Table 1 shows the configuration of each laminate.
In the high-frequency transmission line thus obtained, a transmission loss of DC to 40 was measured using a network analyzer. The results are shown in Table 1. As shown in Table 1, it was almost the same as when the liquid crystal polymer was used as the bonding material, and the effect of reducing the transmission loss in the high frequency region was obtained.

Reference example: Use of conventional epoxy resin, Unit: dB / mm
As shown in Table 1, the siloxane-modified polyimide in Example 1 shows characteristics comparable to the liquid crystal polymer. On the other hand, the adhesive strength of Example 1 is superior to that of Comparative Example 1 as described above. It was.

  As described above, according to the present invention, the multilayer wiring circuit can relax the manufacturing conditions in the multilayer wiring circuit board using the liquid crystal polymer and reduce the transmission loss in the high frequency region, which is a feature of the liquid crystal polymer. A substrate can be provided. Therefore, the multilayer wiring circuit board of the present invention is useful as a multilayer wiring circuit board used in electronic information equipment that is required to be reduced in size, weight, and functionality.

1A to 1C are process schematic diagrams showing a preferred embodiment of a multilayer wiring circuit board and a method of manufacturing the same according to the present invention. FIGS. 2A and 2B are process schematic diagrams showing a preferred embodiment of the multilayer wiring circuit board and the method of manufacturing the same of the present invention. 3A to 3C are sample schematic diagrams for evaluating transmission characteristics in a high-frequency region for verifying the effects of the present invention.

Explanation of symbols

  1, 2, 13 ... Liquid crystal polymer substrate layer, 3 ', 4' ... Wiring circuit, 5, 6 ... Copper foil, 7, 15, 16 ... Siloxane-modified polyimide adhesive sheet, 8, 9: Coverlay film or solder resist, 10, 11, 14 ... wiring board, 12, 17 ... multilayer wiring board.

Claims (7)

A liquid crystal polymer is used as a base material layer, and a plurality of wiring boards provided with a circuit conductor layer having a surface roughness Rz of 0.5 to 3 μm on one side or both sides of the base material layer are interposed between the wiring boards. A multilayer wiring circuit board in which an insulating layer formed of a resin containing a siloxane-modified polyimide is laminated, the thermal deformation temperature Lt (° C.) of the liquid crystal polymer constituting the base material of the wiring board and the siloxane-modified polyimide of the insulating layer A multilayer wiring circuit board, wherein a relationship with a thermal deformation temperature St (° C.) of a resin containing is Lt> St. Siloxane-modified polyimide has a structural unit represented by the following formula (1) and (2), the multilayer printed circuit board according to claim 1 Symbol placement thermal deformation temperature is in the range of 60 to 170 ° C..

(In the formula, Ar ₁ is a tetravalent aromatic group, R ₁ and R ₂ are divalent hydrocarbon groups, R _{3 to} R ₆ are hydrocarbon groups having 1 to ₆ carbon atoms, and n is 1 to 1) Represents an integer of 20.)

(In the formula, Ar ₁ represents a tetravalent aromatic group, and Ar ₂ represents a divalent aromatic group.) The multilayer wiring circuit board according to claim 1 or 2, comprising two or more insulating layers formed of a resin containing siloxane-modified polyimide. By using a material in which the relationship between the thermal deformation temperature Lt (° C.) of the liquid crystal polymer constituting the substrate of the wiring board and the thermal deformation temperature St (° C.) of the resin containing the siloxane-modified polyimide is Lt> St, Is prepared as a base material layer, and two or more wiring boards each having a circuit conductor layer having a surface roughness Rz of 0.5 to 3 μm on the base material layer side are provided on one side or both sides, and siloxane is interposed between the wiring boards. After interposing an insulating layer formed from a resin containing a modified polyimide, heating is performed in a temperature range above the heat deformation temperature St (° C.) of the resin containing the siloxane-modified polyimide and lower than the heat deformation temperature Lt (° C.) of the liquid crystal polymer. A method for producing a multilayer printed circuit board, comprising performing a pressure treatment. The method for producing a multilayer wiring circuit board according to claim 4 , wherein the resin containing the siloxane-modified polyimide has a heat distortion temperature in a range of 60 to 170 ° C. The method for producing a multilayer wiring circuit board according to claim 4 or 5, wherein the insulating layer formed of a resin containing siloxane-modified polyimide is provided in a film form, and the pressure range in the heat and pressure treatment is in the range of 1 MPa to 6 MPa. In the step of preparing two or more wiring boards provided with circuit conductor layers, the wiring board is obtained by etching and removing a copper foil of a laminate of a copper foil and a liquid crystal polymer into an arbitrary shape. The manufacturing method of the multilayer wiring circuit board in any one of 4-6 .

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