TW201702067A - Thermoplastic liquid-crystal polymer film, and circuit board - Google Patents

Abstract

A thermoplastic liquid-crystal polymer film which, after having been thermocompression-bonded to a conductor layer, has a toughness, as measured by a method according to ASTM D882, of 30-100 MPa.

Description

Thermoplastic liquid crystal polymer film and circuit substrate

The present invention relates to a thermoplastic liquid crystal polymer film (hereinafter sometimes referred to as a thermoplastic liquid crystal polymer film or simply a liquid crystal polymer film) which forms an optically anisotropic molten layer, and a circuit substrate.

In recent years, significant progress has been made in the field of information processing such as personal computers and communication devices such as mobile phones. The frequencies used in such electronic and communication devices are developing in the GHz region. However, in general, in such a high frequency band, transmission loss becomes large, and thus it is required to reduce transmission loss.

Not only the conductor loss, but also the dielectric loss is related to the transmission loss of the high frequency signal. Therefore, in order to suppress the transmission loss of the high-frequency signal and increase the information processing speed, that is, the transmission speed of the signal, an electrically insulating substrate material having excellent dielectric characteristics is required.

From the above viewpoint, a thermoplastic liquid crystal polymer film having a dielectric loss smaller than that of the polyimide film is used as an insulating substrate, and the liquid crystal polymer film is bonded to the conductor layer by thermocompression bonding to form a circuit board. Received attention.

As an element for determining the peel strength (peel strength or adhesive strength) when the liquid crystal polymer film is laminated to a conductor, it is conceivable that : Mechanical combination of an anchor effect due to the surface roughness of the conductor layer; chemical combination of the surface treatment component of the conductor layer and the resin. As a technique for improving the quasi-effect of the conductor layer, there is a process of improving the peeling strength when the conductor layer is laminated to the insulating layer by forming irregularities on the conductor layer, and the uneven shape is being studied. Optimized.

For example, Patent Document 1 (International Publication No. WO 2012/020818) discloses a metal-clad laminate which is a metal-clad laminate having a metal foil on one or both sides of a liquid crystal polymer layer, wherein a metal foil The upper surface in contact with the liquid crystal polymer layer is roughened to have protrusions in the surface layer portion. It is also revealed that the aspect ratio (H/L) represented by the ratio of the height H of the protrusion to the width L of the root portion of the protrusion is in the range of 3 to 20, and the height of the protrusion is 0.1 to 2 μm. Within the range, the liquid crystal polymer layer has a thickness of 10 to 2000 μm and a film thickness tolerance of less than 6%.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] International Publication WO2012/020818

When the surface roughness of the conductor layer is increased in order to increase the leveling effect of the conductor layer, high-frequency characteristics are reduced when a circuit board is formed by laminating an insulating layer such as a thermoplastic liquid crystal polymer film, thereby ensuring high-frequency characteristics. From a point of view, it is desirable to use a surface roughness that is low. Conductor layer. On the other hand, when a conductor layer having a low surface roughness excellent in high-frequency characteristics is used, the peel strength at the time of laminating the film is low, and the influence of the surface roughness of the conductor layer on the high-frequency characteristics and the peel strength is opposite. Accordingly, there has been a demand for a thermoplastic liquid crystal polymer film which can produce high peel strength even when a conductor layer having a low surface roughness excellent in high frequency characteristics is laminated.

A first object of the present invention is to provide a thermoplastic liquid crystal polymer film which has a specific peeling strength when it is thermally bonded to a conductor layer having a low surface roughness or the like by a bonded body. Resilience.

A second object of the present invention is to provide a thermoplastic liquid crystal polymer film which has a specific peeling strength when it is thermally bonded to a conductor layer having a low surface roughness or the like by a bonded body. Toughness and specific Young's modulus.

A third object of the present invention is to provide a thermoplastic liquid crystal polymer film which has a low rate of toughness reduction after being thermally pressure-bonded to a bonded body such as a conductor layer, and which can maintain a specific toughness.

A fourth object of the present invention is to provide a circuit board which is formed by pressure-bonding a thermoplastic liquid crystal polymer film to a bonded body such as a conductor layer.

The inventors of the present invention conducted intensive studies to achieve the above object, and as a result, found the following, and completed the present invention. That is, as long as the thermoplastic liquid crystal polymer film is thermocompression bonded to the conductor layer The thermoplastic liquid crystal polymer film having a toughness after thermal compression bonding falling within a specific value can be maintained even when it is thermocompression bonded to a bonded body such as a conductor layer having a low surface roughness. High frequency characteristics, and high peel strength.

The inventors of the present invention have also found the following, and have completed the present invention. That is, as long as it is a thermoplastic liquid crystal polymer film having a specific toughness and a specific Young's modulus, even when it is thermally bonded to a bonded body such as a conductor layer having a low surface roughness, It can maintain good high frequency characteristics and achieve higher peel strength.

The inventors of the present invention have also found the following, and have completed the present invention. That is, by using a thermoplastic liquid crystal polymer film having a specific toughness, and the toughness of the conductor layer or the like and the thermoplastic liquid crystal polymer under the condition that the toughness of the thermoplastic liquid crystal polymer film does not change beyond a specific range. When the film is thermocompression bonded, high peel strength can be maintained even after thermocompression bonding.

That is, the first aspect of the present invention is a thermoplastic liquid crystal polymer film which is obtained by thermocompression bonding a thermoplastic liquid crystal polymer film with a conductor layer, using a thermoplastic liquid crystal polymer measured by a method based on ASTM D882. The toughness of the film is 30 MPa or more and 100 MPa or less.

The thermoplastic liquid crystal polymer film may be a Young's modulus measured by a method based on ASTM D882 of 2.0 GPa or more and 4.0 GPa or less.

It may also be a thermoplastic liquid crystal polymer film which is obtained by thermocompression bonding a thermoplastic liquid crystal film with a conductor layer or the like at a temperature of a melting point of the thermoplastic liquid crystal polymer film of -30 ° C or lower, and a thermoplastic liquid crystal film. The rate of toughness reduction is within 30%.

Further, the second aspect of the present invention is a circuit board in which a thermoplastic liquid crystal polymer film and a conductor layer are laminated.

It is also possible to use a circuit board in which the ten-point average roughness (Rz _JIS ) of the surface of the conductor layer measured by the method based on ISO4287-1997 is 3 μm or less.

It is also possible to use a circuit board in which the bonding strength between the thermoplastic liquid crystal polymer film measured by the method based on JIS C5016-1994 and the conductor layer bonded to the thermoplastic liquid crystal polymer film is 0.6 kN/m or more. .

Further, a third aspect of the present invention is a circuit substrate comprising a thermoplastic liquid crystal polymer film, and a conductor layer laminated on the thermoplastic liquid crystal polymer film, wherein: the method measured by the method based on ASTM D882 is used The toughness of the thermoplastic liquid crystal polymer film after the conductor layer is peeled off from the thermoplastic liquid crystal polymer film is 30 MPa or more and 100 MPa or less.

Since the thermoplastic liquid crystal polymer film of the present invention has a conductor layer having a low surface roughness capable of maintaining good high frequency characteristics (that is, a ten point average of the surface of the conductor layer measured by the method based on ISO4287-1997) When the roughness (Rz _JIS ) is 3 μm or less, the conductor layer can be thermally bonded, and high peel strength can be generated. Therefore, the conductor layer can maintain good high-frequency characteristics (that is, low transmission loss in a high frequency band). ), and the conductor layer is laminated with high peel strength.

Further, the thermoplastic liquid crystal polymer film according to the present invention The thermoplastic liquid crystal polymer film can be laminated with a conductor layer having a low surface roughness capable of maintaining good high-frequency characteristics with high peel strength. Therefore, in the case where the thermoplastic liquid crystal polymer film and the conductor layer are laminated without limiting the uneven shape of the surface of the conductor layer laminated on the thermoplastic liquid crystal polymer film, the distance between the unevenness, and the like to a specific shape or numerical value, It satisfies good high-frequency characteristics and high peel strength, and can improve productivity and cost.

Since the thermoplastic liquid crystal polymer film of the present invention can remarkably reflect the registration effect of the bonded body such as the conductor layer crimped to the thermoplastic liquid crystal polymer film, the surface roughness of the conductor layer capable of maintaining good high frequency characteristics can be achieved ( That is, a conductor layer having a high surface roughness and a high quasi-effect in a range of a ten-point average roughness (Rz _JIS ) of the surface of the conductor layer measured by the method based on ISO4287-1997 is 3 μm or less. It is laminated with the thermoplastic liquid crystal polymer film of the present invention to produce a high peel strength.

Further, the thermoplastic liquid crystal polymer film of the present invention has a low rate of toughness reduction after thermocompression bonding, and can maintain high peel strength even after lamination with a conductor.

1‧‧‧ Thermoplastic liquid crystal polymer film

2‧‧‧ Thermoplastic liquid crystal polymer film

3‧‧‧Adhesive sheets

4‧‧‧Conductor layer (copper foil)

10‧‧‧First unit circuit board

20‧‧‧Second unit circuit board

30‧‧‧Laminated body (circuit board)

1(a) and 1(b) are schematic cross-sectional views for explaining a process of a circuit board according to an embodiment of the present invention, wherein Fig. 1(a) shows a state before lamination, and Fig. 1(b) shows a state after lamination.

[Thermoplastic liquid crystal polymer film]

In the present invention, the thermoplastic liquid crystal polymer film can be used as an insulating base material layer of a unit circuit substrate in which a conductor layer is formed on one or both sides, and can also be used as a circuit board material for bonding a conductor layer (hereinafter Sometimes referred to as adhesive materials). Further, the circuit substrate material may be at least one selected from the group consisting of a bonding sheet and a coverlay, preferably an adhesive sheet.

The thermoplastic liquid crystal polymer film is formed of a liquid crystal polymer which can be melt-formed. The thermoplastic liquid crystal polymer is not particularly limited as long as it is a liquid crystal polymer which can be melt-molded, and examples thereof include thermoplastic liquid crystal polyester or thermoplastic liquid crystal polyester having a guanamine bond introduced into the thermoplastic liquid crystal polyester. Amidoxime and the like.

Further, the thermoplastic liquid crystal polymer may further be derived from an aromatic polyester or an aromatic polyester decylamine, such as a quinone bond, a carbonate bond, a carbodiimide bond, or an isomeric cyanate bond. A polymer such as a bond of an isocyanate.

Specific examples of the thermoplastic liquid crystal polymer used in the present invention include well-known thermoplastic liquid crystal polyesters and thermoplastic liquid crystal polymers derived from the compounds (1) to (4) classified as exemplified below and derivatives thereof. Ester amide. However, in order to form a polymer capable of forming a molten layer of optical anisotropy, a combination of various raw material compounds certainly has an appropriate range.

(1) Aromatic or aliphatic dihydroxy compounds (for representative examples, see Table 1)

[Table 1]

(2) Aromatic or aliphatic dicarboxylic acids (for representative examples, see Table 2)

(3) Aromatic hydroxycarboxylic acid (for representative examples, see Table 3)

(4) Aromatic bisamine, aromatic hydroxylamine or aromatic aminocarboxylic acid (for representative examples, see Table 4)

Representative examples of the liquid crystal polymer obtained from the raw material compounds include copolymers having the structural units shown in Tables 5 and 6.

Among these copolymers, a polymer containing at least p-hydroxybenzoic acid and/or 6-hydroxy-2-naphthoic acid as a repeating unit is preferred, and polymers of the following (i) and (ii) are particularly preferred. (i) a polymer comprising repeating units of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid. (ii) a polymer comprising a repeating unit of the following: an aromatic hydroxycarboxylic acid selected from at least one selected from the group consisting of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid; selected from 4, 4' An aromatic diol of at least one selected from the group consisting of dihydroxybiphenyl and hydroquinone; at least one selected from the group consisting of terephthalic acid, isophthalic acid, and 2,6-naphthalenedicarboxylic acid Aromatic dicarboxylic acid.

For example, in the case of (i) polymers, in thermoplastic liquid crystal polymerization In the case where the compound contains at least a repeating unit of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid, in the liquid crystal polymer, repeating the 6-hydroxyl group of the p-hydroxybenzoic acid of the unit (A) and the repeating unit (B) The molar ratio (A)/(B) of -2-naphthoic acid is preferably (A)/(B)=10/90 to 90/10, more preferably (A)/(B)=50/50. ~85/15 or so, especially good for (A) / (B) = 60/40 ~ 80 / 20 or so.

Further, in the case of the polymer of (ii), an aromatic hydroxycarboxylic acid (C) selected from at least one of the group consisting of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid; selected from 4, 4 An aromatic diol (D) of at least one of the group consisting of '-dihydroxybiphenyl and hydroquinone; and a group selected from the group consisting of terephthalic acid, isophthalic acid and 2,6-naphthalenedicarboxylic acid The molar ratio of each of the repeating units of the aromatic dicarboxylic acid (E) in the liquid crystal polymer of at least one of the groups may be an aromatic hydroxycarboxylic acid (C): the aromatic diol (D): the aromatic Dicarboxylic acid (E) = 30 ~ 80: 35 ~ 10: 35 ~ 10 or so, more preferably (C): (D): (E) = 35 ~ 75: 32.5 ~ 12.5: 32.5 ~ 12.5 or so, especially good For (C): (D): (E) = 40~70:30~15:30~15.

Further, the molar ratio of the repeating structural unit derived from the aromatic dicarboxylic acid to the repeating structural unit derived from the aromatic diol is preferably (D) / (E) = 95 / 100 - 100 / 95. If it deviates from this range, there is a tendency that the degree of polymerization does not rise and the mechanical strength decreases.

Further, the optically anisotropic molten layer (optical anisotropy at the time of melting) mentioned in the present invention can be confirmed, for example, by placing a sample on a heating stage under a nitrogen atmosphere. Heating was performed at elevated temperature, and the transmitted light of the sample was observed.

The thermoplastic liquid crystal polymer preferably has a melting point (hereinafter referred to as Tm ₀ ) falling within the range of 260 to 360 ° C, and more preferably a Tm ₀ of 270 to 350 ° C. Further, Tm ₀ can be obtained by measuring the temperature at which the main endothermic peak appears by using a differential scanning calorimeter (Shimadzu Corporation DSC).

Polyethylene terephthalate, modified polyethylene terephthalate, polyolefin, polycarbonate, polyarylate may be added to the thermoplastic liquid crystal polymer within a range not impairing the effects of the present invention. Polyamides, polyphenylene sulfides, polyetheretherketones, fluororesins and other thermoplastic polymers, various additives, and fillers may be added as needed.

The thermoplastic liquid crystal polymer film used in the present invention can be obtained by extruding a thermoplastic liquid crystal polymer. Any extrusion molding method can be used as long as it can control the direction of the rigid rod-shaped molecules of the thermoplastic liquid crystal polymer, and is known in the industrial production by a well-known T-die method, laminate stretching method, inflation method, and the like. More favorable. In particular, the blow molding method and the laminate stretching method can apply stress not only to the machine direction of the film (hereinafter simply referred to as the MD direction) but also to the direction perpendicular thereto (hereinafter referred to as the TD direction). A film that controls the dielectric properties of the MD direction and the TD direction is obtained.

In the extrusion molding, in order to control the alignment, it is preferred to carry out the stretching treatment, for example, in the extrusion molding by the T-die method, it may be: not only in the MD direction of the film, but The molten body sheet extruded from the T-die is simultaneously stretched in both the MD direction and the TD direction; or, the melt extruded from the T-die is first applied in the MD direction. The sheet is stretched and then stretched in the TD direction.

Further, in the extrusion molding by the blow molding method, the predetermined drawing ratio (equivalent to the stretching ratio in the MD direction) and the blowing ratio ( It corresponds to the stretching ratio in the TD direction), and the cylindrical sheet which is melt-extruded from the ring die is stretched.

The stretching ratio in the MD direction (or the draw ratio) may be, for example, about 1.0 to 10, preferably about 1.2 to 7, and more preferably 1.3 to 7. about. Further, the stretching ratio (or the blowing ratio) in the TD direction may be, for example, about 1.5 to 20, preferably about 2 to 15, more preferably about 2.5 to 14.

The ratio (TD direction/MD direction) of the respective stretching ratios in the MD direction and the TD direction may be, for example, 2.6 or less, preferably about 0.4 to 2.5.

Further, the thermoplastic liquid crystal polymer film may be stretched in response to the demand after extrusion molding. The stretching method itself is a well-known method, and any of biaxial stretching and uniaxial stretching may be employed, but from the viewpoint of easier control of molecular orientation, biaxial stretching is preferred. Further, the stretching can be carried out using a well-known uniaxial stretching machine, a simultaneous biaxial stretching machine, a sequential biaxial stretching machine, or the like.

Further, a known or conventional heat treatment may be performed to adjust the melting point and/or the coefficient of thermal expansion of the thermoplastic liquid crystal polymer film. The heat treatment conditions may be appropriately set depending on the purpose, for example, by a melting point (Tm ₀ ) of the liquid crystal polymer of -10 ° C or more (for example, Tm ₀ -10 to Tm ₀ + 30 ° C or so, preferably Tm ₀ to Tm ₀ Heating at a temperature of about +20 ° C for several hours increases the melting point (Tm) of the thermoplastic liquid crystal polymer film.

The thermoplastic liquid crystal polymer film of the present invention obtained in this manner has excellent dielectric properties, low hygroscopicity, and the like, and is therefore suitable for use as a circuit substrate material.

In addition, the thermoplastic liquid crystal polymer film is caused by its rigid structure, and generally has a high melt viscosity in a low shear region, for example, a melt viscosity of a thermoplastic liquid crystal polymer film at 300 ° C (shear speed of 1,000 sec ^-1 ) It may be 100 Pa ‧ or more, preferably about 200 to 100,000 Pa ‧ (for example, about 150 to 100,000 Pa ‧ s), and more preferably about 200 to 10,000 Pa ‧ s. In addition, the melt viscosity can be measured using a viscoelastic rheometer (for example, AR2000 manufactured by TA Instrucment Japan) at a temperature increase rate of 3 ° C / min, a frequency of 1 Hz, a strain of 0.1%, and a normal stress of 5 N.

The melting point (Tm) of the thermoplastic liquid crystal polymer film may be selected from the range of about 200 to 400 ° C, preferably about 250 to 360 ° C, more preferably from the viewpoint of obtaining heat resistance and processability desired for the film. 260~340 °C or so. In addition, the melting point of the film can be obtained by observing the thermal behavior of the film using a differential scanning calorimeter. That is, the position of the endothermic peak described below may be recorded as the melting point of the film, that is, the test film is heated and completely melted at a rate of 20 ° C /min, and then the melt is rapidly cooled to 50 ° C / min. °C, the endothermic peak that appears after heating at a rate of 20 ° C / min.

The thermoplastic liquid crystal polymer film used in the present invention may have any thickness, and also includes a plate-like or sheet-shaped thermoplastic liquid crystal polymer film having a thickness of 5 mm or less. However, in the case of using a high-frequency transmission line, since the transmission loss becomes smaller as the thickness is thicker, it is preferable to make the thickness as thick as possible. In the case where a thermoplastic liquid crystal polymer film is used as the electrically insulating layer, the film thickness of the film preferably falls within the range of 10 to 500 μm, more preferably falls within the range of 15 to 200 μm. in When the thickness of the film is too thin, the rigidity and strength of the film are reduced. Therefore, a method of laminating a film in a film thickness of 10 to 200 μm to obtain an arbitrary thickness can be used.

In the present invention, it is important that the thermoplastic liquid crystal polymer film to be thermocompression bonded to the conductor layer has a toughness of 30 MPa or more and 100 MPa after thermocompression bonding with the conductor layer measured by the method based on ASTM D882. Hereinafter, it is preferably 35 MPa or more and 100 MPa or less, more preferably 50 MPa or more and 100 MPa or less, and particularly preferably 60 MPa or more and 100 MPa or less, and particularly preferably 70 MPa or more and 90 MPa or less. By using a thermoplastic liquid crystal polymer film having a toughness within the above range after thermocompression bonding with the conductor layer, the peel strength at the time of bonding the volume layer such as the conductor layer can be improved, and the strength can be maintained even after thermocompression bonding. Peel strength.

In the thermoplastic liquid crystal polymer film of the present invention, even if the film is laminated with the copper foil, the crimping temperature (temperature of the heating plate) is set at the melting point of the film Tm-35 ° C using a vacuum hot pressing device. After 10 minutes of thermocompression bonding under a pressure of 4 MPa, the toughness of the film after peeling off the copper foil was also 30 MPa or more and 100 MPa or less. In particular, the following thermoplastic liquid crystal polymer film is preferable in which the crimping temperature is set to any temperature in the range of Tm - 35 ° C or more and Tm - 10 ° C or less under the above-mentioned pressure bonding conditions. Next, the toughness will be 30 MPa or more and 100 MPa or less.

In addition, since the film having higher toughness can significantly reflect the quasi-effect of the conductor layer and has high peel strength, it is possible to form a guide having a high degree of toughness and a high surface roughness. The body layers are combined for crimping to achieve higher peel strength.

In general, the higher the surface roughness of the conductor layer, the higher the registration effect becomes, but the transmission loss becomes large due to the skin effect caused by the surface unevenness becoming large. The surface roughness of the conductor layer can be improved by not increasing the transmission loss (for example, the ten-point average roughness (Rz _JIS ) of the surface of the conductor layer measured by the method according to ISO 4287-1997 is 3 μm or less) It maintains good high frequency characteristics and achieves high peel strength. In the case of a thermoplastic liquid crystal polymer film having a toughness of less than 30 MPa, a large peel strength cannot be obtained in the case of crimping a conductor layer having improved surface roughness within a range in which transmission loss does not become large, due to Special processing is necessary, so the process is cumbersome and the manufacturing conditions are limited. The special processing is to define the uneven shape on the surface of the conductor layer; to limit the distance between the bumps to a specific range.

When a resin film such as a thermoplastic liquid crystal polymer film and a layered body such as a conductor layer are peeled off from the adherend, it is considered that the mechanism of peeling is interfacial peeling and cohesive failure. Kind of mechanism. In the case where the peel strength of the laminate is strong to some extent, the mechanism of the peeling is mainly caused by cohesive failure. When the toughness of the resin film at the time of cohesive failure is strong, the resin film is not easily broken at the time of peeling, so that the peel strength between the bonded body and the resin film is strong.

The method for increasing the toughness of the thermoplastic liquid crystal polymer film is not particularly limited, and for example, the heat resistance of the film can be improved by heat treatment. For example, the toughness imparted to the film can be adjusted by controlling the heat treatment temperature, the heat treatment time, the temperature increase rate, and the like at the time of heat treatment, for example, There is a tendency that the toughness is increased in the thermoplastic liquid crystal polymer film when the heat treatment temperature is increased under a specific temperature increase rate, and the toughness imparted to the thermoplastic liquid crystal polymer film is also increased when the heat treatment time is increased.

The heat treatment temperature is not particularly limited. For example, the thermoplastic liquid crystal polymer film may have a melting point (Tm) of -30 ° C or higher (for example, Tm-20 ° C to Tm + 10 ° C or so, preferably Tm to Tm + 10 ° C). about).

The condition of the heat treatment time is not particularly limited, and may be, for example, about 1 hour to 20 hours (for example, about 5 hours to 15 hours, preferably about 6 hours to 10 hours).

From the viewpoint of improving the toughness of the thermoplastic liquid crystal polymer film, the condition of the temperature increase rate is preferably, for example, 1 ° C / min to 6 ° C / min, more preferably 1 ° C / min to 3 ° C / min, if productivity is considered , especially good at 2 ° C / min.

For example, a thermotropic liquid crystal polyester composed of 6-hydroxy-2-naphthoic acid unit 27 mol% and p-hydroxybenzoic acid unit 73 mol% is heated and mixed at 280 to 300 ° C using a uniaxial extruder. Refining, and then extruding with an injection die having a diameter of 40 mm and a slit spacing of 0.6 mm, thereby producing a thermoplastic liquid crystal polymer film having a melting point of 280 ° C and a thickness of 50 μm, in an oven under a nitrogen atmosphere, The thermoplastic liquid crystal polymer film is subjected to a heat treatment at a temperature increase rate of about 2 ° C / min, a heat treatment temperature of about 280 ° C, and a heat treatment time of about 6 hours, thereby obtaining a thermoplastic liquid crystal polymer film having a toughness of about 80 MPa, and the thermoplastic liquid crystal polymer is obtained. The film is heated at a temperature of about 4 ° C / min, and the heat treatment temperature is A heat treatment of about 280 ° C and a heat treatment time of about 5 hours can obtain a thermoplastic liquid crystal polymer film having a toughness of about 70 MPa.

For example, the toughness of the thermoplastic liquid crystal polymer film can be improved by the heat treatment or the like as described above, and by setting the toughness of the thermoplastic liquid crystal polymer film to a high value, even if the film and the conductor layer are hot pressed After the connection, the toughness of the thermoplastic liquid crystal polymer film can be maintained at 30 MPa or more and 100 MPa or less, and good peel strength can be maintained even after thermocompression bonding.

In order to further improve the peel strength when the thermoplastic liquid crystal polymer film and the conductor layer are thermocompression bonded, the Young's modulus of the thermoplastic liquid crystal polymer film measured by the method based on the ASTM D882 specification is preferably 2.0 GPa or more and 4.0 GPa. Hereinafter, it is more preferably 2.5 GPa or more and 4 GPa or less, and particularly preferably 2.5 GPa or more and 3.5 GPa or less.

The method of adjusting the Young's modulus of the thermoplastic liquid crystal polymer film is not particularly limited, and for example, the Young's modulus can be adjusted by heat treatment.

For example, when the heat treatment temperature is increased, the Young's modulus of the thermoplastic liquid crystal polymer film is lowered. For example, a thermotropic liquid crystal polyester composed of 6-hydroxy-2-naphthoic acid unit 27 mol% and p-hydroxybenzoic acid unit 73 mol% is heated and mixed at 280 to 300 ° C using a uniaxial extruder. Refining, and then extruding with a blow mold having a diameter of 40 mm and a slit interval of 0.6 mm, thereby producing a thermoplastic liquid crystal polymer film having a melting point of 280 ° C and a thickness of 50 μm, which is obtained by using a thermoplastic liquid crystal in an oven under a nitrogen atmosphere. The polymer film is heated at a temperature of about 2 ° C / min, a heat treatment temperature of about 280 ° C, and a heat treatment time of about 6 hours. A thermoplastic liquid crystal polymer film having a toughness of about 80 MPa and a Young's modulus of about 3.5 GPa can be obtained.

Further, if the heat treatment temperature is lowered, the Young's modulus tends to increase. For example, using a uniaxial extruder, the hydroxy group of 6-hydroxy-2-naphthoic acid unit is at 280 to 300 ° C. The thermotropic liquid crystal polyester composed of hydroxybenzoic acid unit 73 mol% was heated and kneaded, and then extruded by a blow mold having a diameter of 40 mm and a slit interval of 0.6 mm to prepare a thermoplastic liquid crystal having a melting point of 280 ° C and a thickness of 50 μm. The polymer film is heat-treated at a temperature of about 2 ° C / min, a heat treatment temperature of about 260 ° C, and a heat treatment time of about 10 hours in an oven under a nitrogen atmosphere to obtain a toughness of about 80 MPa. A thermoplastic liquid crystal polymer film having a Young's modulus of about 5.0 GPa.

There is a tendency that the higher the temperature of the heat treatment of the thermoplastic liquid crystal polymer film, the higher the toughness of the film; the longer the heat treatment time, the higher the toughness of the film. For this reason, when a specific toughness is imparted to the thermoplastic liquid crystal polymer film, the heat treatment temperature can be increased and the heat treatment time can be shortened, and the heat treatment temperature can be lowered and the heat treatment time can be increased. The Young's modulus of the thermoplastic liquid crystal polymer film tends to be affected by, for example, heat treatment time. Sometimes, if the heat treatment time is long, the Young's modulus becomes high, so that the toughness and Young's mode of the thermoplastic liquid crystal polymer film can be considered. The balance of the number is used to adjust the heat treatment temperature and the heat treatment time to set the toughness and the modulus of elasticity within a specific range. For example, the thermoplastic liquid crystal polymer film can be given a specific range of toughness and Young's modulus by appropriately setting the heat treatment temperature according to the heat treatment time condition within a specific range of the Young's modulus.

When the toughness of the thermoplastic liquid crystal polymer film falls within the range of 30 MPa or more and 100 MPa or less and the Young's modulus of the thermoplastic liquid crystal polymer film falls within the range of 2.0 GPa or more and 4.0 GPa or less, the toughness of the film is higher, The lower the modulus of elasticity, the higher the peel strength at the time of pressure contact with a bonded body such as a conductor layer. From the viewpoint of further improving the peeling strength, when the toughness and the Young's modulus of the film are adjusted by heat treatment of the thermoplastic liquid crystal polymer film or the like, it is more preferable to adjust the toughness and the Young's modulus. Ideal.

[conductor layer]

The conductor layer is formed of a metal having at least conductivity, and a circuit is formed on the conductor layer by a well-known circuit processing method. As a method of forming a conductor layer on an insulating base material made of a thermoplastic liquid crystal polymer film, a well-known method can be used, for example, a metal layer can be vapor-deposited, or a metal layer can be formed by electroless plating or electroplating. Further, a metal foil (for example, a copper foil) may be crimped onto the surface of the thermoplastic liquid crystal polymer film by thermocompression bonding.

The metal foil constituting the conductor layer is preferably a metal foil for electrical connection. In addition to the copper foil, various metal foils such as gold, silver, nickel, and aluminum may be used, and may include substantially (for example, 98% by mass). The above) is an alloy foil composed of the metals.

Among these metal foils, copper foil is preferably used. The copper foil is not particularly limited as long as it can be used in a circuit board, and may be any of a rolled copper foil and an electrolytic copper foil.

In addition, the conductor layer can also form an anti-oxidation on its surface. Chemical film. For example, in this case, the preparation step of the unit circuit substrate may include: a thermocompression bonding step of thermocompression bonding the metal foil on one or both sides of the thermoplastic liquid crystal polymer film; and, after thermocompression bonding An oxidation resistant film forming step of forming an oxidation resistant film on the surface of the metal foil.

Further, the step of preparing the unit circuit board may further include a step of attaching the decane coupling agent to the surface of the conductor layer by attaching the decane coupling agent.

Examples of the antioxidant film include an oxidation resistant alloy layer, an oxidation resistant plating layer, and a rust inhibitor layer such as benzotriazole.

Further, the oxidation resistant film may be formed in any order before the circuit processing or after the circuit processing depending on the type of the conductor layer and the oxidation resistant film.

For example, in the case where the metal foil is thermocompression-bonded, it is preferable to use an alloy containing at least a metal forming a metal foil as the oxidation resistant alloy layer from the viewpoint of, for example, improving the adhesion. For example, in the case where the metal foil constituting the conductor layer is a copper foil, the alloy layer may be an alloy containing at least copper. For example, it is preferred to form an oxidation resistant alloy layer before circuit processing.

For example, such an alloy layer can be formed by "FlatBOND GT" or the like sold by MEC Co., Ltd.

In addition, there is a case where an alloy portion containing no copper exists in a portion away from the copper foil. In this case, the portion of the alloy containing no copper can be etched using an etchant. As such an etching liquid, for example, "MEC REMOVER S-651A" (manufactured by MEC Co., Ltd.), "S-PACK H-150" (manufactured by Sasaki Chemical Co., Ltd.), and nitric acid are included. An aqueous solution of an inorganic acid such as an acid.

In order to reduce the influence of the skin effect caused by the unevenness of the conductor layer and maintain low transmission loss, it is preferred that the surface roughness of the conductor layer is small. For the ten-point average roughness (Rz _JIS ) measured by the method based on ISO4287-1997, the surface roughness of the conductor layer may preferably be 3 μm or less, more preferably 2.0 μm or less, and particularly preferably It is 1.5 μm or less. The lower limit of the ten-point average roughness (Rz _JIS ) is not particularly limited, and may be, for example, 0.1 μm or more, 0.3 μm or more, or 0.5 μm or more.

In the invention having the above configuration, the surface of the conductor layer which does not adhere to the adhesive sheet can be made smooth when the laminated body is formed. In addition, although a circuit is processed on the conductor layer, the surface of the conductor remaining after the circuit is processed may be smooth.

The thickness of the conductor layer is preferably, for example, in the range of 1 to 50 μm, more preferably in the range of 5 to 20 μm.

Further, from the viewpoint of improving the adhesion of the conductor layer, a well-known or conventional decane coupling agent may be attached to the surface of the conductor layer (particularly, the alloy layer).

[circuit board]

The circuit substrate (preferably a multilayer circuit substrate) may be a circuit substrate as described below, that is, having one or more unit circuit substrates and one or more circuit substrate materials, wherein the unit circuit substrate is on one or both sides The thermoplastic liquid crystal polymer film formed with a conductor layer is composed of a thermoplastic liquid crystal polymer film for bonding to a conductor layer of the unit circuit substrate. The ten-point average roughness (Rz _JIS ) of the surface of the conductor layer on the side bonded to the circuit substrate material measured by the method based on ISO4287-1997 may be 3 μm or less.

For example, the circuit board of the present invention may be a circuit board or the like having the following configuration.

(i) a circuit board (multilayer circuit board) including a unit circuit board and an adhesive sheet and two or more unit circuit boards laminated via a bonding sheet, wherein the unit circuit board has an insulating layer made of a thermoplastic liquid crystal polymer film (substrate layer) and a conductor layer formed on one or both sides of the film; (ii) a circuit substrate (single layer or double) including a unit circuit substrate and a cover film for covering the conductor layer of the unit circuit substrate a layer circuit substrate), wherein the unit circuit substrate has an insulating layer (base material layer) composed of a thermoplastic liquid crystal polymer film and a conductor layer formed on one or both sides of the film; (iii) having a unit circuit substrate and bonding In the sheet and the cover film, two or more unit circuit boards are laminated via an adhesive sheet, and the outermost layer of the circuit board is a circuit board (multilayer circuit board) composed of a cover film covering a conductor layer of the unit circuit board, the circuit board a configuration in which the above (i) and (ii) are combined; (iv) a plurality of unit circuit substrates having an insulating layer (base material layer) composed of a thermoplastic liquid crystal polymer film, and And (v) includes two or more unit circuit board, and a cover film, two; more blade unit on a circuit board without the circuit board obtained by directly laminated (multilayer circuit board) via the adhesive sheet The unit circuit board above the sheet is directly laminated without passing through the adhesive sheet, and the outermost layer of the circuit board is a circuit board (multilayer circuit board) composed of a cover film covering the conductor layer of the unit circuit board, and the circuit board has the combination described above. (ii) and (iv) constitute a composition.

The circuit substrate may be composed of a high-melting-point liquid crystal polymer film having high heat resistance and a low-melting-point liquid crystal polymer film having lower heat resistance than the high-melting-point liquid crystal polymer film, and may be, for example, selected from an insulating substrate, an adhesive sheet, and a cover. The at least two circuit substrate materials of the film are composed of a high-melting-point liquid crystal polymer film having high heat resistance and a low-melting-point liquid crystal polymer film having lower heat resistance than the high-melting-point liquid crystal polymer film. In this case, the difference in melting point between the high melting point liquid crystal polymer film and the low melting point liquid crystal polymer film is preferably about 0 to 70 ° C, more preferably about 0 to 60 ° C.

For example, in the example shown in FIG. 1, a laminated body (circuit substrate) 30 is formed by laminating the second unit circuit substrate 20 on the first unit circuit substrate 10 via the adhesive sheet 3, wherein the first A unit circuit substrate 10 is a conductor layer (copper foil) 4 bonded to both sides of a thermoplastic liquid crystal polymer film 1 of an insulating layer, and the second unit circuit substrate 20 is a thermoplastic liquid crystal polymer formed by the conductor layer 4 in an insulating layer. The single film (upper surface) of the film 2 is formed, but the illustrated configuration is not intended to limit the circuit substrate of the present invention. For example, the circuit board may have only two conductor layers, or may have four or more conductor layers. Further, in order to cover the conductor layer, the circuit board may have a cover film made of a liquid crystal polymer film on the outermost layer.

The circuit substrate of the present invention may be, for example, a thin liquid crystal polymer The adhesive strength (peeling strength) between the film and the conductor layer is 0.6 kN/m or more (for example, 0.6 to 2 kN/m), preferably 0.8 kN/m or more, and more preferably 1.0 kN/m or more. Further, the adhesive strength (peel strength) may be a value obtained by using a liquid crystal polymer film toward a relative speed of 50 mm per minute by a method based on JIS C5016-1994. The value of the peel strength measured by a tensile tester [DIDECTAL FORCE GAUGE FGP-2, manufactured by NIDEC-SHIMPO CORPORATION] was peeled off in a direction of 90° from the laminate of the conductor layer.

Since the circuit board of the present invention uses a thermoplastic liquid crystal polymer having excellent dielectric properties as an insulating material, it is particularly suitable for use as a high-frequency circuit substrate. The high-frequency circuit does not only include a circuit that transmits only a high-frequency signal, but also a circuit in which a transmission path for transmitting a signal of a non-high-frequency signal is also disposed on the same plane, wherein a signal for transmitting a non-high-frequency signal is used. The transmission path is, for example, a high frequency signal converted into a low frequency signal, and the generated low frequency signal is output to an external transmission path; a transmission path for supplying a power supply for supplying a high frequency corresponding part .

For example, at a frequency of 10 GHz, the relative dielectric constant (? _r ) of the circuit substrate can be, for example, 2.6 to 3.5, more preferably 2.6 to 3.4.

Further, for example, at a frequency of 10 GHz, the dielectric tangent (Tan δ) of the circuit substrate may be, for example, 0.001 to 0.01, more preferably 0.001 to 0.008.

[Method of Manufacturing Circuit Board]

Hereinafter, a method of manufacturing the circuit board of the present invention will be described.

(preparation unit circuit board)

First, one or more insulating base material layers composed of a thermoplastic liquid crystal polymer film and a unit circuit substrate in which a conductor layer is formed on one surface or both surfaces of the base material layer are prepared. As the thermoplastic liquid crystal polymer film and the conductor layer, those having the above-described constitution can be used.

(Prepared for circuit board material bonded to the conductor layer)

As the circuit board material (adhesive material) for bonding to the conductor layer, in addition to the unit circuit board described above, one or more circuit board materials for bonding to the conductor layer of the unit circuit board may be separately prepared. The adhesive material may be a thermoplastic liquid crystal polymer film, and for example, at least one selected from the group consisting of an adhesive sheet and a cover film may be specifically mentioned.

Further, as the liquid crystal polymer film used as the adhesive material, the thermoplastic liquid crystal polymer film described above can be used. According to the configuration of the circuit board, the melting point of the liquid crystal polymer film used as the adhesive material may be the same as the melting point of the base material of the unit circuit board, but it is preferable to use a lower melting point than the liquid crystal polymer film forming the unit circuit board. In this case, the difference in melting point between the two may be, for example, about 0 to 70 ° C, more preferably about 0 to 60 ° C.

(hot crimping step)

The method of thermocompression bonding the thermoplastic liquid crystal polymer film with the conductor layer is not particularly limited, and for example, a batch type vacuum hot pressing method, a roll pressing method, a double belt press method, or the like can be used. The roll pressing method and the double belt pressing method may be a roll-to-roll method or a double belt pressing method.

Polymerization of thermoplastic liquid crystals by batch vacuum hot pressing In the case where the film is laminated with a conductor layer (for example, a metal foil), for example, a vacuum heat pressing device may be used to laminate a thermoplastic liquid crystal polymer film cut into a predetermined size with a metal foil and placed on the vacuum heat pressing device. Thermocompression bonding (batch vacuum thermocompression stacking method) is carried out between two heating plates and under vacuum.

When a thermoplastic liquid crystal polymer film and a conductor layer (for example, a metal foil) are laminated by a roll press method to form a laminate, and a single-sided metal-clad laminate is produced, the thermoplastic liquid crystal polymer film and the metal foil are conveyed. To advance, and to introduce them between the heated metal roll and the rubber roll in contact with the metal roll, so that they are thermocompression bonded between the rolls to form a laminate. A single-sided metal-clad laminate in which a metal foil is bonded to one side of a film. At this time, there may be a preheating step in which the film is aligned with the rubber roller before passing between the rolls, and then the metal foil is temporarily joined to the film stack, and the preheating step may be as follows Such a preheating step is to introduce the contact point of the rubber roller and the metal roller as a reference, and introduce the film in such a manner that the angle at which the film contacts the rubber roller is in the range of 90 to 120°.

In the case where a conductor layer (for example, a metal foil) is laminated on both sides of a thermoplastic liquid crystal polymer film by a roll pressing method to form a laminate, thereby producing a double-sided metal-clad laminate, it is possible to use a heating roller. It is manufactured by pressure-bonding a double-sided metal-clad laminate in which a metal foil is bonded to both surfaces of a thermoplastic liquid crystal polymer film. In this case, the production can be carried out by a manufacturing method of a double-sided metal-clad laminate, which is characterized by performing the following three steps. (1) First step: two pieces of metal foil Preheating is performed separately before contact with the heating roller. (2) Second step: two pieces of metal foil which have been preheated to a temperature of 100 to 250 ° C after the first step are respectively brought into contact with the other pair of heating rolls, and based on the contact points of the pair of heating rolls, On the other hand, the film is transported on the heating roller at an angle θ of 70 to 200°, and is thermally expanded to be in a non-tensioned state. (3) Third step: by performing the second step to be in a non-tensioned state, the two metal foils respectively conveyed on the pair of other heating rolls, and the thermoplastic liquid crystal polymer film conveyed therebetween are heated The rolls are pressure-bonded and integrated, and the thus obtained laminated sheets are conveyed between the heating rolls.

In the case where a thermoplastic liquid crystal polymer film is laminated with a conductor layer (for example, a metal foil) by a double-belt pressing method to form a laminate, the thermoplastic liquid crystal polymer film may be laminated with a metal foil, and then, In a double belt press, a pressure of about 5 to 500 bar is applied at a temperature between the melting point of the thermoplastic liquid crystal polymer film and the deterioration point of the film to press the metal foil and the film to form a laminate. body. In this case, the pressing pressure may be about 5 to 100 bar, and the residence time of the film at a temperature higher than the melting point during pressing may be 0.5 to 1000 seconds, and the temperature may be peeled off. The strength is a temperature of a thermoplastic liquid crystal polymer/metal foil laminate having a thickness of 1 N or more per linear line and a change in dimensional stability of less than ± 0.2%.

The thermocompression bonding temperature at the time of thermocompression bonding the thermoplastic liquid crystal polymer film and the conductor layer is preferably a melting point of the film of Tm -30 ° C or less, more preferably Tm - 35 ° C or less, and particularly preferably Tm - 40 ° C or less. . By performing thermocompression bonding in this temperature range, the rate of decrease in the toughness of the thermoplastic liquid crystal polymer film after thermocompression bonding can be further suppressed.

The rate of decrease in toughness of the liquid crystal polymer film after thermocompression bonding the thermoplastic liquid crystal polymer film and the conductor layer is preferably within 30%, more preferably within 25%, even more preferably within 15%, and even more preferably within 5%. . When the rate of decrease in the toughness of the liquid crystal polymer film after thermocompression bonding falls within this range, higher peel strength can be maintained even after thermocompression bonding.

Further, as long as the toughness after thermocompression bonding with the conductor layer of the thermoplastic liquid crystal polymer film to be thermocompression bonded to the conductor layer is 30 MPa or more and 100 MPa or less, the thermoplastic liquid crystal polymer film can be made large, for example, from 0.5 to 6 MPa. The pressure applied during thermocompression is selected in the range. For example, even if the pressing pressure is 5 MPa or less, particularly 4.5 MPa or less (for example, 0.5 MPa to 3 MPa, preferably 1 to 2.5 MPa), good adhesion between the liquid crystal polymer film and the conductor layer can be achieved.

In the circuit board of the present invention, the adhesive strength (peel strength) between the thermoplastic liquid crystal polymer film and the conductor layer measured in accordance with JIS C5016-1994 is preferably 0.6 kN/m or more, more preferably 0.8 kN/m or more. More preferably, it is 1.0kN/m or more.

Further, the surface of the circuit board material can be surface-treated within a range that does not impair the effects of the present invention. The surface treatment can be carried out by a known method such as ultraviolet irradiation, plasma irradiation, or physical polishing.

[Examples]

Hereinafter, the present invention will be described in detail by way of examples, but the present invention is not limited by the examples. Further, in the following examples and comparative examples, various physical properties were measured by the following methods.

(Toughness (MPa))

The toughness (MPa) of the thermoplastic liquid crystal polymer film was determined by calculation using the following formula (1) based on the measured values of the elongation and the maximum tensile strength measured by the method based on ASTM D882.

Toughness = elongation × maximum tensile strength × 1/2 (1)

Further, the toughness (MPa) of the thermocompression-bonded thermoplastic liquid crystal polymer film is obtained by thermally pressing the thermoplastic liquid crystal polymer film and the conductor layer, and then peeling off the thermoplastic liquid crystal polymer film from the conductor layer, and using the same The method is found.

(Toughness reduction rate after thermocompression bonding (%))

The toughness (MPa) of the thermoplastic liquid crystal polymer film before thermocompression bonding and the toughness (MPa) of the film after thermocompression bonding with the adherend were measured, and the rate of decrease in toughness before and after thermocompression bonding was determined.

Rate of decline of toughness (%) = 100 × (toughness before thermocompression bonding (MPa) - toughness after thermocompression bonding (MPa)) / toughness before thermocompression bonding (MPa)

(Young's Modulus (GPa))

The Young's Modulus (GPa) of the thermoplastic liquid crystal polymer film is obtained by applying a tensile load to the film and determining the displacement thereof by a method based on ASTM D882, and calculating by the following formula (2). .

E=(σ _n+1 -σ _n )/(ε _n+1 -ε _n ) (2)

When the tensile load changes: (Here, E: Young's modulus _{(GPa);:; σ n} + 1 -σ n ε n + 1 -ε n changes the amount of change of the tensile stress at a tensile load The amount of change in tensile strain)

(surface roughness (Rz _JIS ) (μm))

The ten-point average roughness (Rz _JIS ) of the surface of the roughened copper foil on the laminate was measured using a contact surface roughness meter (manufactured by Mitutoyo Corporation, type SJ-201). The measurement system was carried out using a method based on ISO4287-1997. In more detail, the surface roughness (Rz _JIS ) is: sampling a reference length from the roughness curve in the mean line direction thereof, the highest peak of the sampling portion (the apex of the upward convex curve) to the fifth highest The difference between the average value of the elevation of the peak and the average of the lowest valley bottom (the bottom point of the downward concave curve) to the fifth bottom of the sampling portion, the difference is expressed in μm. Ten point average roughness is shown.

(Adhesive strength: Peel strength (kN/m))

According to the method based on JIS C5016-1994, the adhesive material composed of the liquid crystal polymer film is peeled off at a rate of 90° with respect to the laminate of the liquid crystal polymer film and the conductor layer at a speed of 50 mm per minute. The peel strength was measured by a tensile tester [DIDECTAL FORCE GAUGE FGP-2, manufactured by NIDEC-SHIMPO CORPORATION], and the obtained value was defined as the adhesive strength (peel strength) (kN/m).

(Measurement of transmission loss (db/cm))

The S21 parameter at a measurement frequency of 10 GHz was measured in a microstrip line structure using a microwave network analyzer [manufactured by Agilent, Model: 8722ES] and a probe (manufactured by Cascade Microtech, Inc., type: ACP40-250).

[Example 1]

A thermoplastic liquid crystal polymer film having a melting point of 335 ° C, a toughness of 80 MPa, and a Young's modulus of 3.5 GPa was prepared. As a conductor layer, a rolled copper foil (manufactured by Mitsui Metals Co., Ltd., SQ-VLP, thickness: 12 μm) having a surface roughness Rz _JIS of 2.5 μm was laminated on the thermoplastic liquid crystal polymer film, and a vacuum hot pressing device was used. The heating plate was set at 300 ° C (the melting point of the thermoplastic liquid crystal polymer film Tm - 35 ° C), and subjected to thermocompression bonding under a pressure of 4 MPa for 10 minutes to prepare a laminate.

The peel strength of the copper foil and the thermoplastic liquid crystal polymer film and the toughness of the thermoplastic liquid crystal polymer film after thermocompression bonding were measured for the produced laminate. The toughness of the thermoplastic liquid crystal polymer film after thermocompression bonding did not decrease. The results are shown in Table 7.

[Embodiment 2]

A thermoplastic liquid crystal polymer film having a melting point of 325 ° C, a toughness of 68 MPa, and a Young's modulus of 3.0 GPa was prepared. As a conductor layer, a rolled copper foil (manufactured by Mitsui Metals Co., Ltd., SQ-VLP, thickness: 12 μm) having a surface roughness Rz _JIS of 2.5 μm was laminated on the thermoplastic liquid crystal polymer film, and a vacuum hot pressing device was used. The heating plate was set at 295 ° C (melting point of the thermoplastic liquid crystal polymer film Tm - 30 ° C), and thermocompression bonding was carried out for 10 minutes under a pressure of 4 MPa to prepare a laminate.

The peel strength of the copper foil and the thermoplastic liquid crystal polymer film and the toughness of the thermoplastic liquid crystal polymer film after thermocompression bonding were measured for the produced laminate. The toughness reduction rate of the thermoplastic liquid crystal polymer film after thermocompression bonding was 19%. The results are shown in Table 7.

[Example 3]

A thermoplastic liquid crystal polymer film having a melting point of 280 ° C, a toughness of 42 MPa, and a Young's modulus of 2.5 GPa was prepared. As a conductor layer, a rolled copper foil (manufactured by Mitsui Metals Co., Ltd., SQ-VLP, thickness: 12 μm) having a surface roughness Rz _JIS of 2.5 μm was laminated on the thermoplastic liquid crystal polymer film, and a vacuum hot pressing device was used. The heating plate was set at 250 ° C (the melting point of the thermoplastic liquid crystal polymer film Tm - 30 ° C), and thermocompression bonding was carried out for 10 minutes under a pressure of 4 MPa to prepare a laminate.

The peel strength of the copper foil and the thermoplastic liquid crystal polymer film and the toughness of the thermoplastic liquid crystal polymer film after thermocompression bonding were measured for the produced laminate. The toughness reduction rate of the thermoplastic liquid crystal polymer film after thermocompression bonding was 17%. The results are shown in Table 7.

[Example 4]

A thermoplastic liquid crystal polymer film having a melting point of 335 ° C, a toughness of 80 MPa, and a Young's modulus of 3.5 GPa was prepared. A rolled copper foil (JX Nippon Mining & Metal Co., Ltd., BHY-X, thickness: 12 μm) having a surface roughness Rz _JIS of 1.0 μm was laminated as a conductor layer on the thermoplastic liquid crystal polymer film, and vacuum was used. In the hot press apparatus, a hot plate was set at 300 ° C (melting point of the thermoplastic liquid crystal polymer film Tm - 35 ° C), and thermocompression bonding was performed for 10 minutes under a pressure of 4 MPa to prepare a laminate.

The peel strength of the copper foil and the thermoplastic liquid crystal polymer film and the toughness of the thermoplastic liquid crystal polymer film after thermocompression bonding were measured for the produced laminate. The toughness of the thermoplastic liquid crystal polymer film after thermocompression bonding did not decrease. The results are shown in Table 7.

[Example 5]

A thermoplastic liquid crystal polymer film having a melting point of 335 ° C, a toughness of 80 MPa, and a Young's modulus of 3.5 GPa was prepared. A rolled copper foil (JX Nippon Mining & Metal Co., Ltd., BHY-X, thickness: 12 μm) having a surface roughness Rz _JIS of 1.0 μm was laminated as a conductor layer on the thermoplastic liquid crystal polymer film, and vacuum was used. In the hot press apparatus, the heating plate was set at 325 ° C (the melting point of the thermoplastic liquid crystal polymer film Tm - 10 ° C), and thermocompression bonding was carried out for 10 minutes under a pressure of 4 MPa to prepare a laminate.

The peel strength of the copper foil and the thermoplastic liquid crystal polymer film and the toughness of the thermoplastic liquid crystal polymer film after thermocompression bonding were measured for the produced laminate. The toughness reduction rate of the thermoplastic liquid crystal polymer film after thermocompression bonding was 37.5%. The results are shown in Table 7.

[Comparative Example 1]

A thermoplastic liquid crystal polymer film having a melting point of 320 ° C, a toughness of 16 MPa, and a Young's modulus of 4.0 GPa was prepared. As a conductor layer, a rolled copper foil (manufactured by Mitsui Metals Co., Ltd., SQ-VLP, thickness: 12 μm) having a surface roughness Rz _JIS of 2.5 μm was laminated on the thermoplastic liquid crystal polymer film, and a vacuum hot pressing device was used. The heating plate was set at 290 ° C (the melting point of the thermoplastic liquid crystal polymer film Tm - 30 ° C), and thermocompression bonding was carried out for 10 minutes under a pressure of 4 MPa to prepare a laminate.

The peel strength of the copper foil and the thermoplastic liquid crystal polymer film and the toughness of the thermoplastic liquid crystal polymer film after thermocompression bonding were measured for the produced laminate. The toughness of the thermoplastic liquid crystal polymer film after thermocompression bonding did not decrease. The results are shown in Table 7.

[Comparative Example 2]

The thermotropic liquid crystal polyester composed of 27 mol% of 6-hydroxy-2-naphthoic acid unit and 73 mol% of p-hydroxybenzoic acid unit was heated and kneaded at 280 to 300 ° C using a uniaxial extruder. Then, extrusion was carried out using a blow mold having a diameter of 40 mm and a slit interval of 0.6 mm to obtain a film having a thickness of 50 μm. The film had a melting point Tm of 280 ° C and a toughness of 20 MPa.

As a conductor layer, a rolled copper foil (manufactured by Mitsui Metals Co., Ltd., SQ-VLP, thickness: 12 μm) having a surface roughness Rz _JIS of 2.5 μm was laminated on the thermoplastic liquid crystal polymer film, and a vacuum hot pressing device was used. The heating plate was set at 250 ° C (the melting point of the thermoplastic liquid crystal polymer film Tm - 30 ° C), and thermocompression bonding was carried out for 10 minutes under a pressure of 4 MPa to prepare a laminate.

The peel strength of the copper foil and the thermoplastic liquid crystal polymer film and the toughness of the thermoplastic liquid crystal polymer film after thermocompression bonding were measured for the produced laminate. The toughness of the thermoplastic liquid crystal polymer film after thermocompression bonding did not decrease. The results are shown in Table 7.

[Comparative Example 3]

The thermotropic liquid crystal polyester composed of 27 mol% of 6-hydroxy-2-naphthoic acid unit and 73 mol% of p-hydroxybenzoic acid unit was heated and kneaded at 280 to 300 ° C using a uniaxial extruder. Then, extrusion was carried out using a blow mold having a diameter of 40 mm and a slit interval of 0.6 mm to obtain a film having a thickness of 50 μm. The film had a melting point Tm of 280 °C.

The obtained film was subjected to heat treatment. In the heat treatment, the temperature of the film is not fixed, but the surface temperature of the film is fixed at 260 ° C for 4 hours of heat treatment, and then the surface temperature of the film is fixed at 285 ° C for 6 hours of heat treatment, under two-stage temperature conditions. Heat treatment. The obtained thermoplastic liquid crystal polymer film had a melting point Tm of 350 ° C and a toughness of 20 MPa.

A rolled copper foil (manufactured by JX Nippon Mining Co., Ltd., BHY-X, thickness: 12 μm) having a surface roughness Rz _J1S of 1.0 μm was laminated as a conductor layer on the thermoplastic liquid crystal polymer film, and vacuum was used. In the hot press apparatus, a hot plate was set at 300 ° C (melting point of the thermoplastic liquid crystal polymer film Tm - 50 ° C), and thermocompression bonding was performed for 10 minutes under a pressure of 4 MPa to prepare a laminate.

For the laminated body produced, the copper foil and the thermoplastic liquid crystal were measured. The peel strength of the film and the toughness of the thermoplastic liquid crystal polymer film after thermocompression bonding. The toughness of the thermoplastic liquid crystal polymer film after thermocompression bonding did not decrease. The results are shown in Table 7.

[Comparative Example 4]

The thermotropic liquid crystal polyester composed of 27 mol% of 6-hydroxy-2-naphthoic acid unit and 73 mol% of p-hydroxybenzoic acid unit was heated and kneaded at 280 to 300 ° C using a uniaxial extruder. Then, extrusion was carried out using a blow mold having a diameter of 40 mm and a slit interval of 0.6 mm to obtain a film having a thickness of 50 μm. The film had a melting point Tm of 280 °C.

The obtained film was subjected to heat treatment. In the heat treatment, the temperature of the film is not fixed, but the surface temperature of the film is fixed at 260 ° C for 4 hours, and then the surface temperature of the film is fixed at 300 ° C for 6 hours of heat treatment, under two-stage temperature conditions. Heat treatment. The obtained thermoplastic liquid crystal polymer film had a melting point Tm of 335 ° C and a toughness of 18 MPa.

A rolled copper foil (JX Nippon Mining & Metal Co., Ltd., BHY-X, thickness: 12 μm) having a surface roughness Rz _JIS of 1.0 μm was laminated as a conductor layer on the thermoplastic liquid crystal polymer film, and vacuum was used. The hot press apparatus was set at 305 ° C (the melting point of the thermoplastic liquid crystal polymer film Tm - 30 ° C), and subjected to thermocompression bonding under a pressure of 4 MPa for 10 minutes to prepare a laminate.

The peel strength of the copper foil and the thermoplastic liquid crystal polymer film and the toughness of the thermoplastic liquid crystal polymer film after thermocompression bonding were measured for the produced laminate. The toughness of the thermoplastic liquid crystal polymer film after thermocompression bonding did not decrease. The results are shown in Table 7.

From the results of Examples 1 to 3, it is understood that the higher the toughness of the thermoplastic liquid crystal polymer film after thermocompression bonding, the greater the peel strength of the copper foil and the thermoplastic liquid crystal polymer film.

Further, it is understood that the thermoplastic liquid crystal polymer films of Comparative Examples 1 to 4 have a toughness of less than 30 MPa, and have low toughness as in Comparative Examples 1 to 4. The peel strength of the film-based copper foil and the film was 0.6 kN/m or less, which showed a low value.

Comparing Example 4 with Example 5, it is understood that Example 4 is obtained by crimping a thermoplastic liquid crystal polymer film with a copper foil at a temperature of a melting point (Tm) of -35 ° C of the thermoplastic liquid crystal polymer film. The toughness of the film after thermocompression bonding was 80 MPa, and the toughness after thermocompression bonding was not lowered, so that a high peel strength of 1.2 kN/m was produced. On the other hand, since the thermoplastic liquid crystal polymer film is pressed against the copper foil at a temperature of Tm - 10 ° C in Example 5, the toughness of the film after thermocompression bonding is 50 MPa, and the rate of decrease is as high as 37.5%. As a result, in Example 4 in which the peel strength was 0.8 kN/m and the rate of decrease in toughness after thermocompression bonding was kept low, good results were obtained.

Further, as shown in Table 7, in Examples 1 to 5, transmission loss equivalent to Comparative Examples 1 to 4 was obtained, and as described above, Examples 1 to 5 were able to maintain good high-frequency characteristics and achieve high peel strength.

Claims (7)

A thermoplastic liquid crystal polymer film having a toughness of 30 MPa or more and 100 MPa or less as measured by a method based on ASTM D882 after thermocompression bonding a thermoplastic liquid crystal polymer film and a conductor layer. The thermoplastic liquid crystal polymer film according to claim 1, wherein the thermoplastic liquid crystal polymer film has a Young's modulus of 2.0 GPa or more and 4.0 GPa or less as measured by a method based on ASTM D882. The thermoplastic liquid crystal polymer film according to claim 1 or 2, wherein the thermoplastic liquid crystal polymer film is thermocompression bonded to the conductor layer at a temperature of a melting point of Tm-30 ° C or less of the thermoplastic liquid crystal polymer film, the thermoplastic The liquid crystal polymer film has a toughness reduction rate of 30% or less. A circuit board obtained by laminating a thermoplastic liquid crystal polymer film according to any one of claims 1 to 3 and a conductor layer. The circuit board of claim 4, wherein the ten-point average roughness (Rz _JIS ) of the surface of the conductor layer measured by the method based on ISO4287-1997 is 3 μm or less. The circuit substrate of claim 4 or 5, wherein the thermoplastic liquid crystal polymer film is bonded to the conductor layer bonded to the thermoplastic liquid crystal polymer film by a method based on JIS C5016-1994 The strength is 0.6 kN/m or more. A circuit substrate comprising a thermoplastic liquid crystal polymer film and a conductor layer laminated on the thermoplastic liquid crystal polymer film, after peeling the conductor layer from the thermoplastic liquid crystal polymer film, using a method based on ASTM D882 The toughness of the thermoplastic liquid crystal polymer film measured was 30 MPa or more and 100 MPa or less.