JP2018051901A - Metal-clad laminate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metal-clad laminate having a laminated structure which has proper adhesiveness and can be easily peeled off.SOLUTION: There is provided a double-sided metal-clad laminate 100 having a structure having metal layers 101 and 101' on both surfaces of polyimide layers 110 and 110'. The polyimide layers 110 and 110' comprises low thermal expansion polyimide layers 102 and 102' and thermoplastic polyimide layers 103 and 103', the respective thermoplastic polyimide layers 103 and 103' are laminated on a release film 104 to form the double-sided metal-clad laminate 100. The thermoplastic polyimide layers 103 and 103' contains 1 to 10 vol.% of a filler 105.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a metal-clad laminate, and more particularly to a metal-clad laminate used for a flexible circuit board (FPC) used in electronic products.

  FPC is flexible and has the possibility of three-dimensional wiring, and therefore is widely applied to electronic products such as computers and peripheral devices, and communication devices represented by smartphones. The FPC is manufactured by processing a metal layer of a metal-clad laminate having a structure in which a metal layer and an insulating resin layer are laminated.

  Along with the downsizing of electronic devices, the FPC has become thinner, higher density, and multifunctional. When the thickness of the FPC is reduced, the rigidity of the insulating resin layer is reduced. Therefore, in the FPC manufacturing process, defects such as breakage, damage, and peeling of the wiring layer due to bending are likely to occur. Since these defects reduce the yield and reliability of electronic products using FPC, countermeasures are required.

  For the above problems, an adhesive layer is provided on the insulating resin layer in the single-sided metal-clad laminate, and after modifying the surface of the adhesive layer, the modified surface is directly or by interposing a release material, It has been proposed that an insulating resin layer of a single-sided metal-clad laminate is bonded to form a double-sided metal-clad laminate for FPC processing (for example, Patent Document 1 and Patent Document 2).

Japanese Patent Laying-Open No. 2015-168261 (FIG. 1E, etc.) Japanese Patent Laying-Open No. 2015-168262 (FIG. 1D, etc.)

  In the techniques of the above Patent Documents 1 and 2, in order to facilitate the peeling between the insulating resin layer of the single-sided metal-clad laminate and the insulating resin layer (or release material) of the other single-sided metal-clad laminate, The surface energy of the surface of the insulating resin layer is reduced by performing a modification treatment such as plasma treatment or ultraviolet irradiation on the surface of the adhesive layer. Therefore, an extra step for the reforming process is necessary as compared with a normal FPC manufacturing process, which may increase the number of steps, make the equipment complicated, and lower the throughput. On the other hand, when the modification treatment is not performed, the adhesive strength between the insulating resin layers becomes too strong, so that the peel strength becomes large and the peel is difficult or the FPC after the peel is warped. was there.

  Accordingly, an object of the present invention is to provide a metal-clad laminate having a bonded structure that has appropriate adhesiveness and can be easily peeled off.

  As a result of intensive studies, the present inventors have formed a bonding surface in a double-sided metal-clad laminate including two single-sided metal-clad laminates bonded to each other via a release layer on the insulating resin layer side. The present invention was completed by finding that the resin layer to be contained contains a filler at a predetermined volume ratio so that the resin layer can be easily peeled off without modification treatment.

That is, the present invention is a metal-clad laminate having a metal layer (A) / insulating resin layer (B) / release layer (C) / insulating resin layer (D) / metal layer (E),
The insulating resin layer (B) has a resin layer (B1) in contact with the release layer (C), and the resin layer (B1) contains a filler in a range of 1 to 10% by volume. With
The insulating resin layer (D) has a resin layer (D1) in contact with the release layer (C), and the resin layer (D1) contains a filler in a range of 1 to 10% by volume. This is a metal-clad laminate.

  In the present invention, the difference in filler content between the resin layer (B1) and the resin layer (D1) may be 5% by volume or less.

In the present invention, the insulating resin layer (B) and the insulating resin layer (D) may have a multilayer structure including a base layer having a linear thermal expansion coefficient of 20 × 10 ⁻⁶ (1 / K) or less.

  In the present invention, the release layer (C) may contain an elastomer-based pressure sensitive adhesive or a resin-based pressure sensitive adhesive.

In the present invention, the peel strength Ad _B-C between the insulating resin layer (B) and the release layer (C), and the peel strength between the insulating resin layer (D) and the release layer (C). The average value of Ad _D-C (Ad _B-C + Ad _D-C ) / 2 may be within a range of 1 to 30 N / m.

  In the present invention, the resin layer (B1) and the resin layer (D1) may be formed of polyimide.

  Furthermore, in the present invention, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride (BTDA) may be used as 50 mol% or more of the total acid anhydride component constituting the polyimide.

  Furthermore, in this invention, 50 mol% or more of all the diamino components which comprise a polyimide may be 4,4'- diamino diphenyl ether (DAPE).

  In the metal-clad laminate of the present invention, in two single-sided metal-clad laminates bonded together through a release layer, fillers are respectively added to the resin layers forming the bonded surface with the release layer at a predetermined volume ratio. Since it contains, it has moderate adhesiveness, it is easy to peel off, and it can suppress that it becomes impossible to peel or warp occurs after peeling. Since the metal-clad laminate of the present invention is a double-sided metal-clad laminate that can be easily separated into a single-sided metal-clad laminate, it can be peeled off after simultaneously performing circuit wiring on the metal layers on both sides. The efficiency of the FPC manufacturing process can be greatly improved.

  In addition, since the metal-clad laminate of the present invention has higher rigidity than the state of a single-sided metal-clad laminate, it is possible to prevent the occurrence of defects such as breakage, damage, and peeling of the wiring layer due to bending in the FPC manufacturing process. . Therefore, by using the metal-clad laminate of the present invention, the yield and reliability of the FPC itself and electronic products using the FPC can be improved.

It is typical sectional drawing which shows the structure of the double-sided metal-clad laminated board of one embodiment of this invention. It is typical sectional drawing which shows the structure of the two single-sided metal-clad laminates which comprise the double-sided metal-clad laminate of FIG.

  The metal-clad laminate of the present invention has a structure in which a metal layer (A) / insulating resin layer (B) / release layer (C) / insulating resin layer (D) / metal layer (E) are laminated in this order. It is a double-sided metal-clad laminate. That is, the metal layer (A) and the metal layer (E) are respectively located outside, and the insulating resin layer (B) and the insulating resin layer (D) are disposed therebetween, and further, the insulating resin layer (B) and the insulating resin are disposed. A release layer (C) is interposed between the layers (D). Here, the insulating resin layer (B) has a resin layer (B1) in contact with the release layer (C), and the resin layer (B1) contains 1 to 10% by volume of filler. Moreover, the insulating resin layer (D) has a resin layer (D1) in contact with the release layer (C), and the resin layer (D1) contains 1 to 10% by volume of filler.

[Double-sided metal-clad laminate]
An embodiment of the present invention will be described with reference to the drawings as appropriate. FIG. 1 is a schematic cross-sectional view showing a configuration of a double-sided metal-clad laminate 100 according to the present embodiment. FIG. 2 is a schematic cross-sectional view showing the configuration of two single-sided metal-clad laminates 120 and 120 ′ constituting the double-sided metal-clad laminate 100 of FIG. As shown in FIG. 1, the double-sided metal-clad laminate 100 according to the present embodiment includes metal layers 101 and 101 'as a metal layer (A) and a metal layer (E), an insulating resin layer (B), and an insulating resin. A polyimide layer 110, 110 ′ as a layer (D) and a release film 104 as a release layer (C) are provided. Here, the polyimide layers 110 and 110 ′ include low thermal expansion polyimide layers 102 and 102 ′ as a base layer, and thermoplastic polyimide layers 103 and 103 ′ as a resin layer (B 1) and a resin layer (D 1). It is constituted by a plurality of polyimide layers having a laminated structure. Further, the double-sided metal-clad laminate 100 has a structure in which metal layers 101 and 101 ′ are provided on one surface of each of the polyimide layers 110 and 110 ′. The low thermal expansion polyimide layers 102 and 102 ′ laminated on the metal layers 101 and 101 ′, and the thermoplastic polyimide layers 103 and 103 ′ bonded thereto are formed by a casting method. The thermoplastic polyimide layers 103 and 103 ′ are bonded to the release film 104 to form a double-sided metal-clad laminate 100. The thermoplastic polyimide layers 103 and 103 ′ contain a predetermined amount of filler 105. The release film 104 is a film for increasing the mechanical rigidity in the double-sided metal-clad laminate 100, and may have an adhesive layer (not shown) on the surface. The thermoplastic polyimide layer 103 and the release film 104 are bonded to each other at the bonding boundary 107, and the thermoplastic polyimide layer 103 ′ and the release film 104 are bonded to each other at the bonding boundary 107 ′. The polyimide layers 110 and 110 ′ are not limited to the two-layer structure, but may be one layer or may have three or more polyimide layers.

The double-sided metal-clad laminate 100 of the present embodiment can separate the two single-sided metal-clad laminates 120, 120 ′ constituting the double-sided metal-clad laminate 100 from the release film 104 by mechanical force. The peeling strength (peeling strength) required for separating the double-sided metal-clad laminate 100 into two single-sided metal-clad laminates 120 or 120 ′ and the release film 104 is one polyimide layer 110 and the release film 104. peel strength _Ad and _B-C, the average value of peel strength _{Ad D-C} with the other polyimide layer 110 'and a release film 104 with _{(Ad B-C + Ad D} -C) / 2 is, for example 1~30N / M is preferable, and more preferably within a range of 5 to 20 N / m. If the peeling strength does not satisfy 1 N / m, peeling at the bonding boundaries 107 and 107 ′ is likely to occur due to mechanical external force in the FPC manufacturing process. When the peel strength exceeds 30 N / m, it becomes impossible to separate the two single-sided metal-clad laminates 120 and 120 ′ from the release film 104, or even if they can be separated, the metal-clad laminate is stretched and warped at the time of separation. Is likely to occur.

  The double-sided metal-clad laminate 100 has a thickness compared to the single-sided metal-clad laminate 120 or 120 ′ and includes the release film 104, thereby reinforcing the rigidity of the single-sided metal-clad laminate 120 or 120 ′, More excellent mechanical properties can be imparted. Therefore, the double-sided metal-clad laminate 100 breaks or damages the wiring layer due to bending in a FPC processing process including wet process processing such as exposure, development, etching, and plating, baking, and high-temperature processing such as high-speed press. The occurrence of defects such as peeling can be prevented.

As shown in FIG. 2, the double-sided metal-clad laminate 100 of the present embodiment can be applied to and peeled off from a single-sided metal-clad laminate 120 or 120 ′ having polyimide layers 110 and 110 ′ and metal layers 101 and 101 ′. The surfaces 103a and 103a ′ are manufactured by pressure-bonding to both surfaces of the release film 104. When the polyimide layers 110 and 110 ′ in the single-sided metal-clad laminate 120 or 120 ′ are composed of two or more layers, as described above, the thermoplastic polyimide layers 103 and 103 ′ and the low thermal expansion polyimide layers 102 and 102 are used. 'Can contain. Here, the “thermoplastic polyimide layer” refers to a layer having the thermoplasticity necessary to ensure adhesion with other release layers at the thermocompression bonding temperature. The “low thermal expansion polyimide layer” means a linear thermal expansion coefficient of 20 × 10 ⁻⁶ (1 / K) or less, preferably in the range of 1 × 10 ^{−6 to} 17 × 10 ⁻⁶ (1 / K). It refers to a certain polyimide layer.

  For example, the following method can be selected for pressure bonding when the polyimide layers 110 and 110 ′ of the two single-sided metal-clad laminates 120 and 120 ′ are bonded to the release film 104. That is, a hydro press, a vacuum type hydro press, an autoclave pressurizing vacuum press, a continuous thermal laminator, or the like can be used. Among these, a continuous laminator that performs pressurization using a pair of rolls is a more preferable pressure bonding method from the viewpoint of excellent productivity.

The temperature at the time of pressure bonding (press temperature) is not particularly limited and may be heated, but normal temperature is preferable. Moreover, about press pressure, although based also on the kind of press apparatus to be used, 0.1-50 MPa (about 1-about 500 kg / cm < ² >) is suitable. The pressing temperature when heating at the time of pressure bonding is preferably equal to or higher than the glass transition temperature of the thermoplastic polyimide constituting the thermoplastic polyimide layers 103 and 103 ′ located in the outermost layer of the single-sided metal-clad laminates 120 and 120 ′. . If the pressing temperature at the time of pressure bonding becomes too high, there is a concern that defects such as deterioration of the metal layers 101, 101 ′ and the polyimide layers 110, 110 ′ may occur.

<Single-sided metal-clad laminate>
In the production of the single-sided metal-clad laminates 120 and 120 ′, a method in which a plurality of polyamide acid resin layers are sequentially formed and then imidized at once to form polyimide layers 110 and 110 ′ is preferable, but is not limited thereto. Is not to be done. That is, a plurality of polyamic acid resin layers are collectively applied to the metal layers 101 and 101 ′ by a multi-layer die or the like, dried, and then simultaneously imidized by heat treatment to form a plurality of polyimide layers. Alternatively, a plurality of polyamic acid resin layers may be sequentially applied and then dried and imidized together. Moreover, you may form a polyimide layer one layer at a time by performing sequentially from application | coating drying of the resin solution of a some polyamic acid to imidation. In forming a plurality of polyimide layers, each of these treatments can be arbitrarily combined.

<Metal layer>
The metal layers 101 and 101 ′ are preferably metal foils from the viewpoint of adhesiveness. As the metal of the metal foil, copper, aluminum, stainless steel, iron, silver, palladium, nickel, chromium, molybdenum, tungsten, zirconium And metals selected from gold, cobalt, titanium, tantalum, zinc, lead, tin, silicon, bismuth, indium, and alloys thereof. A copper foil is particularly preferable in terms of conductivity. In the case where the double-sided metal-clad laminate 100 and the single-sided metal-clad laminates 120, 120 ′ of the present embodiment are continuously produced, a metal foil having a predetermined thickness is wound into a roll. An elongated metal foil is used.

  The surface roughness of the surfaces of the metal layers 101 and 101 ′ that are in direct contact with the polyimide layers 110 and 110 ′ is preferably 0.5 to 4 μm in Rz. This is because the adhesive strength with the polyimide layers 110 and 110 'is better within this range. Furthermore, if Rz is 0.5 to 2.5 μm, it is more preferable because it is possible to achieve both a suitable adhesive force and a good etching property required when forming a high-density wiring. Here, Rz indicates a ten-point average roughness defined in JIS B 0601 (1994).

<Filler>
In the present embodiment, the polyimide constituting the thermoplastic polyimide layers 103 and 103 ′ located on the outermost layer (outermost surface) of both of the two single-sided metal-clad laminates 120 or 120 ′ to be pressure-bonded to the release film 104 is The filler 105 is preferably contained within a range of 1 to 10% by volume, and more preferably within a range of 2 to 6% by volume. If the content of the filler 105 in the thermoplastic polyimide layers 103 and 103 ′ is less than 1% by volume, the adhesion of the bonding boundaries 107 and 107 ′ becomes strong, and the double-sided metal-clad laminate 100 is replaced with two single-sided metal-clad laminates. When separating into 120 or 120 ′, even if separation becomes impossible or separation is possible, the single-sided metal-clad laminate 120 or 120 ′ is stretched during the separation and warpage is likely to occur. On the other hand, when the content of the filler 105 exceeds 10% by volume, the unevenness of the surface becomes large and the smoothness is deteriorated in appearance, or the adhesive strength between the bonding boundaries 107 and 107 ′ is reduced, resulting in mechanical in the FPC manufacturing process. Exfoliation is likely to occur at the bonding boundaries 107 and 107 ′ due to external force.

  The content of the filler 105 in the thermoplastic polyimide layers 103 and 103 ′ may be the same or different as long as it is within the above range. When the content of the filler 105 is different, the difference in the content of the filler 105 in the thermoplastic polyimide layer 103 and the thermoplastic polyimide layer 103 ′ is 5% by volume or less from the viewpoint of controlling the adhesive strength to the same extent. Is preferred.

  The filler 105 may be distributed throughout the polyimide layers 110 and 110 '. That is, the low thermal expansion polyimide layers 102 and 102 ′ may also contain the filler 105.

  Examples of the material of the filler 105 include silica, alumina, aluminum nitride, and the like. Among these, silica is preferable.

  The shape of the filler 105 is preferably not spherical but spherical in terms of uniformity of dispersion in the resin. Furthermore, the average particle diameter of the filler 105 is more preferably 1 to 10 μm. In the present invention, the spherical shape refers to a true sphere or a rounded particle state having substantially no corners, and the crushed shape refers to a particle state having an arbitrary shape with corners of the crushed particles. Some say, and can be confirmed with an electron microscope or other microscope.

<Release film>
The release film 104 has an effect of increasing the rigidity of the double-sided metal-clad laminate 100, and any material can be used. For example, a resin film, a metal foil, a composite film thereof, or the like can be used. As a resin that can be used for the release film 104, for example, polyester, polypropylene, polyimide, polyethylene, polyvinyl chloride, and the like are preferable. Moreover, as metal foil, metal foil which consists of copper foil, stainless steel foil, aluminum foil, and these alloys can be mentioned, for example. Among the above materials, polyesters such as polyethylene terephthalate (PET) that are easy to handle are preferable.

  The release film 104 preferably has an adhesive layer on both surfaces thereof. As the adhesive constituting the adhesive layer, a pressure-sensitive adhesive is preferable. For example, an elastomer-based pressure-sensitive adhesive or a resin-based pressure-sensitive adhesive is preferably used. Here, as the elastomer-based pressure-sensitive adhesive, for example, a natural rubber-based pressure-sensitive adhesive, a synthetic rubber-based pressure-sensitive adhesive, a thermoplastic elastomer-pressure-sensitive adhesive, and the like are preferable. As the resin-based pressure sensitive adhesive, for example, polyacrylate, polyurethane, polyvinyl chloride, polyvinyl ether and the like are preferable. By providing a pressure-sensitive adhesive layer on both surfaces of the release film 104, heating is not required when the polyimide layers 110 and 110 ′ of the two single-sided metal-clad laminates 120 and 120 ′ are bonded to the release film 104. , Room temperature crimping is possible. In the case where an adhesive layer is provided on the release film 104, the resin layer (B1) and the resin layer (D1) are not necessarily formed of a thermoplastic resin.

<Polyimide>
Next, the polyimide constituting the polyimide layers 110 and 110 ′ will be described. In the present invention, the term “polyimide” means a resin made of a polymer having an imide group in its molecular structure such as polyamideimide, polyetherimide, polyesterimide, polysiloxaneimide, polybenzimidazoleimide, etc. in addition to polyimide.

<Thermoplastic polyimide>
The thermoplastic polyimide constituting the thermoplastic polyimide layers 103 and 103 ′ contains 50 mol% or more of 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride (BTDA) as an acid anhydride component. What was obtained by using an acid anhydride and making it react with a diamino compound is preferable. By including 50 mol% or more of BTDA, the peelability between the thermoplastic polyimide layers 103 and 103 ′ and the release film 104 is improved, and the single-sided metal-clad laminate 120 or 120 ′ (or The risk of warping due to stretching of the circuit processed product). A more preferable content of BTDA is in the range of 70 to 100 mol%.

  As the thermoplastic polyimide constituting the thermoplastic polyimide layers 103 and 103 ′, a diamino compound containing 50 mol% or more of 4,4′-diaminodiphenyl ether (DAPE) is used as a diamino component, and this is reacted with an acid anhydride. What was obtained was made to be preferable. By including DAPE in an amount of 50 mol% or more, the peelability between the thermoplastic polyimide layers 103 and 103 ′ and the release film 104 is improved, and the single-sided metal-clad laminate 120 or 120 ′ (or The risk of warping due to stretching of the circuit processed product). A more preferable content of DAPE is in the range of 70 to 100 mol%.

Among diamino compounds other than DAPE, aromatic diamino compounds represented by NH ₂ —Ar ₁ —NH ₂ are preferred. Here, Ar1 is selected from the group represented by the following formula, and the substitution position of the amino group is arbitrary, but the p and p ′ positions are preferred. Ar1 may have a substituent, but it is preferably not present, or when present, the substituent is preferably a lower alkyl or lower alkoxy group having 1 to 6 carbon atoms. These aromatic diamino compounds may be used alone or in combination of two or more.

Examples of the tetracarboxylic acid compound to be reacted with the diamino compound include aromatic tetracarboxylic acid and acid anhydrides, esterified products, halides, etc., but aromatic tetracarboxylic acid compounds are preferred and are used for synthesizing polyamic acid. In terms of ease, the acid anhydride is preferred. As the aromatic tetracarboxylic acid _{compound, O (CO) 2 Ar2 (} CO) compound represented by the ₂ O is mentioned as suitable. Here, Ar2 is preferably a tetravalent aromatic group represented by the following formula, and the substitution position of the acid anhydride group [(CO) ₂ O] is arbitrary, but a symmetric position is preferred. Ar2 may have a substituent, but preferably does not have it or, when it is present, the substituent is preferably a lower alkyl group having 1 to 6 carbon atoms. Among the more preferred aromatic tetracarboxylic acid compounds, those other than BTDA include biphenyltetracarboxylic anhydride (BPDA), pyromellitic anhydride (PMDA), 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic. It may be acid dianhydride (DSDA) and 4,4′-oxydiphthalic anhydride (ODPA) or combinations thereof. These tetracarboxylic acid compounds may be used alone or in combination of two or more.

<Low thermal expansion polyimide>
Low thermal expansion polyimide layer 102, 102 'polyimide constituting the, the thermoplastic polyimide layer 103, 103 as described above' as in the case of the polyimide constituting the _aromatic diamino compound represented by NH ₂ -Ar1-NH 2 Those obtained by reacting with a tetracarboxylic acid compound are preferred. However, the linear thermal expansion coefficient of the low thermal expansion polyimide layers 102 and 102 ′ is 20 × 10 ⁻⁶ (1 / K) or less, preferably in the range of 1 × 10 ^{−6 to} 17 × 10 ⁻⁶ (1 / K). It is preferable to select an aromatic diamino compound suitable for achieving this condition. For example, those obtained by reacting a diamino compound containing 50 mol% or more of 4,4′-diamino-2,2′-dimethylbiphenyl (m-TB) with a tetracarboxylic acid compound are preferred. Furthermore, it is more preferable to select a diamino compound containing 70 mol% or more.

As the tetracarboxylic acid compound to be reacted with the diamino compound, the same compounds as in the case of the polyimide constituting the thermoplastic polyimide layers 103 and 103 ′ can be used. The aromatic tetracarboxylic acid compound is more preferable in that the linear thermal expansion coefficient is 20 × 10 ⁻⁶ (1 / K) or less, preferably in the range of 1 × 10 ^{−6 to} 17 × 10 ⁻⁶ (1 / K). , Biphenyltetracarboxylic anhydride (BPDA), pyromellitic anhydride (PMDA) or a combination thereof.

<Polyimide layer (insulating resin layer as a whole)>
Regarding the overall linear thermal expansion coefficient of the polyimide layers 110 and 110 ′ of the two single-sided metal-clad laminates 120 and 120 ′ used for the pressure bonding, preferably both the polyimide layers 110 and 110 ′ are 15 × 10 ⁻⁶ to It is in the range of 35 × 10 ⁻⁶ (1 / K), and more preferably in the range of 16 × 10 ^{−6 to} 33 × 10 ⁻⁶ (1 / K). When the overall linear thermal expansion coefficient of the polyimide layers 110 and 110 ′ is out of the above range, in the step of obtaining the single-sided metal-clad laminates 120 and 120 ′, the width direction end portions of the single-sided metal-clad laminates 120 and 120 ′ are obtained. Warpage increases, and stable production tends to be hindered. Furthermore, even in the process of obtaining the double-sided metal-clad laminate 100 by crimping the two single-sided metal-clad laminates 120, 120 ′ and the release film 104, the warp at the end in the width direction is easily folded inward and stable. Production may be hindered.

  The polyimide constituting the thermoplastic polyimide layers 103 and 103 ′ and the low thermal expansion polyimide layers 102 and 102 ′ can be manufactured by the following method, for example. That is, in a solvent, the above diamino compound and tetracarboxylic dianhydride are mixed in an approximately equimolar ratio, and reacted in a reaction temperature range of 0 to 200 ° C., preferably in a range of 0 to 100 ° C., There is a method of obtaining a polyimide by obtaining a polyamide acid resin solution and imidizing it.

  As the solvent, N-methylpyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), dimethyl sulfate, sulfolane, butyrolactone, cresol, phenol, halogenated phenol, cyclohexanone, Examples include dioxane, tetrahydrofuran, diglyme, and triglyme.

  Usually, the synthesis of the polyamic acid is performed in a reaction vessel or the like before application to the metal layers 101 and 101 '. Then, a polyamic acid resin solution is applied and dried on the metal layers 101 and 101 'to form a polyamic acid layer, and the polyamic acid layer is imidized by a subsequent heat treatment to obtain a polyimide layer. Of course, you may apply | coat on the polyamic-acid layer already formed or the polyimide layer.

  As a method of drying and heating imidization treatment, any method such as a batch treatment method and a continuous treatment method can be selected. In the batch processing method, after applying a polyamic acid resin solution to a long metal foil, the laminate is wound in a roll shape without being imidized, and is set in a hot air drying furnace that can be set to a predetermined temperature. And imidation is completed by heat-treating at a high temperature of 200 ° C. or higher. In the continuous treatment method, after applying a polyamic acid resin solution to a long metal foil, the inside of the drying furnace is continuously moved to ensure a predetermined heat treatment time, and finally the temperature is increased to 200 ° C. or higher. This is a method of performing heat treatment.

  Any of these methods may be selected from the viewpoints of productivity, yield, etc., but heat treatment at a high temperature of 200 ° C. or higher is performed under reduced pressure in order to prevent oxidation of the metal layers 101 and 101 ′. It is preferable to carry out in a reducing gas atmosphere or a reducing gas atmosphere and a reduced pressure environment.

  In addition, the solvent of the polyamic acid resin is removed and imidized by heating in the drying and imidization treatment step. At this time, if heat treatment is performed rapidly at a high temperature, a skin layer is formed on the resin surface, and the solvent is removed. However, it is preferable to perform heat treatment while gradually raising the temperature from a low temperature to a high temperature. Moreover, in the heating imidation process, it is preferable to heat-process finally at the temperature of 300-400 degreeC.

  The concentration of the polyamic acid resin solution applied to the metal layers 101 and 101 'is preferably 5 to 30% by weight, more preferably 10 to 20% by weight, although it depends on the degree of polymerization of the polyamic acid that is a polymer. If the polymer concentration is 5% by weight or more, a sufficient film thickness can be obtained by one application, and if it is 30% by weight or less, the viscosity of the resin solution does not become too high and can be applied uniformly and smoothly. Because.

  As described above in detail, the double-sided metal-clad laminate 100 of the present embodiment has the filler 105 at a predetermined volume ratio with respect to the thermoplastic polyimide layers 103 and 103 ′ in the two single-sided metal-clad laminates 120 and 120 ′. Since it contains, it has moderate adhesiveness with respect to the release film 104, and peeling is easy, and it can suppress that it becomes impossible to peel or a curvature generate | occur | produces after peeling. Since the double-sided metal-clad laminate 100 of the present embodiment can be easily peeled off at the bonding boundaries 107 and 107 ′, it can be peeled off after simultaneously performing circuit wiring processing on the metal layers 101 and 101 ′ on both sides. It is possible and the efficiency of the FPC manufacturing process can be greatly improved.

  In addition, since the double-sided metal-clad laminate 100 of this embodiment has higher rigidity than the state of the single-sided metal-clad laminate 120, 120 ′, the wiring layer is broken, damaged, or peeled off by bending in the FPC manufacturing process. It is possible to prevent the occurrence of problems such as. Therefore, by using the double-sided metal-clad laminate 100 of the present embodiment, the yield and reliability of the FPC itself and electronic products using the FPC can be improved.

  Hereinafter, the embodiment of the present invention will be described more specifically with reference to examples. Further, the superiority of the present embodiment will be clarified by showing a comparative example.

1. Various physical properties measurement and performance test method [Measurement of glass transition temperature]
The dynamic viscoelasticity of a polyimide film (10mm x 22.6mm) obtained by etching and removing copper foil was measured at 5 ° C / min from 20 ° C to 500 ° C by DMA to measure the glass transition. The point temperature Tg (tan δ maximum value) was determined.

[Measurement of linear thermal expansion coefficient]
The polyimide film obtained by etching the copper foil was heated to 250 ° C. using a thermomechanical analyzer manufactured by Seiko Instruments Inc., held at that temperature for 10 minutes, and then cooled at a rate of 5 ° C./min. The average thermal expansion coefficient (linear thermal expansion coefficient) from 240 ° C. to 100 ° C. was determined.

[Measurement of peel strength]
A double-sided flexible copper-clad laminate obtained by bonding two single-sided flexible copper-clad laminates through a release layer was cut into 25 mm × 100 mm, and one of the single-sided flexible copper-clad laminates was previously removed by peeling off. The release strength of the release layer of the single-sided flexible copper clad laminate with release layer was measured by a 180 ° peeling method using a tensile tester. The peel strength was measured on the other surface in the same manner, and the average value of both was calculated.

[Appearance properties]
The resin side of the single-sided flexible copper-clad laminate having a size of 250 mm × 250 mm was visually observed, and when a protrusion having a diameter of 100 μm or more was confirmed, this was judged as “poor appearance”.

[Measurement of warpage after peeling]
Create a 10cm x 10cm size sheet from a flexible copper clad laminate, and measure the height from the desk surface of the part that is the most lifted from the desk surface when this sheet is placed on the desk using a caliper, This was the amount of warpage.

2. Synthetic synthesis example 1 of polyamic acid resin (without filler):
31.20 g of N, N dimethylacetamide was placed in a reaction vessel equipped with a thermocouple and a stirrer and capable of introducing nitrogen. In this reaction vessel, 14.67 g (0.073 mol) of 4,4′-diaminodiphenyl ether was dissolved in the vessel with stirring. Next, 23.13 g (0.072 mol) of 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride was added. Thereafter, stirring was continued for 3 hours to obtain a polyamic acid resin solution a having a solution viscosity of 2,960 mPa · s. The solution viscosity is an apparent viscosity value only at 25 ° C. by an E-type viscometer (hereinafter the same). The glass transition temperature of the polyimide obtained from this polyamic acid resin solution a was 312 ° C., and the linear thermal expansion coefficient was 45 × 10 ⁻⁶ (1 / K).

Synthesis example 2 (filler content 1 volume%):
31.20 g of N, N dimethylacetamide was placed in a reaction vessel equipped with a thermocouple and a stirrer and capable of introducing nitrogen. To this reaction vessel, 0.60 g of spherical filler (silica, average particle size 1.2 μm, manufactured by Admatechs, “SE4050”; the same applies hereinafter) was added and dispersed for 3 hours using an ultrasonic dispersing apparatus. In this solution, 14.67 g (0.073 mol) of 4,4′-diaminodiphenyl ether was dissolved in a container with stirring. Next, 23.13 g (0.072 mol) of 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride was added. Thereafter, stirring was continued for 3 hours to obtain a polyamic acid resin solution b having a solution viscosity of 3,160 mPa · s.

Synthesis Example 3 (filler content 10% by volume):
A polyamic acid resin solution c was obtained in the same manner as in Synthesis Example 2 except that the spherical filler was changed to 6.60 g. The solution viscosity of the polyamic acid resin solution c was 3,500 mPa · s.

Synthesis Example 4 (filler content 15% by volume):
A polyamic acid resin solution d was obtained in the same manner as in Synthesis Example 2 except that the spherical filler was changed to 10.50 g. The solution viscosity of the polyamic acid resin solution d was 4,100 mPa · s.

Synthesis Example 5 (without filler):
In a reaction vessel equipped with a thermocouple and a stirrer and capable of introducing nitrogen, 308.00 g of N, N dimethylacetamide was placed. In this reaction vessel, 27.14 g (0.066 mol) of 2,2-bis [4- (4-aminophenoxy) phenyl] propane was dissolved in the vessel with stirring. Next, 14.86 g (0.068 mol) of pyromellitic dianhydride was added. Thereafter, stirring was continued for 3 hours to obtain a polyamic acid resin solution e having a solution viscosity of 2,850 mPa · s. The glass transition temperature of the polyimide obtained from this polyamic acid resin solution e was 290 ° C., and the linear thermal expansion coefficient was 55 × 10 ⁻⁶ (1 / K).

Synthesis Example 6 (filler content 1% by volume):
In a reaction vessel equipped with a thermocouple and a stirrer and capable of introducing nitrogen, 308.00 g of N, N dimethylacetamide was placed. To this reaction vessel, 0.70 g of spherical filler was added and dispersed for 3 hours with an ultrasonic dispersion device. In this solution, 27.14 g (0.066 mol) of 2,2-bis [4- (4-aminophenoxy) phenyl] propane was dissolved in a container with stirring. Next, 14.86 g (0.068 mol) of pyromellitic dianhydride was added. Thereafter, stirring was continued for 3 hours to obtain a polyamic acid resin solution f having a solution viscosity of 2,960 mPa · s.

Synthesis Example 7 (filler content 10% by volume):
A polyamic acid resin solution g was obtained in the same manner as in Synthesis Example 6 except that the spherical filler was changed to 7.30 g. The solution viscosity of the polyamide acid resin solution g was 3,200 mPa · s.

Synthesis Example 8 (filler content 15% by volume):
A polyamic acid resin solution h was obtained in the same manner as in Synthesis Example 6 except that the spherical filler was changed to 11.65 g. The solution viscosity of the polyamide acid resin solution h was 3,700 mPa · s.

Synthesis Example 9
In a reaction vessel equipped with a thermocouple and a stirrer and capable of introducing nitrogen, 297.50 g of N, N-dimethylacetamide was placed. In this reaction vessel, 25.27 g (0.119 mol) of 4,4′-diamino-2,2′dimethylbiphenyl was dissolved in the vessel with stirring. Next, 6.87 g (0.023 mol) of 3,3′-4,4′-biphenyltetracarboxylic dianhydride and 20.36 g (0.093 mol) of pyromellitic dianhydride were added. . Thereafter, stirring was continued for 3 hours to obtain a polyamic acid resin solution i having a solution viscosity of 21,000 mPa · s. The glass transition temperature of the polyimide obtained from this polyamic acid resin solution i was 360 ° C., and the linear thermal expansion coefficient was 15 × 10 ⁻⁶ (1 / K).

Example 1
After applying the polyamic acid resin solution i prepared in Synthesis Example 9 uniformly on one side of a long electrolytic copper foil having a thickness of 12 μm (first layer), the solvent was removed by heating at 130 ° C. Next, the polyamic acid resin solution b prepared in Synthesis Example 2 was uniformly applied to the coated surface side (second layer), and dried by heating at 130 ° C. to remove the solvent. This long laminate was heat-treated in a continuous curing furnace set so that the temperature gradually increased from 300 ° C. to 300 ° C. over a period of about 10 minutes. A 25 μm single-sided flexible copper-clad laminate was obtained. Subsequently, the two single-sided flexible copper-clad laminates were attached to a PET film (total thickness 25 μm) having an acrylic resin pressure sensitive adhesive layer on both sides as a release layer so that each polyimide layer surface was in contact with the release layer. At the same time, a continuous double-sided flexible copper-clad laminate was obtained by continuously supplying at a speed of 10 m / min between a pair of rolls and pressurizing at room temperature. At this time, the linear pressure between the rolls was 5 kN / m. The polyimide layer and the release layer laminated by pressing at room temperature were adhered to each other without being peeled off from each other.

(Example 2)
A long double-sided flexible copper-clad laminate was obtained in the same manner as in Example 1 except that the second layer was formed from the polyamic acid resin solution c prepared in Synthesis Example 3. The polyimide layer and the release layer laminated by pressing at room temperature were adhered to each other without being peeled off from each other.

(Example 3)
A long double-sided flexible copper-clad laminate was obtained in the same manner as in Example 1 except that the second layer was formed with the polyamic acid resin solution f prepared in Synthesis Example 6. The polyimide layer and the release layer laminated by pressing at room temperature were adhered to each other without being peeled off from each other.

Example 4
A long double-sided flexible copper-clad laminate was obtained in the same manner as in Example 1 except that the second layer was formed from the polyamic acid resin solution g prepared in Synthesis Example 7. The polyimide layer and the release layer laminated by pressing at room temperature were adhered to each other without being peeled off from each other.

(Comparative Example 1)
A long double-sided flexible copper-clad laminate was obtained in the same manner as in Example 1 except that the second layer was formed from the polyamic acid resin solution a prepared in Synthesis Example 1. The polyimide layer and the release layer laminated by pressing at room temperature were adhered to each other without being peeled off from each other.

(Comparative Example 2)
A long double-sided flexible copper-clad laminate was obtained in the same manner as in Example 1 except that the second layer was formed from the polyamic acid resin solution d prepared in Synthesis Example 4. The polyimide layer and the release layer laminated by pressing at room temperature were partially peeled off and the sticking property was insufficient.

(Comparative Example 3)
A long double-sided flexible copper-clad laminate was obtained in the same manner as in Example 1 except that the second layer was formed from the polyamic acid resin solution e prepared in Synthesis Example 5. The polyimide layer and the release layer laminated by pressing at room temperature were adhered to each other without being peeled off from each other.

(Comparative Example 4)
A long double-sided flexible copper-clad laminate was obtained in the same manner as in Example 1 except that the second layer was formed from the polyamic acid resin solution h prepared in Synthesis Example 8. The polyimide layer and the release layer laminated by pressing at room temperature were partially peeled off and the sticking property was insufficient.

  The above results are summarized in Table 1.

  As mentioned above, although embodiment of this invention was described in detail for the purpose of illustration, this invention is not restrict | limited to the said embodiment.

  DESCRIPTION OF SYMBOLS 100 ... Double-sided metal-clad laminate, 101, 101 '... Metal layer, 102, 102' ... Low thermal expansion polyimide layer, 103, 103 '... Thermoplastic polyimide layer, 103a, 103a' ... Sticking / peeling surface, 104 ... Release film, 105 ... filler, 107, 107 '... sticking boundary, 110, 110' ... polyimide layer, 120, 120 '... single-sided metal-clad laminate

Claims (8)

A metal-clad laminate having a metal layer (A) / insulating resin layer (B) / release layer (C) / insulating resin layer (D) / metal layer (E),
The insulating resin layer (B) has a resin layer (B1) in contact with the release layer (C), and the resin layer (B1) contains a filler in a range of 1 to 10% by volume. With
The insulating resin layer (D) has a resin layer (D1) in contact with the release layer (C), and the resin layer (D1) contains a filler in a range of 1 to 10% by volume. A metal-clad laminate characterized by that.   The metal-clad laminate according to claim 1, wherein a difference in filler content between the resin layer (B1) and the resin layer (D1) is 5% by volume or less. The insulating resin layer (B) and the insulating resin layer (D) have a multilayer structure including a base layer having a linear thermal expansion coefficient of 20 × 10 ⁻⁶ (1 / K) or less. Metal-clad laminate.   The metal-clad laminate according to any one of claims 1 to 3, wherein the release layer (C) includes an elastomer-based pressure-sensitive adhesive or a resin-based pressure-sensitive adhesive. Wherein a peel strength _{Ad B-C} of the insulating resin layer (B) and the releasing layer (C), average the peel strength _{Ad D-C} of the insulating resin layer (D) and the releasing layer (C) 5. The metal-clad laminate according to claim 1, wherein the value (Ad _B−C + Ad _D−C ) / 2 is in the range of 1 to 30 N / m.   The metal-clad laminate according to any one of claims 1 to 5, wherein the resin layer (B1) and the resin layer (D1) are formed of polyimide.   The metal-clad laminate according to claim 6, wherein 50 mol% or more of the total acid anhydride component constituting the polyimide is 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride (BTDA). The metal-clad laminate according to claim 6 or 7, wherein 50 mol% or more of all diamino components constituting the polyimide is 4,4'-diaminodiphenyl ether (DAPE).

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