JP6774285B2 - Metal-clad laminate - Google Patents

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 an electronic product.

Since FPC has flexibility and potential for three-dimensional wiring, it is widely applied to electronic products such as computers and their peripheral devices, communication devices represented by smartphones, and the like. The FPC is manufactured by circuit processing a metal layer of a metal-clad laminate having a structure in which a metal layer and an insulating resin layer are laminated.

With the miniaturization of electronic devices, FPCs are becoming thinner, denser, and more multifunctional. When the FPC is made thinner, the rigidity of the insulating resin layer is lowered, so that problems such as breakage, damage, and peeling of the wiring layer due to bending are likely to occur in the FPC manufacturing process. Since these defects reduce the yield and reliability of electronic products that use FPC, countermeasures are required.

In response to the above problem, an adhesive layer is provided on the insulating resin layer of the single-sided metal-clad laminate, the surface of the adhesive layer is modified, and then the modified surface is directly or with a release material interposed therebetween. It has been proposed to bond the insulating resin layers of the single-sided metal-clad laminate to form a double-sided metal-clad laminate for FPC processing (for example, Patent Document 1 and Patent Document 2).

Japanese Unexamined Patent Publication No. 2015-168261 (Fig. 1E, etc.) Japanese Unexamined Patent Publication No. 2015-168262 (Fig. 1D, etc.)

In the techniques of Patent Documents 1 and 2, the insulating resin layer of the single-sided metal-clad laminate once bonded and the insulating resin layer (or release material) of the other single-sided metal-clad laminate are easily peeled off. The surface energy of the surface of the insulating resin layer is reduced by performing modification treatment such as plasma treatment and ultraviolet irradiation on the surface of the adhesive layer. Therefore, as compared with the normal FPC manufacturing process, an extra process for the reforming process is required, which may lead to an increase in the number of processes, complication of equipment, and a decrease in throughput. On the other hand, if the modification treatment is not performed, the adhesive strength between the insulating resin layers becomes too strong, so that the peeling strength becomes large, the peeling becomes difficult, and the FPC after peeling becomes warped. was there.

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

As a result of diligent studies, the present inventors have determined a resin layer forming a bonded surface in a double-sided metal-clad laminate including two single-sided metal-clad laminates bonded to each other on the insulating resin layer side. We have found that by containing a filler in a volume ratio, it can be easily peeled off without performing a modification treatment, and completed the present invention.

That is, the present invention
A metal-clad laminate having a metal layer (A) / insulating resin layer (B) / insulating resin layer (C) / metal layer (D).
The insulating resin layer (B) has a resin layer (B1) in contact with the insulating resin layer (C), and the resin layer (B1) contains a filler in the range of 1 to 10% by volume. With
The insulating resin layer (C) has a resin layer (C1) in contact with the insulating resin layer (B), and the resin layer (C1) contains a filler in the range of 1 to 10% by volume. It is a metal-clad laminate characterized by this.

In the present invention, the difference in filler content between the resin layer (B1) and the resin layer (C1) is preferably 5% by volume or less.

Further, in the present invention, the insulating resin layer (B) and the insulating resin layer (C) preferably have a multilayer structure including a base layer having a linear thermal expansion coefficient of 20 × ^10-6 (1 / K) or less. ..

Further, in the present invention, the peel strength between the insulating resin layer (B) and the insulating resin layer (C) is preferably in the range of 1 to 30 N / m.

Further, in the present invention, it is preferable that the resin layer (B1) and the resin layer (C1) are made of polyimide.

Further, in the present invention, it is preferable that 50 mol% or more of the total acid anhydride component constituting the polyimide is 3,3', 4,4'-benzophenone tetracarboxylic dianhydride (BTDA).

Furthermore, in the present invention, it is preferable that 50 mol% or more of all the diamino components constituting the polyimide are 4,4'-diaminodiphenyl ether (DAPE).

Since the metal-clad laminate of the present invention contains a filler in a predetermined volume ratio in each of the resin layers forming the bonded surfaces of the two single-sided metal-clad laminates, it has appropriate adhesiveness and is easy to peel off. , It is possible to prevent the peeling from becoming impossible and the occurrence of warpage after peeling. Since the metal-clad laminate of the present invention is a double-sided metal-clad laminate that can be easily peeled off, it is possible to peel off the metal-clad laminates after simultaneously performing circuit wiring processing on both sides, and the efficiency of the FPC manufacturing process. Can be greatly improved.

Further, since the metal-clad laminate of the present invention has higher rigidity than the state of the 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 the electronic product using the FPC can be improved.

It is a schematic cross-sectional view which shows the structure of the double-sided metal-clad laminate of one Embodiment of this invention. It is a schematic cross-sectional view which shows the structure of the two single-sided metal-clad laminates constituting the double-sided metal-clad laminate of FIG.

The metal-clad laminate of the present invention is a double-sided metal-clad laminate having a structure in which the metal layer (A) / insulating resin layer (B) / insulating resin layer (C) / metal layer (D) are laminated in this order. .. That is, the metal layer (A) and the metal layer (D) are respectively located on the outside, and the insulating resin layer (B) and the insulating resin layer (C) are interposed between them. Here, the insulating resin layer (B) has a resin layer (B1) in contact with the insulating resin layer (C), and the resin layer (B1) contains 1 to 10% by volume of a filler. Further, the insulating resin layer (C) has a resin layer (C1) in contact with the insulating resin layer (B), and the resin layer (C1) contains 1 to 10% by volume of a 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 the configuration of the double-sided metal-clad laminate 100 of the present embodiment. FIG. 2 is a schematic cross-sectional view showing the configurations of the 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 of the present embodiment includes metal layers 101 and 101'as metal layers (A) and metal layers (D), and an insulating resin layer (B) and an insulating resin. The polyimide layers 110 and 110'as the layer (C) are provided. Here, the polyimide layers 110 and 110' include low heat-expandable polyimide layers 102 and 102' as a base layer and thermoplastic polyimide layers 103 and 103' as a resin layer (B1) and a resin layer (C1). It is composed of a plurality of polyimide layers having a laminated structure. Further, the double-sided metal-clad laminate 100 has a structure in which the metal layers 101 and 101'are provided on both surfaces of the polyimide layers 110 and 110'. The low thermal expansion polyimide layers 102, 102'directly adhered to the metal layers 101, 101'and the thermoplastic polyimide layers 103, 103'adhering to the metal layers 101, 101'are both formed by a casting method. The thermoplastic polyimide layers 103 and 103'are bonded at the contact surface 104 to form the double-sided metal-clad laminate 100. The thermoplastic polyimide layers 103 and 103'contain a predetermined amount of the filler 105. The polyimide layers 110 and 110'are not limited to the two-layer structure, respectively, and may be one layer or may have three or more polyimide layers.

In the double-sided metal-clad laminate 100 of the present embodiment, the two single-sided metal-clad laminates 120 and 120'constituting the double-sided metal-clad laminate 100 can be separated by mechanical force. The peel strength (peeling strength) required to separate the double-sided metal-clad laminate 100 into two single-sided metal-clad laminates 120 or 120'is preferably in the range of, for example, 1 to 30 N / m, and further. More preferably, it is in the range of 5 to 20 N / m. If the peel strength is less than 1 N / m, peeling on the contact surface 104 is likely to occur due to a mechanical external force in the FPC manufacturing process. If the peel strength exceeds 30 N / m, it becomes impossible to separate the two single-sided metal-clad laminates 120 or 120', or even if the peeling is possible, the metal-clad laminates are stretched and warped easily during separation. ..

Since the double-sided metal-clad laminate 100 is thicker than the single-sided metal-clad laminate 120 or 120', it is possible to reinforce the rigidity of the single-sided metal-clad laminate 120 or 120'and impart better mechanical properties. it can. Therefore, the double-sided metal-clad laminate 100 is broken or damaged by bending in the FPC processing process including wet process processing such as exposure, development, etching, and plating processing, and processing in a high temperature region such as baking and high-speed pressing. , It is possible to prevent the occurrence of problems such as peeling.

As shown in FIG. 2, the double-sided metal-clad laminate 100 of the present embodiment can be attached / detached from the single-sided metal-clad laminate 120 or 120'having a polyimide layer 110, 110'and a metal layer 101, 101'. It is manufactured by heat-bonding the surfaces 103a and 103a'to each other. When the polyimide layers 110 and 110'in the single-sided metal-clad laminate 120 or 120'consist of two or more layers, the thermoplastic polyimide layers 103 and 103' and the low thermal expansion polyimide layers 102 and 102 are as described above. Can include'. Here, the "thermoplastic polyimide layer" refers to a layer having the thermoplasticity necessary for ensuring the adhesiveness with other polyimide layers at the heat-bonding temperature. The "low thermal expansion polyimide layer" has a linear thermal expansion coefficient of 20 x ^10-6 (1 / K) or less, preferably 1 x ^{10-6 to} 17 x ^10-6 (1 / K). A polyimide layer.

For heat crimping when the polyimide layers 110 and 110'of the two single-sided metal-clad laminates 120 and 120' are bonded together, for example, the following method can be selected. That is, a hydropress, a vacuum type hydropress, an autoclave pressurizing vacuum press, a continuous thermal laminator, or the like can be used. Of these, a continuous thermal laminator that pressurizes using a pair of heating rolls is a more preferable heat crimping method because of its excellent productivity.

The heat crimping temperature (heat pressing temperature) at the time of heat crimping is not particularly limited, but constitutes the thermoplastic polyimide layers 103, 103'located in the outermost layer of the single-sided metal-clad laminates 120, 120'. It is desirable that the temperature is equal to or higher than the glass transition temperature of the thermoplastic polyimide. The hot press pressure is 0.1 to 50 MPa (about 1 to about 500 kg / cm ² ), although it depends on the type of press equipment used. If the press temperature during heat crimping becomes too high, problems such as deterioration of the metal layers 101, 101'and the polyimide layers 110, 110'may occur. Therefore, the glass transition temperature is also relatively low in this respect. It is preferable to bond the plastic polyimide layers 103 and 103'to each other.

<Single-sided metal-clad laminate>
In the production of the single-sided metal-clad laminates 120 and 120', a method of sequentially forming a plurality of polyamic acid resin layers and then imidizing them collectively to form the polyimide layers 110 and 110' is preferable, but the method is limited to this. It is not something that is done. That is, a plurality of polyimide layers may be formed by collectively applying a plurality of polyamic acid resin layers with a multilayer die or the like, drying the resin layers, and then performing imidization by heat treatment collectively. After the resin layers of a plurality of polyamic acids are sequentially applied, they may be dried and imidized all at once. Further, the polyimide layer may be formed one by one by sequentially applying and drying a plurality of polyamic acid resin solutions to imidization. In forming the plurality of polyimide layers, each of these treatments can be arbitrarily combined.

<Metal layer>
It is preferable to use a metal foil for the metal layers 101 and 101'from the viewpoint of adhesiveness, and the metal of the metal foil is copper, aluminum, stainless steel, iron, silver, palladium, nickel, chromium, molybdenum, tungsten, zirconium. , Gold, cobalt, titanium, tantalum, zinc, lead, tin, silicon, bismuth, indium or metals selected from alloys thereof and the like. Copper foil is particularly preferable in terms of conductivity. When the double-sided metal-clad laminate 100 and the single-sided metal-clad laminate 120, 120'of the present embodiment are continuously produced, a metal foil having a predetermined thickness is wound into a roll. A long metal foil is used.

Further, the surface roughness of the surface of the metal layers 101, 101 ′ that is in direct contact with the polyimide layers 110, 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. Further, when 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 the 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 layers (outermost surfaces) of both the two single-sided metal-clad laminates 120 or 120'to be subjected to heat crimping is a filler. It is preferable to contain 105 in the range of 1 to 10% by volume, and more preferably in the 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 adhesive force of the contact surface 104 becomes strong, and the double-sided metal-clad laminate 100 becomes two single-sided metal-clad laminates 120 or 120. At the time of separation into ‘, even if the separation becomes impossible or even if the separation is possible, the single-sided metal-clad laminate 120 or 120 ′ is stretched and warped easily. 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 impaired in appearance, or the adhesion force of the contact surface 104 decreases and the contact is made by a mechanical external force in the FPC manufacturing process. Peeling is likely to occur on the surface 104.

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 contents of the filler 105 are different, the difference in the content of the filler 105 between the thermoplastic polyimide layer 103 and the thermoplastic polyimide layer 103'should be 5% by volume or less from the viewpoint of controlling the adhesive force to the same extent. Is preferable.

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

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

The shape of the filler 105 is preferably spherical rather than crushed from the viewpoint of uniformity of dispersion in the resin. Furthermore, it is more preferable that the average particle size of the filler 105 is 1 to 10 μm. In the present invention, the spherical shape means a true sphere or a rounded particle state having substantially no corners, and the crushed state means a particle state having an arbitrary shape with corners possessed by the crushed particles. Something, which can be confirmed with an electron microscope or another microscope.

<Polyimide>
Next, the polyimides constituting the polyimide layers 110 and 110'will be described. The term polyimide in the present invention means a resin composed of a polymer having an imide group in its molecular structure, such as polyamideimide, polyetherimide, polyesterimide, polysiloxaneimide, and polybenzimidazolimide, 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. It is preferably obtained by reacting an acid anhydride with a diamino compound. By containing 50 mol% or more of BTDA, the peelability between the thermoplastic polyimide layers 103 and 103'is improved, and the single-sided metal-clad laminate 120 or 120'(or circuit-processed one) at the time of separation. Is stretched and the risk of warping is reduced. A more preferred content of BTDA is in the range of 70-100 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) as a diamino component is used, and this is reacted with an acid anhydride. It is preferable that the obtained product is obtained. By containing 50 mol% or more of DAPE, the peelability between the layers of the thermoplastic polyimide layers 103 and 103'is improved, and the single-sided metal-clad laminate 120 or 120'(or circuit-processed one) at the time of separation. ) Is stretched and the risk of warpage is reduced. A more preferred content of DAPE is in the range of 70-100 mol%.

As the diamino compound other than DAPE, an aromatic diamino compound represented by NH _2- Ar1-NH ₂ is preferable. Here, Ar1 is selected from the groups represented by the following formulas, and the substitution position of the amino group is arbitrary, but the p and p'positions are preferable. Ar1 may have a substituent, but preferably does not, or if it does, the substituent is a lower alkyl or lower alkoxy group having 1 to 6 carbon atoms. Only one of these aromatic diamino compounds may be used, or two or more thereof may be used in combination.

Examples of the tetracarboxylic acid compound to be reacted with the diamino compound include aromatic tetracarboxylic acid and its acid anhydride, esterified product, and halide, but aromatic tetracarboxylic acid compound is preferable, and polyamic acid is synthesized. The acid anhydride is preferred in terms of ease. As the aromatic tetracarboxylic acid compound, a compound represented by O (CO) ₂ Ar2 (CO) ₂ O is preferable. Here, Ar @ 2 is preferably a tetravalent aromatic group represented by the following formula, although the substitution position of an acid anhydride group [(CO) 2 _O] is optional, the position of symmetry is preferred. Ar2 may have a substituent, but preferably does not have it, or if it does, the substituent is preferably a lower alkyl group having 1 to 6 carbon atoms. Among the more preferable aromatic tetracarboxylic acid compounds, those other than BTDA include biphenyltetracarboxylic acid anhydride (BPDA), pyromellitic acid anhydride (PMDA), 3,3', 4,4'-diphenylsulfonetetracarboxylic acid. It is preferably an acid dianhydride (DSDA) and a 4,4'-oxydiphthalic acid anhydride (ODPA) or a combination thereof. Only one kind of these tetracarboxylic acid compounds may be used, or two or more kinds may be used in combination.

<Low thermal expansion polyimide>
The polyimide constituting the low thermal expansion polyimide layers 102, 102'is an aromatic diamino compound represented by NH _2- Ar1-NH ₂ as in the case of the polyimide constituting the thermoplastic polyimide layers 103, 103' described above. And the one obtained by reacting with a tetracarboxylic acid compound is preferable. However, the coefficient of linear thermal expansion of the low thermal expansion polyimide layers 102, 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, a compound 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 is preferable. Further, 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 compound as in the case of the polyimide constituting the thermoplastic polyimide layers 103 and 103'described above can be used. A more preferable aromatic tetracarboxylic acid compound for setting the linear thermal expansion coefficient in the range of 20 × 10 ^-6 (1 / K) or less, preferably 1 × 10 ^{-6 to} 17 × 10 ^-6 (1 / K). , Biphenyltetracarboxylic dianhydride (BPDA), pyromellitic dianhydride (PMDA) or a combination thereof.

<Polyimide layer (entire insulating resin layer)>
Regarding the overall coefficient of linear thermal expansion of the polyimide layers 110 and 110'of the two single-sided metal-clad laminates 120 and 120'to be subjected to heat crimping, preferably both polyimide layers 110 and 110' are 15 × ^10-6. It is more preferably 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 coefficient of linear thermal expansion of the polyimide layers 110, 110'is out of the above range, in the step of obtaining the single-sided metal-clad laminate 120, 120', the widthwise end portion of the single-sided metal-clad laminate 120, 120' The warp becomes large, and stable production is likely to be hindered. Furthermore, even in the process of heat-pressing two single-sided metal-clad laminates 120 and 120'to obtain a double-sided metal-clad laminate 100, the warp at the end in the width direction tends to fold inward, which hinders stable production. There is a risk that it will end up.

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

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

Usually, the synthesis of polyamic acid is carried out in a reaction vessel or the like before application to the metal layers 101, 101'. Then, a resin solution of polyamic acid 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, it may be applied on the already formed polyamic acid layer or on the polyimide layer.

As a method for drying and heat imidization treatment, any method such as a batch treatment method or a continuous treatment method can be selected. In the batch processing method, a resin solution of polyamic acid is applied to a long metal foil, and then the laminate is wound into a roll in a non-imidized state in a hot air drying furnace that can be set to a predetermined temperature. This is a method of completing imidization by allowing the resin to stand for a certain period of time and finally heat-treating it at a high temperature of 200 ° C. or higher. In the continuous treatment method, after applying a resin solution of polyamic acid to a long metal foil, it is continuously moved in a drying furnace to secure a predetermined heat treatment time, and finally the temperature is raised to 200 ° C. or higher. This is a method of performing heat treatment.

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

The solvent of the polyamic acid resin is removed and imidized by heating in the drying and imidization treatment steps. At this time, if a rapid heat treatment is performed at a high temperature, a skin layer is formed on the resin surface and the solvent is formed. Is difficult to evaporate and foaming occurs. Therefore, it is preferable to perform the heat treatment while gradually raising the temperature from a low temperature to a high temperature. Further, in the heating imidization step, it is preferable to finally heat-treat at a temperature of 300 to 400 ° C.

The concentration of the polyamic acid resin solution applied to the metal layers 101, 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 as 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 the resin solution can be applied uniformly and smoothly. Because.

As described in detail above, the double-sided metal-clad laminate 100 of the present embodiment is predetermined to the thermoplastic polyimide layers 103 and 103'that form the bonding surface of the two single-sided metal-clad laminates 120 and 120', respectively. Since the filler 105 is contained in the volume ratio of the above, it has an appropriate adhesiveness and is easy to peel off, so that it is possible to prevent the peeling from becoming impossible or the occurrence of warpage after peeling. Since the double-sided metal-clad laminate 100 of the present embodiment can be easily peeled off at the contact surface 104, it is possible to peel off the metal layers 101 and 101'on both sides after simultaneously performing circuit wiring processing. , The efficiency of the FPC manufacturing process can be significantly improved.

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

Hereinafter, embodiments of the present invention will be described in more detail with reference to Examples. Moreover, the superiority of this embodiment will be clarified by showing a comparative example.

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

[Measurement of coefficient of linear thermal expansion]
The polyimide film obtained by etching the copper foil is heated to 250 ° C. using a thermomechanical analyzer manufactured by Seiko Instruments, held at that temperature for 10 minutes, and then cooled at a rate of 5 ° C./min. , The average coefficient of thermal expansion (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 laminating two single-sided flexible copper-clad laminates was cut into a size of 25 mm × 100 mm, and the peel strength was measured by a 180 ° peeling method with a tensile tester.

[Appearance]
The resin surface 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 to be “poor appearance”.

[Measurement of warpage after peeling]
A sheet with a size of 10 cm x 10 cm was prepared from a flexible copper-clad laminate, and when this sheet was placed on the desk, the height of the part that was most raised from the desk surface was measured using a caliper. This was taken as the amount of warpage.

2. Synthesis of polyamic acid resin Synthesis example 1 (without filler):
312.20 g of N, N dimethylacetamide was placed in a reaction vessel equipped with a thermocouple and a stirrer and capable of introducing nitrogen. 14.67 g (0.073 mol) of 4,4'-diaminodiphenyl ether was dissolved in this reaction vessel with stirring in the vessel. Next, 23.13 g (0.072 mol) of 3,3', 4,4'-benzophenonetetracarboxylic dianhydride was added. Then, 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 a value of the apparent viscosity at 25 ° C. by an E-type viscometer (hereinafter, the same applies). The glass transition temperature of the polyimide obtained from the resin solution a of the polyamic acid was 312 ° C., and the coefficient of linear thermal expansion was 45 × 10 ^-6 (1 / K).

Synthesis Example 2 (filler content 1% by volume):
312.20 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 a spherical filler (silica, average particle size 1.2 μm, manufactured by Admatex, “SE4050”; the same applies hereinafter) was added, and the mixture was dispersed by an ultrasonic disperser for 3 hours. 14.67 g (0.073 mol) of 4,4'-diaminodiphenyl ether was dissolved in this solution with stirring in a container. Next, 23.13 g (0.072 mol) of 3,3', 4,4'-benzophenonetetracarboxylic dianhydride was added. Then, 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 resin solution c of polyamic acid was obtained in the same manner as in Synthesis Example 2 except that the amount of the spherical filler was 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 resin solution d of polyamic acid was obtained in the same manner as in Synthesis Example 2 except that the amount of the spherical filler was 10.50 g. The solution viscosity of the polyamic acid resin solution d was 4,100 mPa · s.

Synthesis Example 5 (without filler):
308.00 g of N, N dimethylacetamide was placed in a reaction vessel equipped with a thermocouple and a stirrer and capable of introducing nitrogen. 27.14 g (0.066 mol) of 2,2-bis [4- (4-aminophenoxy) phenyl] propane was dissolved in this reaction vessel with stirring in the vessel. Next, 14.86 g (0.068 mol) of pyromellitic dianhydride was added. Then, 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 the resin solution e of the polyamic acid was 290 ° C., and the coefficient of linear thermal expansion was 55 × 10 ^-6 (1 / K).

Synthesis Example 6 (filler content 1% by volume):
308.00 g of N, N dimethylacetamide was placed in a reaction vessel equipped with a thermocouple and a stirrer and capable of introducing nitrogen. 0.70 g of spherical filler was added to this reaction vessel, and the mixture was dispersed by an ultrasonic disperser for 3 hours. 27.14 g (0.066 mol) of 2,2-bis [4- (4-aminophenoxy) phenyl] propane was dissolved in this solution with stirring in a container. Next, 14.86 g (0.068 mol) of pyromellitic dianhydride was added. Then, 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 resin solution g of polyamic acid was obtained in the same manner as in Synthesis Example 6 except that the amount of the spherical filler was 7.30 g. The solution viscosity of the polyamic acid resin solution g was 3,200 mPa · s.

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

Synthesis example 9
297.50 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, 25.27 g (0.119 mol) of 4,4'-diamino-2,2'dimethylbiphenyl was dissolved with stirring in the vessel. 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. .. Then, stirring was continued for 3 hours to obtain a resin solution i of polyamic acid having a solution viscosity of 21,000 mPa · s. The glass transition temperature of the polyimide obtained from the resin solution i of the polyamic acid was 360 ° C., and the coefficient of linear thermal expansion was 15 × 10 ^-6 (1 / K).

(Example 1)
After uniformly applying the resin solution i of the polyamic acid prepared in Synthesis Example 9 to one side of a long electrolytic copper foil having a thickness of 12 μm (first layer), the solvent was removed by heating and drying 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 is heat-treated in a continuous curing furnace set to start from 130 ° C. and gradually increase the temperature to 300 ° C. over a total time of about 10 minutes to increase the thickness of the polyimide layer. A 25 μm single-sided flexible copper-clad laminate was obtained. Subsequently, the two single-sided flexible copper-clad laminates are laminated with each other on the polyimide layer surfaces, and at the same time, they are continuously supplied between a pair of heating rolls at a speed of 1 m / min and laminated by heating and pressurizing. A double-sided flexible copper-clad laminate was obtained. At this time, the roll surface temperature was 380 ° C., and the linear pressure between the rolls was 134 kN / m. The polyimide layers laminated by heating and pressurizing did not peel off from each other and adhered to 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 of the polyamic acid resin solution c prepared in Synthesis Example 3. The polyimide layers laminated by heating and pressurizing did not peel off from each other and adhered to 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 of the polyamic acid resin solution f prepared in Synthesis Example 6. The polyimide layers laminated by heating and pressurizing did not peel off from each other and adhered to 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 of the polyamic acid resin solution g prepared in Synthesis Example 7. The polyimide layers laminated by heating and pressurizing did not peel off from each other and adhered to 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 of the polyamic acid resin solution a prepared in Synthesis Example 1. The polyimide layers laminated by heating and pressurizing did not peel off from each other and adhered to 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 of the polyamic acid resin solution d prepared in Synthesis Example 4. The polyimide layers laminated by heating and pressurizing were partially peeled off and had insufficient stickability.

(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 of the polyamic acid resin solution e prepared in Synthesis Example 5. The polyimide layers laminated by heating and pressurizing did not peel off from each other and adhered to 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 of the polyamic acid resin solution h prepared in Synthesis Example 8. The polyimide layers laminated by heating and pressurizing were partially peeled off and had insufficient stickability.

The above results are summarized in Table 1.

Although the embodiments of the present invention have been described in detail for the purpose of illustration, the present invention is not limited to the above embodiments.

100 ... Double-sided metal-clad laminate, 101, 101'... Metal layer, 102, 102' ... Low thermal expansion polyimide layer, 103, 103' ... Thermoplastic polyimide layer, 103a, 103a' ... Stickable / peelable surface, 104 ... Contact surface, 105 ... Filler, 110, 110'... Polyimide layer, 120, 120' ... Single-sided metal-clad laminate

Claims (7)

A metal-clad laminate having a metal layer (A) / insulating resin layer (B) / insulating resin layer (C) / metal layer (D).
The insulating resin layer (B) has a resin layer (B1) in contact with the insulating resin layer (C), and the resin layer (B1) contains a filler in the range of 1 to 10% by volume. With
The insulating resin layer (C) has a resin layer (C1) in contact with the insulating resin layer (B), and the resin layer (C1) contains a filler in the range of 1 to 10% by volume. A metal-clad laminate characterized by this. The metal-clad laminate according to claim 1, wherein the difference in filler content between the resin layer (B1) and the resin layer (C1) is 5% by volume or less. The first or second claim, wherein the insulating resin layer (B) and the insulating resin layer (C) 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 peel strength between the insulating resin layer (B) and the insulating resin layer (C) is in the range of 1 to 30 N / m. The metal-clad laminate according to any one of claims 1 to 4, wherein the resin layer (B1) and the resin layer (C1) are formed of polyimide. The metal-clad laminate according to claim 5, wherein 50 mol% or more of the total acid anhydride component constituting the polyimide is 3,3', 4,4'-benzophenone tetracarboxylic dianhydride (BTDA). The metal-clad laminate according to claim 5 or 6, wherein 50 mol% or more of all the diamino components constituting the polyimide is 4,4'-diaminodiphenyl ether (DAPE).

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