JP7428646B2 - Metal-clad laminates and circuit boards - Google Patents

Description

The present invention relates to a metal-clad laminate and a circuit board that can cope with higher frequencies accompanying the miniaturization and higher performance of electronic devices.

In recent years, as electronic devices have become smaller, lighter, and space-saving, flexible printed circuit boards (FPCs) have become thinner, lighter, more flexible, and have superior durability even after repeated bending. ) demand is increasing. FPC can be mounted three-dimensionally and with high density even in a limited space, so its use is expanding to parts such as wiring, cables, and connectors for electronic devices such as HDDs, DVDs, mobile phones, and smartphones. It is being done.

In information processing and communications, efforts are being made to increase the transmission frequency in order to transmit and process large amounts of information, and circuit board materials are required to reduce transmission loss by lowering the dielectricity of the insulating resin layer. ing. Therefore, in order to cope with higher frequencies, FPCs are used in which the dielectric layer is made of liquid crystal polymer, which is characterized by low dielectric constant and low dielectric loss tangent. However, although liquid crystal polymers have excellent dielectric properties, there is room for improvement in heat resistance and adhesion with metal foils, so polyimide is attracting attention as an insulating resin material with excellent heat resistance and adhesion. .

In order to improve the high frequency transmission characteristics of a circuit board, it has been proposed to use polyimide with improved dielectric properties (for example, Patent Documents 1 to 3).

On the other hand, it has also been proposed to produce a double-sided copper-clad laminate in which the thickness of the insulating resin layer is 50 μm or more by bonding the polyimide resin surfaces of two single-sided copper-clad laminates (for example, Patent Documents 4 and 5 ).

Japanese Patent Application Publication No. 2016-193501 Japanese Patent Application Publication No. 2016-192530 International publication WO2018/061727 Patent No. 5886027 Patent No. 6031396

It is expected that the demand for higher frequencies in circuit boards will become stronger in the future, and the level of requirements for high frequency transmission characteristics will become stricter. From this point of view, it becomes necessary to not only improve the dielectric properties of the insulating resin layer but also to increase the thickness of the insulating resin layer. However, in the examples of Patent Documents 1 to 3, the thickness of the insulating resin layer is about 25 μm, and no consideration has been given to increasing the thickness to, for example, more than 50 μm.
On the other hand, Patent Documents 4 and 5 do not consider support for high frequency transmission, nor do they consider the structure of polyimide when a thick insulating resin layer is employed.

An object of the present invention is to provide a metal-clad laminate and a circuit board in which the thickness of an insulating resin layer is sufficiently ensured, and the metal-clad laminate and circuit board are compatible with high-frequency transmission accompanying the improvement in the performance of electronic devices.

The present inventors have found that the above problem can be solved by providing a thick insulating resin layer and considering the dielectric properties of polyimide constituting the insulating resin layer, and have completed the present invention.

That is, the metal-clad laminate of the present invention is a metal-clad laminate including a resin laminate including a plurality of polyimide layers, and a metal layer laminated on at least one side of the resin laminate.
In the metal-clad laminate of the present invention, the resin laminate meets the following conditions i) to iv);
i) The total thickness is within the range of 40 to 200 μm;
ii) comprising a first polyimide layer in contact with the metal layer and a second polyimide layer laminated directly or indirectly on the first polyimide layer;
iii) the ratio of the thickness of the second polyimide layer to the total thickness of the resin laminate is within the range of 70 to 97%;
iv) The following formula (a),
E ₁ =√ε ₁ ×Tanδ ₁ ...(a)
[Here, ε ₁ represents the dielectric constant at 10 GHz measured by a split post dielectric resonator (SPDR), and Tan δ ₁ represents the dielectric loss tangent at 10 GHz measured by a split post dielectric resonator (SPDR). show]
The _E1 value, which is an index indicating dielectric properties, is less than 0.009;
It is characterized by satisfying the following.

In the metal-clad laminate of the present invention, the polyimide constituting the second polyimide layer is a non-thermoplastic polyimide obtained by reacting an acid anhydride component and a diamine component, and the polyimide comprises a tetracarboxylic acid residue and a diamine component. It may contain a residue. In this case, for 100 mole parts of the tetracarboxylic acid residue,
Tetracarboxylic acid residue (BPDA residue) derived from 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) and 1,4-phenylenebis(trimellitic acid monoester) dianhydride At least one type of tetracarboxylic acid residue (TAHQ residue) derived from a compound (TAHQ) and a tetracarboxylic acid residue (PMDA residue) derived from pyromellitic dianhydride (PMDA) and 2,3 ,6,7-Naphthalenetetracarboxylic dianhydride (NTCDA) The total amount of at least one type of tetracarboxylic acid residue (NTCDA residue) may be 80 mole parts or more,
Molar ratio of at least one of the BPDA residue and the TAHQ residue to at least one of the PMDA residue and the NTCDA residue {(BPDA residue + TAHQ residue)/(PMDA residue + NTCDA residue) } may be within the range of 0.4 to 1.5.

In the metal-clad laminate of the present invention, the diamine component contains 80 mol% or more of 4,4'-diamino-2,2'-dimethylbiphenyl (m-TB) based on the total diamine component. Good too.

In the metal-clad laminate of the present invention, the resin laminate has a structure in which at least the first polyimide layer and the second polyimide layer are laminated in this order from the metal layer side, respectively. Good too.

In the metal-clad laminate of the present invention, the resin laminate may have a laminate structure consisting of at least four or more polyimide layers.

The circuit board of the present invention is formed by processing the metal layer of any of the above metal-clad laminates into a wiring circuit.

The metal-clad laminate of the present invention has a resin laminate made of polyimide that is sufficiently thick and has excellent dielectric properties, so it can be suitably used as an electronic material that requires high-speed signal transmission. Can be done.

1 is a schematic cross-sectional view showing the structure of a double-sided copper-clad laminate (double-sided CCL) according to an embodiment of the present invention. FIG. 7 is a schematic cross-sectional view showing the configuration of a modified example of a double-sided CCL. 2 is a diagram illustrating one step of the method for manufacturing the double-sided CCL shown in FIG. 1. FIG.

Embodiments of the present invention will be described below with reference to the drawings as appropriate.

[Metal-clad laminate]
The metal-clad laminate of this embodiment includes a resin laminate including a plurality of polyimide layers, and a metal layer laminated on at least one side of the resin laminate.

<Resin laminate>
The resin laminate satisfies the following conditions i) to iv).

i) The total thickness of the resin laminate is within the range of 40 to 200 μm, preferably within the range of 40 to 180 μm, and more preferably within the range of 50 to 160 μm. If the total thickness of the resin laminate is less than 40 μm, sufficient high frequency transmission characteristics may not be obtained, and if it exceeds 200 μm, problems such as warping may occur. Further, since problems may arise in dimensional stability, flexibility, etc., the total thickness of the resin laminate is preferably 180 μm or less.

ii) The resin laminate includes at least a first polyimide layer in contact with the metal layer and a second polyimide layer laminated directly or indirectly on the first polyimide layer. The polyimide constituting the first polyimide layer is a thermoplastic polyimide, and the polyimide constituting the second polyimide layer is a non-thermoplastic polyimide. The resin laminate preferably has a structure in which at least a first polyimide layer and a second polyimide layer are laminated in this order from the metal layer side. Note that the resin laminate may have any resin layer other than the first polyimide layer and the second polyimide layer. Further, the resin laminate preferably has a layer structure that is symmetrical in the thickness direction with respect to the center in the thickness direction, but may have a layer structure that is asymmetrical in the thickness direction.

iii) In the resin laminate, the ratio of the thickness of the second polyimide layer to the total thickness of the resin laminate is within the range of 70 to 97%, preferably within the range of 75 to 95%. As described later, since the second polyimide layer is a non-thermoplastic polyimide layer having low dielectric properties, the ratio of the thickness of the second polyimide layer to the total thickness of the resin laminate is controlled within the above range. By doing so, circuit boards such as FPCs having excellent high frequency transmission characteristics can be manufactured. If the ratio of the thickness of the second polyimide layer to the total thickness of the resin laminate is less than 70%, the proportion of the non-thermoplastic polyimide layer in the insulating resin layer will be too small, and the dielectric properties may be impaired. If it exceeds 97%, the thermoplastic polyimide layer, which is the first polyimide layer, becomes thinner, so that the adhesion reliability between the resin laminate and the metal layer tends to decrease.

iv) The resin laminate has the following formula (a),
E ₁ =√ε ₁ ×Tanδ ₁ ...(a)
[Here, ε ₁ represents the dielectric constant at 10 GHz measured by a split post dielectric resonator (SPDR), and Tan δ ₁ represents the dielectric loss tangent at 10 GHz measured by a split post dielectric resonator (SPDR). show. Note that √ε ₁ means the square root of ε ₁ . ]
The _E1 value, which is an index indicating dielectric properties, calculated based on Good within range. When the _E1 value is less than 0.009, circuit boards such as FPCs having excellent high frequency transmission characteristics can be manufactured. On the other hand, if the _E1 value exceeds the above upper limit, when used in a circuit board such as an FPC, problems such as electrical signal loss on a high frequency signal transmission path are likely to occur.

In addition, the CTE of the resin laminate as a whole should be controlled within the range of 10 to 30 ppm/K from the viewpoint of suppressing warping and deterioration of dimensional stability when forming a metal-clad laminate. is preferred. In this case, the CTE of the second polyimide layer functioning as a base layer (main layer) in the resin laminate is preferably 1 It is preferably within the range of ~25 ppm/K, more preferably within the range of 10 ~ 20 ppm/K.

(First polyimide layer)
The polyimide constituting the first polyimide layer is a thermoplastic polyimide. The thermoplastic polyimide preferably has a glass transition temperature (Tg) of 360°C or lower, more preferably within the range of 200 to 320°C. Here, thermoplastic polyimide generally refers to polyimide whose glass transition temperature (Tg) can be clearly confirmed. A polyimide having a storage modulus of 1.0×10 ⁹ Pa or more and a storage modulus of less than 3.0×10 ⁸ Pa at 300°C. The resin laminate has one or two first polyimide layers adjacent to one or two metal layers, respectively. In the case of having two first polyimide layers, the constituent polyimides may be of the same type or different types. Note that details of the thermoplastic polyimide will be described later.

(Second polyimide layer)
The polyimide constituting the second polyimide layer is a non-thermoplastic polyimide with low thermal expansion. When having a plurality of second polyimide layers, the polyimides constituting each layer may be of the same type or different types. Here, non-thermoplastic polyimide generally refers to polyimide that does not soften or exhibit adhesive properties even when heated. A polyimide having a storage modulus of 1.0×10 ⁹ Pa or more at 300° C. and a storage modulus of 3.0×10 ⁸ Pa or more at 300° C. Note that details of the non-thermoplastic polyimide will be described later.

<Metal layer>
As the metal layer, metal foil can be preferably used. There are no particular restrictions on the material of the metal foil, but examples include copper, stainless steel, iron, nickel, beryllium, aluminum, zinc, indium, silver, gold, tin, zirconium, tantalum, titanium, lead, magnesium, manganese, and alloys thereof. etc. Among these, copper or copper alloy is particularly preferred. The copper foil may be rolled copper foil or electrolytic copper foil.

The surface of the metal foil used as the metal layer may be subjected to a surface treatment such as rust prevention treatment, siding, aluminum alcoholate, aluminum chelate, or silane coupling agent.

In the metal-clad laminate of this embodiment, the thickness of the metal layer is preferably within the range of 3 to 50 μm, more preferably within the range of 5 to 30 μm, when used for example in the production of FPC. In order to thin the line width, it is most preferably within the range of 5 to 20 μm. The thickness of the metal layer is preferably thicker from the viewpoint of suppressing the increase in conductor loss during high frequency transmission, but on the other hand, if the thickness is too large, it becomes difficult to apply to miniaturization and the flexibility decreases. There is a risk that the adhesiveness between the wiring layer and the insulating resin layer will be impaired when the circuit is processed. Considering such a trade-off relationship, the thickness of the metal layer is preferably within the above range.

In addition, from the viewpoint of achieving both high frequency transmission characteristics and adhesion to the resin laminate, the ten-point average roughness (Rz) of the surface of the metal layer in contact with the first polyimide layer is 1.2 μm or less, and 0.2 μm or less. It is preferably within the range of 0.05 to 1.0 μm. From the same viewpoint, the arithmetic mean height (Ra) of the surface of the metal layer in contact with the first polyimide layer is preferably 0.2 μm or less.

In the metal-clad laminate of this embodiment, commercially available copper foil can be used as the metal layer. Specific examples include copper foil CF-T49A-DS-HD (product name) manufactured by Fukuda Metal Foil and Powder Industries Co., Ltd., copper foil TQ-M4-VSP (product name) manufactured by Mitsui Kinzoku Mining Co., Ltd., and JX Nippon Mining Co., Ltd. Examples include copper foil GHY5-HA-V2 (product name) and BHY(X)-HA-V2 (product name) manufactured by the company.

Next, the structure of the metal-clad laminate of this embodiment will be specifically described with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing the configuration of a double-sided copper-clad laminate (double-sided CCL) 100 according to an embodiment of the present invention. The double-sided CCL 100 includes copper foil layers 10A and 10B as metal layers and a resin laminate 50 as a resin laminate, and has a structure in which the copper foil layers 10A and 10B are laminated on both sides of the resin laminate 50. are doing. Here, the resin laminate 50 is composed of a plurality of polyimide layers, including thermoplastic polyimide layers 20A and 20B as a first polyimide layer, and non-thermoplastic polyimide layers 30A and 30B as a second polyimide layer. and thermoplastic polyimide layers 40A and 40B as a third polyimide layer.

In the double-sided CCL 100, the thermoplastic polyimide layers 20A and 20B are in direct contact with the copper foil layers 10A and 10B, respectively. The thermoplastic polyimide layer 20A and the thermoplastic polyimide layer 20B may have the same thickness or different thicknesses, and the polyimides constituting them may be of the same type or different types.

Further, in the double-sided CCL 100, the non-thermoplastic polyimide layers 30A and 30B may be in contact with the thermoplastic polyimide layers 20A and 20B, respectively, but may not be in direct contact with each other and may be laminated indirectly. The non-thermoplastic polyimide layer 30A and the non-thermoplastic polyimide layer 30B may have the same thickness or different thicknesses, and the polyimides constituting them may be of the same type or different types.

Further, in the double-sided CCL 100, the thermoplastic polyimide layers 40A and 40B are made of thermoplastic polyimide having a glass transition temperature (Tg) of 360° C. or lower, for example, within the range of 200 to 320° C., in order to ensure adhesiveness. It is preferable. The thermoplastic polyimide layers 40A and 40B may be made of the same material as the thermoplastic polyimide layers 20A and 20B. The thermoplastic polyimide layer 40A and the thermoplastic polyimide layer 40B may have the same thickness or different thicknesses, and the polyimides constituting them may be of the same type or different types.

The resin laminate 50 is not limited to the six-layer structure shown in FIG. The resin laminate 50 includes at least the thermoplastic polyimide layers 20A and 20B (first polyimide layer) that are in contact with the copper foil layers 10A and 10B, and the thermoplastic polyimide layers 20A and 20B, respectively, directly or indirectly. It suffices if it includes laminated non-thermoplastic polyimide layers 30A and 30B (second polyimide layer). Therefore, in the case of a double-sided CCL, the resin laminate 50 only needs to include at least four or more polyimide layers. For example, like a double-sided CCL 100A shown in FIG. 2, the resin laminate 50 includes thermoplastic polyimide layers 20A and 20B as a first polyimide layer, and non-thermoplastic polyimide layers 30A and 30B as a second polyimide layer, A five-layer structure including one thermoplastic polyimide layer 40A may be used. Further, the resin laminate 50 may include any layers other than those shown in FIGS. 1 and 2. Although the resin laminate 50 may include resin layers other than the polyimide layer, it is preferable to consist of only a plurality of polyimide layers.

The polyimide layer constituting the resin laminate 50 may contain an inorganic filler, if necessary. Specific examples include silicon dioxide, aluminum oxide, magnesium oxide, beryllium oxide, boron nitride, aluminum nitride, silicon nitride, aluminum fluoride, and calcium fluoride. These can be used alone or in combination of two or more.

The copper foil layers 10A and 10B may have the same thickness and material, or may have different configurations.

<Method for manufacturing metal clad laminates>
The double-sided CCL 100 is preferably manufactured, for example, by the first method or the second method shown below.
(First method)
First, two single-sided copper-clad laminates (single-sided CCL) are prepared. That is, a single-sided copper-clad laminate (single-sided CCL) 70A having a copper foil layer 10A, a thermoplastic polyimide layer 20A, a non-thermoplastic polyimide layer 30A, and a thermoplastic polyimide layer 40A, a copper foil layer 10B, a thermoplastic polyimide layer 20B, A single-sided CCL 70B having a non-thermoplastic polyimide layer 30B and a thermoplastic polyimide layer 40B are respectively produced.
Next, as shown in FIG. 3, the two single-sided CCLs 70A and 70B are arranged with their thermoplastic polyimide layers 40A and 40B facing each other, and the bonding surfaces 60 are thermocompressed using a hot press, thereby producing a double-sided CCL 100. Note that the bonding surface 60 is a thermocompression bonding surface. The two single-sided CCLs 70A and 70B may have exactly the same configuration, or may have different numbers of layers, resin types, metal layers, etc. In addition, when the single-sided CCL 70A, 70B has four or more polyimide layers, a thermoplastic polyimide layer and an adjacent non-thermoplastic polyimide layer are used as a lamination unit, and the lamination unit is alternately repeated. It is preferable to do so.

Each polyimide layer constituting the single-sided CCL 70A, 70B is made by applying a resin solution of polyamic acid, which is a precursor of polyimide, onto the copper foil, which is the raw material for the copper foil layers 10A, 10B, in order to easily control the thickness and physical properties. It is preferable to form by a so-called casting (coating) method in which a coating film is formed by coating and then dried and hardened by heat treatment. In other words, in the single-sided CCL 70A, 70B, the thermoplastic polyimide layers 20A, 20B, the non-thermoplastic polyimide layers 30A, 30B, and the thermoplastic polyimide layers 40A, 40B laminated on the copper foil layers 10A, 10B are all formed by the casting method. Preferably, they are formed sequentially.

In the casting method, a coating film can be formed by applying a polyamic acid resin solution onto a copper foil and then drying it. In forming single-sided CCLs 70A and 70B, it is possible to form the polyamic acid solution by sequentially applying another polyamic acid solution consisting of different constituents on top of the polyamic acid solution, or by applying a polyamic acid solution having the same composition twice. You may apply the above amount. Furthermore, multiple layers of coating films may be laminated simultaneously by multilayer extrusion. Furthermore, it is also possible to once imidize a coating film of polyamic acid to form a single or multiple polyimide layer, and then further apply a resin solution of polyamic acid thereon and then imidize it to form a polyimide layer. . The coating method is not particularly limited, and for example, coating can be performed using a comma, die, knife, lip, or other coater. In this case, the copper foil can be in the form of a cut sheet, a roll, or an endless belt. In order to obtain high productivity, it is efficient to use a roll-like or endless belt-like form to enable continuous production. Furthermore, from the viewpoint of achieving a greater effect of improving the accuracy of the wiring pattern on the circuit board, it is preferable that the copper foil be in the form of a long roll.

The imidization method is not particularly limited, and for example, heat treatment such as heating at a temperature in the range of 80 to 400° C. for a time in the range of 1 to 60 minutes is preferably employed. In order to suppress oxidation of the copper foil layers 10A and 10B, heat treatment is preferably performed in a low oxygen atmosphere. Specifically, heat treatment is performed in an inert gas atmosphere such as nitrogen or rare gas, in a reducing gas atmosphere such as hydrogen, or in a vacuum. It is preferable to do it indoors. By the heat treatment, the polyamic acid in the coating film is imidized to form polyimide.

In the manner described above, single-sided CCLs 70A and 70B having multiple polyimide layers and copper foil layers 10A and 10B can be manufactured. The two single-sided CCLs 70A and 70B thus obtained are arranged so that the surfaces of the thermoplastic polyimide layers 40A and 40B face each other, as shown in FIG. A double-sided CCL 100 can be manufactured. The thermocompression bonding is preferably carried out by forming two single-sided CCLs 70A and 70B into a long length and conveying them in a roll-to-roll manner using a pair of heated rolls. In this case, the conveyance and bonding of the single-sided CCLs are From the viewpoint of performance, it is more preferable to carry out the conveyance speed between the heating rolls within a range of 1 to 10 m/min.

(Second method)
Here, a case will be exemplified in which a single-sided metal-clad laminate (single-sided CCL) or a double-sided metal-clad laminate (double-sided CCL) 100 in which the metal layer is a copper foil layer is manufactured by a casting method.

First, a copper foil (not shown) that will become the copper foil layer 10A is prepared. Then, a resin solution of polyamic acid is applied onto this copper foil and dried to form a first layer coating film. The coating film is a precursor resin layer of thermoplastic polyimide.

Next, a resin solution of polyamic acid is further applied onto the first layer coating film and dried to form a second layer coating film. The second coating film is a non-thermoplastic polyimide precursor resin layer.

Thereafter, while selecting the type of polyamic acid, the third, fourth, fifth, and sixth coating films were sequentially formed in the same manner, and then these were heat-treated to form each precursor. The polyamic acid in the resin layer is imidized. In this way, a single-sided CCL in which a plurality of polyimide layers are laminated is manufactured.

Note that it is also possible to once imidize a single layer or multiple layers of a polyamic acid coating layer to form a single layer or multiple layers of polyimide, and then further form a polyamic acid coating layer thereon.

The single-sided CCL obtained as described above has a structure in which the resin laminate 50 is laminated on the copper foil layer 10A. For example, the resin laminate 50 includes, from the side of the copper foil layer 10A, a thermoplastic polyimide layer 20A, a non-thermoplastic polyimide layer 30A, a thermoplastic polyimide layer 40A, a thermoplastic polyimide layer 40B, a non-thermoplastic polyimide layer 30B, and a thermoplastic polyimide layer 40A. Polyimide layers 20B are laminated in this order.

When the purpose is to manufacture a double-sided CCL 100, thermocompression bonding of copper foil can be further carried out in addition to the above steps.

In the thermocompression bonding process, the copper foil layer 10B is bonded by thermocompression bonding a new copper foil (not shown) to the surface of the single-sided CCL opposite to the copper foil layer 10A (that is, on the thermoplastic polyimide layer 20B). Laminate. As a result, a double-sided CCL 100 having the structure shown in FIG. 1 can be obtained. It is preferable that thermocompression bonding between the new copper foil and the single-sided CCL is carried out while conveying the foil in a roll-to-roll manner using a pair of heating rolls.

In the second method, formation of a coating film by a casting method and imidization can be performed in the same manner as in the first method.

[Polyimide]
Next, preferred polyimides constituting the resin laminate 50 will be explained in the order of non-thermoplastic polyimide and thermoplastic polyimide.

<Non-thermoplastic polyimide>
The non-thermoplastic polyimide constituting the second polyimide layer (non-thermoplastic polyimide layer) contains a tetracarboxylic acid residue and a diamine residue. In the present invention, a tetracarboxylic acid residue refers to a tetravalent group derived from a tetracarboxylic dianhydride, and a diamine residue refers to a divalent group derived from a diamine compound. represents something. The polyimide preferably contains an aromatic tetracarboxylic acid residue derived from an aromatic tetracarboxylic dianhydride and an aromatic diamine residue derived from an aromatic diamine.

(tetracarboxylic acid residue)
The non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer contains 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) and 1,4-phenylenebis(tricarboxylic acid) as tetracarboxylic acid residues. Tetracarboxylic acid residues derived from at least one type of mellitic acid monoester) dianhydride (TAHQ), as well as pyromellitic dianhydride (PMDA) and 2,3,6,7-naphthalenetetracarboxylic dianhydride (NTCDA) contains a tetracarboxylic acid residue derived from at least one type of (NTCDA).

Tetracarboxylic acid residues derived from BPDA (hereinafter also referred to as "BPDA residues") and tetracarboxylic acid residues derived from TAHQ (hereinafter also referred to as "TAHQ residues") maintain order in the polymer. It is easy to form a structure, and by suppressing the movement of molecules, the dielectric loss tangent and hygroscopicity can be lowered. However, on the other hand, the BPDA residue can provide self-supporting properties of the gel film as a polyamic acid of the polyimide precursor, but it also increases the CTE after imidization and lowers the glass transition temperature, resulting in a decrease in heat resistance. become a trend.

From this point of view, the non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer preferably contains a total of BPDA residues and TAHQ residues of 30 or more mole parts per 100 mole parts of the tetracarboxylic acid residue. The content is controlled to be within the range of mol parts or less, more preferably within the range of 40 mol parts or more and 50 mol parts or less. If the total amount of BPDA residues and TAHQ residues is less than 30 mole parts, the formation of an ordered structure of the polymer will be insufficient, resulting in decreased moisture absorption resistance and insufficient reduction of dielectric loss tangent. If it exceeds this, there is a risk that the CTE will increase, the amount of change in in-plane retardation (RO) will increase, and the heat resistance will decrease.

In addition, tetracarboxylic acid residues derived from pyromellitic dianhydride (hereinafter also referred to as "PMDA residues") and tetracarboxylic acid residues derived from 2,3,6,7-naphthalenetetracarboxylic dianhydride Carboxylic acid residues (hereinafter also referred to as "NTCDA residues") have rigidity, so they increase in-plane orientation, keep CTE low, control in-plane retardation (RO), and improve glass transition temperature. It is a residue that plays a role in the regulation of On the other hand, PMDA residues have a small molecular weight, so if their amount is too large, the concentration of imide groups in the polymer will increase, the number of polar groups will increase, and the hygroscopicity will increase, leading to a decrease in the amount of water inside the molecular chain. The effect increases the dielectric loss tangent. Furthermore, NTCDA residues tend to make the film brittle due to the highly rigid naphthalene skeleton and tend to increase the elastic modulus.
Therefore, the non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer preferably contains a total of PMDA residues and NTCDA residues of 40 to 70 mole parts per 100 mole parts of the tetracarboxylic acid residue. The content is within a range of 50 to 60 mole parts, more preferably 50 to 55 mole parts. If the total amount of PMDA residues and NTCDA residues is less than 40 mol parts, CTE may increase or heat resistance may decrease; if it exceeds 70 mol parts, the imide group concentration of the polymer will increase and polarity may increase. There is a risk that the number of groups increases, impairing low hygroscopicity, increasing the dielectric loss tangent, and making the film brittle, resulting in a decrease in self-supporting properties of the film.

Further, the total amount of at least one of BPDA residue and TAHQ residue and at least one of PMDA residue and NTCDA residue is 80 mole parts or more, preferably 90 mole parts or more based on 100 mole parts of the tetracarboxylic acid residue. It is better to be more than 100%.

Further, the molar ratio of at least one of BPDA residue and TAHQ residue to at least one of PMDA residue and NTCDA residue {(BPDA residue + TAHQ residue)/(PMDA residue + NTCDA residue)} is 0. Within the range of 4 or more and 1.5 or less, preferably within the range of 0.6 or more and 1.3 or less, more preferably within the range of 0.8 or more and 1.2 or less, to control the formation of CTE and ordered structure of the polymer. It is good to do.

PMDA and NTCDA have rigid skeletons, so compared to other general acid anhydride components, it is possible to control the in-plane orientation of molecules in polyimide, suppressing the coefficient of thermal expansion (CTE) and improving glass properties. It has the effect of improving the transition temperature (Tg). Furthermore, since BPDA and TAHQ have larger molecular weights than PMDA, increasing the charging ratio reduces the imide group concentration, which is effective in reducing the dielectric loss tangent and moisture absorption rate. On the other hand, when the charging ratio of BPDA and TAHQ increases, the in-plane orientation of molecules in the polyimide decreases, leading to an increase in CTE. Further, the formation of an ordered structure within the molecule progresses, and the haze value increases. From this point of view, the total amount of PMDA and NTCDA to be charged is within the range of 40 to 70 parts by mole, preferably within the range of 50 to 60 parts by mole, based on 100 parts by mole of the total acid anhydride component of the raw material. More preferably, it is within the range of 50 to 55 mole parts. If the total amount of PMDA and NTCDA is less than 40 mol parts per 100 mol parts of the total acid anhydride component of the raw material, the in-plane orientation of the molecules will decrease, making it difficult to lower the CTE, and the Tg As a result, the heat resistance and dimensional stability of the film during heating are reduced. On the other hand, if the total amount of PMDA and NTCDA exceeds 70 mole parts, the moisture absorption rate tends to deteriorate due to an increase in imide group concentration, and the elastic modulus tends to increase.

In addition, BPDA and TAHQ are effective in suppressing molecular movement and lowering the dielectric loss tangent and moisture absorption rate by lowering the imide group concentration, but they increase the CTE of the polyimide film after imidization. From this point of view, the total amount of BPDA and TAHQ to be charged is in the range of 30 to 60 parts by mole, preferably in the range of 40 to 50 parts by mole, based on 100 parts by mole of the total acid anhydride component of the raw material. More preferably, it is within the range of 40 to 45 mole parts.

Tetracarboxylic acid residues other than the above-mentioned BPDA residue, TAHQ residue, PMDA residue, and NTCDA residue contained in the non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer include, for example, 3,3',4 ,4'-diphenylsulfonetetracarboxylic dianhydride, 4,4'-oxydiphthalic anhydride, 2,3',3,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3' -, 2,3,3',4'- or 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 2,3',3,4'-diphenyl ether tetracarboxylic dianhydride, bis (2,3-dicarboxyphenyl)ether dianhydride, 3,3'',4,4''-, 2,3,3'',4''- or 2,2'',3,3' '-p-terphenyltetracarboxylic dianhydride, 2,2-bis(2,3- or 3,4-dicarboxyphenyl)-propane dianhydride, bis(2,3- or 3,4-dicarboxylic dianhydride) carboxyphenyl)methane dianhydride, bis(2,3- or 3,4-dicarboxyphenyl)sulfone dianhydride, 1,1-bis(2,3- or 3,4-dicarboxyphenyl)ethane dianhydride 1,2,7,8-, 1,2,6,7- or 1,2,9,10-phenanthrene-tetracarboxylic dianhydride, 2,3,6,7-anthracenetetracarboxylic dianhydride Anhydride, 2,2-bis(3,4-dicarboxyphenyl)tetrafluoropropane dianhydride, 2,3,5,6-cyclohexane dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride Anhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 4,8-dimethyl-1,2,3,5,6,7-hexahydronaphthalene-1,2,5,6-tetra Carboxylic dianhydride, 2,6- or 2,7-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 2,3,6,7-(or 1,4,5,8 -) Tetrachloronaphthalene-1,4,5,8-(or 2,3,6,7-)tetracarboxylic dianhydride, 2,3,8,9-,3,4,9,10-, 4,5,10,11- or 5,6,11,12-perylene-tetracarboxylic dianhydride, cyclopentane-1,2,3,4-tetracarboxylic dianhydride, pyrazine-2,3, 5,6-tetracarboxylic dianhydride, pyrrolidine-2,3,4,5-tetracarboxylic dianhydride, thiophene-2,3,4,5-tetracarboxylic dianhydride, 4,4'- Examples include tetracarboxylic acid residues derived from aromatic tetracarboxylic dianhydrides such as bis(2,3-dicarboxyphenoxy)diphenylmethane dianhydride and ethylene glycol bisanhydrotrimellitate.

(diamine residue)
The diamine residue contained in the non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer is preferably a diamine residue derived from a diamine compound represented by general formula (A1).

In formula (A1), the linking group X represents a single bond or a divalent group selected from -COO-, and Y independently represents hydrogen, a monovalent hydrocarbon group having 1 to 3 carbon atoms, or an alkoxy group. , n represents an integer of 0 to 2, and p and q independently represent an integer of 0 to 4. Here, "independently" means that in the above formula (A1), the plurality of substituents Y and further the integers p and q may be the same or different. In the above formula (A1), the hydrogen atoms in the two terminal amino groups may be substituted, for example -NR ₃ R ₄ (here, R ₃ and R ₄ independently represent an alkyl group, etc.). (meaning any substituent).

The diamine compound represented by general formula (A1) (hereinafter sometimes referred to as "diamine (A1)") is an aromatic diamine having at least one benzene ring. Since diamine (A1) has a rigid structure, it has the effect of imparting an ordered structure to the entire polymer. Therefore, a polyimide with low gas permeability and low hygroscopicity can be obtained, and the moisture inside the molecular chain can be reduced, so that the dielectric loss tangent can be lowered. Here, the linking group X is preferably a single bond.

Examples of the diamine (A1) include 1,4-diaminobenzene (p-PDA; paraphenylenediamine), 2,2'-dimethyl-4,4'-diaminobiphenyl (m-TB), 2,2'- Examples include n-propyl-4,4'-diaminobiphenyl (m-NPB) and 4-aminophenyl-4'-aminobenzoate (APAB). Among these, most preferred is 2,2'-dimethyl-4,4'-diaminobiphenyl (m-TB), which has a large effect of imparting an ordered structure to the entire polymer due to its rigid structure.

The non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer contains diamine residues derived from diamine (A1), preferably at least 80 moles, more preferably 85 moles, per 100 moles of the diamine residues. It is preferable to contain more than 1 part. By using diamine (A1) in an amount within the above range, an ordered structure is easily formed throughout the polymer due to the rigid structure derived from the monomer, resulting in low gas permeability, low hygroscopicity, and low dielectric loss tangent. Non-thermoplastic polyimide is easily obtained.

Furthermore, when the amount of diamine residues derived from diamine (A1) is within the range of 80 parts by mole to 85 parts by mole with respect to 100 parts by mole of diamine residues in the non-thermoplastic polyimide, it is more rigid. From the viewpoint of having a structure with excellent in-plane orientation, it is preferable to use 1,4-diaminobenzene as the diamine (A1).

Examples of other diamine residues contained in the non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer include 2,2-bis-[4-(3-aminophenoxy)phenyl]propane, bis[4-(3-aminophenoxy)phenyl]propane, and bis[4-(3-aminophenoxy)phenyl]propane. -aminophenoxy)phenyl] sulfone, bis[4-(3-aminophenoxy)biphenyl, bis[1-(3-aminophenoxy)]biphenyl, bis[4-(3-aminophenoxy)phenyl]methane, bis[4 -(3-aminophenoxy)phenyl]ether, bis[4-(3-aminophenoxy)]benzophenone, 9,9-bis[4-(3-aminophenoxy)phenyl]fluorene, 2,2-bis-[4 -(4-aminophenoxy)phenyl]hexafluoropropane, 2,2-bis-[4-(3-aminophenoxy)phenyl]hexafluoropropane, 3,3'-dimethyl-4,4'-diaminobiphenyl, 4 ,4'-methylenedi-o-toluidine, 4,4'-methylenedi-2,6-xylidine, 4,4'-methylene-2,6-diethylaniline, 3,3'-diaminodiphenylethane, 3,3' -diaminobiphenyl, 3,3'-dimethoxybenzidine, 3,3''-diamino-p-terphenyl, 4,4'-[1,4-phenylenebis(1-methylethylidene)]bisaniline, 4,4' -[1,3-phenylenebis(1-methylethylidene)]bisaniline, bis(p-aminocyclohexyl)methane, bis(p-β-amino-t-butylphenyl)ether, bis(p-β-methyl-δ) -aminopentyl)benzene, p-bis(2-methyl-4-aminopentyl)benzene, p-bis(1,1-dimethyl-5-aminopentyl)benzene, 1,5-diaminonaphthalene, 2,6-diamino Naphthalene, 2,4-bis(β-amino-t-butyl)toluene, 2,4-diaminotoluene, m-xylene-2,5-diamine, p-xylene-2,5-diamine, m-xylylenediamine , p-xylylenediamine, 2,6-diaminopyridine, 2,5-diaminopyridine, 2,5-diamino-1,3,4-oxadiazole, piperazine, 2'-methoxy-4,4'-diamino Aromas such as benzanilide, 4,4'-diaminobenzanilide, 1,3-bis[2-(4-aminophenyl)-2-propyl]benzene, 6-amino-2-(4-aminophenoxy)benzoxazole, etc. Diamine residues derived from group diamine compounds, diamines derived from aliphatic diamine compounds such as dimer acid type diamines in which the two terminal carboxylic acid groups of dimer acid are substituted with primary aminomethyl groups or amino groups. Examples include residues.

In non-thermoplastic polyimide, thermal expansion can be controlled by selecting the types of the above-mentioned tetracarboxylic acid residues and diamine residues, and the molar ratio of two or more types of tetracarboxylic acid residues or diamine residues. Modulus, storage modulus, tensile modulus, etc. can be controlled. In addition, when non-thermoplastic polyimide has multiple polyimide structural units, they may exist as blocks or randomly, but from the viewpoint of suppressing variations in in-plane retardation (RO), random Preferably, it exists in

In addition, by making both the tetracarboxylic acid residue and the diamine residue contained in the non-thermoplastic polyimide aromatic groups, the dimensional accuracy of the polyimide film in a high-temperature environment is improved, and in-plane retardation (RO) is improved. This is preferable because the amount of change in can be reduced.

The imide group concentration of the non-thermoplastic polyimide is preferably 33% by weight or less. Here, "imide group concentration" means the value obtained by dividing the molecular weight of the imide group (-(CO) ₂ -N-) in polyimide by the molecular weight of the entire polyimide structure. When the imide group concentration exceeds 33% by weight, the molecular weight of the resin itself decreases, and the low hygroscopicity also deteriorates due to the increase in polar groups. By selecting the combination of the above acid anhydride and diamine compound, the orientation of the molecules in the non-thermoplastic polyimide can be controlled, thereby suppressing the increase in CTE due to a decrease in the imide group concentration and ensuring low hygroscopicity. ing.

The weight average molecular weight of the non-thermoplastic polyimide is, for example, preferably within the range of 10,000 to 400,000, more preferably within the range of 50,000 to 350,000. When the weight average molecular weight is less than 10,000, the strength of the film decreases and tends to become brittle. On the other hand, if the weight average molecular weight exceeds 400,000, the viscosity increases excessively and defects such as uneven thickness and streaks tend to occur in the film during coating operations.

<Thermoplastic polyimide>
The thermoplastic polyimide constituting the first polyimide layer (thermoplastic polyimide layer) contains a tetracarboxylic acid residue and a diamine residue, and contains an aromatic tetracarboxylic acid derived from an aromatic tetracarboxylic dianhydride. Preferably, it contains an acid residue and an aromatic diamine residue derived from an aromatic diamine.

(tetracarboxylic acid residue)
As the tetracarboxylic acid residue used in the thermoplastic polyimide constituting the thermoplastic polyimide layer, use the same ones as those exemplified as the tetracarboxylic acid residue in the non-thermoplastic polyimide constituting the above-mentioned non-thermoplastic polyimide layer. Can be done.

(diamine residue)
The diamine residues contained in the thermoplastic polyimide constituting the thermoplastic polyimide layer are preferably diamine residues derived from diamine compounds represented by general formulas (B1) to (B7).

In formulas (B1) to (B7), R ₁ independently represents a monovalent hydrocarbon group or alkoxy group having 1 to 6 carbon atoms, and the linking group A independently represents -O-, -S-, -CO- , -SO-, -SO ₂ -, -COO-, -CH ₂ -, -C(CH ₃ ) ₂ -, -NH- or -CONH-, and n ₁ is independently Indicates an integer from 0 to 4. However, from equation (B3), those that overlap with equation (B2) are excluded, and from equation (B5), those that overlap with equation (B4) are excluded. Here, "independently" means that in one or more of the above formulas (B1) to (B7), a plurality of linking groups A, a plurality of R ₁ or a plurality of n ₁ are the same. It means that it can be the same or different. In addition, in the above formulas (B1) to (B7), the hydrogen atoms in the two terminal amino groups may be substituted, for example, -NR ₃ R ₄ (here, R ₃ and R ₄ are independently may be any substituent such as an alkyl group).

The diamine represented by formula (B1) (hereinafter sometimes referred to as "diamine (B1)") is an aromatic diamine having two benzene rings. This diamine (B1) has an amino group directly connected to at least one benzene ring and a divalent linking group A in the meta position, which increases the degree of freedom of the polyimide molecular chain and has high flexibility. It is thought that this contributes to improving the flexibility of polyimide molecular chains. Therefore, the use of diamine (B1) increases the thermoplasticity of polyimide. Here, as the linking group A, -O-, -CH ₂ -, -C(CH ₃ ) ₂ -, -CO-, -SO ₂ -, and -S- are preferable.

Examples of the diamine (B1) include 3,3'-diaminodiphenylmethane, 3,3'-diaminodiphenylpropane, 3,3'-diaminodiphenyl sulfide, 3,3'-diaminodiphenylsulfone, 3,3'-diamino Diphenyl ether, 3,4'-diaminodiphenyl ether, 3,4'-diaminodiphenylmethane, 3,4'-diaminodiphenylpropane, 3,4'-diaminodiphenyl sulfide, 3,3'-diaminobenzophenone, (3,3'- Bisamino)diphenylamine and the like can be mentioned.

The diamine represented by formula (B2) (hereinafter sometimes referred to as "diamine (B2)") is an aromatic diamine having three benzene rings. This diamine (B2) has an amino group directly connected to at least one benzene ring and a divalent linking group A in the meta position, which increases the degree of freedom of the polyimide molecular chain and has high flexibility. It is thought that this contributes to improving the flexibility of polyimide molecular chains. Therefore, the use of diamine (B2) increases the thermoplasticity of polyimide. Here, the linking group A is preferably -O-.

Examples of the diamine (B2) include 1,4-bis(3-aminophenoxy)benzene, 3-[4-(4-aminophenoxy)phenoxy]benzenamine, 3-[3-(4-aminophenoxy)phenoxy] Examples include benzeneamine and the like.

The diamine represented by formula (B3) (hereinafter sometimes referred to as "diamine (B3)") is an aromatic diamine having three benzene rings. This diamine (B3) has two divalent linking groups A that are directly connected to one benzene ring and are located in the meta position of each other, which increases the degree of freedom of the polyimide molecular chain and has high flexibility. It is thought that this contributes to improving the flexibility of polyimide molecular chains. Therefore, the use of diamine (B3) increases the thermoplasticity of polyimide. Here, the linking group A is preferably -O-.

Examples of the diamine (B3) include 1,3-bis(4-aminophenoxy)benzene (TPE-R), 1,3-bis(3-aminophenoxy)benzene (APB), 4,4'-[2- Methyl-(1,3-phenylene)bisoxy]bisaniline, 4,4'-[4-methyl-(1,3-phenylene)bisoxy]bisaniline, 4,4'-[5-methyl-(1,3-phenylene) )bisoxy]bisaniline and the like.

The diamine represented by formula (B4) (hereinafter sometimes referred to as "diamine (B4)") is an aromatic diamine having four benzene rings. This diamine (B4) has high flexibility because the amino group directly connected to at least one benzene ring and the divalent linking group A are in the meta position, and it can improve the flexibility of the polyimide molecular chain. It is thought that this contributes. Therefore, the use of diamine (B4) increases the thermoplasticity of polyimide. Here, as the linking group A, -O-, -CH ₂ -, -C(CH ₃ ) ₂ -, -SO ₂ -, -CO-, and -CONH- are preferable.

Diamines (B4) include bis[4-(3-aminophenoxy)phenyl]methane, bis[4-(3-aminophenoxy)phenyl]propane, bis[4-(3-aminophenoxy)phenyl]ether, bis Examples include [4-(3-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)]benzophenone, and bis[4,4'-(3-aminophenoxy)]benzanilide.

The diamine represented by formula (B5) (hereinafter sometimes referred to as "diamine (B5)") is an aromatic diamine having four benzene rings. This diamine (B5) has two divalent linking groups A that are directly connected to at least one benzene ring and are located in meta positions, so that the degree of freedom of the polyimide molecular chain increases and it has high flexibility. It is thought that this contributes to improving the flexibility of polyimide molecular chains. Therefore, the use of diamine (B5) increases the thermoplasticity of polyimide. Here, the linking group A is preferably -O-.

Examples of the diamine (B5) include 4-[3-[4-(4-aminophenoxy)phenoxy]phenoxy]aniline, 4,4'-[oxybis(3,1-phenyleneoxy)]bisaniline, etc. .

The diamine represented by formula (B6) (hereinafter sometimes referred to as "diamine (B6)") is an aromatic diamine having four benzene rings. This diamine (B6) has high flexibility because it has at least two ether bonds, and is thought to contribute to improving the flexibility of the polyimide molecular chain. Therefore, the use of diamine (B6) increases the thermoplasticity of polyimide. Here, as the linking group A, -C(CH ₃ ) ₂ -, -O-, -SO ₂ -, and -CO- are preferable.

Examples of the diamine (B6) include 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), bis[4-(4-aminophenoxy)phenyl]ether (BAPE), and bis[4-aminophenoxy)phenyl]ether (BAPE). Examples include -(4-aminophenoxy)phenyl]sulfone (BAPS), bis[4-(4-aminophenoxy)phenyl]ketone (BAPK), and the like.

The diamine represented by formula (B7) (hereinafter sometimes referred to as "diamine (B7)") is an aromatic diamine having four benzene rings. Since this diamine (B7) has divalent linking groups A with high flexibility on both sides of the diphenyl skeleton, it is thought that it contributes to improving the flexibility of the polyimide molecular chain. Therefore, the use of diamine (B7) increases the thermoplasticity of polyimide. Here, the linking group A is preferably -O-.

Examples of the diamine (B7) include bis[4-(3-aminophenoxy)]biphenyl, bis[4-(4-aminophenoxy)]biphenyl, and the like.

The thermoplastic polyimide constituting the thermoplastic polyimide layer contains 60 moles of diamine residues derived from at least one diamine compound selected from diamines (B1) to diamines (B7) per 100 moles of diamine residues. The content is preferably in the range of 60 to 99 mole parts, more preferably in the range of 70 to 95 mole parts. Since diamines (B1) to diamines (B7) have flexible molecular structures, the flexibility of the polyimide molecular chain can be improved by using at least one diamine compound selected from these in an amount within the above range. It is possible to impart thermoplasticity to the material. If the total amount of diamine (B1) to diamine (B7) is less than 60 parts by mole based on 100 parts by mole of all diamine components, the polyimide resin will lack flexibility and sufficient thermoplasticity will not be obtained.

Further, as the diamine residue contained in the thermoplastic polyimide constituting the thermoplastic polyimide layer, a diamine residue derived from a diamine compound represented by general formula (A1) is also preferable. The diamine compound represented by formula (A1) [diamine (A1)] is as described in the description of the non-thermoplastic polyimide. Since diamine (A1) has a rigid structure and has the effect of imparting an ordered structure to the entire polymer, it can reduce the dielectric loss tangent and hygroscopicity by suppressing the movement of molecules. Furthermore, by using it as a raw material for thermoplastic polyimide, a polyimide with low gas permeability and excellent long-term heat-resistant adhesive properties can be obtained.

The thermoplastic polyimide constituting the thermoplastic polyimide layer contains diamine residues derived from diamine (A1), preferably in a range of 1 to 40 mole parts, more preferably 5 to 30 mole parts. It may be contained within the range of. By using diamine (A1) in an amount within the above range, an ordered structure is formed in the entire polymer due to the rigid structure derived from the monomer, so it has low gas permeability and hygroscopicity, and has a long-term life. A polyimide with excellent heat-resistant adhesive properties can be obtained.

The thermoplastic polyimide constituting the thermoplastic polyimide layer may contain diamine residues derived from diamine compounds other than diamine (A1) and (B1) to (B7) to the extent that the effects of the invention are not impaired.

In thermoplastic polyimide, the coefficient of thermal expansion can be adjusted by selecting the types of the above-mentioned tetracarboxylic acid residues and diamine residues, and the molar ratio of two or more types of tetracarboxylic acid residues or diamine residues. , tensile modulus, glass transition temperature, etc. can be controlled. Furthermore, when the thermoplastic polyimide has a plurality of polyimide structural units, they may exist as blocks or randomly, but it is preferable that they exist randomly.

In addition, by making both the tetracarboxylic acid residue and the diamine residue contained in the thermoplastic polyimide aromatic groups, the dimensional accuracy of the polyimide film in a high-temperature environment is improved, and the in-plane retardation (RO) is reduced. The amount of change can be suppressed.

The imide group concentration of the thermoplastic polyimide is preferably 33% by weight or less. Here, "imide group concentration" means the value obtained by dividing the molecular weight of the imide group (-(CO) ₂ -N-) in polyimide by the molecular weight of the entire polyimide structure. When the imide group concentration exceeds 33% by weight, the molecular weight of the resin itself decreases, and the low hygroscopicity also deteriorates due to the increase in polar groups. By selecting a combination of the diamine compounds described above, the orientation of molecules in the thermoplastic polyimide is controlled, thereby suppressing an increase in CTE due to a decrease in imide group concentration and ensuring low hygroscopicity.

The weight average molecular weight of the thermoplastic polyimide is, for example, preferably within the range of 10,000 to 400,000, more preferably within the range of 50,000 to 350,000. When the weight average molecular weight is less than 10,000, the strength of the film decreases and tends to become brittle. On the other hand, if the weight average molecular weight exceeds 400,000, the viscosity increases excessively and defects such as uneven film thickness and streaks tend to occur during coating operations.

The thermoplastic polyimide constituting the thermoplastic polyimide layer becomes, for example, an adhesive layer in an insulating resin of a circuit board, and therefore a completely imidized structure is most preferable in order to suppress copper diffusion. However, a part of the polyimide may be an amic acid. The imidization rate was determined to be around 1015 cm ^-1 by measuring the infrared absorption spectrum of the polyimide thin film by the single reflection ATR method using a Fourier transform infrared spectrophotometer (commercial product: JASCO Corporation FT/IR620). It is calculated from the absorbance of C═O stretching derived from the imide group at 1780 cm ⁻¹ based on the benzene ring absorber.

(Synthesis of polyimide)
The polyimide constituting the resin laminate 50 can be produced by reacting the acid anhydride and diamine in a solvent to produce a precursor resin, and then ring-closing the precursor resin by heating. For example, a polyimide precursor can be obtained by dissolving an acid anhydride component and a diamine component in approximately equal moles in an organic solvent and stirring at a temperature within the range of 0 to 100°C for 30 minutes to 24 hours to cause a polymerization reaction. Polyamic acid is obtained. In the reaction, the reaction components are dissolved in the organic solvent so that the amount of the precursor to be produced is within the range of 5 to 30% by weight, preferably within the range of 10 to 20% by weight. Examples of organic solvents used in the polymerization reaction include N,N-dimethylformamide, N,N-dimethylacetamide (DMAC), N-methyl-2-pyrrolidone, 2-butanone, dimethylsulfoxide , dimethyl sulfate, cyclohexanone, and dioxane. , tetrahydrofuran, diglyme, triglyme, etc. Two or more of these solvents can be used in combination, and aromatic hydrocarbons such as xylene and toluene can also be used in combination. In addition, the amount of such an organic solvent to be used is not particularly limited, but the amount used is such that the concentration of the polyamic acid solution (polyimide precursor solution) obtained by the polymerization reaction is about 5 to 30% by weight. It is preferable to use it after adjusting it to .

In the synthesis of polyimide, each of the above acid anhydrides and diamines may be used alone or in combination of two or more thereof. Thermal expansion properties, adhesive properties, glass transition temperature, etc. can be controlled by selecting the types of acid anhydrides and diamines and the molar ratio of each when using two or more types of acid anhydrides or diamines. .

It is usually advantageous to use the synthesized precursor as a reaction solvent solution, but it can be concentrated, diluted, or replaced with another organic solvent if necessary. Further, since precursors generally have excellent solvent solubility, they are advantageously used. The method for imidizing the precursor is not particularly limited, and for example, heat treatment such as heating in the above-mentioned solvent at a temperature in the range of 80 to 400° C. for 1 to 24 hours is preferably employed.

<Circuit board>
The circuit board of this embodiment can be manufactured by processing the metal layer of a metal-clad laminate into a pattern by a conventional method to form a wiring layer. Patterning of the metal layer can be performed by any method using, for example, photolithography and etching.

Incidentally, steps that are normally performed when manufacturing a circuit board, such as through-hole processing in the previous process, terminal plating, and external shape processing in the subsequent process, can be performed according to conventional methods.

As described above, the metal-clad laminate of this embodiment can provide excellent impedance matching to the circuit board and improve electrical signal transmission characteristics by using it as a material for a circuit board typified by FPC. Therefore, the reliability of electronic equipment can be improved.

Examples are shown below to explain the features of the present invention more specifically. However, the scope of the present invention is not limited to the examples. In addition, in the following examples, various measurements and evaluations are as follows unless otherwise specified.

[Measurement of viscosity]
The viscosity was measured at 25° C. using an E-type viscometer (manufactured by Brookfield, trade name: DV-II+Pro). The rotational speed was set so that the torque was 10% to 90%, and the value was read when the viscosity stabilized 2 minutes after starting the measurement.

[Measurement of glass transition temperature (Tg)]
The glass transition temperature was determined by heating a polyimide film with a size of 5 mm x 20 mm from 30°C to 400°C using a dynamic viscoelasticity analyzer (DMA: manufactured by UBM, trade name: E4000F). Measurement was performed at 4° C./min and a frequency of 1 Hz, and the temperature at which the change in elastic modulus (tan δ) was maximum was defined as the glass transition temperature. In addition, "thermoplastic" means that the storage elastic modulus at 30°C measured using DMA is 1.0 x 10 ⁹ Pa or more and the storage elastic modulus at 300°C is less than 3.0 x 10 ⁸ Pa. Those exhibiting a storage modulus of 1.0×10 ⁹ Pa or more at 30° C. and a storage modulus of 3.0×10 ⁸ Pa or more at 300° C. were defined as “non-thermoplastic.”

[Measurement of coefficient of thermal expansion (CTE)]
A polyimide film with a size of 3 mm x 20 mm was heated from 30° C. to 265° C. at a constant heating rate while applying a load of 5.0 g using a thermomechanical analyzer (manufactured by Bruker, trade name: 4000SA). After further holding at that temperature for 10 minutes, it was cooled at a rate of 5°C/min, and the average coefficient of thermal expansion (coefficient of thermal expansion) from 250°C to 100°C was determined.

[Measurement of moisture absorption rate]
Two polyimide film test pieces (width 4 cm x length 25 cm) were prepared and dried at 80° C. for 1 hour. Immediately after drying, the sample was placed in a constant temperature and humidity chamber at 23° C./50% RH, left to stand for 24 hours or more, and the weight change before and after was determined using the following formula.
Moisture absorption rate (weight%) = [(weight after moisture absorption - weight after drying) / weight after drying] x 100

[Measurement of dielectric constant and dielectric loss tangent]
The dielectric constant and dielectric loss tangent are determined by calculating the dielectric constant (ε ₁ ) of the resin sheet (resin sheet after curing) at a frequency of 10 GHz using a vector network analyzer (manufactured by Agilent, trade name: Vector Network Analyzer E8363C) and an SPDR resonator. and dielectric loss tangent (Tan δ ₁ ) were measured. The resin sheet used in the measurement was left for 24 hours at a temperature of 24 to 26°C and a humidity of 45 to 55%.
Further, _E1 , which is an index indicating the dielectric properties of the resin laminate, was calculated based on the above formula (a).

[Measurement of surface roughness of copper foil]
Measurement of ten-point average roughness (Rz) and arithmetic average height (Ra):
It was determined using a stylus type surface roughness meter (manufactured by Kosaka Laboratory Co., Ltd., trade name: Surfcorder ET-3000) under the following measurement conditions: Force: 100 μN, Speed: 20 μm, Range: 800 μm. Note that the surface roughness was calculated by a method based on JIS-B0601:1994.

[Measurement of peel strength]
After processing the metal-clad laminate to a width of 1.0 mm, it was cut into 8 cm width x 4 cm length to prepare measurement samples. Using a Tensilon tester (manufactured by Toyo Seiki Seisakusho, product name: Strograph VE-1D), one side of the measurement sample was fixed to an aluminum plate with double-sided tape, and the other side was rotated at 50 mm/min in a 90° direction. The central strength was determined when the sample was peeled off by 10 mm at the same speed. "Copper foil peel strength" is the peel strength when peeling at the interface between the copper foil layer on the cast side and the resin laminate, and "peel strength on the thermocompression bonded side" is the peel strength of the two resin layers bonded by thermocompression. This is the peel strength when the bonded surface is peeled off.

Abbreviations used in the synthesis examples indicate the following compounds.
BTDA: 3,3',4,4'-benzophenonetetracarboxylic dianhydride PMDA: Pyromellitic dianhydride BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride DSDA: 3, 3',4,4'-diphenylsulfone tetracarboxylic dianhydride DAPE: 4,4'-diaminodiphenyl ether BAPP: 2,2-bis[4-(4-aminophenoxy)phenyl]propane m-TB: 2, 2'-dimethyl-4,4'-diaminobiphenyl TPE-R: 1,3-bis(4-aminophenoxy)benzene DMAc: N,N-dimethylacetamide

(Synthesis example 1)
312 g of DMAc was placed in a reaction vessel equipped with a thermocouple and a stirrer and capable of introducing nitrogen. 14.67 g of DAPE (0.073 mol) was dissolved in this solvent in a vessel with stirring. Next, 23.13 g of BTDA (0.072 mol) was added. Thereafter, stirring was continued for 3 hours to prepare a polyamic acid resin solution a having a solution viscosity of 2,960 mPa·s.
Next, polyamic acid resin solution a was evenly applied to one side (Rz; 2.1 μm) of a 12 μm thick electrolytic copper foil so that the thickness after curing would be approximately 25 μm, and then heated and dried at 120°C. and the solvent was removed. Furthermore, stepwise heat treatment was performed from 120° C. to 360° C. within 30 minutes to complete imidization. A polyimide film a (thermoplastic, Tg: 283° C., CTE: 53 ppm/K, moisture absorption: 1.30% by weight) was prepared by etching away the copper foil using an aqueous ferric chloride solution.

(Synthesis example 2)
312 g of DMAc was placed in a reaction vessel equipped with a thermocouple and a stirrer and capable of introducing nitrogen. 6.60 g of spherical filler (silica, average particle size 1.2 μm, manufactured by Admatex, “SE4050”) was added to this reaction container, and dispersed for 3 hours using an ultrasonic dispersion device. 14.67 g of DAPE (0.073 mol) was dissolved in this solution with stirring in a container. Next, 23.13 g of BTDA (0.072 mol) was added. Thereafter, stirring was continued for 3 hours to prepare a polyamic acid resin solution b (silica content: 10% by volume) having a solution viscosity of 3,160 mPa·s.

(Synthesis example 3)
308 g of DMAc was placed in a reaction vessel equipped with a thermocouple and a stirrer and capable of introducing nitrogen. 27.14 g of BAPP (0.066 mol) was dissolved in this solvent with stirring in a container. Next, 14.86 g of PMDA (0.068 mol) was added. Thereafter, stirring was continued for 3 hours to prepare a polyamic acid resin solution c having a solution viscosity of 2,850 mPa·s. Polyimide film c (thermoplastic, Tg: 312°C, CTE: 55 ppm/K, moisture absorption: 0.54% by weight) was prepared in the same manner as in Synthesis Example 1 using resin solution c.

(Synthesis example 4)
308 g of DMAc was placed in a reaction vessel equipped with a thermocouple and a stirrer and capable of introducing nitrogen. 22.57 g of m-TB (0.106 mol) was dissolved in this solvent with stirring in a container. Next, 6.20 g of BPDA (0.021 mol) and 18.37 g of PMDA (0.084 mol) were added. Thereafter, stirring was continued for 3 hours to prepare a polyamic acid resin solution d having a solution viscosity of 20,000 mPa·s. Polyimide film d (non-thermoplastic, Tg: 385°C, CTE: 15 ppm/K) was prepared in the same manner as in Synthesis Example 1 using resin solution d.

(Synthesis example 5)
255 g of DMAc was placed in a reaction vessel equipped with a thermocouple and a stirrer and capable of introducing nitrogen. 22.13 g of TPE-R (0.076 mol) was dissolved in this solvent with stirring in a container. Next, 16.17 g DSDA (0.047 mol) and 6.78 g PMDA (0.031 mol) were added. Thereafter, stirring was continued for 2 hours to prepare a polyamic acid resin solution e having a solution viscosity of 2,640 mPa·s. Polyimide film e (thermoplastic, Tg: 277°C, CTE: 61 ppm/K, moisture absorption: 0.90% by weight) was prepared in the same manner as in Synthesis Example 1 using resin solution e.

(Synthesis example 6)
200 g of DMAc was placed in a reaction vessel equipped with a thermocouple and a stirrer and capable of introducing nitrogen. In this solvent, 1.335 g of m-TB (0.0063 mol) and 10.414 g of TPE-R (0.0356 mol) were dissolved in a vessel with stirring. Next, 0.932 g PMDA (0.0043 mol) and 11.319 g BPDA (0.0385 mol) were added. Thereafter, stirring was continued for 2 hours to prepare a polyamic acid resin solution f having a solution viscosity of 1,420 mPa·s. Polyimide film f (thermoplastic, Tg: 220°C, CTE: 52 ppm/K, moisture absorption: 0.36% by weight) was prepared using resin solution f in the same manner as in Synthesis Example 1.

(Synthesis example 7)
250 g of DMAc was placed in a reaction vessel equipped with a thermocouple and a stirrer and capable of introducing nitrogen. 12.323 g of m-TB (0.0580 mol) and 1.886 g of TPE-R (0.0064 mol) were dissolved in this solvent with stirring in a container. Next, 8.314 g PMDA (0.0381 mol) and 7.477 g BPDA (0.0254 mol) were added. Thereafter, stirring was continued for 3 hours to prepare a polyamic acid resin solution g having a solution viscosity of 31,500 mPa·s. Polyimide film g (non-thermoplastic, Tg: 303°C, CTE: 15.6 ppm/K, moisture absorption: 0.61% by weight) was prepared in the same manner as in Synthesis Example 1 using resin solution g.

[Example 1]
After applying resin solution f uniformly on the surface of a long electrolytic copper foil (Rz: 0.8 μm, Ra: 0.2 μm) so that the thickness after curing is approximately 2 to 3 μm, it was heated at 120 ° C. Dry and remove solvent. Next, the resin solution g was uniformly applied thereon so that the thickness after curing would be about 21 μm, and then heated and dried at 120° C. to remove the solvent. Further, resin solution b was uniformly applied thereon so that the thickness after curing would be about 2 to 3 μm, and then the solvent was removed by heating and drying at 120° C. Further, resin solution f was uniformly applied thereon so that the thickness after curing would be about 2 to 3 μm, and then heated and dried at 120° C. to remove the solvent. Next, the resin solution g was uniformly applied thereon so that the thickness after curing would be about 21 μm, and then heated and dried at 120° C. to remove the solvent. Further, resin solution f was uniformly applied thereon so that the thickness after curing would be about 2 to 3 μm, and then the solvent was removed by heating and drying at 120° C. In this way, after forming six polyamic acid layers, heat treatment was performed stepwise from 120°C to 360°C to complete imidization, and the thickness of the resin laminate was 50 μm. A single-sided copper-clad laminate 1B was prepared in which the thickness ratio of the thermoplastic polyimide layer (the polyimide layer formed using the resin solution g) was 82%.

The polyimide layer of the single-sided copper-clad laminate 1B and the electrolytic copper foil (Rz: 0.8 μm, Ra: 0.2 μm) were simultaneously and continuously fed between a pair of heated rolls at a speed of 4 m/min to bond them by thermocompression ( A double-sided copper-clad laminate 1 having a resin laminate thickness of 50 μm was prepared by setting the roll surface temperature to 320° C. and the linear pressure between the rolls to 134 kN/m. The copper foil peel strength of the double-sided copper-clad laminate 1 exceeded 1.0 kN/m. A polyimide film 1 was prepared by etching away the copper foil of this double-sided copper-clad laminate 1. The dielectric constant ε ₁ of this polyimide film 1 was 3.45, the dielectric loss tangent Tan δ ₁ was 0.0039, and E ₁ calculated from these dielectric properties was 0.0072.

[Example 2]
In the same manner as in Example 1 except that resin solution a was used instead of resin solution b, the thickness of the resin laminate was 50 μm, and a non-thermoplastic polyimide layer (formed by resin solution g) was formed over the entire resin laminate. A single-sided copper-clad laminate 2B having a thickness ratio of 82% (polyimide layer) was prepared.

A single-sided copper-clad laminate 2B and an electrolytic copper foil (Rz: 0.8 μm, Ra: 0.2 μm) were prepared, and in the same manner as in Example 1, a double-sided copper-clad laminate 2 with a polyimide layer thickness of 50 μm was prepared. did. The copper foil peel strength of the double-sided copper-clad laminate 2 exceeded 1.0 kN/m. A polyimide film 2 was prepared by etching away the copper foil of this double-sided copper-clad laminate 2. The dielectric constant ε ₁ of this polyimide film 2 was 3.45, the dielectric loss tangent Tan δ ₁ was 0.0038, and E ₁ calculated from these dielectric properties was 0.0071.

[Example 3]
In the same manner as in Example 1, except that resin solution f was used instead of resin solution b, the thickness of the polyimide layer was 50 μm, and a non-thermoplastic polyimide layer (formed with resin solution g) was applied to the entire resin laminate. A single-sided copper-clad laminate 3B having a thickness ratio of 82% (polyimide layer) was prepared.

A single-sided copper-clad laminate 3B and an electrolytic copper foil (Rz: 0.8 μm, Ra: 0.2 μm) were prepared, and a double-sided copper-clad laminate 3 with a polyimide layer thickness of 50 μm was prepared in the same manner as in Example 1. did. The copper foil peel strength of the double-sided copper-clad laminate 3 exceeded 1.0 kN/m. A polyimide film 3 was prepared by etching away the copper foil of this double-sided copper-clad laminate 3. The dielectric constant ε ₁ of this polyimide film 3 was 3.43, the dielectric loss tangent Tan δ ₁ was 0.0032, and E ₁ calculated from these dielectric properties was 0.0059.

[Example 4]
After applying resin solution f uniformly on the surface of a long electrolytic copper foil (Rz: 0.8 μm, Ra: 0.2 μm) so that the thickness after curing is approximately 2 to 3 μm, it was heated at 120 ° C. Dry and remove solvent. Next, the resin solution g was uniformly applied thereon so that the thickness after curing would be about 34 μm, and then heated and dried at 120° C. to remove the solvent. Further, resin solution c was uniformly applied thereon so that the thickness after curing would be about 2 to 3 μm, and then the solvent was removed by heating and drying at 120° C. Further, resin solution c was uniformly applied thereon so that the thickness after curing would be about 2 to 3 μm, and then heated and dried at 120° C. to remove the solvent. Next, the resin solution g was uniformly applied thereon so that the thickness after curing would be about 34 μm, and then heated and dried at 120° C. to remove the solvent. Further, resin solution f was uniformly applied thereon so that the thickness after curing would be about 2 to 3 μm, and then the solvent was removed by heating and drying at 120° C. In this way, after forming six polyamic acid layers, heat treatment was performed in stages from 120°C to 360°C to complete imidization, and the thickness of the resin laminate was 76 μm. A single-sided copper-clad laminate 4B was prepared in which the thickness ratio of the thermoplastic polyimide layer (the polyimide layer formed using the resin solution g) was 87%.

A single-sided copper-clad laminate 4B and an electrolytic copper foil (Rz: 0.8 μm, Ra: 0.2 μm) were prepared, and in the same manner as in Example 1, a double-sided copper-clad laminate 4 with a resin laminate having a thickness of 76 μm was prepared. Prepared. The copper foil peel strength of the double-sided copper-clad laminate 4 exceeded 1.0 kN/m. A polyimide film 4 was prepared by etching away the copper foil of this double-sided copper-clad laminate 4. The dielectric constant ε ₁ of this polyimide film 4 was 3.20, the dielectric loss tangent Tan δ ₁ was 0.0032, and E ₁ calculated from these dielectric properties was 0.0057.

[Example 5]
After applying resin solution f uniformly on the surface of a long electrolytic copper foil (Rz: 0.8 μm, Ra: 0.2 μm) so that the thickness after curing is approximately 2 to 3 μm, it was heated at 120 ° C. Dry and remove solvent. Next, the resin solution g was uniformly applied thereon so that the thickness after curing would be about 35 μm, and then heated and dried at 120° C. to remove the solvent. Further, resin solution f was uniformly applied thereon so that the thickness after curing would be about 2 to 3 μm, and then heated and dried at 120° C. to remove the solvent. Next, the resin solution g was uniformly applied thereon so that the thickness after curing would be about 34 μm, and then heated and dried at 120° C. to remove the solvent. Further, resin solution f was uniformly applied thereon so that the thickness after curing would be about 2 to 3 μm, and then the solvent was removed by heating and drying at 120° C. After forming five polyamic acid layers in this way, heat treatment was performed in stages from 120°C to 360°C to complete imidization, and the thickness of the resin laminate was 76 μm. A single-sided copper-clad laminate 5B was prepared in which the thickness ratio of the thermoplastic polyimide layer (the polyimide layer formed using the resin solution g) was 90%.

A single-sided copper-clad laminate 5B and an electrolytic copper foil (Rz: 0.8 μm, Ra: 0.2 μm) were prepared, and in the same manner as in Example 1, a double-sided copper-clad laminate 5 with a resin laminate having a thickness of 76 μm was prepared. Prepared. The copper foil peel strength of the double-sided copper-clad laminate 5 exceeded 1.0 kN/m. A polyimide film 5 was prepared by etching away the copper foil of this double-sided copper-clad laminate 5. The dielectric constant ε ₁ of this polyimide film 5 was 3.41, the dielectric loss tangent Tan δ ₁ was 0.0033, and E ₁ calculated from these dielectric properties was 0.0061.

[Example 6]
After applying resin solution f uniformly on the surface of a long electrolytic copper foil (Rz: 0.8 μm, Ra: 0.2 μm) so that the thickness after curing is approximately 2 to 3 μm, it was heated at 120 ° C. Dry and remove solvent. Next, the resin solution g was uniformly applied thereon so that the thickness after curing would be about 21 μm, and then heated and dried at 120° C. to remove the solvent. Further, resin solution b was uniformly applied thereon so that the thickness after curing would be about 2 to 3 μm, and then the solvent was removed by heating and drying at 120° C. Further, the resin solution g was uniformly applied thereon so that the thickness after curing would be about 23 μm, and then heated and dried at 120° C. to remove the solvent. Further, resin solution f was uniformly applied thereon so that the thickness after curing would be about 2 to 3 μm, and then the solvent was removed by heating and drying at 120° C. After forming five polyamic acid layers in this way, heat treatment was performed in stages from 120°C to 360°C to complete imidization, and the thickness of the resin laminate was 50 μm, and the resistance to the entire resin laminate was A single-sided copper-clad laminate 6B was prepared in which the thickness ratio of the thermoplastic polyimide layer (the polyimide layer formed using the resin solution g) was 86%.

A single-sided copper-clad laminate 6B and an electrolytic copper foil (Rz: 0.8 μm, Ra: 0.2 μm) were prepared, and a double-sided copper-clad laminate 6 with a resin laminate thickness of 50 μm was prepared in the same manner as in Example 1. Prepared. The copper foil peel strength of the double-sided copper-clad laminate 6 exceeded 1.0 kN/m. A polyimide film 6 was prepared by etching away the copper foil of this double-sided copper-clad laminate 6. The dielectric constant ε ₁ of this polyimide film 6 was 3.45, the dielectric loss tangent Tan δ ₁ was 0.0039, and E ₁ calculated from these dielectric properties was 0.0072.

[Example 7]
In the same manner as in Example 6, except that resin solution e was used instead of resin solution b, the thickness of the resin laminate was 50 μm, and a non-thermoplastic polyimide layer (formed by resin solution g) was formed over the entire resin laminate. A single-sided copper-clad laminate 7B having a thickness ratio of 86% (polyimide layer) was prepared.

A single-sided copper-clad laminate 7B and an electrolytic copper foil (Rz: 0.8 μm, Ra: 0.2 μm) were prepared, and in the same manner as in Example 1, a double-sided copper-clad laminate 7 with a resin laminate having a thickness of 50 μm was prepared. Prepared. The copper foil peel strength of the double-sided copper-clad laminate 7 exceeded 1.0 kN/m. A polyimide film 7 was prepared by etching away the copper foil of this double-sided copper-clad laminate 7. The dielectric constant ε ₁ of this polyimide film 7 was 3.42, the dielectric loss tangent Tan δ ₁ was 0.0041, and E ₁ calculated from these dielectric properties was 0.0076.

[Example 8]
The resin solution g was uniformly applied to the surface of a long electrolytic copper foil (Rz: 0.8 μm, Ra: 0.2 μm) so that the thickness after curing was approximately 35 μm, and then heated and dried at 120°C. , the solvent was removed. Further, resin solution b was uniformly applied thereon so that the thickness after curing would be about 2 to 3 μm, and then the solvent was removed by heating and drying at 120° C. Further, the resin solution g was uniformly applied thereon so that the thickness after curing would be about 35 μm, and then heated and dried at 120° C. to remove the solvent. Further, resin solution f was uniformly applied thereon so that the thickness after curing would be about 2 to 3 μm, and then the solvent was removed by heating and drying at 120° C. After forming four polyamic acid layers in this way, a stepwise heat treatment was performed from 120°C to 360°C to complete imidization, and the thickness of the resin laminate was 76 μm. A single-sided copper-clad laminate 8B was prepared in which the thickness ratio of the thermoplastic polyimide layer (the polyimide layer formed using the resin solution g) was 93%.

A single-sided copper-clad laminate 8B and an electrolytic copper foil (Rz: 0.8 μm, Ra: 0.2 μm) were prepared, and in the same manner as in Example 1, a double-sided copper-clad laminate 8 with a resin laminate having a thickness of 76 μm was prepared. Prepared. The copper foil peel strength of the double-sided copper-clad laminate 8 exceeded 1.0 kN/m. A polyimide film 8 was prepared by etching away the copper foil of this double-sided copper-clad laminate 8. The dielectric constant ε ₁ of this polyimide film 8 was 3.34, the dielectric loss tangent Tan δ ₁ was 0.0037, and E ₁ calculated from these dielectric properties was 0.0068.

[Example 9]
After applying resin solution f uniformly on the surface of a long electrolytic copper foil (Rz: 0.8 μm, Ra: 0.2 μm) so that the thickness after curing is approximately 2 to 3 μm, it was heated at 120 ° C. Dry and remove solvent. Next, the resin solution g was uniformly applied thereon so that the thickness after curing would be about 21 μm, and then heated and dried at 120° C. to remove the solvent. Further, resin solution b was uniformly applied thereon so that the thickness after curing would be about 2 to 3 μm, and then the solvent was removed by heating and drying at 120° C. Further, the resin solution g was uniformly applied thereon so that the thickness after curing would be about 23 μm, and then heated and dried at 120° C. to remove the solvent. Further, resin solution b was uniformly applied thereon so that the thickness after curing would be about 2 to 3 μm, and then the solvent was removed by heating and drying at 120° C. After forming five polyamic acid layers in this way, heat treatment was performed in stages from 120°C to 360°C to complete imidization, and the thickness of the resin laminate was 50 μm, and the resistance to the entire resin laminate was A single-sided copper-clad laminate 9B was prepared in which the thickness ratio of the thermoplastic polyimide layer (the polyimide layer formed using the resin solution g) was 86%.

The copper foil peel strength of the single-sided copper-clad laminate 9B exceeded 1.0 kN/m. A polyimide film 9 was prepared by etching away the copper foil of this single-sided copper-clad laminate 9B. The dielectric constant ε ₁ of this polyimide film 9 was 3.44, the dielectric loss tangent Tan δ ₁ was 0.0043, and E ₁ calculated from these dielectric properties was 0.0080.

[Example 10]
In the same manner as in Example 4, two single-sided copper-clad laminates 4B were prepared, and the polyimide layer surfaces were bonded together, and at the same time, they were continuously fed between a pair of heating rolls at a speed of 1 m/min to perform thermocompression bonding (roll A double-sided copper-clad laminate 10 having a resin laminate thickness of 152 μm was prepared by setting a surface temperature of 390° C. and a linear pressure between rolls of 134 kN/m. The peel strength of the thermocompression bonded surface of the double-sided copper-clad laminate 10 exceeded 1.0 kN/m. A polyimide film 10 was prepared by etching away the copper foil of this double-sided copper-clad laminate 10. The dielectric constant ε ₁ of this polyimide film 10 was 3.20, the dielectric loss tangent Tan δ ₁ was 0.0032, and E ₁ calculated from these dielectric properties was 0.0057.

[Comparative example 1]
After applying resin solution c uniformly on the surface of a long electrolytic copper foil (Rz: 0.8 μm, Ra: 0.2 μm) so that the thickness after curing is approximately 2 to 3 μm, it was heated at 120 ° C. Dry and remove solvent. Next, resin solution d was uniformly applied thereon so that the thickness after curing would be about 21 μm, and then heated and dried at 120° C. to remove the solvent. Further, resin solution e was uniformly applied thereon so that the thickness after curing would be about 2 to 3 μm, and then heated and dried at 120° C. to remove the solvent. Further, resin solution e was uniformly applied thereon so that the thickness after curing would be about 2 to 3 μm, and then heated and dried at 120° C. to remove the solvent. Next, resin solution d was uniformly applied thereon so that the thickness after curing would be about 21 μm, and then heated and dried at 120° C. to remove the solvent. Further, resin solution c was uniformly applied thereon so that the thickness after curing would be about 2 to 3 μm, and then the solvent was removed by heating and drying at 120° C. In this way, after forming six polyamic acid layers, heat treatment was performed stepwise from 120°C to 360°C to complete imidization, and the thickness of the resin laminate was 50 μm. A single-sided copper-clad laminate 1'B in which the thickness ratio of the thermoplastic polyimide layer (the polyimide layer formed using the resin solution d) was 82% was prepared.

The polyimide layer of the single-sided copper-clad laminate 1'B and the electrolytic copper foil (Rz: 0.8 μm, Ra: 0.2 μm) are simultaneously supplied continuously between a pair of heating rolls at a speed of 4 m/min to heat them. A double-sided copper-clad laminate 1' having a resin laminate thickness of 50 μm was prepared by pressure bonding (roll surface temperature: 390° C., linear pressure between rolls: 134 kN/m). A polyimide film 1' was prepared by etching away the copper foil of this double-sided copper-clad laminate 1'. The dielectric constant ε ₁ of this polyimide film 1' was 3.08, the dielectric loss tangent Tan δ ₁ was 0.0071, and E ₁ calculated from these dielectric properties was 0.0125.

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

10A, 10B...Copper foil layer, 20A, 20B...Thermoplastic polyimide layer, 30A, 30B...Non-thermoplastic polyimide layer, 40A, 40B...Thermoplastic polyimide layer, 50...Resin laminate, 60...Joint surface, 70A, 70B ...Single-sided CCL, 100,100A...Double-sided CCL

Claims (5)

A metal-clad laminate comprising a resin laminate having a laminate structure consisting of at least five or more polyimide layers, and a metal layer laminated on at least one side of the resin laminate,
The resin laminate has a layer structure that is symmetrical in the thickness direction with respect to the center in the thickness direction, and a layer located at the center in the thickness direction or two layers adjacent to the center in the thickness direction are , a thermoplastic polyimide layer with a glass transition temperature of 360°C or less, and the following conditions i) to iv);
i) The total thickness is within the range of 76 μm to 200 μm;
ii) comprising a first polyimide layer in contact with the metal layer and a second polyimide layer laminated directly or indirectly on the first polyimide layer;
iii) the ratio of the thickness of the second polyimide layer to the total thickness of the resin laminate is within the range of 70 to 97%;
iv) The following formula (a),
E ₁ =√ε ₁ ×Tanδ ₁ ...(a)
[Here, ε ₁ represents the dielectric constant at 10 GHz measured by a split post dielectric resonator (SPDR), and Tan δ ₁ represents the dielectric loss tangent at 10 GHz measured by a split post dielectric resonator (SPDR). show]
The _E1 value, which is an index indicating dielectric properties, is less than 0.009;
A metal-clad laminate that satisfies the following requirements. The polyimide constituting the second polyimide layer is a non-thermoplastic polyimide obtained by reacting an acid anhydride component and a diamine component, and contains a tetracarboxylic acid residue and a diamine residue,
With respect to 100 mole parts of the tetracarboxylic acid residue,
Tetracarboxylic acid residue (BPDA residue) derived from 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) and 1,4-phenylenebis(trimellitic acid monoester) dianhydride At least one type of tetracarboxylic acid residue (TAHQ residue) derived from a compound (TAHQ) and a tetracarboxylic acid residue (PMDA residue) derived from pyromellitic dianhydride (PMDA) and 2,3 The total amount of at least one type of tetracarboxylic acid residue (NTCDA residue) derived from ,6,7-naphthalenetetracarboxylic dianhydride (NTCDA) is 80 parts by mole or more,
Molar ratio of at least one of the BPDA residue and the TAHQ residue to at least one of the PMDA residue and the NTCDA residue {(BPDA residue + TAHQ residue)/(PMDA residue + NTCDA residue) } is within the range of 0.4 to 1.5. The metal-clad laminate according to claim 1. The metal-clad laminate according to claim 2, wherein the diamine component contains 4,4'-diamino-2,2'-dimethylbiphenyl (m-TB) in an amount of 80 mol% or more based on the total diamine component. . The metal-clad laminate according to claim 1, wherein the resin laminate has a structure in which at least the first polyimide layer and the second polyimide layer are laminated in this order from the metal layer side. . A circuit board formed by processing the metal layer of the metal clad laminate according to claim 1 into a wiring circuit.

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