WO2022014257A1

WO2022014257A1 - Multilayer polyimide film

Info

Publication number: WO2022014257A1
Application number: PCT/JP2021/023195
Authority: WO
Inventors: 隆宏秋永; 隼平齋藤
Original assignee: 株式会社カネカ
Priority date: 2020-07-17
Filing date: 2021-06-18
Publication date: 2022-01-20
Also published as: TW202208513A; JPWO2022014257A1; CN116133855A; KR20230038757A

Abstract

This multilayer polyimide film (10) comprises a non-thermoplastic polyimide layer (11) and a thermoplastic polyimide layer (12) that is arranged on at least one surface of the non-thermoplastic polyimide layer (11). A non-thermoplastic polyimide that is contained in the non-thermoplastic polyimide layer (11) has tetracarboxylic acid dianhydride residues and diamine residues. The diamine residues include a diamine residue having a biphenyl skeleton, a 4, 4'-diaminodiphenyl ether residue and a p-phenylene diamine residue. The content of the diamine residue having a biphenyl skeleton is from 20% by mole to 35% by mole relative to all diamine residues that constitute the non-thermoplastic polyimide.

Description

Multi-layer polyimide film

The present invention relates to a multi-layer polyimide film.

In recent years, with the expansion of demand for electronic products centered on smartphones, tablet PCs, notebook PCs, etc., the demand for flexible printed wiring boards (hereinafter sometimes referred to as "FPC") is increasing. Above all, a flexible printed wiring board using a multi-layer polyimide film containing a thermoplastic polyimide layer as an adhesive layer is expected to further increase in demand because of its excellent heat resistance and flexibility. Furthermore, in recent years, electronic devices have been made lighter, smaller, and thinner, and there is still a strong demand for miniaturization of FPC wiring.

When producing a fine double-sided FPC or a multi-layer FPC, it is common to use a metal-clad laminate in which a metal foil such as a copper foil is laminated on both sides of a polyimide film. In FPC manufacturing, there is a step of first drilling a hole (hereinafter, may be referred to as “via”) for conducting conduction between layers. By plating the inner wall of the via, both sides of the wiring board can be made conductive. In the via forming process, a through-hole method is used to make through holes in the metal foil and insulating layer (polygonite layer) on both sides with a drill or laser, and the metal foil and insulating layer on one side are cut with a laser or the like, and the other is used. There is a blind via method that leaves the metal leaf on the surface of the surface, but the blind via method is frequently used in order to effectively use the area, especially in the fine FPC.

Conventionally, in such a via forming step, a laminated board is treated with an alkaline potassium permanganate aqueous solution or the like under heating in order to clean the inside of the hole and the surface of the metal foil and remove the resin residue after drilling. Wet desmear treatment is performed. Although polyimide is easily hydrolyzed under alkaline conditions, residual stress is generated by receiving local heating when laser processing is performed. Therefore, in the desmear treatment after the via forming process, the inner wall of the via is formed. Defects such as cracks are likely to occur. Patent Document 1 describes a method of adding a heat treatment step between laser processing and desmear processing to remove residual stress generated by laser processing and suppress the generation of defects. Patent Document 2 discloses a polyimide having resistance to an alkaline solution used in a developing step, an etching treatment step, and a resist stripping step.

Japanese Unexamined Patent Publication No. 2012-186377 Japanese Unexamined Patent Publication No. 2017-179148

Cracks generated on the inner wall of vias due to desmear processing after laser processing deform the plated part in the process after plating processing, causing deterioration of connection reliability, or insulation reliability due to chemical solution entering the cracks. It had a bad influence on the quality because it caused the deterioration of the sex. Cracks are more likely to occur during the formation of blind vias than during the formation of through holes. It should be noted that the present inventor does not generate cracks when the metal foil is removed by etching or the like without laser processing after laser processing, or when the metal foil is removed without laser processing and the metal foil is removed. It became clear by the examination of these. Further, it has been found by the present inventors that cracks are likely to occur when the swelling time and the roughening time are lengthened in the desmear treatment after the laser processing.

If a method of adding a heat treatment step between laser processing and desmear processing as disclosed in Patent Document 1 is adopted as a method for suppressing the occurrence of cracks, the heat treatment process is separately increased, so that the production of the wiring board is performed. It causes a decrease in sex. Further, the method described in Patent Document 1 has room for improvement in suppressing the occurrence of cracks on the inner wall of the via.

Further, although the method described in Patent Document 2 can suppress the tearing of the film in an alkaline environment, there is still room for improvement in suppressing the occurrence of cracks on the inner wall of the via.

The present invention has been made in view of these problems, and an object of the present invention is to provide a multi-layer polyimide film capable of suppressing the occurrence of cracks on the inner wall of a via during desmear treatment after laser processing.

It is important to alleviate the stress generated in the polyimide film during laser processing in order to suppress the occurrence of cracks on the inner wall of the via during desmear processing after laser processing. On the other hand, it is easy to relieve stress by using a polyimide containing a large amount of flexible skeleton, but since such a polyimide has a much larger coefficient of linear expansion than the metal to be bonded, it is used when bonding with a metal foil. It warps or wrinkles. As a result of diligent studies, the present inventors have adopted a polyimide having a specific structure as a non-thermoplastic polyimide used as a core material of a multi-layer polyimide film, while ensuring a linear expansion coefficient comparable to that of a metal. It has been found that the stress generated in the polyimide film during laser processing can be relieved.

The multilayer polyimide film according to the present invention has a non-thermoplastic polyimide layer and a thermoplastic polyimide layer arranged on at least one side of the non-thermoplastic polyimide layer. The non-thermoplastic polyimide contained in the non-thermoplastic polyimide layer has a tetracarboxylic dianhydride residue and a diamine residue. The diamine residue includes a diamine residue having a biphenyl skeleton, a 4,4'-diaminodiphenyl ether residue, and a p-phenylenediamine residue. The content of the diamine residue having the biphenyl skeleton is 20 mol% or more and 35 mol% or less with respect to the total diamine residue constituting the non-thermoplastic polyimide.

In the multilayer polyimide film according to the embodiment of the present invention, the diamine residue having the biphenyl skeleton is a 4,4'-diamino-2,2'-dimethylbiphenyl residue.

In the multilayer polyimide film according to the embodiment of the present invention, the content of the 4,4'-diaminodiphenyl ether residue is 40 mol% or more 70 with respect to the total diamine residue constituting the non-thermoplastic polyimide. It is less than mol%.

In the multilayer polyimide film according to the embodiment of the present invention, the content of the p-phenylenediamine residue is 5 mol% or more and 50 mol% or less with respect to all the diamine residues constituting the non-thermoplastic polyimide. Is.

In the multilayer polyimide film according to the embodiment of the present invention, the tetracarboxylic acid dianhydride residue is 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride residue and pyromellitic acid dianhydride residue. Includes one or more selected from the group consisting of substance residues.

In the multilayer polyimide film according to the embodiment of the present invention, the tetracarboxylic acid dianhydride residue further contains 4,4'-oxydiphthalic acid anhydride residue.

In the multilayer polyimide film according to the embodiment of the present invention, the content of the 4,4'-oxydiphthalic acid anhydride residue is relative to the total tetracarboxylic acid dianhydride residue constituting the non-thermoplastic polyimide. It is 5 mol% or more and 15 mol% or less.

In the multilayer polyimide film according to the embodiment of the present invention, the thermoplastic polyimide contained in the thermoplastic polyimide layer is a 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride residue and pyromellitic acid. It has one or more selected from the group consisting of dianhydride residues and 2,2-bis [4- (4-aminophenoxy) phenyl] propane residues.

In the multilayer polyimide film according to the embodiment of the present invention, the storage elastic modulus of the non-thermoplastic polyimide layer at a temperature of 380 ° C. is less than 0.350 GPa.

In the multilayer polyimide film according to the embodiment of the present invention, the coefficient of linear expansion when the temperature rises from 100 ° C. to 200 ° C. of the non-thermoplastic polyimide layer is 5.0 ppm / K or more and 19.0 ppm / K or less. ..

According to the multilayer polyimide film according to the present invention, it is possible to suppress the occurrence of cracks on the inner wall of the via during the desmear treatment after the laser processing without increasing the man-hours in the manufacturing process of the wiring board.

It is sectional drawing which shows an example of the multilayer polyimide film which concerns on this invention. It is sectional drawing which shows the metal-clad laminated board obtained by using the example of the multilayer polyimide film which concerns on this invention. This is an example of a polarizing microscope image used for discrimination of a hole crack test. It is another example of the polarizing microscope image used for the determination of the hole crack test. It is another example of the polarizing microscope image used for the determination of the hole crack test.

Hereinafter, preferred embodiments of the present invention will be described in detail, but the present invention is not limited thereto. In addition, all of the academic and patent documents described in this specification are incorporated herein by reference.

First, the terms used in this specification will be described. "Polyimide" is a polymer having a structural unit represented by the following general formula (1) as a repeating unit.

In the general formula (1), X represents a tetracarboxylic acid dianhydride residue (a tetravalent organic group derived from a tetracarboxylic acid dianhydride), and Y represents a diamine residue (a divalent organic derived from a diamine). Represents the group).

"Biphenyl skeleton" refers to a bicyclic skeleton in which two benzene rings are bonded by one single bond. Therefore, the diamine residue having a biphenyl skeleton does not include the diamine residue having a condensed ring such as the 9,9-bis (4-aminophenyl) fluorene residue.

The "linear expansion coefficient" is, unless otherwise specified, the linear expansion coefficient at the time of temperature rise from 100 ° C to 200 ° C.

"Non-thermoplastic polyimide" is a film shape (flat) that does not wrinkle or stretch when fixed to a metal fixing frame and heated at a heating temperature of 450 ° C for 2 minutes. A polyimide that retains the film shape). The "thermoplastic polyimide" refers to a polyimide that does not retain its film shape when fixed to a metal fixing frame in a film state and heated at a heating temperature of 450 ° C. for 2 minutes.

The "main surface" of a layered material (more specifically, a non-thermoplastic polyimide layer, a thermoplastic polyimide layer, etc.) refers to a surface orthogonal to the thickness direction of the layered material.

Hereinafter, the compound and its derivatives may be collectively referred to by adding "system" after the compound name.

<Multi-layer polyimide film>
The multilayer polyimide film according to the present embodiment has a non-thermoplastic polyimide layer and a thermoplastic polyimide layer arranged on at least one side (one main surface) of the non-thermoplastic polyimide layer. The non-thermoplastic polyimide contained in the non-thermoplastic polyimide layer has a tetracarboxylic dianhydride residue and a diamine residue. The diamine residue includes a diamine residue having a biphenyl skeleton (a residue derived from a diamine having a biphenyl skeleton), a 4,4'-diaminodiphenyl ether residue, and a p-phenylenediamine residue. The content of diamine residues having a biphenyl skeleton is preferably 20 mol% or more and 35 mol% or less with respect to all the diamine residues constituting the non-thermoplastic polyimide.

Hereinafter, the tetracarboxylic dianhydride may be referred to as "acid dianhydride". A diamine having a biphenyl skeleton may be referred to as "BPDI". 4,4'-diaminodiphenyl ether may be referred to as "ODA". P-phenylenediamine may be referred to as "PDA". Further, the non-thermoplastic polyimide contained in the non-thermoplastic polyimide layer may be simply referred to as "non-thermoplastic polyimide". The thermoplastic polyimide contained in the thermoplastic polyimide layer may be simply referred to as "thermoplastic polyimide".

The present inventors have diligently studied the molecular design of polyimide that can relieve the stress generated in the film during laser processing while maintaining the heat resistance (linear expansion coefficient, etc.) when used for a metal-clad laminate. As a result, the present inventors have optimized the structure of the non-thermoplastic polyimide contained in the multi-layer polyimide film, so that the desmear treatment after laser processing can be performed without significantly changing the manufacturing process of the wiring board. It was found that the occurrence of cracks on the inner wall of the via can be suppressed.

[Structure of multi-layer polyimide film]
Hereinafter, the configuration of the multilayer polyimide film according to this embodiment will be described with reference to the drawings. In addition, in order to make it easier to understand, the drawings to be referred to are schematically shown mainly for each component, and the size, number, shape, etc. of each of the illustrated components are shown for convenience of drawing creation. It may be different from the actual one. Further, in the present specification, for convenience of explanation, in the drawings described later, the same components as those in the drawings described above may be designated by the same reference numerals and the description thereof may be omitted.

FIG. 1 is a cross-sectional view showing an example of a multi-layer polyimide film according to this embodiment. As shown in FIG. 1, the multilayer polyimide film 10 has a non-thermoplastic polyimide layer 11 and a thermoplastic polyimide layer 12 arranged on at least one side of the non-thermoplastic polyimide layer 11. The non-thermoplastic polyimide contained in the non-thermoplastic polyimide layer 11 has a tetracarboxylic dianhydride residue and a diamine residue. Diamine residues include BPDI residues, ODA residues, and PDA residues. The content of the BPDI residue is preferably 20 mol% or more and 35 mol% or less with respect to all the diamine residues constituting the non-thermoplastic polyimide contained in the non-thermoplastic polyimide layer 11.

According to the multi-layer polyimide film 10, it is possible to suppress the occurrence of cracks on the inner wall of the via during the desmear treatment after laser processing. The reason is presumed as follows. In the multilayer polyimide film 10, the non-thermoplastic polyimide contained in the non-thermoplastic polyimide layer 11 has a BPDI residue containing a skeleton having a high degree of free rotation of the molecular chain in a specific range. Further, the non-thermoplastic polyimide contained in the non-thermoplastic polyimide layer 11 has a bent structure ODA residue that contributes to the flexibility of the multi-layer polyimide film 10 and a rigid structure that contributes to the heat resistance of the multi-layer polyimide film 10. It has a PDA residue. From these facts, the multilayer polyimide film 10 can relieve the stress generated in the film during laser processing while maintaining the heat resistance (linear expansion coefficient and the like) when used for the metal-clad laminate. Therefore, according to the multi-layer polyimide film 10, it is possible to suppress the occurrence of cracks on the inner wall of the via during the desmear treatment after the laser processing. In order to more effectively suppress the generation of cracks on the inner wall of the via, the benzene ring in the BPDI residue preferably has a substituent, more preferably an alkyl group, and methyl. It is more preferable to have a group. When the benzene ring in the BPDI residue has a substituent, the symmetry of the primary structure of the polyimide is lowered, so that the packing of the polymer chain is hindered and the stress generated in the film during laser processing is further relaxed. To.

In the multilayer polyimide film 10 shown in FIG. 1, the thermoplastic polyimide layer 12 is provided only on one side of the non-thermoplastic polyimide layer 11, but heat is generated on both surfaces (both main surfaces) of the non-thermoplastic polyimide layer 11. The plastic polyimide layer 12 may be provided. When the thermoplastic polyimide layer 12 is provided on both sides of the non-thermoplastic polyimide layer 11, the two-layer thermoplastic polyimide layer 12 may contain the same type of thermoplastic polyimide, and different types of thermoplastic polyimides may be contained. May include. Further, the thicknesses of the two thermoplastic polyimide layers 12 may be the same or different. Further, in the present invention, both the non-thermoplastic polyimide layer 11 and the thermoplastic polyimide layer 12 may be provided in two or more layers. In the following description, the "multi-layer polyimide film 10" includes a film in which the thermoplastic polyimide layer 12 is provided on only one side of the non-thermoplastic polyimide layer 11 and a thermoplastic polyimide on both sides of the non-thermoplastic polyimide layer 11. A film provided with the layer 12 and a film provided with two or more layers of both the non-thermoplastic polyimide layer 11 and the thermoplastic polyimide layer 12 are included.

The thickness of the multilayer polyimide film 10 (total thickness of each layer) is, for example, 6 μm or more and 60 μm or less. The thinner the thickness of the multilayer polyimide film 10, the easier it is to reduce the weight of the obtained FPC, and the more bendable the obtained FPC is. In order to make it easier to reduce the weight of the FPC while ensuring mechanical strength and to further improve the bendability of the FPC, the thickness of the multilayer polyimide film 10 is preferably 7 μm or more and 30 μm or less, preferably 10 μm or more. It is more preferably 25 μm or less. The thickness of the multilayer polyimide film 10 can be measured using a laser holo gauge.

In order to easily realize the thinning of the FPC while ensuring the adhesion to the metal foil, the thickness of the thermoplastic polyimide layer 12 (when two or more thermoplastic polyimide layers 12 are provided, the respective heats are provided. The thickness of the plastic polyimide layer 12) is preferably 1 μm or more and 15 μm or less. Further, in order to easily adjust the linear expansion coefficient of the multilayer polyimide film 10, the thickness ratio of the non-thermoplastic polyimide layer 11 and the thermoplastic polyimide layer 12 (thickness of the non-thermoplastic polyimide layer 11 / thermoplastic polyimide layer). The thickness of 12) is preferably 55/45 or more and 95/5 or less. When a plurality of layers each of the non-thermoplastic polyimide layer 11 and the thermoplastic polyimide layer 12 are provided, the thickness ratio is the ratio of the total thickness of each. Even if the number of layers of the thermoplastic polyimide layer 12 is increased, it is preferable that the total thickness of the thermoplastic polyimide layer 12 does not exceed the total thickness of the non-thermoplastic polyimide layer 11.

In order to suppress the warp of the multilayer polyimide film 10, it is preferable that the thermoplastic polyimide layers 12 are provided on both sides of the non-thermoplastic polyimide layer 11, and the same kind of heat is provided on both sides of the non-thermoplastic polyimide layer 11. It is more preferable that the thermoplastic polyimide layer 12 containing the thermoplastic polyimide is provided. When the thermoplastic polyimide layers 12 are provided on both sides of the non-thermoplastic polyimide layer 11, the thicknesses of the two thermoplastic polyimide layers 12 are the same in order to suppress the warp of the multilayer polyimide film 10. Is preferable. Even if the thicknesses of the two thermoplastic polyimide layers 12 are different from each other, the thickness of the other thermoplastic polyimide layer 12 is 40% or more and 100% based on the thickness of the thicker thermoplastic polyimide layer 12. If the range is less than the range, the warp of the multilayer polyimide film 10 can be suppressed.

In order to further suppress the occurrence of cracks on the inner wall of the via during the desmear treatment after laser processing, the storage elastic modulus of the non-thermoplastic polyimide layer 11 at a temperature of 380 ° C. is preferably less than 0.350 GPa. It is more preferably less than 200 GPa. Further, from the viewpoint of improving the mechanical strength of the multilayer polyimide film 10 under high temperature, the storage elastic modulus is preferably 0.010 GPa or more, and more preferably 0.050 GPa or more. The storage elastic modulus can be adjusted, for example, by changing the content of BPDI residues. The method for measuring the storage elastic modulus is the same as or similar to that of the examples described later.

When the dynamic viscoelasticity measurement was performed on the non-thermoplastic polyimide layer 11, the temperature indicated by the variation point of the storage elastic modulus is the heat from the viewpoint of stress relaxation during laser processing and when the metal foil is bonded by the laminating method. From the viewpoint of stress relaxation, the range of 270 ° C. or higher and 340 ° C. or lower is preferable, and the range of 280 ° C. or higher and 330 ° C. or lower is more preferable. When the temperature indicated by the inflection point of the storage elastic modulus is within this range, the dimensional change at the temperature (for example, 250 ° C.) for evaluating the dimensional change after heating of the flexible metal-clad laminate can be suppressed. On the other hand, when the temperature indicated by the inflection point of the storage elastic modulus is low, the stress generated in the multilayer polyimide film 10 during cooling after laser processing becomes small.

The coefficient of linear expansion of the non-thermoplastic polyimide layer 11 is preferably 5.0 ppm / K or more and 19.0 ppm / K or less, more preferably 8.0 ppm / K or more and 15.0 ppm / K or less, and further preferably. Is 9.0 ppm / K or more and 12.0 ppm / K or less. When the coefficient of linear expansion of the non-thermoplastic polyimide layer 11 is 5.0 ppm / K or more and 19.0 ppm / K or less, the coefficient of linear expansion of the multilayer polyimide film 10 is set to 14.0 ppm / K or more, which is close to that of copper foil, for example. It can be adjusted to 22.0 ppm / K or less, preferably 16.0 ppm / K or more and 20.0 ppm / K or less, which is closer to the copper foil. As a result, the stress generated in the multilayer polyimide film 10 during cooling after laser processing is reduced, and the occurrence of cracks on the inner wall of the via can be further suppressed during desmear processing after laser processing. The linear expansion coefficient is, for example, the content of residues derived from a monomer having a rigid structure (more specifically, a PDA residue, etc.) and residues derived from a monomer having a bent structure (more specifically, an ODA residue). It can be adjusted by changing the content of (base, etc.). The method for measuring the coefficient of linear expansion is the same as or similar to the embodiment described later.

The non-thermoplastic polyimide layer 11 preferably has a slope of the plastic deformation region in the stress-strain curve of 2.0 or more. When the non-thermoplastic polyimide layer 11 is not easily plastically deformed and has a high yield strength, it exhibits high durability against tearing in an alkaline environment. The plastic deformation region refers to the region of strain after the yield point in the stress-strain curve in the tensile test of the polyimide film. The "difficult to plastically deform" property means that the stress is greatly increased in the plastic deformation region, or the stress required at the time of plastic deformation is large. For example, the inclination of the plastic deformation region is an index for the characteristic of "hard to be plastically deformed". The slope of the plastic deformation region is, for example, the plastic deformation of the graph in which the vertical axis is "stress (unit: MPa)" and the horizontal axis is "strain (unit: mm)" for the result of measuring the tensile properties according to ASTM D882. The slope of the s-s curve in the region. The slope of the s—s curve in the plastic deformation region can be calculated by the following formula. In the following equation, stress1 is a stress at 10% strain, stress2 is a fracture stress, strain1 is a 10% strain, and strain2 is a fracture strain.

Slope of s-s curve in plastic deformation region = (stress2-stress1) / (strine2-strine1)

The inclination of the plastic deformation region of the non-thermoplastic polyimide layer 11 is preferably 2.0 or more, more preferably 2.2 or more, and further preferably 2.5 or more. When the inclination of the plastic deformation region is 2.0 or more, a cohesive structure having a high degree of packing of polymer chains is formed, and the occurrence of tearing can be suppressed even in the continuous FPC processing step. The inclination of the plastic deformation region should be high, but in order to suppress the occurrence of springback and the like, the inclination of the plastic deformation region is preferably 4.5 or less, and 4.0 or less. Is more preferable.

When manufacturing a metal-clad laminate using the multilayer polyimide film 10, the metal foil 13 is attached to at least one side of the multilayer polyimide film 10 (for example, in the case of FIG. 1, the surface 12a of the thermoplastic polyimide layer 12). As a result, the metal-clad laminate 20 shown in FIG. 2 is obtained. The method of adhering the metal foil 13 to the surface 12a of the thermoplastic polyimide layer 12 is not particularly limited, and various known methods can be adopted. For example, a thermal roll laminating device having a pair or more of metal rolls or a continuous processing method using a double belt press (DBP) can be adopted. The specific configuration of the means for performing the thermal roll laminating is not particularly limited, but in order to improve the appearance of the obtained multi-layer polyimide film 10, between the pressure surface and the metal foil 13. It is preferable to place a protective material.

When the thermoplastic polyimide layer 12 is provided on both sides of the non-thermoplastic polyimide layer 11, the double-sided metal-clad laminate (not shown) is formed by laminating the metal foil 13 on both sides of the multilayer polyimide film 10. can get.

[Elements of multi-layer polyimide film]
Next, the elements (components) of the multilayer polyimide film according to the present embodiment will be described in detail.

(Non-thermoplastic polyimide layer)
The non-thermoplastic polyimide contained in the non-thermoplastic polyimide layer has a BPDI residue, an ODA residue, and a PDA residue as diamine residues. In order to further suppress the occurrence of cracks in the inner wall of the via during desmear treatment after laser processing, the total content of BPDI residue, ODA residue and PDA residue is contained in all diamine residues constituting the non-thermoplastic polyimide. The ratio is preferably 50 mol% or more, more preferably 70 mol% or more, further preferably 80 mol% or more, further preferably 90 mol% or more, and even more preferably 100 mol%. But it doesn't matter.

Examples of the diamine (monomer) for forming the BPDI residue include 4,4'-diamino-2,2'-dimethylbiphenyl (hereinafter, may be referred to as "m-TB"), 4,4. '-Diaminobiphenyl, 4,4'-diamino-3,3'-dimethylbiphenyl, 4,4'-diamino-2,2'-dimethoxybiphenyl, 4,4'-diamino-3,3'-dimethoxybiphenyl, Examples thereof include 3,3', 5,5'-tetramethylbenzidine, 4,4'-bis (4-aminophenoxy) biphenyl and the like. In this embodiment, one or more diamines can be used as the diamine for forming the BPDI residue. In order to further suppress the occurrence of cracks on the inner wall of the via during the desmear treatment after laser processing, m-TB is preferable as the diamine (monomer) for forming the BPDI residue. That is, as the BPDI residue, the m-TB residue is preferable.

In order to further suppress the occurrence of cracks on the inner wall of the via during desmear treatment after laser processing while maintaining the linear expansion coefficient, the content of ODA residues with respect to all diamine residues constituting the non-thermoplastic polyimide is set. It is preferably 40 mol% or more and 70 mol% or less, more preferably 45 mol% or more and 65 mol% or less, and further preferably 50 mol% or more and 65 mol% or less. In order to further suppress the occurrence of cracks on the inner wall of the via during desmear treatment after laser processing while maintaining the linear expansion coefficient, the content of PDA residues to all diamine residues constituting the non-thermoplastic polyimide is set. It is preferably 5 mol% or more and 50 mol% or less, more preferably 10 mol% or more and 40 mol% or less, and further preferably 15 mol% or more and 30 mol% or less.

The non-thermoplastic polyimide may have a diamine residue (another diamine residue) other than the BPDI residue, the ODA residue and the PDA residue as the diamine residue. As the diamine (monomer) for forming another diamine residue, an aromatic diamine having high heat resistance is preferable. Specific examples of diamines for forming other diamine residues include 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, and 4,4'-diaminodiphenyl. Propane, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylsulfide, 3,3'-diaminodiphenylsulfone, 4,4'-diaminodiphenylsulfone, 3,3'-diaminodiphenylether, 3,4'- Diaminodiphenyl ether, 1,5-diaminonaphthalene, 4,4'-diaminodiphenyldiethylsilane, 4,4'-diaminodiphenylsilane, 4,4'-diaminodiphenylethylphosphine oxide, 4,4'-diaminodiphenylN-methyl Examples thereof include amines, 4,4'-diaminodiphenyl N-phenylamine, 1,3-diaminobenzene, 1,2-diaminobenzene and the like.

Non-thermoplastic polyimide has an acid dianhydride residue in addition to a diamine residue. As the acid dianhydride (monomer) for forming the acid dianhydride residue, aromatic acid dianhydride is preferable from the viewpoint of improving heat resistance. Further, in order to further suppress the generation of cracks on the inner wall of the via during the desmear treatment after laser processing, the acid dianhydride (monomer) for forming the acid dianhydride residue is an acid having a biphenyl skeleton. Dianhydride is preferred. Specific examples of the acid dianhydride (monomer) for forming the acid dianhydride residue include pyromellitic acid dianhydride (hereinafter, may be referred to as "PMDA"), 3, 3', 4 , 4'-biphenyltetracarboxylic acid dianhydride (hereinafter sometimes referred to as "BPDA"), 2,3,6,7-naphthalenetetracarboxylic acid dianhydride, 1,2,5,6-naphthalene Tetracarboxylic acid dianhydride, 2,2', 3,3'-biphenyltetracarboxylic acid dianhydride, 3,3', 4,4'-benzophenone tetracarboxylic acid dianhydride (hereinafter referred to as "BTDA"). , 2,2', 3,3'-benzophenone tetracarboxylic acid dianhydride, 4,4'-oxydiphthalic acid anhydride (hereinafter, may be referred to as "ODPA"), 3,4 '-Oxydiphthalic anhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, 3,4,9,10-perylenetetracarboxylic acid dianhydride, bis (3,4-dicarboxyphenyl) Phenyl) Propane dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride, 1,1-bis (3,4-dicarboxyphenyl) ethane dianhydride, bis (2,3) -Dicarboxyphenyl) methane dianhydride, bis (3,4-dicarboxyphenyl) ethane dianhydride, bis (3,4-dicarboxyphenyl) sulfonate dianhydride, p-phenylene bis (trimeritic acid monoester) Acid anhydride), ethylene bis (trimellitic acid monoesteric acid anhydride), bisphenol A bis (trimellitic acid monoesteric acid anhydride), derivatives thereof and the like can be mentioned.

From the viewpoint of maintaining the coefficient of linear expansion, the acid dianhydride residue is preferably one or more selected from the group consisting of BPDA residues and PMDA residues. Further, in order to further suppress the generation of cracks on the inner wall of the via during the desmear treatment after laser processing, the BPDA residue having a biphenyl skeleton is preferable as the acid dianhydride residue. When the non-thermoplastic polyimide contains a BPDA residue, in order to further suppress the occurrence of cracks on the inner wall of the via during desmear treatment after laser processing while maintaining the linear expansion coefficient, all the non-thermoplastic polyimides are composed. The content of the BPDA residue with respect to the acid dianhydride residue is preferably 10 mol% or more and 60 mol% or less, more preferably 20 mol% or more and 60 mol% or less, and 30 mol% or more and 60 mol. % Or less is more preferable. When the non-thermoplastic polyimide contains PMDA residues, the content of PMDA residues in the total acid dianhydride residues constituting the non-thermoplastic polyimide is 40 mol% or more and 80 mol% from the viewpoint of maintaining the linear expansion coefficient. It is preferably 40 mol% or more and 75 mol% or less, more preferably 40 mol% or more and 70 mol% or less. When the non-thermoplastic polyimide contains a BPDA residue and a PMDA residue, in order to further suppress the occurrence of cracks on the inner wall of the via during desmear treatment after laser processing while maintaining the coefficient of linear expansion, the BPDA residue and The total content of PMDA residues is preferably 60 mol% or more, more preferably 70 mol% or more, and more preferably 80 mol% with respect to the total acid dianhydride residues constituting the non-thermoplastic polyimide. It is more preferably% or more, and may be 100 mol%.

In order to further suppress the generation of cracks on the inner wall of the via during the desmear treatment after laser processing, one or more non-thermoplastic polyimides are selected from the group consisting of BPDA residues and PMDA residues as acid dianhydride residues. And ODPA residues are preferred. When the non-thermoplastic polyimide contains ODPA residues, in order to further suppress the generation of cracks on the inner wall of the via during the desmear treatment after laser processing, ODPA for the total acid dianhydride residue constituting the non-thermoplastic polyimide is used. The residue content is preferably 5 mol% or more and 15 mol% or less. When the non-thermoplastic polyimide contains one or more selected from the group consisting of BPDA residues and PMDA residues and ODPA residues, the inner wall of the via is subjected to desmear treatment after laser processing while maintaining the coefficient of linear expansion. In order to further suppress the occurrence of cracks, the total content of BPDA residues, PMDA residues and ODPA residues is 80 mol% with respect to the total acid dianhydride residues constituting the non-thermoplastic polyimide. The above is preferable, 90 mol% or more is more preferable, and 100 mol% may be used.

In order to further suppress the occurrence of cracks on the inner wall of the via during the desmear treatment after laser processing while maintaining the good appearance of the surface of the metal-clad laminate, the non-thermoplastic polyimide is represented by the following chemical formula (2). It is preferable to have a segment whose structural unit is a repeating unit. In addition, in this specification, a "segment" means a polymer chain formed from the same repeating unit which constitutes a block copolymer. Further, in the present specification, the "block copolymer" includes any aspect of a pure block copolymer, a random block copolymer, and a copolymer having a tapered block structure.

A segment having a structural unit represented by the chemical formula (2) as a repeating unit (hereinafter, may be referred to as a “specific segment”) can be formed by, for example, sequence polymerization described later.

The non-thermoplastic polyimide layer may contain components (additives) other than the non-thermoplastic polyimide. As the additive, for example, a dye, a surfactant, a leveling agent, a plasticizer, a silicone, a filler, a sensitizer and the like can be used. The content of the non-thermoplastic polyimide in the non-thermoplastic polyimide layer is, for example, 70% by weight or more, preferably 80% by weight or more, and more preferably 90% by weight or more, based on the total amount of the non-thermoplastic polyimide layer. It is more preferable, and it may be 100% by weight.

(Thermoplastic polyimide layer)
The thermoplastic polyimide contained in the thermoplastic polyimide layer has an acid dianhydride residue and a diamine residue. The acid dianhydride (monomer) for forming the acid dianhydride residue in the thermoplastic polyimide is an acid dianhydride for forming the acid dianhydride residue in the non-thermoplastic polyimide described above (monomer). The same compound as the monomer) can be mentioned. The acid dianhydride residue contained in the thermoplastic polyimide and the acid dianhydride residue contained in the non-thermoplastic polyimide may be of the same type or different types from each other.

In order to ensure thermoplasticity, the diamine residue of the thermoplastic polyimide is preferably a diamine residue having a bent structure. In order to more easily secure the thermoplasticity, the content of the diamine residue having a bent structure is preferably 50 mol% or more, preferably 70 mol% or more, based on the total diamine residue constituting the thermoplastic polyimide. % Or more is more preferable, 80 mol% or more is further preferable, and 100 mol% may be used. Examples of the diamine (monomer) for forming a diamine residue having a bent structure include 4,4'-bis (4-aminophenoxy) biphenyl, 4,4'-bis (3-aminophenoxy) biphenyl, and 1,3. -Bis (3-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 2,2-bis [4- (4-aminophenoxy) phenyl] propane (hereinafter referred to as "BAPP"). There is) etc. In order to more easily secure the thermoplasticity, the BAPP residue is preferable as the diamine residue contained in the thermoplastic polyimide.

In order to obtain a thermoplastic polyimide layer having excellent adhesion to a metal foil, it is preferable that the thermoplastic polyimide has one or more selected from the group consisting of BPDA residues and PMDA residues, and BAPP residues.

The thermoplastic polyimide layer may contain components (additives) other than the thermoplastic polyimide. As the additive, for example, a dye, a surfactant, a leveling agent, a plasticizer, a silicone, a filler, a sensitizer and the like can be used. The content of the thermoplastic polyimide in the thermoplastic polyimide layer is, for example, 70% by weight or more, preferably 80% by weight or more, and more preferably 90% by weight or more, based on the total amount of the thermoplastic polyimide layer. Preferably, it may be 100% by weight.

In order to particularly suppress the occurrence of cracks on the inner wall of the via during the desmear treatment after laser processing, the multilayer polyimide film according to the present embodiment preferably satisfies the following condition 1, and more preferably the following condition 2. It is more preferable to satisfy the following condition 3, still more preferably to satisfy the following condition 4, and particularly preferably to satisfy the following condition 5.
Condition 1: The non-thermoplastic polyimide has m-TB residue, ODA residue, PDA residue, BPDA residue and PMDA residue.
Condition 2: The content of the ODA residue with respect to all the diamine residues constituting the non-thermoplastic polyimide satisfying the above condition 1 is 40 mol% or more and 70 mol% or less.
Condition 3: The content of the PDA residue with respect to all the diamine residues constituting the non-thermoplastic polyimide satisfying the above condition 2 is 5 mol% or more and 50 mol% or less.
Condition 4: The non-thermoplastic polyimide satisfying the above condition 3 is a block copolymer having a specific segment.
Condition 5: The above condition 4 is satisfied, and the non-thermoplastic polyimide further has an ODPA residue.

<Manufacturing method of multi-layer polyimide film and manufacturing method of metal-clad laminate>
Next, an example of a method for manufacturing a multi-layer polyimide film according to the present embodiment and an example of a method for manufacturing a metal-clad laminate using the multi-layer polyimide film according to the present embodiment will be described.

[Manufacturing method of multi-layer polyimide film]
(Manufacturing method of polyamic acid)
As a method for producing polyamic acid (synthesis method) which is a precursor of polyimide, any known method or a method in which they are combined can be used. The characteristic of the polymerization method in the production of polyamic acid lies in the order of addition of the monomers, and various physical properties of the polyimide obtained by controlling the order of addition of the monomers can be controlled. When synthesizing polyamic acid using diamine and tetracarboxylic acid dianhydride, the amount of each diamine and the amount of tetracarboxylic acid dianhydride (when using multiple types of tetracarboxylic acid dianhydride, when using multiple types of tetracarboxylic acid dianhydride, By adjusting the amount of each tetracarboxylic acid dianhydride), a desired polyamic acid (polymer of diamine and tetracarboxylic acid dianhydride) can be obtained. The amount of substance ratio (molar ratio) of each residue in the polyimide formed from polyamic acid is consistent with, for example, the amount of substance ratio of each monomer (diamine and tetracarboxylic acid dianhydride) used for the synthesis of polyamic acid. .. The temperature conditions for the reaction between the diamine and the tetracarboxylic dianhydride, that is, the synthetic reaction for the polyamic acid are not particularly limited, but are, for example, in the range of 20 ° C. or higher and 150 ° C. or lower. The reaction time of the polyamic acid synthesis reaction is, for example, in the range of 10 minutes or more and 30 hours or less. In the present embodiment, any method of adding a monomer may be used for producing the polyamic acid. The following methods can be mentioned as a typical method for producing a polyamic acid.

Examples of the method for producing a polyamic acid include a method of polymerizing by the following steps (Aa) and (Ab) (hereinafter, may be referred to as "A polymerization method").
(A-a): A step of reacting an aromatic diamine with an aromatic acid dianhydride in an organic solvent in a state where the aromatic diamine is in excess to obtain a prepolymer having amino groups at both ends (A-a). b): An aromatic dianhydride having a structure different from that used in the step (Aa) is additionally added, and an aromatic acid dianhydride having a structure different from that used in the step (Aa) is further added. A step of adding and polymerizing aromatic diamine and aromatic acid dianhydride so as to be substantially equimolar in all steps.

Further, as a method for producing the polyamic acid, a method of polymerizing by the following steps (Ba) and the step (Bb) (hereinafter, may be referred to as “B polymerization method”) can also be mentioned.
(BA): Aromatic diamine and aromatic acid dianhydride are reacted in an organic solvent with an excess of aromatic acid dianhydride to form a prepolymer having acid anhydride groups at both ends. Obtaining step (B-b): An aromatic acid dianhydride having a structure different from that used in the step (B-a) is additionally added, and the structure is different from that used in the step (B-a). A step of adding and polymerizing aromatic diamine so that the aromatic diamine and the aromatic acid dianhydride in all steps are substantially equimolar.

A synthetic method for setting the order of addition so that a specific diamine or a specific acid dianhydride selectively reacts with an arbitrary or a specific diamine, or an arbitrary or a specific acid dianhydride (for example, the above-mentioned A polymerization method). , B polymerization method, etc.) is described as sequence polymerization in this specification. Among the polymers obtained by sequence polymerization, a polymer having two types of segments is called a diblock copolymer, and a polymer having three types of segments is called a triblock copolymer. On the other hand, a polymerization method in which the order of addition of diamine and acid dianhydride is not set (a polymerization method in which monomers react arbitrarily with each other) is described as random polymerization in the present specification. The polymer obtained by random polymerization is called a random copolymer.

In the present embodiment, sequence polymerization is preferable as a polymerization method for obtaining a polyimide effective for suppressing tearing of a film while maintaining the characteristics of a flexible metal-clad laminate.

The weight average molecular weight of the polyamic acid obtained by the above-mentioned polymerization method is preferably in the range of 10,000 or more and 1,000,000 or less, and more preferably in the range of 20,000 or more and 500,000 or less. It is more preferably in the range of 30,000 or more and 200,000 or less. When the weight average molecular weight is 10,000 or more, it becomes easy to use polyamic acid as a coating film. On the other hand, when the weight average molecular weight is 1,000,000 or less, sufficient solubility in a solvent is exhibited, so that a coating film having a smooth surface and a uniform thickness can be obtained by using a polyamic acid solution described later. The weight average molecular weight used here means a polyethylene oxide equivalent value measured by gel permeation chromatography (GPC).

When obtaining the polyimide, a method of obtaining the polyimide from a polyamic acid solution containing a polyamic acid and an organic solvent may be adopted. Examples of the organic solvent that can be used in the polyamic acid solution include urea-based solvents such as tetramethylurea and N, N-dimethylethylurea; sulfoxide-based solvents such as dimethylsulfoxide; and diphenylsulfones and tetramethylsulfones. Sulfon-based solvent; N, N-dimethylacetamide, N, N-dimethylformamide (hereinafter, may be referred to as "DMF"), N, N-diethylacetamide, N-methyl-2-pyrrolidone, hexamethylphosphate. Amid solvents such as triamide; ester solvents such as γ-butyrolactone; alkyl halide solvents such as chloroform and methylene chloride; aromatic hydrocarbon solvents such as benzene and toluene; phenol solvents such as phenol and cresol; cyclo Ketone-based solvents such as pentanone; ether-based solvents such as tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, dimethyl ether, diethyl ether, diethylene glycol diethyl ether, diethylene glycol dimethyl ether, and p-cresol methyl ether can be mentioned. Usually, these solvents are used alone, but if necessary, two or more kinds may be used in combination as appropriate. When the polyamic acid is obtained by the above-mentioned polymerization method, the reaction solution (solution after the reaction) itself may be used as the polyamic acid solution for obtaining the polyimide. In this case, the organic solvent in the polyamic acid solution is the organic solvent used in the reaction in the above polymerization method. Alternatively, a solid polyamic acid obtained by removing the solvent from the reaction solution may be dissolved in an organic solvent to prepare a polyamic acid solution.

Additives such as dyes, surfactants, leveling agents, plasticizers, silicones, and sensitizers may be added to the polyamic acid solution. Further, a filler may be added to the polyamic acid solution for the purpose of improving various properties of the film such as slidability, thermal conductivity, conductivity, corona resistance, and loop stiffness. Any filler may be used, and preferred examples thereof include fillers made of silica, titanium oxide, alumina, silicon nitride, boron nitride, calcium hydrogen phosphate, calcium phosphate, mica and the like.

The concentration of the polyamic acid in the polyamic acid solution is not particularly limited, and is, for example, 5% by weight or more and 35% by weight or less, preferably 8% by weight or more and 30% by weight or less, based on the total amount of the polyamic acid solution. When the concentration of polyamic acid is 5% by weight or more and 35% by weight or less, an appropriate molecular weight and solution viscosity can be obtained.

(Method for forming non-thermoplastic polyimide layer)
The method for forming the non-thermoplastic polyimide layer is not particularly limited, and various known methods can be applied. For example, a method for forming a non-thermoplastic polyimide layer (polyimide film) through the following steps i) to iv). Can be mentioned.
Step i): A polyamic acid solution containing a precursor of a non-thermoplastic polyimide by reacting an aromatic diamine with an aromatic tetracarboxylic acid dianhydride in an organic solvent (hereinafter referred to as “non-thermoplastic polyamic acid solution”). Step ii): A step of applying a dope solution containing the non-thermoplastic polyimide solution onto a support to form a coating film Step ii): Applying the coating film onto the support. A step of peeling the gel film from the support after heating to obtain a self-supporting polyimide film (hereinafter, may be referred to as "gel film"). Step iv) The above gel film is heated. A step of imidizing the polyamic acid in the gel film and drying it to obtain a polyimide film containing a non-thermoplastic polyimide (a polyimide film that becomes a non-thermoplastic polyimide layer in a multi-layer polyimide film).

In step ii), the method of applying the doping solution on the support is not particularly limited, and a method using a conventionally known coating device such as a die coater, a comma coater (registered trademark), a reverse coater, and a knife coater is adopted. can.

The steps after step ii) are roughly divided into a thermal imidization method and a chemical imidization method. The thermal imidization method is a method in which a polyamic acid solution is applied as a doping solution on a support and heated to proceed with imidization without using a dehydrating ring-closing agent or the like. On the other hand, the chemical imidization method is a method of promoting imidization by using a polyamic acid solution to which at least one of a dehydration ring-closing agent and a catalyst is added as an imidization accelerator as a dope solution. Either method may be used, but the chemical imidization method is more productive.

As the dehydration ring closure agent, an acid anhydride typified by acetic anhydride is preferably used. As the catalyst, tertiary amines such as aliphatic tertiary amines, aromatic tertiary amines, and heterocyclic tertiary amines are preferably used.

As the support to which the dope solution is applied in step ii), a glass plate, aluminum foil, an endless stainless belt, a stainless drum, or the like is preferably used. In step iii), heating conditions are set according to the thickness of the finally obtained film and the production rate, and after at least one of partial imidization and drying is performed, the film is peeled off from the support to form a polyamic acid film (step iii). Gel film) is obtained.

Next, in step iv), water, the residual solvent, the imidization accelerator, etc. are removed from the gel film by fixing the end portion of the gel film and heat-treating it while avoiding shrinkage during curing, and the residue remains. The polyamic acid is completely imidized to obtain a polyimide film containing a non-thermoplastic polyimide. The heating conditions may be appropriately set according to the thickness of the finally obtained film and the production rate.

(Method of forming a thermoplastic polyimide layer)
The thermoplastic polyimide layer is, for example, a polyamic acid containing polyamic acid, which is a precursor of thermoplastic polyimide, on at least one side of a polyimide film (non-thermoplastic polyimide layer) obtained by using the above-mentioned non-thermoplastic polyimide solution. After applying the solution (hereinafter, may be referred to as "thermoplastic polyamic acid solution"), it can be obtained by the same procedure as the above-mentioned method for forming a non-thermoplastic polyimide layer (polyimide film). By this method, a multi-layer polyimide film having a non-thermoplastic polyimide layer and a thermoplastic polyimide layer arranged on at least one side of the non-thermoplastic polyimide layer can be obtained. Further, instead of the thermoplastic polyamic acid solution, a solution containing thermoplastic polyimide (thermoplastic polyimide solution) is used to form a coating film made of the thermoplastic polyimide solution on at least one side of the non-thermoplastic polyimide layer, and this coating is performed. The film may be dried to form a thermoplastic polyimide layer.

Also, for example, after using a coextruding die to form a laminate comprising a layer containing polyamic acid, which is a precursor of non-thermoplastic polyimide, and a layer containing polyamic acid, which is a precursor of thermoplastic polyimide. The obtained laminate may be heated to form a non-thermoplastic polyimide layer and a thermoplastic polyimide layer at the same time. In this method, by using a metal foil as a support, a metal-clad laminate (a laminate of a multilayer polyimide film and a metal foil) can be obtained at the same time as imidization is completed. When producing a multi-layer polyimide film containing three or more polyimide layers, the above-mentioned coating step and heating step are repeated multiple times, or multiple coating films are formed by coextrusion or continuous coating (continuous casting) at one time. The heating method is preferably used. It is also possible to perform various surface treatments such as corona treatment and plasma treatment on the outermost surface of the multi-layer polyimide film.

[Manufacturing method of metal-clad laminate]
When a metal-clad laminate is manufactured using the multilayer polyimide film obtained by the above method, a metal foil is bonded to at least one surface of the multilayer polyimide film as described above. The metal foil is not particularly limited, and any metal foil can be used. For example, a metal foil made of copper, stainless steel, nickel, aluminum, an alloy of these metals, or the like is preferably used. Further, in a general metal-clad laminate, copper foil such as rolled copper foil and electrolytic copper foil is often used, but the copper foil is also preferably used in this embodiment.

In addition, as the metal foil, one that has been subjected to surface treatment or the like according to the purpose and whose surface roughness or the like has been adjusted can be used. Further, a rust preventive layer, a heat resistant layer, an adhesive layer and the like may be formed on the surface of the metal foil. The thickness of the metal foil is not particularly limited, and may be any thickness as long as it can exhibit sufficient functions depending on the intended use.

<Processing of metal-clad laminate>
When a via is formed by laser processing using a metal-clad laminate as a material, the metal-clad laminate can be cut and a hole can be made by irradiating the portion to be processed with a laser. Blind vias can be formed by penetrating a metal-clad laminate to form through holes, or by removing only the exposed polyimide layer after removing a part of the metal foil on the upper surface. When forming the blind via, the metal foil on the upper surface is removed with a laser, and then the output of the laser is reduced to remove the polyimide layer, whereby the blind via can be stably formed.

A known type of laser can be adopted. Short wavelength lasers such as UV-YAG lasers and excimer lasers are preferred because they exhibit very high absorptance for both resins and metals. As for the formation of through holes, a method of directly drilling a through hole is also widely used. As a desmear treatment method after laser processing, a known method can be adopted, for example, a swelling step using an alkaline aqueous solution or a solution containing an organic solvent, an alkaline aqueous solution containing sodium permanganate, potassium permanganate, or the like. A wet desmear treatment method including a roughening step and a neutralization step using the above can be mentioned.

In the case of a double-sided metal-clad laminate, the inner wall of the hole after desmear treatment is plated to make both sides of the metal-clad laminate conductive. As an example of the plating method, there is a method of adhering palladium to the inner wall surface of the hole and then forming an electroless copper plating layer on the inner wall surface using the palladium as a nucleus. In this case, a plating layer having a desired thickness may be formed only by electrolytic copper plating, or a plating layer having a desired thickness may be formed by electrolytic copper plating after thinning the electrolytic copper plating layer. ..

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples.

<Measurement method and evaluation method of physical properties>
First, the storage elastic modulus and the coefficient of linear expansion of the polyimide film, and the evaluation method (hole crack test) of Examples and Comparative Examples will be described.

[Storage modulus at a temperature of 380 ° C]
Using a dynamic viscoelasticity measuring device (“DM6100” manufactured by Hitachi High-Tech Science Co., Ltd.), the dynamic viscoelasticity of a polyimide film is measured in an air atmosphere, and the correlation between the storage elastic modulus and the measured temperature is plotted and measured. The storage elastic modulus at a temperature of 380 ° C. was read. The measurement conditions are shown below.
Sample (polyimide film) width: 9 mm
Sample holder (grasping tool) spacing: 20 mm
Measurement temperature range: 0 ° C to 440 ° C
Temperature rise rate: 3 ° C / min Strain amplitude: 10 μm
Measurement frequency: 1Hz, 5Hz, 10Hz
Minimum tension / compressive force: 100mN
Tension / compression gain: 1.5
Initial force amplitude: 100mN

[Coefficient of linear expansion]
Using a thermal analyzer (Hitachi High-Tech Science Co., Ltd. "TMA / SS6100"), the polyimide film was heated from -10 ° C to 400 ° C in a nitrogen atmosphere, cooled to -10 ° C, and then 400 again. The temperature was raised to ° C., and the coefficient of linear expansion was obtained from the strain amount from 100 ° C. to 200 ° C. at the time of the second temperature rise. The measurement conditions are shown below.
Sample (polyimide film) size: width 3 mm, length 10 mm
Load: 3g (29.4mN)
Temperature rise rate: 10 ° C / min

[Hole crack test]
An electrolytic copper foil (“3EC-M3S-HTE” manufactured by Mitsui Mining & Smelting Co., Ltd.) having a thickness of 12 μm was arranged on both sides of the multi-layer polyimide film obtained in Examples and Comparative Examples described later, and further outside each electrolytic copper foil. With a protective film (Kaneka's "Apical (registered trademark) 125 NPI", thickness: 125 μm) placed on the surface, the laminating temperature is 360 ° C, the laminating pressure is 265 N / cm (27 kgf / cm), and the laminating speed is 1.0 m / min. Laminating was performed under the conditions of (1) to obtain a flexible copper-clad laminate. Next, the obtained flexible copper-clad laminate was cut into a rectangular shape of 5.0 cm × 20.0 cm to obtain a sample for processing. Then, using a UV-YAG laser, blind vias (length 10 x width 10 = 100 pieces, spacing: 1 mm) having a diameter of 75 μm were formed on the processing sample under the laser processing conditions shown in Table 1.

Next, the sample after laser processing was subjected to desmear treatment under the conditions shown in Table 2, and then the copper foil was removed by etching to obtain a sample for evaluation. The manufacturer of the chemical solution used for the desmia treatment was Roam & Haas Electronic Materials Co., Ltd. In addition, a washing step was carried out between the swelling step and the roughening step, between the roughening step and the neutralization step, and after the neutralization step.

Then, the obtained evaluation sample was observed with a polarizing microscope under a cross Nicol at a magnification of 200 times to determine the presence or absence of cracks. Specifically, the state in which light leakage occurs around the holes is judged to be "cracking", and after observing 100 holes, the ratio of the cracked holes ( The crack occurrence rate) was calculated as a percentage. 3 to 5 show an example of a polarizing microscope image used for actual discrimination. FIG. 3 is an example of a hole where no crack has occurred because no light leakage has occurred around the hole. 4 and 5 are examples of holes in which cracks are generated because light leakage occurs around the holes. For holes where the degree of light leakage was so weak that the presence or absence of cracks could not be determined, the cross section of the holes was observed with an electron microscope to determine the presence or absence of cracks.

<Preparation of polyamic acid solution>
Hereinafter, a method for preparing solutions P1 to P12 which are non-thermoplastic polyamic acid solutions and solutions P13 which are thermoplastic polyamic acid solutions will be described. The solutions P1 to P13 were all prepared in a nitrogen atmosphere at a temperature of 20 ° C.

[Preparation of solution P1]
After putting 328.53 g of DMF and 17.70 g of ODA into a glass flask having a capacity of 2 L, 18.01 g of BPDA was gradually added to the flask while stirring the contents of the flask. After visually confirming that BPDA had dissolved, 4.00 g of PMDA was gradually added to the flask while stirring the contents of the flask. After visually confirming that PMDA had dissolved, the contents of the flask were further stirred for 30 minutes. Then, while stirring the contents of the flask, 5.77 g of m-TB was added to the flask, 2.21 g of PDA was added, and then 11.42 g of PMDA was added, and the contents of the flask were further stirred for 30 minutes. did. Then, while stirring the contents of the flask, a PMDA solution prepared in advance (solvent: DMF, PMDA dissolution amount: 0.89 g, PMDA concentration: 7.2% by weight) was added to the flask. When the PMDA solution was added to the flask, it was gradually added so that the viscosity of the contents of the flask did not increase sharply. Then, when the viscosity of the flask contents at the temperature of 23 ° C. reached 2500 poisons, the addition of the PMDA solution and the stirring of the flask contents were stopped to obtain a solution P1 which is a non-thermoplastic polyamic acid solution.

It was confirmed that the polyimide obtained from the polyamic acid in the obtained solution P1 was non-thermoplastic by the method shown below. First, 32.5 g of an imidization accelerator composed of acetic anhydride / isoquinoline / DMF (weight ratio: 11.48 / 3.40 / 18.18) was added to 65 g of the solution P1 to prepare a doping solution. Then, in an atmosphere of 0 ° C. or lower, the doping liquid was defoamed while stirring, and then the doping liquid was applied onto the aluminum foil using a comma coater to form a coating film. Then, the coating film was heated for 100 seconds under the condition of a heating temperature of 115 ° C. to obtain a self-supporting gel film. The obtained gel film is peeled off from the aluminum foil, fixed to a metal fixing frame, heated for 15 seconds under the condition of a heating temperature of 250 ° C., and subsequently heated for 79 seconds under the condition of a heating temperature of 350 ° C. to dry. And imidization to obtain a polyimide film having a thickness of 12.5 μm. When the obtained polyimide film was fixed to a fixed frame made of metal and heated at a heating temperature of 450 ° C. for 2 minutes, the shape (film shape) of the polyimide film was maintained. Therefore, the polyimide obtained from the polyamic acid in the solution P1 was a non-thermoplastic polyimide. As for the solutions P2 to P12 shown below, the polyimide film obtained by the same method as the film forming method using the solution P1 is fixed to a metal fixing frame under the condition of a heating temperature of 450 ° C. When heated for 2 minutes, the shape of the polyimide film (film shape) was maintained. Therefore, the polyimides obtained from the polyamic acids in the solutions P2 to P12 were all non-thermoplastic polyimides.

[Preparation of solution P2]
After putting 328.55 g of DMF and 16.32 g of ODA into a glass flask having a capacity of 2 L, 17.98 g of BPDA was gradually added to the flask while stirring the contents of the flask. After visually confirming that BPDA had dissolved, 2.67 g of PMDA was gradually added to the flask while stirring the contents of the flask. After visually confirming that PMDA had dissolved, the contents of the flask were further stirred for 30 minutes. Then, while stirring the contents of the flask, 7.21 g of m-TB was added to the flask, 2.20 g of PDA was added, and then 12.74 g of PMDA was added, and the contents of the flask were further stirred for 30 minutes. did. Then, while stirring the contents of the flask, a PMDA solution prepared in advance (solvent: DMF, PMDA dissolution amount: 0.89 g, PMDA concentration: 7.2% by weight) was added to the flask. When the PMDA solution was added to the flask, it was gradually added so that the viscosity of the contents of the flask did not increase sharply. Then, when the viscosity of the flask contents at the temperature of 23 ° C. reached 2500 poisons, the addition of the PMDA solution and the stirring of the flask contents were stopped to obtain a solution P2 which is a non-thermoplastic polyamic acid solution.

[Preparation of solution P3]
After putting 328.78 g of DMF and 17.31 g of ODA in a glass flask having a capacity of 2 L, 22.70 g of BPDA was gradually added to the flask while stirring the contents of the flask. After visually confirming that BPDA had dissolved, the contents of the flask were further stirred for 30 minutes. Then, while stirring the contents of the flask, 5.65 g of m-TB was added to the flask, 2.16 g of PDA was added, and then 11.31 g of PMDA was added, and the contents of the flask were further stirred for 30 minutes. did. Then, while stirring the contents of the flask, a PMDA solution prepared in advance (solvent: DMF, PMDA dissolution amount: 0.87 g, PMDA concentration: 7.2% by weight) was added to the flask. When the PMDA solution was added to the flask, it was gradually added so that the viscosity of the contents of the flask did not increase sharply. Then, when the viscosity of the flask contents at the temperature of 23 ° C. reached 2500 poisons, the addition of the PMDA solution and the stirring of the flask contents were stopped to obtain a solution P3 which is a non-thermoplastic polyamic acid solution.

[Preparation of solution P4]
After putting 328.41 g of DMF and 16.51 g of ODA into a glass flask having a capacity of 2 L, 18.20 g of BPDA was gradually added to the flask while stirring the contents of the flask. After visually confirming that BPDA had dissolved, 2.70 g of PMDA was gradually added to the flask while stirring the contents of the flask. After visually confirming that PMDA had dissolved, the contents of the flask were further stirred for 30 minutes. Then, while stirring the contents of the flask, 5.83 g of m-TB was added to the flask, 2.97 g of PDA was added, and then 12.89 g of PMDA was added, and the contents of the flask were further stirred for 30 minutes. did. Then, while stirring the contents of the flask, a PMDA solution (solvent: DMF, PMDA dissolution amount: 0.90 g, PMDA concentration: 7.2% by weight) prepared in advance was added to the flask. When the PMDA solution was added to the flask, it was gradually added so that the viscosity of the contents of the flask did not increase sharply. Then, when the viscosity of the flask contents at the temperature of 23 ° C. reached 2500 poise, the addition of the PMDA solution and the stirring of the flask contents were stopped to obtain a solution P4 which is a non-thermoplastic polyamic acid solution.

[Preparation of solution P5]
After putting 328.29 g of DMF, 5.90 g of m-TB, 3.75 g of PDA and 15.30 g of ODA in a glass flask with a capacity of 2 L, the flask is stirred while stirring the contents of the flask. 18.39 g of BPDA was gradually added to the mixture. After visually confirming that BPDA had dissolved, 15.75 g of PMDA was gradually added to the flask while stirring the contents of the flask. After visually confirming that PMDA had dissolved, the contents of the flask were further stirred for 30 minutes. Then, while stirring the contents of the flask, a PMDA solution (solvent: DMF, PMDA dissolution amount: 0.91 g, PMDA concentration: 7.2% by weight) prepared in advance was added to the flask. When the PMDA solution was added to the flask, it was gradually added so that the viscosity of the contents of the flask did not increase sharply. Then, when the viscosity of the flask contents at the temperature of 23 ° C. reached 2500 poisons, the addition of the PMDA solution and the stirring of the flask contents were stopped to obtain a solution P5 which is a non-thermoplastic polyamic acid solution.

[Preparation of solution P6]
After putting 328.57 g of DMF and 17.64 g of ODA into a glass flask having a capacity of 2 L, 13.95 g of BPDA was gradually added to the flask while stirring the contents of the flask. After visually confirming that BPDA had dissolved, 4.20 g of ODPA was gradually added to the flask while stirring the contents of the flask. After visually confirming that the ODPA had dissolved, 3.99 g of PMDA was gradually added to the flask while stirring the contents of the flask. After visually confirming that PMDA had dissolved, the contents of the flask were further stirred for 30 minutes. Then, while stirring the contents of the flask, 5.75 g of m-TB was added to the flask, 2.20 g of PDA was added, and then 11.38 g of PMDA was added, and the contents of the flask were further stirred for 30 minutes. did. Then, while stirring the contents of the flask, a PMDA solution prepared in advance (solvent: DMF, PMDA dissolution amount: 0.89 g, PMDA concentration: 7.2% by weight) was added to the flask. When the PMDA solution was added to the flask, it was gradually added so that the viscosity of the contents of the flask did not increase sharply. Then, when the viscosity of the flask contents at the temperature of 23 ° C. reached 2500 poisons, the addition of the PMDA solution and the stirring of the flask contents were stopped to obtain a solution P6 which is a non-thermoplastic polyamic acid solution.

[Preparation of solution P7]
After putting 328.81 g of DMF and 15.94 g of ODA into a glass flask having a capacity of 2 L, 17.57 g of BPDA was gradually added to the flask while stirring the contents of the flask. After visually confirming that BPDA had dissolved, 2.60 g of PMDA was gradually added to the flask while stirring the contents of the flask. After visually confirming that PMDA had dissolved, the contents of the flask were further stirred for 30 minutes. Then, while stirring the contents of the flask, 9.86 g of m-TB was added to the flask, 0.72 g of PDA was added, and then 12.44 g of PMDA was added, and the contents of the flask were further stirred for 30 minutes. did. Then, while stirring the contents of the flask, a PMDA solution prepared in advance (solvent: DMF, PMDA dissolution amount: 0.87 g, PMDA concentration: 7.2% by weight) was added to the flask. When the PMDA solution was added to the flask, it was gradually added so that the viscosity of the contents of the flask did not increase sharply. Then, when the viscosity of the flask contents at the temperature of 23 ° C. reached 2500 poisons, the addition of the PMDA solution and the stirring of the flask contents were stopped to obtain a solution P7 which is a non-thermoplastic polyamic acid solution.

[Preparation of solution P8]
After putting 327.90 g of DMF, 4.57 g of m-TB, 5.43 g of PDA and 14.36 g of ODA in a glass flask with a capacity of 2 L, the flask is stirred while stirring the contents of the flask. 16.88 g of BPDA was gradually added to the mixture. After visually confirming that BPDA had dissolved, 17.83 g of PMDA was gradually added to the flask while stirring the contents of the flask. After visually confirming that PMDA had dissolved, the contents of the flask were further stirred for 30 minutes. Then, while stirring the contents of the flask, a PMDA solution prepared in advance (solvent: DMF, PMDA dissolution amount: 0.94 g, PMDA concentration: 7.2% by weight) was added to the flask. When the PMDA solution was added to the flask, it was gradually added so that the viscosity of the contents of the flask did not increase sharply. Then, when the viscosity of the flask contents at the temperature of 23 ° C. reached 2500 poisons, the addition of the PMDA solution and the stirring of the flask contents were stopped to obtain a solution P8 which is a non-thermoplastic polyamic acid solution.

[Preparation of solution P9]
After placing 328.27 g of DMF and 16.71 g of ODA in a glass flask having a capacity of 2 L, 18.41 g of BPDA was gradually added to the flask while stirring the contents of the flask. After visually confirming that BPDA had dissolved, 2.73 g of PMDA was gradually added to the flask while stirring the contents of the flask. After visually confirming that PMDA had dissolved, the contents of the flask were further stirred for 30 minutes. Then, while stirring the contents of the flask, 4.43 g of m-TB was added to the flask, 3.76 g of PDA was added, and then 13.05 g of PMDA was added, and the contents of the flask were further stirred for 30 minutes. did. Then, while stirring the contents of the flask, a PMDA solution (solvent: DMF, PMDA dissolution amount: 0.91 g, PMDA concentration: 7.2% by weight) prepared in advance was added to the flask. When the PMDA solution was added to the flask, it was gradually added so that the viscosity of the contents of the flask did not increase sharply. Then, when the viscosity of the flask contents at the temperature of 23 ° C. reached 2500 poisons, the addition of the PMDA solution and the stirring of the flask contents were stopped to obtain a solution P9 which is a non-thermoplastic polyamic acid solution.

[Preparation of solution P10]
After putting 328.91 g of DMF, 5.27 g of ODA and 16.20 g of BAPP into a glass flask having a capacity of 2 L, 8.48 g of BTDA was gradually added to the flask while stirring the contents of the flask. After visually confirming that BTDA had dissolved, 7.17 g of PMDA was gradually added to the flask while stirring the contents of the flask. After visually confirming that PMDA had dissolved, the contents of the flask were further stirred for 30 minutes. Next, 7.11 g of PDA was added to the flask while stirring the contents of the flask, followed by addition of 14.92 g of PMDA, and the contents of the flask were further stirred for 30 minutes. Then, while stirring the contents of the flask, a PMDA solution prepared in advance (solvent: DMF, PMDA dissolution amount: 0.86 g, PMDA concentration: 7.2% by weight) was added to the flask. When the PMDA solution was added to the flask, it was gradually added so that the viscosity of the contents of the flask did not increase sharply. Then, when the viscosity of the flask contents at the temperature of 23 ° C. reached 2500 poisons, the addition of the PMDA solution and the stirring of the flask contents were stopped to obtain a solution P10 which is a non-thermoplastic polyamic acid solution.

[Preparation of solution P11]
After placing 328.49 g of DMF and 12.29 g of ODA in a glass flask having a capacity of 2 L, 16.06 g of BPDA was gradually added to the flask while stirring the contents of the flask. After visually confirming that BPDA had dissolved, the contents of the flask were further stirred for 30 minutes. Then, while stirring the contents of the flask, 11.58 g of m-TB was added to the flask, 2.21 g of PDA was added, and then 16.96 g of PMDA was added, and the contents of the flask were further stirred for 30 minutes. did. Then, while stirring the contents of the flask, a PMDA solution prepared in advance (solvent: DMF, PMDA dissolution amount: 0.89 g, PMDA concentration: 7.2% by weight) was added to the flask. When the PMDA solution was added to the flask, it was gradually added so that the viscosity of the contents of the flask did not increase sharply. Then, when the viscosity of the flask contents at the temperature of 23 ° C. reached 2500 poisons, the addition of the PMDA solution and the stirring of the flask contents were stopped to obtain a solution P11 which is a non-thermoplastic polyamic acid solution.

[Preparation of solution P12]
In a glass flask with a capacity of 2 L, 329.58 g of DMF, 7.86 g of m-TB, 12.36 g of ODA, and 8.61 g of 9,9-bis (4-aminophenyl) fluorene (hereinafter referred to as "4"). After adding (sometimes referred to as "BAFL"), 16.35 g of BPDA was gradually added to the flask while stirring the contents of the flask. After visually confirming that BPDA had dissolved, 14.01 g of PMDA was gradually added to the flask while stirring the contents of the flask. After visually confirming that PMDA had dissolved, the contents of the flask were further stirred for 30 minutes. Then, while stirring the contents of the flask, a PMDA solution (solvent: DMF, PMDA dissolution amount: 0.81 g, PMDA concentration: 7.2% by weight) prepared in advance was added to the flask. When the PMDA solution was added to the flask, it was gradually added so that the viscosity of the contents of the flask did not increase sharply. Then, when the viscosity of the flask contents at the temperature of 23 ° C. reached 2500 poisons, the addition of the PMDA solution and the stirring of the flask contents were stopped to obtain a solution P12 which is a non-thermoplastic polyamic acid solution.

[Preparation of solution P13]
After putting 673.24 g of DMF and 71.83 g of BAPP in a glass flask having a capacity of 2 L, 7.72 g of BPDA was gradually added to the flask while stirring the contents of the flask. After visually confirming that BPDA had dissolved, 31.30 g of PMDA was gradually added to the flask while stirring the contents of the flask. After visually confirming that PMDA had dissolved, the contents of the flask were further stirred for 30 minutes. Then, while stirring the contents of the flask, a PMDA solution prepared in advance (solvent: DMF, PMDA dissolution amount: 1.15 g, PMDA concentration: 7.2% by weight) was added to the flask. When the PMDA solution was added to the flask, it was gradually added so that the viscosity of the contents of the flask did not increase sharply. Then, when the viscosity of the flask contents at the temperature of 23 ° C. reached 300 poise, the addition of the PMDA solution and the stirring of the flask contents were stopped to obtain a solution P13 which is a thermoplastic polyamic acid solution.

It was confirmed that the polyimide obtained from the polyamic acid in the solution P13 was thermoplastic by the method shown below. First, 30.0 g of an imidization accelerator composed of acetic anhydride / isoquinoline / DMF (weight ratio: 6.89 / 2.14 / 20.97) was added to 60 g of the solution P13 to prepare a doping solution. Then, in an atmosphere of 0 ° C. or lower, the doping liquid was defoamed while stirring, and then the doping liquid was applied onto the aluminum foil using a comma coater to form a coating film. Next, the coating film was heated at a heating temperature of 120 ° C. for 3 minutes to obtain a self-supporting gel film. The obtained gel film is peeled off from the aluminum foil, fixed to a metal fixing frame, heated at a heating temperature of 250 ° C. for 1 minute, and subsequently heated at a heating temperature of 300 ° C. for 200 seconds to dry. And imidization to obtain a polyimide film having a thickness of 20.0 μm. When the obtained polyimide film was fixed to a metal fixing frame and heated at a heating temperature of 450 ° C. for 2 minutes, the shape (film shape) of the polyimide film was not maintained. Therefore, the polyimide obtained from the polyamic acid in the solution P13 was a thermoplastic polyimide.

<Manufacturing of multi-layer polyimide film>
Hereinafter, methods for producing the multilayer polyimide films of Examples 1 to 7 and Comparative Examples 1 to 5 will be described.

[Example 1]
A dope solution was prepared by adding 32.5 g of an imidization accelerator composed of acetic anhydride / isoquinoline / DMF (weight ratio: 11.48 / 3.40 / 18.18) to 65 g of the solution P1. Then, in an atmosphere of 0 ° C. or lower, the doping liquid was defoamed while stirring, and then the doping liquid was applied onto the aluminum foil using a comma coater to form a coating film. Then, the coating film was heated for 100 seconds under the condition of a heating temperature of 115 ° C. to obtain a self-supporting gel film. The obtained gel film is peeled off from the aluminum foil, fixed to a metal fixing frame, heated for 15 seconds under the condition of a heating temperature of 250 ° C., and subsequently heated for 79 seconds under the condition of a heating temperature of 350 ° C. to dry. And imidization to obtain a polyimide film having a thickness of 12.5 μm. Table 4 shows the physical characteristics of the obtained polyimide film (non-thermoplastic polyimide layer). The "physical characteristics of the non-thermoplastic polyimide layer" in Table 4 are the physical characteristics measured using a polyimide film having a thickness of 12.5 μm.

Next, the solution P13 is diluted with DMF until the solid content concentration becomes 8% by weight to prepare a dope solution, and then applied to both sides of the above-mentioned polyimide film (polyimide film obtained by using the solution P1) and applied. A film was formed. The coating amount at this time was adjusted so that the thickness of each formed thermoplastic polyimide layer (adhesive layer) was 3 μm. Next, the coating film was heated at a heating temperature of 120 ° C. for 2 minutes, and subsequently heated at a heating temperature of 350 ° C. for 15 seconds to dry and imidize, to obtain a multilayer polyimide film of Example 1. Table 4 shows the results (crack generation rate) of the hole crack test of the obtained multi-layer polyimide film. The copper-clad laminate produced during the hole crack test had no wrinkles on the surface and had a good appearance.

[Examples 2 to 7 and Comparative Examples 1 to 5]
The multi-layer polyimide films of Examples 2 to 7 and Comparative Examples 1 to 5 were obtained by the same method as in Example 1 except that the non-thermoplastic polyamic acid solution shown in Table 4 was used instead of the solution P1. .. In each of Examples 2 to 7 and Comparative Examples 1 to 5, the amount of the non-thermoplastic polyamic acid solution used was 65 g. Table 4 shows the results (crack generation rate) of the hole crack test of the obtained multi-layer polyimide film. In Examples 2 to 4, Example 6, Example 7, and Comparative Examples 2 to 4, the copper-clad laminates produced during the hole crack test had no wrinkles on the surface and had a good appearance. was gotten. On the other hand, in Example 5, Comparative Example 1 and Comparative Example 5, there were wrinkles on a part of the surface of the copper-clad laminate prepared at the time of the hole crack test.

<Evaluation result>
Table 3 shows the materials used for each of the solutions P1 to P13 and their ratios. The substance amount ratio (molar ratio) of each residue in the polyimide obtained by using each of the solutions P1 to P13 is consistent with the substance amount ratio of each monomer (diamine and tetracarboxylic acid dianhydride) used. rice field. In addition, Table 4 shows the types of non-thermoplastic polyamic acid solutions used, the physical properties of the non-thermoplastic polyimide layer, and the results of the whole crack test (crack generation rate) for each of Examples 1 to 7 and Comparative Examples 1 to 5. )showed that. In addition, in Table 3, "-" means that the said component was not used. Further, in Table 3, the numerical value in the column of "acid dianhydride" is the content ratio (unit: mol%) of each acid dianhydride with respect to the total amount of acid dianhydride used. The numerical value in the column of "diamine" is the content ratio (unit: mol%) of each diamine with respect to the total amount of diamines used.

In Examples 1 to 7, the non-thermoplastic polyimide had an m-TB residue, which is a kind of BPDI residue, an ODA residue, and a PDA residue. In Examples 1 to 7, the content of m-TB residues was 20 mol% or more and 35 mol% or less with respect to all the diamine residues constituting the non-thermoplastic polyimide. In Examples 1 to 7, the crack occurrence rate was 50% or less. The non-thermoplastic polyimides of Examples 1 to 4, 6 and 7 were block copolymers having specific segments, but the non-thermoplastic polyimides of Example 5 were random copolymers.

In Comparative Examples 1 and 2, the content of BPDI residues (m-TB residues) was less than 20 mol% with respect to all the diamine residues constituting the non-thermoplastic polyimide. In Comparative Example 3, the non-thermoplastic polyimide did not have a BPDI residue. In Comparative Example 4, the content of BPDI residues (m-TB residues) exceeded 35 mol% with respect to all the diamine residues constituting the non-thermoplastic polyimide. In Comparative Example 5, the non-thermoplastic polyimide did not have a PDA residue. In Comparative Examples 1 to 5, the crack occurrence rate exceeded 50%.

From the above results, it was shown that the multi-layer polyimide film according to the present invention can suppress the occurrence of cracks on the inner wall of the via during the desmear treatment after laser processing.

10: Multi-layer polyimide film 11: Non-thermoplastic polyimide layer 12: Thermoplastic polyimide layer

Claims

A multi-layer polyimide film having a non-thermoplastic polyimide layer and a thermoplastic polyimide layer arranged on at least one side of the non-thermoplastic polyimide layer.
The non-thermoplastic polyimide contained in the non-thermoplastic polyimide layer has a tetracarboxylic dianhydride residue and a diamine residue, and has a tetracarboxylic dianhydride residue and a diamine residue.
The diamine residue contains a diamine residue having a biphenyl skeleton, a 4,4'-diaminodiphenyl ether residue, and a p-phenylenediamine residue.
A multilayer polyimide film in which the content of diamine residues having a biphenyl skeleton is 20 mol% or more and 35 mol% or less with respect to all the diamine residues constituting the non-thermoplastic polyimide.
The multilayer polyimide film according to claim 1, wherein the diamine residue having the biphenyl skeleton is a 4,4'-diamino-2,2'-dimethylbiphenyl residue.
The 4,4'-diaminodiphenyl ether residue is 40 mol% or more and 70 mol% or less with respect to all the diamine residues constituting the non-thermoplastic polyimide, according to claim 1 or 2. Multi-layer polyimide film.
The item according to any one of claims 1 to 3, wherein the content of the p-phenylenediamine residue is 5 mol% or more and 50 mol% or less with respect to all the diamine residues constituting the non-thermoplastic polyimide. The multi-layer polyimide film described.
The tetracarboxylic dianhydride residue comprises one or more selected from the group consisting of 3,3', 4,4'-biphenyltetracarboxylic dianhydride residue and pyromellitic dianhydride residue. The multilayer polyimide film according to any one of claims 1 to 4.
The multilayer polyimide film according to claim 5, wherein the tetracarboxylic dianhydride residue further contains a 4,4'-oxydiphthalic acid anhydride residue.
Claimed that the content of the 4,4'-oxydiphthalic anhydride residue is 5 mol% or more and 15 mol% or less with respect to the total tetracarboxylic acid dianhydride residue constituting the non-thermoplastic polyimide. Item 6. The multilayer polyimide film according to Item 6.
The thermoplastic polyimide contained in the thermoplastic polyimide layer is one or more selected from the group consisting of 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride residue and pyromellitic acid dianhydride residue. , 2,2-Bis [4- (4-aminophenoxy) phenyl] The multilayer polyimide film according to any one of claims 1 to 7, which has a propane residue.
The multilayer polyimide film according to any one of claims 1 to 8, wherein the non-thermoplastic polyimide layer has a storage elastic modulus of less than 0.350 GPa at a temperature of 380 ° C.
The invention according to any one of claims 1 to 9, wherein the non-thermoplastic polyimide layer has a coefficient of linear expansion during temperature rise from 100 ° C. to 200 ° C. of 5.0 ppm / K or more and 19.0 ppm / K or less. Multi-layer polyimide film.