Multilayer polyimide film

Abstract

The multilayer polyimide film (10) comprises a non-thermoplastic polyimide layer (11) and a thermoplastic polyimide layer (12) disposed on at least one side of the non-thermoplastic polyimide layer (11). The non-thermoplastic polyimide contained in the non-thermoplastic polyimide layer (11) comprises a tetracarboxylic dianhydride residue and a diamine residue. The diamine residue comprises 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 a biphenyl skeleton is greater than or equal to 20 mol % and less than or equal to 35 mol % relative to the total diamine residues constituting the non-thermoplastic polyimide.

Description

Technical Field

[0001] The present invention relates to a multilayer polyimide film. Background Art

[0002] In recent years, with the growing demand for electronic products, primarily smartphones, tablets, and laptops, the demand for flexible printed circuit boards (hereinafter sometimes referred to as "FPCs") has increased. In particular, demand for flexible printed circuit boards made from multilayer polyimide films containing thermoplastic polyimide layers as adhesive layers is expected to grow further due to their excellent heat resistance and flexibility. Furthermore, with the continued advancement of lightweight, miniaturized, and thinner electronic devices in recent years, the demand for even finer FPC wiring remains strong.

[0003] When making fine double-sided FPCs or multi-layer FPCs, a metal-clad laminate made by laminating metal foils such as copper foil to both sides of a polyimide film is usually used as the material. In FPC manufacturing, there is a process of first opening a hole for interlayer conduction (hereinafter sometimes referred to as a "through hole"). The two sides of the wiring board are made conductive by plating the inner wall of the through hole. In the through hole formation process, there are a through hole method that uses a drill or a laser to open a through hole in the metal foil and the insulating layer (polyimide layer) on both sides, and a blind hole method that uses a laser or the like to cut the metal foil and the insulating layer on one side and leave the metal foil on the other side. In particular, in fine FPCs, the blind hole method is frequently used to effectively use the area.

[0004] In the past, in such a through-hole forming process, in order to clean the inside of the hole and the surface of the metal foil or remove resin residue after the hole is opened, a wet decontamination treatment is performed on the laminate using an alkaline potassium permanganate aqueous solution or the like under heating. Polyimide is originally easily hydrolyzed under alkaline conditions, but in the case of laser processing, residual stress is generated due to local heating. Therefore, during the decontamination treatment after the through-hole forming process, defects such as cracks are easily generated on the inner wall of the through-hole. Patent document 1 describes a method of adding a heat treatment process between laser processing and decontamination treatment to remove the residual stress generated during laser processing and suppress the generation of defects. Patent document 2 discloses a polyimide that is resistant to alkaline solutions used in the development process, etching process and resist stripping process.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2012-186377

[0008] Patent Document 2: Japanese Patent Application Laid-Open No. 2017-179148 Summary of the Invention

[0009] Problems to be solved by the invention

[0010] The cracks generated on the inner wall of the through hole due to the decontamination treatment after laser processing become the cause of deformation of the plated part and reduction of connection reliability in the process after the plating treatment, or become the cause of reduction of insulation reliability due to the intrusion of chemical solutions into the cracks, thereby adversely affecting the quality. Cracks are more likely to occur when forming blind holes than when forming through holes. It should be noted that, through the research of the present inventors, it was found that: when the metal foil is removed by etching or the like without performing decontamination treatment after laser processing, or when the metal foil is removed without laser processing, decontamination treatment is performed, no cracks will be generated. In addition, through the research of the present inventors, it was found that: in the decontamination treatment after laser processing, if the swelling time and roughening time are prolonged, cracks will become more likely to occur.

[0011] As a method for suppressing crack formation, the method disclosed in Patent Document 1, which involves adding a heat treatment step between laser processing and desmearing, reduces circuit board productivity due to the additional heat treatment step. Furthermore, the method described in Patent Document 1 leaves room for improvement in suppressing crack formation on the inner walls of through-holes.

[0012] Furthermore, although the method described in Patent Document 2 can suppress the cracking of the thin film in an alkaline environment, there is still room for improvement in suppressing the generation of cracks on the inner wall of the through-hole.

[0013] The present invention has been made in view of these problems, and an object of the present invention is to provide a multilayer polyimide film capable of suppressing the generation of cracks on the inner wall of a through hole during desmear treatment after laser processing.

[0014] Solutions for solving problems

[0015] During the decontamination treatment after laser processing, it is important to mitigate the stress generated in the polyimide film during laser processing in order to suppress the formation of cracks on the inner wall of the through-hole. On the other hand, using a polyimide film containing a large number of flexible skeletons can easily mitigate stress, but such polyimides have a much larger linear expansion coefficient than the metal to which they are bonded, resulting in warping or wrinkling when bonded to metal foil. The present inventors conducted in-depth research and found that by using a non-thermoplastic polyimide with a specific structure as the core material for the multilayer polyimide film, it is possible to ensure a linear expansion coefficient comparable to that of metal and mitigate the stress generated in the polyimide film during laser processing.

[0016] The multilayer polyimide film of the present invention comprises a non-thermoplastic polyimide layer and a thermoplastic polyimide layer disposed on at least one surface of the non-thermoplastic polyimide layer. The non-thermoplastic polyimide contained in the non-thermoplastic polyimide layer comprises tetracarboxylic dianhydride residues and diamine residues. The diamine residues include diamine residues having a biphenyl skeleton, 4,4'-diaminodiphenyl ether residues, and p-phenylenediamine residues. The content of the diamine residues having a biphenyl skeleton is 20 mol% or more and 35 mol% or less relative to the total diamine residues constituting the non-thermoplastic polyimide.

[0017] In the multilayer polyimide film according to one embodiment of the present invention, the diamine residue having a biphenyl skeleton is a 4,4′-diamino-2,2′-dimethylbiphenyl residue.

[0018] In the multilayer polyimide film according to one embodiment of the present invention, the content of the 4,4′-diaminodiphenyl ether residue is 40 mol % or more and 70 mol % or less relative to all diamine residues constituting the non-thermoplastic polyimide.

[0019] In the multilayer polyimide film according to one embodiment of the present invention, the content of the p-phenylenediamine residue is 5 mol % or more and 50 mol % or less relative to all diamine residues constituting the non-thermoplastic polyimide.

[0020] In the multilayer polyimide film according to one embodiment of the present invention, the tetracarboxylic dianhydride residue includes at least one selected from the group consisting of a 3,3′,4,4′-biphenyltetracarboxylic dianhydride residue and a pyromellitic dianhydride residue.

[0021] In the multilayer polyimide film according to one embodiment of the present invention, the tetracarboxylic dianhydride residue further includes a 4,4'-oxydiphthalic anhydride residue.

[0022] In the multilayer polyimide film according to one embodiment of the present invention, the content of the 4,4'-oxydiphthalic anhydride residue is 5 mol% to 15 mol% based on all tetracarboxylic dianhydride residues constituting the non-thermoplastic polyimide.

[0023] In the multilayer polyimide film according to one embodiment of the present invention, the thermoplastic polyimide contained in the thermoplastic polyimide layer has at least one selected from the group consisting of 3,3',4,4'-biphenyltetracarboxylic dianhydride residues and pyromellitic dianhydride residues, and 2,2-bis[4-(4-aminophenoxy)phenyl]propane residues.

[0024] In the multilayer polyimide film according to one embodiment of the present invention, the storage modulus of the non-thermoplastic polyimide layer at a temperature of 380° C. is less than 0.350 GPa.

[0025] In the multilayer polyimide film according to one embodiment of the present invention, the linear expansion coefficient of the non-thermoplastic polyimide layer at a temperature of 100° C. to 200° C. is 5.0 ppm / K or more and 19.0 ppm / K or less.

[0026] Effects of the Invention

[0027] According to the multilayer polyimide film of the present invention, the generation of cracks on the inner wall of the through hole can be suppressed during desmear treatment after laser processing without increasing the man-hours in the manufacturing process of the circuit board. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a cross-sectional view showing an example of the multilayer polyimide film of the present invention.

[0029] Figure 2 This is a cross-sectional view showing a metal-clad laminate obtained by using an example of the multilayer polyimide film of the present invention.

[0030] Figure 3 This is an example of a polarizing microscope image used to determine hole crack testing.

[0031] Figure 4 This is another example of a polarizing microscope image used in hole crack testing.

[0032] Figure 5 This is another example of a polarizing microscope image used in hole crack testing. DETAILED DESCRIPTION

[0033] Hereinafter, preferred embodiments of the present invention will be described in detail, but the present invention is not limited thereto. In addition, all academic documents and patent documents described in this specification are incorporated herein by reference.

[0034] First, the terms used in this specification will be explained: "Polyimide" is a polymer having a structural unit represented by the following general formula (1) as a repeating unit.

[0035]

[0036] In the general formula (1), X represents a tetracarboxylic dianhydride residue (a tetravalent organic group derived from tetracarboxylic dianhydride), and Y represents a diamine residue (a divalent organic group derived from diamine).

[0037] The term "biphenyl skeleton" refers to a skeleton having a bicyclic structure in which two benzene rings are bonded via a single bond. Therefore, a diamine residue having a biphenyl skeleton does not include a diamine residue having a condensed ring such as a 9,9-bis(4-aminophenyl)fluorene residue.

[0038] Unless otherwise specified, the "linear expansion coefficient" refers to the linear expansion coefficient when the temperature is increased from 100°C to 200°C.

[0039] "Non-thermoplastic polyimide" refers to a polyimide that maintains its film shape (flat film shape) without wrinkling or stretching when fixed to a metal fixing frame in a thin film state and heated at 450°C for 2 minutes. "Thermoplastic polyimide" refers to a polyimide that does not maintain its film shape when fixed to a metal fixing frame in a thin film state and heated at 450°C for 2 minutes.

[0040] The "main surface" of a layered object (more specifically, a non-thermoplastic polyimide layer, a thermoplastic polyimide layer, etc.) refers to a surface perpendicular to the thickness direction of the layered object.

[0041] Hereinafter, the term "system" may be added after the compound name to collectively refer to the compound and its derivatives.

[0042] <Multilayer polyimide film>

[0043] The multilayer polyimide film involved in the present embodiment has a non-thermoplastic polyimide layer and a thermoplastic polyimide layer configured 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 with a biphenyl skeleton (a residue derived from a diamine with a biphenyl skeleton), a 4,4'-diaminodiphenyl ether residue, and a p-phenylenediamine residue. With respect to all diamine residues constituting the non-thermoplastic polyimide, the content of the diamine residue with a biphenyl skeleton is preferably 20 mol % or more and 35 mol % or less.

[0044] Hereinafter, 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". Paraphenylenediamine may be referred to as "PDA". In addition, a non-thermoplastic polyimide contained in a non-thermoplastic polyimide layer may be referred to simply as "non-thermoplastic polyimide". A thermoplastic polyimide contained in a thermoplastic polyimide layer may be referred to simply as "thermoplastic polyimide".

[0045] The present inventors conducted extensive research on the molecular design of polyimides that can mitigate the stress generated in films during laser processing while maintaining the heat resistance (linear expansion coefficient, etc.) of metal-clad laminates. As a result, the present inventors discovered that by optimizing the structure of the non-thermoplastic polyimide contained in a multilayer polyimide film, cracking of the inner walls of through-holes can be suppressed during desmear treatment after laser processing, without significantly altering the circuit board manufacturing process.

[0046] [Composition of multilayer polyimide film]

[0047] The following describes the structure of the multilayer polyimide film according to this embodiment with reference to the accompanying drawings. It should be noted that, for ease of understanding, the referenced drawings primarily schematically illustrate the various components. For ease of illustration, the size, number, and shape of the components illustrated may differ from actual conditions. Furthermore, in this specification, for ease of explanation, identical components to those in previously described drawings are denoted by the same reference numerals in subsequent drawings, and their description may be omitted.

[0048] Figure 1 : is a cross-sectional view showing an example of a multilayer polyimide film of the present invention. Figure 1 As shown, the multilayer polyimide film 10 includes a non-thermoplastic polyimide layer 11 and a thermoplastic polyimide layer 12 disposed on at least one surface of the non-thermoplastic polyimide layer 11. The non-thermoplastic polyimide contained in the non-thermoplastic polyimide layer 11 has tetracarboxylic dianhydride residues and diamine residues. The diamine residues include BPDI residues, ODA residues, and PDA residues. The BPDI residue content is preferably 20 mol% or more and 35 mol% or less relative to all diamine residues constituting the non-thermoplastic polyimide contained in the non-thermoplastic polyimide layer 11.

[0049] By utilizing the multilayer polyimide film 10, the generation of cracks on the inner wall of the through-hole can be suppressed during the decontamination treatment after laser processing. The reason is speculated to be as follows. In the multilayer polyimide film 10, the non-thermoplastic polyimide contained in the non-thermoplastic polyimide layer 11 has a BPDI residue having a skeleton with a high degree of free rotation of the molecular chain at a content rate within a specific range. Furthermore, the non-thermoplastic polyimide contained in the non-thermoplastic polyimide layer 11 has an ODA residue of a curved structure that contributes to the flexibility of the multilayer polyimide film 10 and a PDA residue of a rigid structure that contributes to the heat resistance of the multilayer polyimide film 10. Thus, the multilayer polyimide film 10 can alleviate the stress generated in the film during laser processing while maintaining the heat resistance (linear expansion coefficient, etc.) when used for the metal-clad laminate. Therefore, by utilizing the multilayer polyimide film 10, the generation of cracks on the inner wall of the through-hole can be suppressed during the decontamination treatment after laser processing. To more effectively suppress cracking on the inner walls of through-holes, the benzene rings in the BPDI residues preferably have substituents, more preferably alkyl groups, and even more preferably methyl groups. Substituents on the benzene rings in the BPDI residues reduce the symmetry of the polyimide's primary structure, hindering polymer chain packing and further alleviating stress generated in the film during laser processing.

[0050] It should be noted that Figure 1 In the illustrated multilayer polyimide film 10, the thermoplastic polyimide layer 12 is provided only on one side of the non-thermoplastic polyimide layer 11. However, the thermoplastic polyimide layer 12 may be provided on both sides (both main sides) of the non-thermoplastic polyimide layer 11. When the thermoplastic polyimide layer 12 is provided on both sides of the non-thermoplastic polyimide layer 11, the two thermoplastic polyimide layers 12 may comprise the same thermoplastic polyimide or different types of thermoplastic polyimide. Furthermore, the thickness of the two thermoplastic polyimide layers 12 may be the same or different. Furthermore, 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 “multilayer polyimide film 10” includes a film having a thermoplastic polyimide layer 12 only on one side of a non-thermoplastic polyimide layer 11, a film having thermoplastic polyimide layers 12 on both sides of a non-thermoplastic polyimide layer 11, and a film having two or more layers of both a non-thermoplastic polyimide layer 11 and a thermoplastic polyimide layer 12.

[0051] The thickness of the multilayer polyimide film 10 (the 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 lightweight the resulting FPC, and the more improved the bendability of the resulting FPC. In order to make lightweighting of the FPC easier while ensuring mechanical strength and 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, and more preferably 10 μm or more and 25 μm or less. The thickness of the multilayer polyimide film 10 can be measured using a laser hologram micrometer.

[0052] To ensure adhesion to the metal foil and facilitate thinning of the FPC, the thickness of the thermoplastic polyimide layer 12 (when two or more thermoplastic polyimide layers 12 are provided, the thickness of each thermoplastic polyimide layer 12) is preferably 1 μm or more and 15 μm or less. Furthermore, to facilitate adjustment of the linear expansion coefficient of the multilayer polyimide film 10, the thickness ratio of the non-thermoplastic polyimide layer 11 to the thermoplastic polyimide layer 12 (thickness of the non-thermoplastic polyimide layer 11 / thickness of the thermoplastic polyimide layer 12) is preferably 55 / 45 or more and 95 / 5 or less. When multiple layers of the non-thermoplastic polyimide layer 11 and the thermoplastic polyimide layer 12 are provided separately, the thickness ratio is the ratio of the total thickness of each layer. Even if the number of thermoplastic polyimide layers 12 increases, it is preferable that the total thickness of the thermoplastic polyimide layers 12 does not exceed the total thickness of the non-thermoplastic polyimide layers 11 .

[0053] To suppress warping of the multilayer polyimide film 10, it is preferred that thermoplastic polyimide layers 12 be provided on both sides of the non-thermoplastic polyimide layer 11. More preferably, thermoplastic polyimide layers 12 comprising the same type of thermoplastic polyimide be provided on both sides of the non-thermoplastic polyimide layer 11. When thermoplastic polyimide layers 12 are provided on both sides of the non-thermoplastic polyimide layer 11, it is preferred that both thermoplastic polyimide layers 12 have the same thickness to suppress warping of the multilayer polyimide film 10. It should be noted that even if the two thermoplastic polyimide layers 12 have different thicknesses, warping of the multilayer polyimide film 10 can be suppressed as long as the thickness of the other thermoplastic polyimide layer 12 is within a range of 40% or more and less than 100% of the thickness of the thicker thermoplastic polyimide layer 12.

[0054] To further suppress cracking of the through-hole inner wall during desmear treatment after laser processing, the non-thermoplastic polyimide layer 11 preferably has a storage modulus of less than 0.350 GPa at 380°C, more preferably less than 0.200 GPa. Furthermore, to improve the mechanical strength of the multilayer polyimide film 10 at high temperatures, the storage modulus is preferably greater than 0.010 GPa, more preferably greater than 0.050 GPa. The storage modulus can be adjusted, for example, by varying the BPDI residue content. The storage modulus is measured using the same method as in the examples described below, or a method based thereon.

[0055] When the dynamic viscoelasticity of the non-thermoplastic polyimide layer 11 is measured, the temperature indicated by the inflection point of the storage modulus is preferably within the range of 270°C to 340°C, and more preferably within the range of 280°C to 330°C, from the perspective of stress relaxation during laser processing and thermal stress relaxation when laminating the metal foil by lamination. If the temperature indicated by the inflection point of the storage modulus is within this range, dimensional changes at the temperature (e.g., 250°C) at which the dimensional changes of the flexible metal-clad laminate after heating are evaluated can be suppressed. On the other hand, if the temperature indicated by the inflection point of the storage modulus is low, the stress generated in the multilayer polyimide film 10 during cooling after laser processing is reduced.

[0056] The linear expansion coefficient of the non-thermoplastic polyimide layer 11 is preferably 5.0 ppm / K to 19.0 ppm / K, more preferably 8.0 ppm / K to 15.0 ppm / K, and even more preferably 9.0 ppm / K to 12.0 ppm / K. If the linear expansion coefficient of the non-thermoplastic polyimide layer 11 is 5.0 ppm / K to 19.0 ppm / K, the linear expansion coefficient of the multilayer polyimide film 10 can be adjusted to, for example, 14.0 ppm / K to 22.0 ppm / K, which is close to that of copper foil, and ideally, to 16.0 ppm / K to 20.0 ppm / K, which is even closer to that of copper foil. This reduces the stress generated within the multilayer polyimide film 10 during cooling after laser processing, further suppressing the occurrence of cracks on the inner wall of the through-hole during desmearing after laser processing. The linear expansion coefficient can be adjusted by, for example, changing the content of residues derived from monomers having a rigid structure (more specifically, PDA residues, etc.) and the content of residues derived from monomers having a curved structure (more specifically, ODA residues, etc.). The linear expansion coefficient is measured using the same method as in the examples described below or a method based thereon.

[0057] The slope of the plastic deformation region in the stress-strain curve of the non-thermoplastic polyimide layer 11 is preferably 2.0 or more. When the non-thermoplastic polyimide layer 11 is difficult to plastically deform and has a high yield strength, it shows high durability against rupture 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 characteristic of "difficult to plastically deform" means that the stress in the plastic deformation region increases significantly, or the stress required for plastic deformation is large. The characteristic of "difficult to plastically deform" is, for example, an indicator of the slope of the plastic deformation region. The slope of the plastic deformation region is, for example, the slope of the ss curve in the plastic deformation region of a graph with the vertical axis set to "stress (unit: MPa)" and the horizontal axis set to "strain (unit: mm)" for the result of measuring tensile properties according to ASTM D882. The slope of the ss curve in the plastic deformation region can be calculated by the following calculation formula. It should be noted that, in the following formula, stress1 is the stress at 10% strain, stress2 is the fracture stress, strain1 is the 10% strain, and strain2 is the fracture strain.

[0058] The slope of the SS curve in the plastic deformation region = (stress2-stress1) / (strain2-strain1)

[0059] The slope of the plastic deformation region of the non-thermoplastic polyimide layer 11 is preferably 2.0 or greater, more preferably 2.2 or greater, and even more preferably 2.5 or greater. When the slope of the plastic deformation region is 2.0 or greater, a highly stacked aggregate structure of polymer chains is formed, which can also suppress the occurrence of cracks during the continuous FPC processing steps. The higher the slope of the plastic deformation region, the better. However, to suppress the occurrence of springback, the slope of the plastic deformation region is preferably 4.5 or less, and more preferably 4.0 or less.

[0060] When a metal-clad laminate is produced using the multilayer polyimide film 10, at least one surface (e.g. Figure 1 In the case of the thermoplastic polyimide layer 12, the surface 12a) of the thermoplastic polyimide layer 12 is adhered with the metal foil 13. Figure 2 The metal-clad laminate 20 shown is shown. There are no particular limitations on the method for laminating the metal foil 13 to the surface 12a of the thermoplastic polyimide layer 12, and various known methods can be employed. For example, a continuous processing method using a hot roll laminating device or a double belt press (DBP) having a pair or more of metal rolls can be employed. The specific configuration of the hot roll lamination method is not particularly limited, but in order to improve the appearance of the resulting multilayer polyimide film 10, a protective material is preferably disposed between the pressurized surface and the metal foil 13.

[0061] When the thermoplastic polyimide layer 12 is provided on both surfaces of the non-thermoplastic polyimide layer 11 , a double-sided metal-clad laminate (not shown) is obtained by laminating the metal foil 13 on both surfaces of the multilayer polyimide film 10 .

[0062] [Elements of multilayer polyimide film]

[0063] Next, the elements (constituent elements) of the multilayer polyimide film of this embodiment will be described in detail.

[0064] (Non-thermoplastic polyimide layer)

[0065] The non-thermoplastic polyimide contained in the non-thermoplastic polyimide layer has BPDI residues, ODA residues, and PDA residues as diamine residues. To further suppress the occurrence of cracks on the inner wall of the through-hole during desmear treatment after laser processing, the total content of BPDI residues, ODA residues, and PDA residues relative to the total diamine residues constituting the non-thermoplastic polyimide is preferably 50 mol% or greater, more preferably 70 mol% or greater, even more preferably 80 mol% or greater, even more preferably 90 mol% or greater, and may be 100 mol%.

[0066] As the diamine (monomer) for forming the BPDI residue, for example, 4,4'-diamino-2,2'-dimethylbiphenyl (hereinafter, sometimes described as "m-TB"), 4,4'-diaminobiphenyl, 4,4'-diamino-3,3'-dimethylbiphenyl, 4,4'-diamino-2,2'-dimethoxybiphenyl, 4,4'-diamino-3,3'-dimethoxybiphenyl, 3,3',5,5'-tetramethylbenzidine, 4,4'-bis(4-aminophenoxy)biphenyl, etc. can be cited. In the present embodiment, as the diamine for forming the BPDI residue, one or more diamines can be used. In order to further suppress the generation of cracks on the inner wall of the through-hole during the decontamination treatment after laser processing, m-TB is preferably used as the diamine (monomer) for forming the BPDI residue. That is, as the BPDI residue, an m-TB residue is preferably used.

[0067] In order to maintain the linear expansion coefficient and further suppress the occurrence of cracks on the inner wall of the through-hole during desmear treatment after laser processing, the content of ODA residues relative to the total diamine residues constituting the non-thermoplastic polyimide is preferably 40 mol% to 70 mol%, more preferably 45 mol% to 65 mol%, and even more preferably 50 mol% to 65 mol%. In order to maintain the linear expansion coefficient and further suppress the occurrence of cracks on the inner wall of the through-hole during desmear treatment after laser processing, the content of PDA residues relative to the total diamine residues constituting the non-thermoplastic polyimide is preferably 5 mol% to 50 mol%, more preferably 10 mol% to 40 mol%, and even more preferably 15 mol% to 30 mol%.

[0068] The non-thermoplastic polyimide may have a diamine residue (other diamine residue) other than the BPDI residue, the ODA residue, and the PDA residue as the diamine residue. As the diamine (monomer) for forming the other diamine residue, an aromatic diamine having high heat resistance is preferred. Specific examples of the diamine for forming other diamine residues include 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 1,5-diaminonaphthalene, 4,4'-diaminodiphenyldiethylsilane, 4,4'-diaminodiphenylsilane, 4,4'-diaminodiphenylethylphosphine oxide, 4,4'-diaminodiphenyl N-methylamine, 4,4'-diaminodiphenyl N-aniline, 1,3-diaminobenzene, and 1,2-diaminobenzene.

[0069] In addition to the diamine residue, the non-thermoplastic polyimide also has an acid dianhydride residue. As the acid dianhydride (monomer) for forming the acid dianhydride residue, from the viewpoint of improving heat resistance, preferably an aromatic acid dianhydride. In addition, in order to further suppress the generation of cracks on the inner wall of the through-hole during the decontamination treatment after laser processing, as the acid dianhydride (monomer) for forming the acid dianhydride residue, preferably an acid dianhydride with a biphenyl skeleton. Specific examples of the acid dianhydride (monomer) for forming the acid dianhydride residue include pyromellitic dianhydride (hereinafter sometimes referred to as “PMDA”), 3,3′,4,4′-biphenyltetracarboxylic dianhydride (hereinafter sometimes referred to as “BPDA”), 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 2,2′,3,3′-biphenyltetracarboxylic dianhydride, 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (hereinafter sometimes referred to as “BTDA”), 2,2′,3,3′-benzophenonetetracarboxylic dianhydride, 4,4′-oxydiphthalic anhydride (hereinafter sometimes referred to as “ODPA”), and the like. ”), 3,4'-oxydiphthalic anhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, bis(3,4-dicarboxyphenyl)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)sulfone dianhydride, p-phenylenebis(trimellitic acid monoester anhydride), ethylenebis(trimellitic acid monoester anhydride), bisphenol A bis(trimellitic acid monoester anhydride) and derivatives thereof.

[0070] From the perspective of maintaining the linear expansion coefficient, the acid dianhydride residue is preferably one or more selected from the group consisting of BPDA residues and PMDA residues. In addition, in order to further suppress the generation of cracks on the inner wall of the through-hole during the decontamination treatment after laser processing, the acid dianhydride residue is preferably a BPDA residue having a biphenyl skeleton. In the case where the non-thermoplastic polyimide contains a BPDA residue, in order to maintain the linear expansion coefficient and further suppress the generation of cracks on the inner wall of the through-hole during the decontamination treatment after laser processing, the content of the BPDA residue relative to the total acid dianhydride residues constituting the non-thermoplastic polyimide is preferably 10 mol% or more and 60 mol% or less, more preferably 20 mol% or more and 60 mol% or less, and even more preferably 30 mol% or more and 60 mol% or less. When the non-thermoplastic polyimide contains PMDA residues, from the perspective of maintaining the linear expansion coefficient, the content of PMDA residues relative to the total acid dianhydride residues constituting the non-thermoplastic polyimide is preferably 40 mol% or more and 80 mol% or less, more preferably 40 mol% or more and 75 mol% or less, and even more preferably 40 mol% or more and 70 mol% or less. When the non-thermoplastic polyimide contains BPDA residues and PMDA residues, in order to maintain the linear expansion coefficient and further suppress the occurrence of cracks on the inner wall of the through-hole during desmear treatment after laser processing, the total content of BPDA residues and PMDA residues relative to the total acid dianhydride residues constituting the non-thermoplastic polyimide is preferably 60 mol% or more, more preferably 70 mol% or more, even more preferably 80 mol% or more, and may be 100 mol%.

[0071] In order to further suppress the generation of cracks on the inner wall of the through-hole during the decontamination treatment after laser processing, the non-thermoplastic polyimide preferably has one or more of the group consisting of BPDA residues and PMDA residues and ODPA residues as acid dianhydride residues. In the case where the non-thermoplastic polyimide includes ODPA residues, in order to further suppress the generation of cracks on the inner wall of the through-hole during the decontamination treatment after laser processing, the content of ODPA residues relative to the total acid dianhydride residues constituting the non-thermoplastic polyimide is preferably 5 mol % or more and 15 mol % or less. In the case where the non-thermoplastic polyimide includes one or more of the group consisting of BPDA residues and PMDA residues and ODPA residues, in order to further suppress the generation of cracks on the inner wall of the through-hole during the decontamination treatment after laser processing while maintaining the linear expansion coefficient, the total content of BPDA residues, PMDA residues and ODPA residues is preferably 80 mol % or more, more preferably 90 mol % or more, or 100 mol % relative to the total acid dianhydride residues constituting the non-thermoplastic polyimide.

[0072] In order to maintain the appearance of the surface of the metal-clad laminate well, and further suppress the generation of cracks on the inner wall of the through-hole during the decontamination treatment after laser processing, the non-thermoplastic polyimide preferably has a segment having a structural unit shown in the following chemical formula (2) as a repeating unit. It should be noted that, in this specification, "segment" refers to a polymer chain formed by the same repeating units constituting a block copolymer. In addition, in this specification, "block copolymer" includes any of pure block copolymers, random block copolymers, and copolymers with a tapered block structure.

[0073]

[0074] A segment having the structural unit represented by the chemical formula (2) as a repeating unit (hereinafter sometimes referred to as a "specific segment") can be formed, for example, by sequential polymerization as described later.

[0075] The non-thermoplastic polyimide layer may contain ingredients (additives) other than the non-thermoplastic polyimide. As additives, for example, dyes, surfactants, leveling agents, plasticizers, silicones, fillers, sensitizers, etc. 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, more preferably 90% by weight or more, and can also be 100% by weight relative to the total amount of the non-thermoplastic polyimide layer.

[0076] (Thermoplastic polyimide layer)

[0077] The thermoplastic polyimide contained in the thermoplastic polyimide layer has an acid dianhydride residue and a diamine residue. Examples of the acid dianhydride (monomer) used to form the acid dianhydride residue in the thermoplastic polyimide include the same compounds as the acid dianhydride (monomer) used to form the acid dianhydride residue in the non-thermoplastic polyimide. The acid dianhydride residue in the thermoplastic polyimide and the acid dianhydride residue in the non-thermoplastic polyimide may be of the same type or different types.

[0078] In order to ensure thermoplasticity, as the diamine residue possessed by thermoplastic polyimide, a diamine residue with a bent structure is preferably used. In order to more easily ensure thermoplasticity, relative to all the diamine residues constituting the thermoplastic polyimide, the content of the diamine residue with a bent structure is preferably 50 mol% or more, more preferably 70 mol% or more, further preferably 80 mol% or more, and may be 100 mol%. As diamines (monomers) for forming diamine residues with a bent structure, 4,4'-bis(4-aminophenoxy)biphenyl, 4,4'-bis(3-aminophenoxy)biphenyl, 1,3-bis(3-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 2,2-bis[4-(4-aminophenoxy)phenyl]propane (hereinafter, sometimes described as "BAPP") etc. can be cited. In order to more easily ensure thermoplasticity, as the diamine residue possessed by thermoplastic polyimide, a BAPP residue is preferably used.

[0079] In order to obtain a thermoplastic polyimide layer having excellent adhesion to a metal foil, the thermoplastic polyimide preferably contains a BAPP residue and one or more selected from the group consisting of a BPDA residue and a PMDA residue.

[0080] The thermoplastic polyimide layer may also contain ingredients (additives) other than the thermoplastic polyimide. As additives, for example, dyes, surfactants, leveling agents, plasticizers, silicones, fillers, sensitizers, etc. 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, more preferably 90% by weight or more, and may also be 100% by weight relative to the total amount of the thermoplastic polyimide layer.

[0081] In order to particularly suppress the generation of cracks on the inner wall of the through hole during the decontamination treatment after laser processing, the multilayer polyimide film of this embodiment preferably satisfies the following condition 1, more preferably satisfies the following condition 2, further preferably satisfies the following condition 3, further preferably satisfies the following condition 4, and particularly preferably satisfies the following condition 5.

[0082] Condition 1: The non-thermoplastic polyimide has an m-TB residue, an ODA residue, a PDA residue, a BPDA residue, and a PMDA residue.

[0083] Condition 2: The above-mentioned condition 1 is satisfied, and the content of the ODA residue relative to all diamine residues constituting the non-thermoplastic polyimide is 40 mol% or more and 70 mol% or less.

[0084] Condition 3: The above-mentioned condition 2 is satisfied, and the content of the PDA residue relative to all diamine residues constituting the non-thermoplastic polyimide is 5 mol% or more and 50 mol% or less.

[0085] Condition 4: The above condition 3 is satisfied, and the non-thermoplastic polyimide is a block copolymer having specific segments.

[0086] Condition 5: The above condition 4 is satisfied, and the non-thermoplastic polyimide further has an ODPA residue.

[0087] <Method for Manufacturing Multilayer Polyimide Film and Method for Manufacturing Metal-Clad Laminate>

[0088] Next, an example of a method for producing a multilayer polyimide film according to the present embodiment and an example of a method for producing a metal-clad laminate using the multilayer polyimide film according to the present embodiment will be described.

[0089] [Method for producing a multilayer polyimide film]

[0090] (Production Method of Polyamic Acid)

[0091] For the manufacture method (synthesis method) of polyamic acid as a precursor of polyimide, all known methods and methods combining them can be used. The polymerization method in the manufacture of polyamic acid is characterized in that the order of addition of its monomers is controlled by controlling the order of addition of the monomers, and the various physical properties of the obtained polyimide can be controlled. In the case of using diamine and tetracarboxylic dianhydride to synthesize polyamic acid, by adjusting the amount of substance of each diamine and the amount of substance of tetracarboxylic dianhydride (in the case of using multiple tetracarboxylic dianhydrides, the amount of substance of each tetracarboxylic dianhydride), the desired polyamic acid (polymer of diamine and tetracarboxylic dianhydride) can be obtained. The ratio (molar ratio) of the amount of substance of each residue in the polyimide formed by polyamic acid is, for example, consistent with the amount of substance ratio of each monomer (diamine and tetracarboxylic dianhydride) used in the synthesis of polyamic acid. The temperature conditions for the reaction of diamine and tetracarboxylic dianhydride, i.e., the synthesis reaction of polyamic acid are not particularly limited, for example, in the range of more than 20 ° C and less than 150 ° C. The reaction time of the synthesis reaction of polyamic acid is, for example, in the range of 10 minutes to 30 hours. In the present embodiment, the production of polyamic acid can also use any monomer addition method. As a representative method for producing polyamic acid, the following method can be cited.

[0092] Examples of the method for producing the polyamic acid include a method of performing polymerization through the following steps (Aa) and (Ab) (hereinafter, sometimes referred to as “A polymerization method”).

[0093] (Aa): A step of reacting an aromatic diamine with an aromatic 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.

[0094] (Ab): A step of additionally adding an aromatic diamine having a structure different from that used in step (Aa), and further adding an aromatic dianhydride having a structure different from that used in step (Aa), and polymerizing the mixture so that the aromatic diamine and the aromatic dianhydride are substantially equimolar in all steps.

[0095] Moreover, as a manufacturing method of a polyamic acid, the method of carrying out polymerization by following process (Ba) and process (Bb) (it may describe as "B polymerization method" hereinafter) is mentioned.

[0096] (Ba): A step of reacting an aromatic diamine with an aromatic dianhydride in an organic solvent in a state where the aromatic dianhydride is in excess to obtain a prepolymer having anhydride groups at both ends.

[0097] (Bb): A step of adding an aromatic dianhydride having a structure different from that used in step (Ba), and further adding an aromatic diamine having a structure different from that used in step (Ba), and polymerizing the mixture so that the aromatic diamine and the aromatic dianhydride are substantially equimolar in all steps.

[0098] Synthesis methods (e.g., the above-mentioned polymerization method A, polymerization method B, etc.) that set the order of addition so that a specific diamine or a specific acid dianhydride selectively reacts with any or specific diamine or any or specific acid dianhydride are referred to herein as sequential polymerization. Among the polymers obtained by sequential polymerization, polymers having two types of segments are referred to as diblock copolymers, and polymers having three types of segments are referred to as triblock copolymers. In contrast, in this specification, polymerization methods that do not set the order of addition of diamines and acid dianhydrides (polymerization methods in which monomers react randomly with each other) are referred to as random polymerization. Polymers obtained by random polymerization are referred to as random copolymers.

[0099] In the present embodiment, sequential polymerization is preferably used as a polymerization method for obtaining a polyimide that effectively suppresses film cracking while maintaining the characteristics of a flexible metal-clad laminate.

[0100] The weight-average molecular weight of the polyamic acid obtained by the above-mentioned polymerization method is preferably more than 10,000 and the scope of less than 1,000,000, more preferably more than 20,000 and the scope of less than 500,000, more preferably more than 30,000 and the scope of less than 200,000.If the weight-average molecular weight is more than 10,000, then polyamic acid is easily made into coating film.On the other hand, if the weight-average molecular weight is less than 1,000,000, then solvent is demonstrated sufficient solubility, therefore using the polyamic acid solution described later, surface smoothness and uniform thickness coating film can be obtained.The weight-average molecular weight used herein refers to the polyethylene oxide conversion value measured using gel permeation chromatography (GPC).

[0101] 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 employed. Examples of organic solvents that can be used in polyamic acid solutions include urea solvents such as tetramethylurea and N,N-dimethylethylurea; sulfoxide solvents such as dimethyl sulfoxide; sulfone solvents such as diphenyl sulfone and tetramethyl sulfone; amide solvents such as N,N-dimethylacetamide, N,N-dimethylformamide (hereinafter sometimes referred to as "DMF"), N,N-diethylacetamide, N-methyl-2-pyrrolidone, and hexamethylphosphoric triamide; ester solvents such as γ-butyrolactone; halogenated alkyl solvents such as chloroform and dichloromethane; aromatic hydrocarbon solvents such as benzene and toluene; phenolic solvents such as phenol and cresol; ketone solvents such as cyclopentanone; and ether 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. These solvents are generally used alone, but two or more thereof may be used in combination as needed. When obtaining polyamic acid by above-mentioned polymerization process, also can reaction soln (reacted solution) itself be used as the polyamic acid solution for obtaining polyimides.At this moment, the organic solvent in the polyamic acid solution is the organic solvent for reacting in above-mentioned polymerization process.In addition, also can remove the solid polyamic acid that solvent is obtained from reaction soln and be dissolved in the organic solvent and prepare polyamic acid solution.

[0102] In the polyamic acid solution, can add additives such as dye, surfactant, leveling agent, plasticizer, organosilicon, sensitizer.In addition, for the purpose of each characteristic of improving films such as slippage, thermal conductivity, electrical conductivity, corona resistance, ring stiffness, also can add filler in the polyamic acid solution.As filler, can use any filler, as preferred example, can enumerate the filler that comprises silicon-dioxide, titanium oxide, aluminum oxide, silicon nitride, boron nitride, calcium hydrogen phosphate, calcium phosphate, mica etc.

[0103] 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, relative to the total amount of the polyamic acid solution. When the concentration of the polyamic acid is 5% by weight or more and 35% by weight or less, a suitable molecular weight and solution viscosity can be obtained.

[0104] (Method for Forming Non-Thermoplastic Polyimide Layer)

[0105] The method for forming the non-thermoplastic polyimide layer is not particularly limited, and various known methods can be applied. For example, there is a method of forming a non-thermoplastic polyimide layer (polyimide film) through the following steps i) to iv).

[0106] Step i): A step of reacting an aromatic diamine and an aromatic tetracarboxylic dianhydride in an organic solvent to obtain a polyamic acid solution containing a precursor of a non-thermoplastic polyimide (hereinafter sometimes referred to as a “non-thermoplastic polyamic acid solution”).

[0107] Step ii): coating a doping solution containing the non-thermoplastic polyamic acid solution on a support to form a coating film;

[0108] Step iii): After heating the coating film on a support to form a self-supporting polyamic acid film (hereinafter sometimes referred to as "gel film"), the gel film is peeled off from the support.

[0109] Step iv) heating the gel film to imidize the polyamic acid in the gel film, and drying the film to obtain a polyimide film containing non-thermoplastic polyimide (a polyimide film serving as a non-thermoplastic polyimide layer in a multilayer polyimide film).

[0110] In step ii), the method for coating the support with the doping liquid is not particularly limited, and a method using a conventionally known coating apparatus such as a die coater, comma coater (registered trademark), reverse coater, or knife coater can be employed.

[0111] In the process after process ii), it is roughly divided into thermal imidization and chemical imidization. Thermal imidization is a method for imidizing by applying a polyamic acid solution as a doping liquid on a support without using a dehydrating ring-closing agent, etc. and heating it. Another chemical imidization method is a method for promoting imidization by using a solution obtained by adding at least one of a dehydrating ring-closing agent and a catalyst as an imidization accelerator in a polyamic acid solution as a doping liquid. Although either method can be used, the productivity of the chemical imidization method is better.

[0112] As the dehydrating ring-closing agent, an acid anhydride represented by acetic anhydride is suitable, and as the catalyst, a tertiary amine such as an aliphatic tertiary amine, an aromatic tertiary amine, or a heterocyclic tertiary amine is suitable.

[0113] As the support on which the doping liquid is applied in step ii), a glass plate, aluminum foil, an endless stainless steel belt, a stainless steel drum, etc. are preferably used. In step iii), heating conditions are set according to the thickness of the final film and the production speed, and after at least one of partial imidization or drying is performed, the film is peeled from the support to obtain a polyamic acid film (gel film).

[0114] Next, in step iv), the ends of the gel film are fixed and heated while preventing shrinkage during curing. This removes water, residual solvent, imidization accelerator, and the like from the gel film, completely imidizing the remaining polyamic acid to obtain a polyimide film comprising a non-thermoplastic polyimide. The heating conditions can be appropriately set depending on the thickness of the final film and the production rate.

[0115] (Method for Forming Thermoplastic Polyimide Layer)

[0116] Thermoplastic polyimide layer for example can be by using the polyimide film (non-thermoplastic polyimide layer) that obtains at least one-sided coating containing the polyamic acid as the precursor of thermoplastic polyimide by the polyamic acid solution (below, be recorded as " thermoplastic polyamic acid solution " sometimes) after, obtain with the order identical with the forming method of above-mentioned non-thermoplastic polyimide layer (polyimide film).By this method, can obtain having non-thermoplastic polyimide layer and the multilayer polyimide film of the thermoplastic polyimide layer of at least one-sided configuration of non-thermoplastic polyimide layer.In addition, also can replace thermoplastic polyamic acid solution and use the solution (thermoplastic polyimide solution) that comprises thermoplastic polyimide, at least one-sided formation of non-thermoplastic polyimide layer is made of thermoplastic polyimide solution the coating film, and this coating film is dried and forms thermoplastic polyimide layer.

[0117] And, for example, also can use coextrusion die, after formation possesses the layer that comprises the polyamic acid as the precursor of non-thermoplastic polyimide and the duplexer that comprises the layer of the polyamic acid as the precursor of thermoplastic polyimide, obtained duplexer is heated, form non-thermoplastic polyimide layer and thermoplastic polyimide layer simultaneously.In this method, by using metal foil as support, obtain coating metal laminate (duplexer of multilayer polyimide film and metal foil) when imidization is finished.In the situation of the multilayer polyimide film that comprises the polyimide layer more than 3 layers in manufacture, suitable use repeatedly carries out repeatedly above-mentioned coating process and heating process, perhaps forms a plurality of coating films and the disposable method that heats by coextrusion, continuous coating (continuous casting).Also can the outermost surface of multilayer polyimide film be carried out corona treatment, plasma treatment such various surface treatments.

[0118] [Method for Manufacturing Metal-Clad Laminated Plate]

[0119] When using the multilayer polyimide film obtained by the above method to manufacture the metal-clad laminate, as mentioned above, at least the single-sided lamination metal foil of the multilayer polyimide film is applied. For metal foil, there is no particular limitation, and any metal foil can be used. For example, it is suitable to use the metal foil of material such as copper, stainless steel, nickel, aluminium and the alloy of these metals. In addition, in general metal-clad laminate, the copper foils such as rolled copper foil and electrolytic copper foil are used more often. In the present embodiment, the copper foil is also preferably used.

[0120] The metal foil may be subjected to surface treatment to adjust the surface roughness, etc., depending on the intended use. Furthermore, a rust-proof layer, a heat-resistant layer, an adhesive layer, etc. may be formed on the surface of the metal foil. The thickness of the metal foil is not particularly limited, as long as it is a thickness sufficient to function according to its intended use.

[0121] Processing of Metal-Clad Laminates

[0122] When laser processing a through hole in a metal-clad laminate, the metal-clad laminate can be cut to create a hole by irradiating the desired area with a laser. Through holes can be formed by penetrating the metal-clad laminate, or blind vias can be formed by removing only the polyimide layer exposed after removing a portion of the metal foil on the top surface. To form a blind via, the metal foil on the top surface is removed with a laser, and then the polyimide layer is removed by reducing the laser output, resulting in stable blind via formation.

[0123] As the laser, known types can be used. Short-wavelength lasers such as UV-YAG lasers and excimer lasers show very high absorption rates for both resins and metals and are therefore preferred. It should be noted that, regarding the formation of through holes, a method of directly opening through holes with a drill bit is also widely used. As a decontamination treatment method after laser processing, known methods can be used, for example, a wet decontamination treatment method having a swelling step using an alkaline aqueous solution or a solution containing an organic solvent, a roughening step using an alkaline aqueous solution containing sodium permanganate, potassium permanganate, etc., and a neutralization step can be cited.

[0124] In the case of a double-sided metal laminate, the inner wall of the hole after the decontamination treatment is plated to make both sides of the metal laminate conductive. As an example of a plating method, a method in which palladium is attached to the inner wall of the hole and then an electroless copper plating layer is formed on the inner wall surface using the palladium as a core can be cited. In this case, a plated layer of a desired thickness can be formed by only electroless copper plating, or a plated layer of a desired thickness can be formed by thinning the electroless copper plating layer and then electrolytic copper plating can be used to form a plated layer of a desired thickness.

[0125] Example

[0126] Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to these Examples.

[0127] <Measurement and Evaluation Methods of Physical Properties>

[0128] First, the storage modulus and linear expansion coefficient of the polyimide film and the evaluation method (hole crack test) of Examples and Comparative Examples will be described.

[0129] [Storage modulus at 380°C]

[0130] The dynamic viscoelasticity of the polyimide film was measured in air using a dynamic viscoelasticity measuring apparatus ("DM6100" manufactured by Hitachi High-Tech Science Corporation), and the storage modulus was plotted against the measurement temperature. The storage modulus was read at a measurement temperature of 380° C. The measurement conditions are as follows.

[0131] Width of sample (polyimide film): 9 mm

[0132] Sample holder (clamp) spacing: 20 mm

[0133] Measuring temperature range: 0℃~440℃

[0134] Heating speed: 3℃ / min

[0135] Strain amplitude: 10μm

[0136] Measuring frequency: 1Hz, 5Hz, 10Hz

[0137] Minimum tension / compression force: 100mN

[0138] Tension / Compression Gain: 1.5

[0139] Initial value of force amplitude: 100mN

[0140] [Linear expansion coefficient]

[0141] Using a thermal analyzer (TMA / SS6100, manufactured by Hitachi High-Tech Science Corporation), the polyimide film was heated from -10°C to 400°C under a nitrogen atmosphere, then cooled to -10°C and heated again to 400°C. The linear expansion coefficient was determined from the strain measured from 100°C to 200°C during the second heating step. The measurement conditions are shown below.

[0142] Sample (polyimide film) dimensions: width 3 mm, length 10 mm

[0143] Load: 3g (29.4mN)

[0144] Heating rate: 10℃ / min

[0145] [Hole crack test]

[0146] Electrolytic copper foils with a thickness of 12 μm ("3EC-M3S-HTE" manufactured by Mitsui Mining & Smelting Co., Ltd.) were arranged on both sides of the multilayer polyimide film obtained in the examples and comparative examples described later. A protective film ("Apical (registered trademark) 125NPI" manufactured by Kaneka Corporation, thickness: 125 μm) was further arranged on the outer surface of each electrolytic copper foil. In this state, lamination was performed under the conditions of a lamination temperature of 360°C, a lamination pressure of 265N / cm (27 kgf / cm), and a lamination speed of 1.0 m / min 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 processing sample. Next, using a UV-YAG laser, blind holes (length 10 × width 10 = 100, spacing: 1 mm) with a diameter of 75 μm were formed on the processing sample under the laser processing conditions described in Table 1.

[0147] [Table 1]

[0148]

[0149] Next, the laser-processed samples were desmeared under the conditions shown in Table 2, and the copper foil was removed by etching to obtain evaluation samples. It should be noted that the chemical solutions used in the desmearing treatment were manufactured by Rohm and Haas Electronic Materials. Water washing steps were performed between the swelling and roughening steps, between the roughening and neutralization steps, and after the neutralization step.

[0150] [Table 2]

[0151]

[0152] The resulting evaluation samples were then observed under a polarizing microscope at 200x magnification under a crossed Nicol prism to determine the presence of cracks. Specifically, light leakage around the holes was considered "cracked." After observing 100 holes, the percentage of holes with cracks (crack occurrence rate) was calculated. Figures 3 to 5 An example of a polarizing microscope image used for actual judgment is shown in FIG. Figure 3 This is an example of a hole portion in which cracks are not generated because light leakage does not occur around the hole portion. Figure 4 and Figure 5 This is an example of a hole where cracks were formed due to light leakage around the hole. It should be noted that for holes where the light leakage was weak and the presence of cracks could not be determined, the presence of cracks was determined by observing the hole cross section using an electron microscope.

[0153] <Preparation of Polyamic Acid Solution>

[0154] The following describes the preparation methods of solutions P1 to P12, which are non-thermoplastic polyamic acid solutions, and solution P13, which is a thermoplastic polyamic acid solution. Solutions P1 to P13 were all prepared under a nitrogen atmosphere at 20°C.

[0155] [Preparation of Solution P1]

[0156] After placing 328.53g of DMF and 17.70g of ODA in a 2L glass flask, 18.01g of BPDA was slowly added while stirring the contents. After visually confirming the dissolution of BPDA, 4.00g of PMDA was slowly added while stirring the contents. After visually confirming the dissolution of PMDA, the contents were stirred for another 30 minutes. Next, 5.77g of m-TB was added while stirring the contents, followed by 2.21g of PDA and 11.42g of PMDA, and the contents were stirred for another 30 minutes. Next, while stirring the contents, a previously prepared PMDA solution (solvent: DMF, PMDA dissolved: 0.89g, PMDA concentration: 7.2 wt%) was added. The PMDA solution was added slowly to the flask so as not to increase the viscosity of the contents. Then, when the viscosity of the contents in the flask reached 2500 poise at a temperature of 23° C., the addition of the PMDA solution and the stirring of the contents in the flask were stopped, thereby obtaining a solution P1 which was a non-thermoplastic polyamic acid solution.

[0157] The polyimide obtained from the polyamic acid in the obtained solution P1 was confirmed to be non-thermoplastic by the method shown below. First, 32.5 g of an imidization accelerator formed by acetic anhydride / isoquinoline / DMF (weight ratio: 11.48 / 3.40 / 18.18) was added to 65 g of solution P1 to prepare a doping solution. Then, in an atmosphere with a temperature below 0°C, the doping solution was stirred while degassing, and then the doping solution was coated on an aluminum foil using a comma coater to form a coating film. Then, by heating the coating film for 100 seconds at a heating temperature of 115°C, a self-supporting gel film was obtained. The obtained gel film was peeled off from the aluminum foil, fixed on a metal fixing frame, heated for 15 seconds at a heating temperature of 250°C, then heated for 79 seconds at a heating temperature of 350°C, dried and imidized, and a polyimide film with a thickness of 12.5 μm was obtained. The obtained polyimide film is fixed to a metal fixing frame, heated for 2 minutes under the condition of a heating temperature of 450°C, and the shape (film shape) of the polyimide film is maintained. Therefore, the polyimide obtained by the polyamic acid in solution P1 is a non-thermoplastic polyimide. It should be noted that, with respect to the solutions P2 to P12 shown below in the preparation method, the polyimide film obtained by the same method as the film forming method using the solution P1 is also fixed to a metal fixing frame, heated for 2 minutes under the condition of a heating temperature of 450°C, and the shape (film shape) of the polyimide film is maintained. Therefore, the polyimide obtained by the polyamic acid in solutions P2 to P12 is all non-thermoplastic polyimide.

[0158] [Preparation of Solution P2]

[0159] After placing 328.55g of DMF and 16.32g of ODA in a 2L glass flask, 17.98g of BPDA was slowly added to the flask while stirring the contents. After visually confirming the dissolution of BPDA, 2.67g of PMDA was slowly added to the flask while stirring the contents. After visually confirming the dissolution of PMDA, the contents were further stirred for 30 minutes. Next, 7.21g of m-TB was added to the flask while stirring the contents, followed by 2.20g of PDA and 12.74g of PMDA, and the contents were further stirred for 30 minutes. Next, while stirring the contents, a previously prepared PMDA solution (solvent: DMF, PMDA dissolution amount: 0.89g, PMDA concentration: 7.2 wt%) was added to the flask. The PMDA solution was added slowly to prevent a sharp increase in the viscosity of the contents. Then, when the viscosity of the contents of the flask reached 2500 poise at a temperature of 23° C., the addition of the PMDA solution and the stirring of the contents of the flask were stopped, thereby obtaining a solution P2 which was a non-thermoplastic polyamic acid solution.

[0160] [Preparation of Solution P3]

[0161] After placing 328.78g of DMF and 17.31g of ODA in a 2L glass flask, 22.70g of BPDA was slowly added to the flask while stirring the contents. After visually confirming that the BPDA had dissolved, the contents were stirred for another 30 minutes. Next, while stirring the contents, 5.65g of m-TB was added to the flask, followed by 2.16g of PDA and 11.31g of PMDA, and the contents were stirred for another 30 minutes. Next, while stirring the contents, a previously prepared PMDA solution (solvent: DMF, PMDA dissolved: 0.87g, PMDA concentration: 7.2 wt%) was added to the flask. The PMDA solution was added slowly to prevent a sharp increase in the viscosity of the contents. Then, when the viscosity of the contents of the flask reached 2500 poise at a temperature of 23° C., the addition of the PMDA solution and the stirring of the contents of the flask were stopped, thereby obtaining a solution P3 which was a non-thermoplastic polyamic acid solution.

[0162] [Preparation of Solution P4]

[0163] After placing 328.41 g of DMF and 16.51 g of ODA in a 2-liter glass flask, 18.20 g of BPDA was slowly added while stirring the contents. After visually confirming the dissolution of BPDA, 2.70 g of PMDA was slowly added while stirring the contents. After visually confirming the dissolution of PMDA, the contents were stirred for another 30 minutes. Next, 5.83 g of m-TB was added while stirring the contents, followed by 2.97 g of PDA and 12.89 g of PMDA, and the contents were stirred for another 30 minutes. Next, while stirring the contents, a previously prepared PMDA solution (solvent: DMF, PMDA dissolution amount: 0.90 g, PMDA concentration: 7.2 wt%) was added. The PMDA solution was added slowly to the flask so as not to increase the viscosity of the contents. Then, when the viscosity of the contents of the flask reached 2500 poise at a temperature of 23° C., the addition of the PMDA solution and the stirring of the contents of the flask were stopped, thereby obtaining a solution P4 which was a non-thermoplastic polyamic acid solution.

[0164] [Preparation of Solution P5]

[0165] After placing 328.29 g of DMF, 5.90 g of m-TB, 3.75 g of PDA, and 15.30 g of ODA in a 2 L glass flask, 18.39 g of BPDA was slowly added to the flask while stirring the contents. After visually confirming that the BPDA had dissolved, 15.75 g of PMDA was slowly added to the flask while stirring the contents. After visually confirming that the PMDA had dissolved, the contents of the flask were further stirred for 30 minutes. Next, while stirring the contents of the flask, a previously prepared PMDA solution (solvent: DMF, PMDA dissolution amount: 0.91 g, PMDA concentration: 7.2 wt%) was added to the flask. When adding the PMDA solution to the flask, add it slowly so that the viscosity of the contents does not increase sharply. Then, when the viscosity of the contents in the flask reached 2500 poise at a temperature of 23° C., the addition of the PMDA solution and the stirring of the contents in the flask were stopped, thereby obtaining a solution P5 which was a non-thermoplastic polyamic acid solution.

[0166] [Preparation of Solution P6]

[0167] After placing 328.57 g of DMF and 17.64 g of ODA in a 2 L glass flask, 13.95 g of BPDA was slowly added to the flask while stirring the contents. After visually confirming that the BPDA had dissolved, 4.20 g of ODPA was slowly added to the flask while stirring the contents. After visually confirming that the ODPA had dissolved, 3.99 g of PMDA was slowly added to the flask while stirring the contents. After visually confirming that the PMDA had dissolved, the contents of the flask were further stirred for 30 minutes. Next, 5.75 g of m-TB was added to the flask while stirring the contents, followed by 2.20 g of PDA and then 11.38 g of PMDA, and the contents of the flask were further stirred for 30 minutes. Next, while stirring the contents of the flask, a previously prepared PMDA solution (solvent: DMF, PMDA dissolution amount: 0.89 g, PMDA concentration: 7.2 wt %) was added to the flask. The PMDA solution was added slowly to the flask so that the viscosity of the flask contents did not increase dramatically. Then, when the viscosity of the flask contents reached 2500 poise at 23° C., the addition of the PMDA solution and the stirring of the flask contents were stopped, thereby obtaining Solution P6, a non-thermoplastic polyamic acid solution.

[0168] [Preparation of Solution P7]

[0169] After placing 328.81g of DMF and 15.94g of ODA in a 2L glass flask, 17.57g of BPDA was slowly added to the flask while stirring the contents. After visually confirming the dissolution of BPDA, 2.60g of PMDA was slowly added to the flask while stirring the contents. After visually confirming the dissolution of PMDA, the contents were further stirred for 30 minutes. Next, 9.86g of m-TB was added to the flask while stirring the contents, followed by 0.72g of PDA and 12.44g of PMDA, and the contents were further stirred for 30 minutes. Next, while stirring the contents, a previously prepared PMDA solution (solvent: DMF, PMDA dissolution amount: 0.87g, PMDA concentration: 7.2 wt%) was added to the flask. The PMDA solution was added slowly to prevent a sharp increase in the viscosity of the contents. Then, when the viscosity of the contents in the flask reached 2500 poise at a temperature of 23° C., the addition of the PMDA solution and the stirring of the contents in the flask were stopped, thereby obtaining a solution P7 which was a non-thermoplastic polyamic acid solution.

[0170] [Preparation of Solution P8]

[0171] After placing 327.90 g of DMF, 4.57 g of m-TB, 5.43 g of PDA, and 14.36 g of ODA in a 2 L glass flask, 16.88 g of BPDA was slowly added to the flask while stirring the contents. After visually confirming that the BPDA had dissolved, 17.83 g of PMDA was slowly added to the flask while stirring the contents. After visually confirming that the PMDA had dissolved, the contents of the flask were further stirred for 30 minutes. Next, while stirring the contents of the flask, a previously prepared PMDA solution (solvent: DMF, PMDA dissolution amount: 0.94 g, PMDA concentration: 7.2 wt%) was added to the flask. When adding the PMDA solution to the flask, add it slowly so that the viscosity of the contents does not increase sharply. Then, when the viscosity of the contents of the flask reached 2500 poise at a temperature of 23° C., the addition of the PMDA solution and the stirring of the contents of the flask were stopped, thereby obtaining a solution P8 which was a non-thermoplastic polyamic acid solution.

[0172] [Preparation of Solution P9]

[0173] After placing 328.27 g of DMF and 16.71 g of ODA in a 2-liter glass flask, 18.41 g of BPDA was slowly added to the flask while stirring the contents. After visually confirming the dissolution of BPDA, 2.73 g of PMDA was slowly added to the flask while stirring the contents. After visually confirming the dissolution of PMDA, the contents were stirred for another 30 minutes. Next, 4.43 g of m-TB was added to the flask while stirring the contents, followed by 3.76 g of PDA and 13.05 g of PMDA, and the contents were stirred for another 30 minutes. Next, while stirring the contents, a previously prepared PMDA solution (solvent: DMF, PMDA dissolution amount: 0.91 g, PMDA concentration: 7.2 wt%) was added to the flask. The PMDA solution was added slowly to prevent a sharp increase in the viscosity of the contents. Then, when the viscosity of the contents of the flask reached 2500 poise at a temperature of 23° C., the addition of the PMDA solution and the stirring of the contents of the flask were stopped, thereby obtaining a solution P9 which was a non-thermoplastic polyamic acid solution.

[0174] [Preparation of Solution P10]

[0175] After placing 328.91 g of DMF, 5.27 g of ODA, and 16.20 g of BAPP in a 2 L glass flask, 8.48 g of BTDA was slowly added to the flask while stirring the contents. After visually confirming that the BTDA had dissolved, 7.17 g of PMDA was slowly added to the flask while stirring the contents. After visually confirming that the PMDA had dissolved, the contents were stirred for another 30 minutes. Next, 7.11 g of PDA was added to the flask while stirring the contents, followed by 14.92 g of PMDA, and the contents were stirred for another 30 minutes. Next, while stirring the contents, a previously prepared PMDA solution (solvent: DMF, PMDA dissolution amount: 0.86 g, PMDA concentration: 7.2 wt%) was added to the flask. The PMDA solution was added slowly to prevent a sharp increase in the viscosity of the contents. Then, when the viscosity of the contents in the flask reached 2500 poise at a temperature of 23° C., the addition of the PMDA solution and the stirring of the contents in the flask were stopped, thereby obtaining a solution P10 which was a non-thermoplastic polyamic acid solution.

[0176] [Preparation of Solution P11]

[0177] After placing 328.49 g of DMF and 12.29 g of ODA in a 2-liter glass flask, 16.06 g of BPDA was slowly added while stirring the contents. After visually confirming that the BPDA had dissolved, the contents were stirred for another 30 minutes. Next, while stirring the contents, 11.58 g of m-TB was added, followed by 2.21 g of PDA and 16.96 g of PMDA, and the contents were stirred for another 30 minutes. Next, while stirring the contents, a previously prepared PMDA solution (solvent: DMF, PMDA dissolution: 0.89 g, PMDA concentration: 7.2 wt%) was added. The PMDA solution was added slowly to the flask so as not to cause a sharp increase in the viscosity of the contents. Then, when the viscosity of the contents of the flask reached 2500 poise at a temperature of 23° C., the addition of the PMDA solution and the stirring of the contents of the flask were stopped, thereby obtaining a solution P11 which was a non-thermoplastic polyamic acid solution.

[0178] [Preparation of Solution P12]

[0179] After placing 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 sometimes referred to as "BAFL") in a 2 L glass flask, 16.35 g of BPDA was slowly added to the flask while stirring the contents of the flask. After visually confirming that the BPDA had dissolved, 14.01 g of PMDA was slowly added to the flask while stirring the contents of the flask. After visually confirming that the PMDA had dissolved, the contents of the flask were further stirred for 30 minutes. Then, while stirring the contents of the flask, a pre-prepared PMDA solution (solvent: DMF, amount of PMDA dissolved: 0.81 g, concentration of PMDA: 7.2 wt %) was added to the flask. When adding the PMDA solution to the flask, it was added slowly in such a way that the viscosity of the contents of the flask did not rise sharply. Then, when the viscosity of the contents of the flask reached 2500 poise at a temperature of 23° C., the addition of the PMDA solution and the stirring of the contents of the flask were stopped, thereby obtaining a solution P12 which was a non-thermoplastic polyamic acid solution.

[0180] [Preparation of Solution P13]

[0181] After placing 673.24g of DMF and 71.83g of BAPP in a 2L glass flask, 7.72g of BPDA was slowly added to the flask while stirring the flask contents. After visually confirming that BPDA had dissolved, 31.30g of PMDA was slowly added to the flask while stirring the flask contents. After visually confirming that PMDA had dissolved, the flask contents were further stirred for 30 minutes. Then, while stirring the flask contents, a pre-prepared PMDA solution (solvent: DMF, PMDA dissolution amount: 1.15g, PMDA concentration: 7.2 wt%) was added to the flask. When the PMDA solution was added to the flask, it was slowly added in a manner that the viscosity of the flask contents did not rise sharply. Then, when the viscosity of the flask contents reached 300 poise at a temperature of 23°C, the addition of the PMDA solution and the stirring of the flask contents were stopped to obtain solution P13, which was a thermoplastic polyamide acid solution.

[0182] The polyimide obtained from the polyamic acid in solution P13 was confirmed to be thermoplastic by the method shown below. First, 30.0 g of an imidization accelerator formed by acetic anhydride / isoquinoline / DMF (weight ratio: 6.89 / 2.14 / 20.97) was added to 60 g of solution P13 to prepare a doping solution. Then, in an atmosphere at a temperature below 0 ° C, the doping solution was stirred while degassing, and the doping solution was coated on an aluminum foil using a comma coater to form a coating film. Then, by heating the coating film for 3 minutes at a heating temperature of 120 ° C, a self-supporting gel film was obtained. The obtained gel film was peeled off from the aluminum foil, fixed on a metal fixing frame, heated for 1 minute at a heating temperature of 250 ° C, then heated for 200 seconds at a heating temperature of 300 ° C, dried and imidized, and a polyimide film with a thickness of 20.0 μm was obtained. The obtained polyimide film was fixed to a metal fixing frame and heated at 450°C for 2 minutes. However, the shape of the polyimide film (film shape) was not maintained. Therefore, the polyimide obtained from the polyamic acid in solution P13 was a thermoplastic polyimide.

[0183] <Production of multilayer polyimide films>

[0184] Hereinafter, the method for producing the multilayer polyimide films of Examples 1 to 7 and Comparative Examples 1 to 5 will be described.

[0185] [Example 1]

[0186] To 65 g of solution P1, 32.5 g of an imidization accelerator composed of acetic anhydride / isoquinoline / DMF (weight ratio: 11.48 / 3.40 / 18.18) was added to prepare a doping solution. The doping solution was then degassed while stirring in an atmosphere below 0°C, and then coated onto aluminum foil using a comma coater to form a coating film. The coating film was then heated at 115°C for 100 seconds to obtain a self-supporting gel film. The resulting gel film was peeled from the aluminum foil, fixed to a metal mounting frame, and heated at 250°C for 15 seconds, followed by heating at 350°C for 79 seconds, followed by drying and imidization to obtain a polyimide film with a thickness of 12.5 μm. The physical properties of the resulting polyimide film (non-thermoplastic polyimide layer) are shown in Table 4. In addition, the "physical properties of the non-thermoplastic polyimide layer" in Table 4 are physical properties measured using a polyimide film having a thickness of 12.5 μm.

[0187] Next, solution P13 was diluted with DMF to a solid content concentration of 8% by weight, and after preparing a doping solution, it was applied to both sides of the polyimide film (polyimide film obtained using solution P1) to form a coating film. The coating amount at this time was adjusted so that the thickness of each thermoplastic polyimide layer (adhesive layer) formed was 3 μm. Next, the coating film was heated at a heating temperature of 120°C for 2 minutes, and then heated at a heating temperature of 350°C for 15 seconds, dried and imidized, to obtain the multilayer polyimide film of Example 1. The results of the hole crack test of the obtained multilayer polyimide film (crack generation rate) are shown in Table 4. It should be noted that the surface of the copper-clad laminate produced during the hole crack test had no wrinkles, etc., and had a good appearance.

[0188] [Examples 2 to 7 and Comparative Examples 1 to 5]

[0189] The non-thermoplastic polyamic acid solution shown in Table 4 is used to replace solution P1. In addition, the multilayer polyimide films of Examples 2 to 7 and Comparative Examples 1 to 5 are obtained respectively using the same method as Example 1. It should be noted that in Examples 2 to 7 and Comparative Examples 1 to 5, the usage amount of the non-thermoplastic polyamic acid solution is 65g. The result (crack generation rate) of the hole crack test of the obtained multilayer polyimide film is shown in Table 4. It should be noted that, about Examples 2 to 4, Example 6, Example 7 and Comparative Examples 2 to 4, the surface of the copper-clad laminate made when the hole crack test does not have wrinkles, etc., and a copper-clad laminate with good appearance is obtained. On the other hand, about Example 5, Comparative Example 1 and Comparative Example 5, there is wrinkle on a part of the surface of the copper-clad laminate made when the hole crack test.

[0190] <Evaluation Results>

[0191] Table 3 shows the materials used for each of the solutions P1 to P13 and their proportions. The ratio (molar ratio) of the amount of substance of each residue in the polyimide obtained using solution P1 to P13 is consistent with the ratio of the amount of substance of each monomer (diamine and tetracarboxylic dianhydride) used. In addition, in Table 4, for Examples 1 to 7 and Comparative Examples 1 to 5, the types of non-thermoplastic polyamic acid solutions used, the physical properties of the non-thermoplastic polyimide layer, and the results of the hole crack test (crack generation rate) are shown respectively. It should be noted that, in Table 3, "-" means that the component is not used. In addition, in Table 3, the numerical value of the "acid dianhydride" column is the content rate (unit: mole %) of each acid dianhydride relative to the total amount of the acid dianhydride used. The numerical value of the "diamine" column is the content rate (unit: mole %) of each diamine relative to the total amount of the diamine used.

[0192] [Table 3]

[0193]

[0194] [Table 4]

[0195]

[0196] In Examples 1 to 7, the non-thermoplastic polyimide contained m-TB residues (a type of BPDI residue), ODA residues, and PDA residues. In Examples 1 to 7, the content of m-TB residues was 20 mol% or more and 35 mol% or less relative to the total diamine residues constituting the non-thermoplastic polyimide. In Examples 1 to 7, the crack generation rate was 50% or less. It should be noted that the non-thermoplastic polyimides of Examples 1 to 4, 6, and 7 were block copolymers having specific segments, but the non-thermoplastic polyimide of Example 5 was a random copolymer.

[0197] In Comparative Examples 1 and 2, the content of BPDI residues (m-TB residues) relative to the total diamine residues constituting the non-thermoplastic polyimide was less than 20 mol%. In Comparative Example 3, the non-thermoplastic polyimide did not contain BPDI residues. In Comparative Example 4, the content of BPDI residues (m-TB residues) relative to the total diamine residues constituting the non-thermoplastic polyimide exceeded 35 mol%. In Comparative Example 5, the non-thermoplastic polyimide did not contain PDA residues. In Comparative Examples 1 to 5, the crack generation rate exceeded 50%.

[0198] The above results indicate that the multilayer polyimide film of the present invention can suppress the generation of cracks on the inner wall of the through hole during desmear treatment after laser processing.

[0199] Description of Reference Numerals

[0200] 10: Multilayer polyimide film

[0201] 11: Non-thermoplastic polyimide layer

[0202] 12: Thermoplastic polyimide layer

Claims

1. A multilayer polyimide film, wherein: The multilayer polyimide film comprises a non-thermoplastic polyimide layer and a thermoplastic polyimide layer disposed on at least one 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 residues include diamine residues having a biphenyl skeleton, 4,4'-diaminodiphenyl ether residues and p-phenylenediamine residues. The content of the diamine residue having a biphenyl skeleton is 20 mol% or more and 35 mol% or less relative to all diamine residues constituting the non-thermoplastic polyimide.

2. The multilayer polyimide film according to claim 1, wherein The diamine residue having a biphenyl skeleton is a 4,4'-diamino-2,2'-dimethylbiphenyl residue.

3. The multilayer polyimide film according to claim 1 or 2, wherein The content of the 4,4′-diaminodiphenyl ether residue is 40 mol % or more and 70 mol % or less relative to all diamine residues constituting the non-thermoplastic polyimide.

4. The multilayer polyimide film according to claim 1 or 2, wherein The content of the p-phenylenediamine residue is 5 mol% or more and 50 mol% or less relative to all diamine residues constituting the non-thermoplastic polyimide.

5. The multilayer polyimide film according to claim 1 or 2, wherein The tetracarboxylic dianhydride residue includes at least one selected from the group consisting of a 3,3′,4,4′-biphenyltetracarboxylic dianhydride residue and a pyromellitic dianhydride residue.

6. The multilayer polyimide film according to claim 5, wherein The tetracarboxylic dianhydride residues also include 4,4'-oxydiphthalic anhydride residues.

7. The multilayer polyimide film according to claim 6, wherein The content of the 4,4′-oxydiphthalic anhydride residue is 5 mol % or more and 15 mol % or less relative to all tetracarboxylic dianhydride residues constituting the non-thermoplastic polyimide.

8. The multilayer polyimide film according to claim 1 or 2, wherein The thermoplastic polyimide contained in the thermoplastic polyimide layer includes one or more selected from the group consisting of 3,3′,4,4′-biphenyltetracarboxylic dianhydride residues and pyromellitic dianhydride residues, and a 2,2-bis[4-(4-aminophenoxy)phenyl]propane residue.

9. The multilayer polyimide film according to claim 1 or 2, wherein: The storage modulus of the non-thermoplastic polyimide layer at a temperature of 380° C. is less than 0.350 GPa.

10. The multilayer polyimide film according to claim 1 or 2, wherein The non-thermoplastic polyimide layer has a linear expansion coefficient of 5.0 ppm / K or more and 19.0 ppm / K or less when heated at a temperature of 100° C. to 200° C.

11. The multilayer polyimide film according to claim 1 or 2, wherein: The content of the p-phenylenediamine residue is 5 mol% or more and 20 mol% or less relative to all diamine residues constituting the non-thermoplastic polyimide.

12. The multilayer polyimide film according to claim 1 or 2, wherein: The content of the 4,4′-diaminodiphenyl ether residue is 60 mol % or more and 70 mol % or less relative to all diamine residues constituting the non-thermoplastic polyimide.

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