Resin film, metal-clad laminate, circuit board and laminate structure

Abstract

To provide a resin film that is a thin film but is designed to maintain heat dissipation properties and mechanical strength in a practically sufficient range.SOLUTION: A resin film 10 includes a film-shaped insulating resin 11, and a thermally conductive filler 12 contained in a dispersion state in the insulating resin 11. A total thickness of the resin film 10 is in a range of not less than 8 μm and less than 23 μm, thermal conductivity (λz) in a thickness direction is not less than 0.3 W / m K and is less than 2.0 W / m K, and tear resistance measured in a 20 mm width is in a range of 0.3-30.0 N. A volume average particle diameter of the thermally conductive filler 12 is preferably in a range of exceeding 1.0 μm and less than 5 μm. A ratio (D / L ratio) of a volume average particle diameter (D) and a film thickness (L) is preferably in a range of 0.15-0.50.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a resin film, a metal-clad laminate, a circuit board, and a laminate structure that have excellent thermal conductivity and can be suitably used as materials for, for example, semiconductor modules. [Background technology]

[0002] In recent years, there has been an increasing demand for smaller and lighter electronic devices, such as mobile phones and smartphones. The miniaturization of electronic devices has led to increased integration in semiconductor modules, and coupled with faster information processing speeds, it has become increasingly important to have a means for dissipating heat generated within electronic devices. Therefore, studies have been conducted to improve the thermal conductivity (λz) through the thickness direction by blending a thermally conductive filler into polyimides used in applications such as insulating resin layers for circuit boards (e.g., Patent Documents 1 to 3).

[0003] However, when a large amount of thermally conductive filler is added to the insulating resin layer to increase the thermal conductivity (λz) in the thickness direction, some of the thermally conductive filler protrudes from the surface of the insulating resin layer, causing poor appearance and surface smoothness, and poor adhesion to the metal layer. Furthermore, adding a large amount of thermally conductive filler may reduce the mechanical strength of the insulating resin layer. Therefore, the previous approach of adding a large amount of thermally conductive filler to improve the thermal conductivity (λz) in the thickness direction is expected to have limitations. In addition, in the above Patent Documents 1 to 3, the thickness of the insulating resin layer described in the examples is 20 μm or more, so even if a large amount of thermally conductive filler is added, a decrease in mechanical strength is unlikely to become apparent. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication WO2009 / 110387 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-213899 [Patent Document 3] Japanese Patent Application Publication No. 2019-140094 Summary of the Invention [Problem to be solved by the invention]

[0005] The inventors have found that when the thermal conductivity (λz) in the thickness direction is around 0.6 W / m·K, the effect of increasing the thermal conductivity (λz) in the thickness direction tends to plateau, and that reducing the thickness of the insulating resin layer while limiting the amount of thermally conductive filler is more effective in improving heat dissipation characteristics. Furthermore, when applied to applications such as semiconductor modules, as their integration becomes increasingly high, there is likely to be a growing demand for thinner insulating resin layers containing thermally conductive fillers. On the other hand, as the thickness of the insulating resin layer is further reduced, there is concern that serious problems such as cracking and tearing will occur due to a significant decrease in mechanical strength and embrittlement.

[0006] Therefore, an object of the present invention is to provide a resin film that is thin and yet has heat dissipation properties and mechanical strength that are sufficient for practical use. [Means for solving the problem]

[0007] As a result of extensive investigations into solving the above problems, the inventors discovered that it is possible to achieve both heat dissipation properties and sufficient mechanical strength even when the film is made thin, and thus completed the present invention.

[0008] That is, the resin film of the present invention is a resin film comprising a film-like insulating resin and a thermally conductive filler dispersed in the insulating resin. The resin film of the present invention is characterized in that the thickness (L) of the entire resin film is in the range of 8 μm or more and less than 23 μm, the thermal conductivity (λz) in the thickness direction is in the range of 0.3 W / m·K or more and less than 2.0 W / m·K, and the edge tear resistance measured over a 20 mm width is in the range of 0.3 [N] or more and 30.0 [N] or less.

[0009] In the resin film of the present invention, the thermally conductive filler may have a volume average particle diameter in the range of more than 1.0 μm and less than 5 μm, and the ratio of the volume average particle diameter (D) of the thermally conductive filler to the film thickness (L) may be in the range of 0.15 or more and 0.50 or less.

[0010] The resin film of the present invention may have a tear propagation resistance in the range of 7.0 mN or more and 30.0 mN or less.

[0011] In the resin film of the present invention, the content of the thermally conductive filler relative to the entire resin film may be in the range of 10 vol % or more and 50 vol % or less.

[0012] In the resin film of the present invention, the thermally conductive filler may be alumina particles.

[0013] In the resin film of the present invention, the insulating resin may be a polyimide obtained by reacting an acid dianhydride component with a diamine component, in which the acid dianhydride component may contain at least one selected from pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, and 3,3',4,4'-benzophenonetetracarboxylic dianhydride in an amount of 50 mol % or more relative to the total acid dianhydride components, and the diamine component may contain at least one selected from 4,4'-diaminodiphenyl ether and 2,2-bis[4-(4-aminophenoxy)phenyl]propane in an amount of 50 mol % or more relative to the total diamine components.

[0014] The metal-clad laminate of the present invention is a metal-clad laminate comprising an insulating resin layer consisting of a single layer or multiple layers and a metal layer laminated on one or both sides of the insulating resin layer, and at least one layer of the insulating resin layer is composed of the above-mentioned resin film.

[0015] The circuit board of the present invention is a circuit board comprising an insulating resin layer consisting of a single layer or multiple layers, and a conductor circuit layer laminated on one or both sides of the insulating resin layer, and at least one layer of the insulating resin layer is composed of the above-mentioned resin film.

[0016] The laminated structure of the present invention is a laminated structure used in a semiconductor module, a conductor circuit layer electrically connected to an external semiconductor element; an insulating resin layer consisting of a single layer or multiple layers; an adhesive layer; a heat transfer metal layer that mediates heat conduction to an external heat dissipation member; have a structure in which the above are stacked in this order, At least one of the insulating resin layers is formed from the resin film. [Effects of the Invention]

[0017] The resin film of the present invention is thin, yet has heat dissipation properties and mechanical strength sufficient for practical use, and therefore can be widely used industrially as a substrate material for semiconductor modules and circuit boards that require high heat dissipation properties, as well as electronic devices and lighting equipment that use these. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a view showing a cross-sectional structure in a thickness direction of a resin film according to an embodiment of the present invention. [Figure 2] 1 is a view showing a cross-sectional structure in a thickness direction of a metal-clad laminate according to an embodiment of the present invention. [Figure 3] 1 is a diagram showing a cross-sectional structure in a thickness direction of a circuit board according to an embodiment of the present invention. [Figure 4] 1 is a diagram showing a configuration of a laminated structure according to an embodiment of the present invention. [Figure 5] 1 is a diagram showing the configuration of a semiconductor module used to evaluate heat dissipation characteristics in Examples and Comparative Examples. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0020] [Resin film] 1 shows a cross-sectional structure in the thickness direction of a resin film according to one embodiment of the present invention. Resin film 10 of this embodiment includes film-like insulating resin 11 and thermally conductive filler 12 dispersed in insulating resin 11. Resin film 10 of this embodiment may be a single layer or may be composed of multiple layers, but is preferably a single layer.

[0021] <Insulating resin> The insulating resin (matrix resin) 11 constituting the resin film 10 is not particularly limited, and examples thereof include polyimide, epoxy resin, urethane resin, and polyethylene terephthalate, among which polyimide is preferred. The case where the matrix resin is polyimide will be described in detail below.

[0022] Polyimide is a polymer obtained by reacting an acid dianhydride component with a diamine component, and may contain a structural unit represented by the following general formula (1).

[0023] [ka]

[0024] In the above general formula (1), the group Ar represents an acid dianhydride residue derived from an acid dianhydride, and the group R1 represents a diamine residue derived from a diamine compound.

[0025] In the present embodiment, the dianhydride from which the Ar group is derived can be any acid dianhydride generally known as a raw material monomer for polyimide, without particular limitation. However, preferred dianhydrides include pyromellitic dianhydride (PMDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), and 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA). Pyromellitic dianhydride (PMDA) has a rigid structure, which can enhance the heat resistance of the resin film 10. 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) has a structure that includes moderate flexibility, which can enhance the mechanical strength of the resin film 10. 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA) has a structure that moderately suppresses flatness, which can enhance the thermal conductivity of the resin film 10 in the thickness direction.

[0026] Furthermore, the diamine compound from which group R1 is derived can be any compound generally known as a raw material monomer for polyimide, without any particular limitation, but preferred diamine compounds include 4,4'-diaminodiphenyl ether (DAPE) and 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP). 4,4'-diaminodiphenyl ether (DAPE) and 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP) have appropriate flexibility due to their molecular structures, and therefore have the effect of increasing the toughness of resin film 10, thereby increasing the mechanical strength of resin film 10 and improving adhesiveness.

[0027] From the above viewpoints, a preferred combination is one in which the dianhydride component contains at least 50 mol%, preferably at least 80 mol%, of one or more selected from pyromellitic dianhydride (PMDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) and 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA) relative to the total dianhydride components, and the diamine component contains at least 50 mol%, preferably at least 80 mol%, of one or more selected from 4,4'-diaminodiphenyl ether (DAPE) and 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP) relative to the total diamine components. Among these, a combination in which the dianhydride component is 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA) and the diamine component is 4,4'-diaminodiphenyl ether (DAPE), or a combination in which the dianhydride components are pyromellitic dianhydride (PMDA) and 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) and the diamine component is 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP) are particularly preferred.

[0028] Specific examples of other acid dianhydrides that provide the group Ar in general formula (1) include, for example, naphthalene-2,3,6,7-tetracarboxylic dianhydride (NTCDA), naphthalene-1,2,5,6-tetracarboxylic dianhydride, naphthalene-1,2,4,5-tetracarboxylic dianhydride, naphthalene-1,4,5,8-tetracarboxylic dianhydride, naphthalene-1,2,6,7-tetracarboxylic dianhydride, 4,8-dimethyl-1,2,3,5,6,7-hexahydronaphthalene-1,2,5,6-tetracarboxylic dianhydride, 4,8-dimethyl-1,2,3,5,6,7-hexahydronaphthalene-2,3,6,7-tetracarboxylic dianhydride, 2,6-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 2,7-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 2, 3,6,7-tetrachloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 1,4,5,8-tetrachloronaphthalene-2,3,6,7-tetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 2,3,3',4'-biphenyltetracarboxylic dianhydride, 3,3'',4,4''-p-terphenyltetracarboxylic dianhydride, 2,2'',3,3''-p-terphenyltetracarboxylic dianhydride, 2,3,3'',4''-p-terphenyltetracarboxylic dianhydride, 2,2-bis(2,3-dicarboxyphenyl)-propane dianhydride, 2,2-bis(3,4-dicarboxyphenyl)-propane dianhydride, bis(2,3-dicarboxyphenyl)ether dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride, bis(3.4-dicarboxyphenyl)methane dianhydride, bis(2,3-dicarboxyphenyl)sulfone dianhydride, bis(3,4-dicarboxyphenyl)sulfone dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride, 1,1-bis(3,4-dicarboxyphenyl)ethane dianhydride, perylene-2,3,8,9-tetracarboxylic dianhydride, perylene-3,4,9,10-tetracarboxylic dianhydride, perylene-4,5,10,11-tetracarboxylic dianhydride, perylene-5,6,11,12-tetracarboxylic dianhydride, phenanthrene-1,2,7,8-tetracarboxylic dianhydride, phenanthrene-1, Examples include 2,6,7-tetracarboxylic dianhydride, phenanthrene-1,2,9,10-tetracarboxylic dianhydride, cyclopentane-1,2,3,4-tetracarboxylic dianhydride, pyrazine-2,3,5,6-tetracarboxylic dianhydride, pyrrolidine-2,3,4,5-tetracarboxylic dianhydride, thiophene-2,3,4,5-tetracarboxylic dianhydride, and 4,4'-oxydiphthalic dianhydride.

[0029] Other diamine compounds that provide the group R1 in general formula (1) include, for example, 4,6-dimethyl-m-phenylenediamine, 2,5-dimethyl-p-phenylenediamine, 2,4-diaminomesitylene, 4,4'-methylenedi-o-toluidine, 4,4'-methylenedi-2,6-xylidine, 4,4'-methylene-2,6-diethylaniline, 2,4-toluenediamine, m-phenylenediamine, p-phenylenediamine, 4,4'-diaminodiphenylpropane, 3,3'-diaminodiphenylpropane, 4,4'-diaminodiphenylene Tantalum, 3,3'-diaminodiphenylethane, 4,4'-diaminodiphenylmethane, 3,3'-diaminodiphenylmethane, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, 3,3-diaminodiphenyl ether, 1,3-bis(3-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, benzidine, 3,3'-diaminobiphenyl , 3,3'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dimethoxybenzidine, 4,4'-diamino-p-terphenyl, 3,3'-diamino-p-terphenyl, bis(p-aminocyclohexyl)methane, bis(p-β-amino-t-butylphenyl)ether, bis(p-β-methyl-δ-aminopentyl)benzene, p-bis(2-methyl-4-aminopentyl)benzene, p-bis(1,1-dimethyl-5-aminopentyl)benzene, 1,5-diaminonaphthalene, 2,6-diaminonaphthalene, 2,4-bis (β-amino-t-butyl)toluene, 2,4-diaminotoluene, m-xylene-2,5-diamine, p-xylene-2,5-diamine, m-xylylenediamine, p-xylylenediamine, 2,6-diaminopyridine, 2,5-diaminopyridine, 2,5-diamino-1,3,4-oxadiazole, piperazine, 2,2′-dimethyl-4,4′-diaminobiphenyl, 3,7-diaminodibenzofuran, 1,5-diaminofluorene, dibenzo-p-dioxin-2,7-diamine, and 4,4′-diaminobenzyl.

[0030] When synthesizing the polyimide that constitutes the resin film 10, only one type of diamine or acid anhydride may be used, or two or more types may be used in combination.

[0031] <Thermal conductive filler> Any conventionally known thermally conductive filler can be used without any particular limitation as the thermally conductive filler 12. Preferred examples of the thermally conductive filler 12 include alumina, silica, diamond, magnesia, beryllia, boron nitride, silicon nitride, and silicon carbide. Among these, alumina, silica, boron nitride, and silicon nitride are preferred, as they are highly effective in increasing the thermal conductivity of the resin film 10, and alumina is most preferred.

[0032] The content of the thermally conductive filler 12 in the resin film 10 is preferably in the range of 10 vol% to 50 vol%, more preferably in the range of 20 vol% to 40 vol%. If the content of the thermally conductive filler 12 is less than 10 vol%, the heat dissipation characteristics are insufficient when used in electronic components such as semiconductor modules. On the other hand, if the content of the thermally conductive filler 12 exceeds 50 vol%, not only does the effect of improving the heat dissipation characteristics plateau, but the incorporation of a large amount of the thermally conductive filler 12 can have adverse effects such as poor appearance and adhesion of the resin film 10, reduced mechanical properties, and excessively increased viscosity of the polyamic acid solution, making it difficult to fabricate the resin film 10. In other words, even if the content of the thermally conductive filler 12 exceeds 50 vol%, the effect of improving the heat dissipation characteristics is not significantly improved compared to when the content is 50 vol% or less, and negative effects such as reduced mechanical strength and handleability become more significant.

[0033] The particle size of the thermally conductive filler 12 is preferably determined taking into consideration the balance with the thickness of the resin film 10. Specifically, from the viewpoint of uniformly dispersing the filler in the thickness direction of the resin film 10 and improving thermal conductivity, the volume average particle size (D) of the thermally conductive filler 12 is preferably greater than 1.0 μm and less than 5 μm, and more preferably 1.5 μm or greater and 4.0 μm or less. Here, the "volume average particle size" refers to the value at which the cumulative value reaches 50% on a frequency distribution curve obtained by measuring the volumetric particle size distribution using a laser diffraction scattering method. If the volume average particle size (D) of the thermally conductive filler 12 is 1.0 μm or less, it is difficult to form a thermal conduction path in the thickness direction, and the improvement of thermal conduction efficiency is likely to be insufficient. On the other hand, if the volume average particle size (D) is 5 μm or greater, the mechanical strength is likely to decrease, and the thermally conductive filler 12 may protrude from the surface of the resin film 10, causing problems with the appearance and surface smoothness, or problems with adhesion to any layer (e.g., a metal layer) laminated on the resin film 10.

[0034] In this embodiment, two or more types of thermally conductive fillers with different volume average particle diameters (D) can be blended within a range that does not impair the effects of the invention. In this case, since a filler with a smaller particle diameter is less likely to form a filler thermal conduction path than a filler with a larger particle diameter, it is preferable to add the filler with the largest volume average particle diameter (D) at the highest content. In other words, for example, when two types of fillers with different volume average particle diameters (D), D1 and D2, are used in combination and the volume average particle diameter of D1 is larger than the volume average particle diameter of D2, it is preferable to add them in a combination such that the content of D1 is greater than the content of D2.

[0035] The thermally conductive filler 12 has a particle size distribution measured by a laser diffraction scattering method, and the particle size distribution is determined by a frequency distribution curve obtained by measuring the particle size distribution based on the volume. The particle size distribution is determined by a frequency distribution curve obtained by a laser diffraction scattering method and the cumulative value is determined by a value (D 95 ) is preferably 15 μm or less, more preferably 10 μm or less. 95 When the particle size is 15 μm or less, the proportion of coarse particles is controlled to be low, and therefore, the decrease in the mechanical strength of the resin film 10 can be suppressed.

[0036] The thermally conductive filler 12 is preferably spherical in shape. Here, "spherical" means that the shape is spherical or nearly spherical, and the ratio of the average major axis to the average minor axis is 1 or nearly 1 (preferably 0.8 or more). The use of spherical fillers enables high-density filling and uniform dispersion in the resin film 10, thereby improving thermal conductivity.

[0037] The thermally conductive filler 12 is preferably present in the resin film 10 in a uniformly dispersed state in which the thermally conductive filler 12 is uniformly dispersed and agglomeration of particles is suppressed. The uniformly dispersed state effectively exhibits the thermal conductivity efficiency of the thermally conductive filler 12, and allows the resin film 10 to maintain sufficient mechanical strength for practical use even when the resin film 10 is made thinner.

[0038] The resin film 10 of this embodiment may contain optional components such as processing aids, antioxidants, light stabilizers, flame retardants, antistatic agents, surfactants, dispersants, anti-settling agents, heat stabilizers, ultraviolet absorbers, and organic or inorganic fillers other than the thermally conductive filler 12, as long as the effects of the invention are not impaired.

[0039] <Thickness> The overall thickness (L) of the resin film 10 of this embodiment is preferably, for example, in the range of 8 μm or more and less than 23 μm, more preferably 10 μm or more and less than 20 μm, and even more preferably 10 μm or more and 18 μm or less. If the thickness (L) of the resin film 10 is less than 8 μm, the surface smoothness of the film may deteriorate, and the mechanical strength of the resin film 10 may decrease, making it more susceptible to problems such as tearing. Conversely, if the thickness (L) is 23 μm or more, a sufficient heat dissipation effect cannot be obtained.

[0040] Furthermore, in the resin film 10 of the present embodiment, the ratio (D / L ratio) of the volume average particle diameter (D) of the thermally conductive filler 12 to the film thickness (L) is preferably in the range of 0.15 to 0.50, more preferably 0.20 to 0.40. When the resin film 10 contains multiple thermally conductive fillers with different volume average particle diameters (D), the D / L ratio is determined based on the filler with the largest volume average particle diameter (D). If the D / L ratio is below 0.15, it is difficult to form a thermal conduction path in the thickness direction, and the improvement in thermal conduction efficiency is likely to be insufficient. On the other hand, if the D / L ratio exceeds 0.50, the mechanical strength is likely to decrease, and the filler may protrude from the surface of the resin film 10, causing problems with appearance and surface smoothness, or problems with adhesion to any layer (e.g., a metal layer) laminated on the resin film 10.

[0041] <Thermal conductivity in the thickness direction (λz)> The thermal conductivity (λz) in the thickness direction of the resin film 10 of this embodiment is preferably, for example, in the range of 0.3 W / m·K or more and less than 2.0 W / m·K, and more preferably in the range of 0.5 W / m·K or more and 1.8 W / m·K or less. If the thermal conductivity (λz) in the thickness direction is less than 0.3 W / m·K, a sufficient heat dissipation effect cannot be obtained when applied to electronic components such as semiconductor modules. On the other hand, there is no particular upper limit to the thermal conductivity (λz) in the thickness direction, but it is preferable to set it to less than 2.0 W / m·K in consideration of practicality when applied to electronic components such as semiconductor modules.

[0042] <Mechanical properties> The tear propagation resistance of the resin film 10 of this embodiment is preferably in the range of 7.0 mN to 30.0 mN, and more preferably in the range of 9.0 mN to 30.0 mN. If the tear propagation resistance is less than 7.0 mN, it may cause breakage, and processability and flexibility may be impaired. There is no particular upper limit for the tear propagation resistance, but if it exceeds 30.0 mN, the film will need to be thick or the filler content will need to be reduced, making it difficult to ensure sufficient heat dissipation.

[0043] Furthermore, the edge tear resistance of the resin film 10 of this embodiment, measured over a 20 mm width, is preferably in the range of 0.30 N to 30.0 N, more preferably 0.35 N to 30.0 N. Resistance below 0.30 N can cause tearing and impairs processability and flexibility. While there is no particular upper limit for edge tear resistance, a configuration exceeding 30.0 N requires either a large thickness or a small filler content, making it difficult to ensure sufficient heat dissipation.

[0044] In this embodiment, the amount of thermally conductive filler 12, its average particle diameter, and the relationship between the film thickness of the resin film 10 are appropriately controlled, so that the tear propagation resistance and edge tear resistance can be maintained within the above ranges, thereby obtaining mechanical strength sufficient for practical use.

[0045] <Method of manufacturing resin film> The method for producing the resin film 10 of the present embodiment is not particularly limited. When the insulating resin 11 is polyimide, a preferred method is to apply a filler-containing polyamic acid solution, which is a precursor of polyamic acid, to a substrate and disperse the thermally conductive filler 12 in the solution, dry the solution, and imidize the solution to form a film.

[0046] The polyamic acid solution containing the thermally conductive filler 12 can be prepared, for example, by adding a predetermined amount of the thermally conductive filler 12 to a polyamic acid solution containing a solvent obtained by polymerization in advance and dispersing the filler using a stirrer, or by adding an acid dianhydride component and a diamine component while dispersing the thermally conductive filler 12 in a solvent and polymerizing the resulting mixture. Here, the polyamic acid can be produced by a known method in which the acid dianhydride component and the diamine component are used in approximately equimolar amounts and polymerized in a solvent.

[0047] Examples of preferred solvents for use in the polyamic acid solution include N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N,N-diethylacetamide, N-methyl-2-pyrrolidone (NMP), 2-butanone, dimethyl sulfoxide (DMSO), hexamethylphosphoramide, N-methylcaprolactam, dimethyl sulfate, cyclohexanone, dioxane, tetrahydrofuran, diglyme, triglyme, cresol, and water. Two or more of these solvents can be used in combination, and aromatic hydrocarbons such as xylene and toluene can also be used in combination. The solvent content is not particularly limited, but it is preferable to adjust the amount so that the polyamic acid concentration is, for example, about 5 to 70 wt %.

[0048] In this embodiment, in order to uniformly disperse the thermally conductive filler 12 in the resin film 10, it is preferable to adjust the viscosity of the polyamic acid solution serving as the dispersion medium to within a range of, for example, 500 cP to 50,000 cP (500 mPa·s to 50,000 mPa·s).Within this viscosity range, the thermally conductive filler 12 can be maintained in a uniformly dispersed state.

[0049] The substrate is not particularly limited, but for example, a metal foil such as copper foil, which serves as a conductor layer of a heat dissipation substrate or a circuit board, can be preferably used. The filler-containing polyamic acid solution can be applied to the substrate by a known method, and for example, a method appropriately selected from bar coating, gravure coating, roll coating, die coating, etc. can be used.

[0050] After applying a polyamic acid solution containing thermally conductive filler 12 to a substrate, the solution is dried, for example, at a temperature of 140°C or less to remove a certain amount of solvent. The polyamic acid is then imidized by further heat treatment at a high temperature, resulting in a laminate having a substrate on one side of the filler-containing polyimide layer. When a metal foil is used as the substrate, a metal-clad laminate, as described below, can be produced. Then, if necessary, the filler-containing polyimide layer can be peeled off from the substrate to produce the resin film 10 of this embodiment.

[0051] The heat treatment for imidization is preferably carried out in stages for about 15 to 60 minutes at a heating temperature in the range of, for example, 130 to 360°C. Such staged heat treatment can reduce dimensional changes and suppress warping of the resin film 10. If the heat treatment temperature is lower than 130°C, the dehydration ring-closing reaction of polyimide does not proceed sufficiently, while if it exceeds 360°C, the resin film 10 and the metal foil may be deteriorated due to oxidation or the like.

[0052] [Metal-clad laminate] 2 shows a cross-sectional structure in the thickness direction of a metal-clad laminate according to one embodiment of the present invention. The metal-clad laminate 30 of this embodiment includes an insulating resin layer 10A and a metal layer 20 laminated on the insulating resin layer 10A. The metal layer 20 may be laminated on both sides of the insulating resin layer 10A.

[0053] <Insulating resin layer> The insulating resin layer 10A in the metal-clad laminate 30 of this embodiment is composed of a single layer or multiple layers, and at least one layer of the insulating resin layer 10A may be composed of the above-mentioned resin film 10 containing the thermally conductive filler 12. The insulating resin layer 10A may include any layer that does not contain the thermally conductive filler 12, but it is preferable that the entire insulating resin layer 10A be composed of only the resin film 10.

[0054] <Metal layer> The metal layer 20 in the metal-clad laminate 30 of the present invention serves as a conductor layer for a heat dissipation substrate or a circuit board, and examples thereof include conductive metal foils such as copper, aluminum, iron, silver, palladium, nickel, chromium, molybdenum, tungsten, zinc, and alloys thereof. Among these, copper foil or an alloy copper foil containing 90% or more copper is preferably used.

[0055] The preferred thickness range of the metal layer 20 can be set depending on the application of the metal-clad laminate 30. When used as a laminate substrate for a semiconductor module, for example, a range of 5 μm to 50 μm is preferred, and a range of 12 μm to 40 μm is even more preferred. Of these, a range of 30 μm to 40 μm is particularly preferred. If the thickness of the metal layer 20 is less than 5 μm, problems such as wrinkles may occur during transportation in the manufacturing process. Conversely, if it exceeds 50 μm, processability may be reduced. Here, the ratio (LR / LM) of the thickness (LR) of the insulating resin layer 10A to the thickness (LM) of the metal layer 20 is preferably, for example, in the range of 0.2 to 2.0, more preferably in the range of 0.2 to 1.0, and most preferably in the range of 0.5 to 0.6, from the viewpoint of suppressing warpage of the metal-clad laminate 30. If the ratio (LR / LM) is less than 0.2, the insulating resin layer 10A is too thin compared to the thickness of the metal layer 20, resulting in poor processability. If the ratio exceeds 2.0, the insulating resin layer 10A is too thick compared to the thickness of the metal layer 20, resulting in warpage.

[0056] Furthermore, the conductive metal foil used as the metal layer 20 preferably has a surface roughness (Rz) of 0.05 to 3.5 μm on the surface that is bonded to the insulating resin layer 10A to enhance adhesion to the insulating resin layer 10A. If the surface roughness (Rz) of the surface that is bonded to the insulating resin layer 10A is less than 0.05 μm, the metal layer 20 and the insulating resin layer 10A may easily peel off depending on the application of the metal-clad laminate 30, making the metal-clad laminate 30 unsuitable for use as a flexible substrate material, for example. On the other hand, if the surface roughness (Rz) of the surface that is bonded to the insulating resin layer 10A exceeds 3.5 μm, the anchor effect of the roughening improves adhesion between the metal layer 20 and the insulating resin layer 10A, but there is a concern that the wiring shape may be deteriorated when the metal layer 20 is subjected to wiring processing.

[0057] <Metal-clad laminate manufacturing method> The manufacturing method of the metal-clad laminate 30 of this embodiment is as explained in relation to the manufacturing method of the resin film 10, and by using a metal foil as a base material for manufacturing the resin film 10, it is possible to manufacture a single-sided metal-clad laminate in which a metal layer 20 is laminated on one side of the insulating resin layer 10A. Furthermore, it is also possible to form a double-sided metal-clad laminate having a laminated structure of metal foil / insulating resin layer 10A / metal layer 20 by laminating a metal foil on the side of the insulating resin layer 10A opposite to the metal layer 20 by a method such as thermocompression bonding.

[0058] The insulating resin layer 10A of the metal-clad laminate 30 of this embodiment has heat dissipation characteristics sufficient for practical use while avoiding a decrease in mechanical strength caused by the incorporation of the thermally conductive filler 12. Therefore, by using the metal-clad laminate 30 of this embodiment as a substrate material for a semiconductor module or the like, the reliability of the electronic device can be improved.

[0059] [Circuit board] FIG. 3 shows a cross-sectional structure in the thickness direction of a circuit board according to one embodiment of the present invention. Circuit board 40 of this embodiment includes an insulating resin layer 10A consisting of a single layer or multiple layers, and a conductor circuit layer 21 laminated on insulating resin layer 10A. Circuit board 40 can be manufactured by forming conductor circuit layer 21 by patterning metal layer 20 of metal-clad laminate 30 using a conventional method. Patterning of metal layer 20 can be performed using any method, such as photolithography and etching. Circuit board 40 may have any layer other than those shown in FIG. 3. Circuit board 40 may be a flexible circuit board or a rigid circuit board.

[0060] The insulating resin layer 10A of the circuit board 40 of this embodiment has heat dissipation characteristics sufficient for practical use while avoiding a decrease in mechanical strength caused by the incorporation of the thermally conductive filler 12. Therefore, by applying the circuit board 40 of this embodiment to a semiconductor module or the like, the reliability of the electronic device can be improved.

[0061] [Laminated structure] 4 shows the configuration of a laminated structure according to one embodiment of the present invention. The laminated structure 100 of this embodiment is a laminated structure 100 used in, for example, a semiconductor module. This laminated structure 100 has a structure in which a conductor circuit layer 21 electrically connected to an external semiconductor element 70, an insulating resin layer 10A consisting of a single layer or multiple layers, an adhesive layer 50, and a heat transfer metal layer 60 that mediates heat conduction to an external heat dissipation member (not shown) are stacked in this order. In the laminated structure 100 of this embodiment, the conductor circuit layer 21 and the insulating resin layer 10A have the same configuration as the circuit board 40 described above.

[0062] In the laminated structure 100, at least one layer of the insulating resin layer 10A, preferably the entire insulating resin layer 10A, is composed of the resin film 10. Therefore, the insulating resin layer 10A has heat dissipation characteristics sufficient for practical use while avoiding a decrease in mechanical strength due to the incorporation of the thermally conductive filler 12. Therefore, by using the laminated structure 100 of this embodiment in a semiconductor module or the like, the reliability of the electronic device can be improved. Note that the laminated structure 100 may have any layers other than those shown in FIG. 4.

[0063] In addition to increasing density, semiconductor modules are beginning to be used in applications such as automobile daytime running lights that require higher heat dissipation and heat resistance. By using the laminated structure 100 of this embodiment, the durability of the semiconductor module can be improved because it has better heat dissipation and heat resistance than conventional materials. [Example]

[0064] The present invention will be specifically described below based on examples, but the present invention is not limited to the scope of these examples.

[0065] The abbreviations used in the examples represent the following compounds. BTDA: 3,3',4,4'-benzophenonetetracarboxylic dianhydride BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride PMDA: Pyromellitic dianhydride DAPE: 4,4'-diaminodiphenyl ether BAPP: 2,2-bis(4-aminophenoxyphenyl)propane m-TB: 2,2'-dimethyl-4,4'-diaminobiphenyl DMAc: N,N-dimethylacetamide

[0066] The properties evaluated in the examples were evaluated according to the following evaluation methods.

[0067] [Viscosity measurement] The viscosity of the polyamic acid solution was measured using a cone-plate viscometer equipped with a thermostatic water bath (manufactured by Tokimec Co., Ltd.). The measurements were taken at 25°C.

[0068] [Volume average particle diameter D 50 Measurement of The volume-average particle size was determined by measuring the volumetric particle size distribution by laser diffraction using a laser particle size distribution analyzer (Microtrac MT3300EXII manufactured by Microtrac-Bell) and determining the value at which the cumulative value reaches 50% on the frequency distribution curve obtained by volumetric particle size distribution measurement. For the measurement, alumina was placed in a 0.2% by mass aqueous solution of sodium hexametaphosphate and dispersed for 5 minutes at 40 W using the ultrasonic device built into the analyzer, resulting in a refractive index of 1.76 for the alumina.

[0069] [Thermal conductivity through thickness (λz)] The polyimide resin film was cut into a 20 mm x 20 mm piece, and the thermal diffusivity in the thickness direction was measured by the laser flash method (NETZSCH, trade name: Xenon Flash Analyzer LFA447 Nanoflash device), the specific heat by differential scanning calorimetry (DSC), and the density by the water displacement method. The thermal conductivity (W / m K) was calculated based on these results.

[0070] Tear Propagation Resistance (TPR) A 63.5 mm x 50 mm polyimide resin film was used as a test piece, and a 12.7 mm long notch was made in the test piece, and the tear propagation resistance was measured using a light load tear tester manufactured by Toyo Seiki Co., Ltd.

[0071] [End tear resistance] In accordance with JIS C2151 (2019) Method B, edge tear resistance was measured using a 20 mm × 200 mm polyimide film test piece using a Strograph R1 product manufactured by Toyo Seiki Co., Ltd.

[0072] [Workability] When the copper foil of a 20 cm × 30 cm copper-clad laminate was completely etched, if the polyimide film had film defects due to cracks or tears, it was evaluated as ×, and if a good film was obtained without any defects it was evaluated as ○.

[0073] [Chip temperature (evaluation of heat dissipation characteristics)] 5, for a semiconductor module S having a structure in which, from the top, an LED chip (LED) as a semiconductor element 70, a copper circuit layer (Cu) as a conductor circuit layer 21, a polyimide layer (PI) as an insulating resin layer 10A, an adhesive layer (AD) as an adhesive layer 50, and an aluminum layer (Al) as a heat-transfer metal layer 60 are stacked in this order, the heat dissipation characteristics were evaluated by measuring the chip temperature when the LED chip (LED) was operated (light-emitting) for one hour. Note that heat dissipation was performed only from the aluminum layer (Al) side. The LED chip (LED) measured 3 mm x 3 mm x 1 mm thick, generated approximately 2 W of heat, and the copper circuit layer (Cu) measured 3 mm x 3 mm x 35 μm thick. The polyimide layer (PI), adhesive layer (AD), and aluminum layer (Al) all measured 50 mm x 100 mm in plan view, with the thickness of the polyimide layer (PI) indicated in each Example and Comparative Example. The adhesive layer (AD) had a thermal conductivity of 1 W / m K in the thickness direction, a thickness of 100 μm, and a thickness of 1 mm for the aluminum layer (Al).

[0074] (Synthesis Example 1) Under a nitrogen atmosphere, DAPE (17.26 g, 0.086 mol) was dissolved in 255 g of DMAc solvent in a 500 mL separable flask with stirring. BTDA (27.73 g, 0.086 mol) was then added. The solution was then stirred at room temperature for 3 hours to allow polymerization, yielding a pale yellow, viscous polyamic acid solution A with a viscosity of 12,000 cP.

[0075] (Synthesis Example 2) As in Synthesis Example 1, BAPP (29.23 g, 0.071 mol) was dissolved in 255 g of DMAc solvent in a 500 mL separable flask with stirring under a nitrogen atmosphere. PMDA (14.73 g, 0.068 mol) and BPDA (1.05 g, 0.004 mol) were then added. The solution was then stirred at room temperature for 3 hours to carry out the polymerization reaction, yielding a pale yellow, viscous polyamic acid solution B with a viscosity of 10,000 cP.

[0076] (Synthesis Example 3) As in Synthesis Example 1, m-TB (22.21 g, 0.104 mol) was dissolved in 255 g of DMAc solvent in a 500 mL separable flask with stirring under a nitrogen atmosphere. PMDA (22.79 g, 0.104 mol) was then added. The solution was then stirred at room temperature for 3 hours to carry out the polymerization reaction, yielding a pale yellow, viscous polyamic acid solution C with a viscosity of 10,000 cP.

[0077] (Synthesis Example 4) As in Synthesis Example 1, DAPE (21.56 g, 0.107 mol) was dissolved in 255 g of DMAc solvent in a 500 mL separable flask with stirring under a nitrogen atmosphere. PMDA (23.44 g, 0.107 mol) was then added. The solution was then stirred at room temperature for 3 hours to carry out the polymerization reaction, yielding a pale yellow, viscous polyamic acid solution D with a viscosity of 13,000 cP.

[0078] (Combination example 1) 63.1 parts by weight of polyamic acid solution A with a solid content of 15 wt % and aluminum oxide particles (manufactured by Sumitomo Chemical Co., Ltd., product name: AA-3, spherical, volume average particle diameter D50 6.9 parts by weight of the thermally conductive filler [3.4 μm] were mixed in a centrifugal mixer until uniform, to obtain a filler-containing polyamic acid solution E containing a thermally conductive filler. The content of aluminum oxide particles in the insulating resin layer obtained by curing this filler-containing polyamic acid solution E was 20 vol %.

[0079] (Combination examples 2-9) As in Blending Example 1, the polyamic acid solution and aluminum oxide particles shown in Table 1 were mixed in a centrifugal mixer until homogeneous, to obtain filler-containing polyamic acid solutions F to M containing thermally conductive fillers. In Blending Example 4, aluminum oxide particles (manufactured by Sumitomo Chemical Co., Ltd., product name: AA-1.5, spherical, volume average particle diameter D 50 1.6 μm) was also used, and the filler was contained so that the weight ratio of AA-3 to AA-1.5 (AA-3:AA-1.5) was 24:16.

[0080] [Table 1]

[0081] Example 1 The polyamic acid solution E obtained in Formulation Example 1 was applied to copper foil 1 (electrolytic copper foil, manufactured by Fukuda Metal Foil & Powder Co., Ltd., product name: CF-T4MDS-HD-35, thickness: 35 μm, Rz = 1.4 μm) to a thickness of 14.8 μm after curing. The solution was then dried by heating at 90 to 140 °C to remove the solvent. The temperature was then gradually increased over 30 minutes in the temperature range of 130 to 360 °C to produce a flexible substrate laminate consisting of a polyimide layer on copper foil 1. To evaluate the properties of the polyimide layer in the flexible substrate laminate, copper foil 1 was etched away to produce film M1, and the thickness-wise thermal conductivity (λz), tear propagation resistance (TPR), edge tear resistance, and processability were evaluated. Furthermore, when applied to a semiconductor module S with the configuration shown in Figure 5, the chip temperature was measured to evaluate the heat dissipation characteristics.

[0082] (Examples 2 to 8, Comparative Examples 1 and 2) By changing the type and thickness of the polyamic acid solution used, films M2 to M10 were obtained and evaluated in the same manner as in Example 1. In addition, when applied to a semiconductor module S having the configuration shown in Fig. 5, the chip temperature was measured and the heat dissipation characteristics were evaluated.

[0083] (Comparative Example 3) Polyamic acid solution B obtained in Synthesis Example 2 was applied to copper foil 1 to a thickness of 1.5 μm after curing, and the solution was dried by heating at 90 to 140°C to remove the solvent. Next, polyamic acid solution C obtained in Synthesis Example 3 was applied thereon to a thickness of 5.0 μm after curing, and the solution was dried by heating at 120°C to remove the solvent. Next, polyamic acid solution B obtained in Synthesis Example 2 was applied thereon to a thickness of 1.5 μm after curing, and the solution was dried by heating at 90 to 140°C to remove the solvent. The temperature was then increased stepwise over 30 minutes within a temperature range of 130 to 360°C to produce a flexible substrate laminate consisting of three polyimide layers on copper foil 1. The thicknesses of the polyimide layers on copper foil 1 were 1.5 μm / 5.0 μm / 1.5 μm, in the order B / C / B from the copper foil 1 side. To evaluate the properties of the polyimide layer in the laminate for flexible substrates, copper foil 1 was removed by etching to produce film M11, and the thickness thermal conductivity λz, tear propagation resistance (TPR), edge tear resistance, and processability were evaluated. In addition, when applied to a semiconductor module S with the configuration shown in Figure 5, the chip temperature was measured to evaluate the heat dissipation characteristics.

[0084] The above results are summarized in Table 2.

[0085] [Table 2]

[0086] Comparative Example 1 is an example of a conventional design concept for increasing λz, but increasing the filler content to increase λz makes the film brittle, resulting in problems during processing. Comparative Example 3 simulates an example of a processability problem that occurs when the film is thinned without a filler. Regarding processability problems, Comparative Example 1 exhibits film damage in the form of film cracks, whereas Comparative Example 3 exhibits film tearing, demonstrating different modes of failure. From this perspective, the tearing mode can be evaluated by tear propagation resistance, and the cracking mode by edge tear resistance. It is believed that maintaining both physical properties at a certain level is necessary to prevent processability problems. It can also be seen that edge tear resistance varies with film thickness and is not simply proportional to the thickness.

[0087] In Examples 1 to 8, the resin structure, thickness, filler content, volume average particle size of the filler, etc. were appropriately controlled, thereby suppressing processability problems and exhibiting better heat dissipation properties than Comparative Example 2, which used a thin film containing no filler.

[0088] Although the embodiments of the present invention have been described in detail above for the purpose of illustration, the present invention is not limited to the above-described embodiments and various modifications are possible. [Explanation of symbols]

[0089] 10...resin film, 10A...insulating resin layer, 11...insulating resin, 12...thermally conductive filler, 20...metal layer, 21...conductor circuit layer, 30...metal-clad laminate, 40...circuit board, 50...adhesive layer, 60...heat-conductive metal layer, 70...semiconductor element, 100...laminated structure

Claims

1. A resin film comprising a film-shaped insulating resin and a thermally conductive filler dispersed in the insulating resin, the thermally conductive filler is alumina particles, the insulating resin is a polyimide obtained by reacting an acid dianhydride component with a diamine component, the acid dianhydride component contains one or more selected from pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, and 3,3',4,4'-benzophenonetetracarboxylic dianhydride in 50 mol % or more of the total acid dianhydride components, and the diamine component contains one or more selected from 4,4'-diaminodiphenyl ether and 2,2-bis[4-(4-aminophenoxy)phenyl]propane in 50 mol % or more of the total diamine components; The thickness (L) of the entire resin film is in the range of 8 μm or more and less than 23 μm, a ratio (D / L) of a volume average particle diameter (D) of the thermally conductive filler to the film thickness (L) is in the range of 0.20 or more and 0.40 or less; A resin film characterized in that the thermal conductivity (λz) in the thickness direction is in the range of 0.3 W / m K or more and less than 2.0 W / m K, and the edge tear resistance measured at a width of 20 mm is in the range of 0.3 [N] or more and 30.0 [N] or less.

2. 2. The resin film according to claim 1, wherein the tear propagation resistance is in the range of 7.0 mN or more and 30.0 mN or less.

3. 3. The resin film according to claim 1, wherein the content of the thermally conductive filler relative to the entire resin film is in the range of 10 vol % to 50 vol %.

4. A metal-clad laminate comprising a single or multiple insulating resin layer and a metal layer laminated on one or both sides of the insulating resin layer, A metal-clad laminate, wherein at least one of the insulating resin layers is formed from the resin film according to claim 1 .

5. A circuit board comprising an insulating resin layer consisting of a single layer or multiple layers, and a conductor circuit layer laminated on one side or both sides of the insulating resin layer, A circuit board, wherein at least one of the insulating resin layers is formed from the resin film according to claim 1 .

6. A laminated structure for use in a semiconductor module, a conductor circuit layer electrically connected to an external semiconductor element; an insulating resin layer consisting of a single layer or multiple layers; an adhesive layer; a heat transfer metal layer that mediates heat conduction to an external heat dissipation member; have a structure in which the above are stacked in this order, A laminated structure, wherein at least one of the insulating resin layers is formed from the resin film according to claim 1 .

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