Thermosetting insulating film and multilayer insulating sheet

Abstract

The present invention provides: a thermosetting insulating film which is capable of achieving excellent insulating properties when used for the production of a multilayer substrate; and a multilayer insulating sheet which uses this thermosetting insulating film. Provided are: a thermosetting insulating film which contains at least a solid epoxy resin as an epoxy resin, wherein the area change rate R expressed by formula (1) is 222% or less; and a multilayer insulating sheet which uses this thermosetting insulating film. Formula (1): R = 100 × Sp / Si (In formula (1), Sp represents the area (cm2) of a square film after being subjected to vacuum pressure pressing under conditions of a pressing temperature of 175°C, a pressing pressure of 2.5 MPa, and a pressing time of 30 minutes, the square film having a thickness of 100 μm and a horizontal and vertical size of 160 mm × 160 mm, and Si represents the area (cm2) of the film before the vacuum heating pressing is performed.)

Description

Thermosetting insulating films and multilayer insulating sheets

[0001] The present invention relates to a thermosetting insulating film and a multilayer insulating sheet.

[0002] As various electronic devices such as mobile phones, smartphones, and tablet terminals become smaller and more functional, these devices employ multilayer substrates that constitute RF (Radio Frequency) modules, semiconductor IC embedded substrates, etc., and there is a demand for miniaturization of these multilayer substrates. Thermosetting insulating films are used in the manufacture of such multilayer substrates (see, for example, Patent Document 1).

[0003] International Publication No. 2022 / 190600

[0004] Here, the thermosetting insulating film is required to have the ability to embed the periphery of the various components and elements that make up the multilayer substrate with resin, and also to form an insulating layer that insulates the periphery of the various components and elements.

[0005] The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a thermosetting insulating film that can provide excellent insulating properties when used in the manufacture of multilayer substrates, and a multilayer insulating sheet using the same.

[0006] The above object is achieved by the present invention as described below. That is, the thermosetting insulating film of the present invention is a film containing at least a solid epoxy resin as an epoxy resin, and has an area change rate R expressed by the following formula (1) of 222% or less: Formula (1) R = 100 × Sp / Si (in the formula (1), Sp is the area (cm) after a square film having a thickness of 100 μm and dimensions of 160 mm × 160 mm is vacuum-pressed under the conditions of a pressing temperature of 175°C, a pressing pressure of 2.5 MPa, and a pressing time of 30 minutes). ２ ), and Si represents the area (cm ) of the film before the vacuum hot pressing. ２ )

[0007] In one embodiment of the thermosetting insulating film of the present invention, the rate of area change R is preferably 107% or more.

[0008] In another embodiment of the thermosetting insulating film of the present invention, it is preferable that the content of the solid epoxy resin contained in the epoxy resin is 50 mass % or more.

[0009] In another embodiment of the thermosetting insulating film of the present invention, it is preferable that the content of the solid epoxy resin contained in the epoxy resin is 90 mass % or less.

[0010] In another embodiment of the thermosetting insulating film of the present invention, the solid epoxy resin preferably includes a multifunctional solid epoxy resin.

[0011] In another embodiment of the thermosetting insulating film of the present invention, the solid epoxy resin preferably contains at least two or more solid epoxy resins with different equivalent weights.

[0012] Another embodiment of the thermosetting insulating film of the present invention preferably contains an inorganic filler.

[0013] In another embodiment of the thermosetting insulating film of the present invention, the content of the inorganic filler in the film is preferably 30% by mass to 90% by mass.

[0014] Another embodiment of the thermosetting insulating film of the present invention preferably includes a curing agent.

[0015] In another embodiment of the thermosetting insulating film of the present invention, the amount of the curing agent blended relative to 100 parts by mass of the epoxy resin is preferably 0.1 parts by mass to 6 parts by mass.

[0016] In another embodiment of the thermosetting insulating film of the present invention, a square film having a thickness of 100 μm and a length and width of 160 mm × 160 mm is preferably vacuum-pressed at a press temperature of 175°C, a press pressure of 2.5 MPa, and a press time of 30 minutes, after which the film has a thickness of 30 μm to 99 μm.

[0017] Another embodiment of the thermosetting insulating film of the present invention is preferably used in the manufacture of multilayer substrates.

[0018] Another embodiment of the thermosetting insulating film of the present invention is preferably used to encapsulate electronic elements.

[0019] The multilayer insulating sheet of the present invention comprises a first substrate film having at least one release-treated surface, the thermosetting insulating film of the present invention, and a second substrate film having at least one release-treated surface laminated in this order, with the release-treated surface of the first substrate film in close contact with one surface of the thermosetting insulating film and the release-treated surface of the second substrate film in close contact with the other surface of the thermosetting insulating film.

[0020] In one embodiment of the multilayer insulating sheet of the present invention, it is preferable that the peel strength between the thermosetting insulating film and at least one base film selected from the group consisting of the first base film and the second base film is 0.01 N / 250 mm to 2.5 N / 250 mm.

[0021] According to the present invention, it is possible to provide a thermosetting insulating film that can provide excellent insulating properties when used in the manufacture of a multilayer substrate, and a multilayer insulating sheet using the same.

[0022] 1A and 1B are cross-sectional views showing the state of a sample used in measuring the area change rate before and after vacuum pressure pressing. Here, FIG. 1A is a cross-sectional view showing the state before vacuum pressure pressing, and FIG. 1B is a cross-sectional view showing the state after vacuum pressure pressing. It is a plan view showing an example of a printed matter obtained by capturing with a scanner the planar shape of the surface on which the first copper foil is arranged after peeling the PET film from the laminate shown in FIG. 1B. It is a cross-sectional view showing the positional relationship of two PET films, an aluminum plate, and a thermosetting insulating film before and after vacuum pressure pressing for a sample used in a reference evaluation. Here, FIG. 3A is a cross-sectional view showing the state before vacuum pressure pressing, and FIG. 3B is a cross-sectional view showing the state after vacuum pressure pressing.

[0023] The thermosetting insulating film of this embodiment is a film containing at least a solid epoxy resin as an epoxy resin, and has an area change rate R of 222% or less as shown in the following formula (1): R = 100 × Sp / Si Formula (1) In formula (1), Sp is the area (cm) after a square film having a thickness of 100 μm and dimensions of 160 mm × 160 mm is vacuum-pressed under the conditions of a press temperature of 175°C, a press pressure of 2.5 MPa, and a press time of 30 minutes. ２ ), and Si represents the area of ​​the film (cm ) before vacuum hot pressing. ２ ) represents

[0024] When the thermosetting insulating film of this embodiment is used to manufacture a multilayer substrate, the thermosetting insulating film is fluidized by the temperature and pressure during vacuum pressure pressing (curing), expanding in the direction (XY direction) perpendicular to the pressing direction (Z direction). The fluidized thermosetting insulating film then embeds the periphery of the various components and elements constituting the multilayer substrate. By setting the area change rate R to 222% or less, a thickness (thickness in the Z direction) sufficient to insulate the components and elements from their surroundings can be easily ensured. This results in excellent insulation. If the thickness of the thermosetting insulating film actually used is set to 100 μm, for example, after vacuum pressure pressing during the manufacture of the multilayer substrate, the thickness of the thermosetting insulating film (insulating layer) can be set to 30 μm or more, making it easy to ensure a breakdown voltage of 4 kV or more. Note that, from the viewpoint of ensuring excellent insulation, the area change rate R is preferably 212% or less, and more preferably 200% or less. From a similar viewpoint, the thickness of the film used in measuring the area Sp, that is, the thickness of the film after vacuum-pressing a square film having a thickness of 100 μm and dimensions of 160 mm × 160 mm under conditions of a press temperature of 175°C, a press pressure of 2.5 MPa, and a press time of 30 minutes, is preferably 30 μm to 99 μm, and more preferably 35 μm to 99 μm.

[0025] On the other hand, the lower limit of the area change rate R is not particularly limited, but from the viewpoint of more reliably embedding the periphery of components and elements with the fluidized thermosetting insulating film during vacuum pressure pressing (curing) (from the viewpoint of embeddability), it is preferably 107% or more, and more preferably 110% or more.

[0026] The area change rate R is a parameter that has a strong correlation with the fluidity of the thermosetting insulating film when it is fluidized during vacuum pressure pressing, and as will be clear from the experimental data described below, its value can be controlled by the proportion of solid epoxy resin in the epoxy resin, the proportion of inorganic filler in the thermosetting insulating film, and the type of epoxy resin (e.g., equivalent weight, softening point, etc.) blended into the thermosetting insulating film.

[0027] Next, the various components constituting the thermosetting insulating film of this embodiment will be described in detail.

[0028] (A) Epoxy Resin The thermosetting insulating film of this embodiment may contain at least a solid epoxy resin as the epoxy resin, but it is preferable to use a liquid epoxy resin (A2) in combination with the solid epoxy resin (A1). In this specification, the term "solid epoxy resin" refers to a solid epoxy resin that does not have fluidity at room temperature (25°C), and the term "liquid epoxy resin" refers to an epoxy resin that does not fall under the category of solid epoxy resin, in other words, a liquid (or paste) epoxy resin that has fluidity at room temperature (25°C).

[0029] (A1) Solid Epoxy Resin Any known solid epoxy resin can be used as the solid epoxy resin without any particular limitation, but it is preferable to use a solid epoxy resin having an aromatic ring structure in the molecule (aromatic solid epoxy resin). Furthermore, as the aromatic solid epoxy resin, an aromatic solid epoxy resin having two or more epoxy groups in one molecule is more preferable.

[0030] Specific examples of solid epoxy resins include bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol S type epoxy resins, bisphenol AF type epoxy resins, phenol novolac type epoxy resins, tert-butyl-catechol type epoxy resins, naphthol type epoxy resins, naphthalene type epoxy resins, naphthylene ether type epoxy resins, glycidylamine type epoxy resins, glycidyl ester type epoxy resins, cresol novolac type epoxy resins, biphenyl type epoxy resins, dicyclopentadiene type epoxy resins, anthracene type epoxy resins, linear aliphatic epoxy resins, epoxy resins having a butadiene structure, alicyclic epoxy resins, heterocyclic epoxy resins, spiro ring-containing epoxy resins, cyclohexanedimethanol type epoxy resins, trimethylol type epoxy resins, and halogenated epoxy resins.

[0031] Among these various solid epoxy resins, from the viewpoint of improving the insulation reliability and heat resistance of a multilayer substrate produced using a thermosetting insulating film and improving the adhesion between layers in a multilayer substrate produced using a thermosetting insulating film, bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol AF type epoxy resins, naphthol type epoxy resins, naphthalene type epoxy resins, biphenyl type epoxy resins, dicyclopentadiene type epoxy resins, naphthylene ether type epoxy resins, glycidyl ester type epoxy resins, anthracene type epoxy resins, and epoxy resins having a butadiene structure are preferred.

[0032] Furthermore, from the viewpoint of easily obtaining a thermosetting insulating film that has both excellent insulating properties and embeddability, it is preferable to use a polyfunctional solid epoxy resin containing three or more epoxy groups per molecule as the solid epoxy resin. The reason why the above-mentioned effects are obtained by using a polyfunctional solid epoxy resin is unclear, but it is presumed that the polyfunctional solid epoxy resin has a high softening point, which results in a high melting point, and therefore the fluidity of the thermosetting insulating film does not become too high before the softening point is reached, thereby achieving the above-mentioned effects. Specific examples of polyfunctional solid epoxy resins include triphenylmethane-type epoxy resins, naphthol-cresol novolac-type epoxy resins, and tetrakisphenolethane-type epoxy resins.

[0033] Commercially available solid epoxy resins include DIC's EPICLON series 1050, 1055, 3050, 4050, and 7050 (bisphenol A solid epoxy resins), HP-4700 and HP-4710 (naphthalene-type tetrafunctional epoxy resins), N-680, N-670EXP-S, N-685EXP-S, and N-695 (cresol novolac epoxy resins), N-770 and N-775 (phenol novolac epoxy resins), HP-7200, HP-7200H, HP-7200HH, and HP-7200HHH (dicyclopentadiene epoxy resins), and EXA- 7311-G4, HP-6000, HP-6000L (naphthylene ether type epoxy resin), EXA-4750, EXA-4770 (naphthalene type epoxy resin); EPPN-502H (triphenylmethane type epoxy resin), NC-7000L (naphthol novolac type epoxy resin), NC-3000, NC-3000H, NC-3000L, NC-3100 manufactured by Nippon Kayaku Co., Ltd. (biphenylaralkyl type epoxy resin); Epotohto series ESN475V (naphthalene type epoxy resin) and ESN485 (naphthol novolac type epoxy resin) manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.; jER series YX4000, YX4000H, YX4000HS, YL6121HA (biphenyl type epoxy resin), YX8800 (anthracene type epoxy resin), 1003, 1003F, 1007, 1009, 1009F, 1010 (bisphenol A type solid epoxy resin), 4005P, 4007P, 4010P (bisphenol F type solid epoxy resin), 1031S (tetrakisphenolethane type epoxy resin), and YL7760 (bisphenol AF type epoxy resin) manufactured by Mitsubishi Chemical Corporation; OGSOL PG-100 and OGSOL CG-500 (fluorene type epoxy resin) and the like.

[0034] Two or more solid epoxy resins may be used in combination, and it is preferred to use two or more solid epoxy resins in combination. When two or more solid epoxy resins are used in combination, it is preferred that the equivalent weights of the respective solid epoxy resins are different.

[0035] The equivalent weight of the solid epoxy resin used is not particularly limited, but is preferably 50 to 10,000, more preferably 70 to 7,000, and even more preferably 80 to 5,000. By setting the equivalent weight within the above numerical range, the flowability is good, the crosslink density of the cured product of the thermosetting insulating film is sufficient, and the insulating properties are also improved. When a polyfunctional solid epoxy resin is used as the solid epoxy resin, the equivalent weight of the polyfunctional solid epoxy resin is preferably 100 to 500, more preferably 100 to 350, and even more preferably 100 to 200.

[0036] The softening point of the solid epoxy resin used is not particularly limited, but is preferably 30 to 200° C., more preferably 40 to 170° C., and even more preferably 45 to 150° C. By setting the softening point within the above numerical range, the flowability is good, the crosslink density of the cured product of the thermosetting insulating film is sufficient, and the insulating properties are also improved.

[0037] (A2) Liquid Epoxy Resin In order to obtain a thermosetting insulating film of this embodiment that is excellent in both insulating properties and embeddability, it is preferable to use a liquid epoxy resin in combination with a solid epoxy resin as the epoxy resin.

[0038] Specific examples of liquid epoxy resins include bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol AF type epoxy resins, naphthalene type epoxy resins, glycidyl ester type epoxy resins, glycidyl amine type epoxy resins, phenol novolac type epoxy resins, alicyclic epoxy resins having an ester skeleton, cyclohexane type epoxy resins, cyclohexanedimethanol type epoxy resins, glycidyl amine type epoxy resins, and epoxy resins having a butadiene structure. Commercially available liquid epoxy resins include EPICLON series 840, 840-S, 850, 850-S (bisphenol A liquid epoxy resins), 830, 830-S, 835 (bisphenol F liquid epoxy resins), HP-4032D, HP-4032SS (naphthalene type epoxy resins) manufactured by DIC Corporation; ZX-1059 (a mixture of bisphenol A liquid epoxy resin and bisphenol F liquid epoxy resin) manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.; Denacol EX-721 (glycidyl ester type epoxy resin) manufactured by Nagase ChemteX Corporation; Examples of suitable epoxy resins include CELLOXIDE 2021P (alicyclic epoxy resin having an ester skeleton), EPOLEAD PB-3600 (epoxy resin having a butadiene structure); ZX-1658 and ZX-1658GS (liquid 1,4-glycidylcyclohexane type epoxy resins) manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.; and jER series 828, 828EL, 828US, and 828XA (bisphenol A type liquid epoxy resins), 806, 807 (bisphenol F type liquid epoxy resins), 152 (phenol novolac type epoxy resin), and 630 (glycidylamine type epoxy resin) manufactured by Mitsubishi Chemical Corporation.

[0039] The content of solid epoxy resin in the epoxy resin (or the content of liquid epoxy resin) significantly affects the fluidity of the thermosetting insulating film when it is vacuum-heat-pressed (cured) during the manufacture of a multilayer substrate. Therefore, in the thermosetting insulating film of this embodiment, the content of solid epoxy resin (A1) in the epoxy resin (A) also significantly affects the area change rate R, which is strongly correlated with the fluidity during vacuum-heat-pressing (curing). Taking these points into consideration, in order to easily control the area change rate R to 222% or less to ensure excellent insulating properties, the content of solid epoxy resin in the epoxy resin is preferably 50% by mass or more, more preferably 55% by mass or more, even more preferably 60% by mass or more, and particularly preferably 65% ​​by mass or more. From the viewpoint of insulating properties, the higher the content of solid epoxy resin in the epoxy resin, the better; however, if the content is too high, the production of the thermosetting insulating film itself may become difficult. Therefore, from the viewpoint of ease of production of the thermosetting insulating film, the content of the solid epoxy resin in the epoxy resin is preferably 90 mass % or less, and more preferably 85 mass % or less.

[0040] (B) Inorganic Filler The thermosetting insulating film of the present embodiment may contain an inorganic filler. Any known inorganic filler can be used without any particular limitation as the inorganic filler, and examples thereof include silica, alumina, glass, cordierite, silicon oxide, barium sulfate, talc, clay, mica powder, aluminum hydroxide, magnesium hydroxide, calcium carbonate, magnesium carbonate, magnesium oxide, boron nitride, aluminum nitride, manganese nitride, aluminum borate, barium titanate, strontium titanate, calcium titanate, magnesium titanate, bismuth titanate, titanium oxide, barium zirconate, calcium zirconate, zirconium phosphate, and zirconium tungstate phosphate.

[0041] Among these inorganic fillers, silica is preferred from the viewpoint of adjusting the linear expansion coefficient of the multilayer substrate manufactured using the thermosetting insulating film, while alumina and boron nitride are preferred from the viewpoint of improving thermal conductivity. Preferred silicas include amorphous silica, pulverized silica, fused silica, crystalline silica, synthetic silica, and hollow silica, with fused silica being more preferred. Furthermore, spherical silica is preferred. These may be used alone or in combination of two or more. The shape of the inorganic filler is not particularly limited, and examples include spherical, approximately spherical, and fibrous shapes, although spherical or approximately spherical shapes are typically preferred. The linear expansion coefficient of the cured product of the thermosetting insulating film containing the inorganic filler within the range of 25°C to 150°C is not particularly limited and can be selected appropriately depending on the linear expansion coefficient of the base substrate used to manufacture the multilayer substrate. Generally, however, a value of 5 to 60 ppm is preferred.

[0042] The upper limit of the average particle size of the inorganic filler is not particularly limited, but is preferably 10 μm or less, more preferably 5 μm or less, and even more preferably 3 μm or less, from the viewpoint of preventing the inorganic filler from settling during the process of forming a film by applying and drying a raw material solution (varnish) used in producing a thermosetting insulating film. On the other hand, the lower limit of the average particle size of the inorganic filler is preferably 0.01 μm or more, more preferably 0.03 μm or more, even more preferably 0.05 μm or more, particularly preferably 0.07 μm or more, and most preferably 0.1 μm or more, from the viewpoint of preventing an increase in the viscosity of the varnish and a decrease in handleability when the varnish is prepared.

[0043] From the viewpoint of achieving a good balance between insulating properties and embeddability by ensuring appropriate fluidity when the thermosetting insulating film is vacuum hot-pressed in the manufacture of a multilayer substrate, the content of the inorganic filler in the thermosetting insulating film is preferably 30% by mass to 90% by mass, more preferably 33% by mass to 85% by mass, and even more preferably 40% by mass to 75% by mass.

[0044] (C) Curing Agent The thermosetting insulating film of this embodiment may further contain a (C) curing agent for purposes such as adjusting the curing time and curing temperature. Examples of curing agents include known epoxy resin curing agents such as imidazole-based curing agents, amine-based curing agents, and phosphorus-based curing agents. From the viewpoints of storage stability and reactivity, it is preferable to use at least dicyandiamide. A single curing agent may be used, or two or more may be used in combination. The amount of curing agent is not particularly limited, but is preferably 0.1 to 6 parts by mass, and more preferably 1 to 5 parts by mass, per 100 parts by mass of epoxy resin. Note that the term "curing agent" in this specification includes not only curing agents in the narrow sense, but also compounds known as curing catalysts and curing accelerators.

[0045] (D) Other Components The thermosetting insulating film of this embodiment can also contain other components in addition to components (A) to (C) as needed. Examples of such components include coupling agents, ion trapping agents, leveling agents, antioxidants, antifoaming agents, flame retardants, colorants, and reactive diluents. The amount of the other components can be selected appropriately depending on the type and intended use. Generally, the amount of the other components in the thermosetting insulating film is preferably greater than 0% by mass and less than or equal to 10% by mass, and more preferably greater than 0% by mass and less than or equal to 5% by mass.

[0046] The thermosetting insulating film of this embodiment is used in the manufacture of a multilayer substrate. In manufacturing the multilayer substrate, the thermosetting insulating film of this embodiment is laminated onto a base substrate, such as a resin substrate or an inorganic material substrate made of ceramic, silicon, or the like, so as to embed the various components and elements that constitute the multilayer substrate, and then cured using a vacuum pressure press. The multilayer substrate is then completed by repeating the laminating and curing processes. Alternatively, instead of laminating, the thermosetting insulating film of this embodiment may simply be placed on the various components and elements that constitute the multilayer substrate. After curing, the thermosetting insulating film of this embodiment is embedded in the multilayer substrate so as to cover the various components and elements that constitute the multilayer substrate, thereby functioning as an insulating member that insulates these components and elements from each other and also as a protective member that protects the components and elements from the external environment (such as moisture and mechanical shock).

[0047] Furthermore, the thermosetting insulating film of this embodiment may be used for purposes other than the manufacture of multilayer substrates, if necessary. Such purposes are not particularly limited, but include, for example, use in sealing various electronic elements such as semiconductor elements.

[0048] The thickness of the thermosetting insulating film of this embodiment is not particularly limited as long as it is within a range suitable for manufacturing a multilayer substrate, but is preferably 30 μm to 200 μm, more preferably 50 μm to 150 μm. When used for sealing purposes, the thermosetting insulating film of this embodiment is preferably used in a laminated state, and the total thickness is preferably 80 μm to 1200 μm, more preferably 100 μm to 1000 μm.

[0049] To manufacture the thermosetting insulating film of this embodiment, a coating liquid (varnish) is used, in which the components constituting the thermosetting insulating film are dissolved in a solvent. The solvent can be selected appropriately depending on the solubility of each component constituting the thermosetting insulating film (excluding insoluble components such as inorganic fillers, which are added as needed). Examples of the solvent include methylcyclohexane, cyclohexanone, and methyl ethyl ketone (MEK). Two or more solvents can be used in combination as needed. The content of the solvent in the coating liquid is not particularly limited as long as it can be selected appropriately to adjust the viscosity of the coating liquid to a level suitable for application processing. However, it is generally preferred that the content be 10% to 90% by weight, and more preferably 20% to 80% by weight.

[0050] The coating liquid is then applied to one side of a substrate film (such as a polyethylene terephthalate (PET) film with both sides treated for release), forming a coating layer, and this coating layer is dried to form a thermosetting insulating film. Known coating methods, such as the knife method, gravure method, and die method, can be used as the coating method. The drying conditions for the coating layer can be appropriately selected depending on the drying device used, the boiling point and content of the solvent contained in the coating liquid, the thickness of the coating layer, and other factors. For example, when the coating layer is dried using a drying oven, the drying temperature can be 80°C to 120°C, and the drying time can be 5 to 20 minutes.

[0051] From the viewpoint of practicality such as ease of handling, the thermosetting insulating film of this embodiment is preferably used in the form of a multilayer insulating sheet including the thermosetting insulating film of this embodiment and one or more substrate film layers. Typically, it is more preferably used in the form of a three-layer multilayer insulating sheet in which a first substrate film, the thermosetting insulating film of this embodiment, and a second substrate film are laminated in this order. A three-layer multilayer insulating sheet can be produced, for example, by applying a coating liquid to the first substrate film (or the second substrate film) and then drying the applied coating to form a thermosetting insulating film on the first substrate film (or the second substrate film), and then laminating a second substrate film (or the first substrate film) to the side of the thermosetting insulating film opposite to the side on which the first substrate film (or the second substrate film) is provided. When using the multilayer insulating sheet, the substrate film is peeled off from the multilayer insulating sheet at an appropriate timing.

[0052] The materials constituting the first base film and the second base film are not particularly limited, and examples thereof include resin materials such as polyolefin resins such as polypropylene (PP) resin and polymethylpentene resin, polyester resins such as polyethylene terephthalate (PET) resin and polyethylene naphthalate resin, polyimide resin, polyetherimide resin, etc. Furthermore, from the viewpoints of cost, strength, workability, etc., the thickness of the first base film and the second base film is preferably 15 μm to 100 μm, and more preferably 20 μm to 50 μm. One or both sides of the first base film and the second base film may be subjected to a release treatment with a release agent, and examples of the release agent used for the release treatment include silicone-based release agents, long-chain alkyl-based release agents, and fluorine-based release agents.

[0053] It is preferable that at least one surface of each of the first and second substrate films constituting the three-layer multilayer insulating sheet be release-treated. In this case, it is preferable that the release-treated surface of the first substrate film be in close contact with one surface of the thermosetting insulating film, and that the release-treated surface of the second substrate film be in close contact with the other surface of the thermosetting insulating film. Here, the peel strength between the thermosetting insulating film and at least one of the substrate films is preferably 0.01 N / 250 mm to 2.5 N / 250 mm, more preferably 0.05 N / 250 mm to 2.0 N / 250 mm.

[0054] The peel strength can be measured using an autograph (Shimadzu Science Autograph AGS-X (load cell: 5N)) using a measurement sample cut to a width of 250 mm and a length of 250 mm from a two-layer sheet for evaluation consisting of a substrate film (first substrate film or second substrate film) and a thermosetting insulating film that constitute the interface to be measured for peel strength. The measurement sample is fixed to a flat-surfaced sample stage with the substrate film facing up, and one end of the longitudinal direction of the sample is set to 0°. Starting from one end of the sample as the peel initiation point, the substrate film is peeled in a 180° direction (toward the other end) (i.e., at a peel angle of 180°) at a peel speed of 500 mm / min. The peel strength at this time (average of 5 samples) is then measured.

[0055] Specific examples of the present invention will be described below with reference to examples, but the present invention is not limited to the examples described below.

[0056] 1. Preparation of Varnish for Producing Thermosetting Insulating Film A varnish with a viscosity suitable for coating processing was prepared by dissolving the components (A) to (D) listed below (constituent components of the film) in an appropriate amount of methyl ethyl ketone to obtain the raw materials for the varnish for producing thermosetting insulating film shown in Table 1. Table 1 shows the composition of the film constituent components for each example and comparative example.

[0057] (A) Epoxy resin

[0058] (A1) Solid Epoxy Resins Bisphenol F type epoxy resin (manufactured by Mitsubishi Chemical Corporation, jER4005P, softening point: 87°C, equivalent weight: 950 to 1200 g / eq) Bisphenol F type epoxy resin (manufactured by Mitsubishi Chemical Corporation, jER4010P, softening point: 135°C, equivalent weight: 3800 to 4600 g / eq) Triphenylmethane type multifunctional epoxy resin (manufactured by Nippon Kayaku Co., Ltd., EPPN502H, softening point: 60 to 72°C, equivalent weight: 158 to 178 g / eq)

[0059] (A1) Liquid epoxy resins: Glycidylamine type epoxy resin (manufactured by Mitsubishi Chemical Corporation, jER630, equivalent weight: 90 to 106 g / eq); Bisphenol A type epoxy resin (manufactured by Mitsubishi Chemical Corporation, jER828, equivalent weight: 184 to 194 g / eq); Bisphenol F type epoxy resin (manufactured by DIC Corporation, Epiclon 830, equivalent weight: 165 to 177 g / eq).

[0060] (B) Inorganic filler Silica filler (manufactured by Admatechs Co., Ltd., SOC4, average particle size 0.8 to 1.2 μm) Silica filler (manufactured by Denka Company, Ltd., FB-300MDX, average particle size 3.5 to 4.0 μm) Alumina filler (manufactured by Sumitomo Chemical Co., Ltd., AA1.5, average particle size 1.7 μm) Alumina filler (manufactured by Nippon Steel Chemical & Material Co., Ltd., AX3-10, average particle size 3.0 μm) Alumina filler (manufactured by Denka Company, Ltd., ASFP20, average particle size 0.2 to 0.3 μm)

[0061] (C) Curing agent: Dicyandiamide (DICY7, manufactured by Mitsubishi Chemical Corporation); 1-benzyl-2-phenylimidazole (1B2PZ, manufactured by Shikoku Chemical Industry Co., Ltd.); 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU99, manufactured by Hodogaya Chemical Co., Ltd.)

[0062] (D) Other components: Phosphinic acid metal salt flame retardant (Clariant, OP935)

[0063] 2. Evaluation Method (1) Measurement of Area Change Rate R The vacuum pressure press conditions (press temperature: 175°C, press pressure: 2.5 MPa, press time: 30 minutes) used to measure the area change rate R were conditions that simulated the vacuum pressure press conditions used to manufacture multilayer substrates. For reference, the vacuum pressure press conditions used in this measurement are identical or similar to those used to encapsulate electronic elements such as semiconductor devices. Furthermore, the height of the objects (various components and elements that make up the multilayer substrate) embedded in the thermosetting insulating film during multilayer substrate manufacturing is approximately several tens of micrometers, and this height is expected to become even smaller in response to future demands for miniaturization of multilayer substrates. Therefore, taking this into consideration, the height (thickness) of the embedded object (first copper foil) used to measure the area change rate R was set to 18 micrometers.

[0064] The area change rate R was measured as follows. First, a varnish for preparing a thermosetting insulating film was applied to one side of a PET film using a doctor blade to form a coating film, and then this coating film was dried to form a thermosetting insulating film (thickness: 100 μm) on the PET film. Next, the thermosetting insulating film was peeled off from the PET film and cut into a square shape to prepare a thermosetting insulating film measuring 160 mm x 160 mm.

[0065] Next, a second copper foil (thickness: 18 μm) having the same length and width as the second stainless steel plate was placed on the second stainless steel plate. Subsequently, the above-mentioned thermosetting insulating film (length and width: 160 mm × 160 mm) was placed in the center of the second copper foil surface, and a first copper foil (thickness: 18 μm) having the same length and width as the thermosetting insulating film was placed on top of it. Then, a PET film and a first stainless steel plate having the same size as the second stainless steel plate were placed on the first copper foil in this order. This resulted in a laminate in which the second stainless steel plate, the second copper foil, the thermosetting insulating film, the first copper foil, the PET film, and the first stainless steel plate were stacked in this order from bottom to top in the vertical direction. In this laminate, the second stainless steel plate, the second copper foil, the PET film, and the first stainless steel plate have the same length and width, and are laminated so that the positions of the outer peripheral edges of each component coincide.The thermosetting insulating film and the first copper foil also have the same length and width, and are laminated so that the positions of the outer peripheral edges of each component coincide.

[0066] The laminate was placed in a press and subjected to vacuum pressure pressing (pressing temperature: 175°C, pressing pressure: 2.5 MPa, pressing time: 30 minutes). The two stainless steel plates were then removed from the laminate after vacuum pressure pressing to obtain a laminate in which, from top to bottom in the vertical direction, the PET film, the first copper foil, the thermosetting insulating film (cured film) that had been cured while being pressed around the first copper foil, and the second copper foil were laminated in this order.

[0067] Figure 1 shows cross-sectional views of the relative positions of the PET film, first copper foil, second copper foil, and thermosetting insulating film before and after vacuum pressure pressing. In the state before vacuum pressure pressing shown in Figure 1(A), the second copper foil 22, the uncured thermosetting insulating film 10A, the first copper foil 20, and the PET film 30 are arranged in this order from bottom to top. In this state, the outer periphery of the first copper foil 20 coincides with the outer periphery of the thermosetting insulating film 10A. In the state after vacuum heat pressing shown in Figure 1(B), the cured thermosetting insulating film 10B is thinner than the uncured thermosetting insulating film 10A, and its outer periphery has shifted outward relative to the outer periphery of the first copper foil 20.

[0068] Next, the PET film 30 was peeled from the laminate 100 shown in FIG. 1B , and the planar shape of the surface on which the first copper foil 20 was disposed was scanned and imaged. FIG. 2 is a plan view showing an example of a printed matter obtained by scanning the planar shape of the surface on which the first copper foil 20 was disposed after the PET film 30 was peeled from the laminate 100 shown in FIG. 1B . The printed matter shown in FIG. 2 includes an image of the square-shaped first copper foil 20 and the cured thermosetting insulating film 10B positioned so as to surround the first copper foil 20. The image shown in FIG. 2 was cut along the outer contour line L of the planar shape of the cured thermosetting insulating film 10B, and the weight Wp of the cut portion was measured using an electronic balance. The weight Wi of the uncured thermosetting insulating film 10A (160 mm x 160 mm) was also measured using the same procedure. In order to measure the weights Wp and Wi, the same type of paper was used for printing, and the printing conditions using the copier were also the same.

[0069] Then, from the conversion relationship between the area Si (16 cm × 16 cm = 256 cm) of the thermosetting insulating film 10A before curing and the weight Wi, the area Sp corresponding to the weight Wp was calculated, and the area change rate R was further calculated based on equation (1).

[0070] (2) Thickness of Thermosetting Insulating Film After Vacuum Hot Pressing The thickness of the thermosetting insulating film after vacuum hot pressing was determined by the following procedure. First, the total thickness of the sample after peeling off the PET film 30 from the laminate 100 shown in FIG. 1B used to measure the area change rate R (i.e., the sum of the thickness of the first copper foil 20, the thickness of the cured thermosetting insulating film 10B located directly below the first copper foil 20, and the thickness of the second copper foil 22 (thickness Tt shown in FIG. 1B)) was measured using a contact film thickness meter (Millitron 1240, manufactured by Mahl Japan). Next, the thickness of the cured thermosetting insulating film 10B (thickness Tf shown in FIG. 1B) was determined by subtracting the thickness of the first copper foil 20 (18 μm) and the thickness of the second copper foil 22 (18 μm) from the measured total thickness Tt.

[0071] (3) Coefficient of Linear Expansion (CTE) A varnish for preparing a thermosetting insulating film was applied to one side of a PET film using a doctor blade to form a coating, and then the coating was dried to form a thermosetting insulating film (thickness: 100 μm) on the PET film, thereby obtaining an evaluation sheet. Next, the evaluation sheet was heated at 175 ° C for 30 minutes to cure the thermosetting insulating film, and the PET film was peeled off to obtain a film-like cured product. Next, this film-like cured product was cut to obtain a test piece with a width of 5 mm and a length of 15 mm. Next, this test piece was placed in a thermomechanical analyzer ("Thermo Plus TMA8310" manufactured by Rigaku Corporation), and the linear expansion coefficient was measured by the tensile load method. The measurement was performed twice consecutively under the conditions of a load of 1 g and a heating rate of 5 ° C / min. Then, the average linear expansion coefficient (ppm) from 25° C. to 150° C. in the second measurement was calculated as the linear expansion coefficient.

[0072] (4) DSC Peak Temperature A sample of the varnish for producing a thermosetting insulating film that had been dried and solidified was heated from 25°C to 250°C at a heating rate of 10°C / min using a DSC (differential scanning calorimeter), and the maximum value of the endothermic and exothermic peak in the obtained DSC chart was taken as the DSC peak temperature.

[0073] (5) Evaluation of Embeddability and Insulation Properties Assuming the Production of a Multilayer Substrate (5-1) Evaluation of Embeddability After peeling off the PET film 30 from the laminate 100 shown in Figure 1 (B) used to measure the area change rate R, the interface between the outer edge of the first copper foil 20 (thickness: 18 μm) and the cured thermosetting insulating film 10B was observed with a digital microscope (magnification: 35x) around the entire outer periphery of the first copper foil 20, and the presence or absence and number of gaps with a width (length in the direction along the outer periphery of the first copper foil 20) of 200 μm or more were observed. The first copper foil 20 is a component assumed to be embedded during the production of a multilayer substrate.

[0074] (5-2) Insulation Evaluation After peeling off the PET film 30 from the laminate 100 shown in FIG. 1B used to measure the area change rate R, a test specimen was prepared by cutting the area where the first copper foil 20 (thickness: 18 μm) was provided into a 40 mm square. The breakdown voltage of this test specimen was then measured using a breakdown tester (DAC-6041 manufactured by Soken Denki Co., Ltd.). When measuring the breakdown voltage, the test specimen was placed in a container filled with silicone oil, sandwiched between spherical electrodes with a diameter of 20 mm. Next, a voltage was applied to the test specimen at a voltage rise rate of 200 V / sec, and the voltage at which the insulation broke down was measured as the breakdown voltage. The first copper foil 20 is a component intended to be embedded in the manufacturing of a multilayer board.

[0075] (6) Evaluation of Embeddability and Insulation Properties for Sealing Applications (Reference Evaluation) (6-1) Evaluation of Embeddability The evaluation of embeddability was performed using the following procedure. First, a varnish for preparing a thermosetting insulating film was applied to one side of a PET film using a doctor blade to form a coating film, and then this coating film was dried to form a thermosetting insulating film (thickness: 100 μm) on the PET film. Next, a total of 10 thermosetting insulating films with a thickness of 100 μm were prepared using the same procedure as above, and these were laminated in 10 layers to obtain a thermosetting insulating film with a thickness of 1 mm. The thermosetting insulating film was then peeled from the PET film and cut into a square shape to prepare a thermosetting insulating film measuring 100 mm x 100 mm.

[0076] Next, a PET film with the same length and width dimensions as the second stainless steel plate was placed on the second stainless steel plate. Next, an aluminum plate (thickness: 1 mm, length and width: 100 mm x 100 mm) was placed in the center of the PET film surface, and the above-mentioned thermosetting insulating film (thickness: 1 mm, length and width: 100 mm x 100 mm) was placed on top of that. A stainless steel spacer (thickness: 1.1 mm) was also placed along the outer periphery of the PET film surface. Next, a second PET film with the same length and width dimensions as the second stainless steel plate and the first stainless steel plate were placed on the thermosetting insulating film, in that order.

[0077] As a result, from bottom to top in the vertical direction, (i) in the central portion, the second stainless steel plate, the PET film, the aluminum plate, the thermosetting insulating film, the PET film, and the first stainless steel plate were stacked in this order, and (ii) in the portion along the outer periphery, the second stainless steel plate, the PET film, and the spacer were stacked in this order, and further, on the upper side away from the spacer, the PET film and the first stainless steel plate were stacked in this order, to obtain a laminate. In this laminate, (i) the second stainless steel plate, the two PET films, and the first stainless steel plate have the same length and width dimensions and are stacked so that the positions of the outer peripheral edges of each component coincide; (ii) the thermosetting insulating film and the aluminum plate also have the same length and width dimensions and are stacked so that the positions of the outer peripheral edges of each component coincide; and (iii) the spacer has a portion of its outer peripheral edge coinciding with the outer peripheral edges of the second stainless steel plate, the two PET films, and the first stainless steel plate, and is arranged in a ring shape without any gaps so as to surround the thermosetting insulating film and aluminum plate located in the central portion.

[0078] The laminate was placed in a press and subjected to vacuum pressure pressing (pressing temperature: 175°C, pressing pressure: 2.5 MPa, pressing time: 30 minutes). The two stainless steel plates were then removed from the laminate after vacuum pressure pressing to obtain a laminate consisting of a PET film, an aluminum plate, a thermosetting insulating film (cured film) that had been cured while being pressed around the aluminum plate, and a PET film, stacked in this order. In this laminate, the cured film was present, having deformed during vacuum pressure pressing so as to fill the space surrounded by the two PET films and the spacer.

[0079] Figure 3 shows cross-sectional views of the positional relationship between two PET films, an aluminum plate, a spacer, and a thermosetting insulating film before and after vacuum pressure pressing. In the state before vacuum pressure pressing shown in Figure 3(A), the PET film 50 (on the second stainless steel plate side), the aluminum plate 40, the uncured thermosetting insulating film 10A, and the PET film 52 (on the first stainless steel plate side) are arranged in this order from bottom to top. A spacer 60 is also arranged on the outer peripheral surface of the PET film 50 (on the second stainless steel plate side). In this state, the outer peripheral edge of the aluminum plate 40 and the outer peripheral edge of the thermosetting insulating film 10A are aligned.

[0080] On the other hand, in the state after vacuum hot pressing shown in Figure 3 (B), the cured thermosetting insulating film 10B is spread out horizontally so as to fill the space surrounded by the spacer 60, the two PET films 50 and 52, and the aluminum plate 40, and its thickness is the same as the height of the spacer 60.

[0081] Next, the two PET films 50, 52 were peeled off from the laminate 200 shown in Figure 3(B), and the interface between the outer periphery of the aluminum plate 40 and the cured thermosetting insulating film 10B was observed from the side where the surface of the aluminum plate 40 was exposed using a digital microscope (magnification: 35x) to check for and determine the number of gaps with a width (length in the direction along the outer periphery of the aluminum plate 40) of 200 µm or more. The aluminum plate 40 is a component intended to be embedded into the object (electronic element such as a semiconductor element) during encapsulation.

[0082] (6-2) Insulation Evaluation After peeling off the PET films 50 and 52 from the laminate 200 shown in FIG. 1B, a test specimen was prepared by cutting the area where the aluminum plate 40 (thickness: 1 mm) was provided into a 40 mm square. The breakdown voltage of this test specimen was then measured using a breakdown tester (DAC-6041 manufactured by Soken Denki Co., Ltd.). When measuring the breakdown voltage, the test specimen was placed in a container filled with silicone oil, sandwiched between spherical electrodes with a diameter of 20 mm. Next, a voltage was applied to the test specimen at a voltage rise rate of 200 V / sec, and the voltage at which the insulation broke down was measured as the breakdown voltage. The aluminum plate 40 is a component intended for use as an embedded object (electronic element such as a semiconductor element) during encapsulation.

[0083] 3. Evaluation Results Table 1 shows the composition of the thermosetting insulating films of each example and comparative example and the results of various evaluations.

[0084]

[0085]

[0086]

[0087]

[0088]

[0089] 10A: Thermosetting insulating film before curing 10B: Thermosetting insulating film after curing 20: First copper foil 22: Second copper foil 30: PET film 40: Aluminum plate 50, 52: PET film 60: Spacer 100, 200: Laminate L: Outer contour line

Claims

1. A film comprising at least a solid epoxy resin as the epoxy resin, A thermosetting insulating film having an area change rate R of 222% or less, as shown in formula (1) below. ・Formula (1) R=100×Sp / Si [In formula (1) above, Sp is the area (cm²) after vacuum pressing a square film with a thickness of 100 μm and dimensions of 160 mm x 160 mm under the conditions of press temperature: 175°C, press pressure: 2.5 MPa, and press time: 30 minutes.] ２ ) represents the area of ​​the film (cm²) before the vacuum heating press is performed, where Si is the area of ​​the film before the vacuum heating press is performed. ２ ) represents.

2. The thermosetting insulating film according to claim 1, wherein the area change rate R is 107% or more.

3. The thermosetting insulating film according to claim 1 or 2, wherein the content ratio of the solid epoxy resin contained in the epoxy resin is 50% by mass or more.

4. The thermosetting insulating film according to claim 3, wherein the content ratio of the solid epoxy resin contained in the epoxy resin is 90% by mass or less.

5. The thermosetting insulating film according to claim 1 or 2, wherein the solid epoxy resin comprises a polyfunctional solid epoxy resin.

6. The thermosetting insulating film according to claim 1 or 2, wherein the solid epoxy resin comprises at least two solid epoxy resins in equivalent amounts.

7. A thermosetting insulating film according to claim 1 or 2, comprising an inorganic filler.

8. The thermosetting insulating film according to claim 7, wherein the content ratio of the inorganic filler contained in the film is 30% by mass to 90% by mass.

9. A thermosetting insulating film according to claim 1 or 2, comprising a curing agent.

10. The thermosetting insulating film according to claim 9, wherein the amount of the curing agent blended with 100 parts by mass of the epoxy resin is 0.1 parts by mass to 6 parts by mass.

11. A thermosetting insulating film according to claim 1 or 2, wherein a square film with a thickness of 100 μm and dimensions of 160 mm x 160 mm is vacuum-pressed under the conditions of a press temperature of 175°C, a press pressure of 2.5 MPa, and a press time of 30 minutes, and the film thickness of the film after this process is 30 μm to 99 μm.

12. A thermosetting insulating film according to claim 1 or 2, used in the manufacture of a multilayer substrate.

13. A thermosetting insulating film according to claim 1 or 2, used for sealing electronic components.

14. A first substrate film having at least one side treated for release, A thermosetting insulating film according to claim 1 or 2, A second base film, with at least one side treated for mold release, is laminated in this order. The release-treated surface of the first base film is in close contact with one surface of the thermosetting insulating film. The release-treated surface of the second base film is in close contact with the other surface of the thermosetting insulating film. Multilayer insulating sheet.

15. The multilayer insulating sheet according to claim 14, wherein the peel strength of the thermosetting insulating film and at least one base film selected from the group consisting of the first base film and the second base film is 0.01 N / 250 mm to 2.5 N / 250 mm.