Photosensitive laminated resin structures, dry films, cured products and electronic components

Abstract

To provide a photosensitive laminated resin structure that causes few scratch marks and has high heat-dissipating properties but yet offers high resolution, and the like.SOLUTION: The photosensitive laminated resin structure includes a heat radiation layer (A) and a protective layer (B). The heat radiation layer (A) contains a heat-radiating filler with a thermal conductivity of higher than 10 W / m K, with the content of the heat-radiating filler being 50 mass% or more in all the components excluding an organic solvent. In the protective layer (B), the content of the heat-radiating filler is 0-20 mass% of the content of the heat-radiating filler in the heat radiation layer (A).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a photosensitive laminated resin structure having excellent heat dissipation properties and useful for package substrates, resin insulating layers of surface-mounted light-emitting diodes, etc.; a dry film having the photosensitive laminated resin structure; and electronic components such as a printed wiring board having a protective film made of a cured product of the photosensitive laminated resin structure. [Background technology]

[0002] In recent years, with the miniaturization and high performance of electronic devices, there has been a demand for more sophisticated semiconductor elements and higher-density packaging of electronic components. Meanwhile, heat generation has become a major issue in package components that integrate these semiconductor elements and electronic components, and circuit boards on which semiconductor elements and electronic components are mounted are therefore required to have excellent heat dissipation properties. For example, Patent Document 1 discloses a metal base substrate that uses a metal plate such as copper or aluminum, and forms a circuit pattern on one or both sides of the metal plate via an electrically insulating layer such as a prepreg or a thermosetting resin composition. However, in such metal base substrates, the electrical insulating layer has poor thermal conductivity, so good heat dissipation cannot be achieved unless the insulating layer is thin. On the other hand, if the insulating layer is thinned, problems such as insufficient dielectric strength in the thickness direction can arise.

[0003] On the other hand, surface mounting methods such as BGA (ball grid array) and CSP (chip scale package) are widely used as mounting methods for electronic components and semiconductor elements. The solder resist compositions used in such mounting methods (see, for example, Patent Document 2) are required to have functions and properties such as fine pattern formation (photolithography), electrical insulation, and chemical resistance. Silica and precipitated barium sulfate are used as inorganic filler components contained in such compositions, but these inorganic filler components have the property of low thermal conductivity.

[0004] Therefore, recently, in order to improve the heat dissipation properties of the solder resist, the introduction of inorganic fillers such as alumina, which have high thermal conductivity, has been considered (Patent Document 3). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 6-224561 A (Claims) [Patent Document 2] JP 11-288091 A (Claims) [Patent Document 3] JP 2007-254688 A (Claims) Summary of the Invention [Problem to be solved by the invention]

[0006] However, when a high-hardness inorganic filler such as alumina is used in a protective film such as a solder resist formed on the surface of a circuit board, problems arise such as scratches or scraped metal powder adhering to the surface of the protective film (so-called scratch marks) when the boards are stored and transported in a stacked manner during the board manufacturing process, or when the boards are stored in a metal rack or the like and processed, due to contact between the protective films on the surface of the boards and each other or between the protective film on the surface of the board and the metal rack or the like. Furthermore, when forming a pattern using photolithography on a protective film that is highly filled with fillers such as alumina, light (UV) is diffused within the protective film in proportion to the filler content, resulting in a deterioration in resolution. In other words, there is a trade-off between the heat dissipation and resolution of the protective film.

[0007] Therefore, an object of the present invention is to provide a photosensitive laminated resin structure that is less prone to scratch marks, has high heat dissipation properties, and yet provides high resolution, a dry film having the photosensitive laminated resin structure, a cured product of the photosensitive laminated resin structure, and an electronic component having the cured product. [Means for solving the problem]

[0008] As a result of intensive research to solve the above problems, the inventors have succeeded in finding a photosensitive laminated resin structure having a specific laminated structure that is resistant to scratch marks, has high heat dissipation properties, and allows for the formation of high-resolution patterns by photolithography, thereby completing the present invention.

[0009] That is, the photosensitive laminated resin structure of the present invention comprises: A photosensitive laminated resin structure having a heat dissipation layer (A) and a protective layer (B), the heat-dissipating layer (A) contains a heat-dissipating filler having a thermal conductivity of more than 10 W / m K, and the content of the heat-dissipating filler is 50 mass% or more of all components excluding the organic solvent; The protective layer (B) is characterized in that the content of the heat-dissipating filler is 0 to 20 mass % relative to the content of the heat-dissipating filler in the heat-dissipating layer (A).

[0010] In the photosensitive laminated resin structure of the present invention, the heat-dissipating layer (A) preferably contains substantially no photopolymerization initiator.

[0011] In the photosensitive laminated resin structure of the present invention, the thickness of the heat-dissipating layer (A) is preferably greater than the thickness of the protective layer (B).

[0012] The dry film of the present invention is characterized in that at least one surface of the photosensitive laminated resin structure is supported or protected by a film.

[0013] The cured product of the present invention is characterized by comprising the photosensitive laminated resin structure described above or the photosensitive laminated resin structure of the dry film described above.

[0014] The electronic component of the present invention is characterized by comprising the cured product. [Effects of the Invention]

[0015] According to the present invention, it is possible to provide a photosensitive laminated resin structure that is resistant to scratch marks, has high heat dissipation properties, and is capable of forming a high-resolution pattern, a dry film having the photosensitive laminated resin structure, a cured product of the photosensitive laminated resin structure, and an electronic component having the cured product. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a diagram schematically illustrating an example of a dry film of the present invention. [Figure 2] 1A to 1C are process diagrams schematically illustrating an example of a method for producing a printed wiring board using the photosensitive laminated resin structure of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, embodiments of the present invention will be described in detail.

[0018] The photosensitive laminated resin structure of the present invention is a photosensitive laminated resin structure having a heat-dissipating layer (A) and a protective layer (B), wherein the heat-dissipating layer (A) contains a heat-dissipating filler having a thermal conductivity higher than 10 W / m·K, and the content of the heat-dissipating filler is 50 mass% or more in all components excluding organic solvents, and the content of the heat-dissipating filler in the protective layer (B) is 0 to 20 mass% relative to the content of the heat-dissipating filler in the heat-dissipating layer (A).

[0019] In the present invention, it is essential to use a photosensitive laminated resin structure as described above. By providing the heat-dissipating layer (A) containing a heat-dissipating filler with a thermal conductivity higher than 10 W / m·K with the protective layer (B) having a heat-dissipating filler content that is a certain percentage or less (including 0) relative to the heat-dissipating filler content of the heat-dissipating layer (A), it is possible to obtain a cured product that has good resolution, high heat dissipation properties, and is resistant to scratch marks.

[0020] Furthermore, from the viewpoint of high heat dissipation and high resolution, the thickness of the heat dissipation layer (A) is preferably thicker than the thickness of the protective layer (B). For example, the thickness of the heat dissipation layer (A) is preferably more than 1.0 times the thickness of the protective layer (B), more preferably 1.5 times or more, and even more preferably 2.0 times or more.

[0021] The thickness of the heat-dissipating layer (A) is, for example, 3 to 60 μm in order to cover the circuits formed on the underlying substrate without leaving any gaps, but is not limited to this.

[0022] The thickness of the protective layer (B) is, for example, 0.5 to 20 μm, but is not limited to this.

[0023] In the photosensitive laminated resin structure of the present invention, the heat-dissipating layer (A) preferably contains an alkali-soluble resin and a thermally reactive compound. The protective layer (B) preferably contains an alkali-soluble resin, a photopolymerization initiator, and a thermally reactive compound. That is, the unexposed areas of the heat-dissipating layer (A) and the protective layer (B) are preferably soluble in an alkaline aqueous solution.

[0024] In the photosensitive laminated resin structure of the present invention, the heat-dissipating layer (A) may contain a photopolymerization initiator, but preferably does not substantially contain a photopolymerization initiator from the viewpoint of resolution. When this heat-dissipating layer (A) is laminated onto the substrate surface, even if it does not contain a photopolymerization initiator, as long as the protective layer (B) on the outer layer side can be patterned by exposure and development, it becomes possible to simultaneously form a pattern on the protective layer (B) and the heat-dissipating layer (A) by development. In the present invention, "substantially free of photopolymerization initiator" means that the heat-releasing layer (A) alone does not have photopolymerizability.

[0025] The protective layer (B) preferably contains a compound having a function of generating a basic substance upon irradiation with light as a photopolymerization initiator. From the viewpoint of resolution, the protective layer (B) preferably does not substantially contain a low-molecular-weight compound having a radically polymerizable unsaturated double bond and a molecular weight of 1,000 or less.

[0026] The heat-dissipating layer (A) and the protective layer (B) will be described in more detail below.

[0027] [Heat dissipation layer (A)] The heat-dissipating layer (A) is preferably made of an alkali-soluble thermosetting resin composition containing a specific content of the heat-dissipating filler, and more preferably made of an alkali-soluble thermosetting resin composition further containing an alkali-soluble resin and a heat-reactive compound.

[0028] (heat-dissipating filler with thermal conductivity higher than 10 W / m·K) Materials that can be used for the heat-dissipating filler used in the present invention, which has a thermal conductivity higher than 10 W / m·K, include aluminum oxide (Al2O3), diamond, beryllium oxide (BeO), aluminum nitride (AlN), boron nitride, silicon nitride, and magnesia. The heat-dissipating filler may be used alone or in combination of two or more. Among the heat-dissipating fillers, aluminum oxide is chemically stable, cost-effective, and has excellent insulating properties. In particular, the use of spherical aluminum oxide can mitigate the increase in viscosity when highly filled. Examples of spherical aluminum oxide include those with a sphericity of 0.8 or more, as measured below. However, any spherical shape is acceptable, and the aluminum oxide is not limited to being a perfect sphere. Sphericity is measured by taking a photograph with an SEM and calculating the area and perimeter of the observed particles as follows: (Sphericity) = {4π × (area) ÷ (perimeter)} 2 Specifically, the average value of measurements taken on 100 particles using an image processing device is used.

[0029] The average particle size of the exoergic filler is not particularly limited, but is preferably 0.01 μm to 30 μm, more preferably 0.01 μm to 20 μm. When the average particle size is 0.01 μm or more, the viscosity of the composition is not too high, making dispersion easy and coating the composition onto the substrate easier. On the other hand, when the average particle size is 30 μm or less, even when the coating film is thin, the exoergic filler is less likely to protrude, and the sedimentation rate is not too fast, resulting in good storage stability. Furthermore, blending two or more particles with different average particle sizes that have a particle size distribution that results in close packing allows for even higher packing density, which is preferable in terms of both storage stability and thermal conductivity. Herein, the average particle size of the exoergic filler refers to the average particle size (D50) including not only the particle size of primary particles but also the particle size of secondary particles (aggregates), and is the D50 value measured by laser diffraction. An example of a measurement device using the laser diffraction method is Microtrac MT3300EXII manufactured by Microtrac-Bell.

[0030] The content of the heat-dissipating filler in the heat-dissipating layer (A) is 50% by mass or more, preferably 50 to 90% by mass, and more preferably 50 to 80% by mass, based on all components excluding the organic solvent.

[0031] (alkali-soluble resin) The alkali-soluble resin may be any resin containing one or more functional groups selected from phenolic hydroxyl groups and carboxyl groups and capable of being developed with an alkaline aqueous solution. Preferred examples include compounds having a phenolic hydroxyl group, compounds having a carboxyl group, and resins having a phenolic hydroxyl group and a carboxyl group. The alkali-soluble resin may have an ethylenically unsaturated double bond. Examples include carboxyl group-containing resins that have traditionally been used in solder resist compositions. The carboxyl group-containing resin may be a carboxyl group-containing photosensitive resin. The alkali-soluble resin may be used alone or in combination of two or more.

[0032] Specific examples of alkali-soluble resins include the compounds (which may be either oligomers or polymers) listed below.

[0033] (1) Carboxyl group-containing resins obtained by copolymerizing unsaturated carboxylic acids such as (meth)acrylic acid with unsaturated group-containing compounds such as styrene, α-methylstyrene, lower alkyl (meth)acrylates, and isobutylene.

[0034] (2) Carboxylic acid-containing urethane resins obtained by the polyaddition reaction of diisocyanates such as aliphatic diisocyanates, branched aliphatic diisocyanates, alicyclic diisocyanates, and aromatic diisocyanates with carboxyl-containing dialcohol compounds such as dimethylolpropionic acid and dimethylolbutanoic acid, and diol compounds such as polycarbonate polyols, polyether polyols, polyester polyols, polyolefin polyols, acrylic polyols, bisphenol A alkylene oxide adduct diols, and compounds having phenolic hydroxyl groups and alcoholic hydroxyl groups.

[0035] (3) Terminal carboxyl group-containing urethane resins obtained by reacting acid anhydrides with the terminals of urethane resins obtained by polyaddition reaction of diisocyanate compounds such as aliphatic diisocyanates, branched aliphatic diisocyanates, alicyclic diisocyanates, and aromatic diisocyanates with diol compounds such as polycarbonate polyols, polyether polyols, polyester polyols, polyolefin polyols, acrylic polyols, bisphenol A alkylene oxide adduct diols, and compounds having phenolic hydroxyl groups and alcoholic hydroxyl groups.

[0036] (4) Carboxylic acid group-containing urethane resins obtained by the polyaddition reaction of diisocyanates with (meth)acrylates of bifunctional epoxy resins such as bisphenol A epoxy resins, hydrogenated bisphenol A epoxy resins, bisphenol F epoxy resins, bisphenol S epoxy resins, bixylenol epoxy resins, and biphenol epoxy resins, or their partially acid anhydride-modified products, carboxylic acid group-containing dialcohol compounds, and diol compounds.

[0037] (5) A carboxyl group-containing urethane resin that is (meth)acrylated at the terminal by adding a compound having one hydroxyl group and one or more (meth)acryloyl groups in the molecule, such as hydroxyalkyl (meth)acrylate, during the synthesis of the resin (2) or (4) above.

[0038] (6) A carboxyl group-containing urethane resin that is (meth)acrylated at the terminal by adding a compound having one isocyanate group and one or more (meth)acryloyl groups in the molecule, such as an equimolar reaction product of isophorone diisocyanate and pentaerythritol triacrylate, during the synthesis of the resin (2) or (4) above.

[0039] (7) A carboxyl group-containing resin obtained by reacting a multifunctional epoxy resin with (meth)acrylic acid and adding a dibasic acid anhydride such as phthalic anhydride, tetrahydrophthalic anhydride, or hexahydrophthalic anhydride to the hydroxyl groups present in the side chains.

[0040] (8) A carboxyl group-containing resin obtained by reacting a polyfunctional epoxy resin in which the hydroxyl groups of a difunctional epoxy resin have been further epoxidized with epichlorohydrin with (meth)acrylic acid, and then adding a dibasic acid anhydride to the resulting hydroxyl groups.

[0041] (9) A carboxyl group-containing polyester resin obtained by reacting a polyfunctional oxetane resin with a dicarboxylic acid and adding a dibasic acid anhydride to the resulting primary hydroxyl group.

[0042] (10) A carboxyl group-containing resin obtained by reacting a compound having multiple phenolic hydroxyl groups in one molecule with an alkylene oxide such as ethylene oxide or propylene oxide, reacting the resulting reaction product with an unsaturated group-containing monocarboxylic acid, and then reacting the resulting reaction product with a polybasic acid anhydride.

[0043] (11) A carboxyl group-containing resin obtained by reacting a compound having multiple phenolic hydroxyl groups in one molecule with a cyclic carbonate compound such as ethylene carbonate or propylene carbonate, reacting the resulting reaction product with an unsaturated group-containing monocarboxylic acid, and then reacting the resulting reaction product with a polybasic acid anhydride.

[0044] (12) A carboxyl group-containing resin obtained by reacting an epoxy compound having multiple epoxy groups in one molecule with a compound having at least one alcoholic hydroxyl group and one phenolic hydroxyl group in one molecule, such as p-hydroxyphenethyl alcohol, and an unsaturated group-containing monocarboxylic acid, such as (meth)acrylic acid, and then reacting the alcoholic hydroxyl groups of the resulting reaction product with a polybasic acid anhydride, such as maleic anhydride, tetrahydrophthalic anhydride, trimellitic anhydride, pyromellitic anhydride, or adipic anhydride.

[0045] (13) Alkali-soluble polyimide resins obtained by reacting a carboxylic acid anhydride containing a carboxyl group and / or a phenolic hydroxyl group with an amine such as an amine containing a carboxyl group and / or a phenolic hydroxyl group, and, if necessary, with other carboxylic acid anhydrides, amines, or isocyanates.

[0046] (14) An alkali-soluble resin obtained by further adding a compound having one epoxy group and one or more (meth)acryloyl groups in the molecule, such as glycidyl (meth)acrylate, α-methylglycidyl (meth)acrylate, etc., to the alkali-soluble resin described in (1) to (13) above.

[0047] Of the alkali-soluble resins, it is preferable to use an alkali-soluble resin comprising the resin (7) in (7) and (14) for the heat-dissipating layer (A) from the viewpoints of developability and resolution, and it is preferable to use an alkali-soluble resin described in (10) from the viewpoint of insulation reliability. In this specification, (meth)acrylate is a general term for acrylate, methacrylate and mixtures thereof, and the same applies to other similar expressions.

[0048] The alkali-soluble resins described above have many hydrophilic groups such as carboxyl groups in the side chains of the backbone polymer, making them suitable for development with an alkaline aqueous solution. The acid value of the alkali-soluble resin having a carboxyl group is preferably in the range of 40 to 200 mgKOH / g, more preferably 45 to 120 mgKOH / g. When the acid value of the carboxyl group-containing resin is within the above range, the alkali solubility is good, and patterning by alkali development becomes easy.

[0049] The weight-average molecular weight of the alkali-soluble resin varies depending on the resin skeleton, but is generally preferably in the range of 2,000 to 150,000, and more preferably 3,000 to 100,000. When the weight-average molecular weight is within the above range, an excellent balance between the development speed in the development step and the development resistance of the pattern portion is achieved.

[0050] The content of such alkali-soluble resin is suitably in the range of 10 to 45% by mass, preferably 15 to 40% by mass, of all components of the heat-dissipating layer (A) excluding the organic solvent. A content of alkali-soluble resin of 10% by mass or more is preferred because it improves film strength. On the other hand, a content of 45% by mass or less is preferred because it prevents the viscosity of the composition from becoming too high, improving coatability and other properties.

[0051] (thermally reactive compounds) The thermally reactive compound may be a known or commonly used compound having a functional group capable of undergoing a thermosetting reaction, such as a cyclic (thio)ether group. A compound that undergoes a thermosetting reaction with the alkali-soluble resin contained in the heat-dissipating layer (A) is particularly preferred, and an epoxy resin is preferably used. The thermally reactive compound may be used alone or in combination of two or more.

[0052] Examples of epoxy resins include bisphenol A type epoxy resins, brominated epoxy resins, novolac type epoxy resins, bisphenol F type epoxy resins, hydrogenated bisphenol A type epoxy resins, glycidylamine type epoxy resins, hydantoin type epoxy resins, alicyclic epoxy resins, trihydroxyphenylmethane type epoxy resins, bixylenol type or biphenol type epoxy resins, or mixtures thereof, bisphenol S type epoxy resins, bisphenol A type novolac epoxy resins, heterocyclic epoxy resins, biphenyl novolac type epoxy resins, naphthalene group-containing epoxy resins, and epoxy resins having a dicyclopentadiene skeleton.

[0053] The content of the thermally reactive compound is preferably 40% by mass or less, more preferably 2 to 30% by mass, of all components of the heat-dissipating layer (A) excluding the organic solvent. When the content of the thermally reactive compound is 70% by mass or less, undeveloped portions are less likely to remain due to reduced solubility of the unexposed areas in the developer.

[0054] (Low molecular weight compound having a radically polymerizable unsaturated double bond) The heat-dissipating layer (A) may contain a low-molecular-weight compound having a radically polymerizable unsaturated double bond in order to adjust the viscosity of the resin composition, promote photocuring, and improve developability. The molecular weight of such a low-molecular-weight compound is, for example, 1,000 or less.

[0055] Examples of low-molecular-weight compounds having a radically polymerizable unsaturated double bond include (meth)acrylate monomers such as polyester (meth)acrylate, polyether (meth)acrylate, urethane (meth)acrylate, carbonate (meth)acrylate, and epoxy (meth)acrylate. Specific examples of the compounds include hydroxyalkyl acrylates such as 2-hydroxyethyl acrylate and 2-hydroxypropyl acrylate; glycol diacrylates such as ethylene glycol, methoxytetraethylene glycol, polyethylene glycol, and propylene glycol; acrylamides such as N,N-dimethylacrylamide, N-methylolacrylamide, and N,N-dimethylaminopropylacrylamide; aminoalkyl acrylates such as N,N-dimethylaminoethyl acrylate and N,N-dimethylaminopropyl acrylate; polyhydric alcohols such as hexanediol, trimethylolpropane, pentaerythritol, dipentaerythritol, and tris-hydroxyethyl isocyanurate, or their ethylene oxide adducts, propylene oxide adducts, or ε-hydroxyethyl isocyanurate. Examples of suitable low-molecular-weight compounds include polyacrylates such as hydroxycaprolactone adducts; polyacrylates such as phenoxy acrylate, bisphenol A diacrylate, and ethylene oxide or propylene oxide adducts of these phenols; polyacrylates of glycidyl ethers such as glycerin diglycidyl ether, glycerin triglycidyl ether, trimethylolpropane triglycidyl ether, and triglycidyl isocyanurate; and, without limitation, acrylates and melamine acrylates obtained by directly acridating polyols such as polyether polyols, polycarbonate diols, hydroxyl-terminated polybutadienes, and polyester polyols, or by urethane acrylate via diisocyanates, as well as methacrylates corresponding to the above acrylates. The low-molecular-weight compounds having radically polymerizable unsaturated double bonds may be used alone or in combination of two or more.

[0056] The content of the low-molecular-weight compound having a radically polymerizable unsaturated double bond is preferably 1 to 40% by mass, more preferably 2 to 30% by mass, and even more preferably 3 to 20% by mass, of all components of the heat-dissipating layer (A) excluding the organic solvent. When the content of this low-molecular-weight compound is 1% by mass or more, development resistance by light irradiation is easily achieved, and resolution is further improved. On the other hand, when the content is 40% by mass or less, the flexibility of the cured coating film is excellent.

[0057] (antioxidant) The heat-dissipating layer (A) may contain an antioxidant, and a cured product having excellent resistance to electroless gold plating and discoloration after reflow can be obtained.

[0058] Examples of antioxidants include hindered phenol compounds such as 2,6-dialkylphenol derivatives, divalent sulfur compounds, phosphite compounds containing trivalent phosphorus atoms, etc. One type of antioxidant may be used alone, or two or more types may be used in combination.

[0059] The content of the antioxidant is preferably in the range of 0.1% to 10% of all the components of the heat-dissipating layer (A) excluding the organic solvent.

[0060] (polymerization inhibitor) The heat-dissipating layer (A) may contain a polymerization inhibitor, and a photosensitive laminated resin structure with excellent resolution can be obtained.

[0061] Examples of the polymerization inhibitor include phenothiazine, hydroquinone, N-phenylnaphthylamine, chloranil, pyrogallol, benzoquinone, t-butylcatechol, hydroquinone, methylhydroquinone, tert-butylhydroquinone, hydroquinone monomethyl ether, catechol, pyrogallol, naphthoquinone, 4-methoxy-1-naphthol, 2-hydroxy-1,4-naphthoquinone, phosphorus-containing compounds having a phenolic hydroxyl group, nitrosamine compounds, etc. One type of polymerization inhibitor may be used alone, or two or more types may be used in combination.

[0062] The content of the polymerization inhibitor is preferably 5% by mass or less of all the components of the heat-dissipating layer (A) excluding the organic solvent.

[0063] (Photopolymerization initiator) From the viewpoint of resolution, it is preferable that the heat-dissipating layer (A) is substantially free of a photopolymerization initiator. Here, "substantially free of a photopolymerization initiator" means that the heat-dissipating layer (A) as a single layer is not photopolymerizable, but does not exclude the inclusion of a small amount of photopolymerization initiator within a range that does not impair photopolymerization. For example, it is possible that the photopolymerization initiator contained in the protective layer (B) migrates to the heat-dissipating layer (A). Even in such a case, the concentration of the photopolymerization initiator contained in the protective layer (B) is preferably 50% or less of the concentration of the photopolymerization initiator contained in the protective layer (B).

[0064] [Protective layer (B)] The protective layer (B) is preferably made of a photosensitive curable resin composition having a lower content of the heat-dissipating filler than the heat-dissipating layer (A), and more preferably made of a photosensitive curable resin composition further containing an alkali-soluble resin, a photopolymerization initiator, and a heat-reactive compound.

[0065] (alkali-soluble resin) The alkali-soluble resin may be any of the above-mentioned alkali-soluble resins, and may be used singly or in combination of two or more. Among them, from the viewpoints of heat resistance, mechanical properties, and resolution, it is preferable to use an alkali-soluble polyimide resin (13) in (13) and (14) that uses the resin (13), and from the viewpoint of insulation reliability, it is preferable to use the alkali-soluble resin (10).

[0066] The content of the alkali-soluble resin is preferably 10 to 75% by mass, more preferably 15 to 70% by mass, of all components of the protective layer (B) excluding the organic solvent. When the content is 10% by mass or more, the toughness of the cured coating film is improved. When the content is 75% by mass or less, the surface is less susceptible to damage such as scratches during the development process.

[0067] (Photopolymerization initiator) The photopolymerization initiator may be used alone or in combination of two or more. As the photopolymerization initiator, one or more photopolymerization initiators selected from the group consisting of oxime ester-based photopolymerization initiators having an oxime ester group, α-aminoacetophenone-based photopolymerization initiators, and acylphosphine oxide-based photopolymerization initiators can be suitably used.

[0068] Commercially available oxime ester photopolymerization initiators include CGI-325, Irgacure OXE01, and Irgacure OXE02 manufactured by BASF Japan Ltd., and N-1919 and NCI-831 manufactured by ADEKA Corp. Photopolymerization initiators having two oxime ester groups in the molecule can also be suitably used.

[0069] The content of such an oxime ester photopolymerization initiator is preferably 0.01 to 20 parts by mass relative to 100 parts by mass of the alkali-soluble resin. At 0.01 parts by mass or more, coating film properties such as chemical resistance are improved. On the other hand, at 20 parts by mass or less, light absorption at the coating film surface is not too intense, resulting in good deep curing. A more preferred content is 0.5 to 15 parts by mass.

[0070] Specific examples of α-aminoacetophenone-based photopolymerization initiators include 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropanone-1, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butan-1-one, 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]-1-butanone, and N,N-dimethylaminoacetophenone. Commercially available products include Omnirad 907, Omnirad 369, and Omnirad 379 manufactured by IGM Resins.

[0071] Specific examples of acylphosphine oxide photopolymerization initiators include 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, etc. Commercially available products include Lucirin TPO manufactured by BASF and Omnirad 819 manufactured by IGM Resins.

[0072] The content of these α-aminoacetophenone-based photopolymerization initiators and acylphosphine oxide-based photopolymerization initiators is preferably 0.01 to 15 parts by mass relative to 100 parts by mass of the alkali-soluble resin. At 0.01 parts by mass or more, coating film properties such as chemical resistance are also improved. On the other hand, at 15 parts by mass or less, outgassing is reduced, and furthermore, light absorption at the coating film surface is not too intense, resulting in good deep curing. A more preferred range is 0.5 to 10 parts by mass.

[0073] Here, when the photopolymerization initiator is used as a catalyst for the polymerization reaction of a thermally reactive compound described below, the above-mentioned oxime ester photopolymerization initiators and α-aminoacetophenone photopolymerization initiators are preferred because they generate not only photoradicals but also basic substances upon light irradiation, and among these, oxime ester photopolymerization initiators are more preferred because they have excellent resolution.

[0074] (thermally reactive compounds) The heat-reactive compound may be any of the above-mentioned heat-reactive compounds, and may be used singly or in combination of two or more. In particular, a compound that undergoes a heat-curing reaction with the alkali-soluble resin contained in the protective layer (B) is preferred, and the above-mentioned epoxy resin is preferably used.

[0075] The content of the thermally reactive compound is preferably 3 to 50% by mass, more preferably 5 to 40% by mass, of all components of the protective layer (B) excluding the organic solvent. When the content is 3% by mass or more, the toughness of the coating film can be obtained, and when the content is 50% by mass or less, good developability can be obtained.

[0076] (antioxidant) The protective layer (B) may contain an antioxidant. The antioxidants described above can be used, and one type may be used alone or two or more types may be used in combination. A cured product having excellent resistance to electroless gold plating and discoloration after reflow can be obtained.

[0077] The content of the antioxidant is preferably in the range of 0.1% to 10% of all components of the protective layer (B) excluding the organic solvent.

[0078] (polymerization inhibitor) From the viewpoint of resolution, the protective layer (B) may contain the above-mentioned polymerization inhibitor. The content of the polymerization inhibitor in the protective layer (B) is preferably 5% by mass or less based on all components of the protective layer (B) excluding the organic solvent.

[0079] (heat-dissipating filler with thermal conductivity higher than 10 W / m·K) From the viewpoint of scratch resistance, the protective layer (B) does not contain a heat-dissipating filler having a thermal conductivity higher than 10 W / m·K, but may contain such a filler to the extent that it does not affect scratch resistance. That is, from the viewpoint of scratch resistance, the content of the heat-dissipating filler in the protective layer (B) must be 20 mass% or less of the heat-dissipating filler content in the heat-dissipating layer (A). The heat-dissipating filler may be any of the above-mentioned heat-dissipating fillers, and may be used alone or in combination of two or more.

[0080] The content of the exoergic filler in the protective layer (B) is preferably 0 to 20 mass %, more preferably 0 to 10 mass %, of all components in the protective layer (B) excluding the organic solvent.

[0081] In addition, inorganic fillers other than the heat-dissipating filler can be blended into the protective layer (B), but from the viewpoint of scratch resistance, the content of inorganic fillers other than the heat-dissipating filler is preferably 0 to 20 mass % of all components in the protective layer (B) excluding the organic solvent.

[0082] (Low molecular weight compound having a radically polymerizable unsaturated double bond) The protective layer (B) may contain a low molecular weight compound having a radically polymerizable unsaturated double bond. The low molecular weight compound having a radically polymerizable unsaturated double bond may be the low molecular weight compound described above, and one type may be used alone, or two or more types may be used in combination.

[0083] However, from the viewpoint of resolution, it is preferable that the content of low-molecular-weight compounds having a radically polymerizable unsaturated double bond with a molecular weight of 1000 or less is substantially zero, and for example, the content of the low-molecular-weight compounds is 0 to 20% by mass, preferably 0 to 15% by mass, more preferably 0 to 10% by mass, even more preferably 0 to 2% by mass, and particularly preferably 0% by mass, based on all components in the protective layer (B) excluding the organic solvent.

[0084] [Photosensitive laminated resin structure] The photosensitive laminated resin structure of the present invention can be preferably used for forming a protective film for electronic components, particularly a printed wiring board, and particularly preferably for forming a permanent protective film such as a solder resist layer or a coverlay for a flexible printed wiring board. The printed wiring board is not particularly limited, but the photosensitive laminated resin structure of the present invention is preferably a package substrate or a surface-mounted light-emitting diode because of its excellent heat dissipation properties.

[0085] The photosensitive laminated resin structure of the present invention preferably comprises a heat-dissipating layer (A) and a protective layer (B) laminated together.

[0086] [Dry film] The dry film of the present invention is characterized in that at least one surface of the photosensitive laminated resin structure of the present invention is supported or protected by a film. One preferred embodiment is a four-layer dry film 10, as shown in FIG. 1, in which a protective film 14, a heat dissipation layer (A) 13, a protective layer (B) 12, and a support film 11 are laminated in this order. The dry film of the present invention can be laminated so that the protective layer (B) is the surface layer, and the film to be peeled off during lamination can be either the support film or the protective film. Therefore, the layers may be laminated in this order: support film, heat dissipation layer (A), protective layer (B), and protective film. The dry film of the present invention may also be wound into a roll.

[0087] The dry film of the present invention can be produced, for example, as follows. Specifically, the resin composition constituting the protective layer (B) and the resin composition constituting the heat-dissipating layer (A) are first diluted with an organic solvent to an appropriate viscosity and sequentially coated onto a support film (carrier film) using a known technique such as a comma coater. This is then typically dried at a temperature of 50 to 140°C for 1 to 30 minutes to produce a dry film with the protective layer (B) and heat-dissipating layer (A) coated on the support film. A peelable protective film (cover film) can be further laminated on this dry film to prevent dust from adhering to the coating surface. Conventional plastic films can be used as the support film and protective film. It is preferable that the adhesive strength of the protective film be weaker than that between the resin layer and the support film when peeled off. There are no particular limitations on the thickness of the support film and protective film, but they are generally selected appropriately within the range of 10 to 150 μm.

[0088] [Cured product] The cured product of the present invention is characterized by comprising the photosensitive laminated resin structure of the present invention. The cured product of the present invention preferably has a thermal conductivity of 1.5 W / m·K or more when measured by a cyclic heating method.

[0089] [Electronic Components] The electronic component of the present invention is characterized by comprising the cured product of the present invention.

[0090] Since the cured product of the present invention has excellent scratch resistance, it is preferable that the cured product be formed in the electronic component of the present invention so that the protective layer (B) is the outermost layer.

[0091] [Electronic component manufacturing method] As a method for producing electronic components using the photosensitive laminate resin structure of the present invention, an example of a method for producing a printed wiring board will be described based on the steps shown in the process diagram of FIG. 2. Specifically, this production method includes the steps of forming the photosensitive laminate resin structure of the present invention on a printed wiring board on which a conductor circuit has been formed (lamination step), irradiating the photosensitive laminate resin structure with active energy rays in a pattern (exposure step), and developing the photosensitive laminate resin structure with alkali to form a patterned photosensitive laminate resin structure in one step (development step). If necessary, further photocuring or heat curing (post-cure step) may be performed after the alkali development to completely cure the photosensitive laminate resin structure, thereby obtaining a highly reliable printed wiring board. If necessary, a step of heating the photosensitive laminate resin structure (PEB step) may be inserted between the exposure step and the development step, and a patterned photosensitive laminate resin structure may be formed in one step by the development step. This procedure is particularly preferred when an alkali-soluble resin is used in the protective layer (B). Furthermore, when the protective layer (B) contains a compound that generates a basic substance upon irradiation with light, it is preferable to carry out the PEB step from the viewpoint of resolution.

[0092] [Lamination process] In this process, the resin compositions constituting the heat-dissipating layer (A) 3 and the protective layer (B) 4 are sequentially applied to the substrate of the printed wiring board 1 on which the conductor circuit 2 has been formed, followed by drying, to form the heat-dissipating layer (A) 3 and the protective layer (B) 4 directly. Alternatively, the resin compositions constituting the heat-dissipating layer (A) 3 and the protective layer (B) 4 can be formed in the form of dry films, which are then sequentially laminated to the substrate. Alternatively, the heat-dissipating layer (A) 3 and the protective layer (B) 4 can be formed by laminating a two-layer dry film laminate structure onto the substrate. In this case, at least one side of the laminate structure can be supported or protected by a film. The film used can be a plastic film that can be peeled off from the laminate structure. There are no particular limitations on the thickness of the film, but it is generally selected appropriately from the range of 10 to 150 μm. From the standpoint of coating film strength, the interfaces between the layers may be smooth. Commercially available vacuum heating and pressurizing laminators can be used as laminators, such as the Meiki Seisakusho vacuum pressurizing laminator and the Nichigo-Morton vacuum applicator. These lamination processes can also be performed continuously. The lamination process can also be performed using separate devices. In this case, in addition to the vacuum laminator mentioned above, roll laminators, vacuum roll laminators, and vacuum presses can also be used. Commercially available vacuum presses can be used, such as multi-stage presses, multi-stage vacuum presses, quick presses, continuous molding machines, and autoclave molding machines. The operating conditions for the above laminators are 60 to 130°C, pressure 0.1 to 0.7 MPa, heating and pressurizing time 1 to 90 seconds, vacuum level 10 to 10,000 Pa, and vacuum time 1 to 90 seconds.

[0093] [Exposure process] In this process, the photopolymerization initiator contained in the protective layer (B) 4 or the heat dissipation layer (A) 3 is activated in a negative pattern by irradiation with active energy rays, and the exposed areas are cured. The exposure device can be a direct imaging device or an exposure device equipped with a metal halide lamp. The mask used for pattern exposure is a negative mask.

[0094] The active energy rays used for exposure are preferably laser light, scattered light, or parallel light having a maximum wavelength in the range of 350 to 450 nm. By setting the maximum wavelength in this range, the photopolymerization initiator can be activated efficiently. The exposure dose varies depending on the film thickness, etc., but is usually 50 to 1500 mJ / cm. 2 It can be said that:

[0095] [Development process] In this process, unexposed areas are removed by alkaline development to form a negative-type patterned protective film, particularly a coverlay and solder resist. The development method can be a known method such as dipping. The developer can be an alkaline aqueous solution such as sodium carbonate, potassium carbonate, potassium hydroxide, amines, imidazoles such as 2-methylimidazole, or an aqueous tetramethylammonium hydroxide solution (TMAH), or a mixture thereof.

[0096] [Post-cure process] After the development step, the protective film may be further irradiated with light or heated, for example, at 150°C or higher. The heating temperature is, for example, 80 to 170°C, and the heating time is 5 to 100 minutes. The curing of the photosensitive laminated resin structure in the present invention is, for example, a ring-opening reaction of the epoxy resin due to a thermal reaction, and therefore distortion and cure shrinkage can be suppressed compared to when curing proceeds by a photoradical reaction.

[0097] In the PEB step, the exposed portion may be cured by heating the photosensitive laminated resin structure between the exposure step and the development step. The heating temperature is, for example, 70 to 140° C., and the heating time is 2 to 100 minutes. [Example]

[0098] The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the following examples. In the following, "parts" and "%" are all by mass unless otherwise specified.

[0099] (Synthesis Example 1 of Alkali-Soluble Resin) 220 parts of cresol novolac epoxy resin (DIC Corporation, Epicron N-695, epoxy equivalent: 220) was placed in a four-neck flask equipped with a stirrer and reflux condenser, and 214 parts of carbitol acetate was added and dissolved by heating. Next, 0.1 parts of hydroquinone as a polymerization inhibitor and 2.0 parts of dimethylbenzylamine as a reaction catalyst were added. This mixture was heated to 95-105°C, and 72 parts of acrylic acid were slowly added dropwise, allowing the reaction to proceed for 16 hours. The reaction product was cooled to 80-90°C, and 106 parts of tetrahydrophthalic anhydride was added. The reaction was allowed to proceed for 8 hours, cooled, and then discharged. The resin solution of the photosensitive resin having both ethylenically unsaturated bonds and carboxyl groups thus obtained had a nonvolatile content of 65%, an acid value of the solid matter of 100 mgKOH / g, and a weight-average molecular weight Mw of approximately 3,500. The weight average molecular weight of the resulting resin was measured by high performance liquid chromatography using three connected pumps, LC-804, KF-803 and KF-802, manufactured by Shimadzu Corporation.

[0100] (Synthesis Example 2 of Alkali-Soluble Resin) A four-necked 300 mL flask equipped with a nitrogen gas inlet tube, a thermometer, and a stirrer was charged with 6.98 g of 2,2-bis[4-(4-aminophenoxy)phenyl]propane (hereinafter referred to as "BAPP"), 3.80 g of 3,5-diaminobenzoic acid, 8.21 g of Jeffamine XTJ-542 (manufactured by Huntsman, molecular weight 1025.64), and 86.49 g of γ-butyrolactone, and these were dissolved at room temperature. Next, 17.84 g of cyclohexane-1,2,4-tricarboxylic acid-1,2-anhydride and 2.88 g of trimellitic anhydride were added and kept at room temperature for 30 minutes. 30 g of toluene was then added and heated to 160°C. After removing the water generated together with the toluene, the mixture was kept at this temperature for 3 hours and then cooled to room temperature to obtain an imidized product solution. To the imidized product solution, 9.61 g of trimellitic anhydride and 17.45 g of trimethylhexamethylene diisocyanate were added and the mixture was kept at 160°C for 32 hours. This resulted in a resin solution containing 40.1% (non-volatile content) of carboxyl-containing polyamideimide resin. The acid value of the solid content was 83.1 mgKOH / g.

[0101] <Preparation of Resin Composition> The materials described in the examples were blended according to the formulations shown in Table 1 below, premixed in a mixer, and then kneaded in a three-roll mill to prepare resin compositions. Unless otherwise specified, the values ​​in the table are in parts by mass, excluding the organic solvent.

[0102] [Table 1]

[0103] *1: Resin solution of the carboxyl group-containing resin obtained in Synthesis Example 1 above *2: Resin solution of the carboxyl group-containing resin obtained in Synthesis Example 2 above *3: Dipentaerythritol hexaacrylate (manufactured by Nippon Kayaku Co., Ltd.) *4: Bisphenol A novolac epoxy resin (DIC Corporation) *5: Tetramethylbiphenol type epoxy resin (Mitsubishi Chemical Corporation) *6: Oxime ester photopolymerization initiator (manufactured by BASF) *7: Aluminum oxide (manufactured by Nippon Light Metal Co., Ltd.) (average particle size 0.5 μm, thermal conductivity 30 W / m·K) *8: Barium sulfate (manufactured by Sakai Chemical Industry Co., Ltd.) (average particle size 0.3 μm, thermal conductivity 1.5 W / m·K)

[0104] <Preparation of a dry film having a photosensitive laminated resin structure> Using each resin composition obtained as described above, a photosensitive laminated resin structure was prepared as follows. First, a composition shown in Table 1, which corresponds to the protective layer (B) shown in Table 2, was applied to a 35 μm-thick polyethylene terephthalate (PET) support film and dried to prepare a dry film having a protective layer (B). Next, a composition shown in Table 1, which corresponds to the heat-dissipating layer (A) shown in Table 2, was applied to the protective layer (B) and dried to prepare a dry film having a heat-dissipating layer (A). Next, a 15 μm-thick biaxially oriented polypropylene film was laminated on the surface of the heat-dissipating layer (A), to prepare a dry film consisting of four layers: support film (PET film), protective layer (B), heat-dissipating layer (A), and protective film (OPP film).

[0105] [Table 2]

[0106] Using each of the dry films prepared in the Examples and Comparative Examples, the photosensitive laminated resin structures were evaluated as follows.

[0107] (optimal exposure) A single-sided printed wiring board with a 15 μm thick copper circuit was prepared and pretreated using a MEC CZ8100. The protective film in contact with the heat dissipation layer (A) of each dry film in the Examples and Comparative Examples was peeled off, and the heat dissipation layer (A) was attached to the substrate using a vacuum laminator to form a photosensitive laminated resin structure on the substrate. The substrate was exposed to light through a step tablet (Kodak No. 2) using an exposure device equipped with a high-pressure mercury lamp (short arc lamp). After exposure, the substrate was heated at 100°C for 30 minutes, and then the PET film in contact with the protective layer (B) was peeled off. Development (30°C, 0.2 MPa, 1 wt% Na2CO3 aqueous solution) was performed for 60 seconds. The optimal exposure dose was determined when the remaining step tablet pattern had five steps.

[0108] (Measurement of thermal conductivity) A 50 μm Teflon sheet was attached to one side of a 0.8 mm thick etched-out substrate. The protective film in contact with the heat dissipation layer (A) of each dry film of the Examples and Comparative Examples was then peeled off, and the dry films were laminated using a vacuum laminator so that the heat dissipation layer (A) was in contact with the Teflon sheet. Each laminated dry film was then exposed to the entire surface at the optimal exposure dose using an exposure device equipped with a high-pressure mercury lamp and heated at 100°C for 30 minutes. The PET film in contact with the protective layer (B) was then peeled off, and the film was developed with a 1 wt% sodium carbonate aqueous solution at 30°C under a spray pressure of 0.2 MPa for 60 seconds, and then heated at 150°C for 60 minutes to cure. The cured dry film (cured film) was then peeled off from the Teflon sheet to obtain a test specimen for thermal conductivity measurement. The thermal conductivity of each test specimen was measured using an Advance Riko Co., Ltd. "FTC-RT Cyclic Heating Thermal Diffusivity Measurement System." The thermal conductivity of each test piece is shown in Table 2.

[0109] (Resolution evaluation (minimum aperture evaluation)) Test pieces for resolution evaluation were obtained in the same manner as in the preparation of the test pieces described above (Measurement of thermal conductivity), except that, in the preparation of the test pieces described above (Measurement of thermal conductivity), pattern exposure was performed at each optimal exposure dose through a negative mask having a negative pattern with via opening diameters of 500 μm, 300 μm, 150 μm, 100 μm, 80 μm, and 60 μm as a negative mask for resolution evaluation. For each of the obtained test pieces, the pattern openings were observed by SEM to evaluate the minimum opening diameter.

[0110] (scratch resistant) A brass cylinder with a diameter of 1 cm and a height of 2 cm and a 10 g weight were placed and fixed on each test piece described above (Measurement of thermal conductivity). The cylinder with the weight was then slid 5 cm over the test piece at a speed of 1 cm / sec, and the test piece was visually inspected to see if black scratches were formed. The criteria for judgment are as follows: ○: No scratch marks ×: Scratch marks occurred

[0111] The evaluation results shown in Table 2 above show that the photosensitive laminated structures of Examples 1 to 6 have high heat dissipation properties, good resolution, and excellent scratch resistance. [Explanation of symbols]

[0112] 1 printed wiring board 2 Conductor Circuit 3 Heat dissipation layer (A) 4 Protective layer (B) 5. Mask 10 Dry Film 11 Support film 12 Protective layer (B) 13 Heat dissipation layer (A) 14 Protective film

Claims

1. A heat dissipation layer (A) and a protective layer (B) formed on a substrate surface, a photosensitive laminated resin structure in which the heat dissipation layer (A) and the protective layer (B) are laminated on a surface of the substrate in the following order: surface of the substrate, heat dissipation layer (A), protective layer (B), The heat-dissipating layer (A) has a layer thickness of 3 to 60 μm, the heat-dissipating layer (A) is made of an alkali-soluble thermosetting resin composition, does not contain a photopolymerization initiator, and contains an alkali-soluble resin, a thermosetting compound, and a heat-dissipating filler having a thermal conductivity of more than 10 W / m K, and the content of the heat-dissipating filler is 50 mass% or more of all components of the heat-dissipating layer (A) excluding organic solvents; the protective layer (B) is made of a photosensitive curable resin composition, the content of the heat-dissipating filler is 0 to 20 mass% relative to the content of the heat-dissipating filler in the heat-dissipating layer (A), and the photosensitive laminated resin structure contains an alkali-soluble resin, a photopolymerization initiator, and a thermosetting compound.

2. 2. The photosensitive laminated resin structure according to claim 1, wherein the heat-dissipating layer (A) has a thickness greater than that of the protective layer (B).

3. 3. A dry film comprising the photosensitive laminated resin structure according to claim 1 or 2, at least one surface of which is supported or protected by a film.

4. A cured product comprising the photosensitive laminated resin structure according to claim 1 or 2 or the dry film photosensitive laminated resin structure according to claim 3.

5. An electronic part comprising the cured product according to claim 4.

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