Polyimide precursor, thermosetting resin composition, cured film, substrate, electronic component, and method for producing polyimide precursor

Abstract

To provide a polyimide precursor that satisfies a low coefficient of thermal expansion (low CTE) and high toughness and adhesiveness, which traditionally had a trade-off relationship, and in which a change in coefficient of thermal expansion above and below the glass transition point is suppressed despite having a glass transition point (Tg) at a relatively low temperature.　The polyimide precursor is characterized by being obtained by polymerizing a second tetracarboxylic acid dianhydride having a rigid skeleton and a second diamine having a rigid skeleton in the presence of a soluble polyimide of a terminal amine or a terminal acid anhydride obtained by polymerizing a first tetracarboxylic acid dianhydride having a flexible skeleton and a first diamine having a flexible skeleton.

Description

Polyimide precursor, thermosetting resin composition, cured film, substrate, electronic component, and method for producing polyimide precursor

[0001] The present invention relates to a polyimide precursor and a thermosetting resin composition containing the same, which are used, for example, in semiconductor devices.

[0002] In recent years, performance improvements due to miniaturization of semiconductor devices have reached a plateau, and attempts to improve performance through 3D packaging have been made as a solution. This has made it necessary to densely package complex components such as semiconductors, wiring, insulating layers, connections between boards via through-holes, and the use of interposers. Accordingly, it is becoming increasingly important to suppress residual stresses that arise from joining components with different thermal expansion coefficients (linear expansion coefficients and linear thermal expansion coefficients) and from thinning each layer.

[0003] However, metals used in inorganic substrates and wiring generally have a low coefficient of thermal expansion (hereinafter, also referred to as CTE). Therefore, if the organic material applied on top has a high CTE, the difference in CTE between the organic material and the underlying metal causes thermal stress, which leads to warping of the substrate and deformation of the semiconductor device. It is also known that the release of residual stress can cause problems such as interfacial peeling.

[0004] Regarding polyimides used in semiconductor devices, various studies have been conducted to reduce the residual stress. For example, Patent Documents 1 and 2 describe that in polyimide materials with a specific structure, volume shrinkage during thermal imidization causes molecular chains to be highly oriented in the substrate plane, thereby suppressing the CTE to be equal to or lower than that of inorganic substrates.

[0005] However, because these low CTE polyimides have rigid skeletons, their glass transition temperatures (hereinafter also referred to as Tg, as appropriate) at which the segmental motion of molecular chains is released by heat are extremely high, or they do not even reach the thermal decomposition temperature, and therefore, the film does not soften due to heat, and therefore almost no adhesive properties can be expected.

[0006] On the other hand, it is known that adhesiveness can be imparted by using a polyimide with a flexible backbone (for example, Patent Document 3). However, the use of such flexible polyimides increases the CTE, generating large thermal stress. In addition, there is a problem that the CTE changes significantly around the Tg, and the CTE increases significantly above the Tg.

[0007] On the other hand, block copolymerization using addition polymerization of polyimide has also been investigated. For example, Patent Documents 4 and 5 describe a method of preparing a soluble polyimide polymerized with an acid anhydride at the terminal and a polyamic acid polymerized with an amine at the terminal, mixing the two polymers, and then performing block copolymerization. Block copolymerization can reduce the CTE of the polyimide and improve the tensile modulus compared to random copolymerization. Furthermore, controlling the solubility of polyimide in alkaline developers can enable application to photosensitive materials.

[0008] Alternatively, blocking of polyimides by controlling the order of polymerization of polyamic acids has also been investigated. For example, Patent Document 6 describes a polyamic acid composition in which a block component consisting of 4,4'-diaminodiphenyl ether and pyromellitic dianhydride and a block component consisting of paraphenylenediamine and 3,3',4,4'-biphenyltetracarboxylic dianhydride are copolymerized in a specific ratio, and a polyimide obtained by curing the composition. Patent Document 7 describes a polyimide film produced from pyromellitic dianhydride and a polyamic acid composed of 1 mol % or more but less than 20 mol % of diaminobenzanilides and 80 mol % or more but less than 99 mol % of oxydianilines, based on the diamine, and characterized by a thermal expansion coefficient of 10 ppm or more. Patent Document 8 describes a polyimide film produced from pyromellitic dianhydride and a polyamic acid obtained from predetermined amounts of 4,4'-oxydianiline and 3,4'-oxydianiline.

[0009] Japanese Patent Laid-Open No. 60-250031 Japanese Patent Laid-Open No. 61-60725 Japanese Patent Laid-Open No. 9-99518 International Publication No. 2010 / 113412 International Publication No. 2014 / 174838 Japanese Patent Laid-Open No. 2012-153806 Japanese Patent Laid-Open No. 2003-73473 Japanese Patent Laid-Open No. 2003-206353

[0010] However, because a low coefficient of thermal expansion (CTE) generally has a trade-off relationship with toughness and adhesiveness, it is difficult for the above-mentioned polyimides to achieve both a low CTE and high toughness and adhesiveness. Therefore, an object of the present invention is to provide a polyimide precursor and a composition containing the same that can achieve a low coefficient of thermal expansion and high toughness and adhesiveness. Another object of the present invention is to provide a polyimide precursor and a composition containing the same that can be cured to produce a cured product with reduced change in the coefficient of thermal expansion before and after the glass transition point (Tg).

[0011] As a result of extensive research into solving the above-mentioned problems, the present inventors have found that it is difficult to solve all of the above-mentioned problems of the present invention using the conventional blocking method of mixing and polymerizing two polymers or the random copolymerization of polyamic acid, but that the above-mentioned problems can be solved by polymerizing polyamic acid in the presence of an amine-terminated or acid anhydride-terminated soluble polyimide to obtain a block copolymer polyimide.

[0012] [1] A polyimide precursor obtained by polymerizing a second tetracarboxylic dianhydride having a rigid skeleton and a second diamine having a rigid skeleton in the presence of a soluble polyimide having a terminal amine or a terminal acid anhydride obtained by polymerizing a first tetracarboxylic dianhydride having a flexible skeleton and a first diamine having a flexible skeleton.

[0013] [2] The polyimide precursor according to [1], wherein the rigid skeleton has one aromatic ring or two or more aromatic rings that are not linked by ether bonds, and the flexible skeleton has two or more aromatic rings that are linked by ether bonds.

[0014] [3] The polyimide precursor according to [1] or [2], wherein the second tetracarboxylic dianhydride is pyromellitic anhydride, and the second diamine is one or more selected from the group consisting of p-phenylenediamine, 4,4'-diaminobenzanilide, 5-amino-2-(4-aminophenyl)benzimidazole, 2,2'-bis(trifluoromethyl)benzidine, and 2,2'-dimethylbenzidine.

[0015] [4] The polyimide precursor according to [1], [2], or [3], wherein the first tetracarboxylic dianhydride is one or more selected from the group consisting of 4,4'-oxydiphthalic anhydride and 4,4'-(1,4-phenylenedioxy)bisphthalic anhydride, and the first diamine is one or more selected from the group consisting of 1,3-bis(3-aminophenoxy)benzene, 2,2'-bis(4-(4-aminophenoxy)phenyl)propane, 4,4'-bis(3-aminophenoxy)biphenyl, and bis(4-(3-aminophenoxy)phenyl)sulfone.

[0016] [5] A thermosetting resin composition comprising the polyimide precursor according to any one of [1] to [4]. [6] The thermosetting resin composition according to [5], wherein the content of the polyimide precursor is 10% by weight or more and 30% by weight or less.

[0017] [7] A cured film obtained by curing the thermosetting resin composition according to [5] or [6]. [8] A substrate having the cured film according to [7]. [9] An electronic component comprising the cured film according to [7] or the substrate according to [8].

[0018]

[10] A method for producing a polyimide precursor according to any one of [1] to [4], characterized by polymerizing a first tetracarboxylic dianhydride having a flexible skeleton with a first diamine having a flexible skeleton to form a soluble polyimide having a terminal amine or a terminal acid anhydride, and polymerizing a second tetracarboxylic dianhydride having a rigid skeleton with a second diamine having a rigid skeleton in the presence of the soluble polyimide.

[0019] The polyimide precursor of the present invention is a copolymer of a blocked polyimide and a polyamic acid, and thereby provides a thermosetting resin composition that provides a cured polyimide film after heat curing with high heat resistance (dimensional stability), a thermal expansion coefficient comparable to that of metals while maintaining high mechanical strength and toughness, and adhesive properties upon thermocompression bonding. Furthermore, a thermosetting resin composition containing the polyimide precursor of the present invention can be used as a heat-resistant adhesive that suppresses warping due to deformation or thermal stress during the manufacturing process of elements used in semiconductors, etc. Therefore, the use of a cured film obtained by curing the thermosetting resin composition of the present invention can improve the reliability and yield of the cured film and electronic components equipped with a substrate having the cured film.

[0020] A polyimide precursor according to an embodiment of the present invention is described below. The polyimide precursor of the present invention is obtained by polymerizing a second tetracarboxylic dianhydride having a rigid skeleton with a second diamine having a rigid skeleton in the presence of a soluble polyimide having a terminal amine or a terminal acid anhydride, which has been obtained by polymerizing a first tetracarboxylic dianhydride having a flexible skeleton with a first diamine having a flexible skeleton.

[0021] The polyimide precursor of the present invention contains a block copolymer consisting of a block of a soluble polyimide having a terminal amine or terminal acid anhydride obtained by polymerizing a first tetracarboxylic dianhydride having a flexible backbone with a first diamine having a flexible backbone, and a block of a polyamic acid obtained by polymerizing a second tetracarboxylic dianhydride having a rigid backbone with a second diamine having a rigid backbone. Instead of copolymerizing the block of the soluble polyimide with the block of the polyamic acid, the second tetracarboxylic dianhydride and the second diamine are polymerized in the presence of the soluble polyimide having a terminal amine or terminal acid anhydride, thereby obtaining a polyimide precursor having both the flexible backbone of a soluble polyimide and the rigid backbone of a polyamic acid.

[0022] A soluble polyimide can be obtained by polymerizing a monomer that has low structural symmetry and high solubility in a solvent. In the present invention, however, the terminal of the soluble polyimide obtained by polymerizing a first tetracarboxylic dianhydride having a flexible skeleton and a first diamine having a flexible skeleton is made to be an amine or an acid anhydride.

[0023] A polyimide precursor, which is a copolymer of a blocked polyimide and a polyamic acid, is obtained by polymerizing a second tetracarboxylic dianhydride having a rigid skeleton and a second diamine having a rigid skeleton in the presence of a soluble polyimide having a terminal amine or terminal acid anhydride having a flexible skeleton.

[0024] By curing the thermosetting resin composition containing the polyimide precursor of the present invention, a cured product having a low coefficient of thermal expansion, high toughness, and adhesiveness by thermocompression bonding can be obtained. The cured product also has the property of showing a small change in the coefficient of thermal expansion before and after the glass transition temperature.

[0025] Specifically, a soluble polyimide having a flexible backbone and terminated with an amine or an acid anhydride (hereinafter also referred to as a soluble polyimide) is synthesized by polymerizing a first tetracarboxylic dianhydride having a flexible backbone with a first diamine having a flexible backbone. Subsequently, a second tetracarboxylic dianhydride having a rigid backbone with a second diamine having a rigid backbone is polymerized in the presence of the soluble polyimide. The resulting copolymer of blocked polyimide and polyamic acid has the low thermal expansion characteristic of a soluble polyimide having a rigid backbone, as well as high toughness and adhesiveness by thermocompression bonding, making it useful as a polyimide precursor.

[0026] (Compounds Having a Flexible Skeleton: First Tetracarboxylic Acid Dianhydride, First Diamine) The first tetracarboxylic acid dianhydride having a flexible skeleton is a compound represented by the following formula (1). The first diamine having a flexible skeleton is a compound represented by the following formula (2). Hereinafter, these compounds will be collectively referred to as compounds having a flexible skeleton where appropriate. (R in formulas (1) and (2)1 and R 2 are each an organic group having a flexible skeleton and having 1 to 100 carbon atoms.

[0027] Examples of compounds having a flexible skeleton include compounds having two or more aromatic rings linked by ether bonds, such as R 1 and R 2 Examples of compounds include compounds having an ether bond in the organic group represented by the formula:

[0028] Examples of the first tetracarboxylic dianhydride having a flexible backbone include 4,4'-oxydiphthalic anhydride, 4,4'-(1,4-phenylenedioxy)bisphthalic anhydride, etc. The first tetracarboxylic dianhydride may be used alone or in combination.

[0029] Examples of the first diamine having a flexible skeleton include 1,3-bis(3-aminophenoxy)benzene, 2,2'-bis(4-(4-aminophenoxy)phenyl)propane, 4,4'-bis(3-aminophenoxy)biphenyl, and bis(4-(3-aminophenoxy)phenyl)sulfone. These may be used alone or in combination.

[0030] Polymerization of the first tetracarboxylic dianhydride and the first diamine yields a soluble polyimide having a terminal amine or a terminal acid anhydride. Here, "soluble polyimide" refers to a polyimide that is soluble in an organic solvent. In the present invention, a polyimide that dissolves in an amide-based solvent, specifically, a polyimide that dissolves in N-methyl-2-pyrrolidone at room temperature (25°C) at a concentration of 10% by weight or more, is referred to as a "soluble polyimide."

[0031] Whether the soluble polyimide has an amine or acid anhydride terminal is determined by the molar ratio of the first tetracarboxylic dianhydride to the first diamine used in the polymerization. When the polymerization is performed under conditions in which the first diamine is present in excess of the first tetracarboxylic dianhydride, the soluble polyimide will mainly have amine terminals, whereas when the polymerization is performed under conditions in which the first tetracarboxylic dianhydride is present in excess of the first diamine, the soluble polyimide will mainly have acid anhydride terminals.

[0032] From the viewpoint of imparting high toughness and thermocompression-bondable adhesiveness to a cured film obtained by curing a composition containing a polyimide precursor, the Tg of the soluble polyimide is preferably 300°C or less, more preferably 250°C or less, and even more preferably 200°C or less.

[0033] When polymerizing an amine-terminated soluble polyimide, the molar ratio of the first tetracarboxylic dianhydride to the first diamine (first tetracarboxylic dianhydride / first diamine) is, for example, about 1.00 / 1.01 to 1.00 / 1.20. When polymerizing an acid anhydride-terminated soluble polyimide, the ratio of the acid anhydride to the diamine may be reversed, for example, so that the molar ratio (first tetracarboxylic dianhydride / first diamine) is about 1.01 / 1.00 to 1.20 / 1.00.

[0034] (Compounds Having a Rigid Skeleton: Second Tetracarboxylic Acid Dianhydride, Second Diamine) The second tetracarboxylic acid dianhydride having a rigid skeleton is a compound represented by the following formula (3). The second diamine having a rigid skeleton is a compound represented by the following formula (4). Hereinafter, these will be collectively referred to as compounds having a rigid skeleton where appropriate. (R in formulas (3) and (4) 3 and R 4 are each an organic group having a rigid skeleton and having 1 to 100 carbon atoms.

[0035] Examples of compounds having a rigid skeleton include compounds having one aromatic ring and compounds having two or more aromatic rings that are not linked by an ether bond. Examples of aromatic rings include benzene rings, biphenyl rings, and naphthalene rings, which may have a substituent.

[0036] A compound obtained by polymerizing a compound having a rigid skeleton has a high glass transition temperature. Because the second tetracarboxylic dianhydride and the second diamine have rigid skeletons, a polyimide obtained by polymerizing them has a higher glass transition temperature (Tg) than a soluble polyimide.

[0037] From the viewpoint of increasing the heat resistance (dimensional stability) of a cured film (cured product) obtained by curing a composition containing a polyimide precursor, the second tetracarboxylic dianhydride and the second diamine are polymerized to give a polyimide having a Tg of preferably 350°C or higher, more preferably 400°C or higher, and even more preferably 500°C or higher.

[0038] Examples of the second tetracarboxylic dianhydride include pyromellitic anhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, etc. These may be used alone or in combination.

[0039] Examples of the second diamine include p-phenylenediamine, 4,4'-diaminobenzanilide, 5-amino-2-(4-aminophenyl)benzimidazole, 2,2'-bis(trifluoromethyl)benzidine and 2,2'-dimethylbenzidine, 2,5-diaminotoluene, 2,5-diamino-p-xylene, 4,4'-diaminoazobenzene, etc. These may be used alone or in combination.

[0040] By changing the ratio of the compound having a flexible skeleton used in the synthesis of the soluble polyimide to the compound having a rigid skeleton used in the polymerization in the presence of the soluble polyimide, it is possible to adjust the properties of the cured product obtained by curing the polyimide precursor.

[0041] From the viewpoint of providing a cured product obtained by curing the polyimide precursor with a low CTE, high toughness, and high adhesiveness, the weight ratio of the compound having a flexible skeleton to the compound having a rigid skeleton (compound having a flexible skeleton / compound having a rigid skeleton) is preferably 3 / 7 or more and 7 / 3 or less, more preferably 4 / 6 or more and 6 / 4 or less, and even more preferably 9 / 11 or more and 11 / 9 or less.

[0042] The weight average molecular weight of the polyimide precursor is not particularly limited, as it varies depending on the raw materials used and polymerization conditions. However, from the viewpoint of realizing a low CTE, high toughness, and adhesiveness, it is preferably 30,000 to 200,000, more preferably 50,000 to 150,000, and even more preferably 60,000 to 140,000.

[0043] (Thermosetting Resin Composition) The thermosetting resin composition of the present invention contains the above-mentioned polyimide precursor and a solvent that dissolves the polyimide precursor. The solvent may be any solvent that can dissolve the polyimide precursor, and specific examples include N-methyl-2-pyrrolidone and 3-methoxy-N,N-dimethylpropanamide. The solvent may be used alone or in combination.

[0044] (Solid Content Concentration) The solid content concentration (content of polyimide precursor) in the thermosetting resin composition of the present invention is not particularly limited, but is preferably 10 to 30 wt % in the thermosetting resin composition. In the present invention, the solid content refers to components that constitute a cured product when heated and cured.

[0045] (Additives) The thermosetting resin composition may contain additives as long as they do not interfere with the object of the invention. The additives may be selected according to the desired properties, and examples thereof include epoxy resins, acrylic resins, surfactants, antistatic agents, coupling agents, epoxy curing agents, pH adjusters, rust inhibitors, preservatives, antifungal agents, antioxidants, antireducing agents, evaporation accelerators, chelating agents, water-soluble polymers, pigments, and dyes.

[0046] (Cured film, substrate, electronic component) The thermosetting resin composition of the present invention is applied to the surface of a substrate and heated on a hot plate, in an oven, or the like, to obtain a cured film as a cured product of the thermosetting resin composition over the entire surface or in a predetermined pattern (e.g., line-like).

[0047] The method for applying the thermosetting resin composition to the surface of the substrate is not particularly limited, and examples thereof include spin coating, inkjet printing, etc. The means for forming a cured film, which is a film of the cured product, is not limited to heat treatment, and may also be UV treatment, treatment using an ion beam, an electron beam, or gamma rays, etc.

[0048] By using the thermosetting resin composition of the present invention, it is possible to provide a substrate having a cured film of polyimide that has a low thermal expansion coefficient and high toughness and adhesiveness, and an electronic component that includes the cured film or the substrate and whose performance can be improved by miniaturization.

[0049] (Production Method) The present invention can also be practiced as a method for producing a polyimide precursor, comprising: a soluble polyimidization step of polymerizing a first tetracarboxylic dianhydride having a flexible skeleton with a first diamine having a flexible skeleton to form a soluble polyimide having a terminal amine or a terminal acid anhydride; and a block copolymerization step of polymerizing a second tetracarboxylic dianhydride having a rigid skeleton with a second diamine having a rigid skeleton in the presence of the soluble polyimide to form a soluble polyimide / polyamic acid copolymer.

[0050] The soluble polyimide formation step is a step of thermally imidizing a first tetracarboxylic dianhydride and a first diamine, both of which have flexible backbones, to form a soluble polyimide. From the viewpoint of efficiently proceeding with the thermal imidization, the soluble polyimide formation step is preferably performed such that the total concentration of the first tetracarboxylic dianhydride and the first diamine in the solvent is about 20 to 40 wt %.

[0051] The temperature in the soluble polyimidization step may be any temperature at which thermal imidization proceeds, but is preferably 120 to 200°C, and more preferably 140 to 170°C, for example.

[0052] The block copolymerization step is a step of polymerizing a second tetracarboxylic dianhydride and a second diamine in the presence of the soluble polyimide having a terminal amine or a terminal acid anhydride obtained in the soluble polyimidization step, which can produce a copolymer having high toughness and adhesiveness due to its flexible skeleton while maintaining the characteristics of a polyimide having a rigid skeleton.

[0053] In the block copolymerization step, it is preferable to dilute the soluble polyimide obtained in the soluble polyimidization step with a solvent, and then add the second tetracarboxylic dianhydride and the second diamine.

[0054] For example, after diluting with a solvent so that the total concentration of the first tetracarboxylic dianhydride and the first diamine is about 5 to 15% by weight, the second tetracarboxylic dianhydride and the second diamine are added to adjust the total solid concentration to about 10 to 20% by weight, and then the block copolymerization step is carried out.

[0055] The block copolymerization step is carried out at a temperature at which the copolymerization reaction proceeds after the soluble polyimide is cooled. For example, after the soluble polyimide is cooled, a second tetracarboxylic dianhydride and a second diamine are added, and the mixture is heated to 20°C to 70°C. By carrying out the block copolymerization step at a temperature lower than that of the soluble polyimide formation step, it is possible to prevent an amide exchange reaction of the polyamic acid moiety synthesized by the second tetracarboxylic dianhydride and the second diamine, and to obtain a polyimide / polyamic acid copolymer.

[0056] EXAMPLES The present invention will be described below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0057] The names of the compounds used in the examples and comparative examples are shown by abbreviations. These abbreviations will be used in the following description. Compound (1): First tetracarboxylic dianhydride having a flexible backbone ODPA: 4,4'-oxydiphthalic anhydride HQDA: 4,4'-(1,4-phenylenedioxy)bisphthalic anhydride Compound (2): First diamine having a flexible backbone TPE-M: 1,3-bis(3-aminophenoxy)benzene BAPP: 2,2'-bis(4-(4-aminophenoxy)phenyl)propane mBAPB: 4,4'-bis(3-aminophenoxy)biphenyl BAPS-M: bis(4-(3-aminophenoxy)phenyl)sulfone

[0058] Compound (3): Second tetracarboxylic dianhydride having a rigid skeleton PMDA: Pyromellitic anhydride Compound (4): Second diamine having a rigid skeleton DABA: 4,4'-diaminobenzanilide DAPBI: 5-amino-2-(4-aminophenyl)benzimidazole TFMB: 2,2'-bis(trifluoromethyl)benzidine m-TB: 2,2'-dimethylbenzidine PDA: p-phenylenediamine

[0059] Reaction solvent NMP: N-methyl-2-pyrrolidone

[0060] The structures of compounds (1) to (4) used in this example are shown below.

[0061] Example 1: Synthesis of Polymer (A1) A 200 ml three-neck flask was equipped with a condenser (Dimroth condenser), a nitrogen inlet tube, and a thermometer, and nitrogen was introduced. Compound (2) TPE-M (3.1097 g) and 16 wt % (11.0789 g) of the NMP listed in Table 1 were mixed and stirred and dissolved at room temperature using a magnetic stirrer. Compound (1) ODPA (3.0000 g) was then added and polymerized at room temperature for 0.5 hours. A recovery flask was then attached between the flask and the Dimroth condenser via a Tripod, and the mixture was stirred at 155°C for 3.5 hours to thermally imidize the mixture, yielding a soluble polyimide with a terminal amine. Water generated during the imidization was recovered in the recovery flask. The remaining NMP (58.1644 g) was then added and cooled to around 50°C. Compound (3) PMDA was then added, followed by compound (4) DABA, and the mixture was stirred. The mixture was stirred for 3 hours while being heated to 65° C. to obtain a polymer solution, the weight average molecular weight (Mw) of which was measured by GPC and found to be 75,000.

[0062] The weight average molecular weight was measured by diluting the polymer with dimethylformamide (containing phosphoric acid) to a polymer concentration of approximately 1% by weight, using GPC (JASCO GULLIVER 1500, manufactured by JASCO Corporation; intelligent differential refractometer RI-1530), and calculated in terms of polystyrene. Four columns manufactured by Tosoh Corporation, G4000HXL, G3000HXL, G2500HXL, and G2000HXL, were connected in series in this order and used, and the measurement was performed under the conditions of a column temperature of 40°C and a flow rate of 1.0 ml / min.

[0063] [Examples 2 to 11] Synthesis of polymers (A2) to (A11) Polymerization was carried out under the same conditions as in Example 1, except that the raw materials were charged as shown in Tables 1 and 2. The weight average molecular weight of each component is also shown in each table. The numerical values ​​for each component in Tables 1 and 2 indicate the respective amounts (g) used. The solid content concentrations are the concentrations of compounds (1) to (4) in each synthesis example.

[0064]

[0065]

[0066] Comparative Example 1: Synthesis of Polymer (R1) A 200 ml three-neck flask was equipped with a condenser (Dimroth condenser), a nitrogen inlet tube, and a thermometer, and nitrogen was introduced. Compound (4) DABA and NMP were mixed in the amounts shown in Table 3, and compound (3) PMDA was added and stirred at room temperature for 4 hours. The weight average molecular weight measured by GPC was 27,000.

[0067] Comparative Example 2: Synthesis of Polymer (R2) A 200 ml three-neck flask was equipped with a condenser (Dimroth condenser), a nitrogen inlet tube, and a thermometer, and nitrogen was introduced. Compound (2) TPE-M and NMP were mixed in the amounts shown in Table 3, and the mixture was stirred and dissolved at room temperature using a magnetic stirrer. Compound (1) ODPA was added in the amount shown in Table 3, and polymerization was carried out at room temperature for 0.5 hours. A recovery flask was then attached between the flask and the Dimroth condenser via a T-junction tube, and the mixture was stirred at 155°C for 3.5 hours to perform thermal imidization, yielding a soluble polyimide. Water generated during imidization was collected in the recovery flask. The weight-average molecular weight measured by GPC was 37,000.

[0068] Comparative Example 3 Synthesis of Polymer (R3) A 200 ml three-neck flask was equipped with a condenser (Dimroth condenser), a nitrogen inlet tube, and a thermometer, and nitrogen was introduced. Compound (2) TPE-M, compound (4) DABA, and NMP were mixed in the amounts shown in Table 3, followed by addition of compound (1) ODPA and compound (3) PMDA, followed by stirring at room temperature for 4 hours. The weight-average molecular weight measured by GPC was 78,000.

[0069] [Comparative Example 4] Synthesis of Polymer (R4) A 200 ml three-neck flask was equipped with a condenser (Dimroth condenser), a nitrogen inlet tube, and a thermometer, and nitrogen was introduced. Compound (2) TPE-M (3.1097 g) and 16 wt % NMP were mixed and stirred and dissolved at room temperature using a magnetic stirrer. Compound (1) ODPA (3.0000 g) was then added and polymerized at room temperature for 3.5 hours. Subsequently, 34.6217 g of NMP was added, followed by 3.0997 g of compound (3) PMDA and 3.0100 g of compound (4) DABA, followed by stirring and polymerization. The mixture was heated to 65°C and stirred for 3 hours, yielding a blocked polyamic acid polymerization solution. The weight average molecular weight measured by GPC was 86,000.

[0070] Comparative Example 5: Synthesis of Polymer (R5) A 200 ml three-neck flask was equipped with a condenser (Dimroth condenser), a nitrogen inlet tube, and a thermometer, and nitrogen was introduced. Compound (2) TPE-M (3.1097 g) and 16 wt % NMP were mixed and stirred and dissolved at room temperature using a magnetic stirrer. Compound (1) ODPA (3.0000 g) was then added and polymerized at room temperature for 0.5 hours. A round-bottom flask was then attached between the flask and the Dimroth condenser via a Tripod, and the mixture was stirred at 155°C for 3.5 hours to thermally imidize the mixture, yielding a soluble polyimide with a terminal amine (R4a). Water generated during imidization was collected in the round-bottom flask. In a separate flask, 3.0997 g of compound (3) PMDA and 34.6217 g of NMP were mixed, followed by addition of 3.0100 g of compound (4) DABA, followed by stirring. The mixture was heated to 65°C and stirred for 3 hours to obtain an acid anhydride-terminated polyamic acid polymerization solution (R4b). Finally, R4b was added to the flask containing R4a, and the remaining 23.28 g of NMP was used to wash the flask containing R4b. This was then added to the flask containing R4a and stirred at room temperature for 3 hours. The weight average molecular weight measured by GPC was 70,000.

[0071] The amounts (g) of each component in the comparative examples are shown in Table 3.

[0072] [Example 1H] The polymer (A1), which is a polyimide precursor synthesized in Example 1, was used as it was as a thermosetting resin composition (A1), and the following evaluations of the coefficient of thermal expansion (CTE), 5% weight loss temperature (Td5), elongation at break, and peel adhesive strength were carried out.

[0073] [Evaluation of Coefficient of Thermal Expansion (CTE)] Aluminum foil was attached to a 10 cm square glass substrate (0.7 mm thick), and the thermosetting resin composition (A1) was solvent-cast onto it. The film was dried on a hot plate at 80°C for 1.0 hour, then heat-treated stepwise at 130°C for 0.5 hour and 175°C for 0.5 hour, and finally heat-treated in an oven at 350°C for 1.0 hour. The aluminum was removed from the aluminum foil by hydrochloric acid etching (2N hydrochloric acid, room temperature for 0.75 hour), yielding a single film as a cured film. The CTE was measured using a TMA device (TMA7100 manufactured by Hitachi High-Tech Corporation). The temperature range was 30°C to 400°C, and the heating rate was 10°C / min. The CTE value was the value from the second measurement (2nd-Run). The average value before the glass transition point (Tg) was defined as CTE (<Tg), and the average value after Tg was defined as CTE (>Tg). The change in CTE before and after Tg was expressed as ΔCTE. A CTE lower than 20 ppm / K is considered good, and a ΔCTE within ±1 ppm / K is considered good.

[0074] [Evaluation of Heat Resistance (Td5)] Heat resistance was evaluated based on the 5% weight loss temperature. The prepared cured film (A1) was cut into several mm squares and packed into an aluminum pan so that each piece weighed approximately 10 mg. Using a TG-DTA device (STA7200 manufactured by Hitachi High-Tech Corporation), weight change was measured in an air atmosphere at a temperature range of 30°C to 580°C, at a heating rate of 10°C / min. Heat resistance (Td5) was evaluated based on the measurement results, and a temperature of 500°C or higher was rated as good (◎).

[0075] [Evaluation of Breaking Elongation] Breaking elongation was evaluated by a tensile test. The prepared cured film (A1) was cut into 40 x 5 mm strips, and the SS curve of the film was measured using a tensile tester (EZ-Graph manufactured by Shimadzu Corporation). The temperature was room temperature (25°C) and the tensile speed was 50 mm / min. A breaking elongation (εb) of 50% or more was evaluated as good (◎), 30%≦εb<50% was evaluated as fair (○), and εb<30% was evaluated as poor (×).

[0076] [Evaluation of Peel Adhesion Strength] Peel adhesion strength was evaluated using a tensile tester. A 0.2 mm thick aluminum substrate was surface-treated with a 0.4 wt % NaOH aqueous solution at room temperature for 2.5 minutes, then washed with ultrapure water and dried. The thermosetting resin composition (A1) was solvent-cast onto the surface-treated aluminum substrate, dried on a hot plate at 80°C for 1.0 hour, then heat-treated stepwise at 130°C for 0.5 hours, 175°C for 0.5 hours, and finally heat-treated in an oven at 230°C for 1.0 hour. The resulting polyimide film-coated aluminum substrate, i.e., a substrate having a cured film, was cut into 50 x 3 mm strips and thermocompressed to similarly surface-treated 40 x 20 mm strip-shaped aluminum substrates (350°C for 1.0 hour, 0.3 MPa). A 180° peel test was performed using the prepared thermocompression-bonded sample (EZ-Graph, manufactured by Shimadzu Corporation). The temperature was room temperature (25°C) and the pulling speed was 50 mm / min. A peel adhesive strength of 50 N / 25 mm or more is considered to be satisfactory.

[0077] [Examples 2H to 11H] The polymers (A2) to (A11) obtained in Examples 2 to 11 were used as they were as thermosetting resin compositions (A2) to (A11), and evaluations were carried out under the same conditions as in Example 1H.

[0078] [Comparative Examples 1H to 5H] The polymers (R1) to (R5) obtained in Comparative Examples 1 to 5 were used as they were as thermosetting resin compositions (R1) to (R5), and evaluation was carried out under the same conditions as in Example 1H.

[0079] Tables 4 to 6 summarize the results of Examples 1H to 11H and Comparative Examples 1H to 5H.

[0080]

[0081]

[0082] The cured films obtained by curing the thermosetting resin compositions of Examples 1H to 11H exhibited glass transition temperatures of around 200°C, which were derived from the segments consisting of compounds (1) and (2) with flexible skeletons, and therefore had good thermocompression bondability. On the other hand, despite the presence of a glass transition point, they exhibited peculiar behavior in which the CTE hardly changed before and after the glass transition point, and also showed low CTE values ​​comparable to those of metals.

[0083] On the other hand, the cured film obtained by curing the thermosetting resin composition of Comparative Example 1H (R1), which used only compounds (3) and (4) with rigid skeletons, had significantly low breaking elongation and peel adhesive strength. The cured film obtained by curing the thermosetting resin composition of Comparative Example 2H (R2), which used only compounds (1) and (2) with flexible skeletons, had a significantly high CTE, and the CTE changed significantly around the Tg.

[0084] In the thermosetting resin composition of Comparative Example 3H (R3), which is a cured film obtained by randomly copolymerizing compounds (3) and (4) having rigid skeletons with compounds (1) and (2) having flexible skeletons, despite the copolymerization of components having rigid skeletons, the CTE of the cured film was high, and further, the CTE changed significantly around the Tg, and the peel adhesion strength was insufficient. Thus, random copolymerization of low-CTE polyimide with flexible polyimide resulted in an increase in CTE. This is thought to be because the low CTE of polyimide is due to the high degree of planar orientation of the highly planar rigid skeleton, and the flexible component introduced by random copolymerization interferes with the planar orientation of the rigid skeleton, resulting in an increase in CTE even when the rigid structure is contained to a certain extent. Furthermore, because random copolymerization with the flexible component also lowers the Tg, there is also the problem that the CTE increases above the Tg, narrowing the temperature range in which the CTE can be maintained low.

[0085] The cured film obtained by curing the thermosetting resin composition of Comparative Example 4H (R4), which was a blocked polyamic acid, had a high CTE despite being blocked, and the difference in CTE before and after Tg was particularly large. This result is thought to be due to the fact that blocks with rigid skeletons were converted to random copolymers by amide exchange reactions during the heat treatment process. The cured film obtained by curing the thermosetting resin composition of Comparative Example 5H (R5), in which polymers were mixed and polymerized, had a CTE higher than the target, and the CTE changed before and after Tg, and the peel adhesion strength was also insufficient.

[0086] In contrast, the thermosetting resin compositions containing the polyimide precursors of Examples 1H to 11H (A1 to A11) obtained by polymerizing a second tetracarboxylic dianhydride (compound (3)) having a rigid skeleton and a second diamine (compound (4)) having a rigid skeleton in the presence of a terminal amine-soluble polyimide obtained by polymerizing a first tetracarboxylic dianhydride (compound (1)) having a flexible skeleton and a first diamine (compound (2)) having a flexible skeleton all satisfied the requirements of low thermal expansion coefficient (low CTE), high toughness and adhesiveness, and furthermore, despite having a glass transition point (Tg) at a relatively low temperature, the change in the thermal expansion coefficient before and after the glass transition point was suppressed, and cured products with excellent features were obtained.

[0087] The polyimide precursor of the present invention is used, for example, in thermosetting resin compositions for semiconductor devices, cured films, substrates, electronic components including such substrates, and the like.

Claims

1. A polyimide precursor characterized by being obtained by polymerizing a second tetracarboxylic dianhydride having a rigid skeleton and a second diamine having a rigid skeleton in the presence of a soluble polyimide of a terminal amine or terminal acid anhydride obtained by polymerizing a first tetracarboxylic dianhydride having a flexible skeleton and a first diamine having a flexible skeleton.

2. The polyimide precursor according to claim 1, wherein the rigid backbone comprises one aromatic ring or two or more aromatic rings not linked by ether bonds, and the flexible backbone comprises two or more aromatic rings linked by ether bonds.

3. The polyimide precursor according to claim 2, wherein the second tetracarboxylic dianhydride is pyromellitic anhydride, and the second diamine is one or more selected from the group consisting of p-phenylenediamine, 4,4'-diaminobenzanilide, 5-amino-2-(4-aminophenyl)benzimidazole, 2,2'-bis(trifluoromethyl)benzidine, and 2,2'-dimethylbenzidine.

4. The polyimide precursor according to claim 3, wherein the first tetracarboxylic dianhydride is one or more selected from the group consisting of 4,4'-oxydiphthalic anhydride and 4,4'-(1,4-phenylenedioxy)bisphthalic anhydride, and the first diamine is one or more selected from the group consisting of 1,3-bis(3-aminophenoxy)benzene, 2,2'-bis(4-(4-aminophenoxy)phenyl)propane, 4,4'-bis(3-aminophenoxy)biphenyl, and bis(4-(3-aminophenoxy)phenyl)sulfone.

5. A thermosetting resin composition comprising the polyimide precursor according to claim 1.

6. The thermosetting resin composition according to claim 5, wherein the content of the polyimide precursor is 10% by weight or more and 30% by weight or less.

7. A cured film obtained by curing the thermosetting resin composition according to claim 5.

8. A substrate having the cured film according to claim 7.

9. An electronic component comprising the cured film according to claim 7 or the substrate according to claim 8.

10. A method for producing a polyimide precursor according to claim 1, characterized in that a first tetracarboxylic dianhydride having a flexible skeleton and a first diamine having a flexible skeleton are polymerized to form a soluble polyimide having a terminal amine or a terminal acid anhydride, and in the presence of the soluble polyimide, a second tetracarboxylic dianhydride having a rigid skeleton and a second diamine having a rigid skeleton are polymerized.

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