Underfill material, semiconductor package, and semiconductor package production method

Abstract

This underfill material comprises an epoxy resin, a rubber component, and a filler, wherein: the epoxy resin contains an epoxy compound having two epoxy groups in one molecule, having a molecular weight of 650 or less, and having no ring structure other than the epoxy groups; the rubber component contains core-shell type rubber particles having a core part and a shell part; the core part contains a crosslinked polysiloxane; the shell part contains a constituent unit in which a carbon-carbon double bond of glycidyl methacrylate is cleaved; and the filler contains sol-gel silica.

Description

Underfill material, semiconductor package, and method of manufacturing semiconductor package

[0001] The present invention relates to an underfill material, a semiconductor package, and a method for manufacturing the semiconductor package.

[0002] In semiconductor device packaging technology, a liquid curable resin composition called an underfill material is widely used to fill the gap between a substrate and a semiconductor element. Underfill materials can cause residual stress within the cured product due to shrinkage during curing, heating during reflow, and other factors, which can lead to peeling, cracks, and other problems. One known method for alleviating the stress generated in the cured product is to add a rubber component containing core-shell rubber particles to the underfill material to reduce the elastic modulus of the cured product (see, for example, Patent Document 1).

[0003] International Publication No. 2011 / 013326

[0004] In the manufacturing process of semiconductor packages, liquid curable resin compositions known as underfill materials are widely used to fill the gap between the substrate and the semiconductor element. In recent years, as semiconductor packages have become more complex, the gaps to be filled with underfill materials have become increasingly narrow. Therefore, the application of sol-gel silica has been investigated. Sol-gel silica is characterized by its monodispersity and small particle size, making it promising for use in narrow gaps. However, it is known that the addition of sol-gel silica increases the viscosity of underfill materials compared to silica synthesized by conventional methods such as deflagration. Increased viscosity can lead to reduced filling of narrow gaps, resulting in unfilled gaps and significantly longer gap filling times.

[0005] For example, one approach is to adjust the composition of the liquid resin composition to reduce its viscosity. However, increasing the amount of low-viscosity components in the liquid resin composition may result in a decrease in physical properties such as glass transition temperature and fracture toughness when the liquid resin composition is cured. Therefore, an underfill material that maintains fluidity before curing while exhibiting excellent physical properties after curing is desirable.

[0006] The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide an underfill material that maintains fluidity before curing and has excellent physical properties after curing, as well as a semiconductor package obtained using this underfill material and a method for manufacturing the same.

[0007] Means for solving the above problems include the following embodiments. <1> An underfill material comprising an epoxy resin, a rubber component, and a filler, wherein the epoxy resin comprises an epoxy compound having two epoxy groups per molecule, a molecular weight of 650 or less, and containing no ring structures other than the epoxy groups, the rubber component comprises core-shell rubber particles having a core portion containing crosslinked polysiloxane and a shell portion containing a structural unit formed by cleavage of a carbon-carbon double bond of glycidyl methacrylate, and the filler contains sol-gel silica. <2> An underfill material according to <1>, wherein the epoxy compound comprises a compound represented by the following general formula (1):

[0008]

[0009] [In general formula (1), R is a divalent group not containing a ring structure.] <3> The underfill material according to <1> or <2>, wherein the volume average particle diameter of the core-shell rubber particles measured by laser scattering diffraction is 0.05 μm to 1.0 μm. <4> The underfill material according to any one of <1> to <3>, wherein the content of the rubber component is 0.1 parts by mass to 15 parts by mass per 100 parts by mass of the epoxy resin. <5> The underfill material according to any one of <1> to <4>, wherein the content of the filler is 50% by mass or more of the entire underfill material. <6> The underfill material according to any one of <1> to <5>, wherein the viscosity at 110°C measured using a rheometer under conditions of 40 mm parallel plates and a shear rate of 32.5 (1 / s) is 0.2 Pa s or less. <7> A semiconductor package comprising a substrate, a semiconductor element disposed on the substrate, and a cured product of the underfill material according to any one of <1> to <6> that seals the semiconductor element. <8> A method for manufacturing a semiconductor package, comprising: a step of filling a gap between the substrate and the semiconductor element disposed on the substrate with the underfill material according to any one of <1> to <6>; and a step of curing the underfill material.

[0010] According to the present invention, there are provided an underfill material that maintains fluidity before curing and has excellent physical properties after curing, as well as a semiconductor package obtained using this underfill material and a method for producing the same.

[0011] Hereinafter, embodiments for carrying out the present invention will be described in detail. However, the present invention is not limited to the following embodiments. In the following embodiments, components (including element steps, etc.) are not essential unless otherwise specified. The same applies to numerical values ​​and their ranges, and do not limit the present invention.

[0012] In the present disclosure, the term "process" includes not only processes that are independent of other processes, but also processes that cannot be clearly distinguished from other processes as long as the purpose of the process is achieved. In the present disclosure, numerical ranges indicated using "to" include the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In numerical ranges described in stages in the present disclosure, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another staged numerical range. Furthermore, in numerical ranges described in the present disclosure, the upper or lower limit value of that numerical range may be replaced with a value shown in the examples. In the present disclosure, each component may contain multiple corresponding substances. When multiple substances corresponding to each component are present in the composition, the content or amount of each component means the total content or amount of the multiple substances present in the composition, unless otherwise specified. In the present disclosure, each component may contain multiple types of particles. When multiple types of particles corresponding to each component are present in the composition, the particle size of each component means the value for a mixture of the multiple types of particles present in the composition, unless otherwise specified. In the present disclosure, "(meth)acrylic" means at least one of acrylic and methacrylic, "(meth)acrylate" means at least one of acrylate and methacrylate, "(meth)acryloyl" means at least one of acryloyl and methacryloyl, and "(meth)acryloxy" means at least one of acryloxy and methacryloxy.

[0013] <Underfill Material> The underfill material of the present disclosure is an underfill material that includes an epoxy resin, a rubber component, and a filler, wherein the epoxy resin includes an epoxy compound that has two epoxy groups in one molecule, a molecular weight of 650 or less, and does not include any ring structure other than the epoxy groups, the rubber component includes core-shell rubber particles that have a core portion including crosslinked polysiloxane and a shell portion including a structural unit formed by cleavage of a carbon-carbon double bond of glycidyl methacrylate, and the filler includes sol-gel silica.

[0014] The underfill material contains a rubber component containing the aforementioned core-shell rubber particles. This reduces the elastic modulus after curing, provides excellent stress relaxation in the cured product, and provides excellent physical properties such as glass transition temperature and fracture toughness when cured. The underfill material also contains a specific epoxy compound as an epoxy resin. This reduces the viscosity of the underfill material, ensuring good flowability. Furthermore, by reducing the viscosity of the underfill material, even when the filler content is increased, the viscosity increase is suppressed, maintaining excellent flowability. In other words, compared to underfill materials that do not contain the specific epoxy compound, the amount of filler can be changed without impairing the pre-cure flowability, allowing the post-cure thermal expansion coefficient to be adjusted to a desired value. Furthermore, from the perspective of improving gap narrowing, when a filler containing sol-gel silica is used, viscosity increase is likely to occur. Even in such cases, viscosity increase is suppressed, ensuring flowability.

[0015] (Rubber Component) The rubber component contained in the underfill material includes core-shell rubber particles having a core containing crosslinked polysiloxane and a shell containing structural units formed by cleavage of the carbon-carbon double bond of glycidyl methacrylate. The shell of the core-shell rubber particles may cover at least a portion of the core, or may cover the entire core.

[0016] The proportion of the shell portion in the core-shell rubber particles is preferably as small as possible so that the core portion can be covered with the shell portion. From this viewpoint, the mass ratio of the core portion to the shell portion (core portion:shell portion) in the core-shell rubber particles is preferably in the range of 1:1 to 5:1.

[0017] In the core-shell type rubber particles, the polysiloxane contained in the core part is not particularly limited. For example, polyalkylhydrogensiloxane, polydialkylsiloxane, polyarylhydrogensiloxane, polydiarylsiloxane, polyalkylarylsiloxane, and copolymers thereof can be mentioned. Among them, the linear polysiloxane preferably contains polydialkylsiloxane, and polydiC １－５It is more preferable that the composition contains an alkylsiloxane, and even more preferable that the composition contains a polydimethylsiloxane.

[0018] The polysiloxane of the core part has a crosslinked structure. It is believed that the crosslinked structure of the polysiloxane results in the formation of a low-elasticity core part, which makes it easier to relieve stress during thermal cycling. The polysiloxane having a crosslinked structure is a siloxane component that forms a linear polysiloxane, i.e., [RR'SiO ２／２ The crosslinking component is formed from a difunctional siloxane component having a [RSiO] unit and a crosslinking component. ３／２ ]) and a trifunctional siloxane component having a tetrafunctional siloxane unit ([SiO ４／２ It is preferable to use at least one selected from the group consisting of tetrafunctional siloxane components having the formula [RR'SiO ２／２ ] and [RSiO ３／２ In the formula (I), R and R' each independently represent a monovalent organic group, and are preferably hydrogen, an alkyl group, or an aryl group, more preferably an alkyl group having 1 to 5 carbon atoms, and even more preferably a methyl group. In the present disclosure, the siloxane component refers to a siloxane unit that forms a polysiloxane.

[0019] The proportion of crosslinking components in all siloxane components constituting the polysiloxane is not particularly limited. By adjusting this proportion, the hardness of the core portion can be adjusted. The proportion is preferably 0.5 mol% to 20 mol%, and more preferably 2 mol% to 10 mol%. When the proportion is 0.5 mol% or more, unreacted siloxane components tend to be suppressed. When the proportion is 20 mol% or less, the elastic modulus decreases, and stress during thermal cycling of the cured product tends to be efficiently reduced. Furthermore, the proportion of trifunctional siloxane components in all siloxane components constituting the polysiloxane is preferably 2 mol% to 10 mol%, and the proportion of tetrafunctional siloxane components is preferably 2 mol% to 10 mol%.

[0020] The polysiloxane preferably has a substituent having an ethylenic double bond in a portion thereof. As a result, for example, when the polysiloxane of the core portion is polymerized and then the shell portion is formed, the ethylenic double bond contained in the core portion and the polymer constituting the shell portion are grafted by vinyl polymerization, and the core portion and the shell portion can be firmly bonded. Examples of the substituent having an ethylenic double bond include a vinyl group, an allyl group, a (meth)acryloyl group, a (meth)acryloxy group, and an alkyl group having these substituents at its terminal.

[0021] When the polysiloxane partially contains a substituent having an ethylenic double bond, the proportion of the siloxane component having the substituent having an ethylenic double bond is preferably 1 mol % to 10 mol % of the total siloxane components. When this proportion is 1 mol % or more, the effect of grafting tends to be sufficient, and when it is 10 mol % or less, the deterioration of physical properties such as the heat resistance and elastic modulus of the core due to the influence of grafting tends to be suppressed.

[0022] From the viewpoint of the effect of reducing the elastic modulus and fluidity, the proportion of polysiloxane contained in the core portion is preferably 50% by mass to 70% by mass, and more preferably 60% by mass to 70% by mass, based on the total mass of the core portion and the shell portion.

[0023] The shell portion is only required to contain a structural unit (also referred to as a specific structural unit) in which the carbon-carbon double bond of glycidyl methacrylate is cleaved, and may contain a polymer containing the specific structural unit.

[0024] The polymer contained in the shell portion may have an epoxy group in part of its side chain, and the epoxy group may be contained in a specific structural unit. When the polymer contained in the shell portion has an epoxy group in part of its side chain, compatibility with the epoxy resin in the composition improves, and the fracture toughness and adhesiveness after curing, as well as the pot life, tend to be excellent.

[0025] When the polymer contained in the shell portion has an epoxy group in part of its side chain, the proportion of the structural unit (preferably the specific structural unit) having an epoxy group in all structural units of the polymer is not particularly limited, but is preferably 10% by mass or more, more preferably 20% by mass or more, even more preferably 25% by mass or more, and particularly preferably 30% by mass or more. From the viewpoint of reducing the elastic modulus and fluidity, the proportion is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 35% by mass or less.

[0026] The polymer contained in the shell portion may contain structural units other than the specific structural units (also referred to as other structural units). The other structural units may be structural units obtained by cleavage of the carbon-carbon double bond of a (meth)acrylic monomer having an epoxy group in part of the side chain other than glycidyl methacrylate, or structural units obtained by cleavage of the carbon-carbon double bond of a (meth)acrylic monomer such as (meth)acrylic acid or a (meth)acrylic acid ester.

[0027] Examples of (meth)acrylic monomers having an epoxy group in part of the side chain other than glycidyl methacrylate include glycidyl acrylate, 4-hydroxybutyl (meth)acrylate glycidyl ether, and glycidyl methyl (meth)acrylate.

[0028] The amount of rubber component contained in the underfill material is not particularly limited. From the viewpoint of the balance between the low elasticity of the cured product and other properties, the amount of rubber component is preferably 0.1 to 15 parts by mass, more preferably 1 to 15 parts by mass, even more preferably 3 to 15 parts by mass, and particularly preferably 3 to 10 parts by mass, per 100 parts by mass of epoxy resin.

[0029] Furthermore, it has been found that the use of the aforementioned core-shell rubber particles among rubber components can improve the high-temperature resistance of underfill materials. In recent years, there has been an increasing demand for underfill materials compatible with automotive semiconductor devices. Generally, when an underfill material is used to seal the gap between a semiconductor element and a wiring board, a fillet is formed on the side of the semiconductor element to protect the semiconductor element. However, thermal stress caused by the difference in thermal expansion between the wiring board and the semiconductor element can cause cracks in the fillet or damage to the semiconductor element. Furthermore, depending on the underfill material selected, repeated thermal shocks, such as those caused by temperature cycles, can result in insufficient protection of the connection, leading to fatigue failure of the joint even at low cycles. Furthermore, the presence of voids in the underfill material can also result in insufficient protection of the bumps, leading to fatigue failure of the joint at low cycles. Therefore, underfill materials for automotive applications are desired to have particularly excellent high-temperature resistance, and the application of core-shell rubber particles to the underfill material of the present disclosure is particularly useful for improving high-temperature resistance.

[0030] The reason why the use of core-shell rubber particles can improve the high-temperature resistance of underfill materials is not entirely clear, but it can be considered as follows. It is believed that the presence of core-shell rubber particles in the resin of an underfill material suppresses the propagation of small cracks even if they occur at high temperatures. Furthermore, while the mechanical strength of a cured resin is generally relatively weak in areas with low crosslink density, the presence of core-shell rubber particles significantly suppresses cracking even in these areas with low crosslink density, thereby efficiently improving high-temperature resistance. Another contributing factor is believed to be the excellent stress relaxation ability that occurs in the cured product. Furthermore, although the underfill material of the present disclosure contains a specific epoxy resin with a relatively low molecular weight, the presence of core-shell rubber particles suppresses crack propagation, thereby providing particularly good high-temperature resistance.

[0031] Furthermore, from the viewpoint of the high-temperature resistance of the underfill material, the volume average particle diameter of the core-shell rubber particles measured by laser scattering diffraction is preferably in the range of 0.05 μm to 1.0 μm, more preferably in the range of 0.05 μm to 0.5 μm, and particularly preferably in the range of 0.05 μm to 0.2 μm. When the volume average particle diameter of the core-shell rubber particles is in the above range, the core-shell rubber particles are relatively small in particle size, and therefore easily dispersed throughout the resin component, which is thought to effectively suppress the occurrence of cracks at high temperatures. The volume average particle diameter of the core-shell rubber particles can be measured as the particle diameter (D50) at which the cumulative volume from the small diameter side in the volume-based particle size distribution obtained by a laser scattering diffraction particle size distribution analyzer reaches 50%. The volume average particle diameter may also be the primary particle diameter.

[0032] From the viewpoint of the high-temperature resistance of the underfill material, the amount of the core-shell rubber particles contained in the underfill material is preferably 0.1 to 15 parts by mass, more preferably 1 to 15 parts by mass, even more preferably 3 to 15 parts by mass, and particularly preferably 3 to 10 parts by mass, per 100 parts by mass of the epoxy resin.

[0033] The content of the core-shell rubber particles relative to the total mass of the rubber component is not particularly limited, and from the viewpoint of the high temperature resistance of the underfill material, it is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more. The upper limit of the content of the core-shell rubber particles relative to the total mass of the rubber component is not particularly limited, and may be 100% by mass or less, or may be 95% by mass or less.

[0034] The rubber component may contain rubber components other than the core-shell rubber particles. Specific examples of other rubber components include thermoplastic elastomer, NR (natural rubber), NBR (acrylonitrile-butadiene rubber), acrylic rubber, urethane rubber, and silicone rubber. The other rubber components may be used alone or in combination of two or more.

[0035] The core-shell rubber particles may be amorphous or spherical, with spherical particles being preferred from the viewpoint of keeping the viscosity of the underfill material low.

[0036] (Epoxy Resin) The underfill material contains an epoxy resin, and the epoxy resin contains an epoxy compound (specific epoxy compound) that has two epoxy groups in one molecule, has a molecular weight of 650 or less, and does not contain any ring structure other than the epoxy groups.

[0037] By including a specific epoxy compound as an epoxy resin in the underfill material, the viscosity before curing can be reduced. As a result, the amount of filler can be increased without impairing the fluidity of the underfill material. Furthermore, the specific epoxy compound has two epoxy groups per molecule, which provides a better balance between the effect of reducing viscosity before curing and various properties after curing compared to epoxy groups having one or three or more epoxy groups per molecule.

[0038] The molecular weight of the specific epoxy compound may be 650 or less, preferably 500 or less, and more preferably 400 or less. The lower limit of the molecular weight of the specific epoxy compound is not particularly limited, and from the viewpoint of the properties of the cured product, it is preferably 50 or more, and more preferably 100 or more.

[0039] The molecular weight of the specific epoxy compound can be obtained by multiplying the epoxy equivalent (g / eq) measured by a method in accordance with JIS K 7236:2001 (or ISO 3001:1999) by 2.

[0040] Examples of the "ring structure" that the specific epoxy compound does not contain include aromatic rings such as benzene rings, naphthalene rings, and heterocycles, and cyclic saturated hydrocarbons such as cycloalkanes.

[0041] The specific epoxy compound may be a compound represented by the following general formula (1).

[0042]

[0043] In general formula (1), R is a divalent group not containing a ring structure. Preferred examples of R include an alkylene group, an alkyleneoxy group, and a combination thereof. Among these, R is preferably an alkylene group, and more preferably a linear (not branched) alkylene group.

[0044] The number of carbon atoms in the divalent group represented by R is not particularly limited, but is preferably 1 to 8, and more preferably 1 to 6.

[0045] (Epoxy Resin Other Than the Specific Epoxy Compound) From the viewpoint of the balance between the viscosity reducing effect before curing and the various properties after curing, it is preferable that the epoxy resin contains the specific epoxy compound and an epoxy resin other than the specific epoxy compound. In this case, the content of the specific epoxy compound is preferably 1.0 to 50.0 mass%, more preferably 1.0 to 30.0 mass%, even more preferably 5.0 to 20.0 mass%, and particularly preferably 10.0 to 15.0 mass%, of the total epoxy resin.

[0046] When the epoxy resin contains an epoxy resin other than the specific epoxy compound, the type thereof is not particularly limited. Examples thereof include bisphenol-type epoxy resins, naphthalene-type epoxy resins, glycidylamine-type epoxy resins, hydrogenated bisphenol-type epoxy resins, alicyclic epoxy resins, alcohol ether-type epoxy resins, cycloaliphatic epoxy resins, fluorene-type epoxy resins, and siloxane-based epoxy resins. The epoxy resins other than the specific epoxy compound may be used alone or in combination of two or more.

[0047] Among the above epoxy resins, it is preferable to include at least one selected from the group consisting of bisphenol-type epoxy resins, naphthalene-type epoxy resins, and tri- or higher-functional glycidylamine-type epoxy resins, and it is also preferable to include each of a bisphenol-type epoxy resin, a naphthalene-type epoxy resin, and a tri- or higher-functional glycidylamine-type epoxy resin.

[0048] The type of bisphenol epoxy resin is not particularly limited, and examples include bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol AD ​​epoxy resin, etc. For use as an underfill material, the bisphenol epoxy resin is preferably liquid at room temperature (25°C, the same applies below), and a bisphenol F epoxy resin that is liquid at room temperature is more preferable. Bisphenol epoxy resins that are liquid at room temperature are also commercially available. For example, an example of a commercially available bisphenol F epoxy resin that is liquid at room temperature is "Epotohto YDF-8170C" manufactured by Nippon Steel Chemical & Material Co., Ltd.

[0049] The proportion of the bisphenol-type epoxy resin in the total epoxy resin is not particularly limited and can be selected depending on the desired properties of the underfill material. For example, it can be selected from the range of 10% by mass to 90% by mass, or it can be 20% by mass to 70% by mass, 25% by mass to 50% by mass, or 30% by mass to 40% by mass.

[0050] The type of naphthalene-type epoxy resin is not particularly limited. The naphthalene-type epoxy resin used in the underfill material is preferably one that is liquid at room temperature. An example of a naphthalene-type epoxy resin that is liquid at room temperature is 1,6-bis(glycidyloxy)naphthalene. 1,6-bis(glycidyloxy)naphthalene is also available as a commercially available product. An example of a commercially available product is Epiclon HP-4032D, a product name of DIC Corporation.

[0051] When the underfill material contains a naphthalene-type epoxy resin as the epoxy resin, the proportion of the naphthalene-type epoxy resin is not particularly limited. For example, from the viewpoint of suppressing an increase in the thermal expansion coefficient of the cured product, the proportion of the naphthalene-type epoxy resin in the total epoxy resin is preferably 5% by mass or more, and may be 10% by mass or more. From the viewpoint of a balanced property of the underfill material, the proportion is preferably 50% by mass or less, and may be 40% by mass or less, or may be 30% by mass or less.

[0052] The type of tri- or higher functional glycidylamine type epoxy resin is not particularly limited, but the tri- or higher functional glycidylamine type epoxy resin used as the underfill material is preferably liquid at room temperature.

[0053] An example of a tri- or higher functional glycidyl amine type epoxy resin that is liquid at room temperature is triglycidyl-p-aminophenol. Triglycidyl-p-aminophenol is also available as a commercially available product. An example of a commercially available product is "jER-630" manufactured by Mitsubishi Chemical Corporation.

[0054] When the underfill material contains a trifunctional or higher glycidyl amine epoxy resin as the epoxy resin, the proportion of the glycidyl amine epoxy resin is not particularly limited. For example, from the viewpoint of improving heat resistance, the proportion of the glycidyl amine epoxy resin in the total epoxy resin is preferably 10% by mass or more, may be 30% by mass or more, or may be 40% by mass or more. On the other hand, from the viewpoint of the balance of the properties of the underfill material, the proportion is preferably 70% by mass or less, and may be 60% by mass or less.

[0055] The epoxy resin contained in the underfill material may include an epoxy resin that is liquid at room temperature and an epoxy resin that is solid at room temperature. In this case, from the viewpoint of maintaining a sufficiently low viscosity, the proportion of the epoxy resin that is solid at room temperature is preferably 20 mass % or less of the total epoxy resin.

[0056] (Curing Agent) The underfill material may contain a curing agent for the epoxy resin. The type of curing agent is not particularly limited and can be selected depending on the desired properties of the underfill material. Examples include amine curing agents, phenolic curing agents, acid anhydride curing agents, polymercaptan curing agents, polyaminoamide curing agents, isocyanate curing agents, and blocked isocyanate curing agents. One type of curing agent may be used alone, or two or more types may be used in combination.

[0057] The curing agent used in the underfill material is preferably liquid at room temperature, and from the viewpoint of adhesion to the adherend, an amine curing agent is preferable. Examples of amine curing agents include aliphatic amine compounds such as diethylenetriamine, triethylenetetramine, n-propylamine, 2-hydroxyethylaminopropylamine, cyclohexylamine, and 4,4'-diamino-dicyclohexylmethane; aromatic amine compounds such as diethyltoluenediamine, 3,3'-diethyl-4,4'-diaminodiphenylmethane, 2-methylaniline, and 2-ethylaniline; imidazole compounds such as imidazole, 2-methylimidazole, 2-ethylimidazole, and 2-isopropylimidazole; and imidazoline compounds such as imidazoline, 2-methylimidazoline, and 2-ethylimidazoline. Among these, aromatic amine compounds are preferred. The aromatic amine compound may be a polycondensate with formaldehyde. The active hydrogen equivalent of the amine curing agent is preferably 35 g / eq to 75 g / eq, more preferably 40 g / eq to 70 g / eq, and even more preferably 45 g / eq to 65 g / eq.

[0058] From the viewpoint of minimizing unreacted components, the compounding ratio of the epoxy resin and curing agent is preferably set so that the ratio of the number of functional groups in the curing agent (active hydrogens in the case of an amine curing agent) to the number of epoxy groups in the epoxy resin (number of functional groups in the curing agent / number of epoxy groups in the epoxy resin) is within the range of 0.5 to 2.0, more preferably within the range of 0.6 to 1.3, and even more preferably within the range of 0.8 to 1.2 from the viewpoint of moldability and reflow resistance.

[0059] (Filler) The underfill material may contain a filler. When the underfill material contains a filler, it becomes easier to adjust the thermal expansion coefficient after curing to a desired value. In addition, various properties such as thermal conductivity can be improved. The filler only needs to contain sol-gel silica, and may or may not contain other fillers.

[0060] The shape of the sol-gel silica is not particularly limited, and may be particulate or non-particulate such as fibrous. From the viewpoint of flowability, particulate is preferred.

[0061] The sol-gel silica may be prepared by a conventionally known method or may be commercially available. Conventionally known methods include a method in which tetraalkoxysilane, a raw material, is supplied and reacted in the presence of an alcohol containing an alkali catalyst.

[0062] The type of other filler is not particularly limited. Specific examples include inorganic materials such as silica other than sol-gel silica, alumina, calcium carbonate, zirconium silicate, calcium silicate, silicon nitride, aluminum nitride, boron nitride, beryllia, zirconia, zircon, fosterite, steatite, spinel, mullite, titania, talc, clay, and mica. Furthermore, a filler having a flame-retardant effect may be used. Examples of the filler having a flame-retardant effect include aluminum hydroxide, magnesium hydroxide, composite metal hydroxides such as composite hydroxides of magnesium and zinc, and zinc borate.

[0063] Among the above other fillers, silica other than sol-gel silica is preferred from the viewpoint of reducing the coefficient of thermal expansion, and alumina is preferred from the viewpoint of improving thermal conductivity. The fillers may be used alone or in combination of two or more.

[0064] The amount of filler (which may be read as sol-gel silica; the same applies hereinafter) contained in the underfill material is not particularly limited. From the viewpoint of reducing the thermal expansion coefficient after curing, the larger the amount of filler, the better. For example, the filler content is preferably 50% by mass or more of the entire underfill material, and more preferably 60% by mass or more. On the other hand, from the viewpoint of suppressing an increase in viscosity, the smaller the amount of filler, the better. For example, the filler content is preferably 80% by mass or less of the entire underfill material, and may be 70% by mass or less.

[0065] The content of sol-gel silica in the filler is preferably 50% by mass or more of the total filler, more preferably 70% by mass or more, and even more preferably 90% by mass or more. There is no particular upper limit to the content of sol-gel silica in the filler, and it may be 100% by mass or less of the total filler.

[0066] When the filler is particulate, its average particle size is not particularly limited. For example, the volume average particle size is preferably 0.05 μm to 20 μm, and more preferably 0.1 μm to 15 μm. When the volume average particle size of the filler is 0.05 μm or more, the increase in viscosity of the underfill material tends to be further suppressed. When the volume average particle size is 20 μm or less, the filling ability into narrow gaps tends to be further improved. The volume average particle size of the filler can be measured as the particle size (D50) at which the cumulative volume from the small diameter side reaches 50% in the volume-based particle size distribution obtained using a laser scattering diffraction particle size distribution analyzer.

[0067] (Curing Accelerator) The underfill material may contain a curing accelerator. The type of curing accelerator is not particularly limited and can be selected depending on the types of epoxy resin and curing agent, the desired properties of the underfill material, and the like.

[0068] When the underfill material contains a curing accelerator, the amount thereof is preferably 0.1 to 30 parts by mass, and more preferably 1 to 15 parts by mass, per 100 parts by mass of the curable resin component (total of the epoxy resin and the curing agent).

[0069] (Coupling Agent) The underfill material may contain a coupling agent. Examples of the coupling agent include silane compounds such as epoxysilane, phenylsilane, mercaptosilane, aminosilane, phenylaminosilane, alkylsilane, ureidosilane, and vinylsilane, titanium compounds, aluminum chelate compounds, and aluminum / zirconium compounds. Among these, silane compounds (silane coupling agents) are preferred. The coupling agents may be used alone or in combination of two or more.

[0070] When the underfill material contains a coupling agent, the amount of the coupling agent is preferably 0.05 to 5 parts by mass, and more preferably 0.1 to 2.5 parts by mass, per 100 parts by mass of the filler.

[0071] (Colorant) The underfill material may contain a colorant. Examples of the colorant include carbon black, organic dyes, organic pigments, red lead, red iron oxide, etc. The colorants may be used alone or in combination of two or more.

[0072] When the underfill material contains a colorant, the amount of the colorant is preferably 0.01 to 10 parts by mass, and more preferably 0.1 to 5 parts by mass, per 100 parts by mass of the curable resin component (total of the epoxy resin and the curing agent).

[0073] In addition to the components described above, the underfill material may contain various additives known in the art.

[0074] (Uses of Underfill Material) The underfill material can be used in various mounting techniques. In particular, it can be suitably used as an underfill material for use in flip-chip mounting techniques. For example, it can be suitably used to fill gaps between a semiconductor element and a substrate that are joined by bumps or the like.

[0075] The method for filling the gap between the semiconductor element and the substrate with the underfill material is not particularly limited, and can be carried out by a known method using, for example, a dispenser.

[0076] From the viewpoint of sufficiently filling the gap between the semiconductor element and the substrate, it is preferable that the viscosity of the underfill material during filling is sufficiently low. Specifically, the viscosity at 110°C is preferably 0.2 Pa s or less, more preferably 0.15 Pa s or less, and even more preferably 0.10 Pa s or less.

[0077] In this disclosure, the viscosity of the underfill material at 110°C is a value measured using a rheometer (for example, TA Instruments' "AR2000") using 40 mm parallel plates at a shear rate of 32.5 (1 / s).

[0078] The underfill material of the present disclosure has a fracture toughness value of 1.5 MPa when cured. ０．５ It is preferable that the pressure is 1.6 MPa or more. ０．５ More preferably, it is 1.75 MPa or more. ０．５ The upper limit is more preferably 10 MPa or more. ０．５ The fracture toughness value of the cured product is measured as follows: The underfill material is cured at 165°C for 2 hours to prepare a test piece measuring 70.00 mm wide, 8.00 mm wide, 16.00 mm thick, and a notch length of 7.2 mm to 8.8 mm. The fracture toughness value of this test piece is measured at 25°C by three-point bending using an autograph (product name: AGS-X, Shimadzu Corporation). The fracture toughness value is calculated from the maximum fracture strength obtained by the measurement.

[0079] The underfill material of the present disclosure preferably has a glass transition temperature of 125°C or higher when cured, more preferably 130°C or higher, and even more preferably 135°C or higher. The glass transition temperature of the cured product is measured as follows: The underfill material is cured at 165°C for 2 hours to produce a cured product measuring 8 mm in diameter and 20 mm in length. TMA (thermomechanical analysis, for example, TA4000SE manufactured by TA Instruments) is performed on the cured underfill material, and the intersection of tangents before and after the inflection point on the resulting chart is taken as the glass transition temperature. The heating rate is 5°C / min.

[0080] The underfill material of the present disclosure preferably has a coefficient of thermal expansion of 30 ppm / °C or less when cured, more preferably 26 ppm / °C or less, and even more preferably 25 ppm / °C or less. The method for measuring the coefficient of thermal expansion of the cured product is as follows. The underfill material is cured at 165°C for 2 hours to produce a cured product measuring 8 mm in diameter and 20 mm in length. Measurement is performed on the cured underfill material using a TMA (TA4000SE, manufactured by TA Instruments), and the slope connecting the two points of 10°C and 30°C on the resulting chart is divided by the length of the test piece to determine the coefficient of thermal expansion. The heating rate is 5°C / min.

[0081] <Semiconductor Package> A semiconductor package according to the present disclosure includes a substrate, a semiconductor element disposed on the substrate, and the cured underfill material described above that seals the semiconductor element.

[0082] In the semiconductor package, the types of the semiconductor element and the substrate are not particularly limited and can be selected from those commonly used in the field of semiconductor packages. Since the thermal expansion coefficient of the cured underfill material in the semiconductor package is reduced, for example, stress generated between the cured underfill material and the semiconductor element can be effectively suppressed.

[0083] <Method for manufacturing semiconductor package> The method for manufacturing a semiconductor package disclosed herein includes a step of filling a gap between a substrate and a semiconductor element arranged on the substrate with the above-described underfill material, and a step of curing the underfill material.

[0084] In the above method, the types of semiconductor element and substrate are not particularly limited and can be selected from those commonly used in the field of semiconductor packaging. The method of filling the gap between the semiconductor element and the substrate with an underfill material and the method of curing the underfill material after filling are not particularly limited and can be performed by known techniques.

[0085] The underfill material of the present disclosure will be specifically described below using examples, but the scope of the present disclosure is not limited to these examples.

[0086] Examples 1 and 2 and Comparative Examples 1 and 2 (Preparation of Underfill Material) Underfill materials were prepared by mixing the components shown in Table 1 in the amounts (parts by mass) shown in Table 1. Details of each component are as follows.

[0087] Epoxy resin 1... liquid bisphenol F type epoxy resin, epoxy equivalent: 160 g / eq. Epoxy resin 2... p-(2,3-epoxypropoxy)-N,N-bis(2,3-epoxypropyl)aniline, total chlorine content 1500 ppm or less. Epoxy resin 3... neopentyl glycol diglycidyl ether, epoxy equivalent: 108 g / eq.

[0088] Rubber component 1...core-shell rubber particles having a core containing crosslinked polydimethylsiloxane and a shell containing polymethyl methacrylate and glycidyl methacrylate as a structural unit (content of crosslinked polymethylsiloxane: 68% by mass based on the total mass of the core and shell, volume average particle size (primary particles): 98 nm)

[0089] Curing agent 1...diethyltoluenediamine, active hydrogen equivalent: 45 g / eq. Curing agent 2...formaldehyde / 2-ethylaniline polycondensate, active hydrogen equivalent: 63 g / eq.

[0090] Filler 1: Sol-gel silica with a volume average particle size of 1.00 μm Filler 2: Sol-gel silica with a volume average particle size of 0.1 μm

[0091] <Evaluation of Flow Characteristics> (Viscosity at 25°C) The viscosity of the underfill material at 25°C was measured using an EHD rotational viscometer. Specifically, the EHD rotational viscometer was fitted with a cone rotor with a cone angle of 3° and a cone radius of 14 mm, and rotated at 10 revolutions per minute (10 rpm) for 1 minute at 25°C, and the measured value was multiplied by a predetermined conversion factor (0.5) to obtain a value (Pa s). The results are shown in Table 1.

[0092] (Viscosity at 110°C) The viscosity of the underfill material at 110°C was measured using a rheometer. Specifically, the viscosity (Pa s) at 110°C was measured using an HR-2 (trade name, TA Instruments) rheometer under conditions of 40 mm parallel plates and a shear rate of 32.5 (1 / s). The results are shown in Table 1.

[0093] (Narrow Gap Filling Ability) The underfill material was dispensed into a glass jig for evaluation and cured at a curing temperature of 165°C for 2 hours. The glass jig used consisted of two glass plates stacked together, with a 25 µm spacer sandwiched between the two pieces of glass. The time required to fill the gap between the pieces of glass was measured, and all times were sufficiently short, demonstrating good narrow gap filling ability.

[0094] <Evaluation of Cured Product Properties> (Fracture Toughness Value) The underfill material was cured at 165°C for 2 hours to prepare test specimens measuring 70.00 mm in height, 8.00 mm in width, 16.00 mm in thickness, and 7.2 mm to 8.8 mm in notch length. The fracture toughness values ​​of these test specimens were measured at 25°C in three-point bending using an autograph (product name: AGS-X, Shimadzu Corporation). The fracture toughness values ​​were calculated from the maximum fracture strength obtained by the measurement. The results are shown in Table 1.

[0095] (Glass Transition Temperature) The underfill material was cured at 165°C for 2 hours to produce a cured product measuring 8 mm in diameter and 20 mm in length. Thermomechanical analysis (TMA) was performed on the cured underfill material using a TA4000SE manufactured by TA Instruments, and the intersection of the tangent lines before and after the inflection point of the obtained chart was taken as the glass transition temperature. The heating rate was 5°C / min. The results are shown in Table 1.

[0096] (Thermal expansion coefficient) The underfill material was cured at 165°C for 2 hours to produce a cured product measuring 8 mm in diameter and 20 mm in length. TMA was performed on the cured underfill material using a TA4000SE manufactured by TA Instruments, and the slope of the resulting chart connecting the two points of 10°C and 30°C divided by the length of the test piece was used to determine the thermal expansion coefficient. The heating rate was 5°C / min. The results are shown in Table 1.

[0097]

[0098] In Table 1, the curing agent content (equivalent ratio) represents the ratio of epoxy groups in the underfill material to active hydrogen groups in the curing agent, and the filler content (mass %) represents the mass ratio of the filler to the entire underfill material.

[0099] As shown in Table 1, the underfill materials of Examples 1 and 2 containing a rubber component have no problems with narrow gap filling, a small coefficient of thermal expansion, and high glass transition temperatures and fracture toughness values.

[0100] The fracture toughness value is an index of crack resistance and is important for the reliability of the underfill material. In addition, a sufficiently high glass transition temperature and a low thermal expansion coefficient are also important for reliability. The underfill materials of Examples 1 and 2 have excellent fluidity and high fracture toughness values, high glass transition temperatures, and low thermal expansion coefficients.

[0101] The disclosure of Japanese Patent Application No. 2024-135041 is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards mentioned herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard was specifically and individually indicated to be incorporated by reference.

Claims

The rubber composition includes an epoxy resin, a rubber component, and a filler, the epoxy resin contains an epoxy compound having two epoxy groups in one molecule, a molecular weight of 650 or less, and not containing any ring structure other than the epoxy groups; The rubber component includes core-shell rubber particles having a core portion including a crosslinked polysiloxane and a shell portion including a structural unit formed by cleavage of a carbon-carbon double bond of glycidyl methacrylate, The filler is an underfill material containing sol-gel silica. 　 The underfill material according to claim 1 , wherein the epoxy compound comprises a compound represented by the following general formula (1): [In general formula (1), R is a divalent group not containing a ring structure.] 2. The underfill material according to claim 1, wherein the core-shell rubber particles have a volume average particle size of 0.05 μm to 1.0 μm as measured by a laser scattering diffraction method.

2. The underfill material according to claim 1, wherein the content of the rubber component is 0.1 to 15 parts by mass per 100 parts by mass of the epoxy resin. 　 The underfill material according to claim 1 , wherein the content of the filler is 50% by mass or more of the entire underfill material.

2. The underfill material according to claim 1, wherein the viscosity at 110°C measured using a rheometer under conditions of 40 mm parallel plates and a shear rate of 32.5 (1 / s) is 0.2 Pa·s or less. 　 A semiconductor package comprising: a substrate; a semiconductor element disposed on the substrate; and a cured product of the underfill material according to any one of claims 1 to 6, which seals the semiconductor element. 　 a step of filling a gap between a substrate and a semiconductor element disposed on the substrate with the underfill material according to any one of claims 1 to 6; and curing the underfill material.

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