JPWO2020111244A1 - Underfill material, semiconductor package and manufacturing method of semiconductor package - Google Patents

Abstract

The underfill material contains an epoxy resin and a rubber component, and the epoxy resin has two epoxy groups in one molecule, has a molecular weight of 650 or less, and contains a ring structure other than the epoxy groups. Contains no epoxy compounds.

Description

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

In the mounting technology of a semiconductor device, a liquid curable resin composition called an underfill material is widely used to fill a gap between a substrate and a semiconductor element. The underfill material may cause residual stress inside the cured product of the underfill material due to shrinkage during curing, heating during reflow, etc., which may cause peeling, cracks, and the like. As a method for relaxing the stress generated in the cured product, a method of adding a rubber component to the underfill material to reduce the elastic modulus of the cured product is known (see, for example, Patent Document 1).

International Publication No. 2006/019041

While the elastic modulus of the cured product is reduced in the underfill material to which the rubber component is added, the difference in the coefficient of thermal expansion between the substrate and the semiconductor element becomes large, which causes peeling of the sealing portion, cracks, etc. There is a risk. Therefore, it is important to bring the coefficient of thermal expansion of the cured product of the underfill material close to the coefficient of thermal expansion of the substrate or the semiconductor element from the viewpoint of ensuring the reliability of the sealing portion.

As a method of adjusting the coefficient of thermal expansion of the underfill material to a desired value, it is conceivable to increase or decrease the content of the filler. However, if the amount of the filler in the underfill material is increased, the fluidity before curing tends to decrease, and this point becomes a technical constraint and the coefficient of thermal expansion is adjusted only by the content of the filler. Is making it difficult.
Therefore, it is desired to develop a technique capable of controlling the coefficient of thermal expansion after curing to a desired value while maintaining the fluidity of the underfill material before curing.

The present invention has been made in view of such a situation, and an underfill material having a low elastic modulus after curing and capable of reducing the coefficient of thermal expansion after curing while maintaining the fluidity before curing, and this underfill material An object of the present invention is to provide a semiconductor package obtained by using it and a method for producing the same.

Means for solving the above problems include the following embodiments.
<1> An epoxy containing an epoxy resin and a rubber component, the epoxy resin having two epoxy groups in one molecule, a molecular weight of 650 or less, and no ring structure other than the epoxy group. An underfill material containing a compound.
<2> The underfill material according to <1>, wherein the epoxy compound contains a compound represented by the following general formula (1).

[In the general formula (1), R is a divalent group that does not contain a ring structure. ]
<3> The underfill material according to <1> or <2>, wherein the rubber component is in the form of particles.
<4> The underfill material according to any one of <1> to <3>, wherein the rubber component contains core-shell type rubber particles having a core portion and a shell portion.
<5> The underfill material according to <4>, wherein the core-shell type rubber particles are core-shell type rubber particles having a core portion containing polysiloxane and a shell portion containing a polymer.
<6> The underfill material according to <5>, wherein the polymer in the shell portion contains a (meth) acrylic resin.
<7> The underfill material according to any one of <4> to <6>, wherein the volume average particle diameter of the core-shell type rubber particles measured by the laser scattering diffraction method is 0.05 μm to 1.0 μm. ..
<8> Of <1> to <7>, which further contains a curing agent, and the content of the rubber component is 0.1 to 15 parts by mass with respect to a total of 100 parts by mass of the epoxy resin and the curing agent. The underfill material according to any one of the items.
<9> The underfill material according to any one of <1> to <8>, which further contains a filler and the content of the filler is 50% by mass or more of the total amount of the underfill material.
<10> Of <1> to <9>, the viscosity at 110 ° C. measured under the conditions of a 40 mm parallel plate and a shear rate of 32.5 (1 / s) using a rheometer is 1.0 Pa · s or less. The underfill material according to any one of the items.
<11> A substrate, a semiconductor element arranged on the substrate, and a cured product of the underfill material according to any one of <1> to <10> that seals the semiconductor element. A semiconductor package to prepare.
<12> The step of filling the gap between the substrate and the semiconductor element arranged on the substrate with the underfill material according to any one of <1> to <10>, and the underfill material. A method for manufacturing a semiconductor package, which comprises a step of curing the semiconductor package.

According to the present invention, an underfill material having a low elastic modulus after curing and capable of reducing the coefficient of thermal expansion after curing while maintaining the fluidity before curing, and a semiconductor package obtained by using the underfill material and its manufacture thereof. A method is provided.

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, the components (including element steps and the like) are not essential unless otherwise specified. The same applies to the numerical values and their ranges, and does not limit the present invention.

In the present disclosure, the term "process" includes not only a process independent of other processes but also the process if the purpose of the process is achieved even if the process cannot be clearly distinguished from the other process. ..
The numerical range indicated by using "~" in the present disclosure includes the numerical values before and after "~" as the minimum value and the maximum value, respectively.
In the numerical range described stepwise in the present disclosure, the upper limit value or the lower limit value described in one numerical range may be replaced with the upper limit value or the lower limit value of another numerical range described stepwise. .. Further, in the numerical range described in the present disclosure, the upper limit value or the lower limit value of the numerical range may be replaced with the value shown in the examples.
In the present disclosure, each component may contain a plurality of applicable substances. When a plurality of substances corresponding to each component are present in the composition, the content or content of each component is the total content or content of the plurality of substances present in the composition unless otherwise specified. Means quantity.
In the present disclosure, a plurality of types of particles corresponding to each component may be contained. When a plurality of particles corresponding to each component are present in the composition, the particle size of each component means a value for a mixture of the plurality of particles present in the composition unless otherwise specified.
In the present disclosure, "(meth) acrylic" means at least one of acrylic or methacrylic, "(meth) acrylate" means at least one of acrylate or methacrylate, and "(meth) acryloyl" means at least one of acryloyl or methacrylic. And "(meth) acryloxy" means at least one of acryloyl or methacrylic acid.

<Underfill material>
The underfill material of the present disclosure contains an epoxy resin and a rubber component, and the epoxy resin has two epoxy groups in one molecule, has a molecular weight of 650 or less, and does not contain a ring structure. It is an underfill material containing a compound (hereinafter, also referred to as a specific epoxy compound).

The underfill material contains a rubber component. As a result, the elastic modulus after curing is reduced, and the stress relaxation ability generated in the cured product is excellent. The underfill material further contains a specific epoxy compound as an epoxy resin. As a result, the viscosity of the underfill material is reduced and good fluidity is ensured. Further, since the viscosity of the underfill material is lowered, the increase in viscosity is suppressed even if the content of the filler is increased, and excellent fluidity is maintained. That is, as compared with the underfill material containing no specific epoxy compound, the coefficient of thermal expansion after curing can be adjusted to a desired value by changing the amount of the filler without impairing the fluidity before curing.

(Rubber component)
The rubber component contained in the underfill material is not particularly limited. Specific examples of the rubber component include thermoplastic elastomer, NR (natural rubber), NBR (acrylonitrile-butadiene rubber), acrylic rubber, urethane rubber, silicone rubber and the like. As the rubber component, one type may be used alone or two or more types may be used in combination.

The rubber component may be in the form of particles or in liquid form. From the viewpoint of suppressing an increase in the viscosity of the underfill material, it is preferably in the form of particles (rubber particles). The rubber particles may be amorphous or spherical. From the viewpoint of keeping the viscosity of the underfill material low, it is preferably spherical.

The size of the rubber particles is not particularly limited. For example, the volume average particle diameter measured by the laser scattering diffraction method 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 more preferably 0.05 μm to 0.5 μm. It is more preferably in the range of 0.2 μm.

The volume average particle size of the rubber particles can be measured as the particle size (D50) when the cumulative volume from the small diameter side is 50% in the volume-based particle size distribution obtained by the laser scattering diffraction method particle size distribution measuring device. can.

-Core-shell type rubber particles-
The rubber particles may have a core portion and a shell portion made of different materials (hereinafter, also referred to as core-shell type rubber particles). The shell portion of the core-shell type rubber particles may cover at least a part of the core portion, and may cover the entire core portion.

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

Hereinafter, as an example of the core-shell type rubber particles, the core-shell type rubber particles having a core portion containing polysiloxane and a shell portion containing a polymer will be described.
In the core-shell type rubber particles having the above configuration, the polysiloxane contained in the core portion is not particularly limited. Examples thereof include polyalkylhydrogensiloxane, polydialkylsiloxane, polyarylhydrogensiloxane, polydiarylsiloxane, polyalkylarylsiloxane, and copolymers thereof. Among them, the linear polysiloxane preferably _{contains polydialkylsiloxane, more preferably polydiC 1-5} alkylsiloxane, and even more preferably polydimethylsiloxane.

The polysiloxane in the core portion preferably has a crosslinked structure. It is considered that the polysiloxane having a crosslinked structure forms a core portion having low elasticity, which makes it easier to relieve stress during the thermal cycle. The polysiloxane having a crosslinked structure is formed from a siloxane component that forms a linear polysiloxane, that is, _{a bifunctional siloxane component having a [RR'SiO 2/2} ] unit and a crosslinked component. The cross-linking component is selected from the group consisting of a trifunctional siloxane component having a trifunctional siloxane _{unit ([RSiO 3/2} ]) and a tetrafunctional siloxane component having a tetrafunctional siloxane unit ([SiO _4/2]). It is preferable to use at least one of them. R and R'in [RR'SiO _2/2 ] and [RSiO _3/2 ] each independently represent a monovalent organic group, preferably a hydrogen, an alkyl group, or an aryl group, and have 1 carbon number. It is more preferably an alkyl group of ~ 5, and even more preferably a methyl group. In the present disclosure, the siloxane component refers to a siloxane unit that forms a polysiloxane.

When the polysiloxane has a crosslinked structure, the ratio of the crosslinked component to all the siloxane components constituting the polysiloxane is not particularly limited. By adjusting the ratio, the hardness of the core portion can be adjusted. The ratio is preferably 0.5 mol% to 20 mol%, more preferably 2 mol% to 10 mol%. When the ratio is 0.5 mol% or more, the unreacted siloxane component tends to be suppressed. When the ratio is 20 mol% or less, the elastic modulus tends to decrease, and the stress during the thermal cycle of the cured product tends to be efficiently reduced. The proportion of the trifunctional siloxane component in all the siloxane components constituting the polysiloxane is preferably 2 mol% to 10 mol%, and the proportion of the tetrafunctional siloxane component is 2 mol% to 10 mol%. Is preferable.

The polysiloxane preferably has a substituent having an ethylenic double bond in part. As a result, for example, after polymerizing the polysiloxane in the core portion, when 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. The core part and shell part can be firmly connected. Examples of the substituent having an ethylenic double bond include a vinyl group, an allyl group, a (meth) acryloyl group, a (meth) acryloyl group, and an alkyl group having these substituents at the end.

When the polysiloxane has a substituent having an ethylenic double bond in part, the proportion of the siloxane component having a substituent having an ethylenic double bond is 1 mol% to 10 mol% in the total siloxane component. Is preferable. When the ratio is 1 mol% or more, the effect of grafting tends to be sufficiently obtained, and when it is 10 mol% or less, the physical properties such as heat resistance and elastic modulus of the core portion are lowered due to the influence of grafting. Tends to be suppressed.

From the viewpoint of the effect of reducing the elastic modulus and the fluidity, the proportion of polysiloxane contained in the core portion is preferably 50% by mass to 70% by mass with respect to the total mass of the core portion and the shell portion.

The polymer contained in the shell portion is not particularly limited as long as it is a polymer capable of covering the core portion to form the shell portion, and examples thereof include organic polymers such as silicone resin and (meth) acrylic resin. .. Among them, the polymer in the shell portion preferably contains a (meth) acrylic resin.

Examples of the (meth) acrylic resin include (meth) acrylic acid resin, (meth) acrylic acid ester resin, and the like, and it is preferable to include (meth) acrylic acid ester resin. The (meth) acrylic acid ester resin preferably contains _{an alkyl (meth) acrylate resin, more preferably contains a C 1-5} alkyl (meth) acrylate resin, and further preferably contains a methyl (meth) acrylate resin. .. The (meth) acrylic resin may be a polymer of one kind of (meth) acrylic monomer, or may be a copolymer of two or more kinds of (meth) acrylic monomers.

The polymer contained in the shell portion may have an epoxy group in a part of the side chain. For example, the material of the shell portion is preferably the above-mentioned (meth) acrylic resin having an epoxy group in a part of the side chain. When the polymer contained in the shell portion has an epoxy group in a part of the side chain, the compatibility with the epoxy resin in the composition is improved, and the fracture toughness and adhesiveness after curing tend to be excellent, and the pot life tends to be excellent. be.

When the polymer contained in the shell portion has an epoxy group in a part of the side chain, the ratio of the structural unit having an epoxy group to all the structural units of the polymer is not particularly limited and may be 10% by mass or more. It is preferably 20% by mass or more, more preferably 25% by mass or more, and particularly preferably 30% by mass or more. From the viewpoint of reduction of elastic modulus and fluidity, the ratio is preferably 50% by mass or less, more preferably 40% by mass or less, and further preferably 35% by mass or less.

Examples of the (meth) acrylic resin having an epoxy group in a part of the side chain include glycidyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate glycidyl ether, glycidyl methyl (meth) acrylate and the like as constituent units ( Meta) Acrylate resin can be mentioned.

Among them, as the core-shell type rubber particles, core-shell type rubber particles having a core portion containing polysiloxane and a shell portion containing a (meth) acrylic resin are preferable.

The amount of the rubber component contained in the underfill material is not particularly limited. From the viewpoint of reducing the elasticity of the cured product and balancing other properties, the amount of the rubber component is 0.1 part by mass with respect to 100 parts by mass of the resin component (if the epoxy resin and the curing agent are included, the total). It is preferably ~ 30 parts by mass, more preferably 1 part by mass to 15 parts by mass, further preferably 3 parts by mass to 15 parts by mass, and particularly preferably 3 parts by mass to 10 parts by mass. preferable.

Furthermore, among the rubber components, it has been found that the use of the core-shell type rubber particles described above can improve the high temperature resistance of the underfill material. In recent years, there has been an increasing demand for underfill materials that can be used in automotive semiconductor devices. Generally, when the gap between the semiconductor element and the wiring board is sealed by using the underfill material, a fillet is formed on the side surface of the semiconductor element in order to protect the semiconductor element. However, due to the thermal stress caused by the difference in thermal expansion between the wiring substrate and the semiconductor element, the fillet may be cracked or the semiconductor element may be destroyed. Further, depending on the selection of the underfill material, when the underfill material is repeatedly subjected to thermal shock in a temperature cycle or the like, the protection of the connecting portion becomes insufficient, and the joint portion may be fatigued and fractured even in a low cycle. Further, if voids are present in the underfill material, the bumps are not sufficiently protected, and the joint portion may be fatigue-fractured in a low cycle as well. Therefore, it is desired that the underfill material for automobiles has particularly excellent high temperature resistance, and applying the core-shell type rubber particles to the underfill material of the present disclosure is particularly effective in improving the high temperature resistance. It is useful.

The reason why the high temperature resistance of the underfill material can be improved by using the core-shell type rubber particles is not always clear, but it can be considered as follows. It is considered that the presence of core-shell type rubber particles in the resin in the underfill material suppresses the growth of cracks even if small cracks occur at high temperatures. Further, in general, in a cured resin product, the mechanical strength is relatively weak at a place where the crosslink density of the resin is low, and the presence of core-shell type rubber particles also at a place where the crosslink density is low has an effect of suppressing cracks. Is remarkably played, and as a result, it is considered that the high temperature resistance can be efficiently improved. Further, it is considered that the presence of core-shell type rubber particles in the underfill material is one of the reasons why the stress relaxation ability generated in the cured product is excellent.
Further, the underfill material of the present disclosure contains a specific epoxy resin having a relatively low molecular weight, but in the presence of core-shell type rubber particles, the growth of cracks is suppressed, so that particularly good high temperature resistance can be exhibited. it is conceivable that.

The structure of the core-shell type rubber particles preferable from the viewpoint of high temperature resistance of the underfill material is the same as that of the core-shell type rubber particles described above. Among them, from the viewpoint of high temperature resistance, the core-shell type rubber particles are preferably core-shell type rubber particles having a core portion containing polysiloxane and a shell portion containing a (meth) acrylic resin.

Further, from the viewpoint of high temperature resistance of the underfill material, it has the core-shell type rubber particles (preferably a core portion containing polysiloxane and a shell portion containing (meth) acrylic resin, which are measured by a laser scattering diffraction method. The volume average particle diameter of the core-shell type rubber particles) 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 more preferably 0.05 μm to 0.2 μm. It is particularly preferable that the range is. When the volume average particle size of the core-shell type rubber particles is in the above range, the core-shell type rubber particles are easily dispersed in the entire resin component because the particle size is relatively small, and as a result, cracks are satisfactorily generated at high temperature. It is thought that it can be suppressed.

From the viewpoint of high temperature resistance of the underfill material, core-shell type rubber particles (preferably core-shell type rubber particles having a core portion containing polysiloxane and a shell portion containing (meth) acrylic resin) contained in the underfill material. The amount of the resin component (when the epoxy resin and the curing agent are contained, the total) is preferably 0.1 part by mass to 30 parts by mass with respect to 100 parts by mass, and is preferably 1 part by mass to 15 parts by mass. It is more preferably 3 parts by mass to 15 parts by mass, and particularly preferably 3 parts by mass to 10 parts by mass.

When the rubber component contains the core-shell type rubber particles described above, the core-shell type rubber particles having the core-shell rubber particles (preferably a core portion containing polysiloxane and a shell portion containing (meth) acrylic resin) with respect to the total mass of the rubber component. ) Is not particularly limited, and from the viewpoint of high temperature resistance of the underfill material, it is preferably 70% by mass or more, more preferably 80% by mass or more, and 90% by mass or more. More preferred.

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

When the underfill material contains a specific epoxy compound as the epoxy resin, the viscosity before curing can be lowered. As a result, the amount of the filler can be increased without impairing the fluidity of the underfill material. Further, the specific epoxy compound has two epoxy groups in one molecule, and has a viscosity reducing effect before curing as compared with an epoxy group having one or three or more epoxy groups in one molecule. Excellent balance of various characteristics after curing.

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, but from the viewpoint of the characteristics of the cured product, it is preferably 50 or more, and more preferably 100 or more.

The molecular weight of the specific epoxy compound is obtained by multiplying the epoxy equivalent (g / eq) measured by a method according to JIS K 7236: 2001 (or ISO 3001: 1999) by 2.

Examples of the "ring structure" containing no specific epoxy compound include aromatic rings such as benzene ring, naphthalene ring and heterocycle, and cyclic saturated hydrocarbons such as cycloalkane.

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

In the general formula (1), R is a divalent group that does not contain a ring structure. Preferred examples of R include an alkylene group, an alkyleneoxy group, and a combination thereof. Among them, R is preferably an alkylene group, and more preferably a chain-like (not containing a branch) alkylene group.

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

(Epoxy resin other than specific epoxy compounds)
From the viewpoint of the effect of reducing the viscosity before curing and the balance of various properties after curing, the epoxy resin preferably contains a 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% by mass to 50.0% by mass, and more preferably 1.0% by mass to 30.0% by mass of the entire epoxy resin.

When the epoxy resin contains an epoxy resin other than the specific epoxy compound, the type thereof is not particularly limited. For example, bisphenol type epoxy resin, naphthalene type epoxy resin, glycidylamine type epoxy resin, hydrogenated bisphenol type epoxy resin, alicyclic epoxy resin, alcohol ether type epoxy resin, cyclic aliphatic type epoxy resin, fluorene type epoxy resin, and Examples include siloxane-based epoxy resins. As the epoxy resin other than the specific epoxy compound, one type may be used alone or two or more types may be used in combination.

Among the above epoxy resins, it is preferable to contain at least one selected from the group consisting of bisphenol type epoxy resin, naphthalene type epoxy resin and trifunctional or higher functional glycidylamine type epoxy resin, and bisphenol type epoxy resin and naphthalene type epoxy resin. It is also preferable to contain a trifunctional or higher functional glycidylamine type epoxy resin, respectively.

The type of bisphenol type epoxy resin is not particularly limited, and examples thereof include bisphenol A type epoxy resin, bisphenol F type epoxy resin, and bisphenol AD type epoxy resin. In order to use it as an underfill material, the bisphenol type epoxy resin is preferably a liquid at room temperature (25 ° C., the same applies hereinafter), and more preferably a bisphenol F type epoxy resin that is liquid at room temperature. The bisphenol type epoxy resin that is liquid at room temperature is also available as a commercial product.

The ratio of the bisphenol type epoxy resin to the entire epoxy resin is not particularly limited, and can be selected according to the desired properties of the underfill material. For example, it can be selected from the range of 10% by mass to 90% by mass, and may be 30% by mass to 80% by mass, or 40% by mass to 70% by mass. Further, in one embodiment, the proportion of the bisphenol type epoxy resin in the entire epoxy resin may be 70% by mass to 98% by mass, or 80% by mass to 97% by mass.

The type of naphthalene type epoxy resin is not particularly limited. The naphthalene type epoxy resin used for the underfill material is preferably liquid at room temperature. Examples of the naphthalene-type epoxy resin that is liquid at room temperature include 1,6-bis (glycidyloxy) naphthalene. 1,6-bis (glycidyloxy) naphthalene is also available as a commercial product.

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

The type of trifunctional or higher functional glycidylamine type epoxy resin is not particularly limited. The trifunctional or higher functional glycidylamine type epoxy resin used as the underfill material is preferably liquid at room temperature.

Examples of the trifunctional or higher functional glycidylamine type epoxy resin which is liquid at room temperature include triglycidyl-p-aminophenol. Triglycidyl-p-aminophenol is also available as a commercial product.

When the underfill material contains a trifunctional or higher functional glycidylamine type epoxy resin as the epoxy resin, the ratio thereof is not particularly limited. For example, from the viewpoint of improving heat resistance, the proportion of the total epoxy resin is preferably 10% by mass or more, and may be 15% by mass or more, or 20% by mass or more. On the other hand, from the viewpoint of the balance of characteristics as the underfill material, it is preferably 50% by mass or less, and may be 40% by mass or less.

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 solid at room temperature is preferably 20% by mass or less of the total epoxy resin.

(Hardener)
The underfill material may contain an epoxy resin curing agent. The type of curing agent is not particularly limited and can be selected according to the desired properties of the underfill material and the like. Examples thereof include amine curing agents, phenol curing agents, acid anhydride curing agents, polyvinylcaptan curing agents, polyaminoamide curing agents, isocyanate curing agents, blocked isocyanate curing agents and the like. As the curing agent, one type may be used alone or two or more types may be used in combination.

The curing agent used for the underfill material is preferably a liquid at room temperature, and is preferably an amine curing agent from the viewpoint of adhesiveness to the adherend. Examples of the amine curing agent include aliphatic amine compounds such as diethylenetriamine, triethylenetetramine, n-propylamine, 2-hydroxyethylaminopropylamine, cyclohexylamine, 4,4'-diamino-dicyclohexylmethane, diethyltoluenediamine, 3, Aromatic amine compounds such as 3'-diethyl-4,4'-diaminodiphenylmethane and 2-methylaniline, imidazole compounds such as imidazole, 2-methylimidazole, 2-ethylimidazole and 2-isopropylimidazole, imidazoline and 2-methyl Examples thereof include imidazoline compounds such as imidazoline and 2-ethyl imidazoline. Among these, aromatic amine compounds are preferable.

The mixing ratio of the epoxy resin and the curing agent is the ratio of the number of functional groups of the curing agent (active hydrogen in the case of the amine curing agent) to the number of epoxy groups of the epoxy resin from the viewpoint of suppressing the unreacted components of each. The number of functional groups of the curing agent / the number of epoxy groups of the epoxy resin) is preferably set to be in the range of 0.5 to 2.0, and is set to be in the range of 0.6 to 1.3. Is more preferable. From the viewpoint of moldability and reflow resistance, it is more preferable to set it in the range of 0.8 to 1.2.

(Filler)
The underfill material may include a filler. When the underfill material contains a filler, it becomes easy to adjust the coefficient of thermal expansion after curing to a desired value. In addition, various properties such as thermal conductivity can be improved.

The type of filler is not particularly limited. Specifically, silica, alumina, calcium carbonate, zirconium silicate, calcium silicate, silicon nitride, aluminum nitride, boron nitride, beryllia, zirconia, zircon, fosterite, steatite, spinel, mulite, titania, talc, clay. , Inorganic materials such as mica. Further, 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 magnesium and zinc composite hydroxides, and zinc borate.

Among the above-mentioned fillers, silica is preferable from the viewpoint of reducing the coefficient of thermal expansion, and alumina is preferable from the viewpoint of improving thermal conductivity. As the filler, one type may be used alone or two or more types may be used in combination.

The amount of the filler contained in the underfill material is not particularly limited. From the viewpoint of reducing the coefficient of thermal expansion after curing, a larger amount of filler is preferable. For example, the content of the filler is preferably 50% by mass or more, and more preferably 60% by mass or more of the entire underfill material. On the other hand, from the viewpoint of suppressing the increase in viscosity, it is preferable that the amount of the filler is small. For example, the content of the filler is preferably 80% by mass or less of the entire underfill material, and may be 70% by mass or less.

When the filler is in the form of particles, the average particle size thereof 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 the viscosity of the underfill material tends to be further suppressed. When the volume average particle size is 20 μm or less, the filling property into a narrow gap tends to be further improved. The volume average particle size of the packing material can be measured as the particle size (D50) when the cumulative volume from the small diameter side is 50% in the volume-based particle size distribution obtained by the laser scattering diffraction method particle size distribution measuring device. can.

(Curing accelerator)
The underfill material may contain a curing accelerator. The type of the curing accelerator is not particularly limited, and can be selected according to the types of the epoxy resin and the curing agent, the desired properties of the underfill material, and the like.

When the underfill material contains a curing accelerator, the amount thereof is preferably 0.1 part by mass to 30 parts by mass with respect to 100 parts by mass of the curable resin component (total of epoxy resin and curing agent), and 1 part by mass. More preferably, it is from 10 parts by mass to 15 parts by mass.

(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, a silane compound (silane coupling agent) is preferable. As the coupling agent, one type may be used alone or two or more types may be used in combination.

When the underfill material contains a coupling agent, the amount of the coupling agent is preferably 0.05 parts by mass to 5 parts by mass, and 0.1 parts by mass to 2.5 parts by mass with respect to 100 parts by mass of the filler. More preferably, it is by mass.

(Colorant)
The underfill material may contain a colorant. Examples of the colorant include carbon black, organic dyes, organic pigments, lead tan, red iron oxide and the like. As the colorant, one type may be used alone or two or more types may be used in combination.

When the underfill material contains a colorant, the amount thereof is preferably 0.01 part by mass to 10 parts by mass with respect to 100 parts by mass of the curable resin component (total of epoxy resin and curing agent), and is 0.1. More preferably, it is by mass to 5 parts by mass.

The underfill material may contain various additives well known in the art in addition to the above-mentioned components.

(Use of underfill material)
The underfill material can be used in various mounting techniques. In particular, it can be suitably used as an underfill material used in flip-chip type mounting technology. For example, it can be suitably used for filling a gap between a semiconductor element bonded by a bump or the like and a substrate.

The method of filling the gap between the semiconductor element and the substrate by using the underfill material is not particularly limited. For example, it can be carried out by a known method using a dispenser or the like.

From the viewpoint of sufficiently filling the gap between the semiconductor element and the substrate, it is preferable that the underfill material has a sufficiently low viscosity at the time of filling. Specifically, the viscosity at 110 ° C. is preferably 1.0 Pa · s or less, more preferably 0.75 Pa · s or less, and even more preferably 0.50 Pa · s or less.

In the present disclosure, the viscosity of the underfill material at 110 ° C. is measured by a rheometer (for example, "AR2000" of TA Instruments) on a 40 mm parallel plate under the condition of shear rate: 32.5 (1 / s). Is the value to be.

<Semiconductor package>
The semiconductor package of the present disclosure includes a substrate, a semiconductor element arranged on the substrate, and a cured product of the above-mentioned underfill material that seals the semiconductor element.

In the above semiconductor package, the types of the semiconductor element and the substrate are not particularly limited, and can be selected from those generally used in the field of the semiconductor package. Since the thermal expansion coefficient of the cured product of the underfill material is reduced in the above semiconductor package, for example, when stress is generated between the cured product of the underfill material and the semiconductor element, it is excellent in the effect of suppressing the stress. There is.

<Manufacturing method of semiconductor package>
The semiconductor package manufacturing method of the present disclosure includes a step of filling a gap between a substrate and a semiconductor element arranged on the substrate with the above-mentioned underfill material, and a step of curing the underfill material. Has.

In the above method, the types of the semiconductor element and the substrate are not particularly limited, and can be selected from those generally used in the field of semiconductor packaging. The method of filling the gap between the semiconductor element and the substrate using the underfill material and the method of curing the underfill material after filling are not particularly limited, and a known method can be used.

Hereinafter, the underfill material of the present disclosure will be specifically described with reference to Examples, but the scope of the present disclosure is not limited to these Examples.

<< Examples 1 and 2 and Comparative Examples 1 to 4 >>
(Preparation of underfill material)
The components shown in Table 1 were mixed in an amount (parts by mass) shown in Table 1 to prepare an underfill material. The details of each component are as follows.

Epoxy resin 1 ... Liquid bisphenol F type epoxy resin, epoxy equivalent: 160 g / eq
Epoxy resin 2 ... Triglycidyl-p-aminophenol, epoxy equivalent: 95 g / eq
Epoxy resin 3 ... 1,6-bis (glycidyloxy) naphthalene, epoxy equivalent: 143 g / eq
Epoxy resin 4 (specific epoxy compound) ... A compound in which R is an alkylene group having 6 carbon atoms in the general formula (1), epoxy equivalent: 125 g / eq

Rubber component 1 ... Core-shell type rubber particles containing polydimethylsiloxane in which the core portion is crosslinked, and the shell portion contains polymethylmethicone and glycidyl methacrylate as a constituent unit (content of crosslinked polymethylsiloxane: core portion and shell). 68% by mass with respect to the total mass of the part, volume average particle diameter (primary particles): 131 nm)
Rubber component 2 ... Nitrile-butadiene rubber (NBR) particles Rubber component 3 ... Polymethylsilsesquioxane particles Rubber component 4 ... Urethane particles Rubber component 5 ... Polymethylmethacrylate particles Rubber component 6 ... Nylon particles

Hardener 1 ... Diethyl Toluenediamine Hardener 2 ... 3,3'-diethyl-4,4'-diaminodiphenylmethane

Filler: Spherical silica with a volume average particle diameter of 0.5 μm

<Evaluation of flow characteristics>
(Viscosity at 25 ° C)
The viscosity of the underfill material at 25 ° C. was measured using an EHD type rotational viscometer. Specifically, an EHD type rotational viscometer equipped with a cone rotor having a cone angle of 3 ° and a cone radius of 14 mm is rotated at 25 ° C. for 1 minute at 10 times per minute (10 rpm), and the measured value at that time is set to a predetermined value. The value (Pa · s) was obtained by multiplying the conversion coefficient (0.5). The results are shown in Table 1.

(Viscosity at 110 ° C)
The viscosity of the underfill material at 110 ° C. was measured using a rheometer. Specifically, using AR2000 (trade name, TA Instruments) as a rheometer, the viscosity (Pa · s) at 110 ° C. was measured under the conditions of a 40 mm parallel plate and a shear rate of 32.5 (1 / s). .. The results are shown in Table 1.

<Evaluation of cured product characteristics>
(Coefficient of thermal expansion)
The underfill material was cured at 150 ° C. for 2 hours to prepare a test piece having a diameter of 8 mm and a thickness of 20 mm. The coefficient of thermal expansion of this test piece was measured using a thermomechanical analyzer (trade name: TMA2940, TA Instruments) while raising the temperature from 0 ° C. to 300 ° C. at 5 ° C./min by a compression method. The slope of the tangent line at 50 ° C. obtained by the measurement was defined as the coefficient of thermal expansion α1 (ppm / ° C.), and the slope of the tangent line at 150 ° C. was defined as the coefficient of thermal expansion α2 (ppm / ° C.). The results are shown in Table 1.

(Glass-transition temperature)
In the measurement of the coefficient of thermal expansion, the temperature corresponding to the intersection of the slope of the tangent line at 50 ° C. and the slope of the tangent line at 150 ° C. was defined as the glass transition temperature (° C.). The results are shown in Table 1.

(Storage modulus)
The underfill material was cured at 150 ° C. for 2 hours to prepare a test piece having a size of 50 mm × 10 mm × 3 mm. The storage elastic modulus of this test piece was measured from 20 ° C. using a viscoelasticity measuring device (trade name: RSAIII, TA Instruments) under the conditions of a span distance of 40 mm and a frequency of 1 Hz by a three-point bending method. The temperature was raised to 300 ° C. at 5 ° C./min for measurement. Table 1 shows the values of the storage elastic modulus (GPa) at 25 ° C. and the storage elastic modulus (GPa) at 240 ° C.

<Manufacturing and evaluation of semiconductor devices>
The underfill material was underfilled in the gap between the chip and the substrate of the semiconductor device for evaluation by the dispense method, and cured at a curing temperature of 150 ° C. for 2 hours.

The specifications of the semiconductor device used are as follows.
-Chip size: 20 mm x 20 mm x 0.55 mm
(Circuit: Aluminum daisy chain connection, Passivation film: Polyimide (HD4000, manufactured by Hitachi Kasei DuPont Microsystems, Inc., product name))
-Bump: Solder ball (Sn-Ag-Cu, φ80 μm, 7,744 pins)
・ Bump pitch: 190 μm
-Substrate: FR-5 (Solder resist SR7300, manufactured by Hitachi Kasei Co., Ltd., product name, 60 mm x 60 mm x 0.8 mm)
-Gap between chip and substrate: 50 μm

The prepared semiconductor device was treated for 1000 cycles with a thermal cycle of −55 ° C. to 125 ° C. for 30 minutes each. After that, a continuity test was performed to check for aluminum wiring, pad disconnection defects, and fillet crack peeling, and the number of defective packages / evaluation packages was evaluated.

In Table 1, the content (equivalent ratio) of the curing agent represents the ratio of the number of functional groups in the curing agent when the number of epoxy groups in the epoxy resin is 1. The content (% by mass) of the filler represents the mass-based ratio of the filler in the entire underfill material.

As shown in Table 1, the underfill materials of Comparative Examples 3 and 4 containing the rubber component have a lower elastic modulus after curing than the underfill materials of Comparative Examples 1 and 2 not containing the rubber component, but thermally expand. The rate is high. Further, Comparative Example 3 containing 65% by mass of the filler in addition to the rubber component has a lower coefficient of thermal expansion than Comparative Example 4 containing 60% by mass of the filler, but has a higher viscosity than Comparative Example 4.

The underfill materials of Examples 1 and 2 containing the specific epoxy compound in addition to the rubber component have low storage elastic modulus and thermal expansion coefficient, and have obtained advantageous properties in terms of improving reliability. Further, the underfill materials of Examples 1 and 2 have a sufficiently low viscosity and excellent fluidity even if the filler is contained in an amount of 65% by mass or more.

<< Examples 3 to 8 >>
(Preparation of underfill material)
The components shown in Table 2 were mixed in an amount (parts by mass) shown in Table 2 to prepare an underfill material. Details of each component are as described above.

<Evaluation of flow characteristics>
Similar to Examples 1 and 2 and Comparative Examples 1 to 4, the viscosity of the underfill material at 25 ° C. and the viscosity at 110 ° C. were measured.

<Evaluation of cured product characteristics>
The glass transition temperature was measured in the same manner as in Examples 1 and 2 and Comparative Examples 1 to 4.

<Evaluation of high temperature resistance>
A semiconductor device was produced in the same manner as in Examples 1 and 2 and Comparative Examples 1 to 4. The prepared semiconductor device was treated for 1000 cycles with a thermal cycle of −55 ° C. to 150 ° C. for 30 minutes each. Then, a continuity test was performed, and fillet cracks of the underfill material filled in the package were observed using a metallurgical microscope (manufactured by OLYMPUS, BX51). Those with a crack length of 0.05 mm or more were counted.

In Table 2, "-" indicates that the component is not blended. The content (equivalent ratio) of the curing agent represents the ratio of the number of functional groups in the curing agent when the number of epoxy groups in the epoxy resin is 1. The content (% by mass) of the filler represents the mass-based ratio of the filler in the entire underfill material.

As shown in Table 2, in Example 3 in which the core-shell type rubber particles were used as the rubber component, the result of the temperature cycle test was the best.

Claims (12)

Contains epoxy resin and rubber component,
The epoxy resin contains an epoxy compound having two epoxy groups in one molecule, having a molecular weight of 650 or less, and containing no ring structure other than the epoxy groups.
Underfill material. The underfill material according to claim 1, wherein the epoxy compound contains a compound represented by the following general formula (1).

[In the general formula (1), R is a divalent group that does not contain a ring structure. ] The underfill material according to claim 1 or 2, wherein the rubber component is in the form of particles. The underfill material according to any one of claims 1 to 3, wherein the rubber component contains core-shell type rubber particles having a core portion and a shell portion. The underfill material according to claim 4, wherein the core-shell type rubber particles are core-shell type rubber particles having a core portion containing polysiloxane and a shell portion containing a polymer. The underfill material according to claim 5, wherein the polymer in the shell portion contains a (meth) acrylic resin. The underfill material according to any one of claims 4 to 6, wherein the volume average particle diameter of the core-shell type rubber particles measured by a laser scattering diffraction method is 0.05 μm to 1.0 μm. Any one of claims 1 to 7, further comprising a curing agent, wherein the content of the rubber component is 0.1 to 15 parts by mass with respect to a total of 100 parts by mass of the epoxy resin and the curing agent. The underfill material described in the section. The underfill material according to any one of claims 1 to 8, further comprising a filler, wherein the content of the filler is 50% by mass or more of the entire underfill material. Any one of claims 1 to 9, wherein the viscosity at 110 ° C. measured under the conditions of a 40 mm parallel plate and a shear rate of 32.5 (1 / s) using a rheometer is 1.0 Pa · s or less. The underfill material described in the section. A semiconductor comprising a substrate, a semiconductor element arranged on the substrate, and a cured product of the underfill material according to any one of claims 1 to 10, which seals the semiconductor element. package. The step of filling the gap between the substrate and the semiconductor element arranged on the substrate with the underfill material according to any one of claims 1 to 10.
The process of curing the underfill material and
A method for manufacturing a semiconductor package.