JP7137895B2 - Conductive Adhesive Sheet, Method for Manufacturing Conductive Adhesive Sheet, and Semiconductor Device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a conductive adhesive sheet, a method for manufacturing a conductive adhesive sheet, and a semiconductor device.

In recent years, due to the growing awareness of environmental issues, power semiconductor devices have come to be widely used not only for general industrial applications and electric railway applications but also for vehicle applications. Especially for in-vehicle parts, making each part smaller and lighter within a limited allowable size is directly linked to the performance of the vehicle. It's becoming In such a semiconductor device, for example, a power semiconductor element is mounted on a die pad of a DBC (Direct Bonded Copper: registered trademark) substrate via highly heat-resistant high-lead solder. However, the use of hazardous substances containing lead is being regulated, and there is a demand for lead-free products.

As a highly heat-resistant lead-free joining material other than high-lead solder, a joining method using a sintered silver paste that joins nano-order silver fillers at a temperature below the melting point is being studied (see, for example, Patent Document 1). ). The sintered silver paste has high thermal conductivity and is effective for joining power semiconductor elements that handle large currents. However, from the viewpoint of miniaturization and thinning of semiconductor devices, a sheet material that can be used as a bonding material in a thin layer is desired.

Since the thermal conductivity of solder is generally 30 W/m·K, a sheet material with high thermal conductivity is sought as an alternative to solder, and such a sheet material is also provided (for example, patent Reference 2).

Patent No. 6360157 Japanese Patent Publication No. 2016-536467

However, there are few sheet materials on the market that have high thermal conductivity. This is because if the sheet material tries to exhibit thermal conductivity comparable to that of the solder material, the reaction may deteriorate the reliability characteristics of the thermal cycle test and the like. The sheet material also has room for improvement.

The present invention has been made in view of such circumstances, and the conductive adhesive sheet and the conductive adhesive sheet that can obtain a semiconductor device having high electrical conductivity and thermal conductivity and excellent reliability. It is an object of the present invention to provide a manufacturing method of (1) and a semiconductor device formed by bonding semiconductor elements with the conductive adhesive sheet.

As a result of intensive studies aimed at solving the above problems, the inventors have found that the above problems can be solved by the following inventions.

That is, the present disclosure relates to the following.
[1] A conductive resin composition containing (A) an epoxy resin, (B) a phenol curing agent, (C) conductive particles, and (D) negative thermal expansion particles molded into a sheet In the adhesive sheet, the (C) conductive particles have an aspect ratio defined by the maximum length/width perpendicular to the maximum length of 2.0 to 50, and the (D) negatively thermally expanded particles are contained. A conductive adhesive sheet, wherein the amount is in the range of 5 to 20% by mass with respect to the total amount of the resin composition.
[2] The above-mentioned [1], wherein in the conductive adhesive sheet, the orientation index S represented by the following formula (1) of the (C) conductive particles is in the range of 0.6 to 1.0 Sheet for conductive adhesion.
S=1/2(3cos2θ−1) (1)
(In the formula, θ is the angle formed by the maximum major axis of the (C) conductive particles with respect to the main surface of the conductive adhesive sheet.)
[3] The conductive adhesive sheet according to [1] or [2] above, wherein the (C) conductive particles are flat metal particles having a thickness of 5 to 20 μm.
[4] The conductive adhesive sheet according to any one of [1] to [3] above, wherein the (D) negative thermal expansion particles have a thermal expansion coefficient of less than 0 ppm/°C.
[5] The total content of the (A) epoxy resin content and the (B) phenol curing agent content is 5 to 20% by mass relative to the total amount of the resin composition, and the (C) The conductive adhesive sheet according to any one of the above [1] to [4], wherein the total content of the content of the conductive particles and the content of the (D) negative thermal expansion particles is 80 to 95% by mass. .
[6] The conductive adhesive sheet according to any one of [1] to [5] above, wherein the curing shrinkage rate of the conductive adhesive sheet before and after curing is 4% or less.
[7] The conductive adhesive sheet according to any one of [1] to [6] above, wherein a cured product of the resin composition has a coefficient of thermal expansion of 50 ppm/°C or less at 30 to 80°C.
[8] The conductive adhesive sheet according to any one of [1] to [7], which has a thermal conductivity of 30 W/m·K or more.
[9] (A) an epoxy resin, (B) a phenol curing agent, (C) conductive particles, and (D) negative thermal expansion particles are mixed to form a resin composition, and the resin composition is A method for producing a conductive adhesive sheet that is rolled at a pressure of 1 MPa or more to form a sheet, wherein the (C) conductive particles are perpendicular to the maximum major diameter/maximum major diameter of the (C) conductive particles. The aspect ratio defined by the width is 2.0 to 50, and the content of the (D) negative thermal expansion particles is in the range of 5 to 20% by mass with respect to the total amount of the resin composition. A method for producing a conductive adhesive sheet.
[10] The above-described [9], wherein in the obtained conductive adhesive sheet, the orientation index S represented by the following formula (1) of the (C) conductive particles is in the range of 0.6 to 1.0 A method for producing a conductive adhesive sheet.
S=1/2(3cos2θ−1) (1)
(In the formula, θ is the angle formed by the maximum major axis of the (C) conductive particles with respect to the main surface of the conductive adhesive sheet.)
[11] The method for producing a conductive adhesive sheet according to [9] or [10] above, wherein the (C) conductive particles are flat metal particles having a thickness of 5 to 20 μm.
[12] A support member, a cured product of the conductive adhesive sheet according to any one of [1] to [8] provided on the support member, and a cured product of the conductive adhesive sheet and a semiconductor element bonded onto the support member via a semiconductor element.

INDUSTRIAL APPLICABILITY According to the present invention, there is provided a conductive adhesive sheet capable of obtaining a highly reliable semiconductor device having high electrical conductivity and thermal conductivity, a method for producing the conductive adhesive sheet, and the conductive adhesive sheet. It is possible to provide a semiconductor device in which semiconductor elements are bonded by the method.

The invention will now be described in detail with reference to one embodiment.

<Conductive adhesive sheet>
The conductive adhesive sheet of the present embodiment is a sheet of a resin composition containing (A) an epoxy resin, (B) a phenol curing agent, (C) conductive particles, and (D) negative thermal expansion particles. A conductive adhesive sheet formed into a shape, wherein the (C) conductive particles have an aspect ratio defined by the maximum length / width perpendicular to the maximum length of 2.0 to 50, and the ( D) The content of the negative thermal expansion particles is in the range of 5 to 20% by mass with respect to the total amount of the resin composition.

[(A) epoxy resin]
The (A) epoxy resin used in the present embodiment imparts good curability and the like to the resin composition, and the cured product of the resin composition has low hygroscopicity, similar to general epoxy resins for adhesion. , In addition to imparting properties such as high heat resistance, even if the resin composition is highly filled with (C) conductive particles described later, the component that facilitates maintaining the flexibility of the cured product of the resin composition is.
(A) The epoxy resin is not particularly limited, but a liquid epoxy resin is preferably used. Here, the liquid epoxy resin refers to an epoxy resin that is in a liquid or semi-solid state at room temperature (25° C.), and includes, for example, an epoxy resin that is fluid at room temperature (25° C.). The viscosity of the liquid epoxy resin at 25° C. is preferably 100,000 mPa·s or less, more preferably 10,000 to 60,000 mPa·s.
The viscosity of the liquid epoxy resin at 25° C. can be measured with a rotary viscometer.

The weight average molecular weight (Mw) of the liquid epoxy resin is preferably 300 to 3,000, more preferably 500 to 1,000, from the viewpoint of fluidity and flexibility. Here, in the present specification, Mw is a value obtained by converting a chromatogram measured by gel permeation chromatography (GPC) into the molecular weight of standard polystyrene.

A biphenyl-type epoxy resin is preferable as the liquid epoxy resin. The biphenyl-type epoxy resin is an epoxy resin having a biphenyl skeleton, and the biphenyl skeleton in the present embodiment also includes those obtained by hydrogenating at least one aromatic ring among the biphenyl rings.

Specific examples of biphenyl-type epoxy resins include 4,4′-bis(2,3-epoxypropoxy)biphenyl, 4,4′-bis(2,3-epoxypropoxy)-3,3′,5, Epoxy obtained by reacting 5'-tetramethylbiphenyl, epichlorohydrin with 4,4'-biphenol or a biphenol compound such as 4,4'-(3,3',5,5'-tetramethyl)biphenol Resin etc. are mentioned. Among these, 4,4′-bis(2,3-epoxypropoxy)-3,3′,5,5′-tetramethylbiphenyl, 4,4′-(3,3′,5,5′- Glycidyl ether of tetramethyl)biphenyl is preferred. Biphenyl-type epoxy resins may be used singly or in combination of two or more.

Examples of commercial products used as biphenyl-type epoxy resins include YX7105 manufactured by Mitsubishi Chemical Corporation. By using a liquid epoxy resin, particularly a biphenyl-type epoxy resin, it is possible to easily maintain the melt viscosity of the resin composition within a suitable range even when the conductive particles (C) described later are highly filled, and further improve heat resistance. An excellent conductive adhesive sheet can be obtained.

In the present embodiment, one or more epoxy resins other than the biphenyl-type epoxy resin can be blended, regardless of whether they are crystalline or non-crystalline, as long as the effects of the present invention are not impaired. Examples of epoxy resins other than biphenyl-type epoxy resins include cresol novolac-type epoxy resins, phenol novolac-type epoxy resins, bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, bisphenol S-type epoxy resins, dicyclopentadiene-type epoxy resins, Heterocyclic epoxy resins such as triphenolmethane type epoxy resins, triazine nucleus-containing epoxy resins, stilbene type bifunctional epoxy resins, naphthalene type epoxy resins, condensed ring aromatic hydrocarbon-modified epoxy resins, alicyclic epoxy resins, and the like. be done.

The content of (A) the epoxy resin is preferably 4 to 15% by mass, more preferably 4 to 10% by mass, based on the total amount of the resin composition, from the viewpoint of adhesive properties.

[(B) phenol curing agent]
The (B) phenol curing agent used in the present embodiment is not particularly limited as long as it is a known curing agent having two or more phenolic hydroxyl groups in the molecule capable of reacting with the epoxy groups in the epoxy resin (A). can be used without
(B) As the phenol curing agent, specifically, novolak type phenol resins such as phenol novolak resins and cresol novolak resins obtained by reacting phenols such as phenol and alkylphenol with formaldehyde or paraformaldehyde, and these novolak types. Modified novolac-type phenol resins obtained by epoxidizing or butylating phenol resins, dicyclopentadiene-modified phenol resins, paraxylene-modified phenol resins, phenol aralkyl resins, naphthol aralkyl resins, triphenol alkane-type phenol resins, polyfunctional phenol resins, etc. mentioned. These may be used alone or in combination of two or more.
(B) As the phenol curing agent, novolac type phenol resins and phenol aralkyl resins are particularly preferable.

(B) The content of the phenolic curing agent is such that the ratio (b)/(a) of the number of phenolic hydroxyl groups (b) of the (B) phenolic curing agent to the number of epoxy groups (a) of the (A) epoxy resin is A range of 0.3 to 1.5 is preferable, and a range of 0.5 to 1.2 is more preferable. When the ratio (b)/(a) is 0.3 or more, the moisture resistance reliability of the cured product can be improved, and when the ratio (b)/(a) is 1.5 or less, the cured product Strength can be improved.

(B) The content of the phenolic curing agent is preferably 1 to 5% by mass, more preferably 2 to 5% by mass, based on the total amount of the resin composition, from the viewpoint of adhesive properties.

The total content of the above (A) epoxy resin content and (B) phenol curing agent content is preferably 5 to 20 masses relative to the total amount of the resin composition from the viewpoint of adhesive properties and heat resistance. %, more preferably 5 to 15% by mass.

[(C) Conductive particles]
The (C) conductive particles used in the present embodiment have an aspect ratio of 2.0 to 50 defined as the maximum major diameter of the particles/the width orthogonal to the maximum major diameter. If the aspect ratio is less than 2.0, the orientation index of the (C) conductive particles is lowered, leading to deterioration in the thermal conductivity of the resulting cured product of the conductive adhesive sheet. On the other hand, if the aspect ratio exceeds 50, the (C) conductive particles may be exposed on the surface of the conductive adhesive sheet, which may deteriorate the sheet properties or impair the smoothness of the sheet. From this point of view, the aspect ratio of (C) the conductive particles is preferably 3.0-40.
The aspect ratio can be measured by an image-based particle size/particle size distribution measuring method.

(C) As the conductive particles, from the viewpoint of thermal conductivity, metal particles such as gold particles, silver particles, copper particles, nickel particles, aluminum particles, iron particles, etc. are preferable, and gold particles and silver particles are more preferable. , silver particles are more preferred. (C) The shape of the conductive particles is preferably flat from the viewpoint of thermal conductivity.
The thickness (width perpendicular to the maximum length) of the (C) conductive particles is preferably 5 to 20 μm, more preferably 8 to 18 μm. When the thickness of the (C) conductive particles is 5 μm or more, the orientation index of the (C) conductive particles is within the desired range, and the thermal conductivity can be enhanced. On the other hand, when the thickness of the (C) conductive particles is 20 μm or less, good sheet properties and high smoothness can be obtained.
The thickness of the (C) conductive particles can be measured by an image-type particle size/particle size distribution measuring method.

(C) The content of the conductive particles is preferably 60 to 85% by mass, more preferably 70 to 85% by mass, based on the total amount of the resin composition. (C) When the content of the conductive particles is 60% by mass or more, the thermal conductivity of the cured product of the resin composition is improved, and when it is 85% by mass or less, it becomes easy to mold the conductive adhesive sheet.

[(D) Negative thermal expansion particles]
The (D) negative thermal expansion particles used in this embodiment have a negative thermal expansion coefficient that shrinks when heated. Since the conductive adhesive sheet of the present embodiment contains (D) negative thermal expansion particles, the coefficient of expansion of the conductive adhesive sheet can be kept low even when the semiconductor element generates heat. As a result, (C) contact points between the conductive particles are maintained, and good thermal conductivity is maintained.

(D) Negative thermal expansion particles preferably have a thermal expansion coefficient of less than 0 ppm/°C, more preferably -0.1 ppm/°C or less, and still more preferably -0.3 ppm/°C or less. Specifically, zirconium phosphate, zirconium tungstate phosphate (Zr ₂ (WO ₄ ) (PO ₄ ) ₂ , ZWP), LaCu ₃ Fe ₄ O ₁₂ (A-site ordered perovskite structure oxide), Bi _{1- x} Ln _x NiO ₃ (Ln=La, Nd, Eu, Dy, perovskite structure oxide), Al ₂ O ₃ .TiO ₂ , Li ₂ O.Al ₂ O ₃ .nSiO ₂ β-spodumene solid solution, Faujas zeolite (Na , Ca _0.5 , Mg _0.5 , K) _x [Al _x Si _12-x O ₂₄ ]·16H ₂ O, LiAlSiO ₄ , PbTiO ₃ , Sc ₂ W ₃ O ₁₂ , Lu ₂ W ₃ O ₁₂ , ZrW ₂ O ₈ , Mn ₃ XN (X=Cu—Sn, Zn—Sn, etc.). Among them, zirconium phosphate and zirconium tungstate phosphate are readily available, and zirconium phosphate, which has a large absolute value of thermal expansion coefficient and a small true specific gravity, is particularly suitable.
The thermal expansion coefficient can be measured with a laser thermal dilatometer or the like.

(D) The content of the negative thermal expansion particles is 5 to 20% by mass, preferably 8 to 15% by mass, based on the total amount of the resin composition. (D) If the content of the negative thermal expansion particles is less than 5% by mass, the curing shrinkage rate of the resin composition becomes too high and the reliability of the resulting semiconductor device deteriorates. The thermal conductivity of the object decreases.

The total content of the content of the conductive particles (C) and the content of the negative thermal expansion particles (D) is preferably 80 to 95% by mass, more preferably 85 to 95% by mass.

In addition, the total content of (A) the epoxy resin, (B) the phenol curing agent, (C) the conductive particles, and (D) the negative thermal expansion particles is preferably 90% by mass with respect to the total amount of the resin composition. or more, more preferably 95% by mass or more, and still more preferably 98% by mass or more.

[Curing accelerator]
In this embodiment, the resin composition may contain a curing accelerator. The curing accelerator is a component that accelerates the curing reaction between (A) the epoxy resin and (B) the phenolic curing agent. As the curing accelerator, any known curing accelerator can be used without any particular limitation as long as it exhibits the above-described effects.
Specific examples of curing accelerators include 2-methylimidazole, 2-ethylimidazole, 2-isopropylimidazole, 2-undecylimidazole, 1,2-dimethylimidazole, 2,4-dimethylimidazole, and 2-phenylimidazole. , 2-phenyl-4-methylimidazole, 4-methylimidazole, 4-ethylimidazole, 2-phenyl-4-hydroxymethylimidazole, 2-ethyl-4-methylimidazole, 1-cyanoethyl-2-methylimidazole, 2- phenyl-4-methyl-5-hydroxymethylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole, 2-undecylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1- imidazoles such as cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-phenylimidazole; 1,8-diazabicyclo [ 5.4.0]undecene-7 (DBU), 1,5-diazabicyclo[4.3.0]nonene, 5,6-dibutylamino-1,8-diazabicyclo[5.4.0]undecene-7, etc. diazabicyclo compounds and salts thereof; triethylamine, triethylenediamine, benzyldimethylamine, α-methylbenzyldimethylamine, triethanolamine, dimethylaminoethanol, tris (dimethylaminomethyl) phenol and other tertiary amines; trimethylphosphine, triethyl phosphine, tributylphosphine, diphenylphosphine, triphenylphosphine, tri(p-methylphenyl)phosphine, tri(nonylphenyl)phosphine, methyldiphenylphosphine, dibutylphenylphosphine, tricyclohexylphosphine, bis(diphenylphosphino)methane, 1, Examples include organic phosphine compounds such as 2-bis(diphenylphosphino)ethane. Among these, imidazoles are preferable from the viewpoint of good sheet formability. These may be used alone or in combination of two or more.

The content of the curing accelerator is preferably in the range of 0.1 to 5% by mass with respect to the total amount of the resin composition. When the content of the curing accelerator is 0.1% by mass or more, a sufficient effect of accelerating the curability can be obtained, and when it is 5% by mass or less, the humidity resistance reliability of the cured product can be improved.

[Flexible material]
In this embodiment, the resin composition may contain a flexible material. The flexible material is a component that allows the cured product of the resin composition to develop a sheet state. As the flexible material, any known flexible material can be used without any particular limitation as long as the material exhibits the above effects.
Specific examples of the flexible material include silicone oil, phenoxy resin having a weight average molecular weight (Mw) of 10,000 to 100,000, nitrile rubber, and acrylic rubber. Among them, silicone oil and phenoxy resin are preferable from the viewpoint of good sheet properties. These may be used alone or in combination of two or more.

The content of the flexible material is preferably in the range of 0.5 to 5% by mass with respect to the total amount of the resin composition. When the content of the flexible material is 0.5% by mass or more, the cured product of the resin composition has good sheet properties, and when it is 5% by mass or less, excessive increase in the melt viscosity of the resin composition is suppressed. be able to.

[Other ingredients]
In the resin composition used in the present embodiment, in addition to the above components, a coupling agent, an antifoaming agent, and a surfactant that are generally blended in this type of composition to the extent that the effects of the present invention are not impaired. , coloring agents (pigments, dyes), various polymerization inhibitors, antioxidants, inorganic ion exchangers, and other various additives can be blended as necessary. Each of these additives may be used alone or in combination of two or more.
Examples of the coupling agent include silane coupling agents such as epoxysilane, mercaptosilane, aminosilane, alkylsilane, cladesilane, vinylsilane, and sulfidesilane, titanate coupling agents, aluminum coupling agents, and aluminum/zirconium coupling agents. is mentioned.
Carbon black etc. are mentioned as said coloring agent.
Examples of the inorganic ion exchanger include hydrotalcite.

The thermal expansion coefficient of the cured product of the resin composition is preferably 50 ppm/°C or less, more preferably 40 ppm/°C or less at 30 to 80°C.
The coefficient of thermal expansion can be measured by the method described in Examples.

The conductive adhesive sheet of the present embodiment is obtained by molding the resin composition described above into a sheet.
In the conductive adhesive sheet of the present embodiment, the orientation index S of the (C) conductive particles represented by the following formula (1) is preferably in the range of 0.6 to 1.0.
S=1/2(3cos2θ−1) (1)
Here, in formula (1), θ is the angle formed by the maximum major axis of the (C) conductive particles with respect to the main surface of the conductive adhesive sheet.
The orientation index is a numerical representation of the state in which the (C) conductive particles are present in parallel or at an acute angle to the planar direction of the conductive adhesive sheet. The closer the numerical value obtained from the formula (1) is to 1, the smaller the angle formed by the planar direction of the conductive adhesive sheet and the (C) conductive particles, and the smaller the angle formed by the conductive adhesive sheet (C) with respect to the planar direction of the conductive adhesive sheet ( C) shows a state in which the conductive particles are parallel; On the other hand, the closer the numerical value obtained from the formula (1) is to 0, the larger the angle formed between the planar direction of the conductive adhesive sheet and the (C) conductive particles, and the greater the angle between the planar direction of the conductive adhesive sheet and the planar direction of the conductive adhesive sheet. (C) shows that the conductive particles approach vertical.
Favorable thermal conductivity is obtained when the orientation index is within the above range. On the other hand, if the orientation index is less than 0.6, the contact ratio between the (C) conductive particles is low, resulting in poor thermal conductivity.
The orientation index can be measured by the method described in Examples.

The conductive adhesive sheet of the present embodiment preferably has a cure shrinkage rate of 4% or less before and after curing.
The conductive adhesive sheet of the present embodiment preferably has a thermal conductivity of 30 W/m·K or more, more preferably 32 W/m·K or more.
The cure shrinkage and thermal conductivity can be measured by the methods described in Examples.

The electrically conductive adhesive sheet of the present embodiment is suitable as an adhesive sheet material useful for applications requiring thermal conductivity and electrical conductivity, particularly semiconductor adhesive applications. In particular, good thermal conductivity is maintained even when the element generates heat.

<Method for producing conductive adhesive sheet>
In the method for producing a conductive adhesive sheet of the present embodiment, (A) an epoxy resin, (B) a phenol curing agent, (C) conductive particles, and (D) negative thermal expansion particles are mixed to form a resin. A method for producing a conductive adhesive sheet comprising forming a composition and rolling the resin composition at a pressure of 0.1 MPa or more to form a sheet, wherein the (C) conductive particles are the (C) conductive The aspect ratio defined by the maximum major axis/width perpendicular to the maximum major axis of the physical particles is 2.0 to 50, and the content of the negative thermal expansion particles (D) is 5 to 5 with respect to the total amount of the resin composition. It is characterized by being in the range of 15% by mass.

The resin composition contains (A) an epoxy resin, (B) a phenolic curing agent, (C) conductive particles, (D) negative thermal expansion particles, and other various components blended as necessary. It can be prepared by sufficiently mixing with a mixer or the like.
The above (A) epoxy resin, (B) phenolic curing agent, (C) conductive particles, (D) negative thermal expansion particles, and other various components that are optionally blended are the above [conductive adhesive sheet]. can be used.

The conductive particles (C) have an aspect ratio of 2.0 to 50 defined as the maximum length of the particles/the width perpendicular to the maximum length of the particles. If the aspect ratio is less than 2.0, the orientation index of the (C) conductive particles is lowered, leading to deterioration in the thermal conductivity of the resulting cured product of the conductive adhesive sheet. On the other hand, if the aspect ratio exceeds 50, the (C) conductive particles may be exposed on the surface of the obtained conductive adhesive sheet, which may deteriorate the sheet properties and impair the smoothness of the sheet. From this point of view, the aspect ratio of (C) the conductive particles is preferably 3.0-40.
The aspect ratio can be measured by an image-based particle size/particle size distribution measuring method.

The content of the (D) negative thermal expansion particles is in the range of 5 to 20% by mass, preferably in the range of 8 to 15% by mass, based on the total amount of the resin composition. (D) If the content of the negative thermal expansion particles is less than 5% by mass, the curing shrinkage rate of the resin composition becomes too high and the reliability of the resulting semiconductor device deteriorates. The thermal conductivity of the object decreases.

Next, the resin composition is rolled at a pressure of 0.1 MPa or more to form a sheet.
A rolling apparatus capable of controlling heating and pressure is preferably used in order for the conductive particles (C) to develop an orientation index. Considering the material of (C) the conductive particles, a stainless steel material is preferably used as the material of the rolling rolls. Specifically, a roll press machine manufactured by Yuri Roll Machine Co., Ltd. can be used. Furthermore, the orientation index is affected by rolling conditions. A pressure of 0.1 MPa or more is applied to the resin composition when the resin composition passes through the rolling rolls. If the pressure is less than 0.1 MPa, the orientation of the (C) conductive particles may deteriorate, and the thermal conductivity may deteriorate. (C) The orientation index S of the conductive particles is within the above range, and from the viewpoint of improving the orientation of the (C) conductive particles, the pressure is preferably 0.1 to 10 MPa. .1 to 1.0 MPa is more preferable. In addition, when the pressure is 10 MPa or less, it is possible to suppress the (C) formation of a foil of the conductive particles.

The heating temperature is preferably 70 to 100°C, more preferably 75 to 90°C. When the heating temperature is 70° C. or higher, the viscosity of the resin composition does not become too high, and the orientation index S of the (C) conductive particles can be within the range described above. Orientation can be improved. On the other hand, when the heating temperature is 100° C. or lower, the viscosity of the resin composition does not become too low, and the sheet properties of the obtained conductive adhesive sheet can be improved.

The speed at which the resin composition passes through the rolling rolls is preferably 1 to 10 m/min, more preferably 1 to 6 m/min. When the speed is 1 m/min or more, productivity is improved, and when it is 10 m/min or less, it is possible to suppress the occurrence of blurring during sheet molding.

The melt viscosity of the resin composition when heated at 80° C. is preferably 1 to 10 Pa·s, more preferably 3 to 10 Pa·s. When the melt viscosity of the resin composition is within the above range, (C) the conductive particles and (D) the negative thermal expansion particles can be uniformly dispersed in the resin composition.
The melt viscosity can be measured by the method described in Examples.

The conductive adhesive sheet thus obtained may be formed on a support film.
As the support film, a plastic film such as polyethylene, polypropylene, polyester, polycarbonate, polyarylate and polyacrylonitrile having a release agent layer on one side is used.
The thickness of the support film is usually 10 to 50 μm, preferably 25 to 38 μm, from the viewpoint of handleability.

The thickness of the conductive adhesive sheet is preferably 10-100 μm, more preferably 10-50 μm. By setting the thickness of the conductive adhesive sheet to 10 μm or more, the (C) conductive particles can be uniformly dispersed in the conductive adhesive sheet, and exposure to the surface can be suppressed. and (C) the orientation of the conductive particles can be improved.

<Semiconductor device>
The semiconductor device of the present embodiment includes a support member, a cured product of the conductive adhesive sheet provided on the support member, and a cured product of the conductive adhesive sheet provided on the support member. and a semiconductor element bonded to the

For example, the semiconductor device of the present embodiment is temporarily attached to a bonding surface of a silicon chip or the like under the conditions of a temperature of 50 to 80° C., a pressure of 0.1 to 1 MPa, and a heating and pressurizing time of 0.1 to 1 minute. It is mounted on a support member such as a frame, heated and pressurized under the conditions of a temperature of 80° C. to 200° C., a pressure of 0.1 to 5 MPa, and a heating and pressurizing time of 0.1 to 1 minute. It can be produced by heating and curing for 5 to 2 hours.

Examples of the support member include a copper frame, a metal substrate such as aluminum or iron plate, a ceramic substrate, a glass epoxy substrate, and the like.
Examples of semiconductor elements include ICs, LSIs, diodes, thyristors, transistors, and the like.

EXAMPLES Next, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.

(Examples 1 to 7, Comparative Examples 1 to 4)
(1) Preparation of resin composition Each component of the type and blending amount shown in Table 1 is mixed at 25 ° C. using a rotation mixer (manufactured by Thinky Co., model number: ARV-310) to obtain a resin composition. prepared.
In addition, in Table 1, a blank represents no compounding.

(2) Preparation of conductive adhesive sheet The above resin composition is supplied on one side of a release film (manufactured by Toyobo Co., Ltd., trade name: TN-200, thickness 25 μm). A conductive adhesive sheet having a thickness of 20 μm was formed on one side of the release film by passing it through pressure rolls. The pressure roll had a diameter of 150 mm, and the molding conditions were a temperature of 80°C, a speed of 1 m/min, and a roll pressure of 0.1 MPa.

The details of each component shown in Table 1 used in the preparation of the resin composition are as follows.

[(A) epoxy resin]
・ YX7105: liquid epoxy resin, manufactured by Mitsubishi Chemical Corporation, trade name, epoxy equivalent 480, weight average molecular weight 1,000, viscosity 30,000 mPa s

[(A) Thermosetting resin other than epoxy resin]
・ SA-9000: modified polyphenylene ether resin, manufactured by SABIC, trade name

[(B) phenol curing agent]
・BRG-557: phenolic novolak resin, manufactured by Showa Denko Co., Ltd., trade name, hydroxyl equivalent 103
・HE100C-15: phenol aralkyl resin, manufactured by Air Water Inc., trade name, hydroxyl equivalent 170

[(C) Conductive particles]
・ AgC-222: silver powder, manufactured by Fukuda Metal Foil & Powder Co., Ltd., trade name, thickness 15 μm, aspect ratio 3.5

[(C) Conductive particles other than conductive particles]
・ AGF-5S: silver powder, manufactured by Tokuriki Honten Co., Ltd., product name, thickness 10 μm, aspect ratio 1.1

[(D) Negative thermal expansion particles]
・ WF-1: zirconium phosphate, manufactured by Toagosei Co., Ltd., trade name, coefficient of thermal expansion -3 ppm / ° C.
WA-2: zirconium phosphate, manufactured by Toagosei Co., Ltd., trade name, coefficient of thermal expansion -0.5 ppm/°C

[(D) Thermal expansion particles other than negative thermal expansion particles]
・ TFZ-A15P: aluminum nitride, manufactured by Toyo Aluminum Co., Ltd., trade name, coefficient of thermal expansion 4.5 ppm / ° C.

[Curing accelerator]
・ 2P4MHZ-PW: 2-phenyl-4-methyl-5-hydroxymethylimidazole, manufactured by Shikoku Chemical Industry Co., Ltd., trade name

[Flexible material]
・SF-8427: Silicone oil, manufactured by Dow Corning Toray Co., Ltd., trade name ・YX6954BH30: Phenoxy resin, manufactured by Mitsubishi Chemical Corporation, trade name, weight average molecular weight 40,000

An adhesive sheet (hereinafter simply referred to as an adhesive sheet) having a conductive adhesive sheet formed on one side of the release films obtained in Examples 1 to 7 and Comparative Examples 1 to 4 was used under the following measurement conditions. Then, the properties of the conductive adhesive sheet were measured and evaluated. The evaluation results are shown in Table 1.

<Evaluation items>
(1) Sheet property The adhesive sheet was bent 180 degrees, visually observed, and evaluated according to the following criteria.
○: No cracks in the conductive adhesive sheet and no peeling from the release film ×: Cracks in the conductive adhesive sheet or peeling from the release film occurred

(2) Temporary adhesion It is possible to attach a conductive adhesive sheet to a 6 mm x 6 mm silicon chip and a gold chip on the back surface with a gold deposition layer on the bonding surface under the conditions of 65 ° C., 1 second, and 1 MPa pressure. It was judged as ○ when it was not possible, and as × when it was impossible to stick.

(3) (C) Orientation Index of Conductive Particles The cross section of the conductive adhesive sheet is observed using a scanning electron microscope (SEM), and the orientation of (C) the conductive particles with respect to the plane direction of the conductive adhesive sheet. The angle was measured, and (C) the orientation index S of the conductive particles was calculated from the following formula (1).
S=1/2(3cos2θ−1) (1)
(In the formula, θ is the angle formed by the maximum major axis of the (C) conductive particles with respect to the main surface of the conductive adhesive sheet.)

(4) Cure shrinkage rate In accordance with the general test method for thermosetting plastics (JIS K6911: 2006), a conductive adhesive sheet was cut into a size of 10 cm long × 1 cm wide × 0.1 mm thick to prepare a sample. The sample was cured at a temperature of 200° C., and the change in the longitudinal direction before and after curing was measured as shrinkage.

(5) Thermal expansion coefficient The conductive adhesive sheet is cured at 200 ° C. for 2 hours, cut into a size of 3 cm long × 0.5 cm wide × 0.1 mm thick to prepare a sample, and the sample is analyzed by a thermomechanical analyzer ( The temperature was raised from 30° C. to 80° C. by 10° C. per minute using a Seiko Instruments Inc. device name: TMA/SS), and the amount of deformation of the sample was measured as the coefficient of thermal expansion.

(6) Thermal conductivity (laser flash method)
The conductive adhesive sheet was cured at 200° C. for 2 hours, and cut into a size of 1 cm long×1 cm wide×1 mm thick to prepare a sample. The thermal conductivity of the sample was measured by a laser flash method according to JIS R 1611:1997 using a thermal conductivity meter (manufactured by Advance Riko, device name: TC7000).
It should be noted that a thermal conductivity of 30 W/m·K or more was regarded as acceptable.

(7) Thermal conductivity (periodic heating method)
The conductive adhesive sheet was cured at 200° C. for 2 hours, and cut into a size of 1 cm long×1 cm wide×1 mm thick to prepare a sample. The thermal conductivity of the sample at 150° C. was measured by the periodic heating method according to JIS R 1611:1997 using a thermal conductivity meter (manufactured by Advance Riko, device name: FTC-1).
It should be noted that a thermal conductivity of 30 W/m·K or more was regarded as acceptable.

(8) Melt Viscosity The melt viscosity was measured after pulverizing the conductive adhesive sheet into a powder state with a pulverizer. The temperature was raised from room temperature (25° C.) to 80° C. by 10° C. per minute and held at 80° C. for 20 minutes.
A minimum melt viscosity of 1 to 10 Pa·s while held at 80° C. was considered acceptable.

(9) Adhesive strength during heat After temporarily attaching a conductive adhesive sheet to a silicon chip of 6 mm × 6 mm and a back gold chip with a gold vapor deposition layer on the bonding surface under the conditions of 65 ° C., 1 second, and a pressure of 1 MPa, it is solid. 125° C. for 5 seconds under pressure of 0.1 MPa, and further cured in an oven at 180° C. for 1 hour. Using a mounting strength measuring device (manufactured by Besi, device name: 2200 EVO-plus), the hot die shear strength at 260° C. was measured.

(10) reliability test (PCT)
The sample prepared in (9) was allowed to absorb water for 72 hours under conditions of 127 ° C. and 0.25 MPa in a pressure cooker, and then reflowed at 240 ° C. for 90 seconds. investigated (number of samples = 20).

(11) Reliability test (cold heat cycle)
The sample prepared in (9) was subjected to a 1000-cycle test under conditions where one cycle was from -55 ° C to 150 ° C in a thermal cycle tester, and the rate of occurrence of defects (detachment defects) was investigated (number of samples = 20).

Claims (12)

A conductive adhesive sheet formed by molding a resin composition containing (A) an epoxy resin, (B) a phenol curing agent, (C) conductive particles, and (D) negative thermal expansion particles into a sheet. and
The (C) conductive particles have an aspect ratio defined by the maximum length/width perpendicular to the maximum length of 2.0 to 50,
The conductive adhesive sheet, wherein the content of the negative thermal expansion particles (D) is in the range of 5 to 20% by mass with respect to the total amount of the resin composition. The conductive adhesive sheet according to claim 1, wherein the (C) conductive particles have an orientation index S represented by the following formula (1) in the range of 0.6 to 1.0 in the conductive adhesive sheet. sheet.
S=1/2(3cos2θ−1) (1)
(In the formula, θ is the angle formed by the maximum major axis of the (C) conductive particles with respect to the main surface of the conductive adhesive sheet.) 3. The conductive adhesive sheet according to claim 1, wherein the conductive particles (C) are flat metal particles having a thickness of 5 to 20 μm. The conductive adhesive sheet according to any one of claims 1 to 3, wherein the (D) negative thermal expansion particles have a thermal expansion coefficient of less than 0 ppm/°C. The total content of the (A) epoxy resin content and the (B) phenol curing agent content is 5 to 20% by mass with respect to the total amount of the resin composition, and the (C) conductive particles The conductive adhesive sheet according to any one of claims 1 to 4, wherein the total content of the content of (D) and the content of the negative thermal expansion particles is 80 to 95% by mass. The conductive adhesive sheet according to any one of claims 1 to 5, wherein the conductive adhesive sheet has a curing shrinkage rate of 4% or less before and after curing. The conductive adhesive sheet according to any one of claims 1 to 6, wherein a cured product of the resin composition has a thermal expansion coefficient of 50 ppm/°C or less at 30 to 80°C. The conductive adhesive sheet according to any one of claims 1 to 7, which has a thermal conductivity of 30 W/m·K or more. (A) an epoxy resin, (B) a phenol curing agent, (C) conductive particles, and (D) negative thermal expansion particles are mixed to form a resin composition, and the resin composition is heated at a pressure of 0.1 MPa or more. A method for producing a conductive adhesive sheet that is rolled under pressure and formed into a sheet, comprising:
The (C) conductive particles have an aspect ratio defined by the maximum length/width perpendicular to the maximum length of the (C) conductive particles of 2.0 to 50,
A method for producing a conductive adhesive sheet, wherein the content of the (D) negatively thermally expandable particles is in the range of 5 to 20% by mass with respect to the total amount of the resin composition. The conductive adhesive according to claim 9, wherein in the obtained conductive adhesive sheet, the orientation index S represented by the following formula (1) of the (C) conductive particles is in the range of 0.6 to 1.0. sheet manufacturing method.
S=1/2(3cos2θ−1) (1)
(In the formula, θ is the angle formed by the maximum major axis of the (C) conductive particles with respect to the main surface of the conductive adhesive sheet.) 11. The method for producing a conductive adhesive sheet according to claim 9, wherein the (C) conductive particles are flat metal particles having a thickness of 5 to 20 μm. Through a support member, a cured product of the conductive adhesive sheet according to any one of claims 1 to 8 provided on the support member, and a cured product of the conductive adhesive sheet, the A semiconductor device, comprising: a semiconductor element bonded onto a supporting member.