JPWO2016002892A1 - Thermally conductive sheet and semiconductor device - Google Patents

Abstract

A heat conductive sheet comprising a thermosetting resin and a filler dispersed in the thermosetting resin, wherein the heat conductive sheet is measured by the following procedures (a) to (d). The high temperature storage stability factor Q1 of the cured body is 0.7 or more and 1.0 or less. (A) The thermal conductivity in the thickness direction of the cured body is measured, and the obtained measured value is set to λ0. (B) The cured body is stored in an environment of 200 ° C. for 24 hours. (C) Procedure (b) Measure the thermal conductivity in the thickness direction of the cured body after storage by (1) and calculate the obtained measurement value as λ1 (d) Q1 = λ1 / λ0

Description

  The present invention relates to a heat conductive sheet and a semiconductor device.

In a package structure in which a semiconductor chip is molded, it is required to improve heat dissipation characteristics in order to prevent a failure due to heat generation of the semiconductor chip. As a means for improving heat dissipation characteristics, it is generally performed to radiate heat generated in a semiconductor chip to a cooling member. The member on which the semiconductor chip is mounted and the cooling member are joined by a heat conductive material having high heat conductivity.
As a material for the heat conductive material, a heat conductive sheet having a structure including a heat conductive filler in a resin is widely used. Patent Documents 1 and 2 describe examples of such a heat conductive sheet.

  In Patent Document 1, a thermally conductive polymer composition containing a polymer matrix material and a carbon powder obtained by graphitizing a polymer material having an aromatic ring in the main chain by heat treatment is molded. A thermally conductive molded body is described. Patent Document 2 describes a resin composition containing an epoxy resin monomer, a novolac resin, and an inorganic filler.

JP 2002-363421 A International Publication No. 2011/040416 Pamphlet

  For a semiconductor device provided with a heat radiating member via a heat conductive material, it is required to improve stability during use in a high temperature environment. However, with the techniques described in Patent Documents 1 and 2, it has been difficult to obtain sufficient stability.

According to the present invention,
A heat conductive sheet comprising a thermosetting resin and a filler dispersed in the thermosetting resin, wherein the heat conductive sheet is measured by the following procedures (a) to (d). high-temperature storage stability rate to Q ₁ cured product, the thermally conductive sheet is provided at 0.7 to 1.0.
(A) The thermal conductivity in the thickness direction of the cured body is measured, and the obtained measured value is set to λ _0. (b) The cured body is stored in an environment of 200 ° C. for 24 hours. (C) Procedure (b) ), The thermal conductivity in the thickness direction of the cured body after storage is measured, and the obtained measured value is λ ₁ (d) Q ₁ = λ ₁ / λ ₀ is calculated.

  Further, according to the present invention, a heat conductive material, a semiconductor chip bonded to one surface of the heat conductive material, a metal member bonded to a surface opposite to the one surface of the heat conductive material, There is provided a semiconductor device comprising a heat conductive material, a sealing material for sealing the semiconductor chip and the metal member, wherein the heat conductive material is formed of the above-described heat conductive sheet.

  ADVANTAGE OF THE INVENTION According to this invention, the stability at the time of use in the high temperature environment of a semiconductor device can be improved.

  The above-described object and other objects, features, and advantages will become more apparent from the preferred embodiments described below and the accompanying drawings.

It is a typical sectional view of a semiconductor device concerning this embodiment. It is typical sectional drawing which shows the modification of the semiconductor device which concerns on this embodiment.

  Hereinafter, embodiments will be described with reference to the drawings. In all the drawings, the same reference numerals are given to the same components, and the description will be omitted as appropriate.

The heat conductive sheet which concerns on this embodiment contains the thermosetting resin and the filler disperse | distributed in the said thermosetting resin. Also, high temperature storage stability rate to _{Q 1} cured body of the thermal conductive sheet to be measured by the following procedures (a) ~ (d) is 0.7 to 1.0.
(A) The thermal conductivity in the thickness direction of the cured body is measured, and the obtained measured value is λ _0. (b) The cured body is stored in an environment of 200 ° C. for 24 hours. (C) Procedure (b) ), The thermal conductivity in the thickness direction of the cured body after storage is measured, and the obtained measured value is λ ₁ (d) Q ₁ = λ ₁ / λ ₀ is calculated.

In a semiconductor device, for example, by providing a heat radiating member through a heat conductive material formed using a cured body obtained by curing a heat conductive sheet, heat generated inside the device is effectively dissipated to the outside. ing. As a result, failures due to characteristic fluctuations in semiconductor elements and the like are suppressed, and the stability of the semiconductor device is improved.
On the other hand, with respect to semiconductor devices used for in-vehicle applications, etc., it is required to suppress the failure rate in a severe high temperature environment to a very low level and improve its stability to a higher degree. However, it has been difficult to realize a semiconductor device having sufficient stability, particularly in a high temperature environment of 150 ° C. or higher. The inventor diligently studied the factors that cause the stability of the semiconductor device to deteriorate under a high temperature environment. As a result, a decrease in the stability of the semiconductor device in a high temperature environment results in a decrease in the thermal conductivity of the heat conducting material due to the application of a high temperature thermal history, thereby reducing the heat dissipation efficiency for the heat generated from inside the semiconductor device. It was newly found out that it is caused by this.

In the present embodiment, based on such knowledge, the ratio of thermal conductivity before and after storing the cured body of the thermal conductive sheet at 200 ° C. for 24 hours is defined as a high temperature storage stability rate, which is within a certain range. It is to control to. According to this embodiment, the high-temperature storage stability factor Q ₁ (= λ ₁ / λ ₀ ) of the cured body of the heat conductive sheet can be controlled to 0.7 or more and 1.0 or less. This makes it possible to improve the stability of the semiconductor device when used in a high temperature environment.

  Hereinafter, the thermally conductive sheet and the semiconductor device according to the present embodiment will be described in detail.

First, the heat conductive sheet which concerns on this embodiment is demonstrated.
In this embodiment, a heat conductive sheet points out especially the thing of a B stage state. A cured body obtained by applying a thermally conductive sheet to a semiconductor package and curing the sheet functions as a thermally conductive material in the semiconductor package.

The heat conductive material obtained by curing the heat conductive sheet is, for example, a heating element such as a semiconductor chip, or a substrate such as a lead frame on which the heating element is mounted, and a metal plate constituting a heat dissipation member such as a heat sink. Between. Thereby, the heat generated from the heating element can be effectively dissipated to the outside of the semiconductor package.
As an example of a semiconductor package to which the thermally conductive sheet according to the present embodiment is applied, a thermally conductive material, a semiconductor chip bonded to one surface of the thermally conductive material, and opposite to the one surface of the thermally conductive material What is provided with the metal member joined to the surface of the side, and the sealing material which seals the said heat conductive material, the said semiconductor chip, and the said metal member is mentioned. At this time, a cured body obtained by curing the heat conductive sheet is used as the heat conductive material.

  The planar shape of the heat conductive sheet is not particularly limited, and can be appropriately selected according to the shape of the heat radiating member, the heating element, and the like, and may be rectangular, for example. The film thickness of the heat conductive sheet is, for example, 50 μm or more and 500 μm or less. Thereby, the heat | fever from a heat generating body can be more effectively transmitted to a heat radiating member, improving mechanical strength and heat resistance.

Thermally conductive sheet, the following steps (a) ~ high temperature storage stability rate to _{Q 1} cured product as determined by (d) is 0.7 to 1.0.
(A) The thermal conductivity in the thickness direction of the cured body is measured, and the obtained measured value is λ _0. (b) The cured body is stored in an environment of 200 ° C. for 24 hours. (C) Procedure (b) ), The thermal conductivity in the thickness direction of the cured body after storage is measured, and the obtained measured value is λ ₁ (d) Q ₁ = λ ₁ / λ ₀ is calculated. Here, the thermal conductive sheet The cured product refers to a cured product obtained by thermally curing a thermally conductive sheet at 180 ° C. for 1 hour. Hereinafter, similar in description of a method of calculating the high-temperature storage stability rate Q ₂ and high temperature storage stability rate Q _3.

By the high-temperature storage stability rate Q ₁ and less than the above lower limit, even when the long time storage or use in a high temperature environment, the thermal conductivity of the thermally conductive sheet cured product of can be sufficiently maintained. This makes it possible to improve the stability of the semiconductor device when used or stored in a high temperature environment. Moreover, the dielectric breakdown of the heat conductive sheet due to a high-temperature heat history can be suppressed. The upper limit of the high temperature storage stability rate Q ₁ is, although not particularly limited and may be, for example, 1.0. In the present embodiment, from the viewpoint of more effectively improving the stability of the semiconductor device under a high temperature environment, the high temperature storage stability factor Q ₁ is not particularly limited, but is preferably 0.75 or more, for example, 0.8 The above is more preferable, and 0.9 or more is more preferable.

Note that the thermal conductivity λ ₁ and the thermal conductivity λ ₀ of the cured body of the heat conductive sheet are both values measured at 25 ° C. The thermal conductivity of the cured body of the heat conductive sheet can be measured by, for example, a laser flash method.

In the present embodiment, the upper limit value of the thermal conductivity λ ₀ is not particularly limited, but can be set to, for example, 50 W / m · K. In the present embodiment, from the viewpoint of more effectively improving the stability of the semiconductor device under a high temperature environment, the thermal conductivity λ ₀ is preferably 8 W / m · K or more, and more preferably 10 W / m · K or more. 11 W / m · K or more is more preferable, and 12 W / m · K or more is more preferable.

Further, the thermal conductivity λ ₁ of the cured body of the heat conductive sheet is not particularly limited, but is preferably 6 W / m · K or more, more preferably 7 W / m · K or more, and 8 W / m · K or more, for example. More preferred is 9 W / m · K or more. Thereby, the stability of the semiconductor device can be improved more effectively. The upper limit value of the thermal conductivity λ ₁ (25 ° C.) is not particularly limited, but can be set to, for example, 30 W / m · K.

The thermal conductivity λ ₁ and thermal conductivity λ ₀ of the cured body of the thermal conductive sheet, and the high-temperature storage stability Q ₁ calculated from these are the types and blending ratios of the respective components constituting the thermal conductive sheet, and It can be controlled by appropriately adjusting the method for producing the heat conductive sheet. In the present embodiment, the type of the thermosetting resin (A) and the filler (B) is particularly appropriately selected, and the solvent constituting the resin varnish for forming the thermally conductive sheet is appropriately selected. The kneading of the thermosetting resin (A) and the filler (B) under specific conditions, including a step of applying a compression pressure to the heat conductive sheet, and the like, the heat conductivity λ ₁ , It is mentioned as a factor for controlling the thermal conductivity λ ₀ and the high-temperature storage stability Q ₁ .

In the present embodiment, the following steps (e) ~ high temperature storage stability rate _{Q 2} of the cured product as determined by (h), for example 0.7 to 1.0.
(E) The storage elastic modulus at 25 ° C. of the cured body is measured, and the obtained measured value is defined as E ′ _0. (f) The cured body is stored in an environment of 200 ° C. for 24 hours (g) Procedure ( The storage elastic modulus at 25 ° C. of the cured body after storage according to f) is measured, and the measured value obtained is defined as E ′ ₁ (h) Q ₂ = E ′ ₁ / E ′ ₀ is calculated.

By the high-temperature storage stability rate Q ₂ and less than the above lower limit, even when the long time storage or use in a high temperature environment, the mechanical strength in the thermally conductive sheet can be sufficiently maintained. On the other hand, by the high-temperature storage stability rate Q ₂ and more than the above upper limit, even when the long time storage or use under a high-temperature environment, it is possible to sufficiently maintain the stress relaxation effect against external stress. In the present embodiment, from the viewpoint of maintaining mechanical strength and stress relaxation effect, the high temperature storage stability Q ₂ is more preferably 0.8 or more and 1.0 or less, and 0.85 or more and 1.0 or less. Is particularly preferred.

In the present embodiment, the following steps (i) ~ (l) high temperature storage stability rate _{Q 3} of the cured product is measured by, for example 0.7 to 1.0.
(I) The loss elastic modulus at 25 ° C. of the cured body is measured, and the obtained measured value is set to E ″ _0. (j) The cured body is stored in an environment of 200 ° C. for 24 hours (k) Procedure The loss elastic modulus at 25 ° C. of the cured body after storage according to (j) is measured, and the obtained measured value is defined as E ″ ₁ (l) Q ₃ = E ″ ₁ / E ″ ₀ is calculated. Do

The high-temperature storage stability rate Q ₃ by the above-described lower limit, it is possible in particular to stress effectively mitigate generated during temperature cycling. On the other hand, by the high-temperature storage stability rate Q ₃ and more than the above upper limit, increasing the uniformity in thickness of the thermally conductive sheet, it is possible to suppress variations in the resulting thermal stress to variations in thickness . In the present embodiment, from the viewpoint of improving the uniformity of stress relaxation and a thickness, high temperature storage stability rate Q _3, more preferably 0.8 to 1.0, 0.85 or 1.0 The following is particularly preferable.

The storage elastic modulus E ′ ₁ and storage elastic modulus E ′ ₀ and the loss elastic modulus E ″ ₁ loss elastic modulus and E ″ ₀ of the cured body of the heat conductive sheet are measured by, for example, dynamic viscoelasticity measurement (DMA (Dynamic Mechanical Analysis).
Further, the storage elastic modulus E ′ ₁ and storage elastic modulus E ′ ₀ , the loss elastic modulus E ″ _{1 the} loss elastic modulus and E ″ ₀ of the cured body of the heat conductive sheet, and the high-temperature storage stability calculated from them. Q ₂ and high temperature storage stability rate Q ₃ are can be controlled types and proportions of the components constituting the thermally conductive sheet, and by appropriately adjusting the manufacturing method of the thermal conductive sheet.

  A heat conductive sheet contains a thermosetting resin (A) and the filler (B) disperse | distributed in the thermosetting resin (A).

(Thermosetting resin (A))
Examples of the thermosetting resin (A) include epoxy resins, polyimide resins, benzoxazine resins, unsaturated polyester resins, phenol resins, melamine resins, silicone resins, bismaleimide resins, acrylic resins, and cyanate resins. As the thermosetting resin (A), one of these may be used alone, or two or more may be used in combination.
As the thermosetting resin (A), an epoxy resin (A1) is preferable. By using the epoxy resin (A1), the glass transition temperature can be increased, and the thermal conductivity of the thermal conductive sheet can be improved. Moreover, since glass transition temperature can be raised by using cyanate resin, the heat resistance of a heat conductive sheet can be improved.

  Examples of the epoxy resin (A1) include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol E type epoxy resin, bisphenol S type epoxy resin, bisphenol M type epoxy resin (4,4 ′-(1,3- Phenylenediisopridiene) bisphenol type epoxy resin), bisphenol P type epoxy resin (4,4 '-(1,4-phenylenediisopridiene) bisphenol type epoxy resin), bisphenol Z type epoxy resin (4,4' -Cyclohexiene bisphenol type epoxy resin), etc .; phenol novolac type epoxy resin, cresol novolac type epoxy resin, trisphenol group methane type novolac type epoxy resin, tetraphenol group ethane type novo Type epoxy resins, novolak type epoxy resins such as novolak type epoxy resins having a condensed ring aromatic hydrocarbon structure; biphenyl type epoxy resins; xylylene type epoxy resins, arylalkylene type epoxy resins such as biphenyl aralkyl type epoxy resins; Naphthalene type epoxy resins such as renether type epoxy resins, naphthol type epoxy resins, naphthalene diol type epoxy resins, bifunctional or tetrafunctional epoxy type naphthalene resins, binaphthyl type epoxy resins, naphthalene aralkyl type epoxy resins, etc .; anthracene type epoxy resins; phenoxy Type epoxy resin; dicyclopentadiene type epoxy resin; norbornene type epoxy resin; adamantane type epoxy resin; fluorene type epoxy resin.

  As the epoxy resin (A1), one of these may be used alone, or two or more may be used in combination.

  Among the epoxy resins (A1), from the viewpoint of further improving the heat resistance and insulation reliability of the obtained heat conductive sheet, bisphenol type epoxy resin, novolac type epoxy resin, biphenyl type epoxy resin, arylalkylene type epoxy resin, One or more selected from the group consisting of naphthalene type epoxy resins, anthracene type epoxy resins and dicyclopentadiene type epoxy resins are preferred. Among these, it is particularly preferable that a dicyclopentadiene type epoxy resin or a novolac type epoxy resin is included from the viewpoint of improving the thermal conductivity of the heat conductive sheet.

In the present embodiment, the cyanate resin is not particularly limited. For example, the cyanate resin is a compound having an -OCN group in the molecule, and forms a three-dimensional network structure by the reaction of the -OCN group by heating, and is cured. Resin. Specifically, 1,3-dicyanatobenzene, 1,4-dicyanatobenzene, 1,3,5-tricyanatobenzene, 1,3-dicyanatonaphthalene, 1,4-dicyanatonaphthalene, 1, 6-dicyanatonaphthalene, 1,8-dicyanatonaphthalene, 2,6-dicyanatonaphthalene, 2,7-dicyanatonaphthalene, 1,3,6-tricyanatonaphthalene, 4,4'-dicyanatobiphenyl, bis (4-cyanatophenyl) methane, bis (3,5-dimethyl-4-cyanatophenyl) methane, 2,2-bis (4-cyanatophenyl) propane, 2,2-bis (3,5-dibromo -4-Cyanatophenyl) propane, bis (4-cyanatophenyl) ether, bis (4-cyanatophenyl) thioether, bis (4-cyanatophenyl) s Examples of the polyfunctional cyanate resins include luphone, tris (4-cyanatophenyl) phosphite, tris (4-cyanatophenyl) phosphate, and cyanates obtained by reacting novolac resins with cyanogen halides. A prepolymer having a triazine ring formed by trimerizing a cyanate group can also be used. This prepolymer is obtained by polymerizing the above-mentioned polyfunctional cyanate resin monomer using, for example, an acid such as mineral acid or Lewis acid, a base such as sodium alcoholate or tertiary amine, or a salt such as sodium carbonate as a catalyst. It is done.
In this embodiment, when using cyanate resin (especially novolak-type cyanate resin) as a thermosetting resin, you may use an epoxy resin together.

  Although content of the thermosetting resin (A) contained in a heat conductive sheet should just be suitably adjusted according to the objective, it is not specifically limited, 1 mass% with respect to 100 mass% of the said heat conductive sheets It is preferably 30% by mass or less, more preferably 2% by mass or more and 28% by mass or less, and further preferably 5% by mass or more and 20% by mass or less. When the content of the thermosetting resin (A) is not less than the above lower limit value, the handling property is improved, and it becomes easy to form a heat conductive sheet. When the content of the thermosetting resin (A) is not more than the above upper limit value, the linear expansion coefficient and elastic modulus of the heat conductive sheet are further improved, or the heat conductivity of the heat conductive sheet is further improved. Or

  Moreover, in this embodiment, when using together cyanate resin and an epoxy resin, content of cyanate resin is not specifically limited with respect to the whole thermosetting resin, For example, 20 mass% or more and 60 mass% or less are Preferably, 30 mass% or more and 50 mass% or less are more preferable. Thereby, a glass transition temperature is raised and the heat conductive sheet excellent in heat conductivity and heat resistance can be obtained.

(Filler (B))
Examples of the filler (B) include silica, alumina, boron nitride, aluminum nitride, silicon carbide and the like. These may be used alone or in combination of two or more.
In this embodiment, it is formed by aggregating scaly boron nitride as the filler (B) from the viewpoint of improving the thermal conductivity of the cured body of the thermal conductive sheet and the high-temperature storage stability based thereon. More preferably, secondary particles are included. Here, an embodiment including both primary particles of scaly boron nitride and secondary particles obtained by aggregating the primary particles is particularly preferable.

The secondary particles formed by aggregating the flaky boron nitride can be formed, for example, by aggregating the flaky boron nitride using a spray drying method or the like and then firing it. The firing temperature is, for example, 1500 to 2500 ° C.
Thus, when using the secondary particle obtained by sintering flaky boron nitride, from the viewpoint of improving the dispersibility of the filler (B) in the thermosetting resin (A), thermosetting It is particularly preferable to use a dicyclopentadiene type epoxy resin, a novolac type epoxy resin or a biphenyl type epoxy resin as the resin (A).

  The average particle diameter of secondary particles formed by aggregating scaly boron nitride is preferably, for example, 5 μm or more and 180 μm or less. Thereby, the heat conductive sheet excellent in the balance of heat conductivity and electrical insulation can be realized.

  The content of the filler (B) with respect to the entire thermal conductive sheet is preferably, for example, from 65% by mass to 90% by mass, and more preferably from 70% by mass to 85% by mass. By making content of a filler (B) more than the said lower limit, the thermal conductivity and mechanical strength in a heat conductive sheet can be improved more effectively. On the other hand, by setting the content of the filler (B) to the upper limit value or less, the film formability and workability of the resin composition are improved, and the uniformity in the film thickness of the heat conductive sheet is good. can do.

(Curing agent (C))
When using an epoxy resin (A1) as a thermosetting resin (A), it is preferable that a heat conductive sheet contains a hardening | curing agent (C) further. As a hardening | curing agent (C), 1 or more types selected from a hardening catalyst (C-1) and a phenol type hardening | curing agent (C-2) can be used.
Examples of the curing catalyst (C-1) include organic metal salts such as zinc naphthenate, cobalt naphthenate, tin octylate, cobalt octylate, bisacetylacetonate cobalt (II), and trisacetylacetonate cobalt (III); Tertiary amines such as triethylamine, tributylamine, 1,4-diazabicyclo [2.2.2] octane; 2-phenyl-4-methylimidazole, 2-ethyl-4-methylimidazole, 2,4-diethylimidazole, Imidazoles such as 2-phenyl-4-methyl-5-hydroxyimidazole and 2-phenyl-4,5-dihydroxymethylimidazole; triphenylphosphine, tri-p-tolylphosphine, tetraphenylphosphonium tetraphenylborate, triphenyl Phosphine Organic phosphorus compounds such as rephenylborane and 1,2-bis- (diphenylphosphino) ethane; phenolic compounds such as phenol, bisphenol A and nonylphenol; organic acids such as acetic acid, benzoic acid, salicylic acid and p-toluenesulfonic acid; Etc., or mixtures thereof. As the curing catalyst (C-1), one kind including these derivatives can be used alone, or two or more kinds including these derivatives can be used in combination.
Although content of the curing catalyst (C-1) contained in a heat conductive sheet is not specifically limited, 0.001 mass% or more and 1 mass% or less are preferable with respect to 100 mass% of heat conductive sheets.

Examples of the phenolic curing agent (C-2) include phenol novolak resins, cresol novolak resins, trisphenol methane type novolak resins, naphthol novolak resins, aminotriazine novolak resins and the like; Modified phenol resins such as cyclopentadiene-modified phenol resin; Aralkyl type resins such as phenol aralkyl resin having phenylene skeleton and / or biphenylene skeleton, naphthol aralkyl resin having phenylene skeleton and / or biphenylene skeleton; Bisphenol such as bisphenol A and bisphenol F Compound; resol type phenol resin and the like may be mentioned, and these may be used alone or in combination of two or more.
Among these, from the viewpoint of improving the glass transition temperature and reducing the linear expansion coefficient, the phenolic curing agent (C-2) is preferably a novolac type phenol resin or a resol type phenol resin.
Although content of a phenol type hardening | curing agent (C-2) is not specifically limited, 1 mass% or more and 30 mass% or less are preferable with respect to 100 mass% of heat conductive sheets, and 3 mass% or more and 20 mass% or less are more. Preferably, 5 mass% or more and 15 mass% or less are more preferable.

(Coupling agent (D))
Furthermore, the heat conductive sheet may contain a coupling agent (D). The coupling agent (D) can improve the wettability of the interface between the thermosetting resin (A) and the filler (B).

As the coupling agent (D), any commonly used one can be used. Specifically, an epoxy silane coupling agent, a cationic silane coupling agent, an aminosilane coupling agent, a titanate coupling agent, and a silicone oil type. It is preferable to use one or more coupling agents selected from coupling agents.
The addition amount of the coupling agent (D) depends on the specific surface area of the filler (B) and is not particularly limited, but is 0.05% by mass to 3% by mass with respect to 100% by mass of the filler (B). Particularly preferred is 0.1% by mass or more and 2% by mass or less.

(Phenoxy resin (E))
The heat conductive sheet may contain a phenoxy resin (E). By including the phenoxy resin (E), the bending resistance of the heat conductive sheet can be further improved. Moreover, by including a phenoxy resin (E), it becomes possible to reduce the elasticity modulus of a heat conductive sheet, and can improve the stress relaxation force of a heat conductive sheet. Moreover, when a phenoxy resin (E) is included, it can suppress that a void etc. generate | occur | produce due to the fluidity | liquidity reduction by a viscosity raise. Moreover, the adhesiveness of a heat conductive sheet and a heat radiating member can be improved. These synergistic effects can further increase the insulation reliability of the semiconductor device.

  Examples of the phenoxy resin (E) include a phenoxy resin having a bisphenol skeleton, a phenoxy resin having a naphthalene skeleton, a phenoxy resin having an anthracene skeleton, and a phenoxy resin having a biphenyl skeleton. A phenoxy resin having a structure having a plurality of these skeletons can also be used.

  Content of a phenoxy resin (E) is 3 to 10 mass% with respect to 100 mass% of heat conductive sheets, for example.

(Other ingredients)
A heat conductive sheet can contain antioxidant, a leveling agent, etc. in the range which does not impair the effect of this invention.

The heat conductive sheet which concerns on this embodiment can be produced as follows, for example.
First, the above-mentioned components are added to a solvent to obtain a varnish-like resin composition. In the present embodiment, for example, a thermosetting resin (A) or the like is added to a solvent to prepare a resin varnish, and then the filler (B) is put into the resin varnish and kneaded using a stirrer or the like. A resin composition can be obtained. Thereby, a filler (B) can be disperse | distributed more uniformly in a thermosetting resin (A).

  The solvent is not particularly limited, but for example, alcohol solvents such as methanol, ethanol, isopropanol, 1-butanol, or 2-butanol, and / or ketone solvents such as methyl ethyl ketone, cyclohexanone, or methyl isobutyl ketone should be used. Can do. You may use 1 type (s) or 2 or more types from these. Thereby, the heat conductivity of the hardened | cured material of a heat conductive sheet can be improved. This is presumed to be because the type of solvent constituting the resin composition and the orientation of the filler (B) in the thermal conductive sheet formed using the resin composition are correlated. Is done. That is, it is considered that the filler (B) can be prevented from being oriented in the in-plane direction in the thermally conductive sheet and can be made to exist more isotropically.

As a stirrer used for kneading the resin composition, for example, a rotation and revolution vacuum stirrer can be used. That is, after the filler (B) is put into the resin varnish containing the thermosetting resin (A) and premixed, the mixture is defoamed and filled by kneading without shearing using a rotating and rotating vacuum stirrer. It can be uniformly dispersed. Thus, it is possible to improve the high temperature storage stability rate to Q ₁ cured product of the resulting thermally conductive sheet. In particular, in the case of using secondary particles formed by agglomerating flaky boron nitride as the filler (B), kneading without breaking the shape of the secondary particles by using a rotating and rotating vacuum stirrer. It can be performed. This makes it possible to more effectively improve the high temperature storage stability rate Q _1. This is because the shape of the aggregated boron nitride constituting the resin composition and the orientation of the filler (B) in the thermally conductive sheet formed using this resin composition are correlated. It is estimated to be. That is, it is considered that the filler (B) can be prevented from being oriented in the in-plane direction in the thermally conductive sheet and can be made to exist more isotropically.

  Next, the resin composition is formed into a sheet shape to form a resin sheet. In this embodiment, for example, after applying the varnish-like resin composition on a substrate, the resin sheet can be obtained by heat-treating and drying the resin composition. As a base material, the metal foil which comprises a heat radiating member, a lead frame, a peelable carrier material etc. is mentioned, for example. Moreover, the heat processing for drying a resin composition is performed, for example on the conditions of 80-150 degreeC and 1 minute-1 hour. The film thickness of the resin sheet is, for example, 50 μm or more and 500 μm or less.

Next, the resin sheet is compressed by passing between two rolls to remove bubbles in the resin sheet. Thereby, a heat conductive sheet will be obtained. The film thickness of the heat conductive sheet is, for example, 50 μm or more and 500 μm or less.
In this embodiment, by including the step of removing bubbles by applying a compression pressure by the roll in this way, the thermal conductivity of the cured product of the heat conductive sheet and the high temperature storage stability rate calculated based on this it is possible to improve the Q _1. This is because the density of the resin component in the thermally conductive sheet is increased by removing the bubbles, and the secondary aggregated particles contained in the filler (B) are deformed due to the compression pressure. It is estimated that the adhesion of B) to the thermosetting resin (A) is increased.

  In this embodiment, the glass transition temperature of the cured product obtained by heat-treating the resin composition for a heat conductive sheet at 180 ° C. for 1 hour is not particularly limited, but is preferably 180 ° C. or higher, for example, 190 ° C. The above is more preferable, and 200 ° C. or higher is even more preferable. Although the upper limit of the said glass transition temperature is not specifically limited, For example, it can be 250 degrees C or less. As a method for measuring the glass transition temperature of the cured body of the thermally conductive sheet, for example, first, the cured body of the thermally conductive sheet is obtained by curing the obtained thermally conductive sheet at 180 ° C. for 1 hour. Get. Next, the glass transition temperature (Tg) of the obtained cured product is measured by DMA (dynamic viscoelasticity measurement).

Next, the semiconductor device according to the present embodiment will be described.
FIG. 1 is a schematic cross-sectional view of a semiconductor device 100 according to this embodiment. In the following, in order to simplify the description, the positional relationship (vertical relationship or the like) of each component of the semiconductor device 100 may be described as the relationship shown in each drawing. However, the positional relationship in this description is independent of the positional relationship when the semiconductor device 100 is used or manufactured.

  The semiconductor device 100 according to the present embodiment is attached to the heat sink 130, the semiconductor chip 110 provided on the first surface 131 side of the heat sink 130, and the second surface 132 opposite to the first surface 131 of the heat sink 130. The insulating heat conductive sheet 140 and the sealing resin 180 that seals the semiconductor chip 110 and the heat sink 130 are provided. As the heat conductive sheet 140, the heat conductive sheet according to the present embodiment described above can be used.

  The semiconductor device 100 includes, for example, a conductive layer 120, a metal layer 150, a lead 160, and a wire (metal wiring) 170 in addition to the above configuration.

  An electrode pattern (not shown) is formed on the upper surface 111 of the semiconductor chip 110, and a conductive pattern (not shown) is formed on the lower surface 112 of the semiconductor chip 110. The lower surface 112 of the semiconductor chip 110 is fixed to the first surface 131 of the heat sink 130 via a conductive layer 120 such as silver paste. The electrode pattern on the upper surface 111 of the semiconductor chip 110 is electrically connected to the electrode 161 of the lead 160 via the wire 170.

  The heat sink 130 is made of metal.

  In addition to the semiconductor chip 110 and the heat sink 130, the sealing resin 180 seals the wires 170, the conductive layer 120, and part of the leads 160 inside. Another part of each lead 160 protrudes from the side surface of the sealing resin 180 to the outside of the sealing resin 180. In the present embodiment, for example, the lower surface 182 of the sealing resin 180 and the second surface 132 of the heat sink 130 are located on the same plane.

  The upper surface 141 of the heat conductive sheet 140 is attached to the second surface 132 of the heat sink 130 and the lower surface 182 of the sealing resin 180. That is, the sealing resin 180 is in contact with the surface (upper surface 141) of the heat conductive sheet 140 on the heat sink 130 side around the heat sink 130.

  The upper surface 151 of the metal layer 150 is fixed to the lower surface 142 of the heat conductive sheet 140. That is, one surface (upper surface 151) of the metal layer 150 is fixed to a surface (lower surface 142) opposite to the heat sink 130 side in the heat conductive sheet 140.

  In plan view, the outline of the upper surface 151 of the metal layer 150 and the outline of the surface (lower surface 142) on the opposite side of the heat conductive sheet 140 from the heat sink 130 side preferably overlap.

  Further, the entire surface of the metal layer 150 opposite to the one surface (upper surface 151) (lower surface 152) is exposed from the sealing resin 180. In the case of the present embodiment, as described above, the heat conductive sheet 140 has the upper surface 141 attached to the second surface 132 of the heat sink 130 and the lower surface 182 of the sealing resin 180, so The adhesive sheet 140 is exposed outside the sealing resin 180 except for its upper surface 141. The entire metal layer 150 is exposed outside the sealing resin 180.

  In addition, the 2nd surface 132 and the 1st surface 131 of the heat sink 130 are each formed flat, for example.

  Although the mounting floor area of the semiconductor device 100 is not particularly limited, as an example, the mounting floor area may be 10 mm × 10 mm or more and 100 mm × 100 mm or less. Here, the mounting floor area of the semiconductor device 100 is the area of the lower surface 152 of the metal layer 150.

  Further, the number of semiconductor chips 110 mounted on one heat sink 130 is not particularly limited. There may be one or more. For example, it may be 3 or more (6 etc.). That is, as an example, three or more semiconductor chips 110 are provided on the first surface 131 side of one heat sink 130, and the sealing resin 180 collectively seals these three or more semiconductor chips 110.

  The semiconductor device 100 is, for example, a power semiconductor device. The semiconductor device 100 includes, for example, 2 in 1 in which two semiconductor chips 110 are sealed in a sealing resin 180, 6 in 1 in which six semiconductor chips 110 are sealed in a sealing resin 180, or a sealing resin 180. A 7-in-1 configuration in which seven semiconductor chips 110 are sealed can be employed.

Next, an example of a method for manufacturing the semiconductor device 100 according to the present embodiment will be described.
First, the heat sink 130 and the semiconductor chip 110 are prepared, and the lower surface 112 of the semiconductor chip 110 is fixed to the first surface 131 of the heat sink 130 via the conductive layer 120 such as silver paste. Next, a lead frame (not shown) including the lead 160 is prepared, and the electrode pattern on the upper surface of the semiconductor chip 110 and the electrode 161 of the lead 160 are electrically connected to each other through the wire 170. Next, the semiconductor chip 110, the conductive layer 120, the heat sink 130, the wire 170, and a part of the lead 160 are collectively sealed with a sealing resin 180.

  Next, the heat conductive sheet 140 is prepared, and the upper surface 141 of the heat conductive sheet 140 is attached to the second surface 132 of the heat sink 130 and the lower surface 182 of the sealing resin 180. Furthermore, one surface (upper surface 151) of the metal layer 150 is fixed to the surface (lower surface 142) on the opposite side of the heat conductive sheet 140 from the heat sink 130 side. Note that the metal layer 150 may be fixed to the lower surface 142 of the heat conductive sheet 140 in advance before the heat conductive sheet 140 is attached to the heat sink 130 and the sealing resin 180. Next, each lead 160 is cut from a frame (not shown) of the lead frame. Thus, the semiconductor device 100 having the structure as shown in FIG. 1 is obtained.

  FIG. 2 is a schematic cross-sectional view showing a modification of the semiconductor device 100 according to the present embodiment. The semiconductor device 100 according to this modification is different from the semiconductor device 100 shown in FIG. 1 in the points described below, and is otherwise configured in the same manner as the semiconductor device 100 shown in FIG.

  In the case of this modification, the heat conductive sheet 140 is sealed in the sealing resin 180. The metal layer 150 is also sealed in the sealing resin 180 except for the lower surface 152 thereof. The lower surface 152 of the metal layer 150 and the lower surface 182 of the sealing resin 180 are located on the same plane.

FIG. 2 shows an example in which at least two or more semiconductor chips 110 are mounted on the first surface 131 of the heat sink 130. The electrode patterns on the upper surface 111 of the semiconductor chip 110 are electrically connected to each other through wires. For example, a total of six semiconductor chips 110 are mounted on the first surface 131. That is, for example, two semiconductor chips 110 are arranged in three rows in the depth direction of FIG.
In the present embodiment, the heat sink 130 may be a depressed lead or a heat sink.

  Next, examples of the present invention will be described.

(Production of aggregated boron nitride)
A mixture obtained by mixing melamine borate and scaly boron nitride powder was added to an aqueous solution of ammonium polyacrylate and mixed for 2 hours to prepare a slurry for spraying. Subsequently, this slurry was supplied to a spray granulator and sprayed under the conditions of an atomizer rotation speed of 15000 rpm, a temperature of 200 ° C., and a slurry supply amount of 5 ml / min, thereby producing composite particles. Next, the obtained composite particles were baked under a nitrogen atmosphere at 2000 ° C. to obtain aggregated boron nitride.

(Preparation of thermal conductive sheet)
About Examples 1-5 and the comparative example 1, the heat conductive sheet was produced as follows.
First, according to the composition shown in Table 1, a thermosetting resin and a curing agent were added to MEK (methyl ethyl ketone) as a solvent, and this was stirred to obtain a solution of a thermosetting resin composition. Next, after the filler was put into this solution and premixed, the mixture was kneaded without being sheared by a rotating and rotating vacuum stirrer, and defoamed and the filler was uniformly dispersed without breaking the shape of the aggregated boron nitride. A resin composition for a heat conductive sheet was obtained. Next, the obtained resin composition was applied onto a copper foil using a doctor blade method, and then dried by a heat treatment at 100 ° C. for 30 minutes to obtain a B-stage resin sheet having a film thickness of 300 μm. Produced. Next, the obtained resin sheet was compressed by passing between two rolls to remove bubbles in the resin sheet. Thereby, the heat conductive sheet whose film thickness is 100 micrometers was obtained.
The details of each component in Table 1 are as follows.

(Epoxy resin)
Epoxy resin 1: dicyclopentadiene type epoxy resin (HP-7200, manufactured by DIC Corporation)
Epoxy resin 2: biphenyl type epoxy resin (YL6121, manufactured by Mitsubishi Chemical Corporation)
Epoxy resin 3: Epoxy resin having naphthalene aralkyl skeleton (NC-7000, manufactured by Nippon Kayaku Co., Ltd.)
Epoxy resin 4: Epoxy resin having a biphenyl skeleton (YX-4000, manufactured by Mitsubishi Chemical Corporation)
Epoxy resin 5: bisphenol A type epoxy resin (JER828, manufactured by Mitsubishi Chemical Corporation)
(Cyanate resin)
Cyanate resin 1: phenol novolac-type cyanate resin (PT-30, manufactured by Lonza Japan Co., Ltd.))

(Curing agent)
(Curing catalyst C-1)
Curing catalyst 1: 2-phenyl-4,5-dihydroxymethylimidazole (2PHZ-PW, manufactured by Shikoku Chemicals Co., Ltd.)
Curing catalyst 2: Triphenylphosphine (made by Hokuko Chemical Co., Ltd.)
(Phenolic curing agent C-2)
Curing agent 1: Trisphenol methane type novolak resin (MEH-7500, manufactured by Meiwa Kasei Co., Ltd.)

(Filler)
Agglomerated boron nitride produced by the above production example

(Measurement of Tg (glass transition temperature))
About each of Examples 1-5 and the comparative example 1, the glass transition temperature of the hardening body of a heat conductive sheet was measured as follows. First, the obtained heat conductive sheet was cured at 180 ° C. for 1 hour to obtain a cured body of the heat conductive sheet. Next, the glass transition temperature (Tg) of the obtained cured product was measured by DMA (dynamic viscoelasticity measurement). The unit of glass transition temperature in Table 1 is ° C.

(Measurement of thermal conductivity λ ₀ and λ ₁ and high-temperature storage stability Q ₁ )
For each of Examples 1 to 5 and Comparative Example 1 were measured high-temperature storage stability rate to Q ₁ thermally conductive sheet cured product, as follows. First, the obtained heat conductive sheet was cured at 180 ° C. for 1 hour to obtain a cured body of the heat conductive sheet. Then, this cured product, do the following procedure (a) ~ (d) in order to measure the high-temperature storage stability rate Q _1.
(A) The thermal conductivity in the thickness direction of the cured body is measured, and the obtained measured value is λ _0. (b) The cured body is stored in an environment of 200 ° C. for 24 hours. (C) Procedure (b) ) To measure the thermal resistance value in the thickness direction of the cured body after storage, and the obtained measurement value is λ ₁ (d) Q ₁ = λ ₁ / λ ₀ is calculated. The thermal conductivity λ ₀ and the thermal conductivity λ ₁ of the cured body are values measured at 25 ° C. The thermal conductivity of the cured body of the heat conductive sheet was measured using a laser flash method. The unit of λ ₀ and λ ₁ in Table 1 is W / m · K.

(Measurement of storage elastic modulus E ′ ₀ and E ′ ₁ and high temperature storage stability Q ₂ )
For each of Examples 1 to 5 and Comparative Example 1 were measured high-temperature storage stability rate Q ₂ of the thermally conductive sheet cured product, as follows. First, the obtained heat conductive sheet was cured at 180 ° C. for 1 hour to obtain a cured body of the heat conductive sheet. Then, this cured product, do the following procedure (e) ~ (h) in order to measure the high-temperature storage stability rate Q _2.
(E) The storage elastic modulus at 25 ° C. of the cured body is measured, and the obtained measured value is defined as E ′ _0. (f) The cured body is stored in an environment of 200 ° C. for 24 hours (g) Procedure ( The storage elastic modulus at 25 ° C. of the cured product after storage according to f) is measured, and the measured value obtained is defined as E ′ ₁ (h) Q ₂ = E ′ ₁ / E ′ ₀ is calculated. The storage elastic modulus of the cured body of the conductive sheet was measured by DMA (dynamic viscoelasticity measurement). The unit of E ′ ₀ and E ′ ₁ in Table 1 is GPa.

(Loss elastic modulus E ″ ₀ and E ″ ₁ , and high-temperature storage stability Q ₃ )
For each of Examples 1 to 5 and Comparative Example 1 were measured high-temperature storage stability rate Q ₃ of the thermal conductive sheet cured product, as follows. First, the obtained heat conductive sheet was cured at 180 ° C. for 1 hour to obtain a cured body of the heat conductive sheet. Then, this cured product, do the following procedure (i) ~ (l) in order to measure the high-temperature storage stability rate Q _3.
(I) The loss elastic modulus at 25 ° C. of the cured body is measured, and the obtained measured value is set to E ″ _0. (j) The cured body is stored in an environment of 200 ° C. for 24 hours (k) Procedure The loss elastic modulus at 25 ° C. of the cured product after storage according to (j) is measured, and the obtained measured value is defined as E ″ ₁ (l) Q ₃ = E ″ ₁ / E ″ ₀ is calculated. However, the loss elastic modulus of the cured body of the heat conductive sheet was measured by DMA (dynamic viscoelasticity measurement). E _{'' 0} and E _{'' 1} of the unit in the Table 1 is GPa.

(Stability evaluation under high temperature environment)
For each of Examples 1 to 5 and Comparative Example 1, the stability of the semiconductor package in a high temperature environment was evaluated as follows. First, 300 semiconductor packages obtained using a cured body of a heat conductive sheet were prepared as samples. Each sample was then stored in an environment of 200 ° C. for 24 hours. Next, the failure rate of the sample after storage was calculated. Here, the failure rate of less than 1% was evaluated as ◎, the case where the failure rate was 1% or more and less than 3% was given as ◯, and the case where it was 3% or more as x.

  This application claims the priority on the basis of Japanese application Japanese Patent Application No. 2014-138076 for which it applied on July 3, 2014, and takes in those the indications of all here.

Claims (10)

A heat conductive sheet comprising a thermosetting resin and a filler dispersed in the thermosetting resin, wherein the heat conductive sheet is measured by the following procedures (a) to (d). high-temperature storage stability rate _{Q 1} is the heat conductive sheet is 0.7 to 1.0 of the cured product.
(A) The thermal conductivity in the thickness direction of the cured body is measured, and the obtained measured value is set to λ _0. (b) The cured body is stored in an environment of 200 ° C. for 24 hours. (C) Procedure (b) ), The thermal conductivity in the thickness direction of the cured body after storage is measured, and the obtained measured value is λ ₁ (d) Q ₁ = λ ₁ / λ ₀ is calculated. In the heat conductive sheet according to claim 1,
For the cured product, the following steps (e) ~ high temperature storage stability rate Q ₂ of the thermally conductive sheet cured product as determined by (h), the thermally conductive sheet is 0.7 to 1.0 .
(E) The storage elastic modulus at 25 ° C. of the cured body is measured, and the obtained measured value is defined as E ′ _0. (f) The cured body is stored in an environment of 200 ° C. for 24 hours (g) Procedure ( The storage elastic modulus at 25 ° C. of the cured body after storage according to f) is measured, and the measured value obtained is defined as E ′ ₁ (h) Q ₂ = E ′ ₁ / E ′ ₀ is calculated. In the heat conductive sheet of Claim 1 or 2,
For the cured product, the following steps (i) ~ (l) high temperature storage stability rate Q ₃ of the thermally conductive sheet cured product as determined by the heat conductive sheet is 0.7 to 1.0 .
(I) The loss elastic modulus at 25 ° C. of the cured body is measured, and the obtained measured value is set to E ″ _0. (j) The cured body is stored for 24 hours in an environment of 200 ° C. (k) Procedure The loss elastic modulus at 25 ° C. of the cured body after storage according to (j) is measured, and the obtained measured value is defined as E ″ ₁ (l) Q ₃ = E ″ ₁ / E ″ ₀ is calculated. Do In the heat conductive sheet as described in any one of Claims 1-3,
The filler is a thermally conductive sheet containing secondary particles formed by agglomerating scaly boron nitride. In the heat conductive sheet as described in any one of Claims 1-4,
The heat conductive sheet whose lambda _{0 of the} said hardening body is 8.0 W / m * K or more. In the heat conductive sheet as described in any one of Claims 1-5,
The heat conductive sheet whose content of the said filler with respect to the said whole heat conductive sheet is 65 to 90 mass%. In the heat conductive sheet as described in any one of Claims 1-6,
The heat conductive sheet whose film thickness of the said heat conductive sheet is 50 micrometers or more and 500 micrometers or less. In the heat conductive sheet as described in any one of Claims 1-7,
The heat conductive sheet in which the said thermosetting resin contains an epoxy resin and / or cyanate resin. In the heat conductive sheet as described in any one of Claims 1-8,
The heat conductive sheet whose glass transition temperature of the hardening body obtained by heat-processing with respect to the said heat conductive sheet at 180 degreeC for 1 hour is 180 degreeC or more and 250 degrees C or less. A heat conductive material;
A semiconductor chip bonded to one surface of the heat conducting material;
A metal member joined to a surface opposite to the one surface of the heat conducting material;
A sealing material for sealing the heat conductive material, the semiconductor chip and the metal member;
With
The semiconductor device with which the said heat conductive material was formed with the heat conductive sheet as described in any one of Claims 1-9.

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