JP2015117311A - Heat-conductive sheet for semiconductor module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-conductive sheet for a semiconductor module having an epoxy resin layer with excellent thermal conductivity.SOLUTION: In a conductive sheet for a semiconductor module, an epoxy resin layer is formed with a composition including an epoxy monomer having a specific structure, a phenolic curative having a specific structure and boron nitride particles or aluminum nitride particles. The boron nitride particles or aluminum nitride particles are contained in a state of agglomerated particles. The epoxy composition further includes an onium salt-based hardening accelerator.

Description

  The present invention relates to a heat conductive sheet for a semiconductor module, and more particularly to a heat conductive sheet interposed between a semiconductor element and a heat dissipation member in the semiconductor module.

Conventionally, a semiconductor module in which a semiconductor element that generates heat during operation of a power transistor, a thyristor, and the like, and a heat radiating member such as a metal plate or a heat radiating fin for radiating the heat generated by the semiconductor element has been integrated. Widely used in control and the like.
In this type of semiconductor module, a sheet-like member having excellent thermal conductivity is interposed between the module body in which the semiconductor element is resin-molded and the heat radiating member, and the sheet-like member is It is also called “thermal conductive sheet”.

As a heat conductive sheet for this semiconductor module, an epoxy resin layer having an epoxy resin layer formed of an epoxy composition on one or both sides of a base sheet such as a copper foil, or an epoxy resin having no base sheet What consists only of layers is known.
Conventionally, a thermal conductive sheet for a semiconductor module has been required to have high thermal conductivity, and in order to increase the thermal conductivity of the epoxy resin layer, an inorganic material having excellent thermal conductivity such as boron nitride and aluminum oxide. Attempts have been made to highly fill the filler.

In addition, although the thermal conductivity of the semiconductor module thermal conductive sheet is usually improved according to the content of the inorganic filler in the epoxy resin layer, the strength of the epoxy resin layer is reduced when the inorganic filler is excessively contained. In addition, defects such as cracks are likely to occur in the epoxy resin layer.
Moreover, although the heat conductive sheet for semiconductor modules can improve thermal conductivity also by making the thickness of the said epoxy resin layer thin, intensity | strength will be impaired if the thickness of an epoxy resin layer is reduced too much also in that case. It will be.

Against this background, attempts have been made to improve the thermal conductivity of the epoxy resin itself.
For example, in the following Patent Document 1, in order to form an epoxy resin molded body having high thermal conductivity, an epoxy monomer having a mesogen skeleton is used, and a high magnetic field is applied in one direction to form an epoxy resin molded body. Is described.
The epoxy resin having such a mesogenic skeleton easily forms a crystallized portion with a uniform molecular chain in the molded body, and the crystallized portion exhibits higher thermal conductivity than other amorphous portions. It is more advantageous than general epoxy resins in forming an epoxy resin molded article having an excellent rate.

  However, it is not preferable to form the epoxy resin layer by a special manufacturing method described in Patent Document 1 from the viewpoint of productivity of the heat conductive sheet.

Japanese Patent No. 4414674

  This invention makes it a subject to provide the heat conductive sheet for semiconductor modules which can be produced without the manufacturing method being restrict | limited remarkably, and has the outstanding heat conductivity.

  The present invention relating to a semiconductor module thermal conductive sheet for solving such problems includes a module body in which a semiconductor element is resin-molded, and a heat radiating member for radiating heat generated by the semiconductor element. A semiconductor module having a heat conductive sheet for a semiconductor module interposed between the heat dissipating member and the module main body, comprising an epoxy resin layer made of an epoxy composition, An epoxy monomer represented by the formula (1), a phenolic curing agent represented by the following general formula (2), and boron nitride particles or aluminum nitride particles are aggregated, and the boron nitride particles or the aluminum nitride particles are aggregated. It is characterized by containing in the form of particles.

(However, “G” in the formula represents a glycidyl group, “A” represents a biphenyl ring which is unsubstituted or substituted with a hydrocarbon group having 1 to 6 carbon atoms. (It is a group represented by the formula (x), and “n” represents a number from 1 to 15.)

(However, “B” in the formula represents a benzene ring which is unsubstituted or substituted with a hydrocarbon group having 1 to 6 carbon atoms, and “R ¹ ” to “R ⁴ ” are hydrogen atoms or 1 to 6 carbon atoms. And “R ¹ ” to “R ⁴ ” may be the same as or different from each other.)

(However, “R ⁵ ” is any one of a hydroxyl group, a methyl group, an ethyl group, a propyl group, or a hydrogen atom, and “Ph ¹ ”, “Ph ² ”, and “Ph ³ ” are common to each other. Or a substituted or unsubstituted phenyl represented by the following general formula (y), and at least two of the “Ph ¹ ”, “Ph ² ” and “Ph ³ ” have a hydroxyl group. Having substituted phenyl.)

(However, “R ⁶ ” to “R ¹⁰ ” in the formula are any of a hydroxyl group, a methyl group, an ethyl group, a propyl group, or a hydrogen atom.)

In this invention, since the specific epoxy monomer is contained in the epoxy composition with the specific hardening | curing agent, the hardened | cured material which has high thermal conductivity can be formed with the said hardening | curing agent and an epoxy monomer.
Furthermore, in this invention, since the specific inorganic filler is contained in the epoxy composition, the thermal conductivity excellent in the epoxy resin layer formed with the said epoxy composition can be exhibited.
Therefore, according to the present invention, the thermal conductivity sheet for a semiconductor module can be made excellent in thermal conductivity even if it is produced outside a special environment such as a high magnetic field, and the manufacturing method is significantly limited. There is provided a thermally conductive sheet for a semiconductor module that can be produced without any problems.

The schematic sectional drawing which showed the cross-section of the heat conductive sheet of one Embodiment. The schematic sectional drawing of the semiconductor module which showed the use condition of the heat conductive sheet of FIG. 1 typically. The schematic sectional drawing of the semiconductor module which showed the use condition of the heat conductive sheet of other embodiment typically.

Hereinafter, preferred embodiments of the heat conductive sheet for semiconductor module of the present invention (hereinafter also simply referred to as “heat conductive sheet”) will be described.
The heat conductive sheet of this embodiment has an epoxy resin layer formed of a predetermined epoxy composition.
The epoxy composition of this embodiment contains a specific epoxy monomer and a phenolic curing agent, so that the epoxy resin layer contains only an epoxy resin that does not contain an inorganic filler or the like, and the epoxy resin layer has 0.3 W / (m · K) or more. It can exhibit excellent thermal conductivity.
In addition, the epoxy composition of the present embodiment contains a specific inorganic filler. Depending on the content of the inorganic filler and the like, the epoxy resin layer has an excellent heat conductivity of 14 W / (m · K) or more. It is possible to exhibit the nature.
Furthermore, the thermal conductive sheet in the present embodiment exhibits the excellent thermal conductivity as described above in the epoxy resin layer without performing a special operation such as applying a high magnetic field when forming the epoxy resin layer. It can be made.

First, the epoxy composition used for forming the epoxy resin layer will be described.
The epoxy composition in the present embodiment contains an epoxy monomer represented by the following general formula (1) and a phenolic curing agent represented by the following general formula (2).

(However, “G” in the formula represents a glycidyl group, “A” represents a biphenyl ring which is unsubstituted or substituted with a hydrocarbon group having 1 to 6 carbon atoms. (It is a group represented by the formula (x), and “n” represents a number from 1 to 15.)

(However, “B” in the formula represents a benzene ring which is unsubstituted or substituted with a hydrocarbon group having 1 to 6 carbon atoms, and “R ¹ ” to “R ⁴ ” are hydrogen atoms or 1 to 6 carbon atoms. And “R ¹ ” to “R ⁴ ” may be the same as or different from each other.)

(However, “R ⁵ ” is any one of a hydroxyl group, a methyl group, an ethyl group, a propyl group, or a hydrogen atom, and “Ph ¹ ”, “Ph ² ”, and “Ph ³ ” are common to each other. Or a substituted or unsubstituted phenyl represented by the following general formula (y), and at least two of the “Ph ¹ ”, “Ph ² ” and “Ph ³ ” have a hydroxyl group. Having substituted phenyl.)

(However, “R ⁶ ” to “R ¹⁰ ” in the formula are any of a hydroxyl group, a methyl group, an ethyl group, a propyl group, or a hydrogen atom.)

  The epoxy composition in the present embodiment further contains a curing accelerator and an inorganic filler.

In the epoxy monomer, “A” in the general formula (1) is preferably an unsubstituted biphenyl ring.
In the epoxy monomer, “B” in the general formula (x) is preferably an unsubstituted benzene ring.
Further, in the epoxy monomer, “R ¹ ” to “R ⁴ ” in the general formula (x) are preferably all hydrogen atoms.

  That is, it is particularly preferable that the epoxy monomer has a structure represented by the following general formula (3).

（ただし、式中の「ｎ」は、１〜１５の数を表す。）

(However, “n” in the formula represents a number of 1 to 15.)

It is important to employ a phenolic curing agent having a structure represented by the general formula (2).
It is important that the phenolic curing agent has two or more phenyl groups having a hydroxyl group, and all phenyls (“Ph ¹ ”, “Ph ² ” and “Ph ³ ”) have a hydroxyl group. Is preferred.
Further, examples of the phenolic curing agent, it is preferable that the number of hydroxyl groups of the phenyl ( "Ph ^1" - "Ph ^3") is 1 or 2.
Moreover, as said phenol type hardening | curing agent, it is preferable that each phenyl does not have substituents other than a hydroxyl group (it is preferable that other than a hydroxyl group is a hydrogen atom).
That is, it is preferable that the said phenol type hardening | curing agent in this embodiment is 4,4 ', 4 "-methylidyne trisphenol etc. which are shown to following General formula (4), for example.

Depending on the blending ratio with the epoxy monomer and the presence or absence of other blending materials such as a curing accelerator, the epoxy composition of the present embodiment adopts a preferable phenol-based curing agent as described above to achieve a glass transition. A cured product having a temperature of 150 ° C. or higher can be formed.
That is, in order to form an epoxy resin layer having excellent heat resistance, it is preferable to employ a phenolic curing agent such as 4,4 ′, 4 ″ -methylidynetrisphenol in the epoxy composition of this embodiment. .

  The phenolic curing agent is usually contained in the epoxy composition so that the number of hydroxyl groups is substantially the same as the number of glycidyl groups of the epoxy monomer (for example, a ratio between 0.8 times to 1.25 times). Can be made.

  In addition, the epoxy composition of the present embodiment includes other phenolic curing agents, amine curing agents, acid anhydride curing agents, polymercaptan curing agents, polyaminoamide curing agents, and isocyanate curing agents, if necessary. Further, a blocked isocyanate curing agent and the like may be contained within a range in which the effects of the present invention are not significantly impaired.

Moreover, the epoxy composition of the present embodiment contains a curing accelerator together with the phenolic curing agent, and examples of the curing accelerator include onium salts such as a phosphonium salt-based curing accelerator and a sulfonium salt-based curing accelerator. It is preferable to contain a system curing accelerator.
Since many of the phenolic curing agents shown above have a softening temperature exceeding 200 ° C., those that do not exhibit excessive catalytic activity at temperatures of 200 ° C. or less are preferable as curing accelerators to be included in the epoxy composition.
Therefore, the epoxy composition of the present embodiment contains a phosphonium salt-based curing accelerator such as a tetraphenylphosphonium salt-based curing accelerator or a triphenylphosphonium salt-based curing accelerator as the onium salt-based curing accelerator. Is particularly preferable, and it is most preferable to contain tetraphenylphosphonium tetraphenylborate.
The onium salt-based curing accelerator such as tetraphenylphosphonium tetraphenylborate can usually be contained in the epoxy composition so that the ratio with respect to 100 parts by mass of the epoxy monomer is 0.1 parts by mass or more and 5 parts by mass or less. .

The epoxy composition of this embodiment further contains an inorganic filler having excellent thermal conductivity in order to make the epoxy resin layer excellent in thermal conductivity as described above.
More specifically, the epoxy composition of this embodiment contains boron nitride particles or aluminum nitride particles as an essential component.
Moreover, it is important that the boron nitride particles and the aluminum nitride particles are contained in the epoxy composition in the form of aggregated particles in order to make the epoxy resin layer excellent in thermal conductivity.
In general, particles made of boron nitride or aluminum nitride have a plate shape in a single particle state.
On the other hand, the agglomerated particles are formed by aggregating a plurality of plate-like particles, and are usually spherical or indefinite.
As the boron nitride agglomerated particles, for example, plate-like particles sintered together with a sintering agent such as boric acid can be used, and the median diameter determined by measurement with a laser diffraction scattering particle size distribution meter is 10 μm to 100 μm. It is preferable to adopt one.
Further, as the aluminum nitride aggregated particles, those having a median diameter of 1 μm to 100 μm are preferably employed.
As the aluminum nitride agglomerated particles, for example, those obtained by sintering plate-like particles together with a sintering agent such as yttrium oxide, and those having a median diameter of 10 μm to 100 μm are preferably employed.

In addition, the epoxy composition of the present embodiment can contain an inorganic filler other than those described above, and examples of the inorganic filler include metals, metal oxides, metal nitrides, metal carbides, metal hydroxides, Examples thereof include granular materials made of carbon, metal-coated resins, plate-like materials, fibrous materials, and the like.
Examples of the metal include silver, copper, gold, platinum, and zirconium, metal oxides such as aluminum oxide and magnesium oxide, metal nitrides such as silicon nitride, metal carbides such as silicon carbide, and metal hydroxides. Includes aluminum hydroxide and magnesium hydroxide, and examples of carbon include carbon black, graphite, carbon nanotube, and carbon nanohorn.

When the inorganic filler is contained in the epoxy composition of the present embodiment, the inorganic filler is contained so that the volume ratio of the inorganic filler in the cured product of the epoxy composition is usually 30% by volume or more and 90% by volume or less. Can be made.
In the epoxy composition of the present embodiment, the content of inorganic fillers other than boron nitride particles and aluminum nitride particles is preferably 50% by mass or less, particularly preferably 25% by mass or less, based on the whole inorganic filler. Most preferably, it is not more than mass%.

In addition, the epoxy composition contains pigments, dyes, fluorescent brighteners, dispersants, stabilizers, ultraviolet absorbers, antistatic agents, antioxidants, flame retardants, heat stabilizers, lubricants, plasticizers, as necessary. It is also possible to appropriately contain a solvent or the like.
In the present embodiment, a cured product having a rigid molecular structure is formed by the epoxy monomer and the phenolic curing agent.
And in this embodiment, since favorable heat transfer is made | formed by the molecule | numerator-molecule interaction in an epoxy resin layer, if needed, resin and rubber other than the said hardened | cured material are included in an epoxy resin layer. Although it is possible, it is preferable not to contain these polymers which may inhibit the interaction in the epoxy resin layer.
Therefore, it is preferable that the epoxy composition in the present embodiment does not substantially contain a rubber component.
Moreover, it is preferable that the said epoxy composition does not contain the other resin component substantially.

The thermally conductive sheet in the present embodiment can be formed by forming only the above epoxy composition into a sheet or laminating it on another sheet-like member.
In the case where not only heat conduction but also electrical insulation is required for the heat conductive sheet, the heat conductive sheet is provided with two or more epoxy resin layers laminated, and the It is preferable to separately provide a base material layer for supporting the epoxy resin layer.

  Hereinafter, as an example showing one embodiment of the thermally conductive sheet in the present embodiment, a thermally conductive sheet that is excellent in electrical insulation and can also be used as an insulating sheet will be described with reference to the drawings.

This thermally conductive sheet (hereinafter also referred to as “insulating sheet”) having excellent electrical insulation properties is also referred to as two epoxy resin layers 11 and 12 (hereinafter also referred to as “insulating layers”) as shown in FIG. And a base material layer 13 for supporting the insulating layers 11 and 12.
That is, the insulating sheet 10 of the present embodiment is a sheet body having a three-layer laminated structure, and the first insulating layer 11 (hereinafter referred to as “first insulating layer 11”) of the two insulating layers 11 and 12. The other side is constituted by the base material layer 13 and the intermediate layer between the base material layer 13 and the first insulating layer 11 is the second insulating layer 12 (hereinafter also referred to as the other side). , Also referred to as “second insulating layer 12”).

The 1st insulating layer 11 and the 2nd insulating layer 12 consist of the epoxy composition of this embodiment, and consist of the said epoxy composition made into B-stage (semi-hardened).
The insulating layers 11 and 12 of this embodiment are formed of the epoxy composition containing an inorganic filler, and are formed so as to exhibit excellent thermal conductivity.
In addition, when it is going to make high filling with an inorganic filler in order to exhibit the outstanding heat conductivity with respect to the 1st insulating layer 11 and the 2nd insulating layer 12, the said insulating layers 11 and 12 will become weak and will be careful with respect to an insulating sheet. However, the insulating sheet 1 of the present embodiment suppresses cracking and cracking of the insulating layers 11 and 12 by providing the base material layer 13.
In particular, in a semi-cured state containing an unreacted epoxy group called a B stage, unlike the case where the unreacted epoxy group is cured so as to be in a state called a C stage that does not substantially exist in the system. Since the insulating layers 11 and 12 are easily broken even by slight deformation, it can be said that the base material layer 13 plays an important role in the insulating sheet 1 of the present embodiment.

In addition, if an attempt is made to highly fill the inorganic filler, defects such as pinholes and voids are likely to be formed in the insulating layers 11 and 12, but the insulating sheet 10 of the present embodiment is temporarily formed by stacking two insulating layers. Even when a defective portion is formed, the defect is prevented from being continuous in the thickness direction of the insulating sheet.
That is, the electrical reliability of the insulating sheet 10 of this embodiment is ensured by making the insulating layer a laminated structure and by supporting the insulating layer by the base material layer 13.
In addition, when it is going to form a film with the epoxy composition containing only the general thing which has a median diameter of spherical submicron-several micrometers as an inorganic filler, there are many interfaces of resin and an inorganic filler, Since the inorganic fillers are in point contact with each other through the resin, a film having low thermal conductivity may be formed.
In the present embodiment, since such coarse agglomerated particles are contained in the epoxy composition, the contact between the agglomerated particles can be brought into a surface contact state. Since the interface with the inorganic filler can be reduced, a film having high thermal conductivity is formed.
That is, the insulating sheet 10 of this embodiment exhibits excellent thermal conductivity in the thickness direction by containing the aggregated particles in the insulating layer.

The first insulating layer 11 and the second insulating layer 12 preferably have a total volume resistivity of 1 × 10 ¹³ Ω · cm or more so that the insulating sheet 10 can exhibit excellent electrical insulation. More preferably, it is 1 × 10 ¹⁴ Ω · cm or more.
The first insulating layer 11 and the second insulating layer 12 also preferably have an individual volume resistivity of 1 × 10 ¹³ Ω · cm or more, and more preferably 1 × 10 ¹⁴ Ω · cm or more.

In addition, the first insulating layer 11 and the second insulating layer 12 have a thermal conductivity when the epoxy composition is sufficiently cured (C-staged) in order to exhibit excellent thermal conductivity in the insulating sheet 10. It is preferable that the type and amount of the inorganic filler are adjusted so that the rate is 5 W / m · K or more, and the type of the inorganic filler is so that the thermal conductivity is 14 W / m · K or more. It is preferable that the amount is adjusted.
The upper limit of the thermal conductivity is usually about 30 W / m · K.
About the heat conductivity of the molded object formed with the epoxy composition, it can measure normally with a xenon flash analyzer (For example, the product made from NETZSCH, "LFA-447 type").
This thermal conductivity can be measured by other laser flash methods or TWA methods without using a xenon flash analyzer. For example, the laser flash method is measured using “TC-9000” manufactured by ULVAC-RIKO. can do.
And in TWA method, it can measure using "ai-Phase mobile" by an eye phase company.

When the epoxy composition for forming the first insulating layer 11 and the second insulating layer 12 contains boron nitride particles or aluminum nitride particles in the state of aggregated particles, the boron nitride particles or aluminum nitride particles are aluminum oxide particles or Compared to silicon oxide particles and the like, the affinity with the resin is low, and it is difficult to exert excellent cohesive force on the first insulating layer 11 and the second insulating layer 12 only with boron nitride particles and aluminum nitride particles. If excellent adhesiveness is required for the one insulating layer 11 and the second insulating layer 12, it is preferable to contain metal oxide particles such as aluminum oxide particles and silicon oxide particles.
In addition, when making the 1st insulating layer 11 and the 2nd insulating layer 12 exhibit heat conductivity and adhesiveness with sufficient balance, the total amount of the inorganic filler which occupies for the 1st insulating layer 11 and the 2nd insulating layer 12 is 40. It is preferable to set it as volume%-70 volume%.
In order to make the first insulating layer 11 and the second insulating layer 12 exhibit a good balance between thermal conductivity and adhesiveness, the total amount (BN + AlN) of the boron nitride particles and the aluminum nitride particles and the metal oxide are used. The amount of physical particles (MO) is contained in the first insulating layer 11 and the second insulating layer 12 so that the volume ratio [(BN + AlN): MO] is 50:50 to 99.5: 0.5. It is preferable to make it.
Further, the metal oxide particles preferably have a median diameter of 0.1 μm to 30 μm determined by measurement with a laser diffraction / scattering particle size distribution meter.

In addition, the 1st insulating layer 11 and the 2nd insulating layer 12 do not need to form with the same epoxy composition, and may mix | blend the mixture ratio of an epoxy monomer and a hardening | curing agent, content of an inorganic filler, etc. .
Furthermore, it is not necessary for the first insulating layer 11 and the second insulating layer 12 to have the same thickness.
The thicknesses of the first insulating layer 11 and the second insulating layer 12 can usually be about 25 μm to 300 μm.

  In addition, about the said base material layer 13, it can form with the polymer film, metal foil, fiber sheet, etc. which have thickness of 5 micrometers-500 micrometers normally.

  In the case of the polymer film, for example, polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polylactic acid, and polyarylate; polyolefin resins such as polyethylene and polypropylene; polyamide 6, polyamide 6, 6 Aliphatic polyamide resins such as polyamide 11, polyamide 12; aromatic polyamide resins such as poly-p-phenylene terephthalamide and poly-m-phenylene isophthalamide; chlorinated resins such as polyvinyl chloride and polyvinylidene chloride; Fluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-ethylene copolymer Polyimide resins; polycarbonate resins, acrylic resins, polyphenylene sulfide resins; polyurethane resins; polymer, fluorine-based resins such as polyvinylidene fluoride resin film made of a polyvinyl alcohol resin can be used in the formation of the base layer 13.

Moreover, if it is the said metal foil, the base material layer 13 can be formed with metal foil which consists of metals, such as copper, aluminum, nickel, iron, and its alloy.
The metal foil may be a clad foil formed by bonding different metals or a plating foil plated with different metals.

  Furthermore, if it is the said fiber sheet, a polyester fiber nonwoven fabric, a pulp sheet, a glass mat, a carbon fiber sheet, etc. are employ | adopted and the said base material layer 13 can be formed.

  In addition, the base material layer can be formed by a sheet in which these are combined, for example, by using a laminated film in which a metal foil such as an aluminum laminated resin film and a polymer film are laminated. it can.

As a specific usage method of the insulating sheet 10, for example, a usage method as a constituent member of a semiconductor module as shown in FIGS.
First, the usage method of the insulating sheet 10 is demonstrated based on FIG.
FIG. 2 is a schematic view showing a cross section of a semiconductor module. The semiconductor module 100 includes a module body 100x in which a semiconductor element is resin-molded and a heat radiating member 20 for radiating heat generated by the semiconductor element. Insulating sheet 10 is interposed between the two.

The module body 100x includes the semiconductor element 30 and a metal plate 40 that functions as a heat sink for the semiconductor element 30, and is fixed to the upper surface side of the metal plate 40 that is placed flat by solder 50. The semiconductor element 30 is included.
The semiconductor element 30 is smaller than the area of the upper surface of the metal plate 40. In the present embodiment, the semiconductor element 30 is mounted on the metal plate in a bare chip state.

The module main body 100x of the present embodiment includes a rectangular tube-shaped case 60 that forms an outer shell thereof, and the case 60 has a shape that is slightly larger than that of the metal plate 40 in a plan view and a shape in a front view. However, the insulating sheet 10, the metal plate 40, and the semiconductor element 30 are formed to be higher than the total height.
That is, the case 60 has a size capable of including all of the insulating sheet 10, the metal plate 40, and the semiconductor element 30.
The module body 100x further includes the case 60 disposed so as to surround the metal plate 40, and further includes a lead frame 70 that penetrates the side wall of the case 60 and extends inside and outside the case.

In addition, the module body 100x has an end portion of the lead frame 70 in the case electrically connected to the semiconductor element 30 by a bonding wire 80, and an empty space in the case is filled with sealing resin. The mold part 90 is formed.
In the present embodiment, the mold portion 90 has the semiconductor element 30 and the metal plate 40 embedded therein.
And the said insulating sheet 10 of this embodiment is distribute | arranged to the lower surface of the metal plate 40 used as the opposite side to the side in which the said semiconductor element 30 is mounted.
The insulating sheet 10 of the present embodiment has a shape corresponding to the lower surface of the metal plate 40 in a plan view, and the lower surface outer edge 40e of the metal plate 40 and the outer edge of the first insulating layer 11 are aligned. It is bonded to the lower surface of the metal plate 40.
In addition, the insulating sheet 10 of the present embodiment is used for forming the semiconductor module 100 so that the lower surface side is exposed when the upper surface side is embedded in the mold part 90 and the heat radiating member 20 is not provided. .
That is, the semiconductor module 100 of this embodiment is formed such that the lower surface of the mold part 90 is substantially flush with the lower surface of the base material layer 13 of the insulating sheet 10.

  In the present embodiment, as the heat radiating member 20, a plate-like substrate portion 21 whose upper surface is a flat surface larger than the lower surface of the metal plate 40 and a plurality of fins are suspended from the lower surface of the substrate portion 21. A heat dissipating fin having a fin portion 22 is employed.

The semiconductor module 100 of the present embodiment is sealed when the mold portion 90 is formed when the upper surface of the first insulating layer 11 that is a B-staged epoxy resin layer is bonded to the lower surface of the metal plate 40. Resin heat and pressure are utilized.
That is, before the formation of the mold part 90, the metal plate 40 and the insulating sheet 10 are not temporarily bonded to each other, or are not bonded at all. In this case, the first insulating layer 11 and the lower surface of the metal plate 40 are brought into pressure contact with each other when the sealing resin heated and melted to form the mold part 90 is pressurized and filled in the case, so that the metal plate is heated. 40 is bonded and fixed.

Further, the insulating sheet 10 is finally made into a C-stage by forming the first insulating layer 11 and the second insulating layer 12 by heat when forming the mold portion 90 and additional heating performed as necessary. The semiconductor module 100 is provided.
In this way, the insulating sheet 10 constituting a part of the semiconductor module 100 is exposed only on the lower surface side of the base material layer 13 on the lower surface of the module body 100x.
The insulating sheet 10 of the present embodiment has the base layer 13 formed of a metal foil, and the exposed surface of the metal foil is used as a main heat radiating surface from the module main body 100x to the heat radiating member 20. The semiconductor module 100 is provided.

And while the insulating sheet 10 of this embodiment is adhere | attached on the module main body 100x using the adhesiveness of the 1st insulating layer 11 as mentioned above, the base material layer 13 does not show adhesiveness. Therefore, the heat radiating member 20 is bonded and fixed to the module main body 100x to be in contact with the heat radiating member 20.
More specifically, the insulating sheet 10 of the present embodiment is in contact with the upper surface of the substrate portion 21 of the heat dissipation member 20 with heat dissipation grease interposed therebetween.

As described above, in the semiconductor module 100 of the present embodiment, the semiconductor element 30 is directly mounted on the metal plate 40, and the semiconductor element 30 and the metal plate 40 have substantially the same potential.
Therefore, the insulating sheet 10 forms a good heat transfer path between the metal plate 40 and the heat radiating member 20, and the electrical connection between the metal plate 40 and the heat radiating member 20 is interrupted. The semiconductor module 100 is provided as necessary.

  Since the insulating sheet 10 of the present embodiment has excellent electrical insulation and thermal conductivity, it is possible to suppress an excessive increase in the junction temperature of the semiconductor element 30 during the operation of the semiconductor module 100, and the semiconductor module It can prevent 100 failures and prolong the service life.

Such an effect is not limited to the embodiment illustrated in FIG. 2 but also in the semiconductor module illustrated in FIG.
This will be described with reference to FIG.
3 is a schematic diagram showing a cross section of the semiconductor module as in FIG. 2. In FIG. 3, the components denoted by the same reference numerals as those in FIG. 2 are the same as those in FIG. The explanation will not be repeated more than necessary.

  The semiconductor module 100 ′ shown in FIG. 3 is an epoxy resin layer single layer sheet body in which the insulating sheet 10 ′ does not have a laminated structure, and an epoxy composition containing an inorganic filler is B-staged. It differs from the semiconductor module 100 of FIG. 2 in a certain point.

  In addition, the semiconductor module 100 ′ has an insulating sheet 10 ′ formed in the same shape as the planar shape of the case 60 ′, and the mold part 90 ′ is substantially flush with the lower surface of the metal plate 40 ′. It differs from the semiconductor module 100 of FIG. 2 also in the point formed.

  The insulating sheet 10 ′ is used by being adhered to the lower surface of the module main body 100x ′, which is a main part of the semiconductor module 100 ′ excluding the insulating sheet 10 ′, and insulates the metal plate 40 ′. Used to construct 100 '.

  Further, as shown in FIG. 3, the insulating sheet 10 'is used by being interposed between the module main body 100x' and the heat radiating member 20 '.

When forming the semiconductor module 100 ′ as shown in FIG. 3 by using the insulating sheet 10 ′, the insulating sheet 10 ′ is used after first bonding the insulating sheet 10 ′ to the module body side. Further, the heat dissipating member 20 ′ may be adhered, and conversely, after the insulating sheet 10 ′ is once adhered to the upper surface of the substrate portion 21 ′ of the heat dissipating member 20 ′, the heat dissipating member with the insulating layer is produced. The heat dissipation member with an insulating layer may be bonded to the module main body 100x ′.
Further, the insulating sheet 10 ′ is bonded to the module body 100x ′ and the heat radiating member 20 ′ at the same time by, for example, hot pressing the insulating sheet 10 ′ between the module main body 100x ′ and the heat radiating member 20 ′. You may make it make it.

Even in such a case, since the C-staged insulating sheet 10 ′ exhibits excellent electrical insulation and thermal conductivity, the semiconductor module 100 ′ including the insulating sheet 10 ′ as a constituent member has a useful life. Can be prolonged.
Here, detailed description will not be repeated any more. For example, in the embodiment illustrated in FIG. 3, the insulating sheet 10 ′ has two or more insulating layers as illustrated in FIGS. It is also possible to have a base material layer other than the insulating layer.
Moreover, about the heat conductive sheet of this invention, a conventionally well-known technical matter can be suitably employ | adopted in the range in which the effect of this invention is not impaired remarkably.

  In the present invention, the epoxy composition as a material for forming the insulating sheet can also be used for forming the mold parts 90, 90 'and the cases 60, 60'.

  EXAMPLES Next, although an Example is given and this invention is demonstrated in more detail, this invention is not limited to these.

<Preparation of epoxy composition>
The following materials were prepared to adjust the evaluation epoxy composition.

(Epoxy A1): Epoxy equivalent 180 g / eq of the following general formula (3) (epoxy A2): Epoxy equivalent 187 g / eq of the following general formula (3) The substance “Epoxy A1” And “epoxy A2” are structurally the same, but have different values of the average number of repeating units (“n” in the formula).

（ただし、式中の「ｎ」は、１〜１５の数を表す。）

(However, “n” in the formula represents a number of 1 to 15.)

(Epoxy B): Substance represented by the following general formula (5) having an epoxy equivalent of 167 g / eq)

（ただし、式中の「ｎ」は、１〜３の数を表す。）

(However, “n” in the formula represents a number of 1 to 3.)

(Phenol C): 4,4 ', 4 "-methylidynetrisphenol represented by the following general formula (4) having a hydroxyl group equivalent of 97 g / eq

(Phenol D): A substance represented by the following general formula (6) having a hydroxyl group equivalent of 105 g / eq

(Curing accelerator E): Tetraphenylphosphonium tetraphenylborate (TPPK)
(Silane coupling agent F): Phenyltrimethoxysilane (inorganic filler G): Boron nitride aggregated particles (manufactured by Mizushima Alloy Iron Company, trade name “HP-40”)
(Inorganic filler H): Aluminum nitride aggregated particles (manufactured by Furukawa Denshi Co., Ltd., trade name “f-50J”)
(Inorganic filler I): Aluminum oxide particles (manufactured by Showa Denko KK, trade name “CB-P10”)

<Production of test piece 1>
Example 1
The above-mentioned “epoxy A1” and “phenol C” are obtained by changing the number of epoxy groups (EX) by “epoxy A1” and the number of hydroxyl groups (OH) by “phenol C” to 1: 1 (EX: OH). The “curing accelerator E” was blended so that the ratio to 100 parts by mass of “epoxy A1” was 1 part by mass.
An epoxy solution was prepared by adding cyclopentanone so that the proportion of the total of the blends (“epoxy A1”, “phenol C”, and “curing accelerator E”) was 30% by mass.
This epoxy solution was poured into an aluminum cup and heated to a temperature of about 100 ° C. to remove the solvent (cyclopentanone) to produce a dry solid.
Next, this dried solid was placed on a glass plate and stored in a vacuum chamber at 140 ° C. for 10 minutes to melt and degas.
Place a spacer around this glass plate, and put another glass plate on it, and allow it to sufficiently react with “epoxy A1” and “phenol C” while being stored in a dryer at 180 ° C. for 3 hours, A sheet-like cured body having a thickness of 0.45 mm was produced.
It was 0.32 W / m * K as a result of measuring the heat conductivity of this hardening body.

Next, the mixing ratio of “epoxy A1”, “phenol C” and “curing accelerator E” was the same as described above, and a heat conductive sheet was prepared using an epoxy composition containing an inorganic filler.
In the following, the term “parts by mass” means a mass ratio with respect to a total of 100 parts by mass of “epoxy A1” and “phenol C” unless otherwise specified.
First, the silane coupling treatment of the inorganic filler was performed so that the ratio of the silane coupling agent to 100 parts by mass of the inorganic filler was 1.5 parts by mass.
That is, as shown in Table 1, 245.80 parts by mass of “inorganic filler G (BN)” was weighed and accommodated in a bag, and 3.69 parts by mass of “silane coupling agent F” was added. Mix and stir in the bag.
Similarly, after weighing “inorganic filler H (AlN)” so that the ratio of “epoxy A1” and “phenol C” to 100 parts by mass in total is 88.64 parts by mass, 1.33 parts by mass of “silane coupling agent F” was added and mixed and stirred in the bag.
And this "inorganic filler G" and "inorganic filler H" were left still for 2 days or more with the state accommodated in the bag, respectively, and the silane coupling process was performed.

Next, 289.96 parts by mass of cyclopentanone was prepared, and 5.23 parts by mass of a silica-based thickener was added thereto, and further 64.9 parts by mass of “Epoxy A1” and 35.1 parts by mass of “Phenol C”. And after adding 0.65 mass part of "curing accelerator E", this was set to the hot stirrer, and it stirred at the temperature of about 70 degreeC.
Finally, the filler subjected to the coupling treatment was added to prepare a coating solution.
A surface-roughened polyethylene terephthalate resin (PET) film was set on a table so that the roughened surface was facing upward, and the coating solution was applied thereto using an applicator for a thickness of 200 μm.
A sample sheet in which an epoxy resin layer is formed on a PET film by containing the PET film coated with this coating solution in a dryer at 130 ° C. for 10 minutes to volatilize and remove cyclopentanone from the coating film. Obtained.
Four pieces of approximately square sheet pieces each having a side of 50 mm were cut out from this sample sheet, and two of them were superposed so that the coating film was on the inside, and bonded by hot pressing.
Further, the remaining two sheet pieces were similarly bonded by hot pressing.
In addition, the hot press at this time is such that a pressure of 10 MPa is applied in the thickness direction to the two pieces of the stacked sheets, and the temperature is made constant when the temperature reaches 130 ° C. by heating from room temperature, The cooling was carried out when 20 minutes had passed since the start of heating.
Moreover, in this hot press, pressurization was continued during cooling, and cooling in the pressurized state was performed for 20 minutes or more.

The PET films were removed from one side of each of the two laminated sheets (PET film / epoxy resin layer / epoxy resin layer / PET film four-layer laminate) thus obtained, and the epoxy resin layers exposed on the surface were mutually exposed. The samples were stacked so as to contact each other and heat-pressed again to prepare a sample for thermal conductivity measurement.
The heat press at this time is such that a pressure of 5 MPa is applied to the two laminated sheets in the thickness direction, the temperature is constant when the temperature reaches 180 ° C. when heated from room temperature, and heating is started. Cooling was performed at the time when 60 minutes passed later, and the epoxy composition constituting the epoxy resin layer was cured almost completely.
Moreover, also in this hot press, pressurization was continued during cooling, and cooling in the pressurized state was performed for 20 minutes or more.
Finally, the outer PET film was removed from the hot-pressed sheet to obtain a thermally conductive sheet in which four epoxy resin layers were laminated, and this thermally conductive sheet was used as a sample for measuring thermal conductivity.

About the heat conductivity of this heat conductive sheet (4 layer lamination | stacking sample), it shows in Table 1 with the measurement result about the sheet | seat which does not contain the said inorganic filler.
The thermal conductivity is measured by a xenon flash analyzer “LFA-447 type” (manufactured by NETZSCH).

(Examples 2-4, Comparative Examples 1-7)
A sample was prepared and the thermal conductivity was measured in the same manner as in Example 1 except that the composition of the epoxy composition was changed as shown in Tables 1 and 2.
The results are also shown in Tables 1 and 2.

In the results shown in the above table, from the comparison between Examples 1 and 2 and Comparative Example 3 in which the kind of the epoxy monomer was made different while the content of the inorganic filler was substantially the same, the general formula (1 It is useful to form an epoxy resin layer having excellent thermal conductivity by adopting an epoxy monomer having the structure shown in the formula (3), in particular, an epoxy monomer having the structure shown in the general formula (3). Recognize.
Moreover, in the result shown by said table | surface, from the comparison with Example 1 and the comparative example 1 and the comparison with Example 2 and the comparative example 2 which differed in the kind of phenol type hardening | curing agent, the said general Employing a phenolic curing agent having the structure represented by the formula (2), in particular, a phenolic curing agent having the structure represented by the general formula (4) forms an epoxy resin layer having excellent thermal conductivity. It turns out that it is useful for.
Furthermore, in the results shown in the above table, from the comparison between Comparative Example 3 and Comparative Example 4, the phenolic curing agent having the structure shown in General Formula (4) is shown in General Formula (1). It can be seen that it works effectively when combined with an epoxy monomer having a different structure.
From the above, it can be seen that the present invention can provide a thermally conductive sheet excellent in thermal conductivity and an epoxy composition suitable for forming such a thermally conductive sheet.

10: Thermally conductive sheet (insulating sheet), 11: Epoxy resin layer (first insulating layer), 12: Epoxy resin layer (second insulating layer), 20: Heat radiation member, 30: Semiconductor element, 40: Metal plate , 100: semiconductor module, 100x: module body

Claims (4)

Thermal conductivity for a semiconductor module interposed between the heat radiating member and the semiconductor element in a semiconductor module having a module body including the semiconductor element and a heat radiating member for radiating heat generated by the semiconductor element A sheet,
An epoxy resin layer comprising an epoxy composition is provided, and the epoxy composition comprises an epoxy monomer represented by the following general formula (1), a phenol-based curing agent represented by the following general formula (2), and boron nitride particles Or the aluminum nitride particle | grains, The said boron nitride particle | grains or the said aluminum nitride particle | grains are contained in the state of the aggregated particle, The heat conductive sheet for semiconductor modules characterized by the above-mentioned.

(However, “G” in the formula represents a glycidyl group, “A” represents a biphenyl ring which is unsubstituted or substituted with a hydrocarbon group having 1 to 6 carbon atoms. (It is a group represented by the formula (x), and “n” represents a number from 1 to 15.)

(However, “B” in the formula represents a benzene ring which is unsubstituted or substituted with a hydrocarbon group having 1 to 6 carbon atoms, and “R ¹ ” to “R ⁴ ” are hydrogen atoms or 1 to 6 carbon atoms. And “R ¹ ” to “R ⁴ ” may be the same as or different from each other.)

(However, “R ⁵ ” is any one of a hydroxyl group, a methyl group, an ethyl group, a propyl group, or a hydrogen atom, and “Ph ¹ ”, “Ph ² ”, and “Ph ³ ” are common to each other. Or a substituted or unsubstituted phenyl represented by the following general formula (y), and at least two of the “Ph ¹ ”, “Ph ² ” and “Ph ³ ” have a hydroxyl group. Having substituted phenyl.)

(However, “R ⁶ ” to “R ¹⁰ ” in the formula are any of a hydroxyl group, a methyl group, an ethyl group, a propyl group, or a hydrogen atom.)
  The thermally conductive sheet for a semiconductor module according to claim 1, wherein the epoxy composition further contains an onium salt-based curing accelerator.   The thermally conductive sheet for a semiconductor module according to claim 2, wherein the onium salt-based curing accelerator is a phosphonium salt-based curing accelerator.   The thermal conductivity sheet for a semiconductor module according to any one of claims 1 to 3, wherein the thermal conductivity of the epoxy resin layer is 14 W / (m · K) or more.

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