Power module

Abstract

To provide a technique for improving heat radiation performance in a power module including a power semiconductor element.SOLUTION: A power module 10 includes a power semiconductor chip 1 and a Cu circuit 3 provided on one surface of the power semiconductor chip 1. The power module 10 has a sintering layer 2 in which the power semiconductor chip 1 and the Cu circuit 3 are joined by sintering paste and a heat dissipation sheet 4 provided for joining a Cu base plate 5 to the other surface of the Cu circuit 3. In a first lamination structure in which the power semiconductor chip 1, the sintering layer 2, the Cu circuit 3, and the heat dissipation sheet 4 are laminated, a total X1 of thermal resistance in a lamination direction is 0.30 (K / W) or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a power module, for example, a power module having a power semiconductor element and a metal circuit board (heat-conductive metal layer) having the power semiconductor element provided on one surface thereof. [Background technology]

[0002] The market for power modules, which include power semiconductor elements mounted on a metal circuit board for heat transfer, is expanding. Various technologies have been proposed to achieve high heat dissipation in such power modules. For example, a laminate for a finned heat sink-integrated circuit board is known, which includes an integrally molded finned heat sink and substrate containing a highly thermally conductive filler and a crystalline polymer, an insulating layer formed on the substrate and containing an insulating, thermally conductive filler and a crystalline polymer, and a metal layer formed on the insulating layer, in which the highly thermally conductive filler content in the finned heat sink and substrate is 15 to 65 vol %, and the thermally conductive filler content in the insulating layer is 15 to 65 vol % (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-28421 Summary of the Invention [Problem to be solved by the invention]

[0004] However, conventional power modules have a layered structure of "chip (power semiconductor element) / solder / DBC (Direct Bonded Copper) substrate / solder / heat dissipation fins." Solder was used to bond the chip (power semiconductor element) to the DBC substrate, and to bond the DBC substrate to the heat dissipation fins. When the power module is operating, the chip (power semiconductor element) generates heat, but the above structure does not dissipate that heat sufficiently, so a technology to address this was needed.

[0005] The present invention has been made in view of the above circumstances, and has as its object to improve the heat dissipation performance of a power module including a power semiconductor element. [Means for solving the problem]

[0006] According to the present invention, there is provided a power module having a power semiconductor element and a metal circuit board having the power semiconductor element provided on one surface thereof, a bonding layer that bonds the power semiconductor element and the metal circuit board with a sintering paste; a heat dissipation sheet provided for joining a heat dissipation member to the other surface of the metal circuit board; and In a first laminated structure in which the power semiconductor element, the bonding layer, the metal circuit board, and the heat dissipation sheet are laminated, the total thermal resistance in the stacking direction (height direction) is 0.40 (K / W) or less. A power module is provided. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a technology for improving the heat dissipation performance of a power module including a power semiconductor element. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view schematically showing a power module according to an embodiment of the present invention. [Figure 2]1A and 1B are cross-sectional views showing examples of the structure of power modules according to an example and a comparative example. [Figure 3] FIG. 1 is a diagram showing models of power modules according to an example and a comparative example. [Figure 4] FIG. 1 is a diagram showing models of power modules according to an example and a comparative example. [Figure 5] FIG. 10 is a diagram showing thermal conditions in a simulation of heat distribution in an example and a comparative example. [Figure 6] FIG. 10 is a diagram showing the simulation results of heat distribution in an example and a comparative example on a power module model. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The drawings are for illustrative purposes only. The shapes and dimensional ratios of the components in the drawings do not necessarily correspond to the actual products.

[0010] <Summary of the Invention> <Power Module 10> A power module 10 according to this embodiment will be described. FIG. 1 is a cross-sectional view schematically showing the power module 10 according to the embodiment of the present invention. In the following, for ease of explanation, the positional relationships (upper and lower relationships, etc.) of the components of the power module 10 may be described as being as shown in the drawings. However, the positional relationships in this explanation are unrelated to the positional relationships during use or manufacturing of the semiconductor device 100.

[0011] The power module 10 includes a power semiconductor chip 1, a sintering layer 2, a Cu circuit 3, a heat dissipation sheet 4, a Cu base plate 5, a lead frame 6, and a sealing material 7.

[0012] <Power semiconductor chip 1> The power semiconductor chip 1 is, for example, an insulated gate bipolar transistor (IGBT), a diode, or the like. An electrode pattern (not shown) is formed on the upper surface of the power semiconductor chip 1, and a conductive pattern (not shown) is formed on the lower surface of the power semiconductor chip 1. The lower surface of the power semiconductor chip 1 is joined to one surface of the Cu circuit 3 via a sintering layer 2 which is a bonding layer. The electrode pattern on the upper surface of the power semiconductor chip 1 is electrically connected to the lead frame 6.

[0013] <Sintering layer 2> The sintering layer 2 is a bonding layer formed by sintering a sintering paste containing metal particles. As the sintering paste, any one of an Ag sintering paste containing silver particles, an AL sintering paste containing aluminum particles, and a Cu sintering paste containing copper particles can be used.

[0014] The above-described sintering paste is provided and laminated between the power semiconductor chip 1 and the Cu circuit 3, and the power semiconductor chip 1 and the Cu circuit 3 are joined by the sintering layer 2 through a sintering process. The Cu circuit 3 and the lead frame 6 are joined by the sintering layer 2. In the sintering layer 2, a sintering network (metal bonding bus) of metal particles is formed, realizing high thermal conductivity and low electrical resistance. From the viewpoint of improving the bonding property by the sintering layer 2, the Cu circuit 3 and the lead frame are 6 may be subjected to a surface treatment of plating with the metal contained in the sintering paste. Specifically, in the present embodiment, Ag plating may be performed on the surfaces of the Cu circuit 3 and the lead frame 6.

[0015] <Cu circuit 3> The Cu circuit 3 is a metal circuit board made of a metal material having conductivity. The power semiconductor chip 1 is provided on a circuit pattern formed on one surface (the upper surface in the drawing) of the Cu circuit 3 via a sintering layer 2 which is a bonding layer.

[0016] The Cu circuit 3 is a circuit board patterned with thick copper (rolled copper), and has a thickness of, for example, 0.3 mm to 5 mm. For example, thick copper (rolled copper) can be suitably used as the metal material constituting the Cu circuit 3. This gives the Cu circuit 3 a relatively low resistance. At least a portion of the Cu circuit 3 may be covered with a solder resist layer.

[0017] The Cu circuit 3 is formed, for example, by processing a metal layer (such as thick copper) laminated on the upper surface of the base 5A of the Cu base plate 5 via a heat dissipation sheet 4 into a predetermined pattern by cutting and etching, or by attaching the metal layer to the Cu circuit 3 with the heat dissipation sheet 4 after being processed into a predetermined pattern in advance.

[0018] The lower limit of the thickness of the Cu circuit 3 is, for example, 0.3 mm or more. If the thickness is equal to or greater than this value, heat generation in the circuit pattern can be suppressed even in applications requiring high current. Furthermore, the upper limit of the thickness of the circuit pattern 20 is, for example, 5.0 mm or less, preferably 4.0 mm or less, and more preferably 3.0 mm or less. If the thickness is equal to or less than this value, circuit processability can be improved, and the entire substrate can be made thinner.

[0019] <Heat dissipation sheet 4> The heat dissipation sheet 4 is disposed between the Cu circuit 3 and the Cu base plate 5. The heat from the power semiconductor chip 1 is received by the Cu circuit 3 and then transferred to the Cu base plate 5, which is heat dissipation means, via the heat dissipation sheet 4. This allows the heat generated from the power semiconductor chip 1, which is a heat-generating element, to be effectively dissipated to the outside of the power module 10 while maintaining the insulation of the power module 10. This makes it possible to improve the insulation reliability of the semiconductor device.

[0020] The planar shape of the heat dissipation sheet 4 is not particularly limited and can be selected appropriately to match the shapes of the Cu circuit 3 and Cu base plate 5, but can be rectangular, for example. The film thickness of the heat dissipation sheet 4 is, for example, 50 μm or more and 250 μm or less. This allows for improved mechanical strength and heat resistance while more effectively conducting heat from the Cu circuit 3 to the Cu base plate 5. Furthermore, the heat dissipation sheet 4 has an excellent balance between heat dissipation and insulation. The thermal conductivity of the heat dissipation sheet 4 is not particularly limited, but is preferably 10 W / mK (175°C) or more, and more preferably 15 W / mK (175°C) or more.

[0021] [Heat dissipation sheet 4 material] The heat dissipation sheet 4 is, for example, a resin sheet, and is formed using a resin composition for a sheet. The resin composition for a sheet will be described below. In this embodiment, the resin composition for the sheet preferably contains a thermosetting resin (A), a filler (B), a curing agent (C), etc. When the resin composition contains a thermosetting resin, the heat dissipation insulation sheet is a B-staged version of the thermosetting resin (A).

[0022] [Thermosetting resin (A)] Examples of the thermosetting resin (A) include epoxy resins, cyanate resins, polyimide resins, benzoxazine resins, unsaturated polyester resins, phenolic resins, melamine resins, silicone resins, bismaleimide resins, phenoxy resins, and acrylic resins. As the thermosetting resin (A), one of these may be used alone, or two or more may be used in combination. Among these, from the viewpoint of high insulating properties, epoxy resin, phenol resin, and phenoxy resin are preferred as the thermosetting resin (A).

[0023] Examples of epoxy resins include bisphenol type epoxy resins such as 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), and bisphenol Z type epoxy resin (4,4'-cyclohexidienebisphenol type epoxy resin); phenol novolac type epoxy resin, cresol novolac type epoxy resin, trisphenol methane type novolac type epoxy resin, tetraphenol group ethoxylated epoxy resin, and the like. Examples of epoxy resins include novolac-type epoxy resins such as benzophenone-type novolac-type epoxy resins and novolac-type epoxy resins having a condensed ring aromatic hydrocarbon structure; biphenyl-type epoxy resins; aryl alkylene-type epoxy resins such as xylylene-type epoxy resins and biphenyl aralkyl-type epoxy resins; naphthalene-type epoxy resins such as naphthylene ether-type epoxy resins, naphthol-type epoxy resins, naphthalene diol-type epoxy resins, bifunctional to tetrafunctional epoxy-type naphthalene resins, binaphthyl-type epoxy resins, and naphthalene aralkyl-type epoxy resins; anthracene-type epoxy resins; phenoxy-type epoxy resins; dicyclopentadiene-type epoxy resins; norbornene-type epoxy resins; adamantane-type epoxy resins; and fluorene-type epoxy resins. These may be used alone or in combination of two or more.

[0024] Among the epoxy resins, from the viewpoint of further improving heat resistance and insulation reliability, it is preferable to use one or more types selected from the group consisting of bisphenol-type epoxy resins, novolac-type epoxy resins, biphenyl-type epoxy resins, aryl alkylene-type epoxy resins, naphthalene-type epoxy resins, anthracene-type epoxy resins, and dicyclopentadiene-type epoxy resins.

[0025] Examples of phenolic resins include novolac-type phenolic resins such as phenol novolac resin, cresol novolac resin, and bisphenol A novolac resin, and resol-type phenolic resins, etc. One of these may be used alone, or two or more may be used in combination. Among the phenolic resins, phenolic novolac resins are preferred.

[0026] The content of the thermosetting resin (A) is preferably 1% by mass or more, more preferably 5% by mass or more, based on the total amount of the resin composition for the sheet, while the content is preferably 30% by mass or less, more preferably 20% by mass or less, based on the total amount of the resin composition for the sheet. When the content of the thermosetting resin (A) is at least the above lower limit, the handleability of the sheet resin composition improves, the heat radiation insulation sheet can be easily formed, and the strength of the heat radiation insulation sheet is improved. When the content of the thermosetting resin (A) is at most the above upper limit, the linear expansion coefficient and elastic modulus of the heat radiation insulation sheet are further improved, and the thermal conductivity is further improved.

[0027] [Filler (B)] The filler (B) in this embodiment is used from the viewpoint of improving the thermal conductivity of the heat radiation insulation sheet and obtaining strength.

[0028] The filler (B) is preferably a thermally conductive filler. More specifically, from the viewpoint of achieving a balance between thermal conductivity and electrical insulation, examples of the filler (B) include silica, alumina, boron nitride, aluminum nitride, and silicon carbide. These may be used alone or in combination of two or more. Of these, the filler (B) is preferably alumina or boron nitride.

[0029] The content of the filler (B) is preferably 90% by mass or less, more preferably 80% by mass or less, based on the total amount of the resin composition for the sheet, while from the viewpoint of thermal conductivity, the content is preferably 40% by mass or more, more preferably 50% by mass or more, based on the total amount of the resin composition for the sheet.

[0030] [Hardening agent (C)] When an epoxy resin or a phenol resin is used as the thermosetting resin (A), the resin composition for a sheet preferably further contains a curing agent (C).

[0031] As the curing agent (C), one or more selected from the curing catalyst (C-1) and the phenol-based 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 octoate, cobalt octoate, bisacetylacetonate cobalt(II), and trisacetylacetonate cobalt(III); tertiary amines such as triethylamine, tributylamine, and 1,4-diazabicyclo[2.2.2]octane; imidazoles such as 2-phenyl-4-methylimidazole, 2-ethyl-4-methylimidazole, 2,4-diethylimidazole, 2-phenyl-4-methyl-5-hydroxyimidazole, and 2-phenyl-4,5-dihydroxymethylimidazole; triphenylphosphine, tri-p-tolylphosphine, tetraphenylphosphonium tetraphenylborate, triphenylphosphine triphenylborane, and 1,2-bis(diphenylphosphine) Examples of the curing catalyst (C-1) include organic phosphorus compounds such as phenol, bisphenol A, nonylphenol, and the like; organic acids such as acetic acid, benzoic acid, salicylic acid, p-toluenesulfonic acid, and the like; and mixtures thereof. As the curing catalyst (C-1), one of these compounds, including their derivatives, can be used alone, or two or more of these compounds, including their derivatives, can be used in combination. The content of the curing catalyst (C-1) is not particularly limited, but is preferably 0.001% by mass or more and 1% by mass or less based on the total amount of the resin composition for a sheet.

[0032] Examples of the phenolic curing agent (C-2) include novolac-type phenolic resins such as phenol novolac resin, cresol novolac resin, trisphenolmethane-type novolac resin, naphthol novolac resin, and aminotriazine novolac resin; modified phenolic resins such as terpene-modified phenolic resin and dicyclopentadiene-modified phenolic resin; aralkyl-type resins such as phenol aralkyl resins having a phenylene skeleton and / or biphenylene skeleton and naphthol aralkyl resins having a phenylene skeleton and / or biphenylene skeleton; bisphenol compounds such as bisphenol A and bisphenol F; and resol-type phenolic resins, 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 phenolic resin or a resol type phenolic resin.

[0033] The content of the phenolic curing agent (C-2) is not particularly limited, but is preferably 1% by mass or more, more preferably 5% by mass or more, based on the total amount of the resin composition for sheets, while the content is preferably 30% by mass or less, more preferably 15% by mass or less, based on the total amount of the resin composition for sheets.

[0034] [Coupling agent (D)] The resin composition for a sheet may contain a coupling agent (D), which can improve the wettability at the interface between the thermosetting resin (A) and the filler (B).

[0035] The coupling agent (D) is not particularly limited, but it is preferable to use one or more coupling agents selected from, for example, epoxy silane coupling agents, cationic silane coupling agents, amino silane coupling agents, titanate-based coupling agents, and silicone oil-type coupling agents. The content of the coupling agent (D) is not particularly limited, but is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, relative to 100% by mass of the filler (B), and is preferably 3% by mass or less, more preferably 2% by mass or less, relative to 100% by mass of the filler (B).

[0036] [Phenoxy resin (E)] Furthermore, the resin composition for a sheet may contain a phenoxy resin (E), which can improve the flex resistance of the heat dissipation insulation sheet. Furthermore, by including the phenoxy resin (E), it is possible to reduce the elastic modulus of the heat radiation insulation sheet, thereby improving the stress relaxation ability of the heat radiation insulation sheet.

[0037] Furthermore, the inclusion of the phenoxy resin (E) increases viscosity, reducing fluidity and preventing voids. Furthermore, when the heat dissipation insulation sheet is used in close contact with a metal member, the adhesion between the metal and the cured resin composition for the sheet can be improved. These synergistic effects further enhance the insulation reliability of semiconductor devices.

[0038] The phenoxy resin (E) may be, for example, a phenoxy resin having a bisphenol skeleton. Examples of suitable phenoxy resins include phenoxy resins having a naphthalene skeleton, phenoxy resins having an anthracene skeleton, and phenoxy resins having a biphenyl skeleton. Phenoxy resins having a structure containing a plurality of these skeletons can also be used.

[0039] The content of the phenoxy resin (E) is preferably, for example, 3% by mass or more and 10% by mass or less relative to the total amount of the resin composition for a sheet.

[0040] [Other ingredients] The resin composition for sheets may also contain other additives such as antioxidants and leveling agents, as long as the effects of the present invention are not impaired.

[0041] <Cuベースプレート5> The Cu base plate 5 is a type of heat dissipation member, and has a copper plate-shaped base 5A and a plurality of fins 5B extending integrally from the lower surface of the base 5A. The heat dissipation member may be, for example, an aluminum base plate in addition to the Cu base plate 5. Furthermore, as long as it has the function of acquiring heat generated by the power semiconductor chip 1 via the Cu circuit 3 and dissipating it elsewhere, it is not limited to a general heat dissipation member, and may be a part of another configuration (for example, a housing). Even in this case, the heat dissipation sheet 4 is used.

[0042] <Lead frame 6> The lead frame 6 supports and fixes the power semiconductor chip 1 and also electrically connects it to external wiring, and is a component made by pressing or etching a thin plate of a metal material such as copper or iron.

[0043] <Sealing material 7> The sealing material 7 is, for example, a mold resin, and integrally seals the power semiconductor chip 1, the sintering layer 2, the Cu circuit 3, the heat dissipation sheet 4, the Cu base plate 5, and the lead frame 6 inside. In addition to the mold resin, silicone gel or the like may also be used as the sealing material 7. The following describes the structure of integral sealing with a mold resin.

[0044] In this sealing, a portion of the lead frame 6 is sealed, and the remaining unsealed portion is connected to an external device. As for the Cu base plate 5, the upper surface and side surfaces of the base portion 5A of the Cu base plate 5 are covered and sealed with the sealing material 7. The lower surface and fin portion 5B of the Cu base plate 5 are not covered with the sealing material 7. In other words, the sealing material 7 covers and seals the power semiconductor chip 1 so as to cover part or all of the side surfaces in the thickness direction of the base portion 5A of the Cu base plate 5. Here, a configuration in which all of the side surfaces of the base portion 5A of the Cu base plate 5 are covered with the sealing material 7 is exemplified.

[0045] [Components of sealing material 7 (mold resin)] The molding resin of the sealing material 7 is a cured product of a thermosetting composition (C) containing a thermosetting resin (A) and an inorganic filler (B). The thermosetting composition (C) contains a curing accelerator (D).

[0046] [Curing accelerator (D)] The curing accelerator (D) of this embodiment has strong activity, which allows low-temperature curing to be achieved, but if used as is without any special measures, the reaction will proceed during storage, reducing the shelf life. Examples of the curing accelerator (D) include phosphorus atom-containing compounds such as organic phosphines, tetra-substituted phosphonium compounds, phosphobetaine compounds, adducts of phosphine compounds and quinone compounds, or adducts of phosphonium compounds and silane compounds; amidine compounds such as 1,8-diazabicyclo(5,4,0)undecene-7 and imidazole; and nitrogen atom-containing compounds such as tertiary amines such as benzyldimethylamine, amidinium salts, or ammonium salts. Among these, the curing accelerator (D) is preferably an imidazole-based curing accelerator or a phosphorus-based curing accelerator. The imidazole-based curing accelerator preferably contains, for example, an imidazole compound, which is an amidine-based compound. Examples of imidazole compounds include, but are not limited to, 2-methylimidazole, 2-phenylimidazole, imidazole-2-carbaldehyde, 5-azabenzimidazole, and 4-azabenzimidazole. Of these, 2-methylimidazole is preferably used.

[0047] The content of the curing accelerator (D) in the encapsulating resin composition is not particularly limited, but is preferably 0.1 mass % or more and 5 mass % or less, and more preferably 0.2 mass % or more and 4 mass % or less, based on the total encapsulating resin composition. By setting the content of the curing accelerator (D) to the above lower limit or more, the encapsulating resin composition can be appropriately cured. On the other hand, by setting the content of the curing accelerator (D) to the above upper limit or less, the molten state can be prolonged, and the low-viscosity state can be prolonged, which makes it easier to achieve low-temperature encapsulation.

[0048] [Thermosetting resin (A)] Examples of the thermosetting resin (A) include phenolic resin, epoxy resin, unsaturated polyester resin, melamine resin, and polyurethane. These may be used alone or in combination of two or more. Among these, it is preferable to contain at least one of a phenolic resin and an epoxy resin, and it is more preferable to contain an epoxy resin.

[0049] As the epoxy resin, any monomer, oligomer, or polymer having two or more epoxy groups in one molecule can be used, and there are no particular limitations on the molecular weight or molecular structure. Specific examples of epoxy resins include crystalline epoxy resins such as bisphenol-type epoxy resins (e.g., biphenyl-type epoxy resins, bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, and tetramethylbisphenol F-type epoxy resins), stilbene-type epoxy resins, and hydroquinone-type epoxy resins; novolac-type epoxy resins (e.g., cresol novolac-type epoxy resins, phenol novolac-type epoxy resins, and naphthol novolac-type epoxy resins); aralkyl-type epoxy resins (e.g., phenylene-skeleton-containing phenol aralkyl-type epoxy resins, biphenylene-skeleton-containing phenol aralkyl-type epoxy resins, phenylene-skeleton-containing naphthol aralkyl-type epoxy resins, and alkoxynaphthalene-skeleton-containing phenol aralkyl-type epoxy resins); trifunctional epoxy resins (e.g., triphenolmethane-type epoxy resins and alkyl-modified triphenolmethane-type epoxy resins); modified phenol-type epoxy resins (e.g., dicyclopentadiene-modified phenol-type epoxy resins and terpene-modified phenol-type epoxy resins); and heterocycle-containing epoxy resins (e.g., triazine-nucleus-containing epoxy resins). These may be used alone or in combination of two or more. Among these, it is more preferable to use at least one of an aralkyl type epoxy resin and a naphthyl ether type epoxy resin from the viewpoint of improving the balance between the reliability and moldability of the aluminum electrolytic capacitor.

[0050] The ICI viscosity of the thermosetting resin (A) at 150°C is preferably set appropriately depending on the content of the inorganic filler (B), and for example, the upper limit is preferably 60 poise or less, more preferably 50 poise or less, and even more preferably 40 poise or less, thereby improving the fluidity of the encapsulating resin composition and facilitating low-temperature encapsulation. On the other hand, the lower limit of the ICI viscosity of the thermosetting resin (A) at 150° C. is not particularly limited, but may be, for example, 0.01 poise or more. Note that 1 poise is 0.1 Pa·s.

[0051] The content of the thermosetting resin (A) is not particularly limited, but is preferably 1% by mass or more and 50% by mass or less, more preferably 2% by mass or more and 30% by mass or less, and even more preferably 5% by mass or more and 20% by mass or less, based on the total encapsulating resin composition. By setting the content of the thermosetting resin (A) to the above lower limit or more, the flowability and moldability of the encapsulating resin composition can be more effectively improved, and by setting the content of the thermosetting resin (A) to the above upper limit or less, the reliability of the aluminum electrolytic capacitor can be more effectively improved.

[0052] [Inorganic filler (B)] Examples of the inorganic filler (B) include silica, alumina, kaolin, talc, clay, mica, rock wool, wollastonite, glass powder, glass flakes, glass beads, glass fiber, silicon carbide, silicon nitride, aluminum nitride, carbon black, graphite, titanium dioxide, calcium carbonate, calcium sulfate, barium carbonate, magnesium carbonate, magnesium sulfate, barium sulfate, cellulose, aramid, and wood, etc. These may be used alone or in combination of two or more.

[0053] Examples of the silica include crystalline silica (crushed crystalline silica), fused silica (crushed amorphous silica, spherical amorphous silica), and liquid encapsulated silica (spherical amorphous encapsulated silica for liquid encapsulation). Of these, fused spherical silica is preferred from the viewpoint of facilitating low-temperature, low-pressure encapsulation.

[0054] The average particle size of the inorganic filler (B) is not particularly limited, but is typically 1 to 100 μm, preferably 1 to 50 μm, and more preferably 1 to 20 μm. It is believed that an appropriate average particle size contributes to the effect of more uniformly coating the shell containing the molten mixture in the granulation step described below. Furthermore, when the finally obtained core-shell particles are used as a semiconductor encapsulant, the filling ability around the semiconductor element in the mold cavity can be improved. The volumetric particle size distribution of the inorganic filler (B) can be measured using a commercially available laser particle size distribution analyzer (for example, SALD-7000 manufactured by Shimadzu Corporation).

[0055] The content of the inorganic filler (B) is not particularly limited, but is preferably 50% by mass or more and 95% by mass or less, more preferably 60% by mass or more and 95% by mass or less, and even more preferably 65% by mass or more and 85% by mass or less, based on the entire encapsulating resin composition. By setting the content of the inorganic filler (B) to the above lower limit or more, the reliability of the aluminum electrolytic capacitor encapsulated with the encapsulating resin composition can be effectively improved. Also, by setting the content of the inorganic filler (B) to the above upper limit or less, the flowability of the encapsulating resin composition can be improved, and the moldability can be more effectively improved.

[0056] The encapsulating resin composition of the present embodiment may contain the following components in addition to those described above. [Hardening agent (C)] The encapsulating resin composition may contain a curing agent (C). The curing agent (C) is not particularly limited as long as it reacts with the thermosetting resin (A) to cure it, but examples thereof include linear aliphatic diamines having 2 to 20 carbon atoms, such as ethylenediamine, trimethylenediamine, tetramethylenediamine, and hexamethylenediamine, as well as amines such as metaphenylenediamine, paraphenylenediamine, paraxylenediamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenylether, 4,4'-diaminodiphenylsulfone, 4,4'-diaminodicyclohexane, bis(4-aminophenyl)phenylmethane, 1,5-diaminonaphthalene, metaxylenediamine, paraxylenediamine, 1,1-bis(4-aminophenyl)cyclohexane, and dicyanodiamide; resole-type phenolic resins, such as aniline-modified resole resins and dimethyl ether resole resins; phenol novolac resins; and cresol. Examples of suitable phenolic resins include novolac-type phenolic resins such as phenol novolac resins, tert-butylphenol novolac resins, and nonylphenol novolac resins; phenol aralkyl resins such as phenylene skeleton-containing phenol aralkyl resins and biphenylene skeleton-containing phenol aralkyl resins; phenolic resins having a condensed polycyclic structure such as a naphthalene skeleton or an anthracene skeleton; polyoxystyrenes such as polyparaoxystyrene; alicyclic acid anhydrides such as hexahydrophthalic anhydride (HHPA) and methyltetrahydrophthalic anhydride (MTHPA), and aromatic acid anhydrides such as trimellitic anhydride (TMA), pyromellitic anhydride (PMDA), and benzophenonetetracarboxylic acid (BTDA); polymercaptan compounds such as polysulfides, thioesters, and thioethers; isocyanate compounds such as isocyanate prepolymers and blocked isocyanates; and organic acids such as carboxylic acid-containing polyester resins. These may be used alone or in combination of two or more. Among these, from the viewpoint of realizing low-temperature and low-pressure sealing of the encapsulating resin composition, it is more preferable to use at least one of a novolac type phenolic resin and a phenol aralkyl resin.

[0057] The content of the curing agent (C) in the encapsulating resin composition is not particularly limited, but is preferably 1% by mass or more and 12% by mass or less, and more preferably 3% by mass or more and 10% by mass or less, based on the total mass of the encapsulating resin composition. By setting the content of the curing agent (C) to the above lower limit or more, the encapsulating resin composition can be easily cured appropriately, whereas by setting the content of the curing agent (C) to the above upper limit or less, the encapsulating resin composition can maintain appropriate fluidity, making it easier to achieve low-temperature, low-pressure encapsulation.

[0058] [Coupling agent (E)] The encapsulating resin composition may contain, for example, a coupling agent (E). Examples of the coupling agent (E) that can be used include known coupling agents such as various silane-based compounds, such as epoxysilane, mercaptosilane, aminosilane, alkylsilane, ureidosilane, and vinylsilane, titanium-based compounds, aluminum chelates, and aluminum / zirconium-based compounds. More specifically, vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(β-methoxyethoxy)silane, γ-methacryloxypropyltrimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, γ-methacryloxypropyltriethoxysilane, vinyltriacetoxysilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-anilinopropyltrimethoxysilane, γ-anilinopropylmethyldimethoxysilane, γ-[bis(β-hydroxyethyl)]aminopropyltriethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, N-β-(aminoethyl) silane coupling agents such as -γ-aminopropyltriethoxysilane, N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-(β-aminoethyl)aminopropyldimethoxymethylsilane, N-(trimethoxysilylpropyl)ethylenediamine, N-(dimethoxymethylsilylisopropyl)ethylenediamine, methyltrimethoxysilane, dimethyldimethoxysilane, methyltriethoxysilane, N-β-(N-vinylbenzylaminoethyl)-γ-aminopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, hexamethyldisilane, vinyltrimethoxysilane, γ-mercaptopropylmethyldimethoxysilane, 3-isocyanatepropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, and 3-triethoxysilyl-N-(1,3-dimethylbutylidene)propylamine hydrolysate;Examples of titanate-based coupling agents include isopropyl triisostearoyl titanate, isopropyl tris (dioctyl pyrophosphate) titanate, isopropyl tri (N-aminoethyl - aminoethyl) titanate, tetraoctyl bis (ditridecyl phosphite) titanate, tetra (2,2-diallyloxymethyl-1-butyl) bis (ditridecyl) phosphite titanate, bis (dioctyl pyrophosphate) oxyacetate titanate, bis (dioctyl pyrophosphate) ethylene titanate, isopropyl trioctanoyl titanate, isopropyl dimethacryl isostearoyl titanate, isopropyl tridodecyl benzenesulfonyl titanate, isopropyl isostearoyl diacryl titanate, isopropyl tri (dioctyl phosphate) titanate, isopropyl tricumyl phenyl titanate, and tetraisopropyl bis (dioctyl phosphite) titanate. These may be used alone or in combination of two or more.

[0059] The content of the coupling agent (E) in the encapsulating resin composition is not particularly limited, but is preferably 0.05% by mass or more and 3% by mass or less, and more preferably 0.1% by mass or more and 2% by mass or less, based on the total encapsulating resin composition. By making the content of the coupling agent (E) equal to or greater than the above-mentioned lower limit, the dispersibility of the inorganic filler (B) in the encapsulating resin composition can be improved. Furthermore, by making the content of the coupling agent (E) equal to or less than the above-mentioned upper limit, the flowability of the encapsulating resin composition can be improved, thereby improving moldability.

[0060] Furthermore, in addition to the above components, the encapsulating resin composition of the present embodiment may contain various additives, such as a colorant such as carbon black; a release agent such as natural wax, synthetic wax, higher fatty acid or metal salts thereof, paraffin, or polyethylene oxide; an ion scavenger such as hydrotalcite; a stress reducing agent such as silicone oil or silicone rubber; a flame retardant such as aluminum hydroxide; and an antioxidant.

[0061] <Thermal resistance in the first and second laminated structures> The thermal resistance in the laminated structure of the power module 10 will be described.

[0062] <First laminated structure> In the power module 10, a first laminate structure is formed by laminating a power semiconductor chip 1, a sintering layer 2, a Cu circuit 3, and a heat dissipation sheet 4. In this case, in the first laminate structure, the total thermal resistance X1 in the lamination direction (height direction) is 0.30 (K / W) or less. There is no particular restriction on the lower limit of the total thermal resistance X1, but a realistic value is 0.05 or more, preferably 0.06 (K / W) or more, and more preferably 0.07 (K / W) or more. The upper limit of the total thermal resistance X1 is preferably 0.25 (K / W) or less, and more preferably 0.20 (K / W) or less.

[0063] When the total thickness of the first laminate structure is t1 (mm), the ratio X1 / t1 of the total thermal resistance X1 to the total thickness t1 is 0.25 (W / (K·mm)) or less. There is no particular lower limit to the ratio X1 / t1, but a realistic value is 0.02 (W / (K·mm)) or more, preferably 0.03 (W / (K·mm)) or more, and more preferably 0.04 (W / (K·mm)).

[0064] <Second laminated structure> The second laminated structure is a structure in which the power semiconductor chip 1, the sintering layer 2, the Cu circuit 3, the heat dissipation sheet 4, and the Cu base plate 5 are laminated together. That is, the second laminated structure is a structure in which the Cu base plate 5 is further laminated below the heat dissipation sheet 4 of the first laminated structure.

[0065] In the second stacked structure, the total thermal resistance X2 in the stacking direction (height direction) is 0.45 (K / W) or less. There is no particular lower limit to the total thermal resistance X2, but a realistic value is 0.10 (K / W) or more, preferably 0.12 (K / W) or more, and more preferably 0.15 (K / W) or more. The upper limit of the total thermal resistance X2 is preferably 0.35 (K / W) or less, and more preferably 0.25 (K / W) or less.

[0066] When the total thickness of the second laminate structure is t2 (mm), the ratio X2 / t2 of the total thermal resistance X2 to the total thickness t2 is 0.08 (W / (K·mm)). There is no particular lower limit to the ratio X2 / t2, but a realistic value is 0.01 (W / (K·mm)) or more, preferably 0.02 (W / (K·mm)) or more, and more preferably 0.03 (W / (K·mm)).

[0067] <Features and Effects of Power Module 10> The features and effects of this embodiment are summarized as follows: (1) The power module 10 of this embodiment is a power module (10) having a power semiconductor chip 1 and a Cu circuit 3 having the power semiconductor chip 1 provided on one surface thereof, a sintering layer 2 (sintering layer) in which the power semiconductor chip 1 and the Cu circuit 3 (metal circuit board) are bonded together using a sintering paste; a heat dissipation sheet 4 provided for joining a Cu base plate 5 (heat dissipation member) to the other surface of the Cu circuit 3; and In the first laminated structure in which the power semiconductor chip 1, the sintering layer 2, the Cu circuit 3, and the heat dissipation sheet 4 are laminated, the total thermal resistance X1 in the lamination direction is 0.30 (K / W) or less. With this configuration, the power module 10 can achieve excellent heat dissipation performance. Specifically, a sintering layer 2 (sintering paste) is used instead of the conventionally used solder to join the power semiconductor chip 1 and the Cu circuit 3. The sintering layer 2 (sintering paste) has high thermal conductivity, so it can effectively release heat generated by the power semiconductor chip 1 to the outside. Furthermore, instead of the solder conventionally used, a heat dissipation sheet 4 is used to connect the Cu circuit 3 to a member having a heat dissipation function, such as a Cu base plate 5. This allows the heat generated by the power semiconductor chip 1 to be effectively dissipated to the outside. As a result, it is possible to reduce the maximum temperature in the power semiconductor chip 1 and improve the electrical characteristics. Furthermore, the improved heat dissipation reduces thermal stress during continuous use and improves the reliability of bonding parts such as the sintering layer 2 and the heat dissipation sheet 4. (2) The device further includes a Cu base plate 5 (heat dissipation member) joined to the other surface of the Cu circuit 3 by a heat dissipation sheet 4 . (3) In the second laminated structure in which a power semiconductor chip 1, a sintering layer 2, a Cu circuit 3, a heat dissipation sheet 4, and a Cu base plate 5 are laminated, the total thermal resistance X2 in the laminated direction is 0.45 (K / W) or less. (4) The metal particles contained in the sintering paste are either silver particles, aluminum particles, or copper particles. In other words, by using either Ag sintering paste, Al sintering paste, or Cu sintering paste, the thermal resistance of the sintering layer 2 can be significantly lowered compared to that of solder. In other words, heat dissipation can be improved. (5) The power semiconductor chip 1 is further covered with a sealing material 7 . Such a sealing material 7 makes it easy to accommodate miniaturization and thinning of the power module having the power semiconductor chip 1. (6) The sealing material 7 is made of a molding resin. By using a mold resin as the sealing material 7, it becomes easier to accommodate miniaturization and thinning of the power module having the power semiconductor chip 1. (7) The sealing material 7 covers and seals the power semiconductor chip 1 so as to cover part or all of the side surfaces of the Cu base plate 5 (more specifically, the base portion 5A) in the thickness direction. By configuring the Cu base plate 5 so that it is partially or entirely covered with the sealing material 7, it becomes easier to achieve a balance between the strength and heat dissipation properties of the power module 10. (8) The Cu circuit 3 is a circuit board patterned with thick copper (rolled copper) and has a thickness of 0.3 mm to 5 mm. By making the Cu circuit 3 thick, the balance between the thermal resistance and strength of the Cu circuit 3 can be improved, and heat dissipation can be improved. (9) When the total thermal resistance of the first laminate structure in the laminate direction is X1 (W / K) and the total thickness of the first laminate structure is t1 (mm), the ratio X1 / t1 is 0.25 (W / (K·mm)) or less. With this configuration, the power module 10 can easily achieve high heat dissipation and can be made smaller and thinner. (10) If the total thermal resistance of the second laminate structure in the laminate direction is X2 (W / K) and the total thickness of the second laminate structure is t2 (mm), the ratio X2 / t2 is 0.08 (W / (K·mm)) or less. With this configuration, it becomes easier to achieve high heat dissipation properties in the power module 10 including the Cu base plate 5 and to achieve miniaturization and thinning.

[0068] Although the embodiments of the present invention have been described above, these are merely examples of the present invention, and various other configurations may be adopted. Furthermore, the present invention is not limited to the above-described embodiments, and modifications and improvements within the scope of achieving the object of the present invention are included in the present invention. [Example]

[0069] The present invention will be described in detail with reference to examples, but the present invention is not limited to these examples.

[0070] <First Example> Table 1 illustrates the thermal conductivities of the above-described first and second laminated structures (Example 1 and Example 2) along with the thermal conductivity of a comparative example. Example 1 and Example 2 differ in the thickness t of the structure corresponding to the Cu circuit 3, but the other conditions are the same. Among the components in the table, the element corresponding to the first laminated structure is a laminated structure of "chip, sintering, circuit, heat dissipation sheet." The element corresponding to the second laminated structure is a laminated structure of "chip, sintering, circuit, heat dissipation sheet, base substrate." Note that the resin sheet used as the heat dissipation sheet 14 described in the above embodiment, one with a thermal conductivity of 18W, was used as the heat dissipation sheet.

[0071] The sum of the thermal resistances Rth_sum (corresponding to X1 (W / K) in the embodiment) in the stacking direction of the first stacked structure in Examples 1 and 2 was 0.119 (W / K) and 0.168 (W / K), respectively, i.e., 0.30 (W / K) or less. On the other hand, in the comparative example, the configuration excluding the base substrate (corresponding to the first stacked structure) was 0.353 (W / K), i.e., exceeding 0.30 (W / K).

[0072] The sum of the thermal resistances Rth_sum (corresponding to X2 (W / K) in the embodiment) in the stacking direction of the second stacking structure in Examples 1 and 2 was 0.184 (W / K) and 0.233 (W / K), respectively, i.e., 0.25 (W / K) or less. On the other hand, in the configuration including the base substrate of the comparative example, it was 0.473 (W / K), i.e., exceeding 0.45 (W / K).

[0073] In Examples 1 and 2, the ratio Rth_sum / t_sum (corresponding to the ratio X1 / t in the embodiment) of the total thermal resistance in the stacking direction of the first stacked structure to the thickness t_sum of the first stacked structure was 0.156 (W / (K·mm)) and 0.074 (W / (K·mm)), respectively, which is less than 0.25 (W / K). On the other hand, in the comparative example, the configuration excluding the base substrate (corresponding to the first stacked structure) was 0.257 (W / (K·mm)), which is greater than 0.25 (W / (K·mm)).

[0074] In Examples 1 and 2, the ratio Rth_sum / t_sum (corresponding to the ratio X2 / t in the embodiment) of the total thermal resistance in the stacking direction of the second stacking structure to the thickness t_sum in Examples 1 and 2 was 0.067 (W / (K·mm)) and 0.055 (W / (K·mm)), respectively, which is 0.08 (W / K) or less. On the other hand, in the comparative example, it was 0.083 (W / (K·mm)), which is greater than 0.08 (W / (K·mm)). [Table 1]

[0075] <Second Example> In the second example, the power module 10 shown in the embodiment was examined in terms of the heat dissipation performance of the power semiconductor chip 1 with respect to a conventional structure (comparative example) and a simulation model.

[0076] <Simulation model> The simulation models of the example and the comparative example are as follows, and FIG. 2 shows cross-sectional views of examples of the structures of the power modules of the example and the comparative example. (A) Example: From the bottom of the figure, this is a power module in which a Cu base plate, a heat dissipation sheet, a Cu circuit, a sintering layer, and a power semiconductor chip are stacked in this order, and corresponds to the configuration of the power module 10 of the above-mentioned embodiment. (B) Comparative Example: A power module 10 in which, from the bottom of the figure, a Cu base plate, bonding solder, Cu plate, ceramic substrate, Cu circuit, solder, power semiconductor chip, and sealing material are stacked in this order.

[0077] <Simulation conditions> The outline of the simulation conditions is as follows: Figures 3 to 5 and Table 2 show the physical properties and dimensions (thickness) of each component of the simulation examples and comparative examples. Figure 3(a) is a perspective view of the power module seen from above, and Figure 3(b) is a plan view. Figure 4(a) is a perspective view of the power module seen from below, and Figure 4(b) is a bottom view. Figure 5 shows the thermal conditions in the simulation (heat transfer analysis). Simulation software: ANSYS Mechanical 2019R3 Power semiconductor chip: Equipped with IGBT and FWD (Free Wheeling Diode) Base substrate: A convex pole was provided on a Cu base plate, and the back of the Cu base plate and the convex pole surface were cooled with cooling water (65°C). [Table 2]

[0078] <Simulation results> Figure 6 shows the heat distribution on the power module model as a simulation result. In the comparative example, as shown in Fig. 6(a), the maximum temperature on the surface of the power semiconductor chip (here, IGBT) was 184°C. On the other hand, in the example, as shown in Fig. 6(b), the maximum temperature on the surface of the power semiconductor chip (here, IGBT) was 152°C, which was 32°C lower than the temperature in the comparative example. [Explanation of symbols]

[0079] 1. Power semiconductor chip 2. Sintering layer 3 Cu circuit (metal circuit board) 4. Heat dissipation sheet 5 Cu base plate (heat dissipation material) 6 Lead Frame 7. Encapsulating material 10 Power Module

Claims

1. A power module having a power semiconductor element and a metal circuit board having the power semiconductor element provided on one surface thereof, a bonding layer that bonds the power semiconductor element and the metal circuit board with a sintering paste; a heat dissipation sheet provided for joining a heat dissipation member to the other surface of the metal circuit board; and In a first laminated structure in which the power semiconductor element, the bonding layer, the metal circuit board, and the heat dissipation sheet are laminated, a total thermal resistance in the lamination direction is 0.30 (K / W) or less, The heat dissipation sheet is formed using a resin composition for a sheet, The resin composition for a sheet contains a thermosetting resin (A), a filler (B), and a curing agent (C), A circuit pattern is formed on the metal circuit board. Power module.

2. A power module as described in claim 1, further comprising a heat dissipation member joined to the other side of the metal circuit board by the heat dissipation sheet.

3. A power module as described in claim 2, wherein in a second laminated structure in which the power semiconductor element, the bonding layer, the metal circuit board, the heat dissipation sheet, and the heat dissipation member are laminated, the total thermal resistance in the stacking direction (height direction) is 0.45 (K / W) or less.

4. A power module described in any one of claims 1 to 3, wherein the metal particles contained in the sintering paste are either silver particles, aluminum particles or copper particles.

5. A power module described in any one of claims 1 to 4, further comprising an encapsulating material covering the power semiconductor element.

6. A power module as described in claim 5, wherein the sealing material is made of molded resin.

7. A power module described in claim 5 or 6, which is dependent on at least claim 2, wherein the sealing material covers and seals the power semiconductor element so as to cover part or all of the thickness-wise side of the heat dissipation member.

8. A power module described in any one of claims 1 to 7, wherein the metal circuit board is a circuit board patterned from thick copper (rolled copper) and has a thickness of 0.3 mm or more and 5 mm or less.

9. A power module described in any one of claims 1 to 8, wherein the ratio X1 / t1 is 0.25 (W / (K·mm)) or less, where X1 (W / K) is the total thermal resistance in the stacking direction of the first stacked structure and t1 (mm) is the total thickness of the first stacked structure.

10. A power module as described in claim 3, wherein the ratio X2 / t2 is 0.08 (W / (K·mm)) or less, where X2 (W / K) is the total thermal resistance in the stacking direction of the second stacking structure and t2 (mm) is the total thickness of the second stacking structure.

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