JP6829809B2 - Semiconductor device - Google Patents

Description

The present invention relates to a semiconductor device. The present invention particularly relates to a semiconductor device having an improved dielectric strength due to sealing.

In recent years, power modules have come to be widely used in power conversion devices, centering on IGBTs (Insulated Gate Bipolar Transistors). A power module incorporates one or more power semiconductor devices to form part or all of a conversion connection. Then, it has a structure in which the power semiconductor and the base plate or the cooling surface are electrically insulated. An epoxy resin is generally used as a sealing material for realizing an electrically insulating structure. Epoxy sealing resin has high dimensional stability, water resistance, chemical resistance, and electrical insulation, and is suitable as a sealing material.

With the practical application of next-generation semiconductors such as silicon carbide (SiC), semiconductor chips with higher withstand voltage have appeared. For example, with conventional silicon (Si), the withstand voltage is about 1200 V, but with SiC, the withstand voltage reaches 3300 V and 13 kV. With SiC, the withstand voltage becomes high, the operating environment temperature also becomes high, and the electric field strength applied around the insulating substrate tends to increase more and more. In particular, since the triple point where the circuit electrode plate, the insulating substrate, and the encapsulant layer intersect is a very high electric field portion, partial discharge or creeping discharge may occur along the interface starting from the triple point. ..

Shew epoxy resin member solidified conductive foil end portion of the insulating substrate, the powdered alumina Al ₂ O ₃ or aluminum nitride AlN mixed into the resin member, the dielectric constant of the resin as the intermediate value of AlN and silicone gel , A semiconductor device characterized by performing electric field relaxation at the end of a conductor foil is known (for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2000-150724

However, in the conventional technique, the electric field relaxation effect cannot be said to be sufficient, and there is a problem of peeling in the electric field concentration region.

In order to solve the above problems, the present inventors have considered providing a sealing region having a higher dielectric constant and capable of withstanding peeling due to thermal stress in the electric field concentration region. Then, he came up with the idea of solving the above problem by dispersing particles of a resin having a high dielectric constant and a low elastic modulus in the form of powder in a highly heat-resistant sealing material such as epoxy. That is, according to one embodiment, the present invention is a semiconductor device, in which a first circuit electrode plate is provided on a first main surface of an insulating substrate and a second circuit electrode plate is provided on a second main surface. A semiconductor device in which a substrate, a semiconductor element mounted on the first circuit electrode plate, and an output terminal are connected by a conductive connecting member and sealed with a sealing material, which is the insulating substrate. A sealing layer made of a highly dielectric encapsulant is arranged at the intersection of the first main surface and the side surface of the first circuit electrode plate, and the highly dielectric encapsulant is a thermosetting resin main agent. The high-dielectric resin particles contain a curing agent and high-dielectric resin particles, and the high-dielectric resin particles are resin particles having a higher specific dielectric constant and a lower tensile elasticity than the thermocurable resin.

In the semiconductor device, the sealing layer made of the high-dielectric sealing material is formed at the intersection of the second main surface of the insulating substrate and the side surface of the second circuit electrode plate, and / or the upper surface of the semiconductor element. It is preferably further disposed on the electrodes.

In the semiconductor device, it is preferable that the sealing layer made of the highly dielectric sealing material is arranged to have a thickness of 20 μm to 500 μm.

In the semiconductor device, it is preferable that the high-dielectric resin particles are one or more selected from powdered polyvinylidene fluoride or powdered polyvinyl fluoride.

In the semiconductor device, it is preferable that the highly dielectric resin particles are contained in an amount of 50 to 200 parts by mass with respect to 100 parts by mass of the thermosetting resin main agent.

In the semiconductor device, it is preferable that the high-dielectric encapsulant further contains an inorganic filler.

In the semiconductor device, the thermosetting resin main agent is preferably an epoxy resin.

In the semiconductor device, the curing agent is preferably an acid anhydride-based curing agent.

In the semiconductor device, it is preferable that the semiconductor element includes any of a Si semiconductor element, a SiC semiconductor element, and a GaN semiconductor element.

According to the present invention, the triple point is high by arranging the sealing layer made of the highly dielectric sealing material having the above-mentioned predetermined characteristics at least at the triple point where the circuit electrode plate, the insulating substrate, and the sealing layer intersect. It becomes a dielectric region. This makes it possible to prevent the concentration of electric lines of force. Further, the portion where the sealing layer made of the highly dielectric sealing material is arranged becomes a cushioning region formed of a member having a low elastic modulus, and thermal stress can be relaxed. The semiconductor device having such a sealing configuration has improved dielectric strength and is highly reliable.

FIG. 1 is a conceptual diagram showing a cross-sectional structure of a power module, which is an example of a semiconductor device according to the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to the embodiments described below. In particular, the relative dimensions and arrangement of each member shown in the drawings do not limit the present invention.

According to one embodiment, the present invention is a semiconductor device, which comprises a laminated substrate having a first circuit electrode plate on a first main surface and a second circuit electrode plate on a second main surface of an insulating substrate. The semiconductor element mounted on the first circuit electrode plate and the output terminal are connected by a conductive connecting member and sealed with a sealing material. The first to second circuit boards are composed of a first main surface facing and in contact with the insulating substrate, and a second main surface and side surfaces facing the first main surface. Then, at least at the intersection of the first main surface of the insulating substrate and the side surface of the circuit electrode plate, a sealing layer made of a highly dielectric sealing material is arranged. In the present specification, the encapsulant refers to a concept including a material used for encapsulation, and the encapsulant layer made of the encapsulant specifically refers to a layer formed by heat-curing the encapsulant. And.

FIG. 1 is a conceptual cross-sectional view of a power module, which is an example of a semiconductor device according to the present invention. In FIG. 1, the semiconductor element 1 is a power chip such as an IGBT or a diode chip. The semiconductor element 1 is mounted on the laminated substrate 2 via a bonding layer (not shown) such as solder. The laminated substrate 2 is bonded to a metal substrate 3 such as a heat spreader by a bonding layer (not shown) such as solder. An output terminal 4 fixed by a solder joint layer (not shown) stands on the laminated substrate 2. Here, the output terminal 4 is a concept including an external connection terminal, an intermediate terminal, and a circuit electrode plate, and is an external connection terminal in the illustrated embodiment. The output terminal 4 and the semiconductor element 1 are electrically connected by a metal wire 5 which is a conductive bonding member. The case 8 may be a thermoplastic resin such as polyphenylene sulfide (PPS) and is adhered to the metal substrate 3. The sealing layer 6 made of the first sealing material, which is a highly dielectric sealing material, is an intersection between the first main surface of the insulating substrate 22 forming the laminated substrate 2 and the side surface of the first circuit electrode plate 21. It is arranged so as to cover A. Here, the intersection of the intersections does not mean that they intersect in a cross, but that they intersect in a T shape. That is, the intersecting portion is a portion where the first main surface of the insulating substrate 22 and the side surface of the first circuit electrode plate 21 come into contact with each other. Here, the first main surface (also referred to as the upper surface) of the insulating substrate 22 refers to the surface of the two main surfaces of the insulating substrate 22 that is in contact with the first circuit electrode plate 21. The case 8 is filled with a second sealing material to form a sealing layer 7, and a lid 9 is attached to the case 8. Further, as an optional configuration, the sealing layer 10 made of the first sealing material, which is a highly dielectric sealing material, is formed on the second main surface (also referred to as the lower surface) of the insulating substrate 22 and the second circuit electrode plate. It is arranged so as to cover the intersection B with the side surface of the 23, and is also arranged on the upper surface electrode of the semiconductor element 1.

As the semiconductor element 1, various Si devices, SiC devices, GaN devices and the like can be used. Moreover, you may use these devices in combination. For example, a hybrid module using a Si-IGBT and a SiC-SBD can be used. The number of semiconductor elements 1 mounted is not limited to the illustrated form, and a plurality of semiconductor elements 1 can be mounted. The sealing layer 10 made of the first sealing material can be optionally arranged on the upper surface electrode of the semiconductor element 1, that is, the electrode provided on the surface not in contact with the laminated substrate 2. This is because the electric field generated between a nearby metal plate or the like, for example, a circuit electrode plate, can be relaxed so as not to be concentrated on the electrode and the connection portion between the electrode and the wire or the like.

The laminated substrate 2 is composed of an insulating substrate 22, a first circuit electrode plate 21 formed on the upper surface thereof, and a second circuit electrode plate 23 formed on the lower surface thereof. Here, the upper surface and the lower surface represent the upper and lower surfaces in FIG. 1, and the upper surface may be a surface facing the semiconductor element 1 and the lower surface may be a surface facing the metal substrate 3. Specifically, the first circuit electrode plate 21 is arranged inside the outer edge of the insulating substrate 22 on the upper surface of the insulating substrate 22, and the second circuit electrode plate 23 is inside the outer edge of the insulating substrate 22 on the lower surface of the insulating substrate 22. Is placed in. The intersection A between the side surface of the first circuit electrode plate 21 and the upper surface of the insulating substrate 22 is exposed to the outside before sealing, and is in contact with the sealing material after sealing to form a triple point. Part A is sealed with a sealing layer 6 made of the first sealing material, which is the highly dielectric sealing material of the present invention. This is because electric lines of force are concentrated at this intersection A and dielectric breakdown is likely to occur. In the cross-sectional view shown in FIG. 1, the intersection A is indicated by a point, but the intersection A is formed on the entire periphery of the surface of the first circuit electrode plate 21 in contact with the insulating substrate 22. The side surface of the first circuit electrode plate 21 and, optionally, the intersection B between the side surface of the second circuit electrode plate 23 and the lower surface of the insulating substrate 22 are also first sealed with a highly dielectric sealing material. The sealing layer 10 made of a material may be arranged. In the cross-sectional view shown in FIG. 1, the intersection B is also indicated by a point, but the intersection B is formed on the entire periphery of the surface of the second circuit electrode plate 23 in contact with the insulating substrate 22. By covering the intersection and covering the side surface of the circuit electrode plate, the electric lines of force concentrated at the intersection can be dispersed. In both the sealing mode by the sealing layer 6 and the sealing mode by the sealing layer 10, at least the intersection may be covered, the entire side surface of the circuit electrode plate may be covered, or a part of the side surface is covered. You may be. As the insulating substrate 22, a material having excellent electrical insulation and thermal conductivity can be used. Examples of the material of the insulating substrate 22 include Al ₂ O ₃ , Al N, and SiN. In particular, for high withstand voltage applications, a material having both electrical insulation and thermal conductivity is preferable, and AlN and SiN can be used, but the material is not limited thereto. As the first circuit electrode plate 21 and the second circuit electrode plate 23, metal materials such as Cu and Al having excellent workability can be used. Further, Cu or Al that has been subjected to a treatment such as Ni plating may be used for the purpose of preventing rust. Examples of the method of arranging the circuit electrode plates 21 and 23 on the insulating substrate 22 include a direct bonding method (Direct Copper Bonding method) and a brazing material bonding method (Active Metal Brazing method).

The metal wire 5 which is a conductive connecting member may be any as long as it has conductivity, and Al and Cu wires can be typically used. The metal substrate 3 may be, for example, a Cu plate or an Al plate, which is advantageous as a heat radiating body. Another heat dissipation structure may be provided instead of the metal substrate 3.

The high-dielectric sealing material (first sealing material) constituting the sealing layers 6 and 10 contains a thermosetting resin main agent, a curing agent, and high-dielectric resin particles, and is optionally inorganically filled. It is a resin composition which may contain a material. The high-dielectric resin particles are resin particles having a higher relative permittivity ε and a lower tensile elastic modulus E than the thermosetting resin.

The thermosetting resin main agent is not particularly limited, and examples thereof include an epoxy resin, a phenol resin, and a maleimide resin. Epoxy resins having at least two or more epoxy groups in one molecule are particularly preferable for the use of electronic components because they have high dimensional stability, water resistance, chemical resistance, and electrical insulation. Specifically, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol E type epoxy resin, bisphenol S type epoxy resin, bisphenol AD type epoxy resin, naphthalene type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy Examples thereof include, but are not limited to, resins, maleimide naphthol resins, maleimide triazine resins, maleimide resins, glycidyl ester type epoxy resins, and glycidyl amine type epoxy resins. These thermosetting resin main agents may be used alone or in combination of two or more. Physical properties such as heat resistance, toughness, and flame retardancy can be appropriately adjusted by combining the monomer molecules to be copolymerized. The relative permittivity ε of the epoxy resin is about 4.0, and the tensile elastic modulus E is 2 to 4 GPa. The relative permittivity ε of the other resins is approximately less than 4, at most about 5, and the tensile elastic modulus E is approximately 2 or more.

In addition, a reactive diluent having a crosslinkable functional group such as an epoxy group at the terminal can be appropriately mixed with the thermosetting resin main agent as an optional component. This is to adjust the viscosity and the crosslink density. Examples of the reactive diluent include phenylglycidyl ether, 2-ethylhexyl glycidyl ether, n-butyl glycidyl ether, cresyl glycidyl ether, ps-butylphenyl glycidyl ether, allyl glycidyl ether, α-pinene oxide styrene oxide, and the like. Glycydyl methacrylate, 1-vinyl-3,4-epoxycyclohexane can be mentioned, but is not limited thereto. The amount of the reactive diluent added can be appropriately determined by those skilled in the art according to the properties of the thermosetting resin main agent and the like.

The curing agent is not particularly limited as long as it can react with the thermosetting resin main agent and can be cured, but it is preferable to use an acid anhydride-based curing agent. Examples of the acid anhydride-based curing agent include aromatic acid anhydrides, specifically, phthalic anhydride, pyromellitic anhydride, trimellitic anhydride and the like. Alternatively, cyclic aliphatic acid anhydrides, specifically tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, methylnadic anhydride, etc., or aliphatic acid anhydrides, specifically. Examples thereof include succinic anhydride, polyazipic acid anhydride, polysevacinic acid anhydride, and polyazeline acid anhydride. The blending amount of the curing agent is preferably 50 to 170 parts by mass and more preferably 80 to 150 parts by mass with respect to 100 parts by mass of the thermosetting resin main agent. If the blending amount of the curing agent is less than 50 parts by mass, the glass transition temperature may decrease due to insufficient cross-linking, and if it exceeds 170 parts by mass, the moisture resistance, high thermal deformation temperature, and heat stability may decrease.

Further, a curing accelerator can be added to the resin composition as an optional component. As the curing accelerator, imidazole or a derivative thereof, a tertiary amine, a borate ester, a Lewis acid, an organic metal compound, an organic acid metal salt and the like can be appropriately blended. The amount of the curing accelerator added is preferably 0.01 to 50 parts by mass, and more preferably 0.1 to 20 parts by mass with respect to 100 parts by mass of the thermosetting resin main agent.

The highly dielectric resin particles are mainly resins having a higher specific dielectric constant ε and a lower tensile elastic modulus E (GPa) than the thermosetting resin obtained by curing the thermosetting resin main agent and the curing agent. It is a fine particle as a component. Further, it is preferable that the resin has a coefficient of linear expansion close to that of the thermosetting resin. This is because peeling due to thermal stress is unlikely to occur between the thermosetting resin and the highly dielectric resin particles. Further, it is preferable that the resin has a specific gravity close to that of the thermosetting resin. This is because it is easy to disperse in the preparation of the sealing material. When the tensile elastic modulus of the highly dielectric resin particles is smaller than that of the thermosetting resin, the highly dielectric resin particles are elastically deformed when stress is generated and play a role of stress relaxation. The high-dielectric sealing layer itself containing the high-dielectric resin particles also has a stress relaxation effect. As long as the resin is the main component, the highly dielectric resin particles may contain other components as long as the characteristics are not impaired. When the thermosetting resin is an epoxy resin, examples of the highly dielectric resin particles include powdered polyvinylidene fluoride (PVDF particles) and powdered polyvinyl fluoride (PVF particles). Both polyvinylidene fluoride and polyvinyl fluoride have a relative permittivity ε of 8.6 and a tensile elastic modulus E of 0.37 GPa. As the highly dielectric resin particles, one kind selected from these may be used, or two or more kinds may be mixed and used.

The shape of the highly dielectric resin particles is not particularly limited and may be spherical, needle-shaped, foil-shaped, fibrous or the like, but spherical particles are particularly preferable. The average particle size is preferably about 10 to 200 μm, more preferably about 15 to 50 μm, but is not limited to these ranges. The particle size of the high-dielectric resin particles is also determined in relation to the thickness of the high-dielectric sealing layer, which will be described in detail later, and is preferably smaller than the thickness of the high-dielectric sealing layer. If it is smaller than the above average particle size, it may be difficult to handle such as scattering. Further, by setting the average particle size in this range, good dispersibility can be ensured. In this specification, the average particle size refers to a value measured by a laser diffraction method. As these highly dielectric resin particles, a commercially available powdery resin that is solid at room temperature can be used. Alternatively, the cured resin product can be powdered with a mill or the like, and highly dielectric resin particles having a desired particle size can be separated and used. The highly dielectric resin particles are preferably those having a roughened surface. The surface can be roughened by etching or the like. This is advantageous in that the adhesion between the highly dielectric resin particles and the thermosetting resin can be improved, and a sealing material having good dispersibility can be obtained as a whole.

The amount of the highly dielectric resin particles added to the resin composition is preferably 50 to 200 parts by mass and 100 to 175 parts by mass when the mass of the thermosetting resin main agent is 100 parts by mass. Is more preferable. If it is less than 50 parts by mass, the effects of electric field relaxation and thermal stress may not be sufficiently obtained, and if it is more than 200 parts by mass, the resin physical properties such as linear expansion coefficient and elastic modulus may change.

Examples of the inorganic filler that may be optionally added to the resin composition constituting the highly dielectric encapsulant include fused silica, silica, alumina, aluminum hydroxide, titania, zirconia, aluminum nitride, and talc. Examples include, but are not limited to, clay, mica, glass fiber and the like. Due to these inorganic fillers having high thermal conductivity and a small coefficient of linear expansion, the thermal conductivity of the first encapsulant can be further increased and the thermal expansion coefficient can be further reduced as compared with the encapsulating resin itself. .. These inorganic fillers may be used alone or in combination of two or more. Further, these inorganic fillers may be microfillers or nanofillers, and two or more kinds of inorganic fillers having different particle sizes and / or types may be mixed and used. In particular, it is preferable to use an inorganic filler having an average particle size of about 0.2 to 20 μm. The amount of the inorganic filler added is preferably 100 to 600 parts by mass, more preferably 200 to 400 parts by mass, when the mass of the thermosetting resin main agent is 100 parts by mass. If the blending amount of the inorganic filler is less than 100 parts by mass, the coefficient of thermal expansion of the encapsulant becomes high and peeling or cracks may easily occur. If the blending amount is more than 600 parts by mass, the viscosity of the composition may increase and the extrusion moldability may deteriorate. When it is preferable to add an inorganic filler to the high-dielectric encapsulant, it is particularly when the temperature range in the heat cycle test is wide and a large thermal stress is likely to be generated, or when a higher withstand voltage is required.

The highly dielectric encapsulant may contain an optional additive as long as its properties are not impaired. Examples of the additive include, but are not limited to, pigments for coloring resins, flame retardants, plasticizers for improving crack resistance, and silicon elastomers. Those skilled in the art can appropriately determine these optional components and their addition amounts according to the specifications of the semiconductor device.

The method for preparing the resin composition constituting the high-dielectric encapsulant is prepared by mixing the above-mentioned constituent components by a usual method, and preferably by dispersing the high-dielectric resin particles substantially uniformly in the resin composition. can do. Optionally, a step of roughening the highly dielectric resin particles before mixing may be included. The step of roughening the surface can be carried out by etching or the like.

The sealing layer 6 made of the first sealing material, which is a highly dielectric sealing material having the above characteristics, covers at least the intersection A between the side surface of the first circuit electrode plate 21 and the upper surface of the insulating substrate 22. Deploy. Although not shown, it covers all the intersections existing around the entire periphery of the first circuit electrode plate 21. At that time, the thickness of the sealing layer 6 made of the first sealing material may be, for example, 20 μm or more, and usually up to about 500 μm. The thickness referred to here is the distance from the intersection (triple point) to the surface of the sealing layer, and means a portion that is most likely thick. For each circuit electrode plate, the intersection is a quadrangular shape consisting of four substantially straight lines, although it depends on the shape of the circuit electrode plate. The distance from the intersection to the surface of the sealing layer can be evaluated in a cross section perpendicular to each straight line forming the intersection. The suitable thickness of the sealing layer 6 made of the first sealing material also depends on the composition of the first sealing material. For example, when the first sealing material contains an inorganic filler, there is no upper limit to the thickness of the sealing layer made of the first sealing material, and if it is 20 μm or more, it covers the side surface of the first circuit electrode plate 21. A sealing layer having a thickness of about 2 may be formed. When the high-dielectric sealing material constituting the sealing layer 6 does not contain an inorganic filler, the thickness is preferably about 20 to 500 μm. Within the above range, the high-dielectric sealing layer has lower elasticity than the surrounding members, so that stress can be relaxed. However, if a thick sealing layer is formed without containing an inorganic filler, the thermal stress becomes large and exceeds the elastic deformation region. The sealing layer 10 made of the first sealing material can also be arranged at the intersection B between the side surface of the first circuit electrode plate 21 and the upper surface of the insulating substrate 22, and the arrangement mode and thickness thereof are the intersection A. It can be similar to the placement in. Further, the sealing layer 10 made of the first sealing material can be arranged on the upper surface electrode of the semiconductor element 1. As for the arrangement mode, it is preferable to apply the first sealing material so as to cover the entire upper surface of the electrode including the tip of the wire, and the thickness is preferably about 20 to 500 μm. Is not limited.

The sealing layer 7 made of the second sealing material insulates and protects the sealing layer 6 made of the first sealing material, the semiconductor element 1, the laminated substrate 2, and the member including the metal wire 5. The second encapsulant is not particularly limited. A highly dielectric encapsulant constituting the first encapsulant may be used, or other general encapsulant for semiconductor encapsulation may be used. For example, it is preferable to use a sealing material in which the glass transition temperature (Tg) of the sealing layer after curing is 10 ° C. or higher higher than the junction temperature junction temperature (Tj) of the semiconductor element 1, and the sealing layer after curing is preferably used. It is more preferable that the Tg of the material is 200 ° C. or higher. The second encapsulant contains a highly heat-resistant thermosetting resin main agent, a curing agent, and an inorganic filler, and may optionally contain a curing accelerator and various additives. The highly heat-resistant thermosetting resin main agent is not particularly limited, but preferably contains an alicyclic epoxy resin or a maleimide resin. More preferably, the highly heat-resistant thermosetting resin main agent may be a mixture of an alicyclic epoxy resin and a bisphenol A type epoxy resin. In this case, the alicyclic epoxy resin and the bisphenol A type epoxy resin may be mixed at a mass ratio of 1: 1 to 4: 1. Each component of the second encapsulant can be selected from the preferred thermosetting resin main agent, curing agent, inorganic filler, and arbitrary component constituting the highly dielectric encapsulant described in detail above. Further, the sealing mode by the second sealing material is not limited to the illustrated form, and for example, the sealing layer 7 made of the second sealing material is composed of two or more sealing material layers having different compositions. You may be. Further, when the main agent constituting the sealing layer made of the first sealing material and the sealing layer made of the second sealing material is the same, the adhesion between the two is good, which is preferable.

Next, a method for manufacturing the semiconductor device according to the present embodiment will be briefly described. The method for manufacturing a semiconductor device according to the present embodiment includes a step of mounting a semiconductor element 1 on a laminated substrate 2, a step of connecting the semiconductor element 1 and an output terminal 4 with a conductive connecting member 5, and an insulating substrate. The step of sealing the intersection A between the upper surface of the 22 and the side surface of the circuit electrode plate 21 with the first sealing material and the step of sealing with the second sealing material are included. Further, a step of optionally sealing the intersection B between the lower surface of the insulating substrate 22 and the side surface of the circuit electrode plate 23 and / or the upper surface electrode of the semiconductor element with the first sealing material may be included.

The mounting of the semiconductor element 1 on the laminated substrate 2 and the connection between the semiconductor element 1 and the output terminal 4 by the conductive connecting member 5 can be carried out by a usual method known in the field of semiconductor devices. Further, in addition to these steps, a step of attaching necessary members depending on the aspect of the module can be carried out by a usual method. In the step of sealing the intersection A between the upper surface of the insulating substrate 22 and the side surface of the circuit electrode plate 21 with the first sealing material, the first sealing material is arranged only in a desired portion by a dispenser or a spray method. It can be carried out by installing it. The step of sealing the intersection B between the lower surface of the insulating substrate and the side surface of the circuit electrode plate and / or the upper surface electrode of the semiconductor element with the first sealing material is also before the step of sealing with the second sealing material. In the same way, it can be carried out.

In the step of sealing with the second sealing material, the first sealing material is preferably heat-cured to form the sealing layers 6 and 10 made of the first sealing material, and then the second sealing material is further added. It can be carried out by filling. In the embodiment including the illustrated case 8, the second sealing material can be applied by potting to insulate and seal the conductive member including the semiconductor element 1, the laminated substrate 2, and the conductive connecting member 5. In the embodiment without a case, the member partially sealed with the first sealing material can be sealed with the second sealing material by transfer molding. When the composition of the first encapsulant and the second encapsulant are completely the same, it is not necessary to apply each of them separately and seal them, and they can be sealed by one potting or transfer molding. ..

For both the heat curing of the first encapsulant and the heat curing of the second encapsulant, the heat curing step is carried out, for example, at 100 to 120 ° C. for 1 to 2 hours, and then at 175 to 185 ° C. for 1 to 2 hours. However, it is not limited to a specific temperature and time, and it may not be necessary to perform two-step curing. It is also possible to place the first encapsulant in a predetermined place, apply the second encapsulant after temporary curing at 100 to 120 ° C. for 1 to 2 hours without heating, and finally heat cure. .. In any case, the highly dielectric resin particles in the first encapsulant do not react with the thermosetting resin main agent or the curing agent at the curing temperature of the thermosetting resin main agent such as epoxy resin. .. Further, the curing temperature of the second encapsulant is preferably lower than the Tg of the encapsulating layer 7 made of the cured high-dielectric encapsulant.

As a modified form of the semiconductor device according to the present invention, the conductive connecting member may be not only a metal wire but also a lead frame, for example. In a semiconductor device having a lead frame structure, a lead frame is bonded onto a semiconductor element. Examples of the semiconductor device configuration including the lead frame include those disclosed in Japanese Patent Application Laid-Open No. 2005-116702 by Applicants, but the configuration is not limited to a specific configuration. Further, even in the semiconductor device provided with the lead frame structure, the sealing mode of the sealing material is the same as that shown in FIG. 1, in which the sealing layer made of the first sealing material having a high dielectric constant is formed along the surface of the laminated substrate. Is sealed, and a sealing layer made of a second sealing material seals the whole. Further, at this time, on the semiconductor element, a place where electric lines of force near the lead frame are likely to be concentrated, for example, the electrode surface including the tip of the lead frame and the periphery of the lead frame joined so as to face the electrode surface. A sealing layer made of a first sealing material having a high dielectric constant may be optionally arranged on the upper surface as well.

As another modification of the semiconductor device according to the present invention, a semiconductor device having a pin structure may be used. In a semiconductor device having a pin structure, a semiconductor element is mounted on a laminated substrate via a bonding layer, and a plurality of implant pins, which are conductive connecting members, are bonded to an electrode on the opposite side of the laminated substrate of the semiconductor element. The printed circuit board is further fixed to the implant pin so as to face the semiconductor element. One end of the main terminals N, P, and U is attached to the first circuit electrode plate on which the semiconductor element is mounted, and the other end of the main terminal is pulled out to the outside of the module. Further, a control terminal is attached to the upper surface of the first circuit electrode plate to enable electrical connection with the outside of the semiconductor module.

The circuit electrode plate according to the present embodiment preferably has a block shape having a larger thickness than the circuit electrode plate shown in FIG. 1, and the semiconductor element is typically a semiconductor element using a wide bandgap semiconductor. .. The implant pin electrically connects the semiconductor elements or the semiconductor element and the printed circuit board. The implant pin may be made of Cu, but may be a Cu member that has been subjected to a treatment such as Ni plating for the purpose of preventing rust. As the printed circuit board, a polyimide film substrate or an epoxy film substrate on which circuit electrodes such as Cu and Al are formed can be used.

Even in a semiconductor device having a pin structure, the first sealing material having a high dielectric constant is provided in contact with the creeping surface of a laminated substrate on which electric lines of force are concentrated to form a sealing layer. Further, a first sealing material having a high dielectric constant is optionally arranged on the semiconductor element at a place where electric lines of force near the implant pin are likely to be concentrated, that is, on the electrode surface including the tip of the implant pin. May form a sealing layer. Here, the tip of the implant pin means an end portion of the implant pin on the semiconductor element side and in contact with the upper surface electrode. The sealing mode by the second sealing material, which may be a normal sealing material, may be the same as the illustrated form.

Hereinafter, the present invention will be described in more detail with reference to examples of the present invention. However, the present invention is not limited to the scope of the following examples.

(Example)
In Examples 1 to 4, the power module test device shown in FIG. 1 was manufactured and its characteristics were evaluated. The highly dielectric encapsulant (first encapsulant) was arranged at the intersection of the side surface of the first circuit electrode plate and the upper surface of the insulating substrate with a thickness of 200 μm or 500 μm. As the laminated substrate, two Cu circuit electrode plates having a thickness of about 500 μm were thermocompression bonded to both sides of an insulating substrate made of silicon nitride having a thickness of about 3 mm.

A mixture of bisphenol A epoxy resin and alicyclic epoxy resin at a mass ratio of 3: 2 (ME272 manufactured by Pernox) was used as the main epoxy resin for the thermosetting resin of the high-dielectric encapsulant (first encapsulant). Using. As a curing agent, cyclohexane-1,2,dicarboxylic acid anhydride (HV136 manufactured by Pernox) was used. The combination of these main agents and curing agents was used as the basic composition of the resin. The curing agent was used so that the amount of the acid anhydride curing agent was 100 parts by mass with respect to 100 parts by mass of the thermosetting resin main agent. Further, as the inorganic filler, molten silica particles having an average particle size of 5 μm (manufactured by Takimori Co., Ltd., trade name “ZA-30”) were used. The amount added was adjusted so that the total mass of the thermosetting resin main agent and the curing agent was 100 parts by mass, and the total mass of the inorganic filler was 350 parts by mass (Example 1 is of the inorganic filler). No addition). As the highly dielectric resin particles, particles made of polyvinylidene fluoride resin powdered so as to have an average particle size of 25 μm (PVDF particles) were used and mixed in the amounts shown in the table below. The content of PVDF particles was represented by the mass part of the fluororesin powder when the mass of the thermosetting resin main agent was 100 parts by mass. As the composition of the second encapsulant, the same thermosetting resin main agent, curing agent, and inorganic filler as described above were mixed at the same composition ratio, and high dielectric resin particles were not added.

In the test device, the member shown in FIG. 1 is assembled, a high-dielectric encapsulant is placed at a position indicated by reference numeral 6 in the figure by using a dispenser, and the seal is heat-cured to form a first encapsulant. A layer was formed. Then, it is sealed by a casting method with a second encapsulant prepared with the same composition as the first encapsulant except that it does not contain PVDF particles, held at 100 ° C. for 1 hour, and then at 180 ° C. for 1 The semiconductor device of the example was obtained by holding for a long time to form a sealing layer made of a second sealing material.

(Comparison example)
A test device in which the sealing layer made of the first sealing material was not provided and only the sealing layer made of the second sealing material was used was produced and used as Comparative Example 1.

(Dielectric strength evaluation)
An AC voltage with a frequency of 50 Hz and an amplitude of 6 kV was applied between the first circuit electrode plate and the second circuit electrode plate of the insulating substrate for 1 minute, and the one without dielectric breakdown passed and the one with dielectric breakdown failed. And said.

(Heat cycle test)
A heat cycle test was conducted to evaluate heat resistance and adhesion. The test devices of the above Examples and Comparative Examples are exposed at −40 ° C. for 30 minutes and exposed at 175 ° C. for 30 minutes as one cycle, and the heat cycle until the chip of the test device and the sealing resin are peeled off is performed. It was evaluated as the heat cycle withstand capacity. The occurrence of peeling was confirmed visually and by ultrasonic testing equipment.

(Evaluation results)
Table 1 shows the evaluation results of Examples 1 to 4 and Comparative Example 1. In the test device of the example, both the dielectric strength and the heat cycle resistance were improved as compared with the case where the sealing layer made of the highly dielectric sealing material (first sealing material) was not provided.

1 Semiconductor element 2 Laminated substrate 21 1st circuit electrode plate 22 Insulation substrate 23 2nd circuit electrode plate 3 Metal substrate 4 Output terminal 5 Metal wire 6 Encapsulation layer made of 1st encapsulant (high dielectric encapsulant) 7 Sealing layer made of second sealing material 8 Case 9 Lid 10 Sealing layer made of first sealing material (high-dielectric sealing material)

Claims (8)

A laminated substrate having a first circuit electrode plate on the first main surface of the insulating substrate and a second circuit electrode plate on the second main surface, and semiconductor elements and output terminals mounted on the first circuit electrode plate. Is a semiconductor device that is connected with a conductive connecting member and sealed with a sealing material.
A sealing layer made of a highly dielectric sealing material is arranged at the intersection of the first main surface of the insulating substrate and the side surface of the first circuit electrode plate.
The high-dielectric sealing material contains a thermosetting resin main agent, a curing agent, and high-dielectric resin particles.
The high dielectric resin particles, higher relative dielectric constant than the thermosetting resin, Ri Oh pulled at a low modulus of elasticity resin particles,
The high dielectric resin particles with respect to the thermosetting resin main component 100 parts by weight Ru contains 50 to 200 parts by weight, the semiconductor device. A sealing layer made of the highly dielectric sealing material is further arranged on the intersection of the second main surface of the insulating substrate and the side surface of the second circuit electrode plate, and / or on the upper surface electrode of the semiconductor element. The semiconductor device according to claim 1. The semiconductor device according to claim 1 or 2, wherein the sealing layer made of the highly dielectric sealing material is arranged to have a thickness of 20 μm to 500 μm. The semiconductor device according to any one of claims 1 to 3, wherein the highly dielectric resin particles are one or more selected from powdered polyvinylidene fluoride or powdered polyvinyl fluoride. The semiconductor device according to any one of claims 1 to 4 , wherein the high-dielectric encapsulant further contains an inorganic filler. The resin composition according to any one of claims 1 to 5 , wherein the thermosetting resin main agent is an epoxy resin. The resin composition according to any one of claims 1 to 6 , wherein the curing agent is an acid anhydride-based curing agent. The semiconductor device according to any one of claims 1 to 7 , wherein the semiconductor element includes any of a Si semiconductor element, a SiC semiconductor element, and a GaN semiconductor element.

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