Semiconductor device and method for manufacturing the same

Abstract

To provide a semiconductor device and a method for manufacturing the same, the semiconductor device which includes a sealing resin layer containing magnetic particles, possesses electromagnetic wave suppression capability, and prevents the magnetic particles from damaging an element structure.SOLUTION: In a semiconductor device having a substrate 1, a semiconductor element 2 mounted on the substrate 1, and a sealing resin layer 3 covering the semiconductor element 2, the sealing resin layer 3 contains flat magnetic powders 4 and exhibits a concentration gradient of the flat magnetic powders 4 in a thickness direction of the sealing resin layer 3.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a resin-encapsulated semiconductor device and a manufacturing method thereof. [Background technology]

[0002] 2. Description of the Related Art In resin-sealed semiconductor devices, a known method for dealing with electromagnetic waves, such as preventing malfunction of equipment due to electromagnetic noise, is to impart electromagnetic wave suppression capability to the sealing resin of the semiconductor element.

[0003] As a means for imparting electromagnetic wave suppression capability to encapsulating resins, it has been proposed to add particles of magnetic alloys such as sendust or magnetic ceramics such as nickel-zinc ferrite to the encapsulating resin composition. Such encapsulating resins are said to increase the magnetic loss of electromagnetic waves and improve the electromagnetic wave shielding properties (electromagnetic wave suppression capability) for semiconductor elements (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-210447 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in order to obtain sufficient electromagnetic wave suppression capability from an encapsulating resin composition containing magnetic material particles, it is necessary to increase the concentration of magnetic particles in the encapsulating resin composition, which may result in damage to the semiconductor element due to the magnetic particles, leakage between fine wiring, deformation or breakage of wires, or other damage to the delicate element structure.

[0006] Therefore, the sealing resin that comes into contact with the semiconductor element is required to be able to suppress electromagnetic waves without damaging the element structure.

[0007] The present disclosure has been made in consideration of the above circumstances, and aims to provide a semiconductor device having an encapsulating resin layer containing magnetic particles, which has electromagnetic wave suppression capabilities and in which the magnetic particles do not damage the delicate element structure, and a method for manufacturing the same. [Means for solving the problem]

[0008] The present disclosure is based on the discovery that, in a resin-sealed semiconductor device, a sealing resin layer having electromagnetic wave suppression capability can be formed using flat magnetic powder without damaging the element structure.

[0009] That is, the present disclosure relates to the following: [1] A semiconductor device comprising a substrate, a semiconductor element mounted on the substrate, and an encapsulating resin layer covering the semiconductor element, wherein the encapsulating resin layer contains flat magnetic powder and has a concentration gradient of the flat magnetic powder in the thickness direction of the encapsulating resin layer. [2] The semiconductor device of [1], wherein the sealing resin layer has a higher concentration of the flat magnetic powder on the side opposite to the substrate than on the side facing the substrate. [3] A semiconductor device according to [1] or [2], wherein the sealing resin layer contains 80% by mass or more of the total content of the flat magnetic powder in a region within 50% of the thickness of the sealing resin layer from the surface opposite the substrate. [4] A semiconductor device according to any one of [1] to [3], wherein the sealing resin layer contains 50% by mass or more of the total content of the flat magnetic powder in a region within 10% of the thickness of the sealing resin layer from the surface opposite the substrate. [5] The semiconductor device according to any one of [1] to [4], wherein the flat magnetic powder has an insulating coating on the surface. [6] The semiconductor device of any one of [1] to [5], wherein the sealing resin layer is formed of a sealing resin sheet, the sealing resin sheet contains the flat magnetic powder, and has a concentration gradient of the flat magnetic powder in the sheet thickness direction.

[0010] [7] A method for manufacturing a semiconductor device according to any one of [1] to [6], comprising the steps of: stirring a liquid sealing resin composition containing the flat magnetic powder, leaving it to stand, and then causing it to enter a B-stage to produce a sealing resin sheet having a concentration gradient of the flat magnetic powder; covering the semiconductor element mounted on the substrate with the sealing resin sheet; and curing the sealing resin sheet to form the sealing resin layer and seal the semiconductor element. [8] The method for producing a semiconductor device according to [7], wherein a magnetic field is applied when the encapsulating resin composition is allowed to stand.

[0011] [9] A method for manufacturing a semiconductor device according to any one of [1] to [5], comprising the steps of: covering the semiconductor element mounted on the substrate with an encapsulating resin composition containing the flat magnetic powder; and curing the encapsulating resin composition while applying a magnetic field to form the encapsulating resin layer, thereby encapsulating the semiconductor element.

[10] The method for producing a semiconductor device according to [9], wherein the encapsulating resin composition is in a powder form and is compression-molded and cured. [Effects of the Invention]

[0012] According to the present disclosure, a semiconductor device having an encapsulating resin layer that has electromagnetic wave suppression ability and in which magnetic particles are distributed with a concentration gradient without damaging the sophisticated element structure, and a method for manufacturing the same are provided. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a schematic cross-sectional view of an embodiment of a semiconductor device according to the present disclosure. [Figure 2] FIG. 3 is a schematic cross-sectional view for explaining the distribution of flat magnetic powder in a sealing resin layer. [Figure 3] 1A to 1C are schematic cross-sectional views illustrating a manufacturing method of a first embodiment of a semiconductor device according to the present disclosure. [Figure 4] 1A to 1C are schematic cross-sectional views illustrating a manufacturing method of a first embodiment of a semiconductor device according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, the present disclosure will be described in detail with reference to an embodiment. The meanings and definitions of terms used in this disclosure are as follows: The expression "X to Y" (X and Y are numerical values) means a numerical range with X as the lower limit and Y as the upper limit. In a numerical range (e.g., a range of content, etc.), the lower limit and upper limit values ​​described in stages may be combined independently. The lower limit and upper limit values ​​of a numerical range may be replaced with numerical values ​​described in the examples. The average particle size refers to the volume average particle size, which is the median diameter of the equivalent spherical diameters of particles measured with a laser diffraction particle size distribution analyzer.

[0015] [Semiconductor Devices] An outline of one embodiment of a semiconductor device according to the present disclosure is shown in Figure 1. The semiconductor device according to the present disclosure includes a substrate 1, a semiconductor element 2 mounted on the substrate 1, and an encapsulating resin layer 3 that covers the semiconductor element 2. The encapsulating resin layer 3 contains flat magnetic powder 4, and has a concentration gradient of the flat magnetic powder 4 in the thickness direction of the encapsulating resin layer 3. By distributing the flat magnetic powder 4 in the sealing resin layer 3 so as to have a concentration gradient, a semiconductor device can be constructed that maintains the same insulating properties as conventional sealing resins while effectively obtaining electromagnetic wave suppression capabilities due to the high concentration region of the flat magnetic powder 4 in the sealing resin layer 3.

[0016] The sealing resin layer 3 may have a higher concentration of flat magnetic powder 4 on the surface 3 a side opposite to the substrate 1 than on the side facing the substrate 1 . The high concentration of flat magnetic powder 4 on the outer shell side of the semiconductor device makes it easy to effectively obtain electromagnetic wave suppression performance around the semiconductor device. Also, the low concentration of flat magnetic powder 4 near the semiconductor element 2 mounted on the substrate 1 makes it easy to avoid damage to the semiconductor element 2 caused by the flat magnetic powder 4, deformation or breakage of the wire 5, etc.

[0017] 2 is a schematic diagram illustrating the distribution of flat magnetic powder 4 in the encapsulating resin layer 3. The less flat magnetic powder 4 there is on the side of the encapsulating resin layer 3 facing the substrate, the less likely the flat magnetic powder 4 will damage the semiconductor element 2, deform or break the wires 5, etc. From this perspective, as shown in FIG. 2, the encapsulating resin layer 3 in the semiconductor device of the present disclosure may have 80% or more by mass of the total content of flat magnetic powder 4 present in a region X that is within 50% of the thickness of the encapsulating resin layer 3 from the surface 3a opposite the substrate.

[0018] If the flat magnetic powder 4 is densely packed on the surface 3a of the sealing resin layer 3 opposite the substrate 1, the electromagnetic wave suppression ability of the flat magnetic powder 4 can be obtained more effectively, and damage to the semiconductor element 2, deformation or breakage of the wires 5, etc. due to the flat magnetic powder 4 are less likely to occur. From this perspective, in a region Y at a depth of within 10% of the thickness of the sealing resin layer 3 from the surface 3a opposite the substrate 1, 50% by mass or more of the total content of the flat magnetic powder 4 may be present, or 50 to 100% by mass or 70 to 100% by mass may be present.

[0019] The thickness of the semiconductor element 2 resin-encapsulated with the encapsulating resin layer 3 may typically be 50% or less, 40% or less, or 30% or less of the thickness of the encapsulating resin layer 3 (the distance from the surface of the substrate 1 to the surface 3a opposite the substrate 1).

[0020] The total content of the flat magnetic powder 4 in the sealing resin layer 3 may be 1.5 to 7.0 mass%, 2.0 to 6.0 mass%, or 2.5 to 5.0 mass%. If the total content of the flat magnetic powder 4 is 1.5 mass% or more, sufficient electromagnetic wave suppression ability is easily obtained, and if it is 7.0 mass% or less, damage to the semiconductor element 2 due to the flat magnetic powder 4, deformation or breakage of the wires 5, etc. are unlikely to occur.

[0021] The sealing resin layer 3 may be formed of a sealing resin sheet that contains flat magnetic powder 4 and has a concentration gradient of the flat magnetic powder 4 in the sheet thickness direction.

[0022] The flat magnetic powder 4 may have an insulating coating on the surface thereof in order to make it easier to maintain the insulating properties of the sealing resin layer 3.

[0023] [Manufacturing method (1)] The semiconductor device of the present disclosure described above can be manufactured by a first manufacturing method of the present disclosure. The first manufacturing method of the present disclosure is a manufacturing method including the steps of (A1) stirring a liquid sealing resin composition containing the flat magnetic powder, leaving it to stand, and then causing it to enter a B-stage to produce a sealing resin sheet having a concentration gradient of the flat magnetic powder, (A2) covering the semiconductor element mounted on the substrate with the sealing resin sheet, and (A3) curing the sealing resin sheet to form the sealing resin layer and seal the semiconductor element. In this way, by using a sealing resin sheet having a concentration gradient of the flat magnetic powder prepared in advance, the semiconductor device of the present disclosure can be manufactured using a process similar to that of resin sealing of semiconductor elements using a conventional sealing resin sheet. With this type of resin sealing, damage to the semiconductor elements, deformation or breakage of wires, etc. caused by the flat magnetic powder are less likely to occur.

[0024] Each step of the above embodiment will be described below with reference to FIG. In the step (A1), a liquid sealing resin composition containing flat magnetic powder 4 is stirred, allowed to stand, and then brought to a B-stage to produce a sealing resin sheet 13 having a concentration gradient of flat magnetic powder 4. The components of the encapsulating resin composition will be described later. In the encapsulating resin composition, the flat magnetic powder 4 has a large specific gravity. Therefore, when a liquid encapsulating resin composition is stirred and mixed in a container with a solvent added as needed and left to stand, the encapsulating resin composition tends to naturally settle and accumulate at the bottom of the container. By heating in this state to volatilize the solvent and bring the encapsulating resin composition into a B-stage, an encapsulating resin sheet 13 having a concentration gradient of the flat magnetic powder 4 in the sheet thickness direction is obtained.

[0025] When the liquid encapsulating resin composition is allowed to stand, a magnetic field may be applied to the composition so that a concentration gradient of the flat magnetic powder 4 is generated more quickly and more significantly. For example, a magnet may be placed on the outer bottom of the container containing the liquid encapsulating resin composition. The magnet may be a permanent magnet or an electromagnet.

[0026] In the step (A2), the semiconductor element 2 mounted on the substrate 1 is covered with the sealing resin sheet 13 obtained in the step (A1). In this step, for example, as shown in Figure 3, a sealing resin sheet 13 having a concentration gradient of flat magnetic powder 4 in the sheet thickness direction is set in the cavity of a lower die 10 of a mold, with the side with a higher concentration of flat magnetic powder 4 facing the bottom of the cavity. Meanwhile, a substrate 1 on which a semiconductor element 2 is mounted is set in an upper die 20 of the mold. The semiconductor element 2 mounted on the substrate 1 is placed opposite the sealing resin sheet 13, and the upper die 20 and lower die 10 are closed, whereby the semiconductor element 2 is covered with the sealing resin sheet 13.

[0027] Note that the lower mold 10 may be magnetic in order to further reduce the flat magnetic powder 4 present on the side of the sealing resin sheet 13 facing the substrate 1 and to make it easier to concentrate it on the surface 13a opposite to the substrate 1. In this case, the lower mold 10 itself may be made of a magnetic material, or a magnet may be disposed on the bottom or the like of the lower mold 10. The magnet may be a permanent magnet or an electromagnet.

[0028] In the step (A3), the sealing resin sheet 13 is cured to form the sealing resin layer 3, and the semiconductor element 2 is sealed. For example, in the state shown in FIG. 3, the upper mold 20 and the lower mold 10 are closed and compression molded to harden the sealing resin sheet 13, thereby forming the sealing resin layer 3 as the hardened product. The compression molding conditions may be, for example, a temperature of 120 to 200° C. and a pressure of 20 MPa or less.

[0029] [Manufacturing method (2)] The semiconductor device of the present disclosure can also be manufactured by a second manufacturing method of the present disclosure, which includes the steps of (B1) covering the semiconductor element mounted on the substrate with an encapsulating resin composition containing the flat magnetic powder, and (B2) curing the encapsulating resin composition while applying a magnetic field to form the encapsulating resin layer, thereby encapsulating the semiconductor element. In this way, by applying a magnetic field when the flat magnetic powder is in a mobile state within the encapsulating resin composition, the semiconductor device of the present disclosure can be manufactured in the same manner as in resin encapsulation of semiconductor elements using conventional encapsulating resin compositions. This type of resin encapsulation allows for efficient generation of a concentration gradient of the flat magnetic powder. Furthermore, damage to the semiconductor element, deformation or breakage of the wires, etc., caused by the flat magnetic powder are less likely to occur.

[0030] Each step of the above embodiment will be described below with reference to FIG. In the step (B1), the semiconductor element 2 mounted on the substrate 1 is covered with the sealing resin composition 23 containing the flat magnetic powder 4. In this step, for example, as shown in FIG. 4 , a powdered encapsulating resin composition 23 containing flat magnetic powder 4 is filled into the cavity of a lower die 10 of a mold. Meanwhile, a substrate 1 on which a semiconductor element 2 is mounted is set in an upper die 20 of the mold. The semiconductor element 2 mounted on the substrate 1 is placed opposite the encapsulating resin composition 23, and the upper die 20 and the lower die 10 are closed, whereby the semiconductor element 2 is covered with the encapsulating resin composition 23.

[0031] In the step (B2), the encapsulating resin composition 23 is cured while a magnetic field is applied to form the encapsulating resin layer 3, thereby encapsulating the semiconductor element 2. For example, in the state shown in Figure 4, the upper mold 20 and the lower mold 10 with the magnet 11 arranged at the bottom are closed and compression molded to harden the powdered sealing resin composition 23 and form the hardened sealing resin layer 3. As a means for applying a magnetic field to the encapsulating resin composition 23, for example, the lower mold 10 may be magnetic, the lower mold 10 itself may be made of a magnetic material, or a magnet may be disposed on the bottom or the like of the lower mold 10 as shown in Fig. 4. The magnet may be a permanent magnet or an electromagnet. The compression molding conditions may be the same as those in the compression molding in the first production method of the present disclosure.

[0032] The sealing resin composition 23 may be in powder form, or may be compression molded and hardened, so that the flat magnetic powder 4 can move easily within the sealing resin composition 23, creating a concentration gradient, and the semiconductor element 2 can be easily and securely sealed with resin.

[0033] In another embodiment of the method for manufacturing a semiconductor device, the encapsulating resin composition may be in a liquid form or a tablet form, for example. Another embodiment of the manufacturing method may be, for example, transfer molding. Specifically, a substrate on which a semiconductor element is mounted is set in a magnetic mold, and a tablet-shaped encapsulating resin composition is heated in a pot (for example, to 170 to 180°C) to soften it, and then the tablet-shaped encapsulating resin composition is pressed into a cavity of the mold with a plunger to harden it.

[0034] [Sealing resin composition] The encapsulating resin composition used to form the encapsulating resin layer of the semiconductor device of the present disclosure contains a flat magnetic powder. The constituent materials of the encapsulating resin composition other than the flat magnetic powder may be the same as those used in known encapsulating resin compositions, and may include, for example, an epoxy resin, a curing agent, a catalyst, a filler, etc.

[0035] (Flat magnetic powder) Flat magnetic powders are used to impart electromagnetic wave suppression capabilities to the encapsulating resin layers of semiconductor devices. The flat magnetic powders may have soft magnetic properties, such as iron-silicon alloys like electrical steel, iron-based amorphous materials, iron-based nanocrystalline materials, or iron-silicon-aluminum alloys like sendust. They may also be soft ferrites such as manganese-zinc ferrite, nickel-zinc ferrite, or copper-zinc ferrite. Because flat magnetic powders tend to form an oxide layer on their surface, they can easily achieve both electromagnetic wave suppression and insulation, and so may be sendust or iron-silicon-chromium alloys. The flat magnetic powder may be obtained by flattening spherical powder produced by water atomization or gas atomization using an attritor or the like, or may be a commercially available product.

[0036] The flat magnetic powder obtained by the above method is a powder with a thickness of about 1 μm, a scale shape with the major and minor axes of the flat surfaces ranging from several μm to several hundred μm, and a large aspect ratio (major axis / thickness) of 5 or more. The large aspect ratio reduces the demagnetizing field in the flat surface direction of the flat magnetic powder, resulting in a significantly higher magnetic permeability than spherical magnetic powder. Such flat magnetic powder can be oriented in the encapsulating resin composition by the manufacturing method of the present disclosure so that its thickness direction is approximately the same as the thickness direction of the encapsulating resin layer. Therefore, compared to spherical magnetic powder, even with a smaller content in the encapsulating resin layer, it is easy to exhibit good electromagnetic wave suppression performance.

[0037] The average particle size of the flat magnetic powder may be 5 to 70 μm, 10 to 60 μm, or 20 to 50 μm, from the viewpoint of appropriate dispersibility in the encapsulating resin composition. The average particle size of the flaky powder is the median diameter of the equivalent sphere diameter.

[0038] As described above, the flat magnetic powder may have an insulating coating on its surface. The insulating coating may be formed on the surface of the flat magnetic powder by, for example, surface treatment with phosphate. The surface treatment with phosphate can be carried out by immersing the flat magnetic powder in a phosphate treatment solution and then drying it. The phosphate treatment solution may be an aqueous solution (or aqueous dispersion) in which phosphoric acid and one or more metal oxides selected from the group consisting of magnesium oxide, calcium oxide, and zinc oxide are dissolved (or dispersed) in water, and may further contain boric acid.

[0039] (epoxy resin) The epoxy resin has two or more epoxy groups in one molecule and is not particularly limited in terms of molecular structure or molecular weight, as long as it is an epoxy resin commonly used in electronic components. The state is also not particularly limited, and the resin may be either liquid or solid at room temperature (25°C). Examples of epoxy resins include phenol novolac epoxy resins; cresol novolac epoxy resins; aliphatic epoxy resins such as dicyclopentadiene derivatives; and aromatic epoxy resins such as biphenyl, biphenyl aralkyl, naphthyl, and bisphenol types. The epoxy resins may be used alone or in combination of two or more. Among these, cresol novolac epoxy resins and bisphenol epoxy resins are preferred. The bisphenol epoxy resin may be bisphenol A or bisphenol F, or may be bisphenol A.

[0040] The epoxy resin may have a polyoxyalkylene structure. When the epoxy resin is a mixture containing a polyoxyalkylene structure, the mixing ratio of the epoxy resin having the polyoxyalkylene structure and the epoxy resin not having the polyoxyalkylene structure is not particularly limited. When the encapsulating resin composition contains an epoxy resin having a polyoxyalkylene structure, it is possible to improve the electromagnetic wave suppression ability while maintaining the insulating properties.

[0041] The alkylene group constituting the polyoxyalkylene group may be a linear or branched alkylene group having 1 to 6 carbon atoms, from the viewpoint of improving the electromagnetic wave suppression ability of the encapsulating resin composition, etc. Specific examples of the alkylene group include a methylene group, ethylene group, trimethylene group, propylene group, tetramethylene group, and hexamethylene group, and may also be a methylene group or an ethylene group. The degree of polymerization of the polyoxyalkylene group (the number of repeating oxyalkylene groups) may be 2 to 50, or may be 2 to 20. The epoxy resin having a polyoxyalkylene structure may be, for example, one having a bisphenol A skeleton.

[0042] The epoxy equivalent of the epoxy resin may be 140 to 400 g / eq, 150 to 390 g / eq, or 160 to 380 g / eq, from the viewpoint of good insulation properties of the cured product of the encapsulating resin composition.

[0043] The content of the epoxy resin in the encapsulating resin composition may be 3.0 to 35.0 mass %, 4.0 to 30.0 mass %, or 5.0 to 25.0 mass %, from the viewpoints of appropriate fluidity of the encapsulating resin composition, retention of the filler and magnetic powder, etc.

[0044] (hardening agent) Examples of the curing agent include imidazole compounds, phenolic resins, acid anhydrides, aliphatic amines, aromatic amines, dicyandiamide, and dihydrazide compounds. The curing agent may be used alone or in combination of two or more. The encapsulating resin composition may not necessarily contain a curing agent. For example, a phenol resin may be included as a curing agent, and specifically, a phenol novolac resin or the like may be included. When the encapsulating resin composition contains a curing agent, the content thereof may be 0.1 to 15.0 mass %, 0.5 to 10.0 mass %, or 1.0 to 8.0 mass %, from the viewpoint of appropriate curability. In this case, the content of the curing agent may be 30 to 60 parts by mass, 35 to 55 parts by mass, or 40 to 50 parts by mass relative to 100 parts by mass of the epoxy resin.

[0045] (catalyst) Examples of the catalyst (curing accelerator) include imidazole compounds, tertiary amines, phosphorus compounds, urea compounds, etc. The catalyst may be used alone or in combination of two or more. For example, an imidazole compound may be included as a catalyst, specifically, 2-heptadecylimidazole or the like may be included. The content of the catalyst in the encapsulating resin composition may be 0.01 to 5.0 mass %, 0.05 to 3.0 mass %, or 0.1 to 1.0 mass %, from the viewpoint of appropriately accelerating curing. In this case, the content of the catalyst may be 0.5 to 10 parts by mass, 1 to 5 parts by mass, or 1.5 to 3 parts by mass relative to 100 parts by mass of the epoxy resin.

[0046] (filling material) The filler may be, for example, an inorganic filler such as silica, alumina, magnesium oxide, titanium oxide, barium titanate, silicon nitride, aluminum nitride, silicon carbide, or tungsten carbide. These inorganic fillers may be used in combination with an organic substance from the viewpoint of improving dispersibility in the encapsulating resin composition. The filler may be used alone or in combination of two or more types. Among these, silica and alumina may be used from the viewpoints of improving the electromagnetic wave suppression ability of the encapsulating resin composition, reducing the thermal expansion coefficient, and cost.

[0047] The form of the filler is not particularly limited, but from the viewpoint of being evenly contained in the encapsulating resin composition, it may be, for example, powder, flake, fibrous particles, or the like, or may be powder or spherical. The average particle size of the filler particles is not particularly limited, but may be 0.1 to 100 μm, 0.2 to 75 μm, or 0.3 to 50 μm from the viewpoints of dispersibility in the encapsulating resin composition, good fluidity of the encapsulating resin composition, etc. Two or more types of particles having different average particle sizes may be used in combination.

[0048] The content of the filler in the encapsulating resin composition may be 60.0 to 95.0 mass %, 65.0 to 93.0 mass %, or 70.0 to 90.0 mass %, from the viewpoints of appropriate fluidity of the encapsulating resin composition, improving the electromagnetic wave suppression ability, and the like.

[0049] (Other ingredients) In addition to the above-described components, the encapsulating resin composition may contain additives that are generally used in known encapsulating resins, as long as they do not deviate from the gist of the present disclosure. Examples of additives include flame retardants such as phosphazene compounds; release agents such as natural waxes such as carnauba wax, synthetic waxes, and higher fatty acids or their esters; colorants such as carbon black and cobalt blue; modifiers such as silicone oil and silicone rubber; hydrotalcites; ion scavengers, etc. The additives may be used alone or in combination of two or more. The encapsulating resin composition may contain a solvent such as acetone from the viewpoint of ease of mixing and improvement of the flowability of the flat magnetic powder.

[0050] The total content of additives (excluding the solvent) in the encapsulating resin composition may be within a range that does not inhibit the effect of the encapsulating resin layer in the semiconductor device of the present disclosure, and may be 0 to 2.0 mass %, 0 to 1.8 mass %, or 0 to 1.5 mass %.

[0051] (Preparation method) The encapsulating resin composition can be obtained by mixing the above-mentioned components. For example, the components may be blended and mixed using a stirring blade, a universal mixer, a Henschel mixer, or the like.

[0052] In the first production method of the present disclosure, as described above, a solvent may be added and the mixture may be stirred and mixed in a container to obtain a liquid encapsulating resin composition.

[0053] In the second production method of the present disclosure, when a powdered encapsulating resin composition is used, for example, the components may be sufficiently mixed, melted and kneaded, cooled and solidified, and then pulverized. The melt-kneading may be carried out using, for example, a disperse, a kneader, a three-roll mill, a twin-screw roll kneader, a twin-screw heat extrusion kneader, etc. The melt-kneading temperature is a temperature at which the curing reaction of the encapsulating resin composition does not proceed, and may be 70 to 170°C, 75 to 165°C, or 80 to 160°C. The pulverization may be carried out using a cutter mill, ball mill, cyclone mill, hammer mill, vibration mill, grinder mill, speed mill, etc. The pulverized particles may be in the form of a powder having a particle size of, for example, 0.1 to 3.0 μm. The melt-kneaded encapsulating resin composition may be extruded, cut to a predetermined length, and processed into tablets of a predetermined size for use. [Example]

[0054] Next, the present disclosure will be specifically described with reference to examples, but the present disclosure is not limited to these examples in any way.

[0055] [Preparation of sealing resin test pieces] The compositions of the various raw material components used in the examples and comparative examples are shown in Table 1. Details of the various raw material components are as follows. <Epoxy resin> R140: "Epomic (registered trademark) R140" manufactured by Mitsui Fine Chemicals, Inc.; bisphenol A epoxy resin (polycondensation product of bisphenol A and epichlorohydrin), epoxy equivalent weight 210 g / eq BEO-60E: "Rikaresin (registered trademark) BEO-60E" manufactured by New Japan Chemical Co., Ltd.; bisphenol A bis(triethylene glycol glycidyl ether) ether, epoxy equivalent 365 g / eq <Curing agent> BRG-557: "BRG-557" manufactured by AICA Corporation; phenolic novolac resin, hydroxyl equivalent 104g / eq <Catalyst> C17Z: "Curezol (registered trademark) C17Z" manufactured by Shikoku Chemicals Corporation; 2-heptadecylimidazole <Filling material> FB-105: "FB-105" manufactured by Denka Co., Ltd.; spherical fused silica, average particle size 12 μm SO-C2: "Admafine (registered trademark) SO-C2" manufactured by Admatechs Co., Ltd.; spherical fused silica, average particle size 0.5 μm <Magnetic powder> Flat Sendust: "FME4D-AH", manufactured by Sanyo Special Steel Co., Ltd.; Flat Sendust powder, average particle size 45 μm Spherical ferrite: "MZ10S", manufactured by Powder Tech Co., Ltd.; manganese zinc ferrite, average particle size 8 μm <Flame retardant> FP-100: "Ravitor (registered trademark) FP-110", manufactured by Mitsui Fine Chemicals, Inc.; phosphazene flame retardant <Coloring agent> Carbon black: "#30", manufactured by Mitsubishi Chemical Corporation, average particle size 50 nm <Release agent> Carnauba wax: "Carnauba wax No. 1 powder", manufactured by Toyochem Co., Ltd.

[0056] Example 1 To 1 liter of water, 800 g of phosphoric acid, 100 g of magnesium oxide, and 100 g of boric acid were added and stirred to prepare an aqueous solution. Flat Sendust was immersed in this aqueous solution and then dried at 200°C for 1 hour to form an insulating coating on the surface. Note that the flat Sendust in Table 1 refers to the product that had undergone this treatment. 20.8 parts by mass of BEO-60E (epoxy resin), 0.4 parts by mass of C17Z (catalyst), 74.1 parts by mass of FB-105 (filler), 3.2 parts by mass of the above-obtained flat Sendust (magnetic powder) with an insulating coating on its surface, 1.1 parts by mass of FP-100 (flame retardant), 0.3 parts by mass of carbon black (colorant), 0.1 parts by mass of carnauba wax (mold release agent), and 200 parts by mass of acetone were mixed in a beaker with a stirring blade and then allowed to stand at room temperature (25°C) for 48 hours. The mixture was then heated to 50°C to volatilize the acetone and B-stage the mixture (resin composition), yielding an encapsulating resin sheet. The obtained sealing resin sheet was compression molded using a mold (temperature 180° C., pressure 7 MPa, time 5 minutes) to prepare a test piece (10 cm×10 cm, thickness 1 mm).

[0057] Example 2 200 parts of acetone was added to the same component composition as in Example 1, and the mixture was stirred and mixed in a beaker, and then left to stand at room temperature (25°C) for 48 hours with a permanent magnet placed on the outer bottom of the container. Thereafter, the mixture was heated to 50°C to volatilize the acetone and bring the mixture (resin composition) into a B-stage state, thereby obtaining a sealing resin sheet. The obtained sealing resin sheet was compression molded in the same manner as in Example 1 using a mold having a magnetic lower die to prepare a test piece.

[0058] (Comparative Example 1) A test piece was prepared in the same manner as in Example 1, except that no magnetic powder was added.

[0059] (Examples 3 and 4 and Comparative Example 3) The components shown in Table 1 were mixed in a Henschel mixer, and then kneaded in a twin-screw roll kneader at 110° C. until homogeneous. The resulting kneaded mixture was stretched into a sheet using a cold roll and then pulverized using a cutter mill to obtain a powdered encapsulating resin composition (particle size 0.1 to 3.0 μm). The obtained encapsulating resin composition was compression molded (temperature 180° C., pressure 7 MPa, time 5 minutes) using a mold equipped with a magnetic lower die to prepare a test piece (10 cm×10 cm, thickness 1 mm).

[0060] (Comparative Example 2) Using the component compositions shown in Table 1, an encapsulating resin composition was obtained in the same manner as in Example 3. The obtained encapsulating resin composition was used in a normal non-magnetic mold, and the other operations were the same as in Example 3 to prepare a test piece.

[0061] [Evaluation method] For each test piece produced in the examples and comparative examples, the magnetic powder distribution and electromagnetic wave suppression ability were measured and evaluated. Furthermore, the occurrence of wire damage was evaluated by a simulation test of wire bonding in the manufacture of semiconductor devices. The evaluation results are shown in Table 1. The evaluation methods are as follows:

[0062] (Magnetic powder distribution) The test piece was divided into two equal parts parallel to the sides, and a cross section (analysis area) in the thickness direction of the central part (width 0.2 cm) was subjected to elemental analysis using a scanning electron microscope and an energy dispersive X-ray elemental analyzer (SEM / EDS; "JCM-7000 NeoScope (registered trademark)", JEOL Ltd.), and the detected distribution of iron (Fe) was considered to be the distribution of magnetic powder. The percentage of Fe present in the region within 0.1 mm depth (10% of the thickness of the test specimen) from the top surface of the test specimen (top 10%; corresponding to region Y in Figure 2) was measured relative to the total amount of Fe within the analysis range. Similarly, the percentage of Fe present in the region within 0.5 mm depth (50% of the thickness of the test specimen) from the top surface of the test specimen (top 50%; corresponding to region X in Figure 2) was measured. The percentage of Fe present in the top 50% was calculated by subtracting it from the total amount of Fe (100%), and this was taken as the percentage of Fe present in the bottom 50%.

[0063] (Electromagnetic wave suppression ability) The test piece was placed between the high-frequency oscillator and the receiving antenna, and electromagnetic waves (frequency 10 GHz) were generated and the electromagnetic wave intensity was measured. The electromagnetic wave suppression ability [dB] was calculated from the ratio of this electromagnetic wave intensity to the electromagnetic wave intensity when no sample was placed. The electromagnetic wave intensity was measured in accordance with the Transactions of the Institute of Electronics, Information and Communication Engineers, Vol. J97-B, No. 3, pp. 279-285. Electromagnetic wave suppression capability (10 GHz) of 3 dB or more is considered to be good.

[0064] (Wire damage) An evaluation test substrate was prepared by ball-bonding gold wire (diameter 15 μm, length 4 mm) to a height of 250 to 350 μm on the surface of a substrate (glass epoxy material FR-4). A simulation test was performed in which a resin sealing layer was formed on the surface of the evaluation test substrate by compression molding (temperature 180°C, pressure 7 MPa, time 5 minutes) using a mold (cavity dimensions: 55.75 mm × 66 mm, depth 850 μm) using a sealing resin sheet or a powdered sealing resin composition prepared in the same manner as in the Examples and Comparative Examples. The gold wires inside the encapsulating resin layer were examined using transmission X-rays to check for any damage such as deformation or breakage.

[0065] [Table 1]

[0066] As shown in the evaluation results in Table 1, it was confirmed that the manufacturing method of the present disclosure can form an encapsulating resin layer in which the flat magnetic powder is distributed so as to have a concentration gradient (Examples 1 to 4). Furthermore, it was confirmed that this encapsulating resin layer provides good electromagnetic wave suppression performance, and that the flat magnetic powder contained in the encapsulating resin layer does not damage the wire. [Explanation of symbols]

[0067] 1 board 2. Semiconductor elements 3 Sealing resin layer 4 Flat magnetic powder 5 wire 10 Lower mold 11 Magnet 13 Sealing resin sheet 20 Upper mold 23 Sealing resin composition

Claims

1. A semiconductor device comprising: a substrate; a semiconductor element mounted on the substrate; and an encapsulating resin layer covering the semiconductor element, The semiconductor device, wherein the sealing resin layer contains flat magnetic powder and has a concentration gradient of the flat magnetic powder in the thickness direction of the sealing resin layer.

2. 2. The semiconductor device according to claim 1, wherein the sealing resin layer has a higher concentration of the flat magnetic powder on a surface opposite to the substrate than on a surface facing the substrate.

3. 2. The semiconductor device according to claim 1, wherein the sealing resin layer contains 80% by mass or more of the total content of the flat magnetic powder in a region within 50% of the thickness of the sealing resin layer from the surface opposite the substrate.

4. 2. The semiconductor device of claim 1, wherein the sealing resin layer contains 50% by mass or more of the total content of the flat magnetic powder in a region within 10% of the thickness of the sealing resin layer from the surface opposite the substrate.

5. The semiconductor device according to claim 1 , wherein the flat magnetic powder has an insulating coating on the surface thereof.

6. the sealing resin layer is formed of a sealing resin sheet, The semiconductor device according to claim 1 , wherein the sealing resin sheet contains the flat magnetic powder, and has a concentration gradient of the flat magnetic powder in a sheet thickness direction.

7. A method for manufacturing the semiconductor device according to any one of claims 1 to 6, comprising: a step of stirring the liquid encapsulating resin composition containing the flat magnetic powder, leaving it to stand, and then causing it to undergo B-stage transformation to produce an encapsulating resin sheet having a concentration gradient of the flat magnetic powder; a step of covering the semiconductor element mounted on the substrate with the sealing resin sheet; curing the sealing resin sheet to form the sealing resin layer and seal the semiconductor element; The method for manufacturing a semiconductor device includes the steps of:

8. The method for manufacturing a semiconductor device according to claim 7 , wherein a magnetic field is applied when the encapsulating resin composition is allowed to stand.

9. A method for manufacturing the semiconductor device according to any one of claims 1 to 5, comprising: a step of covering the semiconductor element mounted on the substrate with an encapsulating resin composition containing the flat magnetic powder; curing the encapsulating resin composition while applying a magnetic field to form the encapsulating resin layer and encapsulating the semiconductor element; The method for manufacturing a semiconductor device includes the steps of:

10. The method for manufacturing a semiconductor device according to claim 9 , wherein the encapsulating resin composition is in a powder form and is compression-molded and cured.

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