Method for manufacturing electronic component device and stencil-integrated mask frame

Abstract

A method for manufacturing an electronic component device according to the present disclosure is a method in which: in a mounted body having a circuit board and an electronic component element disposed on one surface of the circuit board, a mask frame having a first opening portion provided corresponding to the location where the electronic component element is disposed is disposed on a surface on the side where the electronic component element is disposed; a pressing plate is disposed on the side opposite to the side of the mask frame that faces the mounted body; and in a state in which a liquid thermosetting resin composition is filled in the first opening portion, the thermosetting resin composition is cured by heating and pressurizing the thermosetting resin composition using a pressure bonding device to seal the electronic component element.

Description

Manufacturing method of electronic component device and mask frame with integrated stencil

[0001] The present disclosure relates to a method for manufacturing an electronic component device and a mask frame integrated with a stencil.

[0002] Epoxy resins have been widely used in the fields of molding materials, laminates, adhesive materials, etc. Epoxy resin-based compositions are also widely used in the field of encapsulation technology for elements of electronic components such as transistors and ICs. This is because epoxy resins offer a good balance of various properties, including moldability, electrical properties, moisture resistance, heat resistance, mechanical properties, and adhesion to insert products.

[0003] As a method for encapsulating semiconductor chips using an epoxy resin composition, a method called molded underfill (MUF) is being developed. Unlike conventional encapsulation methods in which the gap between the semiconductor chip and the substrate is encapsulated with a liquid underfill material and then the top of the semiconductor chip is encapsulated, MUF encapsulates the underfill and the top of the semiconductor chip in a single process.

[0004] For example, Japanese Patent Application Laid-Open No. 2021-036581 discloses a method for manufacturing a sealing structure, which includes a printing step of printing a liquid curable resin composition on a substrate and covering the substrate with a first coating of the curable resin composition, and a molding step of covering the first coating of the curable resin composition with the pressing surface of a mold and compression-molding the first coating together with the substrate to form a second coating from the first coating.

[0005] Methods for implementing MUF include transfer molding and compression molding. However, these methods all require large equipment and specialized molds, resulting in high processing costs and limited flexibility for small-lot, multi-item production (especially laboratory-scale evaluation). While JP 2021-036581 A proposes the use of stencil printing to form the encapsulant, it uses a molding machine and mold to perform compression molding. While the process of applying the curable resin composition can be simplified using stencil printing, the preparation of a mold is still required. One aspect of the present disclosure, developed in light of the above-described conventional circumstances, provides a method for manufacturing an electronic component device that allows mold underfill to be easily performed. Another aspect of the present disclosure provides a stencil-integrated mask frame that can be applied to a method for manufacturing an electronic component device.

[0006] Specific means for achieving the above object are as follows: <1> A method for manufacturing an electronic component device, comprising: arranging a mask frame having a first opening corresponding to the location of the electronic component element on a surface of a mount assembly having a circuit board and an electronic component element arranged on one surface of the circuit board, the first opening being provided corresponding to the location of the electronic component element; arranging a pressing plate on the side of the mask frame opposite the side facing the mount assembly; and, with the first opening filled with a liquid thermosetting resin composition, performing a heating and pressurizing treatment with a compression bonding device to harden the thermosetting resin composition and seal the electronic component element. <2> A method for manufacturing an electronic component device according to <1>, comprising: arranging a screen having a second opening corresponding to the location of the electronic component element on the surface of the mount assembly where the electronic component element is arranged; and, subsequently, removing the screen and then disposing the mask frame and the pressing plate. <3> The method for manufacturing an electronic component device according to <2>, wherein the filling of the thermosetting resin composition into the second opening by the stencil printing method is carried out in a reduced pressure environment. <4> The method for manufacturing an electronic component device according to <1>, wherein the thermosetting resin composition is filled into the first opening by a dispensing method in a state in which the mask frame is placed on the surface of the mount body on which the electronic component element is placed, and then the pressing plate is placed. <5> The method for manufacturing an electronic component device according to any one of <1> to <4>, wherein a convex portion that fits into the first opening is provided on the surface of the pressing plate facing the mask frame. <6> A mask frame with an integrated stencil, comprising: a mask frame having a first opening; a stencil body that is detachable from the mask frame, contacts one surface of the mask frame, and has a second opening provided at a location corresponding to the first opening; and a stencil having a wall portion that protrudes from an edge of the second opening in the stencil body toward the surface that contacts the mask frame and covers at least a part of the wall surface of the first opening.

[0007] According to one aspect of the present disclosure, it is possible to provide a method for manufacturing an electronic component device that allows mold underfill to be easily performed. Also, according to another aspect of the present disclosure, it is possible to provide a mask frame integrated with a stencil that can be applied to a method for manufacturing an electronic component device.

[0008] FIG. 1 is a diagram for explaining a method for manufacturing an electronic component device according to the first embodiment; FIG. 2 is a diagram for explaining a method for manufacturing an electronic component device according to the first embodiment; FIG. 3 is a diagram for explaining a method for manufacturing an electronic component device according to the first embodiment; FIG. 4 is a diagram for explaining a method for manufacturing an electronic component device according to the first embodiment; FIG. 5 is a diagram for explaining a method for manufacturing an electronic component device according to the first embodiment; FIG. 6 is a diagram for explaining a method for manufacturing an electronic component device according to the second embodiment; FIG. 7 is a diagram for explaining a method for manufacturing an electronic component device according to the second embodiment; FIG. 8 is a diagram for explaining a method for manufacturing an electronic component device according to the third embodiment; FIG. 9 is a diagram for explaining a method for manufacturing an electronic component device according to the fourth embodiment; FIG. 10 is a diagram for explaining a method for manufacturing an electronic component device according to the fourth embodiment.

[0009] The present disclosure will be described in detail below. However, the present disclosure is not limited to the following embodiments. In the following embodiments, the components (including element steps, etc.) are not essential unless otherwise specified. The same applies to numerical values ​​and their ranges, and do not limit the present disclosure.

[0010] In the present disclosure, the term "process" includes not only processes that are independent of other processes, but also processes that cannot be clearly distinguished from other processes as long as the purpose of the process is achieved. In the present disclosure, numerical ranges indicated using "to" include the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In numerical ranges described in stages in the present disclosure, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another staged numerical range. In the present disclosure, each component may contain multiple corresponding substances. When multiple substances corresponding to each component are present in the composition, the content or amount of each component means the total content or amount of the multiple substances present in the composition, unless otherwise specified. In the present disclosure, particles corresponding to each component may include multiple types of particles. When multiple types of particles corresponding to each component are present in the composition, the particle size of each component means the value for a mixture of the multiple types of particles present in the composition, unless otherwise specified. In the present disclosure, the terms "layer" and "film" include cases where the layer or film is formed over the entire area when the area where the layer or film is present is observed, as well as cases where the layer or film is formed over only a portion of the area. In the present disclosure, the term "laminate" refers to stacking layers, and two or more layers may be bonded together, or two or more layers may be detachable. In the present disclosure, "(meth)acrylic" means at least one of acrylic and methacrylic, and "(meth)acrylonitrile" means at least one of acrylonitrile and methacrylonitrile.

[0011] The method for manufacturing an electronic component device according to the present disclosure includes: a mounting assembly having a circuit board and an electronic component element disposed on one side of the circuit board; a mask frame having a first opening corresponding to the location of the electronic component element disposed on the side of the mounting assembly; a pressing plate disposed on the side of the mask frame opposite the side facing the mounting assembly; a liquid thermosetting resin composition filled in the first opening; a heating and pressurizing process performed with a pressure bonding device to harden the thermosetting resin composition and encapsulate the electronic component element; The method for manufacturing an electronic component device according to the present disclosure involves a heating and pressurizing process performed with a pressure bonding device to harden the thermosetting resin composition and encapsulate the electronic component element; This method allows for easier mold underfilling than methods for encapsulating electronic component elements using transfer molding, compression molding, or the like; Supplying the thermosetting resin composition by the stencil printing method or dispensing method described below allows for easier mold underfilling. Specific examples of the pressure-bonding device include a vacuum laminator, a vacuum press, a hot press, etc. As the pressure-bonding device, a reduced pressure pressure-bonding device is preferred, and a vacuum pressure-bonding device such as a vacuum laminator is more preferred.

[0012] The manufacturing method of the electronic component device of the present disclosure will be described below with reference to the drawings, but the present disclosure is not limited thereto. Furthermore, the size of each part in each drawing is conceptual, and the relative relationship of the size between each part is not limited thereto. In the following description, the same or equivalent parts will be denoted by the same reference numerals, and duplicated descriptions may be omitted.

[0013] First Embodiment A method for manufacturing an electronic component device according to a first embodiment will be described with reference to FIGS. 1 to 5. In the method for manufacturing an electronic component device according to the first embodiment, a liquid thermosetting resin composition is applied by stencil printing. As shown in FIG. 1, a package 10 includes a circuit board 12 and an electronic component element 14 disposed on one side of the circuit board 12. The circuit board used in the present disclosure is not particularly limited. Examples of circuit boards include pre-wired tape carriers, organic substrates such as copper-clad laminates, lead frames, glass substrates, silicon wafers, ceramic substrates, and rewiring layers. The electronic component element used in the present disclosure is also not particularly limited. Examples of electronic component elements include active elements such as semiconductor chips, transistors, diodes, and thyristors, and passive elements such as capacitors, resistors, and coils. The electronic component element 14 shown in FIG. 1 is bonded to the circuit board 12 via solder balls. A gap is provided between the electronic component element 14 and the circuit board 12. The electronic component elements may be bonded to the circuit board via wire bonding, Au-Au ultrasonic bonding, copper microbumps, hybrid bonding, or the like, in addition to solder balls.

[0014] A mask 16 is arranged on the surface of the mounting body 10 on which the electronic component elements 14 are arranged (i.e., on the surface of the circuit board 12 on which the electronic component elements 14 are arranged). The material of the mask is not particularly limited, and metals such as iron, aluminum, SUS, and titanium, and resins such as polyethylene terephthalate (PET), polymethyl methacrylate (PMMA), and phenolic resin are used. The mask may be a metal mask. The method for manufacturing the metal mask is not particularly limited, and examples include laser processing, etching, and additive methods (plating).

[0015] Second openings 18 are provided in the mask 16 in accordance with the locations where the electronic component elements 14 are arranged. The second openings 18 may be provided so that the wall surfaces 20 of the second openings 18 in the mask 16 are in contact with the electronic component elements 14, as shown in second opening 18A, or so that the wall surfaces 20 of the second openings 18 in the mask 16 are not in contact with the electronic component elements 14, as shown in second opening 18B.

[0016] A release layer may be provided on the surface of the mask 16 that contacts the circuit board 12, the surface of the mask 16 opposite to the surface that contacts the circuit board 12, and the wall surface 20. The material that constitutes the release layer is not particularly limited. Specific examples of the material that constitutes the release layer include fluororubber, fluororesin, silicone resin, and polyimide resin.

[0017] The thickness of the stencil is not particularly limited and is selected appropriately depending on the height of the electronic component element. From the viewpoint of ease of handling of the stencil, the thickness of the stencil is preferably 0.1 mm to 10 mm. The size of the second opening is not particularly limited, and the size of the second opening may be set so that the electronic component element fits within the second opening when the stencil is viewed in plan. When the liquid thermosetting resin composition is filled into the second opening by the stencil printing method, the amount of the liquid thermosetting resin composition filled into the second opening is approximately the volume calculated from the area of ​​the second opening and the thickness of the stencil minus the volume of the electronic component element located within the second opening. Therefore, it is desirable to set the size of the second opening and the thickness of the stencil so that the amount of the liquid thermosetting resin composition filled into the second opening is the amount required for MUF sealing of the electronic component element.

[0018] Furthermore, when the wall surface 20 and the electronic component element 14 are in contact as in the second opening 18A, when a liquid thermosetting resin composition is supplied by stencil printing, the thermosetting resin composition is not or is difficult to fill between the electronic component element 14 and the circuit board 12. On the other hand, when a gap exists between the wall surface 20 and the electronic component element 14 as in the second opening 18B, when a liquid thermosetting resin composition is supplied by stencil printing, the thermosetting resin composition is filled between the electronic component element 14 and the circuit board 12 through the gap. Therefore, when determining the size of the second opening, it is desirable to take into account whether the thermosetting resin composition will be filled through the gap between the electronic component element 14 and the circuit board 12.

[0019] In the stencil printing method, the squeegee 22 is moved in the direction of the arrow in Figure 1 to fill the second openings 18 with the thermosetting resin composition 24 supplied onto the stencil 16. The durometer hardness of the squeegee is preferably 50 to 130, more preferably 80 to 100. The squeegee speed is preferably 5 mm / sec to 50 mm / sec, more preferably 20 mm / sec to 30 mm / sec. The set squeegee printing pressure is preferably 0.1 MPa to 1.0 MPa, more preferably 0.2 MPa to 0.4 MPa.

[0020] The supply of the thermosetting resin composition onto the mounting body by the stencil printing method may be carried out under atmospheric pressure or under a reduced pressure environment. From the viewpoint of suppressing the generation of voids in the thermosetting resin composition supplied onto the mounting body, the supply is preferably carried out under a reduced pressure environment, more preferably under an environment of 300 hPa or less, and even more preferably under an environment of 100 hPa or less.

[0021] The thermosetting resin composition used in the present disclosure is not limited in its composition, etc., as long as it is liquid. In the present disclosure, a thermosetting resin composition being "liquid" means that the viscosity measured with an E-type viscometer at 25°C is 1000 Pa·s or less. Specifically, the viscosity is measured using an EHD-type E-type viscometer (cone angle 3°, cone diameter 28 mm), with a measurement temperature of 25°C, a sample volume of 0.7 ml, and the rotation speed set according to the expected viscosity of the sample, with reference to the following, after 1 minute has passed since the start of measurement. (1) When the expected viscosity is 100 Pa·s to 1000 Pa·s: rotation speed 0.5 rotations / minute; (2) When the expected viscosity is less than 100 Pa·s: rotation speed 5 rotations / minute.

[0022] The thermosetting resin composition contains a thermosetting resin. The type of thermosetting resin is not particularly limited, and examples include epoxy resin, phenol resin, thiol resin, urea resin, melamine resin, urethane resin, silicone resin, maleimide resin, and unsaturated polyester resin. The thermosetting resin may be used alone or in combination of two or more types. Among these, epoxy resin is preferred as the thermosetting resin. The type of epoxy resin is not particularly limited as long as it has two or more epoxy groups in one molecule. Below, a thermosetting resin composition using an epoxy resin as the thermosetting resin will be described in detail.

[0023] The epoxy resin imparts curability and adhesiveness to the thermosetting resin composition and imparts heat resistance and durability to the cured product of the thermosetting resin composition. The epoxy resin is preferably a liquid epoxy resin. In the present disclosure, a solid epoxy resin can also be used in combination with the liquid epoxy resin.

[0024] The type of epoxy resin is not particularly limited. Examples of epoxy resins include naphthalene-type epoxy resins; diglycidyl ether-type epoxy resins such as bisphenol A, bisphenol F, bisphenol AD, bisphenol S, and hydrogenated bisphenol A; epoxidized novolac resins of phenols and aldehydes, such as orthocresol novolac-type epoxy resins; glycidyl ester-type epoxy resins obtained by reacting polybasic acids such as phthalic acid and dimer acid with epichlorohydrin; and glycidylamine-type epoxy resins obtained by reacting amine compounds such as diaminodiphenylmethane, isocyanuric acid, and aminophenol with epichlorohydrin. Examples of epoxy resins include bifunctional aliphatic epoxy compounds having two epoxy groups in the molecule, such as alkylene glycol diglycidyl ether, poly(alkylene glycol) diglycidyl ether, and alkenylene glycol diglycidyl ether.

[0025] From the viewpoint of viscosity adjustment, the epoxy equivalent of the epoxy resin is preferably 80 g / eq to 400 g / eq, more preferably 85 g / eq to 350 g / eq, and even more preferably 90 g / eq to 320 g / eq. The epoxy equivalent of the epoxy resin is measured by dissolving a weighed amount of epoxy resin in a solvent such as methyl ethyl ketone, adding acetic acid and a tetraethylammonium bromide acetate solution, and then potentiometric titration with a perchloric acid acetate standard solution. An indicator may be used in this titration.

[0026] Commercially available epoxy resins may be used. Specific examples of commercially available epoxy resins include an amine-type epoxy resin (product name: jER630) manufactured by Mitsubishi Chemical Corporation, a bisphenol F-type epoxy resin (product name: YDF-8170C) manufactured by Nippon Steel Chemical & Material Co., Ltd., a bisphenol A-type epoxy resin (product name: YD-128) manufactured by Nippon Steel Chemical & Material Co., Ltd., a naphthalene-type epoxy resin (product name: HP-4032D) manufactured by DIC Corporation, and the trade name "Epogose PT (general grade)" (Yokkaichi Synthetic Co., Ltd., diglycidyl ether of polytetramethylene glycol, number average molecular weight 700 to 800). The epoxy resin is not limited to these specific examples. One type of epoxy resin may be used alone, or two or more types may be used in combination. The content of the epoxy resin is not particularly limited, and for example, the content is preferably 5% by mass to 30% by mass, more preferably 7% by mass to 28% by mass, and even more preferably 10% by mass to 25% by mass, as a proportion of the solid content of the thermosetting resin composition.

[0027] The thermosetting resin composition may contain a curing agent. The curing agent may be any agent that undergoes a polymerization reaction with the epoxy resin, and may be either liquid or solid as long as the thermosetting resin composition has fluidity at room temperature (25°C). Examples of the curing agent include amine-based curing agents, phenol-based curing agents, and acid anhydride-based curing agents.

[0028] Examples of the amine-based curing agent include linear aliphatic amines, cyclic aliphatic amines, aliphatic aromatic amines, and aromatic amines. From the viewpoint of heat resistance and electrical properties, aromatic amines are preferred, and aromatic amines in which an amino group is directly bonded to an aromatic ring and one or two aromatic rings are contained in one molecule are more preferred. Specific examples of the amine-based curing agent include aromatic amine curing agents with one aromatic ring, such as m-phenylenediamine, 2,3-diaminotoluene, 3,4-diaminotoluene, 2,4-diaminotoluene, 3,5-diethyl-2,4-diaminotoluene, 3,5-diethyl-2,6-diaminotoluene, and 2,4-diaminoanisole; 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylsulfone, 4,4'-methylenebis(2-ethylaniline), 3,3'-diethyl-4,4'-diaminodiphenylmethane, and 3,4'-diaminodiphenylmethane. aromatic amine curing agents having two aromatic rings, such as 3',5,5'-tetramethyl-4,4'-diaminodiphenylmethane and 3,3',5,5'-tetraethyl-4,4'-diaminodiphenylmethane; hydrolysis condensates of aromatic amine curing agents; aromatic amine curing agents having a polyether structure, such as polytetramethylene oxide di-p-aminobenzoate and polytetramethylene oxide di-para-aminobenzoate; condensates of aromatic diamines and epichlorohydrin; and reaction products of aromatic diamines and styrene.

[0029] Commercially available amine curing agents may be used. Specific examples of commercially available amine curing agents include an amine curing agent manufactured by Nippon Kayaku Co., Ltd. (product name: Kayahard-AA) and an amine curing agent manufactured by Mitsubishi Chemical Corporation (product names: jER Cure (registered trademark) 113, jER Cure (registered trademark) W, etc.), but the amine curing agent is not limited to these specific examples. One type of amine curing agent may be used alone, or two or more types may be used in combination.

[0030] Examples of acid anhydride curing agents include phthalic anhydride, maleic anhydride, methyl himic anhydride, himic anhydride, succinic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, chlorendic anhydride, methyltetrahydrophthalic anhydride, 3-methylhexahydrophthalic anhydride, 4-methylhexahydrophthalic anhydride, trialkyltetrahydrophthalic anhydride maleic acid adduct, benzophenonetetracarboxylic anhydride, trimellitic anhydride, pyromellitic anhydride, hydrogenated methylnadic anhydride, trialkyltetrahydrophthalic anhydride having multiple alkyl groups obtained by Diels-Alder reaction from maleic anhydride and a diene compound, and various cyclic acid anhydrides such as dodecenyl succinic anhydride.

[0031] Examples of phenolic curing agents include novolak resins obtained by condensing or co-condensing at least one selected from the group consisting of phenolic compounds (e.g., phenol, cresol, xylenol, resorcinol, catechol, bisphenol A, and bisphenol F) and naphthol compounds (e.g., α-naphthol, β-naphthol, and dihydroxynaphthalene) with an aldehyde compound (e.g., formaldehyde, acetaldehyde, propionaldehyde, benzaldehyde, and salicylaldehyde) in the presence of an acid catalyst; phenol-aralkyl resins; biphenyl-aralkyl resins; and naphthol-aralkyl resins. One type of curing agent may be used alone, or two or more types may be used in combination.

[0032] The ratio of the equivalent number of the functional group of the curing agent (for example, an amino group in the case of an amine-based curing agent, a phenolic hydroxyl group in the case of a phenol-based curing agent, or an acid anhydride group in the case of an acid anhydride-based curing agent) to the equivalent number of the epoxy resin (equivalent number of curing agent / equivalent number of epoxy resin) is preferably set in the range of 0.6 to 1.4, more preferably in the range of 0.7 to 1.3, and even more preferably in the range of 0.8 to 1.2.

[0033] The thermosetting resin composition may contain an inorganic filler. Known or commonly used inorganic fillers can be used as the inorganic filler, and are not particularly limited. Examples of inorganic fillers include silica (e.g., fused silica, crystalline silica), calcium carbonate, clay, alumina, silicon nitride, silicon carbide, boron nitride, calcium silicate, potassium titanate, aluminum nitride, beryllia, zirconia, zircon, fosterite, steatite, spinel, mullite, titania, and other powders, as well as beads of these spheroidized materials and glass fibers. Furthermore, examples of inorganic fillers with flame retardant properties include aluminum hydroxide, magnesium hydroxide, zinc borate, and zinc molybdate. These inorganic fillers may be used alone or in combination. Among these, fused silica is preferred from the viewpoint of reducing the linear expansion coefficient, and alumina is preferred from the viewpoint of high thermal conductivity. The shape of the inorganic filler is preferably spherical from the viewpoints of high loading of the inorganic filler and fluidity and penetration of the thermosetting resin composition into fine gaps.

[0034] The average particle size of the inorganic filler, particularly in the case of spherical silica, is preferably 1 μm to 20 μm, more preferably 1.5 μm to 15 μm, and even more preferably 2 μm to 10 μm. Here, the average particle size refers to the particle size at which the volume cumulative particle size distribution measured using a laser diffraction method is 50%. If the average particle size of the inorganic filler is 1 μm or more, it tends to be easier to disperse the inorganic filler at a high concentration in the thermosetting resin composition. If the average particle size of the inorganic filler is 20 μm or less, the coarse particle components of the inorganic filler are reduced, which tends to prevent insufficient filling of fine gaps in the thermosetting resin composition or streaky defects during printing, and improve surface smoothness.

[0035] The content of the inorganic filler is preferably set in the range of 73% by mass to 93% by mass, more preferably 78% by mass to 91% by mass, relative to the total amount of the thermosetting resin composition. If the content of the inorganic filler is 73% by mass or more, the effect of reducing the thermal expansion coefficient of the cured product of the thermosetting resin composition is obtained, and warping tends to be reduced. If the content of the inorganic filler is 93% by mass or less, an increase in the viscosity of the thermosetting resin composition can be suppressed, and application workability tends to be improved.

[0036] The thermosetting resin composition may contain a coupling agent, if necessary, to strengthen the adhesion between the resin and the inorganic filler or between the resin and the constituent members of electronic components. Any known or commonly used coupling agent may be used as the coupling agent, and is not particularly limited. Examples of the coupling agent include silane compounds having at least one selected from the group consisting of primary amino groups, secondary amino groups, and tertiary amino groups; various silane-based compounds such as epoxysilanes, mercaptosilanes, alkylsilanes, ureidosilanes, and vinylsilanes; titanium-based compounds; aluminum chelates; and aluminum / zirconium-based compounds.

[0037] When the thermosetting resin composition contains a coupling agent, the content of the coupling agent is preferably 0.1% by mass to 2.0% by mass, and more preferably 0.2% by mass to 1.5% by mass, based on the total amount of the inorganic filler and the coupling agent. If the content of the coupling agent is 0.1% by mass or more, the effect of improving the dispersibility of the inorganic filler by the coupling agent tends to be easily obtained. If the content of the coupling agent is 2.0% by mass or less, voids tend to be less likely to occur in the cured product of the thermosetting resin composition.

[0038] The thermosetting resin composition may contain a curing accelerator. The type of the curing accelerator is not particularly limited, and known curing accelerators can be used. Specific examples include cycloamidine compounds such as 1,8-diaza-bicyclo[5.4.0]undecene-7, 1,5-diaza-bicyclo[4.3.0]nonene, and 5,6-dibutylamino-1,8-diaza-bicyclo[5.4.0]undecene-7; cycloamidine compounds containing maleic anhydride, 1,4-benzoquinone, 2,5-toluquinone, 1,4-naphthoquinone, 2,3-dimethylbenzoquinone, 2,6-dimethylbenzoquinone, and 2,3-dimethoxy-5-methyl-1,4-benzoquinone; compounds with intramolecular polarization obtained by adding compounds with π bonds such as quinone, 2,3-dimethoxy-1,4-benzoquinone, and phenyl-1,4-benzoquinone; diazophenylmethane, and phenolic resins; tertiary amine compounds such as benzyldimethylamine, triethanolamine, dimethylaminoethanol, and tris(dimethylaminomethyl)phenol; derivatives of tertiary amine compounds; 2-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, and 2-phenyl-4-methylimidazole; Examples of the curing accelerator include imidazole compounds such as thiphenylimidazole; derivatives of imidazole compounds; organic phosphine compounds such as tributylphosphine, methyldiphenylphosphine, triphenylphosphine, tris(4-methylphenyl)phosphine, diphenylphosphine, and phenylphosphine; phosphorus compounds having intramolecular polarization obtained by adding a compound having a π bond such as maleic anhydride, the above-mentioned quinone compounds, diazophenylmethane, and phenolic resins to an organic phosphine compound; tetraphenylboron salts such as tetraphenylphosphonium tetraphenylborate, triphenylphosphine tetraphenylborate, 2-ethyl-4-methylimidazole tetraphenylborate, and N-methylmorpholine tetraphenylborate; derivatives of tetraphenylboron salts; and adducts of phosphine compounds and tetraphenylboron salts such as triphenylphosphonium-triphenylborane and N-methylmorpholine tetraphenylphosphonium-tetraphenylborate. One type of curing accelerator may be used alone, or two or more types may be used in combination.

[0039] The content of the curing accelerator is preferably 0.1% by mass to 8% by mass based on the total amount of the epoxy resin and the curing agent.

[0040] The thermosetting resin composition may contain an ion trapping agent. The ion trapping agent that can be used in the present disclosure is not particularly limited as long as it is an ion trapping agent that is commonly used in sealing materials used in the manufacture of electronic component devices. Examples of the ion trapping agent include compounds represented by the following general formula (VI-1) or the following general formula (VI-2).

[0041] Mg １－ａ Al ａ (OH) ２ (CO ３ ) ａ／２ ・uH ２ O (VI-1) (In the general formula (VI-1), a is 0<a≦0.5, and u is a positive number.) BiO ｂ (OH) ｃ (NO ３ ) ｄ (VI-2) (In general formula (VI-2), b is 0.9≦b≦1.1, c is 0.6≦c≦0.8, and d is 0.2≦d≦0.4.)

[0042] Ion trapping agents are commercially available. For example, "DHT-4A" (trade name, manufactured by Kyowa Chemical Industry Co., Ltd.) is a commercially available compound represented by general formula (VI-1). For example, "IXE500" (trade name, manufactured by Toagosei Co., Ltd.) is a commercially available compound represented by general formula (VI-2).

[0043] Other examples of the ion trapping agent include hydrous oxides of elements selected from magnesium, aluminum, titanium, zirconium, antimony, etc. One type of ion trapping agent may be used alone, or two or more types may be used in combination.

[0044] When the thermosetting resin composition contains an ion trapping agent, the content of the ion trapping agent is preferably 1 part by mass or more relative to 100 parts by mass of the epoxy resin from the viewpoint of realizing sufficient moisture resistance reliability. From the viewpoint of fully exerting the effects of the other components, the content of the ion trapping agent is preferably 15 parts by mass or less relative to 100 parts by mass of the epoxy resin, more preferably 1 to 10 parts by mass, and even more preferably 2 to 5 parts by mass.

[0045] The average particle size of the ion trapping agent is preferably 0.1 μm to 3.0 μm, and the maximum particle size is preferably 10 μm or less. The average particle size of the ion trapping agent can be measured in the same manner as in the case of the inorganic filler.

[0046] The thermosetting resin composition may contain an antioxidant. Conventionally known antioxidants can be used. The antioxidants may be used alone or in combination of two or more. Specific examples of antioxidants include compounds containing a phenolic hydroxyl group and at least one of a phosphorus atom, a sulfur atom, and an amine in the same molecule, but these compounds may be mentioned multiple times.

[0047] The content of the antioxidant is preferably 0.1% by mass to 10% by mass, more preferably 0.5% by mass to 5% by mass, based on the total amount of the epoxy resin.

[0048] An organic solvent can be blended into the thermosetting resin composition as needed to reduce viscosity. In particular, when a solid epoxy resin and curing agent are used, blending an organic solvent is preferable to obtain a thermosetting resin composition. The organic solvent is not particularly limited, and examples include alcohol-based solvents such as methyl alcohol, ethyl alcohol, propyl alcohol, and butyl alcohol; ketone-based solvents such as acetone and methyl ethyl ketone; glycol ether-based solvents such as ethylene glycol ethyl ether, ethylene glycol methyl ether, ethylene glycol butyl ether, propylene glycol methyl ether, dipropylene glycol methyl ether, propylene glycol ethyl ether, and propylene glycol methyl ether acetate; lactone-based solvents such as γ-butyrolactone, δ-valerolactone, and ε-caprolactone; amide-based solvents such as dimethylacetamide and dimethylformamide; and aromatic solvents such as toluene and xylene. One type may be used alone, or two or more types may be used in combination. Among these, organic solvents with a boiling point of 170°C or higher are preferred from the viewpoint of avoiding bubble formation due to sudden evaporation when curing the thermosetting resin composition.

[0049] The content of volatile matter including organic solvents and the like is not particularly limited as long as it is to an extent that bubbles are not formed when the thermosetting resin composition is cured, and is preferably 5% by mass or less, more preferably 1% by mass or less, and even more preferably 0.1% by mass or less, of the entire thermosetting resin composition. In the present disclosure, the volatile matter of the thermosetting resin composition is calculated based on the weight difference before and after heating the thermosetting resin composition at 180°C for 30 minutes.

[0050] The thermosetting resin composition may contain a release agent. The type of release agent is not particularly limited, and known release agents can be used. Specific examples include higher fatty acids, carnauba wax, and polyethylene wax. The release agent may be used alone or in combination of two or more types. When the thermosetting resin composition contains a release agent, the content of the release agent is preferably 10% by mass or less relative to the total amount of the epoxy resin and the curing agent, and from the viewpoint of exerting its effect, it is preferably 0.5% by mass or more.

[0051] The thermosetting resin composition may contain a colorant (for example, carbon black). The colorant may be used alone or in combination of two or more types.

[0052] When conductive particles such as carbon black are used as the colorant, the content of conductive particles having a particle diameter of 10 μm or more is preferably 1 mass % or less. When the thermosetting resin composition contains conductive particles, the content of conductive particles is preferably 3 mass % or less, and more preferably 0.01 mass % to 1 mass %, based on the total amount of the epoxy resin and the curing agent.

[0053] The thermosetting resin composition may contain rubber particles from the viewpoint of reducing the thermal expansion of the cured product. The rubber particles may be used alone or in combination of two or more types. Examples of suitable rubber particles include rubber particles such as styrene-butadiene rubber (SBR), nitrile-butadiene rubber (NBR), butadiene rubber (BR), urethane rubber (UR), and acrylic rubber (AR). Among these, from the viewpoint of heat resistance and moisture resistance, rubber particles containing acrylic rubber are preferred, and core-shell acrylic rubber particles are more preferred.

[0054] Another example of suitable rubber particles is silicone rubber particles. Examples of silicone rubber particles include silicone rubber particles crosslinked from linear polyorganosiloxanes such as polydimethylsiloxane, polymethylphenylsiloxane, and polydiphenylsiloxane; silicone rubber particles whose surfaces are coated with silicone resin; and core-shell polymer particles comprising a core of solid silicone particles obtained by emulsion polymerization or the like and a shell of an organic polymer such as an acrylic resin. These silicone rubber particles may be amorphous or spherical in shape, and spherical silicone rubber particles are preferred in order to maintain a low viscosity of the thermosetting resin composition. Silicone rubber particles are commercially available from Dow Corning Toray Silicone Co., Ltd., Shin-Etsu Chemical Co., Ltd., and the like.

[0055] When the thermosetting resin composition contains rubber particles, the average particle size of the rubber particles is preferably fine in order to uniformly modify the thermosetting resin composition. The average particle size of the rubber particles is preferably in the range of 0.05 μm to 10 μm, and more preferably in the range of 0.1 μm to 5 μm. When the average particle size of the rubber particles is 0.05 μm or more, dispersibility in the thermosetting resin composition tends to be further improved. When the volume average particle size of the rubber particles is 10 μm or less, the stress reduction improvement effect tends to be further improved, and the permeability and fluidity of the thermosetting resin composition into fine gaps are improved, which tends to reduce the occurrence of voids and unfilled portions. The average particle size of the rubber particles is measured using the same method as for inorganic fillers.

[0056] The thermosetting resin composition can be obtained, for example, by stirring, melting, mixing, dispersing, etc., the components constituting the thermosetting resin composition, either collectively or separately, while optionally applying heat treatment. The equipment used for mixing, stirring, dispersing, etc., of these components is not particularly limited, and examples include a mortar and pestle mill equipped with a stirrer and heater, a three-roll mill, a ball mill, a planetary mixer, a bead mill, etc. The thermosetting resin composition can be obtained by mixing and kneading the above components using these equipment, and degassing as necessary. To improve the dispersibility of the inorganic filler, a mixture in which the inorganic filler is premixed with the epoxy resin may be used. In this case, the content of the inorganic filler in the mixture is preferably 20% to 70% by mass.

[0057] The viscosity of the thermosetting resin composition is not particularly limited. In particular, from the viewpoint of high fluidity, the viscosity at 25°C is preferably 0.1 Pa·s to 50.0 Pa·s, more preferably 1.0 Pa·s to 50.0 Pa·s, and even more preferably 10.0 Pa·s to 50.0 Pa·s.

[0058] Furthermore, the thermosetting resin composition preferably has a viscosity of 0.20 Pa s or less, and more preferably 0.15 Pa s or less, at 110° C. as an indicator of ease of filling a narrow gap of several tens to several hundreds of μm at around 100° C. to 120° C. The viscosity of the thermosetting resin composition at 110° C. is measured using a rheometer AR2000 (manufactured by TA Instruments, aluminum cone 40 mm, shear rate 32.5 / sec).

[0059] Furthermore, the thermosetting resin composition preferably has a thixotropic index [(viscosity at 2.5 rpm) / (viscosity at 10 rpm)], which is the ratio of the viscosity at a rotation speed of 2.5 rpm to the viscosity at a rotation speed of 10 rpm, measured at 25°C using an E-type viscometer, of 0.3 to 1.5, more preferably 0.5 to 1.2. When the thixotropic index is within the above range, the filling ability tends to be further improved. The viscosity and thixotropic index of the thermosetting resin composition can be adjusted to the desired range by appropriately selecting the composition of the epoxy resin, the content of the inorganic filler, etc.

[0060] After the thermosetting resin composition 24 is filled into the second opening 18 by stencil printing, the stencil 16 is removed from the mount body 10. In this way, a thermosetting resin composition layer 26 is formed on the mount body 10 (the surface of the circuit board 12 on which the electronic component elements 14 are arranged). As shown in FIG. 2 , for the electronic component elements 14 arranged in the second opening 18A, the thermosetting resin composition 24 is applied to the upper surface of the electronic component elements 14 to form the thermosetting resin layer 26. On the other hand, for the electronic component elements 14 arranged in the second opening 18B, the thermosetting resin composition 24 is applied to the upper and side surfaces of the electronic component elements 14 and between the electronic component elements 14 and the circuit board 12 to form the thermosetting resin layer 26.

[0061] 3 , a mask frame 30 having first openings 28 provided in accordance with the locations of the electronic component elements 14 is placed on the surface of the mount assembly 10 on which the electronic component elements 14 are placed (i.e., on the surface of the circuit board 12 on which the electronic component elements 14 are placed). In this embodiment, the thickness of the mask frame 30 is set to be thinner than the thickness of the thermosetting resin composition layer 26.

[0062] The material of the mask frame is not particularly limited, and examples thereof include metals such as iron, aluminum, SUS, titanium, etc. The mask frame can be manufactured by the same method as that for the metal mask.

[0063] A release layer may be provided on the surface of the mask frame 30 that comes into contact with the circuit board 12, the surface of the mask frame 30 opposite to the surface that comes into contact with the circuit board 12, and the wall surface of the first opening 28 of the mask frame 30. The material that constitutes the release layer is not particularly limited. Specific examples of the material that constitutes the release layer include fluororubber, fluororesin, silicone resin, and polyimide resin.

[0064] The size of the first opening 28 is not particularly limited, and it is sufficient that the size of the first opening is set so that the electronic component element fits within the first opening when the mask frame 30 is viewed in plan. Note that, in order to prevent the thermosetting resin composition 24 from being interposed between the mask frame 30 and the circuit board 12 and contaminating the surface of the circuit board 12 with the thermosetting resin composition 24 when the mask frame 30 is placed on the mounting body 10, it is preferable to provide the first opening 28 in the mask frame 30 so that the wall surface of the first opening 28 does not come into contact with the electronic component element 14.

[0065] 4, a pressing plate 32 having a smooth surface is placed on the side of the mask frame 30 opposite to the side facing the mount assembly 10. The size of the pressing plate 32 is not particularly limited, and may be any size that can cover the area of ​​the mask frame 30 where the first opening 28 is provided, for example.

[0066] A release sheet may be disposed between the mask frame 30 and the pressing plate 32 to facilitate separation of the mask frame 30 and the pressing plate 32 after the heating and pressurizing treatment by the pressure bonding device. The release sheet may include a substrate containing polyethylene terephthalate resin, polyethylene naphthalate resin, or polybutylene terephthalate resin, or a copolymer or modified resin thereof, and a release layer provided on one side of the substrate, containing resin particles, a binder, and, if necessary, other components. Examples of the resin particles include at least one selected from the group consisting of (meth)acrylic resin, polyolefin resin, polystyrene resin, poly(meth)acrylonitrile resin, and silicone resin. Examples of the binder include (meth)acrylic resin or silicone resin. The release sheet may be disposed so that the surface of the release sheet facing the release layer is in contact with the mask frame 30.

[0067] A pressing plate 32 is placed on the side of the mask frame 30 opposite to the side facing the mounting body 10, and the liquid thermosetting resin composition 24 is filled into the first opening 28. In this state, a heating and pressurizing process is performed while applying pressure in the direction of the arrows in FIG. 4 using a crimping device having a pair of plates 34 and 36, whereby the thermosetting resin composition 24 is cured and the electronic component element 14 is sealed with the cured product of the thermosetting resin composition 24.

[0068] The curing conditions for the thermosetting resin composition using a pressure bonding device are not particularly limited and can be set appropriately based on the components constituting the thermosetting resin composition. For example, the curing conditions for the thermosetting resin composition are preferably 80°C to 165°C and heating for 1 minute to 150 minutes. The pressure condition is preferably 0.5 MPa to 1.0 MPa.

[0069] After the heating and pressurizing treatment, the pressing plate 32 and the mask frame 30 are removed, and as shown in FIG. 5 , an electronic component device 40 is obtained, which includes electronic component elements 14 encapsulated in a cured product 38. The surface of the cured product 38 in the electronic component device 40 may be polished using a grinder, buff, or the like. The cured product 38 may also be post-cured. The post-curing conditions are not particularly limited and can be set appropriately based on the components constituting the thermosetting resin composition. For example, the post-curing conditions may be 100°C to 180°C and heating for 30 to 120 minutes.

[0070] 6 and 7, a method for manufacturing an electronic component device according to a second embodiment will be described. Unlike the first embodiment, the method for manufacturing an electronic component device according to the second embodiment is configured such that the thickness of the mask frame is greater than the thickness of the thermosetting resin composition layer. Furthermore, a protrusion that fits into the first opening of the mask frame is provided on the surface of the pressing plate facing the mask frame.

[0071] In the method for manufacturing an electronic component device according to the second embodiment, as shown in Figures 1 and 2, a thermosetting resin composition is applied to a mount assembly by stencil printing in the same manner as in the first embodiment. Next, as shown in Figure 6, a mask frame 44 having first openings 42 corresponding to the locations of the electronic component elements 14 is placed on the surface of the mount assembly 10 on which the electronic component elements 14 are arranged (i.e., on the surface of the circuit board 12 on which the electronic component elements 14 are arranged). In this embodiment, the thickness of the mask frame 44 is set to be thicker than the thickness of the thermosetting resin composition layer 26.

[0072] Next, as shown in FIG. 7 , a pressing plate 46 is placed on the side of the mask frame 44 opposite the side facing the mount assembly 10. The pressing plate 46 has a protrusion 48 on the surface facing the mask frame 44 that fits into the first opening 42. By using the pressing plate 46 with the protrusion 48, it is possible to adjust the thickness of the thermosetting resin composition 24 for each electronic component element 14. Therefore, electronic component elements of different heights can be encapsulated together. A release sheet may be placed between the mask frame 44 and the pressing plate 46 to allow the mask frame 44 and the pressing plate 46 to be easily separated after the heat and pressure treatment using the crimping device. Details of the release sheet are as described above.

[0073] Next, by performing a heating and pressurizing process using a pressure bonding device in the same manner as in the first embodiment, the thermosetting resin composition 24 is hardened, and the electronic component element 14 is sealed with the hardened thermosetting resin composition 24, thereby producing an electronic component device.

[0074] Third Embodiment A method for manufacturing an electronic component device according to a third embodiment will be described with reference to FIG. 8 . In the method for manufacturing an electronic component device according to the third embodiment, a thermosetting resin composition is supplied onto a mounting body by a dispensing method instead of a stencil printing method. In the method for manufacturing an electronic component device according to the third embodiment, as shown in FIG. 8 , a mask frame 30 having first openings 28 provided corresponding to the positions of the electronic component elements 14 is placed on the surface of the mounting body 10 on which the electronic component elements 14 are arranged. Next, a dispenser 50 is used to fill the first openings 28 with a thermosetting resin composition 24. The amount of thermosetting resin composition 24 filled into the first openings 28 is set to the amount required for sealing the electronic component elements 14 by the MUF.

[0075] Examples of dispensers include air syringe type, tubing type, plunger type, positive load type, screw type (mono pump), and non-contact (jet) type.

[0076] In the method for manufacturing an electronic component device according to the third embodiment, the thermosetting resin composition is directly filled into the first opening using a dispenser, so that the step of preparing a stencil can be omitted, unlike in the first or second embodiment, which uses a stencil printing method. Furthermore, since a stencil is not used in the method for manufacturing an electronic component device according to the third embodiment, contamination of the surface of the circuit board by the thermosetting resin composition, which may occur during the process of removing the stencil after supplying the thermosetting resin composition by the stencil printing method and then arranging the mask frame, is avoided.

[0077] Next, by performing a heating and pressurizing process using a pressure bonding device in the same manner as in the first embodiment, the thermosetting resin composition 24 is hardened, and the electronic component element 14 is sealed with the hardened thermosetting resin composition 24, thereby producing an electronic component device.

[0078] Fourth Embodiment A manufacturing method for an electronic component device according to a fourth embodiment will be described with reference to FIGS. 9 and 10 . In the fourth embodiment, a stencil-integrated mask frame according to the present disclosure is used, and a thermosetting resin composition is applied onto a mounting body by stencil printing. As shown in FIG. 9 , the stencil-integrated mask frame 52 used in the fourth embodiment includes a mask frame 56 having a first opening 54, a stencil body 60 that is detachable from the mask frame 56 and has a second opening 58 that contacts one side of the mask frame 56 and is provided at a location corresponding to the first opening 54, and a stencil 64 having a wall portion 62 that protrudes from the edge of the second opening 58 in the stencil body 60 toward the side that contacts the mask frame 56 and covers at least a portion of the wall surface of the first opening 54. In this embodiment, the height of the wall portion 62 is the same as the thickness of the mask frame 56, and the tip of the wall portion 62 contacts the circuit board 12. However, this is not limiting, and the tip of the wall portion 62 does not necessarily need to contact the circuit board 12. The mask frame 56 and the mask plate 64 may be made of the same material as the mask frame 30 and the mask plate 16 .

[0079] In the manufacturing method for an electronic component device according to the fourth embodiment, a mask frame 52 with an integrated stencil is placed on the surface of the mounting body 10 on which the electronic component elements 14 are arranged. As shown in Fig. 9, a first opening 54 and a second opening 58 in the mask frame 52 with an integrated stencil are provided according to the location where the electronic component elements 14 are arranged. As shown in the second opening 58A, the wall portion 62 may be provided so as to be in contact with the electronic component elements 14, or as shown in the second opening 58B, the wall portion 62 may be provided so as not to be in contact with the electronic component elements 14.

[0080] In the stencil printing method, the thermosetting resin composition 24 supplied onto the stencil body 60 using a squeegee 22 is filled into the second openings 58. Details of the stencil printing method are the same as those in the first embodiment. After filling the second openings 58 with the thermosetting resin composition 24 by the stencil printing method, the stencil 64 is removed from the mount body 10 as shown in FIG. 10 . In this manner, a thermosetting resin composition layer 26 is formed on the mount body 10 (the surface of the circuit board 12 on which the electronic component elements 14 are arranged). At this time, the mask frame 56 is not removed but remains on the circuit board 12, so that the thermosetting resin composition 24 is not interposed between the mask frame 56 and the circuit board 12. This prevents the surface of the circuit board 12 from being contaminated with the thermosetting resin composition 24. Next, a heat and pressure treatment is performed using a pressure bonding device in the same manner as in the first embodiment, whereby the thermosetting resin composition 24 is cured, and the electronic component elements 14 are sealed with the cured thermosetting resin composition 24, thereby producing an electronic component device.

[0081] Other Embodiments The manufacturing method for an electronic component device of the present disclosure can also be suitably applied to repair defects, such as cracks, in a cured product of a thermosetting resin composition. For example, the defect can be repaired by applying a thermosetting resin composition to the defected area with a mask frame in place and then curing the applied thermosetting resin composition using a pressure-bonding device. The manufacturing method for an electronic component device of the present disclosure can also be applied to sealing a curved package. Unlike conventional sealing methods using a mold, the manufacturing method for an electronic component device of the present disclosure uses a mask frame. By using a flexible mask frame, electronic component elements on a curved package can be easily sealed using a pressure-bonding device. Note that the present invention is not limited to the above four embodiments, and various modifications can be made based on publicly known knowledge as long as they do not change the gist of the present disclosure. All documents, patent applications, and technical standards described herein are incorporated by reference to the same extent as if each individual document, patent application, and technical standard were specifically and individually indicated to be incorporated by reference.

Claims

1. A method for manufacturing an electronic component device, comprising: disposing a mask frame having a first opening provided according to a location where an electronic component element is disposed on a surface of a mounting body having a circuit board and the electronic component element disposed on one surface of the circuit board; disposing a pressing plate on a side opposite to the side of the mask frame facing the mounting body; and performing a heating and pressing process with a pressure bonding device in a state where a liquid thermosetting resin composition is filled in the first opening to cure the thermosetting resin composition and seal the electronic component element.

2. The method for manufacturing an electronic component device according to claim 1, wherein the thermosetting resin composition is filled into the second opening by a stencil printing method in a state where a stencil having a second opening provided according to a location where the electronic component element is disposed is disposed on a surface of the mounting body on the side where the electronic component element is disposed; and then, after the stencil is removed, the mask frame and the pressing plate are disposed.

3. The method for manufacturing an electronic component device according to claim 2, wherein the filling of the thermosetting resin composition into the second opening by the stencil printing method is performed in a reduced pressure environment.

4. The method for manufacturing an electronic component device according to claim 1, wherein the thermosetting resin composition is filled into the first opening by a dispensing method in a state where the mask frame is disposed on a surface of the mounting body on the side where the electronic component element is disposed; and then, the pressing plate is disposed.

5. The method for manufacturing an electronic component device according to claim 1, wherein a convex portion that aligns with the first opening is provided on a surface of the pressing plate on the side facing the mask frame.

6. A stencil-integrated mask frame, comprising: a mask frame having a first opening; a stencil body that is detachable from the mask frame, has a second opening provided at a location corresponding to the first opening and in contact with one surface of the mask frame; and a wall portion that protrudes from an edge of the second opening in the stencil body toward a surface side in contact with the mask frame and covers at least a part of a wall surface of the first opening.

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