Molded underfill sealing sheet and method for sealing electronic component mounting substrate using same

Abstract

A molded underfill sealing sheet which is a sheet of a thermosetting resin composition and which has a thickening rate of less than 9, said thickening rate being the ratio (V90 / V0) between the viscosity V90 after 90 seconds from the start of measurement and the viscosity V0 after 0 seconds, at a measurement temperature of 125 DEG C for a measurement time of 150 seconds; the sheet is a molded underfill sealing sheet for an electronic component mounting substrate which is provided with a plurality of electronic components and a substrate, and a space is provided between the electronic components and the substrate.

Description

Technical Field

[0001] The present invention relates to a mold underfill sealing sheet and a method for sealing an electronic component mounted substrate using the same. Background Art

[0002] The sealing of electronic components connected by the flip chip method is generally carried out by underfilling the gap between the electronic component and the substrate with a fluid liquid sealing material and then overmolding with another liquid sealing material or a sealing film (see Patent Documents 1 to 3).

[0003] On the other hand, in order to reduce the number of steps, a molded underfill sealing material that can simultaneously perform underfill sealing and overmold sealing has been proposed (see Patent Document 4).

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2014-131016

[0007] Patent Document 2: Japanese Patent Application Publication No. 2014-229769

[0008] Patent Document 3: Japanese Patent Application Publication No. 2015-178635

[0009] Patent Document 4: Japanese Patent Application Publication No. 2015-71670 Summary of the invention

[0010] Problems to be solved by the invention

[0011] In mold underfill sealing, which performs underfill sealing and overmold sealing at the same time, portions (voids) not penetrated by the sealing material may occur in the spaces between a plurality of electronic components and a substrate, making it difficult to perform underfill sealing stably and sufficiently.

[0012] Means for solving problems

[0013] One aspect of the present invention relates to a molded bottom filling sealing sheet, which is a sheet of a thermosetting resin composition, wherein at a measuring temperature of 125° C. and a measuring time of 150 seconds, the ratio of the viscosity V90 of the sheet 90 seconds after the start of the measurement to the viscosity V0 after 0 seconds (V90 / V0), i.e., the thickening rate, is less than 9; the sheet is a molded bottom filling sealing sheet for an electronic component mounting substrate having a plurality of electronic components and a substrate and a space provided between the electronic components and the substrate.

[0014] In addition, another aspect of the present invention relates to a sealing method for an electronic component mounting substrate, which includes the following steps: (a) a step of preparing an electronic component mounting substrate, the electronic component mounting substrate having a plurality of electronic components and a substrate, and a space is provided between the aforementioned electronic components and the aforementioned substrate; (b) a step of placing the aforementioned sheet on the aforementioned electronic component mounting substrate in a manner in contact with the aforementioned electronic components; (c) a step of heat-molding the placed aforementioned sheet, and filling the molten material of the sheet into the space between the aforementioned electronic components and the aforementioned substrate to solidify it; the heating temperature in the aforementioned heat molding is greater than 110°C and less than 175°C.

[0015] Effects of the Invention

[0016] According to the above-mentioned method of the present invention, when the electronic component mounting substrate with a space between the electronic component and the substrate is molded and sealed, it is difficult to form a part (gap) that is not penetrated by the sealing material in the space between the electronic component and the substrate, and the bottom filling sealing can be implemented stably and fully.

[0017] The novel features of the present invention are described in the appended claims. Both the scheme and content of the present invention, as well as other objects and features of the present invention, can be further understood through the following detailed description with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a conceptual diagram showing an example of a substrate on which electronic components are mounted.

[0019] Figure 2 The diagram shows an example of a substrate center C, a frame line F that surrounds all the multiple electronic components and has the smallest surrounding area, an arbitrary point P of the frame line, an outer edge S of the thermosetting sheet, and an intersection Q of a straight line Lcp passing through the point P and the center C and the outer edge S.

[0020] Figure 3 Process diagram of a sealing method for mounting electronic components on a substrate. DETAILED DESCRIPTION

[0021] The following will illustrate the embodiments of the present disclosure, but the present disclosure is not limited by the following illustrative examples. The following description sometimes exemplifies specific numerical values ​​and materials, but other numerical values ​​and materials may also be applied as long as the effects of the present disclosure can be obtained. In this specification, the description of "numerical value A to numerical value B" includes numerical value A and numerical value B, which can be interpreted as "above numerical value A and below numerical value B". In the following description, when the lower limit and upper limit of the numerical value related to specific physical properties, conditions, etc. are exemplified, as long as the lower limit does not become above the upper limit, any one of the exemplified lower limits and any one of the exemplified upper limits may be arbitrarily combined. When multiple materials are exemplified, one may be selected and used alone, or two or more may be used in combination.

[0022] In addition, the present disclosure includes a combination of matters recorded in two or more claims arbitrarily selected from the plurality of claims recorded in the attached claims. In other words, matters recorded in two or more claims arbitrarily selected from the plurality of claims recorded in the attached claims may be combined as long as no technical contradiction occurs.

[0023] In the following description, the term "comprising" or "including" includes the following expressions: "comprising (or including)", "consisting essentially of", and "consisting of".

[0024] In addition, in this disclosure, "thermosetting resin" may be referred to as "sealing material" regardless of whether it is before or after curing.

[0025] The sheet of the thermosetting resin composition of the embodiment of the present invention (sheet for molding bottom filling sealing) is a sealing material for molding bottom filling sealing for performing bottom filling sealing and overmolding sealing at the same time. The sealing object is an electronic component mounting substrate having a plurality of electronic components and a substrate, and a space is provided between the electronic components and the substrate. In molding bottom filling sealing, the sealing of the electrode portion connecting the electronic component and the substrate (i.e., bottom filling sealing) and the sealing of the entirety including the outer surface of the electronic component (i.e., overmolding sealing) are performed at the same time.

[0026] The molded underfill sealing sheet (hereinafter also referred to as "MUFS sheet") is a sheet of an uncured or semi-cured (B stage) thermosetting resin composition. The semi-cured (B stage) refers to a thermosetting resin composition that is solid at room temperature, but temporarily has fluidity when heated to a predetermined temperature or above, and then loses fluidity as the curing reaction proceeds.

[0027] <Thickening rate>

[0028] By controlling the thickening rate of the sheet to less than 9, the ease with which the sealing material penetrates into the space between the electronic component and the substrate (hereinafter also referred to as "space S") (hereinafter also referred to as "MUF property") can be significantly improved.

[0029] Here, the thickening rate refers to the thickening rate under the measurement conditions of a measurement temperature of 125° C. and a measurement time of 150 seconds (hereinafter referred to as measurement conditions (A)). The thickening rate is the ratio of the viscosity V90 after 90 seconds from the start of the viscosity measurement to the viscosity V0 after 0 seconds (V90 / V0). An example of a specific measurement method using the measurement conditions (A) is shown below.

[0030] As a measuring device for the viscosity increase ratio, for example, MCR102 (manufactured by Anton-Paar) is used. The measuring device has an attached upper plate and lower plate for measurement.

[0031] First, the lower plate was heated to 125° C. and the temperature was stabilized.

[0032] Next, a test piece having a diameter of 25 mmΦ was placed on the surface of the lower plate at 125° C. Thus, the test piece began to be heated to 125° C. The test piece was prepared by cutting out from a MUFS sheet.

[0033] Within 30 seconds after placing the test piece on the lower plate, set the device so that the gap between the upper plate and the lower plate is 0.25 mm. Remove the excess part of the test piece when setting the gap.

[0034] The measurement was started 30 seconds after the test piece was placed on the lower plate. The sealing material viscosity (V0) after 0 seconds (i.e., when the measurement started) and the sealing material viscosity (V90) after 90 seconds were measured, and the ratio of the two (V90 / V0) was calculated as the thickening rate.

[0035] The parameters of the measurement conditions (A) are summarized below.

[0036] Measuring temperature: 125℃

[0037] Measuring time: 0 to 150 seconds

[0038] Test piece size: Φ25mm round

[0039] Shear rate: 20 (1 / s)

[0040] Thickness of thermosetting resin composition (sealing material): 0.25 mm

[0041] Thickening rate: viscosity after 90 seconds / viscosity after 0 seconds

[0042] In order to further improve the MUF property, the thickening rate can be set to less than 8.2, less than 6.0, or less than 3.0. In the mold bottom filling seal, the timing of the sealing material penetrating into the sealed space S is relatively slow, and the sealing material needs to have sufficient fluidity until the space S is fully filled. By controlling the thickening rate within the above range, the sealing material can maintain sufficient fluidity until the space S is fully filled with the sealing material.

[0043] In the above measurement, the viscosity of the sealing material at 125°C is preferably 1000 Pa·s or less, more preferably 100 Pa·s or less. By having such a low viscosity, the MUF property can be further significantly improved. The viscosity at 125°C can be measured at the same time as the thickening rate. Here, the viscosity (V20) of the sealing material is measured 20 seconds after the start of the above measurement.

[0044] <tanδ>

[0045] The maximum value of tanδ (loss tangent) of the sheet for mold underfill sealing under the measurement conditions of a measurement temperature of 125°C and a measurement time of 0 to 70 seconds (hereinafter referred to as measurement conditions (B)) is preferably less than 6, or less than 3, or less than 2.9, or less than 2.7, or less than 2.5. By setting the maximum value of tanδ under the measurement conditions (B) to be within the above range, the warpage of the electronic component mounting substrate that has been mold underfill sealed can be significantly reduced.

[0046] For example, when a MUFS sheet is placed on a silicon wafer with a diameter of 12 inches Φ and a thickness of 775 μm and the MUFS sheet is heat-molded under the following conditions, the warpage after curing can be reduced to less than 12 mm.

[0047] <Conditions>

[0048] Molding pressure: 5MPa

[0049] Molding temperature: 125℃

[0050] Molding time: 10 minutes

[0051] Minimum vacuum degree: 200Pa

[0052] Post mold cure: 150℃ / 3 hours or 180℃ / 1.5 hours

[0053] It is considered that when the maximum value of tan δ is within the above range, the stress remaining in the sealing material (particularly the overmold portion) after curing is easily reduced, thereby reducing the warpage. An example of a specific measurement method using the measurement condition (B) is shown below.

[0054] As a measuring device of tan δ, for example, ARES-LS2 (manufactured by TA Instruments) is used.

[0055] A test piece having a diameter of 25 mm was set in the measuring device. The test piece was prepared by cutting out from a MUFS sheet.

[0056] Next, tan δ is measured at a frequency of 1 Hz, for example.

[0057] The parameters of the measurement conditions (B) are summarized below.

[0058] Measuring temperature: 125℃

[0059] Measuring time: 0 to 70 seconds

[0060] Test piece size: Φ25mm round

[0061] Thickness of thermosetting resin composition (sealing material): 0.25 mm

[0062] From the viewpoint of improving the ease of infiltration of the sealing material into the space (space S) between the electronic component and the substrate (MUF property), the tanδ under measurement condition (B) can be set to 0.2 or more, and can also be set to 0.3 or more. The tanδ under measurement condition (B) is preferably 0.8 or more and less than 3, for example.

[0063] The method of controlling the tanδ under measurement condition (B) within the above range is not particularly limited. For example, methods such as increasing the filler content rate, imparting a surface treatment agent to the filler surface, and selecting a main resin and a curing agent can be cited.

[0064] <Storage modulus>

[0065] The storage modulus of the cured product of the MUFS sheet is, for example, 3 GPa or more, and can also be 5 GPa or more. For example, it is 40 GPa or less, and can also be 30 GPa or less.

[0066] The measurement of the storage modulus of the cured product of the MUFS sheet is carried out in the following order. First, a measurement sample with a length of 50 mm × width of 10 mm × thickness of 2 mm is prepared from the cured product of the MUFS sheet. As the cured product, the one obtained by curing the MUFS sheet by heating at 175 °C for 1 hour is used. Next, the measurement sample is set in a bending measurement jig, and using a viscoelasticity measurement device (DMA6100, manufactured by Hitachi High-Tech Science Corporation), the bending storage modulus in the temperature range of -50 to 300 °C is measured under the conditions of a frequency of 1 Hz and a heating rate of 2.5 °C / min. The storage modulus at 25 °C is read from the measurement results. The storage modulus is an index of the sheet rigidity. The operability of the MUFS sheet with the storage modulus of the cured product within the above range is excellent.

[0067] <Structure of MUFS sheet>

[0068] The MUFS sheet can be a single-layer structure sheet. The single-layer structure sheet refers to a sheet composed of a single thermosetting resin composition. In order to improve the operability, the MUFS sheet can be attached to one release sheet, or the MUFS sheet can be sandwiched between two release sheets.

[0069] Among them, the MUFS sheet can also be a multi-layer structure. The multi-layer structure refers to a structure in which two or more thermosetting resin composition layers with different compositions are laminated. On the other hand, the manufacturing process of the multi-layer structure sheet is more complicated than that of the single-layer structure sheet. From the viewpoint of simplifying the manufacturing process, it is more preferably a single-layer structure sheet.

[0070] The thickness of the MUFS sheet is not particularly limited. For example, it is 50 μm or more, and may also be 100 μm or more, 200 μm or more, or 400 μm or more. The thickness of the MUFS sheet is, for example, 1000 μm or less, and may also be 800 μm or less.

[0071] <Manufacturing method of MUFS sheet>

[0072] The single-layer structured MUFS sheet is formed by molding a thermosetting resin composition into a single sheet. Examples of the molding method include calendering, casting, blown extrusion, T-die extrusion, dry lamination, etc. The MUFS sheet may also be formed on a release sheet and the release sheet may be peeled off during use.

[0073] The release sheet is not particularly limited, and examples thereof include plastic films, paper, non-woven fabrics, metals, etc. Examples of the plastic film include polyolefin-based films, vinyl halide polymer-based films, acrylic resin-based films, rubber-based films, cellulose-based films, polyester-based films, polycarbonate-based films, polystyrene-based films, polyphenylene sulfide-based films, and cycloolefin polymer-based films. A release sheet that has been subjected to a release treatment using silicone or the like may also be used.

[0074] <Thermosetting resin composition>

[0075] The thermosetting resin composition constituting the MUFS sheet contains, for example, a main resin, a curing agent, and a filler.

[0076] (Filler)

[0077] The filler is a solid component that is dispersed in the thermosetting resin composition and does not melt during the sealing manufacturing process. The solid component can be either an inorganic material or an organic material. The solid component can be any of granular, plate-like, and fibrous forms. The thermosetting resin composition may contain an inorganic powder as the filler.

[0078] As the inorganic powder, fused silica, crystalline silica, quartz glass powder, calcium carbonate, aluminum hydroxide, etc. can be used. Among them, silica is particularly preferred, and fused silica is more preferred.

[0079] The filler content rate in the thermosetting resin composition is not particularly limited. For example, it may be 50% by mass or more, and may also be 60% by mass or more, or 70% by mass or more. From the viewpoint of easily making tanδ less than 3 under measurement condition (A), the filler content rate is preferably 70% by mass or more. The upper limit of the filler content rate in the thermosetting resin composition is not particularly limited. For example, it is 90% by mass or less, and may also be 85% by mass or less.

[0080] Compared to the minimum distance between the sealed objects, namely the electronic components (the distance between the outer edges of adjacent electronic components closest to each other) (W), and the height (H) of the space between the electronic components and the substrate, the maximum particle size (Dmax) of the filler is preferably smaller, and the maximum particle size (Dmax) of the filler can be appropriately selected according to the above distance (W) and height (H). The maximum particle size (Dmax) of the filler is, for example, 35 μm or less, 25 μm or less, 20 μm or less, or 10 μm or less.

[0081] The average particle size (D50) of the filler can be appropriately selected according to the above distance (W) and height (H), for example, it is 0.5 μm or more, or 1 μm or more, or 2 μm or more. The average particle size (D50) of the filler is, for example, 20 μm or less, or 10 μm or less, or 5 μm or less (for example, 3 μm or less). The average particle size (D50) of the filler is the median particle size at the cumulative volume 50% of the volume particle size distribution.

[0082] The average particle size (D50) and the maximum particle size (Dmax) of the filler can be measured by a laser diffraction scattering method using a laser diffraction particle size distribution measuring apparatus.

[0083] (Main material: resin)

[0084] The main resin is not particularly limited, but epoxy resin is excellent in heat resistance and cost.

[0085] As epoxy resin, there is no particular limitation, and can be used: biphenyl type epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol AD ​​type epoxy resin, naphthalene type epoxy resin, glycidylamine type epoxy resin, phenol novolac type epoxy resin, phenolphthalein type epoxy resin, polyglycol modified epoxy resin, polyolefin modified bisphenol A type epoxy resin, alicyclic epoxy resin, dicyclopentadiene type epoxy resin, polyether type epoxy resin, silicone modified epoxy resin, etc. These can be used alone, and two or more kinds can also be used in combination. For example, when using bisphenol A type epoxy resin, the content of bisphenol A type epoxy resin contained in the main agent resin is, for example, more than 50% by mass and less than 90% by mass, or more than 60% by mass and less than 90% by mass. For example, when a phenol novolac epoxy resin is used, the content of the phenol novolac epoxy resin in the main resin is, for example, 50 mass % to 90 mass %, or 60 mass % to 90 mass %.

[0086] Among them, from the viewpoint of increasing the glass transition temperature, the main resin preferably contains a solid epoxy resin having a melting point of 50° C. or higher.

[0087] From the viewpoint of easily suppressing the warping of the electronic component mounting substrate after sealing, the main resin preferably contains at least one selected from the group consisting of epoxy resins having an alkylene chain, epoxy resins having a polyoxyalkylene chain, and phenolphthalein epoxy resins as a part of the main resin. The phenolphthalein epoxy resin may also be used in combination with the following epoxy resins: epoxy resins having an alkylene chain and / or epoxy resins having a polyoxyalkylene chain.

[0088] (Epoxy resin having an alkylene chain)

[0089] The content of the epoxy resin having an alkylene chain contained in the main resin is, for example, 5% by mass or more and 30% by mass or less, or 5% by mass or more and 20% by mass or less. The epoxy resin having an alkylene chain is not particularly limited in type as long as it has an alkylene chain, and may be an epoxy-modified product of a polyol having more than 8 carbon atoms. In addition, a bisphenol A type epoxy resin may be used as a basic skeleton.

[0090] The epoxy resin having an alkylene chain may be any of glycidyl ether type, glycidyl ester type, glycidyl amine type, alicyclic epoxy compounds, etc. From the viewpoint of easy availability, glycidyl ether having an alkylene chain (specifically, a diol-modified epoxy resin) or the like is used.

[0091] The number of carbon atoms contained in the alkylene chain is, for example, 1 or more, 2 or more, or 3 or more. The number of carbon atoms in the polyolefin chain is preferably 10 or less, 8 or less, or 6 or less.

[0092] Examples of epoxy resins having an alkylene chain include 1,6-hexanediol diglycidyl ether, resorcinol diglycidyl ether, propylene glycol diglycidyl ether, cyclohexanedimethanol diglycidyl ether, etc. Examples of epoxy resins having an alkylene chain include epoxy-modified polybutadiene, epoxy-modified polyisoprene, epoxy-modified polyethylene, epoxy-modified polypropylene, epoxy-modified (meth)acrylic polymers, and epoxy-modified natural rubber.

[0093] (Epoxy resin having polyoxyalkylene chain)

[0094] The content of the epoxy resin having a polyoxyalkylene chain in the main resin is, for example, 5 mass % to 30 mass % or more, or 5 mass % to 20 mass % or less. The epoxy resin having a polyoxyalkylene chain may have a bisphenol A type epoxy resin as a basic skeleton.

[0095] The epoxy resin having a polyoxyalkylene chain is not particularly limited in type as long as it has a polyoxyalkylene chain, and may be any of a glycidyl ether type, a glycidyl ester type, a glycidyl amine type, an alicyclic epoxy compound, etc. From the viewpoint of easy availability, a glycidyl ether having a polyoxyalkylene chain (specifically, a polyalkylene glycol glycidyl ether) or the like is used.

[0096] Examples of the glycidyl ether type epoxy resin include polyoxyethylene diglycidyl ether, polyoxypropylene diglycidyl ether, polyoxytrimethylene diglycidyl ether, polyoxybutylene diglycidyl ether, polyoxyhexamethylene diglycidyl ether, and polyoxyethylene / polyoxypropylene diglycidyl ether.

[0097] The carbon number of the alkylene group contained in the polyoxyalkylene chain is, for example, 2 or more, preferably 3 or more, and more preferably 4 or more. The carbon number of the alkylene group is preferably 16 or less, and may be 10 or less or 6 or less.

[0098] Specific examples of the alkylene group include an ethylene group, a propylene group, a trimethylene group, a butylene group (1,2-butylene group, 1,3-butylene group, 1,4-butylene group (or tetramethylene group) etc.), a hexamethylene group, an octamethylene group, a decamethylene group and the like.

[0099] The repeating number n of the oxyalkylene unit in the polyoxyalkylene chain is, for example, 3 or more, preferably 4 or more or 5 or more. The repeating number n of the oxyalkylene unit is, for example, 70 or less, 30 or less, or 10 or less.

[0100] (Phenolphthalein type epoxy resin)

[0101] The content of the phenolphthalein epoxy resin contained in the main resin is, for example, 50 mass % or more and 90 mass % or less, or 60 mass % or more and 90 mass % or less.

[0102] The phenolphthalein epoxy resin is a bifunctional epoxy resin having a bulky phenolphthalein skeleton in the molecule. The phenolphthalein epoxy resin may have a glycidyl ether group at the para position of two phenyl groups not bonded to the nitrogen atom, for example. Specifically, phenolphthalein diglycidyl ether (N-phenylphenolphthalein diglycidyl ether) may be mentioned.

[0103] The thermosetting resin composition may contain at least one selected from the group consisting of a polyol having an alkylene chain, a polyol having a polyoxyalkylene chain, an epoxy resin having an alkylene chain, an epoxy resin having a polyoxyalkylene chain, and a phenolphthalein type epoxy resin.

[0104] (polyol having an alkylene chain)

[0105] The content of the polyol having an alkylene chain contained in the thermosetting resin composition is, for example, 5% by mass or more and 30% by mass or less, or 5% by mass or more and 20% by mass or less. The type of the polyol having an alkylene chain is not particularly limited as long as it has an alkylene chain, and may be a polyol having 8 or more carbon atoms. Examples of the polyol having 8 or more carbon atoms include 1,4-cyclohexanedimethanol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 2-methyl-1,1-cyclohexanedimethanol, tricyclo[5.2.1.0 2,6 ] decanedimethanol, 1,9-nonanediol, 2-methyl-1,8-octanediol, 1,10-decanediol, 1,12-dodecanediol, dimer diol, hydrogenated dimer diol, etc. In addition, alcohol-modified polybutadiene, alcohol-modified polyisoprene, alcohol-modified polyethylene, alcohol-modified polypropylene, alcohol-modified (meth) acrylic polymer, alcohol-modified natural rubber, etc. can also be mentioned.

[0106] (polyol having a polyoxyalkylene chain)

[0107] The content of the polyol having a polyoxyalkylene chain contained in the thermosetting resin composition is, for example, 5 mass % to 30 mass % or more, or 5 mass % to 20 mass % or less. The type of the polyol having a polyoxyalkylene chain is not particularly limited as long as it has a polyoxyalkylene chain.

[0108] As the polyol having a polyoxyalkylene chain, for example, polyoxyethylene polyol, polyoxypropylene polyol, polyoxytetramethylene polyol, polyoxyethylene polyoxypropylene polyol, polyoxyethylene polyoxytetramethylene polyol, polyoxypropylene polyoxytetramethylene polyol, etc. can be used. These polyoxyalkylene polyols can be used alone or in combination of two or more. The polyoxyalkylene polyol can have, for example, 2 to 6 hydroxyl groups, or 2 to 4.

[0109] Examples of the polyol constituting the polyol having a polyoxyalkylene chain include diethylene glycol, triethylene glycol, polyethylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, dibutylene glycol, tributylene glycol, polybutylene glycol, polytetramethylene glycol, diglycerol, triglycerol, polyglycerol, polyoxyalkylene glycol (containing one or more alkylene oxides such as ethylene oxide, propylene oxide, and butylene oxide as constituent units of the oxyalkylene group), and mixtures thereof; polyoxyethylene glycerol, polyoxypropylene glyceryl ether, polyoxybutylene glyceryl ether, polyoxyalkylene glyceryl ether (containing one or more alkylene oxides such as ethylene oxide, propylene oxide, and butylene oxide as constituent units of the oxyalkylene group), and the like.

[0110] (Curing agent)

[0111] As the curing agent for the main resin, phenol resin, acid anhydride, amine compound, etc. can be used. Among them, phenol resin is particularly preferred from the viewpoint of being easy to suppress the warping of the electronic component mounted substrate after sealing.

[0112] As phenolic resin, there is no particular limitation, and phenol novolac resin is preferred. Phenol novolac resin is obtained by condensation polymerization of phenols or naphthols (e.g., phenol, cresol, naphthol, alkylphenol, bisphenol, terpene phenol, naphthol, etc.) and formaldehyde. More specifically, phenol novolac resin, cresol novolac resin, aralkylphenol novolac resin, biphenylphenol novolac resin, terpene phenol novolac resin, α-naphthol novolac resin, β-naphthol novolac resin, etc. can be cited. Among these, naphthol novolac resin is preferred from the viewpoint of water resistance. These can be used alone or in combination of two or more.

[0113] Among them, from the viewpoint of increasing the glass transition temperature, the curing agent preferably contains a solid phenol novolac resin having a melting point of 60° C. or higher.

[0114] The amount of the curing agent is suitably controlled within the range of, for example, 30 parts by mass or more and 80 parts by mass or less, and may be 45 parts by mass or more and 60 parts by mass or less, based on 100 parts by mass of the main resin.

[0115] (Curing accelerator)

[0116] The thermosetting resin composition may also contain a curing accelerator. As the curing accelerator, there is no particular limitation, and examples thereof include: imidazole-based accelerators, phosphorus-based curing accelerators, phosphonium salt-based curing accelerators, bicyclic amidines and their derivatives, organic metal complexes, urea compounds of polyamines, and the like. The curing accelerator preferably has latency, and examples of latent curing accelerators include imidazole-based accelerators, phosphorus-based accelerators, and the like. Among the latent curing accelerators, encapsulated imidazole-modified products (microcapsule-type curing accelerators) are particularly preferred.

[0117] The thickening rate can be controlled, for example, by appropriately selecting the type and amount of the curing accelerator. From the viewpoint of easy control of the thickening rate, an imidazole-based accelerator is preferably used.

[0118] The amount of the curing accelerator is suitably controlled within the range of, for example, 1 part by mass or more and 10 parts by mass or less, and may be within the range of 2 parts by mass or more and 5 parts by mass or less, based on 100 parts by mass of the main resin.

[0119] (additive)

[0120] The thermosetting resin composition may further contain additives. Examples of the additives include, but are not limited to, silane coupling agents, carbon black, defoaming agents, leveling agents, pigments, stress relaxants, thermoplastic resins, and ion scavengers.

[0121] There are various types of silane coupling agents, and the properties of the resin composition (for example, viscosity at room temperature) will vary depending on the type. Therefore, it is appropriate to select an appropriate silane coupling agent. The silane coupling agent has a hydrolyzable group (alkoxy, hydroxyl, etc.), and may further have an alkyl group, an aliphatic or aromatic amino group (phenylamino, etc.), an acryloyl group, a methacryloyl group, etc.

[0122] The thermoplastic resin helps suppress the warping of the electronic component mounting substrate after sealing, and also helps gelation or solidification of the MUFS sheet.

[0123] The weight average molecular weight (Mw) of the thermoplastic resin is, for example, 300,000 or less, 200,000 or less, or 100,000 or less. Mw may be, for example, 5,000 or more. When the Mw of the thermoplastic resin is within such a range, the dispersibility is high and the elasticity of the cured product is easily reduced, thereby further improving the effect of suppressing warpage.

[0124] In addition, in this specification, the weight average molecular weight Mw is a polystyrene-equivalent weight average molecular weight measured using gel permeation chromatography (GPC).

[0125] The thermoplastic resin may also have a reactive functional group. Examples of the reactive functional group include an epoxy group, a carboxyl group, a hydroxyl group, an amino group (including an imino group), an amide group, a nitrile group, and a group having a polymerizable carbon-carbon unsaturated bond (e.g., a vinyl group, an allyl group, an acryloyl group, a methacryloyl group, etc.).

[0126] Examples of the thermoplastic resin include diene thermoplastic resins (isoprene rubber, butadiene rubber, styrene-butadiene rubber, chloroprene rubber, etc.), acrylic thermoplastic resins (acrylic rubber, etc.), nitrile thermoplastic resins (nitrile rubber, etc.), urethane thermoplastic resins (urethane rubber, etc.), silicone thermoplastic resins (silicone rubber, epoxy-modified silicone, etc.), polyester thermoplastic resins (crystalline polyester, amorphous polyester, polyester elastomer, etc.), polyamide thermoplastic resins (polyether ester amide, polyamide elastomer, etc.), butyl rubber, ethylene propylene rubber, etc. These may be used alone or in combination of two or more.

[0127] From the viewpoint of easy control of molecular weight and molecular weight distribution, easy introduction of reactive functional groups, and easy dispersion in curable resin compositions, acrylic thermoplastic resins can also be used. Acrylic thermoplastic resins contain (meth)acrylate units. Examples of (meth)acrylate units include (meth)acrylate alkyl units. Examples of (meth)acrylate alkyl units include (meth)acrylate C 1-6 Alkyl ester units (ethyl (meth)acrylate units, propyl (meth)acrylate units, butyl (meth)acrylate units, etc.), and may also be (meth)acrylate C 1-4 Alkyl ester unit. In addition, acrylate and methacrylate are described together as (meth)acrylate.

[0128] The amount of the thermoplastic resin is, for example, 5 parts by mass or more and 30 parts by mass or less, or may be 5 parts by mass or more and 20 parts by mass or less, based on 100 parts by mass of the main resin.

[0129] <Method for sealing a substrate having electronic components mounted thereon>

[0130] Hereinafter, an example of an embodiment of a method for sealing an electronic component mounted substrate using a MUFS sheet will be described.

[0131] The sealing method of the electronic component mounting substrate of the present embodiment includes the following steps: (a) preparing the electronic component mounting substrate, the electronic component mounting substrate having a plurality of electronic components and a substrate, and a space between the electronic components and the substrate; (b) placing the MUFS sheet on the electronic component mounting substrate in contact with the electronic components; (c) heating and molding the placed MUFS sheet, filling the molten material of the sheet into the space between the electronic components and the substrate, and solidifying the sheet. The heating temperature in the heating molding is, for example, not less than 110° C. and not more than 175° C.

[0132] According to the above-mentioned sealing method, a substrate electronic component mounting substrate (hereinafter also referred to as a "sealed body") can be obtained, which comprises a substrate, electronic components mounted on the substrate, and a cured product of a sealing material that seals the electronic components. Therefore, the sealing method of the present embodiment is also a method for manufacturing an electronic component mounting substrate (sealed body). Specifically, the method can be referred to as "a method for manufacturing a sealed body of an electronic component mounting substrate, wherein the sealed body of the electronic component mounting substrate comprises an electronic component mounting substrate and a cured product of a molded bottom filling sealing sheet; the electronic component mounting substrate comprises a plurality of electronic components and a substrate, and a space is provided between the electronic components and the substrate; the cured product of the molded bottom filling sealing sheet performs bottom molding and sealing on the space and simultaneously performs overmolding on the electronic components". The electronic component mounting substrate may be a single-sided sealed body in which only one side of the substrate is sealed with a sealing material, or may be a double-sided sealed body in which both sides are sealed with a sealing material.

[0133] In the electronic component mounting substrate prepared in step (a), a plurality of electronic components are connected to the substrate (specifically, electrodes provided on the substrate) by, for example, a flip chip method. In the flip chip method, the electronic components are mounted on the substrate by means of protruding terminals (also referred to as bumps) arranged in an array. A plurality of bumps are provided on the surface of the electronic component facing the substrate. The bumps constitute a part of the electronic component. The space between the electronic component and the substrate is substantially occupied by the gaps between the plurality of bumps.

[0134] The MUFS sheet used in step (b) has the property of melting by heating and then solidifying. The MUFS sheet may be in the B stage.

[0135] In step (c), the heat forming of the MUFS sheet is performed using a mold. For the mold, the MUFS sheet placed on the electronic component mounting substrate in a manner covering multiple electronic components is pressed against the substrate. The mold can be heated at any time. The MUFS sheet will melt due to heating, and the molten material will cover the surface of the electronic component while filling the space between the electronic component and the substrate, and at the same time fill the space between each electronic component, and then solidify. That is, bottom filling sealing and overmolding sealing are performed at the same time, and the overmolding sealing is used to seal the entire electronic component. Overmolding sealing means that at least the surface of the electronic component is sealed with a sealing material. The pressing surface of the mold can also be covered with a peeling film.

[0136] In the above sealing method, the top view size and shape of the MUFS sheet can also be designed based on the frame line (hereinafter also referred to as "frame line F") that surrounds all the multiple electronic components and has the smallest surrounding area. The top view size of the MUFS sheet can also be larger than the substrate size. From the perspective of simplifying the sealing manufacturing process and cost, it is preferably the same size as the substrate or a smaller size than the substrate.

[0137] Specifically, the distance between an arbitrary point P on the frame line F and the center of the substrate (hereinafter, also referred to as "center C") is set to Lp. In addition, the intersection of a straight line passing through point P and center C (hereinafter, also referred to as "straight line Lcp") and the outer edge of the MUFS sheet (hereinafter, also referred to as "outer edge S") is set to point Q. At this time, the distance between point Q and center C (hereinafter, also referred to as "Lq") may be limited to 0.9Lp or more.

[0138] The distance Lq may be greater than 0.91Lp, greater than 0.93Lp, or greater than 0.96Lp. It should be noted that, ideally, Lp and Lq may satisfy the above relationship in more than 70% and further more than 90% of the track length of the frame line F, or may satisfy the above relationship in 98% to 100%.

[0139] In consideration of the tolerance of the MUFS sheet, the tolerance of the substrate, and the tolerance of the mold, Lq may be set to be 1.0 Lp or more. In addition, the thermosetting sheet may completely cover the substrate in a plan view.

[0140] When the MUFS sheet is circular, the radius R of the MUFS sheet is equivalent to the distance Lq. At this time, the distance Lq (radius R) and the maximum value MLp of the distance Lp satisfy the above relationship such as Lq ≥ 0.9MLp. It should be noted that the maximum value of Lp, i.e., MLp, is the distance Lp when point P is located at the point farthest from the center of the substrate among all the electronic components on the substrate.

[0141] That is, in the present embodiment, the MUFS sheet is placed on the substrate in such a manner that it completely covers a plurality of electronic components or covers a majority of them when viewed from above. When the outer edge S of the MUFS sheet is located further inward (closer to the center C) relative to the frame line F, the distance between point P and point Q is also very small. At this time, the pressure energy applied to the MUFS sheet from the mold is more utilized to fill the molten material of the thermosetting sheet into the space between the electronic components and the substrate. Therefore, the molten material is easily filled into the space between the electronic components and the substrate (it is not easy to form a portion that is not infiltrated by the sealing material), and the bottom filling and sealing can be implemented stably and fully. This effect is particularly significant when multiple electronic components mounted on a large-area substrate are sealed together using packaging technologies such as panel-level packaging (PLP) and wafer-level packaging (WLP).

[0142] In step (c), the pressure applied to the MUFS sheet (or its melt) from the pressing surface of the mold may be, for example, 0.5 MPa to 15 MPa, or 2 MPa to 12 MPa, thereby promoting penetration of the melt into narrow spaces.

[0143] The upper limit of the distance Lq between point Q and center C is not particularly limited from the viewpoint of stably and fully implementing the bottom filling and sealing. However, if the manufacturing cost and ease of handling of the MUFS sheet are taken into consideration, Lq may be, for example, 1.45 Lp or less, 1.2 Lp or less, 1.1 Lp or less, or 1.05 Lp or less.

[0144] The heating molding of the MUFS sheet can also be carried out in a reduced pressure atmosphere. In this case, a better bottom filling part can be formed. The reduced pressure atmosphere can be a pressure atmosphere lower than the atmospheric pressure, for example, preferably a pressure atmosphere below 10000Pa (Pascal), that is, below 100 hectopascals (hPa), or below 5000Pa (Pascal), preferably less than 500Pa (5hPa), and more preferably less than 200Pa (2hPa).

[0145] In the sealed body obtained through step (c), the cured product of the sealing material constitutes the following parts: the bottom filling part that fills the space between the substrate and the electronic component, and the overmolding part that seals the surface of the electronic component that is not opposite to the substrate. The structures of the bottom filling part and the overmolding part are continuous. The boundary between the bottom filling part and the overmolding part cannot be observed even through microscopic observation, and the morphology (organization state) of the bottom filling part and the overmolding part are substantially the same.

[0146] The type of substrate is not particularly limited, and includes, for example, wafers, panels, glass substrates, resin substrates, printed wiring boards, etc. As wafers, silicon wafers, sapphire wafers, compound semiconductor wafers, etc. can be cited. As panels, plate-like components used for liquid crystal panels, organic (or inorganic) LED panels, etc. can be cited. As resin substrates, bismaleimide triazine substrates, polyimide substrates, fluororesin substrates, etc. can be cited. The substrate itself can also be an aggregate of electronic components. The aggregate of electronic components can be, for example, an aggregate of semiconductor chips that have been singulated into a plurality of pieces.

[0147] The electronic component may be an active component or a passive component. The electronic component may be a semiconductor component or a component other than a semiconductor component. The electronic component may also be a semiconductor package such as a BGA (Ball grid array) or a CSP (Chip size package). Specific examples of electronic components include RFIC (Radio frequency identifier), chip multilayer LC filter, dielectric filter, and laminated ceramic capacitor (MLCC).

[0148] The outer shape of the substrate should roughly correspond to the outer shape of the MUFS sheet. The outer shape of the substrate may also be similar to the outer shape of the MUFS sheet. For example, when the outer shape of the substrate is circular, the outer shape of the MUFS sheet may also be circular. When the outer shape of the substrate is rectangular, the outer shape of the MUFS sheet may also be rectangular. When the substrate has a roughly circular outer shape such as an oriented flat wafer, the outer shape of the MUFS sheet may also be circular. In addition, it may also be satisfied that more than 70% of the track length of the outer edge S of the MUFS sheet is similar to the outer shape of the substrate.

[0149] The size of the electronic component is not particularly limited. The area of ​​the surface of the electronic component facing the substrate can be, for example, 1 mm 2 Above, also 3mm 2 In addition, the area of ​​the surface of the electronic component facing the substrate can be, for example, 1600 mm per electronic component. 2 Below, also 2500mm 2 The electronic component size may be determined by measuring any number of electronic components (eg, 10 components) on a substrate and finding an average value.

[0150] The height of the electronic component is not particularly limited, and may be, for example, 5 μm or more and 800 μm or less, or 10 μm or more and 600 μm or less. The height of the electronic component refers to, for example, the distance from the position where the bump contacts the substrate to the maximum height of the electronic component. That is, in this embodiment, even for a substrate on which a plurality of tiny electronic components with a height of about 5 μm are mounted, good bottom filling sealing and overmolding sealing can be performed at the same time.

[0151] The distance between electronic components is not particularly limited, and may be, for example, greater than 5 μm and less than 2000 μm, or greater than 10 μm and less than 1000 μm. The minimum distance (W) between electronic components refers to the distance between the outer edges of adjacent electronic components that are closest to each other (i.e., the gap spacing). That is, in this embodiment, even for a high-density mounted substrate with a gap spacing of about 5 μm, good bottom filling sealing and overmolding sealing can be performed at the same time. The distance (W) between electronic components can be measured by measuring any number of pairs of electronic components (e.g., 10 pairs) on the substrate and finding the average value.

[0152] The height (H) of the space between the electronic component and the substrate may be, for example, greater than 2 μm, greater than 5 μm and less than 100 μm, or greater than 10 μm and less than 80 μm. That is, in this embodiment, even for a substrate with a small bump and a space height of about 2 to 5 μm, good bottom filling sealing and overmolding sealing can be performed at the same time. The height of the space between the electronic component and the substrate may be, for example, less than 40 μm, or less than 15 μm. It should be noted that the height of the space between the electronic component and the substrate refers to the minimum distance between the surface of the electronic component facing the substrate and the substrate. The minimum distance can be obtained by measuring any number of electronic components (for example, 10) on the substrate and finding the average value.

[0153] In the electronic component mounting substrate (sealed body), the maximum thickness T of the cured product of the sealing material may be, for example, less than 1.2 mm, less than 1.0 mm, less than 0.8 mm, or less than 0.4 mm (i.e., less than 400 μm). According to this embodiment, it is effective to perform good bottom filling sealing and overmolding sealing at the same time even when forming a thin sealed body as described above in packaging applications such as PLP and WLP.

[0154] In the sealed body, the maximum thickness T of the cured product of the sealing material refers to the maximum distance from the substrate surface to the surface of the cured product opposite to the substrate. The maximum thickness T can be measured at a plurality of locations (eg, 10 locations) on the substrate and the average value can be obtained.

[0155] Hereinafter, the sealing method will be described in more detail with reference to the drawings.

[0156] Process (a)

[0157] First, a substrate on which a plurality of electronic components are mounted is prepared, with a space being provided between the electronic components and the substrate. Figure 1 1 is a conceptual diagram showing an example of an electronic component mounting substrate 10. The electronic component mounting substrate 10 includes a substrate 11 which is a notch wafer having a circular shape. A plurality of rectangular semiconductor chips as electronic components 12 are mounted on the surface of the substrate 11. It should be noted that Figure 1 These are conceptual drawings and do not necessarily reflect the actual sizes of electronic components.

[0158] Process (b)

[0159] Next, the MUFS sheet 20 is placed on the substrate 11 in contact with the electronic component 12. Here, an arbitrary point on the frame line F that surrounds all the multiple electronic components 12 and has the smallest surrounding area is set as point P. The distance between point P and the center C of the substrate is set as Lp. The intersection of the straight line Lcp passing through point P and the center C of the substrate and the outer edge S of the MUFS sheet is set as point Q. At this time, the distance Lq between point Q and the center C of the substrate 11 satisfies 0.9Lp or more.

[0160] Figure 2 The figure shows an example of the center C of the substrate 11, the frame line F that surrounds the plurality of electronic components 12 and minimizes the enclosed area, an arbitrary point P on the frame line F, the outer edge S of the MUFS sheet 20, and the intersection Q of the straight line Lcp passing through the point P and the center C and the outer edge S. The frame line F is represented by a thicker solid line. The outer edge S of the MUFS sheet 20 is represented by a dotted line. Here, the case where Lq>Lp is shown, but there is also a case where Lq≤Lp. In addition, here, the size of the MUFS sheet 20 is larger than the substrate 11 when viewed from above, but the size of the MUFS sheet 20 may be smaller than the size of the substrate 11.

[0161] Process (c)

[0162] Next, the MUFS sheet 20 placed on the electronic component mounted substrate 10 is heat-molded, the melt of the MUFS sheet 20 is filled into the space between the electronic component 12 and the substrate 11 , and the melt is solidified. Figure 3 This is a process diagram of a method for sealing the electronic component mounting substrate 10 .

[0163] Specifically, if Figure 3As shown in (a), the electronic component mounting substrate 10 is set on a compression molding machine 50. The compression molding machine 50 has: an upper mold 51, a lower mold 52, and a flange portion 53, which also serves as a part of the mold fixed to the periphery of the upper mold 51 by means of an elastic member such as a spring. The upper mold 51 has a flat pressing surface for pressing the MUFS sheet 20. It should be noted that the pressing surface of the upper mold 51, the substrate mounting surface of the lower mold 52, the flange portion 53, etc. can also be covered with a peeling sheet.

[0164] The plurality of electronic components 12 are connected to the surface of the substrate 11 via bumps 121. A space 10S is provided between the surface of the electronic component 12 facing the substrate 11 and the substrate 11. Most of the space 10S is occupied by gaps between the bumps.

[0165] In the heating forming process, Figure 3 As shown in (b), the MUFS sheet 20 placed on the electronic component mounting substrate 10 is covered with the pressing surface of the mold, and the MUFS sheet 20 is compressed while being heated. At this time, a part of the melt of the MUFS sheet 20 penetrates into the space 10S, and the melt solidifies at the same time.

[0166] At least one of the lower mold 52 and the upper mold 51 is heated to a temperature at which the curing reaction of the melt of the MUFS sheet 20 proceeds. The curing reaction of the melt proceeds, and the underfill portion 221 and the overmold portion 222 are formed simultaneously. As a result, the sealed body 100 in which the electronic component mounting substrate 10 is sealed with the cured product 22 can be obtained.

[0167] At least a part of the step (c) may be performed under atmospheric pressure or under reduced pressure as described above. When the heat molding is performed under reduced pressure, air may be sucked out from the space where the compression molding machine 50 is installed.

[0168] The heating temperature is, for example, 80 to 200° C., or 100 to 180° C., and preferably 110 to 140° C. The heating time is, for example, 30 seconds to 30 minutes, or 2 minutes to 20 minutes.

[0169] The sealed body 100 removed from the compression molding machine 50 may be further subjected to post-mold curing. The post-mold curing may be performed at, for example, 100 to 180° C. for about 30 minutes to 3 hours.

[0170] Example

[0171] The present invention will be described in more detail below based on Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[0172] 《Examples 1 to 28 and Comparative Examples 1 to 6》

[0173] <Fabrication of MUFS Sheet>

[0174] (1) Mix the materials according to the formulations shown in each table, and knead them using a roll kneader to prepare a thermosetting resin composition. All the values representing the formulations in the table are in parts by mass.

[0175] (2) At 100 °C, coat the obtained thermosetting resin composition on a release sheet by T-die extrusion and form it into a sheet shape to fabricate a 500-μm-thick MUFS sheet. As the release sheet, use a 50-μm-thick polyethylene terephthalate film treated with silicone release.

[0176] [Evaluation]

[0177] <Measurement of Thickeness Increase Rate>

[0178] For each of the examples (Ex. 1 - 28) and comparative examples (Cmp. 1 - 6), measure the thickening rate of the above-obtained MUFS sheets using the aforementioned method.

[0179] <MUF Property>

[0180] On a circular glass substrate with an outer diameter of 300 mm Φ, install 5 evaluation electronic components (TEG) to fabricate a sample of an evaluation electronic component mounting substrate. At the center C of the substrate and at 4 positions (0°, 90°, 180°, and 270°) that are equiangular with respect to the center C, arrange the electronic components such that the maximum distance Lp from the point P on each electronic component to the substrate center C is 140 mm.

[0181] For the TEG, the bump height corresponding to the space height between the electronic component and the substrate is 30 μm, the size is 25 mm × 25 mm × 300 μm (the height of the electronic component including the bump is 330 μm), the bump size is 20 μm, and the pitch between the centers of the bumps is 40 μm.

[0182] Place a MUFS sheet having a shape similar to the substrate (circular) with Lq = 140 mm = 1.0Lp in contact with the electronic components, align the center of the substrate with the center of the MUFS sheet, and place the MUFS sheet on the sample. Heat and form the MUFS sheet under the following conditions.

[0183] Molding pressure: 5 MPa

[0184] Molding temperature: 125 °C

[0185] Molding time: 10 minutes

[0186] Minimum vacuum degree: 200 Pa

[0187] Post mold cure: 175°C / 1 hour

[0188] Visually evaluate the state (penetration) of the underfill part of the space between the landfill substrate and the electronic component. Observe directly from the back of the glass substrate, and evaluate according to the size of the unpenetrated part (void) of the cured product of the sealing material. The void size is the largest among the 5 evaluation electronic components (TEG). The results are shown in each table.

[0189] ◎: The void size is 500 μm or less.

[0190] 〇: The void size is greater than 500 μm and 750 μm or less.

[0191] △: The void size is greater than 750 μm and 1000 μm or less.

[0192] ×: The void size is greater than 1000 μm.

[0193] Table 1

[0194]

[0195]

[0196]

[0197] It can be understood from Tables 1 to 3 that when the thickening rate is 9 or less, the MUF property is significantly improved.

[0198] <Measurement of tanδ maximum value>

[0199] Measure tanδ of the obtained MUFS sheet using the aforementioned method.

[0200] <Warpage amount>

[0201] Place the MUFS sheet on a silicon wafer with a diameter of 12 inches Φ × a thickness of 775 μm, and heat-mold the MUFS sheet under the following conditions.

[0202] Molding pressure: 5 MPa

[0203] Molding temperature: 125°C

[0204] Molding time: 10 minutes

[0205] Minimum vacuum degree: 200 Pa

[0206] Post mold cure: 150°C / 3 hours or 180°C / 1.5 hours

[0207] The laminate of the post-cured silicon wafer and the sealing material was cooled to room temperature, and the warpage was evaluated according to the following criteria. The height difference between the center of the wafer and the end of the wafer on the surface of the silicon wafer without the sealing material was measured using a laser displacement meter, and the average of these was calculated as the warpage. The warpage was evaluated according to the following criteria. The results are shown in each table.

[0208] ○: Warpage is 12 mm or less.

[0209] △: Warping is greater than 12 mm.

[0210] Table 4

[0211]

[0212]

[0213]

[0214] As can be understood from Tables 4 to 6, when tanδ is less than 6, the warpage in the MUF seal is significantly reduced. The above description is based on the currently preferred embodiment, but the present invention is not limited to the above disclosure. A person skilled in the art can clearly understand various modifications and changes of the present invention by reading the above disclosure. Therefore, the attached claims should be interpreted as including all modifications and changes that do not depart from the true spirit and scope of the present invention.

[0215] Industrial Applicability

[0216] According to the molded bottom filling sealing sheet of the present invention, when an electronic component mounting substrate with a space between the electronic component and the substrate is molded bottom filling and sealing, the warping of the substrate can be reduced. In addition, a sealing method for an electronic component mounting substrate with excellent MUF can be realized. For example, the present invention can be used for sealing integrated circuits used in IOT, autonomous driving, etc., and large-scale integrated circuits.

[0217] Description of Reference Numerals

[0218] 10: Electronic component mounting substrate

[0219] 10S: Space

[0220] 11: Substrate

[0221] 12: Electronic components

[0222] 121: Bump

[0223] 20: MUFS Film

[0224] 22: Cured product

[0225] 221: Bottom filling part

[0226] 222: Overmolded part

[0227] 50: Compression molding machine

[0228] 51: Upper mold

[0229] 52: Lower mold

[0230] 53: Flange

[0231] F: Frame line

[0232] C: Center of substrate

[0233] Point P: Any point on the frame line

[0234] Lp: distance between point P and center C

[0235] Lcp: the straight line passing through point P and center C

[0236] S: Outer edge of the thermosetting sheet

[0237] Q: The intersection of Lcp and the outer edge S

[0238] Lq: The distance between point Q and center C

Claims

1. A molded underfill sealing sheet, which is a sheet of a thermosetting resin composition, At a measurement temperature of 125° C. and a measurement time of 150 seconds, the ratio of the viscosity V90 of the sheet 90 seconds after the start of the measurement to the viscosity V0 after 0 seconds (V90 / V0), i.e., the thickening rate, is less than 9. The mold underfill sealing sheet is a mold underfill sealing sheet for an electronic component mounting substrate including a plurality of electronic components and a substrate with a space provided between the electronic components and the substrate. 2 . The sheet according to claim 1 , which has a viscosity at 125° C. of 1000 Pa·s or less.

3. The sheet according to claim 1, wherein The maximum value of tan δ (loss tangent) of the sheet is 0.2 or more at a measuring temperature of 125° C. and a measuring time of 0 to 70 seconds.

4. The sheet according to claim 3, wherein The maximum value of tan δ is less than 6.

5. The sheet according to claim 1, wherein The thermosetting resin composition includes a main resin, a curing agent, and a filler, wherein the content of the filler is 70% by mass or more.

6. The sheet according to claim 5, wherein The maximum particle size of the filler is less than 35 μm.

7. The sheet according to claim 5, wherein The average particle size of the filler is less than 20 μm.

8. The sheet according to claim 1, wherein The thermosetting resin composition includes at least one selected from the group consisting of a polyol having an alkylene chain, an epoxy resin having an alkylene chain, a polyol having a polyoxyalkylene chain, an epoxy resin having a polyoxyalkylene chain, and a phenolphthalein type epoxy resin.

9. The sheet according to claim 5, wherein The curing agent comprises a solid phenol novolac resin.

10. The sheet according to any one of claims 1 to 9, which is a single-layer structure.

11. The sheet according to any one of claims 1 to 9, wherein When the sheet is placed on a silicon wafer of 12 inches in diameter Φ×775 μm in thickness and the sheet is heat-molded under the following conditions, the warpage after curing is less than 12 mm; Molding pressure: 5MPa Molding temperature: 125℃ Molding time: 10 minutes Minimum vacuum degree: 200Pa Post-mold curing (post-curing): 150°C / 3 hours or 180°C / 1.5 hours.

12. A method for sealing an electronic component mounting substrate, comprising the following steps: (a) preparing an electronic component mounting substrate, the electronic component mounting substrate comprising a plurality of electronic components and a substrate, with a space being provided between the electronic components and the substrate; (b) placing a sheet of a thermosetting resin composition, that is, a mold underfill sealing sheet, on the electronic component mounting substrate so as to be in contact with the electronic component; (c) a step of heating the mounted sheet to form the sheet, filling the melt of the sheet into the space between the electronic component and the substrate, and solidifying the melt; The heating temperature in the heating molding is 110° C. or higher and 175° C. or lower. The ratio of the viscosity V90 of the sheet 90 seconds after the start of the measurement to the viscosity V0 0 seconds after the start of the measurement (V90 / V0), i.e., the thickening rate, was less than 9 at a measurement temperature of 125° C. and a measurement time of 150 seconds.

13. The method for sealing an electronic component mounted substrate according to claim 12, wherein: When the distance between an arbitrary point P on the frame line that surrounds all the plurality of electronic components and has the smallest surrounding area and the center of the substrate is defined as Lp, A distance Lq between a point Q formed by the intersection of a straight line passing through the point P and the center of the substrate and the outer edge of the sheet and the center of the substrate is greater than or equal to 0.9Lp.

14. The method for sealing an electronic component mounted substrate according to claim 12 or 13, wherein: The maximum particle size of the filler is smaller than the height (H) of the space between the electronic component and the substrate and the minimum distance (W) between the electronic components.

15. A sealed body of an electronic component mounted substrate, comprising: An electronic component mounting substrate including a plurality of electronic components and a substrate, wherein a space is provided between the electronic components and the substrate; and a cured product of a molded underfill sealing sheet, wherein the molded underfill sealing sheet is a sheet of a thermosetting resin composition for performing undermold sealing of the space and overmolding of the electronic component; The ratio of the viscosity V90 of the sheet 90 seconds after the start of the measurement to the viscosity V0 0 seconds after the start of the measurement (V90 / V0), i.e., the thickening rate, was less than 9 at a measurement temperature of 125° C. and a measurement time of 150 seconds.

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