Electronic component protective sheet, electronic component mounting substrate, method for covering and protecting electronic component group mounting substrate, and method for manufacturing electronic component group mounting substrate

Abstract

To provide an electronic part protection sheet which is excellent in temporary sticking properties, releasability and migration resistance, and which can be applied also to an electronic part group mounting board having electronic parts with different heights by further good embeddability.SOLUTION: There is provided an electronic part protection sheet for coating and protecting a plurality of electronic parts that are mounted on a board and have different heights. The electronic part protection sheet has a plurality of insulating resin layers with different Young's modulus at 23°C. In the electronic part protection sheet, the adhesive force of a surface in contact with an electronic part group, the adhesive force being measured by a probe tack test, is 0.3-5 N; the adhesive force of an opposite surface, the adhesive force being measured by a probe tack test, is 1 N or less; and the adhesive force of a surface in contact with the electronic part group, the adhesive force being measured by a probe tack test, is greater than a probe tack on the opposite surface.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an electronic component protection sheet for covering and protecting a group of electronic components, consisting of a plurality of electronic components of different heights mounted on the surface of a substrate, along with at least a portion of the surface of the substrate. [Background technology]

[0002] In order to protect electronic components such as IC chips mounted on a substrate from bending or impact to the substrate, and from thermal shock due to temperature changes, the electronic components are covered with resin, either partially or entirely, on the substrate. In recent years, with the remarkable improvement in performance and miniaturization of the electronic components and substrate circuits being protected, the level of protective function required of the covering and protective materials has been increasing. As a method for covering and protecting electronic components, a solvent-free, heat-meltable electronic component protection sheet formed into a sheet has been proposed as an alternative to the conventional conformal coating method. For example, Patent Document 1 discloses a moisture-proof sheet for electronic device components, which is characterized by having a moisture-proof layer made of a forming material whose main component is an aromatic vinyl-conjugated diene block copolymer. Patent Document 2 discloses a substrate protection sheet made of a graft copolymer of an olefin-based monomer, an ethylenically unsaturated carboxylic acid, and an aromatic ethylenically unsaturated monomer. Patent Documents 3 and 4 disclose sheet-shaped resin compositions comprising an epoxy resin, an inorganic filler, and a flame retardant. Patent Document 5 discloses a sealing film for sealing an electronic component mounting board, which includes an insulating layer and an electromagnetic wave shielding layer. Patent Document 6 discloses a manufacturing method for a mounting structure in which a mounting component and a substrate are covered with a laminated sheet having a first thermally conductive layer and a second thermally conductive layer, and FIG. 3(b) discloses a manufacturing method in which the spaces between the mounting components are completely filled with the cured product of the laminated sheet, without leaving any gaps. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-145687 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-06954 [Patent Document 3] Japanese Patent Application Laid-Open No. 2011-246596 [Patent Document 4] Japanese Patent Application Laid-Open No. 2012-054363 [Patent Document 5] Japanese Patent Application Publication No. 2019-021757 [Patent Document 6] WO2019 / 065976 DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0004] However, when using a conventional protective sheet to cover and protect an electronic component mounting board in which the height of the mounted electronic components is not uniform, as shown in Figure 2(a) and Figure 3(a), the protective sheet can shift horizontally as shown in Figure 2(b) or tilt due to tall electronic components as shown in Figure 3(b), resulting in the formation of a protective film in an unintended location. In other words, the protective sheet is required to adhere to the intended electronic components without shifting or tilting (hereinafter referred to as temporary adhesion). Furthermore, the surface of the protective sheet opposite to the intended surface to be placed on the electronic component mounting substrate may stick to the pickup device used to place the protective sheet on the electronic component mounting substrate, hindering rapid placement on the electronic component mounting substrate and reducing productivity. In other words, the protective sheet is required to be quickly released from the pickup device (hereinafter referred to as releasability). Furthermore, conventional protective sheets have had the problem that after forming a protective coating film, migration occurs in conductive parts (such as solder bumps) between electronic components over long-term use (hereinafter referred to as migration resistance). Furthermore, conventional protective sheets lack the ability to fill gaps between electronic components and uneven surfaces of electronic components (hereinafter referred to as "fillability").

[0005] The present invention provides an electronic component protection sheet that has excellent temporary application properties, releasability, and migration resistance, and further has good embeddability, making it applicable to electronic component group mounting boards having electronic components of different heights. [Means for solving the problem]

[0006] As a result of extensive research, the inventors have found that the above-mentioned problems can be solved by using an electronic component protection sheet for covering and protecting a group of electronic components mounted on a substrate by applying heat and pressure, the electronic component protection sheet having an insulating resin layer containing a thermosetting resin, and characterized in that the adhesive strengths of the surface in contact with the group of electronic components and the surface opposite the group of electronic components, as determined by a probe tack test, are each within a predetermined range, and the adhesive strength of the surface in contact with the group of electronic components is greater than the adhesive strength of the surface opposite the group of electronic components, and have thus completed the present invention.

[0007] That is, the present invention provides an electronic component protection sheet for covering and protecting a group of electronic components consisting of a plurality of electronic components of different heights mounted on a substrate, the electronic component protection sheet comprising: the electronic component protection sheet has an insulating resin layer containing a thermosetting resin, The adhesive strength of the surface that comes into contact with electronic components is 0.3 to 5 N in a probe tack test. The electronic component protection sheet has an adhesive strength of 1 N or less on the opposite surface in a probe tack test, and the adhesive strength of the surface in contact with a group of electronic components in a probe tack test is greater than the adhesive strength of the opposite surface in a probe tack test.

[0008] Furthermore, the present invention provides a method for manufacturing a semiconductor device, comprising the steps of: mounting a group of electronic components, each of which has a plurality of electronic components having different heights, on a substrate; A step of preparing the electronic component protection sheet according to the present invention; placing the electronic component protective sheet so that the tallest electronic component among the group of electronic components is in contact with the first insulating resin layer of the electronic component protective sheet; a step of deforming the electronic component protection sheet by applying heat and pressure so as to conform to the shapes of the individual electronic components, thereby covering the group of electronic components and at least a portion of the substrate; and The deformed electronic component protection sheet is thermally cured in a deformed state to form a coating protective layer. The present invention relates to a method for covering and protecting an electronic component mounting board.

[0009] Furthermore, the present invention provides a method for manufacturing a semiconductor device, comprising the steps of: mounting a group of electronic components, each of which has a plurality of electronic components having different heights, on a substrate; A step of preparing the electronic component protection sheet according to the present invention; placing the electronic component protective sheet so that the tallest electronic component among the group of electronic components is in contact with the first insulating resin layer of the electronic component protective sheet; a step of deforming the electronic component protection sheet by applying heat and pressure so as to conform to the shapes of the individual electronic components, thereby covering the group of electronic components and at least a portion of the substrate; and The deformed electronic component protection sheet is thermally cured in a deformed state to form a coating protective layer. The present invention relates to a method for manufacturing an electronic component mounting substrate with a protective coating layer. [Effects of the Invention]

[0010] The present invention provides an electronic component protection sheet that has excellent temporary application properties and releasability, as well as good migration resistance and embeddability, thereby enabling highly reliable electronic component mounting substrates to be provided with a high yield. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is an explanatory diagram of a method for covering and protecting electronic components using an electronic component protection sheet according to the present invention. [Figure 2] FIG. 10 is an explanatory diagram of a conventional electronic component protection sheet when placed. [Figure 3] FIG. 10 is an explanatory diagram of a conventional electronic component protection sheet when placed. [Figure 4] FIG. 2 is a schematic cross-sectional view illustrating a migration resistance test in an example. [Figure 5] FIG. 2 is a schematic cross-sectional view for explaining an embeddability test in an example. DETAILED DESCRIPTION OF THE INVENTION

[0012] An example of an embodiment to which the present invention is applied will be described below. Note that the size and ratio of each component in the following figures are for convenience of explanation and are not limited thereto. Furthermore, in this specification, the expression "any number A to any number B" means that the range includes number A as the lower limit and number B as the upper limit. Furthermore, in this specification, "sheet" includes not only "sheet" as defined by JIS, but also "film." Furthermore, the numerical values ​​specified in this specification are values ​​determined by the methods disclosed in the embodiments or examples. The adhesive strength determined by the probe tack test may also be abbreviated as probe tack adhesive strength or adhesive strength.

[0013] <Method for covering and protecting electronic component mounting boards> First, a method for covering and protecting an electronic component mounting substrate using the electronic component protective sheet of the present invention (hereinafter sometimes abbreviated as covering and protecting method, covering method, or protecting method) will be described. The method for covering and protecting an electronic component-group-mounted substrate of the present invention includes the following steps: mounting an electronic component group consisting of multiple electronic components of different heights on a substrate (step i), preparing an electronic component protective sheet of the present invention described below (step ii), placing an electronic component protective sheet so that the tallest electronic component of the group is in contact with the first insulating resin layer of the electronic component protective sheet (step iii, also referred to as a temporary attachment step), deforming the electronic component protective sheet by applying heat and pressure to conform to the shapes of each electronic component and thereby covering at least a portion of the electronic component group and the substrate (step iv), and thermally curing the deformed electronic component protective sheet in its deformed state to form a covering protective layer (step v). Steps iv and v can be performed consecutively.

[0014] Hereinafter, steps iii to v will be described with reference to FIG. 1 as to the method for covering and protecting an electronic component group mounting board by applying heat and pressure using an electronic component protection sheet.

[0015] (Step iii: Electronic component protection sheet placement step) An electronic component mounting substrate 4 is prepared, in which electronic components 2a and 2b are mounted on a substrate 1 via solder bumps 3. The electronic components 2 are semiconductor chips, capacitors, transistors, inductors, thermistors, etc., and are mounted on the substrate 1 via the solder bumps 3, with a gap between the electronic components 2a and 2b and the substrate 1. Furthermore, the electronic component 2a is designed to be higher than the electronic component 2b. Next, the electronic component protection sheet 10, cut to a predetermined size, is placed on the mounting surfaces of the electronic components 2a and 2b so that the first insulating resin layer 11 contacts the electronic components 2a. Due to the height of the electronic components 2a, the first insulating resin layer 11 comes into contact with the electronic components 2a and is temporarily attached. Note that the electronic component protection sheet 10 may bend and come into contact with the electronic components 2b (not shown in FIG. 1). The first insulating resin layer 11 has a Young's modulus of 5 MPa to 200 MPa at 23°C and is tacky, so it is unlikely to become misaligned after placement.

[0016] Furthermore, a cushioning material 13 may be laminated further outside the insulating resin layer located furthest away, and Fig. 1 shows an example in which a cushioning material is used. Cushioning material 13 may be laminated after electronic component protection sheet 10 is placed, or a laminate in which electronic component protection sheet 10 and cushioning material 13 are previously placed may be placed. Cushioning material 13 is a material that softens or melts when heated and pressurized, and has the function of promoting conformability of electronic component protection sheet 10 to electronic components 2a, 2b and to the gaps between the electronic components. The cushion material 13 is not particularly limited as long as it is a thermoplastic material, but it is preferable that the melting temperature and glass transition point (Tg) are lower than the temperature at which pressure is applied. Suitable examples include polyolefin film, vinyl chloride film, and PVA film. Depending on the depth of the groove, it is usually about 100 μm to 1 mm. When multiple cushion materials 13 are laminated, it is preferable that the total thickness is within this range.

[0017] The thickness of electronic component protection sheet 10 is preferably set to be 0.05 to 2 times the height of the tallest electronic component among the electronic components to be protected. The electronic component mounting board shown in this application is just an example, and the structure of the electronic components and board is not particularly limited, and there may or may not be a gap between electronic components 2a, 2b and board 1. The positions at which the electronic components are mounted are not limited, and the number of electronic components is two or more.

[0018] (Step iv: Covering process with electronic component protection sheet) Next, heating and pressing are performed using a heating and pressing machine 20, whereby the electronic component protection sheet 10 is deformed to conform to the shapes of the individual electronic components, i.e., to conform to the top and side surfaces of electronic components 2a, 2b, and to conform to at least a portion of the electronic component group and substrate 1. The cushioning material 20 softens or melts due to the heat, facilitating the electronic component protection sheet 10 to conform to the irregularities between electronic components on the electronic component mounting substrate 4. It is also preferable to use a release sheet between the heating and pressing machine 20 and the cushioning material 13 during heating and pressing. The release sheet is a sheet made of a base material such as paper or plastic that has been subjected to a known release treatment. Alternatively, a plastic sheet with low polarity such as Teflon (registered trademark) can also be used.

[0019] The heating temperature may be any temperature at which the electronic component protection sheet softens appropriately, deforms to conform to the shapes of the individual electronic components, and penetrates into the gaps between the individual electronic components, and is preferably 100 to 260°C, and more preferably 120 to 240°C. If the temperature is too low, the electronic component protection sheet 10 will not penetrate into the gaps between the individual mounted electronic components. On the other hand, if the temperature is too high, the thermosetting reaction of the thermosetting resin in the electronic component protection sheet 10 will proceed too quickly, and the electronic component protection sheet will not penetrate into the gaps between the mounted electronic components. The pressure when heating and pressing is preferably 0.01 to 10 MPa, more preferably 0.1 to 6.0 MPa. By heating and pressing at the above pressure, the embedding property is further improved without damaging the electronic component. The heating time is usually 0.5 to 30 minutes, preferably 1 to 20 minutes. If the heating time is too short, the electronic component protection sheet will not penetrate easily between the mounted electronic components. On the other hand, if the heating time is too long, the thermosetting resin is more likely to undergo thermal decomposition or oxidation, increasing the possibility of reduced reliability of the bonded area due to reaction products, etc. The heating and pressurizing step is preferably carried out in a vacuum. As a method of heating and pressing, in addition to using a heating and pressing machine, a method in which metal plates of an appropriate weight are stacked so as to achieve a predetermined pressure, and the stack is then placed in an oven is also preferred. On the other hand, as a heating and pressurizing method other than the heating and pressurizing machine, vacuum forming or vacuum pressure forming is also preferred.

[0020] (Step v: Hardening process of the deformed electronic component protection sheet) After heating and pressing, the deformed electronic component protection sheet is further heated in its deformed state at a temperature of 150°C to 230°C for 10 to 60 minutes to thermally cure the thermosetting resin in the insulating resin layer located furthest from the electronic component and the first insulating resin layer, forming a protective coating layer. The protective coating layer firmly adheres to the electronic component and the substrate and functions as a protective layer to prevent and protect the electronic component from damage due to external impacts and scratches. Furthermore, by heating and pressing at a temperature of 150°C or higher for 30 minutes or longer in step (iv), the thermal curing can be completed and the protective coating layer formed. The protective coating layer must be an insulator to prevent short circuits between electronic components, and a surface resistance of 1+E10 Ω or higher is required.

[0021] <Electronic component protection sheet> Next, the electronic component protective sheet of the present invention will be described. As described above, the electronic component protective sheet is used to cover and protect a group of electronic components mounted on a substrate, and has an insulating resin layer containing a thermosetting resin. The insulating resin layer has an adhesive strength of 0.3 to 5 N in a probe tack test on the surface that contacts the electronic components, and an adhesive strength of 1 N or less in a probe tack test on the opposite surface, with the adhesive strength of the surface that contacts the electronic components being greater than the adhesive strength of the opposite surface. The adhesive strength of the surface that contacts the electronic components is more preferably 0.5 to 4 N, and even more preferably 1 to 3.5 N. By making the adhesive strength of the surface that contacts the electronic components 0.5 N or more, temporary adhesion properties are improved. By making the adhesive strength of the surface that contacts the electronic components 5 N or less, reworkability can be achieved. The adhesive strength of the opposite surface as determined by a probe tack test is preferably 1 N or less, more preferably 0.5 N or less, and even more preferably 0.3 N or less. By setting the adhesive strength of the opposite surface to 1 N or less, releasability is improved. Furthermore, by having the adhesive strength of the surface in contact with the electronic components as determined by a probe tack test be greater than the adhesive strength of the opposite surface, reworkability and releasability are improved. The difference between the adhesive strength of the surface in contact with the electronic components as determined by a probe tack test and the adhesive strength of the opposite surface as determined by a probe tack test is preferably at least 0.3 N, more preferably at least 0.5 N, and even more preferably 0.7 N. By keeping the difference within the above range, both releasability and temporary adhesion can be achieved at a high level.

[0022] In this application, the adhesive strength measured by the probe tack test refers to the force (peel force) detected when a stainless steel probe with a diameter of 5 mm (200 g including a weight) is brought into contact with the surface of the insulating resin layer to be measured for 1 second and then the probe is removed from the surface of the insulating resin layer at a speed of 10 mm / second. When the electronic component protection sheet is constructed as a single layer, probe tack can be controlled by UV curing one side or by orienting the content of the inorganic filler in the layer, which will be described later, on one side.

[0023] From the viewpoint of controlling probe tack, an embodiment in which the electronic component protective sheet is formed from multiple insulating resin layers is also preferable. In this case, the insulating resin layers are composed of at least a first insulating resin layer that contacts the electronic components and a second insulating resin layer that is located farthest from the electronic components. In this case, the adhesive strength of the first insulating resin layer in a probe tack test is 0.3 to 5 N, and the adhesive strength of the second insulating resin layer in a probe tack test is 1 N or less.

[0024] Furthermore, the Young's modulus of the above-mentioned first insulating resin layer at 23°C is preferably 5 MPa to 200 MPa, and the Young's modulus of the second insulating resin layer at 23°C is preferably 8 MPa or more higher than the Young's modulus of the first insulating resin layer at 23°C, more preferably 20 MPa or more higher, and even more preferably 50 MPa or more higher. Since the Young's modulus of the second insulating resin layer at 23°C is higher than the Young's modulus of the first insulating resin layer at 23°C, an electronic component protection sheet with excellent temporary adhesion properties, release properties, migration resistance, and embeddability can be obtained.

[0025] <First insulating resin layer> The Young's modulus of the first insulating resin layer at 23°C (hereinafter referred to as Young's modulus (1)) is preferably 5 MPa to 200 MPa, more preferably 20 MPa to 150 MPa, and even more preferably 30 MPa to 100 MPa. By making the Young's modulus (1) 5 MPa or more, conformability to the grooves between electronic components is improved, and by making it 200 MPa or less, temporary adhesion properties are improved. In the present invention, the "Young's modulus at 23°C" can be determined as follows: A sample is left to stand for 24 hours in an environment of 23°C and 50% relative humidity, and then measurement is performed in the same environment. Specifically, a sample with a chuck distance of 25 mm is pulled using a tensile tester at a pulling rate of 50 mm / min, a stress-strain curve is measured, and the linear regression (slope) in the strain (elongation) range of 0.1 to 1% is taken as the Young's modulus at 23°C. The Young's modulus (1) can be controlled by adjusting the type and amount of the thermosetting resin, thermosetting agent, and inorganic filler, which will be described later, or by using a tackifying resin or a thermoplastic resin in combination.

[0026] The first insulating resin layer preferably has a storage modulus at 23°C (hereinafter referred to as storage modulus (1)) of 1.0+E04 Pa to 1.0+E07 Pa. By making the storage modulus (1) 1.0+E04 Pa or more, embeddability is improved, and by making it 1.0+E07 Pa or less, migration resistance is improved. The storage modulus in the present invention refers to the value of the storage modulus at 23°C measured on a measurement sample using a dynamic elastic modulus measuring device DVA-200 (manufactured by IT Measurement & Control Co., Ltd.) under the conditions of a deformation mode of "tensile", a frequency of 10 Hz, a heating rate of 10°C / min, and a measurement temperature range of -50 to 300°C.

[0027] The first insulating resin layer can be formed from a thermosetting resin composition containing a thermosetting resin. The adhesive strength of the first insulating resin layer in a probe tack test is 0.3 to 5 N, so that the first insulating resin layer firmly adheres to the electronic component during temporary attachment, preventing misalignment. Furthermore, the first insulating resin layer can be peeled off and repositioned when correcting the temporary attachment position, providing excellent reworkability. The thermosetting resin composition preferably contains a thermosetting agent, an inorganic filler, a flame retardant, etc. By using these, the above-mentioned Young's modulus at 23°C, storage modulus, and probe tack can be adjusted to a suitable range. [Thermosetting resin] Suitable examples of thermosetting resins include polyurethane resins, polyurethane urea resins, acrylic resins, polyester resins, polyamide resins, epoxy resins, polystyrene, polycarbonate resins, polyamideimide resins, polyesteramide resins, polyetherester resins, and polyimide resins. The thermosetting resin may have a self-crosslinkable functional group. For example, when used under harsh conditions during reflow, the thermosetting resin preferably contains at least one of epoxy resins, urethane resins, urethane urea resins, polycarbonate resins, and polyamides. Furthermore, as long as the resin can withstand embedding, a thermosetting resin and a thermoplastic resin can be used in combination.

[0028] The reactive functional group of the thermosetting resin may be a carboxyl group, a hydroxyl group, an epoxy group, etc. When the thermosetting resin has a carboxyl group, the acid value of the thermosetting resin is preferably 3 to 30 (mgKOH / g), more preferably 4 to 20 (mgKOH / g), and even more preferably 5 to 15 (mgKOH / g), from the viewpoints of embedding property in step iv and migration resistance after curing. When the acid value of the thermosetting resin is within the above range, the curing speed in step iv can be appropriately slowed, so that embeddability is not easily impaired and sufficient crosslink density can be secured, thereby achieving good migration resistance.

[0029] The weight average molecular weight Mw of the thermosetting resin is preferably 20,000 to 200,000. By making it 20,000 or more, it is possible to effectively improve the releasability and temporary adhesion properties. Furthermore, by making it 200,000 or less, it is possible to obtain the effect of improving the embeddability.

[0030] [Hardening agent] A curing agent is preferably used to promote the curing of the thermosetting resin. After the electronic component protection sheet is thermally melted and deformed and comes into contact with the substrate and electronic components, the curing agent thermally crosslinks with the reactive functional groups of the thermosetting resin, thereby strengthening adhesion to the substrate and electronic components and improving migration resistance. The curing agent has a plurality of functional groups capable of reacting with the functional groups of the thermosetting resin. Examples of the curing agent include known compounds such as epoxy compounds, acid anhydride group-containing compounds, imidazole compounds, isocyanate compounds, aziridine compounds, amine compounds, and phenol compounds. Epoxy compounds and aziridine compounds are preferred, and a combination of both is particularly preferred.

[0031] The epoxy compound is a compound having two or more epoxy groups in one molecule. Regarding the properties of the epoxy compound, using a liquid epoxy compound can reduce the Young's modulus. On the other hand, using a solid epoxy compound can increase the Young's modulus. It is preferable to use an epoxy compound that is liquid at 23°C for the first insulating resin layer to reduce the Young's modulus and impart tackiness. As the epoxy compound, for example, a glycidyl ether type epoxy compound, a glycidyl amine type epoxy compound, a glycidyl ester type epoxy compound, a cyclic aliphatic (alicyclic) epoxy compound, or the like is preferred.

[0032] Examples of glycidyl ether type epoxy compounds include bisphenol A type epoxy compounds, bisphenol F type epoxy compounds, bisphenol S type epoxy compounds, bisphenol AD ​​type epoxy compounds, cresol novolac type epoxy compounds, phenol novolac type epoxy compounds, α-naphthol novolac type epoxy compounds, bisphenol A type novolac type epoxy compounds, dicyclopentadiene type epoxy compounds, tetrabromobisphenol A type epoxy compounds, brominated phenol novolac type epoxy compounds, tris(glycidyloxyphenyl)methane, and tetrakis(glycidyloxyphenyl)ethane.

[0033] Examples of the glycidylamine type epoxy compound include tetraglycidyldiaminodiphenylmethane, triglycidyl paraaminophenol, triglycidyl meta-aminophenol, and tetraglycidyl meta-xylylenediamine.

[0034] Examples of the glycidyl ester type epoxy compound include diglycidyl phthalate, diglycidyl hexahydrophthalate, and diglycidyl tetrahydrophthalate.

[0035] Examples of cyclic aliphatic (alicyclic) epoxy compounds include epoxycyclohexylmethyl-epoxycyclohexanecarboxylate, bis(epoxycyclohexyl)adipate, and the like.

[0036] Examples of the aziridine compound include trimethylolpropane-tri-β-aziridinylpropionate, tetramethylolmethane-tri-β-aziridinylpropionate, N,N'-diphenylmethane-4,4'-bis(1-aziridinecarboxamide), and N,N'-hexamethylene-1,6-bis(1-aziridinecarboxamide).

[0037] Examples of the imidazole compound include imidazole compounds such as 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenyl-4-methylimidazole, 2,4-dimethylimidazole, and 2-phenylimidazole. Further examples include latent curing accelerators with improved storage stability, such as a type insoluble in a solvent obtained by reacting an imidazole compound with an epoxy resin, or a type in which an imidazole compound is encapsulated in microcapsules.

[0038] The amount of the curing agent is preferably 3 to 100 parts by mass, more preferably 5 to 60 parts by mass, and even more preferably 5 to 40 parts by mass, relative to 100 parts by mass of the total thermosetting resin. By using the above amount, the adhesive strength, Young's modulus at 23°C, and storage modulus can be adjusted to suitable values.

[0039] Furthermore, it is preferable to use a tackifier resin or a thermoplastic resin in addition to a thermosetting resin for the first insulating resin layer from the viewpoint of improving adhesive strength. Examples of tackifying resins include rosin resins, terpene resins, alicyclic petroleum resins, and aromatic petroleum resins. Suitable examples of thermoplastic resins include polyolefin resins, vinyl resins, styrene-acrylic resins, diene resins, terpene resins, petroleum resins, cellulose resins, polyamide resins, polyurethane resins, polyester resins, polycarbonate resins, and fluorine resins.

[0040] [Inorganic filler] The first insulating resin layer preferably further contains an inorganic filler, which can appropriately increase the adhesive strength, Young's modulus at 23°C, and storage modulus, thereby improving migration resistance, embeddability, and releasability.

[0041] Examples of inorganic fillers include silica, alumina, magnesium hydroxide, barium sulfate, calcium carbonate, titanium oxide, zinc oxide, antimony trioxide, magnesium oxide, talc, kaolinite, mica, basic magnesium carbonate, sericite, and monmo. Lilo No to, Examples of such fillers include inorganic compounds such as bentonite, boron nitride, aluminum nitride, and magnesium oxide (hereinafter referred to as inorganic fillers in the narrow sense), and ion collectors, which will be described later. Among these, silica, talc, mica, kaolinite, or montmorillonite is preferred, and silica and talc are more preferred, from the viewpoint of further improving migration resistance and embeddability.

[0042] The shape of the inorganic filler in the narrow sense is preferably scaly (flake-like). By making the inorganic filler scaly, warping of the electronic component protection sheet during heating and cooling can be suppressed, and embeddability can be further improved. Here, scaly includes thin flakes and plates. The inorganic filler may be scaly as long as the particles as a whole are oval, circular, or may have notches around the fine particles.

[0043] The average particle diameter D50 of the inorganic filler in the narrow sense is preferably 0.5 to 10 μm, and more preferably 0.7 to 7 μm. By making the average particle diameter 0.5 or more, embeddability is improved. By making the average particle diameter D50 10 μm or less, migration resistance can be further improved. The average particle size is the D50 average particle size obtained by measuring the inorganic filler in the narrow sense using a laser diffraction / scattering particle size distribution analyzer LS 13320 (manufactured by Beckman Coulter) with a Tornado dry powder sample module, and is the particle size at which the cumulative value in the particle size cumulative distribution is 50%. During the measurement, the refractive index of the inorganic filler in the narrow sense was set to 1.6.

[0044] The content of the narrowly defined inorganic filler in the first insulating resin layer is preferably 1 to 50 parts by mass, more preferably 5 to 40 parts by mass, and even more preferably 10 to 35 parts by mass, per 100 parts by mass of the thermosetting resin. By setting the content of the narrowly defined inorganic filler within the above range, the Young's modulus can be adjusted to a suitable range, and migration resistance and embeddability can be improved.

[0045] [Ion collector] Ion collectors are also preferred as inorganic fillers. Ion collectors include cation collectors, anion collectors, and amphoteric ion collectors. These ion collectors can be used alone or in combination of two or more. Among these, it is preferable to use cation collectors and amphoteric ion collectors in terms of improving migration resistance. Cation collectors are particularly preferred. The ion collector may be contained in the first insulating resin layer, or may also be contained in the second insulating resin layer described below, or may be contained in both layers.

[0046] Examples of cation scavenger include manganese compounds (e.g., hydrous manganese dioxide), antimony compounds (e.g., crystalline antimonic acid, hydrous antimony pentoxide), zirconium compounds (e.g., zirconium hydroxide, zirconium phosphate, zirconium molybdate, zirconium tungstate), silicate compounds (e.g., aluminosilicates, synthetic aluminosilicates), phosphate compounds (e.g., titanium phosphate, tin phosphate), cerium(III) oxalate, ammonium molybdophosphate, potassium hexacyanoferrate(III) cobalt(II), natural green sand, stabilized green sand, and Mn2+-type green sand, which can be used alone or in combination. Among these, antimony compounds and zirconium compounds have a high ability to capture cations, thereby improving migration resistance. As the cation scavenger, known products such as IXE-100 and IXE-300 (manufactured by Toagosei Co., Ltd.) can be used.

[0047] Furthermore, anion scavenger can also be used. Examples of anion scavenger include bismuth compounds (such as hydrated bismuth oxide and hydrated bismuth nitrate), magnesium-aluminum composite oxides (such as magnesium aluminum hydrotalcite), and phosphate compounds (such as lead hydroxide phosphate). These can be used alone or in combination of two or more. Among these, magnesium-aluminum composite oxides are preferred because of their high ability to capture anions. As the anion scavenger, known products such as IXE-500, IXE-530, IXE-550, IXE-700F, IXE-700D, and IXE-800 (manufactured by Toagosei Co., Ltd.) can be used.

[0048] The amphoteric ion collector includes a cation collector and an anion collector, and is preferably a mixture of a cation collector appropriately selected from the zirconium compounds, antimony compounds, phosphate compounds, etc., and an anion collector appropriately selected from the bismuth compounds, magnesium-aluminum compounds, etc., as already explained.

[0049] As the ion collector, known products such as IXEPLAS-A1, IXEPLAS-A2, IXEPLAS-B1, IXE-600, IXE-633, IXE-6107, and IXE-6136 (manufactured by Toagosei Co., Ltd.) can be used.

[0050] The average particle diameter D50 of the ion collector is preferably 0.1 to 10 μm, and more preferably 0.1 to 3 μm. By making the average particle diameter 0.1 or more, embeddability is improved. By making the average particle diameter D50 10 μm or less, migration resistance can be further improved. The average particle size is determined in the same manner as for the inorganic filler in the narrow sense described above.

[0051] The ion collector is preferably blended in an amount of 0.1 to 20 parts by mass, more preferably 0.3 to 10 parts by mass, per 100 parts by mass of the thermosetting resin. By blending 0.1 to 20 parts by mass, it becomes easier to obtain an electronic component mounting substrate with a coating protective layer having improved migration resistance.

[0052] The thickness of the first insulating resin layer in the protective sheet of the present invention is preferably 10 to 150 μm, more preferably 50 to 130 μm. By setting the thickness within the above range, both temporary adhesion property and embeddability can be achieved.

[0053] <Second insulating resin layer> In the electronic component protection sheet of the present invention, the second insulating resin layer is located farthest from the electronic components, and has an adhesive strength of 1 N or less in a probe tack test. In addition, the Young's modulus at 23°C (hereinafter referred to as Young's modulus (2)) is preferably 30 MPa to 1000 MPa, more preferably 50 MPa to 800 MPa, and even more preferably 70 MPa to 500 MPa. By setting the adhesive strength to 1 N or less, releasability is improved. Furthermore, by setting the Young's modulus (2) to 30 MPa or more, breakage of the electronic component protection sheet at the corners of the electronic components (hereinafter referred to as crack resistance) is suppressed, and by setting it to 1000 MPa or less, conformability to the grooves between electronic components is improved. The method for determining the Young's modulus (2) is the same as that for the first insulating resin layer described above.

[0054] The second insulating resin layer preferably has a storage modulus at 23°C (hereinafter referred to as storage modulus (2)) of 1.0+E06 Pa to 1.0+E10 Pa. By making the storage modulus (2) 1.0+E06 Pa or more, the release property is improved, and by making it 1.0+E10 Pa or less, the migration resistance is improved. The storage modulus (2) is determined in the same manner as in the case of the first insulating resin layer described above.

[0055] The second insulating resin layer, like the first insulating resin layer, can be formed from a thermosetting resin composition containing a thermosetting resin. The thermosetting resin composition preferably contains a curing agent, an inorganic filler in the narrow sense, an ion scavenger, a flame retardant, etc. By using these, the Young's modulus and storage modulus at 23°C can be adjusted to the preferred ranges, thereby improving the releasability, embeddability, etc.

[0056] The thermosetting resin may be the same as that for the first insulating resin layer, and the acid value, weight average molecular weight, etc. may also be the same.

[0057] Examples of the curing agent include the same ones as those in the case of the first insulating resin layer described above, and it is preferable to use an epoxy compound and an aziridine compound in combination. The Young's modulus can be increased by using an epoxy compound that is solid at 23°C as the epoxy compound. The amount of the curing agent is preferably 3 to 100 parts by mass, more preferably 5 to 60 parts by mass, and even more preferably 5 to 40 parts by mass, relative to 100 parts by mass of the total thermosetting resin. By using the above amount, the Young's modulus and storage modulus at 23°C can be adjusted to suitable values.

[0058] As for the inorganic filler and ion collector in the narrow sense, the same ones as those in the first insulating resin layer can be exemplified. From the viewpoint of improving releasability, the amount of inorganic filler in the narrow sense is preferably 5 to 70 parts by mass, more preferably 7 to 55 parts by mass, and even more preferably 10 to 35 parts by mass, per 100 parts by mass of the thermosetting resin in total. From the viewpoint of improving migration resistance, the amount of the ion collector to be blended is preferably 5 to 40 parts by mass, more preferably 7 to 30 parts by mass, and even more preferably 10 to 25 parts by mass, per 100 parts by mass of the thermosetting resin in total.

[0059] The second insulating resin layer may further contain a colorant, a silane coupling agent, an antioxidant, a plasticizer, an ultraviolet absorber, a leveling adjuster, and the like, as required.

[0060] The thickness of the second insulating resin layer in the protective sheet of the present invention is preferably from 1 to 75 μm, more preferably from 5 to 50 μm. By setting the thickness within the above range, the embedding ability between electronic components can be improved.

[0061] <Middle class> The protective sheet of the present invention can further include an insulating resin layer containing a thermosetting resin as an intermediate layer between the first insulating resin layer and the second insulating resin layer. The Young's modulus of the intermediate layer at 23°C (hereinafter also referred to as Young's modulus (3)) preferably satisfies the following formula: By satisfying the following formula, temporary adhesion and migration resistance are improved, and the intermediate layer relieves the pressure in the heat pressing process, resulting in a coated protective film that is less susceptible to cracking. Young's modulus (2) > Young's modulus (3) > Young's modulus (1) (Equation 1)

[0062] The breaking elongation at 23°C of each of the first insulating resin layer, the second insulating resin layer, and the optional intermediate layer that constitute the protective sheet of the present invention is preferably 50 to 1500%, more preferably 100 to 1400%. By ensuring this range, conformability to the uneven shape in step iv can be improved, and multiple electronic components of different heights can be appropriately coated and protected. In the present invention, the elongation percentage is defined as 100% when a sample is stretched to a length of 100 mm and breaks at 200 mm. The method for measuring the elongation percentage will be described in detail in the Examples.

[0063] Furthermore, in the electronic component protection sheet of the present invention, a hard coat layer or a fiber layer can be laminated on the outer side of the second insulating resin layer from the viewpoint of improving protection.

[0064] <Method of manufacturing electronic component protection sheet> The method for producing an electronic component protective sheet involves coating an insulating resin composition for a first insulating resin layer on a release sheet and drying it to form the first insulating resin layer. Similarly, separately, a release sheet is coated with an insulating resin composition for an insulating resin layer intended to be positioned farthest from the electronic component group and drying it to form the insulating resin layer intended to be positioned farthest from the electronic component group. The two insulating resin layers are then superimposed to form the protective sheet. Alternatively, one of the insulating resin compositions may be coated on a release sheet and dried to form one of the insulating resin layers, and the other insulating resin composition may be directly coated on the resin layer and dried to form the other insulating resin layer. In the case of an embodiment in which a cushioning material is provided, the cushioning material can be provided by peeling off the release sheet on the insulating resin layer intended to be located farthest from the electronic components and laminating the cushioning material on top of it. Alternatively, the thermosetting resin composition may be applied directly to the cushioning material to form the insulating resin layer intended to be located farthest from the electronic components, and then the first insulating resin layer may be formed.

[0065] <Applications of electronic component protection sheets> The electronic component protection sheet of the present invention exhibits practically sufficient adhesion regardless of whether the substrate is metal, resin, fiber, ceramic, glass, or conductive silicon. Metals that can be used include aluminum, copper, brass, stainless steel, iron, and chromium. Resins that can be used include epoxy resin, polyethylene terephthalate, polyimide, polyamide, polyethylene, polypropylene, polyolefin graft polymer, polystyrene, and polyvinyl chloride. Therefore, the electronic component protection sheet can also be used effectively to bond different materials with different polarities. The protective sheet for electronic components of the present invention can be suitably used to protect various substrates, namely, rigid substrates, FPC substrates, and the like.

[0066] The electronic parts using the electronic part protective sheet of the present invention are preferably provided in electronic devices such as liquid crystal displays, touch panels, notebook PCs, mobile phones, smartphones, and tablet terminals. [Example]

[0067] The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples. Note that the "parts" and "%" below are values ​​based on "parts by mass" and "% by mass", respectively. Furthermore, Examples 1 to 4, 7 to 10, 12 to 15, 25, and 30 are to be read as reference examples in order to conform to the claims.

[0068] The raw materials used in the examples are listed below. <Thermosetting resin> [Synthesis of thermosetting resin 1] A glass flask equipped with a stirrer, thermometer, reflux condenser, nitrogen inlet tube, and pressure reducing equipment was charged with 166 parts of terephthalic acid, 146 parts of adipic acid, 212 parts of 3-methyl-1,5-pentanediol, and 25 parts of ethylene glycol. The mixture was stirred while passing nitrogen gas through the flask. The temperature was gradually raised under normal pressure and the mixture was allowed to react at 200-230°C for approximately 8 hours, yielding a liquid with an acid value of 43. Next, 0.01 parts of tetra-n-butoxytitanium was added, and after nitrogen substitution, the mixture was stirred at 180°C for 30 minutes in a sealed container. The mixture was then allowed to react for 2 hours at 230°C and 5 mmHg, yielding a polyester diol with an acid value of 1.1, a hydroxyl value of 114.2, a molecular weight of 982, and a hue of 10 (APHA method, the same applies below). Next, 734 parts of the polyester diol, 23.9 parts of dimethylolpropionic acid, 219 parts of toluene diisocyanate, and 242 parts of toluene were placed in a reaction vessel equipped with a stirrer, thermometer, reflux condenser, dropping device, and nitrogen inlet tube, and reacted for 8 hours at 50° C. under a nitrogen atmosphere. To this was added 1,200 parts of toluene to obtain a solution of a urethane prepolymer having an isocyanate group at its terminal. Next, the obtained prepolymer solution was heated to 70°C, and while maintaining that temperature, a solution containing 20.0 parts of 1,3-diaminopropane, 3.1 parts of benzylamine, 600 parts of 2-propanol, and 961 parts of toluene was added dropwise over 1 hour. After the dropwise addition, the mixture was allowed to react at 70°C for an additional 6 hours, yielding a polyurethane resin (A-1) with a molecular weight (Mw) of 130,000, an acid value of 10 mgKOH / g, a Tg of 20°C, and a solids content of 25%.

[0069] [Synthesis of thermosetting resin 2] A reaction vessel equipped with a stirrer, thermometer, reflux condenser, dropping device, and nitrogen inlet tube was charged with 414 parts of a diol (number average molecular weight (hereinafter referred to as "Mn") = 1006) esterified using adipic acid, terephthalic acid, and 3-methyl-1,5-pentanediol, 8 parts of dimethylolbutanoic acid, 145 parts of isophorone diisocyanate, and 40 parts of toluene, and the mixture was reacted for 3 hours at 90°C under a nitrogen atmosphere. Next, 300 parts of toluene was added to obtain a solution of a urethane prepolymer having an isocyanate group at its terminal. Next, 816 parts of the resulting urethane prepolymer solution was added to a solution of 27 parts isophoronediamine, 3 parts di-n-butylamine, 342 parts 2-propanol, and 576 parts toluene, and the mixture was allowed to react at 70°C for 3 hours, after which the mixture was cooled. 144 parts toluene and 72 parts 2-propanol were added and mixed to obtain a polyurethane resin (A-2) solution with a non-volatile content of 30%. The resin (A-2) had an Mw of 54,000 and an acid value of 5 mgKOH / g.

[0070] <Curing agent> Curing agent 1: Bisphenol A epoxy compound "jER828" (epoxy equivalent = 189g / eq) manufactured by Mitsubishi Chemical Corporation Hardener 2: Tetraphenolethane epoxy resin "jER1031s" (tetrafunctional, epoxy equivalent = 200g / eq) manufactured by Mitsubishi Chemical Corporation Hardener 3: Vinyl ether modified bisphenol A epoxy resin "EXA4850-150" (epoxy equivalent weight 450, molecular weight 900) manufactured by DIC Corporation Curing agent 4: Aziridine compound, "ChemiTite PZ-33" manufactured by Nippon Shokubai Co., Ltd. Curing agent 5: Hexamethylene diisocyanate-biuret form, "Duranate 24A-100" (solid content 100%, NCO 23.5% by mass), manufactured by Asahi Kasei Corporation Curing agent 6: Polyvalent carbodiimide "Carbodilite V-03" manufactured by Nisshinbo Chemical Co., Ltd.

[0071] <Inorganic filler> Inorganic filler 1: MicroAce P-2 (talc, average particle diameter D50 is 5.0 μm (manufactured by Nippon Talc Co., Ltd.) Inorganic filler 2: IXE PLUS-A1 (a mixture of a zirconia-based inorganic cation scavenger and a hydrotalcite-based inorganic anion scavenger, with an average particle diameter D50 of 0.5 μm (manufactured by Toagosei Co., Ltd.) Inorganic filler 3: IXE300 (antimony-based inorganic cation collector, average particle diameter D50 is 0.5 μm (manufactured by Toagosei Co., Ltd.)) Inorganic filler 4: SS50 (silica, average particle size D50 is 4.5 μm (Tosoh Silica Corporation))

[0072] <Average particle size D50 of inorganic filler> The average particle diameter D50 is the D50 average particle diameter value obtained by measuring conductive fine particles using a laser diffraction / scattering particle size distribution analyzer LS13320 (manufactured by Beckman Coulter) with a Tornado dry powder sample module, and is the particle diameter at which the cumulative value in the particle diameter cumulative distribution is 50%. The refractive index was set to 1.6.

[0073] [Creation of insulating resin layer 1] A thermosetting resin composition was obtained by adding 100 parts of thermosetting resin 1 (solid content), 20 parts of curing agent 3, 0.5 parts of thermosetting agent 4, and 11.4 parts of inorganic filler 1 to a container, adding a mixed solvent of toluene and isopropyl alcohol (2:1 by mass ratio) to a nonvolatile content of 45% by mass, and stirring with a disperser for 10 minutes. This thermosetting resin composition was applied to a releasable substrate using a doctor blade to a dry thickness of 40 μm. The coating was then dried at 100°C for 2 minutes to obtain a laminate sheet in which the releasable substrate and resin layer 1 were laminated.

[0074] [Creation of insulating resin layers 2 to 22, 101 to 102] Laminated sheets in which insulating resin layers 2 to 22 and 101 to 102 were laminated on a peelable substrate were obtained in the same manner as in the preparation of insulating resin layer-1, except that the blending amounts in Table 1 were changed.

[0075] The following physical properties of the resulting insulating resin layer were measured. The results are shown in Table 1.

[0076] <Measurement of adhesive strength by probe tack test> A stainless steel probe with a diameter of 5 mm (200 g including a weight) was brought into contact with the surface of the insulating resin layer of a laminated sheet in which a release substrate and an insulating resin layer were laminated for 1 second, and the force detected when the probe was removed from the surface of the adhesive layer at a speed of 10 mm / sec was measured. The measurement was carried out five times, and the average value was calculated.

[0077] <Measurement of Young's modulus at 23°C> The laminated sheet in which the release substrate and the insulating resin layer were laminated was left to stand for 24 hours at 23°C and a relative humidity of 50%. After that, the release substrate was peeled off, and the insulating resin layer was placed in a constant temperature and humidity chamber at 23°C and a relative humidity of 50%. The stress-strain curve was measured using a tensile tester "EZ Tester" (manufactured by Shimadzu Corporation) at a tensile speed of 50 mm / min and a gauge length of 25 mm, and the linear regression (slope) in the strain (elongation) range of 0.1 to 0.3% was taken as the Young's modulus at 23°C.

[0078] <Storage modulus at 23°C> The laminated sheet, in which the release substrate and the insulating resin layer were laminated, was left to stand at 23°C and a relative humidity of 50% for 24 hours. The release substrate was then peeled off, and the insulating resin layer was subjected to measurements using a dynamic elastic modulus measuring device DVA-200 (manufactured by IT Measurement & Control Co., Ltd.) under the conditions of "tensile" deformation mode, a frequency of 10 Hz, a heating rate of 10°C / min, and a measurement temperature range of -50°C to 300°C, to determine the storage modulus at 23°C. The storage modulus at 120°C and 170°C was also measured.

[0079] <Measurement of elongation rate> A laminated sheet consisting of a release substrate and an insulating resin layer was cut into a size of 200 mm wide x 600 mm long, and then the insulating resin layer was peeled off from the release substrate to prepare a measurement sample. A tensile test (test speed 50 mm / min) was performed on the measurement sample at an effective tensile size of 200 x 230 mm using a small tabletop testing machine EZ-TEST (manufactured by Shimadzu Corporation) under conditions of a temperature of 25°C and a relative humidity of 50%, and the elongation at break was determined.

[0080] [Table 1]

[0081] [Example 1] The insulating resin layer 8 and the insulating resin layer 1 were laminated together using a hot roll laminator to obtain an electronic component protection sheet with a release substrate, which was laminated in the order of release substrate / second insulating resin layer (resin layer 8) / first insulating resin layer (resin layer 1) / release substrate. The lamination conditions were 70°C and 3 kgf / cm. 2 It was decided. Hereinafter, the "second insulating resin layer" may be abbreviated as the "outer insulating resin layer", and the "releasable substrate" covering the "outer insulating resin layer" may be abbreviated as the "outer releasable substrate".

[0082] [Examples 2 to 22, Comparative Examples 1 and 2] Protective sheets for electronic components with a peelable substrate of Examples 2 to 22 and Comparative Examples 1 and 2 were obtained in the same manner as in Example 1, except that the combination of insulating resin layers was changed as shown in Table 2.

[0083] [Example 23] The insulating resin layer 1 and the insulating resin layer 14 were laminated together using a hot roll laminator, resulting in a laminate structure in the following order: releasable substrate / intermediate insulating resin layer (resin layer 14) / first insulating resin layer (resin layer 1) / releasable substrate. Next, the release substrate on the insulating resin layer 14 side was peeled off, and the insulating resin layer 12 was laminated to the exposed surface using a hot roll laminator, thereby obtaining an electronic component protection sheet with a release substrate, which was laminated in the order of outer release substrate / insulating resin layer 12 / insulating resin layer 14 / insulating resin layer 1 / release substrate. The lamination conditions were 70°C and 3 kgf / cm 2 It was decided.

[0084] [Example 24] An electronic component protection sheet with a peelable substrate of Example 24 was obtained in the same manner as in Example 23, except that the combination of insulating resin layers in Table 3 was changed.

[0085] [Examples 25 to 30] Protective sheets for electronic devices with a peelable substrate of Examples 25 to 30 were obtained in the same manner as in Example 1, except that the combination of insulating resin layers was changed as shown in Table 4.

[0086] The electronic component protection sheets obtained in each of the examples and comparative examples were evaluated for temporary adhesion, releasability, migration resistance, and embeddability. The results are shown in Tables 2 and 3.

[0087] <Temporary adhesion> The electronic component protection sheet with the release substrate was cut to a width of 25 mm and a length of 100 mm, and the release substrate on the side of the first insulating resin layer was peeled off to expose the first insulating resin layer, which was then attached to a 125 μm thick polyimide film with a width of 30 mm and a length of 150 mm at 23°C and 3 kgf / cm 2 The film was roll laminated and attached under the conditions. Next, the outer release substrate was peeled off, and a 25 μm PET film was attached to the exposed outer insulating resin layer surface via double-sided acrylic adhesive tape "DF715" manufactured by Toyochem Co., Ltd. (thickness of the acrylic adhesive layer on each side: 35 μm), and this was used as the measurement sample. A T-peel test was carried out using a tensile tester at a pulling rate of 50 mm / min to measure the adhesive strength between the first insulating resin layer and the polyimide film. ◎: Adhesive strength is 0.5N or more. Very good results. ◯: Adhesion strength is 0.25 or more and less than 0.5. Good results. △: Adhesion strength is 0.1 or more and less than 0.25. No problem in practical use. ×: Adhesion strength is less than 0.1. Not practical.

[0088] <Releasability> The electronic component protection sheet with the release substrate was cut to a width of 25 mm and a length of 100 mm, the outer release substrate was peeled off, and the exposed outer insulating resin layer surface was attached to a 125 μm thick polyimide film of a width of 30 mm and a length of 150 mm at 23°C and 3 kgf / cm 2 The film was roll laminated and attached under the conditions. Next, the release substrate on the first insulating resin layer side was peeled off, and a 25 μm PET film was attached to the exposed surface of the first insulating resin layer via double-sided acrylic adhesive tape "DF715" manufactured by Toyochem Co., Ltd. (thickness of the acrylic adhesive layer on each side: 35 μm), and this was used as the measurement sample. A T-peel test was carried out using a tensile tester at a pulling rate of 50 mm / min to measure the adhesive strength between the outer insulating resin layer and the polyimide film. ◎: Adhesion strength is 0.1 or less. Very good results. ◯: Adhesion strength is greater than 0.1 and less than 0.25. Good results. △: Adhesion strength is greater than 0.25 and less than 0.5. No practical problems. ×: Adhesion strength exceeds 0.5 N. Not practical.

[0089] <Migration resistance test> The migration test will be described with reference to Figure 4. A laminate of 18 μm thick copper foil and 25 μm thick polyimide film was etched to form comb-shaped conductor patterns 200, 300 with a line / space of 0.1 mm / 0.1 mm and electrodes 200', 300' continuous with both comb-shaped conductor patterns on the polyimide film 1, as shown in the plan view of Figure 4(1). The release substrate on the first insulating resin layer side was peeled off from the electronic component protection sheet with the release substrate, and as shown in the plan view of FIG. 4(2), the exposed first insulating resin layer was placed on top of it to cover both comb-shaped conductive patterns 200, 300 and expose both electrodes 200′, 300′. This was then heat-pressed under conditions of 150°C, 2.0 MPa, and 3 minutes. After the outer release substrate was peeled off, the resultant was further heat-treated in an electric oven at 160°C and normal pressure for 60 minutes to cure the first insulating resin layer and the outer insulating resin layer. As shown in FIGS. 4(3) and 4(4), both comb-shaped conductive patterns were covered with the cured product 10′ of the electronic component protection sheet, which was used as an evaluation sample. A voltage of 50V was applied between the comb-shaped conductors of the evaluation sample in an atmosphere of 85°C and 85% RH (relative humidity), and the change in resistance was measured continuously for 1000 hours. Note that the term "leak touch" below refers to a dielectric breakdown due to a short circuit, resulting in an instantaneous drop in resistance and current flow. If there is no leak touch, the insulation does not decrease. The evaluation criteria are as follows: ◎: Resistance after 1000 hours is 10 8 Ω or more, no leak touch. A good result. ○: Resistance after 1000 hours is 10 7 Ω or more, no leak touch. A good result. △: Resistance after 1000 hours is 10 7 Ω or more, leak touch once. No practical problems. ×: Resistance after 1000 hours is 10 7 Less than 100%. Leak touch occurred more than twice. Not suitable for practical use.

[0090] <Embeddability> [Preparation of test board] A test board was prepared, consisting of a glass epoxy substrate on which two types of electronic components 2a and 2b were mounted in a grid pattern at 0.5mm intervals. The thickness of the board was 0.3mm, the height of electronic component 2a was 2mm, the height of electronic component 2b was 1mm, and the planar dimensions of electronic components 2a and 2b were 2cm x 2cm. A schematic cross-sectional view of the test board is shown in Figure 5.

[0091] The electronic component protection sheet with the release substrate was cut to a 10 cm x 10 cm size, and the release substrate on the first insulating resin layer side was peeled off. The sheet was then placed on a test substrate so that the first insulating resin layer was in contact with the electronic component 2a. The release substrate on the second insulating resin layer side was then peeled off, and two types of films (0.05 mm thick TPX (product name: Opulent X-44B, manufacturer: Mitsui Chemicals Tohcello Co., Ltd.) and 2.0 mm thick PVC film (product name: Celeb T, manufacturer: Okamoto)) were laminated in this order as cushioning materials on the exposed surface, followed by a cardboard layer to prevent sticking. This was then heat-pressed against the substrate surface from above at 5 MPa and 160°C for 20 minutes. After heat pressing, the sheet was cooled, and the cushioning material and cardboard were peeled off to prepare a measurement sample. The measurement sample was polished in the thickness direction to form a cross section for observation, and the fillability was evaluated by observing 10 grooves between electronic components with an electron microscope. The evaluation criteria were as follows: ⊚: All grooves are filled in. This is a very good result. ○: Nine grooves were filled in. This is a good result. △: Eight grooves are filled in. No practical problems. ×: Not all grooves were filled in. Not practical.

[0092] [Table 2]

[0093] [Table 3]

[0094] [Table 4]

[0095] The results in Tables 2 to 4 show that the electronic component protection sheet of the present invention was excellent in all of temporary adhesion property, releasability, migration resistance, and embeddability. This confirmed that the electronic component protection sheet can be applied to small substrates with complex uneven shapes. [Explanation of symbols]

[0096] 1 board 2. Electronic Components 3 Solder 4. Electronic component mounting board 10 Electronic component protection sheet 10' Hardened electronic component protection sheet 11 First insulating resin layer 12 Second insulating resin layer 13 Cushioning material 14 Conventional electronic component protection sheets 15 Protective coating layer 20 Heat and pressure bonding device 100 Polyimide film 200, 300 Comb-shaped conductor pattern 200', 300' electrode

Claims

1. An electronic component protection sheet for covering and protecting a group of electronic components consisting of a plurality of electronic components of different heights mounted on a substrate, the electronic component protection sheet has an insulating resin layer containing a thermosetting resin including a polyurethane urea resin and a curing agent having a functional group reactive with a functional group of the thermosetting resin; the curing agent includes an epoxy compound, and further includes any one of an aziridine compound and a carbodiimide compound; The adhesive strength A of the surface in contact with the electronic component group is 0.8 to 4 N as determined by a probe tack test, The adhesive strength B of the opposite surface measured by a probe tack test is 0.3 N or less, The adhesive strength of the surface in contact with the electronic components as determined by a probe tack test is greater than the adhesive strength of the opposite surface as determined by a probe tack test, and the difference between adhesive strength A and adhesive strength B is 0.5 N or more; The electronic component protection sheet, wherein the insulating resin layer has a first insulating resin layer in contact with the group of electronic components and a second insulating resin layer located farthest from the group of electronic components.

2. 2. The electronic component protection sheet according to claim 1, wherein the content of the curing agent is 3 to 100 parts by mass with respect to 100 parts by mass of the thermosetting resin.

3. The Young's modulus of the first insulating resin layer at 23°C is 5 MPa to 200 MPa, the Young's modulus of the second insulating resin layer at 23°C is 30 MPa to 1000 MPa; 3. The electronic component protection sheet according to claim 1, wherein the Young's modulus of the second insulating resin layer at 23°C is higher by 8 MPa or more than the Young's modulus of the first insulating resin layer at 23°C.

4. The first insulating resin layer has a storage modulus at 23°C of 1.0+E04 Pa to 5.0+E08 Pa, the second insulating resin layer has a storage modulus at 23°C of 1.0+E06 Pa to 5.0+E09 Pa; 4. The electronic part protection sheet according to claim 1, wherein the second insulating resin layer has a higher storage modulus at 23° C. than the first insulating resin layer.

5. 5. The electronic component protection sheet according to claim 3, wherein the first insulating resin layer and the second insulating resin layer each contain an inorganic filler.

6. 6. The electronic part protection sheet according to claim 5, wherein the inorganic filler is at least one selected from the group consisting of silica, talc, and an ion collector.

7. 7. The electronic component protection sheet according to claim 6, wherein the first insulating resin layer contains 5 to 20% by mass of silica, and the second insulating resin layer contains 5 to 40% by mass of silica.

8. 7. The electronic component protection sheet according to claim 6, wherein the first insulating resin layer and the second insulating resin layer each contain silica or talc, and at least one of the first insulating resin layer and the second insulating resin layer contains an ion scavenger.

9. The electronic component protection sheet according to any one of claims 3 to 8, wherein the first insulating resin layer and the second insulating resin layer each independently have a breaking elongation at 23°C of 50 to 1500%.

10. The electronic component protection sheet according to any one of claims 3 to 9, wherein the insulating resin layer has an intermediate layer between the first insulating resin layer and the second insulating resin layer.

11. An electronic component mounting substrate, in which a group of electronic components consisting of a plurality of electronic components of different heights mounted on the substrate is covered with a cured product of the electronic component protection sheet according to any one of claims 1 to 10.

12. a step of mounting a group of electronic components consisting of a plurality of electronic components of different heights on a substrate; A step of preparing the electronic component protection sheet according to any one of claims 3 to 10; placing the electronic component protective sheet so that the tallest electronic component among the group of electronic components is in contact with the first insulating resin layer of the electronic component protective sheet; a step of deforming the electronic component protection sheet by applying heat and pressure so as to conform to the shapes of the individual electronic components, thereby covering the group of electronic components and at least a portion of the substrate; and a step of thermally curing the deformed electronic component protection sheet in a deformed state to form a coating protective layer. A method for covering and protecting a substrate on which a group of electronic components is mounted.

13. a step of mounting a group of electronic components consisting of a plurality of electronic components of different heights on a substrate; A step of preparing the electronic component protection sheet according to any one of claims 3 to 10; placing the electronic component protective sheet so that the tallest electronic component among the group of electronic components is in contact with the first insulating resin layer of the electronic component protective sheet; a step of deforming the electronic component protection sheet by applying heat and pressure so as to conform to the shapes of the individual electronic components, thereby covering the group of electronic components and at least a portion of the substrate; and a step of thermally curing the deformed electronic component protection sheet in a deformed state to form a coating protective layer. A method for manufacturing a substrate with an electronic component group mounted thereon and having a protective coating layer.

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