Electronic component protective sheet, electronic component mounting substrate, method for manufacturing the same, and method for covering and protecting an electronic component mounting substrate.

Abstract

To provide an electronic component protective sheet which is excellent in temporary stretchability, releasability, and migration resistance, and is applicable also to an electronic component group mounting substrate having electronic components having different heights by good embedding property.SOLUTION: There is provided an electronic component protective sheet for coating and protecting a plurality of electronic components which are mounted on a substrate and have different heights, wherein the electronic component protective sheet has a plurality of insulating resin layers having different Young's moduli at 23°C, adhesive force by a probe tack test of a surface contacting the electronic component group is 0.3 to 5 N, adhesive force by the probe tack test of the opposite surface is 1 N or less, and the adhesive force by the probe tack test of the surface contacting the electronic component group is larger than a probe tack of 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 an electronic component group composed of a plurality of electronic components having different heights mounted on the surface of a substrate, covering at least a part of the surface of the substrate as a whole.

Background Art

[0002] In order to protect electronic components such as IC chips mounted on a substrate from bending or impact on the substrate or from thermal shock due to temperature changes, the electronic components are covered and protected with resin for a part or the entire surface of the substrate. In recent years, with the remarkable improvement in performance and miniaturization of the electronic components and substrate circuits to be protected, the required level of the protection function for the covering and protecting material has been increasing. As a method for covering and protecting electronic components, a heat-meltable electronic component protection sheet formed in a solvent-free sheet shape has been proposed as a means to replace the conventionally performed conformal coating. For example, Patent Document 1 discloses a moisture-proof sheet for electronic device components, which is characterized by including a moisture-proof layer made of a forming material mainly composed of an aromatic vinyl-conjugated diene block copolymer. Patent Document 2 discloses a sheet for substrate protection, which is composed of a graft copolymer of an olefin monomer, an ethylenically unsaturated carboxylic acid, and an aromatic ethylenically unsaturated monomer. Patent Documents 3 and 4 disclose a sheet-like resin composition composed of an epoxy resin, an inorganic filler, and a flame retardant. Patent Document 5 discloses a sealing film for sealing an electronic component mounting substrate, which includes an insulating layer and an electromagnetic wave shielding layer. Patent Document 6 discloses a manufacturing method of a mounting structure covering a mounted component and a substrate with a laminated sheet including a first heat conduction layer and a second heat conduction layer, and FIG. 3(b) discloses a manufacturing method of filling the space between mounted components with a cured product of the laminated sheet without gaps.

Prior Art Documents

[0003] [Patent Document 1] Japanese Patent Publication No. 2003-145687 [Patent Document 2] Japanese Patent Publication No. 2010-06954 [Patent Document 3] Japanese Patent Publication No. 2011-246596 [Patent Document 4] Japanese Patent Publication No. 2012-054363 [Patent Document 5] Japanese Patent Publication No. 2019-021757 [Patent Document 6] WO2019 / 065976 [Disclosure of the Invention] [Problems that the invention aims to solve]

[0004] However, as shown in Figures 2(a) and 3(a), when a substrate with a group of electronic components whose heights are not uniform is covered and protected with a conventional protective sheet, there is a problem in that the protective sheet may shift horizontally as shown in Figure 2(b) or tilt due to taller electronic components as shown in Figure 3(b), resulting in the formation of a protective film in a location other than the intended one. In other words, the protective sheet needs to adhere to the intended electronic components without shifting or tilting (hereinafter referred to as temporary adhesion). Furthermore, when placing the protective sheet onto the circuit board with the electronic components, the side of the protective sheet opposite to the intended placement surface would stick to the pickup device, hindering quick placement onto the circuit board and reducing productivity. In other words, the protective sheet requires quick release from the pickup device (hereinafter referred to as "releaseability"). Furthermore, conventional protective sheets had a problem where, after forming a protective coating, migration would occur at conductive points between electronic components (e.g., solder bumps) due to long-term use (hereinafter referred to as migration resistance). Furthermore, conventional protective sheets lacked the ability to fill gaps between electronic components and into uneven surfaces (hereinafter referred to as "fillability").

[0005] The present invention provides an electronic component protective sheet that offers excellent temporary adhesion, release properties, and migration resistance, and furthermore, good embedding properties, making it applicable to substrates on which electronic component groups with electronic components of different heights are mounted. [Means for solving the problem]

[0006] As a result of diligent research, the inventors have found that the above problem can be solved by using an electronic component protection sheet for covering and protecting a group of electronic components mounted on a substrate by heating and pressurizing, wherein the electronic component protection sheet has an insulating resin layer containing a thermosetting resin, and the adhesive strength measured by probe tack tests on the surface in contact with the group of electronic components and the opposite surface are both within a predetermined range, and the adhesive strength on the surface in contact with the group of electronic components is greater than the adhesive strength on the opposite surface. This has led to the completion of the present invention.

[0007] In other words, the present invention is an electronic component protective sheet for covering and protecting a group of electronic components consisting of multiple electronic components of different heights mounted on a substrate, The electronic component protective sheet has an insulating resin layer containing a thermosetting resin, The adhesive strength measured by probe tack testing on the surface in contact with the electronic components was 0.3 to 5 N. This invention relates to an electronic component protective sheet in which the adhesive strength measured by probe tack test on the opposite side is 1N or less, and the adhesive strength measured by probe tack test on the side in contact with the group of electronic components is greater than the adhesive strength measured by probe tack test on the opposite side.

[0008] Furthermore, the present invention relates to a process of mounting a group of electronic components consisting of multiple electronic components of different heights onto a substrate. The process of preparing the electronic component protective sheet described in the present invention, A step of placing an electronic component protection sheet such that the tallest electronic component among the group of electronic components contacts the first insulating resin layer in the electronic component protection sheet. A step of deforming the electronic component protection sheet along the shape of each individual electronic component by heating and pressing, and covering at least a part of the group of electronic components and the substrate, and A method for covering and protecting a substrate on which a group of electronic components is mounted, including a step of thermally curing the deformed electronic component protection sheet in the deformed state to form a covering protection layer.

[0009] Furthermore, the present invention includes a step of mounting a group of electronic components composed of a plurality of electronic components having different heights on a substrate, A step of preparing the electronic component protection sheet described in the present invention, A step of placing an electronic component protection sheet such that the tallest electronic component among the group of electronic components contacts the first insulating resin layer in the electronic component protection sheet. A step of deforming the electronic component protection sheet along the shape of each individual electronic component by heating and pressing, and covering at least a part of the group of electronic components and the substrate, and A method for manufacturing a substrate on which a group of electronic components with a covering protection layer is mounted, including a step of thermally curing the deformed electronic component protection sheet in the deformed state to form a covering protection layer.

Effects of the Invention

[0010] According to the present invention, it is possible to provide an electronic component protection sheet that is excellent in tenting properties and release properties, and further excellent in migration resistance and embedding properties. As a result, a highly reliable substrate on which a group of electronic components is mounted can be provided with a high yield.

Brief Description of the Drawings

[0011] [Figure 1] It is an explanatory diagram of a method for covering and protecting an electronic component using the electronic component protection sheet in the present invention. [Figure 2] It is an explanatory diagram when placing a conventional electronic component protection sheet. [Figure 3] It is an explanatory diagram when placing a conventional electronic component protection sheet. [Figure 4] It is a schematic plan view for explaining the migration resistance test in the embodiment. [Figure 5] It is a schematic cross-sectional view for explaining the embedding property test in the embodiment.

Mode for Carrying Out the Invention

[0012] Hereinafter, an example of an embodiment to which the present invention is applied will be described. Note that the sizes and ratios of the respective members in the following drawings are for convenience of explanation and are not limited thereto. In the present specification, the description "arbitrary number A to arbitrary number B" includes number A as the lower limit value and number B as the upper limit value within the range. Also, in the present specification, the "sheet" includes not only the "sheet" defined in JIS but also the "film". Further, the numerical values specified in the present specification are values obtained by the methods disclosed in the embodiments or examples. Also, the adhesive force by the probe tack test may be abbreviated as probe tack adhesive force or adhesive force.

[0013] <Coating protection method for substrate with electronic component group mounted> First, a coating protection method for a substrate with an electronic component group mounted using the electronic component protection sheet of the present invention (hereinafter sometimes abbreviated as coating protection method, coating method, or protection method) will be described. The present invention provides a method for protecting a substrate mounted on an electronic component group, comprising the steps of: mounting an electronic component group consisting of multiple electronic components of different heights onto a substrate (step i); preparing an electronic component protection sheet of the present invention, described later (step ii); placing the electronic component protection sheet so that the tallest electronic component among the electronic component group is in contact with the first insulating resin layer of the electronic component protection sheet (step iii, also called the temporary attachment step); deforming the electronic component protection sheet by heating and pressing to conform to the shape of each electronic component, thereby covering at least a part of the electronic component group and the substrate (step iv); and heat-curing the deformed electronic component protection sheet in its deformed state to form a protective coating layer (step v). This method allows the substrate mounted on an electronic component group to be protected by a protective coating layer formed from the electronic component protection sheet of the present invention. Steps (iv) and (v) can also be performed as a series of steps.

[0014] The following describes the method of protecting a substrate with mounted electronic components by heating and pressurizing using an electronic component protection sheet, with reference to Figure 1, for steps iii to v.

[0015] (Process iii; Electronic component protective sheet placement process) A circuit board 4 is prepared, on which electronic components 2a and 2b are mounted using solder bumps 3. Electronic components 2 include semiconductor chips, capacitors, transistors, inductors, thermistors, etc., and are mounted on circuit board 1 via solder bumps 3, with a gap between electronic components 2a and 2b and circuit board 1. Also, electronic component 2a is designed to be higher than electronic component 2b. Next, the first insulating resin layer 11 of 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 it is in contact with the electronic component 2a. Due to the height of the electronic component 2a, the first insulating resin layer 11 is in contact with the electronic component 2a and temporarily adhered. Note that the electronic component protection sheet 10 may also bend and come into contact with the electronic component 2b (not shown in Figure 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 shift position after being placed.

[0016] Furthermore, a cushioning material 13 may be laminated on the outermost part of the insulating resin layer, and Figure 1 shows an example in which cushioning material is used. The cushioning material 13 may be laminated after the electronic component protection sheet 10 is placed, or a laminate of the electronic component protection sheet 10 and cushioning material 13 may be placed in advance. The cushioning material 13 is a material that softens or melts when heated or pressurized, and has the function of promoting the conformability of the electronic component protection sheet 10 to the electronic components 2a and 2b, and to the gaps between the electronic components. The cushioning material 13 is not particularly limited as long as it is a thermoplastic material, for example, but it is preferable that it has a melting temperature and glass transition temperature (Tg) lower than the temperature under pressure. Suitable examples include polyolefin films, vinyl chloride films, and PVA films. The thickness is usually about 100 μm to 1 mm, depending on the depth of the groove. When multiple layers of cushioning material 13 are laminated, it is preferable that the total thickness is within this range.

[0017] The thickness of the electronic component protective sheet 10 is preferably set to 0.05 to 2 times the height of the tallest electronic component to be protected. The electronic component mounting substrate shown in this invention is merely an example, and the structure of the electronic components and the substrate is not particularly limited. There may or may not be a gap between the electronic components 2a and 2b and the substrate 1. The placement of the mounted electronic components is not limited, and the number of electronic components is two or more.

[0018] (Process iv; coating process with protective sheet for electronic components) Next, by heating and pressurizing with the heating and pressurizing machine 20, the electronic component protective sheet 10 deforms to conform to the shape of the individual electronic components, that is, to conform to the top and side surfaces of the electronic components 2a and 2b, and to follow at least a part of the group of electronic components and the substrate 1. The cushioning material 20 softens or melts due to the heat, promoting the electronic component protective sheet 10 to conform to the unevenness between the electronic components on the substrate 4 on which the group of electronic components is mounted. It is also preferable to place 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 substrate such as paper or plastic that has undergone a known release treatment. Alternatively, a low-polarity plastic sheet such as Teflon (registered trademark) can be used.

[0019] The heating temperature should be such that the electronic component protection sheet softens sufficiently, deforms to conform to the shape of each electronic component, and can penetrate into the gaps between the electronic components. Preferably, the temperature is 100 to 260°C, and more preferably 120 to 240°C. If the temperature is too low, the ability of the electronic component protection sheet 10 to penetrate into the gaps between the mounted electronic components will decrease. 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, reducing the ability of the electronic component protection sheet to penetrate between the mounted electronic components. The preferred pressure for heating and pressurizing is 0.01 to 10 MPa, and more preferably 0.1 to 6.0 MPa. Heating and pressurizing at the above pressures improves embedding ability without damaging the electronic components. The heating time is typically 0.5 to 30 minutes, with a range of 1 to 20 minutes being preferable. If the heating time is too short, the penetration of the electronic component protection sheet between the mounted electronic components will decrease. On the other hand, if the time is too long, thermal decomposition and oxidation of the thermosetting resin are more likely to occur, increasing the possibility of reduced reliability of the adhesive site due to reaction products, etc. The above heating and pressurizing process is preferably carried out under vacuum conditions. In addition to using a heating and pressurizing machine, another preferred method of heating and pressurizing is to stack metal plates of appropriate weight to achieve a predetermined pressure and then place this stacked material into an oven. On the other hand, as a heating and pressurizing method other than a heating and pressurizing machine, vacuum forming or vacuum pressure forming are also preferred.

[0020] (Process v; curing process for deformed electronic component protective sheets) After heating and pressurizing, the deformed electronic component protective sheet is further heated at a temperature of 150°C to 230°C for 10 to 60 minutes in its deformed state. This heat-cures the thermosetting resin in the furthest insulating resin layer and the first insulating resin layer, forming a protective coating layer. The protective coating layer adheres firmly to the electronic components and substrate, functioning as a protective layer to prevent and protect the electronic components from damage caused by external impacts and scratches. Alternatively, the heat curing can be completed and the protective coating layer formed by heating and pressurizing at a temperature of 150°C or higher and for a time of 30 minutes or more in step (iv). The protective coating layer must be an insulator to prevent short circuits between electronic components, and a surface resistance of 1 + E10Ω or higher is required.

[0021] <Protective sheet for electronic components> Next, the electronic component protection sheet of the present invention will be described. As described above, the electronic component protection sheet is for covering and protecting 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 as measured by a probe tack test on the surface in contact with the electronic components, and an adhesive strength of 1 N or less on the opposite surface, with the adhesive strength of the surface in contact with the electronic components being greater than that of the opposite surface. The adhesive strength of the surface in contact with the electronic components is more preferably 0.5 to 4 N, and even more preferably 1 to 3.5 N. Setting the adhesive strength of the surface in contact with the electronic components to 0.5 N or higher improves temporary adhesion. Setting the adhesive strength of the surface in contact with the electronic components to 5 N or less provides reworkability. The adhesive strength measured by probe tack testing on the opposite side is preferably 1N or less, more preferably 0.5N or less, and even more preferably 0.3N or less. Setting the adhesive strength of the opposite side to 1N or less improves release properties. Furthermore, a greater adhesive strength measured by probe tack testing on the side in contact with the electronic components than on the opposite side improves reworkability and release properties. The difference between the adhesive strength measured by a probe tack test on the surface in contact with the electronic components and the adhesive strength measured by a probe tack test on the opposite surface is preferably 0.3 N or more, more preferably 0.5 N or more, and even more preferably 0.7 N. By keeping it within the above range, both release properties and temporary adhesion properties can be highly balanced.

[0022] In this invention, the adhesive force measured by the probe tack test refers to the force (peeling force) detected when a stainless steel probe with a diameter of 5 mmφ (200 g including a weight) is brought into contact with the surface of the insulating resin layer being 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 constructing an electronic component protective sheet as a single layer, probe tack can be controlled by UV curing one side or by orienting the amount of inorganic filler in the layer (described later) to one side.

[0023] An embodiment in which the electronic component protective sheet is formed from multiple insulating resin layers is also preferred from the viewpoint of controlling probe tack. In this case, the insulating resin layers consist of at least a first insulating resin layer in contact with the group of electronic components and a second insulating resin layer located furthest from the group of electronic components. At this time, the adhesive force of the first insulating resin layer measured by probe tack test is 0.3 to 5 N, and the adhesive force of the second insulating resin layer measured by probe tack test is 1 N or less.

[0024] Furthermore, the Young's modulus of the 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. By having a Young's modulus at 23°C that is higher than that of the first insulating resin layer at 23°C, an electronic component protective sheet can be made with excellent temporary adhesion, release properties, migration resistance, and embedding properties.

[0025] <First insulating resin layer> The Young's modulus of the first insulating resin layer at 23°C (hereinafter abbreviated 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. Setting Young's modulus (1) to 5 MPa or higher improves its ability to follow grooves between electronic components, while setting it to 200 MPa or lower improves its ability to temporarily adhere. Furthermore, the "Young's modulus at 23°C" in this invention can be determined as follows: The sample is left to stand for 24 hours in an environment of 23°C and 50% relative humidity, and then the measurement is performed in the same environment. Specifically, a sample with a chuck distance of 25 mm is pulled using a tensile testing machine at a tensile speed of 50 mm / min, the stress-strain curve is measured, and the linear regression (slope) in the region where the strain (elongation) is 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 thermosetting resins, thermosetting agents, and inorganic fillers described later, or by using tackifying resins and thermoplastic resins in combination.

[0026] Furthermore, the first insulating resin layer preferably has a storage modulus at 23°C (hereinafter abbreviated as storage modulus (1)) of 1.0+E04Pa to 1.0+E07Pa. Setting the storage modulus (1) to 1.0+E04Pa or higher improves embedding properties, while setting it to 1.0+E07Pa or lower improves migration resistance. In this invention, the storage modulus is the value of the storage modulus at 23°C measured using a dynamic modulus measuring device DVA-200 (manufactured by IT Measurement Control Co., Ltd.) on a sample under the conditions of deformation mode "tensile", frequency 10 Hz, heating rate 10°C / min, and measurement temperature range -50 to 300°C.

[0027] The first insulating resin layer can be formed from a thermosetting resin composition containing a thermosetting resin. Since the first insulating resin layer has an adhesive strength of 0.3 to 5 N as measured by probe tack testing, it adheres firmly to electronic components during temporary placement, preventing misalignment. Furthermore, it offers excellent reworkability as it can be peeled off and repositioned when correcting the temporary placement. Furthermore, the thermosetting resin composition preferably contains a thermosetting agent, an inorganic filler, a flame retardant, etc. By using these, the Young's modulus at 23°C, the storage modulus, and the 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, polyamide-imide resins, polyesteramide resins, polyether ester resins, and polyimide resins. Thermosetting resins may have self-crosslinkable functional groups. For example, when used under harsh conditions during reflow soldering, it is preferable that the thermosetting resin contains at least one of epoxy resins, urethane resins, urethane urea resins, polycarbonate resins, and polyamides. Furthermore, thermosetting resins and thermoplastic resins can be used in combination, provided that they can withstand embedding.

[0028] Reactive functional groups of thermosetting resins include carboxyl groups, hydroxyl groups, epoxy groups, etc. When carboxyl groups are present, 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 viewpoint of embedding performance in step iv and migration resistance after curing. Because the acid value of the thermosetting resin is within the above range, the curing rate in step iv can be moderately slowed, making it less likely to impair embedding properties and ensuring sufficient crosslinking density, thus enabling good migration resistance.

[0029] The weight-average molecular weight Mw of the thermosetting resin is preferably between 20,000 and 200,000. A value of 20,000 or higher effectively enhances release properties and temporary bonding properties. Conversely, a value of 200,000 or lower improves embedding properties.

[0030] [Hardening agent] To accelerate the curing of the thermosetting resin, it is preferable to use a curing agent. The curing agent causes the electronic component protective sheet to undergo thermal melting and deformation, and after it comes into contact with the substrate and electronic components, it thermally crosslinks with the reactive functional groups of the thermosetting resin, thereby strengthening the adhesion to the substrate and electronic components and improving migration resistance. The curing agent has multiple functional groups that can react with the functional groups of the thermosetting resin. Examples of known curing agents include epoxy compounds, acid anhydride group-containing compounds, imidazole compounds, isocyanate compounds, aziridine compounds, amine compounds, or phenol compounds. Epoxy compounds and aziridine compounds are preferred, and using both in combination is particularly preferred.

[0031] The epoxy compound described above is a compound having two or more epoxy groups in one molecule. Regarding the properties of the epoxy compound, using a liquid form can lower its Young's modulus. On the other hand, using a solid form can increase its Young's modulus. For the first insulating resin layer, it is preferable to use a liquid epoxy compound at 23°C to lower its Young's modulus and impart tackiness. Preferred epoxy compounds include, for example, glycicyl ether type epoxy compounds, glycicylamine type epoxy compounds, glycidyl ester type epoxy compounds, and cyclic aliphatic (alicyclic) epoxy compounds.

[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, tetrabrom bisphenol A type epoxy compounds, brominated phenol novolac type epoxy compounds, tris(glycidyloxyphenyl)methane, tetrakis(glycidyloxyphenyl)ethane, and the like.

[0033] Examples of glycidylamine-type epoxy compounds include tetraglycidyldiaminodiphenylmethane, triglycidylparaaminophenol, triglycidylmetaaminophenol, and tetraglycidylmetaxylylenediamine.

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

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

[0036] Examples of aziridine compounds 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] Imidazole compounds include 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenyl-4-methylimidazole, 2,4-dimethylimidazole, and 2-phenylimidazole. Furthermore, there are latent curing accelerators with improved storage stability, such as those in which the imidazole compound is reacted with an epoxy resin to make it insoluble in solvents, or those in which the imidazole compound is encapsulated in microcapsules.

[0038] The amount of curing agent added 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, per 100 parts by mass of the total thermosetting resin. By using the above amounts, the tackiness, Young's modulus at 23°C, and storage modulus can be adjusted to suitable values.

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

[0040] [Inorganic filler] The first insulating resin layer preferably further contains an inorganic filler. By including an inorganic filler, the adhesive strength, Young's modulus at 23°C, and storage modulus can be moderately increased, improving migration resistance, embedding properties, and release properties.

[0041] Examples of inorganic fillers include inorganic compounds such as silica, alumina, magnesium hydroxide, barium sulfate, calcium carbonate, titanium dioxide, zinc oxide, antimony trioxide, magnesium oxide, talc, kaolinite, mica, magnesium carbonate base, sericite, montmorillonite, bentonite, boron nitride, aluminum nitride, and magnesium oxide (hereinafter referred to as inorganic fillers in the narrow sense), as well as ion scavenging agents, which will be discussed later. Among these, silica, talc, mica, kaolinite, or montmorillonite are preferred from the viewpoint of further improving migration resistance and embedding properties, with silica and talc being more preferred.

[0042] In the narrow sense, the shape of the inorganic filler is preferably flaky. By making the inorganic filler flaky, warping of the electronic component protective sheet during heating and cooling can be suppressed, and the embedding ability can be further improved. Here, flaky includes thin flakes and plate-like shapes as well. The inorganic filler only needs to be flaky as a whole particle, and may be elliptical, circular, or have notches around the fine particles.

[0043] The average particle size D50 of the inorganic filler in the narrow sense is preferably 0.5 to 10 μm, and more preferably 0.7 to 7 μm. An average particle size of 0.5 μm or more improves embedding ability. An average particle size D50 of 10 μm or less can further improve migration resistance. The average particle size is the D50 average particle size obtained by measuring inorganic fillers in the narrow sense using a Beckman Coulter LS 13320 laser diffraction / scattering particle size distribution analyzer with a Tornado Dry Powder sample module. This is the particle size at which the cumulative value in the particle size cumulative distribution is 50%. The refractive index of the inorganic fillers in the narrow sense was set to 1.6 during the measurement.

[0044] The content of the 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 thermosetting resin. By setting the content of the inorganic filler in the narrow sense within the above range, the Young's modulus is adjusted to a suitable range, improving migration resistance and embedding properties.

[0045] [Ion collecting agent] As an inorganic filler, ion scavenging agents are also preferred. Ion scavenging agents include cation scavenging agents, anion scavenging agents, and dual ion scavenging agents. These ion scavenging agents can be used individually or in combination of two or more types. Among these, the use of cation scavenging agents and dual ion scavenging agents is preferred in that they improve migration resistance. Cation scavenging agents are particularly preferred. The ion collecting agent may be included in the first insulating resin layer, the second insulating resin layer described later, or both layers.

[0046] Examples of cation capture agents include manganese compounds (such as hydrated manganese dioxide), antimony compounds (such as crystalline antimony acid and hydrated antimony pentoxide), zirconium compounds (such as zirconium hydroxide, zirconium phosphate, zirconium molybdate, and zirconium tungstate), silicate compounds (such as aluminosilicate and synthetic aluminosilicate), phosphate compounds (such as titanium phosphate and tin phosphate), cerium(III) oxalate, ammonium molybdphosphate, potassium hexacyanoiron(III)cobalt(II), natural green sand, stabilized green sand, and Mn2+-type green sand, which can be used individually or in combination of two or more. Among these, antimony compounds and zirconium compounds have a high ability to capture cations, and can therefore enhance migration resistance. For the cation capture agent, known products such as IXE-100 and IXE-300 (manufactured by Toagosei Co., Ltd.) can be used.

[0047] Furthermore, anion scavenging agents can also be used. Examples of anion scavenging agents 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), which can be used individually or in combination of two or more. Among these, magnesium-aluminum composite oxides are preferred because of their high ability to capture anions. For the anion scavenging agent, 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 dual ion scavenging agent includes a cation scavenging agent and an anion scavenging agent. Preferably, the dual ion scavenging agent is a mixture of a cation scavenging agent appropriately selected from, for example, zirconium compounds, antimony compounds, phosphate compounds, etc., as described above, and an anion scavenging agent appropriately selected from bismuth compounds, magnesium-aluminum compounds, etc.

[0049] For both ion scavenging agents, 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 size D50 of the ion adsorbent is preferably 0.1 to 10 μm, and more preferably 0.1 to 3 μm. Embedding performance is improved by increasing the average particle size to 0.1 μm or more. Migration resistance can be further improved by reducing the average particle size D50 to 10 μm or less. The average particle size is determined in the same way as the inorganic filler in the narrow sense described above.

[0051] The ion collecting agent is preferably added in an amount of 0.1 to 20 parts by mass, and more preferably 0.3 to 10 parts by mass, per 100 parts by mass of thermosetting resin. Adding 0.1 to 20 parts by mass makes it easier to obtain a substrate with a protective coating that has improved migration resistance and is used to mount electronic components.

[0052] The thickness of the first insulating resin layer in the protective sheet of the present invention is preferably 10 to 150 μm, and more preferably 50 to 130 μm. This thickness allows for both temporary adhesion and embedding properties to be achieved.

[0053] <Second insulating resin layer> In the electronic component protective sheet of the present invention, the second insulating resin layer is located furthest from the group of electronic components, and its adhesive strength, as determined by a probe tack test, is 1N or less. In addition, the Young's modulus at 23°C (hereinafter abbreviated as Young's modulus (2)) is preferably 30MPa to 1000MPa, more preferably 50MPa to 800MPa, and even more preferably 70MPa to 500MPa. By setting the adhesive strength to 1N or less, release properties are improved. Furthermore, by setting Young's modulus (2) to 30MPa or more, fracture of the electronic component protective sheet at the corners of electronic components (hereinafter referred to as crack resistance) is suppressed, and by setting it to 1000MPa or less, the ability to follow grooves between electronic components is improved. Furthermore, the method for determining Young's modulus (2) is the same as in the case of the first insulating resin layer described above.

[0054] Furthermore, the second insulating resin layer preferably has a storage modulus at 23°C (hereinafter abbreviated as storage modulus (2)) of 1.0+E06Pa to 1.0+E10Pa. Setting the storage modulus (2) to 1.0+E06Pa or higher improves release properties, while setting it to 1.0+E10Pa or lower improves migration resistance. Furthermore, the method for determining the storage modulus (2) is the same as in the case of the first insulating resin layer described above.

[0055] The second insulating resin layer can be formed from a thermosetting resin composition containing a thermosetting resin, similar to the first insulating resin layer. Furthermore, the thermosetting resin composition preferably includes a curing agent, an inorganic filler in the narrow sense, and an ion scavenging agent, a flame retardant, etc. By using these, the Young's modulus and storage modulus at 23°C mentioned above can be adjusted to a suitable range, thereby improving release properties or embedding properties.

[0056] Examples of thermosetting resins are the same as those for the first insulating resin layer described above, and the same applies to the acid value, weight-average molecular weight, etc.

[0057] The curing agent can be similar to that used for 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. The amount of curing agent added 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, per 100 parts by mass of the total thermosetting resin. By using the above amounts, the Young's modulus and storage modulus at 23°C can be adjusted to suitable values.

[0058] Examples of inorganic fillers and ion scavenging agents in the narrow sense are similar to those in the case of the first insulating resin layer described above. From the viewpoint of improving release properties, 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 total thermosetting resin. From the viewpoint of improving migration resistance, the amount of ion collecting agent added 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 total thermosetting resin.

[0059] The second insulating resin layer may further contain, as needed, colorants, silane coupling agents, antioxidants, plasticizers, UV absorbers, leveling modifiers, and the like.

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

[0061] <Middle class> The protective sheet of the present invention may further have 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 bonding properties and migration resistance are improved, and the intermediate layer mitigates the pressure of the hot pressing process, resulting in a protective coating that is less prone to cracking. Young's modulus (2) > Young's modulus (3) > Young's modulus (1) ... (Equation 1)

[0062] The elongation at break at 23°C for each of the first insulating resin layer, the second insulating resin layer, and the optional intermediate layer constituting the protective sheet of the present invention is preferably 50 to 1500%, and more preferably 100 to 1400%. By setting the elongation at break within this range, the ability to conform to uneven shapes in step iv is improved, and multiple electronic components of different heights can be appropriately covered and protected. In this invention, the elongation rate is defined as 100% when a 100 mm long sample is stretched and broken at 200 mm. The method for measuring the elongation rate will be explained in detail in the examples.

[0063] Furthermore, the electronic component protective sheet of the present invention may have a hard coat layer or a fiber layer laminated on the outside of the second insulating resin layer to further improve its protective properties.

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

[0065] <Applications of electronic component protective sheets> The electronic component protective sheet of the present invention exhibits practically sufficient adhesion regardless of whether the substrate is metal, resin, fiber, ceramic, glass, or conductive silicon. Suitable metals include aluminum, copper, brass, stainless steel, iron, and chromium. Suitable resins include epoxy resin, polyethylene terephthalate, polyimide, polyamide, polyethylene, polypropylene, polyolefin-based graft polymers, polystyrene, and polyvinyl chloride. Therefore, this electronic component protective sheet can be suitably used for adhesion between dissimilar materials with different polarities. The electronic component protective sheet of the present invention can be suitably used to protect various substrates, namely rigid substrates, FPC substrates, and other types of substrates.

[0066] Electronic components using the electronic component protective sheet of the present invention are preferably incorporated into electronic devices such as liquid crystal displays, touch panels, notebook PCs, mobile phones, smartphones, and tablet terminals. [Examples]

[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 following "parts" and "%" are values ​​based on "parts by mass" and "mass%", respectively.

[0068] The raw materials used in the examples are listed below. <Thermosetting resin> [Synthesis of thermosetting resin 1] In a glass flask equipped with a stirrer, thermometer, reflux condenser, nitrogen inlet tube, and vacuum equipment, 166 parts terephthalic acid, 146 parts adipic acid, 212 parts 3-methyl-1,5-pentanediol, and 25 parts ethylene glycol were charged. The mixture was stirred while passing nitrogen gas through it, and the temperature was gradually increased under atmospheric pressure. The mixture was reacted at 200-230°C for approximately 8 hours to obtain a liquid with an acid value of 43. Next, 0.01 parts tetra-n-butoxytitanium was charged, and after purging with nitrogen, the mixture was stirred at 180°C for 30 minutes under a sealed container. The mixture was then reacted at 230°C and 5 mmHg for 2 hours to obtain a polyester diol with an acid value of 1.1, a hydroxyl value of 114.2, a molecular weight of 982, and a color of 10 (APHA method, the same applies hereafter). Next, 734 parts of the polyester diol, 23.9 parts of dimethylolpropionic acid, 219 parts of toluene diisocyanate, and 242 parts of toluene were charged into a reaction vessel equipped with a stirrer, thermometer, reflux condenser, dropping device, and nitrogen inlet tube, and the mixture was reacted at 50°C under a nitrogen atmosphere for 8 hours. To this, 1200 parts of toluene were added to obtain a solution of urethane prepolymer having isocyanate groups at its ends. Next, the solution of the obtained prepolymer was heated to 70°C, and while maintaining this temperature, a solution of 20.0 parts 1,3-diaminopropane, 3.1 parts benzylamine, 600 parts 2-pronol, and 961 parts toluene was added dropwise over 1 hour. After the dropwise addition was complete, the reaction was continued at 70°C for a further 6 hours to obtain a polyurethane resin (A-1) with a molecular weight (Mw) of 130,000, an acid value of 10 mg KOH / g, a Tg of 20°C, and a solid content of 25%.

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

[0070] <Hardening agent> Hardener 1: Bisphenol A type epoxy compound "jER828" (epoxy equivalent = 189 g / eq), manufactured by Mitsubishi Chemical Corporation. Hardener 2: Tetraphenolethane type epoxy resin "jER1031s" (tetrafunctional, epoxy equivalent = 200g / eq), manufactured by Mitsubishi Chemical Corporation. Hardener 3: Vinyl ether-modified bisphenol A type epoxy resin "EXA4850-150" (epoxy equivalent 450, molecular weight 900), manufactured by DIC Corporation. Hardener 4: Aziridine compound, "Chemitite PZ-33" manufactured by Nippon Shokubai Co., Ltd. Hardener 5: Hexamethylene diisocyanate-buuret compound, "Duranate 24A-100" (100% solids, 23.5% NCO by mass), manufactured by Asahi Kasei Corporation. Hardener 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 zirconia-based inorganic cation scavenging agent and hydrotalcite-based inorganic anion scavenging agent, with an average particle diameter D50 of 0.5 μm (manufactured by Toagosei Co., Ltd.)) Inorganic filler 3: IXE300 (Antimony-based inorganic cation scavenging agent, average particle diameter D50 of 0.5 μm (manufactured by Toagosei Co., Ltd.)) Inorganic filler 4: SS50 (silica, average particle size D50 is 4.5 μm (Tosoh Silica Co., Ltd.))

[0072] <Average particle size of inorganic filler D50> The average particle size D50 is the value obtained by measuring conductive fine particles using a Tornado Dry Powder sample module with a Beckman Coulter LS13320 laser diffraction / scattering particle size distribution analyzer. It represents the particle size at which the cumulative value in the particle size cumulative distribution reaches 50%. The refractive index was set to 1.6.

[0073] [Creation of insulating resin layer 1] A thermosetting resin composition was obtained by placing 100 parts of thermosetting resin 1 (solids), 20 parts of curing agent 3, 0.5 parts of thermosetting agent 4, and 11.4 parts of inorganic filler 1 into a container, adding a mixed solvent of toluene:isopropyl alcohol (mass ratio 2:1) to achieve a non-volatile content concentration of 45% by mass, and stirring with a disperser for 10 minutes. This thermosetting resin composition was coated onto a release substrate using a doctor blade to achieve a dry thickness of 40 μm. A laminated sheet was then obtained by drying at 100°C for 2 minutes, with the release substrate and resin layer 1 laminated together.

[0074] [Creation of insulating resin layers 2-22 and 101-102] Laminated sheets were obtained by the same procedure as for insulating resin layer-1, except that the proportions of the materials in Table 1 were changed, with insulating resin layers 2-22 and 101-102 laminated on a releaseable substrate.

[0075] The following physical properties were measured for the obtained insulating resin layer. 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 (weighted to 200 g) was brought into contact with the surface of the insulating resin layer of a laminated sheet, which consisted of a release substrate and an insulating resin layer, for 1 second. The force detected was then measured when the probe was lifted from the surface of the adhesive layer at a speed of 10 mm / second. Five measurements were taken, and the average value was calculated.

[0077] <Measurement of Young's modulus at 23°C> A laminated sheet consisting of a release agent and an insulating resin layer was left standing for 24 hours at 23°C and 50% relative humidity. After that, the insulating resin layer from which the release agent had been peeled off was subjected to a tensile test using an "EZ Tester" (Shimadzu Corporation) in a constant temperature and humidity chamber at 23°C and 50% relative humidity, with a tensile speed of 50 mm / min and a gauge length of 25 mm. The stress-strain curve was measured, and the linear regression (slope) in the region of strain (elongation) of 0.1 to 0.3% was defined as the Young's modulus at 23°C.

[0078] <Storage modulus at 23°C> A laminated sheet consisting of a release substrate and an insulating resin layer was left standing for 24 hours at 23°C and 50% relative humidity. Afterward, the insulating resin layer, from which the release substrate had been peeled off, was measured using a dynamic modulus measuring device DVA-200 (manufactured by IT Measurement Control Co., Ltd.) under the conditions of "tensile" deformation mode, frequency 10 Hz, heating rate 10°C / min, and measurement temperature range -50°C to 300°C. The storage modulus at 23°C was determined. In addition, the storage modulus at 120°C and 170°C was also measured.

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

[0080] [Table 1]

[0081] [Example 1] By laminating insulating resin layer 8 and insulating resin layer 1 using a hot roll laminator, an electronic component protective sheet with a release substrate was obtained, consisting of a release substrate / second insulating resin layer (resin layer 8) / first insulating resin layer (resin layer 1) / release substrate in that order. The lamination conditions were 70°C and 3 kgf / cm². 2 That's what I decided. Hereinafter, the "second insulating resin layer" will be abbreviated as the "outer insulating resin layer," and the "release substrate" covering the "outer insulating resin layer" will be abbreviated as the "outer release substrate."

[0082] [Examples 2-22, Comparative Examples 1-2] As shown in Table 2, Examples 2-22 and Comparative Examples 1-2 were obtained by the same procedure as in Example 1, except that the combination of insulating resin layers was changed.

[0083] [Example 23] The insulating resin layer 1 and the insulating resin layer 14 were bonded together using a hot roll laminator, resulting in a laminated structure in the following order: release substrate / intermediate insulating resin layer (resin layer 14) / first insulating resin layer (resin layer 1) / release substrate. Next, the release substrate on the insulating resin layer 14 side was peeled off, and the insulating resin layer 12 was bonded to the exposed surface using a hot roll laminator, thereby obtaining an electronic component protective sheet with a release substrate, in which the outer release substrate / insulating resin layer 12 / insulating resin layer 14 / insulating resin layer 1 / release substrate were laminated in that order. The bonding conditions were 70°C and 3 kgf / cm². 2 That's what I decided.

[0084] [Example 24] Except for changing the combination of insulating resin layers shown in Table 3, the same procedure as in Example 23 was used to obtain the electronic component protective sheet with a peelable substrate of Example 24.

[0085] [Examples 25-30] As shown in Table 4, the electronic component protective sheets with peelable substrates of Examples 25 to 30 were obtained by the same procedure as in Example 1, except that the combination of insulating resin layers was changed.

[0086] The temporary adhesion, release properties, migration resistance, and embedding properties of the electronic component protection sheets obtained in each example and comparative example were evaluated. The results are shown in Tables 2 and 3.

[0087] <Temporary Tension> An electronic component protective sheet with a release substrate was cut to a width of 25 mm and a length of 100 mm. The release substrate on the first insulating resin layer side was peeled off to expose the first insulating resin layer, which was then coated onto a polyimide film measuring 30 mm in width and 150 mm in length, with a thickness of 125 μm, at 23°C and 3 kgf / cm². 2 It was roll-laminated and attached under these 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 Toyo Chem Co., Ltd.'s double-sided acrylic adhesive tape "DF715" (thickness of the acrylic adhesive layer on each side: 35 μm). This was used as the measurement sample. A T-peel test was performed using a tensile testing machine at a tensile speed of 50 mm / min to measure the adhesive strength between the first insulating resin layer and the polyimide film. ◎: Adhesive strength of 0.5N or higher. This is an excellent result. ○: Adhesion strength is 0.25 or higher and less than 0.5. This is a good result. △: Adhesive strength is between 0.1 and 0.25. No practical problems. ×: Adhesive strength is less than 0.1. Not practical for use.

[0088] <Release> A protective sheet for electronic components with a release substrate is cut to a width of 25 mm and a length of 100 mm. The outer release substrate is peeled off, and the exposed outer insulating resin layer is coated with a polyimide film measuring 30 mm in width and 150 mm in length, with a thickness of 125 μm, at 23°C and 3 kgf / cm². 2 It was roll-laminated and attached under these conditions. Next, the release substrate on the insulating resin layer side of the first sample was peeled off, and a 25 μm PET film was attached to the exposed surface of the first insulating resin layer via a double-sided acrylic adhesive tape "DF715" manufactured by Toyo Chem Co., Ltd. (thickness of the acrylic adhesive layer on each side: 35 μm). This was used as the measurement sample. A T-peel test was performed using a tensile testing machine at a tensile speed 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. This is a very good result. ○: Adhesion strength is above 0.1 and below 0.25. This is a good result. △: Adhesive strength is above 0.25 and below 0.5. No practical problems. ×: Adhesive strength exceeds 0.5N. Not practical for use.

[0089] <Migration resistance test> The migration test will be explained with reference to Figure 4. By etching a laminate of 18 μm thick copper foil and 25 μm thick polyimide film, comb-shaped conductor patterns 200 and 300 with a line / space of 0.1 mm / 0.1 mm, and electrodes 200' and 300' continuous with both comb-shaped conductor patterns were formed 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 protective sheet with the release substrate, and as shown in the plan view of Figure 4(2), the double-comb conductor patterns 200 and 300 were covered, and the exposed first insulating resin layer was placed on top to an extent that both electrodes 200' and 300' were exposed. It was then heat-pressed at 150°C, 2.0 MPa, and 3 min. to remove the outer release substrate, and then further heated in an electric oven at 160°C at atmospheric pressure for 60 min. to cure the first insulating resin layer and the outer insulating resin layer. As shown in Figures 4(3) and (4), the double-comb conductor patterns were covered with the cured product 10' of the electronic component protective sheet, and this was used as an evaluation sample. The evaluation sample was subjected to a voltage of 50V applied between the comb-shaped conductors in an atmosphere of 85°C and 85%RH (relative humidity), and the change in resistance was measured continuously for 1000 hours. Note that "leakage touch" below refers to dielectric breakdown due to a short circuit, resulting in a momentary decrease in resistance and the flow of current. If there is no leakage touch, the insulation performance does not decrease. The evaluation criteria are as follows. ◎: Resistance value after 1000 hours is 10 8 Omega or higher, no leaks. Good results. ○: Resistance value after 1000 hours is 10 7 Omega or higher, no leaks. Good results. △: Resistance value after 1000 hours is 10 7 Ω or higher, one leak touch detected. No practical issues. ×: The resistance value after 1000 hours is 10 7 Less than 2 leaks detected. Not practical for use.

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

[0091] An electronic component protective sheet with a release-type substrate was cut to 10cm x 10cm. The release-type substrate on the first insulating resin layer side was peeled off, and the sheet was placed on the test substrate so that the first insulating resin layer was in contact with the electronic component 2a. Then, the release-type substrate on the second insulating resin layer side was peeled off, and two types of films (0.05mm thick TPX (product name: Opulan X-44B, manufacturer: Mitsui Chemicals Tohcello Co., Ltd.) and 2.0mm thick PVC film (product name: Celeb T, manufacturer: Okamoto)) were laminated in that order as cushioning material, and cardboard was further laminated to prevent sticking. The substrate surface was then hot-pressed from above under conditions of 5MPa and 160℃ for 20 minutes. After hot-pressing, it was cooled, the cushioning material and cardboard were peeled off, and the sample was used for measurement. The thickness of the sample was polished to form a cross-section for observation, and the embedding ability was evaluated by observing 10 grooves between electronic components with an electron microscope. The evaluation criteria were as follows: ◎: All grooves are filled. This is a very good result. ○: Nine grooves have been filled. This is a good result. △: Eight grooves are embedded. This does not pose a practical problem. ×: Not all grooves are filled. Not practical.

[0092] [Table 2]

[0093] [Table 3]

[0094] [Table 4]

[0095] As shown in Tables 2-4, the electronic component protective sheet of the present invention exhibited excellent temporary adhesion, release properties, migration resistance, and embedding properties. This confirmed that the electronic component protection sheet can be applied to small substrates with complex shapes and uneven surfaces. [Explanation of Symbols]

[0096] 1 circuit board 2 Electronic components 3 Handa 4. Circuit board with electronic components mounted on it 10 Electronic component protective sheets 10' Cured Electronic Component Protective Sheet 11. First insulating resin layer 12. Second insulating resin layer 13 Cushioning material 14 Conventional electronic component protective sheets 15. Protective coating layer 20 Heat-sealing device 100 Polyimide Film 200, 300 comb-type conductor pattern 200', 300' electrode

Claims

1. An electronic component protective sheet for covering and protecting a group of electronic components consisting of multiple electronic components of different heights mounted on a circuit board, The aforementioned electronic component protective sheet has an insulating resin layer containing a thermosetting resin, The insulating resin layer comprises a first insulating resin layer in contact with the group of electronic components and a second insulating resin layer located furthest from the group of electronic components. 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. An electronic component protective sheet characterized in that the Young's modulus of the second insulating resin layer at 23°C is 8 MPa or more higher than the Young's modulus of the first insulating resin layer at 23°C.

2. The first insulating resin layer has a storage modulus of 1.0 + E04 Pa to 5.0 + E08 Pa at 23°C. The second insulating resin layer has a storage modulus of 1.0 + E06 Pa to 5.0 + E09 Pa at 23°C. The electronic component protective sheet according to claim 1, characterized in that the storage modulus at 23°C is higher for the second insulating resin layer than for the first insulating resin layer.

3. The electronic component protective sheet according to claim 1 or 2, characterized in that the first insulating resin layer and the second insulating resin layer each contain an inorganic filler.

4. The electronic component protective sheet according to claim 3, characterized in that the inorganic filler is at least one selected from the group consisting of silica, talc, and ion collecting agents.

5. The electronic component protective sheet according to claim 4, characterized in that 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.

6. The electronic component protective sheet according to claim 4, characterized in that 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 or the second insulating resin layer contains an ion collecting agent.

7. The electronic component protective sheet according to any one of claims 1 to 6, wherein the insulating resin layer further comprises a curing agent, and the content of the curing agent is 3 to 100 parts by mass per 100 parts by mass of the thermosetting resin.

8. The electronic component protective sheet according to any one of claims 1 to 7, characterized in that the elongation at break of the first insulating resin layer and the second insulating resin layer at 23°C is independently 50 to 1500%.

9. A substrate on which a group of electronic components consisting of multiple electronic components of different heights mounted on the substrate is covered with a cured product of the electronic component protective sheet described in any one of claims 1 to 8.

10. The process of mounting a group of electronic components consisting of multiple electronic components of different heights onto a circuit board. A step of preparing an electronic component protective sheet according to any one of claims 1 to 8, A step of 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 protective sheet by heating and pressurizing it to conform to the shape of each electronic component, thereby covering at least a portion of the group of electronic components and the substrate. and A method for protecting a substrate on which a group of electronic components are mounted, comprising the step of heat-curing the deformed electronic component protective sheet in its deformed state to form a protective coating layer.

11. The process of mounting a group of electronic components consisting of multiple electronic components of different heights onto a circuit board. A step of preparing an electronic component protective sheet according to any one of claims 1 to 8, A step of 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 protective sheet by heating and pressurizing it to conform to the shape of each electronic component, thereby covering at least a portion of the group of electronic components and the substrate, and A method for manufacturing a substrate on which a group of electronic components with a protective coating layer is mounted, comprising the step of heat-curing the deformed electronic component protective sheet in its deformed state to form a protective coating layer.

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