JP6735071B2 - Sealing resin sheet - Google Patents

Description

The present invention relates to a sealing resin sheet.

2. Description of the Related Art Today, with the spread of mobile devices such as mobile phones, there is an increasing demand for miniaturization and high functionality of circuit boards used in electronic devices. In order to meet such demands, the packaging density of electronic components in multilayer printed wiring boards and the like has been improved, and electronic components themselves have been miniaturized and wiring and the like have been miniaturized.

Insulating layers and the like of multilayer printed wiring boards are required to have a laminating property capable of filling fine electronic components and wirings. As resin compositions considering such performance, cyanate ester resin, epoxy resin, thermoplastic resin, talc And a resin composition for printed wiring boards containing silica have been proposed (see Patent Document 1).

JP, 2010-202865, A

As measures for improving the mounting density of electronic components, efforts have been made to reduce the size of electronic components themselves, miniaturize wiring, and the like, and to arrange electronic components. For example, an electronic component-embedded substrate technology for embedding and embedding an electronic component, which has been mounted on the surface of the substrate so far, inside the substrate (within the range in the thickness direction), is being developed.

As a procedure for manufacturing an electronic component-embedded substrate, one or more electronic components are arranged in an opening provided in the substrate, a sealing resin sheet for sealing is arranged on the substrate so as to cover the opening, and a sealing is performed. A procedure for heating and pressing the sealing resin sheet for stopping to flow the sealing resin sheet to fill the opening of the substrate and finally to heat cure the sealing resin sheet has been studied. According to this, a plurality of openings are formed in one substrate, a predetermined number of electronic components are arranged in the openings, and the opening and By embedding electronic components, it is possible to collectively manufacture electronic component-embedded substrates in which a plurality of electronic components are embedded in one substrate.

In consideration of the above manufacturing procedure, when the encapsulating resin sheet placed on the substrate is misaligned, the required properties of the encapsulating resin sheet for electronic component built-in boards are the filling properties of the opening of the board. It is required to have removability so that the encapsulating resin sheet can be peeled off and reattached to the correct position.

Lowering the viscosity of the encapsulating resin sheet is effective for improving the filling property (fluidity), and reducing the filler content can be mentioned as a measure for lowering the viscosity. In this case, tackiness (stickiness) due to the organic component appears, and removability deteriorates. On the other hand, when the filler content is increased, the elastic modulus is increased and the removability is improved, but the viscosity of the sealing resin sheet is increased and the filling property is decreased. Thus, the filling property and the removability are in a trade-off relationship, and there is a strong demand for a sealing resin sheet that achieves both of them.

It is an object of the present invention to provide a sealing resin sheet that has both filling properties and removability.

As a result of intensive studies, the present inventors have found that the above problems can be solved by adopting the following configuration, and have completed the present invention.

That is, the present invention has a tack force at 25° C. of 150 g or less,
The present invention relates to a sealing resin sheet having a minimum melt viscosity of 50 Pa·s or less in a temperature range of 50°C to 150°C.

In the encapsulating resin sheet, the tack force at 25° C. (hereinafter, also simply referred to as “tack force”) is 150 g or less, so that good removability can be exhibited. At the same time, since the minimum melt viscosity in the temperature range of 50° C. to 150° C. (hereinafter, also simply referred to as “minimum melt viscosity”) is 50 Pa·s or less, the viscosity of the encapsulating resin sheet is reduced, It can exhibit excellent filling properties. If the tack force is too large, even if the sealing resin sheet is placed on the substrate and then peeled off, the sealing resin sheet is unlikely to peel off from the substrate, and the sealing resin sheet may be damaged in some cases. Regarding the minimum melt viscosity, since the electronic component is arranged inside the opening, not only the surface structure of the electronic component but also the space between the inner wall of the opening and the electronic component needs to be densely filled. If the minimum melt viscosity is too high, the opening will not be sufficiently filled with the encapsulating resin sheet, voids will occur inside the opening, and the reflow resistance etc. will decrease and the reliability of the electronic component built-in board will decrease. There is a risk.

The encapsulating resin sheet preferably contains an inorganic filler having an average particle size of 0.1 to 10 μm. The encapsulating resin sheet preferably contains the inorganic filler in an amount of 65 to 85% by weight based on the total solid content of the encapsulating resin sheet. With these configurations, it is possible to easily achieve both the removability by controlling the tack force and the filling property by controlling the minimum melt viscosity.

（式中、Ｒ１〜Ｒ４は、それぞれ独立して水素又はメチル基である。ただし、Ｒ１〜Ｒ４の全てが水素である場合を除く。） The encapsulating resin sheet preferably contains an epoxy resin represented by the following chemical formula (1).

(In the formula, R1 to R4 are each independently hydrogen or a methyl group, except when all of R1 to R4 are hydrogen.)

Among the organic components, there is a compound having low crystallinity, which does not return to the crystalline state before melting even if it is once melted by heating and then has a lower crystallinity. In the case of an organic component having low crystallinity, tack may increase and removability may decrease. The epoxy resin represented by the above chemical formula (1) as an organic component (hereinafter, also referred to as “crystalline epoxy resin”) maintains crystallinity even after thermal melting, and thus suppresses an increase in tack. It is possible to improve the removability.

The encapsulating resin sheet preferably contains the epoxy resin represented by the chemical formula (1) in an amount of 5 to 15% by weight based on the total solid weight of the encapsulating resin sheet. By setting the content of the crystalline epoxy resin within the above range, the removability and the filling property can be exhibited at a higher level.

In the encapsulating resin sheet, R1 to R4 in the chemical formula (1) are preferably all methyl groups. As a result, the rigidity of the skeleton of the crystalline epoxy resin is increased and the crystallinity is also increased, and good removability can be exhibited more efficiently.

The encapsulating resin sheet may be for encapsulating electronic components in an electronic component built-in substrate or for interlayer insulation. The encapsulating resin sheet can be suitably applied to a process that requires removability and filling properties.

It is a figure which shows typically one process of the manufacturing method of the electronic component built-in board which concerns on one Embodiment of this invention. It is a figure which shows typically one process of the manufacturing method of the electronic component built-in board which concerns on one Embodiment of this invention. It is a figure which shows typically one process of the manufacturing method of the electronic component built-in board which concerns on one Embodiment of this invention. It is a figure which shows typically one process of the manufacturing method of the electronic component built-in board which concerns on one Embodiment of this invention. It is a figure which shows typically one process of the manufacturing method of the electronic component built-in board which concerns on one Embodiment of this invention.

Hereinafter, a polarizing plate according to an embodiment of the present invention will be described with reference to the drawings. However, in some or all of the drawings, portions unnecessary for description are omitted, and there are portions illustrated in an enlarged or reduced form for ease of explanation.

<Sealing resin sheet>
The encapsulating resin sheet 3 (see FIG. 1D) according to one embodiment of the present invention is a sheet-like object having a constant thickness, and its plan view shape is a circle, a rectangle, a square, or the like in accordance with the substrate shape. It can be appropriately selected. Sealing resin sheet 3 is typically provided in a state of being laminated on a support (not shown) such as a polyethylene terephthalate (PET) film. It should be noted that the support may be subjected to a mold release treatment in order to easily peel off the sealing resin sheet 3.

The tack force at 25° C. of the sealing resin sheet is preferably 150 g or less, more preferably 140 g or less, and further preferably 130 g or less. When the tack force is within the above range, good removability can be achieved. The smaller the tacking force is, the more preferable. However, from the viewpoint of workability and filling property (fluidity) after placing the encapsulating resin sheet on the substrate, 0 g or more is preferable, and 5 g or more is more preferable.

The minimum melt viscosity of the sealing resin sheet 3 in the temperature range of 50° C. to 150° C. is preferably 50 Pa·s or less, more preferably 40 Pa·s or less, further preferably 30 Pa·s or less. By setting the minimum melt viscosity of the encapsulating resin sheet 3 within the above range, it is possible to improve the filling property into the opening of the substrate and suppress the generation of voids, and to obtain a highly reliable electronic component-containing substrate. You can On the other hand, if the minimum melt viscosity is too low, it may be difficult to maintain the sheet shape or the tack force at room temperature may increase, so 1 Pa·s or more is preferable, and 3 Pa·s or more is more preferable. ..

The sealing resin sheet 3 preferably contains an epoxy resin and a phenol resin. Thereby, good thermosetting property can be obtained.

The epoxy resin is not particularly limited. For example, triphenylmethane type epoxy resin, cresol novolac type epoxy resin, biphenyl type epoxy resin, modified bisphenol A type epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, modified bisphenol F type epoxy resin, dicyclopentadiene type Various epoxy resins such as epoxy resin, phenol novolac type epoxy resin, and phenoxy resin can be used. These epoxy resins may be used alone or in combination of two or more kinds.

（式中、Ｒ１〜Ｒ４は、それぞれ独立して水素又はメチル基である。ただし、Ｒ１〜Ｒ４の全てが水素である場合を除く。） From the viewpoint of securing the toughness after curing of the epoxy resin and the reactivity of the epoxy resin, an epoxy equivalent of 150 to 250, a softening point or a melting point of 50 to 130° C., which is solid at room temperature is preferable, and from the viewpoint of reliability, Triphenylmethane type epoxy resin, cresol novolac type epoxy resin, and biphenyl type epoxy resin are more preferable. Among these, a biphenyl type epoxy resin is preferable, and it is particularly preferable to include an epoxy resin represented by the following chemical formula (1).

(In the formula, R1 to R4 are each independently hydrogen or a methyl group, except when all of R1 to R4 are hydrogen.)

Among the organic components, there is a compound having low crystallinity, which does not return to the crystalline state before melting even if it is once melted by heating and then has a lower crystallinity. In the case of an organic component having low crystallinity, tack may increase and removability may decrease. Since the epoxy resin represented by the above chemical formula (1) as an organic component retains its crystallinity even after being melted by heat, it is possible to suppress an increase in tack and to improve removability. You can

The encapsulating resin sheet preferably contains the epoxy resin represented by the chemical formula (1) in an amount of 5 to 15% by weight, more preferably 8 to 12% by weight, based on the total solid content of the encapsulating resin sheet. .. By setting the content of the crystalline epoxy resin within the above range, the removability and the filling property can be exhibited at a higher level.

In the encapsulating resin sheet, R1 to R4 in the chemical formula (1) are preferably all methyl groups. As a result, the rigidity of the skeleton of the crystalline epoxy resin is increased and the crystallinity is also increased, and good removability can be exhibited more efficiently.

The phenol resin is not particularly limited as long as it causes a curing reaction with the epoxy resin. For example, a phenol novolac resin, a phenol aralkyl resin, a biphenyl aralkyl resin, a dicyclopentadiene type phenol resin, a cresol novolac resin, a resole resin or the like is used. These phenol resins may be used alone or in combination of two or more.

From the viewpoint of reactivity with the epoxy resin, it is preferable to use a phenol resin having a hydroxyl group equivalent of 70 to 250 and a softening point of 50 to 110° C. Among them, phenol novolac is preferable from the viewpoint of high curing reactivity. Resin can be used suitably. Further, from the viewpoint of reliability, low hygroscopic materials such as phenol aralkyl resin and biphenyl aralkyl resin can be preferably used.

From the viewpoint of curing reactivity, the mixing ratio of the epoxy resin and the phenol resin is such that the total amount of hydroxyl groups in the phenol resin is 0.7 to 1.5 equivalents relative to 1 equivalent of the epoxy groups in the epoxy resin. The amount is preferably 0.9 to 1.2 equivalents.

The lower limit of the total content of the epoxy resin and the phenol resin in the encapsulating resin sheet is preferably 10% by weight or more, more preferably 12% by weight or more. When it is at least 10% by weight, good adhesion to electronic devices, substrates and the like can be obtained. On the other hand, the upper limit of the total content is preferably 30% by weight or less, more preferably 28% by weight or less. When it is 30% by weight or less, the hygroscopicity of the sealing resin sheet can be reduced.

The sealing resin sheet 3 may contain a thermoplastic resin as long as the solvent resistance is satisfied.

The encapsulating resin sheet preferably contains an inorganic filler. The shape of the inorganic filler is not particularly limited, and may be any shape such as spherical shape (including ellipsoidal shape), polyhedral shape, polygonal columnar shape, and indefinite shape. From the viewpoint of achievement and proper fluidity, spherical shape is preferable.

The inorganic filler is not particularly limited, and various conventionally known fillers can be used. Examples thereof include quartz glass, talc, silica (such as fused silica and crystalline silica), alumina, aluminum nitride, and silicon nitride. , And boron nitride powder. These may be used alone or in combination of two or more. Among them, silica and alumina are preferable, and silica is more preferable, because the linear expansion coefficient can be favorably reduced.

As silica, silica powder is preferable, and fused silica powder is more preferable. Examples of the fused silica powder include spherical fused silica powder and crushed fused silica powder, and spherical fused silica powder is preferable from the viewpoint of fluidity.

The average particle diameter of the inorganic filler is preferably in the range of 0.1 to 10 μm, more preferably 0.5 to 5 μm. The average particle size can be derived by using a sample arbitrarily extracted from the population and using a laser diffraction/scattering particle size distribution measuring device. If the average particle size of the inorganic filler is too small, the viscosity of the encapsulating resin sheet tends to be high, and the filling property tends to be low or the tack force tends to increase, and if it is too large, the voids in the openings of the substrate The filling may be insufficient.

The encapsulating resin sheet preferably contains the inorganic filler in an amount of 65 to 85% by weight, and more preferably 70 to 83% by weight, based on the total solid weight of the encapsulating resin sheet. By setting the content of the inorganic filler in the above range, it is possible to easily achieve both the removability by controlling the tack force and the filling property by controlling the minimum melt viscosity.

The encapsulating resin sheet 3 preferably contains a curing accelerator.

The curing accelerator is not particularly limited as long as it accelerates the curing of the epoxy resin and the phenol resin, and examples thereof include organophosphorus compounds such as triphenylphosphine and tetraphenylphosphonium tetraphenylborate; 2-phenyl-4, Imidazole compounds such as 5-dihydroxymethylimidazole and 2-phenyl-4-methyl-5-hydroxymethylimidazole; and the like. Among them, 2-phenyl-4,5-dihydroxymethylimidazole is preferable because the curing reaction does not rapidly proceed even when the temperature rises during kneading and the encapsulating resin sheet 3 can be produced well.

The content of the curing accelerator is preferably 0.1 to 5 parts by weight based on 100 parts by weight of the total of the epoxy resin and the phenol resin.

The encapsulating resin sheet 3 preferably contains a flame retardant component. As a result, it is possible to reduce the spread of combustion when a component is short-circuited or heat is generated. As the flame retardant composition, for example, various metal hydroxides such as aluminum hydroxide, magnesium hydroxide, iron hydroxide, calcium hydroxide, tin hydroxide and complex metal hydroxides; phosphazene flame retardants should be used. You can

The encapsulating resin sheet 3 preferably contains a silane coupling agent. The silane coupling agent is not particularly limited, and examples thereof include 3-glycidoxypropyltrimethoxysilane.

The content of the silane coupling agent in the sealing resin sheet 3 is preferably 0.1 to 3% by weight. When the content is 0.1% by weight or more, the strength of the encapsulating resin sheet after curing can be increased and the water absorption rate can be reduced. On the other hand, when the content is 3% by weight or less, generation of outgas can be suppressed.

The encapsulating resin sheet 3 preferably contains a pigment. The pigment is not particularly limited, and examples thereof include carbon black.

The content of the pigment in the sealing resin sheet 3 is preferably 0.1 to 2% by weight. Good marking properties are obtained as it is 0.1% by weight or more. On the other hand, when the content is 2% by weight or less, the strength of the cured encapsulating resin sheet can be secured.

In addition to the above components, other additives may be appropriately added to the resin composition, if necessary.

<<Method for manufacturing encapsulating resin sheet>>
The method for producing the encapsulating resin sheet 3 is not particularly limited, but a method of preparing a kneaded product and processing the obtained kneaded product into a sheet shape is preferable. Specifically, the above-mentioned components are melt-kneaded by a known kneader such as a mixing roll, a pressure kneader and an extruder to prepare a kneaded product, and the obtained kneaded product is processed into a sheet. As the kneading conditions, the temperature is preferably equal to or higher than the softening point of each component described above, for example, 30 to 150° C., considering the thermosetting property of the epoxy resin, preferably 40 to 140° C., more preferably 60 to 120° C. ℃. The time is, for example, 1 to 30 minutes, preferably 5 to 15 minutes.

The kneading is preferably performed under reduced pressure conditions (under reduced pressure atmosphere). The upper limit of the pressure under the reduced pressure condition is preferably 0.1 kg/cm ² or less, more preferably 0.05 kg/cm ² or less. The lower the lower limit of the pressure under the reduced pressure condition is, the more preferable, but it may be 1×10 ⁻⁴ kg/cm ² or more in view of productivity and physical limit. As a result, it is possible to prevent gas from being mixed into the kneaded product, and to suppress the generation of pores in the obtained kneaded product.

The kneaded product after melt-kneading is preferably processed in a high temperature state without cooling. The processing method is not particularly limited, and examples thereof include a flat plate pressing method, a T-die extrusion method, a roll rolling method, a roll kneading method, an inflation extrusion method, a coextrusion method, and a calender molding method. The processing temperature is preferably equal to or higher than the softening point of each component described above, and is 40 to 150° C., preferably 50 to 140° C., more preferably 70 to 120° C. in consideration of the thermosetting property and moldability of the epoxy resin. ..

The thickness of the sealing resin sheet 3 is not particularly limited, but is preferably 50 to 700 μm. Within the above range, it is possible to satisfactorily fill the opening of the substrate. Further, by making the sealing resin sheet thin, the amount of heat generated can be reduced, and curing shrinkage hardly occurs. As a result, the amount of package warpage can be reduced, and a more reliable electronic component built-in substrate can be obtained.

The encapsulating resin sheet 3 may have a single-layer structure or a multi-layer structure in which two or more encapsulating resin sheets are laminated, but there is no fear of delamination, and the sheet thickness is highly uniform. A single-layer structure is preferable because it easily lowers moisture absorption.

The encapsulating resin sheet 3 may be for encapsulating electronic components in the electronic component built-in board as described above, or for interlayer insulation in a multilayer circuit board. Further, a SAW (Surface Acoustic Wave) filter; a MEMS (Micro Electro Mechanical Systems) such as a pressure sensor and a vibration sensor; an IC such as an LSI; a semiconductor such as a transistor; a capacitor; a resistor; a surface mount type electronic device such as a CMOS sensor. It can also be used for sealing.

<< Manufacturing method of electronic component built-in board >>
1A to 1E are diagrams schematically showing one step of a method for manufacturing an electronic component-embedded substrate according to an embodiment of the present invention. Although the manufacturing procedure of the electronic component built-in substrate is not particularly limited, one or more electronic components 2 are arranged in the opening O provided in the substrate 1, and the sealing resin sheet 3 is provided on the substrate so as to cover the opening O. 1 and then heat press from the upper surface side of the encapsulating resin sheet 3 to flow the encapsulating resin sheet to fill the opening O of the substrate 1 and heat cure the encapsulating resin sheet 3. It can be preferably adopted.

(Substrate preparation process)
The substrate 1 (see FIG. 1A) is not particularly limited, and examples thereof include a metal substrate such as a copper substrate, a (multilayer) printed wiring board, a ceramic substrate, and a silicon substrate.

(Opening process)
Next, the opening O is formed in the substrate 1 (see FIG. 1B). The method of forming the opening O is not particularly limited, and examples thereof include etching, laser processing, and punching processing. The number of openings formed on one substrate is not particularly limited, and may be appropriately changed according to the intended design of the electronic component built-in substrate.

(Electronic component placement process)
As shown in FIG. 1C, one or more electronic components 2 are arranged inside the opening O formed in the substrate 1. The electronic component is not limited at all, and any electronic component such as a semiconductor chip, a capacitor, a sensor device, a light emitting element, or a vibrating element can be used. Although one electronic component 2 is arranged in one opening O in FIG. 1C, the number of electronic components arranged in one opening is not limited to one, and the target electronic component is not limited to one. It may be appropriately changed according to the design of the component-embedded substrate.

(Filling process)
In the filling step, as shown in FIGS. 1D and 1E, the encapsulating resin sheet 3 is laminated on the substrate 1 so as to cover the opening O, and then the upper surface side of the encapsulating resin sheet 3 is hot-pressed and sealed. The resin sheet 3 is made to flow to fill the opening O of the substrate 1, and after filling, the sealing resin sheet 3 is thermoset.

As the hot pressing conditions for hot pressing the encapsulating resin sheet 3 to fill the openings O, the temperature is, for example, 50 to 100° C., preferably 60 to 90° C., and the pressure is, for example, 0. It is 1 to 3.0 MPa, preferably 0.5 to 2.5 MPa, and the time is, for example, 5 to 120 minutes, preferably 10 to 60 minutes. Further, in consideration of the improvement in adhesion and followability of the encapsulating resin sheet 3 to the inner wall of the opening O and the electronic component 2, it is preferable to press under a reduced pressure condition (for example, as a gauge pressure of −90 to −100 kPaG). ..

After the filling of the opening is completed, the encapsulating resin sheet 3 is heat-cured. As a condition for the thermosetting treatment, the heating temperature is preferably 100° C. or higher, more preferably 120° C. or higher. On the other hand, the upper limit of the heating temperature is preferably 200°C or lower, more preferably 190°C or lower. The heating time is preferably 5 minutes or longer, more preferably 10 minutes or longer. On the other hand, the upper limit of the heating time is preferably 120 minutes or less, more preferably 60 minutes or less. In addition, the pressure may be increased if necessary, preferably 0.5 MPa or more, more preferably 1.0 MPa or more. On the other hand, the upper limit is preferably 5.0 MPa or less, more preferably 3.0 MPa or less. Thereby, the electronic component built-in substrate 10 in which the electronic component 2 is embedded in the substrate 1 is obtained.

Hereinafter, preferred embodiments of the present invention will be illustratively described in detail. However, the materials, compounding amounts, and the like described in this example are not intended to limit the scope of the present invention to them unless otherwise specified.

The components used in the examples will be described.
Epoxy resin 1: YX4000H (biphenyl type epoxy resin, epoxy equivalent 190 g/eq.) manufactured by Mitsubishi Chemical Corporation.
Epoxy resin 2: YSLV-80XY (bisphenol F type epoxy resin, Epokin equivalent 200 g/eq.) manufactured by Nippon Steel Chemical Co., Ltd.
Epoxy resin 3: Epicoat 828 manufactured by Mitsubishi Chemical Corporation (epoxy equivalent 190 g/eq.)
Phenolic resin 1: MEH-7500-3S manufactured by Meiwa Kasei Co. (hydroxyl group equivalent 103 g/eq.)
Phenol resin 2: MEH-7851-SS (phenol resin having a biphenylaralkyl skeleton, hydroxyl equivalent 203 g/eq.) manufactured by Meiwa Kasei Co., Ltd.
Thermoplastic resin: SIBSTER 072T (styrene-isobutylene-styrene block copolymer) manufactured by Kaneka Corporation
Inorganic filler 1: FB-5SDC manufactured by Denki Kagaku Kogyo Co., Ltd. (fused spherical silica, average particle size 5 μm)
Inorganic filler 2: FB-9454FC manufactured by Denki Kagaku Kogyo Co., Ltd. (fused spherical silica, average particle size 17 μm)
Inorganic filler 3: SO-25R (fused spherical silica, average particle size 0.5 μm) manufactured by Admatechs Co., Ltd.
Carbon black: Mitsubishi Chemical Corporation #20
Curing accelerator: 2PHZ-PW (2-phenyl-4,5-dihydroxymethylimidazole) manufactured by Shikoku Chemicals Co., Ltd.
Silane coupling agent: Shin-Etsu Chemical Co., Ltd. KBM-403 (3-glycidoxypropyltrimethoxysilane)

[Examples 1 to 4 and Comparative Examples 1 to 3]
Each component was blended according to the blending ratio shown in Table 1 and melt-kneaded under reduced pressure (0.01 kg/cm ² ) at 60 to 120° C. for 10 minutes by a roll kneader to prepare a kneaded product. Next, the obtained kneaded product was molded into a sheet shape (100 mm×100 mm) by a flat plate pressing method to prepare a sealing resin sheet having a thickness of 200 μm.

(Evaluation)
The following items were evaluated with respect to the produced sealing resin sheet. The results are shown in Table 1.

(Minimum melt viscosity)
Five pieces, each having a diameter of 25 mm and punched out in a circular shape, were laminated to form a cylindrical measurement sample having a diameter of 25 mm and a thickness of 1 mm. About this measurement sample, the minimum melt viscosity was measured by a rheometric scientific viscoelasticity measuring device “ARES” (measurement conditions: measurement temperature range 50 to 150° C., heating rate 10° C./min, frequency 1 Hz, strain amount 10%). When the change in viscosity was tracked by, the minimum value of viscosity was measured.

(Tack force)
A measurement sample (diameter 25 mm, thickness 200 μm) was obtained by punching each uncured sealing resin sheet into a circular shape having a diameter of 25 mm. RSA3 (manufactured by TA Instruments) was used as an evaluation device, and the upper plate separated from the sample sandwiched between the upper plate (diameter 8 mm) and the lower plate (diameter 25 mm) of the parallel plate compression geometry (manufactured by TA Instruments). The load at that time was measured and used as the tack force. Specifically, a double-sided tape was attached to one surface of the measurement sample, and the tape surface was attached to the lower plate of the jig. In that state, the sample ambient temperature was held for 5 minutes to stabilize the sample ambient temperature at 25° C., and the upper plate was brought close to the measurement sample until a slight contact was made. From there, the upper plate was further pressed against the measurement sample, and when a load of 100 N was applied to the upper plate, the movement of the upper plate was reversed so that the upper plate was separated from the measurement sample. The maximum load (adhesive force) when the upper plate separated from the measurement sample was taken as the tack force.

(Removability)
Under room temperature (25° C.) conditions, each encapsulating resin sheet was placed on a 100×100 mm square, 0.5 mm thick SUS plate in a state where the separator was peeled off, and allowed to stand for 3 minutes. After that, when the sealing resin sheet could be peeled again from the SUS plate without breaking, cracking, or residue of the sealing resin sheet, "○" was given, and the sealing resin sheet had breakage, cracking, or residue. The case was evaluated as "x".

(Resin filling property)
A 10 mm×8 mm pattern (opening) was formed on a 150 mm×150 mm copper plate (thickness: 500 μm) by etching. The encapsulating resin sheet was placed on the patterned copper plate, and vacuum-pressed at 100° C. for 100 kN for 30 seconds to fill the resin in the pattern (opening). Then, observe the front and back surfaces in the pattern (opening) with an optical microscope (20 times), and if there are no voids or if the maximum diameter of the void is 1 μm or less, “◯”, the maximum diameter of the void is 1 μm. When it exceeded, it was evaluated as "x".

As can be seen from Table 1, in the encapsulating resin sheets of Examples 1 to 4, both the removability and the resin filling property were good. On the other hand, in Comparative Examples 1 to 3, one or both of the removability and the resin filling property was inferior.

DESCRIPTION OF SYMBOLS 1 substrate 2 electronic component 3 encapsulating resin sheet 10 electronic component built-in substrate

Claims (4)

An encapsulating resin sheet for encapsulating electronic components in an electronic component-embedded substrate, in which electronic components are embedded and embedded within a range in the thickness direction of the substrate,
Tack force at 25 ℃ is less than 150g,
Minimum melt viscosity in the temperature range of 50 ° C. to 150 DEG ° C. is Ri der less 50 Pa · s,
Including an inorganic filler having an average particle size of 5 to 10 μm,
A sealing resin sheet containing the inorganic filler in an amount of 65 to 85% by weight based on the total solid weight of the sealing resin sheet. The encapsulating resin sheet according to claim 1, comprising an epoxy resin represented by the following chemical formula (1).

(In the formula, R1 to R4 are each independently hydrogen or a methyl group, except when all of R1 to R4 are hydrogen.) The encapsulating resin sheet according to claim 2, wherein the epoxy resin represented by the chemical formula (1) is contained in an amount of 5 to 15% by weight based on the total solid content of the encapsulating resin sheet. The encapsulating resin sheet according to claim 2 or 3, wherein R1 to R4 in the chemical formula (1) are all methyl groups.

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