Resin sheet for sealing

Abstract

A sealing resin sheet 1 is a resin sheet for sealing an element 21. The sealing resin sheet 1 includes: a matrix 4 formed from a heat-curable resin; a first domain 5 formed from a non-layered filler, the first domain 5 being dispersed in the matrix; and a second domain 6 formed from a layered filler, the second domain 6 being dispersed in the matrix. The sealing resin sheet 1 includes a codispersion region 3 in which the second domain 6 is located between the first domains 5.

Description

Technical Field

[0001] The present invention relates to a resin sheet for sealing, and more particularly to a resin sheet for sealing for sealing an element.

Background Art

[0002] Conventionally, an element mounted on a substrate has been sealed by pressing using a sealing sheet containing a thermosetting resin and spherical silica, and then the thermosetting resin has been thermoset to form a cured body from the sealing sheet (see, for example, Patent Document 1 below).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In recent years, with the high functionality of electronic devices, miniaturization has been required for semiconductor elements and electronic components provided therein. Along with this, improvement in dimensional accuracy during curing has been required for the resin (cured body) that protects semiconductor elements and electronic components.

[0005] Specifically, there is a demand to further reduce the amount of the cured body that enters between the semiconductor element or electronic component and the substrate from the side edge of the semiconductor element or electronic component. Alternatively, when sealing a plurality of elements having different sizes and designs or a plurality of elements connected to terminals having different sizes and designs, it may not be possible to uniformly seal all the plurality of elements.

[0006] However, the sealing sheet described in Patent Document 1 contains the same spherical silica, and such silica easily rolls smoothly along with the flow of the thermosetting resin during heat curing, and therefore, there is a problem that the above requirements cannot be satisfied.

[0007] The present invention provides a resin sheet for sealing that can reduce the amount of cured product that enters between an element and a substrate.

Means for Solving the Problems

[0008] The present invention [1] is a resin sheet for sealing for sealing an element, and includes a matrix formed from a thermosetting resin, a first domain formed from a non-layered filler and dispersed in the matrix, and a second domain formed from a layered filler and dispersed in the matrix, and the second domain has a co-dispersion region located between the first domains.

[0009] The present invention [2] includes the resin sheet for sealing according to [1], wherein the average value a of the maximum length A of the second domain and the average value b of the maximum length B of the first domain obtained by the following first to fourth steps satisfy the following formula (1).

[0010] 0.2 < a / b < 5 (1) First step: Obtain one field image by TEM observation of the resin sheet for sealing. Second step: Ten observers observe the one field image, and measure the maximum length A of the largest second domain among the second domains and the maximum length B of the largest first domain among the first domains. Third step: Obtain the average value a of the ten observers for the maximum length A and the average value b of the ten observers for the maximum length B. Fourth step: Substitute the average value a and the average value b into the formula (1).

[0011] The present invention [3] includes the resin sheet for sealing according to [2], wherein the average value a of the maximum length A of the second domain is larger than the average value b of the maximum length B of the first domain.

[0012] The present invention [4] includes the resin sheet for sealing according to [2] or [3], wherein the average value a of the maximum length A of the second domain is 1 μm or more and 10 μm or less.

[0013] The present invention [5] includes the resin sheet for sealing according to any one of [1] to [4], wherein the resin sheet for sealing is observed by TEM to obtain a single field image, and the second domain confirmed in the single field image has an aspect ratio of 2 or more.

[0014] The present invention [6] includes the resin sheet for sealing according to any one of [1] to [5], wherein the resin sheet for sealing is observed by TEM to obtain a single field image, and the first domain confirmed in the single field image has a substantially circular shape.

Advantages of the Invention

[0015] The resin sheet for sealing of the present invention includes a first domain formed from a non-layered filler and a second domain formed from a layered filler, and the second domain has a co-dispersion region located between the first domains. Therefore, even when the thermosetting resin is softened once by heating and the matrix becomes easily flowable, the flow of the material of the resin sheet for sealing can be suppressed as much as possible by the co-dispersion region. Therefore, when forming the cured body, the amount of the cured body entering between the element and the substrate can be reduced.

[0016] In addition, when the resin sheet for sealing of the present invention is arranged on a plurality of elements having different sizes and designs, and further on a plurality of elements connected to terminals having different sizes and designs, and heated to form a cured body, the amount of the cured body entering these gaps can be controlled to uniformly seal the plurality of elements.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

DETAILED DESCRIPTION OF THE INVENTION

[0018] An embodiment of the resin sheet for encapsulation of the present invention will be described with appropriate reference to FIGS. 1 to 2.

[0019] Note that FIGS. 1 to 2 are image processing diagrams of TEM photographs of the resin sheet for encapsulation in Example 3 described later.

[0020] The resin sheet 1 for encapsulation is a resin sheet for encapsulating an element and has a substantially plate shape (film shape) extending in a plane direction orthogonal to the thickness direction (see FIG. 3A).

[0021] As shown in FIG. 1, the resin sheet 1 for sealing has a matrix region 2 and a co-dispersion region 3. Specifically, in a single field image (described later) obtained by TEM observation of the resin sheet 1 for sealing, the resin sheet 1 for sealing has a matrix region 2 and a co-dispersion region 3.

[0022] <Matrix region> The matrix region 2 is a region other than the co-dispersion region 3 in the resin sheet 1 for sealing. The matrix region 2 is composed of a matrix 4 with respect to the co-dispersion region 3.

[0023] The matrix 4 is a resin matrix for constituting the resin sheet 1 for sealing.

[0024] The matrix 4 is formed from a thermosetting resin.

[0025] Examples of the thermosetting resin include, for example, epoxy resin, silicone resin, urethane resin, polyimide resin, urea resin, melamine resin, unsaturated polyester resin, and the like. These can be used alone or in combination of two or more.

[0026] Preferably, the thermosetting resin is an epoxy resin. The epoxy resin will be described in detail in the later preparation method.

[0027] The thermosetting resin may be either before complete curing (including B-stage or A-stage) or after complete curing (C-stage). However, in the TEM observation described later, the thermosetting resin is preferably after complete curing (C-stage).

[0028] <Co-dispersion region> The co-dispersion region 3 is a particle domain dispersed in the matrix 4.

[0029] The co-dispersion region 3 includes a first domain 5 and a second domain 6 having different shapes from each other, and is a region where the first domain 5 and the second domain 6 are both dispersed (scattered).

[0030] <First Domain> The first domain 5 is a cured body reinforcement region for ensuring the strength of the cured body when the resin sheet 1 for sealing is pressed to form a sealing body and then the sealing body is heated and cured to obtain a cured body.

[0031] The first domain 5 is formed from a non-layered filler.

[0032] The shape of the non-layered filler is not particularly limited as long as it is other than the shape of the layered filler of the second domain 6 described below. When the resin sheet 1 for sealing is observed by TEM to obtain a single field image, examples of the shape of the non-layered filler when confirmed in a single field image (described later) include a substantially circular shape (see Fig. 1) (including a substantially elliptical shape), for example, a polygonal shape such as a substantially square shape or a substantially triangular shape (excluding a flat substantially rectangular shape), and the like.

[0033] As shown in Fig. 1, the shape of the non-layered filler when confirmed in a single field image is preferably a substantially circular shape. If the shape of the non-layered filler when confirmed in a single field image is a substantially circular shape, it has excellent dispersibility and can uniformly suppress the flow of the resin sheet for sealing.

[0034] Note that the average value b of the maximum length B of the first domain 5 in a single field image will be described in detail later.

[0035] Specifically, examples of the material of the non-layered filler include silicate compounds (silicon compounds) such as quartz (silicic acid) and silica (anhydrous silicic acid) (excluding silicate compounds described later), for example, aluminum compounds such as aluminum oxide (alumina) and aluminum nitride. These can be used alone or in combination of two or more. Preferably, the material of the non-layered filler is a silicate compound, and more preferably, silica. That is, preferably, the non-layered filler is a silicate compound filler, and more preferably, a silica filler.

[0036] <Second Domain> The second domain 6 is a flow adjustment region when forming a sealing body and a cured body (described later) from the resin sheet 1 for sealing. Specifically, it is a flow reduction region during curing for reducing the fluidity of the cured body when heating the resin sheet 1 for sealing to form the cured body. Specifically, when pressing the resin sheet 1 for sealing to form a sealing body and then heating and curing the sealing body, first, it is also a region for improving the fluidity during sealing and reducing the fluidity during curing for reducing the fluidity of the cured body by subsequent heating while increasing the fluidity of the sealing body.

[0037] The second domain 6 is formed from a layered filler.

[0038] The layered filler is, for example, a filler having a structure (three-dimensional structure) in which layers extending two-dimensionally (in the plane direction) are stacked in the thickness direction. The layered filler has a shape in which a plurality of thin layers 7 are laminated in its thickness direction.

[0039] Specifically, as shown in the upper figure of FIG. 1, when observing the resin sheet 1 for sealing by TEM to obtain a single field image, the shape of the layered filler when confirmed in a single field image (described later) includes a flat rectangular shape (plate shape) (including a shape in which a part of the periphery is an arc shape).

[0040] In a single field image, the average value a (see FIG. 2) of the maximum length A of the second domain 6 will be described in detail later.

[0041] Specifically, examples of the material of the layered filler include silicate compounds, boron compounds such as boron nitride, and carbon-based substances such as carbon (graphite). Preferably, silicate compounds are mentioned.

[0042] The silicate compound is called a phyllosilicate.

[0043] Specifically, examples of the silicate compound include smectites such as montmorillonite, beidellite, nontronite, saponite, hectorite, sauconite, and stevensite, for example, kaolinite, for example, halloysite, for example, talc, and for example, mica. As the silicate compound, preferably, from the viewpoint of improving the miscibility with the thermosetting resin, smectite is mentioned, and more preferably, montmorillonite is mentioned.

[0044] Further, the layered filler may be an unmodified product with an unmodified surface, or may also be a modified product with a surface modified by an organic component. Preferably, from the viewpoint of obtaining excellent affinity with the thermosetting resin, the surface of the layered filler is modified by an organic component. Specifically, examples of the layered filler include a silicate compound with a surface modified by an organic component, more preferably, an organic smectite with a surface modified by an organic component, and even more preferably, an organic bentonite with a surface modified by an organic component.

[0045] Examples of the organic component include organic cations (onium ions) such as ammonium, imidazolium, pyridinium, and phosphonium.

[0046] Examples of the ammonium include dimethyldistearylammonium, distearylammonium, octadecylammonium, hexylammonium, octylammonium, 2-hexylammonium, dodecylammonium, trioctylammonium, and the like. Examples of the imidazolium include methylstearylimidazolium, distearylimidazolium, methylhexylimidazolium, dihexylimidazolium, methyloctylimidazolium, dioctylimidazolium, methyldodecylimidazolium, didodecylimidazolium, and the like. Examples of the pyridinium include stearylpyridinium, hexylpyridinium, octylpyridinium, dodecylpyridinium, and the like. Examples of the phosphonium include dimethyldistearylphosphonium, distearylphosphonium, octadecylphosphonium, hexylphosphonium, octylphosphonium, 2-hexylphosphonium, dodecylphosphonium, trioctylphosphonium, and the like. The organic cations can be used alone or in combination of two or more. Preferably, ammonium is used, and more preferably, dimethyldistearylammonium is used.

[0047] As the organosilicate compound, preferably, an organomodified smectite whose surface is modified with ammonium, and more preferably, an organomodified bentonite whose surface is modified with dimethyldistearylammonium are used.

[0048] <One field image obtained by TEM observation of the resin sheet 1 for sealing> The matrix region 2 and the co-dispersion region 3 (and further, the matrix 4, the first domain 5, and the second domain 6 that constitute them) in the resin sheet 1 for sealing are observed by one field image (FIG. 1 and FIG. 2) obtained by TEM (transmission electron microscope) observation of the resin sheet 1 for sealing.

[0049] Note that the sample preparation for TEM observation and the conditions of TEM and the like will be described in detail in the later examples.

[0050] The matrix region 2 observed in this single field of view image is a continuous single region (continuous phase). In the single field of view image, the matrix 4 is formed as a homogeneous region. Therefore, in the above-mentioned single field of view image, the matrix 4 is identified as a uniform gray (substantially no difference in shading) region.

[0051] The covariance region 3 observed in this single field of view image is dispersed (scattered) in the matrix region 2 and observed.

[0052] In the covariance region 3, the first domain 5 and the second domain 6 are both dispersed.

[0053] The first domain 5 includes a single domain 8 existing alone and / or a chain domain 9 in which a plurality of single domains 8 are connected in one direction. The chain domain 9 may be partially branched.

[0054] Preferably, the first domain 5 includes both the single domain 8 and the chain domain 9.

[0055] In a single field of view image, the lower limit of the ratio of the number of chain domains 9 to the total of the number of single domains 8 and the number of chain domains 9 is, for example, 0.01, preferably 0.1, and the upper limit is, for example, 0.8, preferably 0.7.

[0056] Regarding the number of chain domains 9, when two adjacent first domains 5 are connected, they are counted as one.

[0057] The second domain 6 is located between adjacent first domains 5 in the covariance region 3. Specifically, the second domain 6 includes a second domain 6 located between a plurality of adjacent single domains 8, a second domain 6 located between an adjacent single domain 8 and a chain domain 9, a second domain 6 located between a plurality of adjacent chain domains 9, and the like. Among these, the second domain 6 located between a plurality of adjacent chain domains 9 exists at the highest ratio (such as an area ratio).

[0058] In addition, when it is difficult to identify the presence of the second domain 6 in a single field image, as shown in the upper figure of FIG. 1, only the above-described portion is enlarged and the presence of the layered filler is identified by confirming the presence of the thin layer 7.

[0059] Further, the average value a of the maximum length A of the second domain 6 and the average value b of the maximum length B of the first domain 5 obtained by the following first to fourth steps satisfy, for example, the following formula (1).

[0060] 0.2 < a / b < 5 (1) First step: The sealing resin sheet 1 is observed by TEM to obtain a single field image.

[0061] Second step: Ten observers observe a single field image, and measure the maximum length A of the largest second domain among the second domains and the maximum length B of the largest first domain among the first domains.

[0062] Third step: Obtain the average value a of the ten observers of the maximum length A and the average value b of the ten observers of the maximum length B.

[0063] Fourth step: Substitute the average value a and the average value b into formula (1).

[0064] In the first step, a single field image obtained by TEM observation is shown in FIGS. 1 and 2.

[0065] In the second step, as shown in FIG. 2, among the plurality of second domains 6, the maximum length A of the largest second domain is measured by each of the ten observers. The measurement of the maximum length A of the second domain 6 is carried out by ten observers in consideration of the possibility of slight deviation by the observers. As described above, the presence of the second domain 6 may be difficult to identify, and therefore, the maximum length A of the second domain 6 may vary depending on the observer. Therefore, the number of observers is set to 10, and the variation (error) is reduced by obtaining the average value a thereof, thereby improving the measurement accuracy.

[0066] Specifically, the maximum length A1 of the second domain 6 measured by the first observer, the maximum length A2 of the second domain 6 measured by the second observer (which may be different from A1),..., the maximum length A10 of the second domain 6 measured by the tenth observer (which may be different from A1 and A2) are each obtained.

[0067] The same applies to the average value b of the maximum length B of the first domain 5. Note that the maximum length B of the first domain 5 corresponds to the maximum length B of the single domain 8. Regarding the chain domain 9, the maximum length B of the single domain 8 constituting it is taken as the maximum length B of the first domain 5.

[0068] In the third step, the average value a is obtained as the calculation result of (A1 + A2 + ··· + A10) / 10. The average value b is the same as above.

[0069] When there are a first non-layered filler and a second non-layered filler having a plurality of different median diameters (described later) for the average value b of the maximum length B of the first domain 5, the above-mentioned average value b depends on the median diameter of the first non-layered filler with a large size.

[0070] If the above formula (1) is satisfied, the cured body can surely cover the peripheral side surface of the element, and while ensuring good sealing characteristics, the amount of the cured body entering between the element and the substrate can be reduced.

[0071] When the lower limit of formula (1) is exceeded, since the layered filler is in a state of being overly dispersed with respect to the size of the non-layered filler, the flow may not be suppressed as much as possible. Also, when the upper limit of formula (1) is exceeded, since the dispersion of the layered filler in the resin sheet is insufficient with respect to the size of the non-layered filler, the cured body may not be able to uniformly and surely cover the peripheral side surface of the element.

[0072] Preferably, the average value a of the maximum length A of the second domain is greater than the average value b of the maximum length B of the first domain. As a result, the contribution of the second domain containing the layered filler to the resin flow increases, so that the amount of the cured body entering between the element and the substrate can be further reduced.

[0073] That is, the average value a of the maximum length A of the second domain and the average value b of the maximum length B of the first domain preferably satisfy the following formula (2). Further, the average value a and the average value b more preferably satisfy the following formula (3), and still more preferably satisfy the following formula (4).

[0074] 1 < a / b (2) 1.3 < a / b (3) 1.5 < a / b (4) In addition, the average value a of the maximum length A of the second domain and the average value b of the maximum length B of the first domain preferably satisfy the following formula (5), and more preferably satisfy the following formula (6).

[0075] a / b < 3 (5) a / b < 2 (6) Specifically, the lower limit of the average value a of the maximum length A of the second domain 6 is, for example, 0.1 μm, preferably 1 μm. Also, the upper limit of the average value a of the maximum length A of the second domain 6 is, for example, 30 μm, preferably 10 μm. When the average value a of the maximum length A of the second domain 6 is less than the above-described lower limit, the layered filler is in an overly dispersed state, so that the flow may not be suppressed as much as possible. When the average value a of the maximum length A of the second domain 6 exceeds the above-described upper limit, the dispersion of the layered filler in the resin sheet is insufficient, so that the cured body may not be able to uniformly and surely cover the peripheral side surface of the element.

[0076] In addition, the lower limit of the aspect ratio of the second domain 6 (layered filler) when confirmed in a single field image (described later) is, for example, 1.5, preferably 2, and more preferably 3. The upper limit of the aspect ratio of the second domain 6 is, for example, 100 or less.

[0077] Note that the aspect ratio of the second domain 6 is the average value x of the maximum length (width) X in the direction orthogonal to the maximum length A (width direction). This average value x is obtained in accordance with the measurement method of the average value a described above.

[0078] If the aspect ratio of the second domain 6 is equal to or greater than the above-described lower limit, when the resin flows, the second domain of the layered filler can further suppress the flow of the first domain of the non-layered filler. Therefore, the flow of the material of the resin sheet for sealing can be suppressed as much as possible.

[0079] In the observation of one field image, the lower limit of the area ratio of the matrix region 2 in the resin sheet 1 for sealing is, for example, 5 area%, preferably 10 area%. The upper limit of the area ratio of the matrix region 2 in the resin sheet 1 for sealing is, for example, 50 area%, preferably 40 area%.

[0080] In the observation of one field image, the lower limit of the area ratio of the co-dispersion region 3 in the resin sheet 1 for sealing is, for example, 50 area%, preferably 60 area%, more preferably 70 area%. The upper limit of the area ratio of the co-dispersion region 3 in the resin sheet 1 for sealing is, for example, 95 area%, preferably 90 area%, more preferably 85 area%.

[0081] In one field image, the lower limit of the ratio of the number of the second domains 6 in the total number of the first domains 5 and the second domains 6 is, for example, 1%, preferably 5%. The upper limit of the ratio of the number of the second domains 6 in the total number of the first domains 5 and the second domains 6 is, for example, 50%, preferably 30%.

[0082] In one field image, the lower limit of the ratio of the number of the second domains 6 to the number of the first domains 5 is, for example, 0.01, preferably 0.05. The upper limit of the ratio of the number of the second domains 6 to the number of the first domains 5 is, for example, 1, preferably 0.5.

[0083] If each of the above ratios is within the above range, the flow of the material of the sealing resin sheet can be suppressed as much as possible, and the amount of the cured product entering between the element and the substrate can be reduced.

[0084] <Manufacture of the Sealing Resin Sheet> To manufacture this sealing resin sheet 1, the above-mentioned thermosetting resin, non-layered filler, and layered filler are blended to prepare a mixture (composition).

[0085] Note that an epoxy resin, which is a preferred example of the thermosetting resin, is prepared as an epoxy resin composition containing a main agent, a curing agent, and a curing accelerator.

[0086] Examples of the main agent include bifunctional epoxy resins such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, modified bisphenol A type epoxy resin, modified bisphenol F type epoxy resin, and biphenyl type epoxy resin; and polyfunctional epoxy resins having three or more functional groups such as phenol novolac type epoxy resin, cresol novolac type epoxy resin, tris(hydroxyphenyl)methane type epoxy resin, tetraphenylol ethane type epoxy resin, and dicyclopentadiene type epoxy resin. These main agents can be used alone or in combination of two or more. Preferably, the main agent is a bifunctional epoxy resin, and more preferably, bisphenol F type epoxy resin.

[0087] The lower limit of the epoxy equivalent of the main agent is, for example, 10 g / eq., preferably 100 g / eq. The upper limit of the epoxy equivalent of the main agent is, for example, 300 g / eq., preferably 250 g / eq.

[0088] The lower limit of the softening point of the main agent is, for example, 50°C, preferably 70°C, more preferably 72°C, and even more preferably 75°C. The upper limit of the softening point of the main agent is, for example, 130°C, preferably 110°C, and more preferably 90°C.

[0089] If the softening point of the main agent is equal to or higher than the above-mentioned lower limit, in the process shown in FIG. 3C, the sealing resin sheet 1 can flow. Therefore, the time of the process shown in FIG. 3C can be shortened, and one surface in the thickness direction of the sealing resin sheet 1 in the process shown in FIG. 3C can be made flat.

[0090] The curing agent is a latent curing agent that cures the above-mentioned main agent by heating. Examples of the curing agent include phenolic resins such as novolac-type phenolic resins. If the curing agent is a phenolic resin, the phenolic resin together with the main agent, and their cured products have high heat resistance and high chemical resistance. Therefore, the cured product is excellent in sealing reliability.

[0091] The curing accelerator is a catalyst (heat curing catalyst) that accelerates the curing of the main agent by heating. Examples of the curing accelerator include organic phosphorus compounds, for example, imidazole compounds such as 2-phenyl-4,5-dihydroxymethylimidazole (2PHZ-PW). Preferably, an imidazole compound is mentioned.

[0092] The lower limit of the content ratio of the thermosetting resin (preferably, an epoxy resin composition) in the mixture (solid content) (corresponding to the sealing resin sheet 1) is, for example, 5% by mass, preferably 15% by mass, more preferably 17% by mass. The upper limit of the content ratio of the thermosetting resin (preferably, an epoxy resin composition) in the mixture (solid content) is, for example, 30% by mass, preferably 25% by mass, more preferably 20% by mass, still more preferably 18% by mass.

[0093] The lower limit of the ratio of the main agent in the mixture is, for example, 1% by mass, preferably 3% by mass, more preferably 10% by mass. The upper limit of the ratio of the main agent in the mixture is, for example, 30% by mass, preferably 15% by mass, more preferably 12.5% by mass. The lower limit of the ratio of the main agent in the epoxy resin composition is, for example, 30% by mass, preferably 50% by mass. The upper limit of the ratio of the main agent in the epoxy resin composition is, for example, 80% by mass, preferably 70% by mass.

[0094] The ratio of the curing agent is set to be the following equivalent ratio. Specifically, the lower limit of the total hydroxyl groups in the phenolic resin relative to 1 equivalent of epoxy groups in the main agent is, for example, 0.7 equivalent, preferably 0.9 equivalent. The upper limit of the total hydroxyl groups in the phenolic resin relative to 1 equivalent of epoxy groups in the main agent is, for example, 1.5 equivalents, preferably 1.2 equivalents. Specifically, the lower limit of the content of the curing agent relative to 100 parts by mass of the main agent is, for example, 20 parts by mass, preferably 40 parts by mass. The upper limit of the content of the curing agent relative to 100 parts by mass of the main agent is, for example, 80 parts by mass, preferably 60 parts by mass. The lower limit of the content of the curing accelerator relative to 100 parts by mass of the main agent is, for example, 0.05 part by mass. The upper limit of the content of the curing accelerator relative to 100 parts by mass of the main agent is, for example, 5 parts by mass.

[0095] Examples of the shape of the non-layered filler include shapes such as a substantially spherical shape and a substantially needle shape (shapes other than layered shapes). Preferably, a substantially spherical shape is included.

[0096] The lower limit of the content ratio of the non-layered filler in the mixture is, for example, 50% by mass, preferably 55% by mass, more preferably 60% by mass, and even more preferably 65% by mass. The upper limit of the content ratio of the non-layered filler in the mixture is, for example, 90% by mass, preferably 85% by mass, more preferably 80% by mass, and even more preferably 75% by mass.

[0097] If the content ratio and / or the number of parts of the non-layered filler is not less than the above-described lower limit, the sealing resin sheet 1 in the process shown in FIG. 1C can flow.

[0098] Also, the non-layered filler can include a first non-layered filler and a second non-layered filler having a median diameter smaller than the median diameter of the first non-layered filler.

[0099] The lower limit of the median diameter of the first non-layered filler is, for example, 1 μm, preferably 3 μm. The median diameter of the first non-layered filler is, for example, 50 μm, preferably 30 μm.

[0100] The upper limit of the median diameter of the second non-layered filler is, for example, 0.9 μm, preferably 0.8 μm. The lower limit of the median diameter of the second non-layered filler is, for example, 0.01 μm, preferably 0.1 μm.

[0101] The lower limit of the ratio of the median diameter of the first non-layered filler to the median diameter of the second non-layered filler is, for example, 2, preferably 5. The upper limit of the ratio of the median diameter of the first non-layered filler to the median diameter of the second non-layered filler is, for example, 50, preferably 20.

[0102] The materials of the first non-layered filler and the second non-layered filler may be the same or different from each other.

[0103] Furthermore, the surface of the non-layered filler may be partially or entirely surface-treated with a silane coupling agent or the like.

[0104] When the non-layered filler includes the first non-layered filler and the second non-layered filler, the lower limit of the content ratio of the first non-layered filler in the mixture is, for example, 30% by mass, preferably 40% by mass in the mixture. The upper limit of the content ratio of the first non-layered filler in the mixture is, for example, 60% by mass, preferably 50% by mass in the mixture. The lower limit of the number of parts by mass of the second non-layered filler with respect to 100 parts by mass of the first non-layered filler is, for example, 30 parts by mass, preferably 40 parts by mass, more preferably 50 parts by mass. The upper limit of the number of parts by mass of the second non-layered filler with respect to 100 parts by mass of the first non-layered filler is, for example, 70 parts by mass, preferably 60 parts by mass, more preferably 55 parts by mass.

[0105] The shape of the layered filler is layered and includes a plate shape, a flake shape, etc. Also, the layered filler has cleavability.

[0106] The lower limit of the content ratio of the layered filler in the mixture is, for example, 1% by mass, preferably 2% by mass, more preferably 3% by mass, still more preferably 3.5% by mass, particularly preferably 4% by mass, and most preferably 4.5% by mass. The upper limit of the content ratio of the layered filler in the mixture is, for example, 25% by mass, preferably 15% by mass, more preferably 10% by mass, still more preferably 9% by mass, particularly preferably 8% by mass, and most preferably 7% by mass.

[0107] In addition, the lower limit of the content part number of the layered filler with respect to 100 parts by mass of the non-layered filler is, for example, 1 part by mass, preferably 2 parts by mass, more preferably 3 parts by mass, and still more preferably 5 parts by mass. The upper limit of the content part number of the layered filler with respect to 100 parts by mass of the non-layered filler is, for example, 25 parts by mass, preferably 20 parts by mass, more preferably 15 parts by mass, still more preferably 10 parts by mass, and particularly preferably 8 parts by mass.

[0108] The lower limit of the median diameter of the layered filler is, for example, 1 μm, preferably 5 μm, and more preferably 10 nm. The upper limit of the median diameter of the layered filler is, for example, 100 μm, preferably 50 μm, and more preferably 10 μm.

[0109] In addition, the median diameter of the layered filler is determined as the D50 value (cumulative 50% median diameter) based on the particle size distribution obtained by the particle size distribution measurement method in the laser scattering method, for example.

[0110] As the layered filler, commercially available products can be used. Specifically, Esbe series (manufactured by Hoejun) and the like are used.

[0111] In addition, for example, a thermoplastic resin, a pigment, a silane coupling agent, and other additives can be added to the mixture.

[0112] Among the above-mentioned additives, the thermoplastic resin and the silane coupling agent can form the matrix 4 together with the thermosetting resin, and the pigment can form the first domain 5 together with the non-layered filler.

[0113] Examples of the thermoplastic resin include natural rubber, butyl rubber, isoprene rubber, chloroprene rubber, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-acrylic acid ester copolymer, polybutadiene resin, polycarbonate resin, thermoplastic polyimide resin, polyamide resin (such as 6-nylon and 6,6-nylon), phenoxy resin, acrylic resin, saturated polyester resin (such as PET), polyamideimide resin, fluororesin, styrene-isobutylene-styrene block copolymer, and the like. These thermoplastic resins can be used alone or in combination of two or more.

[0114] Preferably, from the viewpoint of improving the dispersibility with the thermosetting resin, the acrylic resin is mentioned as the thermoplastic resin.

[0115] Examples of the acrylic resin include a carboxyl group-containing (meth)acrylic acid ester copolymer (preferably a carboxyl group-containing acrylic acid ester copolymer) obtained by polymerizing a monomer component containing a (meth)acrylic acid alkyl ester having a linear or branched alkyl group and other monomers (copolymerizable monomers).

[0116] Examples of the alkyl group include alkyl groups having 1 to 6 carbon atoms such as methyl, ethyl, propyl, isopropyl, n-butyl, t-butyl, isobutyl, pentyl, and hexyl.

[0117] Examples of the other monomers include carboxyl group-containing monomers such as acrylic acid, methacrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid.

[0118] The lower limit of the weight average molecular weight of the thermoplastic resin is, for example, 100,000, preferably 300,000. The upper limit of the weight average molecular weight of the thermoplastic resin is, for example, 1,000,000, preferably 900,000. The weight average molecular weight is measured by gel permeation chromatography (GPC) based on the standard polystyrene conversion value.

[0119] The ratio of the thermoplastic resin (solid content ratio) is adjusted so as not to inhibit the thermosetting of the thermosetting resin. Specifically, the lower limit of the ratio of the thermoplastic resin (solid content ratio) in the mixture is, for example, 1% by mass, preferably 2% by mass. The upper limit of the ratio of the thermoplastic resin (solid content ratio) in the mixture is, for example, 10% by mass, preferably 5% by mass.

[0120] In addition, the thermoplastic resin may be prepared by diluting with an appropriate solvent.

[0121] Examples of the pigment include black pigments such as carbon black. The lower limit of the particle diameter of the pigment is, for example, 0.001 μm. The upper limit of the particle diameter of the pigment is, for example, 1 μm. The lower limit of the ratio of the pigment to the mixture is, for example, 0.1% by mass, and the upper limit is, for example, 2% by mass. The particle diameter of the pigment is the arithmetic mean diameter obtained by observing the pigment with an electron microscope.

[0122] Examples of the silane coupling agent include a silane coupling agent containing an epoxy group. Examples of the silane coupling agent containing an epoxy group include 3-glycidoxy dialkyldialkoxysilanes such as 3-glycidoxypropylmethyldimethoxysilane and 3-glycidoxypropylmethyldiethoxysilane, and 3-glycidoxyalkyltrialkoxysilanes such as 3-glycidoxypropyltrimethoxysilane and 3-glycidoxypropyltriethoxysilane. Preferably, 3-glycidoxyalkyltrialkoxysilane is mentioned. The lower limit of the content ratio of the silane coupling agent in the mixture is, for example, 0.1% by mass, preferably 1% by mass. The upper limit of the content ratio of the silane coupling agent in the mixture is, for example, 10% by mass, preferably 5% by mass.

[0123] Optionally, a solvent is further blended to prepare a varnish of the mixture. The solvent is not particularly limited, and examples thereof include ketone solvents such as acetone and alcohol solvents such as methanol. Preferably, a ketone solvent is mentioned.

[0124] The lower limit of the solid content concentration in the varnish is, for example, 40% by mass, preferably 60% by mass. The upper limit of the solid content concentration in the varnish is, for example, 99% by mass, preferably 90% by mass.

[0125] The above-described respective components (including additives and solvents) are blended and mixed.

[0126] As the mixing conditions, for example, conditions under which the non-layered filler and the layered filler are sufficiently dispersed with respect to the thermosetting resin are selected.

[0127] For example, using a mixer such as a rotary-revolution mixer, a disper, a bead mill, a homomixer, or a planetary mixer, the above-described respective components are stirred and mixed. Preferably, using a rotary-revolution mixer, the above-described respective components are stirred and mixed.

[0128] The rotation-revolution mixer is a device that simultaneously performs rotation (self-rotation) about a rotation center (first center) located inside the container (such as a cylindrical container) that houses the mixture, and rotation (revolution) about a rotation center (second center) located outside the container. Also, the axis of the first center and the axis of the second center may be parallel or may intersect. Preferably, they intersect at an inclination angle (for example, an inclination angle of 30 degrees or more and 60 degrees or less).

[0129] In the case of a rotation-revolution mixer, a shearing force based on rotation and a centrifugal force based on revolution can be simultaneously applied to the mixture. As a result, the non-layered filler and the layered filler are sufficiently dispersed in the thermosetting resin.

[0130] Note that commercially available products can be used as the rotation-revolution mixer. Specifically, the "Awatori Rentaro" series manufactured by Shinki Co., Ltd. etc. are used.

[0131] Specifically, if the mixer is a rotation-revolution mixer, the lower limit of the rotation speed is, for example, 1,000 rpm, and the upper limit of the rotation speed is 10,000 rpm. The lower limit of the revolution speed is, for example, 1,000 rpm, and the upper limit of the revolution speed is 10,000 rpm. The lower limit of the mixing time is, for example, 1 minute, preferably 3 minutes, and the upper limit thereof is, for example, 30 minutes, preferably 10 minutes.

[0132] Also, if the mixer is a rotation-revolution mixer, the lower limit of the centrifugal force on the container is, for example, 10 MPa, preferably 100 MPa, and the upper limit thereof is, for example, 10,000 MPa.

[0133] The timing of mixing may be either during the blending of each component or after blending, and preferably is both during and after blending. Specifically, first, the thermosetting resin, non-layered filler and layered filler (and further additives) are blended, and then they are stirred with the above-described mixer (first mixing), after which a solvent is added, and then they are stirred with the above-described mixer (second mixing).

[0134] Note that the second mixing conditions may be different from, for example, the first mixing conditions, or may be the same. Preferably, they are the same.

[0135] Thereafter, the varnish is applied to a release sheet (not shown), and then dried by heating to produce a sealing resin sheet having a sheet shape.

[0136] Note that this sealing resin sheet is in the B-stage (semi-cured state), specifically, in a state before the C-stage. That is, it is in a state before complete curing. The sealing resin sheet is formed from an A-stage composition into a B-stage sheet by heating in the above drying or heating in extrusion kneading.

[0137] The lower limit of the thickness of the sealing resin sheet is, for example, 10 μm, preferably 25 μm, more preferably 50 μm. The upper limit of the thickness of the sealing resin sheet is, for example, 3000 μm, preferably 1000 μm, more preferably 500 μm, still more preferably 300 μm, and particularly preferably 100 μm.

[0138] From the viewpoint of reliably producing a flaky sample for TEM observation, the B-stage sealing resin sheet 1 can be made into a C-stage by heating (atmospheric pressure heating without pressing) to obtain a C-stage sealing resin sheet 1. Note that one field image obtained when the B-stage sealing resin sheet 1 is subjected to TEM observation is substantially the same as one field image obtained when the C-stage sealing resin sheet 1 is subjected to TEM observation. That is, the co-dispersion region 3 in the B-stage sealing resin sheet 1 and the co-dispersion region 3 in the C-stage sealing resin sheet 1 are organized substantially identically.

[0139] <Sealing multilayer resin sheet> The sealing resin sheet may be provided in the sealing multilayer resin sheet together with a second sealing resin sheet.

[0140] The encapsulation multilayer resin sheet includes an encapsulation resin sheet and a second encapsulation resin sheet in this order on one side in the thickness direction. Specifically, the encapsulation multilayer resin sheet includes an encapsulation resin sheet and a second encapsulation resin sheet disposed on the entire surface of one side in its thickness direction. Preferably, the encapsulation multilayer resin sheet includes only the encapsulation resin sheet and the second encapsulation resin sheet.

[0141] In one field image obtained by TEM observation of the second encapsulation resin sheet, it is the same as, for example, the above-described encapsulation resin sheet 1 except that a co-dispersion region 3 containing a non-layered filler (second domain 6) is not observed.

[0142] The lower limit of the thickness of the second encapsulation resin sheet is, for example, 25 μm, preferably 50 μm, more preferably 100 μm, and still more preferably 150 μm. The upper limit of the thickness of the second encapsulation resin sheet is, for example, 1000 μm, preferably 500 μm, and more preferably 300 μm.

[0143] The encapsulation multilayer resin sheet is prepared by bonding the encapsulation resin sheet and the second encapsulation resin sheet together.

[0144] <Manufacture of Electronic Element Package> A method for manufacturing an electronic element package by encapsulating an electronic element as an example of an element with an encapsulation resin sheet will be described with reference to FIGS. 3A to 3D.

[0145] (Example of Using Encapsulation Resin Sheet) In this method, as shown in FIG. 3A, first, the encapsulation resin sheet 1 is prepared. The encapsulation resin sheet 1 has a first surface and a second surface facing each other in the thickness direction.

[0146] Separately, as shown in FIG. 3B, the electronic element 21 is prepared.

[0147] The electronic elements 21 are mounted on the substrate 22 in plural, for example. The plural electronic elements 21 and the substrate 22 are provided on an element mounting substrate 24 together with bumps 23. That is, this element mounting substrate 24 includes the plural electronic elements 21, the substrate 22, and the bumps 23.

[0148] The substrate 22 has a substantially flat plate shape extending in the plane direction. Terminals (not shown) electrically connected to electrodes (not shown) of the electronic elements 21 are provided on one surface 25 in the thickness direction of the substrate 22.

[0149] Each of the plural electronic elements 21 has a substantially flat plate shape (chip shape) extending in the plane direction. The plural electronic elements 21 are arranged at intervals in the plane direction. The other surface 28 in the thickness direction of the plural electronic elements 2 is parallel to the one surface 25 in the thickness direction of the substrate 22. Electrodes (not shown) are provided on each of the other surfaces 28 in the thickness direction of the plural electronic elements 21. The electrodes of the electronic elements 21 are electrically connected to the terminals of the substrate 22 via the bumps 23 described below. Note that a gap (space) 26 is provided between the other surface 28 in the thickness direction of the electronic element 21 and the one surface 25 in the thickness direction of the substrate 22.

[0150] The bumps 23 electrically connect the respective electrodes (not shown) of the plural electronic elements 21 and the respective terminals of the substrate 22. The bumps 23 are arranged between the electrodes of the electronic elements 21 and the terminals of the substrate 22. Examples of the material of the bumps 23 include metals such as solder and gold. The thickness of the bumps 23 corresponds to the thickness (height) of the gap 26. The thickness of the bumps 23 is appropriately set according to the use and purpose of the element mounting substrate 24.

[0151] Next, as shown in FIG. 3B, the sealing resin sheet 1 is arranged on the plural electronic elements 21. Specifically, the other surface in the thickness direction of the sealing resin sheet 1 is brought into contact with the one surface in the thickness direction of the plural electronic elements 21.

[0152] Next, as shown in FIG. 3C, the resin sheet 1 for sealing and the element mounting substrate 24 are pressed. Preferably, the resin sheet 1 for sealing and the element mounting substrate 24 are hot-pressed at a low temperature.

[0153] For example, by a press 27 having two flat plates, while sandwiching the resin sheet 1 for sealing and the element mounting substrate 24 in the thickness direction, they are pressed. Note that the flat plates of the press 27 are provided with a heat source (not shown), for example.

[0154] The pressing conditions (pressure, time, and further temperature, etc.) are not particularly limited, and conditions are selected such that the resin sheet 1 for sealing can enter between the plurality of electronic elements 21 while the element mounting substrate 24 is not damaged. More specifically, the pressing conditions are set so as to sufficiently apply shear stress to the resin sheet 1 for sealing, whereby the resin sheet 1 for sealing flows and enters between adjacent electronic elements 21, and while covering the respective peripheral side surfaces of the plurality of electronic elements 21, it can contact one surface 25 in the thickness direction of the substrate 22 that does not overlap with the electronic elements 21 in plan view.

[0155] Specifically, the lower limit of the pressing pressure is, for example, 0.05 MPa, preferably 0.1 MPa. The upper limit of the pressing pressure is, for example, 10 MPa, preferably 5 MPa. The lower limit of the pressing time is, for example, 0.3 minutes, preferably 0.5 minutes. The upper limit of the pressing time is, for example, 10 minutes, preferably 5 minutes.

[0156] Specifically, the lower limit of the heating temperature is, for example, 40°C, preferably 60°C. The upper limit of the heating temperature is, for example, 100°C, preferably 95°C.

[0157] Due to the pressing (application of shear stress) of the resin sheet 1 for sealing, the resin sheet 1 for sealing plastically deforms corresponding to the outer shape of the electronic element 21. The other surface in the thickness direction of the resin sheet 1 for sealing deforms into a shape corresponding to one surface in the thickness direction and the peripheral side surfaces of the plurality of electronic elements 21.

[0158] Note that the resin sheet 1 for sealing plastically deforms while maintaining the B-stage.

[0159] As a result, the sealing resin sheet 1 covers the circumferential side surfaces of the plurality of electronic elements 21, and in a plan view, contacts one surface 25 in the thickness direction of the substrate 22 that does not overlap with the electronic element 21.

[0160] As a result, a sealing body 31 that seals the electronic element 21 is formed (produced) from the sealing resin sheet 1. One surface in the thickness direction of the sealing body 31 becomes a flat surface.

[0161] Thereafter, as shown in Fig. 3D, the sealing body 31 is heated to form a cured body 41 from the sealing body 31.

[0162] Specifically, the sealing body 31 and the element mounting substrate 24 are taken out of the press 27, and subsequently, the sealing body 31 and the element mounting substrate 24 are heated in a dryer under atmospheric pressure.

[0163] The lower limit of the heating temperature (curing temperature) is, for example, 100°C, preferably 120°C. The upper limit of the heating temperature (curing temperature) is, for example, 200°C, preferably 180°C. The lower limit of the heating time is, for example, 10 minutes, preferably 30 minutes. The upper limit of the heating time is, for example, 180 minutes, preferably 120 minutes.

[0164] By heating the above-described sealing body 31, a cured body 41 that is C-staged (fully cured) is formed from the sealing body 31. One surface in the thickness direction of the cured body 41 is an exposed surface.

[0165] Note that it is allowed that the edge of the sealing body 31 with a slight entry into the gap further slightly enters the inside of the gap 26 to become the cured body 41, but the degree thereof is suppressed to be as small as possible.

[0166] And as shown in FIGS. 1 to 2, the resin sheet 1 for sealing includes a first domain 5 formed of a non-layered filler and a second domain 6 formed of a layered filler, and the second domain 6 has a co-dispersion region 3 located between the first domains 5. Therefore, even if the thermosetting resin is once softened by heating and the matrix 4 becomes easy to flow, the co-dispersion region 3 can suppress the flow of the material (mixture) of the resin sheet 1 for sealing as much as possible. Therefore, as shown in FIG. 3D, when forming the cured body 41, the amount of the cured body 41 entering between the electronic element 21 and the substrate 22 can be reduced.

[0167] When the resin sheet 1 for sealing is disposed on a plurality of electronic elements 21 having different sizes and designs, and further on a plurality of electronic elements 21 connected to terminals having different sizes and designs, and heated to form the cured body 41, the amount of the cured body 41 entering these gaps can be controlled to uniformly seal the plurality of electronic elements 21.

[0168] Also, if the above formula (1) (0.2 < a / b < 5) is satisfied, the circumferential side surface of the electronic element 21 can be reliably covered, and while ensuring good sealing characteristics, the amount of the cured body 41 entering between the electronic element 21 and the substrate 22 can be reduced.

[0169] Furthermore, when the average value a of the maximum length A of the second domain is larger than the average value b of the maximum length B of the first domain, the amount of the cured body 41 entering between the electronic element 21 and the substrate 22 can be further reduced.

[0170] Also, if the average value a of the maximum length A of the second domain 6 is 1 μm or more, the flow of the material of the resin sheet 1 for sealing can be suppressed as much as possible. If the average value a of the maximum length A of the second domain 6 is 10 μm or less, the cured body 41 can reliably cover the circumferential side surface of the electronic element 21.

[0171] If the second domain 6 confirmed in one field image has an aspect ratio of 2 or more, the flow of the material of the resin sheet 1 for sealing can be suppressed as much as possible.

[0172] If the first domain 5 confirmed in one field of view image has a substantially circular shape, a cured body 41 with excellent strength can be formed.

[0173] (Example using a multilayer resin sheet for encapsulation) A method of manufacturing an electronic element cured body package 50 by encapsulating a plurality of electronic elements 21 with a multilayer resin sheet 11 for encapsulation and then forming a cured body 41 will be described with reference to FIGS. 4A to 4D.

[0174] As shown in FIG. 4A, a multilayer resin sheet 11 for encapsulation is prepared. Specifically, a resin sheet 1 for encapsulation and a second resin sheet 12 for encapsulation are bonded together.

[0175] As shown in FIG. 4B, a plurality of electronic elements 21 mounted on a substrate 22 are prepared.

[0176] Subsequently, the multilayer resin sheet 11 for encapsulation is disposed on the electronic elements 21 such that the other surface in the thickness direction of the resin sheet 1 for encapsulation contacts one surface in the thickness direction of the electronic elements 21.

[0177] As shown in FIG. 4C, thereafter, the resin sheet 1 for encapsulation and the element mounting substrate 24 are pressed.

[0178] By pressing, the resin sheet 1 for encapsulation flows and enters between adjacent electronic elements 21.

[0179] On the other hand, since the second resin sheet 12 for encapsulation does not have the co-dispersion region 3, even when pressed, its fluidity does not improve, and entry between adjacent electronic elements 21 is suppressed.

[0180] Thereby, an encapsulation body 31 for encapsulating a plurality of electronic elements 21 is formed from the multilayer resin sheet 11 for encapsulation.

[0181] If the resin sheet 1 for sealing contains a non-layered filler at a ratio equal to or higher than the above-described lower limit, and the second resin sheet 12 for sealing contains a non-layered filler at a ratio equal to or higher than the above-described lower limit, then the resin sheet 1 for sealing and the second resin sheet 12 for sealing can flow by the pressing shown in FIG. 4C below.

[0182] At this time, the resin sheet 1 for sealing contacts the electronic element 21, while the second resin sheet 12 for sealing is located on the opposite side of the electronic element 21 with respect to the resin sheet 1 for sealing. That is, the edge facing the gap 26 in the sealing body 31 is formed from the resin sheet 1 for sealing. On the other hand, one surface in the thickness direction of the sealing body 31 is formed from the second resin sheet 12 for sealing.

[0183] Thereafter, as shown in FIG. 4D, the sealing body 31 is heated to form a cured body 41 from the sealing body 31.

[0184] This multi-layer resin sheet 11 for sealing can also achieve the same effects as the resin sheet 1 for sealing described above.

[0185] In particular, if the resin sheet 1 for sealing and the second resin sheet 12 for sealing contain a main agent of an epoxy resin having a softening point of 50°C or higher and 130°C or lower, then in the process shown in FIG. 4C, the resin sheet 1 for sealing and the second resin sheet 12 for sealing can flow. Therefore, the time for the process shown in FIG. 4C can be shortened, and one surface in the thickness direction of the second resin sheet 12 for sealing in the process shown in FIG. 4C can be made flat.

[0186] Furthermore, if the resin sheet 1 for sealing and the second resin sheet 12 for sealing contain a phenolic resin as a curing agent together with the main agent of the epoxy resin, then the cured body 41 has high heat resistance and high chemical resistance. Therefore, the cured body 41 is excellent in sealing reliability.

[0187] In the process shown in FIG. 4C, the second resin sheet 12 for sealing is fluidized under pressure, and one surface in the thickness direction becomes flat. Further, in the process shown in FIG. 4C, in the multilayer resin sheet 11 for sealing, as described above, together with the second resin sheet 12 for sealing, the resin sheet 1 for sealing is softened and fluidized under pressure and deformed following the outer shape of the electronic element 21. In the process shown in FIG. 4C, it is allowed that the resin sheet 1 for sealing slightly enters the gap 26.

[0188] Then, in the process shown in FIG. 4D, the flow of the resin sheet 1 for sealing is suppressed based on the decrease in the complex viscosity η* accompanying the temperature rise, and excessive entry into the gap 26 is suppressed. That is, in the cured body 41 in which the multilayer resin sheet 11 for sealing including the resin sheet 1 for sealing is cured, the cured body entry length Y can be reduced.

[0189] Modification In each of the following modifications, members and processes similar to those in the above-described embodiment are denoted by the same reference numerals, and detailed descriptions thereof are omitted. Further, each modification can achieve the same effects as those of the embodiment unless otherwise specified. Furthermore, the embodiment and its modifications can be appropriately combined.

[0190] Although not shown, in one field image, the resin sheet 1 for sealing may have a monodisperse region of the second domain 6 surrounded only by the matrix 4 without the second domain 6 being located between the first domains 5. At the same time, in one field image, the resin sheet 1 for sealing has a monodisperse region in which the first domain 5 is surrounded only by the matrix 4.

[0191] Further, in the preparation of the mixture, the thermosetting resin, the non-layered filler, and the layered filler can be mixed without using a solvent. In this case, the thermosetting resin, the non-layered filler, and the layered filler are kneaded using a known kneader.

[0192] The second resin sheet 12 for sealing in the multilayer resin sheet 11 for sealing may be multilayered.

[0193] As an example of an element, an electronic element 21 disposed with a gap 26 interposed therebetween with respect to one surface 25 in the thickness direction of a substrate 22 is given, and this is encapsulated with a resin sheet 1 for encapsulation. However, for example, although not shown in the drawings, an electronic element 21 that contacts one surface 25 in the thickness direction of the substrate 22 can be given, and this can be encapsulated with the resin sheet 1 for encapsulation.

[0194] Also, as an example of an element, an electronic element 21 is given, but a semiconductor element can also be given.

Example

[0195] Preparation examples, examples, and comparative examples are shown below to more specifically explain the present invention. Note that the present invention is not limited to any preparation examples, examples, and comparative examples. Also, specific numerical values such as compounding ratios (content ratios), physical property values, and parameters used in the following description can be replaced with the upper limits (numerical values defined as "below" and "less than") or lower limits (numerical values defined as "above" and "exceeding") of the corresponding compounding ratios (content ratios), physical property values, parameters, etc. described in the above "Mode for Carrying Out the Invention".

[0196] Each component used in the preparation example is shown below.

[0197] Layered filler: Esben NX manufactured by Hojun Co., Ltd. (organophilic bentonite whose surface is modified with dimethyldistearylammonium) (silicate compound) Main agent: YSLV-80XY manufactured by Nippon Steel Chemical Co., Ltd. (bisphenol F type epoxy resin, epoxy equivalent 200 g / eq., softening point 80 °C) Hardener: LVR-8210DL manufactured by Gunei Chemical Co., Ltd. (novolak type phenol resin, latent hardener, hydroxyl equivalent: 104 g / eq., softening point: 60 °C) Hardening accelerator: 2PHZ-PW manufactured by Shikoku Kasei Kogyo Co., Ltd. (2-phenyl-4,5-dihydroxymethylimidazole) Acrylic resin: HME-2006M manufactured by Negami Kogyo Co., Ltd., a carboxyl group-containing acrylate copolymer (acrylic polymer), weight average molecular weight: 600,000, glass transition temperature (Tg): -35°C, methyl ethyl ketone solution with a solid content concentration of 20% by mass Silane coupling agent: KBM-403 (3-glycidoxypropyltrimethoxysilane) manufactured by Shin-Etsu Chemical Co., Ltd. First non-layered filler: FB-8SM (spherical fused silica powder (inorganic filler), median diameter 7.0 μm) Second non-layered filler: Inorganic filler obtained by surface-treating SC220G-SMJ (average particle diameter 0.5 μm) manufactured by Admatechs Co., Ltd. with 3-methacryloxypropyltrimethoxysilane (product name: KBM-503 manufactured by Shin-Etsu Chemical Co., Ltd.). Inorganic filler surface-treated with 1 part by mass of silane coupling agent per 100 parts by mass of inorganic filler.

[0198] Carbon black: #20 manufactured by Mitsubishi Chemical Corporation, pigment, particle diameter 50 nm

[0199] Preparation Examples 1 to 6 and Comparative Preparation Example 1 According to the formulation shown in Table 1, each component was blended in a container to prepare a mixture in the container. Subsequently, the container was set in a rotation-revolution mixer and the mixture was stirred (first mixing). Thereafter, an appropriate amount of solvent (methyl ethyl ketone) was added to the container, and then it was set in the rotation-revolution mixer again to stir the mixture containing the solvent (second mixing).

[0200] The type, conditions, etc. of the rotation-revolution mixer are shown below. Rotation-revolution mixer: Awatori Rentaro, model "AR-100" (First mixing) Rotation speed: 2000 rpm Revolution speed: 2000 rpm Mixing time: 5 minutes (Second mixing) Rotation speed: 2000 rpm Revolution speed: 2000 rpm Mixing time: 5 minutes Thereby, a varnish of the mixture was prepared.

[0201] Next, after applying varnish to the surface of the release sheet, it was dried at 120°C for 2 minutes to produce a resin sheet 1 for sealing with a thickness of 65 μm. The resin sheet 1 for sealing was in the B-stage.

[0202] Preparation Example 7 According to the formulation described in Table 2, a varnish of the mixture was prepared in the same manner as in Preparation Example 1. Subsequently, after applying the varnish to the surface of the release sheet, it was dried at 120°C for 2 minutes to produce a second resin sheet 12 for sealing with a thickness of 195 μm. The second resin sheet 12 for sealing was in the B-stage.

[0203] Examples 1 to 6 and Comparative Example 1 A multi-layer resin sheet for sealing with a thickness of 260 μm was produced by laminating a resin sheet for sealing and a second resin sheet for sealing in a combination of preparation examples as shown in Table 3.

[0204] Evaluation The following items were evaluated. The results are described in Table 3. <TEM Observation> (1) Presence or absence of a co-dispersion region First, each of the multi-layer resin sheets for sealing of Examples 1 to 6 and Comparative Example 1 was heated at 150°C for 1 hour to produce a C-stage sheet. Samples (thin slices) were produced by sampling the C-stage sheet. Specifically, the C-stage sheet was set in a FIB processing apparatus (FB2200 manufactured by Hitachi), and using an ion beam with an acceleration voltage of 10 to 40 kV and a microprobe, the C-stage sheet was cut in the thickness direction to obtain samples.

[0205] Thereafter, the cross-section of the C-stage sheet was observed at an acceleration voltage of 200 kV using a field emission transmission electron microscope (FE-TEM) (JEM-2800 manufactured by JEOL).

[0206] From one field image of the TEM observation, the presence or absence of a co-dispersion region 3 where the second domain 6 is located between the first domains 5 was confirmed.

[0207] One field image (image processing diagram) of the TEM photograph of the C-stage sheet in Example 3 is shown in FIGS. 1 to 2.

[0208] (2) Average value b of the maximum length B of the first domain, average value a of the maximum length A of the second domain 6, a / b By performing the above-described first to fourth steps, the average value b of the maximum length B of the first domain and the average value a of the maximum length A of the second domain 6 were calculated respectively. Subsequently, a / b was obtained.

[0209] (3) Area ratio of the matrix region and ratio of the number of the first domains The area ratio of the matrix region, the ratio of the number of the first domains, etc. were obtained.

[0210] <Evaluation of the cured body> (1) Cured body penetration length By performing the following steps A to E, the cured body penetration length Y was measured.

[0211] Step A: As shown in FIG. 5A, a sample sheet 61 having a length of 10 mm, a width of 10 mm, and a thickness of 260 μm was prepared from the sealing multilayer resin sheet 11 of each example and each comparative example.

[0212] Step B: As shown in FIG. 5B, a dummy element mounting substrate 74 in which a dummy element 71 having a length of 3 mm, a width of 3 mm, and a thickness of 200 μm was mounted on a glass substrate 72 via a bump 23 having a thickness of 20 μm was prepared.

[0213] Step C: As shown in FIG. 5C, the dummy element 71 on the dummy element mounting substrate 74 was sealed with the sample sheet 61 by a vacuum flat press at a temperature of 65° C., a pressure of 0.1 MPa, a degree of vacuum of 1.6 kPa, and a pressing time of 1 minute to form a sealing body 31 from the sample sheet 61.

[0214] Step D: As shown in FIG. 5D, the sealing body 31 was thermally cured by heating at 150° C. under atmospheric pressure for 1 hour to form a cured body 41 from the sealing body 31.

[0215] Step E: As shown in the enlarged view of FIG. 5D, with reference to the side edge 75 of the dummy element 71, measure the length Y of the cured body entering the gap 26 between the dummy element 71 and the glass substrate 72 from the side edge 75.

[0216] Then, the length Y of the cured body entering was evaluated according to the following criteria. ○: The length Y of the cured body entering was 0 μm or more and 20 μm or less. △: The length Y of the cured body entering was more than 20 μm and 30 μm or less, or less than 0 μm and -5 μm or more. ×: The length Y of the cured body entering was more than 30 μm or less than -5 μm.

[0217] During the evaluation, "minus" means that a space (see the thick dashed line in FIG. 5D) protruding outside the side edge 75 of the dummy element 71 is formed. The absolute value of "minus" corresponds to the protruding length of the space.

[0218] [Table 1]

[0219] [Table 2]

[0220] [Table 3] Note that the above invention was provided as an exemplary embodiment of the present invention, but this is merely an example and should not be construed in a limiting sense. Modifications of the present invention obvious to those skilled in the art are included in the scope of the following claims.

Industrial Applicability

[0221] The resin sheet for sealing is used for sealing elements.

Explanation of Reference Numerals

[0222] 1 Resin sheet for sealing 3 Co-dispersion region 4 Matrix 5 First domain 6 Second domain 21 Electronic component 21 A Maximum length of the largest second domain B Maximum length of the largest first domain a Average value of the maximum length of the second domain b Average value of the maximum length of the first domain

Claims

1. A resin sheet for sealing for sealing an element, a matrix formed from a thermosetting resin, a first domain formed from a non-layered filler and dispersed in the matrix, a second domain formed from a layered filler and dispersed in the matrix and the thermosetting resin contains an epoxy resin, the upper limit of the content ratio of the epoxy resin in the resin sheet for sealing is 13% by mass, the second domain has a co-dispersion region located between the first domains, A resin sheet for sealing, characterized in that the lower limit of the content ratio of the non-layered filler in the resin sheet for sealing is 50% by mass.

2. The resin sheet for sealing according to claim 1, characterized in that the average value a of the maximum length A of the second domain and the average value b of the maximum length B of the first domain obtained by the following first to fourth steps satisfy the following formula (1). 0.2 < a / b < 5 (1) First step: Observing the resin sheet for sealing by TEM to obtain a single field image. Second step: Ten observers observe the single field image, and measure the maximum length A of the largest second domain among the second domains and the maximum length B of the largest first domain among the first domains. Third step: Obtaining the average value a of the ten observers of the maximum length A and the average value b of the ten observers of the maximum length B. Fourth step: Substituting the average value a and the average value b into the formula (1).

3. The resin sheet for sealing according to claim 2, characterized in that the average value a of the maximum length A of the second domain is larger than the average value b of the maximum length B of the first domain.

4. The resin sheet for sealing according to claim 2, characterized in that the average value a of the maximum length A of the second domain is 1 μm or more and 10 μm or less.

5. The resin sheet for sealing according to claim 1, characterized in that the resin sheet for sealing is observed by TEM to obtain a single field image, and the second domain confirmed in the single field image has two or more aspect ratios.

6. The resin sheet for sealing according to claim 1, characterized in that the resin sheet for sealing is observed by TEM to obtain a single field image, and the first domain confirmed in the single field image has a substantially circular shape.

Images