JP2020076051A - Resin sheet for sealing - Google Patents

Abstract

To provide a resin sheet for sealing that has increased thermal conductivity.SOLUTION: The present invention provides a resin sheet for sealing that includes a first filler and a second filler, and a thermoplastic resin, the first filler being a secondary aggregate formed by aggregating thermally anisotropic boron nitride crystals, in which thermal conductivity differs depending on the direction, so as to be isotropic, wherein the thermal conductivity after thermosetting is 5 W/m K or more.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a sealing resin sheet.

  In recent years, as the speed of data processing of electronic device devices (for example, semiconductor devices) has increased, the amount of heat generated from electronic devices (for example, semiconductor chips) has increased, and it is important to design electronic device devices with heat dissipation properties. The sex is increasing. The heat has various adverse effects not only on the electronic device device itself but also on the electronic device body incorporating it.

  Therefore, conventionally, a thermosetting resin composition containing a thermally conductive secondary aggregate in which scaly boron nitride is aggregated has been proposed (see, for example, Patent Document 1). The secondary aggregate of boron nitride has high thermal conductivity and electrical insulation. Therefore, when used in an electronic device device, it can be expected to be an electronic device device having high heat dissipation. Here, the general crystal structure of boron nitride is scaly, and the thermal conductivity in the a-axis direction (plane direction) of the crystal is several to several times the thermal conductivity in the c-axis direction (thickness direction). It has ten times the thermal anisotropy. Therefore, in Patent Document 1, it is used as a secondary aggregate that is aggregated so as to require isotropicity.

JP, 2014-40533, A

  However, when the secondary agglomerate of boron nitride is contained in the resin sheet, there is a problem that the sheet becomes hard and brittle due to the reason that the resin enters the voids in the secondary agglomerate, and the followability is poor. Therefore, the resin sheet containing a secondary aggregate of boron nitride is used only in a place where the influence of the hardness of the sheet does not matter, despite having high thermal conductivity and electrical insulation. I couldn't. For example, Patent Document 1 describes that it can be used for joining a power semiconductor element that is a heat source and a heat sink. In such applications, the hardness of the resin sheet has almost no effect. However, it is considered that the sheet cannot be used as a sealing resin sheet in which the sheet followability is a problem.

  The present invention has been made in view of the above problems, and an object thereof is to provide a sealing resin sheet having higher heat conductivity.

  The inventors of the present application have found that the above problems can be solved by adopting the following configuration, and have completed the present invention.

That is, the sealing resin sheet according to the present invention,
Including a first filler and a second filler different from the first filler,
The first filler is a secondary agglomerate obtained by aggregating a boron nitride crystal having thermal anisotropy with different thermal conductivity depending on the direction so as to have isotropicity,
The thermal conductivity after thermosetting is 3 W / m · K or more.

According to the above configuration, the first filler and the second filler different from the first filler are included, and the first filler has a thermal anisotropy having different thermal conductivity depending on the direction. It is a secondary aggregate obtained by aggregating the crystals of 1. Therefore, the thermal conductivity of the sealing resin sheet can be increased by the first filler. Further, by containing the second filler different from the first filler, it is possible to reduce the increase in viscosity and the increase in elastic modulus of the sheet. That is, since the first filler is a secondary agglomerate of boron nitride, it may cause a high viscosity and a high elastic modulus of the sheet due to the reason that the resin enters the voids in the secondary agglomerate. By including it together with the second filler, the content of the first filler can be relatively reduced, and the increase in viscosity and the increase in elastic modulus can be reduced. In addition, by selecting the second filler, it is possible to exert functions other than thermal conductivity (for example, reduction of linear expansion coefficient).
Further, since the thermal conductivity after thermosetting is 3 W / m · K or more, the thermal conductivity is excellent. According to the research conducted by the present inventors, it is extremely difficult to achieve a thermal conductivity of 3 W / m · K or more without using boron nitride as a filler.
As described above, according to the above-described configuration, since the increase in viscosity and the increase in elastic modulus are reduced even when boron nitride is included as a filler, a sealing resin sheet having higher thermal conductivity than conventional is provided. can do.

  In the above structure, the average particle size of the first filler is preferably 1 μm or more and 80 μm or less.

  In recent years, there has been a demand for thinner electronic device devices in which electronic devices are sealed with a sealing resin sheet. Therefore, when the average particle diameter of the first filler is 1 μm or more and 80 μm or less, it becomes easy to reduce the thickness of the electronic device device.

  In the above structure, the maximum particle size of the first filler is preferably 200 μm or less.

  When the maximum particle diameter of the first filler is 200 μm or less, it becomes easier to make the electronic device device thinner.

  In the above structure, it is preferable that the second filler is at least one of alumina and fused silica.

Alumina (aluminum oxide, Al ₂ O ₃ ) has a relatively high thermal conductivity, although lower than boron nitride. Further, since it is not an agglomerate, the resin does not enter the inside of the alumina particles, so that higher viscosity and higher elastic modulus of the sheet are less likely to occur than when the secondary agglomerate is used. Therefore, by using alumina as the second filler, it is possible to maintain the thermal conductivity while reducing the occurrence of high viscosity and high elastic modulus of the sheet.
Further, fused silica has a low linear expansion integer and is close to a semiconductor material. Therefore, if fused silica is used as the second filler, warpage of the electronic device device can be further suppressed.
If both alumina and fused silica are used, the effects of both can be obtained.

It is sectional drawing which shows typically the resin sheet for sealing which concerns on one Embodiment of this invention. It is a figure which shows typically one process of the manufacturing method of the electronic device apparatus which concerns on one Embodiment of this invention. It is a figure which shows typically one process of the manufacturing method of the electronic device apparatus which concerns on one Embodiment of this invention. It is a figure which shows typically one process of the manufacturing method of the electronic device apparatus which concerns on one Embodiment of this invention. It is a figure which shows typically one process of the manufacturing method of the electronic device apparatus which concerns on one Embodiment of this invention. It is a figure which shows typically one process of the manufacturing method of the electronic device apparatus which concerns on one Embodiment of this invention.

  Hereinafter, the present invention will be described in detail with reference to embodiments, but the present invention is not limited to these embodiments.

  [Sealing resin sheet]

  FIG. 1 is a sectional view schematically showing a sealing resin sheet (hereinafter, also simply referred to as “resin sheet”) according to an embodiment of the present invention. Resin sheet 11 is typically provided in a state of being laminated on separator 11a such as a polyethylene terephthalate (PET) film. It should be noted that the separator 11a may be subjected to a mold release treatment in order to easily peel off the resin sheet 11.

The thermal conductivity of the resin sheet 11 after thermosetting is 3 W / m · K or more, preferably 4 W / m · K or more, and more preferably 5 W / m · K or more. Since the thermal conductivity after thermosetting is 3 W / m · K or more, the thermal conductivity is excellent. As a method of setting the thermal conductivity after thermosetting to 3 W / m · K or more, as will be described later, it can be achieved by incorporating a first filler.
In the present invention, the “thermal conductivity after thermosetting” refers to the thermal conductivity after heating at a pressure of 3 MPa and a temperature of 90 ° C. for 5 minutes, and further at 150 ° C. for 30 minutes.

  The resin sheet 11 includes a first filler and a second filler different from the first filler.

  The first filler is a secondary agglomerate obtained by aggregating boron nitride crystals having thermal anisotropy having different thermal conductivities depending on directions so as to have isotropicity.

  The average particle size of the first filler is preferably 1 μm or more and 80 μm or less, more preferably 3 μm or more and 70 μm or less. By setting the average particle size of the first filler to 1 μm or more, it is possible to preferably impart thermal conductivity. On the other hand, by setting the average particle diameter of the first filler to 80 μm or less, it becomes easy to reduce the thickness of the electronic device device manufactured using the resin sheet 11.

The maximum particle size of the first filler is preferably 200 μm or less, and more preferably 180 μm or less. By setting the maximum particle size of the first filler to 200 μm or less, it becomes easier to make the electronic device device thinner.
In addition, in this specification, the average particle diameter and the maximum particle diameter of a filler mean the value obtained by measuring with a laser diffraction type particle size distribution measuring apparatus.

  The shape of the first filler, that is, the secondary aggregate is not limited to a spherical shape as long as thermal isotropy is secured, and may be another shape such as a scale shape. However, when the resin sheet 11 is manufactured, considering that the blending amount of the secondary aggregate can be increased while ensuring the fluidity of the thermosetting resin, the secondary aggregated particles are spherical. Is preferred. When the first filler has a shape other than spherical, the average particle diameter means the length of the long side in the shape.

  The secondary agglomerates can be manufactured by using a predetermined boron nitride crystal according to a known method. Specifically, a predetermined boron nitride crystal is fired to be crushed, or a predetermined boron nitride crystal is aggregated by a known method such as spray drying, and then fired to be sintered (grain growth). .. Here, the firing temperature is not particularly limited, but is generally 2,000 ° C.

  As the secondary aggregate, known ones can be used. Specific products include "PT" series manufactured by Momentive Performance Materials Japan K.K. (for example, "PTX60"), "HP series" manufactured by Mizushima Iron & Steel Co., Ltd. (for example, "HP"). -40 ", etc.), and“ SHOB NU UHP ”series manufactured by Showa Denko KK (for example,“ SHOB NU UHP-EX ”etc.).

The second filler is not particularly limited as long as it is different from the first filler, but it may have a certain degree of thermal conductivity, or may impart a function other than thermal conductivity to the resin sheet 11. It is preferably possible, for example, a metal nitride such as aluminum nitride, silicon nitride, gallium nitride; for example, silicon dioxide, aluminum oxide, magnesium oxide, titanium oxide, zinc oxide, tin oxide, copper oxide, nickel oxide. Metal oxides such as; hydroxides such as aluminum hydroxide, boehmite, magnesium hydroxide, calcium hydroxide, zinc hydroxide, silicic acid, iron hydroxide, copper hydroxide, barium hydroxide; for example, zirconium oxide water Hydrate, tin oxide hydrate, basic magnesium carbonate, hydrotalcite, dawsonite, borax, zinc borate What hydrated metal oxides; silicon carbide, calcium carbonate, barium titanate, and the like potassium titanate. Among them, at least one of alumina and fused silica is preferable.
Alumina (aluminum oxide, Al ₂ O ₃ ) has a relatively high thermal conductivity (36 W / m · K), though lower than that of boron nitride. Further, since it is not an agglomerate, the resin does not enter the inside of the alumina particles, so that higher viscosity and higher elastic modulus of the sheet are less likely to occur than when the secondary agglomerate is used. Therefore, by using alumina as the second filler, it is possible to maintain the thermal conductivity while reducing the increase in the viscosity and the increase in the elastic modulus of the sheet.
Further, fused silica has a low linear expansion integer (0.5 × 10 ⁻⁶ / K) and is close to a semiconductor material. Therefore, when fused silica is used as the second filler, warpage of the electronic device device can be further suppressed.
If both alumina and fused silica are used, the effects of both can be obtained.

  The average particle size of the second filler is not particularly limited, but is, for example, 0.005 μm or more and 80 μm or less. The maximum particle size of the second filler can be, for example, 200 μm or less. The shape of the second filler is also not particularly limited, and may be spherical, for example.

  The content of the first filler is preferably 20% by volume or more and 80% by volume or less, and more preferably 25% by volume or more and 75% by volume or less with respect to the entire resin sheet 11. When the content is 20% by volume or more, the thermal conductivity can be suitably imparted. Further, when the content is 80% by volume or less, it is possible to suppress extremely high viscosity and high elastic modulus of the sheet.

  The content of the second filler varies depending on the material selected, but is preferably 5% by volume or more and 65% by volume or less, and 10% by volume or more and 60% by volume or less with respect to the entire resin sheet 11. More preferably.

  The total content of the first filler and the second filler is preferably 25% by volume or more and 85% by volume or less, and 30% by volume or more and 80% by volume or less with respect to the entire resin sheet 11. Is more preferable.

  The resin sheet 11 preferably contains a thermosetting resin and a thermoplastic resin.

  The thermosetting resin is preferably epoxy resin or 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.

  From the viewpoint of ensuring the reactivity of the epoxy resin, an epoxy equivalent of 150 to 250 and a softening point or melting point of 50 to 130 ° C. that is solid at room temperature are preferable. Among them, triphenylmethane type epoxy resin, cresol novolac type epoxy resin, and biphenyl type epoxy resin are more preferable from the viewpoint of reliability. In addition, a bisphenol F type epoxy resin is preferable because it can impart flexibility to the thermosetting resin sheet 11.

  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. From the viewpoint of high curing reactivity, phenol novolac resin can be preferably used. 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 of the hydroxyl groups in the phenol resin is 0.7 to 1.5 equivalents with respect to 1 equivalent of the epoxy groups in the epoxy resin. The amount is preferably 0.9 to 1.2 equivalents.

  The content of the thermosetting resin in 100% by weight of all components other than the filler is preferably 70% by weight or more, more preferably 75% by weight or more, and further preferably 80% by weight or more. When it is 70% by weight or more, the CTE1 of the cured product can be reduced. On the other hand, the content of the thermosetting resin is preferably 95% by weight or less, more preferably 92% by weight or less, further preferably 90% by weight or less, and particularly preferably 88% by weight or less.

  The resin sheet 11 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 2-methylimidazole (trade name: 2MZ) and 2-undecylimidazole (trade name: C11). -Z), 2-heptadecylimidazole (trade name; C17Z), 1,2-dimethylimidazole (trade name; 1.2DMZ), 2-ethyl-4-methylimidazole (trade name; 2E4MZ), 2-phenylimidazole (Brand name: 2PZ), 2-phenyl-4-methylimidazole (Brand name: 2P4MZ), 1-benzyl-2-methylimidazole (Brand name: 1B2MZ), 1-benzyl-2-phenylimidazole (Brand name: 1B2PZ) ), 1-cyanoethyl-2-methylimidazole (trade name; 2MZ-CN), 1-cyano Cyl-2-undecyl imidazole (trade name; C11Z-CN), 1-cyanoethyl-2-phenylimidazolium trimellitate (trade name; 2PZCNS-PW), 2,4-diamino-6- [2'-methyl Imidazolyl- (1 ')]-ethyl-s-triazine (trade name; 2MZ-A), 2,4-diamino-6- [2'-undecylimidazolyl- (1')]-ethyl-s-triazine ( Trade name: C11Z-A), 2,4-diamino-6- [2'-ethyl-4'-methylimidazolyl- (1 ')]-ethyl-s-triazine (trade name: 2E4MZ-A), 2, 4-diamino-6- [2'-methylimidazolyl- (1 ')]-ethyl-s-triazine isocyanuric acid adduct (trade name; 2MA-OK), 2-phenyl-4,5-dihydroxyme Examples include imidazole-based curing accelerators such as luminimidazole (trade name; 2PHZ-PW) and 2-phenyl-4-methyl-5-hydroxymethylimidazole (trade name; 2P4MHZ-PW) (all of which are Shikoku Chemicals Co., Ltd. )).

  Among them, 2-phenyl-4,5-dihydroxymethylimidazole and 2-phenyl-4-methyl-5-hydroxymethylimidazole are preferable. Since 2-phenyl-4,5-dihydroxymethylimidazole promotes curing at high temperature, it is possible to suppress curing by heat in the embedding step. Further, 2-phenyl-4-methyl-5-hydroxymethylimidazole promotes curing at a relatively low temperature, but is suitable when it is desired to quickly proceed with thermal curing after the embedding step.

  The content of the curing accelerator is preferably 0.2 parts by weight or more, more preferably 0.5 parts by weight or more, still more preferably 0.8 parts by weight or more, based on 100 parts by weight of the total of the epoxy resin and the phenol resin. Is. The content of the curing accelerator is preferably 5 parts by weight or less, more preferably 2 parts by weight or less based on 100 parts by weight of the total of the epoxy resin and the phenol resin.

  The resin sheet 11 preferably contains a thermoplastic resin. Thereby, the heat resistance, flexibility, and strength of the obtained resin sheet for sealing can be improved. The thermoplastic resin is preferably one that can function as an elastomer.

  Examples of the thermoplastic resin include acrylic elastomers, urethane elastomers, silicone elastomers, and polyester elastomers. Among them, acrylic elastomers are preferable from the viewpoints of easy flexibility and good dispersibility with the epoxy resin.

  The acrylic elastomer is not particularly limited, and one or more kinds of esters of acrylic acid or methacrylic acid having a linear or branched alkyl group having 30 or less carbon atoms, particularly 4 to 18 carbon atoms. Examples thereof include polymers (acrylic copolymers) and the like. As the alkyl group, for example, methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, t-butyl group, isobutyl group, amyl group, isoamyl group, hexyl group, heptyl group, cyclohexyl group, 2- Examples thereof include ethylhexyl group, octyl group, isooctyl group, nonyl group, isononyl group, decyl group, isodecyl group, undecyl group, lauryl group, tridecyl group, tetradecyl group, stearyl group, octadecyl group, and dodecyl group.

  Further, the other monomer forming the polymer is not particularly limited, and examples thereof include acrylic acid, methacrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid or crotonic acid. Such as a carboxyl group-containing monomer, an acid anhydride monomer such as maleic anhydride or itaconic anhydride, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4- (meth) acrylic acid Hydroxybutyl, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate or (4-hydroxymethylcyclohexyl) -Methyla Hydroxyl group-containing monomer such as relate, styrenesulfonic acid, allylsulfonic acid, 2- (meth) acrylamido-2-methylpropanesulfonic acid, (meth) acrylamidopropanesulfonic acid, sulfopropyl (meth) acrylate or (meth) Examples thereof include sulfonic acid group-containing monomers such as acryloyloxynaphthalene sulfonic acid, and phosphoric acid group-containing monomers such as 2-hydroxyethyl acryloyl phosphate. Among them, it is preferable that at least one of a carboxyl group-containing monomer, a glycidyl group (epoxy group) -containing monomer, and a hydroxyl group-containing monomer is contained from the viewpoint that the viscosity of the resin sheet 11 can be increased by reacting with the epoxy resin.

  The thermoplastic resin may have a functional group. As the functional group, a carboxyl group, an epoxy group, a hydroxyl group, an amino group and a mercapto group are preferable, and a carboxyl group is more preferable.

The weight average molecular weight of the thermoplastic resin is preferably 500,000 or more, more preferably 800,000 or more. On the other hand, the weight average molecular weight of the thermoplastic resin is preferably 2,000,000 or less, more preferably 1.5,000,000 or less. When the weight average molecular weight is within the above numerical range, the viscosity is appropriate and the handling during blending becomes easy.
The weight average molecular weight is a value measured by GPC (gel permeation chromatography) and calculated in terms of polystyrene.

  The content of the thermoplastic resin in 100% by weight of all components other than the filler is preferably 5% by weight or more, more preferably 10% by weight or more, further preferably 11% by weight or more, still more preferably 12% by weight or more. is there. When it is 5% by weight or more, the flexibility and flexibility of the resin sheet can be obtained. On the other hand, the content of the thermoplastic resin is preferably 30% by weight or less, more preferably 20% by weight or less. When it is 30% by weight or less, the storage elastic modulus of the resin sheet 11 does not become too high, and both the embeddability and the flow regulation can be satisfied.

  The resin sheet 11 may include a flame retardant component as needed. As a result, it is possible to reduce the expansion 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 resin sheet 11 may include 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 resin sheet 11 is preferably 0.1 to 3% by weight. When the content is 0.1% by weight or more, the hardness of the 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 resin sheet 11 preferably contains a pigment. The pigment is not particularly limited, and examples thereof include carbon black.

  The content of the pigment in the resin sheet 11 is preferably 0.1 to 2% by weight. When it is 0.1% by weight or more, good marking property is obtained. When the content is 2% by weight or less, the strength of the resin sheet after curing 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 resin sheet 11 is prepared by dissolving and dispersing a resin or the like for forming the resin sheet 11 in an appropriate solvent to prepare a varnish, and applying the varnish on the separator 11a to a predetermined thickness to form a coating film. After that, the coating film can be formed by drying it under predetermined conditions. If necessary, a plurality of resin sheets may be laminated and heated and pressed (for example, 90 ° C. for 60 seconds) to obtain the resin sheet 11 having a desired thickness. The coating method is not particularly limited, and examples thereof include roll coating, screen coating, and gravure coating. The drying conditions are, for example, a drying temperature of 70 to 160 ° C. and a drying time of 1 to 30 minutes. Alternatively, the resin sheet 11 may be formed by applying a varnish on the separator to form a coating film and then drying the coating film under the drying conditions. After that, the resin sheet 11 is attached to the separator 11a together with the separator. When the resin sheet 11 particularly contains a thermoplastic resin (acrylic resin), an epoxy resin, and a phenol resin, all of these are dissolved in a solvent, and then coated and dried. Examples of the solvent include methyl ethyl ketone, ethyl acetate, toluene and the like.

  The thickness of the resin sheet 11 is not particularly limited, but is, for example, 100 to 2000 μm, and more preferably 110 to 1800 μm. Within the above range, the electronic device can be excellently sealed.

  The resin sheet 11 may have a single-layer structure or a multi-layer structure in which two or more resin sheets having different compositions are laminated, but there is no fear of delamination, and the sheet thickness has high uniformity. A single-layer structure is preferable because it easily lowers moisture absorption.

  The resin sheet 11 includes a SAW (Surface Acoustic Wave) filter; a MEMS (Micro Electro Mechanical Systems) such as a pressure sensor and a vibration sensor; a semiconductor such as an IC such as an LSI, a transistor and a semiconductor chip; a capacitor; a resistor; Used for device encapsulation. Among them, it can be preferably used for sealing an electronic device (specifically, SAW filter, MEMS) that requires hollow sealing, and particularly preferably used for sealing a SAW filter.

[Method of manufacturing hollow package]
2A to 2E are diagrams schematically showing one step of the method for manufacturing the electronic device apparatus according to the embodiment of the present invention.
In this embodiment, a case where the electronic device device is a hollow package will be described. Specifically, a case will be described in which the SAW chip 13 mounted on the printed wiring board 12 is hollow-sealed with the resin sheet 11 to manufacture a hollow package. However, the present invention is not limited to this example, and a similar method can be adopted for manufacturing an electronic device device having no hollow portion.

(SAW chip mounting substrate preparation process)
In the method for manufacturing a hollow package according to this embodiment, first, as shown in FIG. 2A, a stack 15 in which a plurality of SAW chips 13 are mounted on a printed wiring board 12 is prepared (step A).
The SAW chip 13 corresponds to the electronic device of the present invention. The printed wiring board 12 corresponds to the support of the present invention.
The SAW chip 13 can be formed by dicing a piezoelectric crystal on which a predetermined comb-shaped electrode is formed into individual pieces by a known method. For mounting the SAW chip 13 on the printed wiring board 12, a known device such as a flip chip bonder or a die bonder can be used. The SAW chip 13 and the printed wiring board 12 are electrically connected to each other via a protruding electrode 13a such as a bump. A hollow portion 14 is maintained between the SAW chip 13 and the printed wiring board 12 so as not to obstruct the propagation of surface acoustic waves on the surface of the SAW filter. The distance (width of the hollow portion) between the SAW chip 13 and the printed wiring board 12 can be set appropriately, and is generally about 10 to 100 μm.

(Resin sheet preparation process)
Further, in the hollow package manufacturing method according to the present embodiment, the resin sheet 11 is prepared (step B). As described above, the resin sheet 11 contains a secondary agglomerate obtained by agglomerating boron nitride crystals having thermal anisotropy whose thermal conductivity varies depending on the direction so as to have isotropicity.

(Resin sheet placement process)
Next, as shown in FIG. 2B, the laminated body 15 is arranged on the lower heating plate 41 with the surface on which the SAW chip 13 is mounted facing upward, and the resin sheet 11 is arranged on the surface of the SAW chip 13. (Step C). In this step, first, the laminated body 15 may be arranged on the lower heating plate 41, and then the resin sheet 11 may be arranged on the laminated body 15, or the resin sheet 11 may be laminated first on the laminated body 15. After that, the laminated body in which the laminated body 15 and the resin sheet 11 are laminated may be arranged on the lower heating plate 41. The separator 11a is preferably not peeled off at this stage.

(Embedding process)
Next, as shown in FIG. 2C, the SAW chip 13 is embedded in the resin sheet 11 by hot pressing with the lower heating plate 41 and the upper heating plate 42 (step D). Note that the embedding step is a step from the start of embedding the SAW chip 13 to the entire embedding of the SAW chip 13.

The hot pressing conditions for embedding the SAW chip 13 in the resin sheet 11 are preferably such that the SAW chip 13 can be suitably embedded in the resin sheet 11, and the temperature is, for example, 40 to 150 ° C., preferably The pressure is 60 to 120 ° C., and the pressure is, for example, 0.1 to 10 MPa, preferably 0.5 to 8 MPa.
Further, in consideration of improvement of adhesion and followability of the resin sheet 11 to the SAW chip 13 and the printed wiring board 12, it is preferable to press under a reduced pressure condition. The reduced pressure condition is, for example, 0.1 to 5 kPa, and more preferably 0.1 to 100 Pa.

(Primary thermosetting process)
After the embedding step, the resin sheet 11 is heated and primary thermoset while maintaining a state in which the laminated body 15 and the resin sheet 11 are pressed in a direction of approaching each other (step E). Thereby, the sealing body 16 is obtained.
After the step D, that is, after embedding the electronic device in the encapsulating resin sheet, the inventors tentatively heat the encapsulating resin sheet without applying the pressure to cause primary thermosetting. In this case, since the resin sheet 11 is almost not thermoset, the thickness of the resin sheet 11 which is deformed to be thin due to the pressure at the time of embedding is returned to the direction in which it is slightly thickened (spring back). It was found that it was cured under the condition. It was speculated that the springback causes the distance between the secondary aggregates to be larger than that at the time of embedding, which causes the improvement of the thermal conductivity to be hindered.
On the other hand, according to the present embodiment, after the SAW chip 13 is embedded in the resin sheet 11, the resin is maintained while the laminated body 15 and the resin sheet 11 are kept pressed so as to suppress springback. The sheet 11 is heated to be primary thermoset. Therefore, the distance between the secondary agglomerates can be suppressed from becoming longer than that at the time of embedding, and the thermal conductivity can be improved.
The term "primary thermosetting" refers to thermosetting that does not cause springback even if the pressure is released after the primary thermosetting, or has little effect of springback, and is not complete thermosetting. Good.
The pressure applied in the primary thermosetting step may be such that the pressure applied during the embedding step is temporarily released, and then the pressure is applied again. You may perform the pressurization in a thermosetting process.
The condition of the first thermosetting step (step E) is 0.8 or more when the thermal conductivity of the resin sheet 11 after thermosetting at a pressure of 3 MPa and a temperature of 150 ° C. for 1 hour is set to 1. Is preferable, and it is more preferable that the condition is 0.85 or more.
The condition of thermosetting at a pressure of 3 MPa and a temperature of 150 ° C. for 1 hour is a condition assuming a case where the encapsulating resin sheet is completely thermoset under a pressurizing condition such that springback does not occur.
If the condition of the step E is 0.8 or more when the thermal conductivity of the resin sheet 11 after thermosetting for 1 hour at a pressure of 3 MPa and a temperature of 150 ° C. is 0.8 or more, spring back is performed. Even in this case, the thermal conductivity can be 0.8 or more as compared with the case where no springback occurs. Therefore, the thermal conductivity can be improved more preferably.
The specific numerical value of each condition of the step E can be appropriately set according to the constituent material of the resin sheet 11, but the pressure condition is, for example, preferably 0.01 to 20 MPa, more preferably 0.05 to 18 MPa. . Moreover, as the temperature condition of the step E, for example, 50 to 200 ° C. is preferable, and 60 to 180 ° C. is more preferable. The heat curing time in the step E is preferably 10 seconds to 3 hours, more preferably 20 seconds to 2 hours.

(Secondary thermosetting process)
Next, the separator 11a is peeled off, and the resin sheet 11 is subjected to a second thermosetting treatment (see FIG. 2D). The conditions for the secondary thermosetting treatment can be appropriately set according to the conditions for the primary thermosetting treatment and the constituent materials of the resin sheet 11, but for example, the heating temperature is preferably 100 ° C. or higher, more preferably 120 ° C. That is all. On the other hand, the upper limit of the heating temperature is preferably 200 ° C or lower, more preferably 180 ° C or lower. The heating time is preferably 10 minutes or longer, more preferably 30 minutes or longer. On the other hand, the upper limit of the heating time is preferably 180 minutes or less, more preferably 120 minutes or less. Moreover, the pressure may be increased if necessary, and the pressure is preferably 0.1 MPa or more, more preferably 0.5 MPa or more. On the other hand, the upper limit is preferably 10 MPa or less, more preferably 5 MPa or less.
In the first thermosetting process, if the resin sheet 11 is completely thermoset, the second thermosetting process may not be performed. Further, the timing of peeling the separator 11a is not limited to after the first thermosetting and before the second thermosetting.

(Dicing process)
Subsequently, the sealing body 16 may be diced (see FIG. 2E). This makes it possible to obtain the hollow package 18 for each SAW chip 13.

(Board mounting process)
If necessary, a rewiring and bumps may be formed on the hollow package 18, and a board mounting step of mounting the rewiring and bumps on a separate board (not shown) may be performed. A known device such as a flip chip bonder or a die bonder can be used to mount the hollow package 18 on the substrate.

  In the embodiment described above, the case where the support of the present invention is the printed wiring board 12 has been described, but the support of the present invention is not limited to this example, and may be, for example, a ceramic substrate, a silicon substrate, a metal substrate, or the like. May be.

  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 Examples and Comparative Examples will be described.
Epoxy resin: Nippon Steel Chemical Co., Ltd. YSLV-80XY (bisphenol F type epoxy resin, Epokin equivalent: 200 g / eq., Softening point: 80 ° C.)
Phenol resin: LVR8210DL manufactured by Gunei Chemical Co., Ltd. (Novolak type phenol resin, hydroxyl group equivalent: 104 g / eq., Softening point: 60 ° C.)
Thermoplastic resin: ME-2000M manufactured by Negami Kogyo Co., Ltd. (carboxyl group-containing acrylate polymer, weight average molecular weight: about 600,000, Tg: -35 ° C, acid value: 20 mgKOH / g)
Carbon black: Mitsubishi Chemical Corporation # 20
Filler 1: Secondary aggregate of boron nitride (manufactured by Mizushima Alloy Iron Co., Ltd., product name: HP-40 (average particle size: 40 μm, maximum particle size: 180 μm))
Filler 2: Alumina (manufactured by Admatechs, product name: AE-9104SME (average particle size: 3 μm, maximum particle size: 10 μm))
Filler 3: FB-5SDC manufactured by Denki Kagaku Kogyo Co., Ltd. (spherical fused silica, average particle size 5 μm, maximum particle size: 20 μm)
Curing accelerator 1: 2PHZ-PW (2-phenyl-4,5-dihydroxymethylimidazole) manufactured by Shikoku Chemicals Co., Ltd.
Curing accelerator 2: 2P4MHZ-PW (2-phenyl-4-methyl-5-hydroxymethylimidazole) manufactured by Shikoku Chemicals Co., Ltd.

[Production of resin sheet for sealing]
According to the compounding ratio shown in Table 1, each component was dissolved and dispersed in methyl ethyl ketone as a solvent to obtain a varnish having a concentration of 90% by weight. This varnish was applied on a release-treated film made of a polyethylene terephthalate film having a thickness of 38 μm and subjected to silicone release treatment, and then dried at 110 ° C. for 3 minutes. This sheet was laminated to obtain a thermosetting resin sheet having a thickness of 220 μm.

(Measurement of thermal conductivity after thermosetting)
First, the parallel plate method was used to heat and thermoset the encapsulating resin sheets of Examples and Comparative Examples while pressing them. At this time, after heating at a pressure of 3 MPa and a temperature of 90 ° C. for 5 minutes, it was heated at 150 ° C. for 30 minutes.
Next, the thermal conductivity of these sealing resin sheets after thermosetting was measured. The thermal conductivity was calculated from the following formula. The results are shown in Table 1.
(Thermal conductivity) = (Thermal diffusion coefficient) x (Specific heat) x (Specific gravity)

<Thermal diffusion coefficient>
After the encapsulating resin sheet was produced, it was heated at a pressure of 3 MPa and a temperature of 90 ° C. for 5 minutes, and then at 150 ° C. for 30 minutes. Using this sample, the thermal diffusion coefficient was measured using a xenon flash method heat measuring device (LFA 447 nanoflash, manufactured by Netti Japan).

<Specific heat>
It was determined by a measuring method in accordance with JIS-7123 standard using DSC (manufactured by TA instrument, Q-2000).

<Specific gravity>
It measured by the Archimedes method using the electronic balance (Shimadzu Corporation make, AEL-200).

(Evaluation of sealing property)
A SAW chip having the following specifications, on which an aluminum comb-shaped electrode was formed, was mounted on a ceramic substrate under the following bonding conditions to produce a SAW chip mounting substrate including the ceramic substrate and the SAW chip mounted on the ceramic substrate. The gap width between the SAW chip and the ceramic substrate was 20 μm.

<SAW chip>
Chip size: 1.2 mm square (thickness 150 μm)
Bump material: Au (height 20 μm)
Number of bumps: 6 bumps Number of chips: 100 (10 x 10)

<Bonding conditions>
Device: Panasonic Electric Works Co., Ltd. Bonding conditions: 200 ° C, 3N, 1sec, ultrasonic output 2W

A sealing resin sheet was placed on the SAW chip mounting substrate.
Then, under the conditions shown below, the SAW chip was embedded in a sealing resin sheet by vacuum pressing with a parallel plate method.

<Vacuum press conditions>
Temperature: 60 ℃
Pressure: 4MPa
Vacuum degree: 1.6 kPa
Press time: 1 minute

  After opening to atmospheric pressure, a first thermosetting treatment was further performed under the following conditions.

<Primary thermosetting treatment conditions>
Temperature: 90 ℃
Pressure: 3MPa
Press time: 5 minutes

  The obtained sealed body was peeled off at the interface between the substrate and the sealing resin (sealing resin sheet) to expose the element surface of the SAW chip. Then, it observed with the optical microscope. "○" means that the encapsulating resin sheet follows the SAW chip well, and the SAW chip is encapsulated without any void between the SAW chip and the encapsulating resin sheet. The case where the resin sheet had poor followability and the SAW chip was sealed in the state where there was a void between the SAW chip and the sealing resin sheet was evaluated as "x". The results are shown in Table 1.

11 Resin Sheet for Hollow Encapsulation 11a Support 13 SAW Chip 16 Encapsulation 18 Hollow Package

Claims (4)

A first filler and a second filler different from the first filler and a thermoplastic resin,
The first filler is a secondary agglomerate obtained by aggregating a boron nitride crystal having thermal anisotropy with different thermal conductivity depending on the direction so as to have isotropicity,
A resin sheet for encapsulation, which has a thermal conductivity of 5 W / mK or more after thermosetting.   The encapsulating resin sheet according to claim 1, wherein the average particle size of the first filler is 1 μm or more and 80 μm or less.   The encapsulating resin sheet according to claim 1 or 2, wherein the maximum particle size of the first filler is 200 µm or less.   The encapsulating resin sheet according to any one of claims 1 to 3, wherein the second filler is at least one of alumina and fused silica.

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