JP7702701B2 - Manufacturing method of electronic device, and electronic device - Google Patents

Description

The present disclosure relates to a method for manufacturing an electronic device, and the electronic device. More specifically, the present disclosure relates to a method for manufacturing an electronic device including a substrate, a mounting component, and an encapsulant interposed in a gap between the substrate and the mounting component, and to an electronic device including an encapsulant made from an encapsulating resin composition.

Patent Document 1 discloses an underfill material containing an epoxy compound, an epoxy curing agent, and a curing accelerator. The curing accelerator contains imidazole and a phosphonium salt, which controls the reactivity of the underfill material while maintaining the viscosity, thereby curing the underfill material and sealing the gap between the substrate and the mounted components in the electronic device.

JP 2019-156997 A

The object of the present disclosure is to provide a method for manufacturing an electronic device in which voids are less likely to occur in the sealing material even when the gap between the electrodes of the mounted components and the gap between the substrate and the mounted components are narrowed, and to provide an electronic device.

A method for manufacturing an electronic device according to one embodiment of the present disclosure includes a mounting step, an injection step, and a sealing step. In the mounting step, a mounting component is surface mounted on a substrate via a plurality of electrodes. In the injection step, a thermosetting encapsulating resin composition is injected between the substrate and the mounting component. In the encapsulating step, the encapsulating resin composition is cured to produce an encapsulant. The shortest pitch between the plurality of electrodes is 100 μm or less, and the distance between the substrate and the mounting component is 25 μm or less. In the encapsulating step, the encapsulating resin composition is cured by heating under pressure.

An electronic device according to one aspect of the present disclosure is manufactured by the method for manufacturing the electronic device.

FIG. 1 is a schematic cross-sectional view showing an electronic device according to an embodiment of the present disclosure. 2A through 2E are schematic cross-sectional views illustrating some of the steps for making an electronic device of the present disclosure.

1. Overview First, the background to the invention according to the present disclosure will be described.

Conventionally, encapsulants for electronic devices have been produced using a method known as underfill, in which a mounting component with electrodes, such as a semiconductor element, is stacked on a substrate using a flip chip technique, and then a liquid sealing material (underfill material) is injected to fill the gap between the substrate and the mounting component.

In the underfill method, as described above, the underfill material is filled and then cured, and the gap between the substrate and the mounted components is sealed with the cured underfill material. For this reason, it is widely used as a method for producing sealing materials for electronic devices.

In recent years, the increasing performance of electronic devices has led to a demand for miniaturization of electronic devices (hereinafter also referred to as "fineness"). That is, the boards and mounted components in electronic devices are being miniaturized, and the spacing between the board and mounted components, and the spacing between the electrodes of mounted components, are being reduced to achieve finer pitches and finer gaps (sometimes referred to as narrow gaps/pitches).

However, when filling the gap between the substrate and the mounted components in an electronic device with underfill material to seal the gap, there is a problem that voids tend to occur in the underfill material as electronic devices become finer. Therefore, in order to ensure the connection reliability of electronic devices when producing finer electronic devices, it is necessary to suppress the occurrence of voids in the sealing material when producing the sealing material that seals the gap between the substrate and the mounted components.

However, in order to manufacture electronic devices that aim to improve performance by miniaturizing (fine) the distance (also called the gap) between the substrate and the mounted components, and the distance (also called the pitch) between the electrodes of the mounted components, it was difficult to fill the gaps sufficiently by simply filling with sealing material and then heating and curing it. It was also found that in this case, voids remained in the sealing material. The inventors discovered that one of the reasons for this is that when electronic devices are fined, with conventional manufacturing methods, the sealing material does not flow sufficiently in the gaps between the substrate and the mounted components, and even if it does flow, voids are likely to occur in the sealing material before it hardens.

Therefore, in order to solve the above problems, the inventors conducted intensive research and discovered the conditions for manufacturing electronic devices to produce miniaturized electronic devices, and the composition and physical properties of an encapsulating resin composition for producing an encapsulant for miniaturized electronic devices.

1 is a schematic cross-sectional view showing an electronic device according to an embodiment of the present disclosure. The manufacturing method of the electronic device 1 of this embodiment includes a mounting process, an injection process, and a sealing process. In the mounting process, the mounting component 3 is surface-mounted on the substrate 2 via a plurality of electrodes 33. In the injection process, a thermosetting encapsulating resin composition is injected between the substrate 2 and the mounting component 3. In the encapsulating process, the encapsulating resin composition is cured to produce an encapsulant 4. The shortest pitch between the plurality of electrodes 33 is 100 μm or less, and the interval between the substrate 2 and the mounting component 3 is 25 μm or less. In the encapsulating process, the encapsulating resin composition is cured by heating under pressure. According to this embodiment, by injecting the encapsulating resin composition into the gap between the substrate 2 and the mounting component 3 and heating under pressure, even if a gap that causes a void is generated in the encapsulating resin composition during injection, the gap can be crushed or discharged to the outside before the encapsulating resin composition hardens. Therefore, even if the distance between the electrodes 33 of the mounted components 3 in the electronic device 1 and the distance between the substrate 2 and the mounted components 3 are narrowed, voids are unlikely to occur in the sealing material 4 .

The inventors have also found an encapsulating resin composition suitable for producing an encapsulating material 4 in a fined electronic device 1 by heating and thermosetting under pressure in the above-mentioned encapsulation process. That is, the encapsulating resin composition of this embodiment is a thermosetting encapsulating resin composition for producing an encapsulating material 4 that seals the gap between the substrate 2 and the mounting component 3 mounted on the substrate 2. The encapsulating resin composition has a viscosity of 0.15 Pa·s or less at 100°C. Therefore, when producing the encapsulating material 4 from the encapsulating resin composition, the encapsulating resin composition can have a suitable fluidity when injected, and can be sufficiently filled in the gap between the substrate 2 and the mounting component 3. As a result, when producing a fined electronic device 1, the encapsulating resin composition is interposed between the substrate 2 and the mounting component 3 and heated under pressure, making it difficult for voids to occur in the encapsulating material 4. In this embodiment, the fined electronic device 1 refers to one having a shortest pitch of 100 μm or less and a gap of 25 μm or less. The pitch refers to the dimension between a plurality of electrodes in the mounting component 3, and the gap refers to the distance between the substrate 2 and the mounting component 3. However, this is not intended to limit the use of the encapsulating resin composition of this embodiment to only the production of the above-mentioned fine electronic device 1, and for example, the encapsulating resin composition of this embodiment can be applied regardless of the pitch distance and gap distance.

In this manner, in this embodiment, the encapsulating resin composition is interposed in the gap between the substrate 2 and the mounted component 3, and the encapsulating material 4 can be produced from the encapsulating resin composition by heating and pressurizing. Even if the encapsulating resin composition is caused to flow, voids are unlikely to form in the encapsulating resin composition, and as a result, voids in the encapsulating material 4 in the electronic device 1 can be reduced. This ensures the connection reliability in the electronic device 1.

2. Details The following describes the details of the encapsulating resin composition of the present embodiment and the electronic device 1. In this specification, the expression "A and/or B" means any one of "A", "B", or "A and B".

<Sealing resin composition>
First, preferred characteristics (physical properties) of the encapsulating resin composition will be described.

The encapsulating resin composition of this embodiment has a viscosity of 0.15 Pa·s or less at 100°C. In this case, for example, when applying the encapsulating resin composition, more uniform filling properties and a good filling speed under the mounting component 3 can be achieved. This makes it less likely that voids will be generated in the encapsulating material 4 when the encapsulating resin composition is heated under pressure. It is more preferable that the viscosity of the encapsulating resin composition when heated to 100°C is 0.10 Pa·s or less, and even more preferable that it is 0.08 Pa·s or less. The viscosity of the encapsulating resin composition at 100°C is obtained by measuring the viscosity at 100°C using a rheometer at a rotation speed of 1 rpm.

When the encapsulating resin composition of this embodiment is heated from 25°C under at least one heating condition with a heating rate of 0.5°C/min to 50°C/min, the viscosity at the time of reaching the curing temperature is preferably 0.150 Pa·s or less. In this embodiment, the "curing temperature" refers to the temperature at which the viscosity reaches 100 times or more of the initial viscosity within 2 hours from the start of heating. The curing temperature is obtained by applying the encapsulating resin composition to the stage of a rheometer with a rheometer, heating the stage to a temperature in the range of 80°C to 150°C, and then measuring the viscosity of the encapsulating resin composition after 2 hours under the condition of a rotation speed of 1 rpm. In addition, the "viscosity at the time of reaching the curing temperature" of the encapsulating resin composition is obtained by placing the encapsulating resin composition on a stage that has been heated to a temperature in the range of 80°C to 150°C using a rheometer and measuring the viscosity under the condition of a rotation speed of 1 rpm. The curing temperature varies depending on the components constituting the encapsulating resin composition, the blending ratio of the components, the mixing method when preparing the composition, etc., but in this embodiment, by adjusting the composition components and/or the composition ratio, it is possible to control the viscosity of the encapsulating resin composition at the time when it reaches the curing temperature to be 0.150 Pa s or less. The viscosity when heated to the curing temperature is more preferably 0.10 Pa s or less, and even more preferably 0.08 Pa s or less.

The viscosity of the encapsulating resin composition at 25°C is preferably less than 0.05 Pa·s. In this case, when molding the encapsulating resin composition, even at a temperature near room temperature (25°C), i.e., without preheating the encapsulating resin composition, the coating workability by jet dispensing, for example, and the discharge stability can be improved. In addition, in this case, good filling properties under the mounting components 3 such as semiconductor elements can be achieved. The viscosity of the encapsulating resin composition at 25°C is more preferably 0.04 Pa·s or less, and even more preferably 0.03 Pa·s or less. The lower limit of the viscosity of the encapsulating resin composition at 25°C is not particularly limited, but may be, for example, 0.01 Pa·s or more.

The encapsulating resin composition preferably has a bubble breaking property. Here, the "bubble breaking property" in the present disclosure can be confirmed as follows. First, a suitable container having a bottom area of 450 mm ² and a height of 55 mm or more is prepared, and the encapsulating resin composition is placed in the container so that the height from the bottom of the container is 20 mm. Next, the container is depressurized at a temperature of 25° C. and 200 Pa/10 min. After 10 minutes have passed since the start of depressurization, the inside of the container is checked, and the encapsulating resin composition is sprayed (foamed) by the depressurization, and the presence or absence of the encapsulating resin composition adhering to the wall surface of the container is confirmed. Then, if the height of the adhesion from the bottom surface of the container on the wall surface inside the container is 40 mm or less, it can be said that the encapsulating resin composition has excellent bubble breaking property. If the encapsulating resin composition has a bubble breaking property, even if the gap between the electrodes of the mounting components and the gap between the substrate and the mounting components are narrowed in the electronic device 1, when the encapsulating material is produced from the encapsulating resin composition by a method using underfill, the generation of voids in the encapsulating material 4 is particularly unlikely to occur. In the above, the height of the deposit on the wall surface is preferably 35 mm or less, more preferably 30 mm or less, and particularly preferably no spillage of the encapsulating resin composition occurs and no deposit forms on the wall surface (i.e., substantially 0 mm).

The preferred characteristics of the encapsulating resin composition described above can be realized by appropriately adjusting the components of the composition described below. However, the physical properties of the encapsulating resin composition are not limited to those described above.

As shown in FIG. 1, the encapsulating resin composition according to this embodiment can be suitably used as an encapsulant 4 that encapsulates between a substrate 2 and a mounting component 3 in an electronic device 1. For example, the encapsulating resin composition may be an encapsulating material 40, and specifically, can be suitably used as an underfill material. When the encapsulating resin composition is used as an encapsulating material (underfill material) and an encapsulating material 4 is prepared from the encapsulating resin composition, voids are less likely to occur in the encapsulating material 4. In particular, the encapsulating resin composition according to this embodiment can be suitably used to prepare an encapsulating material 4 in an electronic device 1 in which the shortest pitch between multiple electrodes is 100 μm or less and the distance between the substrate 2 and the mounting component 3 is 25 μm or less.

Next, we will explain in detail the components that can be contained in the encapsulating resin composition.

[Epoxy resin]
In the present embodiment, the encapsulating resin composition contains an epoxy resin (A). In the present embodiment, the epoxy resin (A) is a thermosetting component.

The epoxy resin (A) contains a bisphenol-type epoxy resin (A1) and an aromatic amino epoxy resin (A2). That is, the encapsulating resin composition preferably contains at least one or both of the bisphenol-type epoxy resin (A1) and the aromatic amino epoxy resin (A2).

The bisphenol type epoxy resin (A1) contains at least one selected from the group consisting of, for example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, and bisphenol S type epoxy resin, and derivatives of these resins. The bisphenol type epoxy resin (A1) preferably contains a bisphenol F type epoxy resin in particular. In this case, the encapsulating resin composition can be imparted with better thermosetting properties. The bisphenol F type epoxy resin is a compound in which two phenol skeletons are bonded via one methylene chain. The bisphenol F type epoxy resin may have a substituent in the phenol skeleton.

The viscosity of the bisphenol type epoxy resin (A1) at 100°C is preferably, for example, 0.01 Pa·s or more and 0.50 Pa·s or less.

The aromatic aminoepoxy resin (A2) can impart better thermosetting properties to the encapsulating resin composition while maintaining the storage stability of the encapsulating resin composition.

The aromatic aminoepoxy resin (A2) preferably has an aromatic ring, an amino group bonded to the aromatic ring, and three or more epoxy groups in one molecule. In other words, the aromatic aminoepoxy resin (A2) is preferably trifunctional or more.

It is more preferable that the aromatic amino epoxy resin (A2) has an aromatic ring, an amino group bonded to the aromatic ring, an epoxy group bonded to the amino group, and an epoxy group bonded to a position other than that of the amino group bonded to the aromatic ring. In other words, when the aromatic amino epoxy resin (A2) has three or more epoxy groups, it is preferable that at least one of them is bonded to an amino group bonded to the aromatic ring.

Specific examples of aromatic aminoepoxy resins (A2) include N,N-diglycidyl-p-glycidyloxyaniline, etc. Note that aromatic aminoepoxy resins (A2) are not limited to the above compounds.

The viscosity of the aromatic aminoepoxy resin (A2) at 100°C is preferably 0.01 Pa·s or more and 0.50 Pa·s or less.

It is more preferable that the encapsulating resin composition contains both the bisphenol-type epoxy resin (A1) and the aromatic amino epoxy resin (A2). In this case, it is easy to proceed with a moderate curing reaction of the components in the encapsulating resin composition, and therefore it is easy to seal the gap between the substrate 2 and the mounted component 3 with the encapsulant made from the encapsulating resin composition.

When the encapsulating resin composition contains a bisphenol type epoxy resin (A1) and an aromatic amino epoxy resin (A2), it is preferable that the mass ratio of the total amount of the bisphenol type epoxy resin (A1) and the aromatic amino epoxy resin (A2) to the epoxy resin (A) is 30 mass% or more and 70 mass% or less.

When the encapsulating resin composition contains a bisphenol type epoxy resin (A1) and an aromatic amino epoxy resin (A2), the total content of the bisphenol type epoxy resin (A1) and the aromatic amino epoxy resin (A2) relative to the total amount of the encapsulating resin composition is preferably 5% by mass or more and 40% by mass or less, more preferably 10% by mass or more and 35% by mass or less, and even more preferably 20% by mass or more and 30% by mass or less. Within this range, the fluidity of the encapsulating resin composition is more easily maintained, and the gap between the substrate 2 and the mounted component 3 can be filled well. Therefore, the gap between the substrate 2 and the mounted component 3 can be sufficiently sealed, and voids are less likely to occur in the encapsulating material 4 made from the encapsulating resin composition.

The components that may be contained in the epoxy resin (A) in the encapsulating resin composition are not limited to those described above, and may contain resins having epoxy groups other than those described above.

It is preferable that the encapsulating resin composition further contains phosphoric acid (B) and phosphoric acid polyester (C).

[Phosphoric acid (B)]
The phosphoric acid (B) has a structure shown in formula (1) below.

When the encapsulating resin composition contains phosphoric acid (B), it can promote the effect of improving the dispersibility in the encapsulating resin composition by the phosphoric acid polyester (C) described below. It is preferable that phosphoric acid (B) is mixed with phosphoric acid polyester (C) to prepare a mixture and then blended into the encapsulating resin composition.

[Phosphate polyester (C)]
The encapsulating resin composition preferably contains a phosphate polyester (C). When the encapsulating resin composition contains the phosphate polyester (C), the dispersibility of the components contained in the encapsulating resin composition is easily increased.

Furthermore, when the encapsulating resin composition contains the phosphate polyester (C), the effect of reducing the CTE of the cured product produced from the encapsulating resin composition is not easily hindered. In other words, the thermal expansion coefficient of the cured product of the encapsulating resin composition can be maintained low. Note that CTE means Coefficient of Thermal Expansion, and may be referred to as "coefficient of thermal expansion" or "coefficient of linear expansion" hereinafter.

When the encapsulating resin composition contains phosphoric acid (B) and phosphate polyester (C), the dispersibility of the filler is unlikely to decrease even if the proportion of the inorganic filler (D) described below is increased. Therefore, the proportion of the filler (D) in the encapsulating resin composition can be easily increased, and it is easier to achieve a lower CTE of the cured product produced from the encapsulating resin composition.

The phosphate polyester (C) may have a structure shown in the following formula (2).

In formula (2), R ₁ , R ₂ , and R ₃ are, for example, each independently a substituent selected from the group consisting of an alkyl group, an alkenyl group, and an alkynyl group. R ₁ , R _{2 ,} and R ₃ may each independently be a long chain or a branched chain. At least one of R ₁ , R 2 , and R ₃ may be a hydrogen atom. That is, phosphoric acid polyester (C) is a compound in which at least two hydrogen atoms in formula (1) of phosphoric acid (B) are each independently substituted with R ₁ , R ₂ , and R ₃ .

In formula (2), at least one of R ₁ , R ₂ , and R ₃ may be a substituent having a polyester structure. That is, when one of R ₁ , R ₂ , and R ₃ is a substituent having a polyester structure, the others may be at least one selected from a hydrogen atom, an alkyl group, an alkenyl group, an aralkyl group, an aryl group, and a polyoxyalkylene group. When two of R ₁ , R ₂ , and R ₃ are substituents having a polyester structure, the others may be at least one selected from a group consisting of a hydrogen atom, an alkyl group, an alkenyl group, an aralkyl group, an aryl group, and a polyoxyalkylene group. When R ₁ , R ₂ , and R ₃ are all substituents having a polyester structure, the substituents having a polyester structure may all be substituents having the same polyester structure, or may each independently be a substituent having a different polyester structure. The polyester structure includes a polymer having an ester group obtained from a dicarboxylic acid and a diol, a polymer having an ester group obtained by polycondensation of a hydroxycarboxylic acid, and a polymer obtained by ring-opening polymerization of a cyclic ester compound such as lactone.

The substituents R ₁ , R ₂ , and R ₃ may each contain a phosphorus atom, and for example, the phosphate polyester (C) may be a compound derived from polyphosphoric acid represented by the following formula (3). That is, the phosphate polyester (C) may have two or more phosphorus atoms in one molecule.

In formula (3), n is 2 or more. When the phosphate polyester (C) is derived from formula (3), at least two of the hydrogen atoms in formula (3) may be substituted with a group selected from the group consisting of an alkyl group, an alkenyl group, and an alkynyl group. The phosphate polyester (C) may also have a hydroxyl group at the end. When n=1, it corresponds to the phosphate (B) represented by formula (1).

The phosphate polyester (C) is not limited to the above, and may include, for example, a reaction product obtained by reacting an appropriate alkyl ether, polyalkylene glycol monoalkyl ether, etc. with a phosphate esterifying agent.

Specific examples of phosphate polyester (C) products include phosphate polyesters that may be included in the BYK-W series (e.g., BYK-W9010, etc.) and DISPERBYK series (e.g., DISPERBYK-111, etc.) manufactured by BYK-Chemie Japan Co., Ltd.

The mass proportion of the phosphate polyester (C) relative to the total amount of the encapsulating resin composition is preferably greater than 0 mass% and less than 100 mass%, more preferably 0.01 mass% or more and 90 mass% or less, even more preferably 0.02 mass% or more and 50 mass% or less, and particularly preferably 0.05 mass% or more and less than 10 mass%.

In addition, when the encapsulating resin composition contains both phosphoric acid (B) and phosphoric acid polyester (C), the dispersibility of the components in the encapsulating resin composition can be further improved. Therefore, the dispersibility of the encapsulating resin composition is further improved, so that good fluidity can be maintained. This makes it easier for the encapsulating resin composition to flow in the gap between the substrate 2 and the mounted component 3, and therefore makes it easier to sufficiently fill the gap with the encapsulating material 4.

When the encapsulating resin composition contains silica (D1) described later, the total mass ratio of phosphoric acid (B) and phosphate polyester (C) to silica (D1) is preferably 0.05% by mass or more and 1.0% by mass or less. In this case, the CTE of the cured product of the encapsulating resin composition can be further reduced. The mass ratio of the phosphate polyester (C) is more preferably 0.1% by mass or more and 0.5% by mass or less, and even more preferably 0.2% by mass or more and 0.4% by mass or less. In this case, the encapsulating resin composition can be given better fluidity, which makes it easier to fill the gaps with the encapsulating resin composition.

[Inorganic filler (D)]
The encapsulating resin composition preferably contains an inorganic filler (D). The inorganic filler (D) can contribute to a decrease in the linear expansion coefficient of the cured product produced from the encapsulating resin composition. In addition, when the encapsulating resin composition contains the above-mentioned phosphoric acid (B) and phosphoric acid polyester (C), the dispersibility of the encapsulating resin composition is not easily decreased even if the encapsulating resin composition contains the inorganic filler (D). Therefore, the viscosity of the encapsulating resin composition is not easily increased excessively, the fluidity can be maintained, and the thixotropy is not easily deteriorated. As a result, even if the content of the inorganic filler (D) is increased, the fluidity of the encapsulating resin composition is not easily deteriorated, and the linear expansion coefficient of the encapsulating resin composition can be reduced.

It is preferable that the inorganic filler (D) contains silica (D1), and it is also preferable that at least a part of the silica (D1) is surface-treated with a coupling agent. In this case, the compatibility between the epoxy resin (A) and the silica (D1) in the encapsulating resin composition can be improved, which can further contribute to improving the dispersibility of the encapsulating resin composition. In addition, in this case, it is easy to reduce the viscosity of the encapsulating resin composition when heated to 100 ° C. The coupling agent is, for example, a silane coupling agent. Examples of the silane coupling agent include compounds having at least one functional group selected from the group consisting of an epoxy group, an amino group, a (meth)acryloyl group, and a phenyl group. It is preferable that the silane coupling agent is a silane coupling agent having a phenyl group. That is, it is preferable that at least a part of the silica (D1) is surface-treated with a silane coupling agent having a phenyl group. In this case, the dispersibility of the encapsulating resin composition can be further improved.

When the inorganic filler (D) contains silica (D1), it is preferable that the silica (D1) contains a first silica filler (D11) and a second silica filler (D12) having an average particle size different from that of the first silica filler (D11). In this disclosure, the "average particle size" is the volume average diameter. The volume average diameter is calculated from the particle size distribution obtained by measurement using a laser diffraction/scattering method. The particle size distribution can be measured, for example, by a laser diffraction particle size distribution measuring device, and an example of the laser diffraction particle size distribution measuring device is the LA-960 series manufactured by Horiba, Ltd.

The average particle size of the first silica filler (D11) is preferably 0.1 μm or more and 1.5 μm or less, and in this case, the standard deviation in the particle size distribution of the first silica filler (D11) is preferably 0.01 or more and less than 1.0. The average particle size of the second silica filler (D12) is preferably 10% or more and 50% or less of the average particle size of the first silica filler (D11), and the standard deviation in the particle size distribution of the second silica filler (D12) is preferably 0.01 or more and less than 1.0. Here, the "standard deviation in the particle size distribution" in this disclosure is an index indicating the width or narrowness of the particle size distribution. The standard deviation in the particle size distribution can be used to determine whether the particle size of the particles is uniform or not. The standard deviation in the particle size distribution can be calculated as follows. As with the above average particle size (volume average diameter), the standard deviation can be calculated from the particle size data of each particle and the average particle size in the particle size distribution obtained by measuring using the laser diffraction/scattering method. When the silica particles in each of the first silica filler (D11) and the second silica filler (D12) of the silica (D1) in the encapsulating resin composition have a standard deviation in particle size distribution of 0.01 or more and less than 1.0, the viscosity of the encapsulating resin composition can be further reduced. This ensures the flowability of the encapsulating resin composition. Therefore, when the encapsulating resin composition is used to seal the gap between the substrate and the semiconductor element, it is possible to achieve better moldability.

The average particle size of the first silica filler (D11) is preferably 0.1 μm or more and 1.0 μm or less. The standard deviation in the particle size distribution of the first silica filler (D11) is preferably 0.01 or more and 0.60 or less, more preferably 0.02 or more and 0.40 or less, even more preferably 0.02 or more and 0.36 or less, and particularly preferably 0.05 or more and 0.36 or less. The average particle size of the second silica filler (D12) is not particularly limited as long as it satisfies the above, but the average particle size of the second silica filler (D12) can be, for example, 0.01 μm or more and 0.75 μm or less. The standard deviation in the particle size distribution of the second silica filler (D12) is preferably 0.01 or more and less than 0.10, more preferably 0.02 or more and 0.08 or less, even more preferably 0.03 or more and 0.08 or less, and particularly preferably 0.04 or more and 0.06 or less.

It is preferable that the first silica filler (D11) and the second silica filler (D12) are both wet silica. Wet silica is amorphous silica synthesized in a liquid. For example, wet silica can be produced by at least one method selected from the group consisting of a precipitation method and a sol-gel method. It is particularly preferable that the wet silica is produced by the sol-gel method. In this case, the average particle size of the wet silica particles can be kept relatively small, such as 0.1 μm or more and 1.5 μm or less, and the particle size distribution can be made less likely to vary. That is, in this case, the particle size of the first silica filler (D11) and the second silica filler (D12) can be easily made uniform. The sol-gel method is a synthesis method in which a solid substance is obtained from a sol state in which fine particles such as colloids are dispersed in a solution, via a gel state in which fluidity is lost, and an appropriate synthesis method may be adopted. In addition, the first silica filler (D11) of the present disclosure can be confirmed to be produced by the sol-gel method by cutting a suitable particle of the first silica filler (D11) and observing its cross section. Specifically, for example, the cured product of the sealing resin composition is cut, the cut surface is observed with an electron microscope, etc., and the particle size of silica on the cut surface is measured, so that it can be determined that it is produced by the sol-gel method. The second silica filler (D12) and the third silica filler (D13) described later can also be confirmed to be produced by the sol-gel method in the same manner as the first silica filler (D11).

It is also preferable that the silica (D1) further contains a third silica filler (D13) whose average particle size is different from both the first silica filler ( D11 ) and the second silica filler (D12). That is, it is also preferable that the encapsulating resin composition contains the first silica filler (D11), the second silica filler (D12), and the third silica filler (D13). When the silica (D1) contains the third silica filler (D13), the average particle size of the third silica filler (D13) is not particularly limited as long as it is smaller than the average particle size of the second silica filler (D12). The standard deviation in the particle size distribution of the third silica filler (D13) is preferably 0.01 or more and less than 0.10, more preferably 0.02 or more and 0.09 or less, even more preferably 0.03 or more and 0.08 or less, and particularly preferably 0.04 or more and 0.06 or less. When the encapsulating resin composition contains the third silica filler (D13), the encapsulating resin composition can have a particularly low fluidity, and can have good thixotropy even if the fluidity of the encapsulating resin composition is low. The mass ratio of the third silica filler (D13) is preferably 5% by mass or more and 40% by mass or less with respect to the total amount of silica (D1). If the mass ratio of the third silica filler (D13) with respect to the total amount of silica (D1) is 5% by mass or more, the thixotropy can be made better, and if it is 40% by mass or less, good fluidity can be maintained.

When the silica (D1) contains a third silica filler (D13), the third silica (D13) is also preferably a wet silica. In this case, the third silica filler (D13) is also preferably a wet silica produced by a sol-gel method. In this case, it is easy to adjust each of the first silica filler (D11), the second silica filler (D12), and the third silica filler (D13) to be silica particles with a uniform particle size.

The first silica filler (D11) may be surface-treated with a coupling agent. The surface treatment of the silica filler can be performed, for example, by reacting wet silica prepared by a sol-gel method with a coupling agent (e.g., a silane coupling agent). The second silica filler (D12) and the third silica filler (D13) may also be surface-treated with a coupling agent.

The mass ratio of the first silica filler (D11) to the second silica filler (D12) in the silica (D1) is preferably within the range of 60:40 to 98:2. When the silica (D1) further contains a third silica filler (D13), the mass ratio of the first silica filler (D11), the second silica filler (D12), and the third silica filler (D13) is preferably within the range of 60:30:10 to 90:8:2.

When the inorganic filler (D) is contained, the content of the inorganic filler (D) relative to the total amount of the encapsulating resin composition is preferably 50% by mass or more and 75% by mass or less. In this case, it is possible to further reduce the CTE of the encapsulating resin composition. In this embodiment, even if the proportion of the inorganic filler (D) is relatively high, the fluidity of the encapsulating resin composition can be particularly well maintained. Therefore, it is possible to prevent the encapsulating resin composition from being left unfilled in the gaps. The content of the inorganic filler (D) is preferably 50% by mass or more and 70% by mass or less, and more preferably 55% by mass or more and 65% by mass or less.

The inorganic filler (D) may contain fillers other than silica as long as they do not impair the effects of the present disclosure.

The encapsulating resin composition may contain other suitable compounds, resins, additives, etc., in addition to those described above. Preferred components of the additives that may be contained in the encapsulating resin composition in this embodiment will be described in more detail below.

[Antifoaming agent (E)]
The encapsulating resin composition preferably further contains a defoaming agent (E). The defoaming agent (E) may have a function of suppressing foaming in the encapsulating resin composition (defoaming function) in the encapsulating resin composition. Bubbles (air bubbles) may be formed when the liquid envelops air when the components that may be contained in the encapsulating resin composition are mixed to prepare the composition. As a result, air bubbles are enclosed in the encapsulating resin composition, which may be a cause of voids in the encapsulating material. When the encapsulating resin composition contains the defoaming agent (E), the formed air bubbles can be broken, suppressed, or deaerated in preparing the encapsulating resin composition to suppress foaming of the encapsulating resin composition. Therefore, when an encapsulating material is produced from the encapsulating resin composition, voids can be further prevented from being generated in the encapsulating material.

Specific examples of antifoaming agents (E) include BYK1799 manufactured by BYK Japan Co., Ltd. However, examples of antifoaming agents (E) are not limited to the above.

[Surface conditioner (F)]
The encapsulating resin composition preferably further contains a surface conditioner (F). The surface conditioner (F) can have a function of adjusting the surface tension of the encapsulating resin composition. When the encapsulating resin composition contains the surface conditioner (F), it is easy to adjust the viscosity of the encapsulating resin composition when heated. In particular, in this embodiment, the surface conditioner (F) can further reduce the viscosity of the encapsulating resin composition when heated to 100 ° C. For this reason, the fluidity can be further improved when filling between the substrate 2 and the mounting component 3 to prepare an encapsulant from the encapsulating resin composition. In addition, the surface conditioner (F) may have a defoaming function similar to the above defoaming agent (E).

Examples of surface conditioners (F) include polyether-modified polydimethylsiloxane, acrylic copolymers, etc. Specific examples of commercially available surface conditioners (F) include BYK-306 and BYK-3441 manufactured by BYK Japan K.K.

[Curing aid (G)]
The encapsulating resin composition preferably contains a curing aid (G). In this case, it can contribute to the storage stability of the encapsulating resin composition. In addition, in this case, when the encapsulating resin composition is cured, the speed of the curing reaction can be controlled. The curing aid (G) includes a curing accelerator. The curing aid (G) has a function of promoting the progress of the reaction of the curable component in the encapsulating resin composition. In this embodiment, the curing aid (G) can suppress the curing reaction from proceeding too much when curing the epoxy resin (A) in the encapsulating resin composition. In other words, the curing aid (G) is unlikely to excessively increase the curing reactivity of the encapsulating resin composition, and can proceed with curing at a good curing rate. Therefore, even if the encapsulating resin composition begins to cure due to a temperature rise during molding of the encapsulating resin composition, it is difficult to prevent the curing from progressing rapidly, and the fluidity is unlikely to be impaired during molding. As a result, the encapsulating resin composition can be cured after being sufficiently filled between the substrate 2 and the mounting component 3.

It is preferable that the curing aid (G) contains a chelate compound (G1). In this case, the metal atom in the chelate compound (G1) can coordinate with the oxygen atom in the epoxy resin (A), so that excessive thermosetting reaction of the epoxy resin (A) in the encapsulating resin composition can be suppressed. This can further improve the storage stability of the encapsulating resin composition. In addition, in this case, excessive increase in the viscosity of the encapsulating resin composition can also be suppressed. Therefore, the fluidity of the encapsulating resin composition can be better maintained.

The chelate compound (G1) contains at least one compound selected from the group consisting of, for example, aluminum acetylacetonate, titanium acetylacetonate, titanium tetraacetylacetonate, titanium acetoacetate, zirconium ethylacetoacetate, and zirconium tetraacetylacetonate. It is preferable that the chelate compound (G1) contains aluminum acetylacetonate.

When the curing aid (G) is contained, the mass ratio of the curing aid (G) to the epoxy resin (A) is preferably 0.01% by mass or more and 2.0% by mass or less, more preferably 0.03% by mass or more and 1.5% by mass or less, and even more preferably 0.1% by mass or more and 1.0% by mass or less. If it is within this range, the curing property of the epoxy resin (A) in the encapsulating resin composition can be improved, and the gap between the substrate 2 and the mounted component 3 can be sufficiently sealed with the cured product of the encapsulating resin composition.

The content of the chelate compound (G1) relative to the curing aid (G) is preferably 20% by mass or more and 100% by mass or less, more preferably 30% by mass or more and 90% by mass or less, and even more preferably 50% by mass or more and 70% by mass or less.

[Coupling Agent (H)]
The encapsulating resin composition preferably contains a coupling agent (H). Examples of the coupling agent (H) include a silane coupling agent. When the encapsulating resin composition contains a silane coupling agent, the compatibility of the components in the encapsulating resin composition is improved, and the dispersibility of the encapsulating resin composition is easily increased. In addition, when the encapsulating resin composition contains silica (D1), the dispersibility of the encapsulating resin composition is easily increased. As the silane coupling agent, an appropriate coupling agent can be adopted, but it may be an epoxy silane coupling agent such as 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 3-glycidoxypropyltriethoxysilane.

The additives that may be included in the encapsulating resin composition are not limited to those mentioned above. Examples of additives other than those mentioned above include appropriate curing agents, fluxes, viscosity adjusters, leveling agents, stress reducing agents, and pigments.

It is preferable that the encapsulating resin composition does not contain organic solvents or contains 0.5 mass% or less of organic solvents.

The encapsulating resin composition can be obtained, for example, by blending the above components and adding appropriate additives as necessary. Specifically, the encapsulating resin composition can be prepared, for example, by the following method.

First, the components that can be included in the encapsulating resin composition described above are mixed together, either simultaneously or sequentially, to obtain a mixture. This mixture is stirred and mixed while being heated or cooled as necessary.

Next, additives are added to the mixture as necessary, and the mixture is stirred again while being heated or cooled as necessary until it is uniformly dispersed. This allows the encapsulating resin composition to be obtained. To stir the mixture, for example, a disperser, planetary mixer, ball mill, three-roll mill, and bead mill can be used in appropriate combination as necessary.

The encapsulating resin composition can be cured, for example, by heating, thereby obtaining a cured product of the encapsulating resin composition. The heating conditions, such as the heating temperature, heating time, and maximum heating temperature, can be appropriately adjusted depending on the type of epoxy resin (A) and the type of curing agent, etc.

The glass transition temperature Tg of the cured product of the encapsulating resin composition is preferably 100°C or higher. If the glass transition temperature Tg is 100°C or higher, the cured product of the encapsulating resin composition can have heat resistance. It is more preferable that the glass transition temperature Tg is 110°C or higher. The glass transition temperature can be measured, for example, by TMA (Thermomechanical Analysis).

The linear expansion coefficient (CTE) of the cured product of the encapsulating resin composition at or below the glass transition temperature Tg is preferably 15 ppm/°C or more and 50 ppm/°C or less, more preferably 40 ppm/°C or less, and even more preferably 30 ppm/°C or less. In this case, the encapsulating resin composition and the cured product of the encapsulating resin composition are less likely to warp due to heating. Therefore, the cured product of the encapsulating resin composition is less likely to crack. The linear expansion coefficient of the cured product of the encapsulating resin composition is obtained by calculating the slope of the tangent based on the dimensional change at a temperature below Tg and the dimensional change at any temperature above Tg from the Tg obtained by the measurement using TMA.

As already mentioned, the encapsulating resin composition of this embodiment can be suitably used as an underfill material. The encapsulating resin composition can be particularly suitably used as a post-supply underfill material in flip chip mounting.

<Electronic Devices>
The electronic device 1 includes a substrate 2 supporting mounted components 3 such as semiconductor elements, the mounted components 3 mounted face-down on the substrate 2, and a sealant 4 sealing a gap between the substrate 2 and the mounted components 3. The sealant 4 is made of a cured product of the liquid sealing resin composition described above.

The electronic device 1 and its manufacturing method will be described in detail.

Figure 1 shows an example of an electronic device 1 of this embodiment. The electronic device 1 shown in Figure 1 comprises a substrate 2 having conductor wiring 21, a mounting component 3 having an electrode (bump electrode 33 in Figure 1) and mounted on the substrate 2 by bonding the bump electrode 33 to the conductor wiring 21, and an encapsulant 4 covering the bump electrode 33. The encapsulant 4 is made of a cured product of the encapsulating resin composition described above.

The substrate 2 is, for example, a motherboard, a package substrate, or an interposer substrate. For example, the substrate 2 includes an insulating substrate made of glass epoxy, polyimide, polyester, ceramic, or the like, and conductive conductor wiring 21, such as copper, formed on the surface of the insulating substrate. The substrate 2 may include a plurality of conductor wirings 21. The conductor wiring 21 includes, for example, electrode pads.

The mounted component 3 is, for example, a semiconductor chip. The semiconductor chip is, for example, a flip-chip type chip such as a BGA (ball grid array), an LGA (land grid array), or a CSP (chip size package). The semiconductor chip may be a PoP (package on package) type chip.

The mounting component 3 has a plurality of bump electrodes 33. The bump electrodes 33 have solder. For example, as shown in FIG. 1, the bump electrodes 33 have a pillar 31 and a solder bump 32 provided at the tip of the pillar 31. The solder bump 32 is made of solder, and therefore the bump electrodes 33 have solder. The pillar 31 is made of copper, for example. It is preferable that the pitch between adjacent bump electrodes 33 of the plurality of electrodes (bump electrodes 33) in the mounting component 3 is 100 μm or less.

The melting point of the solder (e.g., the solder in the solder bump 32) of the bump electrode 33 is not particularly limited, but may be a temperature at which it can melt at or below the mounting temperature (e.g., 220 to 260°C) when mounting a mounting component 3 such as a semiconductor chip. The composition of the solder is not particularly limited and may be an appropriate composition, for example, Sn-Ag solder and Sn-Ag-Cu solder. The structure of the bump electrode 33 with solder is not limited to the above, and for example, the bump electrode 33 may have only a spherical solder bump 32 (solder ball). In other words, the bump electrode 33 does not need to have a pillar.

In this embodiment, the mounting component 3 has multiple electrodes (multiple bump electrodes 33 in FIG. 1). The shortest pitch between the bump electrodes 33 in the mounting component 3 is 100 μm or less. In addition, in the electronic device 1, the distance (gap) between the substrate 2 and the mounting component 3 is 25 μm or less. In other words, the electronic device 1 of this embodiment is a fine device that has been fined.

In the electronic device 1 shown in Figure 1, the sealing material 4 fills the entire gap between the substrate 2 and the mounted component 3. As a result, the sealing material 4 covers the entire bump electrode 33 and also covers the joint between the bump electrode 33 and the conductor wiring 21. In other words, this sealing material 4 is what is known as an underfill.

The manufacturing method of the electronic device 1 of this embodiment includes a mounting step, an injection step, and a sealing step. In the mounting step, the mounting components 3 are surface-mounted on the substrate 2 via a plurality of electrodes 33. In the injection step, a thermosetting sealing resin composition is injected between the substrate 2 and the mounting components 3. In the sealing step, the sealing resin composition is cured to prepare a sealing material. The shortest pitch between the plurality of electrodes 33 is 100 μm or less, and the interval between the substrate 2 and the mounting components 3 is 25 μm or less. The sealing step includes curing the sealing resin composition by heating under pressure. As a result, even if the interval between the electrodes 33 of the mounting components 3 in the electronic device 1 and the interval between the substrate 2 and the mounting components 3 are narrowed, voids are unlikely to occur in the sealing material 4. In particular, even if the shortest pitch between the electrodes 33 is 100 μm or less, and the interval between the substrate 2 and the mounting components 3 is 25 μm or less as described above, voids are unlikely to occur in the sealing material 4.

The manufacturing method of the electronic device 1 will be specifically described with reference to Figures 2A to 2E. However, the manufacturing method of the electronic device 1 is not limited to the method described below, and it is sufficient that the gap between the substrate 2 and the mounted components 3 in the electronic device 1 can be covered and sealed with the sealing resin composition described above.

First, a substrate 2 having conductor wiring 21 and a mounting component 3 having bump electrodes 33 are prepared (see FIG. 2A), and the substrate 2 is placed on a stage 72. The bump electrodes 33 of the mounting component 3 are held by a bonding head 71 so as to face the substrate 2 supported on the stage 72. In this state, the bonding head 71 is moved toward the stage 72 as shown in FIG. 2B. This places the mounting component 3 on the substrate 2. At this time, the mounting component 3 and the substrate 2 are aligned so that the bump electrodes 33 of the mounting component 3 and the conductor wiring 21 of the substrate 2 overlap (mounting process). Then, the bump electrodes 33 and the conductor wiring 21 are electrically connected. In the mounting process, pressure may not be applied, that is, the mounting component 3 may be mounted on the substrate 2 under normal pressure.

Next, the substrate 2 and the mounted components 3 are aligned as described above, and the substrate 2 with the mounted components 3 placed thereon is placed in a heating device. The heating device is preferably a heating furnace capable of applying pressure by air pressure, for example. Specifically, the heating furnace may be a pressurized oven (pressure oven), a pressurized reflow oven, or the like.

Next, the gap between the substrate 2 and the mounting component 3 is filled with an encapsulating resin composition (hereinafter, in FIG. 2C to FIG. 2E, the material containing the encapsulating resin composition is described as "encapsulating material 40") (see FIG. 2C) (injection process). The encapsulating material 40 is preferably filled in a state heated to 100°C. In this case, it is easy to fill the gap between the substrate 2 and the mounting component 3 by making it flow better. The encapsulating material 40 may be filled at room temperature (e.g., 25°C). Any appropriate method may be adopted for filling, and examples of the filling method include a method using a dispenser, a screen printing method, an inkjet method, and a dipping method. The encapsulating resin composition may be injected into the gap between the substrate 2 and the mounting component 3 under reduced pressure. In this embodiment, the encapsulating resin composition has high bubble breaking properties, so that even if the pressure is reduced when injecting the encapsulating resin composition, the encapsulating resin composition is unlikely to adhere to the details of the mounting component 3, thereby contaminating the mounting component 3.

Next, the heating furnace is heated while increasing the pressure in the heating furnace, thereby subjecting the sealing material 40 and the bump electrodes 33 to a heat treatment (sealing process). Therefore, even if air bubbles remain in the prepared sealing material 40, the pressure in the furnace increases when the sealing material 40 is heated and gradually hardened, so that the air bubbles can be made smaller and the air bubbles can be degassed from the sealing material 40. In addition, moisture that may be generated from the substrate 2 can be dissolved in the sealing resin composition, so that voids due to moisture can be made less likely to occur. Therefore, by heating while applying pressure, the voids in the sealing material 4 can be reduced. Furthermore, compared to when the sealing resin composition is decompressed, the sealing resin composition is less likely to foam, so that the mounting component 3 such as a semiconductor element is less likely to be contaminated. In addition, since the sealing material 40 can be filled while having a moderate fluidity, the fillet shape of the sealing material 4 (the shape of the sealing material 40 that protrudes from the outer periphery of the mounting component 3) can be stabilized.

The heating and pressurizing conditions in the heating furnace are set appropriately, but for example, it is preferable to heat the material to a temperature of 100°C or more and 200°C or less at a temperature rise rate of 3 to 5°C/min. The pressure in the heating furnace can be 0.1 MPa or more and 0.8 MPa or less. The time for the heat treatment can be, for example, 30 minutes or more and 5 hours or less.

This hardens the sealing material 40 to produce the sealing material 4 (see FIG. 2D). After the heat treatment, the pressure in the heating furnace is released and the temperature in the heating furnace is lowered. The temperature in the heating furnace can be lowered by either leaving it to cool or by cooling.

As a result, the electronic device 1 is obtained (see FIG. 2E). If necessary, the encapsulating material 40 may be post-cured by further heating after the pressure is released. In this embodiment, the encapsulating material 4 in the electronic device 1 is heated (after-cured) to further harden it. This can further increase the connection strength between the substrate 2 and the mounted components 3 in the electronic device 1. The conditions for the heat treatment in the after-cure may be set appropriately depending on the composition of the encapsulating resin composition and/or the electronic device manufacturing process. In the heat treatment, the maximum heating temperature is preferably, for example, 150° C. or higher and 200° C. or lower. In the above, an example of the heat treatment is described, but is not limited to the above, and for example, the maximum heating temperature may also be set appropriately depending on the composition of the encapsulating resin composition.

As described above, the electronic device 1 shown in FIG. 1 is obtained by mounting the mounting component 3 on the substrate 2. In the manufacturing method of the electronic device 1 of this embodiment, as described above, the sealing material 4 includes heat-curing the sealing resin composition by applying pressure to the sealing resin composition (sealing material 40) while heating the sealing material 4. Therefore, even if the gap between the electrodes 33 of the mounting component 3 in the electronic device 1 and the gap between the substrate 2 and the mounting component 3 are narrowed and the sealing resin composition is injected between the substrate 2 and the mounting component 3 and cured, it is possible to make it difficult for voids to occur in the sealing material 4. In the electronic device 1 manufactured in this manner, the connection is reinforced by filling the gap between the substrate 2 and the mounting component 3 with the sealing material 4, and the conduction between the substrate 2 and the mounting component 3 is also ensured. In addition, according to this embodiment, pressure and heat can be applied in the heating device, so that the electronic device 1 can be moved from the heating device to another device after mounting to remove moisture and the like in the electronic device 1 (baking), and the like, and the like, can be omitted. Therefore, the tact (manufacturing efficiency) during manufacturing can be improved.

The order of steps in the manufacturing method of the electronic device 1 does not have to be as described above. For example, the mounting component 3 may be placed on the substrate 2, the bump electrode 33 may be placed on the conductor wiring 21, and then the encapsulating resin composition may be placed to cover the bump electrode 33. Conversely, the encapsulating resin composition may be placed to cover the bump electrode 33, and then the mounting component 3 may be placed on the substrate 2, and the bump electrode 33 may be placed on the conductor wiring 21. In addition, as long as the encapsulating resin composition can be placed to cover the bump electrode 33 during each step of the manufacturing process, the encapsulating resin composition may be placed at any time and in any position on the mounting component 3 and the substrate 2.

Specific examples of the present disclosure are presented below. However, the present disclosure is not limited to the examples.

1. Preparation of resin composition [Examples 1 to 7 and Comparative Examples 1 to 3]
The components shown in Table 1 below were charged into a mixer in the mixing ratios (parts by mass) shown in Table 1, stirred and mixed, and uniformly dispersed using a three-roll mill to obtain a resin composition. Details of the components shown in Table 1 are as follows.
(Epoxy resin)
Bisphenol type epoxy resin: bisphenol F type epoxy resin (manufactured by Tohto Kasei Co., Ltd., product name YDF8170. Epoxy equivalent 175 eq./g).
Aromatic amino epoxy resin: jRR Corporation product name 636.
(Mixture of phosphoric acid and polyester phosphate)
Mixture of phosphoric acid and phosphate polyester: BYK Japan Co., Ltd., product name BYK-W 9010 (composition: phosphate polyester content 90% by weight or more and less than 100% by weight, phosphoric acid content 1% by weight or more and less than 10% by weight).
(Additives)
Hardener: Amine hardener (manufactured by Nippon Kayaku Co., Ltd., product name Kayabard A-A, amine equivalent 65 eq./g).
Surface conditioner 1: Polyether modified polydimethylsiloxane (manufactured by BYK Japan Co., Ltd., product name BYK-306).
Surface conditioner 2: Acrylic copolymer (BYK Japan Co., Ltd., product name BYK-3441).
Defoamer: BYK Japan Co., Ltd., product name BYK1799 (a mixture of hydrophobic particles and polysiloxane).
Coupling agent: epoxy silane (silane coupling agent. Product name KBM403, manufactured by Shin-Etsu Chemical Co., Ltd.).
Curing aid 1: Imidazole-based curing catalyst (manufactured by Shikoku Kasei Co., Ltd., product name 2E4MZ. Imidazole-based compound).
Curing aid 2: Metal chelate curing aid (manufactured by Kawaken Fine Chemicals Co., Ltd., product name Aluminum Chelate A (W). Aluminum trisacetylacetonate).
Colorant: Carbon black (product name MA100, manufactured by Mitsubishi Chemical Corporation).
Phosphorus derivatives: triphenylphosphine.
(Inorganic filler)
Silica 1: Silica prepared by a sol-gel method and surface-treated with a silane coupling agent having a phenyl group (average particle size 1.0 μm. Standard deviation in particle size distribution is 0.04 to 0.5).
Silica 2: Silica prepared by a sol-gel method and surface-treated with a silane coupling agent having a phenyl group (average particle size: 0.3 μm. Standard deviation in particle size distribution: 0.04 to 0.5).
Silica 3: Silica prepared by a sol-gel method and surface-treated with a silane coupling agent having a phenyl group (average particle size: 0.1 μm. Standard deviation in particle size distribution: 0.04 to 0.5).
Silica 4: Silica produced by the sol-gel method and not surface-treated (average particle size: 1.0 μm, standard deviation in particle size distribution: 0.04 to 0.5).
Silica 5: Silica produced by the sol-gel method and not surface-treated (average particle size: 0.3 μm, standard deviation in particle size distribution: 0.04 to 0.5).
Silica 6: Silica produced by the sol-gel method and not surface-treated (average particle size: 0.1 μm, standard deviation in particle size distribution: 0.04 to 0.5).

2. Evaluation 2.1. Viscosity (at 25°C)
The viscosity of the resin composition prepared in 1 above was measured using a BM type viscometer (Model No. TVB-10, manufactured by Toki Sangyo Co., Ltd.) at a temperature of 25°C, rotor No. 6, and a rotation speed of 20 rpm. Based on the obtained measurement results, the viscosity was evaluated according to the following criteria.
A: Viscosity is less than 15 Pa·s.
B: Viscosity is 15 Pa·s or more and 50 Pa·s or less.
C: Viscosity exceeds 50 Pa· s .

2.2. Hot viscosity (viscosity at 100°C)
The viscosity of the resin composition prepared in 1 above was measured using a rheometer (Anton Paar, model MCR-10) at a temperature of 100° C. and a rotation speed of 1 rpm. Based on the measurement results obtained, the viscosity was evaluated according to the following criteria.
A: Viscosity is less than 0.10 Pa·s.
B: Viscosity is 0.10 Pa·s or more and 0.15 Pa·s or less.
C: Viscosity exceeds 0.15 Pa· s .

In addition, when the resin composition prepared in 1. above was heated from 25°C at a heating rate of 30°C/min, the viscosity at the time of reaching the curing temperature was 0.15 Pa·s or less in all of Examples 1 to 7, whereas it was more than 0.15 Pa·s in Comparative Examples 1 to 3. The curing temperature was obtained by applying the encapsulating resin composition to the stage of the rheometer, heating the stage to 80°C to 150°C, and then measuring the viscosity of the encapsulating resin composition after heating at 100°C for 2 hours at a rotation speed of 1 rpm using a rheometer. In addition, the viscosity of the encapsulating resin composition at the time of reaching the curing temperature was obtained by using a rheometer to leave the encapsulating resin composition on a stage that had been heated to a temperature in the range of 80°C to 150°C in advance, heating at 150°C for 2 hours, and then measuring the viscosity at a rotation speed of 1 rpm.

2.3. Foam Breaking Property 10 g of the encapsulating resin composition was weighed and placed in a suitable container having a height of 55 mm or more, sealed, and degassed by reducing the pressure at 200 Pa/10 min at a temperature of 25° C. After 10 minutes, the encapsulating resin composition was blown out from the liquid surface due to the reduced pressure and attached to the wall of the container, and the height of the attached matter from the wall of the container was measured. The measurement results (mm) are shown in Table 1.

In Examples 1 to 7, the foaming depth was 45 mm or less, and in Examples 1 to 6, the foaming depth was 40 mm or less. In particular, in Examples 3 to 6, the foaming depth was 30 mm or less, and the degree of foaming was very low. In contrast, in Comparative Examples 1 to 3, foaming occurred with such force that it exceeded the upper limit of the container height of 55 mm, and adhered to the upper surface of the container. As a result, it was suggested that Examples 1 to 7 had high foam breaking properties, had few voids in the resin composition, and were unlikely to produce voids in the encapsulant when cured, whereas Comparative Examples 1 to 3 had low foam breaking properties, had voids remaining in the resin composition, and were likely to leave voids in the encapsulant when cured.

In each of the examples and comparative examples, the bubble breaking properties were confirmed at room temperature (25°C). However, even at temperatures of 100°C or higher, the viscosity of the encapsulating resin composition in Examples 1 to 7 is lower and the surface tension is higher than at 25°C, and therefore it is presumed that the composition has excellent bubble breaking properties similar to those at 25°C.

2.4. Fluidity Two flat glass plates were placed on a heatable stage with a gap of 25 μm between them, and the temperature of the stage was set to 100° C. to heat the two glass plates. After the temperature of the glass plates reached 100° C., the resin composition prepared in 1. above was injected into the 25 μm gap and allowed to flow through the gap by utilizing capillary action. The time it took for the resin composition to travel a distance of 30 mm from the start of injection was measured. Based on the results obtained by the measurement, the evaluation was performed according to the following criteria.
A: The time required to advance 30 mm is less than 400 seconds.
B: The time required to advance 30 mm is 400 seconds or more and less than 500 seconds.
C: The time required to advance 30 mm is 500 seconds or more.

2.5 Voids Using the resin composition prepared in 1 above, an electronic device was produced as follows.

A Walts TEG FC200JY (10mm x 10mm x 300μm) manufactured by WALTS was prepared as the semiconductor chip (FC-BGA: Flip Chip Ball Grid Array).

As a substrate, we prepared an R-G535E manufactured by Panasonic Corporation that had been processed (52.5 mm x 52.5 mm x 1.2 μm) so that the above chip could be mounted.

The substrate was placed on the stage of a pressure oven, and the semiconductor chip was flip-chip mounted and aligned.

Next, the resin composition prepared in 1. above was heated to 100°C and filled into the gap between the substrate and the semiconductor chip. Then, in a heating device having a heating furnace, the resin composition was placed in the gap between the substrate and the semiconductor chip and heated at a heating temperature of 100°C for 2 hours while repeatedly pressurizing and depressurizing at a maximum pressure of 0.7 MPa, thereby curing the resin composition.

After continuing or releasing the pressure, the resin composition between the substrate and the semiconductor chip was heated at 150°C for 2 hours to completely harden. This resulted in an electronic device for testing. The voids in the encapsulant of this electronic device were examined using an ultrasonic flaw detector (SAT). As a result, cases where no voids were found were rated as "A", cases where 10 or fewer micro voids of 200 μm or less were found were rated as "B", and cases where more than 10 voids were found were rated as "C".

1 Electronic device 2 Substrate 3 Mounting component 4 Encapsulating material

Claims (7)

a mounting process of surface-mounting a mounting component on a substrate via a plurality of electrodes;
an injection step of injecting a thermosetting encapsulating resin composition that is liquid at room temperature between the base material and the mounting component;
and an encapsulation step of curing the encapsulating resin composition to produce an encapsulant,
the shortest pitch between the plurality of electrodes is 100 μm or less, and the distance between the substrate and the mounting component is 25 μm or less;
The method for producing an electronic device, wherein in the encapsulating step, the encapsulating resin composition is cured by heating in a heating furnace while repeatedly increasing and decreasing the pressure in the heating furnace . The encapsulating resin composition has a viscosity of 0.15 Pa·s or less at 100°C.
The method for manufacturing an electronic device according to claim 1 . The encapsulating resin composition has a characteristic that, when heated under any one of temperature rising conditions of a temperature rising rate of 0.5°C/min to 50°C/min from 25°C, the viscosity at the time when the curing temperature is reached is 0.15 Pa s or less.
The method for producing an electronic device according to claim 1 or 2. The encapsulating resin composition contains an epoxy resin (A), a phosphoric acid (B), and a phosphoric acid polyester (C).
The method for manufacturing an electronic device according to claim 1 . The encapsulating resin composition contains at least one of an antifoaming agent (E) and a surface conditioner (F).
The method for manufacturing an electronic device according to claim 1 . When the encapsulating resin composition is poured into a container having a bottom area of 450 ^mm2 and a height of 55 mm so that the liquid level is 20 mm from the bottom of the container, when the inside of the container is reduced in pressure at 200 Pa/10 min at a temperature of 25°C, the encapsulating resin composition is sprayed onto the wall surface of the container to a height of 40 mm or less from the bottom of the container.
The method for manufacturing an electronic device according to claim 1 . 7. An electronic device manufactured by the method for manufacturing an electronic device according to claim 1 .
Electronic devices.

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