JP2024050508A - Epoxy resin composition, electronic device, and method for producing electronic device - Google Patents

Abstract

To provide an epoxy resin composition capable of both reinforcing an electronic component and providing an electrical connection between an electronic component and a substrate and enhancing the heat resistance and heat cycle resistance of a side-fill section even when a side-fill section is prepared in parallel with reflow soldering.SOLUTION: There is provided an epoxy resin composition which comprises an epoxy compound (A), an amine-based curing agent (B) and an inorganic filler (C). A cured material of the epoxy resin composition has a glass transition temperature of 125°C or more and a linear expansion coefficient of 35 ppm/°C or lower, as measured by thermomechanical analysis. When the epoxy resin composition is heated from a state at 25°C and the temperature is increased at a rate of 5°C/min, the temperature at which the viscosity of the epoxy resin composition reaches 200 Pa s while the viscosity is increased is 150°C or more.SELECTED DRAWING: Figure 5

Description

The present disclosure generally relates to an epoxy resin composition, an electronic device, and a method for manufacturing an electronic device, and more particularly to an epoxy resin composition, an electronic device having a side fill part made from the epoxy resin composition, and a method for manufacturing an electronic device having a side fill part made from the epoxy resin composition.

Patent Document 1 discloses a composition that includes an epoxy resin, an imidazole compound, a thixotropic agent, and an activator, and the epoxy resin contains at least one selected from the group consisting of naphthalene-type epoxy resins, biphenyl aralkyl-type epoxy resins, trisphenolmethane-type epoxy resins, biphenyl-type epoxy resins, and dicyclopentadiene-type epoxy resins in an amount of 20 wt % or more relative to the total epoxy resin.

Patent Document 2 discloses that the adhesive composition contains (A) an epoxy resin, (B) an aromatic amine with two amino groups in one molecule, (C) a filler, and (D) an acrylate compound, and that, relative to 100% by mass of the adhesive composition, the amount of component (A) is 25% by mass to 80% by mass, the amount of component (B) is 5% by mass to 50% by mass, the amount of component (C) is 5% by mass to 50% by mass, and the amount of component (D) is 1% by mass to 15% by mass.

International Publication No. 2021/187117 Patent No. 6013406

The objective of the present disclosure is to provide an epoxy resin composition that, when used to create a side fill portion for reinforcing an electronic component flip-chip mounted on a substrate, can achieve both the reinforcement of the electronic component by the side fill portion and the electrical connection between the electronic component and the substrate, even when the side fill portion is created in parallel with reflow soldering, and can also improve the heat resistance and heat cycle resistance of the side fill portion; an electronic device that includes a side fill portion made from this epoxy resin composition; and a method for manufacturing an electronic device that includes a side fill portion made from the epoxy resin composition.

The epoxy resin composition according to one embodiment of the present disclosure contains an epoxy compound (A), an amine-based curing agent (B), and an inorganic filler (C). The cured product of the epoxy resin composition has a glass transition temperature of 125°C or higher and a linear expansion coefficient of 35 ppm/°C or lower, as measured by thermomechanical analysis. When the epoxy resin composition is heated from a state of 25°C at a temperature increase rate of 5°C/min, the temperature at which the viscosity of the epoxy resin composition increases and reaches 200 Pa·s is 150°C or higher.

An electronic device according to one aspect of the present disclosure includes a substrate, an electronic component flip-chip mounted on the substrate, and a side fill portion disposed on the periphery of the gap between the substrate and the electronic component. The side fill portion includes a cured product of the epoxy resin composition.

A method for manufacturing an electronic device according to one embodiment of the present disclosure is a method for manufacturing an electronic device including a substrate having a first surface and a second surface opposite to the first surface, a first electronic component flip-chip mounted on the first surface of the substrate, a second electronic component flip-chip mounted on the second surface of the substrate, and a side fill portion located on the periphery of a gap between the first surface and the first electronic component. In this manufacturing method, the first surface of the substrate and the first electronic component face each other, and the epoxy resin composition is disposed on the periphery of a gap between the first surface and the first electronic component. In this state, the first electronic component is reflow soldered onto the first surface of the substrate while the epoxy resin composition is cured to produce the side fill portion. Then, the second electronic component is reflow soldered onto the second surface of the substrate.

According to one aspect of the present disclosure, when used to create a side fill portion for reinforcing an electronic component flip-chip mounted on a substrate, even if the side fill portion is created in parallel with reflow soldering, it is possible to achieve both the reinforcement of the electronic component by the side fill portion and the electrical connection between the electronic component and the substrate, and to improve the heat resistance and heat cycle resistance of the side fill portion.

FIG. 1 is a cross-sectional view of a substrate in an embodiment of the present disclosure. FIG. 2 is a cross-sectional view of a substrate on which the solder paste and the uncured body are provided in the embodiment. FIG. 3 is a cross-sectional view of the electronic device or an intermediate product used in manufacturing the electronic device in the above embodiment. FIG. 4 is a cross-sectional view of an intermediate product provided with solder paste in the above embodiment. FIG. 5 is a cross-sectional view of an electronic device manufactured from an intermediate product in the above embodiment. FIG. 6 is a graph showing a model of a reflow profile and a change in viscosity of an epoxy resin composition over time in reflow soldering in the above embodiment.

When manufacturing electronic devices by flip-chip mounting electronic components on a substrate, the electronic components may be reinforced with a side fill portion made by curing a resin composition.

When manufacturing electronic devices, the electronic devices can be manufactured efficiently by curing the resin composition to create the side fill portion in parallel with reflow soldering of the substrate to the electronic components for flip chip mounting.

According to the results of the inventor's investigation, when the side fill portion is produced in parallel with reflow soldering, it is not easy to enhance the heat resistance and heat cycle resistance of the side fill portion while simultaneously reinforcing the electronic component with the side fill portion and electrically connecting the electronic component to the board. For example, with the techniques disclosed in Patent Documents 1 and 2, even if the side fill portion is produced from a composition, it is difficult to enhance the heat resistance and heat cycle resistance of the side fill portion.

Therefore, the present disclosure provides an epoxy resin composition that can enhance the heat resistance and heat cycle resistance of the side fill portion 2 while simultaneously reinforcing the electronic component 4 with the side fill portion 2 and electrically connecting the electronic component 4 to the substrate 1.

Embodiments of the present disclosure will be described below with reference to Figures 1 to 6. Note that the present disclosure is not limited to the following embodiments. The following embodiments are merely a part of the various embodiments of the present disclosure, and various modifications are possible depending on the design as long as the object of the present disclosure can be achieved. The mechanism of action of the embodiments may be described below, but this mechanism is presumed, and therefore the present disclosure should not be interpreted as being limited by the description of the mechanism.

All figures referenced in the following description are schematic diagrams, and the dimensional ratios of the components in the figures do not necessarily reflect the actual dimensional ratios.

The epoxy resin composition according to this embodiment contains an epoxy compound (A), an amine-based curing agent (B), and an inorganic filler (C). The cured product of the epoxy resin composition has a glass transition temperature of 125°C or higher and a linear expansion coefficient of 35 ppm/°C or lower, as measured by thermomechanical analysis. When the epoxy resin composition is heated from 25°C at a temperature increase rate of 5°C/min, the temperature at which the viscosity of the epoxy resin composition increases to 200 Pa·s is 150°C or higher.

Because the epoxy resin composition has the above-mentioned viscosity characteristics, when flip-chip mounting the electronic component 4 on the substrate 1, even if the side fill portion 22 is prepared in parallel with reflow soldering, the epoxy resin composition is unlikely to hinder the electrical connection between the substrate 1 and the electronic component 4 by soldering. Therefore, the side fill portion 2 can reinforce the electronic component 4 and electrically connect the electronic component 4 to the substrate 1 at the same time. Furthermore, the glass transition temperature of the cured product is 125°C or higher and the linear expansion coefficient is 35 ppm/°C or lower, so that the heat resistance and heat cycle resistance of the side fill portion 2 prepared from the epoxy resin composition are improved. Therefore, even if the side fill portion 2 is subjected to a thermal load or further repeatedly subjected to a thermal load, the occurrence of deformation and breakage of the side fill portion 2 is suppressed. As a result, excessive stress is unlikely to occur at the contact point between the substrate 1 and the electronic component 4 formed by soldering. Therefore, the electrical connection between the electronic component 4 and the substrate 1 can be maintained when subjected to a thermal load.

The details of the method for measuring the glass transition temperature, the linear expansion coefficient, and the viscosity are described in the Examples section below. The time when the viscosity of the epoxy resin composition increases and reaches 200 Pa·s is, in other words, the time when a point with a positive differential value and a viscosity of 200 Pa·s appears on the viscosity curve of the epoxy resin composition drawn on a coordinate plane with the vertical axis representing viscosity and the horizontal axis representing temperature. That is, the time when the viscosity of the epoxy resin composition increases and reaches 200 Pa·s is the time when the viscosity of the epoxy resin composition decreases to less than 200 Pa·s and then increases to reach 200 Pa·s when the viscosity of the epoxy resin composition at 25°C is 200 Pa·s or more, and is the time when the viscosity of the epoxy resin composition increases and reaches 200 Pa·s for the first time when the viscosity of the epoxy resin composition at 25°C is less than 200 Pa·s. Hereinafter, the temperature of the epoxy resin composition when the viscosity of the epoxy resin composition increases and reaches 200 Pa·s is also referred to as the curing start temperature.

The epoxy compound (A) is a compound having an epoxy group, and may be a monomer, an oligomer, or a prepolymer. The epoxy compound (A) is preferably liquid. When the epoxy compound (A) contains multiple components, even if some of the components in the epoxy compound (A) are solid, it is preferable that the epoxy compound (A) as a whole is liquid by dissolving the solid components in another component.

The epoxy compound (A) preferably contains an epoxy compound (A1) consisting of at least one of aminoglycidyl ether and naphthalene type epoxy resin. The aminoglycidyl ether preferably contains an aminoglycidyl ether having three or more functionalities (i.e., having three or more epoxy groups in one molecule). In this case, the glass transition temperature of the cured product of the epoxy resin composition is increased, and the glass transition temperature can be 125°C or higher. Therefore, the heat resistance of the electronic device can be improved. The total ratio of the aminoglycidyl ether and the naphthalene type epoxy resin is preferably 50% by mass or more relative to the epoxy resin composition. In addition, the ratio of the epoxy compound (A1) is preferably 18% by mass or more relative to the epoxy compound (A). In this case, the glass transition temperature of the cured product can be further increased. This ratio is more preferably 30% by mass or more, and even more preferably 50% by mass or more. The epoxy compound (A) may contain only the epoxy compound (A1), but the ratio of the epoxy compound (A1) may be 85% by mass or less, or 75% by mass or less relative to the epoxy compound (A).

Trifunctional aminoglycidyl ethers contain, for example, compounds shown in the following formula:

Naphthalene-type epoxy resins contain, for example, the compound shown in the following formula. In the following formula, G is a glycidyl group.

The epoxy compound (A) may contain a compound other than the epoxy compound (A1) (hereinafter also referred to as the epoxy compound (A2)) as long as the glass transition temperature of the cured product can be 125°C or higher. For example, the epoxy compound (A2) may contain at least one selected from the group consisting of biphenyl aralkyl type epoxy resins; trisphenolmethane type epoxy resins; biphenyl type epoxy resins; dicyclopentadiene type epoxy resins; glycidyl ether type epoxy resins; glycidyl ester type epoxy resins; olefin oxide type (alicyclic) epoxy resins; bisphenol type epoxy resins such as bisphenol A type epoxy resins and bisphenol F type epoxy resins; hydrogenated bisphenol type epoxy resins such as hydrogenated bisphenol A type epoxy resins and hydrogenated bisphenol F type epoxy resins; alicyclic epoxy resins; phenol novolac type epoxy resins; cresol novolac type epoxy resins; aliphatic epoxy resins, and triglycidyl isocyanurate.

When the epoxy compound (A) contains the epoxy compound (A2), it is preferable that the epoxy compound (A) contains at least one selected from the group consisting of bisphenol A type epoxy resins, bisphenol F type epoxy resins, hydrogenated bisphenol A type epoxy resins, and hydrogenated bisphenol F type epoxy resins. In this case, it is easy to reduce the viscosity of the composition (X) and to improve the physical properties of the cured product of the composition (X).

When the epoxy compound (A) contains the epoxy compound (A2), the ratio of the epoxy compound (A2) to the epoxy compound (A) is preferably 25% by mass or more and 75% by mass or less. This ratio is more preferably 35% by mass or more, and even more preferably 40% by mass or more. This ratio is more preferably 60% by mass or less, and even more preferably 50% by mass or less.

The proportion of the epoxy compound (A) is preferably 20% by mass or more and 45% by mass or less relative to the epoxy resin composition. This proportion is more preferably 25% by mass or more, and even more preferably 30% by mass or more. This proportion is more preferably 43% by mass or less, and even more preferably 40% by mass or less.

The amine-based curing agent (B) can cause the curing of the epoxy resin composition to proceed moderately slowly when the epoxy resin composition is heated. This allows the curing initiation temperature to be 150°C or higher. In addition, the amine-based curing agent (B) can increase the glass transition temperature of the cured product, which allows the glass transition temperature to be 125°C or higher.

It is preferable that the amine-based curing agent (B) contains at least one of a carboxylic acid hydrazide and an imidazole compound. In this case, the curing reaction of the epoxy resin composition does not proceed easily at 25°C, and therefore the storage stability of the epoxy resin composition can be improved.

When the amine-based curing agent (B) contains an imidazole compound, the viscosity of the epoxy resin composition is particularly likely to be low.

The melting point of the imidazole compound is preferably 110°C or higher. In this case, the reliability of the electrical connection between the electronic component 4 and the board 1 can be further improved. This is presumably because the reactivity of the composition (X) when the composition (X) is heated is appropriately suppressed, thereby suppressing the increase in viscosity of the composition (X) during reflow soldering, and therefore the composition (X) is less likely to hinder reflow soldering. It is more preferable that the melting point of the imidazole compound is 150°C or higher. It is also preferable that the melting point of the imidazole compound is 250°C or lower. In this case, the curing of the composition (X) is less likely to be suppressed excessively, and therefore the insufficient curing of the side fill portion 2 can be suppressed, and the physical properties such as the glass transition temperature of the side fill portion 2 can be sufficiently improved, thereby ensuring the reinforcing effect of the electronic component 4.

The imidazole compound contains, for example, at least one of 2-phenyl-4-methyl-5-hydroxymethylimidazole and 2-phenyl-4,5-dihydroxymethyl-imidazole shown in the following formula.

When the amine-based curing agent (B) contains an imidazole compound, the ratio of the imidazole compound is preferably 3.5% by mass or more and 5.5% by mass or less relative to the epoxy compound (A). If this ratio is 3.5% by mass or more, the reaction of the epoxy resin composition when heated is less likely to be excessively suppressed. If this ratio is 5.5% by mass or more, the curing reaction of the epoxy resin composition proceeds sufficiently, and the heat cycle resistance can be improved. It is more preferable that this ratio is 4% by mass or more, and even more preferable that it is 5% by mass or more. It is more preferable that this ratio is 7% by mass or less, and even more preferable that it is 6% by mass or less.

When the amine-based curing agent (B) contains a carboxylic acid hydrazide, the glass transition temperature of the cured product can be improved and the linear expansion coefficient can be reduced. In addition, when the above-mentioned imidazole compounds having a hydroxymethyl group, such as 2-phenyl-4-hydroxymethyl-5-methylimidazole and 2-phenyl-4,5-dihydroxymethyl-imidazole, are heated, they generate formaldehyde, which can cause bubbles to form in the cured product. However, when the amine-based curing agent (B) contains a carboxylic acid hydrazide, bubbles are less likely to form. The carboxylic acid hydrazide contains, for example, isophthalic acid hydrazide shown in the following formula.

When the amine-based curing agent (B) contains a carboxylic acid hydrazide, the ratio of the carboxylic acid hydrazide to the epoxy compound (A) is preferably 10% by mass or more and 30% by mass or less. If this ratio is 10% by mass or more, the improvement of the glass transition temperature and the reduction of the linear expansion coefficient of the cured product can be further promoted. If this ratio is 30% by mass or less, the storage stability of the epoxy resin composition can be further improved. This ratio is more preferably 15% by mass or more, and even more preferably 20% by mass or more. This ratio is more preferably 29% by mass or less, and even more preferably 27% by mass or less.

The proportion of the amine-based curing agent (B) is preferably 3% by mass or more and 30% by mass or less relative to the epoxy resin composition.

The inorganic filler (C) can reduce the linear expansion coefficient of the cured product.

The proportion of the inorganic filler (C) is preferably 45% by mass or more and 85% by mass or less based on the total of the epoxy compound (A), the amine-based curing agent (B), and the inorganic filler (C). In this case, it is possible to achieve a linear expansion coefficient of 35 ppm/°C or less, or 30 ppm/°C or less, of the cured product. This proportion is more preferably 50% by mass or more, and even more preferably 60% by mass or more. This proportion is more preferably 80% by mass or less, and even more preferably 75% by mass or less.

The epoxy resin composition may further contain a coupling agent. The proportion of the coupling agent is preferably 0.1% by mass or more and 2% by mass or less based on the epoxy resin composition. The epoxy resin composition may contain a pigment such as carbon black. The proportion of the pigment is preferably 0.1% by mass or more and 0.3% by mass or less based on the epoxy resin composition.

It is preferable that the epoxy resin composition has fluidity at 25°C.

The epoxy resin composition can be used as a material for producing the side fill portion 2 in an electronic device, i.e., as a side fill material.

An electronic device having a side fill portion 2 made from an epoxy resin composition includes, for example, a substrate 1, an electronic component 4 flip-chip mounted on the substrate 1, and a side fill portion 2 disposed on the periphery of the gap between the substrate 1 and the electronic component 4 (see Figures 3 and 5). This side fill portion 2 includes a cured product of the epoxy resin composition.

An overview of an electronic device equipped with a side fill section 2 is given below.

An electronic device having a side fill portion 2 made from an epoxy resin composition includes, for example, a substrate 1, an electronic component 4 flip-chip mounted on the substrate 1, and a side fill portion 2 disposed on the periphery of the gap between the substrate 1 and the electronic component 4, and the side fill portion 2 includes a cured product of the epoxy resin composition.

The substrate 1 is, for example, a printed wiring board, but is not limited to this. The electronic component 4 is, for example, a bare chip, but is not limited to this.

The electronic device may include a substrate 1 having a first surface 14 and a second surface 15 opposite the first surface 14, an electronic component 4 (also called the first electronic component 4) flip-chip mounted on the first surface 14 of the substrate 1, an electronic component 5 (also called the second electronic component 5) flip-chip mounted on the second surface 15 of the substrate 1, and a side fill portion 2 located on the periphery of the gap between the first surface 14 and the first electronic component 4 (see FIG. 5).

When manufacturing an electronic device, the first electronic component 4 is placed opposite the first surface 14 of the substrate 1 and an epoxy resin composition is disposed on the peripheral portion of the gap between the first surface 14 and the first electronic component 4. In this state, the first electronic component 4 is reflow soldered onto the first surface 14 of the substrate 1, and the epoxy resin composition is cured in parallel to this to create the side fill portion 2. Then, the second electronic component 4 is reflow soldered onto the second surface 15 of the substrate 1.

Reflow soldering is performed by, for example, placing solder paste 31 between the solder bumps 44 of the electronic component 4 and the conductors (conductor wiring) of the substrate 1, and then heating the solder bumps 44 and the solder paste 31 in a reflow process. The solder in each of the solder bumps 44 and the solder paste 31 is a lead-free solder, such as a SAC (Sn-Ag-Cu) solder with a melting point of about 220°C.

In this embodiment, the epoxy resin composition can be heated and cured in parallel with the soldering by the reflow process to produce the side fill portion 2. When manufacturing an electronic device including the substrate 1, the first electronic component 4, the second electronic component 4, and the side fill portion 2 as described above, the epoxy resin composition can be heated and cured when the first electronic component 4 is reflow soldered to produce the side fill portion 2, and then the side fill portion 2 can be further heated when the second electronic component 4 is reflow soldered to further promote curing. Therefore, even when the curing of the epoxy resin composition is allowed to proceed moderately slowly, the epoxy resin composition can be sufficiently cured, and therefore the electronic component 4 (first electronic component 4) can be sufficiently reinforced by the side fill portion 2.

After the second electronic component 4 is reflow soldered, it is preferable that the reaction rate of the side fill portion 2 is 85% or more.

Figure 6 shows a model of the change in heating temperature over time (reflow profile) and the change in viscosity (resin viscosity) of the epoxy resin composition over time in reflow soldering. First, the temperature is raised to a temperature (for example, 150 to 180°C) below the melting point of the solder (shown as "Mp" in Figure 6) and maintained at this temperature for 60 to 120 seconds to perform preheating. Next, the temperature is raised to a temperature (for example, 220 to 260°C) above the melting point of the solder to melt the solder. Next, the temperature is lowered to solidify the solder. In this embodiment, the viscosity of the epoxy resin composition is preferably sufficiently reduced during preheating, and even if the temperature exceeds the melting point of the solder in this state, the viscosity of the epoxy resin composition is maintained low for a while. Therefore, the epoxy resin composition is less likely to hinder reflow soldering, and the self-alignment effect can be well exerted. Therefore, the reliability of the electrical connection between the board 1 and the electronic component 4 (first electronic component 4) is increased. Next, the reaction of the epoxy resin composition proceeds rapidly, and the viscosity of the epoxy resin composition increases. This produces the side fill portion 2. In this embodiment, as described above, the epoxy resin composition is heated and cured when the first electronic component 4 is reflow soldered to produce the side fill portion 2, and then the side fill portion 2 is further heated when the second electronic component 4 is reflow soldered to produce the side fill portion 2. This allows the side fill portion 2 to be sufficiently cured.

The above is merely a model, and the actual reflow profile and resin viscosity may not necessarily be as shown above.

It is preferable that the epoxy resin composition does not flow excessively when heated. In this case, the epoxy resin composition is prevented from flowing to the contacts, and the epoxy resin composition is prevented from impeding the electrical connection of the contacts. It is preferable that the epoxy resin composition has a suitable thixotropy so that the epoxy resin composition does not flow excessively.

Explain electronic devices in more detail.

The substrate 1 is, for example, a mother substrate, a package substrate, or an interposer substrate. For example, the substrate 1 includes an insulating substrate 11 made of glass epoxy, polyimide, polyester, ceramic, or the like, and conductor wiring 12 made of a conductor such as copper formed on a first surface 14 of the insulating substrate 11. The conductor wiring includes, for example, an electrode pad. In the embodiment, the substrate 1 also includes conductor wiring 13 made of a conductor such as copper formed on a second surface 15 of the insulating substrate 11.

The electronic component 4 includes, for example, a semiconductor chip 41. The semiconductor chip 41 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 41 may also be a PoP (package on package) type chip.

The electronic component 4 comprises a semiconductor chip 41 and a plurality of bump electrodes 42 on one surface of the semiconductor chip 41. The bump electrodes 42 comprise solder. For example, as shown in FIG. 1, the bump electrodes 42 comprise pillars 43 and solder bumps 44 provided at the tips of the pillars 43. The solder bumps 44 are made of solder, and therefore the bump electrodes 42 comprise solder. The pillars 43 are made of copper, for example.

The melting point of the solder (for example, the solder in the solder bump 44) provided in the bump electrode 42 is preferably 210°C or more and 230°C or less. In this case, when the side fill portion 2 is produced in parallel with reflow soldering in the embodiment, it is easy to achieve a good electrical connection between the electronic component 4 and the substrate 1 via the bump electrode 42. The solder is a lead-free solder selected from the group consisting of, for example, SAC (Sn-Ag-Cu) solder with a melting point of about 220°C, low Ag solder such as Sn-1.0Ag-0.5Cu solder with a melting point of 219°C, and high thermal fatigue resistance solder such as SnAgCuBiSbN solder with a melting point of 221°C. The composition of the solder is not limited to the above. The structure of the bump electrode 42 with solder is not limited to the above, and for example, the bump electrode 42 may have only a spherical solder bump 44 (solder ball). In other words, the bump electrode 42 does not need to have a pillar 43.

Explain the manufacturing process for electronic devices.

First, a substrate 1 is prepared (see Figure 1). One of the two main surfaces of this substrate 1 is called the first surface 14, and the other surface (facing the opposite side to the first surface 14) is called the second surface 15.

Solder paste 31 is applied onto the electrode pads of the conductor wiring 12 on the first surface 14 of the substrate 1 (see FIG. 2). The solder contained in the solder paste 31 is preferably the same solder that can be contained in the above-mentioned solder bumps 44. The solder paste 31 is formed into a pattern by an appropriate method such as screen printing.

Next, an epoxy resin composition is placed on the first surface 14 of the substrate 1 to form an uncured body 21 (see FIG. 2). The uncured body 21 is an uncured molded body formed from the epoxy resin composition. The uncured body 21 is formed, for example, using a syringe. The uncured body 21 is placed at a position on the first surface 14 where the periphery of the electronic component 4 is placed. The uncured body 21 is placed, for example, at the periphery of the electronic component 4 when the electronic component 4 is mounted. The uncured body 21 is placed, for example, around the entire periphery of the electronic component 4. The shape of the uncured body 21 placed on the first surface 14 of the substrate 1 is, for example, ball-shaped, and in this case, multiple ball-shaped lumps of the uncured body 21 are placed at intervals around the entire periphery of the electronic component 4. The shape of the uncured body 21 placed on the first surface 14 may be an appropriate shape such as a line shape. The uncured body 21 may be formed into a continuous frame shape.

Next, the electronic component 4 is placed on the substrate 1 (see FIG. 3). Specifically, the electronic component 4 is placed on the first surface 14 of the substrate 1 so that the bump electrodes 42 are placed on the solder paste 31 and the periphery of the electronic component 4 is placed on the uncured body 21 on the first surface 14. As a result, the first surface 14 of the substrate 1 and the electronic component 4 face each other, and the epoxy resin composition is placed on the periphery of the gap between the first surface 14 and the electronic component 4.

Next, the electronic components 4 are reflow soldered onto the first surface 14 of the substrate 1, and at the same time, the epoxy resin composition constituting the uncured body 21 is cured to produce the side fill portion 2. For example, the substrate 1 on which the electronic components 4 are mounted is heated in a reflow furnace, whereby the bump electrodes 42 and the solder paste 31 are heated and at the same time the epoxy resin composition of the uncured body 21 is heated.

For example, as in the model of the reflow profile and the change in resin viscosity over time shown in Figure 6 above, preheating is performed first. In preheating, the atmosphere around the substrate 1 is heated to a temperature lower than the melting point (Mp) of the solder and maintained at that temperature. This temperature and the time for which this temperature is maintained are adjusted so that the epoxy resin composition is appropriately softened and its viscosity is reduced, and the viscosity of the epoxy resin composition is maintained at a low level. This temperature is preferably lower than the curing start temperature of the epoxy resin composition, or not excessively higher than the curing start temperature of the epoxy resin composition. This temperature is, for example, 150°C or higher and 180°C or lower. The time for which the temperature of the atmosphere is maintained is, for example, 60 seconds or higher and 120 seconds or lower.

The atmosphere is then heated to a temperature exceeding the melting point (Mp) of the solder, and maintained at this temperature. This melts the solder and advances the curing reaction of the epoxy resin composition. As a result, the solder of the bump electrode 42 and the solder in the solder paste 31 melt, and the epoxy resin composition of the uncured body 21 cures, producing the side fill portion 2. This temperature and the time for which it is maintained at this temperature are adjusted so that the solder melts sufficiently, and the reaction of the epoxy resin composition is appropriately suppressed so that the solder melts in a state where the viscosity of the epoxy resin composition is sufficiently low. This temperature is, for example, 220°C or higher and 260°C or lower. The time for which the temperature is maintained is, for example, 30 seconds or higher and 60 seconds or lower.

Then, the temperature of the atmosphere is lowered to solidify the solder. This completes the manufacturing process of the electronic device.

If necessary, the electronic device may be subjected to a post-cure process in which the side fill portion 2 is further heated to further harden the side fill portion 2.

When an electronic device is manufactured as described above, even if the temperature of the atmosphere during the reflow process exceeds the melting point of the solder, the viscosity of the epoxy resin composition of the uncured body 21 remains low for a while, so the viscosity of the epoxy resin composition can be maintained low until the solder melts and flows appropriately. Therefore, the epoxy resin composition is less likely to interfere with reflow soldering, and the self-alignment effect can be exhibited well.

In this embodiment, since the curing start temperature of the epoxy resin composition is 150°C or higher, it is easy to set heating conditions that maintain the viscosity of the epoxy resin composition low until the solder melts and becomes appropriately fluid during the reflow process.

The electronic device shown in FIG. 3 manufactured as described above can be used as an intermediate product to manufacture another electronic device shown in FIG. 5.

The electronic device shown in FIG. 5 includes a substrate 1, a first electronic component 4 flip-chip mounted on a first surface 14 of the substrate 1, a second electronic component 5 flip-chip mounted on a second surface 15 of the substrate 1, and a side fill portion 2 located on the periphery of the gap between the first surface 14 and the first electronic component 4. The first electronic component 4 is the electronic component 4 in the electronic device shown in FIG. 3 above.

The second electronic component 5 may have the same structure as the first electronic component 4. That is, the second electronic component 5 may include a semiconductor chip 51 and a bump electrode 52, and the bump electrode 52 may have a pillar 53 and a solder bump 54. A method for manufacturing this electronic device will now be described.

An intermediate product and a second electronic component 5 are prepared. The intermediate product is the electronic device shown in FIG. 3 above, but the above-mentioned post-cure is not performed when the intermediate product is manufactured. In other words, the side fill portion 2 in the intermediate product does not need to be sufficiently cured.

Solder paste 32 is applied onto the electrode pads of the conductor wiring 13 on the second surface 15 of the substrate 1 in the intermediate product (see FIG. 4). The solder contained in the solder paste 32 is preferably the solder that can be contained in the above-mentioned solder bumps 54. The solder paste 32 is formed into a pattern by an appropriate method such as screen printing.

Next, the intermediate product is placed so that the second surface 15 of the substrate 1 faces upward, and the second electronic component 5 is placed on the second surface 15 of the substrate 1 so that the bump electrodes 42 of the second electronic component 5 are placed on the solder paste 32 (see Figure 5).

Next, the second electronic component 5 is reflow soldered onto the second surface 15 of the substrate 1, and at the same time, the side fill portion 2 is heated to further harden it. For example, the intermediate product on which the second electronic component 5 is mounted is heated in a reflow furnace, whereby the bump electrodes 52 and the solder paste 32 are heated and the side fill portion 2 is heated at the same time.

This produces the electronic device shown in Figure 5. The side fill portion 2 in the electronic device is further hardened when the second electronic component 5 is reflow soldered, so it can be sufficiently hardened without a separate post cure.

(Aspects)
The epoxy resin composition according to the first aspect contains an epoxy compound (A), an amine-based curing agent (B), and an inorganic filler (C). A cured product of the epoxy resin composition has a glass transition temperature of 125° C. or higher and a linear expansion coefficient of 35 ppm/° C. or lower, as measured by thermomechanical analysis. When the epoxy resin composition is heated from a state of 25° C. at a temperature increase rate of 5° C./min, the temperature at which the viscosity of the epoxy resin composition increases and reaches 200 Pa s is 150° C. or higher.

In the second embodiment, the epoxy compound (A) in the first embodiment contains an epoxy compound (A1) consisting of at least one of an aminoglycidyl ether and a naphthalene-type epoxy resin. The proportion of the epoxy compound (A1) relative to the epoxy compound (A) is 18% by mass or more.

In a third embodiment, in the first or second embodiment, the proportion of the inorganic filler (C) is 45% by mass or more and 85% by mass or less relative to the epoxy resin composition.

In a fourth aspect, in any one of the first to third aspects, the amine-based curing agent (B) contains at least one of a carboxylic acid hydrazide and an imidazole compound.

In a fifth aspect, in any one of the first to fourth aspects, the amine-based curing agent (B) contains an imidazole compound, and the melting point of the imidazole compound is 110°C or higher.

In a sixth aspect, in any one of the first to fifth aspects, the amine-based curing agent (B) contains an imidazole compound, and the proportion of the imidazole compound relative to the epoxy compound (A) is 3.5% by mass or more and 5.5% by mass or less.

In a seventh aspect, in any one of the first to sixth aspects, the amine-based curing agent (B) contains a carboxylic acid hydrazide, and the proportion of the carboxylic acid hydrazide relative to the epoxy compound (A) is 10% by mass or more and 30% by mass or less.

In an eighth aspect, in any one of the first to seventh aspects, the proportion of the inorganic filler (C) is 45% by mass or more and 85% by mass or less with respect to the total of the epoxy compound (A), the amine-based curing agent (B), and the inorganic filler (C).

In a ninth aspect, in any one of the first to eighth aspects, the epoxy resin composition is a side fill material.

The electronic device (10) according to the tenth aspect includes a substrate (1), an electronic component (4) flip-chip mounted on the substrate (1), and a side fill portion (2) disposed on the periphery of the gap between the substrate (1) and the electronic component (4). The side fill portion (2) includes a cured product of the epoxy resin composition according to any one of the first to ninth aspects.

An eleventh aspect is a method for manufacturing an electronic device (10). The electronic device (10) includes a substrate (1) having a first surface (14) and a second surface (15) opposite to the first surface (14), a first electronic component (4) flip-chip mounted on the first surface (14) of the substrate (1), a second electronic component (5) flip-chip mounted on the second surface (15) of the substrate (1), and a side fill portion (2) located on the periphery of a gap between the first surface (14) and the first electronic component (4). In the method for manufacturing an electronic device (10), the first surface (14) of a substrate (1) and a first electronic component (4) face each other, and an epoxy resin composition according to any one of the first to eighth aspects is disposed on the periphery of the gap between the first surface (14) and the first electronic component (4), and the first electronic component (4) is reflow soldered onto the first surface (14) of the substrate (1) while the epoxy resin composition is cured to produce a side fill portion (2). Then, a second electronic component (5) is reflow soldered onto the second surface (15) of the substrate (1).

1. Preparation of Epoxy Resin Compositions and Their Physical Properties Materials shown in Table 1 below were prepared, and epoxy resin compositions having the compositions shown in "Components and blending amounts (parts by mass)" in Tables 2 to 7 below were prepared.

The following physical properties of each epoxy resin composition are shown in the "Physical Properties" column in Tables 2 to 7.

"Viscosity" is the viscosity of the epoxy resin composition measured using an E-type viscometer at a rotation speed of 5 rpm.

"Thixotropy" is the thixotropy index of an epoxy resin composition. The thixotropy index is the ratio of the viscosity of an epoxy resin composition measured with an E-type viscometer at a rotation speed of 0.5 rpm to the viscosity of an epoxy resin composition measured with an E-type viscometer at a rotation speed of 5 rpm.

The "linear expansion coefficient" is the linear expansion coefficient below the glass transition temperature of the cured product obtained by heating the epoxy resin composition at 150°C for 1 hour and then at 180°C for 1 hour. The linear expansion coefficient described in the above description of the embodiment of the invention is the linear expansion coefficient α1 below the glass transition temperature.

"Glass transition temperature" is the glass transition temperature of the cured product of the epoxy resin composition measured by the following method.

A 3 mm thick silicone rubber was placed between two glass plates as a spacer, and the epoxy resin composition was filled between the glass plates. The epoxy resin composition was cured by heating in an oven at 150°C for 1 hour and then at 180°C for 1 hour to obtain a cured product. The cured product was cut to produce a sample measuring 15 mm x 3 mm in plan view and 3 mm thick.

The glass transition temperature of this sample was measured using a Seiko Instruments Inc. TMA (thermomechanical analysis) device (model number TMA7100) under conditions of a compression force of 9.8 mN and a temperature program of 30°C to 300°C at 5°C/min.

The "elastic modulus" is the elastic modulus at 25°C of the cured product obtained by heating the epoxy resin composition at 150°C for 1 hour and then at 180°C for 1 hour. To measure the elastic modulus, first, a 1mm-thick silicone rubber was sandwiched between two glass plates as a spacer, and the epoxy resin composition was filled between the glass plates. The epoxy resin composition was cured by heating in an oven at 150°C for 1 hour and then at 180°C for 1 hour to obtain a cured product. The cured product was cut to prepare a sample with dimensions of 50mm x 5mm in plan view and 1mm thick. The elastic modulus of this sample was measured using a DMA (thermo-mechanical analysis) device (model number DMA7100) manufactured by Seiko Instruments Inc. under the conditions of bending (double-supported beam), frequency of 10Hz, and temperature program of 0°C to 260°C at 10°C/min.

"Cure start temperature" is an evaluation of the cure start temperature of the epoxy resin composition measured using the method below.

When the epoxy resin composition was heated from 25°C at a temperature increase rate of 5°C/min, the temperature at which the viscosity of the epoxy resin composition increased to 200 Pa·s (curing initiation temperature) was measured.

Specifically, the viscosity change of the epoxy resin composition was measured using an Anton Paar rheometer (product name: MCR302) using an aluminum plate with a diameter of 25 mm under the following conditions: measurement gap 1.0 mm, temperature range 25°C to 200°C, heating speed 5°C/min, and rotation speed 1.0 rpm, and based on the results, the temperature at which the viscosity of the epoxy resin composition increased and reached 200 Pa·s was identified.

As a result, the test results were rated as follows: "A" for a curing start temperature of 150°C or higher and lower than 200°C, "B" for a curing start temperature of 135°C or higher and lower than 150°C, and "C" for a curing start temperature lower than 135°C.

2. Evaluation (1) Connectivity Evaluation Using the epoxy resin composition, a semiconductor device (electronic device) was produced as follows.

A Walts KIT WLP(S)300P/400P Ni/Au (30 mm x 30 mm x 0.978 mm) manufactured by WALTS was prepared as substrate 1.

A Walts WLP TEG 0.4 mm Pitch (6.0 mm x 6.0 mm x 400 μm) manufactured by WALTS was prepared as a chip (electronic component 4). This chip has 144 bump electrodes, each with a solder bump height of 210 μm, and the pitch between adjacent solder bumps is 400 μm. The solder contained in the solder bumps is SnAgCu solder with a melting point of 220°C.

A 100 μm thick metal mask with an opening of 200 μm diameter was used to print and apply SnAgCu solder paste with a melting point of 220°C to the substrate.

After printing the solder paste, the epoxy resin composition was applied onto the substrate using a Musashi Engineering air dispenser (model number: 350PC) to form ball-shaped lumps of the epoxy resin composition spaced apart from one another at positions on the substrate that correspond to the periphery of the chip. Five ball-shaped lumps were formed at each of the positions that correspond to the four corners of the periphery of the chip.

A Toray Engineering Co., Ltd. model FC3000S flip chip bonder was used, and the chip was held on the bonding head of the flip chip bonder. The chip was mounted on the substrate while applying a load of 5 N to the substrate, while aligning the bump electrodes of the chip with the conductive wiring of the substrate.

Then, the board with the chips mounted on it was heated twice in a reflow furnace, hardening the epoxy resin composition in parallel with the reflow soldering. In the reflow furnace, the board with the chips mounted on it was heated each time under the following conditions:

Preheating was performed by raising the temperature of the atmosphere from room temperature to a temperature of 150-180°C and maintaining this temperature for 90±30 seconds. The temperature was then increased and maintained within the range of 220°C, the melting point of the solder, to 255°C±15°C for 30-60 seconds. The temperature was then lowered to room temperature.

This resulted in a semiconductor device for testing.

The connectivity of this semiconductor device was evaluated as follows:

The electrical resistance between the bump electrodes near the periphery of the chip and the conductor wiring on the substrate was measured. This electrical resistance was compared with the electrical resistance measured in the same manner for a semiconductor device manufactured without creating a side fill portion. As a result, cases where no change was observed between the two (a change of less than 20%) were rated as "A," cases where a change of 20% or more was observed were rated as "B," and cases where no electrical resistance was detected were rated as "C."

(2) Curing Rate 10 mg±1 mg of the epoxy resin composition before being heated in a reflow furnace was weighed out into an aluminum pan for a differential scanning calorimeter (DSC7000X, manufactured by Hitachi High-Technologies Corporation), and the epoxy resin composition was measured using the differential scanning calorimeter under conditions of a temperature rise speed of 10° C./min, a _N2 gas flow rate of 30 ml/min, and a temperature range of 30° C. to 300° C., and the calorific value (initial calorific value) was calculated from the area of the obtained peak.

As described above, the epoxy resin composition was weighed into an aluminum pan, and the epoxy resin composition was placed together with the aluminum pan on a 0.65 mm thick ceramic substrate. The composition was heated twice in a reflow furnace under the same conditions as in the above connectivity evaluation, and then measured using a differential scanning calorimeter under the same conditions. The heat generation amount (heat generation amount after reflow curing) was calculated from the peak area in the same manner.

From these results, the reaction rate was calculated using the following formula:

[(Initial heat generation amount) - (Heat generation amount after reflow curing)) / (Initial heat generation amount)] x 100

(3) Heat cycle resistance Using the epoxy resin composition, a test semiconductor device was prepared in the same manner as in the case of the connectivity evaluation. A temperature cycle test was carried out on this semiconductor device, with one cycle consisting of exposure to -40°C for 5 minutes and then exposure to 125°C for 5 minutes. The electrical resistance value between the bump electrode near the periphery of the semiconductor device and the conductor wiring before the test was compared with the similar electrical resistance value in the semiconductor device after 1000 cycles of the test, and the case where no change was observed between the two (the change was less than 20%) was evaluated as "A", the case where a change of 20% or more was observed was evaluated as "B", and the case where no electrical resistance value was detected was evaluated as "C".

REFERENCE SIGNS LIST 1: Substrate 14: First surface 15: Second surface 2: Side fill portion 4: Electronic component (first electronic component)
5. Secondary Electronic Components

Claims (11)

An epoxy resin composition,
An epoxy compound (A),
An amine-based curing agent (B);
Contains an inorganic filler (C),
a cured product of the epoxy resin composition has a glass transition temperature of 125° C. or higher and a linear expansion coefficient of 35 ppm/° C. or lower, as measured by thermomechanical analysis;
When the epoxy resin composition is heated from a state of 25° C. at a temperature increase rate of 5° C./min, the temperature at which the viscosity of the epoxy resin composition increases to reach 200 Pa s is 150° C. or higher.
Epoxy resin composition. The epoxy compound (A) contains an epoxy compound (A1) composed of at least one of an aminoglycidyl ether and a naphthalene-type epoxy resin,
The ratio of the epoxy compound (A1) to the epoxy compound (A) is 18 mass% or more.
The epoxy resin composition according to claim 1. The ratio of the inorganic filler (C) is 45% by mass or more and 85% by mass or less with respect to the epoxy resin composition.
The epoxy resin composition according to claim 1 or 2. The amine-based curing agent (B) contains at least one of a carboxylic acid hydrazide and an imidazole compound.
The epoxy resin composition according to claim 1 or 2. The amine-based curing agent (B) contains an imidazole compound,
The melting point of the imidazole compound is 110° C. or higher.
The epoxy resin composition according to claim 1 or 2. The amine-based curing agent (B) contains an imidazole compound,
The ratio of the imidazole compound is 3.5% by mass or more and 5.5% by mass or less with respect to the epoxy compound (A).
The epoxy resin composition according to claim 1 or 2. The amine-based curing agent (B) contains a carboxylic acid hydrazide,
The ratio of the carboxylic acid hydrazide to the epoxy compound (A) is 10% by mass or more and 30% by mass or less.
The epoxy resin composition according to claim 1 or 2. The proportion of the inorganic filler (C) is 45% by mass or more and 85% by mass or less with respect to the total of the epoxy compound (A), the amine-based curing agent (B), and the inorganic filler (C).
The epoxy resin composition according to claim 1 or 2. Side fill material,
The epoxy resin composition according to claim 1 or 2. A substrate;
an electronic component flip-chip mounted on the substrate;
a side fill portion disposed on a peripheral portion of a gap between the substrate and the electronic component;
The side fill portion comprises a cured product of the epoxy resin composition according to claim 1 or 2.
Electronic device. 1. A method for manufacturing an electronic device, comprising:
The electronic device comprises:
a substrate having a first surface and a second surface opposite the first surface;
a first electronic component flip-chip mounted on the first surface of the substrate;
a second electronic component flip-chip mounted on the second surface of the substrate;
a side fill portion located at a peripheral portion of a gap between the first surface and the first electronic component,
The manufacturing method includes: in a state in which the first surface of the substrate and the first electronic component face each other and the epoxy resin composition according to claim 1 or 2 is disposed on a peripheral portion of a gap between the first surface and the first electronic component, reflow soldering the first electronic component onto the first surface of the substrate while curing the epoxy resin composition in parallel to preparing the side fill portion, and then reflow soldering the second electronic component 4 onto the second surface of the substrate.
A method for manufacturing an electronic device.

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