JP2003041095A - Epoxy resin composition for sealing capacitor and capacitor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an epoxy resin composition for sealing a capacitor having an excellent molding property, moisture resistance and post-moisture absorption reflow crack resistance, and enabling improving the properties of the capacitor. SOLUTION: The epoxy resin composition for sealing a capacitor contains an epoxy resin and a filler. The filler comprises >=70% spherical silica by mass based on the whole fillers, and <=5% filler having particle diameters of >=64 μm and <=0.1% filler having particle diameters of >=100 μm, by mass based on the whole fillers. Further, the epoxy resin composition has a melt viscosity of <=10 Pa.s at 175 deg.C measured by a Koka(R) type flow tester.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an epoxy resin composition for encapsulating a capacitor used for encapsulating a capacitor element such as a tantalum chip, and a capacitor device encapsulated with this epoxy resin composition. Is.

[0002]

2. Description of the Related Art Capacitors are electronic components used in various electronic devices. Especially, chip type capacitors are small and thin, and are currently used in many fields. The capacitors are classified into ceramic capacitors, aluminum electrolytic capacitors, tantalum capacitors, film capacitors, etc., depending on the material of the dielectric. Of these, the tantalum capacitor is obtained by anodizing the surface of a powder tantalum sintered body,
Specifically, a tantalum oxide film (Ta ₂ O ₅ ) is used as a dielectric, and an anode is made of tantalum (Ta) on one side and a cathode is made of manganese dioxide (MnO ₂ ) on the other side. Thus, a capacitor element is formed, and the capacitor device is manufactured by sealing the capacitor element with a sealing material containing a thermosetting resin as a main component.

[0003]

By the way, as a sealing material for the above-mentioned capacitor element, a composition containing a general-purpose type epoxy resin has been often used so far. Conventionally, the level required for various characteristics of such a sealing material has not been high.

However, as the use of the capacitor device is expanded to the fields of digital home appliances, communication device parts, vehicle-mounted parts, etc., it is spurred to reduce the size and thickness of the capacitor device itself, so that the conventional characteristics cannot be satisfied. Has become.

That is, in order to promote miniaturization and thinning, it may be necessary to set the thickness of the sealing material in the capacitor device to about 100 μm in the thin portion.
Strict demands have been made on the encapsulant with respect to properties such as moldability, moisture resistance, and crack resistance during reflow after moisture absorption.

On the other hand, by changing the cathode material of the capacitor element from the conventional manganese dioxide (MnO ₂ ) to a conductive polymer having a conductivity of about 100 times, low impedance can be realized, that is, so-called high functionality. Molecular capacitors are being developed. However, in such a capacitor, the conductive polymer of the cathode is very soft and is easily affected by external factors, that is, it is easily stressed, and thus is damaged or deformed. There is a problem that the characteristics of the capacitor are deteriorated. Therefore, the sealing material is required to be more strict in terms of its characteristics.

Further, as a solder used when mounting the capacitor device on a printed wiring board or the like, a so-called lead-free solder, which does not contain lead, has been used recently from the viewpoint of environmental problems. However, when lead-free solder is used, the reflow temperature may rise higher than that of normal solder.Therefore, the encapsulant for encapsulating the capacitor element may not have moisture resistance or crack resistance during reflow after moisture absorption. Further improvement was required.

The present invention has been made in view of the above points, and is excellent in moldability, moisture resistance, and crack resistance during reflow after absorption of moisture, and at the same time, for encapsulating a capacitor that can obtain high characteristics of the capacitor. It is an object to provide an epoxy resin composition and a capacitor device.

[0009]

The epoxy resin composition for encapsulating a capacitor according to claim 1 of the present invention is an epoxy resin composition for encapsulating a capacitor containing an epoxy resin and a filler, which is used as a filler. 70% by mass or more of the filler is spherical silica, 5% by mass or less of the filler having a particle size of 64 μm or more and 0.1% by mass or less of the total filler of 100 μm or more are used. 175 ° C measured with a Koka type flow tester
It has a melt viscosity of 10 Pa · s or less.

The invention of claim 2 is characterized in that, in claim 1, the cured product has a linear expansion coefficient of 1.2 × 10 ^-5 / ° C. or less.

According to a third aspect of the present invention, in an epoxy resin composition for capacitor encapsulation containing an epoxy resin and a filler, 90% by mass or more of the total filler is spherical silica, and the particle size is 64 μm. The above filler is 5% by mass or less of the total filler, and the filler having a particle size of 100 μm or more is 0.1% by mass or less of the total filler, and is measured by using a Koka type flow tester. The melt viscosity at 175 ° C. is 5 Pa · s or less, and the linear expansion coefficient of the cured product is 1.2 × 10 ⁻⁵ / ° C. or less.

The invention according to claim 4 is, in any one of claims 1 to 3, an epoxy resin selected from the following formulas (1) and (2) as the epoxy resin, in an amount of 50% by mass relative to the total amount of the epoxy resin. % Or more is used.

[0013]

[Chemical 2]

A capacitor device according to a fifth aspect is characterized in that a capacitor element is encapsulated with the epoxy resin composition for encapsulating a capacitor according to any one of the first to fourth aspects. is there.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.

In the present invention, the epoxy resin for preparing the epoxy resin composition for encapsulating a capacitor (hereinafter, also simply referred to as "epoxy resin composition") is not particularly limited, but for example, orthocresol. Various polyfunctional epoxy resins such as novolac type epoxy resin, biphenyl type epoxy resin, dicyclopentadiene type epoxy resin, naphthalene type epoxy resin and bisphenol A type epoxy resin can be used.

Preferably, the epoxy resin is an epoxy resin selected from the above formulas (1) and (2), that is, an epoxy resin having a skeleton represented by the formulas (1) and (2). It is preferable to use one containing one or both of the epoxy resins in an amount of 50% by mass or more based on the total amount of the epoxy resins. By doing so, the adhesive strength of the epoxy resin composition to the capacitor element can be increased and high adhesion can be obtained, the moisture absorption rate of the epoxy resin composition can be reduced, and cracking during reflow heating can occur. Can be prevented. Further, there is an advantage that the viscosity of the epoxy resin composition is lowered to improve the moldability. Here, the whole epoxy resin may be occupied by only the epoxy resin represented by the formula (1) or the formula (2). On the other hand, when the compounding amount of the epoxy resin selected from the formulas (1) and (2) is less than 50% by mass, it may not be possible to obtain high adhesiveness or reduce the moisture absorption rate, and the moisture resistance may be low. May decrease.

Further, in the present invention, it is necessary to use the following as the filler. That is, it is necessary to use a material in which 70% by mass or more of the filler is spherical silica. As described above, when the majority of the filler is not spherical but has a shape close to a sphere, the stress applied to the conductive polymer of the cathode is reduced especially in so-called functional polymer capacitors. ESR of capacitor element (equivalent series resistance)
It is possible to prevent adverse effects such as large fluctuations in. Where ESR (equivalent series resistance)
Is a measure of the ease with which electricity is taken in and out when the capacitor device is repeatedly charged and discharged, and the smaller the value, the better. Also, by adopting spherical silica,
The fluidity is secured, the moldability can be improved, and the linear expansion coefficient (α1) described later can be reduced,
The moisture resistance and the crack resistance during reflow after absorbing moisture can be enhanced. On the contrary, when the compounding amount of the spherical silica is less than 70% by mass with respect to the total amount of the filler, the ESR (equivalent series resistance) of the capacitor device increases, and the amount of heat generation increases when charging and discharging are repeated. . It is preferable to use, as the filler, 90% by mass or more of spherical silica with respect to the total amount of the filler. By doing so, the ESR (equivalent series resistance) can be significantly reduced, and it becomes easy to cope with higher frequencies. Here, the entire filler may be occupied only by spherical silica. It should be noted that examples of silica other than spherical silica include crushed silica.

Further, as the filler of the present invention, in addition to the above conditions, it is necessary to use a filler having the following particle size distribution. That is, 5% by mass or less of the filler having a particle diameter of 64 μm or more is present with respect to the total amount of the filler, and
It is necessary to have a particle size distribution such that a filler having a particle size of 100 μm or more is present in an amount of 0.1% by mass or less. When a filler having such a particle size distribution is used, the E
SR (equivalent series resistance) can be reduced to easily cope with higher frequencies, and LC (LeakageCurrent:
The leakage current) can be reduced and the reliability can be improved. However, if the filler having a particle size of 64 μm or more is 5.
If it is present in an amount of more than 0% by mass, it becomes impossible to obtain excellent characteristics of the capacitor device as described above.
Moreover, even if the filler having a particle size of 64 μm or more is present in an amount of 5.0% by mass or less, if the filler having a particle size of 100 μm or more is present in an amount exceeding 0.1% by mass, the above-mentioned characteristics of the capacitor device are excellent. It is impossible to get to. In addition,
In the present invention, the practical lower limit of the content of the filler having a particle size of 64 μm or more is 0% by mass.
The practical lower limit of the filler content of μm or more is also 0% by mass.

The filler is not particularly limited as long as it satisfies the above-mentioned conditions, but is most effective for reducing the linear expansion coefficient (α1) described later, for example. Preference is given to using fused silica. Further, the compounding amount of the filler is preferably 70 to 90 mass% with respect to the total amount of the epoxy resin composition.

The epoxy resin composition for encapsulating capacitors according to the present invention contains the above-mentioned epoxy resin and a filler, but the following components may be blended if necessary.

That is, various polyhydric phenol compounds such as phenol novolac resin, cresol novolac resin, and phenol aralkyl resin can be used as the curing agent.

As the curing aid, phosphorus-based, imidazole-based, amine-based and the like can be used.

As the release agent, carnauba wax, stearic acid, montanic acid, carboxyl group-containing polyolefin or the like can be used.

Further, in addition to the above components, a silane coupling agent, a flame retardant, a silicone flexibility-imparting agent and the like can be added.

An epoxy resin composition for encapsulating capacitors according to the present invention contains the above epoxy resin and a filler,
Further, it can be prepared by blending other components as necessary, uniformly mixing the components with a mixer, a blender or the like, and then heat-kneading them with a kneader or a roll. Further, the kneaded product may be cooled and solidified as needed, and may be pulverized into powder or the like before use.

In the epoxy resin composition prepared as described above, the melt viscosity at 175 ° C. measured using a Koka type flow tester is 10 Pa · s or less. Here, the Koka type flow tester is a constant load type orifice extrusion type that pushes out the test material put in the heating cylinder from the orifice with a plunger under a constant load and expands and records the descending speed of the plunger at this time. A type of flow tester, which is proposed by the Society of Polymer Science. The epoxy resin composition flows on the surface of the capacitor element when sealing the capacitor element, but if the melt viscosity at a temperature (175 ° C.) substantially equal to the molding temperature is as low as 10 Pa · s as described above. The effect of the epoxy resin composition on the capacitor element, for example, stress applied to the cathode formed of a very soft conductive polymer in the functional polymer capacitor described above can be reduced. Therefore, ESR (equivalent series resistance) and LC (leakage current) of the capacitor element
A capacitor device can be manufactured without deteriorating the characteristics such as. However, if the melt viscosity at 175 ° C. exceeds 10 Pa · s, the fluidity deteriorates and the moldability decreases, and if the injection pressure is increased to promote the fluidization, this has an effect on the capacitor element. However, the characteristics of the manufactured capacitor device are deteriorated.

Preferably, the epoxy resin composition has a temperature of 175 ° C. measured by using a Koka type flow tester.
Has a melt viscosity of 5 Pa · s or less. When such an epoxy resin composition is used, the fluidity becomes extremely good, so that it is possible to obtain high moldability and it is possible to significantly reduce the effect on the capacitor element. It is possible to prevent characteristic deterioration and obtain high reliability. In addition,
The practical lower limit of the melt viscosity at 175 ° C is 1 Pa · s.
Is.

Further, in the above epoxy resin composition, the linear expansion coefficient (α1) of the cured product is 1.2 × 10 ^-5 / ° C.
The following is preferable. The reason for this is that when the epoxy resin composition covering the surface of the capacitor element is heated and cured, or when the capacitor device is mounted on a printed wiring board or the like by reflow heating, the molding shrinkage of the epoxy resin composition causes the capacitor element to shrink. This is because it is possible to reduce stress such as shear stress that acts on the surface of the. Therefore, the capacitor element is not damaged or deformed, and ESR (equivalent series resistance) or LC
It is possible to prevent deterioration of electrical characteristics such as (leakage current) and obtain a highly reliable capacitor device. However, the linear expansion coefficient (α1) of the cured product is 1.2 × 1
If it exceeds 0 ^-5 / ° C, the moisture resistance or the crack resistance during reflow after moisture absorption may be deteriorated. By the way, even if the linear expansion coefficient (α1) of the cured product is 1.2 × 10 ⁻⁵ / ° C. or less, if the above-mentioned spherical silica is less than 90 mass% with respect to the total amount of the filler, melting at 175 ° C. Viscosity 5Pa
・ It becomes difficult to change to s. The linear expansion coefficient (α1) of the cured product is preferably as small as possible by increasing the compounding amount of the filler in the epoxy resin composition or by bringing the shape of the filler closer to a sphere. The practical lower limit is 0.8 × 10 ⁻⁵ / ° C.

Then, a capacitor device can be manufactured by encapsulating and molding a capacitor element using the above-mentioned epoxy resin composition. For example, a capacitor element having a tantalum oxide film (Ta ₂ O ₅ ) as a dielectric is set in a transfer molding die, and transfer molding is performed to seal the capacitor element into a molded product (package) made of an epoxy resin composition. The capacitor device described above can be manufactured. Moreover, the epoxy resin composition for capacitor encapsulation according to the present invention can be particularly preferably used for producing a so-called functional polymer capacitor in which one electrode is formed of a soft conductive polymer. is there.

[0031]

EXAMPLES The present invention will be specifically described below with reference to examples.

The epoxy resin is an o-cresol novolac type epoxy resin "E" manufactured by Sumitomo Chemical Co., Ltd.
OCN195XL-3 "and" EOCN195XL-1 "
5 ", a dicyclopentadiene type epoxy resin represented by the formula (1)," XD1000-2 "manufactured by Nippon Kayaku Co., Ltd.
L "," YX-4000H "manufactured by Yuka Shell Epoxy Co., Ltd., which is a biphenyl type epoxy resin represented by the formula (2).
Was used.

As the curing agent, phenol novolac resin "H-4" manufactured by Meiwa Kasei Co., Ltd. and "VR9305" manufactured by Mitsui Chemicals, Inc. were used.

As the flame retardant, brominated epoxy resin "ESB400T" manufactured by Sumitomo Chemical Co., Ltd. and antimony trioxide were used.

Further, carnauba wax was used as a release material, carbon black was used as a colorant, and 2-phenylimidazole (2PZ) was used as a curing aid.

The fillers shown in Table 1 were used. That is, “MC, which is a crushed silica manufactured by Tatsumori Co., Ltd.
F-200 "(referred to as (B))," ZA- "made by Tatsumori Co., Ltd.
30 "(referred to as (D)) and" RD-8 "manufactured by Tatsumori Co., Ltd.
(Referred to as (E)) and spherical silica “FB-60” manufactured by Denki Kagaku Kogyo Co., Ltd. (referred to as (A)) and “FB-875FC” manufactured by Denki Kagaku Kogyo Co. ((C)). Used). Both silicas were treated with γ-glycidoxypropyltrimethoxysilane before use.

[0037]

[Table 1]

Next, the respective components were blended in the blending amounts shown in Table 2, and the ingredients were blended in a blender for 3 minutes to homogenize them.
After kneading with a roll heated to 100 ° C for 10 minutes and cooling,
It was crushed to a predetermined particle size by a crusher to obtain a granular molding material composed of an epoxy resin composition for encapsulating a capacitor.

With respect to the molding materials of Examples 1 to 10 and Comparative Examples 1 to 4 thus obtained, the gel time at 175 ° C., the spiral flow and the melt viscosity were measured. A Koka type flow tester was used to measure the melt viscosity. The results are shown in Table 2.

(Linear Expansion Coefficient (α1)) Examples 1 to 1 above
Transfer molding was performed using the molding materials of No. 10 and Comparative Examples 1 to 4. The molding conditions are molding temperature 175 ± 5 ° C., injection speed 8 seconds, injection pressure 7 MPa, cure time 90.
Seconds, after being molded at 175 ° C. for 6 hours, the size (diameter 5 mm, height 30 mm)
To obtain a molded product. The linear expansion coefficient (α
1) was measured with a dilatometer. The results are shown in Table 2.

(Hygroscopic rate) A molded product was obtained in the same manner as in the case of the coefficient of linear expansion (α1). This molded product is then heated to a temperature of 85
After being left for 72 hours in an atmosphere of ° C and a humidity of 85% RH, the moisture absorption rate was measured. The results are shown in Table 2.

(Purin Adhesion) The adhesiveness of the molding materials of Examples 1 to 10 and Comparative Examples 1 to 4 was evaluated as follows. That is, using the above molding material, molding temperature 175 ± 5 ° C., injection speed 8 seconds, injection pressure 7MP
a, curing time of 90 seconds, 25 mm square copper (C
u) flat plate 2 with a diameter of 11.3 mm and a height of 10.0
A pudding mold 1 having a size of mm was produced by transfer molding as shown in FIG. After molding, after-curing was performed at 175 ° C. for 6 hours. Then, the shear adhesion strength between the pudding-type molded product 1 and the flat plate 2 was measured. The results are shown in Table 2.

[0043]

[Table 2]

(LC characteristics and ESR characteristics) The cathode is MnO.
_The tantalum chip formed in ₂ was sealed using the molding materials of Examples 1 to 10 and Comparative Examples 1 to 4 to obtain a tantalum chip capacitor package for electrical characteristic evaluation. on the other hand,
A tantalum chip having a cathode formed of a conductive polymer was sealed with the above molding material to obtain a functional polymer tantalum chip capacitor package for electrical property evaluation. And for each package, JIS C510
The LC characteristics and ESR characteristics were tested based on 1-1. The results are shown in Table 3 with the following criteria. "○" ... Little variation within standard "△" ... Large variation within standard "X" ... Large variation outside standard (reflow resistance) Using the molding materials of Examples 1 to 10 and Comparative Examples 1 to 4, External shape 15 mm x 19 mm x thickness 2.4
Transfer molding was performed on a die for 80 mm QFP of 80 mm. The molding conditions were a molding temperature of 175 ± 5 ° C., an injection speed of 8 seconds, an injection pressure of 7 MPa, and a cure time of 90 seconds, and after-curing at 175 ° C. for 6 hours after the molding, a package for performance evaluation was obtained.

This package has a temperature of 85 ° C. and a humidity of 85%
After leaving it in the RH atmosphere for 168 hours to absorb moisture, IR
Reflow (EIAJ standard) was performed and the presence or absence of package cracks was observed. In Table 3, the number of packages observed in the denominator and the number of packages with cracks in the numerator are shown.

(Moisture resistance reliability) After the reflow-treated package was left in an atmosphere of a temperature of 133 ° C. and a humidity of 100% RH for 500 hours, the occurrence of open defects was inspected. The number of packages tested in the denominator in Table 3 is
Indicates the number of packages with open defects in the molecule.

[0047]

[Table 3]

As can be seen from Tables 2 and 3, it is confirmed that each of the examples has excellent moldability, moisture resistance, and crack resistance during reflow after moisture absorption. With regard to the characteristics of the capacitor, excellent evaluations were obtained for all the examples.

On the other hand, in Comparative Examples 1, 3 and 4, spherical silica having a predetermined particle size distribution was not blended,
In addition, it is confirmed that the characteristics of the capacitor device cannot be obtained high because the melt viscosity of Comparative Example 2 is too high, and the linear expansion coefficient (α1) of all Comparative Examples is too large.

[0050]

As described above, the capacitor-encapsulating epoxy resin composition according to claim 1 of the present invention is used as a filler in a capacitor-encapsulating epoxy resin composition containing an epoxy resin and a filler. 70% by mass or more of the filler is spherical silica, 5% by mass or less of the filler having a particle size of 64 μm or more and 0.1% by mass or less of the total filler of 100 μm or more are used. With some,
Since the melt viscosity at 175 ° C. measured using a Koka type flow tester is 10 Pa · s or less, fluidity can be ensured and moldability can be improved, and the influence on the capacitor element during encapsulation molding It is possible to produce a capacitor device which is reduced in quality and does not impair the characteristics of the capacitor element, and which is excellent in moisture resistance and crack resistance during reflow after moisture absorption.

The invention of claim 2 has a coefficient of linear expansion of 1.
Since it is 2 × 10 ⁻⁵ / ° C. or less, when the epoxy resin composition is heated and cured, it is possible to reduce the stress such as the shear stress acting on the surface of the capacitor element due to the molding shrinkage. It is possible to obtain a highly reliable capacitor device by preventing deterioration of electrical characteristics.

According to a third aspect of the invention, in the epoxy resin composition for capacitor encapsulation containing an epoxy resin and a filler, 90% by mass or more of the total filler is spherical silica, and the particle size is 64 μm. The above filler is 5% by mass or less of the total filler, and the filler having a particle size of 100 μm or more is 0.1% by mass or less of the total filler, and is measured by using a Koka type flow tester. Since the melt viscosity at 175 ° C. is 5 Pa · s or less and the linear expansion coefficient is 1.2 × 10 ⁻⁵ / ° C. or less, fluidity can be secured and moldability can be enhanced, and sealing can be achieved. In addition to being able to reduce the influence on the capacitor element during molding and preventing the characteristic deterioration of the capacitor element, when the epoxy resin composition is heated and cured, the capacitor element shrinks due to molding shrinkage. It is possible to reduce stress such as shear stress acting on the surface of the capacitor, and to more reliably obtain a highly reliable capacitor device having excellent moisture resistance and crack resistance during reflow after absorption of moisture.

The invention according to claim 4 uses, as the epoxy resin, an epoxy resin selected from the above formulas (1) and (2) in an amount of 50% by mass or more based on the total amount of the epoxy resin. In addition, the adhesive force of the epoxy resin composition can be increased to obtain high adhesion, the moisture absorption rate of the epoxy resin composition can be reduced, and the occurrence of cracks during reflow heating can be prevented. Is.

Further, in the capacitor device according to a fifth aspect of the present invention, since the capacitor element is encapsulated using the epoxy resin composition for encapsulating a capacitor according to any one of the first to fourth aspects, the ESR (equivalent series resistance) ) And LC (leakage current).

[Brief description of drawings]

1A and 1B show a pudding-type molded product for evaluating adhesion, where FIG. 1A is a plan view and FIG. 1B is a front view.

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Claims (5)

[Claims] 1. In an epoxy resin composition for encapsulating a capacitor, which comprises an epoxy resin and a filler, 70% by mass or more of the total filler is spherical silica, and the filler having a particle size of 64 μm or more is the whole filler. 5% by mass or less of the filler,
Filler with a particle size of 100 μm or more is 0.1% by mass of the total filler.
In addition to using the following, the melt viscosity at 175 ° C. measured using a Koka type flow tester is 10P.
An epoxy resin composition for encapsulating a capacitor, characterized in that it is not more than a · s. 2. The linear expansion coefficient of the cured product is 1.2 × 10 ⁻⁵ /
The epoxy resin composition for capacitor encapsulation according to claim 1, wherein the epoxy resin composition has a temperature of not higher than 0 ° C. 3. An epoxy resin composition for encapsulating a capacitor, which comprises an epoxy resin and a filler, wherein 90% by mass or more of the total filler is spherical silica, and the filler having a particle size of 64 μm or more is the whole filler. 5% by mass or less of the filler,
Filler with a particle size of 100 μm or more is 0.1% by mass of the total filler.
In addition to using the following, the melt viscosity at 175 ° C. measured using a Koka type flow tester is 5 Pa.
・ S or less and the linear expansion coefficient of the cured product is 1.2 ×
An epoxy resin composition for encapsulating a capacitor, which is 10 ^-5 / ° C or less. 4. An epoxy resin containing an epoxy resin selected from the following formulas (1) and (2) in an amount of 50% by mass or more based on the total amount of the epoxy resin. The epoxy resin composition for capacitor encapsulation according to any one of 1 to 3. [Chemical 1] 5. A capacitor device comprising a capacitor element encapsulated with the epoxy resin composition for capacitor encapsulation according to any one of claims 1 to 4.