JPH11269248A - Epoxy resin composition for sealing discrete element and resin-sealed semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an epoxy resin composition for sealing discrete elements showing a high moisture-vapor resistance reliability and adhesion property, and a resin-sealed semiconductor device. SOLUTION: An epoxy resin composition for sealing is an epoxy resin composition containing an epoxy resin and a hardener, wherein a compound of the formula (wherein n is a number with an average of 0 to 5) is used as the above- mentioned epoxy resin. A resin-sealed semiconductor device is prepared by sealing discrete elements mounted on a lead frame using the above-mentioned epoxy resin composition.

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 used for sealing a discrete element (also referred to as an "individual semiconductor element"), and a resin-sealed semiconductor device using the same.

[0002]

2. Description of the Related Art Thermosetting resin compositions are used for sealing and packaging discrete elements (eg, transistors, diodes, photoelectric conversion elements, thermistors, varistors, thyristors, photocouplers, resistors, capacitors, transformers, etc.). The method used is generally used, and sealing with an epoxy resin composition is preferable in terms of balance between economy and performance, and is widely used.

In order to reduce the size and thickness of electronic components, ICs,
In the LSI field, the semiconductor mounting method has shifted from the conventional pin insertion method to the surface mounting method. In the discrete field as well, the trend has been progressing, but until now there has been no strict requirement in the market such as moisture resistance after soldering. For sealing small-signal electronic components such as surface-mounted diodes and transistors, general-purpose ortho-cresol epoxy resins have been used, particularly in view of cost and market needs. Diodes also tend to move to surface-mount type diodes according to the trend. Regarding the resin composition to be used, the epoxy resin composition was also the mainstream because of the thickness of the package and the low requirements for user use. Transistors are categorized into those that tend to shift to surface-mount type transistors according to the flow, and large full-mold packages that can output high power.

However, recently, a very high level of moisture resistance reliability has been demanded for discrete components mainly for use in vehicles and also for packages of pin insertion type as well as surface mounting type. Resin encapsulation of a semiconductor device is performed, for example, by mounting a semiconductor element on a metal for a lead frame, electrically connecting the semiconductor element to the lead frame using a bonding wire or the like, and using a mold to achieve moisture resistance reliability. This is performed by sealing the entire semiconductor element and a part of the lead frame with a sealing resin.

By the way, when the cured resin material in the sealing portion absorbs moisture, the absorbed moisture rapidly expands due to the thermal shock of soldering when the electronic component is mounted on the motherboard, and cracks are formed inside the cured resin material. As a result, a problem arises in that the reliability of moisture resistance is reduced, so that a countermeasure is required. In the case of the surface mount method, in the infrared reflow and soldering processes, etc.
Since the entire package is heated at a high temperature, the demand for improving the moisture resistance has been particularly strong. Particularly in the field of in-vehicle applications, there is a growing demand for small-signal electronic components such as surface-mounted transistors, particularly discrete elements, to improve infrared reflow and moisture resistance after soldering. Also, in the case of a large package, the shape becomes complicated, the filling of the thin portion is difficult, and depending on the type of lead frame plating, the adhesion may become a problem, and there may be a problem of molding failure such that the package expands immediately after molding. There are often.

The multiple mold sealing is used to seal an optical semiconductor such as a photocoupler (an optical semiconductor of a discrete element), and an inner sealing material that directly covers a light emitting element and a light receiving element and an inner sealing. It has at least two layers with an outer sealing material covering the stopper. As the inner encapsulant, a resin composition generally used for encapsulating a semiconductor cannot be used because of its poor light transmissivity, and therefore, a material taking light transmissivity into consideration is used. However, as a basic component of the material, a general ortho-cresol type epoxy resin is used. As the outer sealing material, the same sealing material as a general material is used. With respect to such multiple molds, the surface mounting method is increasingly used, and the entire package is heated at a high temperature in an infrared reflow process, a soldering process, or the like. Therefore, the adhesion between the chip and the REIT frame and the adhesion between the inner sealing material and the outer sealing material are reduced, and there is a concern that the moisture resistance may be reduced.

[0007]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an epoxy resin composition for sealing a discrete element and a resin-encapsulated semiconductor device which are excellent in adhesion to a lead frame and reliability in moisture resistance after moisture absorption soldering. It is to provide a sealing method.

[0008]

The epoxy resin composition for sealing a discrete element contains an epoxy resin and a curing agent as essential components. The present inventor has conducted various studies on the type of epoxy resin in order to solve the above-mentioned problems while using an epoxy resin in accordance with general requirements. As a result, the inventors have obtained the prospect that the above-mentioned problems can be solved by employing an epoxy resin having a specific structure, and have completed the present invention.

That is, the epoxy resin composition for sealing according to the present invention is an epoxy resin composition containing an epoxy resin and a curing agent, wherein a compound represented by the following structural formula (1) is used as the epoxy resin. It is characterized by being.

[0010]

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[0011] The resin-encapsulated semiconductor device according to the present invention comprises:
The epoxy resin composition according to the present invention is used as an epoxy resin composition for sealing a discrete element. In this case, although the type of the semiconductor device is not limited, for example, the semiconductor device has a three-phase structure in which a discrete element is a wireless type surface mount diode and a resin layer is interposed between an anode and a cathode. At times, the epoxy resin composition is particularly preferably employed.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (Epoxy resin composition) As the epoxy resin, an epoxy resin represented by the following structural formula (1) is always used, but other epoxy resins may be used in combination.

[0013]

Embedded image

The epoxy resin represented by the above structural formula (1) is available from Dainippon Ink and Chemicals, Inc. EXA7200,
It is commercially available from Nippon Chemical Co., Ltd. The amount of the epoxy resin represented by the structural formula (1) is preferably 20 to 100% by weight based on the entire epoxy resin used. If the amount is less than 20% by weight, the effect of improving the moisture resistance, the effect of improving the adhesion to the lead frame, or the effect of improving the adhesion to the inner sealing material is reduced.

The epoxy resin used in combination with the epoxy resin represented by the structural formula (1) is not particularly limited as long as it has two or more epoxy groups in one molecule. Is preferably relatively less colored.
As a preferred example, an orthocresol type, a bisphenol type, a bromine-containing type naphthalene type epoxy, or the like can be used in combination. These may be used alone or in combination.

The curing agent is not particularly limited as long as it reacts with the epoxy resin. However, a curing agent having relatively little coloring is preferable for sealing the optical semiconductor. Preferred examples include phenol novolak, cresol novolak,
Phenol aralkyl, naphthol aralkyl and other various polyhydric phenol compounds can be used. When another curing agent is used in combination, it is preferable that the amount of the curing agent is limited to 50% by weight or less of the whole curing agent.

The mixing ratio of the curing agent is as follows.
It is preferable to set the equivalent of the curing agent in the range of 0.5 to 1.5 with respect to the equivalent, particularly preferably 0.7 to 1.0.
It is. If the equivalent of the curing agent is less than 0.7, the releasability will be poor, and if it exceeds 1.0, the moisture absorption will increase and the reliability tends to deteriorate. In the epoxy resin composition, a curing accelerator is usually used for promoting the curing. The curing accelerator is not particularly limited as long as it has an action of accelerating the reaction between the epoxy resin and the curing agent, but a relatively less colored one is preferred. Preferred examples include organic phosphines such as triphenylphosphine; tertiary amines such as diazabicycloundenecene; 2-methylimidazole;
Imidazoles such as -phenylimidazole and the like can be used. These may be used alone or in combination.

It is preferable that the compounding ratio of the curing accelerator is 0.05 to 1.0% by weight based on the whole sealing resin. If the amount of the curing accelerator is less than 0.05% by weight, the gelation time tends to be slow, and the curing workability tends to be significantly reduced.
This is because curing proceeds rapidly, and as a result, heat generation may increase, causing cracks and foaming.

The resin encapsulation with the epoxy resin composition is usually performed using a mold, and in order to facilitate the demolding, the epoxy resin composition according to the present invention is mixed with a release agent. Preferably. As the release agent, for example,
Natural carnauba-based, higher fatty acid, polyethylene-based wax and the like can be used, and they may be used alone or in combination of two or more. Specifically, carnauba wax, stearic acid, montanic acid, carboxyl group-containing polyolefin and the like are preferably used. These may be used alone or in combination. The mixing ratio of the release agent is preferably 0.05 to 1.5% by weight of the whole composition.

[0020] The effect of increasing the amount is exhibited, and
In order to make the rack less likely to occur,
Inorganic fillers should be used even in epoxy resin compositions
Is preferred. As the inorganic filler, it is particularly limited
None, but fused silica, crystalline silica, alumina, silicon nitride
Element, etc., which are used alone.
Or they may be used together. Filling ratio of composition
It is preferably 65 to 90% by weight of the whole. Especially,
The coefficient of linear expansion of the entire composition is 1.1 to 5 (× 10 ^-Five/ ℃)
It is preferable to determine the compounding amount so as to fall within the range.

The epoxy resin composition for sealing according to the present invention may optionally contain a coloring agent, a low-stressing agent, a flame retardant, a silane coupling agent, a silicone flexible agent and the like in an appropriate amount. . Examples of the coloring agent include carbon black and titanium oxide. When encapsulating an optical semiconductor, especially as an inner encapsulant for multiple molds,
It is preferable not to add a colorant that reduces the light transmittance. Examples of the low stress agent include silicone gel, silicone rubber, silicone oil and the like. Examples of the flame retardant include antimony trioxide, a halogen compound, a phosphorus compound and the like. The colorant, the stress reducing agent, the flame retardant and the like may be used in combination of two or more.

The epoxy resin composition of the present invention can be produced by uniformly mixing the above-mentioned components with a mixer, a blender or the like, and then heating and kneading with a roll, a kneader or the like. After kneading, if necessary, the mixture may be cooled and solidified, and may be pulverized into powder or the like. The order of compounding the components is not particularly limited. More specifically, the epoxy resin composition of the present invention is, for example, a three-roll or the like after melt-mixing or melt-mixing an epoxy resin, a curing agent, a curing accelerator, a release agent, a filler, and other components. The mixture can be produced by cooling and solidifying the mixture, pulverizing the mixture, and, if necessary, compressing the mixture into tablets. When the property is liquid at room temperature, it can be produced by dissolution mixing or melt kneading. (Encapsulation of a semiconductor device) The epoxy resin composition thus obtained is prepared by transfer molding a tablet in the case of a solid using a mold, and casting, potting, printing in the case of a liquid. By casting and curing by the method, a discrete element mounted on a lead frame of an optical semiconductor device or another semiconductor device can be sealed.

As the lead frame, a lead frame made of copper or a copper alloy in terms of electric conductivity, and a lead frame made of a 42 alloy alloy in terms of a coefficient of thermal expansion are generally used. Since these lead frames have low adhesion to bonding wires such as gold wires, the parts of the lead frame to be connected to the bonding wires are pre-plated with silver or gold, and then connected to the bonding wires. We try to improve reliability. Copper-based lead frames are often plated with nickel or silver.

The semiconductor device according to the present invention is applicable when the discrete element is a wireless type surface mount diode and has a three-phase structure in which a resin layer is interposed between an anode and a cathode. It is particularly preferable to apply the epoxy resin composition. The semiconductor device according to the present invention, by applying the epoxy resin composition according to the present invention, is excellent in moisture resistance reliability and moldability in a transistor field which has not been particularly regarded until now, and particularly in a surface mount mini transistor field. In this case, it is possible to obtain the effect of excellent moisture resistance after soldering and excellent moldability in the field of large power transistors.

The semiconductor device according to the present invention is the copper-based frame whose lead frame may be plated on the surface, wherein the epoxy resin composition has a coefficient of linear expansion of 1.1 × 10 ^−5. / ° C to 2.5 × 10 ^-5 / ° C, it is easy to obtain particularly excellent moisture resistance effect. In the semiconductor device according to the present invention, when the epoxy resin composition of the present invention is used as the inner sealing material of the multiple mold, the adhesion to the lead frame is improved, and the moisture resistance after soldering is improved. When the epoxy resin composition of the present invention is used as an outer sealing material, the adhesion to a lead frame is improved. In addition, when the epoxy resin composition of the present invention is used as the inner sealing material and the outer sealing material, the adhesion to the lead frame is improved, and the adhesion between the inner sealing material and the outer sealing material is improved. And the moisture resistance after soldering is further improved.

[0026]

EXAMPLES (Examples 1 to 5 and Comparative Examples 1 to 4: Encapsulation of Surface Mount Diodes) Epoxy resin compositions were manufactured according to the formulations shown in Tables 1 and 2, and semiconductor devices were encapsulated.
The epoxy resin (A) has the above structural formula (1) (n = 0 to 5 in the formula), and the units in the formulations in Tables 1 and 2 are on a weight basis. Tables 1 and 2 also show the properties of each epoxy resin composition, that is, the coefficient of linear expansion, the glass transition temperature, the flexural modulus and the moisture absorption.

The manufacturing conditions for the epoxy resin composition were as follows, and the semiconductor sealing conditions were as follows. (Production conditions of epoxy resin composition) Each component was uniformly mixed by a mixer or the like, and then kneaded by a roll, a kneader or the like. That is, the mixture was kneaded at 85 ° C. for 5 minutes using a biaxial heating roll, and then cooled. Then, it was pulverized with a pulverizer to obtain a sealing material. (Sealing condition) A surface mount diode (Schottky diode) copper frame was used as a semiconductor element. Using a transfer press, the above diode was sealed and molded at a molding pressure of 70 kg / cm ^{2 at a} molding temperature of 175 ° C. and a molding time of 90 seconds to obtain a molded product of a semiconductor device.

Further, for each epoxy resin composition,
A moisture resistance evaluation test was performed by the following evaluation method, and the results are also shown. (Moisture Resistance Evaluation Test) The resin-encapsulated semiconductor device obtained as described above was pretreated at 85 ° C., 85% RH and 72 hr, and then subjected to solder immersion at 260 ° C. × 10 s. PCT and TCT tests were performed. Here, PC
The T test is an evaluation test for counting the number of circuit failures after processing at 2 atmospheres, 121 ° C. and 300 hours.
CT test is -65 ° C, 30 minutes → room temperature, 5 minutes → 150
This is an evaluation test for counting the number of circuit failures when 1000 cycles are performed with one cycle at 30 ° C. for 30 minutes.

[0029]

[Table 1]

[0030]

[Table 2]

(Examples 6 to 11 and Comparative Examples 5 to 8: Encapsulation of Surface Mounted Transistor) Epoxy resin compositions were manufactured according to the formulations shown in Tables 3 and 4, and semiconductor devices were encapsulated. The epoxy resin (A) has the above structural formula (1), and the units in the formulations in Tables 3 and 4 are on a weight basis. Tables 3 and 4 also show the properties of each epoxy resin composition, that is, the coefficient of linear expansion, the glass transition temperature, the flexural modulus and the moisture absorption.

The manufacturing conditions for the epoxy resin composition were as follows, and the semiconductor sealing conditions were as follows. (Production conditions of epoxy resin composition) Each component was uniformly mixed by a mixer or the like, and then kneaded by a roll, a kneader or the like. That is, the mixture was kneaded at 85 ° C. for 5 minutes using a biaxial heating roll, and then cooled. Then, it was pulverized with a pulverizer to obtain a sealing material. (Sealing condition) A TO-3P type power transistor Ni plating frame was used as a semiconductor element. Using a transfer press, the above-described transistor was sealed and molded under the following molding conditions to obtain a molded semiconductor device. After molding, 1
Treated at 75 ± 3 ° C. for 6 hours.

Molding temperature: 175 ± 5 ° C. Injection pressure: 120 ± 20 kgf / cm ² Injection speed: 7 to 12 sec Cure time: 90 ± 10 sec Further, for each epoxy resin composition, a moisture resistance reliability evaluation test was performed by the following evaluation method. And an adhesion evaluation test, and the results are shown in Tables 3 and 4. (Appearance of Package Immediately after Molding) The resin-encapsulated semiconductor device obtained as described above was observed for appearance immediately after molding, and those having welds, pinholes, or blisters were counted as defectives. (Moisture Resistance Reliability Evaluation Test) The resin-encapsulated semiconductor device obtained as described above was pretreated at 85 ° C., 85% RH and 72 hr, and then subjected to 260 ° C. × 10 s solder immersion. A PCT test and a TCT test were performed. Here, the PCT test is an evaluation test for counting the number of circuit failures after processing at 2 atmospheres and 121 ° C. for 200 hours, and the TCT test is −65 ° C., 30 minutes → normal temperature, 5 minutes → This is an evaluation test for counting the number of circuit failures when 1000 cycles are performed with 150 ° C. and 30 minutes as one cycle. (Adhesion evaluation test) Pudding molded product with an adhesion area of 1 cm ² (Frustoconical molded product: bottom diameter 11.3 mm, height 1)
(0.0 mm) was transfer-molded on a flat metal plate under the above-mentioned molding conditions. Thereafter, after molding, the plate was treated at 175 ± 3 ° C. for 6 hours, and then the shear strength was measured.

[0034]

[Table 3]

[0035]

[Table 4]

(Examples 12 to 14 and Comparative Examples 9-1)
0: Multiple mold sealing) Epoxy resin with the composition shown in Table 5
The composition was manufactured, and the semiconductor device was sealed. Epoxy
The resin (A) has the structural formula (1), and
The unit in the formulation of 5 is based on weight. Table 5 shows each
Properties of the epoxy resin composition, that is, coefficient of linear expansion, glass
Transition temperature, flexural modulus, moisture absorption, and adhesive strength
did. Adhesion strength is measured at the test speed using an autograph measuring machine.
2mm / min, weight 100kgf / cm ^TwoUnder the condition
Was.

The production conditions for the epoxy resin composition were as follows, and the semiconductor encapsulation conditions were as follows. (Production conditions of epoxy resin composition) Each component was uniformly mixed by a mixer or the like, and then kneaded by a roll, a kneader or the like. That is, the mixture was kneaded at 85 ° C. for 5 minutes using a biaxial heating roll, and then cooled. Then, it was pulverized with a pulverizer to obtain a sealing material. (Sealing Conditions) A comb-shaped aluminum wiring element was used as a semiconductor element, and transfer molding was performed under the following molding conditions to obtain a molded article of a semiconductor device (16 DIP package). After molding, it was treated at 175 ± 3 ° C. for 6 hours.

Molding temperature: 175 ± 5 ° C. Injection pressure: 70 ± 20 kgf / cm ² Injection speed: 7 to 12 sec Cure time: 90 ± 10 sec Further, for each epoxy resin composition, a moisture resistance reliability evaluation test was performed by the following evaluation method. And an adhesion evaluation test, and the results are shown in Table 6. (Moisture Resistance Reliability Evaluation Test) The resin-encapsulated semiconductor device obtained as described above was pretreated at 85 ° C., 85% RH and 72 hr, and then subjected to 260 ° C. × 10 s solder immersion. A PCT test and a TCT test were performed. Here, the PCT test is an evaluation test for counting the number of circuit failures after processing at 2 atmospheres and 121 ° C. for 300 hours, and the TCT test is −65 ° C., 30 minutes → normal temperature, 5 minutes → This is an evaluation test for counting the number of circuit failures when 1000 cycles are performed with 150 ° C. and 30 minutes as one cycle. (Adhesion evaluation test) Pudding molded product with an adhesion area of 1 cm ² (Frustoconical molded product: bottom diameter 11.3 mm, height 1)
(0.0 mm) was transfer-molded on a flat metal plate under the above-mentioned molding conditions. Thereafter, after molding, the plate was treated at 175 ± 3 ° C. for 6 hours, and then the shear strength was measured.

The adhesion between the inner sealing material and the outer sealing material was also evaluated. Transfer molding a molded product (50 mm x 80 mm) with a thickness of 1.5 mm using the inner sealing material under the above-mentioned molding conditions, and then treating at 175 ± 3 ° C for 6 hours, and then superimposing the molded product on one surface side to form an outer 1. Use sealing material.
A 5 mm thick molded product (50 mm x 80 mm) was transfer molded under the above molding conditions, then treated at 175 ± 3 ° C for 6 hours, and then split with a nipper to determine the state of interface destruction between the inner sealing material and the outer sealing material. Observed.

[0040]

[Table 5]

[0041]

[Table 6]

[0042]

The sealing epoxy resin composition of the present invention is basically the same as the conventional epoxy resin composition, but has high moisture resistance reliability. This epoxy resin composition has excellent moisture resistance reliability in the field of small signals (diodes, transistors, etc.) for surface mounting, which has not been regarded as important so far, and particularly, has excellent moisture resistance reliability after moisture absorbing solder processing. Excellent adhesion to the lead frame or adhesion between the inner sealing material and the outer sealing material in multiple molds.

In the epoxy resin composition of the present invention, when the epoxy resin accounts for 20 to 100% by weight of the total epoxy resin used, the above-mentioned effect of further improving the moisture resistance reliability or the adhesion is exhibited. Particularly when the epoxy resin composition of the present invention is used for at least the inner sealing material of the inner sealing material and the outer sealing material of the multiple mold, the adhesion between the inner sealing material and the outer sealing material is further improved. Increase.

When the epoxy resin composition of the present invention is used particularly for encapsulating diodes and transistors, it has excellent moisture resistance reliability and moldability in the fields of diodes and transistors, which have not been regarded as particularly important until now. In the field of mounted mini-transistors, it has excellent moisture resistance reliability after soldering, and in the field of large power transistors, it has excellent moldability. The resin-encapsulated semiconductor device according to the present invention has high humidity resistance because the semiconductor is encapsulated using the epoxy resin composition according to the present invention. In a semiconductor device having a three-layer structure (anode, resin, cathode) of a surface-mounted diode wireless type, the effect of the epoxy resin composition is particularly remarkable.

The lead frame of the semiconductor device according to the present invention is a copper-based frame whose surface may be plated, and the epoxy resin composition has a linear expansion coefficient of 1.1 × 10 ⁻⁵ / ° C. or more. When it is 2.5 × 10 ⁻⁵ / ° C., it is particularly excellent in moisture resistance.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Takayuki Ichikawa 1048 Kadoma Kadoma, Osaka Pref.Matsushita Electric Works, Ltd.

Claims (9)

[Claims] An epoxy resin for sealing a discrete element, wherein the epoxy resin composition comprises an epoxy resin and a curing agent, wherein the epoxy resin is a compound represented by the following structural formula (1). Resin composition. Embedded image 2. The epoxy resin composition for sealing a discrete element according to claim 1, wherein the epoxy resin represented by the structural formula (1) accounts for 20 to 100% by weight of the total epoxy resin used. 3. The discrete element encapsulation is a multi-mold encapsulation and is for at least an inner encapsulant of an inner encapsulant and an outer encapsulant of a multi-mold.
The epoxy resin composition for sealing a discrete element according to claim 1 or 2. 4. The epoxy resin composition for sealing a discrete element according to claim 1, wherein the discrete element is a diode or a transistor. 5. A resin-sealed semiconductor device in which a discrete element is sealed with the epoxy resin composition according to any one of claims 1 to 4. 6. The resin-encapsulated semiconductor device according to claim 5, wherein said discrete element is surface-mounted on a wiring board. 7. The discrete element is multi-mold sealed, and the epoxy resin composition is used as at least an inner sealing material of an inner sealing material and an outer sealing material of the multi-mold. 6. The resin-sealed semiconductor device according to 5. 8. The semiconductor device according to claim 5, wherein the discrete element is a wireless type surface mount diode and has a three-phase structure in which a resin layer is interposed between an anode and a cathode. Resin-sealed semiconductor device. 9. The lead frame of the semiconductor device is a copper-based frame whose surface may be plated, and the epoxy resin composition has a coefficient of linear expansion of 1.1 × 1.
9. The method according to claim 5, wherein the temperature is 0 ^-5 / ° C. to 2.5 × 10 ^-5 / ° C.
The resin-encapsulated semiconductor device according to any one of the above.