JPH11269350A - Semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject device having excellent moistureproof reliability, moldability and high frequency properties by sealing semiconductor elements with an epoxy resin composition including fluororesin powder in a specified ratio. SOLUTION: This device is obtained by sealing semiconductor elements by a well-known molding method such as ordinary low-pressure transfer molding with an epoxy resin composition including 10-80 wt.% fluororesin powder preferably polytetrafluoroethylene or the like based on the whole epoxy resin composition. The above-mentioned fluororesin powder has preferably a maximum particle diameter of <=200 μm, an average particle diameter of 5-40 μm and a melting point of >=100 deg.C. The above mentioned epoxy resin composition comprises an epoxy resin such as preferably a crystalline biphenyl-type epoxy resin having an epoxy equivalent of 150-230 g/eq, and as a hardner component, a phenolic resin such as preferably a phenol-aralkyl resin having a hydroxyl equivalent of 100-250 g/eq and others.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device in which a semiconductor element is resin-sealed with a low dielectric constant epoxy resin composition whose relative dielectric constant is significantly reduced.

[0002]

2. Description of the Related Art Conventionally, a resin-encapsulated semiconductor device in which a semiconductor element is resin-molded by transfer molding is excellent in reliability, mass productivity, low cost, etc., and is therefore a ceramic-encapsulated semiconductor device. Widely used with semiconductor devices.

[0003]

However, in recent years, the operating frequency has tended to increase further in order to improve the functions and performance of semiconductor devices such as microprocessors. Also,
In the field of information and communication, small electronic devices such as mobile phones and PHSs have come to use frequency bands close to gigahertz with respect to their frequency bands, and communication using a two-digit gigahertz band has also been developed. Is being promoted. As described above, as the frequency of semiconductors increases, semiconductor devices that require high reliability are:
At present, ceramic-encapsulated semiconductor devices with excellent high-frequency characteristics are widely used, but low-cost resin-encapsulated semiconductor devices with excellent mass productivity and various reliability are being considered. . For this reason, development of a low dielectric constant epoxy resin composition for a mold used in a resin-sealed semiconductor device is required.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and in a situation where the frequency of a semiconductor device is increasing, the resin sealing with an epoxy resin composition corresponding to a high frequency and having a reduced dielectric constant is performed. It is an object of the present invention to provide a stopped semiconductor device.

[0005]

In order to achieve the above object, a semiconductor device of the present invention comprises an epoxy resin composition containing a fluororesin powder in a proportion of 10 to 80% by weight of the entire epoxy resin composition. Is used to seal the semiconductor element.

The present inventors have conducted a series of studies on an epoxy resin composition used for resin sealing in order to obtain a resin-sealed semiconductor device having excellent high-frequency characteristics. As a result of repeated studies aimed at reducing the relative dielectric constant of the cured product of the epoxy resin composition, it was found that the above-mentioned object was achieved when the epoxy resin composition was mixed with the fluororesin powder at a specific ratio. The invention has been reached. That is, conventionally, JP-A-55-5928 and JP-A-58-689 have been disclosed.
For example, as disclosed in JP-A-55-55 and JP-A-59-149038, an epoxy resin composition containing a fluororesin-based powder for semiconductor encapsulation has been proposed. Since the purpose of use of the fluororesin powder is different from the present invention, the compounding amount is extremely small,
The purpose of the present invention cannot be achieved by conventional use, and the present invention has been found from such a completely different viewpoint.

[0007] Among the above fluororesin powders,
Polytetrafluoroethylene has a melting point of 320 to 330
It has the highest heat resistance at ℃ and the extremely high melt viscosity compared to other fluororesins, so it has excellent shape stability and is suitable as a filler for epoxy resin compositions.

[0008]

Next, an embodiment of the present invention will be described in detail.

The epoxy resin composition used in the present invention can be obtained by using an epoxy resin and a phenol resin as a curing agent component, and is usually in the form of a powder or a tablet obtained by compressing the powder. . Alternatively, after the resin composition is melt-kneaded, the resin composition is formed into granules such as substantially columnar granules.

The epoxy resin is not particularly limited as long as it is solid at room temperature, and includes conventionally known epoxy resins such as biphenyl type epoxy resin and cresol novolak type epoxy resin. Above all, from the viewpoint that the melt viscosity can be reduced and the melt viscosity becomes low after compounding the filler, specifically, the epoxy equivalent is 150 to 230 g / e.
A crystalline biphenyl type epoxy resin having a melting point of 60 to 160 ° C. at q is preferably used.

As the phenol resin, phenol novolak, cresol novolak, bisphenol A
Examples include type novolak, naphthol novolak, and phenol aralkyl resin, and it is particularly preferable to use those having low viscosity. Among them, the hydroxyl equivalent is 80-30.
It is preferable to use one having a softening point of 120 ° C. or less at 0 g / eq. Particularly preferably, the hydroxyl equivalent is 100 to 2
50 g / eq, softening point 60-110 ° C. When a biphenyl type epoxy resin is used as the epoxy resin, it is preferable to use a phenol aralkyl resin as a curing agent.

It is preferable that the mixing ratio of the epoxy resin and the phenol resin is such that the hydroxyl group equivalent in the phenol resin is in the range of 0.5 to 1.6 with respect to 1 equivalent of the epoxy group in the epoxy resin. More preferably 0.8-1.
2 is set.

Usually, an inorganic filler may be used in the epoxy resin composition for encapsulating a semiconductor together with the epoxy resin and the phenol resin. As the inorganic filler, various inorganic fillers conventionally used,
For example, silica powder, tankal, titanium white and the like can be mentioned. Among them, spherical silica powder, milled silica powder,
Crushed silica powder is preferably used, and it is particularly preferable to use fused spherical silica powder. And it is preferable to use a thing with a maximum particle diameter of 100 micrometers or less as said inorganic filler. In addition, it is preferable to use those having an average particle size of 1 to 20 μm together with the maximum particle size.

The content of the inorganic filler is preferably set in the range of 0 to 60% by weight of the entire epoxy resin composition. It is more preferably 0 to 30% by weight, particularly preferably 0 to 20% by weight. That is, when the content of the inorganic filler exceeds 60% by weight, the melt viscosity of the encapsulating resin increases, so that the filling property deteriorates.

The epoxy resin composition used in the present invention uses a fluororesin powder having a maximum particle size of 200 μm or less and a melting point of 200 ° C. or more. More preferably, the melting point is 100 ° C. or higher. Also, together with the maximum particle size,
It is preferable to use one having an average particle size of 1 to 50 μm, particularly preferably 5 to 40 μm. Further, the fluororesin powder includes a secondary particle obtained by heat-treating the fluororesin powder to cause fusion and aggregation. Examples of the fluororesin powder include polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkoxy copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and polychlorotrifluoroethylene (PCT).
FE) and fluororesin powders such as tetrafluoroethylene-ethylene copolymer (ETFE). Among them, it is particularly preferable to use a PTFE resin powder having the largest fluorine content from the viewpoint of shape stability at high temperatures.

The content of the fluororesin powder must be set in the range of 10 to 80% by weight of the whole epoxy resin composition. It is more preferably from 20 to 75% by weight, particularly preferably from 40 to 70% by weight. That is, if the content of the fluororesin powder is too small, such as less than 10% by weight, the effect of reducing the relative dielectric constant of the cured epoxy resin composition itself is insufficient, and if the content exceeds 80% by weight, the content is too large.
This is because the melt viscosity during low-pressure transfer molding becomes too high.

The epoxy resin composition used in the present invention may contain, in addition to the above epoxy resin, phenolic resin, inorganic filler and fluororesin powder, a curing accelerator, a stress reducing agent, a pigment, Various additives such as a release agent, a flame retardant, and a coupling agent can be appropriately compounded.

As the curing accelerator, conventionally known curing accelerators, for example, 1,8-diaza-bicyclo (5,4,0)
Examples include tertiary aminos such as undecene-7 and triethylenediamine, imidazoles such as 2-methylimidazole, and phosphorus-based curing accelerators such as triphenylphosphine and tetraphenylphosphonium tetraphenylborate.

Examples of the stress reducing agent include silicone compounds such as side chain ethylene glycol type dimethyl siloxane and acrylonitrile-butadiene rubber.

Examples of the pigment include carbon black and titanium oxide. Further, as the release agent,
Examples include polyethylene wax, carnauba wax, and fatty acid salts. Further, examples of the flame retardant include a brominated epoxy resin, and a flame retardant auxiliary such as antimony trioxide is used.

The coupling agent is γ-
Glycidoxypropyltrimethoxysilane, β- (3,
Silane coupling agents such as 4-epoxycyclohexyl) ethyltrimethoxysilane.

The epoxy resin composition used in the present invention can be obtained, for example, as follows. That is, a predetermined amount of epoxy resin, phenolic resin, inorganic filler and fluororesin powder, and other additives such as the above-mentioned curing accelerator, release agent, pigment, etc. are blended, and a hot roll, extruder, kneader or the like is used. After sufficiently mixing by melt dispersion, it can be obtained by cooling, pulverizing, and optionally compression-molding into a tablet shape.

The method for encapsulating a semiconductor device using the epoxy resin composition thus obtained is not particularly limited, and can be performed by a known molding method such as ordinary low pressure transfer molding.

Next, examples will be described together with comparative examples.

First, the following materials were prepared. [Epoxy resin a] o-cresol novolak epoxy resin (epoxy equivalent 195)

[Epoxy resin b] 3,3 ', 5,5'-
Tetramethylbiphenyl diglycidyl ether (epoxy equivalent 192)

[Phenol resin c] Phenol novolak resin (hydroxyl equivalent 106)

[Phenol resin d] Phenol aralkyl resin (hydroxyl equivalent 170)

[Silica powder] Fused spherical silica powder (average particle size: 15 μm)

[Phosphorus-based curing accelerator] triphenylphosphine

[Flame retardant] Brominated phenol novolak epoxy resin (epoxy equivalent 280)

[Flame retardant aid] Antimony trioxide

[Releasing agent] Carnauba wax

[Pigment] Carbon black

[Silane coupling agent] β- (3,4-
Epoxycyclohexyl) ethyltrimethoxysilane

[PTFE powder α] average particle size 0.3 μm,
Maximum particle size of 200 μm or less, true specific gravity of about 2.2, melting point of 320
° C

[PTFE powder β] Secondary particle obtained by heat-treating the above-mentioned PTFE powder α and fusing and aggregating the primary particles to an average particle diameter of 7 μm.

[PTFE powder γ] The above-mentioned PTFE powder α is subjected to a heat treatment to form primary particles having an average particle diameter of 30 μm.
Secondary particles fused and aggregated up to

[0039]

Examples 1 to 13 and Comparative Examples 1 to 8 The above components were blended at the ratios shown in Tables 1 to 3 below.
The mixture was melt-kneaded for 5 minutes with a heated roll, cooled, and then pulverized to obtain a 10-mesh pass epoxy resin composition powder.

[0040]

[Table 1]

[0041]

[Table 2]

[0042]

[Table 3]

Using the thus obtained epoxy resin composition powder, transfer molding was performed under the conditions of a molding pressure of 70 kg / cm ² , a mold temperature of 175 ° C. and a molding time of 2 minutes, and post-curing was performed at 175 ° C. By carrying out for 5 hours, a disk-shaped cured body having a thickness of 3 mm and a diameter of 50 mm was produced. Then, the diameter of the main electrode is 30 mm with silver paste,
After preparing a silver electrode having a guard electrode diameter of 32 mm and a counter electrode diameter of 45 mm, a measurement frequency of 1 MHz and a temperature of 25 ° C.
The relative capacitance was calculated by measuring the capacitance and conductance of the cured product. The results are shown in Tables 4 to 6 below.

Further, a silicon chip (TEG) having aluminum wiring on the surface thereof, which is die-bonded to a 42 alloy lead frame with a commercially available epoxy silver paste, using the epoxy resin composition powder, is transfer-molded (condition: gold). Mold temperature 175 ± 5 ℃, injection pressure 70 ± 5kg
/ Cm ² ), and post-curing was carried out at 175 ° C. for 5 hours to produce a 16-pin dual in-line package (16 pin DIP) type resin mold package semiconductor device. The semiconductor device was left in a watertight container at 121 ° C. × 2 atm for a predetermined time (200 hours, 500 hours, 1500 hours) to perform a moisture resistance test. And the aluminum wiring resistance on the silicon chip is 100
A case of Ω or more was evaluated as defective, and the number of defective packages with respect to the total number of packages put into the moisture resistance test was counted. The results are shown in Tables 4 to 6 below.

Further, fluidity was evaluated using the epoxy resin composition powder. That is, first, a tablet (diameter: 24.5) was prepared using the epoxy resin composition powder.
mm × 20 mm in thickness). The tablet was inserted into a spiral spiral flow mold pot heated to a specified temperature (175 ± 5 ° C.) in advance, and clamped to increase the mold clamping pressure to 210 ± 10 kg / cm ² . Next, when the mold clamping pressure reaches 210 ± 10 kg / cm ² , the epoxy resin composition is injected with a plunger, and after the injection pressure reaches 70 ± 5 kg / cm ² , 1
An injection pressure was applied for 50 minutes. Next, the plunger pressure of the transfer molding machine was released, and the mold clamping pressure was released to open the mold. Then, the spiral length of the molded product was measured up to a minimum of 2.5 mm, and was determined as a spiral flow value (E
MMI 1-66). The results are shown in Tables 4 to
It is shown in Table 6.

[0046]

[Table 4]

[0047]

[Table 5]

[0048]

[Table 6]

From the results of Tables 4 to 6, the relative permittivity of the product of the example is lower than that of the product of the comparative example, and the effect of reducing the relative permittivity is apparent. Further, the spiral flow value of the product of Example was an appropriate value, and there was no problem with respect to fluidity. Furthermore, in the moisture resistance test, no defective package was generated after leaving for 200 hours, 500 hours or 1500 hours, and it was found that the device was excellent in moisture resistance reliability.

On the other hand, Comparative Examples 1 and 2 in which PTFE powder was not blended had excellent moisture resistance reliability without any problem with respect to the moisture resistance test, but had a high relative dielectric constant, and further had a mold. There were many Usubari inside. Further, in Comparative Examples 3 and 4 in which the content of the PTFE powder was less than 10% by weight, the moisture resistance reliability was excellent as in Comparative Examples 1 and 2, but the relative dielectric constant was reduced. Was not obtained and the relative dielectric constant was high. Further, the products of Comparative Examples 5 and 6 had extremely low spiral flow values and were inferior in moldability, so that cured products and semiconductor packages could not be actually molded. Further, Comparative Example 7, which is the remaining comparative example product,
Similarly, for the eight products, the cured product and the semiconductor package could not be formed.

[0051]

As described above, the semiconductor device of the present invention is resin-sealed with the epoxy resin composition containing the fluororesin powder at a specific ratio. As described above, since the epoxy resin composition used for resin encapsulation is a low dielectric constant epoxy resin composition in which the relative dielectric constant is significantly reduced, the resin is encapsulated by a cured body of the epoxy resin composition. Semiconductor devices have excellent high-frequency characteristics as well as excellent moisture resistance reliability and moldability.

From the above, the semiconductor device of the present invention is not only characterized by the conventional features of being excellent in various reliability and mass productivity, being inexpensive, but also being resin-encapsulated for high frequency operation. Semiconductor device, which can be said to be an alternative to the conventional ceramic sealed semiconductor device.

Claims (3)

[Claims] 1. A semiconductor device in which a semiconductor element is encapsulated with an epoxy resin composition containing a fluororesin powder in a proportion of 10 to 80% by weight of the entire epoxy resin composition. 2. The semiconductor device according to claim 1, wherein said fluororesin is polytetrafluoroethylene. 3. An epoxy resin composition for semiconductor encapsulation, comprising a fluororesin powder in a proportion of 10 to 80% by weight of the whole epoxy resin composition.