JPH06326220A - Resin-sealed semiconductor device - Google Patents

Abstract

PURPOSE:To form a resin composition with biphenyl type epoxy resin and polymerization products of phenol and aralkyl ether and organic boron salt of an organic phosphine group component and an inorganic filler and thereby prevent the generation of internal defects, such as voids. CONSTITUTION:Biphenyl type epoxy resin represented in a formula 1 provides more than two epoxy resin groups and biphenyl skeletons per molecule, (in the formula, R stands for hydrogen atom or a methyl group where it is acceptable even if they are different from each other and (n) stands for an integral number from 0 to 2.) A curing agent, which is represented by a formula II is a polymerization product of phenol and aralkyl having two hydrogen groups per molecule and blended by equivalent weight from 0.5 to 1.5 for the epoxy resin. (The letter (m) stands for an integral number from 1 to 10 in the formula.) A cure promotion agent, which is represented by Formula III is organic boron salt of an organic phosphite group compound. (R<1> to R<6> stands for a phenol group, a butyr group and a cyclohexane ring and they are acceptable even if they are different from each other. 50 to 90 volume % of inorganic filler is blended with the whole resin composition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin-encapsulated semiconductor device which is encapsulated with an epoxy resin composition and is particularly excellent in solder reflow resistance.

[0002]

2. Description of the Related Art As a packaging system for semiconductor elements such as transistors, ICs and LSIs, a resin encapsulation system which is excellent in mass productivity is widely used. As an encapsulating material, a phenol novolac resin is used as a curing agent in an o-cresol novolac type epoxy resin which is excellent in moldability, hygroscopicity and heat resistance, and an epoxy resin composition in which a filler and various additives are mixed is widely used. It is used.

By the way, in response to needs such as miniaturization, weight reduction, and high performance of various electronic devices, semiconductor devices used therefor are strongly required to have high packaging density, and recently, surface mounting type semiconductors suitable for high density packaging. Devices are becoming mainstream. Moreover, packages are becoming smaller and thinner year after year. Along with that, the resin sealing layer is significantly thinned.

In particular, TSOP (Thin Small Outline)
Package), TSOJ (Thin Small Outline J-lead
Package), TQFP (Thin Quad Flat Packag
The demand for thin surface mount packages with a thickness of around 1 mm such as e) is increasing, and the development of ultra-thin surface mount packages with a thickness of 0.5 mm or less is also underway.

However, as the resin sealing layer becomes thinner, water easily enters the package, and the mechanical strength of the resin layer becomes smaller, so that the package may be damaged by a small force. become. Also, for surface mount semiconductors, soldering (mounting) by infrared rays or vapor reflow method is performed on the printed circuit board.
The package is exposed to high temperatures above 200 ° C. Therefore, when the package absorbs moisture, the absorbed moisture rapidly evaporates, and the vapor pressure swells the package, causing peeling at the interface between the chip and the sealing resin and cracking in the package. As a result, in the semiconductor device, the element characteristics are apt to change and the aluminum wiring on the element surface is easily corroded, so that various reliability after mounting is deteriorated.

Therefore, it is strongly desired to improve the solder reflow resistance (the crack resistance of the package at the time of solder reflow) in the thin surface-mounting resin-sealed semiconductor device.

There are the following two routes for the moisture to enter the package. One is diffusion and transmission from the resin sealing layer,
The other is penetration from the interface between the lead frame and the sealing material. In order to improve the solder reflow resistance required for the package of the surface mount semiconductor device, the reduction of such invading water is a very important issue.

In order to solve the above problems, various measures have been studied so far, and it has been particularly effective to reduce the moisture absorption and the adhesion of the sealing material. For example, JP-A-3-207714
As disclosed in Japanese Patent Application Laid-Open No. 4-48759 or Japanese Patent Application Laid-Open No. 4-48759, a package is made of an epoxy resin composition composed of an epoxy resin having a biphenyl skeleton and a phenol aralkyl resin curing agent, and Japanese Patent Application Laid-Open No. 4-5022.
No. 3, JP-A-4-199856 or JP-A-4-19
As proposed in Japanese Patent No. 9857, it becomes possible to significantly improve the solder reflow resistance by forming a package from a low hygroscopic epoxy resin composition having a naphthalene skeleton.

[0009]

However, the above-mentioned prior art is considerably effective in improving the solder reflow resistance, but the encapsulating material itself has poor storage stability even at a relatively low temperature near room temperature. However, there is a defect that voids are likely to occur inside the molded product during molding, and it is difficult to obtain a molded product with stable quality. Further, if the sealed product is left at a high temperature, the joint between the aluminum electrode on the surface of the semiconductor element and the gold wire that electrically connects the lead frame is easily corroded in a short time, and the connection reliability is significantly deteriorated. was there.

In view of the above situation, the object of the present invention is to seal with an epoxy resin composition which has few internal defects such as voids and which has excellent solder reflow resistance and connection reliability between the electrode and the gold wire. It is to provide a resin-encapsulated semiconductor device stably.

[0011]

Means for Solving the Problems The inventors of the present invention include various additives such as a filler, a coupling agent, and a release agent, a curing accelerator that is considered to affect the above properties, mixing conditions of each material, and molding. The conditions were carefully studied. As a result, they have found that the above problems can be improved by using a specific curing accelerator, and have reached the present invention. The gist of the present invention is as follows.

(A) General formula [1]

[0013]

[Chemical 4]

(Wherein R represents a hydrogen atom or a methyl group, which may be different from each other, n represents an integer of 0 to 2), and (b) a general formula [2]. ]

[0015]

[Chemical 5]

(Wherein m represents an integer of 1 to 10), (c) a general formula [3].

[0017]

[Chemical 6]

(Wherein R ^{1 to} R ⁶ represent a phenyl group, a butyl group or a cyclohexane ring and may be different from each other), and (d) the composition as a whole. A resin-encapsulated semiconductor device, which is encapsulated with an epoxy resin composition containing 50 to 90% by volume of an inorganic filler.

The epoxy resin represented by the above general formula [1] is a biphenyl type epoxy resin having two or more epoxy groups per molecule and a biphenyl skeleton. In addition, as long as the object of the present invention is not impaired, bisphenol A, F or S type epoxy resin, novolac type epoxy resin, o-cresol novolak type epoxy resin, and polynaphthalene having a naphthalene skeleton, which are generally used for semiconductor encapsulation, are used. A functional epoxy resin, a tri- or tetra (hydroxyphenyl) alkane epoxy resin, an alicyclic epoxy resin, a brominated bisphenol A type epoxy resin, a brominated phenol novolac type epoxy resin and the like may be used in combination.

The curing agent represented by the general formula [2] is 1
It is a polycondensation product of a phenol having at least two hydroxyl groups per molecule and an aralkyl ether, and is 0.5 to 1.5 equivalents, preferably 0.8 to 1.
Add 2 equivalents. If the amount is less than 0.5 equivalents, the curing of the epoxy resin will be insufficient and the cured product will have poor heat resistance, moisture resistance and electrical properties. On the other hand, if it exceeds 1.5 equivalents, the curing agent component becomes excessive and a large amount of phenolic hydroxyl groups remain in the cured resin, resulting in poor electrical properties and moisture resistance. The curing agent may be used in combination with a condensate of a phenol and a aldehyde such as a phenol novolac resin as long as the object of the present invention is not impaired.

The curing accelerator represented by the above general formula [3] is an organic boron salt of an organic phosphine compound. Specific examples include triphenylphosphine / triphenylboron, tributylphosphine / triphenylboron, tricyclohexylphosphine / triphenylboron and the like. These curing accelerators can be used in combination with amines, imidazoles or salts thereof as long as the object of the present invention is not impaired.

The above-mentioned curing accelerator can be used in the same manner as a usual curing accelerator, but in order to reduce voids generated during molding, it is heated and dissolved in the curing agent at 120 ° C. or higher in advance. It is desirable to use. The curing accelerator is 1 to 15 mmol with respect to 100 parts by weight of the epoxy resin,
It is preferable to mix it in the range of 5 to 10 mmol.

Further, the total amount of the resin composition is 50 to 90.
Incorporate a volume% of inorganic filler. The inorganic filler is added for the purpose of improving the thermal expansion coefficient, thermal conductivity, elastic modulus, etc. of the cured product, and if the blending amount is less than 50% by volume, these properties cannot be sufficiently improved, and When the content exceeds the volume%, the viscosity of the resin composition remarkably increases, the fluidity decreases, and molding becomes difficult.

As the inorganic filler, fused silica, crystalline silica, alumina, calcium carbonate, zirconium silicate,
Fine powders of calcium silicate, talc, clay, mica and the like can be used. The average particle size of these fillers is preferably in the range of 0.1 to 30 μm, and when it is less than 0.1 μm, the viscosity of the resin composition increases, and when it exceeds 30 μm, the resin component and the filler are easily separated. However, the cured product becomes non-uniform, the properties of the cured product vary, and the filling property into a narrow gap decreases.

When the filler is blended in an amount of 75% by volume or more, it is preferable that the filler particles have a spherical shape rather than a square shape and that the particle size distribution is in a wide range of 0.1 to 100 μm. Since such a filler easily has a close-packed structure, the viscosity of the material does not increase even if the compounding amount is increased, and a composition having excellent fluidity can be obtained. As such a spherical filler, there is fused silica that is made spherical by dropping silica powder from the upper part of a furnace heated to a high temperature and melting it in the middle.

In the present invention, a softening agent or the like can be used as needed to strengthen the resin cured product and reduce the elastic modulus. A flexible agent that is incompatible with the epoxy resin composition can reduce the elastic modulus of the cured product without lowering the glass transition temperature, so that the butadiene-acrylonitrile-based copolymers or their terminals or side chains can be used. Amino groups, epoxy groups, butadiene-based flexible agents such as modified copolymers having a carboxyl group, acrylonitrile-butadiene-styrene copolymer, and amino groups, hydroxyl groups at the terminal or side chains,
A modified silicone-based elastomer having an epoxy group, a carboxyl group, or the like is used, and a silicone-based flexible agent is particularly effective from the viewpoint of moisture resistance and purity.

The amount of the softening agent blended is preferably 2 to 20% by weight based on the total resin composition. If the blending amount is less than 2% by weight, there is almost no effect on the toughness and low elastic modulus of the cured product. On the other hand, if it exceeds 20% by weight, the fluidity of the resin composition and the mechanical strength at high temperature are remarkably lowered, and the flexible agent is raised on the surface of the cured resin to stain the molding die, which is not preferable.

In addition to the above-mentioned various additives, various silane compounds, titanium compounds, aluminum chelates, aluminum / zirconium compounds can be used as coupling agents for increasing the adhesion between the resin component and the filler. Known additives such as compounds can be used. Further, known compounds such as carnauba wax, montanic acid wax, and polyalkylene wax may be used as a release agent.
Known compounds such as carbon black, titanium oxide, red lead and red iron oxide may be used as the colorant.

The above materials are usually mixed rolls,
A sealing material can be obtained by melting and kneading at 50 to 100 ° C. using an extruder, a kneader or the like.

[0030]

The reason why the semiconductor device of the present invention exhibits excellent solder reflow resistance is considered as follows.

First, the biphenyl type epoxy resin used in the present invention is more hydrophobic in chemical structure than conventional ones, and since the cured product has a high density, packing of the molecular chains becomes dense. Therefore, it is considered that the formed mesh structure does not allow water to easily pass through. Therefore, it is considered that the sealing material using such a resin has low hygroscopicity itself. In addition, such a resin has a low glass transition temperature of the cured product and the resin is flexible,
The residual stress generated by curing is small, and the encapsulating material using the same has excellent adhesiveness to chips and lead frames, and it is considered that the amount of water that enters the package from these interfaces is greatly reduced.

It is considered that the reason why the solder reflow resistance is remarkably improved is that the amount of water entering the package is significantly reduced as described above.

Particularly, when the curing accelerator represented by the general formula [3] is used, excellent solder reflow resistance is exhibited because the molecular chain of the sealing resin is obtained by using the curing accelerator of the present invention. It is considered that the packing is denser, the moisture absorption rate is smaller, the flexibility of the cured product is higher, and the adhesive strength is higher. Furthermore, it is considered that the curing accelerator used in the present invention has a latent reaction accelerating property, so that the melt viscosity of the resin composition at the time of curing is lowered and the wettability with respect to the sealed object is improved.

The reason why the resin composition used in the present invention is excellent in storage stability is that the organic boron salt of the organic phosphine compound, which is a curing accelerator, does not promote the curing reaction so much at around room temperature and is 150 ° C. or higher. This is because it has the property of promptly promoting the curing reaction. In addition, this curing accelerator,
One of the reasons is that the activity as a promoter does not change much even if it absorbs moisture during storage.

The resin composition used in the present invention is less likely to cause voids during molding because the above curing accelerator selectively reacts with low molecular weight components in the epoxy resin and the curing agent at a relatively low temperature. It is considered that this is because it has an effect of reducing volatile components generated when the resin is cured. In particular, if the curing accelerator is previously heated and dissolved in the curing agent at 120 ° C or higher,
It is considered that the above effects are more prominent in that the generation of voids can be further reduced.

The resin-encapsulated semiconductor device of the present invention is 200
The excellent bonding reliability between the gold wire and the aluminum electrode when left at a high temperature of ℃ or higher is that the organic boron salt of the organic phosphine compound, which is a curing accelerator, suppresses thermal decomposition of the resin, It is considered that free halogen compounds that promote corrosion of the aluminum intermetallic compound are less likely to be generated.

The above-mentioned curing accelerator has the effect of imparting excellent characteristics to the encapsulating material made of the biphenyl type epoxy resin composition and greatly improving various reliability of the semiconductor device after encapsulation. , Which is totally unexpected.

[0038]

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

[Examples 1 to 6 and Comparative Examples 1 to 3] The epoxy resin compositions shown in Table 1 were kneaded by a twin-screw roll heated to about 60 to 80 ° C for about 10 minutes, cooled, pulverized and sealed. I got the stopping material. In Examples 4 to 6 in the table, the curing accelerator was previously heated and melted in a phenol aralkyl resin at 140 ° C. for 15 minutes.

Various sealing materials shown in Table 1 were used at 4 ° C. for one day and four nights.
After storage in an atmosphere of 0 ° C. and 20% RH for 7 days, the transferability was evaluated under the conditions of 180 ° C., 70 kg / cm ² and 90 seconds, and the moldability and various characteristics of the molded product were evaluated. The results are shown in Table 2.

In the table, the melt viscosity is 0.98 MPa under a load of 2 g of a sealing material from a nozzle of a mold of a Koka type flow tester heated to 180 ° C. (inner diameter 1 mmφ × length 10 mm).
It was calculated from the maximum flow velocity when extruded with.

For spiral flow, a mold for spiral flow measurement specified in EMMI-1-66 is sandwiched between upper and lower hot plates of a transfer molding machine, and 20 g of a sealing material is molded under the above-mentioned conditions. The length was evaluated.

The hardness at the time of heating was measured by a Barcol hardness tester immediately after the disk having a diameter of 20 mmφ was transfer molded and the molding die was opened.

The internal void of the molded product has the above-mentioned diameter of 20 mm.
The disc of φ was observed and evaluated by a soft X-ray fluoroscope.

Saturated moisture absorption rate is 90 mm diameter x 2 mm thickness
Put the disc into a polytetrafluoroethylene-SUS double pressure vessel, and in an atmosphere of 60 ° C / 100% RH,
The moisture absorption rate after 40 hours of moisture absorption was taken.

In FIG. 1 and FIG. 2, each sealing material is placed at a temperature of 40.degree.
The time-dependent change in fluidity (spiral flow) when stored in a thermo-hygrostat having a humidity of 20% RH for a predetermined time is shown.

From Table 2 and FIGS. 1 and 2, the encapsulating material of this example has excellent storage stability, few voids and good moldability, and the molded product has low moisture absorption and high adhesiveness. I understand.

[0048]

[Table 1]

[0049]

[Table 2]

Next, the above diameter 90 mmφ × thickness 2 mm
The disc was heated in a constant temperature bath at 180 ° C. for a predetermined time to deteriorate it, and then the mill grinder TI-100 type (manufactured by HEIKO).
Crushed with. 5 g of the fine powder was put into a polytetrafluoroethylene-SUS double pressure vessel together with 50 ml of pure water and heated at 120 ° C. for 300 hours, and the free halogen ions extracted in the pure water were subjected to ion chromatography 10 type (D).
ionex). The results are shown in Table 3.
The extraction amount was converted and displayed per unit weight of the molded product.

From Table 3, in the sealed product of this example, the amount of halogen ions extracted from the molded product is small both at the initial stage and after the heat deterioration.

[0052]

[Table 3]

Next, a silicon chip (6 mm × 6 mm) having aluminum zigzag wiring formed on the surface is mounted on a 42 alloy lead frame, and a gold wire (30 μm) is provided between the aluminum electrode on the chip surface and the lead frame.
After wire bonding with φ), the whole is sealed with the materials of Examples 4 and 5 and Comparative Examples 1 to 3 in Table 1 under the above conditions, and post-cured at 180 ° C. for 5 hours to perform surface mounting. Type QFP-IH was created. Each semiconductor device was tested for solder reflow resistance, humidity resistance reliability, and high temperature storage reliability test.

The solder reflow resistance test is a test in which the above resin-encapsulated semiconductor device is left at 85 ° C./85% RH for 168 hours, and then heated in an infrared reflow furnace at 240 ° C. for 90 seconds. The number of cracks generated was examined.

For the moisture resistance reliability test, the above semiconductor device
After leaving it in a thermo-hygrostat at ℃ and 95% RH for 72 hours,
Perform vapor reflow treatment at 5 ° C / 90 seconds, and
After soaking in salt water and standing for 500 hours at 65 ° C. and 95% RH, the number of elements in which aluminum corrosion occurred was examined.

In the high temperature leaving reliability test, the above semiconductor device was left in a high temperature bath at 200 ° C. for 200 hours, and the connection failure of the joint portion of the gold wire and the aluminum wiring was examined. The results are summarized in Table 4.

From Table 4, it can be seen that the semiconductor device of this embodiment is extremely excellent in reliability such as solder reflow resistance, moisture resistance, and high temperature storage characteristics.

[0058]

[Table 4]

The encapsulating material of each of the above examples is excellent in storage stability and moldability, and also excellent in hygroscopicity and adhesiveness. Further, the amount of free halogen ions extracted with pure water after the molded product is deteriorated by heating is small, and the sealed semiconductor device has excellent reliability.

[0060]

The resin-encapsulated semiconductor device of the present invention is excellent in solder reflow resistance, humidity resistance reliability and high temperature storage reliability, and particularly excellent in connection reliability between a gold wire and an aluminum electrode joint at high temperature. Therefore, the packaging density can be increased.

[Brief description of drawings]

FIG. 1 is 4 of each sealing material used in Examples 1 to 3 and Comparative Example.
It is a graph which shows the relationship between the number of days of storage in 0 degreeC and 20% RH, and fluidity (spiral flow).

FIG. 2 shows 4 of each sealing material used in Examples 4 to 6 and Comparative Example.
It is a graph which shows the relationship between the number of days of storage in 0 degreeC and 20% RH, and fluidity (spiral flow).

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuhiro Suzuki 7-1-1 Omika-cho, Hitachi-shi, Ibaraki Hitachi Ltd. Hitachi Research Laboratory (72) Inventor Toshiaki Ishii 7-chome, Omika-cho, Hitachi-shi, Ibaraki No. 1 Hitachi Ltd. Hitachi Research Laboratory

Claims (5)

[Claims] 1. (a) General formula [1]: (In the formula, R represents a hydrogen atom or a methyl group and may be different from each other, n represents an integer of 0 to 2.), (b) a general formula [2] 2] (In the formula, m represents an integer of 1 to 10.), (c) General formula [3] (In the formula, R ^{1 to} R ⁶ represent a phenyl group, a butyl group and a cyclohexane ring and may be different from each other.), And (d) 50 to 90 relative to the whole composition. A resin-encapsulated semiconductor device, which is encapsulated with an epoxy resin composition containing a volume% of an inorganic filler. 2. The curing agent represented by the general formula [2] is
With respect to the epoxy resin represented by the general formula [1],
The resin-encapsulated semiconductor device according to claim 1, wherein the resin-encapsulated semiconductor device is mixed in an amount of 5 to 1.5 equivalents. 3. The epoxy resin composition according to claim 1 or 2, wherein the curing accelerator represented by the general formula [3] is an epoxy resin composition previously dissolved in the curing agent (b). Resin-sealed semiconductor device. 4. The curing accelerator represented by the general formula [3] is blended in an amount of 1 to 15 mmol with respect to 100 parts by weight of the epoxy resin represented by the general formula [1]. 3. The resin-encapsulated semiconductor device according to item 3. 5. The particle size distribution of the inorganic filler is from 0.1 to 1.
The resin-encapsulated semiconductor device according to any one of claims 1 to 4, which is a spherical filler having a diameter of 00 µm.