JPH1034647A - Resin granule for molding and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the generation of voids by a method wherein a thermosetting resin composition, the diameter, length and true specific gravity of each of which is within the specified ranges, is kneaded and vacuum-deaerated and then discharged into the shape of a round bar and finally cut into the predetermined lengths. SOLUTION: A molding resin granule 41 is set its diameter substantially 0.5-5mm and its length 0.5-5mm. Further, the contained air and volatile component of the granule are removed so as to obtain the compressibility of 90-99% and the true specific gravity after hardening of 1.5-2.5. As a result, the molding resin granule 41 turns into a nearly cylindrical shape with both rounded end edge parts. Since no corner as is present in a ground article is present, no trouble of the generation of dust due to the breakage of a corner is hard to develop at the handling of the molding resin granule 41. Furthermore, since granulation is performed within a kneader under vacuum deaerated state, the air and volatile component containing within the granule is very small as compared with those in the ground article or the like of a thermosetting resin composition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a molding resin granule used for semiconductor encapsulation and the like, and a method for producing the same.

[0002]

2. Description of the Related Art In order to enhance the reliability of semiconductor elements and circuits, they are sealed with a thermosetting resin composition to prevent mechanical shock and external environmental conditions (moisture, dirt, temperature, etc.). Protection is widely practiced. For the resin sealing, for example, a transfer molding apparatus as shown in FIG. 8 is used.

[0003] This apparatus comprises an upper die 1 fixed to a base 3.
And a lower die 2 that can move up and down.
In the center of the thermosetting resin tablet 6 which is a sealing material
Is provided, and a plunger 4 for pushing the tablet 6 downward is provided above and below the chamber 5 so as to be able to move up and down. 7 is the upper die 1
And a plurality of cavities symmetrically formed in the lower die 2, and each cavity 7 is communicated with a central portion where the tablet 6 is arranged by a runner (not shown). And lower die 2
In each of the cavities 7, a lead frame on which a semiconductor element is mounted is placed.

[0004] Resin sealing by the above device is performed as follows. That is, first, the tablet 6 is moved to the chamber 5 while the lower die 2 is lifted and united with the upper die 1.
Charge inside. Then, the tablet 6 is melted by heating to about 180 ° C., and the plunger 4 is lowered and pressed to inject the molten liquid into the cavity 7 via the runner. Thus, the semiconductor element on the lead frame can be sealed with resin.

However, in the above method, when the molten liquid is pressed by the plunger 4 and injected into each cavity 7, the air in the chamber 5 is mixed with the molten liquid, and a "void" is formed in the sealing resin. There is a problem that a so-called void is easily formed. The formation of the voids adversely affects the mechanical strength, moisture resistance, and the like of the molded product, and thus impairs the performance of the semiconductor device.

Therefore, as shown in FIGS. 9 (a) and 9 (b), a decompression box 11 is provided above the chamber 5,
A vacuum transfer molding method for evacuating the air in the decompression box 11 to increase the degree of vacuum in the chamber 5 has been proposed and implemented (Japanese Patent Application Laid-Open No. 60-132716). According to this, when the tablet 6 is melted, the atmosphere is maintained at a high vacuum level, so that there is an advantage that voids are not easily formed in the sealing resin.

Incidentally, since the tablet 6 used as a sealing material has a complicated manufacturing process and a high cost, recently, as an alternative form, for example, after crushing a lump of a thermosetting resin composition by impact pulverization, It has been proposed to use a coarsely crushed classified product obtained by classification or a crushed classified product obtained by similarly subjecting a product subjected to impact pulverization to cold forming, followed by pulverization again and classification.

[0008]

However, the coarsely crushed and classified product has a low yield and does not reduce the cost, and the crushed and classified product is the same as a tablet in terms of complicated steps. Not valid as a tablet replacement. In addition, since these classified products are formed into a square shape by impact pulverization, there is a problem that dust is generated at the time of handling, the working environment is deteriorated, and material waste is increased. Most of all, since these classified products contain a large amount of air and volatile components inside, even if the vacuum transfer molding method is used to prevent the formation of voids, the air contained in the material itself is not used. And the like remain in the sealing resin as large voids. Therefore, there is a problem that the advantages of the vacuum transfer molding method cannot be utilized.

The present invention has been made in view of such circumstances, and can be obtained at a low cost and easily. In addition, since the amount of air and the like contained therein is reduced, voids are not formed during vacuum transfer molding. It is an object of the present invention to provide a molding resin granule capable of minimizing generation and a method for producing the same.

[0010]

According to the first aspect of the present invention, there is provided a thermosetting resin composition comprising a thermosetting resin composition having a diameter of 0.5 to 5 mm and a length of 0.5 to 5 mm. 5-5
mm, and has a compression ratio of 90 to 99% and a true specific gravity after curing of 1.5 to 2.5. And
The invention according to claim 2, wherein the thermosetting resin composition comprises:
A molding resin granule which is an epoxy resin composition. The invention according to claim 3 is a molding method wherein the heating loss rate when heated at 175 ° C. for 1 hour is set to 0.01 to 0.1% by weight. Resin granules.

The invention according to claim 4 of the present invention provides:
The step of mixing the thermosetting resin composition, the step of introducing the mixture into a kneader and kneading in a molten state, and the kneaded material, after deaeration under reduced pressure on the outlet side of the kneader,
A step of discharging in a round bar shape from a circular discharge port having a diameter of 0.5 to 5 mm, and a cutter which rotates the round bar-shaped discharge material in contact with the opening end surface of the discharge port, and has a substantially circular shape having a length of 0.5 to 5 mm. And continuously cutting into columnar granules.

That is, the present inventors have conducted a series of studies on a new type of thermosetting resin composition for molding which is inexpensive and has less voids, instead of a tablet. As a result, rather than pulverizing the thermosetting resin composition into granules, the thermosetting resin composition is kneaded, then degassed under reduced pressure, then discharged into a round bar and cut into a predetermined length to obtain a substantially circular shape. The present inventors have found that the use of columnar granules results in an excellent molding material which is easy to handle and has few voids, and has reached the present invention.

In the present invention, “substantially 0.5 to 5 mm in diameter” means that the granules of the thermosetting resin composition satisfies the above numerical values strictly, but the diameter is 0.5 to 5 mm.
It is used for the purpose of including the case where the diameter of the granules obtained by being discharged from the 5 mm die discharge port is slightly different from the diameter of the discharge port.

In the present invention, the term "substantially columnar" refers to those having a complete columnar shape, having some irregularities on both end surfaces and the peripheral surface, and those having a slight warp or twist as a whole. It is used for the purpose of including. Then, the cross-sectional shape of the substantially columnar granule (for example, a portion shown by oblique lines in FIG. 3) is not a case where it is a perfect circle as shown in FIG.
There are cases such as an ellipse as shown in FIG. 4B, a square as shown in FIG. 4C, and a rectangle as shown in FIG. 5A. FIG. 5 (b)
In some cases, the shape may be a pentagon or more polygon.
However, if the cross-sectional shape is polygonal, the corners must be rounded. In addition, these cross-sectional shapes have the longest diameter (major diameter: a in each figure) among the diameters passing through the center (shown by O in each figure) except for the case of a perfect circle shown in FIG. ) And the shortest diameter (minor axis: indicated by b in each drawing) (major axis a / minor axis b) should be about 1-2.

[0015]

Next, the present invention will be described in detail.

The thermosetting resin composition used in the present invention may be any thermosetting resin composition conventionally used for semiconductor encapsulation and the like. Generally, the thermosetting resin component is used. A composition is used in which a curing agent component, an inorganic filler, and the like are blended in an appropriate ratio.

The thermosetting resin component includes an epoxy resin, a maleimide resin, a polyester resin and the like, and among them, the epoxy resin is preferable. As the epoxy resin, those having two or more epoxy groups in one molecule are preferably used. For example, cresol novolak type epoxy resin, phenol novolak type epoxy resin, bisphenol A novolak type epoxy resin,
Bisphenol A type epoxy resin, biphenyl type epoxy resin and the like can be mentioned. These may be used alone or in combination of two or more. Among them, those having an epoxy equivalent of 100 to 300 and a softening point of 50 to 130 ° C. are particularly preferably used.

As the curing agent component, a phenol novolak resin is usually used. The phenol novolak resin preferably has a hydroxyl equivalent of 70 to 150 and a softening point of 50 to 110 ° C. When this novolak-type curing agent and the epoxy resin are combined, the combination ratio is such that the hydroxyl group of the novolak-type curing agent is 0.5 to 2.0 equivalents per equivalent of epoxy group in the epoxy resin. It is preferable to set More preferably, it is in the range of 0.8 to 1.2 equivalents.

Further, as the inorganic filler, silica powders such as crystalline silica and fused silica powder are used, and they are used alone or in combination. And the said inorganic filler is mix | blended normally about 70 to 95 weight% with respect to the whole composition.

In addition to these materials, if necessary, various additives such as a silane coupling agent, a curing accelerator, a release agent, a flame retardant, a flame retardant auxiliary, and a coloring agent may be appropriately compounded. it can.

The resin granules for molding of the present invention can be produced using the above-mentioned thermosetting resin composition, for example, according to the procedure shown in FIG. That is, first, an appropriate amount of each of the thermosetting resin compositions is measured and mixed by the mixer 21. Next, the mixture is quantitatively supplied to the kneader 23 via the quantitative meter 22. The kneading machine 23
Is set at the same temperature as the feed section 24 at room temperature, the kneading section 25 for kneading the material under heating, and the kneading section 25,
And a deaeration unit 27 that is depressurized and evacuated by a deaeration device 26 such as a vacuum pump. As shown in FIG.
The thermosetting resin composition is fed in the direction of the arrow by the rotation of the screw shaft 29 disposed therein. The thermosetting resin composition remains in a powder state when passing through the feed section 24. In the kneading section 25, the resin component is heated and melted into a clay-like or rice-cake-like high-viscosity material. . Then, in that state, it is introduced into the die cutter unit 33 and a discharge port 37 described later
(See FIG. 7). Reference numeral 30 denotes a material supply port, 31 denotes a decompression chamber connected to the deaerator 26, 32 denotes a paddle for kneading, and 34 denotes a screw shaft rotation drive unit.

FIG. 7 shows the details of the die cutter section 33.
Shown in In the figure, reference numeral 35 denotes a die set to the same temperature as the kneading section 25, and a plurality of kneaded material introduction paths 36 provided in the die 35, and the end face 3 of the die 35
The kneaded material is discharged in a round bar shape from a plurality of discharge ports 37 opened to 5a. Also, 38
Is a cutter for cutting the kneaded material discharged in a round bar shape into a predetermined length, and is configured to rotate in the circumferential direction while being in contact with the die end surface 35a. (The same number as the number). In addition, 3
Reference numeral 9 denotes a rotary shaft for rotating the cutter 38, which can simultaneously blow air to each cutter 38 via an air supply path 40 formed therein. Thereby, the cutter 38 heated at the time of cutting the kneaded material can be cooled immediately after cutting, so that heat does not accumulate in the cutter 38, and it is possible to prevent the resin material from burning and the blade itself from being thermally degraded. Therefore, the cutter 38 can be favorably used for a long time.

As shown in FIG. 2, the molding resin granules 41 obtained in this manner have a substantially columnar shape, and both ends are slightly rounded. The reason why the both end edges have a slightly rounded shape is that a sharp cut surface cannot be obtained because the kneaded material discharged from the discharge port 37 has a clay-like or rice cake-like high viscosity. Things. Note that the axis of the cylinder may not be straight, but may be slightly warped or twisted, resulting in distortion of the cylinder itself depending on the distortion of the pressure applied when the cylinder is extruded from the discharge port 37.

Since the molding resin granules 41 do not have corners such as pulverized products, when handling them, the inconvenience of chipping off the corners and forming dust is unlikely to occur. And, during the granulation, since deaeration is performed in the kneader 23 under reduced pressure, the air and volatile components contained therein are extremely reduced as compared with the conventional pulverized thermosetting resin composition and the like. I have. Therefore, using the above-mentioned resin granules 41 for molding, and using an apparatus (a material supply unit whose design has been changed to supply the granules) as shown in FIGS. When molding such as semiconductor encapsulation is performed by the transfer molding method, almost no voids are generated in the molded body, and a molded article of excellent quality can be obtained.

In the present invention, the resin granules 41 for molding have a diameter D of substantially 0.5 to 5 mm,
The length must be set to 0.5-5 mm. If the particle size is smaller than the above range, there is a disadvantage that the particles are easily broken and the particles are easily formed. On the other hand, if the particle size is larger than the above range, voids are easily generated during molding.

The compression ratio of the molding resin granules 41 is 90 to 99%, and the true specific gravity after curing is 1.5 to 90%.
Air and volatile components must be removed to 2.5. That is, when the compression ratio and the true specific gravity are smaller than the above ranges, the molding resin granules 4
This is because, when vacuum forming is carried out using No. 1, a large number of voids are generated in the formed body, and there is no superiority in characteristics with conventional crushed and classified products, and conversely, a value larger than the above range should be used. Is technically difficult. In particular, the heating loss rate at the time of heating at 175 ° C. for 1 hour is 0.01%.
Those exhibiting characteristics such as to be 0.1 to 0.1% by weight are particularly preferred. That is, according to this characteristic, voids are hardly generated in the molded body.

In the present invention, the "compression ratio" and "true specific gravity" can be measured or calculated as follows.

[How to determine the compression ratio] The curing conditions were 175 ° C.
× 50 kgf / cm ² × 2 minutes (aftercure: 5 hours ×
(175 ° C.), the compression ratio was calculated according to the following equation for the cured granules obtained.

[0029]

## EQU1 ## Compressibility C (%) = [(W / V) / ρ] × 100 W: Weight of granules V: Volume of granules ρ: Specific gravity of hardened granules

[Method of Determining True Specific Gravity] The cured granules obtained in the same manner as described above were subjected to an underwater substitution method (JIS K-71).
12A method) to measure the true specific gravity.

In the kneading machine 23, the kneading section 2
Usually, the heating temperature of 5 is preferably set to 40 to 100 ° C, and particularly preferably set to 50 to 70 ° C. If the heating temperature is higher than 100 ° C., the reaction of the kneaded material proceeds, the viscosity increases, and the predetermined resin performance may not be obtained. Conversely, if the heating temperature is lower than 40 ° C., the kneading becomes insufficient and the deaeration efficiency is reduced. It is.

The degree of vacuum in the degassing section 27 is usually 5
It is preferable to set the pressure to 0 to 400 Torr, and it is particularly preferable to set the pressure to 100 to 400 Torr. In a vacuum region higher than 50 Torr, the degassing effect does not increase so much even though the energy cost for degassing increases, and conversely, in a vacuum region lower than 400 Torr, the degassing effect tends to be insufficient. It is.

Further, in the kneader 23, the rotation speed of the screw shaft 29 is appropriately set according to the composition of the forming material to be used, but it is usually preferable to set it to 60 to 200 rpm.

The diameter of the discharge port 37 of the die 35 is
This defines the diameter of the molding resin granule 41 of the present invention, and needs to be set to 0.5 to 5 mm.
If it is smaller than 0.5 mm, the manufacturing cost is high, and if it is larger than 5 mm, voids are likely to be generated during molding. Also, the rotation speed of the cutter 38 is
In consideration of the discharge speed of the kneaded material by the screw shaft 29, the speed is adjusted so that the cutting length is 0.5 to 5 mm. If the length of the molding resin granules 41 is shorter than 0.5 mm, the granules are easily broken and dusted,
Conversely, if it is longer than 5 mm, voids are likely to occur during molding.

The shape and arrangement of the paddles 32 in the screw shaft 29 are appropriately set in consideration of the physical properties of the thermosetting resin composition to be used, and are not limited to the embodiment shown in FIG. Absent.

Next, an embodiment will be described.

[0037]

Examples 1 to 8 Resin granules for molding were obtained by using the thermosetting resin composition having the following composition according to the above-mentioned method. At that time, as shown in Tables 1 and 2 below, the production conditions of the granules were changed.

[Blending Composition of Thermosetting Resin Composition] Cresol novolak type epoxy resin (epoxy equivalent 195) 7 parts by weight Phenol novolak resin (hydroxyl equivalent 175, softening point 76 ° C.) 8 << crystalline silica powder 85 >> phosphoric acid curing Accelerator 0.1 燃 Flame retardant 3 離 Release agent 0.5 〃

[0039]

[Table 1]

[0040]

[Table 2]

Of the resin granules for molding thus obtained, Examples 1 to 5 and Example 8
The compression ratio was determined and the true specific gravity after curing was determined. Further, the heating loss rate when heated at 175 ° C. for 1 hour was also determined. Furthermore, using each molding resin granule,
Vacuum transfer molding machine (CPS-40L, TOWA
(Manufactured by Towa Co., Ltd.), the semiconductor element was actually sealed. Then, a molding void test was performed by the following method. These results are summarized in Tables 3 and 4 below.

[Molding Void Test] Molding conditions: Molding temperature: 175 ° C. Injection pressure: 100 kgf / cm ² Injection time: 7 seconds Package QFP80 pin, length 20 mm × width 14 mm
× Thickness 2.7mm Molded void evaluation: SAT and soft X-ray measurement revealed a diameter of 0.
Count voids of 1 mm or more (count for 32 cavities and find the average number per cavity).

[0043]

[Table 3]

[0044]

[Table 4]

[0045]

As described above, since the molding resin granules of the present invention are hardly formed with corners, dust is less likely to occur due to chipping of the corners during handling. Since the air is degassed under reduced pressure during granulation, the amount of air and volatile components contained therein is very small as compared with the conventional pulverized thermosetting resin composition. Therefore, when molding such as semiconductor encapsulation is performed by vacuum transfer molding using the resin granules for molding, almost no voids are generated in the molded body, and a molded article of excellent quality can be obtained. Moreover,
This resin granule for molding has an advantage that it can be obtained cheaply and easily as compared with a tablet.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a procedure for producing a molding resin granule of the present invention.

FIG. 2 is an explanatory view of a form of a molding resin granule of the present invention.

FIG. 3 is an explanatory view of a cross-sectional shape of a molding resin granule of the present invention.

4A is an explanatory view of an example of a cross-sectional shape of the resin granule for molding of the present invention, FIG. 4B is an explanatory view of another example of the same cross-sectional shape, and FIG. It is explanatory drawing of further another example of.

FIG. 5 (a) is an explanatory view of an example of a cross-sectional shape of the resin granule for molding of the present invention, and FIG. 5 (b) is an explanatory view of another example of the same cross-sectional shape.

FIG. 6 is a partial sectional view of an example of a kneader used in the present invention.

FIG. 7 is a partial sectional view of an example of the kneading machine.

FIG. 8 is a configuration diagram of a conventional transfer molding apparatus.

9A is a configuration diagram of a vacuum transfer molding apparatus, and FIG. 9B is a side view thereof.

[Explanation of symbols]

 41 Resin granules for molding

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Shoichi Kimura 1-1-2 Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Corporation

Claims (4)

[Claims] 1. The thermosetting resin composition is formed into substantially cylindrical granules having a diameter of 0.5 to 5 mm and a length of 0.5 to 5 mm, and has a compression ratio of 90 to 99%. A molding resin granule, wherein the true specific gravity after curing is set to 1.5 to 2.5. 2. The molding resin granule according to claim 1, wherein the thermosetting resin composition is an epoxy resin composition. 3. A molding resin granule having a heating loss rate of 0.01 to 0.1% by weight when heated at 175 ° C. for 1 hour. 4. A step of mixing a thermosetting resin composition,
A step of introducing the mixture into a kneader and kneading in a molten state, and after kneading the kneaded substance under reduced pressure on the front side of the discharge port of the kneader, from a circular discharge port having a diameter of 0.5 to 5 mm into a round bar shape. The step of discharging, and the above-mentioned round rod-shaped discharge material, the cutter rotating in contact with the opening end face of the discharge port, a length of 0.5
A step of continuously cutting so as to obtain a substantially columnar granule of about 5 mm in size.