JP2000043107A - Method for molding thermoplastic resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for molding thermoplastic resin in which generation of a sink and a void in moldings is decreased. SOLUTION: In relation to the method for molding thermoplastic resin, thermoplastic resin 4 is filled into the cavity 2 of a die 1 through a gate 3. The gate 3 is closed. Coefficient of gate is set-up to >=0.023. After the gate 3 is closed, thermoplastic resin 4 filled in the cavity 2 is compressed. Fluidity of thermoplastic resin 4 filled in the cavity 2 is enhanced and also uniformity of the filling state of thermoplastic resin 4 in the cavity 2 can be contrived.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for molding a thermoplastic resin used for obtaining a semiconductor package (TO220 or the like) by performing semiconductor encapsulation molding.

[0002]

2. Description of the Related Art Conventionally, as a method of semiconductor encapsulation molding for encapsulating electric and electronic parts typified by semiconductors such as diodes and transistor integrated circuits, and semiconductor devices having these electric and electronic parts mounted on a substrate. The transfer molding method using epoxy resin or silicone resin, the hermetic sealing method using glass, metal, or ceramic has been adopted. Low-pressure transfer molding using epoxy resin, which is excellent in quality, has become mainstream.

However, in semiconductor encapsulation molding using a thermosetting resin such as an epoxy resin, a large amount of loss occurs on a cull or a runner during molding, and burrs are generated. In addition, since the cured product of the thermosetting resin cannot be recycled, burrs and the like cannot be reused. Therefore, recently, it has been studied to perform semiconductor encapsulation molding by injection molding of a thermoplastic resin.

[0004]

However, even if semiconductor encapsulation is performed with a thermoplastic resin using a mold having a structure similar to that of a mold for molding a thermosetting resin, the surface of the molded product still remains. There is a problem that shrinkage occurs or voids are formed inside the molded product.

The present invention has been made in view of the above points, and has as its object to provide a method of molding a thermoplastic resin which can reduce the occurrence of shrinkage and voids.

[0006]

According to a first aspect of the present invention, there is provided a method of molding a thermoplastic resin, comprising: filling a cavity of a mold with a thermoplastic resin through a gate;
In the thermoplastic resin molding method for closing the gate, after setting the gate coefficient to 0.023 or more and closing the gate 3,
It is characterized in that the thermoplastic resin 4 filled in the cavity 2 is compressed.

According to a second aspect of the present invention, there is provided a method for molding a thermoplastic resin.
After the thermoplastic resin 4 is filled into the cavity 2 and before the gate 3 is closed, the thermoplastic resin 4 filled in the cavity 2 is compressed.

[0008]

Embodiments of the present invention will be described below.

FIG. 2 shows an example of the mold 1. The mold 1 includes an upper fixed mold 10 and a lower movable mold 11, and the movable mold 11 is formed to be vertically movable with respect to the fixed mold 10. The fixed die 10 is provided with an upper die receiving recess 12 which is opened on the lower surface.
3 are stored. The movable mold 11 is provided with a lower mold storage recess 16 which is opened on the upper surface.
A lower mold 17 is housed in 6. Then, the cavity 2, the gate 3, and the runner 5 are formed between the upper mold 13 and the lower mold 17 by clamping the lower mold 17 so that the lower surface of the upper mold 13 and the upper surface of the lower mold 17 match.

The fixed die 10 is provided with a vertically long sprue bush 14, and the sprue bush 14 is formed with a sprue 15 communicating with the runner 5. In addition, the movable die 11 is provided with a vertically long gate cut jig 18 so as to be vertically movable. The upper end of the gate cut jig 18 is sharpened at an acute angle, and the tip is formed as a contact portion 18a. A jig operation plate 19 that moves up and down by a molding machine or the like that moves the movable mold 11 up and down is provided below the gate cut jig 18, and the gate cuts in response to the up and down movement of the jig operation plate 19. The jig 18 moves up and down. The upper end of the gate cutting jig 18 is inserted into the gate 3 and the runner 5 through an insertion hole 22 provided in the lower die 17, and from this state, the gate cutting jig 18 is further moved upward to contact the contact portion 18a. The upper mold 1
By making contact with the lower surface of the gate 3, the gate 3 is closed and the conduction between the cavity 2 and the runner 5 is cut off. The closing of the gate 3 is called gate cut. Further, the movable die 11 is provided with a pair of vertically long compression pins 21 movably up and down. A pin operation plate 20 that moves up and down by a driving device such as a hydraulic cylinder or an air cylinder is provided below the compression pin 21 so that the compression pin 21 moves up and down in response to the up and down movement of the pin operation plate 20. It has become. And compression pin 2
The upper end of 1 is formed so as to be freely inserted into cavity 2 through introduction hole 23 provided in lower mold 17.

In the mold 1 as described above, the gate coefficient indicating the size of the gate 3 when the thermoplastic resin 4 flows into the cavity 2 from the runner 5 through the gate 3 is given by:
It is set to be 0.023 or more. The gate coefficient is defined by the cross-sectional area of the gate 3 (the cross-sectional area between the contact portion 18a of the gate cutting jig 18 and the lower surface of the upper die 13) with respect to the molded product (package) formed by the die 1. In the following equation (A), gate coefficient = cross-sectional area of gate 3 (mm ² ) / volume of molded product (mm ³ ) (A). And this gate coefficient is 0.
Since it is 023 or more, the fluidity of the thermoplastic resin 4 filled in the cavity 2 can be improved, and the occurrence of shrinkage and voids in the molded product can be reduced. In addition, the internal stress of the molded product can be reduced, and damage and peeling of the semiconductor due to the internal stress can be reduced. When the gate coefficient is 0.035 or more, the above-described effect is remarkably exhibited. The upper limit of the gate coefficient is 0.08, depending on the shape of the molded product. is there. Incidentally, the gate coefficient of the mold used for the usual semiconductor encapsulation molding of epoxy resin is 0.001 or less.

The injection molding of a molded article using the mold 1 can be performed as follows. First, the movable mold 11 is moved upward so as to approach the fixed mold 10, and the upper surface of the lower mold 17 is aligned with the lower surface of the upper mold 13 to clamp the mold. At this time, the upper end of the gate cutting jig 18 projects to the gate 3 and the runner 5 so that the gate coefficient becomes 0.023 or more. The upper end of the compression pin 21 is located below the introduction hole 23, and
A compression margin 24 having a vertical length B is formed between the compression pin 3 and the upper end of the compression pin 21. Further, the semiconductor or the like to be sealed is arranged at a position to be the cavity 2 before clamping.

Next, a nozzle (not shown) of the injection machine is pressed against the sprue bush 14, and the thermoplastic resin 4 heated and melted from the injection machine is injected into the sprue 15 as shown by an arrow a in FIG. I do. The injection pressure at this time is 100
１０００1000 kg / cm ² , preferably 300-700 k
g / cm ² . Further, as the thermoplastic resin 4, an arbitrary resin such as polyphenylene sulfide resin (PPS resin) can be used. Even if a plurality of kinds of thermoplastic resins 4 are used in combination or a filler such as glass fiber is compounded. Good.

The thermoplastic resin 4 injected and injected as described above is introduced into the runner 5 from the sprue 15 and then injected and filled into the cavity 2 from the runner 5 through the gate 3. Between the injection injection into the sprue 15 and the filling into the cavity 2, the compression pin 21 is moved upward by the length B of the compression allowance 24 as shown by an arrow B in FIG. Filled thermoplastic resin 4
Is compressed by the compression pin 21. The pressure at this time is 100 to 1
000 kg / cm ² , preferably 300-700 kg /
It is set to cm ^2. Compression by compression pin 21 is 100
If it is less than kg / cm ^2, less likely to fill uniformly the thermoplastic resin 4 into the cavity 2, there is a possibility that voids or shrinkage occurs in the molded article, also compressed by the compression pin 21 to 1000 kg / cm ² If it exceeds, the pressure applied to the semiconductor or the like to be sealed becomes too strong, and may be damaged.
By compressing the thermoplastic resin 4 filled in the cavity 2 in this manner, the thermoplastic resin 4 can be uniformly filled in the cavity 2 and the occurrence of voids and shrinkage in the molded product can be reduced. Can be done.

After filling the cavity 2 with the thermoplastic resin 4 as described above, the injection of the thermoplastic resin 4 is stopped, and the contact portion 18a as shown by the arrow C in FIG.
Until the abutment comes into contact with the lower surface of the upper die 13.
Is moved upward to close the gate 3. Thereafter, as shown by an arrow d in FIG.
Is moved upward, and the thermoplastic resin 4 filled in the cavity 2 is compressed by the compression pin 21. The pressure at this time is 100 ~
1000 kg / cm ² , preferably 300 to 700 kg
/ Cm ² . Compression by compression pin 21 is 10
If it is less than 0 kg / cm ^2, less likely to fill uniformly the thermoplastic resin 4 into the cavity 2, there is a possibility that voids or shrinkage occurs in the molded article, also compressed by the compression pin 21 to 1000 kg / cm ² If it exceeds, the pressure applied to the semiconductor or the like to be sealed becomes too strong, and may be damaged. After the gate 3 is closed in this manner, the thermoplastic resin 4 filled in the cavity 2 is further compressed, so that the uniformity of the filling of the thermoplastic resin 4 in the cavity 2 is further increased, and voids and voids are formed in the molded product. The occurrence of shrinkage can be further reduced.

Thereafter, the thermoplastic resin 4 is cooled and solidified, and at the same time, the movable mold 11 is moved downward to open the mold, and the molded article is removed from the molded article, thereby producing a molded article.

[0017]

The present invention will be described below in detail with reference to examples.

(Examples 1 to 24 and Comparative Examples 1 to 1)
2) A semiconductor package (with a TO220 fin) was molded using the mold 1 set to the gate coefficient shown in Table 1. The thermoplastic resin 4 is a graft copolymer of an acrylonitrile styrene copolymer and an ethylene / glycidyl methacrylate copolymer (Japan, based on 100 parts by weight of a linear PPS resin (product number W-202A manufactured by Kureha Chemical Industry Co., Ltd.)). and fat Co. No. A4400) 5 parts by weight, a milled fiber (Nippon Sheet Glass Co. of No. REV8) and 72 parts by weight, the inorganic ion exchanger _{(composition: Sb 2 Bi 1.4 O 6. 4} (OH)
_{0.9 (NO 3) 0.4 · 0.6H} 2 O) was prepared by blending 1 part by weight.

According to the procedure described in the above embodiment, the thermoplastic resin 4 is heated and melted by an injection machine having a cylinder temperature of 300 ° C., then injected into a mold 1 having a temperature of 180 ° C. Resin 4 was charged. At this time, the injection pressure (filling pressure) was set to 600 kg / cm ² , and the filling time was set to 1 second. Further, as shown in FIGS. 1B and 1D, the pressure at which the thermoplastic resin 4 filled in the cavity 2 was compressed by the compression pin 21 was set as shown in Table 1.
After the step of FIG. 1D, the molded article (semiconductor package) was formed by cooling the thermoplastic resin 4 filled in the cavity 2 for 30 seconds.

In the first to twelfth embodiments, the cross section of the gate 3 is shown.
9 mm product^TwoAnd the volume of the molded product is 257 mm^ThreeAs
The sheet coefficient was 0.035. In Examples 13 to 24
The cross-sectional area of the gate 3 is 5.9 mm^TwoAnd the volume of the molded product
257mm^ThreeAnd the gate coefficient was set to 0.023. ratio
In Comparative Examples 1 to 12, the sectional area of the gate 3 was 2.57 mm. ^Two
And the volume of the molded product is 257 mm^ThreeThe gate factor as
It was set to 0.01. As an injection molding machine, Nissei Plastic Industry
PS40 / 5TM manufactured by Co., Ltd. was used.

Examples 1 to 24 and Comparative Examples 1 to 1
The molded article obtained in 2 was evaluated for voids.
In this void evaluation, the inside of the molded product was observed with an ultrasonic probe to check for the presence of voids of 0.2 mm or more, and those having no voids were marked with a circle. Although there were some voids, there was no practical problem at all. The samples were marked with a triangle, and those having many voids and having practical problems were marked with a cross.

The molded products obtained in Examples 1 to 24 and Comparative Examples 1 to 12 were evaluated for shrinkage. In the evaluation of shrinkage, the surface of the molded product was visually checked, and a mark indicating no shrinkage was marked with a circle, and a mark indicating a slight shrinkage but having no practical problem was marked with a mark. Crosses were given to those with problems.

The molded products obtained in Examples 1 to 24 and Comparative Examples 1 to 12 were evaluated for chip damage. In this chip damage evaluation, the state of the semiconductor inside the molded product was confirmed, and a circle was given to a semiconductor without any breakage or peeling of the semiconductor, and to a semiconductor with some damage or peeling but having no practical problem at all. In addition, those having a practical problem due to a large number of breakage and peeling of the semiconductor were marked with a cross.

The results are shown in Table 1.

[0025]

[Table 1] As shown in Table 1, void evaluation and shrinkage evaluation were higher in Examples 1 to 24 than in Comparative Examples 1 to 12. In Examples 1 to 24, chip damage can be reduced by compressing with the compression pin 21 at a predetermined pressure.

[0026]

As described above, according to the first aspect of the present invention, in a method for molding a thermoplastic resin in which a cavity is filled with a thermoplastic resin through a gate and then the gate is closed, a gate coefficient is set to 0. After the gate is closed and the thermoplastic resin filled in the cavity is compressed, the fluidity of the thermoplastic resin filled in the cavity can be improved and the thermoplastic resin in the cavity can be improved. The filling degree can be made uniform, and the occurrence of shrinkage and voids in the molded product can be reduced.

According to the invention of claim 2 of the present invention, after filling the cavity with the thermoplastic resin and before closing the gate, the thermoplastic resin filled in the cavity is compressed. The uniformity of the filling condition can be further improved, and the occurrence of shrinkage and voids in the molded product can be further reduced.

[Brief description of the drawings]

FIG. 1 illustrates an example of an embodiment of the present invention, and (a) to (d) are cross-sectional views.

FIG. 2 is a cross-sectional view of the above-mentioned mold.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mold 2 Cavity 3 Gate 4 Thermoplastic resin

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Takahide Suzuki 1048 Odakadoma, Kadoma, Osaka Pref. DA06

Claims (2)

[Claims] 1. A method for molding a thermoplastic resin in which a mold is filled with a thermoplastic resin through a gate and then closing the gate, wherein the gate coefficient is set to 0.023 or more, and the gate is closed. A method of molding a thermoplastic resin, comprising compressing a thermoplastic resin filled in a thermoplastic resin. 2. The method of molding a thermoplastic resin according to claim 1, wherein the thermoplastic resin filled in the cavity is compressed after filling the cavity with the thermoplastic resin and before closing the gate. .