JPH11198185A - Resin sealing mold having injection presser equalizing mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mold, which is excellent in maintainability and workability, the structure of which is simple and the simultaneous change of which and the change of the cushioning mechanisms can be executed by a method wherein the cushioning mechanisms of the transfer mold are housed in the mold. SOLUTION: In a first mold 1, a plurality of pots 8 arranged in series and plungers 9 driven by an injection press are provided. In a second mold 2, resin wells 11, each of which communicates with cavities through runners in opposite to each pot 8, and cylinder parts 13, each of which connects to each resin well 11, are provided. Each slide block 14 sliding in the smaller diametral portion 13a of each cylinder part has a flange loosely fitting to the larger diametral portion 13b of each cylinder part so as to arrange a spring 15 having characteristics optimum each pair of molds between each flange and a second mounting plate 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin mold for electronic parts, and more particularly to a resin mold having a multi-plunger type injection pressure equalizing mechanism.

[0002]

2. Description of the Related Art Conventionally, this type of transfer molding die is disclosed in Japanese Utility Model Laid-Open No. 146919/1991.
As shown in the schematic partial cross-sectional view of FIG. 3, in the mold divided into the upper chase 34 and the lower chase 32, the cavities 35 are arranged along the joints of the molds corresponding to the arrangement positions of the lead frames L. In the lower chase 32, a cylinder 31 is fixedly arranged side by side, and a transfer end in which a lower end is mounted via a disc spring 39 laminated on an operation plate 37 which can move up and down. 38 are provided. A concave portion 30 is formed on the lower surface of the upper chase 34 facing the pot P formed by the upper end of the transfer 38 and the cylindrical body 31, and a gate 33 for communicating the concave portion 30 with the cavity 35 is formed.

In the method of using the transfer molding die, first, in a mold open state, a resin tablet and a lead frame L are set on a lower chase 32, then the upper chase 34 is lowered to close the die, and then the mold is closed. Each transfer 38 is raised by the injection press A of the molding machine, and the tablet melted in the pot P is injected into the cavity 35 through the gate 33 to form a molded product.

That is, this type of resin-enclosed mold is generated due to a variation in the amount of resin tablets put into each pot due to a buffer provided between each plunger (transfer) and the injection press. The change in the injection pressure is absorbed to maintain the pressure in the pot at an equal pressure. In addition to the above-mentioned disc springs, an elastic body made of a heat-resistant resin, an external cylinder or a damper using hydraulic pressure or spring pressure, or the like is used for these buffers.

Another transfer mold is disclosed in Japanese Patent Application Laid-Open No. Hei 6-328515. That is, as shown in the cross-sectional view of FIG. 4, a plurality of cavities are formed between mating surfaces of a pair of molds, pots 207 communicating with the cavities are provided, and a tablet loaded in these pots is A plurality of plungers 300 for extruding into each cavity are provided, and in a transfer molding die for simultaneously pressing and driving these plungers, a plurality of protruding pins 106c for releasing the resin from the mold can be moved to the protruding plate 106a. Provided,
Further, an urging tool 106g for urging these protruding pins 106c toward the mating surface side of the mold and a buffer spring 106
h is provided.

[0006] In the transfer molding die formed in this manner, the projecting pin 1 facing the resin reservoir 104a is selected according to the level of the resin injection pressure into the cavity.
The amount of movement of 06c toward the base plate 100 is adjusted by the urging of the urging tool 106g and the buffer spring 106h (see the upper mold partial sectional view in FIG. 5). Thereby, the injection pressure of the resin into each cavity is balanced, and as a result, the amount of the resin injected into each cavity is made uniform.

[0007]

In the transfer mold of the prior art shown in FIG. 3 described above, a buffer such as an external cylinder or a damper is provided between each plunger and an injection press by a hydraulic or spring. Therefore, when changing molds by changing the product type, it is necessary to replace buffer cylinders, dampers, etc. and set the conditions for buffer pressure in accordance with the molding die conditions. Bad
Further, there is a disadvantage that the frequency of maintenance is high because oil leaks from the hydraulic pipe of the buffer source occur.

In another transfer mold shown in FIGS. 4 and 5, the amount of resin in the cavity is directly absorbed by the movable urging member and the buffer spring. There is a disadvantage that the finished product is not uniform and a quality problem occurs.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a transfer molding die in which a buffer mechanism is accommodated in the die, thereby simplifying and reducing the structure of the plunger and the injection press, and simultaneously performing a buffer exchange operation by replacing the die. An object of the present invention is to provide a mold excellent in maintainability and workability by also exchanging a mechanism.

[0010]

A resin mold having an injection pressure equalizing mechanism according to the present invention is a split mold having a cavity for resin sealing a plurality of semiconductor elements.
A plurality of cylindrical pots provided in a first mold, a plunger driven by an injection press to slide in the pot, and a position in the second mold facing the pot of the first mold. And a cylinder that is connected to the cavity by a runner, and a cylinder portion that is connected to the resin reservoir, and is provided in the cylinder portion, and is provided on an inner wall of the cylinder portion in accordance with a change in pressure of the resin in the resin reservoir. An injection pressure equalizing mechanism including a slide block slidable along and a buffer member for urging the slide block in the axial direction is provided.

A coil spring is used as the cushioning member, and the tension of the coil spring is set in advance for each mold so as to have characteristics that are optimal for the use conditions of each mold.

The cylinder portion connected to the resin reservoir has a small-diameter portion and a large-diameter portion, into which a slide block having a tubular portion and a flange portion is inserted. The small diameter portion of the cylinder portion slides with the large diameter portion of the cylinder portion.

The position of the slide block in the axial direction is determined before the resin is injected by the flange portion contacting the step between the small diameter portion and the large diameter portion of the cylinder portion by the tension of the coil spring. The slide block moves against the reaction force of the coil spring due to the pressure in the reservoir, so that the slide block is in a balanced position. By changing the axial length of the cylindrical portion of the slide block, the volume of the resin pool provided in the first mold can be easily changed.

It is preferable that a plurality of cylindrical pots provided in the first mold are arranged in parallel and in series at equal intervals.

[0015] The resin sealing mold of the present invention includes a movable slide block on one surface of a resin pool in which the resin extruded by the plunger stays in response to a change in resin pressure at the time of injection.
A means for supporting the block and absorbing a change in pressure with a spring of the cushioning material is provided, so that when the type is changed, that is, in the mold changing operation, the equal pressure mechanism in which the molding conditions are set in the mold is used. Therefore, there is no need for adjustment work such as setting conditions of the cushioning material and the equal pressure mechanism depending on the injection molding conditions and the like.

[0016]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a schematic longitudinal sectional view of one embodiment of a resin sealing mold having an injection pressure equalizing mechanism of the present invention,
FIG. 2 is a schematic longitudinal sectional view in a direction perpendicular to FIG.

The split mold is formed by a first mold 1 and a second mold 2, and is clamped by a fixing member 5 via a first mounting plate 3 and a second mounting plate 4, respectively. Is mounted on the first plate 6 and the second plate 7.

In the first mold 1, four cylindrical pots 8 are provided in series at equal intervals, and in each pot 8, a plunger 9 slidable on a cylindrical inner surface is provided. It is connected to a bar 10 of an injection press (not shown) by 9a, so that the inside of the pot 8 is reciprocally driven by the reciprocation of the injection press.

The second mold 2 has a first mold when the mold is closed.
The resin pool 11 is located at a position facing each pot 8 of the mold 2.
Is provided. As shown in FIG. 2, the resin reservoir 11 is provided with a cavity 1 provided in the molds 1 and 2 by a runner 11a.
2 is connected. The lead frame L on which the semiconductor element S is mounted is accommodated in the cavity 12.

A cylinder 13 is provided in connection with the top of each resin reservoir 11. The cylinder portion 13 includes two portions 13a and 13b having large and small inner diameters.
The inner diameter of the portion 13a on the side closer to
The inner diameter of b is larger than that. A slide block 14 having a cylindrical portion that fits into the small diameter portion 13a of the cylinder portion 13 is inserted. Slide block 1
A flange is formed on the head of the cylinder 4 to fit into the large-diameter portion 13b of the cylinder portion 13. When the flange contacts the inner step of the cylinder portion 13, one position of the slide block 14 is determined.

Large-diameter portion 13b of the inner diameter of each cylinder portion 13
Is provided with a coil spring 15 having one end in contact with the head of the slide block 14 and the other end in contact with the second mounting plate 4. The tension of the coil spring 15 is set in advance for each mold so as to have characteristics that are optimal for the use conditions of each mold, and is incorporated in advance.

The operation of the thus formed mold will be described. First, the second mold 2 is opened, and the plunger 9 is retracted to a predetermined position. Then, a predetermined amount of resin tablet is charged into each pot 8, and the cavity 1 of the first mold 1 is further charged.
2, a lead frame L on which a semiconductor element S to be resin-sealed is mounted. The second mold 2 is closed and the mold is clamped, the resin in the pot 8 is melted, and the plunger 9 is advanced by a bar 10 of an injection press that drives the co-extrusion directly to press the melted resin, and the runner 11a is pressed. And into the cavity 12. When the resin is solidified, the plunger 9 is retracted, and after the second mold 2 is opened, a molded product is projected from the cavity 12 by a projection pin (not shown) provided on the first mold 1, and the plunger 9 is removed. By moving forward, the lead frame L on which the resin-sealed semiconductor element S is mounted, and the resin in the resin reservoir 11 and the runner 11a can be taken out in series.

In the above-described enclosing operation, the amount of each resin initially charged into each pot 8 usually has a slight variation. Therefore, there is a difference in the injection pressure in each pot 8 and each resin reservoir 11 when the plunger 9 presses the resin to fill the cavity 12. Resin pool 11
Slidable slide block 14 provided following
However, due to the difference in pressure, the cylinder 13 moves against the tension of the coil spring 15 provided in the large diameter portion 13b of the cylinder 13 and changes the volume of the resin reservoir 11. This change in volume corrects the variation in the amount of resin charged in each pot 8. This is made possible by maintaining the pressure inside each resin injection path at the time of injection and filling.

Although the mold in the above description has a cavity for sealing the semiconductor element mounted on the lead frame with a resin, a mold having a cavity for resin sealing of another electronic component may be used. Also, the electronic component can be sealed in the same process.

Although the coil spring has been described as the cushioning member, another elastic member having a function equivalent to that of the coil spring, such as a leaf spring or a disc spring, may be used.

[0026]

As described above, according to the present invention, the equal pressure mechanism of the optimum molding condition set for each mold is separately provided in each mold and managed for each mold. It is not necessary to individually set the conditions at the time of mold change, which significantly reduces the mold change work and setup time, and also makes the injection press and plunger directly connected to the molding press machine. Since the space for providing the equal pressure mechanism is not required, there is an effect that the structure of the molding press is simplified, downsized, and easy to handle.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view of a resin sealing mold having an injection pressure equalizing mechanism according to the present invention.

FIG. 2 is a schematic partial longitudinal sectional view in a direction perpendicular to FIG.

FIG. 3 is a schematic partial longitudinal sectional view of a transfer molding die according to a conventional technique.

FIG. 4 is a longitudinal sectional view of another transfer mold according to the related art.

FIG. 5 is a partial sectional view of the upper mold of FIG. 4;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st metal mold 2 2nd metal mold 3 1st mounting plate 4 2nd mounting plate 5 Fixing member 6 1st plate 7 2nd plate 8 Pot 9, 300 Plunger 9a Lot 10 Bar of an injection press DESCRIPTION OF SYMBOLS 11 Resin pool 11a Runner 12, 35 Cavity 13 Cylinder part 13a Small diameter part 13b Large diameter part 14 Slide block 15 Coil spring 30 Depression 31 Cylindrical body 32 Lower chase 33 Gate 34 Upper chase 37 Working plate 38 Transfer 39 Disc spring 100 Base plate 104a Resin pool 106a Projection plate 106c Projection pin 106g Urging tool 106h Buffer spring 207 Pot A Injection press L Lead frame S Semiconductor element P Pot

Claims (7)

[Claims] 1. A split mold having a cavity for resin-sealing a plurality of electronic components, comprising: a plurality of cylindrical pots provided in a first mold; A plunger that slides in the pot; and a second mold having a resin reservoir provided at a position of the first mold facing the pot and communicating with the cavity by a runner. A cylinder portion connected to the reservoir, a slide block provided in the cylinder portion, and slidable along an inner wall of the cylinder portion in response to a change in pressure in the resin reservoir; A resin sealing mold having an injection pressure equalizing mechanism, including a buffer member biasing in a direction. 2. The resin sealing mold according to claim 1, wherein the cushioning member includes a coil spring that supports the slide block in an axial direction. 3. The resin-sealed mold having an injection pressure equalizing mechanism according to claim 1, wherein the buffer member has a predetermined tension suitable for a molding process using the mold for each mold. 4. The resin mold according to claim 1, wherein the cylinder portion has a small diameter portion and a large diameter portion. 5. The injection pressure according to claim 1, wherein the slide block has a cylindrical portion that slides on a small diameter portion of the cylinder portion and a flange portion that fits on a large diameter portion of the cylinder portion. A resin-sealed mold having an equal pressure mechanism. 6. The resin having an injection pressure equalizing mechanism according to claim 1, wherein the volume of the resin reservoir can be changed by changing the axial length of the cylindrical portion of the slide block. Sealing mold. 7. The resin sealing mold having an injection pressure equalizing mechanism according to claim 1, wherein the plurality of cylindrical pots provided on the first mold are arranged in series.