JPS59225913A - Method and apparatus for concurrent cast molding in plural molds by plural plungers - Google Patents

Abstract

PURPOSE:To maintain a given molding pressure by orderly retracting plungers for pots filled with greater amounts of synthetic resin even when the amounts of the synthetic resin packed into the pots are uneven. CONSTITUTION:Plungers 5 to cast a synthetic resin are pushed up to a limiting upper position, and then a synthetic resin is packed into pots 4. Top force 1 and a bottom force 2 are clamped together. A liquid-pressure cylinder device 10 is operated, a press frame 11 is moved upwards, a plunger holding frame 6 is pushed down toward the bottom force 2, and synthetic resin 3 in the pots 4 are cast into molds. As the plunger holding frame 6 makes pushing movements, the mold pushing forces to be loaded on the plungers orderly from the pots having greater amounts of synthetic resin reach given molding pressures and thereby the plungers reaching given molding pressures are orderly retracted to discharge back-pressure liquid into a tank through a pressure governor valve 9, so that the pressure of the back-pressure liquid is kept at its initial set pressure and also the casting speed of synthetic resin by the liquid-pressure cylinder 10 can be kept constant.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention involves charging semiconductor devices into a large number of molds recessed within the mold, and simultaneously injecting a thermosetting synthetic resin into the large number of molds. The present invention relates to a method and apparatus suitable for encapsulation molding with resin. More specifically, by simultaneously pressurizing multiple synthetic resin injection plungers with a hydraulic cylinder device via a back pressure liquid whose pressure is regulated to the molding force, variations in the amount of synthetic resin filled into the pot can be prevented. The present invention relates to a method and apparatus capable of injecting and molding a synthetic resin into a mold with a uniform molding force and injection speed even if the resin is injected into a mold.

Conventionally, when semiconductor elements are encapsulated with synthetic resin, in order to enable mass production and save consumption of injection resin JjFJ, for example, Japanese Patent Application Laid-Open No. 56-11236 (hereinafter referred to as the former) and Utility Model Application No. 57 A technique disclosed in Japanese Patent No. 123222 (hereinafter referred to as the latter) has been developed.

The former discloses a technique in which a plurality of plungers are simultaneously pressurized with pressure oil supplied from the same hydraulic circuit, and each plunger injects synthetic resin into the mold under pressure. As the plunger tends to be pressurized sequentially from the plunger closer to the pressure source as the liquid flows, there will be variations in the synthetic resin injection speed and the synthetic resin injected into each mold will be non-uniform. In addition, since each plunger slides inside the pot while pressurizing the resin filled in the pot, the resin attached to the sliding surface of the plunger is squeezed in, increasing the sliding resistance of the plunger. The sliding resistance differs between each bot, and as a result, the injection speed of each plunger varies, causing disturbances in the resin injection speed and injection pressure.
The resin injected into the mold lacks homogeneity, and the latter presses the plunger via a compression coil spring, but if the spring force is weaker than the resin injection pressure, the coil spring will close to the compression limit. The excess amount of resin filling cannot be absorbed by the retreat of the plunger, and if the pressure is too strong than the injection pressure, the coil springs will not bend, so the plunger will not be able to retreat and the spring function will not be exerted. Therefore, it is necessary to adjust the spring force of each plunger according to the injection pressure, which is a troublesome operation. When the variation is absorbed by each spring, the product of the spring constant and the amount of deflection of the spring becomes the injection pressure, so the difference in the amount of deflection of the spring in each plunger becomes the difference in the injection pressure between each plunger, and the mold This method has drawbacks such as the amount of resin injected into the mold is not uniform, leading to the occurrence of defective molded products.

The present invention is a method and apparatus that eliminates the above-mentioned conventional drawbacks.The present invention will be described in detail below with reference to the drawings. A semiconductor element loading mold and a plurality of passages for introducing synthetic resin into these molds at the shortest distance are recessed, and the lower mold 2 is penetrated by a plurality of filling bots 4 of synthetic resin 3 that communicate with the passages, respectively. It is set up. A synthetic resin injection plunger 5 is slidably inserted into each of these filling pots 4, and the synthetic resin injection plungers 5 are connected to a plurality of mutually connected plunger holding frames 6 disposed apart from the lower mold 2. The back pressure liquid is fitted into a communicating back pressure chamber 7, and a back pressure liquid having a molding force applied to the synthetic resin injection tip of each plunger 5 after injection is completed is applied to the back pressure chamber 7 at a set pressure by a pressure pump (not shown). The pressure is supplied via the control valve 8, and a pressure regulating valve 9 is interposed in the pressure feeding circuit between the back pressure chamber 7 and the set pressure control valve 8.

The plunger holding frame 6 is detachably fixedly held by a pressurizing frame 11 operated by a hydraulic cylinder device 10. The hydraulic cylinder device 10 is connected to a switching valve 1 by a pressure pump (not shown).
2. It has a pressurizing circuit that supplies pressurized liquid through the injection pressure control valve 13 and the injection speed adjustment valve 14, and a return circuit that returns to the liquid reservoir via the switching valve 12, and further includes a synthetic resin in the mold. In order to keep the molding pressure constant, a stopper 15 is provided for regulating the length of the pressurizing stroke. Note that 16 is a molding pressure gauge, and 17 is an injection pressure gauge.

Therefore, first, a semiconductor element is encapsulated in each of a plurality of semiconductor element loading molds using a known operation, and the back pressure chamber 7 is filled with a back pressure liquid whose pressure is adjusted to the molding pressing force. After pushing the plunger 5 up to the maximum position shown in the figure,
Synthetic resin is charged and filled into each of the bottles 4, the upper mold 1 and the lower mold 2 are brought together to clamp the molds, and then pressurized liquid is pumped through the pressure circuit to form a hydraulic cylinder device. 10, the pressurizing frame 11 is moved upward as shown in the figure, and the plunger holding frame 6 is moved upward.
is pushed toward the lower mold 2.

In this case, since the back pressure liquid in the back pressure chamber 7 acts on the pressure receiving surface 5' of each plunger 5 by a synthetic resin molding force, each plunger 5 is attached to the plunger holding frame as shown in FIG. moves upward integrally with the plunger holding frame 6 while maintaining the upper limit position without moving relative to the plunger body 6;
The synthetic resin 3 in the pot 4 is injected into the mold.

However, the amount of synthetic resin 3 filled in the pot 4 is often uneven in each pot 4, and as the plunger holding frame 6 is pushed, the load is applied to the plunger in order from the pot with the largest filling amount. As the molding pressing force reaches a predetermined molding pressure, as shown in FIG. 2, the plunger that has reached the predetermined molding pressure is sequentially retreated and the back pressure liquid in the back pressure chamber is discharged into the tank through the pressure regulating valve 9. The back pressure hydraulic pressure in the back pressure chamber is maintained at the initial set pressure, and the synthetic resin injection rate by the hydraulic cylinder device 10 is maintained constant.

In this way, even if the amount of synthetic resin filled in each pot is uneven, a predetermined molding pressure is maintained by sequentially retreating from the plunger of the pot with a larger amount of synthetic resin filled. A constant injection rate can be maintained by actuation of the hydraulic cylinder arrangement. Since a stopper 15 is provided on the lower piston rond of the hydraulic cylinder device, the pushing stroke length of the plunger holding frame 6 is regulated, and each plunger is lowered in the back pressure chamber 7 by retreating. Since the pushing stroke is stopped before reaching the ultimate position, there is no risk of loading each plunger with a forming force that exceeds a predetermined forming pressure.

As described above, in the present invention, even if there is variation in the order in which a predetermined molding pressure is reached in each pot due to non-uniformity in the amount of synthetic resin in the pot, the plunger is retracted to absorb the variation and completely eliminate the variation. By maintaining a uniform predetermined molding pressure in each plunger and applying a constant pressurized injection rate by a hydraulic cylinder device to all plungers, the amount of resin filled in each pot can be prevented from being uneven. However, the synthetic resin can be injected at a predetermined molding pressure into the mold at a constant pressurized injection rate by a hydraulic cylinder device via a back pressure liquid whose pressure is regulated to a predetermined molding pressure. It has the excellent effect of being able to mold a homogeneous molded product in the mold.

Furthermore, by making the plunger holding frame removable from the pressurizing frame, there is an advantage that holding frames holding different numbers of plungers can be replaced at any time depending on the number of pots.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is an explanatory diagram at the start of resin injection, and FIG. 2 is an explanatory diagram at the end of resin injection. 1... Upper mold 2... Lower mold 3... Filled synthetic resin 4... Pot 5... Synthetic resin injection plunger 6... Plunger holding frame 7... Back pressure chamber 8.
...Set pressure control valve 9...Pressure regulating valve 10...
Hydraulic cylinder device 11...pressure frame 13...
Injection pressure control valve 14...Pressurization speed adjustment valve Representative: Patent attorney Yujo - 1 other person 59 Figure 1 Figure 2

Claims (3)

[Claims] (1) While supporting a plurality of synthetic resin injection plungers with a back pressure liquid whose pressure is regulated to the synthetic resin molding pushing force, pressurize the back pressure liquid with a liquid pressure having a constant injection speed, and use each of the plungers to A method in which synthetic resin in a pot is simultaneously injected into multiple molds. (2) A pressurizing frame operated by a hydraulic cylinder device having a constant injection speed, and a plurality of pressurizing frames supported by a back pressure liquid attached to the pressurizing frame and regulated to a molding pressing force by a pressure regulating valve. A plunger holding frame body having a synthetic resin injection plunger, and a plurality of synthetic resin filling holes communicating with a plurality of molds, and each of the synthetic resin injection plungers is slidably fitted into each pot L7. Synthetic resin injection molding equipment comprising a mold and. (3) The device according to claim 2, wherein the plunger support frame is removably attached to the pressurizing frame.