JPH07266388A - Injection molding method, mold, and machine - Google Patents

Abstract

PURPOSE:To improve the appearance of a molded product, and cause neither cracking nor warps nor bends on the molded product. CONSTITUTION:A mold provided with a pinpoint gate 34 is used, a valve pin 51 is moved forward up to a set position in a resin flow path 33 formed between a runner a pinpoint gate 34 in the middle of a dwell process, a resin flow path 33 and cavity 36 are intercepted, the valve pin 51 is moved forward up to a forward movement limit position between the pinpoint gate 34 and cavity 36 in succession further, the resin in the pinpoint gate 34 is pressed into the cavity 36 and enters a cooling process after that. Since an amount of resin following a change of volume during the dwell process can be pressed into the cavity and not only acquisition of a molded product having a uniform quality and stabilized dimensional accuracy but also prevention of generation of a sink or a warp in the molded product are possible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding method, a mold and an injection molding machine.

[0002]

2. Description of the Related Art Conventionally, in an injection molding machine, a resin melted by heating in a heating cylinder is injected, filled in a mold cavity, and then cooled and solidified in the cavity. The mold is opened and the molded product is ejected by the ejector pin so that the molded product can be taken out.

For this purpose, a screw is rotatably and rotatably arranged in the heating cylinder, and the resin is injected from an injection nozzle by advancing the screw. The resin injected from the injection nozzle enters the mold and then flows into the cavity through the sprue, runner and gate. When a die having a pinpoint gate with a reduced diameter is used as the gate, when the die is opened, a portion where the resin is solidified in the runner in the gate portion (hereinafter referred to as "runner portion"). It is automatically cut and separated from the molded product.

In this case, since the molded product can be taken out in the state where the gate portion is cut, the work of cutting the gate by the secondary processing can be omitted. By the way, when a mold having the pinpoint gate is used, the runner portion and the molded product are automatically cut and separated at the gate portion, but the runner portion is discarded as it is, so the resin consumption Will increase.

Therefore, a mold provided with a hot runner is provided. In this type of mold, the hot runner is either insulated by a heat insulating material or heated by a heater or the like, and the resin in the hot runner is always in a molten state. Then, a needle valve faces the pinpoint gate, and the pinpoint gate is mechanically opened and closed by the needle valve. That is, the needle valve is opened when the resin is filled in the cavity, and the needle valve is closed when the molded product is taken out.

In this case, since the molded product can be taken out with the hot runner left, the runner portion is not formed. Therefore, when the mold is opened, the inside of the hot runner and the molded product are automatically cut and separated at the gate portion.

[0007]

However, in the conventional injection molding machine described above, when the mold is opened, the runner portion and the molded product are cut and separated by forced pulling at the gate portion. The cut surface of is not smooth, and the appearance of the molded product is deteriorated. In particular,
If the pinpoint gate has a large diameter, the gate portion may be convex, the gate trace may remain, or the gate may be recessed. As a result, when an impact is applied during use of the molded product, cracks are likely to occur in the molded product due to the notch effect in the cut surface.

On the other hand, when the diameter of the pin point gate is reduced, the resistance in the resin flow path increases, so the injection pressure must be increased. Moreover, the pressure distribution in the cavity is not uniform, and the pressure difference between the vicinity of the gate portion and the portion away from the gate portion becomes large. As a result, residual stress remains in the molded product, causing warpage, bending, and the like.

Therefore, it is conceivable to lower the injection pressure by using a multi-point gate, but in order to use a multi-point gate, a large number of runners are required, and the runner portion to be discarded by that much is required. Will increase. Also,
A mold equipped with a hot runner has the same problem, and therefore, there is a mold in which each pinpoint gate is opened and closed by a needle valve. in this case,
It is necessary to dispose a needle pin for each pinpoint gate and a cylinder unit for advancing and retracting the needle pin in the mold. Therefore, the size of the mold is increased and the cost of the mold is increased.

Further, in the case of taking a large number of pieces, the pitch of the gate interval needs to be equal to or larger than the diameter of the cylinder unit, so that the mold becomes large. INDUSTRIAL APPLICABILITY The present invention can solve the problems of the conventional injection molding machine and improve the appearance of the molded product, and reduce the injection pressure without causing cracks, warpage, bending, etc. in the molded product. It is an object of the present invention to provide an injection molding method, an injection molding die, and an injection molding machine, which are capable of reducing the size of the die and reducing the cost of the die.

[0011]

Therefore, in the injection molding method of the present invention, a mold provided with a pinpoint gate is used, and the mold is formed between the runner and the pinpoint gate during the pressure holding process. In the resin flow path, the valve pin is advanced to a set position, the resin flow path and the cavity are blocked, and then the valve pin is further advanced to the advance limit position between the pin point gate and the cavity,
The resin in the pinpoint gate is pushed into the cavity, and then the cooling process is started.

In another injection molding method of the present invention, the runner is a hot runner. In still another injection molding method of the present invention, a lead frame on which a semiconductor chip is mounted is pre-loaded in the cavity, and the cavity is filled with resin to seal the lead frame and the semiconductor chip in an injection step. . Further, in the mold of the present invention, a fixed side holding part, a fixed side mold part which is held by the fixed side holding part, includes a fixed side mold plate and has a runner, and a movable side holding part, A movable-side mold part that is held by the movable-side holding part and has a movable-side mold plate that forms a cavity between the fixed-side mold plate and the fixed-side mold plate; It has a pressure plate and a plurality of valve pins having a rear end fixed to the pressure plate and movably arranged between a retracted limit position, a gate closed position, and an advanced limit position.

The fixed template includes a pin point gate formed between the cavity and the cavity, and a resin flow path connecting the pin point gate and the runner, and the valve pin includes: The pinpoint gate is closed at the gate closing position, and the pinpoint gate is advanced to the advance limit position to push the resin in the pinpoint gate into the cavity.

In another mold of the present invention, the runner is a hot runner. In still another mold of the present invention, a valve pin guide is formed on the inner wall of the resin passage. Further, in the injection molding machine of the present invention, a fixed-side holding part, a fixed-side mold part that is held by the fixed-side holding part, includes a fixed-side mold plate and has a runner, and a movable-side holding part. A mold having a movable mold part that is held by the movable mold holding part and that has a movable mold plate that forms a cavity between the fixed mold plate and the fixed mold plate; Drive source.

The mold is provided with a pressure plate movably arranged in the fixed side mold part, a rear end of which is fixed to the pressure plate, and the mold is advanced by the drive source to set a backward limit. A plurality of valve pins that take a position, a gate closed position, and a forward limit position, the fixed-side template is a pinpoint gate formed between the cavity and the cavity,
A resin flow path connecting between the pinpoint gate and the runner, wherein the valve pin closes the pinpoint gate at the gate closing position and advances to the forward limit position to move the resin inside the pinpoint gate. Is pushed into the cavity.

In another injection molding machine of the present invention, a plurality of the drive sources and the pressure plates are arranged and are independently operated.

[0017]

According to the present invention, as described above, in the injection molding method, the mold provided with the pinpoint gate is used, and it is formed between the runner and the pinpoint gate during the pressure holding process. Advance the valve pin to the set position in the resin flow passage, shut off the resin flow passage and the cavity,
Subsequently, the valve pin is further advanced to the advance limit position between the pin point gate and the cavity, the resin in the pin point gate is pushed into the cavity, and then the cooling step is started.

In this case, a pressure stroke is formed between the tip of the valve pin and the cavity 36 when the resin flow path and the cavity are cut off during the pressure holding step. Subsequently, in the latter half of the pressure-holding step, when the valve pin is advanced by the pressurizing stroke, the resin in the pin point gate is pushed into the cavity. In another injection molding method of the present invention, the runner is a hot runner. In this case, the resin in the hot runner is always in a molten state.

In still another injection molding method of the present invention, a lead frame on which a semiconductor chip is mounted is previously loaded in the cavity, and the cavity is filled with resin in the injection step to form the lead frame and the semiconductor chip. Seal. In this case, the mold is closed and the mold is clamped after the lead frame on which the semiconductor chip is mounted is loaded into the cavity, and the resin is injected from the injection nozzle.
The resin injected from the injection nozzle passes through the hot runner and the resin flow path, fills the cavity through the pin point gate, and seals the lead frame and the semiconductor chip.

Further, in the mold of the present invention, the fixed-side holding part, the fixed-side mold part held by the fixed-side holding part, having the fixed-side mold plate and having the runner, and the movable-side holding part. And a movable side mold part that is held by the movable side holding part and has a movable side mold plate that forms a cavity between the fixed side mold plate and the fixed side mold plate, and a movable side mold part that is movable in the fixed side mold part. The pressure plate is provided, and the rear end is fixed to the pressure plate and has a plurality of valve pins movably arranged between a backward limit position, a gate closing position, and a forward limit position.

The fixed-side template includes a pinpoint gate formed between the cavity and the cavity, and a resin flow path connecting the pinpoint gate and the runner, and the valve pin includes: The pinpoint gate is closed at the gate closing position, and the pinpoint gate is advanced to the advance limit position to push the resin in the pinpoint gate into the cavity.

That is, in the injection step, the valve pin is at the retracted limit position, and the resin flow path and the cavity are communicated with each other through the pin point gate. Then, the resin supplied through the resin flow path enters the cavity through the pin point gate. In the middle of the pressure-holding process, the valve pin is advanced to the gate closing position to close the pin point gate and shut off the resin flow path and the cavity. At this time, a pressure stroke is formed between the tip of the valve pin and the cavity.

Subsequently, in the latter half of the pressure-holding step, the valve pin is advanced by the pressurizing stroke to reach the advance limit position. As a result, the resin in the pinpoint gate is pushed into the cavity. In another mold of the present invention, the runner is a hot runner. In this case, the resin in the hot runner is always in a molten state.

In yet another mold of the present invention, a valve pin guide is formed on the inner wall of the resin passage. In this case, in the injection process, the resin supplied through the resin flow path enters the cavity through the pin point gate, and at that time, the valve pin supports the valve pin. Further, in the injection molding machine of the present invention, a fixed-side holding part, a fixed-side mold part that is held by the fixed-side holding part, includes a fixed-side mold plate and has a runner, and a movable-side holding part. A mold having a movable mold part that is held by the movable mold holding part and that has a movable mold plate that forms a cavity between the fixed mold plate and the fixed mold plate; Drive source.

The mold is provided with a pressure plate movably arranged in the fixed side mold part, and a rear end fixed to the pressure plate, and is moved forward by the drive source to move backward. A plurality of valve pins that take a position, a gate closed position, and a forward limit position, the fixed-side template is a pinpoint gate formed between the cavity and the cavity,
A resin flow path connecting between the pinpoint gate and the runner, wherein the valve pin closes the pinpoint gate at the gate closing position and advances to the forward limit position to move the resin inside the pinpoint gate. Is pushed into the cavity.

In this case, in the injection step, the valve pin is at the retracted limit position, and the resin flow path and the cavity are communicated with each other through the pin point gate. Then, the resin supplied through the resin flow path enters the cavity through the pin point gate. In the middle of the pressure-holding process, the valve pin is advanced to the gate closing position to close the pin point gate and shut off the resin flow path and the cavity. At this time, a pressure stroke is formed between the tip of the valve pin and the cavity.

Subsequently, in the latter half of the pressure-holding step, the valve pin is advanced by the pressurizing stroke to reach the advance limit position. As a result, the resin in the pinpoint gate is pushed into the cavity. In another injection molding machine of the present invention, a plurality of drive sources and pressure plates are arranged,
Each can be operated independently. In this case, the timing for opening and closing the pinpoint gate can be set independently for each cavity.

[0028]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a sectional view of an essential part of an injection molding machine according to the first embodiment of the present invention. In the figure, 1
Reference numeral 1 denotes a fixed side holding portion, and the fixed side holding portion 11 has a fixed side mounting plate 12, a spacer block 13, a receiving plate 14, a hot runner block 16 and a fixed side mold plate 17 as fixed side mold parts. It is attached. On the other hand, 21 is a movable side holding part, and a movable side mounting plate 22, a spacer block 23, a receiving plate 24 and a movable side mold plate 27 are attached to the movable side holding part 21 as movable side mold parts.

Then, the injection nozzle 29 of the injection device (not shown) advances in the injection process, and the tip of the injection nozzle 29 is brought into contact with the end surface of the hot runner block 16. The movable platen (not shown) is moved forward and backward (moved in the vertical direction in the figure) by a mold clamping device (not shown) to bring the movable side mold plate 27 and the fixed side mold plate 17 into contact with and separate from each other at the parting line. .

A hot runner 31 is formed in the hot runner block 16 in parallel with the parting line, and in the stationary mold plate 17, the hot runner block 16 is erected perpendicularly to the parting line. A hot runner nozzle 32 is provided, and a resin flow path 33 is formed in the hot runner nozzle 32. The hot runner 31 is insulated by a heat insulating material or heated by a heater (not shown) or the like, and the resin in the hot runner 31 is always in a molten state.

Therefore, the resin injected from the injection nozzle 29 passes through the hot runner 31 and the resin flow path 33 and is formed between the fixed side mold plate 17 and the movable side mold plate 27 via the pinpoint gate 34. The filled cavity 36 is filled. Then, the resin filled in the cavity 36 is cooled to form a molded product, which is ejected by the ejector device when the mold is opened.

For that purpose, the ejector pin 38 is provided. The ejector pin 38 is disposed with its tip facing the cavity 36, and after the mold is opened, the molded product is moved to the movable side mold plate 27.
And separate it from the bottom. The ejector pin 38 extends rearward (downward in the figure) through the movable side mold plate 27 and the receiving plate 24, and the head portion 39 formed at the rear end is clamped and fixed by the ejector plates 41 and 42. To be done. Then, the rod 43 can come into contact with the ejector plate 42, and the ejector pin 38 is moved as the rod 43 moves forward.
Is advanced.

Incidentally, 40 is fixed to the movable side mold plate 27,
A guide pin whose front end enters into the fixed-side template 17 and a return pin 45 whose front end faces the parting line. The guide pin 45 includes a movable side mold plate 27 and a receiving plate 24.
The head portion 46 formed at the rear end of the ejector plate 41 and 42 is fixed by being sandwiched by the ejector plates 41 and 42. Further, the return spring 4 is provided between the movable side mold plate 27 and the ejector plate 41.
8 are provided.

By the way, in order to open and close the pinpoint gate 34 during the pressure holding step, the valve pin 51 is opened.
Is provided. The valve pins 51 are arranged by the number of the pinpoint gates 34 with their tips facing the pinpoint gates 34, and penetrate the fixed side mold plate 17, the hot runner block 16 and the receiving plate 14 to the rear (upper side in the figure).
And the head portion 52 formed at the rear end is sandwiched and fixed by the pressure plates 56 and 57. Then, the rod 59 is fixed to the pressure plate 57 by the screw 60, and the valve pin 51 is advanced as the rod 59 is advanced by the drive source 62.

Reference numeral 63 designates the fixed side mounting plate 12 and the receiving plate 1.
4 is a guide pin disposed between the pressure plate 56 and the pressure plate 56 and guiding the pressure plates 56 and 57. Next, the operation of the injection molding machine having the above configuration will be described with reference to FIGS. 2 is a state diagram of a pressure holding process of an injection molding machine according to the first embodiment of the present invention, FIG. 3 is a die opening state diagram of the injection molding machine according to the first embodiment of the present invention, and FIG. It is a drawing of a molded product taken out of the injection molding machine in the first embodiment.

First, in the injection step, the valve pin 51 is retracted as shown in FIG.
The resin injected from passes through the hot runner 31 and the resin flow path 33, and is filled into the cavity 36 formed between the fixed-side mold plate 17 and the movable-side mold plate 27 via the pinpoint gate 34. . When the injection process is completed, a pressure holding process is subsequently performed to hold the resin pressure in the cavity 36. Then, in the middle of the pressure holding step, the rod 59
Is advanced by the drive source 62 (FIG. 1), and the valve pin 51 is accordingly advanced to close the pin point gate 34 in the gate closed position. At this time,
The resin flow path 33 and the cavity 36 are blocked. Subsequently, in the latter half of the pressure holding step, the valve pin 51 is connected to the pin point gate 34 and the cavity 3 as shown in FIG.
6 is advanced to the forward limit position between 6 and.

Then, after a lapse of a certain time in the cooling step, as shown in FIG. 3, the movable platen (not shown) is retracted, the movable side holding portion 21 is also retracted, and the movable side mold plate 27 side is moved. The mold opening is performed with the molded product M left. At this time, the valve pin 51 is placed at the forward limit position. Then, the rod 43 is advanced as shown in FIG. 4, and the ejector pin 38 is advanced along with the rod 43. At this time, the ejector pin 38 separates the molded product M from the movable side mold plate 27 and pushes it down.

In the injection molding machine having the above-mentioned structure, the drive source 62 is disposed outside the fixed-side holding portion 11, so that a plurality of molds can be used in common and the cost of the injection molding machine can be reduced. can do. To replace the mold, only the screw for fixing the pressure rod 59 and the pressure plate 57 needs to be removed. Since it is not necessary to dispose the cylinder unit in the mold, the mold can be downsized and the cost of the mold can be reduced. Further, even when a large number of pieces are taken, the pitch of the gate intervals can be reduced, so that the mold can be downsized.

Next, details of the hot runner nozzle 32 will be described with reference to FIGS. FIG. 5 is a sectional view of a hot runner nozzle according to the first embodiment of the present invention,
6 is a sectional view taken along the line AA of FIG. 5, FIG. 7 is a sectional view taken along the line BB of FIG. 6, and FIG. 8 is a first state diagram of the pinpoint gate pressure-holding step in the first embodiment of the present invention. FIG. 9 shows the first of the present invention.
Second step of holding pressure of pinpoint gate in the embodiment
FIG.

As shown in FIGS. 5 to 7, a pinpoint gate 34 is formed at the tip of the hot runner nozzle 32, and the valve pin 5 is opposed to the pinpoint gate 34.
1 is arranged so that it can move back and forth. The diameter of the portion other than the tip of the hot runner nozzle 32 is larger than that of the tip, and the resin flow path 3 is provided between the hot runner nozzle 32 and the valve pin 51.
3 is formed.

In the injection step, as shown in FIG. 5, the valve pin 51 is at the retracted limit position, and the resin flow path 33 and the cavity 36 are communicated with each other through the pin point gate 34. Then, the resin supplied through the resin flow path 33 enters the cavity 36 through the pin point gate 34, and at that time, the valve pin 51 is laterally pushed by the flow of the resin.

Therefore, the valve pin guide 71 is provided upstream of the pin point gate 34 in the resin flow path 33.
Are formed to support the valve pin 51. Therefore, it is possible to prevent the valve pin 51 from bending to one side due to the resin pressure. In this case, the valve pin guides 71 are formed so as to project from the inner wall of the hot runner nozzle 32 at three locations in the circumferential direction.

During the pressure-holding step, the valve pin 51 is advanced to the gate closing position as shown in FIG. 8 to close the pinpoint gate 34 and shut off the resin flow path 33 and the cavity 36. Therefore, the outer diameter of the valve pin 51 is set to be slightly smaller than the inner diameter of the pin point gate 34. Further, at this time, the pressurization stroke S is formed between the tip of the valve pin 51 and the cavity 36.

Subsequently, in the latter half of the pressure holding process, the valve pin 51 is advanced by the pressurizing stroke S as shown in FIG. 9, and the pin point gate 34 and the cavity 36 are moved.
It reaches the forward limit position between and. As a result, the resin in the pinpoint gate 34 is pushed into the cavity 36.
In this case, the stroke S is set corresponding to the amount of resin that accompanies the change in the volume of the resin in the cavity 35 that occurs during the pressure holding step.

That is, since the resin in the cavity has elasticity during the pressure holding step, the volume also changes due to the change in the pressure applied from the outside. Further, the resin in the cavity contracts as the temperature decreases, and the volume changes.
Therefore, by pushing the resin corresponding to the change in the volume into the cavity 36, not only a molded product of uniform quality and stable dimensional accuracy can be obtained, but also a sink or a warp occurs in the molded product. Can be prevented.

Thus, the resin flow path 3 is formed during the pressure holding process.
Since 3 and the cavity 36 are cut off, the cut surface of the molded product becomes smooth, and the appearance of the molded product is improved. Further, since it is not necessary to increase the diameter of the pinpoint gate 34, the gate portion does not have a convex shape, a gate mark does not remain, or a concave shape is not formed. Therefore, it is possible to prevent cracks from being generated in the molded product during use of the molded product.

Furthermore, since it is not necessary to reduce the diameter of the pinpoint gate 34, it is possible to prevent the resistance in the resin passage from increasing. Therefore, the pressure distribution in the cavity 36 becomes uniform. as a result,
It is possible to prevent warpage and bending of the molded product. Also, since it is not necessary to use a multi-point gate,
Less resin is wasted.

Next, a second embodiment of the present invention will be described. FIG. 10 is a sectional view of an essential part of an injection molding machine according to the second embodiment of the present invention. In the figure, reference numeral 11 denotes a fixed side holding portion, to which the fixed side mounting plate 12, spacer block 13, receiving plate 14, hot runner block 16 and fixed side template 17 are attached. On the other hand, 2
Reference numeral 1 denotes a movable side holding portion, to which a movable side mounting plate 22, a spacer block 23, a receiving plate 24, and a movable side template 27 are attached.

Then, the injection nozzle 29 of the injection device (not shown) advances in the injection process, and the tip of the injection nozzle 29 is brought into contact with the end surface of the hot runner block 16. The movable platen (not shown) is moved forward and backward (moved in the vertical direction in the figure) by a mold clamping device (not shown) to bring the movable side mold plate 27 and the fixed side mold plate 17 into contact with and separate from each other at the parting line. .

A hot runner 31 is formed in the hot runner block 16 in parallel with the parting line, and in the stationary mold plate 17, the hot runner block 16 is erected perpendicularly to the parting line. A hot runner nozzle 32 is provided, and a resin flow path 33 is formed in the hot runner nozzle 32. The hot runner 31 is insulated by a heat insulating material or heated by a heater (not shown) or the like, and the resin in the hot runner 31 is always in a molten state.

Therefore, the resin injected from the injection nozzle 29 passes through the hot runner 31 and the resin flow path 33 and is formed between the fixed side mold plate 17 and the movable side mold plate 27 via the pinpoint gate 34. The filled cavity 36 is filled. The resin filled in the cavity 36 is cooled to form a molded product, which is ejected by the ejector device when the mold is opened.

Therefore, the ejector pin 38 is provided. The ejector pin 38 is disposed with its tip facing the cavity 36, and after the mold is opened, the molded product is moved to the movable side mold plate 27.
And separate it from the bottom. The ejector pin 38 extends rearward (downward in the figure) through the movable side mold plate 27 and the receiving plate 24, and the head portion 39 formed at the rear end is clamped and fixed by the ejector plates 41 and 42. To be done. Then, the rod 43 can come into contact with the ejector plate 42, and the ejector pin 38 is moved as the rod 43 moves forward.
Is advanced.

By the way, the valve pin 51 for opening and closing the pinpoint gate 34 during the pressure holding step.
Is provided. The valve pins 51 are arranged by the number of the pinpoint gates 34 with their tips facing the pinpoint gates 34, and penetrate the fixed side mold plate 17, the hot runner block 16 and the receiving plate 14 to the rear (upper side in the figure).
And the head portion 52 formed at the rear end is sandwiched and fixed by the pressure plates 56 and 57. Then, a rod 59 is disposed on the pressure plate 57 so as to be able to come into contact with and separate from the pressure plate 57, and the valve pin 51 is advanced as the rod 59 is advanced by the drive source 62.

A guide pin 63 is arranged between the fixed side mounting plate 12 and the receiving plate 14, and the pressure plate 56,
Guide 57. A return spring 75 is provided so as to surround the guide pin 63, and the pressure plates 56, 5
7 is urged toward the fixed side mounting plate 12 side. Therefore, the pressure plates 56 and 57 are advanced by the drive source 62 and retracted by the return spring 75.

Here, the moving stroke of the pressure plates 56 and 57 is set to be longer than the length of the resin flow path 33,
At the backward limit position of the valve pin 51, the valve pin 51
Is not in the hot runner 31 and the resin flow path 33. Therefore, since the valve pin 51 is not subjected to the resin pressure in the injection process, the hot runner nozzle 32
There is no need to form a valve pin guide inside.

Next, the operation of the injection molding machine having the above construction will be described with reference to FIG. FIG. 11 is a state diagram of the pressure holding process of the injection molding machine according to the second embodiment of the present invention.
First, in the injection step, the valve pin 51 is
The resin which is retreated as shown in FIG. 2 and is injected from the injection nozzle 29 passes through the hot runner 31 and the resin flow path 33, and through the pinpoint gate 34, the fixed-side template 17
The cavity 36 formed between the movable mold 27 and the movable mold 27 is filled.

When the injection process is completed, a pressure holding process is subsequently performed, and the resin pressure in the cavity 36 is maintained and the resin cooling is started. Then, in the middle of the pressure-holding step, the rod 59 is moved forward by the drive source 62, the valve pin 51 is moved forward accordingly, and the pin point gate 34 is closed at the gate closing position. At this time, the resin flow path 33 and the cavity 36 are blocked by the valve pin 51. Subsequently, in the latter half of the pressure holding step, the valve pin 51 is advanced to the advance limit position between the pin point gate 34 and the cavity 36 as shown in FIG.

The mold opening step after the cooling step and the step of projecting the molded product M (FIG. 4) are the same as those in the first embodiment. Further, when the ejector plates 41 and 42 are retracted and the pressure rod 59 is retracted after the projecting step is completed, the pressure plates 56 and 57 are retracted while being in contact with the pressure rod 59 by the return force of the return spring 75. However, with this retreat, the valve pin 51
Will also retreat. Then, the ejector pin 38 and the valve pin 51 are returned to their original positions.

Next, the case of exchanging the mold will be described. In the second embodiment, since the pressure rod 59 and the pressure plate 57 are not directly connected to each other, when the pressure rod 59 is retracted, the pressure plate 57 and the pressure rod 5 are moved.
9 and 9 can be separated. Therefore, the mold can be easily removed from the injection molding machine. In the injection molding machine configured as described above, since the drive source 62 is disposed outside the fixed-side holding portion 11, it is possible to use a plurality of molds in common, and the cost of the injection molding machine can be reduced. it can. To replace the mold, the pressure rod 59 may be retracted and separated from the pressure plate 57.

Since it is not necessary to dispose the cylinder unit in the mold, the mold can be downsized and the cost of the mold can be reduced. Further, even when a large number of pieces are taken, the pitch of the gate intervals can be reduced, so that the mold can be downsized. Next, the details of the hot runner nozzle 32 will be described with reference to FIGS.

FIG. 12 is a sectional view of a hot runner nozzle according to the second embodiment of the present invention, and FIG. 13 is a sectional view taken along line CC of FIG. As shown in the figure, the hot runner nozzle 32
A pin point gate 34 is formed at the tip of the valve pin 51, and a valve pin 51 is arranged to face the pin point gate 34 so as to be movable back and forth. The diameter of the portion other than the tip of the hot runner nozzle 32 is larger than that of the tip, and the resin flow path 33 is formed between the hot runner nozzle 32 and the valve pin 51.

In the injection step, the valve pin 51 is in the retracted limit position as shown in FIG. 11, and the resin flow path 33 and the cavity 36 are communicated with each other through the pin point gate 34. Then, the resin supplied through the resin flow path 33 enters the cavity 36 through the pinpoint gate 34. In the middle of the pressure-holding process, the valve pin 51 is advanced to the gate closing position as shown in FIG. 12 to close the pin point gate 34 and shut off the resin flow path 33 and the cavity 36. At this time, a pressure stroke Sa is formed between the tip of the valve pin 51 and the cavity 36.

Subsequently, in the latter half of the pressure-holding step, the valve pin 51 is advanced by the pressurizing stroke Sa to reach the advance limit position between the pin point gate 34 and the cavity 36. As a result, the resin in the pinpoint gate 34 is pushed into the cavity 36. Therefore, not only a molded product of uniform quality and stable dimensional accuracy can be obtained, but also sinking or warpage of the molded product can be prevented.

Next, a third embodiment of the present invention will be described. FIG. 14 is a sectional view of an essential part of an injection molding machine according to the third embodiment of the present invention. In the figure, reference numeral 11 denotes a fixed side holding portion, to which the fixed side mounting plate 12, spacer block 13, receiving plate 14, hot runner block 16 and fixed side template 17 are attached. On the other hand, 2
Reference numeral 1 denotes a movable side holding portion, to which a movable side mounting plate 22, a spacer block 23, a receiving plate 24, and a movable side template 27 are attached.

Then, the injection nozzle 29 of the injection device (not shown) advances in the injection process, and the tip of the injection nozzle 29 is brought into contact with the end surface of the hot runner block 16. The movable platen (not shown) is moved forward and backward (moved in the vertical direction in the figure) by a mold clamping device (not shown) to bring the movable side mold plate 27 and the fixed side mold plate 17 into contact with and separate from each other at the parting line. .

A hot runner 31 is formed in the hot runner block 16 in parallel with the parting line, and in the stationary mold plate 17, the hot runner block 16 is erected perpendicularly to the parting line from the hot runner block 16. Further, the first and second hot runner nozzles 32A and 32B are arranged, and the resin flow paths 33A and 33B are formed in the hot runner nozzles 32A and 32B. The hot runner 31 is insulated by a heat insulating material or heated by a heater (not shown) or the like, and the resin in the hot runner 31 is always in a molten state.

Therefore, the resin injected from the injection nozzle 29 is the hot runner 31 and the resin flow path 33A.
The first and second cavities 36A and 36B formed between the fixed-side mold plate 17 and the movable-side mold plate 27 through the pinpoint gates 34A and 34B. In this case, the first and second cavities 36A, 36B
In the above, molded articles having different sizes and shapes are molded.

The resin filled in the cavities 36A, 36B is cooled to form a molded product, which is ejected by the ejector device when the mold is opened. Therefore, ejector pins 38A and 38B are provided. The ejector pins 38A and 38B are arranged with their tips facing the cavities 36A and 36B, and separate the molded product from the movable-side mold plate 27 and push it down after the mold is opened. The ejector pins 38A and 38B extend rearward (downward in the drawing) through the movable side mold plate 27 and the receiving plate 24, and the rear ends are clamped and fixed by the ejector plates 41 and 42. Then, the rod 43 can be brought into contact with the ejector plate 42, and the ejector pins 38A and 38B are advanced as the rod 43 moves forward.

By the way, valve pins 51A and 51B are provided to open and close the pinpoint gates 34A and 34B during the pressure holding step. The valve pin 51
A and 51B are arranged by the number of the pinpoint gates 34A and 34B with their tips facing the pinpoint gates 34A and 34B, and penetrate the fixed side mold plate 17, the hot runner block 16 and the receiving plate 14 to the rear ( (Upper in the figure)
And the rear end of the pressure plates 56A, 56B, 57A,
It is clamped and fixed by 57B. The first and second rods 5 are attached to the pressure plates 57A and 57B, respectively.
9A and 59B are arranged so that they can come into contact with and separate from each other, and the rod 59
As A and 59B are advanced by the drive source 62, the valve pins 51A and 51B are advanced.

Next, the operation of the injection molding machine having the above construction will be described. First, in the injection step, the valve pins 51A and 51B are retracted as shown in FIG. 14, and the resin injected from the injection nozzle 29 passes through the hot runner 31 and the resin flow paths 33A and 33B, and the pinpoint gate 34A. , 34B between the fixed-side mold plate 17 and the movable-side mold plate 27 to form cavities 36A, 36B.
To be filled.

When the injection process is completed, a pressure holding process is subsequently performed, and the resin pressure in the cavities 36A and 36B is maintained, and the resin cooling is started. Then, in the middle of the pressure-holding step, the rods 59A and 59B drive the drive source 6
2 is moved forward by the valve pin 51.
A and 51B are advanced to close the pinpoint gates 34A and 34B in the gate closed position. At this time, the inside of the resin flow paths 33A and 33B and the cavity 3 respectively.
6A and 36B are shut off by valve pins 51A and 51B. Subsequently, in the latter half of the pressure-holding step, the valve pins 51A and 51B are connected to the pinpoint gates 34A and 3A.
4B and the cavities 36A, 36B are advanced to the advance limit position.

In this case, not only the cavities 36A and 36B differ from each other in size and shape, but also the injection nozzle 29
The position from is different. Therefore, the timing for opening and closing the pinpoint gates 34A and 34B should be set for each cavity
By independently setting 6A and 36B, it is possible to adjust the amount of resin filled in the cavities 36A and 36B and the filling time.
The quality of the molded product can be improved.

Next, a fourth embodiment of the present invention will be described. FIG. 15 is a sectional view of an essential part of an injection molding machine according to the fourth embodiment of the present invention. As shown in the figure, cavity 3
6A and 36B have the same size and shape, but the distances of the cavities 36A and 36B from the injection nozzle 29 are different. Therefore, by independently setting the timing for opening and closing the pinpoint gates 34A, 34B for each of the cavities 36A, 36B, the cavities 36A,
Since the amount of the resin filled in 6B can be adjusted and the filling time can be adjusted, the quality of the molded product can be improved.

Next, a fifth embodiment of the present invention will be described. FIG. 16 is a sectional view of a hot runner nozzle and a cavity in the fifth embodiment of the present invention. in this case,
A cylindrical heating member 76 is arranged in the hot runner nozzle 32, and the resin flow path 33 is formed inside the heating member 76. Then, the valve pin 51 is arranged in the resin flow path 33 so as to be movable back and forth.

A sub-runner 77 is arranged at a position facing the tip of the pin point gate 34, and the resin passing through the pin point gate 34 enters the cavity 78 via the sub-runner 77. And the sub-runner 7
A secondary gate 79 is formed between 7 and the cavity 78. In the first to fifth embodiments, the injection nozzle 29 is arranged in the direction perpendicular to the mold clamping direction.
It may be arranged on the fixed side holding portion 11 side in the mold clamping direction. Further, as the drive source of the drive sources 62, 62A, 62B, a hydraulic device, a pneumatic device, or a motor whose operating shaft moves linearly can be used.

Next, a sixth embodiment of the present invention will be described. FIG. 17 is a sectional view of an essential part of an injection molding machine according to the sixth embodiment of the present invention. In this case, it is applied to a mold for semiconductor encapsulation, and cavities 81 are formed between the fixed-side mold plate 17 and the movable-side mold plate 27 so as to correspond to a plurality of lead frames, and the sub-runner 82 is provided between the cavities 81. Connect.

In this embodiment, the pitch between the cavities 81 can be set small, and the resin can be directly supplied from the hot runner nozzles 32 to the cavities 81. %] Can be improved to near. Next, the operation of the injection molding machine having the above configuration will be described with reference to FIG.

FIG. 18 is a drawing showing the condition of taking out a molded product of the injection molding machine according to the sixth embodiment of the present invention. First, as shown in FIG. 17, after the lead frame on which the semiconductor chip is mounted is loaded into the cavity 81, the mold is closed and the mold is clamped, and the resin is injected from the injection nozzle 29. The resin injected from the injection nozzle 29 passes through the hot runner 31 and the resin flow path 33, fills the cavity 81 via the pinpoint gate 34, and seals the lead frame and the semiconductor chip.

When the injection process is completed, the pressure holding process is subsequently performed, and the resin pressure in the cavity 81 is maintained. Then, the rod 59 is moved forward by the drive source 62 in the middle of the pressure-holding step, and the valve pin 51 is moved forward accordingly, closing the pin point gate 34 at the gate closing position. At this time, the hot runner 31 and the cavity 81 are shut off by the valve pin 51.
Then, in the latter half of the pressure holding step, the valve pin 51
Is advanced to the advance limit position between the pin point gate 34 and the cavity 36, and the resin in the pin point gate 34 is pushed into the cavity 81.

Then, after a lapse of a certain time in the cooling step, the movable platen (not shown) is retracted, and the mold is opened with the molded product left on the movable mold plate 27 side. At this time, the valve pin 51 is placed at the forward limit position. Subsequently, as shown in FIG. 18, the rod 43 is advanced, and the ejector pin 38 is advanced along with the rod 43. At this time, the ejector pin 38 is a molded product Ma.
Is separated from the movable side mold plate 27 and pushed down.

When a high-grade thermoplastic resin is used as the sealing resin, the adhesion between the lead frame and the resin becomes low. However, by pushing the resin in the pinpoint gate 34 into the cavity 81 The resin pressure can be increased at the end. Therefore, the lead frame and the semiconductor chip can be sufficiently sealed.

Next, a seventh embodiment of the present invention will be described. FIG. 19 is a sectional view of an essential part of an injection molding machine according to the seventh embodiment of the present invention. In the figure, reference numeral 11 denotes a fixed-side holding portion, to which the fixed-side mounting plate 12, the spacer block 13, the receiving plate 14, and the fixed-side template 17 are attached. On the other hand, reference numeral 21 denotes a movable side holding portion, to which the movable side mounting plate 22, spacer block 23, receiving plate 24 and movable side template 27 are attached.

Then, the injection nozzle 29 of the injection device (not shown) advances in the injection process, and the tip of the injection nozzle 29 is brought into contact with the end face of the abutting portion between the receiving plate 14 and the stationary mold plate 17. In addition, the movable platen (not shown) advances and retreats (moves up and down in the figure) by a mold clamping device (not shown).
The movable side mold plate 27 and the fixed side mold plate 17 are brought into contact with and separated from each other at the parting line.

A runner 84 is formed along the parting line between the receiving plate 14 and the fixed-side mold plate 17, and the runner 84 is erected in the fixed-side mold plate 17 from the runner 84 perpendicularly to the parting line. A runner nozzle 85 is provided, and a resin flow path is formed in the runner nozzle 85. Therefore, the resin injected from the injection nozzle 29 passes through the runner 84 and the resin flow path and passes through the pinpoint gate 3
A cavity 36 formed between the fixed-side mold plate 17 and the movable-side mold plate 27 is filled with the through hole 4.

The resin filled in the cavity 36 is cooled to form a molded product, which is ejected by the ejector device when the mold is opened. Therefore, the ejector pin 38 is provided. The ejector pin 38 is disposed so that its tip faces the cavity 36, and after the mold is opened, the molded product is separated from the movable-side mold plate 27 and pushed down. Then, the ejector pin 38 penetrates the movable side mold plate 27 and the receiving plate 24 and is rearward (downward in the drawing).
, And the rear end is clamped and fixed by the ejector plates 41 and 42. Then, the ejector plate 4
The rod 43 can come into contact with the rod 2, and the ejector pin 38 is moved forward as the rod 43 moves forward.

Reference numeral 86 is fixed to the fixed side mounting plate 12, and the spacer block 13, the receiving plate 14, and the fixed side template 1 are attached.
7, a guide pin that penetrates through the movable-side mold plate 27 and the receiving plate 24 and has a tip that enters the spacer block 23. By the way, a valve pin 51 is provided to open and close the pinpoint gate 34 during the pressure holding step.
The valve pins 51 are arranged by the number of the pinpoint gates 34 with their tips facing the pinpoint gates 34, penetrate the fixed-side mold plate 17 and the receiving plate 14 and extend rearward (upward in the figure), and Are clamped and fixed by the pressure plates 56 and 57. Then, the pressure plate 57
The rod 59 is fixed to the drive source 62.
The valve pin 51 is advanced as it is advanced by.

Next, the operation of the injection molding machine having the above construction will be described with reference to FIGS. FIG. 20 is a state diagram of a pressure-holding process of an injection molding machine in the seventh embodiment of the present invention, FIG. 21 is a mold opening state diagram of the injection molding machine in the seventh embodiment of the present invention, and FIG. FIG. 23 is a state diagram of a molded product taken out from the injection molding machine in the seventh embodiment, FIG. 23 is a state diagram of an injection process of a runner nozzle and a cavity in the seventh embodiment of the present invention, and FIG. 24 is a seventh embodiment of the present invention. 26 is a first state diagram of the runner nozzle and cavity pressure holding step, and FIG. 25 is a second state diagram of the runner nozzle and cavity pressure holding step in the seventh embodiment of the present invention.
Is a mold opening state diagram of a mold according to a seventh embodiment of the present invention,
FIG. 27 is a process drawing of a die according to the seventh embodiment of the present invention.

First, in the injection step, the valve pin 51 is retracted as shown in FIGS. 19 and 23, and the resin injected from the injection nozzle 29 passes through the runner 84 and the runner nozzle 85 and passes through the pinpoint gate 34. A cavity 36 formed between the fixed-side mold plate 17 and the movable-side mold plate 27 is filled with the through-hole. When the injection process is completed, a pressure holding process is subsequently performed to hold the resin pressure in the cavity 36. Then, in the middle of the pressure-holding step, as shown in FIG.
9) advanced by the valve pin 5
1 is advanced to close the pinpoint gate 34 in the gate closed position. At this time, the runner nozzle 8
The resin flow path in 5 and the cavity 36 are blocked by the valve pin 51. Further, a pressure stroke Sa is formed between the tip of the valve pin 51 and the cavity 36.
Then, from this time, the screw in the heating cylinder (not shown) can be retracted to start the measurement. Therefore, the molding time can be shortened.

Subsequently, in the latter half of the pressure holding step, the valve pin 51 is advanced to the advance limit position between the pin point gate 34 and the cavity 36 as shown in FIGS. Then, after a lapse of a certain period of time in the cooling step, as shown in FIGS. 21 and 26, the movable platen (not shown) is retracted, the movable-side holding portion 21 is also retracted, and the movable-side template 27 is molded. The mold opening is performed with the product Mb left. At this time, the space between the receiving plate 14 and the fixed-side mold plate 17 is also opened with the runner portion 88 left on the receiving plate 14 side.

Then, as shown in FIGS. 22 and 27, the rod 43 is advanced, and the ejector pin 38 is advanced along with the rod 43. At this time, the ejector pin 38 separates the molded product Mb from the movable side mold plate 27 and pushes it down. On the other hand, the rod 59 is retracted by the drive source 62, and the valve pin 51 is retracted accordingly, separating the runner portion 88 from the receiving plate 14.

The present invention is not limited to the above embodiments, but various modifications can be made based on the spirit of the present invention, and they are not excluded from the scope of the present invention.

[0092]

As described above in detail, according to the present invention, in the injection molding method, the mold having the pinpoint gate is used, and the runner and the pinpoint gate are connected during the pressure holding process. In the resin flow passage formed between them, the valve pin is advanced to a set position to block the resin flow passage and the cavity, and then the valve pin is further advanced to the advance limit position between the pin point gate and the cavity. The resin in the pinpoint gate is pushed into the cavity, and then the cooling process is started.

Since the resin corresponding to the change in volume during the pressure-holding process can be pushed into the cavity, not only a molded product of uniform quality and stable dimensional accuracy can be obtained, but also It is possible to prevent warpage. Further, since the resin flow path and the cavity are cut off during the pressure holding step, the cut surface of the molded product becomes smooth and the molded product has a good appearance.

Since it is not necessary to increase the diameter of the pinpoint gate, the gate portion does not have a convex shape, a gate mark does not remain, or a concave shape is not formed. Therefore, it is possible to prevent cracks from being generated in the molded product during use of the molded product. Furthermore, since it is not necessary to reduce the diameter of the pinpoint gate, it is possible to prevent the resistance in the resin flow path from increasing. Therefore, the pressure distribution in the cavity becomes uniform, and it is possible to prevent the molded product from warping and bending.

Since it is not necessary to use a multi-point gate, the amount of resin discarded can be reduced. In another injection molding method of the present invention, a lead frame on which a semiconductor chip is mounted is preloaded in the cavity, and the cavity is filled with resin in an injection step,
The lead frame and the semiconductor chip are sealed.

In this case, by pushing the resin in the pinpoint gate into the cavity, the resin pressure can be increased at the end of filling. Therefore, the lead frame and the semiconductor chip can be sufficiently sealed. Further, in the mold of the present invention, a fixed side holding part, a fixed side mold part which is held by the fixed side holding part, includes a fixed side mold plate and has a runner, and a movable side holding part, A movable-side mold part that is held by the movable-side holding part and has a movable-side mold plate that forms a cavity between the fixed-side mold plate and the fixed-side mold plate; A pressure plate and a rear end fixed to the pressure plate,
And a plurality of valve pins movably arranged between a backward limit position, a gate closed position, and a forward limit position.

The fixed template includes a pin point gate formed between the cavity and the cavity, and a resin flow path connecting the pin point gate and the runner, and the valve pin includes: The pinpoint gate is closed at the gate closing position, and the pinpoint gate is advanced to the advance limit position to push the resin in the pinpoint gate into the cavity.

Therefore, since it is not necessary to dispose the cylinder unit in the mold, the mold can be downsized and the cost of the mold can be reduced. Further, even when a large number of pieces are taken, the pitch of the gate intervals can be reduced, so that the mold can be downsized. In still another mold of the present invention, a valve pin guide is formed on the inner wall of the resin passage. In this case, in the injection process, the resin supplied through the resin flow path enters the cavity through the pin point gate,
At that time, the valve pin supports the valve pin. Therefore, it is possible to prevent the valve pin from bending to one side due to the resin pressure.

Further, in the injection molding machine of the present invention,
A fixed-side holding part, a fixed-side mold part held by the fixed-side holding part, having a fixed-side mold plate and having a runner formed therein, a movable-side holding part, and held by the movable-side holding part, The mold includes a movable mold part having a movable mold plate that forms a cavity between the fixed mold plate and a fixed mold plate, and a drive source attached to the fixed holding part.

The mold is provided with a pressure plate movably arranged in the fixed-side mold part, a rear end of which is fixed to the pressure plate, and the mold is advanced by the drive source to be retracted. A plurality of valve pins that take a position, a gate closed position, and a forward limit position, the fixed-side template is a pinpoint gate formed between the cavity and the cavity,
A resin flow path connecting between the pinpoint gate and the runner, wherein the valve pin closes the pinpoint gate at the gate closing position and advances to the forward limit position to move the resin inside the pinpoint gate. Is pushed into the cavity.

In this case, since the drive source is disposed outside the fixed side holding portion, it is possible to use a plurality of molds together, and the cost of the injection molding machine can be reduced. In another injection molding machine of the present invention, a plurality of the drive sources and the pressure plates are arranged and are independently operated. In this case, the timing for opening and closing the pinpoint gate can be set independently for each cavity.

Therefore, even if the size, shape, etc. of the cavities are different or the distance from the injection nozzle of the cavities is different, the amount of resin to be filled in each cavity is adjusted and the filling time is adjusted. It is possible to improve the quality of the molded product.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part of an injection molding machine according to a first embodiment of the present invention.

FIG. 2 is a state diagram of a pressure holding process of the injection molding machine according to the first embodiment of the present invention.

FIG. 3 is a mold opening state diagram of the injection molding machine according to the first embodiment of the present invention.

FIG. 4 is a drawing of a molded product taken out of the injection molding machine according to the first embodiment of the present invention.

FIG. 5 is a cross-sectional view of the hot runner nozzle according to the first embodiment of the present invention.

6 is a cross-sectional view taken along the line AA of FIG.

7 is a sectional view taken along line BB of FIG.

FIG. 8 is a first state diagram of a pinpoint gate pressure maintaining step in the first example of the present invention.

FIG. 9 is a second state diagram of the pinpoint gate pressure maintaining step in the first example of the present invention.

FIG. 10 is a sectional view of an essential part of an injection molding machine according to a second embodiment of the present invention.

FIG. 11 is a state diagram of a pressure holding process of the injection molding machine according to the second embodiment of the present invention.

FIG. 12 is a sectional view of a hot runner nozzle according to a second embodiment of the present invention.

FIG. 13 is a sectional view taken along line CC of FIG.

FIG. 14 is a sectional view of an essential part of an injection molding machine according to a third embodiment of the present invention.

FIG. 15 is a sectional view of an essential part of an injection molding machine according to a fourth embodiment of the present invention.

FIG. 16 is a sectional view of a hot runner nozzle and a cavity in a fifth embodiment of the present invention.

FIG. 17 is a sectional view of an essential part of an injection molding machine according to a sixth embodiment of the present invention.

FIG. 18 is a drawing of a molded product taken out of the injection molding machine according to the sixth embodiment of the present invention.

FIG. 19 is a cross-sectional view of essential parts of an injection molding machine according to a seventh embodiment of the present invention.

FIG. 20 is a state diagram of a pressure holding process of an injection molding machine according to the seventh embodiment of the present invention.

FIG. 21 is a mold opening state diagram of an injection molding machine according to a seventh embodiment of the present invention.

FIG. 22 is a drawing of a molded product taken out of the injection molding machine according to the seventh embodiment of the present invention.

FIG. 23 is a state diagram of the injection process of the runner nozzle and the cavity according to the seventh embodiment of the present invention.

FIG. 24 is a first state diagram of a runner nozzle and cavity pressure holding step in a seventh example of the present invention.

FIG. 25 is a second state diagram of the runner nozzle and cavity pressure holding step in the seventh example of the present invention.

FIG. 26 is a die opening state diagram of a die according to a seventh embodiment of the present invention.

FIG. 27 is a process drawing of the metal mold in the seventh embodiment of the present invention.

[Explanation of symbols]

11 Fixed Side Holding Part 17 Movable Side Template 21 Movable Side Holding Part 31 Hot Runner 33 Resin Flow Path 34, 34A, 34B Pinpoint Gate 36, 36A, 36B Cavity 51, 51A, 51B Valve Pin 56, 56A, 56B, 57, 57A, 57B Pressure plate 62, 62A, 62B Drive source 71 Valve pin guide 84 Runner

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location B29L 31:34

Claims (8)

[Claims] 1. An injection molding method using a mold provided with a pinpoint gate, comprising: (a) during a pressure-holding step,
In the resin flow path formed between the runner and the pinpoint gate, the valve pin is advanced to the gate blocking position to block the resin flow channel and the cavity, and (b) subsequently,
The injection molding method characterized in that the valve pin is further advanced to the advance limit position between the pin point gate and the cavity, the resin in the pin point gate is pushed into the cavity, and (c) after that, a cooling step is performed. . 2. The injection molding method according to claim 1, wherein the runner is a hot runner. 3. The lead frame on which a semiconductor chip is mounted is previously loaded into the cavity, and the cavity is filled with resin in the injection step to seal the lead frame and the semiconductor chip. Injection molding method. 4. (a) a fixed-side holding part, (b) a fixed-side mold part that is held by the fixed-side holding part, includes a fixed-side mold plate and has a runner, and (c) a movable side. Holding part,
(D) a movable mold part having a movable mold plate that is held by the movable mold holder and forms a cavity between the movable mold plate and the fixed mold plate; and (e) moves in the fixed mold part. A pressure plate freely arranged, and (f) a plurality of valve pins whose rear end is fixed to the pressure plate and are movable between a backward limit position, a gate closing position, and a forward limit position. And (g) the fixed-side template includes a pinpoint gate formed between the cavity and the cavity, and a resin flow path connecting the pinpoint gate and the runner. h) The mold in which the valve pin closes the pinpoint gate at the gate closing position and advances to the advance limit position to push the resin in the pinpoint gate into the cavity. 5. The mold according to claim 4, wherein the runner is a hot runner. 6. The mold according to claim 4, wherein a valve pin guide is formed on the inner wall of the resin passage. 7. (a) a fixed-side holding part, a fixed-side mold part held by the fixed-side holding part, having a fixed-side mold plate and having a runner, a movable-side holding part, and the movable part. A mold having a movable side mold part that is held by a side holding part and that has a movable side mold plate that forms a cavity between the fixed side mold plate and the fixed side mold plate; (C) the mold has a pressure plate movably disposed in the fixed-side mold section, and a rear end of the mold is fixed to the pressure plate. A plurality of valve pins that are moved forward to take a backward limit position, a gate closed position, and a forward limit position; A resin flow path connecting between the pinpoint gate and the runner; (E) the valve pin is
An injection molding machine, characterized in that the pinpoint gate is closed at the gate closing position, and the pinpoint gate is advanced to an advance limit position to push the resin in the pinpoint gate into the cavity. 8. The injection molding machine according to claim 7, wherein a plurality of the drive sources and the pressure plates are provided and are independently operated.