JPH05104562A - Production device for semiconductor device - Google Patents

Abstract

PURPOSE:To adjust the set value of speed automatically even when resin injection conditions are varied by detecting the temperature drop of a sensing section generated by flowing a resin while being brought into contact with the sensing section or a metal plate, determining the position of the front of the flow of the resin by a detecting signal and providing a means, in which the speed of a plunger is controlled. CONSTITUTION:A plunger 8 is pressed and moved, and a thermo-setting resin is injected from the pot 6 of a molding die 1 to a cavity 2, thus sealing a semiconductor element 5. The sensing section 24 of a temperature sensor brought into contact directly or through a metal plate is mounted to a path 3 from the outlet of the pot 6 up to the inlet of the cavity 3 at the time. The temperature drop of the sensing section 24 generated by bringing the resin into contact with the sensing section 24 or the metal plate and flowing the resin is detected, and the speed of travel of the plunger 8 is controlled by a control means 23 by a detecting signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for manufacturing a resin-sealed semiconductor device, and more particularly to a transfer molding type resin molding apparatus capable of accurately controlling a resin injection rate.

[0002]

2. Description of the Related Art Conventionally, resin-encapsulated semiconductor devices made of thermosetting resin have been widely produced. As a device for this, a transfer m
old) type molding equipment is used. The transfer molding method is a thermosetting resin molding method, in which the material is plasticized in the transfer pot (heating chamber), and the heated mold cavity (molding die) is molded. This is a method in which a resin is press-fitted into the resin injection portion of the upper mold and the lower mold corresponding to (1) and is molded.

An outline of the configuration of such a conventional transfer mold type resin sealing device will be described below with reference to FIG. The molding die 1 is an upper molding die 1a.
And the lower mold 1b, which are combined to form a cavity 2 and a runner 3. Runner (ru
nner) 3 refers to a portion from the outlet of the pot to the inlet (gate) 4 of the pot in the path for pouring the molten material into the cavity, or the material portion solidified therein. The semiconductor element (pellet) 5 is mounted on the lead frame,
It is sandwiched between the upper mold die 1a and the lower mold die 1b and placed inside the cavity. The pot 6 is a supply port of a molding die that supplies the molding resin material 7. The plunger 8 pressurizes the plasticized resin 7 and injects it into the mold. That is, the pot 6 and the plunger 8 form a pair, and the pot and the plunger correspond to the cylinder and the piston, respectively. The servo motor 9 is
A control motor that is used in a servo mechanism or the like and can accurately change the number of revolutions according to a command.
The plunger 8 is driven by a control command from the controller 13 via the belt 11, the gear 10b, and the ball screw 12.
Is moved up and down under pressure. A pressure sensor 14 is provided at the bottom of the cavity 2, the injected resin comes into contact with the pressure sensor 14, and the resin pressure is detected via the pressure monitoring device 15.

The outline of the operation of the above apparatus is as follows.
The molding die 1 is heated to 160 ° C. to 190 ° C. by heating means such as a heater block (not shown). The thermosetting resin 7 is usually made of a material called a tablet, which is formed by compressing and hardening a certain amount in a cylindrical shape for easy handling. The preheated tablet is put into the pot 6 and further heated by the mold in the pot 6 to melt,
It is pressurized by the plunger 8 and flows into and fills the cavity 2 through the runner 3 and the gate 4. The resin is heated by the mold 1 and is cured while being pressed. In this state, the resin is cured for a predetermined time, and after the resin is completely cured, the upper mold die 1a and the lower mold die 1b are separated from each other, and the resin-sealed semiconductor element is taken out of the die.

The resin used for resin encapsulation of semiconductor devices is thermosetting, and if injection is not completed in a short time, the resin will begin to cure and will not be filled or void (void defect).
Will be caused. But if injected too quickly,
The bonding wire of the bonded semiconductor chip placed in the cavity is deformed, or the frame of the lead frame or the like is deformed. That is, the resin injection speed into the cavity has an appropriate injection speed range in which the above defects do not occur.

Generally, in the transfer molding method, it is desirable that the speed of the resin flowing in the runner is as high as possible, and the speed of the resin injected into the cavity after reaching the gate is reduced to the appropriate injection speed. Consider a case where resin is injected into a mold having a plurality of cavities. The resin charged into the pot is pressed into the mold by the plunger, branched into a plurality of runners, flows, and injected into each cavity. At this time, the filling is completed from the cavity close to the pot. Assuming that the moving speed of the plunger is constant, the resin injection speed of the other unfilled cavities is gradually increased every time the filling of one cavity is completed. The resin injection rate of all cavities,
In order to always maintain the appropriate value, it is necessary to reduce the speed of the plunger in multiple stages according to the progress of resin filling.

Conventionally, the resin injection speed of the transfer mold apparatus is controlled by hydraulic pressure control and multi-stage injection speed control by a servo motor, and closed loop control by a sensor is not performed, and open loop control is common. ..
A pressure sensor is used as the sensor, and the resin pressure is monitored, but it is not used for controlling the resin injection rate.

In the conventional device example shown in FIG. 11, as a sensor, a pressure sensor 14 is provided at the bottom of the cavity, and pressure monitoring is performed by a pressure monitoring device 15, but this is an open loop control and the monitoring result is a controller. Since it is not returned to 13, automatic control of the resin injection speed is not performed. Further, this resin pressure rises sharply when the resin injection is completed, and is not suitable for controlling the resin injection rate.

Therefore, in the conventional apparatus shown in FIG. 11, for example, for each shot (soht, a series of molding steps),
When the amount of resin put into the pot fluctuates, the position at which the moving speed of the plunger is changed must be adjusted according to the amount of fluctuation. However, in the prior art, there is no effective means for determining the shift position, and when the amount of injected resin changes, the resin injection speed into the cavity deviates from an appropriate value, and the flow of bonding wires and the deformation of the lead frame occur. I will end up.

[0010]

As described above, in the transfer molding type sealing device, since the thermosetting resin is used as the molding material, the injection speed of the resin injected into the cavity is too slow. Even if it is too fast, defects will occur. That is, the resin injection speed into the cavity is
There is an appropriate injection rate range where defects do not occur. The resin injection speed into the cavity changes depending on the moving speed of the plunger for press-fitting the resin in the pot into the mold and the state of the load (cavity) connected to the pot via the runner. Therefore, in order to always maintain the resin injection speed into the cavity within the appropriate injection speed range, it is necessary to control the moving position of the plunger and the moving speed of the plunger at that position. In the prior art, since the setting of the shift position of the moving speed of the plunger is obtained by trial, it takes a long time and labor, which is a problem.

When the amount of resin charged into the pot changes from shot to shot, or when characteristics such as resin viscosity and resin injection conditions such as mold temperature change, the speed of movement of the plunger is changed. It is necessary to adjust the position setting value, but in the prior art there is no effective means for this,
For example, if the amount of resin changes and the timing of reducing the resin injection speed into the cavity is delayed, defects such as displacement of the bonding wire and deformation of the lead frame occur, which is a problem.

The present invention has been made in view of the above problems, and in a transfer molding type molding apparatus, it is easy to set the shift position of the moving speed of the plunger,
In addition, if the resin injection conditions such as the amount of resin supplied to the pot change from shot to shot, the set value of the shift position of the moving speed of the plunger is adjusted to maintain the resin injection speed into the cavity at an appropriate value. By doing so, it is an object of the present invention to provide a resin-sealing manufacturing apparatus capable of preventing defects such as deformation of a bonding wire or a lead frame of a molded product.

[0013]

SUMMARY OF THE INVENTION The present invention provides a transfer mold type manufacturing apparatus for sealing a semiconductor element by moving a plunger under pressure to inject a thermosetting resin from a pot of a molding die into a cavity. In the path from the outlet of the pot to the cavity inlet, directly or through a metal plate, the sensing part of the temperature sensor provided in contact with the sensing part or the sensing part generated by the resin flowing in contact with the sensing part or the metal plate. An apparatus for manufacturing a semiconductor device, comprising: means for detecting a temperature decrease and controlling the moving speed of the plunger according to the detection signal.

[0014]

The present inventor discovered the following during the experiment for monitoring the temperature of the resin moving in the mold. That is, the temperature sensor was attached so that the sensing surface of the temperature sensor was a part of the inner surface of the runner, and the temperature of the resin passing through the surface was examined. The temperature of the sensor before passing through the resin is equal to the mold temperature. It was found that at the same time that the resin having a temperature lower than the mold temperature passed over the sensor, the temperature of the sensor dropped and then recovered gradually. That is, it is possible to know that the front end position of the resin flow reaches the position where the sensing unit is provided at the time when the temperature of the sensor decreases. Therefore, for example, when moving the plunger and injecting the resin put in the pot into the cavity via the runner, the temperature sensor is attached in front of the cavity and it is detected that the tip of the resin flow reaches the front of the cavity. Then, by slowing down the moving speed of the plunger and setting the resin injection speed into the cavity to an appropriate value, it is possible to prevent the occurrence of defects in the molded product. The slowing down of the plunger is always performed immediately before the resin is injected into the cavity, even if the amount of resin injected into the pot varies.

Further, two temperature sensors are arranged at a predetermined distance in the resin flow path, and by monitoring the time when the tip of the resin flow passes over each sensor, the temperature of the resin at that time is monitored. It is also possible to detect the moving speed.

In the manufacturing apparatus of the present invention, the temperature sensor is arranged in a desired number at a desired position of the resin injection path in the mold, and the resin is in contact with the sensing portion of the temperature sensor or a thin metal plate abutting the sensing portion. The detection signal of the temperature drop of the sensing part caused by the flow is output. The means for controlling the moving speed of the plunger has a controller with a built-in microprocessor, takes in the detection symbol, and is required to determine the tip position of the resin flow in the mold and the moving speed of the resin. Based on these data, the real time of the moving speed of the plunger is adjusted.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the manufacturing apparatus of the present invention will be described with reference to FIG. FIG. 1 is a diagram showing an outline of the configuration of the device, and the same reference numerals as those in FIG. 11 represent the same parts. 11 is different from the conventional device shown in FIG. 11 in that instead of the pressure sensor, the temperature sensor 24 is exposed on the surface (metal) of the sensing portion in the path (runner) 3 from the outlet of the pot 6 to the cavity inlet (gate) 4. And a means for fetching the detection signal of the temperature sensor into the controller 23 and controlling the moving speed of the plunger by the closed loop control.

First, an experiment for monitoring the resin temperature by the temperature sensor, which has led to the present invention, will be described. FIG. 2 shows an apparatus used for the experiment, and reference numeral 24 is a sensing portion of the temperature sensor, which is exposed to the runner 3. Reference numeral 25 denotes a temperature sensor main body, which can display the temperature of the sensing unit 24. Set the mold 1 temperature to 160 ℃ ~ 190 ℃, 70
The molding resin material 7 preheated to 90 ° C. to 90 ° C. is put into the pot 6. The plunger 8 is operated to inject the resin 7 into the runner 3. It was found that the temperature of the sensing part was lowered at the same time when the resin having a temperature lower than that of the mold passed over the sensing part 24. FIG. 3 shows the temperature change of the temperature sensor, the horizontal axis is the elapsed time, and the time t
₀ is the time when the plunger 8 starts, and t ₁ is the time when the resin passes through the sensing portion 24. The sensor temperature is
Although it decreases when passing through the resin, it gradually recovers and then approaches the mold temperature. That is, the tip position of the resin flow can be known by detecting the temperature decrease of the sensor.

The temperature sensor has been used for molding a thermoplastic resin. However, in the case of a thermosetting resin, the resin is hardened and adhered to the surface of the sensing portion, which is not suitable for measuring the temperature of the resin. Although not currently used, the function of the temperature sensor in the present invention is to detect the tip position of the resin flow due to the temperature decrease, and the accuracy of the absolute value of the temperature measurement value is not required. do not become. The resin that hardens and adheres to the surface of the sensing unit is removed together with the runner at the time of mold release, and it is not necessary to clean it for each shot.

The mounting position of the sensing portion of the temperature sensor will be described with reference to FIGS. 4 and 5. The sensing unit 24 is fitted and attached to a hole opened in a normal runner (a resin flow path from the outlet of the pot to the inlet of the cavity) 3. If the top surface of the sensing portion 24 projects into the runner 3, it disturbs the flow of resin, and if it retracts too much into the mounting hole, the resin flows into the hole and hardens, which hinders the release of the runner. It is most desirable that there is no step between the inner surface of the runner 3 and the top surface of the sensing portion, but experience has shown that the value of h shown in FIG. 4 is preferably less than 2 mm.

An example of eliminating the step between the runner and the sensing portion is shown in FIG. This is an embodiment in which the temperature sensing portion is provided in contact with the path from the outlet of the pot to the inlet of the cavity via the metal plate. The same figure (a) is an example which the hole which arrange | positions the sensing part 24 does not penetrate, but leaves the metal plate 26 of the same body as a metal mold, for example, 0.5 mm thick, and the same figure (b) shows the sensing part 24. In any of the examples, a metal plate 27 serving as a stopper is added to the top surface of the runner. In either case, no step is formed in the runner portion where the sensing unit 24 is arranged, and the runner is easily released.

As the temperature sensor, an optical resin thermometer (manufactured by Nireco Co., Ltd.) was used in this embodiment, but the temperature sensor is not limited to this. Other types of thermometers may be used as long as they have an appropriate response speed. Further, the temperature decrease of the sensing unit may be detected by detecting the relative value of the temperature decrease, or by the amount obtained by processing the measurement data such as the slope (Δθ / Δt) of the temperature decrease. It doesn't matter.

Next, the process of resin-sealing the semiconductor pellets 5 using the apparatus of FIG. 1 will be described with reference to FIG. The molding die 1 is heated to a temperature θ ₀ (for example, 160 ° C to 19 ° C).
0 ℃). Molding resin material preheated to 70 ℃ -90 ℃ 7
Is added to pot 6. Servo motor 9 at time t ₀
Is started, and the plunger 8 is moved at a preset speed v ₀ . The resin 7 in the pot 6 is pressurized by the movement of the plunger 8 and flows in the runner 3 toward the cavity 2. When the tip of the resin flow contacts the sensing unit 24, the temperature of the sensing unit decreases. At the same time when the signal of temperature decrease is taken into the controller 23 (time t ₁ ), the rotation speed of the servo motor 9 is slowed down,
The moving speed of the plunger 8 is reduced to a preset speed v ₁ . When the speed of the plunger 8 is v ₁ , the resin injection speed into the corresponding cavity has an appropriate value and deformation of the bonding wire and the like is prevented. Time t
_{When the} filling of the resin in the cavity is almost completed in ₂ , the pressure of the resin rapidly rises, and the load cell attached to the plunger (not shown) causes the plunger to enter the pressure control area and stops at time t ₃ .

A second embodiment of the manufacturing apparatus of the present invention will be described with reference to FIG. The figure is a block diagram of a multi-cavity picking device for resin-sealing eight ICs at a time, and shows a plan view of the lower die 1b above a cross-sectional view of the die 1b. As shown in the figure, the runner 43 is connected from the pot 6 and the cavities 45, 45 ′ and 46, 4 are connected to the runner 43.
Four pairs of symmetrical cavities 6'and 47, 47 'and 48,48' are connected respectively. Temperature sensor 3
5, 36, 37 and 38 are cavities 45,
The temperature detection signals are provided in front of the gates of 46, 47, and 48, and the respective temperature detection signals are taken in by the controller 33.
FIG. 8 shows the relationship between the temperature value (° C.) of each temperature sensor and the elapsed time during the operation of this manufacturing apparatus, and FIG. 9 shows the relationship between the moving speed of the plunger 8 and the elapsed time. That is, in this encapsulation device, eight ICs are resin-encapsulated at one time by providing temperature sensors at four locations. in this case,
Although the injection is completed from the cavities 45, 45 'on the side closer to the pot, when the plungers are moved at the same speed, the cavities 48, 48' at the end are not
The injection speed is many times higher than the resin injection speed of 5,45 '. Therefore, by sensing the injection state with a temperature sensor, the speed of the plunger can be gradually decreased, and 8 ICs can be injected at almost the same injection speed.

That is, in FIGS. 8 and 9, the plunger is started at time t ₀ at speed v ₀ , and the tip of the resin flow is introduced into each of the cavities 45, 46, 47 and 48 at time t _1. , T ₂ , t ₃ , t ₄ in sequence,
The speed of the plunger gradually decreased to v ₁ , v ₂ , v ₃ , and v _4, and at time t ₅ , the resin filling of the eight cavities was almost completed, and the speed of the plunger entered the pressure control area. , Stop at time t ₆ .

Next, a third embodiment of the present invention will be described with reference to FIG. In the figure, the sensing parts 54a and 54b of the two temperature sensors are provided at a predetermined distance d so as to be exposed to the runner 52, and the detection signal is the controller 5
Taken in 3. The resin inflow velocity at this position can be known by detecting the front end time of the resin flow passing over each sensing portion. By detecting the resin inflow rate, it is possible to know whether there is a characteristic change such as the viscosity of the molding resin material or an abnormality such as the temperature of the molding die. Further, it becomes easy to set the position where the speed of the plunger is changed and the speed change, and to adjust the set value.

In the above embodiment, the means for controlling the moving speed of the plunger includes a controller that takes in the detection signal from the temperature sensor, processes it, and outputs a necessary control command, and the rotation speed accurately according to the command. The servo motor (AC motor) that can be changed and a mechanism that converts the rotation of the servo motor into the vertical movement of the plunger in proportion to the number of revolutions are included, but the present invention is not limited thereto. The present invention can be applied even when the pressure movement of the plunger is performed by hydraulic control instead of the servo motor, but the control by the servo motor is more preferable.

[0028]

As described above, according to the present invention, in the resin molding apparatus of the transfer molding system, the runner is provided with the sensing portion of the temperature sensor to reduce the temperature drop of the temperature sensor when the resin flows over the sensing portion. Since the means for detecting and controlling the moving speed of the plunger based on the detection signal is provided, it becomes easy to set the shift position of the moving speed of the plunger, and, for example, the amount of resin supplied for each shot varies. When the injection conditions change, it becomes possible to easily maintain the resin injection speed into the cavity at an appropriate value by adjusting the set value of the shift position of the moving speed of the plunger. That is, according to the present invention, it is possible to provide a manufacturing apparatus for resin encapsulation that can prevent the occurrence of defects such as deformation of a bonding wire of a molded product or a lead frame.

[Brief description of drawings]

FIG. 1 is a diagram showing an outline of a configuration of a first embodiment of a manufacturing apparatus of the present invention.

FIG. 2 is a diagram showing an outline of a configuration of an apparatus used for a resin temperature monitoring experiment using a temperature sensor.

FIG. 3 is a diagram showing an example of experimental data obtained by the apparatus shown in FIG.

FIG. 4 is a cross-sectional view showing an embodiment in which the sensing part of the temperature sensor is provided in direct contact with the runner.

FIG. 5 is a cross-sectional view showing an embodiment in which the sensing part of the temperature sensor is attached to the runner so as to be in contact with the runner via a metal plate.

FIG. 6 is a diagram showing changes over time in the temperature of the sensing unit and the speed of the plunger when the apparatus of FIG. 1 is operated.

FIG. 7 is a diagram showing an outline of a configuration of a second embodiment of the manufacturing apparatus of the present invention.

FIG. 8 is a diagram showing a change with time in the temperature of the sensing unit when the device of FIG. 7 is operated.

9 is a diagram showing a change with time of the speed of the plunger when the device of FIG. 7 is operated.

FIG. 10 is a diagram showing an outline of the configuration of a third embodiment of the manufacturing apparatus of the present invention.

FIG. 11 is a diagram showing an outline of a configuration of a conventional manufacturing apparatus.

[Explanation of symbols]

 1 Molding Mold 1a Upper Molding Mold 1b Lower Molding Mold 2 Cavity 3 Runner 4 Gate 5 Semiconductor Element (Pellet) 6 Pot 7 Molding Resin Material 8 Plunger 9 Servo Motor 13 Controller 14 Pressure Sensor 23 Controller 24 Temperature Sensor Sensing Part 33 Controller 35-38 Temperature sensor sensing part 45-48 Cavity 45'-48 'Cavity 52 Runner 54a Temperature sensor sensing part 54b Temperature sensor sensing part

Claims (1)

[Claims] 1. A transfer molding method manufacturing apparatus for sealing a semiconductor element by moving a plunger under pressure and injecting a thermosetting resin into a cavity from a pot of a molding die, from a pot outlet to a cavity inlet. In the path of, directly or through a metal plate, the sensing part of the temperature sensor, which is provided in contact with the sensing part, detects the temperature drop of the sensing part caused by the resin flowing in contact with the sensing part or the metal plate, Means for controlling the moving speed of the plunger by a signal, and a semiconductor device manufacturing apparatus.