JPH0449256B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method and apparatus for resin-sealing a semiconductor element onto a lead frame, and particularly relates to an improvement in the plunger drive section thereof. It is something.

[Conventional technology]

In general, a resin sealing device for semiconductor devices includes an upper platen 1, a lower platen 2, and
Tie bar 3 provided between these two platens,
It consists of a movable platen 4 that is movably provided along this tie bar 3 and its driving part, and an upper mold 5 is installed on the upper platen 1 and a lower mold 6 is installed on the movable platen 4. The upper mold 5 and the lower mold 6 are clamped together by hydraulic pressure, and the lead frame and semiconductor element placed between the two molds are sealed with resin.

The structure of a conventional plunger portion in such a device is shown in FIG. In the figure, 7 is a tablet insertion hole into which a sealing resin 8 is inserted, and 9 is a plunger that is slidably arranged using the insertion hole 7 as a cylinder.This is a hydraulic plunger drive unit (not shown). It is driven to inject the resin 8 into the mold.

[Problem that the invention seeks to solve]

However, in order to perform resin sealing, it is necessary to maintain the pressing force of the plunger for a predetermined period of time (hereinafter referred to as pressurizing time) once the mold is filled with resin. However, in the conventional device as described above, the plunger is driven by hydraulic pressure and is simply controlled by a hydraulic pressure gauge, so it is not possible to know when the mold is filled with resin.
Therefore, in conventional devices, the pressurization time is defined as the number of seconds after the plunger starts moving.
It is controlled by (resin injection time) + (pressurization time), and therefore, the actual pressurization time is very inaccurate and has many variations, and there is a problem that the quality of resin sealing is not stable.

Therefore, it is conceivable to monitor the drive oil pressure of the plunger with an oil pressure gauge, and to manage the pressurization time by determining the time when the oil pressure reaches the target oil pressure as the time when the resin is filled. However, there is a time lag in the oil pressure gauge, and there are times when it is not clear whether the target oil pressure has actually been reached due to resin filling, or whether the target oil pressure has been reached due to an abnormality in the oil pressure control valve, etc. be. Furthermore, it is very difficult to accurately set the injection pressure using a hydraulic control valve.

This invention was made in view of this point, and allows the resin injection pressure to be set easily and with high precision.
Moreover, it is an object of the present invention to provide a resin sealing method and apparatus for a semiconductor element that can accurately detect the start point of the pressurization time.

By the way, the inventor of the present invention has already developed and filed an application for a device in which the drive method is changed from hydraulic to electric, in order to eliminate the complexity of maintenance in conventional hydraulically driven devices. This device is equipped with a motor for driving a moving platen and a plunger motor for driving a plunger, and the rotational force of each motor is converted into thrust by a driving force conversion mechanism consisting of a ball screw, a nut, etc. This drives the moving platen and plunger upward. In this device, the driving source, the motor, and the plunger are mechanically connected, so by controlling the number of pulses, current, etc. applied to the motor, the position of the plunger, resin injection pressure, etc. can be controlled with extremely high precision. It is believed that this can eliminate the problems with the conventional device, such as variations in the quality of resin sealing.

[Means for solving problems]

Therefore, in the method for resin-sealing a semiconductor element according to the present invention, in a method for resin-sealing a semiconductor element on a lead frame, the position of a plunger is detected by a plunger position detector, and a change in the output of this position detector is provided. It is detected that the pressing force of the plunger has reached a desired value when the pressure becomes less than a specified value, and counting of the pressurizing time of the plunger is started from the time of this detection.

Further, the resin sealing device for a semiconductor element according to the present invention is a device in which the plunger is driven by a plunger motor, and includes plunger pressurizing force control means for limiting the current supplied to the plunger motor;
A plunger position detector detects the position of the plunger, and when the change in the detection result becomes less than a specified value, it detects that the pressurizing force has reached the desired value, and starts counting the pressurizing time from that point. The pressurization time counting means is provided.

[Effect]

In this invention, the plunger is driven by a motor to which a certain constant current is supplied, and therefore, when the pressing force of the plunger reaches a desired pressure, that is, when the mold is filled with resin, the plunger moves. When the change in the output of the detector that detects becomes below a certain value, this is detected and the pressurization time starts counting.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
Here, in the following explanation, the case of a single plunger will be explained as an example. FIG. 1 is a diagram showing a functional block of a plunger drive section in a resin sealing device for semiconductor elements according to an embodiment of the present invention.
This embodiment is provided with a plunger motor 10 that provides a driving force for driving the plunger 9, and a plunger position detector 11 that detects the position of the plunger 9.
The motor current is limited at a predetermined position of the plunger 9 by the plunger pressurizing force control means 12 which receives the detection signal as input, and the pressurizing time is controlled by the pressurizing time counting means 17 which receives the position detection signal as input. It is designed to start counting.

FIG. 2 shows an overall configuration diagram of a resin sealing device for semiconductor elements to which the plunger drive section is applied. In this embodiment, as described above, the movable platen 4 is also driven by the platen driving motor 51, and is completely electric. Moreover, the plunger is provided in the lower mold 6,
It is designed to be driven via a plunger motor 10 attached to the moving platen 4, a gear train 52, and the like.

FIG. 3 shows a specific configuration example for realizing the functional block of the plunger drive section shown in FIG. I use a yometer. Further, 13 is a microcomputer, which receives the output signal of the potentiometer 11 as input, exchanges signals with external devices 15 such as the movable platen driving motor 51, and controls the current flow of the AC servo motor 10. (torque) and control the rotation speed. 14 receives the command from this microcomputer 13 and operates the above AC.
This is a servo amplifier that controls the drive of the servo motor 10, and the microcomputer 13 constitutes the plunger pressurizing force control means 12 and pressurizing time counting means 17 shown in FIG.

Further, 16 is a plunger drive mechanism for converting the rotational force of the AC servo motor 10 into a thrust force for moving the plunger 9. This plunger drive mechanism 16 is driven by the AC servo motor 1
2, a nut 16b fixed to the plunger 9, a ball screw 16c screwed into the nut 16b, and a plunger drive shaft 16a connected to the output shaft of the engine 0 via a gear train 52 shown in FIG. Drive shaft 16a, ball screw 1
Bevel gear pair 16d, 16 provided at one end of 6c
It is composed of e.

Next, the operation will be explained.

First, the operation before the plunger operates, that is, until the mold is clamped, will be explained. When the operation start switch is turned on, the platen drive motor 51
begins to rotate, and the rotation is converted into a thrust force via a driving force conversion mechanism (not shown), thereby causing the movable platen 4 to rise. And upper mold 5 and lower mold 6
When they come into contact with each other and a certain tightening pressure is reached, the servo lock is applied to the motor 51,
Mold clamping is performed.

Resin sealing is performed in this mold-clamped state, and the operation of the plunger in this case will be explained with reference to FIGS. 4 and 5. FIG. 4 is a flowchart showing a plunger operation control program stored in the memory of the microcomputer 13, and FIG. 5 is a diagram showing its driving pattern.

First, when the above mold clamping is completed, the plunger 9
The AC servo motor 10 for driving starts rotating, and this rotational force is transmitted to the ball screw 16c via a pair of bevel gears 16d and 16e. As the ball screw 16c rotates, the nut 16b, that is, the plunger 9, which is screwed into the ball screw 16c rises. Then,
The microcomputer 13 detects that the plunger 9 has started to rise in step 20, and then in steps 21 to 26 controls the speed of the motor 10 to reduce the moving speed of the plunger 9 by 3 until the resin injection is completed. Control in stages. That is, the motor speed is V0 (low speed) until position P0, and the motor speed is V0 (low speed) until position P1.
Move the plunger 9 at V1 (high speed) and then at motor speed V2 (low speed). At this time, when it is detected that the plunger 9 has risen to position P1, in step 25, the current to the motor 10 is limited (torque limited) in order to bring the resin injection pressure to the desired pressure, and this causes the plunger to move upward. 9. Limit the pressing force.

The resin is injected in this way, but as mentioned above, the pressing force of the plunger 9 is set to a predetermined pressure by limiting the motor current, so as the resin injection progresses, the position of the plunger 9 does not fluctuate. Become. When the mold is filled with resin and the injection is completed, the positional variation of the plunger 9 becomes less than a certain specified value, and it is then detected that the resin injection is completed (step 27). From this point on, counting of the pressurization time is started (step 28). At the same time, the motor speed is driven at ultra-low speed V3 to maintain the injection pressure at the set pressure. Furthermore, at this motor speed V3,
Plunger 9 is actually stopped. If pressurization time-up is detected in this state, the current limitation of the motor is no longer necessary, so it is turned off (steps 29 to 31).

Next, in steps 32 to 35, the plunger 9 is separated from the resin, and in steps 36 to 41, the lead frame and the semiconductor element, which have been sealed with resin, are taken out, that is, ejected. During steps 32 to 41, as shown in FIG. 5, the plunger 9 descends by P2 at motor speed V4.
It is controlled to increase at V5 and further increase by P3 at motor speed V6. And then step 42~
The mold surface is cleaned in step 48, and the plunger 9 is returned to the origin of the main drive pattern in steps 49 and 50. During this time, plunger 9 once rises by P4 at motor speed V7, then descends to position P5, and after cleaning is completed, the plunger 9 continues to move at motor speed P4.
Controlled by V9 to descend to the origin.

In this embodiment of the device, the plunger 9 is
Since the drive is controlled by the AC servo motor 10 and the microcomputer 13, oil leakage, which was a problem with the conventional hydraulic drive system, is eliminated, and a clean and easy-to-maintain device can be realized. Furthermore, in this embodiment, the position of the plunger 9 is continuously detected, and the fact that the mold is filled with resin is detected based on the change in the detection output. The starting point can be known very accurately, variations in the pressurization time can be suppressed, and resin sealing can always be performed with stable quality. The injection pressure is also set by limiting the current supplied to the motor.
Compared to the case where hydraulic pressure is adjusted with a valve as in the conventional device, this can be done easily and with high precision, and high-quality resin sealing can be performed.

In addition, in the above embodiment, the point at which the motor current is limited is set by moving the platen at high speed (motor speed V1).
However, this may be, for example, immediately after the plunger start is detected, and the same effect as in the above embodiment can be achieved.

Furthermore, in the above embodiment, a case was shown in which a potentiometer was used as the plunger position detector, but
This may be any other detector, such as an absolute type rotary encoder, as long as it can continuously detect the position of the plunger.

〔Effect of the invention〕

As described above, according to the resin encapsulation method and apparatus for a semiconductor element according to the present invention, the plunger is driven by a motor, and the current of the motor is limited at a predetermined position of the plunger, so that the pressing force of the plunger is The injection pressure can be easily and accurately set, and the pressurization time count is started when it is detected that the positional fluctuation of the plunger has fallen below the specified value. This has the effect that time variations can be suppressed and stable high-quality resin sealing can always be performed.

[Brief explanation of the drawing]

FIG. 1 is a functional block diagram of a plunger drive section of a resin sealing device for semiconductor devices according to an embodiment of the present invention, FIG. 2 is an overall configuration diagram of the device, and FIG. 3 is a function diagram of the functions shown in FIG. 1 above. FIG. 4 is a flowchart for explaining the operation of the plunger of the device; FIG. 5 is a diagram showing the drive pattern of the plunger of the device; FIG. The figure is a block diagram of a conventional resin sealing device for semiconductor elements, and FIG. 7 is an enlarged view showing the plunger portion thereof. 5... Upper mold, 6... Lower mold, 9... Plunger, 1
0... AC servo motor, 11... Potentiometer (plunger position detector), 12... Plunger pressing force control means, 13... Microcomputer, 14
... Servo amplifier, 17... Pressure time counting means.
Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] 1. In a semiconductor element resin sealing method for resin-sealing a semiconductor element on a lead frame, the position of a plunger is detected by a plunger position detector, and a change in the output of the position detector is detected. Resin sealing for semiconductor devices, characterized in that it detects that the pressing force of the plunger has reached a desired value when the pressure falls below a specified value, and starts counting the pressurizing time of the plunger from the time of this detection. Method. 2. A semiconductor device resin sealing device for resin-sealing a semiconductor device onto a lead frame, which includes a plunger provided in the upper mold or the lower mold for injecting and pressing the resin, and a plunger for driving the plunger. a plunger motor that provides a driving force; a plunger pressurizing force control means that limits the current supplied to the plunger motor to control the pressurizing force of the plunger; a plunger position detector that detects the position of the plunger; and a plunger position detector that detects the position of the plunger. pressurizing time counting means for detecting that the pressurizing force of the plunger has reached a desired value due to a change in the output of the device falling below a specified value, and starting counting the pressurizing time of the plunger from the time of detection; A resin sealing device for semiconductor elements, characterized by comprising: