JPS6278839A - Resin sealing device for semiconductor element - Google Patents

Abstract

PURPOSE:To achieve energy saving of a plunger while facilitating its maintenance by a method wherein the plunger is driven by a motor while reducing the pressurizing force of the plunger in proportion to the lapse of pressurizing time during the resin sealing process. CONSTITUTION:When mold clamping is finished, a plunger 9 driving AC sevomotor 10 is driven to lift the plunger 9. Then a microcomputer 13, detecting that the plunger 9 has started lifting, controls the moving speed of the plunger 9 until resin feeding is finished. As soon as resin feeding is detected to be finished, pressurizing time counting is started. At this time, the thermosetting resin is gradually cured. Resultantly, the current to the plunger motor 10 is slowly deminished to reduce the pressurizing forced on the plunger 9.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a resin sealing device for semiconductor devices for resin-sealing semiconductor devices onto a lead frame, and particularly relates to an improvement of the plunger drive portion thereof. be.

[Conventional technology]

In general, a resin sealing device for semiconductor devices includes an upper platen 1. As shown in FIG. A lower platen 2, a tie bar 3 provided between these two platens, and a movable platen 4 movably provided along the tie bar 3. The upper mold 5 is installed on the upper platen 1, the lower mold 6 is installed on the movable platen 4, and the movable platen 4 is driven by hydraulic pressure to form the upper mold 5 and the lower mold 6. Clamp the mold and
The lead frame and semiconductor element placed between both molds are sealed with resin.

The structure of a conventional plunger part in such a device is shown in FIG. The plunger is driven by a hydraulic plunger drive unit (not shown).
The resin 8 is injected into the mold.

[Problem that the invention seeks to solve]

However, with the hydraulic drive system of this conventional device, maintenance such as checking and preventing oil leaks and replacing seal members is extremely complicated, and the drive of the plunger 9 is only controlled by hydraulic pressure. There was a problem in that the speed etc. of the plunger 9 could not be adjusted and stable resin sealing could not be achieved.

Therefore, the inventor of the present invention has already developed and filed an application for a resin sealing device for semiconductor elements in which the driving of the movable platen 4 and the plunger 9 are electrified to solve the various problems of the conventional hydraulic drive system.

FIG. 5 shows such an electrically driven type resin sealing device for semiconductor elements, and the structure of this device will be explained below along with its function. In the figure, the same reference numerals as in FIG. 3 indicate the same or equivalent parts, and 18 is an AC servo motor that provides driving force to drive the movable platen 4 upward. The power is transmitted to the movable platen 4 via a transmission system and a driving force conversion mechanism that converts the rotational force from the power transmission system into thrust. In this manner, the movable platen 4 is driven, and the lower mold 6 containing the lead frame and the semiconductor element is pressed against the upper mold 5 with a predetermined pressing pressure to clamp the mold.

Further, 10 is a plunger motor for driving a plunger provided in the lower mold 6, and the rotational force of this plunger motor 10 is transmitted to a driving force conversion mechanism (not shown) via a gear train 19 and the like. , where it is converted into thrust to drive the plunger. As the plunger rises, resin is injected into the mold, and the semiconductor element is sealed with the resin.

By the way, in such a motorized resin sealing device, it is very important how to effectively use the power of each motor 7.10 as a drive source, that is, how to reduce the motor power. It will happen. Therefore, in the apparatus shown in FIG. 5 above, in order to effectively use the motor power for driving the moving platen, a two-stage reduction gear is constructed using gears, clutches, etc. as a power transmission system.
Until mold clamping, a transmission system with a small reduction ratio is used to feed the movable platen 4 at high speed, and during mold clamping, the transmission system is switched to a transmission system with a large reduction ratio, so that a large mold clamping pressure can be obtained with a small motor. . Therefore, it is considered that if the motor power of the plunger motor 10 is used effectively in the same way, the energy saving of the entire apparatus can be achieved.

The present invention was made in view of the above situation, and an object of the present invention is to obtain a resin sealing device for semiconductor elements that can save energy by eliminating unnecessary motor power when using a plunger motor. .

Here, focusing on the conventional resin sealing process, when the resin injection pressure of the plunger reaches a predetermined pressure, the predetermined pressure is held for a certain period of time (this is called cure time). However, since the resin used is a thermosetting resin, it gradually hardens over time during the curing time, and despite this, the initial resin injection pressure is maintained during the curing time. This makes no sense at all and is considered a waste of motor power.

[Means for solving problems]

Therefore, the resin sealing device for semiconductor elements according to the present invention includes a pressure detection means for detecting that the pressure of the plunger, which is the resin injection pressure, has reached a desired value, and a pressure detection means for detecting that the pressure of the plunger, which is the resin injection pressure, has reached a desired value, and A plunger pressurizing force control means is provided which reduces the pressurizing force as the pressurizing time elapses.

[Effect]

In this invention, the point at which the curing time starts to be counted is detected when the pressing force of the plunger reaches a desired value, and the resin hardens as time elapses from the starting point. The pressurizing force is controlled to gradually decrease.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a functional block of a plunger driving 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 pressing force detection means 11 that detects that the pressing force of the plunger 9 has reached a desired value. The pressing force of the plunger 9 is reduced as the pressurizing time elapses by means of a plunger pressurizing force control means 12 which receives a detection signal from the detecting means 11 as input. Incidentally, the overall configuration diagram of a resin sealing device for a semiconductor element to which the plunger driving section is used is the same as that shown in FIG. 5.

FIG. 2 shows a specific configuration example for realizing the functional blocks of the plunger drive section shown in FIG. 1, and in this embodiment, an AC-+-bo motor is used as the plunger motor 10. Further, 17 is a potentiometer for detecting the position of the plunger 9, and 13 is a microcomputer, which uses the output signal of the potentiometer 17 as input to perform communication with an external device 15 such as a movable platen drive motor 51. It is used to exchange signals, control the rotational speed of the AC servo motor 10, and limit current (torque). 14 receives the command from this microcomputer 13 and operates the AC servo motor 10.
This is a servo amplifier that performs drive control. in this way,
The potentiometer 17 and the microcomputer 1
3 constitute the pressurizing force detecting means 11 and the plunger pressurizing force controlling means 12 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, and this is attached to the output shaft of the AC servo motor 0 as shown in FIG. A plunger drive shaft 16a connected via a gear train 19 etc., a NAND 16b fixed to the plunger 9, a ball screw 16C2 screwed into this nut 16b, and a plunger drive shaft 16a and a ball screw 16C provided at one end of the shaft, respectively. It is composed of a pair of bevel gears 16d and t6e.

Next, the operation will be explained.

The operation before the plunger operates, that is, until the mold is clamped, is the same as the operation shown in FIG. 5, so a description thereof will be omitted.

Then, resin sealing is performed in the mold-clamped state. When the mold-clamping is completed, the AC servo motor 10 for driving the plunger 9 begins to rotate, and this rotational force is applied to the bevel gear pair 16d, 16e. Through the ball screw 16c
is transmitted to. As the ball screw 16c rotates, the Nand 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, and thereafter controls the speed of the motor 10 until the injection of resin is completed, so that the moving speed of the plunger 9 can be set in three stages, e.g., low speed, high speed, and low speed. Control. At this time, the current to the motor 10 is limited (torque limited) in order to make the resin injection pressure, that is, the pressing force of the plunger 9, a desired pressure.

The resin is injected in this way, but as mentioned above, the pressing force of the plunger 9 is set to a predetermined pressure due to the motor current limit, so as the resin injection progresses, the positional fluctuation of the plunger 9 decreases. . When the injection of resin is completed, the position fluctuation of the plunger 9 becomes below a certain specified value, and at this point, it is detected that the injection of resin is completed, and from this detection point, the pressurization time (cure time) starts counting. do. Here, since the resin is a thermosetting resin, the resin hardens as the curing time elapses. Therefore, along with this, the plunger motor 1
The current supplied to the plunger 9 is gradually reduced to reduce the pressing force of the plunger 9.

When the pressure time-up is detected, the next step is to separate the plunger 9 from the resin, and to eject the semiconductor element that has been sealed with the resin.Then, the mold surface is cleaned, and then a series of resin sealing steps are performed. finish.

In the device of this embodiment, the plunger 9 is driven and controlled by the AC servo motor 10 and the microcomputer 13, and the pressing force of the plunger 9 is reduced as the curing time elapses during the resin placement process. Therefore, compared to the conventional case in which the initial pressurizing force is maintained until the end of the curing time, energy saving can be achieved.

In addition, in the above embodiment, a case has been described in which the pressing force of the plunger is reduced as the curing time elapses during the sealing process, but it is also possible to reduce the mold clamping force of the movable platen along with the pressing force of the plunger. According to such an embodiment, even more energy saving can be achieved. However, when reducing the mold clamping force, it is necessary to reduce the pressing force of the platen as a premise.

〔Effect of the invention〕

As described above, according to the resin sealing device for semiconductor elements according to the present invention, the plunger is driven by a motor, and the pressurizing force of the plunger is reduced as the pressurizing time elapses during the resin sealing process. This has the effect of making maintenance easier and achieving energy savings.

[Brief explanation of drawings]

FIG. 1 is a functional block diagram of a plunger drive section of a resin sealing device for semiconductor elements according to an embodiment of the present invention, and FIG. 2 is a diagram showing a specific configuration for realizing the functional block.
Fig. 3 is a configuration diagram of a conventional resin sealing device for semiconductor elements, Fig. 4 is an enlarged view showing the plunger portion thereof, and Fig. 5 is an electric drive type resin sealing device for semiconductor elements already developed by the inventor of the present invention. It is a block diagram of a device. 5... Upper mold, 6... Lower mold, 9... Plunger, 10... AC servo motor, Machining 1... Pressing force detection means, 12... Plunger pressing force control means, 13...
- Microcomputer, 17... Potentiometer. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] (1) In a semiconductor device resin sealing device for resin-sealing a semiconductor device onto a lead frame, a plunger is provided in the upper mold or the lower mold to inject and press the resin, and the plunger is driven. a plunger motor that provides a driving force for the plunger; a pressurizing force detection means that detects when the pressurizing force of the plunger has reached a desired value; 1. A resin sealing device for a semiconductor element, comprising: a plunger pressurizing force control means.