JPH041012A - Resin sealing device - Google Patents

Abstract

PURPOSE:To maintain a high control accuracy and improve repeatability by employing an electric-powered servo system for regulating the speed and pressure of a transfer piston. CONSTITUTION:In a process of pouring resin 10, the speed of a servomotor 24 is so controlled as to permit a ball screw shaft 38 to be moved upwardly while regulating its speed. In this manner a transfer block 42 is moved upwardly to raise a transfer piston 20 via a sealed fluid L while regulating its speed in order to seal the resin 10 in a cavity 6. In a process of dwelling, the torque of the servomotor 24 is so controlled as to permit a liquid L in the transfer block 42 to attain a predetermined pressure, thereby moving the ball screw shaft 38 upwardly while regulating its force and then the transfer block 42 is moved upwardly while its force is being regulated, the upward force of the transfer piston 20 is regulated via the sealed fluid L and the pressure applied to the resin 10 within the cavity 6 is maintained at a predetermined level.

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a resin sealing device for sealing with resin a lead frame on which an IC chip is mounted, for example.

[Conventional technology]

Generally, a lead frame on which an IC chip is mounted is sealed to prevent contamination and damage from the surrounding atmosphere. For example, there are two methods for hermetically sealing the IC chip: using a ceramic or metal lid, and another method using resin to seal the IC chip.
There is a method of surrounding the chip. The former has been widely used for applications requiring high reliability, and the latter for applications requiring low complexity. FIG. 3 shows the vicinity of a transfer piston for a conventional resin sealing press. In the figure, 2 is an upper mold, 4 is a lower mold, 6 is a cavity for accommodating an IC chip sealed with resin, and 8 is a transfer piston. This transfer piston 8 has a resin (tablet) 10 for resin sealing placed on its tip, and is driven by hydraulic pressure to be able to press and seal the resin 10 into the cavity 6 . The IC chip is placed in the cavity 6 in advance, and with the upper mold 2 and the lower mold 4 in strong contact with each other, the IC chip is encapsulated with a resin 10 by the pressure of the transfer piston 8, and is sealed with the resin. . Speed control or pressure control when the transfer piston 8 is pressed has conventionally been performed by a hydraulic valve in a large-scale hydraulic control unit. In the figure, reference numeral 12 is a fixed crown, and 14 is a movable platen.

[Problem to be solved by the invention 1] However, in speed control or pressure control of a transfer piston using a hydraulic valve, it is basically impossible to maintain a high temperature, and the characteristics vary due to changes in oil temperature, etc. Therefore, there was a problem of poor reproducibility. In recent years, as semiconductors have become more highly integrated and thinner, molding conditions,
In particular, the requirements for the behavior of transfer pistons are becoming stricter, and the reality is that conventional control using hydraulic valves is no longer able to meet these demands. In addition, in the past, speed control or pressure control was basically performed using hydraulic valves in the hydraulic control unit, which inevitably required the use of large amounts of oil, and vibrators and valves were required to handle this oil. As a result, there is a problem in that maintenance and management to prevent oil leakage from these devices is difficult. Furthermore, hydraulic control inevitably generates oil mist, which contaminates the semiconductor pellet and reduces the reliability of the semiconductor. The first aspect of the present invention is to control the pressing force of the transfer piston, in particular, by providing a hydraulic pressure sealing part in the transfer block and detecting the hydraulic pressure. To detect pressure and accurately feedback control the pressing force from this detected value using an electric servo system, in particular, to solve problems such as variations in oil temperature and to always be able to perform pressure control with high reproducibility. It is an object. In addition, the second invention utilizes the same electric servo system to reduce the weight of each element in the control loop when performing speed control or pressure control. l! In addition to eliminating the need for installation, we realized that the time when speed control is required and the time when pressure control is required can be separated in time, and by switching between these two functions, we can provide two types of control at low cost and rationally. The purpose is to run without interference. Furthermore, in both the wood carving 1 and the 2nd invention, there are problems that were unavoidable by using conventional hydraulic control units, such as difficult maintenance such as oil leakage, or the quality of the semiconductor pellet due to the generation of oil mist. The purpose of each is to solve problems such as a decrease in [Means for Solving the Problem] The first invention provides a resin sealing device equipped with a transfer piston for a sealing press, which includes an electric motor driven by an electric signal from a servo amplifier, and a rotational movement of the electric motor. a transmission means for converting the output of the transmission means into a linear motion, and a transfer block that moves linearly integrally with the linear motion that is the output of the transmission means, and the linear motion of the transfer block is transmitted through a sealed liquid. a pressing means for pressing the transfer piston; a means for detecting the pressure of the sealed liquid; The above object has been achieved by providing a controller that performs feedback control of the pressure value. The second invention provides a resin sealing device equipped with a transfer piston for a sealing press, which includes: an electric motor driven by an electric signal from a servo amplifier; a transmission means for converting rotational motion of the electric motor into linear motion; a pressing means that has a transfer block that linearly moves integrally with the linear movement that is the output of the transmission means, and that presses the transfer piston through a liquid that is sealed against the linear movement of the transfer block; means for detecting the moving speed of the transfer piston, means for detecting the pressure of the sealed liquid, and operating an electric signal sent from the servo amplifier to the electric motor so that the detected moving speed becomes a set value. a control loop that feedback-controls the moving speed of the transfer piston as a quantity; and a control loop that feedback-controls the pressure value of the liquid using a signal sent from the servo amplifier to the electric motor as a manipulated variable so that the detected pressure value becomes a set value. The above object is achieved by providing a controller that switches between the control loops and executes one of the control loops. [Operation] In the first invention, first, the electric motor is driven by an electric signal from a servo amplifier. This rotary motion of the electric motor is converted into linear motion by the transmission means. Thereafter, the transfer block moves linearly as a unit due to the linear movement output from the transmission means, and the transfer piston receives the linear movement of the transfer block via the sealed liquid. On the other hand, the pressure of this sealed liquid is detected by a pressure sensor, and an electric signal sent from the servo motor to the electric motor is used as a manipulated variable so that the detected pressure value becomes a set value. is controlled by feedback. In the past, for example, a load cell was used to detect pressure, which was extremely costly, but in this first invention, the transfer piston is pressed through a sealed liquid. Therefore, it has become possible to detect the pressure of this liquid, and it has become possible to detect the pressing force at a much lower cost than in the past. In the second invention, the pressing force is basically controlled by the first invention.
The same effect as the invention is performed. However, if speed control is combined with this, interference will occur if both are simply implemented. Therefore, a control loop that performs feedback control of the moving speed of the transfer piston and a control loop that performs feedback control of the liquid pressure value (transfer piston pressing force) are switched by a predetermined trigger. This switching can be done, for example, when the moving side l1l (stroke) of the transfer piston reaches a predetermined value, or when the pressing force of the transfer piston slows down to a predetermined value, or when a timer is activated after control is started. The time when the count up can be used as a trigger condition. Note that the moving speed of the transfer piston does not necessarily have to be detected "directly"; it is possible to detect the moving speed or rotational speed of a member that corresponds to the moving speed of the transfer piston (for example, the rotational speed of an electric motor). Alternatively, the detection of the moving speed of the transfer piston may be replaced with the detection of the moving speed of the transfer piston.

[Example] Hereinafter, an example of the present invention will be described in detail based on the drawings. FIG. 1 shows a resin feudal device corresponding to an embodiment of the second invention (including the first invention). In the figure, 20 is a transfer piston for sealing press, 22 is a servo amplifier, and 24 is a servo motor (electric motor) driven by an electric signal from the servo amplifier 22.
, 26 is a transmission device for converting the rotational motion of the servo motor 24 into linear motion. This transmission device M26 includes a first boot 130 attached to the output shaft 28 of the electric motor, a timing belt 32, a second pulley 34, a ball screw nut 36 rotated by the 27th pulley 34, and a ball screw nut 36 that is rotated by the 27th pulley 34. It is composed of a ball shaft 38 that moves up and down as it rotates. In addition, the code|symbol 40 is a bearing for rotatably supporting the 2nd pulley 34. A transfer block 42 is connected to the upper end of the ball screw shaft 38. This transfer block 42 has a hollow structure, and the transfer piston 20 can move up and down within it. Lower surface 44 of transfer piston 20 and transfer block 42
A liquid Lffiff is sealed in the hollow space between the two. Therefore, when the ball screw shaft 38 moves upward, the transfer block 42 moves upward together with it, and this movement causes the transfer piston 20 to move upward via the sealed liquid chamber. Note that the reference numeral 10 indicates a molding resin (tablet) placed in the pot portion of the lower mold 4. The structure for enclosing the resin 10 is the same as the conventional one, and has already been explained using FIG. 3, so the same or similar parts as in FIG. Omitted. Here, in this embodiment, a speed sensor 50 for detecting the rotational speed of the servo motor 24 is provided as a sensor for detecting the moving speed of the transfer piston 20, and the pressure of the liquid, that is, the transfer A pressure sensor 52 is built into the transfer block 42 to detect the pressure when the piston 20 is pressed. Reference numeral 54 is a pressure detector amplifier for converting the output from this pressure sensor 52 into an electrical signal. Next, the operation of this embodiment will be explained. Each state in which the upper mold 2 and the lower mold 4 are clamped and the molding resin 10 is sealed in the cavity 6 of both molds 2.4 will be explained in order. In FIG. 2, during the filling step (A+ to A4), the resin is sealed into the cavity 6 under "speed control" as shown in the figure. When the cavity 6 is filled with the resin 10, the resin 10
enters a pressure holding step (Aa to As) in which it is thermally cured. In this pressure holding step, the resin is "pressure controlled" and thermal curing progresses at a predetermined speed. When the heat curing in the pressure holding process is completed, the servo motor 24 is rotated in the opposite direction again by "speed control", thereby the transfer piston returns (A5 to A7), and then the upper mold 2 and the lower mold 4 are rotated. The mold is opened and the entire process is completed. Returning to FIG. 1 again, during the injection process of the resin 10,
A speed feedback control loop is composed of the controller 23, the servo motor 24, the speed sensor 50, and the servo amplifier 22. That is, by controlling the speed of the servo motor 24, the speed of the 17th belt 30, the timing belt 32, and the 27th belt 34 is controlled.
The rotation speed of the ball screw nut 36 is controlled through the
This causes the ball screw shaft 38 to move upward while its speed is controlled. The upward movement of the ball screw shaft 38 causes the transfer block 42 to move upward while being controlled in speed, and the transfer piston 2o is raised in a controlled manner through the sealed liquid, transferring the resin 10 into the cavity 6. Also, during the pressure holding process, a pressure feedback control loop is configured by the servo motor 24, pressure sensor 52, pressure detector amplifier 54, and servo amplifier 22, with the controller 23 as the center. That is, the servo motor 24 is force-controlled (torque-controlled) so that the pressure of the liquid in the transfer block 42 becomes the set pressure, so that the 17th timing belt 32,
The ball screw nut 36 is force-controlled via the twenty-seventh relay 34, and thereby the ball screw shaft 38 moves upward while being force-controlled. This ball screw shaft 38
The upward movement causes the transfer block 42 to rise while being force-controlled, and the transfer piston 20 is force-controlled upward via the sealed liquid reservoir, thereby setting the pressing force of the resin 10 in the cavity 6. The pressure is maintained at a certain level. When the pressure holding process is completed and the transfer piston 20 returns, a speed feedback control loop is formed, as in the case of injection, and the transfer block 42 descends under speed control. Due to this lowering, the transfer piston 20 is lowered by the negative pressure generated in the sealed liquid chamber or by being pressed by the protrusion 46 of the transfer block 42. In addition, in this example, the transition from the injection process to the pressure holding process,
In other words, the transition from speed control to pressure control was performed based on the fact that the stroke of the transfer piston 20 reached a predetermined value, but the pressure of the liquid tank was also monitored by the pressure detector 52 during the injection process. It is also possible to switch from speed control to pressure control when this liquid pressure exceeds a set injection pressure. Effects of the Invention As explained above, according to the present invention, in speed control and pressure control of the transfer piston, control by an electric servo system is adopted instead of control by a conventional hydraulic valve, so that the control accuracy is high. can be maintained and reproducibility can be improved. In addition, since a hydraulic control device that requires a large amount of oil is not used, there is no fear of so-called oil leaks, which not only simplifies maintenance management, but also prevents the semiconductor pellet from being contaminated by oil mist. , it becomes possible to improve the molding quality of semiconductors. Also, in order to detect the pressing force of the transfer piston,
Since a hydraulic pressure enclosure is provided to detect the hydraulic pressure, pressure control can be performed at a much lower cost than using a load cell or the like. Furthermore, most of the elements of the speed control system and pressure control system are used together, and each control loop is switched over time to function, which reduces the cost of the entire device and eliminates the need for interference between the two controls. It can function independently without any need.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view, partially including a block diagram, showing a resin sealing device to which an embodiment of the present invention is applied, and FIG. 2 is a diagram showing the process of speed control and pressure control during resin sealing. FIG. 3 is a sectional view for explaining the configuration when performing resin sealing. DESCRIPTION OF SYMBOLS 10... Resin (tablet), 20... Transfer piston, 22... Servo amplifier, 23... Controller, 24... Servo motor (electric motor), 26... Transmission device, 42... Transfer block, 50... Speed sensor, 52... Pressure sensor, L... (sealed state) liquid. Sub-agents Tsuyoshi Makino Hiroya Kei Nonzan

Claims (2)

[Claims] (1) A resin sealing device equipped with a transfer piston for a sealing press, comprising: an electric motor driven by an electric signal from a servo amplifier; a transmission means for converting rotational motion of the electric motor into linear motion; and the transmission means. a pressing means for pressing the transfer piston through a liquid that has a transfer block that linearly moves integrally with the linear movement that is the output of the transfer block, and that is in a sealed state to prevent the linear movement of the transfer block; means for detecting the pressure of the liquid that has been detected; and a controller that feedback-controls the pressure value using an electric signal sent from the servo amplifier to the electric motor as a manipulated variable so that the detected pressure value becomes a set value. A resin sealing device characterized by: (2) A resin sealing device equipped with a transfer piston for a sealing press, comprising: an electric motor driven by an electric signal from a servo amplifier; a transmission means for converting rotational motion of the electric motor into linear motion; and the transmission means. a transfer block that moves linearly integrally with the linear movement that is the output of the transfer piston; means for detecting the moving speed; means for detecting the pressure of the sealed liquid; and an electric signal sent from the servo amplifier to the electric motor as a manipulated variable so that the detected moving speed becomes a set value. a control loop that feedback-controls the moving speed of the transfer piston, and a control loop that feedback-controls the pressure value of the liquid using a signal sent from the servo amplifier to the electric motor as a manipulated variable so that the detected pressure value becomes a set value. A resin sealing device comprising: a controller that switches between and executes one of the above;