JPS61177218A - Multi-plunger type transfer molding machine - Google Patents

Abstract

PURPOSE:To contrive to prevent defective phenomena such as the generation of unloaded portions and voids due to undersupply, the generation of flashes due to oversupply of material or the like from occurring by a method wherein a stroke, which is proper and necessary for molding a tablet in each pot is given and, in addition, the pouring time of resin is made possible to be controlled at proper period of time. CONSTITUTION:In order to reduce the scattering in heights of tablet 17 at each plunger 12, firstly, the plunger is lowered (or raised) to the face of an un-compacted tablet through a cylinder 4 and a spring 22 under the control of pressure by a pressure reducing valve so as to touch with the face of the un-compacted tablet softly. Secondly, the position of the plunger is fixed to a movable frame 1 by means of a ball screw shaft 20 and an electromagnetic brake 23. Thirdly, a plurality of plungers are simultaneously lowered (or raised) at proper speed by proper stroke by means of a motorized servomotor and a worm jack 9. In addition, molding is done by controlling the feeding speed and amount of resin.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a transfer molding machine used for resin sealing of electronic parts such as semiconductors, and particularly to a 1J transfer molding machine aimed at improving molding yield in a multi-plunger mold. Regarding.

[Background of the invention]

As described in Machine Design Vol. 27, No. 12 (November 1,983 issue), pages 87 to 89, plunger (also called multi-plunger) molding is a small part of the mold that is installed in the center of the mold in the conventional transfer molding method. This method eliminates the big pot and the runners connected to it, and injects resin under pressure directly into the tee from multiple small pots that correspond to each gap in the mold. The usage efficiency of resin, which was supposed to be around 50 inches, has been increased to 80
It can be greatly increased. In addition, compared to the conventional breheating process, the load time spent on the ingate can be reduced to zero, and in addition, gelation time and curing time can be shortened by using a small amount of 1/gin. However, since the multi-plunger molding method uses multiple pots provided for each cavity, the pressure injection force changes due to variations in the amount of resin supplied into the pots. This has the disadvantage that unfilled parts, voids, etc. occur in the molded product, resulting in a defective product.

Therefore, in order to keep the pushing pressure of each granger constant,
Some models use a pressurized injection method using a cylinder using N2 gas, etc. However, even if the temperature of the mold is uneven, even the slightest clogging will cause the injection time to change, making it impossible to fill the cavity within a specified time. Filling is not possible, resulting in unfilled areas and voids.

[Purpose of the invention]

The purpose of the present invention is to minimize the incidence of defective products due to variations in tablets, regardless of variations in the height of tablets filled in multiple pots. To provide a high-yield transfer molding machine that can give a stroke and control injection time to an appropriate time.

[Summary of the invention]

The key point of the present invention is that the tablet height varies from plunger to plunger, and the plunger is lowered (or raised) to the tablet surface by pressure control with a pressure reducing valve using a cylinder and spring to make a soft touch, and then the plunger is moved to the pole screw 2. Place the magnetic brake on the movable frame #
The object is to fix the plunger and simultaneously lower (or raise) multiple plungers to an appropriate speed and stroke using an electric servo motor and a worm jack to control the feeding speed and amount of resin for molding.

[Embodiments of the invention]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a multi-plunger type transfer molding machine.

The upper mold l is firmly fixed to an upper mold stand 3, and the upper mold stand 3 is fixed to a guide rod 5. On the other hand, the lower mold stand 2 is firmly fixed to the lower mold stand 4, and is guided by a guide rod 5 by an elevating cylinder 8 to move up and down. The structure is such that it goes up and down again as it goes up and down. The worm jack 9 is raised and lowered via the electric motor 11 and the coupling 11, and a cross-section taken along the line ■-■ in the figure is shown in FIG.

The plunger 12 is fixed to the piston 13, and the piston 1
The cylinder 14, which is raised and lowered in sequence with the raising and lowering of the cylinder 3, is fixed to the upper moving frame 6. The piston 113 also transmits an axial load to the ball shaft 20 via the thrust bearing 23.

''-The double screw shaft 20 engages with the nut 19 and moves up and down as it rotates. One end of the pole screw shaft 20 has a spline shape and can fit into the electromagnetic brake 23 to transmit torque, and is also slidable in the upward and downward directions. Further, a thrust bearing 21.23 is attached to one end of the pole screw shaft 20, and a spring 22 is interposed between the thrust bearings 21 and 23 to prevent the back eye from constantly pushing down the pole screw shaft 20. are doing. The switching valve 25 is switched to the cylinder 1 via the pressure reducing valve.
By supplying air to the B boat No. 4, the piston 13 rises and pushes up the pole screw shaft 20 against the force of the spring 220. A heating bottle 15 is provided in the upper mold 1 (normally 10 to 10 in multi-plunger type).
A tablet 1'7 (approximately 30 mm) is inserted into the bot 15 by an insertion device (not shown), heated, and then pressure-fed by the plunger 12 and molded in the cavity 18. In addition, 7 is the upper frame, lO is the coupling,
16 is a rod. Next, the motion 1 and the collar of the present invention will be explained using FIGS. 1 to 4. A lead frame (not shown) is loaded into the lower mold with the lower mold stand 4 and the lower mold 2 in the lowered state shown in FIG. It rises and is completely crimped with the upper mold. On the other hand, the tablet 17 is inserted into the bot 15 in the upper mold 1 by an insertion device (not shown), and heating is started.
From this point on, the moving frame 6 is as shown in FIG.
It descends at high speed and stops at a position of 2 to 3M above the top surface of the tablet 17 (the position is set in advance), and then the air pressure in the cylinder 14 is transferred to the B boat via the pressure reducing valve 24 and the switching valve 25. By switching to the positive side, the plunger 112, piston 13, and ball screw IJ-1 shaft 20 are lowered by the force of the spring 22, and the stop position of each plunger is reached by soft touching the top surface of the tablet 17. The reason why the plunger 12 is individually lowered is because the plunger 12 is lowered at different positions by the upper moving frame 6, whereas the rotational energy of the pole screw shaft 20 is lowered by the tablet. By touching 17, it will be absorbed and stop accurately. This is because during the entire descent, a gap is created between the tablets 17 due to the rotational energy, making it impossible to stop them accurately. At this time, the electromagnetic brake 20 is in an open state, and the pole screw shaft 20 is supported by the thrust bearings 21I and 23 and rotates.

Thereafter, the tablet 17 is sufficiently heated.Furthermore, after the heating is completed, the electromagnetic brake 23 is in the closed 1 state, and due to the relationship between the pole screw shaft 20 and the nut 119, it becomes impossible to move up and down with respect to the upper moving frame 6.

That is, the relative position between the upper movable frame 6 and the plunger 12 is fixed. Here, the pole screw shaft 20, the nut 19
The reason why the electromagnetic brake 23 is used is that the electric charge directly applied to the plunger 12 can be counteracted by a large load by holding the rotational force due to the inclination angle of the pole screw shaft 20 with the electromagnetic brake 23. Thereafter, the upper moving frame 6 is pushed down by the electric motor 11 through the coupling 10 to the rod 16 of the worm jack 9, and is lowered together with the Keplunger 12, the pole screw 19, and the piston 13 at a predetermined low speed. .

Note that the speed and amount of this descent slightly vary depending on the type of resin and the sealing partner. Therefore, it is the most important factor and the biggest factor that affects the incidence of defective products. In the present invention, as shown in Fig. 4, in order to accurately control the feeding speed and amount of resin, as shown in Fig. 5, fine adjustments that were impossible with the conventional hydraulic plunger method can be made. By controlling the electric motor 11 using the speed and position setting device 26, digital control device 27, and drive device 28 shown in FIG. ) to a.

It is possible to arbitrarily adjust a', a', etc., but by changing the feed amount (plunger stroke) in the same way, good molding with no excess or deficiency is possible.

Further, when curing the resin, it is also necessary to control the torque of the electric servo motor and maintain the pressure at a constant low pressure. After the resin has hardened, the lower mold 2 is lowered, while the upper movable frame 6 is further lowered to raise the bot 15-', and then lowered again to completely remove the debris inside the bot 15. The moving frame 6 is raised at high speed by the electric servo motor 11, and air is again fed into the cylinder 4 to raise the plunger 12, piston 13, and pole screw shaft 20, and waits until the next cycle.

It goes without saying that the electromagnetic brake opens and closes during this operation.

Another function of the cylinder 14 is to provide alignment between the pot 15 and the plunger 12 when the resin is pumped from the al I5.

〔Effect of the invention〕

According to the present invention, defective phenomena such as unfilled areas, voids, and fringing due to excess are virtually eliminated, making it possible to create a multi-plunger molding machine with high reliability (high molding yield) and good resin yield. Become.

[Brief explanation of the drawing]

gt diagram is a front view of a multi-plunger type transfer molding machine according to an embodiment of the present invention, FIG. The figure is a relationship between the plunger stroke and the pumping pressure by the plunger, and FIG. 5 is a block diagram of the electric motor control device. 1... Upper mold, 2... Lower mold, 3... Upper mold stand,
4...Lower mold stand, 6...Upper moving frame, 12...
- Plunger, 13... Piston, 17... Tablet 20-... Pole screw shaft, 22... Spring, 24... Pressure reducing valve, 25... Switching valve.

Claims (1)

[Claims] 1. In a multi-plunger type transfer molding machine that injects resin into a mold by lowering or raising a plurality of plungers, each of the plungers can soft touch the tablet to a different height position. A cylinder, a pressure reducing device, a piston, a spring for assisting the upward and downward movement of the ball screw shaft, the ball screw shaft for fixing the position with the movable frame after a soft touch, a nut, and an electromagnetic brake are provided. Multi-plunger type transfer molding machine. 2. A patent claim characterized in that a worm jack that simultaneously moves the plurality of plungers up and down, a movable frame, and an electric servo motor that drives these are provided to control the resin feeding speed and feeding amount to appropriate values. A multi-plunger transfer molding machine according to item 1.