JPH05326595A - Molding of semiconductor resin - Google Patents

Abstract

PURPOSE:To prevent inferiority such as uncharge, etc., by lifting up a plunger to the position where the gap between the topside of the resin lying inside a pot and the topside of an upper cull part vanishes at the injection stage into a cavity, and heating the resin placed on the plunger for a certain time, and then, equalizing the temperature of the resin, and injecting it into the cavity. CONSTITUTION:When a plunger 6 is lifted up until the gap with a top force 1 vanishes and resin 21 is heated for a certain time, the whole resin 21 is heated from four sides, being given the heat, too, conducted from the upper mold in addition to the heat conducted from the pot 7 of the bottom force 3, so the temperature of the resin 21 becomes more uniform. Moreover, since there is no gap between the resin 21 and the top force 1, the air layer between the top force 1 and the bottom force 3 vanishes. Hereby, it ceases to entrain air into a product at injection of resin by a synergetic effect of the two effects that the temperature of the resin becomes uniform and that the air layer vanishes, and it can lead to the improvement of quality by preventing the occurrence of defects such as voids, uncharge, etc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor resin method for resin-sealing a semiconductor element mounted on a lead frame.

[0002]

2. Description of the Related Art Usually, a resin molding apparatus as shown in FIG. 4 is used as a means for resin-molding a semiconductor element mounted on a lead frame.

In FIG. 4, the upper mold 1 is fixed to the upper platen 2 and is kept at a fixed position. The lower die 3 is fixed to the movable platen 4, and a plunger 6 and a pot 7 for injecting resin into the cavity 5 of the upper die 1 and the lower die 3 are provided in the central portion of the lower die 3. The plunger 6 is fixed to the plunger holder 8. Reference numeral 9 is a load cell, which is a sensor for detecting the injection pressure of the plunger 6.

Reference numeral 10 denotes a servo motor, the driving force of which is transmitted to a ball screw 14 via a pulley 11, a belt 12 and a pulley 13. A resolver 10a for detecting the position is directly connected to the servo motor 10. The lower part of the ball screw 14 is fixed to the plate 17 by a fixture 16 via a bearing 15. A slide unit 18 is arranged on the plate 17 on the left and right sides, and a slide base 19 is attached to be slidable up and down. The rotation of the ball screw 14 causes the slide base 19 to move, whereby the plunger 6 moves up and down.

The plate 17 is attached to the movable platen 4, and the servo motor 10, the slide unit 18, and the fixture 16 are also fixed. Further, the cavity 5 portions of the upper mold 1 and the lower mold 3 each have an eject pin 20 capable of projecting for releasing the molded product from the mold. The molding sequence according to the above configuration will be described below.

The resin 21 and the lead frame 22 preheated to about 75 ° C. by a preheater (not shown) are set in the pot 7 and on the lower mold 3 by a carrying device. At this time, the position of the plunger 6 is set at a position where the upper surface of the resin 21 and the upper surface of the lower mold 3 are aligned with each other, or a position 1 to 2 mm lower than that.

When the setting of the resin 21 and the lead frame 22 is completed, the lower mold 3 rises to a position in contact with the upper mold 1 and touches the mold. After that, the mold is clamped at the set pressure. The plunger 6 starts to rise by driving the servo motor 10 and injects the resin 21. The resin 21 is injected into the cavity 5 through the cull portion 23 and the runner 24, and after the set injection pressure is detected by the load cell 9, the injection pressure is maintained until the curing is completed.

When the curing is completed, the plunger 6 descends to the resin feeding position, the mold clamping is released, and the lower mold 3 starts descending. Simultaneously with the lowering, the eject pin 20 of the upper mold 1 projects and the resin-molded lead frame 21 is released from the upper mold.

The lower mold 3 is lowered to a position where it can be taken out by automatic handling. When reaching this position, lower mold 3
The eject pin 20 of 1 is protruded by 1 to 2 mm, and the resin-molded lead frame 21 is knocked out from the lower mold 3,
It is transported to the next process by automatic handling.

Next, the resin burrs generated near the cavities 5, runners 24, and pots 7 of the upper mold 1 and the lower mold 3,
It is removed by a dust collecting mechanism provided near the mold. At this time, the upper surface of the plunger 6 is cleaned in the same state as the upper surface of the lower mold 3 or in a state of protruding by 1 to 2 mm. After cleaning, the plunger 6 descends and returns to the position where the next resin is charged, and the series of molding steps is completed.

Further, each position of the plunger 6 is input to the control unit from an operation input unit (not shown) in advance, and the plunger 6 is operated by a command from the control unit to the servomotor 10, and the position thereof is the resolver 10a. It is input to the control unit and the positioning is controlled. The determination as to whether the injection pressure has reached the set value is made by inputting a pressure signal from the load cell 9 provided under the transfer 6 and constantly making a comparison.

[0012]

However, the resin 21 preheated by the preheater has a temperature variation of about ± 3 ° C., which sometimes causes air entrainment during injection to generate voids in the molded product.

The position of the plunger 6 for charging the resin 21 into the pot 7 is usually a position where the upper surface of the resin 21 and the upper surface of the lower mold 3 are coincident with each other as shown in FIG. Is.

There is a gap A between the upper surface of the resin 21 and the upper surface of the cull portion 23 before the injection is started, and the side surface and the lower surface of the resin 21 are heated by the heat transfer from the lower mold 3,
The upper surface has poor heat transfer, and if temperature variations due to the preheater are taken into consideration, the temperature variations become larger and voids and unfilling due to gate clogging tend to occur, which is a major quality problem.

Further, when the resin 21 charging position is set to be higher by the A dimension in advance as shown in FIG. 5B, the resin 21 melts near the pot end 7a during the mold clamping after the resin 21 charging,
Resin burrs occur every time the mold is clamped. The present invention solves the above problems, and an object of the present invention is to provide a semiconductor resin molding method in which voids, burrs, unfilling, etc. do not occur in a molded product.

[0016]

According to the present invention, a semiconductor element mounted on a lead frame is housed in a cavity of an upper and lower mold, and a semiconductor element is molded with a resin injected into the cavity from a pot by a plunger. In the method, in the step of injecting the resin placed on the plunger into the cavity, the plunger is raised to a position where there is no gap between the upper surface of the resin in the pot and the upper surface of the upper mold cull portion, and after heating for a certain period of time, the resin is heated. This is a semiconductor resin molding method in which the temperature is made uniform and a resin is injected into the cavity.

[0017]

After the die is touched, the resin 21 is raised until there is no gap with the upper die 1, and the resin 21 is heated for a certain period of time. In addition to the heat conduction from the pot 7 of the lower die 3 of the related art, the resin 21 is removed from the upper die 1. In consideration of the heat conduction of, the entire resin 21 is heated from the four sides, and the temperature of the resin 21 becomes more uniform.
In addition, since there is no gap between the resin 21 and the upper mold 1, the air layer between the upper mold 1 and the lower mold 3 also disappears. Due to the two synergistic effects of uniforming the resin temperature and eliminating the air layer, air is not trapped in the product when the resin is injected, and voids, unfilling, etc. can be prevented.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

The operation will be described with reference to FIGS. FIG. 1A shows a state in which the resin 21 preheated by a preheater (not shown) is put into the pot 7 of the lower mold 3 by the transfer device. At the same time, the lead frame 22 is also set in the lower mold 3. The plunger 6 is positioned such that the upper surface of the resin 21 matches the upper surface of the lower mold 3. Resin 21
After being charged, the lower mold 3 rises and contacts the upper mold 1 and is clamped as shown in FIG. At this time, there is a gap A between the upper surface of the resin 21 and the upper surface of the upper mold cull portion 23.

Thereafter, the plunger 6 is raised by the dimension A and stopped and positioned as shown in FIG. 1C, and the upper surface of the resin 21 comes into contact with the upper surface of the cull portion 23, and the entire resin 21 is heated to a uniform temperature.

After a lapse of a certain time after heating, the plunger 6 starts injection as shown in FIG. 2A, and the resin 21 is injected into the cavity 5 of the lead frame 22 through the cull portion 23 and the runner 24. The pressure of the plunger 6 is detected by the load cell 9 below the plunger 6, and after detecting that the set injection pressure is reached, the resin 21 is waited for the resin 21 to cure.

When the resin 21 is completely cured, the plunger 6 descends to the resin feeding position as shown in FIG. 2 (b). afterwards,
At the same time when the lower die 3 starts descending, the lead frame 22 on which the eject pin 20 above the cavity 5 of the upper die 1 projects as shown in FIG. The eject pin 20 of the upper mold 1 returns to the original position when the lower mold 3 is completely lowered.

The lower mold 3 is lowered to a position where it can be taken out by a carry-out device (not shown). Figure 3
The eject pin 20 of the lower mold 3 is 1 to 2 m as shown in (a).
m The lead frame 22 formed by extrusion is knocked out. After the knockout is completed, the lead frame 22 that has been molded by a transport device (not shown) is transported to the next step.
When the conveyance is completed, the eject pin 20 of the lower mold 3 returns to the original state.

Thereafter, as shown in FIG. 3 (b), the plunger 6 rises to a position protruding by 1 to 2 mm from the upper surface of the lower mold 3,
Cleaning of the upper and lower cavities 5, the runner 24, the upper surface of the plunger 6 and the like is performed by a dust collecting mechanism provided in the vicinity of the mold. After that, the plunger 6 moves to the position of FIG. 1A where the resin 21 can be carried in and waits for the resin 21 and the lead frame 22 to be set.

After the die is touched, the resin 21 is raised until there is no gap with the upper die 1, and the resin 21 is heated for a certain period of time.
In addition to the heat conduction from the pot 7 of the lower mold 3 of the conventional resin 21, the heat conduction from the upper mold 1 is also added to heat the entire resin 21 from four sides. The state of temperature is improved and the temperature of the resin 21 becomes more uniform. In addition, since there is no gap between the resin 21 and the upper mold 1, the air layer between the upper mold 1 and the lower mold 3 also disappears. Due to the two synergistic effects of the uniform resin temperature and the absence of the air layer, air is not entrained in the product at the time of resin injection, voids, unfilling, etc. can be prevented from occurring and the quality is improved. (Other embodiments)

In one embodiment of the present invention, the temperature of the resin is made more uniform by adding the resin heating step, but a heater dedicated to the cull portion is provided in the upper die cull portion so as not to affect other portions. The same effect can be obtained by performing heat insulation and controlling the temperature.

[0027]

According to the present invention, after the mold is clamped, the transfer is raised to a position where there is no gap between the upper surface of the resin and the upper surface of the upper mold cull portion to make the resin temperature more uniform, thereby preventing the entrainment of air during injection. It is possible to prevent defects such as voids and non-filling and to improve quality.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view showing a resin molding process which is an embodiment of the present invention,

FIG. 2 is a partial cross-sectional view showing a resin molding process which is an embodiment of the present invention,

FIG. 3 is a partial cross-sectional view showing a resin molding process which is an embodiment of the present invention,

FIG. 4 is a configuration diagram of a resin molding device,

FIG. 5 is a partial sectional view of a pot and a plunger portion showing a conventional problem.

[Explanation of Codes] 1 ... Upper mold 3 ... Lower mold 5 ... Cavity 6 ... Plunger 7 ... Pot 21 ... Resin 22 ... Lead frame 23 ... Cull portion

Claims (1)

[Claims] 1. A method of molding a semiconductor element mounted on a lead frame in a cavity of an upper and lower mold and molding the semiconductor element with a resin injected into the cavity from a pot by a plunger. During the step of injecting the resin into the cavity, the plunger is raised to a position where there is no gap between the upper surface of the resin in the pot and the upper surface of the upper mold cull portion, and after heating for a certain period of time, the resin temperature is made uniform and the resin is kept in the cavity. A method for molding a semiconductor resin, which comprises: