JPH0631352A - Method for controlling press - Google Patents

Abstract

PURPOSE:To reduce impact generated by a pressing force on a product by moving a lead frame at low speed until clamped and moving the clamped lead frame at high speed when press work is performed on it. CONSTITUTION:A movable part such as a stripper plate 6 and a punch 5 is moved at high speed for a period when the stripper plate 6 is moved downward from an upper position until just before it is abutted on a feed plate 9. From just before the stripper plate 6 is abutted on the feed plate until the lead frame 10 is clamped in between a lower die 11, the striper plate is moved at low speed. When the clamped lead frame 10 is worked with working tools, it is moved at high speed and worked. Consequently, a product such as a thin package that is weak against an impact may be adequately performed with press work.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control method for a press machine.

[0002]

2. Description of the Related Art Lead frames are manufactured as products by mounting semiconductor chips and resin-molding them, and then subjecting them to necessary processing such as resin removal, dam bar cutting, and lead bending. FIG. 2 shows a processing stage in the dam bar cutting process. In the dam bar cutting step, the dam bar of the lead frame 10 is cut and removed by using the punch 5 formed in a comb shape. In FIG. 2, 6 is a stripper plate for guiding the punch 5, 7 is a punch holder, and 8 is a movable platen. Further, 9 is a feed plate for supporting and carrying the lead frame 10, 11 is a lower die, and 12 is a die frame. The feed plate 9 is supported by a spring 13 so as to be movable up and down with respect to the lower die 11.

The lead frame 10 is in a state where the feed plate 9 is in an upper position with respect to the lower die 11 (the state shown in FIG. 2).
Is conveyed to the next stage, positioned at the next stage, and subjected to required processing. When processing the lead frame 10, first, the movable platen 8 moves downward and the stripper plate 6 pushes down the feed plate 9. The stripper plate 6 moves down while pushing down the feed plate 9 until the lead frame 10 is clamped to the lower die 11. When the lead frame 10 is clamped and the movement of the stripper plate 6 is restricted, the movable platen 8 and the punch holder 7 descend, and along with this, the punch 5 moves downward to form the lead frame 10 with the lower die 11. Give.

[0004]

A conventional lead frame processing machine repeats the above-described processing operation every time the lead frame is fed by a constant size. The stripper plate hits the feed plate and pushes it down once each time. After punching the punch, it descends and stops until the upper die hits the lower die. In a punching process such as a press, it is necessary to move the punch at a certain speed or more in order to suppress cutting flash. For example, when forming a lead frame, burrs rapidly increase when the speed is 35 mm or less per second. Further, in order to suppress wear of the punch, it is preferable that the punch speed be a certain speed or higher. This is because when the punch speed is less than a certain speed, the punch is easily worn due to the lateral pressure from the processed product.

Therefore, in the press working of the lead frame, the press mechanism is driven so that the punch punches the lead frame at a constant speed or more. As described above, in a lead frame processing machine, the movable parts such as the stripper plate 6 move at a considerable speed, and therefore, when the stripper plate 6 hits the feed plate 9 or the upper die hits the lower die, it is considerably difficult. The impact force of is generated. This impact force affects the lead frame on which the semiconductor chip is mounted, which may cause a functional failure or even destroy it. Therefore, in actual press working, a certain upper limit is set as the punching speed so as not to give an excessive impact to the product. The upper limit of the punch speed is, for example, about 100 mm / sec.

Even if the punch speed is too fast, the wear of the punch progresses. Therefore, when setting the punch speed, it is preferable to set the speed under the condition that the wear of the punch is minimized. Since lead pitches of recent lead frames are becoming narrower, it is important to minimize the occurrence of burrs. Further, since the dam bar cut punch and the like use an extremely narrow punch in accordance with the lead pitch, the problem of punch life is important from the viewpoint of productivity and economy. In addition, since the number of large and thin semiconductor packages has recently increased, the impact of press working has a great influence on the reliability of the product. The present invention has been made to solve the above problems, and an object of the present invention is to minimize the influence of the impact force exerted on the product by the press force during press working and reduce the workability such as punching. An object of the present invention is to provide a control method of a press working machine that can perform working without performing the work.

[0007]

The present invention has the following constitution in order to achieve the above object. That is, the lead frame is supported by the feed plate and is fed at a fixed size, the feed plate is pushed down by the stripper plate during press working, and the lead frame is clamped by the stripper plate and the lower die to perform the required processing. In the method, a movable part such as a stripper plate and a punch is moved at high speed until the stripper plate moves downward from the upper position and immediately before coming into contact with the feed plate, and the stripper plate comes into contact with the feed plate. It is characterized in that it moves at a low speed from immediately before until the lead frame is clamped between the lower die and when it is processed by a processing tool on the clamped lead frame at a high speed. . In addition, after processing the lead frame, move the processing tool at high speed when moving it upward in the return direction, and move the stripper plate at low speed when releasing the lead frame clamp by the stripper plate and the lower die. It is characterized by moving with and returning to the original position. Further, when the lead frame is clamped by the stripper plate and the lower die, the separation distance between the working end surface of the processing tool and the processing surface of the lead frame of the workpiece is processed into the lead frame at high speed by accelerating the processing tool. The feature is that the positions are set apart from each other by a distance required for applying.

[0008]

The lead frame is supported by the feed plate and is fed at a constant size while being subjected to the required processing by the processing machine. In this control method, when the stripper plate moves downward to clamp the lead frame, it is moved at low speed when the stripper plate and the feed plate come into contact with each other, so that the impact force when the stripper plate and the feed plate come into contact with each other can be suppressed. The stripper plate and lower die reduce the impact force when clamping the lead frame. As a result, it is possible to avoid the adverse effect of the impact force exerted on the product. Further, when a product such as a punching process is performed on a product, the punching speed is set to a required high speed so that a favorable process without burrs can be performed and abrasion of the punch can be suppressed. .

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 shows an embodiment in which a lead frame is pressed according to the control method for a press machine according to the present invention. In a processing machine that performs dam bar cutting or lead bending processing on a lead frame, control has not hitherto been made so as to positively change the press speed during one press cycle. It is characterized in that the press speed is changed within the cycle for processing. Therefore, in the embodiment, the speed of the press is controlled using the crank press machine using the servo motor so that the speed can be easily controlled.

Graph A in FIG. 1 shows the change over time in the punch position within one press cycle. The vertical axis represents the distance from the bottom dead center of the punch position, and the horizontal axis represents time. Graph B shows correspondingly the number of rotations of the servo motor which controls the punch position. Point a is the punch position at the time of starting the work, and the punch is in the top dead center position. The punch accelerates from this top dead center position a and starts to descend. As shown in FIG. 2, when the punch 5 starts to descend, the punch 5 descends integrally with the upper die, that is, the movable platen 8, the punch holder 7, the stripper plate 6, and the like. During this descent (range a to b in the figure), the servomotor is controlled to a constant rotation speed as shown in graph B, and the upper die descends at a constant speed. During this descent, the motor rotation speed is set to a high speed. In the example, it was set to 900 rpm.

When the upper die is lowered to the position just before the stripper plate 6 contacts the upper surface of the feed plate 9, the lowering speed is started to be reduced. Graph A in Figure 1
Point b is the start of deceleration. The deceleration period of the upper die is from immediately before the stripper plate 6 contacts the feed plate 9 until the stripper plate 6 pushes down the feed plate 9 and clamps the lead frame 10 with the lower die 11 and the stripper plate 6. C in graph A
The points are the positions where the lead frame is clamped. From point b to point c, the rotation speed of the servo motor is gradually decreased as shown in graph B. The rotation speed of the servo motor when clamping the lead frame in the embodiment is 100 rpm. The moving speed of the upper die at this time is 16.7 mm / sec.

Incidentally, FIG. 3 shows a state immediately after the lead frame 10 is clamped by the stripper plate 6 and the lower die 11 in the embodiment. It can be seen that the spring 13 contracts and the feed plate 9 contacts the lower surface of the stripper plate 6 and is pushed down. The punch 5 starts descending toward the lead frame 10 after the stripper plate 6 clamps the lead frame 10. When the lead frame 10 is processed by the punch 5, it is necessary to set the punch speed to a certain speed or higher as described above. Therefore, from the position of the point c where the lead frame is clamped, the rotation speed of the servo motor is rapidly increased to accelerate the punch 5 to obtain a required punch speed.
In the graph A, point d is the upper surface position of the lead frame 10, and e
The dots indicate the height position of the cutting edge of the lower die 11. That is, d
Lead frame 1 when the punch edge is lowered to the point
Processing for 0 starts, and the punch blade edge is lowered to the height of the cutting edge of the die, and punching is completed.

In the embodiment, the rotation speed of the servo motor is raised to 550 rpm between the position c and the position d when the lead frame 10 is soft clamped, and the rotation speed of the servo motor is increased from the position d to the point e. It was increased to 620 rpm. The punching speed was 56.5 mm / s at the position where the punch blade edge contacts the upper surface of the lead frame 10 (point d), and 65.4 mm / s at the die cutting edge position of the lower die (point e). In the graph B, point P indicates the rotation speed of the servo motor at the position where the lead frame is clamped, and point Q indicates the rotation speed of the servo motor when the punch edge contacts the lead frame.

The punch 5 moves at a position slightly lower than the cutting edge height (point e) of the die, from the bottom dead center to a height of 0.6 mm at a high speed in the embodiment, and decelerates from this height position to reach bottom dead. Move down to the point position. In the graph B, the R point is the final rotation speed of the servo motor when it is lowered at a high speed, and is 700 rpm at the R point. The punch descending speed at this time is 58.8 mm / sec.
In the embodiment, since the pressing mechanism using the crank press is used, the lowering speed of the punch decreases as it approaches the bottom dead center. It is due to the structure of this press that the rotation speed of the servo motor is increased while the descending speed of the punch is decreased.

After the punch 5 descends to the bottom dead center position, the servo motor is reversely rotated to raise the punch 5. Graph B
Shows that when it goes up from the bottom dead center to the return direction, it is rotated in the reverse direction. In the case of the movement in the return direction, the control in which it is lowered is just reversed. That is, when the punch 5 is lifted to remove the punch 5 from the lead frame 10, the punch 5 is moved at high speed, and when the stripper plate 6 is lifted to release the clamp of the lead frame 10, it is moved at low speed. After the stripper plate 6 is separated from the feed plate 9, the stripper plate 6 is moved at high speed to return to the original position. In the graph A, point g shows a portion where the clamp of the lead frame 10 is slowly released.

As described above, in this embodiment, the rotation speed of the servomotor is controlled according to the movement position of the punch 5 or the stripper plate 6 in the cycle, and when the lead frame 10 is clamped, it is clamped at a low speed. However, when punching the lead frame, by setting the punching speed to a high speed, it is possible to perform processing without giving an impact force to the product, and burrs occur during processing. It is possible to suppress and to perform good processing. Also, since the lowest point position when the upper die descends can be set with high accuracy as the bottom dead center of the crank press, the lower position of the upper die press after punching is set to the position before the upper die press collides. By setting it, it is possible to prevent the press of the upper die from hitting the lower die. As a result, it is possible to avoid the impact when the press collides and prevent the product from being adversely affected.

In the above example, the press motor was moved up and down by rotating the servo motor forward and backward, but if the lowest point position of the press is set appropriately, the servo motor will rotate in one direction and the rotation speed will be at an appropriate position. May be controlled. In FIG. 1, a graph C shows control when the servo motor is rotated in one direction.

In order to move the lead frame at a low speed when clamping the lead frame and to obtain a required punching speed when punching as in the above embodiment, after the lead frame is clamped, the punch 5 is pressed. Lead frame 10
It requires a slight movement stroke before it comes into contact with.
That is, as shown in FIG. 3, the punch 5 clamps the lead frame 10 with the stripper plate 6 and then accelerates the lead frame 10 to hit the lead frame 10 at high speed, so that the required speed cannot be reached if the moving stroke is short. Because.

For this reason, in the processing machine of the embodiment, the punch 5 is set so as to be retracted largely as compared with the normal punch arrangement position. FIG. 4 shows the arrangement of the punches 5 in a normal processing machine. Lead frame 1 for normal processing
Although the distance between the blade edge of the punch 5 and the upper surface of the lead frame 10 is about 0.1 mm when 0 is clamped, the distance between the blade edge of the punch 5 and the lead frame is 1 to 1.
It was set to about 5 mm. In the above example, after the lead frame 10 was clamped, the time required for the punch 5 to start descending and to contact the lead frame 10 was 0.03 seconds. Punch 5
The acceleration of is actually performed within such a short time.

According to the method of the present invention as shown in the above embodiment, the moving speed of a press such as a punch or a stripper plate is partially reduced within one cycle, so that the cycle time may become long. By distinguishing the part that moves at low speed from the part that moves at high speed, it is possible to move the high-speed moving part at a higher speed than ever before. Therefore, by compensating for the time loss in the low-speed moving part, efficiency can be improved. Processing becomes possible. In addition, by moving the mold at a low speed when clamping or unclamping the lead frame as described above,
It is possible to effectively suppress the impact force on the product and avoid adverse effects. The lead frame after resin molding is warped due to the shrinking action of the resin. Since this warp is corrected and held by the clamp pressure during clamping, if the clamp is released abruptly, there is a problem that internal destruction occurs during release. Thus, it is effective to perform soft release when releasing the clamp of the lead frame.

In the above embodiment, the dam bar cutting process was mainly described as an example, but the above control method can be applied in the same manner to other processes such as resin dropping and lead bending. In the processing machine that supports the lead frame with the feed plate and feeds the product on multiple processing stages at a constant size, the operations such as pressing the feed plate with the stripper plate are common, so the soft clamp described above is used. Suitable processing can be performed by soft release. Further, there is an effect that the processing can be performed without applying an excessive impact force at the time of processing, and the generation of noise due to the impact can be prevented.

[0022]

As described above, according to the control method of the press machine according to the present invention, when the lead frame is clamped, it is possible to process the product without giving an impact force by clamping it at a low speed. Therefore, even a product such as a thin package which is weak in impact force can be suitably pressed. In addition, when processing a product, it is possible to manufacture a good product without flash by increasing the punch speed, which suppresses abrasion of the punch and enables press processing with excellent productivity and economy. It can be carried out. In addition, the work environment can be improved by suppressing the generation of noise during the work, and so on.

[Brief description of drawings]

FIG. 1 is a graph showing an example of a control method of a press machine.

FIG. 2 is an explanatory diagram showing an overall configuration of a press device.

FIG. 3 is a cross-sectional view of an embodiment with a lead frame clamped.

FIG. 4 is a cross-sectional view of a conventional example with a lead frame clamped.

[Explanation of symbols]

 5 Punch 6 Stripper plate 7 Punch holder 9 Feed plate 10 Lead frame 11 Lower die

Claims (3)

[Claims] 1. A press working in which a lead frame is supported by a feed plate and is fed at a constant size, and the press plate is pushed down by a stripper plate during press working, and the lead frame is clamped by a stripper plate and a lower die to perform a desired working. In the control method of the machine, moving parts such as a stripper plate and a punch are moved at a high speed until the stripper plate moves downward from a position up to immediately before abutting against the feed plate, and the stripper plate moves the feed plate. Move the workpiece at a low speed immediately before it contacts the lower die until the lead frame is clamped between the lower die and at a high speed when processing the clamped lead frame with a processing tool. A characteristic method of controlling a press machine. 2. After processing the lead frame, the processing tool is moved at a high speed when moving upward in the return direction, and when the lead frame is clamped by the stripper plate and the lower die, the stripper is moved. The control method of the press machine according to claim 1, wherein the plate is moved at a low speed to return to the original position. 3. The lead frame is accelerated at a high speed by accelerating the processing tool for the distance between the working end surface of the processing tool and the processing surface of the lead frame of the workpiece when the lead frame is clamped by the stripper plate and the lower die. The method for controlling a press machine according to claim 1 or 2, characterized in that the position is set with a distance required to perform processing on.