JPH09276952A - Press die for lead frame punching - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate fear for seizure of a punch by reducing increase of punching clearance due to regrinding as to produce a good product having reduced shear droop and burr up to complete the die life. SOLUTION: An inclined face 38 inclined against a reference face 36 of a lead frame stock or lead frame is arranged at the peripheral wall of a punch 28, the punch 28 is tapered off, an inclined face 64 is arranged at the inner face of a punch inserting hole 62 facing to the inclined face 38 of punch 28, the punch inserting hole 62 is formed widening along depth, an inclined face 68 is arranged at the inner face of a punching hole 66 of a die 32 facing to the inclined face 38 of punch 28, the punched hole 66 of die 32 is formed widening along depth.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stamping die used for punching a lead frame of a semiconductor package or the like.

[0002]

2. Description of the Related Art Conventionally, a lead frame is manufactured from a material such as a thin metal flat plate by using a working die attached to a press machine, or a semiconductor die is individually manufactured by dam bar cutting, lead forming or the like from a resin-molded lead frame. I am making a package. This pressing die is composed of upper and lower dies, and punches the lead frame material placed on the die of the lower die by vertically moving a punch provided in the upper die. In addition, when manufacturing a semiconductor package, usually, a rectangular lead frame in which a number of sections are sequentially and continuously arranged and connected in an elongated shape is used.
After a semiconductor element such as a semiconductor integrated circuit chip is attached to the center of each section and resin-molded, cutting for individualization is performed.

FIG. 4 is a longitudinal sectional view showing a structure of a main part of a press die for punching such a semiconductor lead frame when punching out a material. In the figure, 10 is a punch for punching, 12 is a punch guide thereof, 14 is a die, and 16 is a lead frame punching material made of a thin metal flat plate placed on the die 14. The punch 10 usually has an upper surface (reference surface) of the lead frame material 16 placed on the die 14 on its peripheral wall, and a surface 18 to be arranged in the vertical direction, and has, for example, a rectangular parallelepiped shape. The edge of the tip sharply protrudes to form a blade. The punch guide 12 is a block, and a through hole 2 having a rectangular parallelepiped space for guiding and supporting the punch 10 inserted in the center thereof.
There is 0. Then, a clearance having a constant width L1 is provided in the horizontal direction between each vertical surface 18 of the punch 10 and each inner surface 22 of the punch insertion hole 20 facing each other. Therefore, each inner surface 22 is also a vertical surface.

The die 14 is also a block, and has a through hole 24 for punching at a position facing the punch insertion hole 20 at the center thereof. The punching hole 24 of the die 14 is a pyramidal space that is narrow at the inlet side and wide at the outlet side, and the edge of the hole 24 at the inlet side sharply protrudes to form a blade. Then, a clearance having a constant width L2 is provided in the horizontal direction between each cutting edge of the punch 10 and each cutting edge of each punching hole 24, and each inner surface 26 of the punching hole 24 is formed in the vertical direction of the upper surface of the lead frame material 16. It is tilted at an angle of θ 1. Therefore, each inner surface 26 is a slope. The punching hole 24 of the die 14 is widened for the purpose of favorably dropping the punched material waste.

A die 1 is manufactured by using such a pressing die.
When punching the lead frame from the material 16 placed on the No. 4, in order to improve the accuracy, the width L2 of the punching clearance is used.
Is suitably 3 to 5% of the plate thickness of the material 16. For example, when punching out a material 16 having a plate thickness L3 of 0.15 mm,
Clearance width L1 is 3 μm, clearance width L2
Is 5 μm. Also, the angle θ1 of each slope 26 of the die 14
Is usually 6 to 10 minutes, so the angle θ is an example.
Set 1 to 6 minutes. If the clearance width L1 is made too small, the lubricating oil will not enter, and the punch 10 will be prone to baking.

[0006]

However, when the punching of the material 16 is repeated several hundred thousand to several million times (shots) using the frame processing die, the tip edge blade of the punch 10 and the hole of the die 14 are formed. The edge is worn and loses its sharpness. Then, it becomes difficult to punch out the material 16 and the processing accuracy is lowered. Therefore, the punch 10 and each blade portion of the die 14 are ground again by the same amount, and each blade is sharply reformed before use.
The shaving area of the punch 10 and the die 14 by such re-polishing is shown as a dotted area, and the maximum amount of the shaving width L4 is about 3 mm. However, when the cutting is performed in this manner, the width L1 of the clearance between the outer surface 18 of the punch 10 and the inner surface 22 of the punch guide 12 does not change, but the width of the punching clearance between the respective facing edges of the punch 10 and the die 14 does not change. Changes from L2 to L5, and the initial value of 5 μm becomes 10.2 μm. Therefore,
The clearance setting of 5 μm increases the clearance of 5.2 μm, and the clearance is twice as strong.

Then, the influence of the increased punching clearance on the cutting point of the material 16 becomes large, and the sag (round shape of the cutting surface) generated at the cutting start point and the burr generated at the cutting end point (downward following the fracture surface). (Protruding part) grows larger. Therefore, since the increase in punching clearance becomes noticeable as the quality of the lead frame as a product deteriorates, it is difficult to sufficiently utilize the length L6 of the die 14 which can be bladed, and the press working die is extremely economical. It has become a thing.

The present invention has been made by paying attention to such a conventional problem, and it is a good product with less sagging and burrs until the life of the die is reduced by reducing the increase of punching clearance due to re-polishing. It is an object of the present invention to provide a press working die for punching a lead frame which is capable of being machined and has no fear of punch seizure.

[0009]

In order to achieve the above object, in a lead frame punching press die according to the present invention, a punch for punching a lead frame from a material or a part of the lead frame is provided in a punch guide. A die having a through hole for punching provided at a position opposite to the punch insertion hole and inserted into the through hole, and a lead frame punching material is provided between the punch and the punch guide and the die. Alternatively, the lead frame is arranged.

Then, an inclined surface that is inclined with respect to the lead frame material or the reference surface of the lead frame is provided in at least one direction of the peripheral wall of the punch, the punch is tapered, and the punch insertion hole facing the inclined surface of the punch is formed. By forming a slope on the inner surface of the, the punch insertion hole is formed deeply,
Further, an inclined surface is provided on the inner surface of the punching hole of the die opposite to the inclined surface of the punch, and the punching hole of the die is formed in a divergent manner.

[0011]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a vertical cross-sectional view showing a structure of a main part of a press die for punching a lead frame to which the present invention is applied when punching a material. 2 in the figure
8 is a punch for punching, 30 is its punch guide, 32
Is a die, and 34 is a lead frame punching material composed of a thin metal flat plate placed on the die 32. The punch 28 is composed of a base portion and a blade portion which are integrally connected. Then, the blade portion is provided with inclined surfaces 38 that are inclined by an angle θ2 with respect to the vertical direction of the upper surface (reference surface) 36 of the lid frame material 34 in four different circumferential walls, and the main portion thereof is formed into a tapered pyramid shape. Form.

In the case of such a sloped surface of a punch, an ordinary profile polishing machine is used in the case of a simple shape, and in the case of a complicated shape, a wire cutting machine such as a wire profiler (trademark) dedicated to punching is used. use. For example,
In the case of forming one side surface of the blade portion of the conventional punch, FIG.
The wire cutting machine 42 is installed with respect to the punch 40 which is arranged so as to be orthogonal to the XY axes as shown in FIG.
Then, the wire 5 guided by the roller 48 in order to process one side surface 46 of the blade portion 44 of the punch 40 into a predetermined shape.
0 can be further supported by the wire guide 52 and the wire holder 54 to determine the path of the wire 50. Then, one side surface 46 is formed by electric discharge machining, and the punch 40 is further rotated to form each of the other side surfaces, whereby the main part of the blade portion 44 is made into a rectangular parallelepiped shape, and the rounded surface 58 is formed on each side surface portion connected to the base portion 56. Can be formed. Therefore, when the one side surface 38 of the blade portion of the punch 28 according to the present invention is formed into a slope, the wire holder 54 is moved in the X axis, the Y axis, or in an appropriate direction to move the straight portion of the wire 50 in the vertical direction. You can incline from. The shape of the rounded surface 58 may be changed by changing the shape of the wire contact surface 60 of the wire guide 52.

The punch guide 30 is a block, and the through hole 62 for guiding and supporting the insertion punch 28 provided in the central portion thereof has a pyramidal space. Then, between the inclined surfaces 38 of the punch 28 and the inner surfaces 64 of the punch insertion holes 62 facing each other, at a position where the front end surface of the punch 28 coincides with the lower surface of the punch guide 30 in the horizontal direction, a constant width L1
To provide clearance. As a matter of course, each inner surface 64 is also an inclined surface parallel to each opposed inclined surface 38 and has the same inclination angle θ2. In this way, the width L1 of the clearance between each surface 38, 64 of the punch 28 and punch insertion hole 62
If the thickness is set to an appropriate value of 3 μm, the lubricating oil can be sufficiently injected into each clearance, and the injected lubricating oil flows down on the slope 64, so that the lubricating oil can be easily kept between the punch 28 and the punch guide 30, and the punch The burn-in of 28 can be prevented.

The die 32 has the same structure as the conventional die 14. Therefore, a through hole 66 for punching is provided at a position facing the punch insertion hole 62 in the central portion of the block, and the entrance side thereof is narrowed, and the exit side thereof is widened into a wide pyramidal space,
The edge on the inlet side is formed into a blade. And punch 28
A punching clearance of a constant width L2 is provided in the horizontal direction between each cutting edge formed at the tip edge portion of each of the punching holes 66 and each cutting edge formed at the hole edge portion of each punching hole 66, and each inner surface 68 of the punching hole 66 is formed. Lead frame material 34
The upper surface (reference surface) 36 of the above is inclined by an angle θ1. Of course, each inner surface 68 is a slope. The slopes 64 and 68 of the punch guide 30 and the die 32 can be easily processed by an ordinary wire cutting machine.

When a lead frame is punched out of a material 34 having a plate thickness of 0.15 mm using such a pressing die, appropriate values for increasing the processing accuracy are set, for example, in the punch 28 and the punch guide 30 as in the conventional case. The clearance width L1 is 3 μm, the clearance width L2 between the punch 28 and the die 32 is 5 μm, and the angle θ1 of each slope 68 of the die 32 is
To 6 minutes. Also, the punch 28 and the punch guide 30
The angle .theta.2 of each of the slopes 38, 64 is set to half the angle .theta.1 of the slope 68 of the die 32, that is, 3 minutes. And
For the lead frame material 34 placed on the die 32,
Although punching is carried out, punching is still several hundred thousand.
When repeated several million times, the blades of the punch 28 and the die 32 are worn out. Therefore, naturally punch 28 and die 32
The same amount of re-polishing is required for each blade.

However, since the clearance width L1 between the punch 28 and the punch guide 30 is an inclined surface, the facing surfaces 38 and 64 of the punch 28 and the punch guide 30 become smaller as the punch 28 is machined, and the punch 28 becomes smaller.
Is minimum at bottom dead center of. For example, as shown in FIG. 3, when the tip of the blade of the punch 28 is projected 1 mm from the lower surface of the punch guide 30, the clearance width L1 is 3 μm.
It becomes 0.9 μm smaller than m and becomes 2.1 μm. Therefore, in order to prevent the punch 28 from sticking,
In order to keep the width of 2.1 μm at the bottom dead center, the punch guide 30 must also be re-polished by the same amount. The top dead center of the punch 28 is located at a position where the blade tip is slightly inward (upper) from the exit of the punch insertion opening 62.

The punch 28 and the punch guide 30 as described above are provided.
The points that can be cut by re-polishing the die 32 are shown as dotted areas. Therefore, the maximum amount of cutting width L4 is 3
mm, the width L5 of the punching clearance is 7.6.
μm, there is little increase in punching clearance due to re-polishing, the length L6 of the punch 28 and the die 32 that can be bladed is fully utilized to extend the die life, and there is little sagging or burr until the die life is completed. Can process various products.
Moreover, the punching clearance is increased by adjusting the angle .theta.2 of the slopes 38 and 64 of the punch 28 and the punch guide 30 to the die 3
It can be suppressed to a smaller value as it approaches the angle θ1 of the second slope 68. In the case of such a normal punching, even when the punch 28 is projected to a necessary and sufficient position, a minimum clearance between the punch 28 and the punch guide 30 is ensured, and the die life is fulfilled. The dimensions of the product must be set within the tolerance even after re-polishing. Further, since it is necessary to re-polish the lower surface of the punch guide 30 by the same amount at the same time as the re-polishing of the punch 28, the thickness of the punch guide 30 is set so as to have sufficient strength even after the re-polishing.

In the above embodiment, the slopes 38 are provided in four different directions on the peripheral wall of the blade of the punch 28, and the slopes 38 and the inner surface of the hole 62 of the punch guide 30 are formed as the opposite slopes 64, respectively. However, the inner surface of the hole of the punch guide may be formed as an inclined surface that faces the inclined surface, by providing an inclined surface in one or a plurality of directions on the peripheral wall of the blade of the punch.

Further, in the above embodiment, the case where the semiconductor lead frame is manufactured by punching from the material using the press working die has been described, but this press working die is a dam bar cut from a resin-molded lead frame, It can also be used when the semiconductor packages are individually manufactured by punching such as lead forming.

[0020]

According to the present invention described above, the hole entrance side of the die gradually expands each time re-polishing is performed, but the tip of the punch also becomes thicker, so that an increase in punching clearance can be suppressed. . Therefore, there is little increase in punching clearance, the punchable length of the die and the die can be fully utilized to extend the life of the die, and it is possible to process a good product with less sagging and burrs until the life of the die is completed. In particular, punches for punching a lead frame out of a material are effective because many of them have thin blades and have complicated shapes.

Further, at the position where the punch is retracted into the punch guide, there is sufficient clearance between the slopes facing each other, so that a large amount of lubricating oil can be injected and the lubricating oil is kept on the slope. Since it becomes easier, there is no danger of punch sticking. Moreover, since the punching clearance between the punch and the punch guide near the bottom dead center can be set to a minimum, the quality of the product is stabilized. If the peripheral wall of the punch is provided with an inclined surface and the blade portion is thickened, the buckling strength of the punch can be increased.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing a structure of a main part of a lead frame punching press die to which the present invention is applied during material punching.

FIG. 2 is a perspective view showing a wire arrangement state when a wire cutting machine dedicated to punching is used for processing one side surface of a blade portion of a conventional punch.

FIG. 3 is a vertical sectional view showing a positional relationship between a punch and a punch guide at a bottom dead center position of a lead frame punching press die to which the present invention is applied (oblique lines and the like are omitted).

FIG. 4 is a vertical cross-sectional view showing a structure of a main part of a conventional die for punching a lead frame when punching a material.

[Explanation of symbols]

28 ... Punch 30 ... Punch Guide 32 ... Die 34
... Lead frame material 36 ... Upper surface (reference surface) 38, 64, 68 ... Slope 42
… Punching dedicated wire cutting machine 62… Punch insertion hole 66… Punching hole

Claims (1)

[Claims] 1. A punch for punching a lead frame from a material or punching a part thereof from a lead frame is inserted into a through hole provided in a punch guide to be guided and supported, and a punch through hole is provided at a position opposite to the punch insertion hole. In a lead frame punching press die in which a die provided with holes is provided and a lead frame punching material or a lead frame is placed between those punches and punch guides and the die, in at least one direction of the peripheral wall of the punch. Is provided with an inclined surface inclined to the lead frame material or the reference surface of the lead frame, the punch is tapered, and an inclined surface is provided on the inner surface of the punch insertion hole opposite to the inclined surface of the punch. Is formed in a wide range,
Further, a lead frame punching press working die is characterized in that an inclined surface is provided on the inner surface of the punching hole of the die opposite to the inclined surface of the punch, and the punching hole of the die is formed in a divergent manner.