JP2546978B2 - Tie bar cutting mold - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tie bar cutting die for cutting and removing a tie bar member for connecting lead members arranged and led out from a resin body forming an outer shell of an electronic device.

[0002]

2. Description of the Related Art Generally, in a process of assembling an electronic device such as an IC or an LSI, a semiconductor chip having an integrated circuit is mounted on a lead frame, and the mounted semiconductor chip and a lead portion of the lead frame are formed by a thin metal wire. After wiring, the structure of the semiconductor chip including the lead portion and the thin metal wire was resin-sealed to form the outer body of the electronic device. Then, in the subsequent finishing step, unnecessary tie bar portions that connect the lead portions led out from the resin body that is the outer shell are cut and removed, and further lead bending processing is performed to complete the electronic device for the first time. Was there. The tie bar cutting and removing process in this finishing process was performed by a press die.

FIGS. 3 (a) and 3 (b) are perspective views of an upper die (a) and a lower die (b) of a tie bar cutting die showing a conventional example. Conventionally, this cutting die is composed of an upper die 4 and a lower die 3 as shown in FIG. 3, and the upper die 4 has a plurality of punches 1 extending downward and a slit-like shape for slidingly guiding the punches 1. A stripper 5 having a hole for holding the lead portion of the lead frame with a spring force is provided. On the other hand, a die 2 having an escape hole 7 into which a resin body enters and a plurality of slit-shaped holes 6 extending outward from the peripheral portion of the escape hole 7 is attached to the lower mold 3.

FIG. 4 is an enlarged view of a portion of the die shown in FIG. In the die of the tie bar cutting die described above, as described above, the slit-shaped holes 6 that fit with the punches are formed side by side along the periphery of the escape holes 7 in FIG. And
As shown in FIG. 4, the inner wall of the slit-shaped hole 6 has a taper having a cutting edge portion 6a having a wall perpendicular to the front and back surfaces of the die and an inclined wall for expanding the hole so that the cutting piece is easily dropped. And a barb 6b.

FIGS. 5A to 5D are perspective views showing a process of cutting and removing the tie bar using the tie bar cutting die shown in FIG. First, as shown in FIG. 5A, the lead frame is conveyed with the upper die and the lower die open. Then, the resin body of the lead frame is inserted into the clearance hole of the die 2 and the lead portion 13 of the lead frame is placed on the die 2. Next, as shown in FIG. 5B, the upper die is lowered and the stripper 5 holds the lead portion 13. Next, FIG.
As shown in (c), the upper die is further lowered, the punch 1 is lowered against the spring pressure of the stripper 5 and inserted into the slit-shaped hole, the tie bar portion 14 is cut, and falls as a cutting piece 14a. Then, as shown in FIG. 5D, the upper die again rises and returns to the original top dead center.

As described above, the operation of the press machine shown in FIGS. 5A to 5D is repeated to cut and remove the tie bars from the resin bodies of a large amount of electronic devices. The life of most of the dies of this kind was determined by the life of the die. Therefore, in this die, in order to further prolong the life of the die, a super-hard alloy having high wear resistance has been used as the material of the die.

However, this super hard alloy material is not only expensive but also has a difficulty in workability, and in the usual cutting process, it is necessary to rely on electric discharge machining or grinding process in order to spend a great deal of machining time. It was Moreover, in this tie bar cutting die, the slit-shaped holes 6 and the pitch accuracy of the holes are required to be high, and it is necessary to manufacture them in units of 1 micron meter. As a result, the die processing cost becomes high and the price of the die as a whole. More than half of it came to fortune. However, at present, although the cost of the die is high, it has a much longer life and is advantageous from the viewpoint of total cost, compared with a die made of cheap tool steel which is easier to process.

[0008]

In the above-mentioned conventional tie bar cutting die, as shown in FIG. 4, the cutting edge portion 6 of the slit-like hole 6 necessary for the die itself to have strength.
The tapered barb 6b was made longer and thicker than the length a. This not only wastes expensive materials, but also wastes a great number of man-hours for digging the tapered barb 6b from a thick plate material. Although the die has a long life, it has to be manufactured and replaced at the end of the life, which requires a great deal of cost. Further, even if the die is replaced, it takes a lot of time to align and fix the punch with the punch.

Therefore, an object of the present invention is to provide a tie bar cutting die which is easy to replace the die, has a longer life, and is inexpensive.

[0010]

A feature of the present invention is to provide a tie bar cutting die for cutting and removing a tie bar member connecting a plurality of lead members arranged and led out from the periphery of a resin body forming an outer shell of an electronic device. A plurality of punches extending below the die and corresponding to the tie bar member, and escape holes into which the resin body is inserted are formed, and a plurality of slit-like holes extending outward from the periphery of the escape holes and into which the punches can be fitted. And a plate-shaped die in which the side wall surface of the slit-shaped hole is perpendicular to the front and back surfaces and a cutting edge is formed, and the punch is attached to the lower mold with the front or back of the die facing up. On the other hand, it is a tie bar cutting die including a positioning means for positioning and fixing the die so that the position of the slit-like hole does not change.

[0011]

Next, the present invention will be described with reference to the drawings.

1A and 1B are a plan view and a AA of a lower die in an embodiment of a tie bar cutting die of the present invention.
It is sectional drawing. As shown in FIG. 1, the lower die of the tie bar cutting die has an escape hole 7 into which a resin body of an electronic device enters.
Has a plurality of slit-shaped holes 8 extending outward from the peripheral edge of the escape hole 7 and into which punches (not shown) can be fitted, and the side wall surfaces of the slit-shaped holes 8 are opposite to the front and back surfaces. A plate-shaped die 2a having a vertical cutting edge 8a
And a frame portion 9a for positioning the die 2a so that the position of the slit-shaped hole 8 does not change with respect to the punch even when the die 2a is attached to the die holder 9 with the front side or the back side up.
A pressing plate 10 for fastening and fixing the die 2a to the die holder 9 with the pressing bolts 11 is provided for the tapered surface 12a of the die 2a which enters the frame portion 9a.

That is, the die 2a of the present invention has only the cutting edge portion 8a having a surface perpendicular to the front and back surfaces of the die 2a having no taper portion. And the taper barb 8b
Is provided on the die holder 9 side. Further, the outer shape and the position of the slit-shaped hole 8 are symmetrical with respect to the line B-B, so that the front surface and the back surface of the die 2a can be used as a mounting surface during processing of the product. Further, the die 2a has tapered surfaces 12a at both ends in the direction perpendicular to the B-B line. This means that even if either the front surface or the back surface of the die 2a is used, it can be held and fixed by the tapered surface 12b of the holding plate 10. In other words, it facilitates die replacement.

FIGS. 2A and 2B are perspective views for explaining the procedure for attaching the die shown in FIG. To attach the die 2a, first, as shown in FIG. 2 (a), the die 2a is inserted into a frame portion 9a indicated by diagonal lines. This determines the position of the die 2a in the X and Y directions. Next, the bolt 11
While tightening, insert the holding plate 10 into the die holder 9,
By tightening the bolts 11, the tapered surfaces 12a at both ends of the die 2a are pressed and fixed by the tapered surfaces 12b of the holding plate 10, and the die 2a is brought into close contact with the surface of the die holder 9 to determine the height direction.

By making the thickness of the die 2a only at the cutting edge portion in this way, the material cost becomes 1/10 of the conventional cost.
Further, by eliminating the tapered portion, the cutting edge portion can be simultaneously processed, and the processing cost can be reduced to 1/12. Further, by making the shape of the cutting edge of the die straight, both sides of the die can be used, and the life of the die can be doubled.

On the other hand, since the above-mentioned die mounting mechanism is not a mechanism for directly tightening the die directly with bolts or the like to locally generate stress, the die is not cracked due to over-tightening. In addition, there is an advantage that the die can be replaced in 1/5 of the time required in the prior art without requiring skilled skill due to the simplified mounting method.

[0017]

As described above, according to the present invention, a die for forming a cutting edge portion on a surface perpendicular to the front and back surfaces by eliminating a tapered surface portion forming a burr hole through which a cutting piece passes and reducing the thickness. By installing a mounting mechanism on the lower mold with one of the front and back surfaces of this die facing up, expensive materials can be reduced by reducing the thickness, and the processing process can be performed by using only the vertical surface. This has the effect of simplifying and greatly reducing the processing cost and making the die inexpensive. Further, since both sides of the die can be used by providing the cutting edge portions on the front and back surfaces, there is an effect that the life can be simply doubled as compared with the conventional one.

On the other hand, the die mounting mechanism includes a frame portion for positioning the die and a fixing mechanism for pressing and fixing the taper surfaces at both ends of the die to be inserted into the frame portion. Is unnecessary and the die can be easily attached in a short time.

[Brief description of drawings]

FIG. 1 is a plan view and a cross-sectional view taken along the line AA of a lower mold in an embodiment of a tie bar cutting mold of the present invention.

FIG. 2 is a perspective view for explaining a procedure for attaching the die of FIG.

FIG. 3 is a perspective view of an upper die (a) and a lower die (b) of a tie bar cutting die showing a conventional example.

4 is an enlarged view showing a portion of the die of FIG. 3. FIG.

5 is a perspective view showing a process of cutting and removing a tie bar using the tie bar cutting die of FIG. 3;

[Explanation of symbols]

 1 Punch 2, 2a Die 3 Lower Die 4 Upper Die 5 Stripper 6,8 Slit-shaped Hole 6a, 8a Cutting Edge 6b, 8b Tapered Depth 7 Escape Hole 9 Die Holder 9a Frame 10 Presser Plate 11 Bolt 12a Tapered Surface 12b Reverse taper surface 13 Lead part 14 Tie bar part

Claims (2)

(57) [Claims] 1. A tie bar cutting die for cutting and removing a tie bar member connecting a plurality of lead members arranged side by side from a periphery of a resin body forming an outer shell of an electronic device and extending downward from an upper die and corresponding to the tie bar member. A plurality of punches, and an escape hole into which the resin body enters, and a plurality of slit-shaped holes that extend outward from the periphery of the escape hole and into which the punch can fit, and the side of the slit-shaped hole. A plate-shaped die in which the wall surface is perpendicular to the front and back surfaces and a cutting edge portion is formed, and even if the die is attached to the lower die with the front or back of the die facing up, the position of the slit-like hole does not change with respect to the punch. A tie bar cutting die, comprising a positioning means for positioning and fixing the die so as not to exist. 2. The positioning means is provided in the lower mold, surrounds the die at four corners, and encloses the die to position the die, and a frame member for positioning the die in one direction. 2. The tie bar cutting die according to claim 1, further comprising a die fixing member having a tapered surface that pushes a tapered surface formed on both sides and that fixes the die.