JP2001352029A - Lead frame for semiconductor ic, and cutting method for tie bar - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cutting method, where dam burrs are removed effectively without leaving a corner burr, when a tie bar installed outside the package of a semiconductor IC is cut and the service life of a tool can be prolonged. SOLUTION: Tie bars 5, which connect outer leads 4 extending to the outside of the package 1 in which an IC chip is resin-molded, are provided. Grooves 15 for tearing off strips, which are extended so as to cross the tie bars 5 along the longitudinal direction of the outer leads 4 are formed in the boundary parts between the outer leads 4 of the tie bars 5. Interruption parts 16 which partition the grooves 15 for the tearing off strips into the front and the rear are formed halfway of the grooves 15 for the tearing off strips.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead frame used for manufacturing a semiconductor IC, and more particularly, to a structure of a tie bar for connecting outer leads extending outside a package after resin molding. And a method for cutting the tie bar.

[0002]

2. Description of the Related Art Generally, a semiconductor IC is manufactured through a resin molding step, a plating step, a lead processing step, and the like. FIG. 7 is a plan view showing a state in which the IC chip mounted on the lead frame is resin-molded in the resin molding step.

In FIG. 1, reference numeral 1 denotes a package in which an IC chip is formed in a resin mode, and 2 denotes a lead frame. The lead frame 2 includes frame frames 3 provided along the longitudinal direction on both sides thereof, a number of outer leads 4 extending between the frame frames 3 and extending outward from the package 1, and each outer lead. 4 is provided with a tie bar 5 for connecting the components 4, 4 and 5 together.

As shown in FIG. 7, a tie bar 5 is formed on the lead frame 2, and the tie bar 5 is unexpectedly deformed until the inner leads located in the package 1 are molded with resin. And prevents the resin from flowing out of order during the resin molding.

[0005] In the resin mode of the IC chip, the package 1
After that, it is necessary to electrically separate the outer leads 4 from each other, and therefore, for example, the tie bar 5 is cut in a subsequent lead processing step. And
After the cutting of the tie bar 5, cutting of an unnecessary portion of the lead frame 2 and bending of the outer lead 4 are performed.

FIG. 8 shows a state immediately before cutting the tie bar 5, in which 1 is a package, 4 is an outer lead, and 5 is a tie bar. Reference numeral 8 denotes a dam that protrudes around the outer lead 4 of the package 1 during resin molding. The dam burrs 8 are made of the same material as the mold resin of the IC chip (for example, epoxy resin and glass filler).

FIGS. 9 to 11 show a tie bar cutting jig 1.
The state when cutting the tie bar 5 using 0 is shown. The tie bar cutting jig 10 includes a punch 11 and a die 1.
2 is provided. The punch 11 has a predetermined length from the position of the dam beam 8 close to the package 1 to the outside of the tie bar 5, and has a width W2 of the punch 11 in the width direction.
In order to prevent the punch 11 from digging into the outer lead 4 due to a variation in the pitch or displacement of the outer lead 4, the distance between the outer leads 4 is slightly narrower than the facing distance between the adjacent outer leads 4. Is set to As an example, the distance Δ2 from the side end of the outer lead 4 to the punch 11 is set to about 50 μm.

On the other hand, the die 12 has a punch fitting portion 13 into which the punch 11 is fitted, and a gap C2 between the punch fitting portion 13 and the punch 11 has a droop or warp at a cut portion of the tie bar 5. It is set to a very small value to prevent this from happening. For example, the gap C2 is
It is set to 0.013 mm. Then, the punch 11 descends and fits into the punch fitting portion 13 of the die 12,
The tie bar 5 and the dam bur 8 are cut and removed at the same time.

[0009]

When the tie bar 5 is cut using the tie bar cutting jig 10 as described above, the width dimension W2 of the punch 11 is set slightly smaller than the interval between the outer leads 4 facing each other. Because of the necessity, after the tie bar 5 is cut, the remaining portions 8a and 8b of the dam beam 8 exist from the corner between the outer lead 4 and the tie bar 5 to the adjacent portion of the package 1 as shown in FIG. become. Hereinafter, especially the dam beam 8a remaining at the corner between the outer lead 4 and the tie bar 5 is referred to as a corner beam.

As described above, when cutting the tie bar 5,
After the cutting, the corners 8a remain.
If C is transferred to the subsequent outer lead 4 bending process, the following inconvenience occurs.

That is, in the bending process of the outer lead 4, a portion adjacent to the remaining portion of the corner 8a is bent, and accordingly, the upper portion of the corner 8a is in the tension direction and the lower portion is in the compression direction. Each of them undergoes deformation, and as a result, the corners 8a are peeled off from the outer leads 4, and the peeled-off corners 8a are scattered on a package, an outer lead, a processing tool, a device, or the like, which causes various problems. . For example, when performing various tests, if the scattered corner 8a adheres to the outer lead 4 and is interposed between the outer lead 4 and a contact pin (not shown) of the IC socket, poor contact between the outer lead 4 and the pin contact is caused. And a normal test result cannot be obtained.

Further, conventionally, the tie bar 5 and the dam beam 8 are cut off simultaneously by the punch 11 and the die 12 of the tie bar cutting jig 10. However, since the dam beam 8 contains a hard glass filler, There is a problem that the punch 11 and the die 12 are severely worn and the tool life is short.

Furthermore, the punch 1 of the tie bar cutting jig 10
Since the gap C2 between the die 1 and the die 12 needs to be set to an extremely small value, it is required to have a high dimensional accuracy, and maintenance is difficult and the cost is increased accordingly.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and enables the tie bar to be effectively removed without leaving a corner at the same time when the tie bar is cut. It is an object of the present invention to provide a semiconductor IC lead frame capable of cutting a tie bar accurately without maintaining high dimensional accuracy, and a tie bar cutting method for the lead frame.

[0015]

According to a first aspect of the present invention, there is provided a lead frame for a semiconductor IC having a tie bar for connecting outer leads extending outside a package formed by resin molding an IC chip. At the boundary between the tie bar and the outer lead, a shredding groove extending across the tie bar along the longitudinal direction of the outer lead is formed, and the shredding groove is provided in the middle of the shredding groove. It is characterized by providing a cut-off part to be divided before and after.

In the tie bar cutting method according to the second aspect of the present invention,
2. The lead frame according to claim 1, wherein a punch having a width narrower than a length defined by the shredding grooves at both ends of a tie bar and a punch fitting portion having a width dimension substantially corresponding to a distance between adjacent outer leads are formed. When the punch is pressed against the tie bar and fitted into the punch fitting portion of the die by using the set die, the tie bar is cut apart from the outer lead by cutting the tie bar at the boundary of the cutting groove.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is a plan view showing a main part of a lead frame of a semiconductor IC according to a first embodiment of the present invention. FIG. 2 is a sectional view taken along line AA of FIG. The same reference numerals are given to the portions corresponding to the related art.

The lead frame of this embodiment is an IC
At the boundaries between the outer leads 4 at both ends of the tie bar 5 for connecting the plurality of outer leads 4 extending outwardly of the package 1 in which the chip is resin-molded,
A shredding groove 15 extending across the tie bar 5 along the longitudinal direction of the outer lead 4 is formed. In the middle of the shredding groove 15, there is a break 16 that partitions the shredding groove 15 back and forth. Is provided. That is,
The shredding groove 15 is not formed continuously across the tie bar 5, but is interrupted by an interruption portion 16 provided on the way.

In this embodiment, the above-mentioned groove 15 is formed in a V-shaped cross section as shown in FIG. 2, but is formed in a U-shaped cross section as shown in FIG. 3 (a). Alternatively, as shown in FIG. 3B, each of the front and back surfaces of the tie bar 5 may be provided with a slit 15 for cutting. The break 16 is a flat portion flush with the surfaces of the outer lead 4 and the tie bar 5 and is formed by cutting off a part of the tie bar 5.
In addition, such a groove 15 and a break 16 can be easily formed by a technique such as etching.

As described above, by providing the break 16 in the middle of the shredding groove 15, as shown in FIG. Even when the tie bar 5 flows into the slitting groove 15, the tie bar 5 is blocked by the break portion 16 and does not flow out further than that, and the original resin leakage preventing function of the tie bar 5 is secured.

FIGS. 4 and 5 show a tie bar cutting jig 10.
5 shows a state when the tie bar 5 is cut using. The tie bar cutting jig 10 includes a punch 11 and a die 12. The punch 11 has a predetermined length from the position of the dam beam 8 close to the package 1 to the outside of the tie bar 5, and the dimension W1 in the width direction of the punch 11 is, as shown in FIG. The tie bar 5 is set so as to be narrower in width than the length divided by the slits 15 at both ends of the tie bar 5, that is, between the left and right slits 15 sandwiching the tie bar 5. Therefore, the distance Δ1 from the side end of the outer lead 4 to the punch 11 is as shown in FIG.
Is larger than the distance Δ2 (Δ1> Δ
2) Therefore, it is possible to effectively prevent the occurrence of a cutting failure such as the punch 11 biting into the outer lead 4 due to a variation in the pitch of the outer lead 4 or a displacement.

On the other hand, the die 12 has a punch fitting portion 13 into which the punch 11 is fitted. The punch fitting portion 13 is set to have a width dimension substantially matching the interval between the outer leads 4 adjacent to each other. ing. Therefore, the gap C1 between the punch fitting portion 13 and the punch 11 is larger than the gap C2 shown in FIG. 11 (C1> C).
2) It is not necessary to form the tie bar cutting jig 10 with strict dimensional accuracy.

To remove the tie bar 5 and the dam beam 8,
First, when the punch 11 is lowered, after the punch 11 comes into contact with the tie bar 5, the tie bar 5 is pressed downward by the punch 11, so that stress concentration occurs at the bottom of the slit 15 of the tie bar 5, The tie bar 5 is cut off at the boundary of the cutting groove 15 and separated from the outer lead 4.

When the tie bar 5 is torn apart in this manner, the dam burrs 8 located at the corners between the outer lead 4 and the tie bar 5 are bent, so that the conventional burrs 8a do not occur. . Also, under the influence, punch 11
Before cutting the dam 8 with the die 12
The pressing of 1 causes the burrs 8 to be bent and removed.

As described above, in this embodiment, since the corner 8a unlike the conventional case does not occur, the scatter of the burrs is prevented in the next outer lead bending step, and the contact failure at the time of the test is greatly improved. You. Moreover, the punch 11 and the die 12
Therefore, the tool life of the punch 11 and the die 12 can be maintained long.

After the cutting of the tie bar 5, there may be a slight remaining portion 8b of the dam bur in the adjacent portion of the package 1 as shown in FIG. However, the rest 8b
Has almost no effect on the scatter of burrs in the next outer lead bending step, so there is no problem.

[0027]

The method for cutting a tie bar of a semiconductor IC according to the first aspect of the present invention and the lead frame according to the second aspect of the present invention are characterized in that the tie bar is formed by a shredded groove provided at the boundary between the tie bar and the outer lead. Since the tie bar is cut off and cut, not only can the tie bar be left uncut, the cutting can be reliably performed, but also the dam burrs can be effectively removed without leaving the corners. For this reason, scattering of the corners is prevented when the outer lead is bent in the subsequent process, and the contact failure at the time of the test is largely improved, and the test yield is improved.

Moreover, when a punch is used as a tie-bar cutting jig, the distance from the outer lead to the punch can be increased, so that the punch may not move to the outer lead due to a variation in the pitch of the outer lead or a displacement. It is possible to effectively prevent the occurrence of cutting defects such as biting.

Further, since the dam burrs are mainly bent by only the punches and are not cut by both the punches and the dies, the tool life can be maintained long and the running cost can be reduced. Further, the gap between the die and the punch can be made large, and it is not necessary to form the tie bar cutting jig with strict dimensional accuracy, so that the maintenance of the tie bar cutting jig becomes easy.

In particular, in the semiconductor IC lead frame according to the first aspect, the shredding groove provided at the boundary between the tie bar and the outer lead is not formed continuously across the tie bar, but is provided in the middle thereof. Due to the shape of the dam that breaks back and forth due to the break, the part of the dam beam that flowed out during resin molding is blocked by the break even if it flows into the shredding groove located near the package. Therefore, the tie bar does not flow outward, and the original resin leakage preventing function of the tie bar can be secured.

[Brief description of the drawings]

FIG. 1A is a plan view showing a main part of a lead frame after resin molding of a semiconductor IC according to an embodiment of the present invention, and FIG.

FIG. 2 is an enlarged sectional view taken along the line AA of FIG.

FIG. 3 is a cross-sectional view showing a modification of the shape of the shredding groove formed in the lead frame after resin molding of the semiconductor IC of the present invention.

FIG. 4 is a plan view showing a state where the tie bar of the lead frame shown in FIG. 1 is cut using a tie bar cutting jig.

FIG. 5 is a longitudinal sectional view showing a positional relationship between a lead frame of a semiconductor IC and a tie bar cutting jig according to the embodiment of the present invention.

FIG. 6 is a plan view showing a state after the tie bar and the dam beam are separated from the lead frame of the semiconductor IC of the present invention by using a tie bar cutting jig.

FIG. 7 is a plan view showing a state in which a conventional IC chip mounted on a lead frame is resin-molded.

FIG. 8 is a plan view showing a state immediately before cutting a tie bar in a conventional lead frame.

FIG. 9 is a longitudinal sectional view showing a state where a tie bar of a conventional lead frame is cut using a tie bar cutting jig.

FIG. 10 is a plan view showing a state in which a tie bar of a conventional lead frame is cut using a tie bar cutting jig.

FIG. 11 is a sectional view taken along the line BB of FIG. 9;

FIG. 12 is a plan view showing a state after a tie bar and a dam beam are simultaneously cut using the tie bar cutting jig shown in FIGS. 9 to 11;

[Explanation of symbols]

1 package, 2 lead frame, 4 outer leads, 5 tie bars, 8 dam beam, 8a square beam, 1
0 Tie bar cutting jig, 11 punch, 12 dies, 13
Punch insertion part, 15 groove for shredding, 16 break part.

Claims (2)

[Claims] 1. A lead frame provided with a tie bar for connecting outer leads extending outside a package in which an IC chip is resin-molded, wherein the tie bar has a boundary portion with the outer lead, A semiconductor characterized in that a groove for cutting is formed extending across the tie bar along the longitudinal direction of the outer lead, and a cut-off portion for dividing the groove for cutting back and forth is provided in the middle of the groove for cutting. IC lead frame. 2. A method for separating a tie bar of a lead frame according to claim 1, wherein the punch has a narrower width than a length defined by the slits at both ends of the tie bar, and the outer leads of the outer leads adjacent to each other. Using a die having a punch fitting portion having a width dimension substantially corresponding to the interval, when the punch is pressed against the tie bar and fitted into the punch fitting portion of the die, the tie bar is pulled along the cutting groove. A tie bar cutting method characterized by cutting and separating from an outer lead.