JP2830737B2 - Lead frame with bus bar and semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead frame with a bus bar and a semiconductor device, and more particularly to a device for preventing a bonding wire from coming into contact with a bus bar.

[0002]

2. Description of the Related Art Among lead frames, there is a lead frame with a bus bar in which power and ground bus bars are provided inside inner leads.

Usually, when this lead frame with a bus bar is punched by a press, the cut surface is dripped on the punch side and burrs are generated on the die side. Therefore, in order to ensure the flatness of the bonding area, as shown in FIG.
It is often taken on the burr side without any. In this case, since the pressing direction of the press is naturally constant between the inner lead 2 and the bus bar 1, the bus bar 1 also has a cross-sectional shape in which burrs 7 and drooping 6 occur on the same side as the inner lead 2.

When the pulling direction is determined by giving priority to the flatness of the bonding area surface 2a of the inner lead 2, the burr 7 comes above the inner lead 2, but the pulling direction of the bus bar 1 is the same. The burr 7 also comes above the 1.

However, a LOC (Lea) bonding a lead frame on the semiconductor chip 4 via the insulating film 3 is used.
In the (d On Chip) type, since the bonding wire 5 is looped from the inner lead 2 to the semiconductor chip 4 over the bus bar 1, the burr 7 of the bus bar 1 is short-circuited even if it comes into contact with the bonding wire 5 even a little. There is an inconvenience. It is difficult to control burrs consistently, and the resin thickness on the chip is very thin, wire bonding must be performed within this dimension, and large loops cannot be drawn, so there is always a cause for failure Will be.

[0006] Therefore, all the pulling directions are reversed, and FIG.
, The upper side of the inner lead 2 and the bus bar 1
Of the bus bar 1 so that the portion of the bus bar 1 to which the bonding wire can come into contact is loosened. Then, a droop 6 is applied to the bonding area surface of the inner lead 2, and the coining portion 2 b must be deeply inserted into the inner lead 2 in order to eliminate the dripping and obtain a flatness.

[0007] However, due to the specification, since the product is a product in which an insulating film is attached to the lead, it is not preferable that a step of coining is formed on the lead in terms of attaching the film, and the number of steps is increased.

There is also a bus bar coating method for coating an insulating material on a bus bar, but this method is also not preferable because the number of coating steps increases.

[0009]

As described above, in a conventional lead frame with a bus bar, if the lead is pulled out in a fixed direction, if the pulling out direction is a positive direction, a short circuit accident occurs due to the contact between the bus bar and the bonding wire. Is concerned.
On the other hand, if the direction is reversed, a coining step is required, and the step formed by coining is not preferable in attaching the film.

It is an object of the present invention to provide a lead frame with a bus bar and a semiconductor device which eliminates the above-mentioned drawbacks of the prior art and does not cause a short circuit accident during wire bonding.

[0011]

The lead frame with a bus bar according to the present invention is formed by press working so that the direction in which the burrs of the inner leads come out and the direction in which the burrs of the bus bar come out are opposite.

Further, the semiconductor device according to the present invention includes a lead frame with a bus bar which is pressed so that a direction in which burrs of inner leads protrude and a direction in which burrs of bus bars protrude are opposite to each other. With the burr of the inner lead facing up and the burr of the bus bar facing down, the semiconductor chip bonded via an insulating film and the semiconductor chip and the inner lead are wire-bonded over the bus bar. And a bonding wire.

[0013]

[Function] If the lead frame is pressed so that the burrs of the inner lead and the burrs of the bus bar are opposite to each other with the punching direction partially different, the inner lead can be moved beyond the bus bar. When wire bonding the semiconductor chip with the semiconductor chip, if the burr of the inner lead is on the top and the burr of the bus bar is on the bottom, the upper surface of the bus bar to which the bonding wire approaches is a whol surface. Short-circuiting of the bonding wire to the bus bar is greatly reduced. Further, since the surface of the inner lead from which the burr is formed is on the upper side, a flat surface can be obtained on the bonding area surface without coining.

[0014]

Embodiments of the present invention will be described below. FIG. 1 is a sectional view of a main part of a lead frame with a bus bar mounted on a semiconductor chip. This lead frame with busbar is
Inside the inner lead 2 constituting the signal lead, a bus bar for power supply and ground is further provided. A press working method is adopted in forming the bus bar 1
And the other leads including the inner lead 2 have different press punching directions.

When the inner lead 2 is to be pulled out, normal punching in the normal direction is performed, and only the punching for forming the bus bar 1 is pressed in the reverse punching direction. Then, as shown in FIG. 1, a cross-sectional shape in which the direction in which the burrs 7 of the inner leads 2 protrude and the direction in which the burrs 7 of the bus bar 1 protrude is obtained as a lead frame with a bus bar.

In order to perform reverse punching, a punch is erected on a lower die constituting a die, and a die is incorporated into a stopper of the upper die to partially reverse the die. Others have the usual mold structure.

Then, as shown in FIG. 2, when the lead frame material is press-punched, first, a punched shape portion 8 around the inner lead 2 and the like except for the bus bar 1 is punched out. The inner leads 2 and the like are formed (FIG. 2A). At this time, not only the side surface but also the tip surface of the inner lead 2 and the like are removed, but the portion to be the bus bar 1 is left wider than the bus bar. Next, the punched portions 9 on both sides of the bus bar 1 are reversely punched (FIG. 2).
(B)). Note that the lead and the bus bar may be pulled out in reverse order. By sequentially removing the lead frames, a lead frame product with a bus bar shown in FIG. 2C is finally obtained.

In this embodiment, since the punch is inserted from below the bus bar 1, the bus bar has an inverted cross-sectional shape as shown in FIG. Either of the lead frames can be turned upward for ease of use of the product. However, the bus bar 1 that has been drawn upside down should be so that the sagged surface with the sag 6 on the upper side and the burr surface with the burr 7 on the lower side come. Turn. Then, in the inner lead 2 that has been positively removed, the direction in which the burr 7 comes out is on the upper side, and the surface on which the burr 6 comes is on the lower side.

The lead frame in this state is bonded to the semiconductor chip 4 via the insulating film 3. When the bonding pad of the semiconductor chip 4 and the inner lead 2 are wire-bonded beyond the bus bar 1, no burrs come to the upper edge of the bus bar 1 where the bonding wire 5 comes closest. And the distance between the bus bar 1 and the
The short-circuit of the bonding wire 5 coming into contact with the bus bar 1 is greatly reduced. Further, since the bonding area surface of the inner lead 2 is a flat burr surface, the flatness of the bonding area surface can be ensured without deeply coining. Since no coining step and no bus bar coating are required, workability is improved.

[0020]

According to the present invention, since the direction in which the burrs of the inner leads come out and the direction in which the burrs of the bus bars come out are reversed, the burr surface of the inner leads is placed upward, and If the surface is lowered, the flatness of the inner lead bonding area surface can be secured without coining, and the risk of short-circuiting between the bonding wire and the bus bar due to the drooping edge of the bus bar can be effectively avoided. .

[Brief description of the drawings]

FIG. 1 is a sectional view of an inner lead and a bus bar for describing an embodiment of a lead frame with a bus bar and a semiconductor device according to the present invention.

FIG. 2 is a plan view of a punched shape for forming a lead and a bus bar according to the present embodiment.

FIG. 3 is a cross-sectional view of an inner lead and a bus bar, both of which have a burr surface on the upper side in a conventional example.

FIG. 4 is a cross-sectional view of an inner lead and a bus bar, both of which have a drooping surface on the upper side in a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Bus bar 2 Inner lead 3 Insulating film 4 Semiconductor chip 5 Bonding wire 6 Burr 7 Burr 8 Forward punched part 9 Reverse punched part

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Claims (2)

(57) [Claims] 1. A lead frame with a bus bar, characterized in that the lead frame is pressed so that the direction of the burr of the inner lead and the direction of the burr of the bus bar are reversed. 2. A lead frame with a bus bar which is pressed so that the direction of the burr of the inner lead and the direction of the burr of the bus bar are opposite to each other. A semiconductor chip adhered via an insulating film, with a surface on which the burrs emerge from the surface facing up and a surface from which burrs emerge from the bottom facing down, and a bonding wire for wire bonding the semiconductor chip and the inner lead over the bus bar. A semiconductor device characterized by the above-mentioned.