JPH1187598A - Lead frame - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve reliability and operativity in wire bonding by forming a support bar of a wide lead and a narrow lead and boring a rectangular through hole on a wide lead part in the vicinity of a border between the wide lead and the narrow lead. SOLUTION: A support bar 4 comprising a wide lead 2 and a narrow lead 3 which extend from an X-shaped pad 1 for example in X directions is formed. A rectangular through hole 12 is bored on the wide lead 2 in the vicinity of a border between the wide lead 2 and the narrow lead 3 forming the support bar 4, while mechanical strength is reduced by making a side of the through hole 12 to which the narrow lead 3 is connected short. Further, by making a structure where the narrow lead 3 is connected, a developed stress is concentrated to make it easy to deform in a lead lengthwise direction. Thus even if a stress due to difference in thermal expansion occurs, the support bar 4 deforms in the lead lengthwise direction to release the stress, so that deformation such as twisting, rotation, shift to right or left or the like can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a lead frame.

[0002]

2. Description of the Related Art In the manufacture of a semiconductor device, a semiconductor chip is mounted on a pad of a lead frame by an adhesive such as silver paste in a die attachment process. The bonding needs to provide a heating effect, and is heated to, for example, about 200 ° C.

Since the metal of the lead frame material and the semiconductor chip have different coefficients of thermal expansion, a stress due to the difference in thermal expansion is inevitably generated due to the heat history of returning to normal temperature, and the support bar supporting the pad. Are deformed such as shift, rotation or torsion. The deformation may occur when the pad is square or rectangular, but is remarkable when the pad is X-shaped or cross-shaped.

The pad is often lowered from the inner lead surface by pushing down a part of a support bar supporting the pad, which is called depressing. The depressing is to reduce the distance between the semiconductor chip and the inner lead and the height difference by lowering the pad, thereby reducing the length of the bonding wire and preventing a short circuit, and further reducing the thickness of the semiconductor device. .

However, if the deformation occurs on the support bar, the position of the support bar will change even if the depressing is performed. There is a problem that the wire bonding cannot be performed smoothly because it does not enter the groove of the heat block of the worktable, or the semiconductor chip is tilted when the pad is tilted, which also hinders the wire bonding. In addition, the inclination of the pad becomes a major obstacle to the thinning of the semiconductor device.

A technique for preventing the deformation of the support bar has been proposed. For example, JP-A-63-232
No. 359 discloses that a part of the support bar is bent in an S-shape, that an annular member is provided on a part of the support bar, or that a wrinkled member is provided. According to this, the stress for deforming the support bar is absorbed, and there is an effect of preventing deformation.

[0007]

However, in the semiconductor device, the semiconductor chip becomes relatively large due to the high integration and the multi-functionality, and the thermal stress due to the difference in thermal expansion with the pad increases, so that the semiconductor device is not supported. Deformation is seen. In particular, if the pad is X
FIG. 4 shows the pad portion 1 and the support bar.
As shown in an enlarged view of the four parts, there are deformations such as rotation, shift or twist, which hinder the wire bonding. In addition, there is a problem that the thickness of the semiconductor device cannot be reduced due to the inclination of the pad.

According to the present invention, the support bar does not rotate, shift, twist, or the like even if it receives a heat history due to die attach or resin sealing, and the wire between the semiconductor chip and the inner lead is formed without tilting the pad. An object of the present invention is to provide a lead frame which can perform bonding with good reliability and workability and is effective for manufacturing a thin semiconductor device.

[0009]

SUMMARY OF THE INVENTION The gist of the present invention is to
In a lead frame provided with inner leads around pads supported by a bar and outer leads connected to the inner leads, the support bar has a wide lead.
And a wide lead and a narrow lead.
The lead frame has a square through hole formed in a wide lead portion near the boundary of the lead.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the present invention will be described with reference to the drawings. In this embodiment, a lead frame in which pads are X-shaped will be described. In the drawing,
Numeral 1 denotes an X-shaped pad, and a support bar 4 consisting of a wide lead 2 and a narrow lead 3 is formed extending from the pad 1 in the X direction.

Reference numeral 5 denotes a plurality of inner leads formed around the pad 1, and an outer lead 6 is formed continuously with the inner leads 5. Reference numeral 7 denotes a tie bar formed at the boundary between the inner lead 5 and the outer lead 6 to prevent the resin from leaking to the outside at the time of resin sealing. 8 is a slit formed on the back side of the outer lead 6, 9 is a side rail, and 10 is a guide hole.

After that, a semiconductor chip 11 indicated by a broken line is attached to the pad 1 with an adhesive such as silver paste or epoxy adhesive and heated and bonded as described above.
At this time, the support bar 4 is prevented from being deformed due to a difference in thermal expansion between the lead frame material and the semiconductor chip 11 as follows.

A rectangular through hole 12 is formed in the wide lead 2 near the boundary between the wide lead 2 and the narrow lead 3 forming the support bar 4, and the rectangular through hole 12 is formed. The mechanical strength is reduced by shortening the side to which the narrow lead 3 is connected, and the stress generated by the structure in which the narrow lead 3 is connected thereto is concentrated. It is easy to deform in the lead length direction. As a result, even if the stress due to the difference in thermal expansion is generated, the support bar-4 is deformed in the lead length direction to release the stress, and deformation such as twisting, rotation, and shifting to the left and right is prevented. It is.

The square through-holes formed in the wide lead 2 of the support bar 4 are not limited to the square through-holes 12 of this embodiment, but may be triangular through-holes 13 shown in FIG. , (B) a trapezoidal through-hole 14, (c) a drum-shaped through-hole 15,
The two-stage rectangular through hole 16 shown in FIG.

The lead frame 17 of the present invention is constructed as described above, and can be manufactured by a press method or an etching method. As described above, the semiconductor chip 11 is bonded and mounted on the pad 1 via the adhesive, and the terminals of the semiconductor chip 11 and the inner leads 5 are wire-bonded, and then are sealed with resin.

In the above-described embodiment, the support bar for the X-shaped pad 1 is used. However, the present invention can be applied to a support bar for a pad having an arbitrary shape such as a square or a rectangle.

[0017]

According to the present invention, the rectangular through hole is formed in the wide lead portion near the boundary between the wide lead and the narrow lead of the support bar. The mechanical strength of the narrow lead connection side of the through hole is reduced. Further, since the narrow lead is connected to the middle part of the portion where the mechanical strength is reduced, the thermal stress generated by the die attach is concentrated and receives the stress by deforming the back surface of the square through hole. Absorption, twisting of the support bar, no rotation and no shift occur. Thus, the wire bonding can be performed with high reliability without hindrance, and there is an effect that the pads do not tilt and effectively contribute to the thinning of the semiconductor device.

[Brief description of the drawings]

FIG. 1 is a view showing a lead frame according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining an operation in one embodiment of the present invention.

FIG. 3 is a view showing various shapes of a support bar according to the present invention.

FIG. 4 is a view for explaining a problem of a support bar of a conventional lead frame.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pad 2 Wide lead 3 Narrow lead 4 Support bar 5 Inner lead 6 Outer lead 7 Tie bar 8 Slit 9 Side rail 10 Guide hole 11 Semiconductor chip 12 Square through hole 13 Triangular through hole 14 trapezoidal through-hole 15 drum-shaped through-hole 16 two-step square-shaped through-hole 17 lead frame

Claims (1)

[Claims] 1. A lead frame having an inner lead provided around a pad supported by a support bar and an outer lead connected to the inner lead. A lead frame formed of a lead, wherein a square through hole is formed in a wide lead portion near a boundary between the wide lead and the narrow lead.