JPH08111496A - Lead frame and manufacturing method thereof - Google Patents

Abstract

(57) [Summary] (Correction) [Purpose] Deformation of the pad is prevented by suppressing or eliminating the processing distortion caused by dimple processing, and the depth of the lead frame is about 1/2 of the thickness. It is possible to perform dimple processing. In the method of manufacturing the lead frame 1 by stamping, the pad 5 of the lead frame press-molded into a predetermined shape is heat treated, and then stamped so that a plurality of dimples 6 are scattered on the back surface side of the pad 5.

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 assembling a semiconductor device, and more particularly to a lead frame having a plurality of dimples on the back side of a pad for mounting a semiconductor chip and a method for manufacturing the same. .

[0002]

2. Description of the Related Art Packages used for semiconductor devices are roughly classified into ceramic sealing type and resin sealing type.
A resin-sealed type, which has a low manufacturing cost, is often used.

A semiconductor chip 9 is fixed to the pad 5 of the lead frame 1 by Ag paste or the like, and after the semiconductor chip 9 and the tips of the inner leads 4 are electrically connected by a bonding wire 8 such as Au or Al, the inner The leads 4, the semiconductor chip 9 and the like are resin-sealed to form a semiconductor device as shown in FIG. 3, and the outer leads 2 led out from the package 10 are bent and formed in a J shape or a gull wing shape to be completed.

In recent years, with the high integration of the semiconductor chip 9 and the miniaturization of the package size, the occupied area of the semiconductor chip 9 and the pad 5 for mounting the same has increased with respect to the package size, and the pad 5 and the packaging. Due to the poor adhesion to the resin for the package, the crack of the package 10 has become a problem.

In order to solve this, a method has been proposed and widely used in which a plurality of dimples 6 are scattered on the back surface side of the pad 5 on which the semiconductor chip 9 is to be mounted to improve the adhesiveness with the resin.

[0006]

Here, considering the manufacturing efficiency of the lead frame, as a means for forming the dimples 6 on the back surface side of the pad 5 when the lead frame 1 is formed by the stamping method, The lead frame 1 having a desired shape can be obtained by a consistent stamping operation by using a die apparatus having the punch 11 for dimple processing shown in FIG. 2, but the dimples 6 are formed by the stamping method. Since a large processing strain is given to the support bar 3 and the support bar 3 and the dimensional accuracy is deteriorated, the depth of the dimple 6 is at most 1/4 to 1 of the lead frame material plate thickness.
/ 3 was considered the limit.

Therefore, the shape processing is performed by the stamping method, and only the dimple processing is performed by the etching processing method, but this leads to an increase in the processing steps and an increase in the manufacturing cost, which is not an effective countermeasure. It was

[0008]

The present invention relates to a lead frame in which a plurality of dimples 6 are scattered on the back surface side of a pad 5 and a method of manufacturing the same, and in particular, in a method of manufacturing by stamping, press molding into a predetermined shape. After heat treating the pad 5 of the lead frame 1 thus formed, the pad 5
The present invention provides a method for manufacturing a lead frame, characterized by performing stamping processing so that a plurality of dimples 6 are scattered on the back surface side of the.

[0009]

According to the present invention, the pad 5 is formed before or after the step of performing the dimple processing on the back surface side of the pad 5.
By reducing or eliminating the processing strain caused by the dimple processing by reducing the hardness of the pad by heat treatment, not only the deformation of the pad is prevented but also about 1/2 of the plate thickness of the lead frame 1 is prevented. It becomes possible to perform dimple processing to the depth of.

[0010]

Embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a view showing the outer appearance of a lead frame 1 according to the present invention. A pad 5 for mounting a semiconductor chip 9, a support bar 3 for connecting and supporting the pad 5 to an outer frame, and a semiconductor chip 9 are shown. The inner lead 4 electrically connected to the inner lead 4, the outer lead 2 electrically connected to the external conductive pattern and extending from the inner lead 4, and the tie bar 7 connecting the inner lead 4 with a predetermined space therebetween are predetermined. The shape is stamped by a progressive die apparatus, and a plurality of dimples 6 are further processed on the back surface side of the pad 5.

First, the pad 5 of the lead frame 1 which has been processed into a predetermined shape is heat-treated to have a hardness lower than that of a region other than the pad 5 such as the inner lead 4 and the outer lead 2, and then the pad 5 is removed. Dimple processing is performed as shown in FIG.

The inner leads 4, which are most susceptible to external force during processing into a predetermined shape, are connected to each other or the pad 5 without processing the tips thereof.
It is also possible to prevent deformation by leaving the connection with the peripheral edge of the inner lead 4 and releasing the connected state of the tips of the inner leads 4 simultaneously with the dimple processing.

Here, the method of performing the dimple processing after the heat treatment step of the pad 5 has been described, but the present invention is not limited to this, and the dimple processing station is provided in the progressive die apparatus to perform the shape processing. It is also possible to perform depressing at the same time and then perform heat treatment, which makes it possible to reduce the number of stamping processes.

FIG. 2 shows an essential part of the dimple-processing punch 11, which is provided with a plurality of quadrangular pyramid-shaped projections 12, and the depth of the dimple 6 depends on the protrusion amount of the dimple-processing punch. It can be easily changed by adjusting.

The lead frame 1 thus completed
Since the outer lead 2 and the inner lead 4 are not subjected to the hardness lowering operation by the heat treatment, the mechanical strength is maintained, the inner lead 4 has no adverse effect on the bonding property, and the outer lead 2 has the spring property. There is no adverse effect on.

A semiconductor chip 9 is fixed to the pad 5 of the lead frame 1 with Ag paste or the like, and the semiconductor chip 9 and the tips of the inner leads 4 are electrically connected by a bonding wire 8 such as Au or Al. The leads 4, the semiconductor chip 9 and the like are resin-sealed to form a semiconductor device as shown in FIG. 3, and the outer leads 2 led out from the package 10 are bent and formed in a J shape or a gull wing shape to be completed.

Although the dimples 6 are regularly arranged in the vertical and horizontal directions in the embodiment, the present invention is not limited to this, and the dimples 6 may be arranged irregularly.

[0019]

As described above, according to the present invention, since the depth of the dimple 6 can be increased, even if the pad size with respect to the package size increases,
Since sufficient adhesion can be obtained and the moisture resistance is improved, package cracks are also prevented.

Further, since the mechanical strength of the inner lead 4 and the outer lead 2 which requires a predetermined hardness can be maintained by decreasing the hardness of only the pad 5, the wire bonding property and the spring property of the outer lead are adversely affected. Not even give.

[Brief description of drawings]

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

FIG. 2 is a schematic view of a main part of a dimple processing punch.

FIG. 3 is a schematic view of a main part showing the inside of a semiconductor device.

FIG. 4 is a conceptual diagram showing a dimple processing state in the embodiment of the present invention.

[Explanation of symbols]

 1 Lead Frame 2 Outer Lead 3 Support Bar 4 Inner Lead 5 Pad 6 Dimple 7 Tie Bar 8 Bonding Wire 9 Semiconductor Chip 10 Package 11 Dimple Punch 12 Protrusion

Claims (3)

[Claims] 1. A lead frame comprising a pad for mounting a semiconductor chip, a plurality of inner leads radially arranged at a predetermined distance from the pad, and an outer lead extending from the inner lead. A lead frame, wherein a plurality of dimples are scattered on the back surface side of the pad, and the hardness of the pad is lower than that of other portions. 2. A lead frame comprising a pad for mounting a semiconductor chip, a plurality of inner leads radially arranged at a predetermined distance from the pad, and an outer lead extending from the inner lead. In a method of manufacturing by a stamping process, the pad of a lead frame press-molded into a predetermined shape is heat treated, and then a stamping process is performed so that a plurality of dimples are scattered on the back surface side of the pad. Method. 3. A lead frame comprising a pad for mounting a semiconductor chip, a plurality of inner leads radially arranged at a predetermined distance from the pad, and an outer lead extending from the inner lead. In a method of manufacturing by a stamping process, a lead frame is press-molded into a predetermined shape, the back surface side of the pad is stamped so that a plurality of dimples are scattered, and the pad is heat-treated. Method.