JPH0964267A - Lead frame - Google Patents

Abstract

(57) Abstract: In a lead frame for a semiconductor device, the inner lead is prevented from being deformed, the bonding wire length is shortened to improve the bonding property, and the wire deformation after resin sealing is prevented to reduce the defective rate of short circuit. And perform stable assembly. A lead frame (1) of the present invention is provided with an insulator (2) for fixing an inner lead (4) on a tip end portion of an inner lead (4) and a surface opposite to a bonding surface. This prevents deformation of the inner leads 4 and
Since the tip can be bonded, the bonding wire 6 can be shortened. Therefore, it is possible to improve the defects such as the deformation due to the long bonding wire 6 in the bonding process and the short circuit between the bonding wires 6 due to the resin fluctuation after the resin sealing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead frame, and more particularly to a lead frame connected to an electrode pad of a semiconductor device by wire bonding.

[0002]

2. Description of the Related Art A conventional lead frame will be described with reference to the drawings.

The lead frame 1 shown in FIG. 7 is obtained by first forming a pattern of the inner leads 4 by etching or pressing, and then performing plating and downset processing. 1
Due to the increase in the number of pins and the narrower pitch of the inner leads 4, defects such as shorts and vertical variations due to deformation of the inner leads 4 have occurred in the manufacturing process of the lead frame 1 and the assembly process of the semiconductor device. Therefore, as a means for preventing the deformation of the inner leads 4, a method of fixing the inner leads 4 with an insulator 2 as shown in FIG. 8 was used. This is obtained by sticking it to the inner lead 4 although the insulating material 2, especially a polyimide tape with a single-sided adhesive is mainly used after the conventional patterning and plating. As a more effective method, there is a means for fixing the tips of the inner leads 4 as shown in FIG. 9, FIG. 10 or FIG.
As a result, the deformation of the inner lead 4 can be suppressed as compared with the structure of fixing the intermediate portion of the inner lead 4 as shown in FIG.

On the other hand, in the method of manufacturing the lead frame 1, particularly in the etching process, there is a method of cutting the tips of the inner leads 4. This is because it is difficult to form the shape of the tips of the inner leads 4 by a normal manufacturing method only with the narrowing of the pitch of the inner leads 4, so that all the tips of the inner leads 4 are adjacent to each other during the etching process. After the inner lead 4 is connected to the inner lead 4 by plating, the inner lead 4 is fixed with the insulator 2, and the tip of the inner lead 4 is separated by using a mold to form the original shape. However, also in this case, the structure for fixing the tip end portion of the inner lead 4 shown in FIGS. 9 and 10 is stronger than the structure for fixing the intermediate portion of the inner lead 4 in FIG. It can be said that it is advantageous in consideration of sex.

Using the lead frame 1 thus obtained as shown in FIG. 9, FIG. 10 or FIG.
It is mounted on the island 3 via a paste, and then the semiconductor element electrode pad and the inner lead 4 are electrically connected by a thin metal wire (hereinafter referred to as a wire).

[0006]

In recent years, as the size of semiconductor elements has been reduced, the wire length is becoming longer because the inner lead pitch is also limited. When wire bonding is performed using the conventional lead frame shown in FIG. 7, as shown in FIG. 12, there is no problem in the bondability when the semiconductor element 5 is large, but as shown in FIG. As the semiconductor element 5 becomes smaller, the wire 6 becomes longer, causing a problem that the wire 6 hangs down and comes into contact with the adjacent inner lead or the end of the island 3.

On the other hand, even when the tip end portion of the inner lead 4 shown in FIG. 9, FIG. 10 or FIG. Although the problem of poor contact with the wire is improved, as shown in FIG. 14 or FIG. 15, the length of the wire 6 has the insulator 2 arranged at the tip, so that the wire jumps over the insulator 2 further. Since wire bonding must be performed on the inner side of the inner lead 4,
The wire 6 becomes longer than in the structure of No. 3. As a result, the deformation of the wire 6 due to the resin flow in the resin sealing step increases, and as shown in FIG.
There is a problem that poor contact between them is likely to occur.

An object of the present invention is to provide a lead frame in which there is no poor contact between a wire and an inner lead or an island, and poor contact between wires after resin encapsulation.

[0009]

According to the present invention, there are provided an island on which a semiconductor element is mounted, and a plurality of inner leads which are arranged around the island and are electrically connected to the electrode pads of the semiconductor element via metal wires. In a lead frame for a semiconductor device having the above, an insulator for fixing each of the plurality of inner leads is arranged on a surface of the inner lead opposite to a surface on which the thin metal wire is bonded, or a tip of the inner lead. It is characterized in that the stepped portion formed in the portion is filled with an insulating material for fixing each of the inner leads so as to be flush with the surface of the inner leads.

[0010]

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

FIG. 1 is a plan view of the first embodiment of the present invention, FIG. 2 is a cross-sectional view in which a semiconductor element is mounted on the lead frame of FIG. 1 and is connected by a wire, and FIG. 3 shows the inner lead of FIG. It is sectional drawing explaining an example of a bonding method. In the first embodiment of the present invention, as shown in FIG.
Similar to the conventional lead frame 1 shown in FIG. 7, a pattern including the inner leads 4 is formed by etching or pressing. Next, the bonding area of the inner lead 4 is plated. Next, FIG. 8 or FIG. 9 or FIG.
An insulating material 2 such as a polyimide tape is attached to the surface of the conventional lead frame 1 opposite to the surface to be bonded shown in (1), and thereafter, if necessary, tip cutting processing and down setting processing are performed.

Next, as shown in FIG. 2, the semiconductor element 5 is mounted on the island 3 of the lead frame 1 thus obtained via Ag paste, and wire bonding is performed with the wire 6. As an example of the wire bonding method, as shown in FIG. 3, the lead frame 1 is installed on the heater plate 7 of the bonding device to perform the wire bonding, but the insulator 2 is formed on the surface opposite to the bonding surface.
Since it is attached, it becomes possible to bond to the tip of the inner lead 4 and the length of the wire 6 can be shortened. Further, since the tip end portion is fixed, it is possible to obtain the same or higher effect as the conventional one with respect to the deformation of the inner lead 4.

FIG. 4 is a sectional view for explaining another example of the inner lead bonding method of FIG. As another example of the bonding method using the lead frame 1 of FIG. 1, as shown in FIG. 4, a groove to be fitted with the insulator 2 is previously provided at a position corresponding to the insulator 2 of the heater plate 7 of the bonding apparatus. Keep it. By fitting the insulator 2 in this groove and disposing the inner lead 4 on the heater plate 7,
The inner lead 4 can be in close contact with the heater plate 7 over the entire surface except the insulator 2, and the bondability is further improved.

FIG. 5 is a sectional view showing a semiconductor device mounted on a lead frame according to a second embodiment of the present invention and connected by wires. As shown in FIG. 5, in the lead frame 1 according to the second embodiment of the present invention, first, a pattern including the inner leads 4 is formed by etching or pressing. Next, half etching or coining is applied to a portion of the inner lead 4 where the insulator 2 is filled, to form a stepped portion. Next, the step portion is filled with the insulator 2, and the inner lead 4 and the insulator 2 are molded so that they are flush with each other, and then plating or down-setting is performed.

FIG. 6 is a sectional view for explaining an example of a method of bonding the inner leads shown in FIG. As shown in FIG. 6, the lead frame 1 thus obtained is placed on the heater plate 7 of the bonding apparatus for wire bonding, but the surfaces of the inner lead 4 and the insulator 2 are on the same plane. Therefore, the surface of the heater plate 7 can be completely adhered, and the bondability can be further improved.

[0016]

As described above, according to the present invention, since the inner lead is fixed to the tip of the inner lead and the surface opposite to the bonding surface by the insulator, the inner lead is prevented from being deformed, and Wire bonding can be performed at the position of the tip of the inner lead, and the wire length can be dramatically shortened. This allows
Problems such as wire sagging, curling during wire bonding, deformation of the wire after resin encapsulation, and contact with an adjacent wire, which have occurred due to long wires in the past, can be improved. The short-circuit defect rate can be reduced (0%), and stable assembly can be performed.

[Brief description of drawings]

FIG. 1 is a plan view of a first embodiment of the present invention.

FIG. 2 is a cross-sectional view in which a semiconductor element is mounted on the lead frame of FIG. 1 and is connected by a wire.

FIG. 3 is a cross-sectional view illustrating an example of a method of bonding the inner leads of FIG.

FIG. 4 is a cross-sectional view illustrating another example of the inner lead bonding method of FIG.

FIG. 5 is a cross-sectional view in which a semiconductor element is mounted on a lead frame according to a second embodiment of the present invention and connected by wires.

FIG. 6 is a cross-sectional view illustrating an example of a method of bonding the inner leads of FIG.

FIG. 7 is a plan view of a first example of a conventional lead frame.

FIG. 8 is a plan view of a second example of a conventional lead frame.

FIG. 9 is a plan view of a third example of a conventional lead frame.

FIG. 10 is a partially enlarged plan view of a portion fixed with an insulator in FIG.

FIG. 11 is a plan view of a fourth example of a conventional lead frame.

FIG. 12 is a cross-sectional view in which a large-sized semiconductor element is mounted on a conventional lead frame and connected by wires.

FIG. 13 is a cross-sectional view showing a hung state of a wire when a small semiconductor element is mounted on a conventional lead frame.

FIG. 14 is a cross-sectional view of a fixing portion showing a state of a wire when a tip portion of an inner lead of a conventional lead frame is fixed with an insulator.

FIG. 15 is a cross-sectional view of a semiconductor element mounting portion showing a state of a wire when a tip portion of an inner lead of a conventional lead frame is fixed with an insulator.

FIG. 16 is a plan view showing a contact state of wires after resin-encapsulation by fixing an end portion of an inner lead of a conventional lead frame with an insulator.

[Explanation of symbols]

 1 Lead Frame 2 Insulator 3 Island 4 Inner Lead 5 Semiconductor Element 6 Wire 7 Heater Plate

Claims (3)

[Claims] 1. A lead frame for a semiconductor device, comprising: an island on which a semiconductor element is mounted; and a plurality of inner leads arranged around the island and electrically connected to an electrode pad of the semiconductor element via a thin metal wire. A lead frame, wherein an insulator for fixing each of the plurality of inner leads is arranged on a surface of the inner lead opposite to a surface to which the thin metal wire is bonded. 2. The lead frame according to claim 1, wherein the insulator is arranged at the tip of a plurality of inner leads. 3. The lead frame according to claim 1, wherein the insulator is filled in a stepped portion formed at a tip portion of the inner lead so as to be flush with a surface of the inner lead.