JPH10326855A - Lead frame and semiconductor device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lead frame which can cope with reduction in the width of an outer lead accompanied with fabrication of multi pin structure, in lead frames for resin packaged semiconductor device, etc. SOLUTION: Dam bar parts are formed noncontinuously to connect leads with each other. Dam bars 8 for connecting outer leads 7 with each other are formed not linearly but staggeredly. Thus, thanks to the staggered arrangement rather than a linear arrangement, a pitch of a dam bar 8 becomes two times larger than that of the conventional linear arrangement. Therefore, a punch for punching out a dam bar and a die pocket for removing metallic pieces of separated dam bar may be arranged staggeredly at a pitch two times larger than conventionally, thereby realizing such a structure that the punch and receiving mould can work easily.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a lead frame for a resin-encapsulated semiconductor device or the like.

[0002]

2. Description of the Related Art As a semiconductor device using a lead frame, as is well known, a semiconductor chip on which an integrated circuit is formed is attached to an island of the lead frame with an adhesive or the like, and a plurality of electrode pads on the semiconductor chip and a plurality of electrode pads are formed. The corresponding leads are connected by thin metal wires, and then the semiconductor chip and its periphery are integrally molded with a synthetic resin or the like and sealed. On the outside of the resin molded package,
In order to make each lead electrically independent, first disconnect the connection between the lead called a dam bar and the lead,
Next, the semiconductor device is cut off from the outer frame of the lead frame, and the lead is appropriately bent or cut as necessary to manufacture a semiconductor device.

FIG. 4 is a plan view of a conventional lead frame for a semiconductor device.

After connecting the fine metal wires to the leads corresponding to the electrode pads by a wire counter, the region P in FIG. 4 is sealed with a resin using a resin sealing device called a molding device. Furthermore, the connection between the leads, commonly called a dam bar, is punched out continuously by punching and pressing using a receiving die, and each lead is cut off from the outer frame of the lead frame to electrically connect each lead. After that, the leads are bent or cut as needed to form one semiconductor device.

[0005]

In the conventional semiconductor device as described above, with the recent increase in the number of pins in the package, the number of electrode pads and the number of leads corresponding thereto increase, and the width of the inner lead itself and the lead pitch are increased. Tend to become smaller and smaller. Accordingly, the width and pitch of the outer leads also tend to become smaller. For example, in general
In a package called QFP (quard flat package), when the outer shape is 208 pins of 28 mm square, the outer lead width is 0.2 mm, the outer lead pitch is 0.5 mm,
The distance between the leads is 0.3 mm. In this case, a 52-pin lead is placed within a length of 28 mm on each side of the package outer shape. To remove the dam bar connecting the lead and the lead, a 0.5 mm pitch with a length of 0.3 mm is required. It is clear that a punch and a receiving die with high precision are required. Furthermore, the number of pins is 256 for the same outer shape.
When using pins, the outer lead width is 0.15 mm, the outer lead pitch is 0.4 mm, and the distance between leads is 0.2
5 mm. In this case, the length of one side of the package outer shape 2
A 64-pin lead will be placed in the length of 8 mm, and in order to remove the dam bar connecting the lead and lead, a punch with a precision of 0.25 mm long and 0.4 mm pitch and a receiving die are required. It is clear that When punching a dam bar, it is necessary to punch a large number of leads evenly without impairing the lead width, so high accuracy of the punch is required as well as a receiving die for punching a dam bar. High precision is also required. As the lead width becomes narrower and the lead pitch becomes narrower, a punch with high precision and a receiving die are required to continuously punch out the connection between the lead called a dam bar and the lead with a press, There has been a problem that the cost of making the mold becomes more expensive, and the number of production days becomes longer.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a lead frame capable of coping with a reduction in the outer lead width accompanying the increase in the number of pins. Another object of the present invention is to provide a method of easily and continuously pressing a lead-to-lead connection portion called a dam bar with high precision and ease.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to achieve the above object. 2. The lead frame according to claim 1, wherein the lead frame comprises an island for mounting a semiconductor element and a plurality of leads arranged so that the tips gather around the island. Are connected not linearly but at least every other one. Therefore, for example, when dam bars are continuously designed, the outer shape of the package is 20 mm square.
In the case of 8 pins, since the outer lead width is 0.2 mm and the outer lead pitch is 0.5 mm, the punching of the dam bar requires an accuracy of 0.5 mm pitch. In the case of a staggered design, the punching of the dam bar is twice as rough as 1.0mm pitch, but the same package with outer lead width of 0.2mm and outer lead pitch of 0.5mm can be manufactured. It is possible. Therefore, the pitch of the punch for punching the dam bar connecting the leads is not 0.5 mm but a double pitch of 1.0 mm, that is, the interval between the punches can be doubled. is there. Therefore, if the punching accuracy is divided into the dimensional accuracy of the punch itself and the pitch between the punches, it is clear that the pitch between the punches is doubled and the processing accuracy is reduced by half. Therefore, it is possible to reduce the cost of producing the mold and shorten the number of production days.

According to a second aspect of the present invention, there is provided a semiconductor device comprising: the lead frame according to the first aspect;
A semiconductor chip having a plurality of electrode pads, a thin metal wire connecting the electrode pad and each lead of the lead frame, a sealing portion for sealing the semiconductor and the thin metal wire and some of the leads, It is characterized by having. Therefore, since the pitch of the punches is doubled, in the package manufacturing process, the maintenance of the dam bar punching device called trimming and the punches and receiving dies are facilitated. For example, in the case of a conventional lead frame in which a dam bar is designed continuously, a 28 mm square 2
In the case of 08 pins, the outer lead width is 0.2 mm, the outer lead pitch is 0.5 mm, and the distance between the leads, that is, the length of the dam bar is 0.3 mm.
Since the 0.3mm long dam bar is continuously cut off from the lead as metal scrap, it falls into the through hole of the receiving mold and does not adhere on the way. Must be removed. If the dam bar once punched remains on the receiving mold, it will cause harm, such as attaching to the lead of the next package that is continuously transported, damaging the shape of the lead, and promoting consumption of the punch and the receiving die itself. Will be done. As described above, it is a well-known fact that it is not easy to maintain a dam bar punching device called a trimming device and a punching punch and a receiving mold in a package manufacturing process. Therefore, according to the present invention, the pitch of the punch is doubled, so that the metal waste of the separated dam bar can be easily removed completely. In the semiconductor manufacturing process, a dam bar punching device called a trimming and a punch punch are provided. In addition, the maintenance of the receiving mold becomes easy, the number of man-hours for maintenance is reduced, and the manufacturing unit price can be reduced.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to the following drawings.

FIG. 1 is a plan view of a lead frame used in a semiconductor device according to a first embodiment of the present invention. FIG. 1 shows a part thereof. Actually, the same thing is formed continuously in a certain direction (right direction in the figure), and formed to be long. 1 is a lead frame outer frame,
It refers to a frame-shaped object shown at the top and bottom and left and right end positions shown in the same figure, and supports internal parts described later. In the outer frame, holes for transporting (sprocket holes) at the time of transport are appropriately provided at positions located above and below in the figure. An island 2 is a place where the semiconductor chip is mounted and fixed. This island is located in the inner area as viewed from the outer frame, and generally has a part (generally, but not necessarily, the center) at the center position of the lead frame. I do.
Reference numeral 3 denotes a suspension lead, which extends from the outer frame toward the island and supports the island. In this example, four corners are provided so as to be supported at four corners that are symmetrical positions of the island. However, there is no limitation that the suspension leads 3 must be provided at four corners, and they may be provided as appropriate. In this regard, a known range may be used.
Reference numeral 4 denotes an inner lead, which is provided in a plurality as shown in the figure, and extends from four sides of the outer frame toward the island, respectively. These leads are connected to the respective electrode pads 5a of the semiconductor chip when the semiconductor chip is mounted later, and are electrically connected. Usually, a lead inside the region p to be molded is called an inner lead, and a lead located outside the region p is called an outer lead.

A portion called a dam bar connecting each outer lead is formed not in a straight line but in a staggered shape. The width of the dam bar 8 is usually about 0.2 mm. Therefore, for example, a 28 mm square 20
In an 8-pin plastic package, the outer lead width is 0.2 mm, the outer lead pitch is 0.5 mm, and the lead-to-lead spacing, that is, the length of the dam bar is 0.3 mm. The pitch and the pitch of the outer dam bar are twice the lead pitch
1.0mm, the size of the dam bar to be separated is 0.3mm long
0.2 mm. By arranging the dam bars in a staggered shape instead of linearly, the pitch of the dam bars is twice as large as the dam bar pitch when the dam bars are linearly arranged as shown in FIG. Accordingly, the pitch of the punch for punching the dam bar and the pitch of the pocket of the receiving mold provided for removing the metal dust of the separated dam bar may be provided in a staggered arrangement twice as large as the conventional one. The receiving die has a structure that is much easier to process.

FIG. 2 is a plan view of a lead frame used in a semiconductor device according to a second embodiment of the present invention.

[0013] The dam bar extends in the direction in which the lead extends.
It is formed in three columns in a direction perpendicular to each other, and connects the respective leads. In this case, since the pitch of the dam bars in each row is designed to be three times the lead pitch, it is clear that the machining of the punches and the receiving dies required for the dam bar punching process is further facilitated. is there.

FIG. 3 is a cross-sectional view of a pressing step for punching a dam bar. Considering the length and width of the dam bar 8 to be cut off, the tip cross-sectional dimension of the punch 12 is, for example, 0.2 mm in a 28 mm square 208 pin plastic package.
It is required to be 2 mm wide and 0.3 mm long, to be manufactured accurately according to the pitch of the dam bar, and to be accurately assembled with the pocket part of the receiving die 10. Therefore, with the increase in the number of pins and the reduction in thickness of the plastic package, the pitch between the punch 12 and the pocket portion of the receiving die 10 is becoming smaller and smaller, and higher processing accuracy is being demanded. However, according to the present invention, the pitch can be increased, the punching punch 12 and the receiving die 10 can be easily processed, and the number of manufacturing days can be reduced.

[0015]

According to the present invention, no matter how small the lead width and lead pitch of the lead frame are, the dam bar portion connecting the leads is formed discontinuously, so that the punching process is not required. In addition to providing the required punching punch and the ease of processing of the receiving die, the maintainability associated with the semiconductor device manufacturing process is improved, and the manufacturing cost is greatly reduced.

[Brief description of the drawings]

FIG. 1 is a plan view of a lead frame for a semiconductor device according to a first embodiment of the present invention.

FIG. 2 is a plan view of a lead frame for a semiconductor device according to a second embodiment of the present invention.

FIG. 3 is a cross-sectional view of a step of punching out a dam bar of a semiconductor device in an example of the prior art.

FIG. 4 is a view showing a lead frame for a semiconductor device in an example of the prior art. DESCRIPTION OF SYMBOLS 1 Lead frame 2 Island 3 Hanging lead 4 Inner lead 5 IC chip (semiconductor element) 5a Electrode pad 6 Gold wire (fine metal wire) 7 Outer lead 8 Dam bar 8a Dam bar cut piece 9 Package 10 Trimming receiving mold 11 Trimming upper mold 12 Trimming punch 13 Pressure

Claims (2)

[Claims] In a lead frame having an island for mounting a semiconductor element and a plurality of leads arranged so that the tips gather around the island, a connection for connecting at least one side of the lead to the lead. A lead frame, wherein the parts are not linear but are shifted at least every other one. 2. The lead frame according to claim 1, a semiconductor chip having a plurality of electrode pads, a thin metal wire connecting the electrode pad and each lead of the lead frame, and the semiconductor and the thin metal wire. And a sealing portion for sealing some of the leads.