JP2001024131A - Lead frame, manufacture thereof and semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent plating silver from leaking along the side surfaces of inner leads when silver plating is applied in the manufacturing process of a lead frame from leaking out of a mold area by a method wherein plating silver leaking preventive dam bars are formed between the inner leads and the mold area. SOLUTION: In a lead frame whose inner lead tips are plated 7 with silver, in addition to dam bars 5 which prevent sealing resin from leaking out at the time of resin sealing, additional dam bars 9 made of metallic material are formed in the manufacturing process of the lead frame and cut off after silver plating. Further, dam bars made of UV-curing resin are formed on the middle parts of the inner leads 4. With this constitution, a desilvering process after resin sealing can be eliminated and, further, solder plating swellings of outer leads and short-circuiting between outer leads which are caused by the leaking silver can be avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor lead frame and a method of manufacturing the same, and more particularly, to improving the reliability of a semiconductor device by preventing silver leakage when silver plating is applied to an inner lead of a lead frame. It is about.

[0002]

2. Description of the Related Art FIG. 4 is a plan view showing an example of a conventional lead frame on which an integrated circuit chip is mounted. The frame 1 has a die pad 2 for mounting and fixing an integrated circuit chip substantially at the center. Further, the die pad 2 is supported on the frame 1 by a tie bar 3. A large number of thin inner leads 4 extend from the inner wall of the frame 1 toward the die pad 2, and each inner lead 4 prevents the resin from flowing out when the resin is sealed in the molding area 6 in the molding process. Supported by a dam bar 5 for The dam bar 5 serves as a reinforcing member when wiring the integrated circuit chip mounted and fixed to the die pad 2 and the tip of the inner lead 4 on the die pad side with a wire, and cuts the dam bar 5 between the leads after resin sealing. Silver plating 7 is applied to the tip of the inner lead 4 extending from the inner wall of the frame 1 toward the die pad 2 on the die pad 2 side. The reason for applying the silver plating 7 is to promote the alloy of the inner lead and the wire when the integrated circuit chip mounted on and fixed to the die pad 2 and the tip of the inner lead 4 are wired with a wire, thereby increasing the strength of the thermocompression bonding of the wire bonding. That's why.

There are two main types of silver plating depending on the difference in the portion to be plated.

1) Partial silver plating for plating the entire die pad 2 and the tip of the lead 4.

[0005] 2) Ring silver plating in which plating is applied only to the tip of the lead 4.

In the manufacturing process of the lead frame as described above, first, a metal plate as a material is formed into a shape such as a die pad 2, a tie bar 3, an inner lead 4, a dam bar 5, and an outer lead 8 by etching or stamping. . After the formation of the shape, a silver plating 7 is applied to the tip of the inner lead 4. In the case of the above-mentioned partial plating, plating is applied to the die pad 2 in addition to the inner lead 4. Then, if necessary, apply polyimide tape to inner leads 4
The die pad 2 is depressed at an appropriate position of the tie bar 5 below the surface of the inner lead 4 to obtain a finished lead frame.

[0007]

As described above, the lead frame for a semiconductor is provided with silver plating 7 on the tip of the inner lead 4 shown in FIG. 4 on the die pad side, so that the integrated circuit chip and the inner lead 4 are connected at the time of assembling the semiconductor device. In order to increase the thermocompression bonding force of the wire to be tied, the silver plating 7 is absolutely necessary. However, when silver plating 7 is applied, it is difficult to completely mask portions that do not require silver plating, regardless of the type of silver plating described above, and leakage to the side surfaces of the inner leads cannot be particularly suppressed. The leaked silver plating passes through the mold area 6 in FIG.
The silver plating leaked from the mold area 6 to between the dam bars 5 is subjected to desilvering using a desilvering agent after sealing the inside of the mold area 6 with resin, but it is difficult to completely remove the leaked silver. . In a semiconductor device in which silver leakage is included even if it is extremely small, the semiconductor device does not operate stably for a long period of time due to solder plating blisters in a later step of solder plating and leakage between outer leads 8 due to residual silver leakage. Was.

Therefore, when silver plating is applied to the tip of the inner lead on the die pad side, even if silver plating leaks, it is possible to prevent silver from leaking out of the mold area 6 and to assure a stable operation of the semiconductor. It was highly desirable to provide a frame.

[0009]

A substantially rectangular die pad on which an integrated circuit chip is mounted and an inner lead arranged on the periphery of the die pad and having one end directed toward the die pad are formed. In the lead frame, the resin is prevented from flowing out at the time of resin sealing, and in addition to the dam bar serving as a reinforcing member of the lead frame, one metal dam bar is further etched or stamped in the lead frame manufacturing process. This is achieved by cutting after providing silver plating.

[0010] It is also achieved by providing a UV-curable resin dam bar at an intermediate portion of the inner lead.

[0011]

[Function] By providing a metal metallic or UV-curable resin dam bar between the inner lead tip and the mold area, the side of the lead can be used when applying silver plating to the tip of the inner lead in the lead frame manufacturing process. It can be prevented from leaking out of the transmission mold area.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is an overall view of a lead frame showing a first embodiment of the present invention. The frame 1 has a die pad 2 for mounting and fixing an integrated circuit chip substantially at the center.
Further, the die pad 2 is supported on the frame 1 by a tie bar 3. A large number of thin inner leads 4 extend from the inner wall of the frame 1 toward the die pad 2, and a silver plating 7 is applied to the tip of the die pad side. When the silver plating 7 is applied, it is difficult to completely mask a portion that does not require the silver plating 7, and in particular, the leakage of the silver plating to the side surface of the inner lead 4 cannot be suppressed. The silver plating that has leaked out along the side surface of the inner lead 4 is formed from the tip of the inner lead 4 to the mold area 6.
It is stopped by a damping bar 9 for preventing silver plating made of a metallic material provided by etching or stamping in the lead frame manufacturing process. Silver plating is performed on the space between the inner leads 4 of the damping bar 9 for preventing leakage of silver plating, and then punched out by a mold. FIG. 2 is a partial plan view of the lead frame after punching out the silver-plated leakage-preventing dam bar 9 with a mold. Although it remains as the protruding portion 10 of the lead 4, the shape becomes the same as that of the conventional lead frame shown in FIG. 4, and the electrical function is not affected. After punching out the silver plating leakage preventing dam bar 9 with a mold, the inside of the mold area 6 is sealed with a resin in a molding process. By doing so, there is no silver plating leaking to the dam bar 5, and not only the desilvering step after resin sealing is not required, but also
Solder plating swelling due to the residual silver plating leakage of the outer leads 8 and leakage between the outer leads due to the residual silver plating leakage are suppressed, and the semiconductor device can operate stably for a long period of time. Furthermore, the projections 10 of the silver plating leakage dam bar punched out by the mold become a part of the inner leads 4 and also prevent the outer leads 8 from coming off when the semiconductor device is mounted on the substrate. After resin sealing, the dam bar 5 between the outer leads 8 is cut.

FIG. 3 is a partial plan view of a lead frame showing a second embodiment of the present invention.

In the example shown in FIG. 3, a UV-curable resin dam bar 11 is used in place of the above-described dam bar 9 for preventing leakage of silver plating shown in FIG. In the UV-curable resin dam bar 11, shapes such as a die pad 2, a tie bar 3, an inner lead 4, a dam bar 5, and an outer lead 8 were produced by etching or stamping a metal plate as a material in a lead frame manufacturing process. Thereafter, a resin having an appropriate width is applied from the tip of the inner lead 4 to the molding area 6.
It is applied so as to enter the space between the inner leads 4 and cured by ultraviolet rays to form the shape. Thereafter, silver plating 7 is applied to the tip of the inner lead 4. In the case of the above-mentioned partial plating, plating is applied to the die pad 2 in addition to the inner lead 4. When applying silver plating 7,
The silver plating that has leaked along the side surface of the inner lead 4 is stopped by a UV-curable resin dam bar 11 provided between the mold area 6 and the tip of the inner lead 4. Thereafter, the inside of the mold area 6 is sealed with resin. By doing so, there is no silver plating leaking to the dam bar 5, so that the desilvering step after resin sealing is not necessary, but also the solder plating blister due to the silver plating leakage of the outer lead 8 and the outer plating due to the silver plating leakage remain. Leakage between leads is suppressed, and stable operation of the semiconductor device for a long period of time becomes possible. After resin sealing, the dam bar 5 between the outer leads 8 is cut.

Although the embodiment according to the present invention has been described above, in this embodiment, the shape of the metallic or UV-curable resin dam bar provided by etching or stamping is linear. Although described, any shape may be used as long as the silver plating does not leak out of the mold area.

[0017]

As described above, the present invention provides a lead frame manufacturing process by providing a dam bar made of a material metal or a UV curable resin between a tip end of an inner lead of a lead frame and a molding area. When silver plating is applied to the tip of the inner lead, the silver plating can be prevented from leaking out of the mold area along the lead side, so that the desilvering step after resin sealing can be omitted, and the outer lead There is an excellent effect that a solder plating blister due to leaking silver and a leak between outer leads can be completely prevented, and a semiconductor device capable of operating stably for a long period of time can be supplied.

[Brief description of the drawings]

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

FIG. 2 is a partial plan view showing the first embodiment of the present invention.

FIG. 3 is a partial plan view showing a second embodiment of the present invention.

FIG. 4 is a plan view showing a conventional method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Frame frame 2 ... Die pad 3 ... Tie bar 4 ... Inner lead 5 ... Dam bar 6 ... Mold area 7 ... Silver plating 8 ... Outer lead 9 ... Silver plating leak prevention dam bar 10 ... Silver plating leakage prevention material metal dam bar Projection after cutting 11 UV curable resin dam bar for preventing silver plating leakage

[Procedure amendment]

[Submission date] August 30, 2000 (2008.3.
0)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Name of invention

[Correction method] Change

[Correction contents]

Patent application title: LEAD FRAME, METHOD OF MANUFACTURING LEAD FRAME, AND SEMICONDUCTOR DEVICE

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

Claims (6)

[Claims] 1. A lead frame comprising: a substantially square die pad on which an integrated circuit chip is mounted; and inner leads arranged on the periphery of the die pad, one end of which is directed to the die pad, and the tip of the inner lead is silver-plated. In addition to the dam bar serving as a reinforcing member for the lead frame, which prevents leakage of the resin during resin sealing, another metal dam bar is provided by etching or stamping in the lead frame manufacturing process. A lead frame characterized by being cut after plating. 2. A lead frame, comprising: a substantially square die pad on which an integrated circuit chip is mounted; and inner leads arranged on the periphery of the die pad, one end of which is directed toward the die pad, and the tip of the inner lead is silver-plated. A lead frame, wherein a dam bar made of UV-curable resin is provided at an intermediate portion of the inner lead. 3. A method for manufacturing a lead frame, wherein a dam bar made of a material metal provided on an intermediate portion of the inner lead according to claim 1 by etching or stamping is silver-plated and then cut. 4. A method of manufacturing a lead frame, wherein a UV-curable resin dam bar is provided at an intermediate portion of the inner lead before silver plating is performed. 5. A semiconductor using a lead frame according to claim 1, wherein a dam bar made of a metallic material is provided at an intermediate portion of said inner lead by etching or stamping, and is subjected to silver plating and then cut. apparatus. 6. A dam bar made of a UV-curable resin is provided at an intermediate portion of the inner lead.
A semiconductor device using the lead frame described in the above.