JPH0766352A - Lead frame - Google Patents

Abstract

(57) [Abstract] [Purpose] With multiple pins, the outer lead is molded without deformation such as twisting or deviation, and the tip can be made highly precise with the same flatness, resulting in excellent mountability and heat dissipation. Get the leadframe. [Constitution] The inner lead has a finer lead pitch and width made of another material thinner than the outer lead, and the inner lead is joined to the outer lead formed separately of another material having a large plate thickness. It is a lead frame.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-pin lead frame having excellent mountability.

[0002]

2. Description of the Related Art In a semiconductor device, a semiconductor chip (hereinafter referred to as a chip) is mounted on a pad of a lead frame, and a chip terminal and an inner lead are welded and connected by a thin wire.
After that, the inside of the tie bar of the lead frame is packaged with resin, ceramic, or the like, the tie bar protruding from the package is cut off, and the outer lead is molded into a predetermined shape.

The technical progress of electronic equipment in which a semiconductor device is incorporated is remarkable, and the semiconductor device is required to have a high density, a small size, and a thin shape, and to be excellent in mountability.

Due to such circumstances, the lead frame for semiconductor devices has a large number of pins, the lead pitch and width are narrow, and the inner leads are particularly finer.

To manufacture a multi-pin lead frame, for example, as described in Japanese Patent Laid-Open No. 3-283643, a material metal plate is partially thinned by etching or the like, and an inner lead is formed in the thinned region. There is a lead frame manufacturing method for forming the. In this case, since the inner leads having a fine lead pitch and width are formed in the thin region, fine processing can be performed and a multi-pin lead frame is manufactured.

The semiconductor device is required to have excellent mountability because it is provided at a predetermined position on the circuit board. Therefore, the outer leads protruding from the package sealed with resin or ceramic are formed into a predetermined shape such as a gull wing shape or a J shape. Mold and process.

[0007]

In forming the outer lead, if the thickness of the outer lead is thin and the lead is narrow, it is possible to prevent twisting and deviation and to position the processing tip on the same plane. It is difficult to obtain a predetermined shape and requires a high level of skill and skill. Further, during handling such as transportation and inspection after the forming process, the bent portion may be deformed and the outer lead tip may shift to one side or may be displaced in the vertical direction, which may hinder the mounting on the circuit board.

The outer lead is one of the passages for dissipating the heat generated when the semiconductor device is used to the outside.
Since heat dissipation is an important issue in semiconductor devices that are required to have high density and high speed as in recent years, it is necessary to enhance heat dissipation through the outer leads. Furthermore, the outer lead must have strength to maintain its shape during and after mounting.

On the other hand, since the inner lead has a function of connecting to a high-density chip as described above, it must be finely formed, and it must also have wire-bonding property with a chip terminal.

Although the outer lead and the inner lead are continuous bodies, they have different functions that must be handled as described above, and there are differences in the strictness of shape formation and the molding process. For this reason, it is difficult to obtain a lead frame having a large number of pins, good outer-lead molding workability, and excellent mountability and heat dissipation, and there is room for improvement.

An object of the present invention is to provide a lead frame having a large number of pins, the outer lead having no deformation such as twisting or deviation, and a molding process capable of accurately forming the same flatness of the tip portion, and having excellent mountability and heat dissipation. And

[0012]

SUMMARY OF THE INVENTION The gist of the present invention is that the inner lead is formed from another material thinner than the outer lead to have a fine pitch and width of the lead, and is formed separately from another material having a large plate thickness. It is on a lead frame in which the front end of the outer lead and the end of the inner lead are joined.

[0013]

In the present invention, since the inner leads are made of a material thinner than the outer leads, the pitch and the width are finely formed, and the multi-pins, for example, those having 160 pins or more can be obtained in good shape. In addition, the outer lead is made of another material with a plate thickness thicker than that of the inner lead, so it has good moldability and can be accurately machined into a prescribed shape, and its mechanical strength is ensured so that it does not deform during handling. Excellent mountability.

Since the inner lead and the outer lead are made of different materials, the inner lead is made of a thin metal plate that can be processed in a fine shape, for example, Ni or Ni alloy having a small coefficient of thermal expansion, and the outer lead is made of a thick plate. It is possible to increase the heat dissipation while having a large number of pins by forming a large width from thicker copper or copper alloy having a high thermal conductivity.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings based on an embodiment. In the drawings, 1 is an inner lead, which is made of a thin metal plate, for example, Ni or iron-Ni alloy having a thickness of less than 0.15 mm. The inner lead 1 is formed by pressing or etching,
For example, in order to manufacture a multi-pin lead frame having 200 pins or more, it is preferable to form it by etching. The end portion 1a joined to the outer lead of the inner lead 1 is shown in FIG.
As shown in FIG. 3, when the inner lead 1 is formed, it is connected by the connecting piece 2.

Reference numeral 3 is an outer lead, which is stamped and formed from a separate metal plate thicker than the inner lead 1 such as copper or copper alloy having a thickness of 0.25 mm. The outer lead 3 can be made wider than the inner lead 1 in width and pitch of the lead, and the formation thereof is relatively easy. Since the outer lead 3 is made of a thick metal plate,
The mechanical strength is not so weak that the subsequent molding process can be performed with good shape.

Reference numeral 4 is a side rail, and 5 is a guide wheel. The end portion 1a of the inner lead 1 and the tip portion of the outer lead 3 are joined and integrated with each other via a joining agent 6 such as a conductive paste. There is. In this embodiment, the inner lead 1 is joined to the lower end of the outer lead 3 but may be joined to the upper end.

Reference numeral 7 denotes a pad for mounting a chip, which is formed of the same metal plate as the inner lead 1 in this embodiment. Reference numeral 8 is a support bar that supports the pad 7.
The pad 7 can be made of a material different from that of the inner lead 1, and its formation is arbitrary.

As described above, in the lead frame of the present invention, the inner leads 1 and the outer leads 3 are made of a thin metal plate which is fine in both lead pitch and width, while the outer leads 3 are formed. Is formed of a metal plate having a large plate thickness, good moldability, high thermal conductivity and different from the inner lead 1.

[0020]

In the lead frame of the present invention, the inner lead and the outer lead are separately formed from different metal plates having different thickness and properties and are joined together. With multiple pins, the outer lead has excellent moldability for mounting and good heat dissipation.

[Brief description of drawings]

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

FIG. 2 is a view showing a cross section of a lead frame according to one embodiment of the present invention.

FIG. 3 is a diagram showing an inner lead in one embodiment of the present invention.

FIG. 4 is a diagram showing an outer lead according to one embodiment of the present invention.

[Explanation of symbols]

 1 Inner lead 2 Connection piece 3 Outer lead 4 Side rail 5 Guide hole 6 Bonding agent 7 Pad 8 Support bar

Claims (1)

[Claims] 1. In a lead frame in which a plurality of inner leads are arranged around a pad and the inner leads are continuous with the outer leads, the inner leads are thinner than the outer leads and the lead pitch and width are different. The lead frame is characterized in that the inner lead is joined to the outer lead which is finely formed and which is separately formed from another material having a large plate thickness.