JP3147189B2 - Lead frame and manufacturing method thereof - Google Patents

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 a method of manufacturing the same, and more particularly, to a lead frame structure for mounting a semiconductor integrated circuit chip.

[0002]

2. Description of the Related Art In the field of high-output type semiconductor integrated circuits, in order to use high power, a lead for current supply uses a power plate instead of a bonding wire in order to prevent an increase in inductance at a connection portion with a wire. In many cases, a method of connecting to a bonding pad of a chip through a chip is used. In addition, in order to reduce the number of leads in accordance with high integration, when a plurality of pads are dropped on a ground line, a method of providing a ground plate and connecting all of them to the ground line has become effective.

[0003] Further, since the calorific value is large, a large heat radiating plate made of a metal plate having good heat radiating properties tends to be required instead of the die pad.

[0004] In such a power device, as shown in FIG.
The power plate 14 and the power plate 14 are electrically connected to the lead frame main body 15 by welding via tongues provided at predetermined positions, thereby forming a lead frame structure. Here, reference numeral 13 denotes an insulating film interposed for mutual electrical insulation, and 1 denotes a semiconductor chip.

[0005] For this reason, there is a case where each component is distorted due to the influence of the bending accuracy of the tongue piece and the accuracy of the welding position, and the welding portion is peeled off.

The ground plate 12, the power plate 14, and the lead frame body 15 are usually made of copper or a copper alloy, and copper has a low electric resistance. There is a problem that not only the welding itself is difficult, but also the welding strength is weak, so that reliable welding is difficult.

[0007] Furthermore, if welding is to be performed, expensive welding equipment is required, which raises the problem of increasing production costs.

[0008]

As described above, in the conventional power device, the connection between the grounding ground plate, the power plate, and the like and the lead frame main body is established through the tongue pieces provided at predetermined portions. Since welding is performed, welding strength is weak and reliable welding is difficult, and connection failure and deformation are apt to occur, which has caused a decrease in reliability as a device.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a highly reliable lead frame in which a conductive plate such as a ground plate or a power plate is securely connected to a lead frame body. I do.

[0010]

Therefore, in the lead frame of the present invention, at least one conductive plate is laminated and fixed to a lead frame main body in which a plurality of leads are arranged via an insulating layer. Electrical connection is achieved by integrally plating and joining the conductive plate and at least one lead of the lead frame body.

In the method for manufacturing a lead frame according to the present invention, the conductive plate and at least one lead of the lead frame main body are immersed in a plating tank in a state where they are overlapped with each other and are integrally plated to join the two. The connection is made to at least one lead of the frame body.

[0012]

According to the above construction, since the electrical connection is achieved by plating the constituent metal of the conductive plate and the lead frame body integrally, it is possible to easily and very reliably perform the electrical connection. Become.

Further, in a plating step which must be performed, predetermined leads to be electrically connected to the lead frame main body are overlapped with the conductive plate, and the other portions are provided with an insulating member interposed therebetween. By plating, plating and bonding are achieved simultaneously, and the process is simplified and the cost is reduced. At this time, the region that is not joined is covered with the insulating member and is not plated.

Further, if a conductive plate made of a low-resistance copper foil having good workability and flexibility is used and is integrally plated and joined, a fine and high-precision connection becomes possible. Also, there is no peeling or distortion.

[0015]

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

FIG. 1 is a sectional view showing a main part of a power device formed by the method of the first embodiment of the present invention.

In this device, the lead frame has a predetermined lead of a lead frame body 5 mainly composed of copper.
The first made of a copper plate that serves as a ground plate
A conductive plate 2 (conductive plate) and a second conductive plate 4 (conductive plate) laminated as an upper layer and connected to a power supply line and serving as a power plate made of a copper plate and integrally covering a predetermined region. It is characterized by being joined by a plating layer to achieve electrical connection between them.

That is, the device is fixed to a first conductive plate 2 which functions as a ground plate while mounting a semiconductor chip 1 thereon, and an insulating layer 11 made of a polyimide film over the first conductive plate 2. And a second conductive plate 4 as a power plate connected to the first conductive plate 4 and an upper layer, which is similarly fixed via an insulating layer 11, and
And a lead frame main body 5 in which a plurality of inner leads are arranged so as to surround the semiconductor chip mounting portion of the conductive plate 2. The lead frame main body 5 is sealed with a sealing resin D.

A gold plating layer 3 and a gold bump 3P are formed at the tip of the inner lead (lead bonding portion) of the lead frame main body 5, and the first or second gold bump 3P is formed through the gold bump 3P. The electrical connection is achieved by integrally plating the tongue piece T (joining area) provided with the gold plating layer 3 on the corresponding area of the second conductive plate. Furthermore, each inner lead is connected via a bonding wire so as to connect to each bonding pad on the semiconductor chip.

Next, the manufacturing process of the lead frame will be described.

First, as shown in FIG. 2A, a strip material is processed by a usual stamping method or etching method, and inner leads 6, outer leads 7, and tie bars 8 facing the semiconductor chip mounting area a. Mold into a normal lead frame shape including 9 is a sidebar. Next, after performing a coining process to secure the flat width of the tip of the inner lead, apply an insulating tape so as to avoid the bonding area of the tip of the inner lead, fix and fix the tape to a surface side area other than the bonding area. Avoid formation of plating layers. Then, a gold plating layer 3 and a gold bump 3P are formed at the tip of the inner lead corresponding to the joint of the lead frame body 5.

On the other hand, as shown in FIG. 2 (b) and FIG. 2 (c), a copper plate having good heat radiation is processed by a normal stamping method, and a first plate serving as a ground plate is formed. A conductive plate 2 and a second conductive plate 4 as a power plate connected to a power supply line are formed. After punching the first and second conductive plates 2 and 4 so as to have the tongue piece T, the surface excluding the joining region is covered with an insulating polyimide film 11. And the tongue piece T
Then, a gold plating layer 3 is formed.

Then, as shown in FIG. 2D, a first conductive plate 2, a second conductive plate 4, and a lead frame main body 5 are sequentially laminated, and the first and second conductive plates 2, 4 tongue pieces T
Are plated on the respective inner leads 6 of the lead frame main body 5 to form a plating layer integrally and electrically connected.

Thereafter, the semiconductor chip is fixed to the first conductive plate, wire bonding is performed, and resin sealing is performed to complete the device as shown in FIG.

In the device thus formed, the lead and the conductive plate are integrally plated and joined, so that the joining operation is easy, there is no peeling, and low-cost, high-precision connection is ensured. It is possible to do. Further, since this plating is performed in the plating step for the bonding area, no additional step is required.

In the above embodiment, the bonding is performed by gold plating. However, the present invention is not limited to this.
A laminated structure of plating and Pd plating, or another metal plating layer such as an Ag plating layer, a Pd plating layer, and a Sn plating layer may be used.

In the above-described embodiment, the power plate and the ground plate are formed of a single conductive plate, but may be formed by forming a desired pattern on an insulating substrate such as a film carrier. good. At this time, the pattern of the signal line and the ground line is formed by patterning a copper thin film formed by sputtering and electrolytic plating by a photolithography method, after performing a surface treatment on the resin film surface, and directly pressing a thin copper foil. A copper thin film was formed by forming a copper thin film by fixing it via an adhesive or by patterning it, or by applying an insulating resin such as a polyimide resin on the surface of a thin copper foil and curing it. Thereafter, a method of patterning by a photolithography method or the like can be similarly employed.

Embodiment 2 Next, a second embodiment of the present invention will be described in which the ground plate and the power supply plate are made of copper foil.

In this lead frame, the first and second conductive plates are made of copper foil, and these are joined to the leads of the lead frame body by a gold plating layer formed integrally. It is characterized by having.

That is, as shown in FIG. 3, a first conductive plate 22 made of a copper foil having a thickness of about 0.02 to 0.1 μm, on which the semiconductor chip 1 is mounted and which serves as a ground plate, A second conductive plate 24 made of copper foil having a thickness of about 0.02 to 0.1 μm as a power plate laminated on the upper layer via an insulating layer 11 and connected to a power supply line; And a lead frame main body 5 in which a plurality of inner leads are provided so as to surround the semiconductor chip mounting portion of the first conductive plate 2.

The other parts are formed in the same manner as in the first embodiment.

In the device thus formed, in addition to the effect of the first embodiment, the conductive plate is formed by attaching a polyimide film to a flexible copper foil.
The connection with the lead can be satisfactorily achieved without causing distortion or peeling, and the inductance can be reduced because of low resistance.

In the second embodiment, the power plate and the ground plate are formed by attaching a copper foil to a polyimide film and performing punching. However, the copper foil is attached to an insulating substrate such as a film carrier. After that, the copper foil may be selectively removed by etching to form a desired pattern.

[0034]

As described above, according to the present invention, at least one conductive plate is laminated on a lead frame main body having a plurality of inner leads arranged thereon via an insulating layer to establish electrical connection. In doing so, since the conductive plate and the corresponding lead of the lead frame body are joined by plating them integrally,
Bonding is easy, extremely strong and reliable electrical connection is possible, and a low-cost and highly reliable lead frame can be obtained.

[Brief description of the drawings]

FIG. 1 is a view showing a semiconductor device using a lead frame formed by a method according to a first embodiment of the present invention;

FIG. 2 is a manufacturing process diagram of the semiconductor device.

FIG. 3 is a diagram showing a semiconductor device using a lead frame formed by a method according to a second embodiment of the present invention;

FIG. 4 is a diagram showing a conventional semiconductor device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 semiconductor chip 2 first conductive plate 3 gold plating layer 4 second conductive plate 5 lead frame main body P sealing resin a semiconductor chip mounting area 6 inner lead 7 outer lead 8 tie bar 9 side bar T tongue 11 Polyimide film.

Claims (2)

(57) [Claims] 1. A semiconductor device comprising: a conductive plate; and a lead frame main body laminated on the conductive plate via an insulating layer and having a plurality of leads disposed on a surface of the semiconductor chip such that a front end comes to a periphery of a semiconductor chip. A lead frame, comprising: a conductive plate having a bonding region on which a metal plating layer is formed; and a lead frame body having a metal plating layer and a metal bump formed at a lead bonding portion corresponding to the bonding region of the conductive plate. A lead frame, wherein a bonding region of the conductive plate and the lead bonding portion are bonded by a metal plating layer integrally formed so as to cover them. 2. A conductive plate forming step of forming a conductive plate having a bonding region on which a metal plating layer is formed, and a step of laminating the conductive plate on the conductive plate via an insulating layer, the tip of which is provided at the periphery of the semiconductor chip. A lead frame main body forming step of forming a lead frame main body in which a metal plating layer and a metal bump are formed at a lead bonding portion corresponding to the bonding region, while arranging a plurality of leads on the surface so that The lead and the conductive plate to be electrically connected to the lead frame main body are overlapped with each other so that the bonding region of the conductive plate is connected to the corresponding lead bonding portion of the lead frame main body, and the other portion is Is a plating bonding step of integrally plating and connecting the conductive plate and the lead frame body with an insulating member interposed therebetween. The method of the lead frame, which comprises a.