JPH0656872B2 - Lead frame for semiconductor device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a lead frame used for fixing a semiconductor chip such as an IC or LSI, and more particularly to a semiconductor in which a shape of a finger connected to an electrode of the semiconductor chip is improved. The present invention relates to a lead frame of a device.

[Background technology]

2. Description of the Related Art Conventionally, a metallic lead frame has been used for assembling a semiconductor device in which a semiconductor chip is integrated with a resin mold and a plurality of pins are projected. This lead frame is formed by punching a thin metal plate with a press or by etching, and its shape supports rectangular tabs 2 for mounting the semiconductor chip 1 at its four corners, as shown in FIG. The tab leads 3, a plurality of fingers 4 having inner ends facing the periphery of the tabs 2, a frame 5 supporting the fingers 4 and outer ends of the tab leads 3, and provided at regular intervals along both side edges of the frame 5. And the sprocket holes 6 formed therein.

In order to assemble a semiconductor device using such a lead frame 7, first, the semiconductor chip 1 is mounted on the tab 2, and then each electrode of the semiconductor chip 1 and the inner end of the finger 4 corresponding thereto is attached with a wire or a wire. Direct connection is made without using it, then the inner region of the rectangular frame portion 5 is molded with a synthetic resin to cover the semiconductor chip 1, and then the frame portion 5 is cut off to obtain a flat lead or in-line type semiconductor device.

By the way, although the lead frame 7 is provided with thin tab leads 3 and fingers 4, a semiconductor device having a small number and a large number of pins is desired in recent years, and the number of fingers 4 tends to increase.
Therefore, the width of one finger 4 is inevitably smaller and is, for example, about 0.3 mm.

When such a finger 4 is used for assembling a semiconductor device, it is possible to absorb a dimensional error due to its flexibility and connect it to the electrode of the semiconductor chip, but it is easy to contact the adjacent finger 4, Connection work becomes very difficult, and there is a risk of disconnection.

[Object of the Invention]

The present invention has been made in view of the above points, and provides a lead frame for a semiconductor device, which allows the finger to have appropriate flexibility and rigidity, facilitates the assembly work of the semiconductor device, and provides stable finger connection. Is what you are trying to do.

[Outline of Invention]

As a configuration for achieving the above object, the present invention provides a lead frame of a semiconductor device having a finger whose one end side is directly connected to an electrode of a semiconductor chip, in which an intermediate portion other than both ends of the finger is preset, for example. It is characterized in that a groove extending in the longitudinal direction of the finger is formed on the formed surface.

〔Example〕

FIG. 1 is a perspective view showing a cross section of a part of a finger,
FIG. 2 is a vertical cross-sectional view of the tip of the finger. In the figure, the finger 4 is made of a conductive metal foil, has a groove 4a on the lower surface of the central portion along the lower side in the longitudinal direction, and has flange portions 4b, 4c on both sides. As shown by the chain double-dashed line in FIG. 3, the groove 4a is formed in an intermediate portion of the finger 4 excluding the base portion 4d and the tip portion 4e. The second moment of area for bending is increased.

Further, a bump 4f connected to the electrode of the semiconductor chip 1 is formed on the tip 4e of the finger 4. A concave portion 4g in a direction substantially orthogonal to the groove 4a is formed on a lower surface of a portion connecting the tip portion 4e and the intermediate portion, and a bump 4f protruding from the concave portion 4g from the upper surface of the finger 4 is formed.

It should be noted that, except for this finger, the lead frame has the same structure as that of the conventional example, and therefore description of each part of the lead frame which can be regarded as equivalent is omitted.

FIG. 4 is a perspective view showing another example of the finger 4.
A metal thin film 4h is further laminated on the upper surface of the finger 4 of the embodiment. By doing so, the rigidity of the finger 4 can be further increased.

FIG. 5 shows a step of molding the lead frame having the finger structure.

First, as shown in FIGS. (A) and (b), a film 8 made of synthetic resin such as polyimide or polyester and having a thickness of about 35 μ to 70 μ is used.
Pressed by push-back method to make device holes 9
To provide. In the push back method, as shown in (a), a desired portion is first punched out by a pressing die, then the receiving die is raised again, and (b) as shown in the figure, the cutout piece 10 is fitted and held in the device hole 9 once drilled. Is the way. Therefore, after processing, the film 8 is maintained in the state of the device hole 9 in which the device holes 9 are not opened, and can be handled as a single sheet.
When the device hole 9 is formed, other window portions such as the sprocket hole 6 can be formed at the same time.

Next, a conductive metal layer 11 made of copper or the like is formed on the film 8 which is not opened by a means such as electroless plating or vapor deposition as shown in FIG. Further, a photoresist layer 12 is applied on the conductive metal layer 11 as shown in FIG.
A dry film-like resist layer of about 150 μ is attached,
By exposing to a desired pattern by applying a photomask 13 and then washing, only the exposed portion is removed to form a resist layer 12 as shown in FIG.
The conductive metal layer and photoresist layer after push-back have a function as a temporary fixing means for preventing unnecessary detachment of the cut-out piece 10, so that it can be removed like a thin-film push-backed article such as a film. Although it is easy to do, it is especially effective for temporary fixing.

Next, a peeling treatment is performed on the film 8 with selenious acid, caustic soda, or the like, and a metal such as nickel is electroformed. As a result, as shown in (f), the conductive metal layer 11 on which the resist layer 12 is not formed is formed. A lead frame 7 having a desired pattern is formed on the above.

When electroforming the lead frame with metal such as nickel, 0.
07% or less brightener (0.01-0.04% carbon, sulfur
0.01 to 0.04% and the sum of these is 0.07% or less) is used. The content of the brightening agent is usually about 0.1%, but if the content is high like this, the temperature of the lead frame at the time of joining with the IC chip causes the nickel to become brittle.
Therefore, the content of the brightener must be limited to 0.07% or less. Further, if no brightening agent is contained, sufficient mechanical strength cannot be obtained, and there is a risk of short-circuiting with the adjacent lead due to deformation during processing.

After electroforming, the resist layer 12 is removed, and then the cut-out piece 10 that closes the window portion including the device hole 9 is pulled out, so that the lead frame 7 having the cross section as shown in FIG. Is formed in. In this case, since the conductive metal layer 11 has a thickness, for example, about 5 to 10 μ, which is provided to secure conductivity for electroforming, the pull-out force is small and the lead frame 13 cannot be deformed. Absent.

Although the lead frame 7 is formed on the synthetic resin film 8 in the above embodiment, a conductive metallic stainless film or the like may be used instead of the synthetic resin film 8.

In this case, the conductive metal layer 11 made of copper or the like as shown in FIG. 5 (c) is not newly provided, and the photoresist layer 12 is formed on the stainless film 8 and directly electroformed. It is possible to form the lead frame 7 made of nickel, copper, gold or alloys thereof on the stainless film.

FIG. 6 is a diagram showing a resist pattern of a finger portion in the above manufacturing process.

In the finger part, the resist layer for the finger of the desired pattern
In addition to 12, the non-resist portion 14 at the position corresponding to the finger 4
A resist portion 12a is formed along the longitudinal direction in the center, and the above-mentioned groove 4a is formed corresponding to the resist portion 12a.
Is formed.

Further, a circular non-resist portion 15 separated by the resist layer 11 is formed at the tip of the non-resist portion 14, and when electroforming is performed on a metal having such a resist layer 11, electroforming is performed. In the initial stage after the start, the finger 4 main body is formed separately from the metal layer growing on the circular non-resist portion 15 separated by the resist layer 11, but is separated as the electroforming further progresses. The metal on the non-resist portion 15 and the main body of the finger that have been used are connected to each other across the resist layer 11. Since the thickness of the metal laminated by electroforming depends on the current density, the metal layer on the dot-shaped non-resist portion 15 becomes thicker than that of the flat-shaped finger 4 main body portion. A bump 4f as shown in FIG. 2 is formed.

When forming the metal thin film 4h as shown in FIG. 4, a second electroforming process may be performed in addition to the electroforming process described above.

Also, when electroforming a lead frame with a metal such as nickel, it is possible to make a lead frame in which two layers, a layer not containing a brightening agent and a layer containing a brightening agent, are superposed. If electroforming is performed without adding a brightener, the surface will be roughened and the irregularities will become remarkable, so temperature concentration during joining with the IC chip, especially when joining in a pressure-welded state, tends to occur, ensuring reliable joining. It can be anything. On the other hand, if a layer containing a brightener is provided on the side opposite to the joint surface, the mechanical strength of the lead frame can be secured. The content of the brightening agent is the same as described in the above example.
It is desirable to limit it to 0.07% or less.

〔The invention's effect〕

The present invention is as described above, and since the groove is provided along the longitudinal direction at the intermediate portion in the longitudinal direction excluding both ends of the finger, the finger can have appropriate flexibility and rigidity. Assembly work of the device becomes easy. Further, it becomes possible to manufacture a semiconductor device having stable performance by eliminating connection failure due to disconnection of fingers.

[Brief description of drawings]

FIG. 1 is a perspective view showing a cross section of a part of a finger of an embodiment of the present invention, FIG. 2 is a cross sectional view in the longitudinal direction of the finger, FIG. 3 is a plan view showing a part of the finger, and FIG. FIG. 5 is a perspective view showing another embodiment of the finger in FIG. 5, FIG. 5 is a view showing a manufacturing process of a lead frame in the embodiment of the present invention, FIG. 6 is an enlarged view of a resist pattern of a finger portion, and FIG. It is a top view which shows a general lead frame shape. 2 ... tab, 3 ... tab lead, 4 ... finger, 4a ...
… Slits, 7 …… Lead frame, F …… Longitudinal direction of finger.

Continued Front Page (72) Eiji Sakata Eiji Sakata 4680 Ikata, Katshiro-cho, Tagawa-gun, Fukuoka Prefecture Kyushu Hitachi Maxell Co., Ltd. (56) Reference JP 57-2535 (JP, A) JP 61- 101059 (JP, A) Actually opened 55-99150 (JP, U)

Claims (1)

[Claims] 1. In a lead frame of a semiconductor device having a finger whose tip portion is directly connected to an electrode of a semiconductor chip, at a middle portion of the finger excluding the tip portion and the base end portion in the longitudinal direction of the finger. A lead frame for a semiconductor device, characterized in that a groove is formed along the lead frame.