JPH05267546A - Semiconductor device - Google Patents

Abstract

PURPOSE:To provide a semiconductor device in which a finger and a semiconductor chip are securely joined with each other and an inexpensive lead frame is used. CONSTITUTION:A bumped connection part 4a for connection with an electrode of a semiconductor chip 1 is disposed on a finger 4, and a connection surface side of a connection part 4a is coated with a contact member 12 such as gold, tin and solder. Accordingly, no greater amount of expensive gold is required for an entire bump, and joining is ensured with a metal-aluminum alloy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead frame for fixing semiconductor chips such as IC and LSI.

[0002]

2. Description of the Related Art Conventionally, a metal lead frame has been used for assembling a semiconductor device in which a semiconductor chip is integrated with a resin mold to project a plurality of pins. This lead frame is a thin copper foil metal plate punched with a press,
As shown in FIG. 11, the shape is formed by etching or the like, and the tab leads for supporting the rectangular tabs 2 for mounting the semiconductor chip 1 at the four corners thereof and a plurality of fingers for exposing the inner ends to the peripheral edges of the tabs 2 are formed. 4 and a frame portion 5 that supports the outer ends of the fingers 4 and the tab leads 3.
And sprocket holes 6 provided at regular intervals along both edges of the frame portion 5.

In order to assemble a semiconductor device using such a lead frame 7, the semiconductor chip 1 is first mounted on the tab 2.
After mounting, the electrodes of the semiconductor chip 1 and the inner ends of the fingers 4 corresponding to the electrodes are directly connected without using wires or wires, and then the inner region of the rectangular frame portion 5 is molded with synthetic resin to form the semiconductor chip 1 Then, the frame portion 5 is cut off to obtain a semiconductor device.

[0004]

By the way, the tips of the fingers 4 of the lead frame 7 are connected to the electrodes 1a of the semiconductor chip 1 by soldering or other means as shown in FIG. Is an aluminum pad formed in a thin film on the silicon 1b and is located at a position recessed from the surrounding protective film 1c.

Therefore, a connection portion 4a such as a bump is formed at the tip of the finger 4 to facilitate connection with the electrode 1a. The finger 4 and the connection portion 4a are formed of a copper foil metal plate. In this case, the connection with the electrode 1a tends to be incomplete. Therefore, if the entire connection portion 4a is made of gold, the connection is easy and reliable, but the amount of gold material used increases and the cost is high. Is expected to become.

[0006]

The present invention has been made in view of the above points, and a bump-shaped connecting portion 4a for connecting to an electrode of the semiconductor chip 1 is arranged on the finger 4, and the connecting portion 4a is connected as described above. The surface side is covered with a contact material 12 such as gold, tin, or solder.

[0007]

According to such a semiconductor device, for example, a copper foil finger and an aluminum electrode are bonded to each other by using the same gold-aluminum alloy as in the conventional case, and the connection strength is not deteriorated as compared with the conventional case, and a solid gold bump is formed. Since it is not formed, the manufacturing cost can be reduced.

[0008]

1 to 6 are views showing a lead frame molding process in an embodiment of the present invention. First, as shown in FIG. 1, a resist layer 9 having a desired pattern is formed on a substrate 8 made of a conductive metal such as stainless steel. The resist layer 9 is laminated only on the position where the lead frame 7 is not formed, and the shape of the non-resist portion 8a is a lead frame shape of a desired pattern.

Next, a peeling process is performed on the substrate 8 by using caustic soda when the resist is an alkali developing type and by using a solvent such as methylene chloride when the resist is a solvent type. Thereafter, a metal such as copper, nickel or gold is laminated on this substrate 8 by electroforming. As a result, as shown in FIG. 2, the metal layer 10 is formed only on the non-resist portion 8a excluding the resist layer 9.

A part of the laminated body of the substrate 8 and the metal layer thus formed into a single plate is press-formed as shown in FIG.
As described above, bending processing is performed so as to project to the metal layer side. This molded portion is a tab 2 located at the center of the lead frame 7.
3 shows a pair of fingers 4 that extend toward the tabs 2 and that are the tips of the fingers 4.
The finger 4 includes a flat finger base 4b, a connecting portion 4c extending obliquely from the base 4b, and a tip 4d extending from the connecting portion 4c substantially parallel to the finger base 4b. The tab 2 is not particularly necessary.

Next, electroforming is performed again on the metal layer 10 of the laminated body deformed as described above, and the second metal layer 11 of copper, nickel or the like as shown in FIG. 4 is laminated. In this electroforming process, since the connecting portion 4c is inclined with respect to the flat finger base portion 4b and the tip portion 4d, the growth rate of the electroformed metal layer 11 is slow in the connecting portion 4c.

Further, since the tip portion 4d of the finger 4 is connected to the connecting portion 4c by the thin neck portion, the current density is increased and the metal grows more in this portion. Therefore,
As can be seen from the figure, the wall thickness t2 of the connecting portion 4c is smaller than the wall thickness t1 of the finger base portion 4b and is minimum, and the wall thickness t3 of the tip portion 4d is maximum (t3>t1> t2).

Further, as shown in FIG. 5, a contact member 1 made of a material such as gold, tin or solder is attached to the tip 4d of the finger 4.
2 is applied. This contact material 12 is for improving the connection with the general aluminum electrode 1a of the semiconductor chip 1, and is applied to the upper surface of the tip end portion 4d of the finger 4 with the resist layer 13 covering the other portion. Alternatively, it may be plated.

Finally, if only the substrate 8 is peeled from the laminated body, the lead frame 7 having the fingers 4 as shown in FIG. 6 is obtained.
Is obtained. The tip portion 4d of the obtained finger 4 constitutes a connecting portion 4a having a thickness in the protruding direction, such as a bump, and the thin connecting portion 4c provides appropriate flexibility.

In particular, by reducing the wall thickness t2 of the connecting portion 4c, it is possible to reduce the processing force at the time of joining with the semiconductor chip and prevent the finger base portion 4b from being deformed or laterally displaced. This portion serves as a buffer region. Available.

By using the above-mentioned press working method, this buffer area can be obtained at the same time by the press working when making the tip portion 4d, so that no special working is required and the working can be simplified. 7 to 10 are manufacturing process explanatory diagrams showing a modified example of the present invention.

That is, as shown in FIG. 7, the first electroforming process is performed in the state where the resist layer 9 is formed on the substrate 8 as in the first embodiment. However, a contact material 12 such as gold, tin, or solder is previously formed on the non-resist portion of the substrate 8.
Is applied or plated.

Next, as shown in FIG. 8, the entire laminated body is subjected to press working, and the portions corresponding to the fingers are bent so that the substrate 8 is projected. The bent shape is composed of the finger base portion 4b, the connecting portion 4c, and the tip portion 4d as in the above-described embodiment, and the connection portion 4a such as a bump is similarly formed by pressing on the lower surface of the tip portion 4d. To do.

Next, a second electroforming process is performed on the metal layer 10 to form a second metal layer 11 on the metal layer 10 as shown in FIG. At this time, as described above, the wall thickness is increased in the order of the tip portion 4d, the finger base portion 4b, and the connecting portion 4c.

Finally, when the substrate 8 is peeled off, the lead frame 7 having the fingers 4 having the shape as shown in FIG. 10 is obtained.
Particularly, in this case, the side of the finger 4 to be joined to the semiconductor chip remains the press shape and size of the substrate 8, so that the accuracy of the finger 4 can be improved according to the press accuracy, and the number of pins can be further increased. Can handle.

Although the two-layer metal layers formed by primary and secondary electroforming are integrally used in the above-mentioned embodiment, only the secondary electroformed metal layer is subjected to the peeling treatment between the primary electroforming and the secondary electroforming. It is also possible to obtain a lead frame by using, and at this time, the primary electroformed metal material can be made of an inexpensive material as compared with nickel, which is a secondary electroformed material such as copper.

Further, the substrate 8 only having the resist layer 9 formed thereon is first pressed into a desired shape, and then primary electroforming, or primary electroforming and secondary electroforming are carried out, and the substrate 8 is subjected to this electroforming to form a metal layer. It is also possible to peel off and use the lead frame as it is.

As described above, in the above-described embodiment, since the lead frame including the fingers is basically formed by electroforming, even a lead frame having a large number of fingers which is difficult to punch by press molding is etched. It can be easily formed without using an inexpensive manufacturing method such as, etc., and at the same time, it is possible to easily form the bumps at the tips of the fingers and the flexible connecting portions that support the bumps by secondary electroforming at the same time. Can be done.

When connecting to the semiconductor chip 1 using the lead frame 7 having such fingers, first, the bump-shaped connecting portions 4a at the tips of the fingers of the lead frame 7 are aligned so as to face the electrodes 1a. Then, a gold-aluminum alloy is formed by heating and pressurizing with a bonding tool from the back surface side of the connection portion 4a for connection. During this pressurization,
This pressing force acts so as to push and deform the connecting portion 4a in the pressurizing direction, and this force is transmitted to the finger base portion 1 to exert an influence, but the connecting portion between the connecting portion 4a and the finger base portion 4b is affected. 4c is arranged, and the connecting portion 4c exhibits greater flexibility than the finger base portion 4b. Therefore, the above-mentioned pressing force is relieved by the flexible connecting portion 4c, and the influence on the finger base portion 4b can be reduced. This is relatively the same even when the semiconductor chip 1 side is pressed to the finger 4 side. Since the periphery of the bonded portion of the bump portion is covered with gold or the like, it is possible to prevent oxidation.

Therefore, even if the joint between the connecting portion 4a and the electrode 1a is inclined, the connecting portion 4 following the connecting portion 4a is formed.
c absorbs this inclination, and even the finger base portion (which is generally wider than the connection portion) is inclined, or lateral displacement does not occur and the pitch with adjacent fingers is not disturbed, and the connection work is facilitated. be able to.

[0026]

As described above, according to the present invention, the bump-shaped connecting portion 4a for connecting to the electrode of the semiconductor chip 1 is arranged on the finger 4, and the connecting surface side of the connecting portion 4a is made of gold, tin,
Since it is covered with the contact material 12 such as solder, the connection between the electrode 1a of the semiconductor chip and the connection portion 4a at the tip of the finger is surely performed, and the connection portion 4a can be protected without being excessively oxidized. It is possible to reduce the amount of expensive contact material 12 such as a gold material used, and to reduce the cost.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a lead frame manufacturing process in an embodiment of the present invention, which is a resist layer forming process.

FIG. 2 is a metal layer forming step of the same manufacturing process.

FIG. 3 is a bending process of the manufacturing process.

FIG. 4 is a second metal layer forming step in the same manufacturing process.

FIG. 5 is a contact material forming step in the same manufacturing process.

FIG. 6 is a lead frame obtained by the same manufacturing process.

FIG. 7 is a resist layer forming step in the description of the lead frame manufacturing step in another example.

FIG. 8 is a press working process of the same manufacturing process.

FIG. 9 is a second metal layer forming step in the same manufacturing process.

FIG. 10 is a lead frame obtained by the manufacturing process.

FIG. 11 is a plan view of a general lead frame using the present invention.

FIG. 12 is a cross-sectional view showing the relationship between bumps at the tips of fingers and electrodes of a semiconductor chip.

[Explanation of symbols]

 1 Semiconductor Chip 1a Electrode 4 Finger 4a Connection Part 4b Finger Base 4c Connection Part 4d Finger Tip

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Eiji Sakata, Eiji Sakata 4680 Ikata, Hachijo-machi, Tagawa-gun, Fukuoka Prefecture Kyushu Hitachi Maxell, Ltd.

Claims (1)

[Claims] 1. A semiconductor chip (1) is attached to a finger (4).
A semiconductor device in which a bump-shaped connecting portion (4a) for connecting to the electrode is arranged, and the connecting surface side of the connecting portion (4a) is covered with a contact material (12) such as gold, tin or solder.