JP2509882B2 - Method for manufacturing semiconductor device - 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 for fixing semiconductor chips such as IC and LSI.

[0002]

2. Description of the Related Art Heretofore, a metal 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 a thin copper foil metal plate punched with a press,
As shown in FIG. 11, the tab leads are formed by etching or the like and support rectangular tabs 2 to which the semiconductor chip 1 is attached at their four corners, and a plurality of fingers whose inner ends are exposed to the peripheral edges of the tabs 2. 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 tip of the finger 4 of the lead frame 7 is connected to the electrode 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 connecting 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 connecting 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.

For this reason, it has been proposed to use gold efficiently by plating the connecting portion with gold. For example, the one disclosed in Japanese Patent Laid-Open No. 47275/1972 discloses a lead frame material which is partially pre-formed. The lead frame is obtained by applying gold-plated craft and pressing this.
The gold clad at the tip end for bonding in consideration of pressing accuracy is made wider than the desired lead width, resulting in waste of gold.

The one disclosed in Japanese Patent Laid-Open No. 55-6862 has an inner lead formed by etching, and the surface of the inner lead is plated with gold. Since the entire inner lead is plated, efficient use of gold is possible. After all, there is waste.

[0008]

The present invention has been made in view of the above points, and a bump-shaped connecting portion (4a) connected to an electrode of a semiconductor chip (1) is arranged on a finger (4), In a method of manufacturing a semiconductor device in which the connection surface side of the connection portion (4a) is covered with a contact material (12) such as gold, tin, or solder, a resist layer (so as to expose a portion corresponding to the finger (4)). The contact material (12) is preliminarily applied to a portion of the electroforming substrate (8) provided with 9) corresponding to the connecting portion (4a), and the finger (4) is electroformed on the upper surface thereof. The substrate (8) is peeled off.

[0009]

According to such a method of manufacturing a semiconductor device, for example, a copper foil finger and an aluminum electrode are joined 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. Since it does not form gold bumps,
The manufacturing cost can be reduced.

Moreover, since the contact material of the connecting portion is directly formed on the substrate having high surface accuracy, the surface of the contact material separated from the substrate, that is, the surface connected to the electrode of the semiconductor chip has high accuracy, and the connection is made. Highly reliable product can be obtained.

[0011]

1 to 4 are views showing a molding process of a lead frame 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 is the lead frame shape of the 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. After that, a contact material 12 such as gold, tin, or solder is applied to the non-resist portion of the substrate 8 by coating or electroforming. Then, a metal such as copper or nickel is laminated on the upper surface by electroforming to form the metal layer 10.

Next, as shown in FIG. 2, 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 a finger base portion 4b, a connecting portion 4c, and a tip portion 4d. Similarly, a connection portion 4a such as a bump is formed by pressing on the lower surface of the tip portion 4d.

Next, a second electroforming process is performed on the metal layer 10 to form a second metal layer 11 of copper, nickel or the like on the metal layer 10 as shown in FIG. In this electroforming process, the flat finger base 4b and the flat tip 4d are connected to the connecting portion 4c.
Since the metal layer 11 is inclined, 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 of the connecting portion 4c is smaller than the wall thickness of the finger base portion 4b and is minimum, and the wall thickness of the tip portion 4d is maximum.

Finally, the substrate 8 is peeled off to obtain the lead frame 7 having the fingers 4 having the shape as shown in FIG. Particularly, in this case, the side of the finger 4 to be joined with 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.

The substrate 8 on which the resist layer 9 has just been formed is first pressed into a desired shape, then the contact material 12 is applied, and then primary electroforming or primary electroforming and secondary electroforming is performed to obtain the substrate 8. It is also possible to peel off the metal layer formed by electroforming to obtain a 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. Can be easily formed without using an unstable manufacturing method such as the above, and at the same time, the bumps at the finger tips and the flexible connecting portions supporting the bumps can be simultaneously and easily formed by secondary electroforming. Is something that 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 connecting portion 4a to connect. 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 exerts greater flexibility than the finger base portion 4b. Therefore, the 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 joined portion of the bump portion is covered with gold or the like, oxidation can be prevented.

Therefore, even if the joint between the connecting portion 4a and the electrode 1a is tilted, 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 not inclined or lateral shift occurs and the pitch with adjacent fingers is not disturbed, and the connection work is facilitated. be able to.

[0021]

As described above, according to the present invention, bump-shaped connecting portions (4a) connected to the electrodes of the semiconductor chip (1) are arranged on the fingers (4), and the above-mentioned connecting portions (4a) are connected. In a method of manufacturing a semiconductor device in which a contact surface side is covered with a contact material (12) such as gold, tin, solder, etc., electroforming in which a resist layer (9) is provided so that a portion corresponding to a finger (4) is exposed. The contact material (12) is previously applied to a portion of the substrate (8) corresponding to the connection portion (4a), and the finger (4) is electroformed on the upper surface thereof, and then the substrate (8) is attached. Since it is peeled off, 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 4 is also formed.
a can be protected without being excessively oxidized, and the amount of the expensive contact material 12 such as a gold material used for them can be reduced, and the cost can be reduced.

In particular, since the contact material 12 is first formed on the substrate 8, the accuracy thereof is reproduced as it is, so that highly reliable connection is possible.

[Brief description of drawings]

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

FIG. 2 is a bending process of the manufacturing process.

FIG. 3 is a second metal forming step of the manufacturing process.

FIG. 4 is a lead frame obtained by the same manufacturing process.

FIG. 5 is a plan view of a general lead frame using the present invention.

FIG. 6 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 8 substrate 9 resist layer

Claims (1)

(57) [Claims] 1. A semiconductor chip (1) is attached to a finger (4).
A method for manufacturing a semiconductor device in which a bump-shaped connecting portion (4a) for connecting to the electrode is provided, and the connecting surface side of the connecting portion (4a) is covered with a contact material (12) such as gold, tin, or solder. In the above, in the electroforming substrate (8) provided with a resist layer (9) so that a portion corresponding to the finger (4) is exposed, a portion corresponding to the connecting portion (4a) is previously attached to the contact material (12). And a finger (4) is electroformed on its upper surface, and then the substrate (8) is peeled off.