JPH1022432A - Manufacture of lead frame - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain deformation and unevenness of the distal ends of inner leads when a connection piece is removed, by carrying out coining and correction in a state that the distal ends of a plurality of inner leads are connected by a connection piece with respect to each group of inner leads, with each group consisting of inner leads on each side of every coining line. SOLUTION: Inner leads 4 are divided into eight groups corresponding to the sides of a coining line 14. In addition, there is no connection piece at a boundary portion A between the inner lead groups belonging to their respective sides of adjacent different coining lines 14, and only the distal ends of the plurality of inner leads 4 belonging to each group are connected by the same connection piece 13. Therefore, even when coining and correction of the distal ends of the inner leads 4 are carried out in this state, as only the inner leads 4 which are coined and bent in the same direction are connected, the stress generated by coining and bending is satisfactorily cancelled in the same direction, thus preventing generation of distortion of the inner leads 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a lead frame, and more particularly to a method for forming a leading end of a lead frame.

[0002]

2. Description of the Related Art In recent years, semiconductor devices have been required to be smaller, thinner and more highly integrated, and the lead frame used for such devices has been decreasing in both lead width, lead interval and plate thickness. Production requires extremely high technology, and research is ongoing.

As a semiconductor device satisfying the above requirements, a so-called QFP in which leads are arranged on four side surfaces of a package.
(Quad Flat Package) is generally widely used.

A lead frame used in the QFP generally has a shape as shown in FIG. That is, the lead frame 1 includes a semiconductor element mounting portion 2, a support bar 3 that supports the semiconductor element mounting portion 2, a plurality of inner leads 4 provided to surround the semiconductor element mounting portion, and an inner lead. Tie bar 5 to connect
And a plurality of outer leads 6 continuous with the respective inner leads. In addition, the area | region divided by the support bar for convenience is called 1st quadrant-4th quadrant, respectively, as shown in FIG. In the following description, each quadrant is assumed to be symmetric.

Normally, such a lead frame is formed by stamping or etching a strip-shaped metal material such as an iron-based or copper-based material into a desired pattern and then performing a plating step or the like.

Thereafter, a semiconductor element is mounted, and wire bonding is performed to electrically connect the semiconductor element and the tip of the inner lead with a bonding wire such as a gold wire. In particular, when the forming process is performed by stamping, deformation such as jumping of the tip of the inner lead frequently occurs.

When wire bonding is performed in such a state that the tip of the inner lead is deformed, the tip of the inner lead 4 rises from the plate 8 of the bonding machine as shown in FIG. For this reason, the connection of the bonding wire 11 must be performed while the tip of the inner lead 4 is pressed against the plate 8 by the capillary 9 of the bonding machine, and a bonding error is extremely likely to occur.

Therefore, as a measure for preventing deformation of the tip of the inner lead, in order to prevent displacement of the tip of the inner lead,
In each quadrant, the shape is processed by leaving the connecting pieces that connect the tips of all the inner leads adjacent to each other, and after a process such as heat treatment or plating processing, a method of finally removing this connecting piece is used. I have.

In this method, as shown in FIG. 5, a coining 7 for securing an effective flat width required for wire bonding is performed on the tip of the inner lead 4 in a state where the tip of the inner lead 4 is connected by a connecting piece 13. . However, since the inner leads 4 may be deformed by coining, as shown in FIG. 4, if necessary, in order to keep the inner leads 4 from rising or falling due to coining within a certain range, as shown in FIG. An angle θ is given to the coining punch 15, and correction is performed to bend the tip of the inner lead 4 to the back side of the wire bonding planned surface while coining. This correction is performed at right angles to the coining line 14.

By the way, the coining punch 15 is appropriately divided corresponding to the elongated shape of the inner lead. For example, when the coining punch 15 is divided into eight as shown in FIG. 7, an octagonal shape is formed on the lead frame. A coining line will be formed.

In such a case, when the bending straightening is performed at right angles to the coining line 14, each inner lead 4
Although the tip is bent corresponding to the side direction of the coining line 14, as shown in FIG. 6, since two different coining lines 14 exist in each quadrant, the tip of the inner lead 4 also corresponds to this. Each quadrant will be bent in two different directions.

However, since the tips of the inner leads 4 are collectively connected by one connecting piece 13 for each quadrant irrespective of the coining line 14 and the coining direction, the stresses generated by the coining and bending processes are different in these two directions. The inner lead 4 is not released due to the presence of the connecting piece 13 that connects the different lead groups at the boundary portion A of the inner lead group that is bent so that the inner lead 4 is distorted. Even if the connecting piece is removed in this state,
It was not possible to solve the problem of deformation of the tip of the inner lead 4, in particular, variation such as rising and falling between the inner lead from the support bar and the inner lead near the center, which hinders wire bonding. .

[0013]

As described above, according to the conventional method for manufacturing a lead frame, it is not possible to suppress deformation or variation of the tip of the inner lead when the connecting piece is removed, and there is no problem during wire bonding. There was a problem of coming. The present invention has been made in view of the above circumstances, and an object of the present invention is to solve the above-mentioned problem and to provide a lead frame of excellent bonding property and stable quality.

[0014]

In order to achieve the above object, according to the present invention, the inner leads on each side of each coining line formed in a polygonal shape are grouped, and a plurality of tips of the inner leads are provided for each group. Coining and straightening are performed in a state where the connecting pieces are connected, and then the connecting pieces are removed. With this, even when coining and straightening are performed on the tip of the inner lead in a different direction for each quadrant, only the tips of the plurality of inner leads having the same coining direction are connected by the connecting piece, and the coining and straightening are performed in different directions. Since the inner lead group is separated from the inner lead group, the stress generated by coining and correction can be satisfactorily released in the same direction.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method for manufacturing a lead frame according to the present invention will be described in detail with reference to the drawings.

First, a copper band material represented by an alloy 194 or the like is stamped and formed into a desired shape by a stamping method. At this time, as shown in FIGS. 1 and 2, the tips of the inner leads are formed in such a manner that the inner leads 4 corresponding to the sides of the coining line 14 are grouped and the tips are connected by connecting pieces 13. In the present embodiment, since the coining punch 15 is divided into eight parts, the coining shape is octagonal.
The number of inner lead groups connected by the same connecting piece 13 at the tip is also eight groups, two groups in each quadrant.

After this, coining and inner lead 4
Perform tip correction. As shown in FIG. 4, the coining punch 15 has an arbitrary angle θ, and a die (not shown).
Is also angled accordingly. The coining of the tip of the inner lead 4 is performed by the coining punch 15 and the die. At this time, since the coining punch 15 has the angle θ, the tip of the inner lead 4 is bent downward by the angle θ. This plays a role of correction for suppressing the variation of the tip of the inner lead 4. Note that the angle θ is such that the tip of all the inner leads 4 after correction is, for example, 0.0 with respect to the wire bonding surface.
It is determined to be within the range of 00 mm to -0.050 mm.

Here, as shown in FIGS. 1 and 2, the inner lead 4 is divided into eight groups corresponding to the sides of the coining line 14, and adjacent different coining lines 14 are provided.
There is no connecting piece at the boundary part A of the inner lead group belonging to each side of
Since only the tip is connected by the same connecting piece 13,
Even if the tip of the inner lead 4 is corrected in this state, only the inner leads 4 that are subjected to the coining and the bending correction are connected in the same direction, so that the stress generated by the coining and the bending correction is good in the same direction. And the inner lead 4 is not distorted.

Then, a predetermined treatment such as a heat treatment or a plating treatment is performed in a state where the tips of the inner leads 4 are connected by the connection pieces 13 as described above.

After that, the connecting pieces 13 are removed to separate the inner leads from each other, thereby completing the lead frame.

According to the lead frame formed in this way, since deformation and variation such as jumping and jumping of the tip of the inner lead are minimized, it is necessary to always perform wire bonding in a stable state. And yield is greatly improved.

In this embodiment, an example has been described in which the inner leads are divided into a plurality of groups corresponding to the respective sides of the coining line, and the tips of all the inner leads belonging to each group are connected by one connecting piece. Without being limited to this, each group may be further divided into a plurality of groups, and the tips of a plurality of inner leads belonging to the group may be connected to each of the divided groups. One embodiment is shown in FIG.

When the number of leads connected by one connecting piece is reduced as much as possible, the stress and strain due to coining and correction are more satisfactorily dispersed, so that deformation and variation of the tip of the inner lead can be suppressed.

In this embodiment, the formation of the lead frame by stamping has been described. However, the present invention is not limited to this, and the lead frame can be formed by, for example, an etching method. Further, the present invention can be applied to any type of lead frame such as DIP regardless of the shape and extension direction of the lead, other than the lead frame used for the QFP.

Although a copper-based material is used as the lead frame material, it goes without saying that other materials, for example, a material made of an iron-nickel alloy may be used.

Furthermore, in this embodiment, the tip of the inner lead is corrected at the same time as the coining, but each step may be performed separately. In addition, the present invention is, of course, effective even when only coining is performed without performing correction.

[0027]

As described above, according to the method for manufacturing a lead frame of the present invention, the inner leads on each side of each coining line formed in a polygonal shape are grouped, and a plurality of inner leads are formed for each group. Since the coining and straightening are performed in a state where the lead tip is connected by the connecting piece, the stress generated by coining and straightening can be released well in the same direction, without distortion of the lead,
It is possible to obtain a lead frame with excellent bonding properties and stable quality without deformation or variation of the inner lead tip.

[Brief description of the drawings]

FIG. 1 is a view showing a lead frame of the present invention.

FIG. 2 is an enlarged view of a main part of the lead frame of the present invention.

FIG. 3 is a view showing another embodiment of the lead frame of the present invention.

FIG. 4 is a view showing a coining step of a lead frame.

FIG. 5 is a view showing a conventional lead frame.

FIG. 6 is an enlarged view of a main part of a conventional lead frame.

FIG. 7 is a diagram showing a coining state of a lead frame.

FIG. 8 is a diagram showing a conventional wire bonding state.

FIG. 9 is a view showing a lead frame used for the QFP.

FIG. 10 is an explanatory diagram when a lead frame is divided into four parts.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Lead frame 2 Semiconductor element mounting part 3 Support bar 4 Inner lead 5 Tie bar 6 Outer lead 7 Coining 8 Plate 9 Capillary 10 Semiconductor element 11 Bonding wire 12 Pusher block 13 Connecting piece 14 Coining line 15 Coining punch A Different inner Lead group boundary θ Angle attached to coining punch

Claims (1)

[Claims] A semiconductor element mounting part, a support bar supporting the semiconductor element mounting part, and a plurality of inner leads arranged so as to surround the semiconductor element mounting part.
A method for manufacturing a lead frame, wherein a plurality of outer leads continuous with each inner lead are provided, and the tip of the inner lead is subjected to coining.In the method of manufacturing a lead frame, inner leads of each side of each polygonal coining line are formed. A lead forming step of punching between the inner leads so that a plurality of inner lead tips are connected by a connection piece for each group; a step of coining the inner lead tips; and Removing the connecting piece for connecting the lead frame.