JP2001127232A - Lead frame and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-reliability lead frame by increasing adhesion intensity between sealing resin and a mounting part for a semiconductor device such as a die pad etc. SOLUTION: This is a lead frame which has through holes 30 formed by press working for increasing adhesion intensity between sealing resin 16 and a mounting part 12 in a mounting part 12 for a semiconductor device, a plurality of through holes 30 are formed into a slitlike shape, and the through holes are arranged adjacently. Besides, small segment parts interposed by adjoining through holes 30 are formed inbetween into a shape twisted as against the direction of extraction of the through holes 30.

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 having improved adhesion strength between a die pad on which a semiconductor element is mounted and a sealing resin, and a preferable method of manufacturing the same. .

[0002]

2. Description of the Related Art FIG. 5 shows a semiconductor device in which a semiconductor element 14 is mounted on a die pad 12 of a lead frame 10 and sealed with a sealing resin 16. In such a resin-encapsulated semiconductor device, adhesion between the encapsulation resin 16 and the die pad 12 at the time of encapsulation poses a problem. When the adhesion between the sealing resin 16 and the die pad 12 is insufficient, the thermal expansion coefficient between the die pad 12 and the sealing resin 16 is considerably different. This is because stress is generated, and cracks are generated in the sealing resin 16 and moisture is absorbed at the interface between the sealing resin 16 and the die pad 12, which causes a problem that the reliability of the product is reduced.

For this reason, in a conventional lead frame, a method of performing dimple processing on the surface of the die pad opposite to the surface on which the semiconductor element is mounted, or forming a through hole in the die pad is performed. These are to increase the adhesion area between the sealing resin and the die pad, or to improve the adhesion strength between the sealing resin and the die pad by an anchor action. FIG. 6 shows an example in which a slit-shaped through hole 18 is formed in the die pad 12 of the lead frame. The difference in thermal expansion coefficient between the die pad and the semiconductor element mounted on the die pad makes it possible to absorb the tension generated at the interface between them. This is a conventional example (JP-A-63-310151).

[0004]

FIG. 7 shows a die pad 1.
FIG. 3 is a view for explaining the adhesion between a sealing resin 16 and a sealing resin 16. FIG.
7A shows an example in which the contact surface between the sealing resin 16 and the die pad 12 is formed as a flat surface, FIG. 7B shows an example in which a dimple process is performed on the back surface of the die pad 12 to form a concave portion 20, and FIG.
(c) is an example in which a through hole 18 is formed in the die pad 12. In the example shown in FIG. 7B, the adhesion strength is improved by increasing the contact area between the die pad 12 and the sealing resin 16, and in the example shown in FIG. Of the through hole 1
The adhesion strength is improved by the anchoring action of the sealing resin 16 that has entered the surface 8.

However, the method of dimple processing or forming a through hole in the die pad does not always provide sufficient adhesion strength between the die pad and the sealing resin. For this reason, as shown in FIG.
A method of improving the adhesion strength between the die pad 12 and the sealing resin 16 by forming a through hole 22 having a non-return shape in 2 has also been considered. However, such a check hole 2
There is a problem that processing is not easy to form 2.
Further, when dimple processing is performed on the entire surface of the die pad, there is a problem that the flatness of the die pad is impaired.

The present invention has been made in order to solve these problems.
A lead frame that can improve the adhesion strength between the die pad and the sealing resin, can obtain the required flatness, and can be provided as a highly reliable lead frame, and is easy to process and suitable for mass production. And a preferred method of manufacturing the same.

[0007]

To achieve the above object, the present invention comprises the following arrangement. That is, a lead frame in which a through hole for improving the adhesion strength between a sealing resin and a mounting portion is formed in a mounting portion of a semiconductor element by press punching, wherein the through hole is formed in a slit shape, and The small pieces that are arranged adjacent to each other and that are sandwiched between the adjacent through holes are formed in a shape twisted with respect to the direction in which the through holes are pulled out. Further, since the through hole is formed near the periphery of the mounting portion, the adhesion strength between the sealing resin and the mounting portion at the periphery of the mounting portion is improved, and the reliability of the lead frame can be improved. This is preferable in that it can be performed. In addition, it is preferable that the mounting portion is a die pad supported by the support bar and formed integrally with the support bar, the lead, and the like, since the lead frame can be manufactured by a series of press punching.

In addition, a required material such as a lead and a die pad is formed by processing a plate material for manufacturing a lead frame, and a plurality of slit-shaped through holes are formed on the die pad to improve the adhesion strength between the die pad and a sealing resin. A method of manufacturing a lead frame in which holes are formed adjacent to each other,
The through hole is formed by press-cutting the plate material, and when forming a through hole adjacent to the previously formed through hole, a small piece portion sandwiched between the through hole and the through hole adjacent to the through hole is formed. The width of the small piece portion is set so as to be twisted with respect to the drawing direction of the through-hole, and press-cutting is performed. In addition, setting the width dimension of the small piece portion to 60% to 80% of the thickness of the plate material and performing the press punching process includes:
This is preferable in that it can be punched into a shape twisted with respect to the pulling direction of the through hole.

[0009]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In a lead frame according to the present invention, a plurality of slit-shaped through holes are formed in a die pad on which a semiconductor element is mounted. FIG.
Next, an embodiment in which a through hole 30 is formed in the die pad 12 is shown.

FIG. 1A shows a through hole 3 near each corner in the plane of a die pad 12 formed in a square shape.
This is an example in which 0 is formed. The through holes 30 are formed in a short straight line, and are formed in parallel at regular intervals in a direction orthogonal to a diagonal line of the die pad 12. In the figure, three through holes 30 are formed, but the number of through holes 30 is not particularly limited as long as it is two or more. A support bar 32 supports the die pad 12. FIG. 1B shows an example in which an L-shaped through hole 30 is formed near each corner of the die pad 12. The through-holes 30 have corner portions arranged on a diagonal line of the die pad 12, and straight hole portions on both sides are formed in the die pad 1.
2 are arranged parallel to the side edges. Arranging the through holes 30 in parallel at regular intervals is the same as in the embodiment shown in FIG.

FIG. 1C shows an example in which a through hole 30 is formed near the side edge of the die pad 12 in parallel with the side edge of the die pad 12. The through holes 30 have the same length and are arranged at predetermined intervals. FIG. 1D shows an example in which a bent through hole 30 symmetrical with respect to a diagonal line of the die pad 12 is formed at each corner of the die pad 12. FIG. 1 (e) shows the through hole 3 near the side edge of the die pad 12 in a direction perpendicular to the side edge.
This is an example in which 0 is formed. FIG. 1F shows an example in which a through hole 30 is formed near the corner of the die pad 12 in parallel with the diagonal direction of the die pad 12. Also in these embodiments, the through holes 30 are formed at predetermined intervals in parallel with each other.

As described above, in the lead frame according to the present invention, the through holes 30 formed in the die pad 12 are formed to have a narrow slit shape, and the through holes 30 are arranged close to each other. The hole 30 is formed by press punching. FIG. 2 shows a method of forming the through holes 30 in the die pad 12 by press punching. FIG.
(a) shows a state in which a first through hole 30a is first formed at a predetermined position of the die pad 12.

FIG. 2B shows a step of forming a second through hole 30 b in the die pad 12. The lead frame is clamped by the mold 34 and the through-hole 30 is
And punching. First through hole 30a previously punched
The second through-hole 30b, which has been punched next, is arranged such that the holes are arranged in parallel and sufficiently close to each other as described above. As described above, the reason why the through-holes 30 are arranged close to each other is that when the through-holes 30 are approached to perform the punching process, the pressing force of the mold 34 does not sufficiently act on the workpiece, and the punch 36 This is to take advantage of the fact that the workpiece is twisted by the action of pulling out the through hole 30.

In FIG. 2 (c), the portion A is a portion for holding the workpiece when forming the through hole 30b. If the clamping area of the portion A becomes very small, the force for holding the workpiece is reduced. Does not sufficiently act on the workpiece, and when the punch 36 punches out the through-hole 30b, the processed portion is twisted. FIG. 2D shows the small piece portion 40 sandwiched between the through holes 30a and 30b after the press punching.
Indicates a state twisted slightly downward to the right.

As described above, the through holes 30 are formed in the die pad 12.
When the through-hole 30 is approached and press-cutting is performed, the small piece portion 40 sandwiched between the through-holes 30 has a shape twisted in the direction in which the through-hole 30 is removed. Actually, the angle at which the small piece portion 40 is twisted varies depending on the material of the workpiece, the thickness of the workpiece, the hole size of the through-hole 30, and the like, but the purpose is to improve the adhesion strength between the die pad 12 and the sealing resin 16. Is the distance between adjacent through holes 30 (FIG. 2 (c)
A) is 60% of the plate thickness of the plate material to be processed.
When it is set to about 80%, the small piece portion 40 is twisted to a required degree, and the adhesion strength with the sealing resin 16 can be effectively improved.

FIG. 3 shows that when the through-hole 30 is formed in the die pad 12, the twisting direction of the small piece portion 40 formed in the middle of the through-hole 30 is changed by changing the order in which the through-hole 30 is removed. 3A, 3B, and 3C show the order in which the through-holes 30 are removed and the twist direction of the small piece portion 40 at that time. As described above, when the workpiece is clamped by the mold, the clamping force becomes insufficient.
The small piece portion 40 is twisted. Therefore, the through hole 30
By changing the order in which the small pieces are removed, the twisting direction of the small piece portion 40 can be changed. FIG. 3A shows an example in which the small pieces 40 are twisted in the same direction, and FIG.
Is twisted downward, FIG. 3 (c) shows the opposing small piece 4
0 is an example of twisting upward.

When manufacturing a lead frame from a plate material by press punching, the through hole 30 may be formed in the die pad 12 in an appropriate step of a series of press punching steps. That is, for example, after the outer shape of the die pad 12 is formed, the through-hole 30 can be punched out, and in a process before forming the outer shape of the die pad 12, the through hole 30 can be appropriately formed in accordance with the position of the die pad 12. It is also possible to machine the hole 30. When a lead frame is manufactured by press blanking, a product is manufactured through many blanking processes.
It is easy to design to form a through hole, and it is easy to form the through hole 30 in the die pad 12.

Further, since the small piece portion 40 can be formed into a shape twisted in the direction in which the through hole 30 is removed by merely punching the through hole 30 with the punch 36, a process for manufacturing a lead frame by a conventional press punching process. There is an advantage that the apparatus can be used as it is and no complicated processing is required. As a result, it is possible to easily mass-produce the lead frame including the die pad 12 in which the small piece portions 40 sandwiched between the adjacent through holes 30 are twisted in the drawing direction of the through holes 30.

When the lead frame is formed by etching, the through hole 30 may be formed in the die pad by the above-described method after forming the lead frame into a predetermined shape. As described above, also for the lead frame formed by etching, by forming the through hole 30 in the die pad 12 by the above method, the small piece portion 4 sandwiched by the through hole 30 is formed.
0 may have a shape twisted with respect to the direction in which the through hole 30 is pulled out.

In each of the examples of forming the die pad 12 shown in FIG. 1, the through holes 3 are formed in the die pad 12 by the above-described method.
0 is formed. The small piece portion 40 sandwiched between the through holes 30 is formed in a shape twisted with respect to the drawing direction of the through hole 30. The twisting direction of the small piece portion 40 changes depending on the order in which the through holes 30 are removed. Therefore, even when four or more through holes 30 are formed adjacent to each other, the torsion direction of the small piece portion 40 is selected by selecting the order in which the through holes 30 are removed. You just have to decide.

FIG. 4 shows a semiconductor device 14 attached to the die pad 12.
The figure shows an enlarged view of a state in which is mounted and resin-sealed. A through hole 30 is formed in the die pad 12, and the through hole 30 is filled with the sealing resin 16. Small piece part 4 sandwiched between through holes 30
Since 0 has a shape twisted with respect to the direction in which the through hole 30 is removed, the small piece portion 40 acts on the sealing resin 16 in a wedge-like manner, and the adhesion strength between the die pad 12 and the sealing resin 16 is improved. Can be done. In FIG. 4, reference numeral 38 denotes a silver paste for joining the semiconductor element 14 to the die pad 12.

The small piece portion 40 formed on the die pad 12 acts to prevent the sealing resin 16 from becoming difficult when the resin is sealed, thereby preventing the die pad 12 from reversing. Therefore, the adhesion between the die pad 12 and the sealing resin 16 is improved. It is effective as a method to make it. In the embodiment shown in FIG. 1, the through holes 30 are formed near the corners and near the side edges of the die pad 12 because the adhesion between the die pad 12 and the semiconductor element 14 tends to be a problem. This is because the adhesiveness of the peripheral edge portion 12 to the sealing resin is improved. Thus, the through-hole 30 is formed in the peripheral portion of the die pad 12.
Is advantageous in that the flatness of the entire die pad 12 is good and the heat dissipation from the die pad 12 is not impaired.

In the above embodiment, a so-called quad type lead frame in which leads are arranged around the die pad 12 has been described as an example. However, the shape of the leads of the lead frame is not particularly limited. In addition, the die pad 12 formed on the lead frame is not limited to a square, but can be applied to an appropriate shape such as a rectangle. Further, the present invention can be suitably applied to a lead frame in which a lead and a die pad are integrally formed. However, a composite type lead is formed by joining a heat sink formed separately to a lead frame having no die pad. The same applies to the case of forming a frame. That is, by forming the through-hole by the same punching process as in the above embodiment on the heat sink on which the semiconductor element is mounted, it is possible to form a small piece portion having a shape twisted with respect to the through-hole removing direction, This makes it possible to improve the adhesion strength between the heat sink and the sealing resin.

[0024]

As described above, in the lead frame according to the present invention, since the small piece portion sandwiched between the through holes formed in the mounting portion is formed in a shape twisted in the direction in which the through hole is removed, The sealing resin and the small piece portion are wedge-engaged, and the adhesion strength between the sealing resin and the mounting portion can be effectively increased. This makes it possible to improve the reliability of the semiconductor device in which the semiconductor element is mounted on the lead frame according to the present invention and sealed with resin. Further, according to the method for manufacturing a lead frame according to the present invention, it is possible to easily form a small piece portion to be wedge-engaged with the sealing resin on the die pad, and to easily mass-produce the lead frame by pressing. Can be.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a configuration of a die pad portion of a lead frame according to the present invention.

FIG. 2 is an explanatory diagram showing a method of forming a through hole in a die pad by press punching.

FIG. 3 is an explanatory view showing the order in which through holes are extracted and the twisted state of a small piece portion.

FIG. 4 is an enlarged cross-sectional view showing a portion near a die pad in a state where a lead frame is resin-sealed.

FIG. 5 is a cross-sectional view illustrating a configuration of a resin-sealed semiconductor device.

FIG. 6 is an explanatory view showing a conventional example in which a through hole is formed in a die pad.

FIG. 7 is an explanatory diagram showing a contact portion between a die pad and a sealing resin.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Lead frame 12 Die pad 14 Semiconductor element 16 Sealing resin 18 Through hole 20 Depression 22 Through hole 30, 30a, 30b Through hole 32 Support bar 34 Die 36 Punch 40 Small piece

Claims (5)

[Claims] 1. A lead frame in which a through hole for improving the adhesion strength between a sealing resin and a mounting portion is formed in a mounting portion of a semiconductor element by press punching, wherein the through hole is formed in a slit shape. And a plurality of small pieces sandwiched between adjacent through holes are formed in a shape twisted with respect to a direction in which the through holes are removed. 2. The lead frame according to claim 1, wherein the through hole is formed near a periphery of the mounting portion. 3. The lead frame according to claim 1, wherein the mounting portion is a die pad supported by the support bar and formed integrally with the support bar, the lead and the like. 4. A plurality of slit-shaped through holes for processing a plate material for manufacturing a lead frame to form a required pattern such as a lead and a die pad, and to improve an adhesion strength between the die pad and a sealing resin in the die pad. A method of manufacturing a lead frame in which a hole is formed adjacently, wherein the through hole is formed by pressing the plate material, and the through hole is formed adjacent to the previously formed through hole. ,
Manufacturing a lead frame by setting a width of the small piece so that a small piece sandwiched between the through hole and the through hole adjacent to the through hole is twisted with respect to a drawing direction of the through hole, and performing press-cutting. Method. 5. The method of manufacturing a lead frame according to claim 4, wherein a width dimension of said small piece portion is set to 60% to 80% of a thickness of said plate material and press-cutting is performed.