JP2001127231A - Lead frame and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-reliability lead frame which does not generate any dislocation of inner leads, when the lead frame and a radiating board are compression-bonded with an adhesive layer inbetween. SOLUTION: In a manufacturing method for a lead frame composed by arranging inner leads 10a surrounding a region where a semiconductor device is to be mounted, and by adhering the tip sides of the inner leads 10a to the peripheral brim part of a radiating board 12 formed as a separate substance from a lead frame 10 with an adhesive layer between insulating them electrically, a fixing tape 20 for preventing variations of the inner lead 10a is glued to radiating-board-12-adhering side surfaces of the inner leads 10a to be at positions inner than the internal peripheral brim of the adhesive layer 14, and the lead frame 10 to which the fixing tape 20 is glued and the radiating board 12 having the adhesive layer 14 at its external peripheral brim are positioned, and the lead frame 10 and the radiating board 12 are thermocompression-bonded into a body and fixed with the adhesive layer 14 inbetween.

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 formed by bonding a heat sink to inner leads and a preferable method of manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, a composite type lead frame formed by bonding a heat sink formed separately from a lead frame to inner leads has been provided. FIG. 7 shows an example of a lead frame in which a heat sink 12 is bonded to a lead frame 10 via a resin film 14. The inner lead 10a of the lead frame 10 is arranged so as to surround a mounting portion on which the semiconductor element is mounted, and a heat radiating plate 12 is bonded to a tip end of the inner lead 10a. The resin film 14 has an adhesive layer 14 on both sides of an electrically insulating film 14a.
b is formed. A resin film 14 is adhered to a peripheral portion of the heat radiating plate 12, and the lead frame 10 and the heat radiating plate 12 are electrically insulated and bonded via the resin film 14.

When bonding the lead frame 10 and the heat radiating plate 12, the heat radiating plate 12 with the resin film 14 adhered to the periphery is aligned with the lead frame 10, and the lead frame 10 and the heat radiating plate 12 are pressed by a pressing plate. Are pressed in the thickness direction, and heated and pressed. The resin film 14 is used to electrically insulate and bond the lead frame 10 and the heat radiating plate 12. The material and the like are not limited as long as the resin film 14 has adhesiveness and electrical insulation. Absent. The heat radiating plate 12 is a mounting portion on which the semiconductor element is mounted, and has a function of dissipating heat generated from the semiconductor element, and is usually formed of the same metal material as the lead frame 10. In FIG. 7, the semiconductor element 16 is mounted on the heat sink 12, and the semiconductor element 16 and the inner lead 10a are mounted.
Are electrically connected by wire bonding.

[0004]

Conventionally, an extremely large variety of products have been provided for lead frames, and products having a large number of pins and an extremely small interval between leads have been produced. In the case of such a product, as shown in FIG. 7, when the lead frame 10 and the heat sink 12 are thermocompression-bonded via an adhesive such as a resin film 14, the resin film 14 is heated and softened, and the inner leads 10a Is displaced from a proper position or twisted and fixed. Such a problem may be caused by a flaw in the pressure plate used in the thermocompression bonding operation, improper parallelism of the pressure plate, or wrinkling of the resin film 14.

[0005] As a method for preventing the problem that the inner lead 10a is displaced when the heat radiating plate 12 is crimped to the lead frame 10, a fixing tape for preventing the displacement of the lead is pasted to the inner lead 10a in advance. There is a way to keep it. As an example of the use of the fixing tape to prevent the inner leads of the lead frame from shifting, as the inner leads do not disperse, paste the fixing tape where it is molded to the shape where the tips of the inner leads are connected, and then In addition, there is a method of removing the connecting portion at the tip of the inner lead to form an independent lead. In this case, by cutting and removing the connecting portion at the tip of the inner lead, the tip of the inner lead becomes a free end, thereby preventing the inner lead from being displaced from a predetermined position due to residual distortion or the like.

The present invention uses a fixing tape for the purpose of preventing the inner lead 10a from being displaced when the heat radiating plate 12 is fixed to the inner lead 10a by pressing.
As a lead frame formed by bonding a heat sink formed separately from the lead frame to the lead frame, it is possible to provide a highly reliable product with no problems such as misalignment of the inner lead. It is an object of the present invention to provide a method of manufacturing a lead frame which is formed with a large number of pins and can reliably produce a good product even in the case of a lead frame in which the interval between leads is extremely small.

[0007]

To achieve the above object, the present invention comprises the following arrangement. That is, the inner lead is arranged so as to surround the region where the semiconductor element is mounted, and the tip side of the inner lead is electrically insulated via a bonding layer to the peripheral portion of a heat sink formed separately from the lead frame. In the lead frame, the tip of the inner lead extends inward from the inner peripheral edge of the adhesive layer, and a fixing tape is attached to a surface of the tip facing the heat sink. And By attaching the fixing tape to the tip of the inner lead, the displacement of the inner lead can be prevented, and the lead frame and the heat sink can be crimped without interfering with the adhesive layer, providing a highly reliable lead frame Is done. Further, an inner lead is arranged so as to surround a region where the semiconductor element is mounted, and a tip side of the inner lead is electrically insulated through a bonding layer to a peripheral portion of a heat sink formed separately from the lead frame. In the lead frame bonded by bonding, a fixing tape is attached to a surface of the inner lead on the side to which the heat radiating plate is adhered, outside the outer peripheral edge of the adhesive layer. Further, in the lead frame, the fact that the fixing tape is attached outside the outer peripheral edge of the heat sink has an advantage that the thickness of the fixing tape is not particularly limited. Further, since the fixing tape is formed thinner than the thickness of the adhesive layer, there is an advantage that the lead frame and the heat radiating plate can be suitably pressed. Further, as the adhesive layer, a resin film having an adhesive layer formed on both surfaces is preferable.

Further, an inner lead is arranged so as to surround a region where the semiconductor element is mounted, and a distal end side of the inner lead is electrically connected to a peripheral portion of a heat sink formed separately from the lead frame via an adhesive layer. In the method for manufacturing a lead frame insulated and adhered to a surface of the inner lead to which the heat sink of the inner lead is adhered, which is located inside the inner peripheral edge of the adhesive layer or located outside the outer peripheral edge of the adhesive layer, Affixing a fixing tape for preventing the dispersion of the inner leads, aligning the lead frame to which the fixing tape is stuck and a heat sink having the adhesive layer formed on the outer peripheral edge thereof, and setting the lead frame via the adhesive layer And the radiator plate is thermocompressed to be integrally fixed. Further, the fixing tape is characterized by using a tape formed thinner than the thickness of the adhesive layer.

[0009]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is an explanatory view showing a method for manufacturing a lead frame according to the present invention.
FIG. 1A shows an inner lead 10 of a lead frame 10.
A state is shown in which a fixing tape 20 for preventing the displacement of the inner lead 10a is attached to the tip end of a. Fig. 1 (a)
The upper surface of the inner lead 10a is a bonding surface, and the fixing tape 20 is a surface opposite to the bonding surface.
That is, the heat radiation plate 12 is attached to the surface to be bonded. In addition,
FIG. 1A shows a state in which the fixing tape 20 is adhered in a state where the tip portions of the adjacent inner leads 10a are connected to each other. Reference numeral 10b denotes a connecting portion that connects the distal ends of the inner leads 10a. The connecting portion 10b has a width of 0.1m.
m.

The fixing tape 20 is provided for the purpose of preventing the inner leads 10a from being displaced and displaced, and uses a fixing film provided with an adhesive layer 20a on one surface of a resin film such as a polyimide film. Connecting part 10b
Is removed by pressing after attaching the fixing tape 20. Therefore, the fixing tape 20 is connected to the connecting portion 1 so as not to overlap the position cut by the press working.
It is pasted at a position retracted from 0b.

FIG. 1B shows a state in which the connecting portion 10b at the tip of the inner lead 10a is cut and removed. Since the distal end portion of the inner lead 10a is held by the fixing tape 20, variation in the inner lead 10a is prevented. FIG. 3 is a plan view showing a state where the fixing tape 20 is attached to the lead frame 10. A fixing tape 20 is attached so as to connect between the tips of the inner leads 10a. Of course, the manufacturing method of the lead frame 10 is not limited to the method of connecting the tips of the inner leads 10a by the connecting portions 10b. After the inner leads 10a are formed into independent lead shapes, the fixing tape is applied between the tips of the inner leads 10a. 20 may be pasted.

FIG. 1C shows a step of bonding the heat sink 12 to the lead frame 10 via the resin film 14.
A thermosetting adhesive layer 1 is formed on both sides of a film 14a formed of an electrically insulating resin material as an adhesive layer on a peripheral portion of a surface of the heat radiating plate 12 which is bonded to the lead frame 10.
4b is attached, and the heat sink 12
And the inner lead 10a are aligned and crimped.
In this crimping operation, as shown in FIG.
It is necessary to arrange so that the resin film 14 and the fixing tape 20 adhered to each other do not overlap. This is because if the fixing tape 20 and the resin film 14 interfere with each other at the time of press bonding, the lead frame 10 and the heat radiating plate 12 are not securely pressed. Further, in the pressure bonding operation between the lead frame 10 and the heat radiating plate 12, the pressing force at the time of pressure bonding reliably acts on the entire surface of the resin film 14.
Is equal to or less than the thickness of the resin film 14.

FIG. 2 shows a process in which the lead frame 10 and the heat sink 12 are heated and pressed by the pressure plates 30 and 31 via the resin film 14 so that the lead frame 10 and the heat sink 12 are integrally pressed. . The fixing tape 20 and the resin film 14 are arranged so as not to interfere with each other, and since the fixing tape 20 is formed thinner than the resin film 14, the pressing force reliably acts on the resin film 14,
The heating cures the adhesive layer 14b and the lead frame 1
0 and the heat sink 12 are integrally bonded. In addition, since the fixing tape 20 is attached to the distal end of the inner lead 10a, it is possible to prevent the inner lead 10a from being displaced or twisted during crimping. The method of fixing the distal end portion of the inner lead 10a with the fixing tape 20 is effective in reducing the deformation at the distal end side of the inner lead 10a in which the lead interval is particularly narrow and particularly high positional accuracy is required for wire bonding or the like. There is an advantage that can be prevented.

As in this embodiment, the inner lead 10
The fixing tape 20 is attached to the lower surface side of a, that is, the surface of the inner lead 10a facing the heat radiating plate 12 because the fixing tape 20 does not directly contact the pressing surface of the pressing plate 31. From the inner lead 10
There is also an advantage that the adhesive of the fixing tape 20 does not ooze out on the bonding surface (upper surface) a, and the bonding surface is not stained with the adhesive or the like. Of course, when the fixing tape 20 is adhered to the bonding surface side of the inner lead 10a, the pressing force by the pressing plates 30, 31 does not act uniformly by the thickness of the fixing tape 20.

FIG. 1D shows a lead frame in which a lead frame 10 and a heat sink 12 are crimped by the above method. The fixing tape 20 is adhered to the tip of the inner lead 10a, and the resin film 14 is located on the outer periphery of the heat sink 12 outside the fixing tape 20. FIG. 4 shows a plan view of a portion where the lead frame 10 and the heat sink 12 are crimped. The inner lead 10a of the lead frame 10 is bonded to the peripheral edge of the heat sink 12 via the resin film 14, and the fixing tape 20 is bonded to the tip of the inner lead 10a along the inner peripheral edge of the resin film 14. To indicate that Since the tip of the inner lead 10a is supported by the fixing tape 20, displacement of the tip of the inner lead 10a is prevented, and a highly reliable composite lead frame can be obtained.

FIG. 5 shows another embodiment of the method for manufacturing a lead frame according to the present invention. In the embodiment described above,
The fixing tape 20 is attached to the tip of the inner lead 10 a so as to be located inside the inner peripheral edge of the resin film 14. As a method for preventing the fixing tape 20 and the resin film 14 from interfering with each other, A method is also possible in which the fixing tape is attached so as to be located outside the outer peripheral edge of the fixing tape. FIG. 5A shows a state in which the lead frame 10 and the heat sink 12 are aligned with each other, and
The fixing tape 21 attached to the lower surface of the heat sink 12a
An example in which the outer peripheral edge is attached further outside than the outer peripheral edge is shown.

FIG. 5B shows a lead frame in which the lead frame 10 and the heat sink 12 are pressure-bonded via the resin film 14 and integrated. Since the fixing tape 21 is located outside the outer peripheral edge of the heat sink 12, the resin film 14 and the fixing tape 21 do not interfere with each other.
4, the lead frame 10 is securely pressed. FIG.
2 shows a planar arrangement in a state where the fixing tape 21 is attached to the outside of the outer peripheral edge of the heat sink 12. Since the fixing tape 21 is attached to the surface of the inner lead 10a opposite to the bonding surface, the adhesive of the fixing tape 21 is prevented from oozing on the bonding surface of the inner lead 10a, as in the above embodiment. it can. Also in the case of the present embodiment, the inner leads 10 are fixed by the fixing tape 21.
By fixing “a”, it is possible to prevent displacement and variation of the inner lead 10a. When the fixing tape 21 is attached to the outside of the outer peripheral edge of the heat sink 12, it is not necessary to form the fixing tape 21 thinner than the thickness of the adhesive film 14.

FIG. 6 shows the resin film 14 and the fixing tape 2.
This is another example in which the fixing tape 21 is positioned outside the outer peripheral edge of the resin film 14 so as not to interfere with the fixing tape 21. This embodiment is characterized in that the fixing tape 21 is arranged outside the resin film 14 in the region of the heat sink 12. In this case, the thickness of the fixing tape 21 is set smaller than the thickness of the resin film 14. Also in the case of the present embodiment, the inner leads 10 are fixed by the fixing tape 21.
It is possible to prevent the displacement and variation of “a”, and the heat sink 12 is securely pressed to the inner lead 10a.

As in the above-described embodiment, the fixing tape 2
The method for arranging the lead frame 10 and the heat radiating plate 12 by arranging the resin films 14 so as not to interfere with each other is as follows: a fixing tape 20 to be attached to the tip of the inner lead 10a; It is also possible to use together with a fixing tape 21 to be attached to a position outside of the fixing tape 21. By attaching the fixing tape 20 and the fixing tape 21 to the inner leads 10a, it is possible to further prevent deformation such as displacement of the inner leads 10a.

In each of the above embodiments, the resin film 14 for bonding the lead frame 10 and the heat radiating plate 12 is temporarily bonded to the heat radiating plate 12 in advance, and the lead frame 10 and the heat radiating plate 12 are aligned with each other to perform final pressure bonding. However, it is also possible to temporarily bond the resin film 14 to the lead frame 10, align the resin film 14 with the heat radiating plate 12, and perform full pressure bonding. In the case of the embodiment shown in FIG. 5, by temporarily bonding the resin film 14 to the tip side of the inner lead 10a, there is an effect that the displacement of the lead of the inner lead 10a can be prevented. Also, the resin film 14 may be any as long as it can electrically insulate the lead frame 10 and the heat radiating plate 12 and can be integrally bonded, and an appropriate adhesive such as a film having an adhesive property on the surface is used. be able to.

[0021]

According to the lead frame and the method of manufacturing the same according to the present invention, as described above, displacement of the inner lead occurs when the lead frame and the heat radiating plate are pressure-bonded via the adhesive layer. Even a lead frame that is adhered without any trouble and has many pins and leads arranged at a high density can be provided as a highly accurate and highly reliable lead frame.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a method for manufacturing a lead frame according to the present invention.

FIG. 2 is an explanatory view showing a step of crimping a lead frame and a heat sink.

FIG. 3 is an explanatory view showing a state in which a fixing tape is attached to a lead frame.

FIG. 4 is an explanatory view showing a state in which a heat sink is crimped to a lead frame.

FIG. 5 is an explanatory view showing another method of manufacturing the lead frame.

FIG. 6 is a cross-sectional view showing a configuration example of a lead frame in which a heat sink is bonded to inner leads.

FIG. 7 is an explanatory view showing a conventional structure of a lead frame in which a heat sink is integrally crimped to the lead frame.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Lead frame 10a Inner lead 10b Connecting part 12 Heat sink 14 Resin film 14a Film 14b Adhesive layer 16 Semiconductor element 20, 21 Fixing tape 20a Adhesive layer 30, 31 Pressure plate

Claims (7)

[Claims] An inner lead is arranged so as to surround a region on which a semiconductor element is mounted, and a tip side of the inner lead is
In a lead frame, which is electrically insulated and bonded to a peripheral portion of a heat sink formed separately from the lead frame via an adhesive layer, a tip end of the inner lead is located inside an inner peripheral edge of the adhesive layer. A fixing tape attached to a surface of the distal end portion facing the heat radiating plate. 2. An inner lead is disposed so as to surround a region where the semiconductor element is mounted, and a tip side of the inner lead is
In a lead frame, which is electrically insulated and bonded to a peripheral portion of a heat radiating plate formed separately from the lead frame via an adhesive layer, heat radiation of the inner lead outside an outer peripheral edge of the adhesive layer is provided. A lead frame, wherein a fixing tape is attached to a surface on a side to which the plate is adhered. 3. The lead frame according to claim 2, wherein the fixing tape is attached outside an outer peripheral edge of the heat sink. 4. The fixing tape according to claim 1, wherein said fixing tape is formed thinner than a thickness of said adhesive layer.
Or the lead frame according to 3. 5. The method according to claim 1, wherein the adhesive layer is a resin film having an adhesive layer formed on both surfaces.
5. The lead frame according to 2, 3 or 4. 6. An inner lead is arranged so as to surround a region where the semiconductor element is mounted, and a tip side of the inner lead is
In a method for manufacturing a lead frame, which is electrically insulated and bonded to a peripheral portion of a heat sink formed separately from the lead frame via an adhesive layer, a position inside the inner peripheral edge of the adhesive layer or the adhesive layer A fixing tape for preventing variation of the inner lead is attached to a surface of the inner lead to which the heat radiating plate is bonded, which is located outside the outer peripheral edge of the inner lead. A method for manufacturing a lead frame, comprising: positioning a heat sink having the adhesive layer formed thereon; and thermally fixing the lead frame and the heat sink via the adhesive layer to fix them together. 7. The method for manufacturing a lead frame according to claim 6, wherein the fixing tape is formed to be thinner than the thickness of the adhesive layer.