JPH08293575A - Lead frame provided with heat sink and manufacture - Google Patents

Abstract

PURPOSE: To provide a lead frame equipped with a heat sink, wherein a grounding lead and a heat sink are easily bonded together without oxidization and discoloration, and the lead frame equipped with a heat sink can be manufactured by the use of the same lead frame and a heat sink when bonding pads are identical in position even if a semiconductor chip is different in grounding lead specifications. CONSTITUTION: A lead frame provided with a heat sink is manufactured through such a method that a grounding lead 5b is bonded to a heat sink 2 as an ultrasonic tool 10 is made to slide ultrasonically on the lead 5b of a lead frame 5 pressing against it. By this method, a lead frame provided with a lead frame can be obtained, wherein the grounding lead 5b is bonded to the heat sink 2 penetrating through an insulating film 3 even if the insulating film 3 is interposed between the grounding lead 5b and the heat sink 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead frame with a heat radiating plate integrally laminated with a frame-shaped insulating film interposed between the heat radiating plate and the lead frame, and a manufacturing method thereof.

[0002]

2. Description of the Related Art Conventionally, a lead frame with a heat radiating plate is integrated by interposing a frame-shaped insulating film 3 between the lead frame 1 and the heat radiating plate 2 as shown in a plan view of the main part of FIG. The semiconductor chip 4 is mounted on the heat dissipation plate 2 in a portion exposed from the central portion of the frame-shaped insulating film 3 in the mounting process. Further, each bonding pad of the semiconductor chip 4 and each lead 5 of the lead frame 1 are connected by a bonding wire as shown by a dotted line in FIG.

In manufacturing such a lead frame with a heat radiating plate, a lead frame 1 or a heat radiating plate 2 having a plurality of bonding projections 6 on its outer peripheral edge as shown in FIG. Adhesive is applied to both sides of the film 3 and temporarily attached, and then the heat dissipation plate 2 or the lead frame 1 is further aligned and superposed thereon, and thermocompression bonded to be integrated.

A plurality of joint projections 6 formed on the heat dissipation plate 2.
Is for joining the ground lead 5a of the lead 5 of the lead frame 1 in order to make the heat sink 2 function as a ground plane or a power plane. That is,
A protrusion 6 for joining is formed in advance on the outer peripheral edge of the heat sink 2 in accordance with the specifications of the grounding lead of the semiconductor chip 4, and as shown in FIG. 6, the protrusion 6 for joining is crank-shaped by substantially the thickness of the insulating film 3. Then, the grounding leads 5a are superposed on the joining projections 6, and the welding electrodes 8 are pressed from above and below to join them by electric resistance welding.

In the conventional lead frame with a heat sink, the joint 7 between the heat sink 2 and the ground lead 5a is thus formed.
Is formed by projecting from the outer peripheral edge of the heat dissipation plate 2, because if the ground lead 5a is directly welded to the heat dissipation plate 2 itself, the heat generated at the welding electrode 8 diffuses to the heat dissipation plate 2 and the heat dissipation plate 2 side is exposed. Only the ground lead 5a of the lead frame 1 is melted and cut if it cannot be melted and is forcibly welded. Therefore, the bonding projection 6 having a width substantially the same as the width of the ground lead 5a.
Is provided on the outer peripheral edge of the heat radiating plate 2 and electric resistance welding is performed on the heat radiating plate 2 to suppress heat diffusion and enable welding.

Also, the ground lead 5a of the lead frame 1
As another method for establishing electrical connection between the heat sink 2 and the heat sink 2, there is thermocompression bonding. Also in the method by thermocompression bonding, it is necessary to form the bonding projection 6 on the outer peripheral edge of the heat dissipation plate 2 in order to prevent the diffusion of heat to the heat dissipation plate 2. After that, the grounding lead 5a and the joining projection 6 of the heat sink 2 are plated with metal, and then the two are joined by thermocompression bonding. As metal plating at that time, A
u / Au, Ag / Ag, Au / Ag, Au / Sn, Pb
There are combinations such as Sn / PbSn.

[0007]

As described above, in the conventional lead frame with a radiator plate, the heat for joining the ground lead of the lead frame and the radiator plate diffuses to the radiator plate, which makes joining difficult. In order to prevent this, it is necessary to form a bonding protrusion having a width substantially equal to the lead width on the outer peripheral edge of the heat dissipation plate in accordance with the ground lead specifications of each semiconductor chip.

Therefore, even if the bonding pad position of the semiconductor chip is the same, the position of the joint portion of the ground lead changes every time the ground lead specification is different. A heat dissipation plate having parts has to be manufactured, and the increase in cost due to the increase in variety has become a big problem. Moreover, it is necessary to perform a crank-shaped bending process on the joint projection of the heat sink, and this process also causes a cost increase.

In addition, when the grounding lead of the lead frame and the joining projection of the heat dissipation plate are joined, the grounding lead is exposed to a high temperature by electric resistance welding or thermocompression bonding, which causes a problem that the lead is oxidized or discolored. there were.

Even in the thermocompression bonding method after metal plating, there is no change in manufacturing the lead frame and the heat radiating plate for each of the grounding lead specifications described above, and the cost increase due to the increase in the variety of products as in the case of electric resistance welding. There was a problem.
Further, the thermocompression bonding method requires metal plating, which further increases the cost.

In view of the above conventional circumstances, the present invention can easily join the ground lead and the heat sink without causing oxidation or discoloration. Further, even if the ground lead specifications of the semiconductor chip are different, the bonding pad position is different. If they are the same,
It is an object of the present invention to provide a lead frame with a heat radiating plate and a method for manufacturing the same, which can use the same lead frame and heat radiating plate and can reduce the variety of products and simplify the manufacturing.

[0012]

In order to achieve the above object, the present invention is applied to the production of a lead frame with a heat sink, in which a frame-shaped insulating film is interposed between the heat sink and the lead frame to integrally laminate them. The method is characterized by using ultrasonic sliding for electrical connection between the ground lead of the lead frame and the heat dissipation plate.

That is, the grounding lead and the heat radiating plate are electrically joined to each other by electrically sliding the grounding lead and the heat dissipation plate by pushing the ultrasonic tool against the grounding lead of the lead frame. Even if the insulating film is interposed between the plate and the plate, the ground lead and the heat sink can be joined by penetrating the insulating film.

Therefore, the lead frame with a heat sink provided by the present invention is a lead frame with a heat sink that is integrally laminated by interposing a frame-shaped insulating film between the heat sink and the lead frame. It is characterized in that the ground lead of the lead frame penetrates the insulating film and is electrically joined to the heat dissipation plate.

[0015]

In the present invention, ultrasonic sliding is used for joining the ground lead of the lead frame and the heat dissipation plate in place of the joining by heat as in the conventional electric resistance welding or thermocompression bonding.
The oxide film on the metal surface is worn away by the vibration and pressing pressure of the ultrasonic tool, and the ground lead can be directly bonded to the heat sink itself without causing an excessive temperature rise, thus preventing oxidation or discoloration of the lead. it can.

Moreover, according to the ultrasonic sliding, even if the insulating film is present between the ground lead and the heat sink, the insulating film is pierced by the vibration and pressing pressure of the ultrasonic tool and penetrates the insulating film. The ground lead and the heat sink can be joined. Further, even if the grounding lead is not bent beforehand, the portion contacting the ultrasonic tool is bent by the pressing pressure, penetrates the insulating film and is joined to the heat dissipation plate.

As a result, it is not necessary to provide a bonding projection on the outer peripheral edge of the heat dissipation plate, so that even if the ground lead specifications are different, if the bonding pad positions are the same, the same lead frame is used, that is, Manufacture a lead frame with a heat sink by using a ground lead and the same lead frame in which all other leads have the same shape, and joining any lead as a ground lead to the heat sink according to the ground lead specifications. Is possible. Further, as for the heat dissipation plate, it is possible to specify a heat dissipation plate having no joining protrusion and having the same outer peripheral edge as the outer peripheral edge of the insulating film.

Ultrasonic sliding is a method in which electric energy generated by a thyristor conversion high frequency oscillator is converted into mechanical longitudinal vibration by a piezo-vibrator, and this vibration is transmitted to an ultrasonic tool to machine a workpiece. . In order to join the ground lead and the heat sink, the frequency of ultrasonic sliding is 15-80.
The amplitude of KHz and ultrasonic sliding is preferably in the range of 1 to 50 μm. Further, the pressing force in the vertical direction by the ultrasonic tool is preferably in the range of 0.01 to 100 kg / mm ² , but a higher pressure is required as the insulating film is interposed and the thickness thereof is thicker.

The bonding strength between the grounding lead and the heat dissipation plate joined by such ultrasonic sliding is 500 to 1000 g per 0.1 mm of lead width, and the strength for supporting the heat dissipation plate having a weight of about 1 to 10 g is as follows. It is enough.

The material of the lead frame and the heat dissipation plate is not particularly limited as long as it can be joined by ultrasonic sliding, and for example, copper and copper alloys, chromium, nickel, zinc, and alloys thereof can be used. Can be used. Further, as the insulating film, a conventionally used polyimide resin is suitable, but the insulating film is not limited to this.

[0021]

Embodiment 1 Hereinafter, a specific example of the present invention will be described with reference to the drawings. FIG.
Shows the case where the joint portion 7 of the ground lead 5b and the heat dissipation plate 2 is formed in the central portion of the outer peripheral edge and the inner peripheral edge of the frame-shaped insulating film 3.

In this case, for example, a rectangular radiator plate 2 made of copper and having a thickness of 0.20 mm is formed, and the rectangular radiator plate 2 is formed.
A frame-shaped insulating film 3 having a thickness of 0.025 mm and made of a polyimide resin whose outer peripheral edge has the same shape as the outer peripheral edge and whose inner central portion is cut as a semiconductor chip mounting portion is prepared. An adhesive is applied to both sides of the frame-shaped insulating film 3, and the heat dissipation plate 2 and the insulating film 3 are superposed so that their outer peripheral edges are aligned with each other and temporarily fixed.

Further, the lead frame 1 is aligned and placed on the insulating film 3, and the whole is integrated by thermocompression bonding. In the lead frame 1, all the leads 5 have the same shape, and the tips of the leads 5 are located on the inner peripheral edge of the insulating film 3. The lead frame 1 is made of copper and has a thickness of 0.15 mm.

Next, the heat dissipation plate 2, the insulating film 3 and the lead frame 1 which are laminated and thermo-compressed as described above are placed on the stage 9, and the ground lead 5b of the leads 5 of the lead frame 1 should be joined. Ultrasonic tool 1 on the point
0 was contacted and ultrasonically slid. As a result, the grounding lead 5b that was straight was bent at its contact portion with the ultrasonic tool 10 through the insulating film 3 and was bent, and was joined to the heat dissipation plate 2.

As the ground lead 5, an arbitrary lead is selected as the ground lead 5b according to the ground lead specifications of the semiconductor chip. Further, the frequency of ultrasonic sliding used in this joining was 40 KHz, and the amplitude was 10 μm, and the pressing force in the vertical direction by the ultrasonic tool 10 was 30 kg /
It was set to mm ² .

By this ultrasonic sliding, the lead frame with a heat sink shown in FIGS. 3 and 4 was obtained. Ground lead 5
The joint 7 between the heat radiating plate 2 and the heat radiating plate 2 is located between the inner peripheral edge and the outer peripheral edge of the insulating film 3.
The size of the tool surface is, for example, about 0.5 mm in length and width.

In this lead frame with a heat radiating plate, all the leads 5 can have the same shape, and any lead can be used as the ground lead 5b later according to the specifications of the semiconductor chip 4. Further, the heat radiating plate 2 does not need a joining projection. Therefore, if the semiconductor chip 4 has the same bonding pad position, the same lead frame 1 and heat sink 2 can be specified, so that the types of these can be small and it is very effective in cost reduction.

Embodiment 2 FIG. 2 shows a case where the joint 7 between the ground lead 5b and the heat sink 2 is formed near the outer peripheral edge or the inner peripheral edge of the frame-shaped insulating film 3.

In the case of the structure in which the joint portion 7 projects outside the outer peripheral edge of the insulating film 3, the outer peripheral edge of the heat dissipation plate 2 is formed to be larger than the outer peripheral edge of the insulating film 3, or as in the conventional case. A protrusion for joining may be provided on the outer peripheral edge of the. Further, in the case where the joint portion 7 has a structure protruding in the center direction from the inner peripheral edge of the insulating film 3, the shape of the heat dissipation plate 2 is formed so that the inner peripheral edge is larger than the inner peripheral edge of the insulating film 3.

In these cases as well, the ground lead 5b can be joined to the heat dissipation plate 2 by ultrasonic sliding similar to that of the first embodiment, but since the insulating film 3 does not exist between them, the ultrasonic wave is not used. The pressing pressure of the tool 10 is smaller than that in the first embodiment, and can be set to, for example, about 10 kg / mm ² .

When the joint portion 7 is on the outer peripheral edge or the inner peripheral edge of the insulating film 3 and in the vicinity thereof, the ground lead 5 is used.
The ultrasonic tools 10 are used to form the joints 7 of b.
Alternatively, the ground lead 5b can be bonded to the heat sink 2 by penetrating the insulating film 3 in the same manner as in the first embodiment.

In this case, similarly to the first embodiment, it goes without saying that all the leads 5 can have the same shape, and any lead can be adopted as the ground lead 5b later according to the specifications of the semiconductor chip.

[0033]

According to the present invention, by using ultrasonic sliding for joining the ground lead and the heat dissipation plate, oxidation or discoloration of the lead due to heat during joining does not occur and the oxide film on the metal surface is destroyed. Since they are joined together, the contact resistance at the joining interface can be made extremely small, and good quality and highly reliable joining can be achieved.

Moreover, since the grounding lead and the heat sink can be joined through the insulating film, it is not necessary to provide a joining projection on the outer peripheral edge of the heat sink and bend it into a crank shape as in the conventional case. The ground lead can also have the same shape as the other leads.

Therefore, even if the semiconductor chip has different ground lead specifications, the same lead frame is used if the bonding pad positions are the same, and the ground lead is determined from the leads according to the respective ground lead specifications. ,
It can be joined to a heat sink. In this way, the types of lead frames and heat sinks can be reduced, and the cost of lead frames with heat sinks can be significantly reduced by simplifying the manufacturing process.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing an embodiment of a method of manufacturing a lead frame with a heat sink according to the present invention.

FIG. 2 is a schematic cross-sectional view showing another embodiment of a method of manufacturing a lead frame with a heat sink according to the present invention.

FIG. 3 is a schematic plan view showing a main part of an embodiment of a lead frame with a heat dissipation plate according to the present invention.

FIG. 4 is a schematic sectional view showing an embodiment of a lead frame with a heat sink according to the present invention.

FIG. 5 is a schematic plan view showing a main part of a conventional lead frame with a heat sink.

FIG. 6 is a schematic cross-sectional view showing a conventional method for manufacturing a lead frame with a heat sink.

FIG. 7 is a schematic plan view showing a specific example of a conventional heat dissipation plate.

FIG. 8 is a schematic plan view showing a specific example of an insulating film.

[Explanation of reference symbols] 1 lead frame 2 heat sink 3 insulating film 4 semiconductor chip 5 lead 5a ground lead 5b ground lead 6 joining protrusion 7 joining portion 8 welding electrode 9 stage 10 ultrasonic tool

Claims (6)

[Claims] 1. A lead frame with a heat radiating plate integrally laminated by interposing a frame-shaped insulating film between the heat radiating plate and the lead frame, wherein a ground lead of the lead frame penetrates the insulating film to form the heat radiating plate. A lead frame with a heat sink characterized by being electrically joined. 2. The ground lead of the lead frame and all other leads have the same shape.
Lead frame with heat sink described in. 3. A method of manufacturing a lead frame with a heat radiating plate, wherein a frame-shaped insulating film is interposed between the heat radiating plate and the lead frame so as to be integrally laminated, while pressing an ultrasonic tool against the ground lead of the lead frame. A method for manufacturing a lead frame with a heat dissipation plate, characterized in that the grounding lead and the heat dissipation plate are electrically joined by ultrasonically sliding. 4. A method of manufacturing a lead frame with a heat radiating plate, wherein a frame-shaped insulating film is interposed between the heat radiating plate and the lead frame so as to be integrally laminated, while pressing an ultrasonic tool against the ground lead of the lead frame. A method for manufacturing a lead frame with a heat dissipation plate, characterized in that the ground lead and the heat dissipation plate are electrically joined by penetrating the insulating film by ultrasonic sliding. 5. All the leads of the lead frame have the same shape, and any one of these leads is bonded to a heat dissipation plate as a ground lead.
The method for manufacturing a lead frame with a heat sink according to claim 4. 6. The frequency of ultrasonic sliding is 15 to 80 KH.
z, and the amplitude of ultrasonic sliding is 1 to 50 μm, and the pressing force in the vertical direction by the ultrasonic tool is 0.01 to 10
It is 0 kg / mm ² , It is characterized by the above-mentioned 3-5.
A method for manufacturing a lead frame with a heat sink according to any one of 1.