JPH08139253A - Manufacture of lead frame and semiconductor device - Google Patents

Abstract

PURPOSE: To provide a lead frame with a heat sink without any caulking, which maintain adequate adhesion with resin. CONSTITUTION: A pattern is formed so that a lead 12 is extended in a direction crossing thin connection lines 10. A heat sink 13 is laid out closer to one of the interlocking thin lines 10. The heat sink 13 is fixed to either the thin connection lines 10 or a tie bar 11 by a plurality of retention parts. A grounding lead 15 for connecting a heat sink 13 and thin lines 10 and one portion of the tie bar 11 are subjected to bending, thus enabling the tip of the lead 12 to be superposed to an area above the heat sink 13 by the length used for binding. A shearing machining part is provided to create a protrusion by exposing the material of the heat sink 13 at a boundary 23 between a thick part 20 and a thin part 21 on the reverse side of the heat sink 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead frame having a heat sink and a method for manufacturing a semiconductor device.

[0002]

2. Description of the Related Art A semiconductor device called a video pack (trade name) in which deflection circuits such as TV, HDTV, and CRT are integrated has been commercialized by the present applicant. Although a ceramic substrate to which semiconductor elements and other components are fixed is housed in a single package, the product is supplied by resin molding as a natural aim of cost reduction. Further, a method of using a lead frame like other semiconductor devices so as to be easily put into a manufacturing line is disclosed in, for example, Japanese Patent Laid-Open No. 6-163.
No. 786.

Referring to FIG. 7, 1 is two connecting strips, 2
Is a tie bar, one end of the lead 3 is connected to the tie bar 2, and the other end of the lead 3 is superposed on the heat sink 4 and bent to a part of the ground lead 5 for holding the heat sink 4 on the tie bar 2. By providing the portion 6, the tip portion of the lead 3 is superposed on the heat dissipation plate 4. D with heat sink
The IP type and SIP type lead frames process heat sinks from thick plates, and other parts from thin plates.
In contrast to joining by caulking, the above method is for processing from a single deformed material having a thick part and a thin part,
It has the advantage of being able to reduce costs.

However, moving the heat sink 4 with respect to the position of the tie bar 2 requires that the heat sink 4 be held by two ground leads 5. If the heat radiating plate 4 is made up of a thin wall portion, it is still necessary to make the heat radiating plate 4 at a thick wall portion because it is necessary to give the heat radiating plate 4 a heat capacity of a certain amount or more. Therefore, for example, when the heat radiation plate 4 having a size of 25 × 12 mm is formed, the weight of the heat radiation plate 4 causes the heat radiation plate 4 to move to the left and right, which makes it impossible to perform accurate alignment in the assembly process. There may still be thick leads for discrete type power semiconductor devices, but if a lead width of, for example, about 0.5 mm is required for integrated circuits, fixing the heat sink 4 becomes almost impossible.

Therefore, the applicant of the present application proposes to shift the lead 3 instead of shifting the heat radiating plate 4, although it is not yet known. That is, the heat radiating plate 4 is fixed to the frame, and the ground lead 5 and a part of the frame body are bent to overlap the lead 3 and the heat radiating plate 4.

[0006]

FIG. 8 shows a cross-sectional view of a resin-molded device formed as described above. The lead frame is plated with metal such as nickel and has excellent weather resistance, and the parts corresponding to the circuit element mounting part of the heat sink 4 and the wire bonding area of the lead 3 are plated with silver. The metal plating with excellent adhesiveness is applied. After such metal plating is applied, the plate material is processed to manufacture a lead frame.

By the way, the nickel plating has a problem that the adhesion to the mold resin 6 is poor, and moisture or the like often enters from the interface between the resin 7 and the heat dissipation plate 4 to lower the reliability of the element. In the lead frame using the above-mentioned caulking, since the heat sink is processed after plating, the material is entirely exposed at the end faces of the heat sink, and the problem of weak adhesion with the resin does not occur. However, since the lead frame to be obtained by the present inventor is processed from a deformed material composed of a thick plate and a thin plate, a portion where the end surface 8 of the heat dissipation plate 4 remains covered with the nickel plating is inevitably generated. . The material is exposed on the end surface 10 of the thin portion 9, but the plate thickness cannot be increased due to restrictions such as bending after forming the lead frame and reducing the lead pitch. Therefore, there was a drawback that it was not possible to obtain a strong adhesion with the resin 7 and the moisture resistance was poor. It is similar to JP-B-48-26427, JP-B-49-47982 and JP-B-49-36504. Although the technology of is published, both are formed from materials with the same thickness,
The target is a single transistor, not an integrated circuit having a large number of pins. Small size and thick lead. Therefore, it is presumed that sufficient strength is obtained even if the lead is held only at the root part.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems of the prior art, in which a heat dissipation plate made of a thick plate is held in a frame made of a thin plate at a plurality of points and a part of the frame is bent. It is a lead frame to obtain a structure in which the tip of the lead is overlapped with the upper part of the heat sink by shifting the lead with, and the end face of the heat sink coated with metal plating is subjected to shirring processing to expose the material of the heat sink. It is characterized by

[0009]

According to the present invention, since the lead tips and the heat radiating plate are superposed on each other by not moving the heat radiating plate but moving the connecting strips in position, a plurality of heat radiating plates are formed. It can be fixed to the connecting strips or tie bars in place. Therefore, it is possible to prevent the shake due to the weight of the heat sink.

Further, since the material is exposed on the end surface of the heat dissipation plate by the shirring process to form the projections, the adhesion with the resin can be increased.

[0011]

An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a plan view showing a lead frame of the present invention. In the figure, 10 is two connecting strips extending in parallel, 11 is a tie bar connecting the connecting strips 10 to a ladder strip, and 12 is a direction orthogonal to the connecting strips 10, that is, parallel to the tie bar 11. A plurality of extending leads for external connection, 13 is a heat sink for fixing circuit elements to the surface, 14 is a connecting strip 10 or tie bar 1 for connecting the heat sink 13.
1 is a holding portion for fixing to 1, 1 is a ground lead for connecting the heat radiating plate 13 and the connecting strip 10, and 16 is a feed hole for feeding a lead frame. One heat radiating plate 13 and components attached thereto are made into one unit, and a large number of these units are connected in the lateral direction to form a lead frame. Connection strip 1
0 and the tie bar 11 constitute a frame body of the lead frame.

The heat dissipation plate 13 is a part 11 of the adjacent tie bar 11.
It is made of a thick plate having a plate thickness of about 2 mm together with a, and the other parts are machined from a thin plate having a plate thickness of about 0.3 mm. Heat sink 1
3 is a heat sink 1 by bending the holding portion 14.
The surface of No. 3 is processed to be lower than the surface of the connecting strip 10 in the height direction. Similar processing is also applied to a part 11a of the adjacent tie bar. The adjacent tie bar 11a may be omitted. Further, the same processing as the holding portion 14 is also applied to the connecting portion between the ground lead 15 and the heat dissipation plate 13.

One end of the lead 12 is connected to the expanded portion 10a of the connecting strip 10, and the other end is superposed on the heat radiating plate 13. Thus, the tip portion of the other end is brought close to the bonding pad for connection of the element fixed to the surface of the heat dissipation plate 13 to enable wire bonding. The ground lead 15 is directly connected to the connection strip 10 without providing the expansion portion 10a. Then, the ground lead 15 is bent 17 in a region corresponding to the expanded portion 10a, and the connecting strip 10 and the lead 12 are shifted to the heat radiating plate 13 side by the amount consumed by the bending. Similar bending process for tie bar 11 1
8 has been given. The grounding lead 15 and the tie bar 11 to which the bending processes 17 and 18 are formed are thin portions. Bending 17,
The shape of 18, that is, whether the cross-sectional shape is U-shaped or Z-shaped is arbitrary. Other examples include U-shape and Ω-shape. However, since the connecting strip 10 is provided with the feed hole 16, after the bending, the distance between the two connecting strips 10 is within a certain allowable error range, and the bending process 1
It is a condition for carrying out the manufacturing process that the levelness of the lead frame is maintained except for the portions 7 and 18.
Reference numeral 19 on the heat sink 12 indicates a circuit element mounting portion, and in this embodiment, a ceramic substrate on which the circuit element is mounted is mounted. Although two ground leads 15 are shown as examples, one or three or more ground leads 15 may be provided. Further, the ground lead 15 does not exist, and the bending process 18 of the tie bar 11 is performed.
Good as only.

A method of manufacturing the lead frame will be described below with reference to FIGS. 2 and 3. 2A is a plan view showing the material before pattern formation, and FIG. 2B is a plan view immediately after forming the pattern by punching or etching. FIG. 3A is a cross-sectional view in the state of FIG.
FIG. 3B is a cross-sectional view showing a state in which the holding portion 14 is bent after the pattern is formed, and FIG.
8 is a cross-sectional view in a state where 8 is applied.

2 (A) and 3 (A), the material before processing is a thin portion 20 having a plate thickness of about 0.5 mm and a plate thickness of about 2.
It is a plate-shaped material composed of a 0 mm thick portion 21 and one surface of which forms a horizontal surface. The thick portion 21 extends in the lateral direction of the drawing with a constant width. The entire surface of the material is metal plated, such as nickel plated. Figure 2 (B)
As shown in FIG. 10, since the bending processes 17 and 18 are not performed immediately after the pattern formation, the tip end portion of the lead 12 has a heat dissipation plate 13
Does not overlap with. The thick portion 21 exactly coincides with the position of the heat dissipation plate 13. The long side 13a of the heat sink 13 is cut by the thin portion 20, and the short side 13b of the heat sink 13 is cut by the thick portion 13b.

From the state shown in FIG. 2B, first, the holding portion 14 is bent. By this processing, as shown in FIG. 3B, the heat dissipation plate 13 is stepped in the height direction with the surface of the connecting strip 10. Reference numeral 22 is the ground lead 15 and the connecting strip
The connecting part with 0 is shown. After the heat radiation plate 13 is stepped, the ground lead 15 near the connecting portion 22 is bent 17 as shown in FIG. 3 (C). The bending process 18 for the tie bar 11 is simultaneously performed at the same position. As a result, the leads 12 and the connecting strips 10 are integrally shifted by the length consumed by the bending processes 17 and 18 toward the heat dissipation plate 13, and the tip portions of the leads 12 overlap the heat dissipation plate 13. The result of superposition becomes the state shown in FIG. Bending process 1
The areas used for Nos. 7 and 18 are shown by the shaded areas in FIG. Although depending on the processing shape, the bending process 17 can be provided with a length that is about twice the length of the expanded portion 10a of the connecting strip in the vertical direction in the drawing.

The lead frame formed as described above is
Since one of the connecting strips 10 is shifted,
The heat dissipation plate 13 can be held on the lead frame by the holding portions 14 at a plurality of positions. Therefore, even if the heat radiating plate 13 has a considerable weight, it can be firmly held, and it does not hinder the alignment such as pattern recognition in the assembly process. Moreover, since there is no "caulking" and it can be processed from a single plate-shaped material, the merit of being able to manufacture at low cost can be maintained.

FIG. 4 is a plan view of the lead frame seen from the back surface, that is, the side opposite to the surface on which the elements are mounted. Since the long side 13a of the heat dissipation plate 13 is cut by the thin part 21 and the short side 13b of the heat dissipation plate 13 is cut by the thick part 20, the long side 13a of the heat dissipation plate 13 is formed in parallel with the thick part. A boundary portion 23 between the thin portion 20 and the thin portion 21 extends. Then, the shearing portion 24, which is the greatest feature of the present invention, is formed on the boundary portion 23. The shearing portion 24 is formed over substantially the entire length of the long side 13a except for the intersection with the short side 13b. Further, as shown in the figure, it may be separated into a plurality of places.

FIG. 5 is an enlarged perspective view showing the shearing portion 24. The surface of the heat dissipation plate 13 is covered with the nickel plating layer 25, and the material of the lead frame is exposed at the portion cut after plating. The short side 13b of the heat sink 13,
The end of the thin portion 21 of the long side 13a corresponds to the exposed surface of the material. The shirring processing portion 24 is performed in the step shown in FIG. 2B, and performs processing for plastically deforming the material from above the boundary portion 23. By this processing, the material of the heat radiating plate 13 is partially exposed, and since it is a plastic deformation, the crushed material is extruded to form the protrusion 26. The exposed parts of the material are shown by hatching.

A method of manufacturing a semiconductor device using the above lead frame is as follows. FIG. 6 is a sectional view showing the completed semiconductor device. First, the mounting portion 19 of the heat sink 13
A ceramic substrate on which a circuit element such as a transistor is mounted is fixedly attached, and the bonding pad on the ceramic substrate (not shown) and the tip portion of the lead 12 are wire-bonded with a bonding wire so that the back surface of the heat sink 13 is exposed. The main part is molded with resin 7. After that, the device is completed by cutting off unnecessary portions of the lead frame.

Since the heavy heat dissipation plate 13 is firmly held by the frame body, the semiconductor device according to the present invention can be manufactured inexpensively without causing any trouble in the assembly process. And according to the present invention, the boundary portion 23 of the heat dissipation plate 13
Since the shirring portion 24 is applied to expose the surface of the material and the protrusion 26 is formed, the adhesive force with the resin 7 increases at this portion. Therefore, it is possible to prevent the entry of water from the interface between the heat dissipation plate 13 and the resin 7, prevent the resin from peeling and improve the moisture resistance.

Although the above embodiment has shown the example in which the ceramic substrate 3 is mounted, it is obvious that it can be applied to a DIP type or SIP type IC having a heat radiating plate. In this case, instead of the ceramic substrate, the silicon semiconductor chip after the element formation is die-bonded to the mounting portion 19, and the steps after the die-bonding are the same as above.

[0023]

As described above, according to the present invention,
Since one of the connecting strips 10 is shifted,
The heat dissipation plate 13 can be held on the lead frame by the holding portions 14 at a plurality of positions. Therefore, even if the heat radiating plate 13 has a considerable weight, it can be firmly held, and it does not hinder the alignment such as pattern recognition in the assembly process. Moreover, since there is no "caulking" and it is possible to process from a single plate-shaped material, the merit of being able to manufacture at low cost can be maintained.

Further according to the present invention, the shirring process 2
Since the adhesive strength to the resin can be increased by 4, the resin peeling can be prevented and the moisture resistance can be improved. As a result, the plate thickness of the thin portion 21 can be made thin, and there is also an advantage that the lead pitch can be made finer and the ease of cross processing can be maintained.

[Brief description of drawings]

FIG. 1 is a plan view for explaining the present invention.

FIG. 2 is a plan view for explaining the present invention.

FIG. 3 is a cross-sectional view for explaining the present invention.

FIG. 4 is a back view for explaining the present invention.

FIG. 5 is a perspective view for explaining the present invention.

FIG. 6 is a cross-sectional view for explaining the present invention.

FIG. 7 is a plan view for explaining a conventional example.

FIG. 8 is a cross-sectional view for explaining a conventional example.

Claims (2)

[Claims] 1. A frame, a heat radiating plate for fixing circuit elements, and a radiating plate for holding the heat radiating plate at a plurality of points on the frame and bending the surface to make the surface of the heat radiating plate uneven. And a plurality of leads, one end of which overlaps the upper portion of the heat dissipation plate with a space in between, and the other end of which is held by the frame body and extends in parallel with each other. A lead frame which is bent and overlaps with the heat radiating plate by shifting the leads by the length consumed by the bending, wherein the lead frame is made of a deformed material composed of a thick plate and a thin plate, and the thick plate portion. And the back side of the heat sink is coated with metal plating, and the end face of the heat sink is shirred to expose the material of the heat sink and to form a protrusion by the material. Characterized by being Lead frame that. 2. A frame, a heat radiating plate for fixing circuit elements, and a heat radiating plate which is held on the frame at a plurality of points and is bent so that the surface of the heat radiating plate is uneven. And a plurality of leads, one end of which overlaps the upper portion of the heat dissipation plate with a space in between, and the other end of which is held by the frame body and extends in parallel with each other. A lead frame which is bent and overlaps with the heat radiating plate by shifting the leads by the length consumed by the bending, wherein the lead frame is made of a deformed material composed of a thick plate and a thin plate, and the thick plate portion. And the back side of the heat sink is coated with metal plating, and the end face of the heat sink is shirred to expose the material of the heat sink and to form a protrusion by the material. The lead flare And fixing the semiconductor element on the heat sink, wire bonding, and resin molding so as to expose the back surface of the heat sink and seal the shirring portion and the protrusion inside. Of manufacturing a semiconductor device.