JPH08125095A - Lead frame - Google Patents

Abstract

PURPOSE: To prevent the deflection of a lead to be increased in length in order to form a lead frame with an uncaulked heat sink. CONSTITUTION: A pattern is so formed as to extend leads 12 in the direction perpendicular to metallic strips 10. A heat sink 13 is disposed near one of the strips 10. The heat sink 13 is fixed to the strands 14 or tie bars 11 by a plurality of holders 14. Bents 17, 18 are provided at a ground lead 15 for coupling the heat sink 13 to the strips 10, and the part of the bar 11, and edge the end of the lead 12 is superposed above the heat sink 13 by the length consumed at the bents 17, 18. The lead 12 is not fixed to the other member except its root part, and coupled by a lead tie bar 30 for gathering the plurality of the leads 12. The root part of the lead 12 is connected to the strips 10 via the extended part 10a of the strips 10.

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 leads 3 instead of shifting the heat dissipation plate 4. That is, the heat radiating plate 4 is fixed to the frame, and the ground lead 5 is bent to overlap the lead 3 and the heat radiating plate 5.

[0006]

However, shifting the leads 3 means that the leads 3 can no longer be held on other parts of the frame except their roots. Since the lead 3 needs to have a length that overlaps with the heat dissipation plate 4 and a length that is exposed to the outside of the resin, a length of about 25 mm is required to match the above dimensions. Fixing such a long-sized lead only at the root portion has a drawback in that the lead tip portion is shaken, which also hinders the alignment in the assembly process.

Incidentally, Japanese Patent Publication Nos. 48-26427 and 4
Similar technologies are disclosed in Japanese Patent Publication No. 9-47982 and Japanese Patent Publication No. 49-36504, but both of them are made of a material having the same thickness, and are intended for a single transistor, and the number of pins is It is not intended for many integrated circuits. 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-mentioned conventional problems, and has a structure in which a lead is shifted by bending a part of a frame body and the tip of the lead is superposed on an upper portion of a heat dissipation plate. In the lead frame to be obtained, a plurality of leads are connected to each other by a lead tie bar, and a portion extending more than a required length as a lead is connected to a connecting strip by a flat plate-shaped expansion portion, thereby It is intended to provide a lead frame that prevents blurring.

[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 a plurality of leads are collectively connected to each other by the lead tie bar, it is possible to suppress the horizontal deviation of the leads. Furthermore, since the portion extending more than the required length as the lead is connected to the connecting strip by the flat expansion portion, it is possible to prevent the lead from becoming unnecessarily long,
The mechanical strength of the lead can be improved.

[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 13 is connected to the expanded portion 10a of the connecting strip 10, and the other end thereof 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.

2, the lead tie bar 30 extends orthogonally to the leads 12 and connects the leads 12 to each other. The adjacent tie bar 11 and the ground lead 15 are not connected. This is lead 12
This is because the position is shifted. That is, lead 1
The second group is not fixed to other members except that it is connected to the expanded portion 10a of the connecting strip at its root. Reference numeral 3
The ones are only close together. When the lead 12 is divided into a plurality of blocks due to the presence of the ground lead 15, the leads 12 are connected to each other in units of blocks divided by the ground lead 15. Lead 12
Can be connected with two or more, but in terms of strength 3
It is desirable to connect with blocks of more than one. If the ground lead 15 is not provided, all the leads 12 are connected in a straight line.

Although the lead tie bar 30 described above is not fixed to other members, it forms the plurality of leads 12 in a ladder shape, so that the leads 12 are much more mechanical than the leads 12 are independent of each other. Strength can be improved. Therefore, the deviation of the lead 12 occurs only in the tip portion of the lead 12 located on the heat dissipation plate 13 side of the lead tie bar 30, and this length is almost equal to the length accommodated in the resin. It is possible to prevent the blurring of the tip that causes a problem.

The ground lead 15 is the lead 1 after the completion of the device.
Since the same length as that required by 2 is required, the bent portion 17 of the ground lead 15 is provided farther than the required length. Along with this, lead 1
2 must extend longer than the required length. The greatest feature of the present invention resides in the expanded portion 10a of the connecting strip 10. That is, the required length of the lead 12 longer than necessary is not simply extended to connect the lead 12 and connected to the connecting strip 10, but the extension portion 1 of the connecting strip 10 formed in a flat plate shape.
By connecting to the connecting strip 10 via 0a, the lead 12 having a narrow width is prevented from being unnecessarily lengthened. As a result, the mechanical strength of the lead 12 can be improved as compared with the case where the lead 12 is simply extended, and the deviation of the lead 12 in the assembly process is prevented.

A method of manufacturing the lead frame will be described below with reference to FIGS. 3 and 4. FIG. 3A is a plan view showing the material before pattern formation, and FIG. 3B is a plan view immediately after forming the pattern by punching or etching. FIG. 4A is a cross-sectional view in the state of FIG.
4B is a cross-sectional view showing a state after 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.

3 (A) and 4 (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. Referring to FIG. 3B, since the bending processes 17 and 18 are not performed immediately after the pattern is formed, the tip portions of the leads 12 do not overlap the heat dissipation plate 13. The thick portion 21 exactly coincides with the position of the heat dissipation plate 13.

From the state shown in FIG. 3B, the holding portion 14 is first bent. By this processing, as shown in FIG. 4B, 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. 4C. 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.

Further, since a large number of leads 12 are reinforced by the lead tie bars 30 and further connected to the expanded portion 10a of the connecting strip 10, the mechanical strength of the leads 12 is increased and the leads associated with the bending processes 17 and 18 are increased. There is no shake. The method of manufacturing a semiconductor device using the above lead frame is as follows. FIG. 5 is a plan view showing the semiconductor device after completion. First, the ceramic substrate 23 on which circuit elements such as transistors are mounted is fixed to the mounting portion 19 of the heat sink 13, and the bonding pads and leads 12 on the ceramic substrate 23 are fixed.
The tip portion of the heat-radiating plate 13 is wire-bonded with the bonding wire 24, and the main portion of the resin 2
Mold at 5.

The above-mentioned molding step is performed by setting the lead frames in the upper and lower molds having the same space as the outer shape of the resin 25 and injecting the resin into the space of the mold. A dam matching the space is arranged between the leads 12. The dam is provided integrally with the upper mold or the lower mold, and its surface is in close contact with the surface of the other mold. Normally, the gap between the dam and the lead 12 cannot be completely zero, and resin leakage usually occurs. By arranging the lead tie bar 30 near the resin 25, the lead tie bar 30 also has a function of stopping the resin leakage. The lead tie bar 30 is tightly sandwiched by the upper and lower molds.

After the molding step, unnecessary portions of the lead frame are cut off to separate the individual semiconductor devices. The portion to be cut is the holding portion 14 and the lead tie bar 3
0, and the tip portions of the lead 12 and the ground lead 15. Although connected by the extension part 10a, the extension part 10
It goes without saying that the smaller the length of a in the vertical direction of the drawing, the greater the strength. Further, there is a problem even if the ground lead 15 becomes unnecessarily long. Furthermore, it is difficult to cut at the bent portion 17 of the ground lead 15. For these reasons, the lead 12 is connected to the expansion portion 10a (see FIG. 2).
The chain line 22a) is cut. Ground lead 15 is lead 1
Cut at the same position as the cutting position of 2. Folding part 17,
If the bent portions 17 and 18 are folded within the expanded portion 10a of the connecting strip after forming 18, the ground lead 15 can be easily cut, and the lead 12 and the ground lead 1 can be easily cut.
The mechanical strength of 5 can be maximized. The ground lead 15 is used to apply the ground potential GND, and at the same time as applying the ground potential to the circuit, it also applies the ground potential to the heat sink 13 to expect a shielding effect.

In the above-mentioned embodiment, an example in which the ceramic substrate 23 is mounted is shown.
It is obvious that it can also be applied to ICs such as molds. In this case, instead of the ceramic substrate 23, a silicon semiconductor chip whose elements have been formed is die-bonded to the mounting portion 19,
The steps after die bonding are the same as above.

[0025]

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 in accordance with the present invention, a plurality of leads 1
Since the two are connected by the lead tie bar 30, there is an advantage that the mechanical strength of the lead 12 can be increased and the blurring of the lead 12 can be prevented when the bent portions 17 and 18 are formed and in the assembly process. Moreover, by arranging the lead tie bar 30 near the resin 25, the mechanical strength can be improved, and at the same time, a function of stopping the resin leakage can be provided.

Further, according to the present invention, since the lead 12 is connected to the connecting strip 10 via the expansion portion 10a, the lead 12 having a narrow width is not unnecessarily extended, and therefore the mechanical strength of the lead 12 is improved. It also has the advantage that

[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 plan view for explaining the present invention.

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

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

FIG. 6 is a plan view for explaining a conventional example.

Claims (2)

[Claims] 1. A connecting strip extending in parallel, a tie bar extending in a direction orthogonal to a direction in which the connecting strip extends, a heat radiating plate for fixing a circuit element, and the heat radiating plate. And a holding portion for holding the connecting strips or tie bars at a plurality of positions and bending the surface to make the surface of the heat sink uneven, and overlapping one end with a space above the heat sink. A plurality of leads whose ends are held by the connecting strips and extend parallel to each other; and a ground lead which extends in parallel with the leads and has one end held by the heat dissipation plate and the other end held by the connecting strips. The tie bar and the ground lead are bent at a portion close to the connection strip, and the distance between the connection strips is reduced by the length consumed by the bending, and the tip of the lead is The plurality of leads are overlapped with the heat sink. The other end of the lead is divided into a plurality of blocks by a ground lead, is not held by other members except the other end portion, and is connected to each other by a lead tie bar at a position where it does not overlap with the heat dissipation plate. Is connected to an expansion portion of the flat connecting strip. 2. The lead frame according to claim 1, wherein a root portion of the lead and a bent portion of the ground lead are positionally aligned with each other.