JP2798891B2 - Lead frame and method of manufacturing semiconductor device - Google Patents

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 of 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 a TV, HDTV, and CRT are integrated has been commercialized by the present applicant. Although a ceramic substrate to which a semiconductor element or the like is fixed is housed in one package, products are supplied by resin molding as a natural aim of reducing costs. Also, a method using a lead frame as in other semiconductor devices so as to be easily put into a manufacturing line is disclosed in, for example, Japanese Patent Application Laid-Open No. 6-163.
No. 786.

Referring to FIG. 5, reference numeral 1 denotes two connecting strips;
Is a tie bar, one end of the lead 3 is connected to the tie bar 2, the other end of the lead 3 is superimposed on the heat sink 4, and is bent into a part of a 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 overlapped with the heat sink 4. D with heat sink
IP type and SIP type lead frames process heatsinks from thick plates, and process other parts from thin plates.
In contrast, the above method is to process from a single deformed material having a thick part and a thin part,
It has the merit that cost can be reduced.

[0004]

However, moving the radiator plate 4 with respect to the position of the tie bar 2 necessitates holding the radiator plate 4 with two ground leads 5. If the radiator plate 4 is composed of a thin portion,
Since it is necessary to provide the heat radiating plate 4 with a heat capacity of a certain amount or more, it is an absolute condition that the heat radiating plate 4 is constituted by a thick portion. For this reason, when the heat radiating plate 4 having a size of, for example, 25 × 12 mm is formed, the heat radiating plate 4 is displaced right and left due to its weight, and there is a disadvantage that accurate positioning cannot be performed in the assembling process. Thick leads for discrete power semiconductor devices are still possible, but if a lead width of, for example, about 0.5 mm is required for an integrated circuit, the fixing of the heat sink 4 becomes almost impossible.

Incidentally, Japanese Patent Publication No. 48-26427 and Japanese Patent Publication No. Sho 4
Similar technologies are disclosed in Japanese Patent Application Publication No. 9-47982 and Japanese Patent Publication No. 49-36504, but all of them are formed of a material having the same thickness and are also intended for a single transistor. It is not intended for many integrated circuits. For this reason, the chip mounting portion is held at one or two points, and it can be considered that these small-sized components do not cause blurring when mounting the chip.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and has an arrangement in which the leads extend in a direction perpendicular to the extending direction of the connecting strips, and The connecting strip and the tie bar are fixed at a plurality of places, and the ground lead and the tie bar are simultaneously bent to form an overlapping portion between the lead tip and the heat sink.

[0007]

According to the present invention, the heat radiation plate is not moved, but the connecting strip is moved in position to form the overlapping portion of the lead tip and the heat radiation plate. It can be fixed to a connecting strip or tie bar at a point. Therefore, it is possible to prevent blurring due to the weight of the heat sink.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a plan view showing a lead frame of the present invention. In the figure, reference numeral 10 denotes two connecting strips extending in parallel, 11 a tie bar connecting the connecting strips 10 to a ladder strip, and 12 a direction perpendicular to the connecting strips 10, that is, parallel to the tie bar 11. A plurality of external connection lead groups, 13 is a heat radiating plate for fixing circuit elements on the surface, 14 is a heat radiating plate 13 connecting the connecting strip 10 or tie bar 1.
Reference numeral 15 denotes a grounding lead for connecting the heat radiating plate 13 to the connecting strip 10, and 16 denotes a feed hole for feeding a lead frame. One heat radiating plate 13 and parts attached to the heat radiating plate 13 constitute one unit, and a large number of such units are connected in a horizontal direction to form a lead frame.

The radiator plate 13 is a part 11 of the adjacent tie bar 11.
a is formed of a thick plate having a thickness of about 2 mm, and the other portions are processed from a thin plate having a thickness of about 0.3 mm. Heat sink 1
3 is a heat sink 1 by bending the holding portion 14.
3 is processed so as to be one step lower in the height direction than the surface of the connecting strip 10. A part 11a of the adjacent tie bar is also subjected to the same processing. The adjacent tie bar 11a may not be provided. The connection between the ground lead 15 and the radiator plate 13 is also processed in the same manner as the holding portion 14.

One end of the lead 13 is connected to the extension 10 a of the connecting strip 10, and the other end of the lead 13 overlaps the heat sink 13. Thus, the wire bonding can be performed by bringing the tip portion of the other end close to the connection bonding pad of the element for fixing to the surface of the heat radiating plate 13. The grounding lead 15 is directly connected to the connecting strip 10 without providing the extension 10a. The ground lead 15 is bent in a region corresponding to the extension 10a, and the connecting strip 10 and the lead 12 are shifted toward the heat sink 13 by the amount consumed in the bending. Since the shift cannot be performed only by the bending 17 of the ground lead 15, the tie bar 11 is also bent at the portion corresponding to the bending 17. The ground lead 15 to be bent 17 and 18 and the tie bar 11 are formed of thin portions. The shape of the bending processes 17 and 18, that is, whether the cross-sectional shape is U-shaped or Z-shaped is arbitrary. Other examples include a U-shape and an Ω-shape. However, connecting strip 1
Since the feed hole 16 is provided in the lead frame 0, the distance between the two connecting strips 10 after bending is within a certain allowable error range. Maintaining the levelness is a condition for performing the manufacturing process. In addition, the code | symbol 1 on the heat sink 12
Reference numeral 9 denotes a circuit element mounting portion. In this embodiment, a ceramic substrate on which the circuit element is mounted is mounted. Although two ground leads 15 have been described, one or three or more ground leads 15 may be provided.

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

Referring to FIGS. 2A and 3A, the material before processing is a thin portion 20 having a thickness of about 0.5 mm and a thickness of about 2.
It is a single plate-like material that is composed of a thick part 21 of 0 mm and has one surface forming a horizontal plane. The thick portion 21 extends at a constant width in the horizontal direction in the drawing. Referring to FIG. 2 (B), since the bending processes 17 and 18 are not performed immediately after the pattern is formed, the tip of the lead 12 does not overlap with the heat sink 13. The thick portion 21 exactly matches the position of the heat sink 13.

From the state shown in FIG. 2B, first, a bending process is performed on the holding portion 14. By this processing, as shown in FIG. 3B, a step in the height direction with respect to the surface of the connecting strip 10 is performed. Reference numeral 22 indicates a connecting portion between the ground lead 15 and the connecting strip 10. After the heat sink 13 is stepped, FIG.
As shown in (C), the grounding lead 15 near the connecting portion 22
Is subjected to bending processing 17. Bending 18 to tie bar 11
Are applied simultaneously at the same position. As a result, bending process 1
The lead 12 and the connecting strip 10 are integrally shifted to the heat radiating plate 13 by a length corresponding to the length consumed in the steps 7 and 18, and the leading end of the lead 12 overlaps the heat radiating plate 13. The result of the superposition is as shown in FIG. The regions to be subjected to the bending processes 17 and 18 are shown by hatched portions in FIG. Although it depends on the processing shape, it is possible to provide the bending process 17 with a length that is approximately twice the length of the expanded portion 10a of the connecting strip.

The lead frame formed as described above is
Since one of the connecting strips 10 was shifted,
The heat radiating plate 13 can be held on the lead frame by a plurality of holding portions 14. Therefore, even if the heat radiating plate 13 has a considerable weight, it can be held firmly, and there is no hindrance to positioning such as pattern recognition in the assembling process. In addition, since there is no "caulking" and processing can be performed from a single plate-like material, the advantage of inexpensive manufacturing can be maintained.

A method for manufacturing a semiconductor device using the above lead frame is as follows. FIG. 4 is a plan view showing the completed semiconductor device. First, the mounting portion 19 of the heat sink 13
A ceramic substrate 23 on which a circuit element such as a transistor is mounted is fixed, and a bonding pad on the ceramic substrate 23 and a tip end of a lead 12 are wire-bonded with a bonding wire 24 so that the back surface of the heat sink 13 is exposed. The part is molded with a resin 25, and unnecessary portions of the lead frame are cut off to separate the semiconductor device into individual semiconductor devices. The lead 12 is connected to the extension 10a (see FIG. 1).
In FIG. 22a). Ground lead 15 is lead 1
Cut at the same position as the cutting position of 2. Since it is not easy to cut at the bent portion 17, if the bent portions 17, 18 are folded within the extension 10a of the connecting strip after forming the bent portions 17, 18, the ground lead 15 is cut. Is easy. The ground lead 15 is used to apply the ground potential GND, and applies the ground potential to the circuit board at the same time as the circuit board.

Although the above embodiment shows an example in which the ceramic substrate 23 is mounted, a DIP type having a heat sink, a SIP
Obviously, the present invention can be applied to an IC such as a mold. In this case, instead of the ceramic substrate 23, a silicon semiconductor chip on which element formation has been completed is die-bonded to the mounting portion 19,
The steps after die bonding are the same as above.

[0017]

As described above, according to the present invention,
Since one of the connecting strips 10 was shifted,
The radiator plate 13 can be held on the lead frame by a plurality of holding portions 14. Therefore, even if the heat radiating plate 13 has a considerable weight, it can be held firmly, and there is no hindrance to positioning such as pattern recognition in the assembling process. In addition, since there is no "caulking" and processing can be performed from a single plate-like material, the advantage of inexpensive manufacturing can be maintained.

[Brief description of the 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 plan view for explaining the present invention.

FIG. 5 is a plan view for explaining a conventional example.

Claims (3)

(57) [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 radiator plate for fixing a circuit element, and the radiator plate A holding portion for holding the connecting strip or tie bar at a plurality of locations and bending the surface of the radiating plate to be stepped, and one end overlapping the upper portion of the radiating plate with a space therebetween. A plurality of leads whose ends are held by the connecting strip and extend in parallel with each other, and a ground lead that extends in parallel with the lead and has one end connected to the heat sink and the other end connected to the connecting strip. These are processed from a single deformed material consisting of a thick portion and a thin portion, and the radiator plate is processed from the thick portion, and the connecting strip, lead, tie bar, and ground are provided. The lead is processed from the thin portion, and the ground lead and the Bent at a portion where the Iba are close to the connecting strip, the lead frame min only the lead tip of the length consumed by bending said is characterized in that it overlaps with the radiator plate. 2. A deformed material comprising a thick portion and a thin portion is prepared, and a connecting strip extending in parallel from the deformed material and a direction in which the connecting strip extends are orthogonal to each other. A tie bar extending in the direction of the heat sink, a heat sink for fixing circuit elements, a holding portion for holding the heat sink at the connecting strip or the tie bar at a plurality of locations, and one end having a space above the heat sink. A plurality of leads which are overlapped with each other and the other ends of which are held by the connecting strip and extend in parallel with each other; and one end of which is parallel to the leads and one end of which is connected to the heat sink and the other end of which is connected to the connecting strip. A lead frame including a ground lead, wherein the heat sink is processed from the thick portion,
The lead, the tie bar, and the grounding lead are processed from the thin portion, and the holding portion is bent to form a surface of the heat radiating plate so as to be stepped relative to a surface of the connecting strip. The grounding lead and the tie bar Are bent at a portion close to the connecting strip, and the tip of the lead is overlapped with the heat sink by the length of the bent and consumed, and the distance between the connecting strips is reduced by the consumed length. The circuit element is fixed to the surface of the heat sink, the main part is resin-molded, and the bent part of the tie bar and the ground lead is cut off to connect the molded heat sink with the lead and the ground lead. A method for manufacturing a semiconductor device, comprising: 3. The lead frame according to claim 1, wherein the heat radiating plate has a rectangular shape and is connected to the connecting strip or tie bar by the holding portions at four corners. Of manufacturing a semiconductor device.