JP2005019545A - Lead frame with heat sinking plate and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lead frame with a heat sinking plate, which copes with a size reduction in a semiconductor device, restrains cracks from occurring in sealing resin, and is excellent in adhesion property to the sealing resin. <P>SOLUTION: The lead frame 10 is equipped with the heat sinking plate 11 provided with a protruding overhang 19 which is provided around its circumference or a part of its circumference at a middle point in the direction of thickness of the heat sinking plate 11. The method of manufacturing the lead frame 10 is also provided. The circumference of the heat sinking plate 11 is partially crushed with a crushing punch 30 provided with a back guide 30a to form the overhang 19. The bottom 20 of the overhang 19 is preferably roughened, and the tip of the overhang 19 is subjected to blunting processing. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a lead frame used in a semiconductor device, and more particularly to a lead frame with a heat sink and a method for manufacturing the same.
[0002]
[Prior art]
In order to prevent the semiconductor device from becoming high temperature during use due to high functionality, high integration, high-speed operation, etc., and preventing the function of the semiconductor element from deteriorating, a heat radiating means for releasing generated heat to the surroundings is provided. As this heat dissipation means, for example, when a heat sink is attached to a lead frame and a semiconductor element is mounted and resin sealing is performed, this heat sink is exposed from the bottom surface of the semiconductor device to improve heat dissipation. Has been proposed.
[0003]
In recent years, semiconductor devices are required to be miniaturized, and resin-encapsulated semiconductor devices (semiconductor packages) are manufactured as close to the semiconductor chip size as possible. For this reason, even in a semiconductor device in which a semiconductor chip is mounted on a lead frame with a heat sink, the resin seal is formed slightly larger than the plane of the heat sink, and as with conventional semiconductor devices, heat dissipation is performed. The bottom of the plate is exposed.
Although the heat radiating plate is made of copper, copper alloy or the like having excellent heat conductivity, since the adhesiveness with the sealing resin is not sufficient, it is described in, for example, Patent Document 1 in order to prevent resin peeling and the like. In addition, there is one in which an overhang portion is formed around the heat sink covered with resin.
[0004]
[Patent Document 1]
Japanese Patent Publication No.55-23463 (Fig. 1)
[0005]
[Problems to be solved by the invention]
This overhang is formed by crushing a part of the outer peripheral edge of the heat sink with a mold device, but if the width of the crushed part is large, the shape of the overhang will be stable, but at the end of the overhang In addition, there is a problem that the heat sink has a large planar size and cannot be adapted to miniaturization of a semiconductor device.
In addition, if the width of the crushed part is small, the shape of the overhang is not stable and warping occurs, and the tip of the warping is sharp, sharply cracked (mold crack) in the resin package formed by resin sealing. There is a problem that contributes to the occurrence.
SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and a lead frame with a heat sink having no problem as described above, and a lead frame with a heat sink having excellent adhesion to a sealing resin and a method for manufacturing the same. The purpose is to provide.
[0006]
[Means for Solving the Problems]
The lead frame with a heat sink according to the first invention that meets the above-mentioned object is a lead frame with a heat sink provided with a heat sink in which a protruding portion is formed at an intermediate position in the thickness direction of the entire circumference or a part of the circumference. And the blunting process is performed at the front-end | tip of the said overhang | projection part, and the protrusion length is controlled. As a result, it is possible to prevent cracks from entering the sealing resin due to the wedge action caused by the tip of the overhanging portion. Further, the semiconductor device can be downsized by restricting the protruding length of the overhanging portion.
[0007]
Moreover, the lead frame with a heat sink according to the second invention is the lead frame with a heat sink according to the first invention, wherein the bottom surface of the protruding portion is roughened. As a result, the overhanging portion bites into the sealing resin, the familiarity between the bottom surface of the overhanging portion and the sealing resin is improved, and a semiconductor device with higher adhesion between the sealing resin and the lead frame can be provided.
[0008]
A method for manufacturing a lead frame with a heat sink according to a third aspect of the present invention is a method for manufacturing a lead frame with a heat sink, comprising a heat sink having a protruding overhang formed at an intermediate position in the thickness direction around all or part of the circumference. In manufacturing the heat radiating plate, a crushing punch provided with a back guide having a protrusion length allowance (protruding allowance) of the overhanging portion between the heat radiating plate and the outer periphery of the heat radiating plate. The projecting portion is formed by crushing the end portion. This back guide limits the protruding length of the overhanging portion during crushing processing, can ensure a predetermined length of overhanging portion, and the tip of the overhang is in contact with the back guide and blunted.
[0009]
And the manufacturing method of the lead frame with a heat sink according to the fourth invention is the manufacturing method according to the third invention, wherein the crushing punch has a roughened horizontal pressing surface forming a bottom surface of the overhanging portion. Has been. As a result, the bottom surface of the overhang portion can be roughened to improve the adhesion with the sealing resin. Further, the roughening of the crushing punch can be easily performed by, for example, electric discharge machining.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention.
1A is a plan view of a lead frame with a heat sink according to the first embodiment of the present invention, FIG. 1B is a side sectional view of the lead frame with the heat sink, and FIG. 2 is the heat sink. 3 is a cross-sectional view of a semiconductor device using a lead frame with a heat sink, FIG. 3 is a cross-sectional view showing a method of manufacturing a heat sink of the lead frame with the heat sink, FIG. 4 is an explanatory view of the lead frame with the heat sink, and FIG. It is explanatory drawing of the lead frame with a heat sink which concerns on 2nd Embodiment.
[0011]
First, a lead frame 10 with a heat sink according to a first embodiment of the present invention will be described with reference to FIG. 1, FIG. 2, and FIG.
As shown in FIGS. 1A and 1B, a heat sink-equipped lead frame 10 according to a first embodiment of the present invention includes a heat sink 11 made of copper or copper alloy disposed in the center, and It has a plurality of leads 12 arranged radially around the periphery, and a support bar 13 that supports the corners of the central heat sink 11 from the periphery.
[0012]
As shown in FIG. 4, the plurality of leads 12 and the support bar 13 are made of a single sheet of thin copper, copper alloy, or iron-Ni alloy (may be other metal or alloy). (Or strip material) 14 is formed by pressing or etching, and the central portion is a space. In FIG. 4, 15 is a pilot hole, 16 is a slit provided around the lead 12, and 17 is a square hole.
Then, the heat sink 11 on which the semiconductor element 18 is mounted is disposed on the center portion surrounded by the leads 12 as shown in FIG. 2, and the corner portion thereof is caulked and joined to the tip of the surrounding support bar 13 ( It may be welded).
[0013]
The heat radiating plate 11 is made of a material having good thermal conductivity (for example, copper or copper alloy), has a relatively large thickness, and a projecting protruding portion 19 is provided at an intermediate position in the thickness direction of the entire circumference. The protruding length p (see FIG. 2) of the overhanging portion 19 is, for example, about 1/4 to 2/3 times the thickness of the heat sink 11, and the bottom surface 20 is planar, and the top surface continues from the end of the bottom surface 20. 21 has an arcuate cross section. The tip of the overhanging portion 19 is not sharp, but for example, a blunting process for rounding the tip is performed. In addition, in this embodiment, although the overhang | projection part 19 is provided in the perimeter of the heat sink 11, it may be divided into plurality and may be formed partially.
[0014]
And it is preferable that the bottom face 20 of the overhang | projection part 19 is roughened and many fine unevenness | corrugations are formed in the whole surface. The surface roughening method may be a pressing process using a crushing punch or, for example, a blast process, and the surface roughness (Ra) is about 0.5 to 20 μm. The heat sink 11 located on the upper side of the overhang portion 19 protrudes from the heat sink 11 located on the lower side of the overhang portion 19 because the overhang portion 19 is pressed around the lower portion of the heat sink 11 by pressing. This is because it was formed by crushing and causing plastic deformation to project.
[0015]
FIG. 2 shows a semiconductor device 22 using the lead frame 10 with a heat sink, and a semiconductor element 18 is mounted on the heat sink 11 provided with a projecting portion 19 around it. Each pad portion 23 on the upper side of the semiconductor element 18 and the corresponding tip portion of the lead 12 are connected by a bonding wire 24.
The bottom of the semiconductor device 22 is resin-sealed with a sealing resin 25 with the bottom of the radiator plate 11 exposed at the center and the leads 12 exposed around it. When the projecting portion 19 is provided in the intermediate portion in the height direction around the heat sink 11 and the bottom surface 20 of the projecting portion 19 is roughened, the adhesion between the heat sink 11 and the sealing resin 25 is further improved. As a result, the semiconductor device 22 is firmly sealed with resin.
[0016]
Next, a method for manufacturing the lead frame 10 with a heat sink will be described with reference to FIGS.
Lead frames other than the heat sink 11 are formed by pressing or etching the sheet material 14 as shown in FIG. In this case, the center of the sheet material 14 is a space portion, and the periphery of each lead 12 and the support bar 13 is held by the sheet frame 26.
[0017]
As shown in FIG. 3, the heat radiating plate 11 located at the center of the radially arranged leads 12 is formed by pressing. A copper plate (or copper alloy plate) 27 having a predetermined size is prepared in advance, placed on a support base 28 of the mold apparatus, and pressed and held by a presser 29 from above. In this state, the crushing punch 30 provided with the back guide 30 a is raised as shown on the left side of FIG. 3 to crush the lower side of the outer peripheral end portion of the copper plate 27 to form the overhang portion 19. At the time of the crushing process, the protruding tip comes into contact with the back guide 30a and is rounded and has no sharpness. That is, the blunting process is performed. Further, the protruding length p of the overhanging portion 19 is regulated by the installation position of the back guide 30a of the crushing punch 30 and can be set to a desired protruding length. In FIG. 3, with the center line m as a reference, the right side shows before crushing and the left side shows during crushing. Reference numeral 31 denotes a guide.
[0018]
A step portion 32 for forming a back guide 30 a is provided inside the crushing punch 30. The width (projection length allowance) of the stepped portion 32 from the inner peripheral surface of the crushing punch 30 is determined so as to obtain the desired projecting length p of the overhanging portion 19. The horizontal pressing surface 33 that forms the stepped portion 32 is preferably roughened, and the surface thereof is roughened, for example, with a surface roughness (Ra) in the range of 0.1 to 20 μm. The rough surface is formed by electric discharge machining. The vertical wall surface 34 forming the back guide 30a is substantially perpendicular to the horizontal pressing surface 33, but the corners of the vertical wall surface 34 intersect at right angles, or the horizontal pressing surface 33 and the vertical wall surface 34 are smoothly connected to each other. Rounding processing (R processing) is performed.
[0019]
Accordingly, the copper plate 27 is held by the support base 28 and the presser 29, and the crushing punch 30 provided with the back guide 30a has a certain height (for example, the horizontal pressing surface 33 is 1/5 to 1 to the thickness of the copper plate 27). When the height is raised to about 3/3, the outer peripheral end portion of the heat radiating plate 11 is crushed, and the overhanging portion 19 is formed around the copper plate 27. The tip of the overhanging portion 19 is subjected to a blunting process, and the bottom surface 20 is preferably subjected to a roughening process. In addition, the process which crimps and connects the front-end | tip part of the support bar 13 to the corner | angular part of the heat sink 11 is performed separately from this press process.
Through the above process, the lead frame 10 with a heat sink having the heat sink 11 provided with the projecting portion 19 around the periphery is completed.
[0020]
Although the lead frame with a heat sink and the manufacturing method thereof according to the first embodiment have been described for use in a chip size package (CSP) semiconductor device, the type (QFP) semiconductor device as shown in FIG. It can also be applied to a lead frame with a heat sink used in the above. That is, FIG. 5 shows a lead frame with a heat sink according to the second embodiment of the present invention, except that the lead is substantially divided into an inner lead 36 and an outer lead 37. Since it is the same as the lead frame 10 with a heat sink according to the first embodiment, the same components are denoted by the same reference numerals and detailed description thereof is omitted.
Furthermore, the lead frame with a heat sink and the manufacturing method thereof according to the present invention can be applied to those used in various semiconductor devices such as SOP and TO220 type in addition to the above.
In the embodiment described above, a copper plate is used as the heat radiating plate 11, but the present invention is applied even if the heat radiating plate is a metal having good thermal conductivity (for example, aluminum or aluminum alloy).
[0021]
【The invention's effect】
As is apparent from the above description, the lead frame with a heat sink according to claims 1 and 2 is blunted at the tip of the overhang portion formed in the middle position in the thickness direction around the entire periphery or part of the heat sink. Therefore, cracks can be prevented from entering the sealing resin due to the wedge action caused by the tip of the overhanging portion, and the long-term life of the semiconductor device can be secured.
In particular, the lead frame with a heat sink according to claim 2 has a roughened bottom surface of the overhanging portion, so that the overhanging portion bites into the sealing resin and the conformability of the bottom surface of the overhanging portion and the sealing resin is improved. In addition, it is possible to provide a semiconductor device having higher adhesion between the sealing resin and the lead frame, and thus having a longer lifetime.
[0022]
And in the manufacturing method of the lead frame with a heat sink according to claims 3 and 4, the outer periphery of the heat sink is formed by a crushing punch provided with a back guide having a projection length allowance of an overhanging portion between the heat sink and the heat sink. Since the overhanging portion is formed by crushing the end portion, the protruding dimension of the overhanging portion can be regulated and appropriately formed, and the miniaturization of the semiconductor device can be ensured.
In particular, in the method of manufacturing a lead frame with a heat sink according to claim 4, the crushing punch has a roughened horizontal pressing surface that forms the bottom surface of the overhang portion, so that the bottom surface of the overhang portion is roughened. Thus, the adhesion with the sealing resin can be improved, and a semiconductor device having a smaller size and a longer life can be provided.
[Brief description of the drawings]
FIG. 1A is a plan view of a lead frame with a heat sink according to a first embodiment of the present invention, and FIG. 1B is a side sectional view of the lead frame with a heat sink.
FIG. 2 is a cross-sectional view of a semiconductor device using the lead frame with the heat sink.
FIG. 3 is a cross-sectional view showing a method of manufacturing the heat sink of the lead frame with the heat sink.
FIG. 4 is an explanatory diagram of the lead frame with the heat sink.
FIG. 5 is an explanatory diagram of a lead frame with a heat sink according to a second embodiment of the present invention.
[Explanation of symbols]
10: Lead frame with heat sink, 11: Heat sink, 12: Lead, 13: Support bar, 14: Sheet material, 15: Pilot hole, 16: Slit, 17: Square hole, 18: Semiconductor element, 19: Overhang , 20: bottom surface, 21: top surface, 22: semiconductor device, 23: pad portion, 24: bonding wire, 25: sealing resin, 26: sheet frame, 27: copper plate, 28: support base, 29: pressing tool, 30 : Punch for crushing, 30a: back guide, 31: guide, 32: stepped portion, 33: horizontal pressing surface, 34 vertical wall surface, 36: inner lead, 37: outer lead

Claims (4)

It is a lead frame with a heat radiating plate provided with a heat radiating plate in which a projecting protruding portion is formed at an intermediate position in the thickness direction of the entire circumference or part of the circumference,
A lead frame with a heat radiating plate, characterized in that a blunting process is performed on the tip of the overhanging portion to regulate the protruding length. The lead frame with a heat sink according to claim 1, wherein a bottom surface of the projecting portion is roughened. A method for manufacturing a lead frame with a heat sink, comprising a heat sink with a protruding overhang formed at a middle position in the thickness direction around all or part of the circumference,
In manufacturing the heat radiating plate, the outer peripheral end of the heat radiating plate is crushed with a crushing punch provided with a back guide having a projection length allowance of the protruding portion between the heat radiating plate. A method of manufacturing a lead frame with a heat sink, wherein the projecting portion is formed. 4. The method of manufacturing a lead frame with a heat sink according to claim 3, wherein the crushing punch has a roughened horizontal pressing surface forming a bottom surface of the overhang portion. Manufacturing method.

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