JPH08162594A - Composite lead frame and semiconductor package - Google Patents

Abstract

(57) [Abstract] [Purpose] To make the composite lead frame, in which a substrate is joined to a lead frame, maintain the lead strength while making the thickness of the upper and lower mold resins uniform during molding to achieve a thin profile. [Structure] A composite lead frame is constructed by bonding a substrate 3 on which a semiconductor chip is mounted to an inner lead 4 of a lead frame 1. The joint portion 4a of the inner lead 4 of the lead frame 1 is half-etched to be thinner than the outer lead 5. This thinned joint 4
It is preferable that the thickness a be equal to or less than 1/2 of the outer lead 5 of the lead frame 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite lead frame in which a substrate on which a semiconductor chip is mounted is joined to a lead frame, and a semiconductor package.

[0002]

2. Description of the Related Art Normal Q used for semiconductor packages
The FP type lead frame is formed by pressing or etching a copper strip into a predetermined pattern, but has the advantage of high mechanical strength because it uses a relatively thick copper strip. There is. However, such a lead frame alone cannot sufficiently satisfy the electrical characteristics and the heat radiation characteristics with respect to the demand for higher integration and higher output of LSI logic packages and the like.

Therefore, in order to cope with this, a multilayer lead frame (ASIC packaging technology handbook, P
215, December 1992, Science Forum). In addition, as disclosed in JP-A-5-63130, the lead frame is used as an intermediate layer,
A multi-layered lead frame has been reported in which an insulating material layer is arranged on the upper and lower sides, a signal layer is arranged on the upper surface, and a ground material layer is arranged on the lower surface.

However, with the increasing integration of semiconductor chips year by year, it is required to further increase the lead frame pin count and pitch. However, since the above-mentioned multi-layer lead frame is based on a normal QFP type lead frame, the inner lead pitch is currently limited to about 0.2 mm, and it is not possible to meet the demand for further fine pin count. There is a situation.

Therefore, a composite lead frame for connecting the substrate and the lead frame has been developed. As shown in FIG. 3, this is provided with a normal lead frame 1 and a substrate 3 having lead patterns 2 formed on the front and back surfaces,
The lead pattern 2 of the substrate 3 and the inner lead 4 of the lead frame 1 are joined together. Since the lead pattern 2 formed on the substrate 3 is formed by etching a copper foil, its pitch can be made narrower than 0.2 mm, so that it is possible to satisfy the demand for fine pin count.

[0006]

By the way, since a semiconductor package manufactured using a lead frame is indispensable to be light, thin, short, and small, not only the width and the length but also the dimension restriction in the thickness direction is emphasized. In order to reduce the thickness, it is said that it is preferable to balance the upper and lower thicknesses of the mold resin and position the semiconductor chip in the center of the package in the thickness direction.

However, although the above-mentioned composite lead frame is excellent in achieving fine pin count, as shown in FIG. 4, the semiconductor chip 6 is mounted on this and the gold wire 7 is used for bonding.
Further, when the semiconductor package is formed by sealing with the molding resin 8, the thickness of the substrate is added to the thickness of the copper strip for the lead frame as it is, so that it is impossible to achieve the thinning. Further, since the substrate 3 is bonded to the lead frame 1 so as to be adhered thereto, the semiconductor chip 6 mounted on the substrate 3 is located closer to the lower side of the package, and the thickness of the upper and lower mold resins 8 is uniform during molding. I can't. It should be noted that if the overall thickness of the lead frame 1 is made thin, the above-described thinning and uniform resin thickness can be achieved. However, if this is done, the strength of the outer leads 5 of the lead frame 1 becomes weaker, and when mounting on a printed circuit board or the like. It becomes a problem.

In order to meet the demand for thinning, TA
A composite lead frame in which a B tape and a lead frame are connected has also been developed, but it is inferior to the conventional QFP type lead frame in terms of lead strength and electrical characteristics.

It is an object of the present invention to solve the above-mentioned problems of the prior art in a composite lead frame in which a substrate is joined to a lead frame, and to maintain the lead strength while keeping the upper and lower mold resins uniform in thickness. An object is to provide a lead frame and a semiconductor package that can be thinned.

[0010]

A composite lead frame of the present invention is a composite lead frame in which a substrate on which a lead pattern is formed and a semiconductor chip is mounted is joined to an inner lead of the lead frame. The joint portion with and is half-etched to be thinner than the outer lead of the lead frame. It is preferable that the thickness of the joint portion is ½ or less of the thickness of the outer lead from the viewpoint of thinning.

A semiconductor package of the present invention is constructed by using this composite lead frame, in which a semiconductor chip is mounted on a substrate and the semiconductor chip and a lead pattern formed on the surface of the substrate are bonded to each other, The whole is resin-sealed.

[0012]

As the lead frame material used in the present invention, 42 alloy (42% Ni-remaining Fe) or copper alloy having high mechanical strength can be used. The substrate may be single-layer wiring or multi-layer wiring. Connection between the semiconductor chip and the lead pattern on the substrate is performed by wire bonding or the like. The lead pattern of the substrate and the inner lead of the lead frame are joined by, for example, thermocompression bonding. In that case, in order to improve the bondability, Au, Ag, Al, Sn may be added to the joint portion of the inner lead.
It is good to apply plating such as.

Since the inner lead joint portion of the lead frame is etched, it can be thinly finished. Since the roughness of this joint portion is increased by etching, the joint strength with the substrate is significantly improved. Furthermore, if the thickness of the joint portion to be half-etched is smaller than the thickness of the outer leads of the lead frame, the vertical position of the substrate can be shifted and the semiconductor chip can be brought closer to the center of the package. An epoxy resin is generally used as the resin.

[0014]

Embodiments of the present invention will be described below. FIG. 1 is a sectional view of a composite lead frame according to this embodiment.

The composite lead frame 10 is constructed by joining the substrate 3 to the lead frame 1. The substrate 3 is made of, for example, glass epoxy resin. It has a semiconductor chip mounting portion 11 on which a semiconductor chip is mounted,
Lead patterns 2 are formed on the front and back surfaces. The lead pattern 2 is formed by etching a copper foil,
The lead patterns 2 on the front and back surfaces are connected by through holes 9. Since the lead pattern 2 on the substrate 3 is formed by etching, it is possible to satisfy the demand for fine lead multi-pins.

On the other hand, the lead frame 1 is formed of 42 alloy, for example. The shape is a QFP type in which a hole for mounting the substrate 3 is formed in the center, and has an inner lead 4 joined to the substrate 3 and an outer lead 5 connected to a printed circuit board or the like. The connecting portion 4a of the inner lead 4 joined to the substrate 3 is made thinner than the thickness of the outer lead 5 of the lead frame 1 by half etching rather than pressing. The thickness of the outer lead 5 is not more than 1/2.

The joining of the substrate 3 and the lead frame 1 is performed by joining the lead pattern 2 formed on the substrate 3 to the joining portion 4a of the inner lead 4 of the lead frame 1 which is thinned by half etching. This joining is performed by thermocompression bonding, for example. The joint portion 4a of the inner lead 4 is preliminarily plated with Ag and joined to the lead pattern 2 formed of a copper foil. Inner lead 4
Since the connecting portion 4a of 1 is half-etched and thinned, the substrate 3 and the lead frame 1 come close to each other,
The total thickness where the substrate 3 and the lead frame 1 are joined is remarkably thin as compared with the case where half etching is not performed.

For the half etching of the joint portion 4a of the inner lead 4, when the lead frame is formed by etching, the processing step can be used as it is. Further, when the lead frame is formed by pressing, an etching step may be added after the processing.

In order to manufacture a semiconductor package by using the composite lead frame 10 thus formed, as shown in FIG. 2, the semiconductor chip 6 is formed on the chip mounting portion 11 at the center of the substrate 3 via the silver paste. Die bonding. The bonding pad formed on the surface of the semiconductor chip 6 and the lead pattern 2 on the substrate 3 are wire-bonded with a gold wire 7 or the like. After that, the entire structure except the outer leads 5 is sealed with the molding resin 8. After sealing, the outer leads protruding from the mold resin 8 are bent to complete the semiconductor package.

As described above, in the semiconductor package using the composite lead frame of this embodiment, since the joint portion 4a of the lead frame 1 is half-etched to be thin, the thickness of the molding resin at the time of molding varies from top to bottom. Since they can be the same, they are excellent in preventing resin cracks. Further, since the upper and lower thicknesses of the molding resin 8 can be balanced and the position of the semiconductor chip 6 in the package can be centered in the thickness direction, the thickness of the package can be reduced as compared with the case of using the same type of lead frame. Can be realized.

The outer lead 5 needs to be formed into a girl wing shape, but only the connecting portion 4a of the inner lead 4 of the lead frame 1 is thinned to form the outer lead 5.
Since the thickness of copper holds the thickness of copper strip, it is excellent in strength,
It is possible to secure the strength of the outer leads 5 when mounted on the printed circuit board. Furthermore, since the joint portion 4a of the inner lead 4 is finished by half etching, it is possible to have a finer number of pins than when a lead frame material having the same thickness is used. Further, since the half-etched surface is roughened, the bonding strength with the substrate 3 is improved to about 1.5 times that of the conventional one.

In the experiment, a lead frame having a thickness of 0.2 mm was used, and the thickness of the joint portion by half etching was set to 0.
It was set to 1 mm. When a substrate having a thickness of 0.2 mm is bonded to this, the thickness of the conventional composite lead frame type package is 3.0 mm, whereas the thickness of the composite lead frame type package of the present embodiment is 2. It was 5 mm, and it was confirmed that it could be made thinner.

[0023]

According to the present invention, the joint portion of the lead frame is thinner than the thickness of the outer lead, so that the semiconductor package can be made thinner than the conventional one. Further, since the outer lead can secure the thickness, it can maintain the mechanical strength. Further, since the joint portion of the inner lead is etched, the lead can be miniaturized. Further, by thinning the joint portion, the position of the semiconductor chip can be brought closer to the center of the package, so that the thickness of the mold resin can be made uniform.
In particular, if the thickness of the connecting portion is set to 1/2 or less of the outer lead, the thickness can be further reduced, the strength can be maintained, and the vertical thickness can be made uniform.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a composite lead frame of the present invention.

FIG. 2 is a cross-sectional view showing an example of a semiconductor package manufactured using the composite lead frame of the present invention.

FIG. 3 is a sectional view showing a conventional composite lead frame.

FIG. 4 is a cross-sectional view showing a semiconductor package manufactured using a conventional composite lead frame.

[Explanation of symbols]

 1 lead frame 2 lead pattern 3 substrate 4 inner lead 4a inner lead connecting portion 5 outer lead 6 semiconductor chip 7 gold wire 8 mold resin 10 composite lead frame 11 chip mounting part

Claims (3)

[Claims] 1. A composite lead frame in which a substrate on which a lead pattern is formed and a semiconductor chip is mounted is joined to an inner lead of a lead frame, the joint portion of the inner lead with the substrate is half-etched to form a lead frame. A composite lead frame characterized by being made thinner than the thickness of the outer leads. 2. The composite lead frame according to claim 1, wherein the thickness of the joint portion of the inner lead is 1/2 or less of the outer lead of the lead frame. 3. A semiconductor chip is mounted on the substrate of the composite lead frame according to claim 1, the semiconductor chip and the lead pattern formed on the substrate surface are connected, and the entire lead frame except the outer leads is made of resin. A semiconductor package characterized by being molded.