JP2000223603A - Semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor device wherein it is possible to position a semiconductor device mounting an element chip at a high precision and obtain a high heat radiation effect even with the device mounted on a substrate. SOLUTION: A lead frame 2 mounting a semiconductor element chip 6 has a mounting land 4 a plurality parts 4a-4c of which are exposed from a window frame 9 and will be recognized when mounting, this enabling the positioning utilizing the mounting lands made of a metal, etc., having a higher machining accuracy than ceramics and hence the plane positioning to be executed at a high precision in mounting a semiconductor device. The back side of the mounting land 4 is exposed through a window 1a of a base frame 1 and hence the exposed back side of the land 4 is recognized to enable the positioning in the height direction of the semiconductor device to be made at a high precision. From the exposed back side of the land 4, the heat generated by a semiconductor chip 6 is radiated to raise the radiation effect.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a semiconductor device,
In particular, the present invention relates to a semiconductor device suitable for being applied to a semiconductor device used for an optical device such as a CCD.

[0002]

2. Description of the Related Art In recent years, various semiconductor devices using ceramic as a package material have been proposed. For example, FIGS. 5A and 5B are a partially cutaway plan view and a cross-sectional view taken along line E-E of an example of a CCD image pickup device. Are sequentially mounted and integrated with the low-melting glass 103. A CCD chip 106 is mounted on the base frame 101 with a metal paste 107. The lead frame 102 has a plurality of external leads 105
The CCD device chip 106 and the external lead 105 are electrically connected by a thin metal wire 108. Further, a glass cap 110 is fixed on the window frame 109 by an adhesive 111 to seal the CCD element chip 106.

In such a conventional CCD image pickup device, since the ceramic material forming the base frame 101 and the window frame 109 has low thermal conductivity, the heat generated when the heat generated in the CCD chip 106 is radiated through the package. There is a problem that is low. In particular, as described above, in an optical device such as a semiconductor device having a CCD element chip mounted thereon, there is a problem that heat generated by the CCD element chip is trapped in a package or an element chip, thereby increasing dark current and deteriorating sensitivity. there were. Also, in this type of optical device, it is required that the optical axis position of the semiconductor device be positioned with high accuracy with respect to the optical system. However, the tolerance of the external dimensions of ceramic is lower than that of a lead frame made of metal. If a ceramic package is used for positioning when mounting a semiconductor device on an optical device, there is a problem that positional accuracy is deteriorated, and the mounting requires adjustment of the optical system of the device and the semiconductor device.

Among the above problems, the latter problem of positioning is disclosed in Japanese Patent Application Laid-Open No. 3-209746.
A technique has been proposed in which a part of the back surface of a chip mounting island of a lead frame is exposed to the outside of a package, and the exposed surface is used as a reference surface when mounting a semiconductor device. Further, as another technique, a technique has been proposed in which a part of an externally derived lead of a lead frame projecting from a package is recognized by an optical method, and a semiconductor device is positioned using the recognized external lead. I have. Furthermore, in order to solve the former problem of heat radiation, a technology has been proposed in which a heat sink is provided in a part of a package and heat generated in an element chip is radiated to the outside of the package via the heat sink.

[0005]

However, the technique described in the above-mentioned publication is not suitable for selecting the position of the surface of an element chip mounted on a chip mounting island in a direction parallel or perpendicular to a reference plane. Is effective, but not effective when the semiconductor device is set at a predetermined position on the surface of the mounting board. Therefore, when it is required to align the center position of the CCD element with the optical axis of the optical system in the optical device equipped with the above-described CCD element, the technology described in the publication cannot be used as it is. Can not. In this case, it is possible to use an external lead that is exposed outside the package. However, the external lead is formed in a narrow width, and is easily formed when forming the package. Since the element chip is deformed, the position with respect to the chip mounting island on which the element chip is mounted tends to be unstable, and there is a problem in accurately positioning the element chip using the external lead.

In a structure in which a heat sink is provided in a semiconductor device in order to dissipate heat from an element chip, a package just above the element chip, such as a CCD element, has a transparent structure for introducing light into the element chip. The required structure makes it impossible to arrange a heat sink on the element chip. In a structure in which a heat sink is arranged on the back side of an element chip, in a semiconductor device having a structure in which the back side of the semiconductor device is in contact with a mounting substrate, such as a DIP semiconductor device, the heat sink is in contact with the mounting substrate. As a result, the heat dissipation through the heat sink is reduced, and it is difficult to obtain an effective heat dissipation effect.

SUMMARY OF THE INVENTION It is an object of the present invention to enable a semiconductor device having an element chip mounted thereon to be positioned and mounted on a mounting board with high accuracy, and to obtain a high heat radiation effect even when mounted on the mounting board. It is intended to provide a semiconductor device capable of performing the following.

[0008]

According to the present invention, there is provided a semiconductor device comprising:
In a semiconductor device in which a semiconductor element chip is mounted on a mounting land of a lead frame and the mounting land and the semiconductor element chip are sealed with a package, a plurality of portions of the mounting land are exposed from the package. Further, the mounting land has a back surface opposite to a surface on which the semiconductor element chip is mounted exposed through a window provided in the package. For example,
A base frame made of ceramic and having a window opened in a central region thereof, a lead frame fixed on the base frame at a position covering the window with a mounting land and an external lead, and on the lead frame. A semiconductor element chip mounted on the mounting land of the lead frame and electrically connected to the external lead, and a semiconductor frame mounted on the window frame to seal the semiconductor element chip. A glass cap, and a plurality of locations on the outer side of the mounting land are projected outward from the window frame and are exposed. In this case, it is preferable that the wind frame has a configuration in which a concave portion is formed inward on a part of an outer surface, and a part of an outer side of the mounting land is exposed in the concave portion. .

By recognizing a plurality of mounting lands exposed from the package, positioning using mounting lands made of metal or the like, which has higher processing accuracy than ceramics, can be performed, and when mounting a semiconductor device, It is possible to perform planar positioning with high accuracy. Also, by recognizing the exposed back surface of the mounting land, the semiconductor device can be accurately positioned in the height direction.
Further, the heat generated in the semiconductor element chip is radiated from the exposed back surface of the mounting land, and the radiating effect can be enhanced.

[0010]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a partially cutaway plan view of a package according to an embodiment in which the present invention is applied to a CCD imaging device. FIGS. 2A and 2B are AA line and BB line in FIG.
It is each sectional drawing of a line. In these figures, a lead frame 2 is fixedly supported by a low melting point glass 3 on a base frame 1 formed of a ceramic or the like into a rectangular thick plate shape and having a rectangular window 1a opened in the center thereof. . The lead frame 2 has a rectangular mounting land 4 having a size larger than that of the window 1a of the base frame 1 disposed at a central portion, and a plurality of external leads 5 on both sides thereof.
Are arranged. And, on the mounting land 4, C
The CD element chip 6 is mounted with an Ag epoxy paste 7, and the electrode pads of the CCD element chip 6 and the external leads 5 are electrically connected to each other by thin metal wires 8. A window frame 9 having a rectangular frame shape is mounted on the lead frame 2 so as to surround the mounting land 4, the CCD element chip 6, and the thin metal wire 8, and is fixed by the low melting point glass 3. A transparent glass cap 1 is placed on the wind frame 9.
0, and fixed by the adhesive 11, and the CC
The D element chip 6 is sealed.

Here, the back surface of the mounting land 4 of the lead frame 2 is exposed to the back surface of the package through the window 1a of the base frame 1. In the wind frame 9, a plurality of recesses 12, which are recessed inward from the outer surface side, are formed at a plurality of locations on the peripheral edge, here, two locations on one side. Further, the lead frame 2 is formed to have an outer dimension such that an outer edge on one side of the mounting land 4 reaches the recess 12 of the wind frame 9, and the mounting land is provided at a position where the recess 12 exists. 4 corresponding two locations 4a, 4 on the outer edge
b is configured to be exposed from the outer surface of the wind frame 9. Further, a protruding piece 4c protruding outward is integrally formed at one corner of the other side of the mounting land 4, and the outer edge of the protruding piece 4c protrudes from the outer surface of the wind frame 9 and is exposed. I have. In the case of the lead frame 2 of the present embodiment in which common lead terminals 5a and 5b such as a power supply or a ground are integrally formed on the mounting land 4, a part of the common lead terminals 5a and 5b is projected and exposed. You may make it do.

In the CCD image pickup device constructed as described above, the CCD image pickup device is mounted on a mounting substrate 20 as shown in the plan view and the cross-sectional view taken along the line CC in FIGS. 3 (a) and 3 (b). Is optically coupled to the imaging optical system 21. In this mounting, the lead frame 2 is passed through the opening hole 22 opened in the mounting substrate 20 and further through the window 1 a provided in the base frame 1 from the back side of the mounting substrate 20.
Of the mounting land 4 can be confirmed. Therefore, the back surface of the mounting land 4 is used as a reference plane for positioning, and the reference plane is positioned so as to be a plane perpendicular to the optical axis of the imaging optical system 21, so that the CCD imaging for the imaging optical system 21 is performed. The position of the element in the optical axis direction can be set with high accuracy. Also, in the case of a package made of ordinary ceramics or other insulating materials, it takes a lot of man-hours, such as polishing, to secure the flatness of the chip mounting portion, resulting in an increase in cost. Since the CCD element chip 6 is mounted on the metal mounting land 4, a process such as polishing is not required.
In addition, since the flatness of the mounting surface of the mounting land 4 can be suppressed to about 10 μm, a high-performance image with low distortion can be obtained at low cost.

Further, a total of three places 4a, 4b on one side of the mounting land 4 exposed from the package and one place 4c on the other side are confirmed by an optical method from the upper surface side of the CCD image sensor. After forming the position scales 24 at these three positions, the position scales 24 are mounted on the mounting board 20.
The positioning of the CCD image sensor on the mounting board 20 can be set with high accuracy by positioning the positioning mark 23 in advance. In this case, in particular, in this embodiment, since the positioning is performed by using the three places 4a, 4b, and 4c of the mounting land 4 on which the CCD element chip 6 is directly mounted, it is projected from the package as in the related art. Compared to the case where positioning is performed using the external lead that is provided separately from the mounting land, the influence of the displacement between the CCD element and the external lead, which is caused by deformation of the external lead, etc. High precision positioning is possible. Incidentally, in the case of this embodiment, the positioning can be performed with an accuracy of about ± 50 μm.

On the other hand, the mounted CCD image pickup device
Since the back surface of the mounting land 4 on which the D element chip 6 is mounted is exposed through the window 1a of the base frame 1, the heat generated by the CCD element chip 6 is transferred to the base frame 1 via the metal mounting land 4. Through the window 1a
Further, since heat is radiated through the opening hole 22 of the mounting board 20, the heat resistance is low, the temperature rise during driving of the CCD element chip 6 can be limited, and dark current noise due to heat is reduced.
The performance of the CD element chip 6 is improved. Further, in this configuration, even when the size of the opening hole 22 provided in the mounting board 20 is small, the mounting board 20 and the mounting land 4 are provided in the window 1 a of the base frame 1 by the thickness of the base frame 1. Since a space is secured therebetween, heat can be dissipated using the space, and heat radiation can be improved.

Here, the plurality of exposed portions of the mounting lands exposed from the package may all be exposed to recesses provided in the package. In this way, by exposing the outer periphery of the mounting land in the recess, the mounting land does not protrude outside of the package. Short circuit is prevented. When the mounting of the CCD image pickup device is not affected, a configuration may be adopted in which all of a plurality of mounting lands are projected out of the package and exposed without providing recesses in the window frame or the base frame.

In the first embodiment, an example is shown in which the present invention is applied to a CCD image pickup device having a two-dimensionally arranged CCD element chip mounted thereon. The same can be applied to a CCD line sensor. The second embodiment of the present invention applied to this CCD line sensor is shown in FIG.
(A) and (b) show a plan view and an enlarged sectional view taken along the line DD. Note that parts equivalent to those in the first embodiment are denoted by the same reference numerals. In this embodiment, a CCD line sensor element chip 6A is mounted on a mounting land 4 of a lead frame 2 fixed on a base frame 1, and a window frame 9 and a glass cap 10 constitute a package. The base frame 1 is provided with a window 1 a for exposing the back surface of the mounting land 4, and a concave portion 12 is provided at each of both ends in the longitudinal direction of the window frame 9. 4d are respectively exposed.

Also in the second embodiment, the positioning of the CCD line sensor in the optical axis direction is possible by the back surface of the mounting land 4 exposed from the window 1a of the base frame 1, and both ends of the package are exposed. Positioning in the planar direction is possible by both side portions 4d of the mounting land. Since the positioning of the CCD line sensor in the planar direction is performed in a one-dimensional direction, three or more exposed portions as in the first embodiment are not required. Further, it goes without saying that the heat generated in the CCD line sensor element chip 6A can be effectively radiated from the back surface of the mounting land 4 through the window 1a of the base frame 1.

[0018]

As described above, according to the present invention, since a plurality of mounting lands of the lead frame on which the semiconductor chip is mounted are exposed from the package, the plurality of mounting lands are exposed. By recognizing,
Positioning using a mounting land made of metal or the like having higher processing accuracy than ceramic can be performed, and planar positioning when mounting a semiconductor device can be performed with high precision. In addition, since the back surface of the mounting land is exposed through the window provided in the package, the height of the semiconductor device can be accurately positioned by recognizing the exposed back surface of the mounting land. Becomes further,
The heat generated in the semiconductor element chip is radiated from the exposed back surface of the mounting land, and the heat radiation effect can be enhanced.

[Brief description of the drawings]

FIG. 1 is a partially broken plan view of a first embodiment in which the present invention is applied to a CCD imaging device.

FIG. 2 is a sectional view taken along line AA and line BB in FIG. 1;

FIG. 3 is a plan view showing a state where the CCD image pickup device of FIG. 1 is mounted and a cross-sectional view taken along line CC of FIG.

FIG. 4 is a plan view and an enlarged cross-sectional view taken along line DD of a second embodiment in which the present invention is applied to a CCD line sensor.

5A and 5B are a plan view and a cross-sectional view taken along line E-E of a conventional CCD image pickup device, respectively.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Base frame 2 Lead frame 3 Low melting glass 4 Mounting land 4a-4d Exposed location 5 External lead 6 CCD element chip 6A CCD line sensor element chip 7 Ag epoxy paste 8 Fine metal wire 9 Wind frame 10 Glass cap 11 Adhesive 12 Concave part Reference Signs List 20 mounting board 21 imaging optical system 22 opening hole 23 positioning mark 24 position scale

Claims (6)

[Claims] 1. A semiconductor device having a semiconductor element chip mounted on a mounting land of a lead frame and sealing the mounting land and the semiconductor element chip with a package, wherein a plurality of portions of the mounting land are exposed from the package. A semiconductor device characterized by the above-mentioned. 2. The semiconductor device according to claim 1, wherein said mounting land has a back surface opposite to a surface on which said semiconductor element chip is mounted, exposed through a window provided in said package. 3. The semiconductor device according to claim 1, wherein the semiconductor element chip is a two-dimensional CCD element chip, and at least three outer lands of the mounting land are exposed from the package. 4. The semiconductor device according to claim 1, wherein the semiconductor element chip is a one-dimensional CCD element chip, and each of the mounting lands is partially exposed at both ends in a longitudinal direction thereof from the package. apparatus. 5. A base frame made of ceramic and having a window opened in a central region thereof, and a lead frame having mounting lands and external lead-outs and fixed on the base frame at a position covering the window. A wind frame fixed on the lead frame, a semiconductor element chip mounted on the mounting land of the lead frame and electrically connected to the external lead, and the semiconductor element mounted on the wind frame. A semiconductor device comprising: a glass cap for sealing a chip; and a plurality of locations on an outer side of the mounting land projecting outward from the wind frame and exposed. 6. The window frame according to claim 5, wherein a concave portion is formed in a part of an outer surface inwardly, and a part of an outer edge of the mounting land is exposed in the concave portion. 13. The semiconductor device according to claim 1.