JP2004172472A - Ceramic package and semiconductor device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ceramic package which can prevent the occurrence of cracks due to thermal expansion even when a substrate and a heat sink each having a thermal expansion coefficient rather different with each other are integrally formed, as the ceramic package in which a metal heat sink and ceramics are integrally formed. <P>SOLUTION: In the ceramic package 10 in which the metal heat sink 14 is bonded to the ceramic substrate 12, a plurality of recessed holes 20 are formed in the opposite side face of the heat sink 14 to the region on which the ceramic substrate 12 is bonded, thus making a thin working part 18. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a ceramic package in which a ceramic substrate and a heat sink are integrally formed, and a semiconductor device using the same. More specifically, the present invention relates to a ceramic package that prevents a ceramic substrate from cracking due to a difference in thermal expansion between a ceramic substrate and a heat sink, and a semiconductor device using the same.
[0002]
[Prior art]
2. Description of the Related Art In a semiconductor device on which a semiconductor element with high power consumption is mounted, the heat generated by the semiconductor element is large, so that it is necessary to efficiently release the heat generated by the semiconductor element. For cooling the semiconductor device, a method of attaching a heat sink to a package substrate, a method of directly bonding a semiconductor element to the heat sink, and the like are used in addition to a heat dissipating mechanism using a fan (see, for example, Patent Document 1).
[0003]
[Patent Document 1]
JP-A-5-212247
[Problems to be solved by the invention]
However, in a semiconductor device using a ceramic package, a substrate made of ceramic and a heat radiating plate made of metal have different coefficients of thermal expansion. For this reason, the problem that cracks occur in the ceramic substrate due to the difference in thermal expansion between the ceramic substrate and the heat sink due to the heat generated by the semiconductor element, and the warp of the heat sink adversely affects the semiconductor element mounted on the ceramic package. There is a problem that.
[0005]
Therefore, as shown in FIG. 7, a method using a material approximated to the coefficient of thermal expansion of the ceramic substrate 12, for example, an alloy plate or a laminated plate of copper tungsten, copper molybdenum, or the like, as the heat sink 14, There has been proposed a method of forming a buffer groove 30 for buffering a thermal stress in the substrate 14.
By using such an alloy plate or a laminated plate as the radiator plate 14, the thermal stress generated between the radiator plate 14 and the ceramic substrate 12 can be reduced, and the brazing portion between the ceramic substrate 12 and the radiator plate 14 can be reduced. Thus, the problem that cracks occur in the ceramic package 10 and the problem that the ceramic package 10 warps can be avoided.
However, a tungsten plate or a molybdenum plate having a coefficient of thermal expansion similar to that of a ceramic substrate, or an alloy or a laminate of these and a copper plate is an expensive material, and has a problem that the material cost increases.
[0006]
[Means for Solving the Problems]
The present inventor has conducted various studies to solve the problems described above. As a result, even if a ceramic package using a metal material whose coefficient of thermal expansion is significantly different from that of a ceramic substrate such as a mere copper plate as a heat radiating plate, By devising the shape of the plate, it has been conceived that it is possible to reduce the thermal stress caused by the difference in the coefficient of thermal expansion between the ceramic substrate and the heat sink, and thus completed the present invention.
The present invention has the following configuration.
That is, in a ceramic package in which a metal heat radiating plate is joined to a ceramic substrate, a large number of concave holes are formed on a surface of the heat radiating plate opposite to a region joined to the ceramic substrate, so that thin processing is performed. It is characterized in that a portion is formed.
Thus, the thickness of the heat radiating plate bonded to the ceramic substrate can be changed at each position. Therefore, even if there is a difference in thermal expansion between the ceramic substrate and the radiator plate, the resulting thermal stress is dispersed, and a crack is generated in the bonding portion between the ceramic substrate and the radiator plate. Warpage of the semiconductor device can be prevented.
[0007]
Further, it is preferable that the concave holes are individually formed to have non-uniform depth dimensions.
This makes it easier to disperse the thermal stress generated between the ceramic substrate and the heat sink.
Further, it is preferable that the concave hole is formed in a tapered hole whose diameter gradually decreases toward the bottom.
Thereby, press working can be easily performed, and the heat radiation efficiency of the heat radiating plate can be improved.
Further, it is preferable that the thinned portion is formed by a concave hole having a different opening diameter.
This makes it easier to further disperse the thermal stress generated between the ceramic substrate and the heat sink.
Furthermore, it is preferable that the concave holes are arranged in a staggered manner.
According to this, cracks and warpage due to thermal expansion of the semiconductor device using the ceramic package can be more suitably prevented.
[0008]
Further, it is preferable that the concave hole is formed by press working.
According to this, the manufacturing cost of the ceramic package can be reduced.
Further, a semiconductor device is characterized in that a semiconductor element is mounted on a ceramic package corresponding to any of the above.
According to this, it is possible to provide a semiconductor device in which cracks and warpage due to differences in thermal expansion due to differences in materials are less likely to occur even though a ceramic package in which a heat sink is integrally formed is used. Further, the yield of the semiconductor device can be improved. Further, the weight of the heat sink can be reduced, and the weight of the ceramic package and the semiconductor device can be reduced.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
(1st Embodiment)
Hereinafter, preferred embodiments of a ceramic package according to the present invention will be described in detail with reference to the drawings.
FIG. 1 is a plan view of the ceramic package according to the first embodiment. FIG. 2 is a bottom view of the ceramic package, and FIG. 3 is a cross-sectional view taken along line AA of FIG.
The ceramic package 10 in the present embodiment is formed by bonding a ceramic substrate 12 made of alumina and a heat sink 14 made of a copper plate to each other by brazing. In the present embodiment, silver-copper brazing is used for brazing material 16, but other brazing materials may of course be used. In the ceramic substrate 12, a through hole 12a is formed at a central portion in plan view. The portion where the through hole 12a is formed becomes the mounting portion 12b of the semiconductor element by joining the heat sink 14 to the bottom surface of the ceramic substrate 12.
The semiconductor device is formed by attaching a semiconductor element to the mounting portion 12b of the ceramic package 10 by die, and electrically connecting the semiconductor element and an inner pattern 12c formed on the ceramic substrate 12 by wire bonding or the like.
[0010]
As shown in FIG. 3, in the ceramic package 10 according to the present embodiment, the surface of the heat dissipation plate 14 opposite to the surface (region) to which the ceramic substrate 12 is joined has a width smaller than the member width (W1) of the ceramic substrate 12. The thin processed portion 18 is formed over a slightly wide range (W2). The thinned portion 18 is formed by forming a number of concave holes 20 adjacent to each other.
As shown in FIG. 2, the concave hole 20 is composed of two types of concave holes 20 having different diameters of a large-diameter hole 20a and a small-diameter hole 20b having a circular planar shape.
The large-diameter holes 20a are arranged in a vertical and horizontal lattice, and the small-diameter holes 20b are arranged in the middle of the adjacent large-diameter holes 20a.
[0011]
The concave hole 20 can be formed, for example, by forming the large-diameter hole 20a first by progressive press working and then forming the small-diameter hole 20b by progressive press working like the large-diameter hole 20a. When the concave hole 20 is formed by the press working, the flesh of the radiator plate 14 removed by the press must escape to another part. The method of forming the concave hole 20 is preferable. After the formation of the concave hole 20 by press working, the outer edge of the heat sink 14 is cut into a predetermined size and shaped.
[0012]
As described above, when the thin-walled portion 18 is formed by alternately arranging the large-diameter holes 20a and the small-diameter holes 20b on the lower surface (outer surface) of the heat sink 14, the concave portion 20 adjacent to the lower surface of the heat sink 14 is formed. By forming the protrusions 22 in the middle and forming a large number of protrusions 22, the surface area of the heat radiating plate 14 increases, and the heat radiation efficiency can be improved. Note that the protrusions 22 are formed at the same height as the thickness of the heat sink 14.
In addition, since the large holes 20a and the small holes 20b are alternately arranged in the concave holes 20 formed on the lower surface of the heat radiating plate 14, the projections 22 are dispersed on the lower surface of the heat radiating plate 14. (Randomly). This means that the material thickness of the heat radiating plate 14 at a portion brazed to the ceramic substrate 12 is not uniform in a plane in contact with the ceramic substrate 12. In other words, it means that the portions having the same thickness at the joining portion between the heat sink 14 and the ceramic substrate 12 are not linearly continuous.
[0013]
As described above, the heat radiating plate 14 and the ceramic substrate 12 according to the present embodiment are configured such that the portions adhered with the same thickness are not arranged linearly, thereby preventing the heat radiating plate 14 from extending in a specific direction. Thus, thermal stress due to the difference in thermal expansion at the bonding portion with the ceramic substrate 12 can be dispersed and absorbed.
By configuring the heat radiating plate 14 in this manner, the ceramic package 10 can be formed using materials having greatly different coefficients of thermal expansion, such as the ceramic substrate 12 and the heat radiating plate 14 made of a copper plate. (Not shown), it is possible to prevent the ceramic substrate 12 from being cracked and the heat sink 14 from being warped.
[0014]
Further, the concave hole 20 is formed as a tapered hole whose diameter gradually decreases as it approaches the ceramic substrate 12 from the lower end surface of the heat sink 14. When the cross-sectional shape of the concave hole 20 is tapered in this manner, when forming the concave hole 20 by press working, it becomes easy to secure a place where the meat of the heat sink 14 escapes, so that the finish of the press working is improved.
[0015]
In the present embodiment, a copper plate having a width of 8.3 mm, a length of 17.8 mm, and a thickness of 1.0 mm is used as the heat sink 14. The thickness of the thin-walled portion 18 is 0.3 mm, the diameter of the large-diameter hole 20a is 2.0 mm, and the diameter of the small-diameter hole 20b is 0.8 mm. The warpage δ (see FIG. 3) of the radiator plate 14 of the semiconductor device having the semiconductor element mounted on the ceramic package 10 of this embodiment was measured and found to be 50 μm. On the other hand, the warpage of the heat radiating plate 14 in the case of using the ceramic package 10 in which the heat radiating plate 14 formed of a single plate-shaped copper plate having the same thickness and the same shape without the concave hole 20 is joined to the ceramic substrate 12. The amount δ was 175 μm. From this, the heat sink 14 in which the concave hole 20 is processed can suppress the warpage of the heat sink 14 at the time of mounting the semiconductor element to about one third.
[0016]
(Second embodiment)
In the first embodiment, the ceramic package 10 in which two types of concave holes 20 having different diameters are formed on the lower surface of the heat sink 14 has been described. By the way, the shape of the concave hole 20 achieves the object of the present invention if the expansion of the heat sink 14 in a certain direction can be made as small as possible at the portion where the heat sink 14 and the ceramic substrate 12 are joined. can do.
That is, the thin-walled portion 18 does not necessarily need to be formed by the concave holes 20 having different diameters, and the respective concave holes 20 may not be arranged in a staggered manner.
[0017]
A second embodiment will be described with reference to FIGS. Note that the ceramic package 10 of the present embodiment is different from the first embodiment only in the arrangement of the concave holes 20, and the configuration of the ceramic substrate 12 and the like of the present embodiment is the same as that of the first embodiment. This is the same as the code used. Therefore, in the present embodiment, these detailed descriptions are omitted.
[0018]
As shown in FIG. 4, the thin-walled processed portion 18 according to the present embodiment is configured by arranging concave holes 20 having the same circular planar shape in a lattice shape. In the present embodiment, the region 24 in the middle part between the adjacent concave holes 20 is larger than that in the first embodiment. That is, since the volume of the heat radiation plate 14 is larger than that of the first embodiment, there is an advantage that the heat radiation efficiency can be improved.
[0019]
Further, in the present embodiment, as shown in FIG. 5, the concave holes 20 are provided so that the depths thereof are not uniform. That is, the concave hole 20 is processed so that the depth of the concave hole 20 is random. Thereby, even if the concave holes 20 are regularly formed in the heat radiating plate 14, the thickness of the heat radiating plate 14 at the portion joined to the ceramic substrate 12 in three dimensions differs depending on the location. . Therefore, it is possible to prevent a difference in thermal expansion between the ceramic substrate 12 and the heat radiating plate 14 from appearing only in a specific direction, to buffer thermal stress, and to obtain a ceramic package in which cracks and warping of the heat radiating plate are not easily generated. it can.
[0020]
Although the ceramic package according to the present invention has been described in detail above, the present invention is not limited to the above-described embodiment.
For example, the concave hole 20 need not necessarily be formed by press working, but may be formed by processing such as cutting.
Further, the planar shape of the concave hole (press hole) 20 may be a shape such as a honeycomb shape other than the circular shape, for example.
Further, in the above-described embodiment, the concave hole 20 formed in the heat sink 14 has a shape in which all the pressed portions are accommodated within the range of the heat sink 14, but not necessarily the area of the heat sink 14. It is not necessary that all the recesses 20 be completely contained therein. For example, as shown in FIG. 6, a part of the shape of the concave hole 20 may be lost at the outer peripheral edge of the heat sink 14.
Further, in the above embodiment, the example in which the copper plate is used for the heat radiating plate has been described, but the present invention is similarly applied to a case where other materials such as an iron plate and an aluminum plate are used in addition to the copper material. be able to.
[0021]
【The invention's effect】
By using the ceramic package according to the present invention, the following operational effects can be obtained.
That is, by forming a thin-walled portion with a large number of concave holes on the heat radiating plate bonded to the ceramic substrate, the thickness of the heat radiating plate at the bonding portion between the ceramic substrate and the heat radiating plate can be made non-uniform. Therefore, even if there is a difference in the amount of thermal expansion between the ceramic substrate and the radiator plate, cracks may occur in the bonded portion between the ceramic substrate and the radiator plate due to the presence of the stress relief part caused by this. In addition, it is possible to prevent the semiconductor device using the ceramic package from being warped, thereby improving the yield.
[0022]
In addition, the unevenness in the depth of the plurality of concave holes facilitates dispersion of thermal stress generated between the ceramic substrate and the heat sink.
Further, since the concave hole is formed in a tapered shape, the press working can be easily performed, and the heat radiation efficiency of the heat radiating plate can be improved.
Also, by forming the thin-walled portions with concave holes having different opening diameters or forming the concave holes in a staggered arrangement, cracks due to thermal expansion of a semiconductor device using a ceramic package integrally formed with a metal heat sink are formed. It is possible to more suitably prevent the occurrence of warpage.
[0023]
Further, by forming the plurality of concave holes by press working, it is possible to reduce the manufacturing cost of the ceramic package.
Furthermore, the semiconductor device using the above-described ceramic package has a remarkable effect that a crack is hardly generated and warpage can be reduced, so that a semiconductor device having a precise shape can be obtained. Play.
[Brief description of the drawings]
FIG. 1 is an explanatory plan view of a ceramic package according to a first embodiment.
FIG. 2 is an explanatory bottom view of the ceramic package.
FIG. 3 is a sectional view taken along line AA of FIG. 2;
FIG. 4 is an explanatory bottom view of a ceramic package according to a second embodiment.
FIG. 5 is an explanatory sectional view taken along line AA of FIG. 4;
FIG. 6 is an explanatory bottom view showing an example of another embodiment.
FIG. 7 is an explanatory front view showing an example of a conventional technique.
[Explanation of symbols]
REFERENCE SIGNS LIST 10 ceramic package 12 ceramic substrate 14 heat sink 16 brazing material 18 thin processed portion 20 concave hole (press hole)
22 Protrusion 24 Area 30 in the middle of adjacent press holes 30 Buffer groove

Claims (7)

In a ceramic package formed by joining a metal heat sink to a ceramic substrate,
A ceramic package, wherein a thin-walled portion is formed by forming a number of concave holes on a surface of the heat sink opposite to a region joined to the ceramic substrate. The ceramic package according to claim 1, wherein the concave holes are individually formed to have non-uniform depth dimensions. The ceramic package according to claim 1, wherein the concave hole is formed in a tapered hole whose diameter is gradually reduced toward a bottom. The ceramic package according to claim 1, wherein the thinned portion is formed by a concave hole having a different opening diameter. The ceramic package according to claim 1, wherein the concave holes are arranged in a staggered manner. The ceramic package according to any one of claims 1 to 5, wherein the concave hole is formed by press working. A semiconductor device, wherein a semiconductor element is mounted on the ceramic package according to claim 1.

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