JP4916068B2 - Method for manufacturing composite semiconductor device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a composite semiconductor device, and more particularly to a metal base plate on which electric circuit components are mounted and fixed via a joining member such as solder.
[0002]
[Prior art]
[0003]
FIG. 4 shows the internal configuration of this type of composite semiconductor device.
The figure shows the state of the assembly with the insulating case removed before the composite semiconductor device is completed.
In the figure, reference numeral 1 denotes a metal base plate made of a material such as copper, and has a plurality of screw attachment holes 2 for attachment to an external member such as a heat radiating fin.
An insulating substrate 4 formed of a material such as alumina having a metal layer 3 on both surfaces is mounted and fixed on the metal base plate 1 via a bonding member (not shown) such as solder. In addition, the first external electrode 5, a semiconductor element 6 such as a diode or a thyristor on the first external electrode 5, and a second electrode 8 on the semiconductor element 6 via a thermal buffer plate 7 such as molybdenum (Mo). Is mounted and fixed.
Note that a plurality (in the figure, a pair) of the above-described configuration are formed on the metal base plate 1.
[0004]
When the above is placed in a reflow furnace having a temperature profile of about 25 ° C. to 250 ° C. and soldered, the result is as shown in FIG.
That is, in the above case, the thermal expansion coefficients of the insulating substrate 4 made of alumina and the metal base plate 1 made of copper are different from 7.1 × 10 ↑ -6 and 16.5 × 10 ↑ -6, respectively. Since the plate 1 has a larger thermal expansion coefficient, the metal base plate 1 warps upwardly in a convex shape.
[0005]
FIG. 6 shows an assembly in which the soldered assembly as shown in FIG. 5 is housed in an insulating case 9, filled with a filler 10 such as an epoxy resin in the insulating case 9, and sealed with resin.
FIG. 7 shows a state in which the composite semiconductor device 11 is completed by filling with a filler 10 such as an epoxy resin and curing at about 150 ° C.
In the above case, the thermal expansion coefficient of the metal base plate 1 made of copper and the epoxy resin as the filler 10 are 16.5 × 10 ↑ -6 and 25 × 10 ↑ -6, respectively, and the thermal expansion coefficient of the epoxy resin. Due to the fact that the metal base plate 1 is larger and the periphery of the metal base plate 1 is surrounded by the insulating case 9, the metal base plate 1 having a warp curved upward is pressed downward by the epoxy resin. As shown in the figure, the warpage is changed to a concave curve downward.
[0006]
FIG. 8 shows a state where the composite semiconductor device 11 completed as described above is attached to the heat radiating fins 12 using screw attachment holes (not shown) of the metal base plate 1. In this case, a gap D is formed between the metal base plate 1 and the radiating fin 12 due to the curved concave warp, and the thermal resistance is deteriorated. Further, when screwing to the heat radiating fins 12, the metal base plate 1 is corrected so as to be flat, and mechanical stress is applied to the semiconductor element 6 (not shown) on the metal base plate 1 to improve electrical characteristics. It will deteriorate, which is not preferable.
[0007]
Therefore, conventionally, as shown in FIG. 9, a correction means is provided which preliminarily curves in a convex shape toward the upper side in the opposite direction, corresponding to the curved concave warp of the metal base plate 1 shown in FIG. ing. In this case, by using the metal base plate 1 having a convex curved warp, the reverse warp caused by thermal expansion in the solder fixing process is canceled out, and the flat metal base plate 1 is finally obtained.
[0008]
[Problems to be solved by the invention]
Since the conventional composite semiconductor device is configured as described above, the problem of warping of the metal base plate 1 could be solved, but it has been found that there is a new problem.
That is, as shown in FIG. 10, with respect to the metal base plate 1 that is convexly convex upward, the component parts of the composite semiconductor device, particularly the insulating substrate 4 that is in direct contact with the upper surface is provided on the upper surface side, such as solder. When fixed by the bonding member 13, since the upper surface of the metal base plate 1 is curved, the outer peripheral gap is relatively larger than the central portion of the insulating substrate 4, and the amount of solder applied to the outer peripheral portion is large. Decreases and the wettability of solder deteriorates. For this reason, the thermal resistance to the metal base plate 1 increases, which adversely affects the electrical characteristics of the composite semiconductor device. Further, after the assembly is placed in the insulating case 9 (see FIG. 6), mechanical stress is applied to the end portion of the insulating substrate 4 when the resin is sealed by filling with epoxy resin or by curing stress. However, since the end portion is not sufficiently protected by the solder, there is a problem to be solved such as a possibility that a crack may occur.
[0009]
OBJECT OF THE INVENTION
The present invention has been made to solve the above problems. When a metal base plate having a convex warp curved upward is used, the solder contact with the metal base plate is good and the thermal resistance is low. It is an object of the present invention to provide a composite semiconductor device that is small and prevents cracks from occurring even when stress is applied to an end portion of an insulating substrate due to stress during encapsulation of an epoxy resin or curing.
[0010]
[Means for Solving the Problems]
In the method of manufacturing a composite semiconductor device, wherein an electric circuit component including an insulating substrate, an external electrode, a semiconductor element, and a heat buffer plate is mounted and fixed on a metal base plate via a heat bonding member such as solder. The metal base plate is bent in advance so as to be convex upward so as to offset the warp caused by heating, and the upper surface of the metal base plate on which the electric circuit components are mounted and fixed is flat without being curved. The present invention is characterized in that the method of manufacturing a composite semiconductor device is a surface.
[0011]
Also, the method for manufacturing a composite semiconductor device of the present invention is characterized in that the metal base plate has at least one “f” -shaped bent portion without bending upward.
[0012]
[Action]
In the present invention, since the upper surface of the metal base plate on which the electric circuit components are mounted and fixed is a flat surface, a gap that is relatively larger than the center portion is not formed particularly in the outer peripheral portion of the insulating substrate. . For this reason, the wettability of the solder is not adversely affected, and the predetermined amount of solder applied does not become insufficient. As a result, the outer peripheral portion of the insulating substrate can be covered with the surface tension of the solder without excess or deficiency, and a joint portion having a wide contact area as a whole can be obtained as compared with the conventional solder joint portion. As a result, the thermal resistance to the metal base plate can be reduced, and the end of the insulating substrate is completely protected by the joining member, so that the stress when the epoxy resin is sealed in the insulating case or during curing is reduced. Even if it adds to the outer peripheral part of an insulated substrate, generation | occurrence | production of a crack can be prevented effectively.
[0013]
In the present invention, since the metal base plate has at least one bent portion without bending upward, the required current capacity, the required electric circuit, etc. Accordingly, the number of “f” -shaped bent portions can be increased, and an optimum composite semiconductor device realizing the above-described effect can be designed.
[0014]
【Example】
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows a metal base plate used in the composite semiconductor device of the present invention, FIG. 1 (a) is a front view thereof, and FIG. 1 (b) is a plan view thereof.
In the present invention, a metal base plate 1 having a “f” -shaped bent portion having a flat upper surface on which an electric circuit component is mounted and fixed without being curved upwardly as shown in the figure. Is used.
[0015]
In other words, the metal base plate 1 is bent in a “h” shape at the central portion 1a, and the distance H from the lower surface of the central portion to the alternate long and short dash line L connecting the both end portions 1b is curved convexly upward. The dimension is made to correspond to the radius of curvature of the conventional metal base plate 1 made.
For example, in the embodiment of the present invention, H = 350 to 450 μm.
A plurality of screw mounting holes 2 are provided as in the prior art.
FIG. 2A is a diagram in which the above-described metal base plate 1 is used and electric circuit components are mounted and fixed on the upper surface of the metal base plate 1 as in the conventional case.
[0016]
That is, on the metal base plate 1, an insulating substrate 4 having metal layers 3 on both surfaces, a first external electrode 5 on the insulating substrate 4, a semiconductor element 6 on the first external electrode 5, and the semiconductor element 6 On the heat buffer plate 7 and the second external electrode 8 are sequentially placed on the heat buffer plate 7 through a jig (not shown), and then the components are soldered by a reflow furnace or the like. The
[0017]
FIG. 2B shows an enlarged view of a portion A in FIG. As is clear from this figure, by using the metal base plate 1 having a flat upper surface, the outer peripheral portion of the joining member 13 such as solder does not have an excess or deficiency in the amount of application, and the joining member 13 itself. The surface tension of the insulating substrate 4 and the metal base plate 1 can provide a sufficient contact area. For this reason, the thermal resistance to the metal base plate 1 is improved and the outer peripheral portion of the insulating substrate 4 is sufficiently protected by the bonding member 13, so that the assembly is housed in the insulating case 9 and filled with epoxy resin. When the resin is sealed or when stress during curing is applied, problems such as cracks occurring in the outer peripheral portion of the insulating substrate do not occur.
[0018]
FIGS. 3A and 3B are views showing a modification of another metal base plate used in the composite semiconductor device of the present invention.
FIG. 3A shows the metal base plate 1 having a pair of left and right bent portions 1 c formed on the metal base plate 1, and FIG. Three places are formed in total.
[0019]
The “f” -shaped bent portion 1c can be increased or decreased depending on the number of electric circuit components mounted / fixed on the upper flat surface 1d, the required electric circuit configuration, etc. Ensure the degree.
In short, it is only necessary that the upper flat surface 1d is formed between both ends of the metal base plate 1 or between the first “f” -shaped bent portions 1c or between the “f” -shaped bent portions 1c. .
[0020]
Also in the above modification, the surface on which the electric circuit components are mounted and fixed is not a curved surface but a flat surface, so that the gap between the insulating substrate 4 and the metal base plate 1 is uniform, and in particular, a joining member at the outer periphery. A sufficient contact area of 13 can be ensured. For this reason, similarly to the above, it can sufficiently withstand the mechanical stress applied to the end portion of the insulating substrate 4 when the epoxy resin is sealed or cured, and the occurrence of cracks and the like can be prevented.
[0021]
【Effect of the invention】
As described above, according to the present invention, since the upper surface of the metal base plate on which the electric circuit components are mounted and fixed is made flat, a relatively larger gap is formed in the outer peripheral portion of the insulating substrate than the central portion. It will not be done. For this reason, the wettability of the solder is not adversely affected, and the predetermined amount of solder applied does not become insufficient. As a result, the outer peripheral portion of the insulating substrate can be covered with the surface tension of the solder without excess or deficiency, and a joint portion having a wide contact area as a whole can be obtained as compared with the conventional solder joint portion. As a result, the thermal resistance to the metal base plate can be reduced, and the end of the metal base plate is completely protected by the joining member. Therefore, when the epoxy resin is sealed in the insulating case or during curing Even if stress is applied to the outer peripheral portion of the insulating substrate, there is an excellent effect such that cracks do not occur.
[Brief description of the drawings]
FIG. 1 shows a metal base plate used in a composite semiconductor device of the present invention, wherein (a) is a front view thereof and (b) is a plan view thereof.
FIGS. 2A and 2B show a state in which electric circuit components are mounted on the metal base plate. FIG. 2A is a front view thereof, and FIG. 2B is an enlarged view of a portion A in FIG.
FIG. 3 shows a metal base plate used in the composite semiconductor device of the present invention, and (a) and (b) are front views showing other modified examples.
FIG. 4 is a front view showing an intermediate step of a composite semiconductor device assembled using a conventional metal base plate.
5 is a front view showing a state in which the assembly shown in FIG. 4 is heated in a reflow furnace or the like and soldered between components, and the metal base plate is curved.
6 is a cross-sectional view showing a state in which the assembly of FIG. 5 is housed in an insulating case, filled with epoxy resin, and sealed with resin. FIG.
FIG. 7 is a front view showing an appearance of a conventional composite semiconductor device completed through the above steps.
FIG. 8 is a front view showing a state in which the conventional composite semiconductor device is screwed to an external member such as a heat radiating fin.
FIG. 9 is a front view of a metal base plate to which a warp in a reverse direction is applied in advance in order to eliminate the inconvenience in a conventional composite semiconductor device.
FIG. 10 is a partially enlarged view showing a state where the conventional metal base plate is soldered to an insulating substrate.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Metal base board 1a Center part 1b End part 1c Characteristic bent part 1d Upper surface flat surface 2 Screw attachment hole 3 Metal layer 4 Insulating substrate 5 1st external electrode 6 Semiconductor element 7 Thermal buffer board 8 2nd external electrode 9 Insulating case 10 Filler 11 Composite semiconductor device 12 Radiating fin 13 Joining member

Claims (2)

In a method for manufacturing a composite semiconductor device, in which an electric circuit component including an insulating substrate, external electrodes, a semiconductor element, and a heat buffer plate is mounted and fixed on a metal base plate via a heat bonding member such as solder.
The metal base plate is bent in advance so as to be convex upward so as to cancel the warp due to heating,
A method of manufacturing a composite semiconductor device, wherein an upper surface of a metal base plate on which the electric circuit components are mounted and fixed is not a curved surface but a flat surface. 2. The method of manufacturing a composite semiconductor device according to claim 1, wherein the metal base plate has at least one “f” -shaped bent portion without being bent upward. 3.

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