JPH0831990A - Heat radiating fin - Google Patents

Abstract

PURPOSE:To prevent the bends of metallic layers, etc., and prevent the deformation of a heat radiating fin, by providing a ceramic board on a first metallic layer on the rear surface of a ceramic circuit board, and by bonding to the ceramic board in a laminar way in succession a second metallic layer and the main body of the heat radiating fin via respective aluminum based brazing materials. CONSTITUTION:On the rear surface of a ceramic circuit board 13, a first metallic layer 21 made of an aluminum material which has an area enough to cover the board 13 is provided. On the first metallic layer 21, a ceramic board 18 which has an area enough to cover the layer 21 is laminated. Then, on the ceramic board 18, a second metallic layer 22 made of an aluminum material which has an area enough to cover the board 18 is laminated. Further, on the second metallic layer 22, a main body 19 of a heat radiating fin which has an area enough to cover the layer 22 is formed in a laminar way. In these cases, the laminar layers present between the first mtallic layer 21 and the main body 19 of the heat radiating fin are bonded to each other via aluminum based brazing materials. Thereby, the bends of the respective laminar layers can be prevented by the absorptions of their thermal deformations, and as a result, the deformation of the main body 19 of the heat radiating fin can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation fin for radiating heat generated from a silicon semiconductor chip mounted on a ceramic circuit board to the atmosphere.

[0002]

2. Description of the Related Art Conventionally, as this type of heat dissipating fin, a fin body formed by cutting a highly heat-conductive ceramic such as aluminum nitride (hereinafter referred to as AlN) is attached to a silicon semiconductor chip or a ceramic substrate with an adhesive. It is known that it is glued. In this radiating fin, the fin body has a coefficient of thermal expansion matched with that of the semiconductor chip or the ceramic substrate, so that warpage does not occur even if heat is applied to the semiconductor chip or the ceramic substrate and the fin body.

[0003]

However, in the above-mentioned conventional heat radiation fin, the fin body is formed by cutting the hard and brittle AlN, so that the number of machining steps of the fin body increases and the manufacturing cost is increased. However, the fin body may be chipped by a relatively small impact. Further, since the thermal conductivity of the conventional radiating fin is relatively small, there is a problem that the radiating characteristic of the fin body is not so good. Furthermore,
When the fin body is adhered to the silicon semiconductor chip or the ceramic substrate via solder with the conventional heat dissipating fin, it is necessary to perform a metallizing treatment on the adhering surface in advance.
This caused the deformation of the fin body.

An object of the present invention is to provide a radiating fin which can absorb thermal deformation and prevent warping, reduce the number of man-hours required for processing the fin main body, and is less likely to be damaged by impact. Another object of the present invention is to provide a heat dissipation fin which can improve heat dissipation characteristics and can be adhered even after a semiconductor chip is mounted on a ceramic circuit board.

[0005]

The structure of the present invention for achieving the above object will be described with reference to FIGS. 1, 3 and 5 to 7 corresponding to the embodiments. The first aspect of the present invention is a radiation fin 11 that is directly adhered to the back surface of a ceramic circuit board 13 having a chip 12 mounted on the front surface via solder or an adhesive as shown in FIG. A first metal layer 21 made of an aluminum material having an area capable of covering the back surface, a ceramic substrate 18 having an area capable of coating the first metal layer 21, and an aluminum material having an area capable of coating the ceramic substrate 18. The second metal layer 22 and the fin body 19 made of an aluminum material having an area capable of covering the second metal layer 22 are each made of Al.
These are laminated and adhered in this order through a brazing filler metal.
A second aspect of the present invention is a radiation fin 11 that is directly bonded to the back surface of a ceramic circuit board 13 having a chip 12 mounted on the front surface thereof via solder or an adhesive as shown in FIG.
A first metal layer 21 made of an aluminum material having an area capable of covering the back surface of the ceramic circuit board 13, and a ceramic substrate 18 having an area capable of covering the first metal layer 21.
And a fin body 19 made of an aluminum material having an area capable of covering the ceramic substrate 18 are laminated and adhered in this order through an Al-based brazing material.

The third aspect of the present invention is, as shown in FIG. 3, a radiation fin 11 which is directly adhered to the outer surface of a chip 12 mounted on a ceramic circuit board 13 via a solder or an adhesive. And a first metal layer 21 made of an aluminum material having an area capable of covering
, A second metal layer 22 made of an aluminum material having an area that can cover the ceramic substrate 18, and a fin made of an aluminum material having an area that can cover the second metal layer 22. Body 1
9 is laminated and adhered in this order through an Al-based brazing material. A fourth aspect of the present invention is a radiating fin that is directly bonded to an outer surface of a chip mounted on a ceramic circuit board via a solder or an adhesive, and is made of an aluminum material having an area capable of covering the outer surface of the chip. A metal layer, a ceramic substrate having an area capable of covering the first metal layer, and a fin body made of an aluminum material having an area capable of covering the ceramic substrate were laminated and adhered in this order through an Al-based brazing material. It is a thing.

Further, as shown in FIG. 6, the ceramic substrate 1
8. A plurality of heat conduction through holes 111 are provided at positions facing the chip 12 of FIG.
It is also possible to fill 1 with aluminum material 112, respectively. Further, the thickness of the second metal layer 22 is preferably ⅔ or less of the thickness of the first metal layer 21. Further, as shown in FIG. 5, the fin main body 99 is a corrugated fin having ridges 99a, and it is preferable that the fin main body 99 is cut in a direction orthogonal to the ridges 99a to be divided into a plurality of pieces.

[0008]

In the radiating fin shown in FIG. 1, the heat generated from the chip 12 spreads through the ceramic circuit board 13 to the entire surface in the first metal layer 21 having high thermal conductivity, and
It is transmitted to the second metal layer 22 having a large thermal conductivity through the ceramic substrate 18, further spreads over the entire surface in the second metal layer 22 and is transmitted to the fin body 19, and is diffused from the fin body 19 to the atmosphere. The radiating fin shown in FIG. 3 radiates heat similarly to the radiating fin shown in FIG. 1, except that the heat generated by the chip 12 directly spreads over the entire surface in the first metal layer 21 having a large thermal conductivity. Be seen.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described in detail with reference to the drawings. As shown in FIG. 1, the heat radiation fin 11 is directly adhered to the back surface of the thin film multilayer ceramic circuit board 13 on which the silicon semiconductor chip 12 is mounted via an adhesive. The ceramic circuit board 13 is composed of a plurality of Al ₂ O ₃ boards 1.
4 and a plurality of tungsten conductors 16 forming a circuit,
It is formed by simultaneous firing at a high temperature of around 600 ° C. and laminating and adhering. The semiconductor chip 12 is die-bonded to the surface of the ceramic circuit board 13 using Al-Si solder at 420 ° C., and then the Au wire 17 is applied at 300 ° C.
It is mounted by wire bonding. In this example, three semiconductor chips 12 are mounted on the surface of the ceramic circuit board 13 with a predetermined gap. These semiconductor chips 12 form a square having a side of 33 mm.

The radiation fin 11 is a ceramic circuit board 13.
The three first metal layers 21 and the three first metal layers 21 each having a surface area which can be covered with the ceramic circuit board 13 and is disposed at a position facing the semiconductor chip 12 on the back surface of Ceramic substrates 18 having different areas, three second metal layers 22 having an area capable of covering the three ceramic substrates 18, and three second metal layers 22
And three fin bodies 19 having an area capable of covering The first and second metal layers 21 and 22 are made of an aluminum alloy containing 97% or more of aluminum, and the ceramic substrate 18 is made of Al ₂ O _{3 in} this example. The first metal layer 21, the second metal layer 22 and the ceramic substrate 18 form a square having a side of 40 mm.
The thicknesses of the first and second metal layers 22 and the ceramic substrate 18 are 0.2 mm, 0.4 mm and 0.635 mm, respectively.

A ceramic substrate 18 is formed on the first metal layer 21.
Is placed with an Al-7.5% Si foil (weight%, the same applies hereinafter) having a thickness of 30 μm sandwiched therebetween, and the second metal layer 22 is provided on the ceramic substrate 18 with a thickness of 30 μm of Al-7.5% Si.
It is placed with a foil sandwiched between them, and in this state 2 kgf / c
By applying a load of m ² and heating in a vacuum furnace at 630 ° C. for 30 minutes, the first metal layer 21, the ceramic substrate 18, and the second metal layer 22 are laminated and bonded.

As shown in FIGS. 1 and 2, the fin main body 19 is composed of a plurality of first fins 19 which are provided laterally at predetermined intervals.
The protrusion 19a and the first protrusion 19a are connected to the first protrusion 19a.
a plurality of second protrusions 19b provided laterally offset from a by a predetermined distance, and first and second protrusions 19a, 19b
It is a corrugated louver fin made of aluminum having a window 19c formed therebetween. The first projections 19a and the second projections 19b are alternately arranged in the vertical direction. Fin body 19
Is formed by pressing an aluminum alloy plate having a thickness of 0.3 mm and containing 87% or more of aluminum, and the length and width thereof are substantially the same as those of the metal layers 21 and 22, and the height thereof is 6 mm. . The above laminated and laminated second
On the metal layer 22, the fin body 19 is Al-having a thickness of 60 μm.
A 7.5% Si foil is sandwiched between them, and a load of 20 g / cm ² is applied to them in this state at 630 ° C. for 3 hours in a vacuum furnace.
By heating for 0 minutes, the fin body 19 is bonded to the second metal layer 22 to form the heat radiation fin 11. 3 above
The heat dissipating fins 19 are adhesive so that the first metal layer 21 is located on the back surface of the ceramic circuit board 13, that is, on the back surface of the Al ₂ O ₃ substrate 14 located at the lowermost position, directly below the three semiconductor chips 12. It is directly bonded to the ceramic circuit board 13 by bonding with an epoxy resin.

The operation of the radiation fin thus constructed will be described. The heat generated from the silicon semiconductor chip 12 spreads over the entire surface in the first metal layer 21 having a large thermal conductivity through the thin film multilayer ceramic circuit board 13 and also through the ceramic substrate 18, the second metal having a large thermal conductivity. It is transmitted to layer 22. This heat further spreads over the entire surface in the second metal layer 22 and is transmitted to the fin body 19,
Smoothly dissipates into the atmosphere. As a result, the temperature rise of the semiconductor chip 12 can be suppressed low. Although the ceramic circuit board 13 and the fin body 19 have different thermal expansion coefficients, the first and second metal layers 21 and 22 having small deformation resistance are adhered to both surfaces of the ceramic substrate 18, and the thermal expansion of the ceramic substrate 18 is increased. Since the coefficient is substantially the same as that of the ceramic circuit board 13, even if they are adhered by an adhesive material, it is possible to prevent the adhered surfaces from peeling due to a thermal cycle.

FIG. 3 shows a second embodiment of the present invention. 3, the same reference numerals as those in FIG. 1 indicate the same parts. In this example,
The heat radiation fin 11 is directly adhered to the outer surface of the silicon semiconductor chip 12 mounted on the thin film multilayer ceramic circuit board 13 formed in the same manner as in the first embodiment via solder. The semiconductor chip 12 is mounted on the surface of the ceramic circuit board 13 via solder bumps 51. The solder bumps 51 are formed by projecting solder on the electrodes on the surface of the semiconductor chip 12, and are formed of Cu balls plated with Ni and Au composite plating, or of an alloy of Pb and Sn. The solder bumps 51 raised on the electrodes of the semiconductor chip 12 are temporarily fixed to the terminals of the tungsten conductor 16 of the ceramic circuit board 13 by the adhesive force of the flux, and the solder bumps 51 are melted by heating in this state. Chip 12 is ceramic circuit board 13
Will be implemented in. The semiconductor chip 12 has a square shape with one side of 33 mm.

The radiation fin 19 has a first metal layer 21 having an area capable of covering the outer surface of the semiconductor chip 12, and a ceramic substrate 18 having an area capable of covering the first metal layer 21.
And a second having an area capable of covering the ceramic substrate 18.
The metal layer 22 and the fin body 19 having an area capable of covering the second metal layer 22 are provided. The first metal layer 21, the second metal layer 22, and the ceramic substrate 18 are made of the same material and have the same dimensions as the first metal layer, the second metal layer, and the ceramic substrate of the first embodiment. The second metal layer 22 and the ceramic substrate 18 are laminated and adhered in the same manner as the first metal layer, the second metal layer and the ceramic substrate of the first embodiment.

Further, the fin main body 19 is a corrugated louver fin formed in the same shape with the same material as in the first embodiment, and the fin main body 19 is laminated and adhered to the second metal layer 22 in the same manner as in the first embodiment. The heat radiation fins 11 are formed by being adhered on the above. The surface of the heat dissipation fin 19 that is bonded to the outer surface of the semiconductor chip 12 via solder, that is, the back surface of the first metal layer 21 is pre-plated with Ni, and the outer surface of the semiconductor chip 12 is back surface with Ni metallization or the like in advance. Processing is performed. The radiating fin 19 is placed on the outer surface of the semiconductor chip 12 via a Sn-3.5% Ag solder foil having a thickness of 50 to 100 μm, and in this state, a load of 10 g / cm ² is applied to the radiating fin 19 in a reflow furnace at 260 ° C. It is directly bonded to the outer surface of the semiconductor chip 12 by heating for 1 to 3 minutes.

In the radiation fin thus constructed, the operation is the same as that of the first embodiment except that the heat generated from the silicon semiconductor chip 12 is directly spread over the entire surface of the first metal layer 21 having a large thermal conductivity. Since it is the same, repeated description is omitted.

In the first and second embodiments, the fin main body includes the first projection, the second projection provided laterally offset from the first projection, and the window formed between the first and second projections. Although the corrugated louver fin made of aluminum having the above is given, the fin main body 79 may be a corrugated honeycomb fin made of aluminum having a substantially honeycomb cross section as shown in FIG. A plurality of ridges 99a extending in the vertical direction at predetermined intervals
Alternatively, an aluminum corrugated fin having openings 99b formed at both ends of these ridges 99a may be used.
When the fin main body 99 is adhered to the ceramic substrate of FIG. 1 through the second metal layer, the fin main body 9 can be divided into a plurality of pieces by cutting the fin main body 99 in a direction orthogonal to the ridge 99a.
Warp due to the difference in thermal expansion coefficient when 9 is adhered to the ceramic substrate can be reduced, which is preferable.
Although not shown, the fin body may be an aluminum pin fin having a large number of pins protruding from the mounting plate.

Further, as shown in FIG. 6, a plurality of heat conduction through holes 111 are provided at positions facing the chips 12 of the ceramic substrate 18 of the first embodiment, and these through holes 111 are filled with aluminum materials 112, respectively. You may. In this case, the heat of the first metal layer 21 can be transferred to the second metal layer 22 more smoothly through the aluminum material 112. Although not shown, the ceramic substrate 18 of the second embodiment may be provided with a through hole for heat conduction filled with an aluminum material. Further, in the first embodiment, the heat radiation fin is directly adhered to the ceramic circuit board by the epoxy adhesive, but the Sn-thickness of 50 to 100 μm is used.
It may be directly bonded via 3.5% Ag solder. In addition, in the second embodiment described above, the radiation fin has a thickness of 50 to 100.
Although it was directly adhered to the outer surface of the silicon semiconductor chip through the Sn-3.5% Ag solder foil of μm, it may be directly adhered through the paste-like cream solder, or directly by the epoxy adhesive. May be. In the first and second embodiments, the ceramic substrate formed between the first and second metal layers is made of Al ₂ O ₃ , but this is only an example and is made of AlN or SiC. You may form.

In the first and second embodiments, the thicknesses of the first metal layer, the second metal layer and the ceramic substrate are 0.4 mm, 0.2 mm and 0.635 mm, respectively. The thickness of the layer may be in the range of 0.1 to 1.0 mm, and the thickness of the second metal layer is 2 times the thickness of the first metal layer.
The thickness of the ceramic substrate is less than or equal to / 3 and is within the range of 0 to 0.5 mm.
It may be 10 times and 0.1 to 1.0 mm. Therefore, as shown in FIG. 7, the fin body 19 is directly formed on the back surface of the ceramic substrate 18 without using the second metal layer.
You may adhere | attach via a brazing material. In this case, the adhesion portion of the fin body 19 to the ceramic substrate 18 serves as the second metal layer. The thickness is limited as described above
If the thickness of the metal layer is less than 0.1 mm, the heat dissipation performance of the heat generated in the chip is not sufficient, and if the thickness of the first and second metal layers exceeds 1.0 mm and 0.5 mm, respectively, the adhesion occurs. This is because cracks and fractures are likely to occur during subsequent stress relaxation. If the thickness of the ceramic substrate is less than 0.1 mm, the insulation properties and mechanical strength will be poor, and if it exceeds 1.0 mm, the thermal resistance will increase in the case of Al ₂ O ₃ . However, this is not the case when AlN or SiC, which is a ceramic having high thermal conductivity equivalent to that of aluminum, is used. Further, although Al-7.5% Si foil is exemplified as the Al-based brazing material in the first and second embodiments, other than this, Al-13% Si and Al-9.5% Si foils are used.
A foil made of -1.0% Mg, Al-7.5% Si-10% Ge, etc. can also be used.

[0021]

As described above, according to the present invention, the first metal layer made of an aluminum material, the ceramic substrate, and the second metal layer made of an aluminum material are formed on the back surface of the ceramic circuit board on which the chip is mounted. Since the fin body and the fin body are laminated and adhered in this order through the Al-based brazing material,
The thermal deformation due to the difference in thermal expansion coefficient between the fin body and the ceramic substrate can be absorbed by the first and second metal layers having low deformation resistance. Further, since the ceramic substrate, which is the base portion of the heat radiation fin, is made of a material having a coefficient of thermal expansion substantially equal to that of the ceramic circuit board, even if the heat radiation fin is directly adhered to the ceramic circuit board, peeling does not occur due to thermal cycles. Absent. Further, as compared with the conventional heat dissipating fin having a fin body formed of AlN, the present invention can reduce the number of man-hours for processing the fin body, are less likely to be damaged even when an impact is applied to the fin body, and further dissipate heat of the fin body. Can be improved.

Further, even after the semiconductor chip is mounted on the ceramic circuit board, the radiation fins can be bonded to the ceramic circuit board without melting and peeling off the already soldered portions of the semiconductor chip and the ceramic circuit board. If a plurality of through holes for heat conduction are provided at positions facing the chip of the ceramic substrate, and these through holes are filled with aluminum materials, respectively, the heat of the first metal layer passes through the aluminum materials and the second heat is smoothly transferred. It is transmitted to the metal layer or the fin body. Further, a first metal layer made of an aluminum material, a ceramic substrate, a second metal layer made of an aluminum material, and a fin body are laminated and adhered in this order on the outer surface of the chip mounted on the ceramic circuit board through an Al-based brazing material. Also, the same effect as described above can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view of a ceramic circuit board including a radiation fin according to a first embodiment of the present invention.

FIG. 2 is a view on arrow A in FIG.

FIG. 3 is a sectional view corresponding to FIG. 1 showing a second embodiment of the present invention.

FIG. 4 is a sectional view of a fin body showing a third embodiment of the present invention.

FIG. 5 is a sectional view corresponding to FIG. 4, showing a fourth embodiment of the present invention.

FIG. 6 is a sectional view corresponding to FIG. 1 showing a fifth embodiment of the present invention.

FIG. 7 is a sectional view corresponding to FIG. 1 showing a sixth embodiment of the present invention.

[Explanation of symbols]

 11, 79, 99 Heat dissipation fin 12 Silicon semiconductor chip 13 Thin film multilayer ceramic circuit board 18 Ceramic substrate 19 Fin body 21 First metal layer 22 Second metal layer 111 Heat conduction through hole 112 Aluminum material

Claims (7)

[Claims] 1. A radiating fin (11) directly bonded to the back surface of a ceramic circuit board (13) having a chip (12) mounted on the front surface through a solder or an adhesive, the ceramic circuit board (13) A first metal layer (21) made of an aluminum material having an area capable of covering the back surface of the ceramic substrate, a ceramic substrate (18) having an area capable of coating the first metal layer (21), and the ceramic substrate (18) The second metal layer (22) made of an aluminum material having an area capable of coating the aluminum and the fin body (19) made of an aluminum material having an area capable of coating the second metal layer (22) are each made of an Al-based solder. A radiating fin characterized by being laminated and adhered in this order through a material. 2. A heat dissipation fin (11) directly bonded to the back surface of a ceramic circuit board (13) having a chip (12) mounted on the front surface via solder or an adhesive, the ceramic circuit board (13) A first metal layer (21) made of an aluminum material having an area capable of covering the back surface of the ceramic substrate, a ceramic substrate (18) having an area capable of coating the first metal layer (21), and the ceramic substrate (18) The radiating fin according to claim 1, wherein a fin body (19) made of an aluminum material having an area capable of covering the above is laminated and adhered in this order via an Al-based brazing material. 3. A radiation fin (11) directly bonded to the outer surface of a chip (12) mounted on a ceramic circuit board (13) via a solder or an adhesive, and covering the outer surface of the chip (12). A first metal layer (21) made of an aluminum material having a possible area, and the first metal layer (2)
(1) a ceramic substrate (18) having an area capable of coating, a second metal layer (22) made of an aluminum material having an area capable of coating the ceramic substrate (18), and the second metal layer (2)
A radiating fin characterized in that the fin body (19) made of an aluminum material having an area capable of covering 2) is laminated and adhered in this order via an Al-based brazing material. 4. A heat radiation fin (11) directly bonded to the outer surface of a chip (12) mounted on a ceramic circuit board (13) via a solder or an adhesive, and covering the outer surface of the chip (12). A first metal layer (21) made of an aluminum material having a possible area, and the first metal layer (2)
The ceramic substrate (18) having an area capable of coating 1) and the fin body (19) made of an aluminum material having an area capable of coating the ceramic substrate (18) are respectively arranged in this order via an Al-based brazing material. The radiation fin according to claim 3, which is laminated and adhered. 5. A plurality of heat conduction through holes (111) are provided at positions of the ceramic substrate (18) facing the chips (12), and the plurality of heat conduction through holes (111) are made of an aluminum material (112). ) The radiation fins according to any one of claims 1 to 4, each of which is filled with. 6. The thickness of the second metal layer (22) is the first metal layer (21).
The radiating fin according to any one of claims 1 to 5, wherein the radiating fin has a thickness of ⅔ or less. 7. The fin body (99) is a corrugated fin having ridges (99a), and the fin body (99) is divided into a plurality of pieces by cutting in a direction orthogonal to the ridges (99a). The radiation fin according to any one of claims 1 to 6.