JP3171234B2 - Ceramic circuit board with heat sink - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a ceramic circuit board for a semiconductor device such as a power module board.
More particularly, the present invention relates to a ceramic circuit board having a heat sink for dissipating heat generated from a heating element such as a semiconductor chip.

[0002]

2. Description of the Related Art Conventionally, as a ceramic circuit board of this kind, as shown in FIG. 6, a ceramic board 3 is formed of AlN, and first and second copper plates 1 and 2 are laminated and adhered to both sides of the ceramic board 3. Structure 4 is converted to AlSiC
There is known a heat sink 8 joined to the upper surface of a heat sink 8 formed of a composite material via solder 6. In the circuit board 9, the first and second copper plates 1 and 2 are joined to the ceramic substrate 3 in a state where the ceramic substrate 3 and the second copper plate 2 are stacked on the first copper plate 1 and a load of 0.5 ~ 2kg
f / cm ² and 1065 to 1075 ° C. in N ₂ atmosphere
The structure 4 is formed by a direct bond copper (DBC) method of heating the second copper plate 2 of the structure 4 into a circuit having a predetermined pattern by etching . Thereafter, a heat sink 8 having Ni plating formed on the upper surface is joined to the first copper plate 1 of the structure 4 via the solder 6, and a semiconductor chip or the like (not shown) is mounted on the second copper plate 2. In the ceramic circuit board thus configured, heat generated by the semiconductor chip and the like is radiated from the surface of the heat sink 8 via the second copper plate 2, the ceramic substrate 3, the first copper plate 1, and the solder 6. I have.

[0003]

However, the above-mentioned conventional ceramic circuit board has a disadvantage that the thermal resistance of the solder 6 used for joining the heat sink 8 and the first copper plate 1 is relatively large. Therefore, there still remains a problem to be solved in which heat generated from the semiconductor chip or the like cannot be effectively dissipated from the heat sink 8 to the outside. In order to solve this problem, it is conceivable to braze the heat sink 8 and the first copper plate 1 via a metal having a small thermal resistance value. However, such a brazing of the metal generally needs to be performed at a relatively high temperature. This causes an increase in the internal stress of the heat sink 8, the first or second copper plates 1, 2 and the ceramic substrate 3 due to the brazing at a high temperature, and the heat generation and non-heat generation of the semiconductor chip and the like. When the temperature repeatedly changes between the high temperature and the low temperature, cracks may be generated in the ceramic substrate 3 or the like. An object of the present invention is to provide a ceramic circuit board with a heat sink that improves heat radiation characteristics. Another object of the present invention is to provide a ceramic circuit board with a heat sink having a long heat cycle life.

[0004]

The invention according to claim 1 is
As shown in FIGS. 1 and 2, a structure 14 in which first and second aluminum plates 11 and 12 or first and second copper plates are laminated and bonded to both surfaces of a ceramic substrate 13 via the aluminum plate 11 or the copper plate, respectively. This is an improvement of the ceramic circuit board with a heat sink bonded to the heat sink 16. Its characteristic configuration is that the structure 14 and the heat sink 1
6 is a purity 99 having an Al melting point depressed layer 17a formed on both surfaces.
It is at the place where it is joined via the aluminum foil 17 of not less than% by weight.

The invention according to claim 2 is the invention according to claim 1, wherein the Al melting point depressing layer 17a is formed of an Al—Si alloy layer, an Al—Cu alloy layer, an Al—Mg alloy layer, an Al—Ni alloy layer.
It is a ceramic circuit board with a heat sink, which is an alloy layer, an Al-Ag alloy layer or an Al-Ce alloy layer. In the circuit board according to claim 1 or 2, the heat sink 16 is connected to the aluminum plate 1 by using an aluminum foil 17 having a high thermal conductivity and a purity of 99% by weight or more instead of the conventional brazing material or solder.
1 or a copper plate, so that heat radiation characteristics are improved. Also,
The bonding can be performed at a temperature lower than the melting point of Al by the Al melting point lowering layer 17a. Further, since the aluminum foil 17 has a small deformation resistance, the ceramic substrate 13 does not crack even if a heat cycle is applied to the circuit board after bonding.
Its life can be lengthened.

The invention according to claim 3 is the invention according to claim 1 or 2, wherein, as shown in FIG. 1, the joint surfaces of the structure 14 and the heat sink 16 with the aluminum foil 17 are formed by Ni plating 11a. , 16a. In the circuit board according to the third aspect, by applying the Ni platings 11a and 16a, the heat sink 16 can be easily joined to the aluminum plate 11 or the copper plate at a relatively low temperature.

The invention according to claim 4 is the invention according to claims 1 to 3
The invention according to any one of the above, wherein the ceramic substrate 13
The heat sink 16 is a ceramic circuit board with a heat sink formed of 1N, Si ₃ N ₄ or Al ₂ O ₃ , and the heat sink 16 is formed of Cu, Al or AlSiC-based composite material.
In the circuit board according to the fourth aspect, the ceramic substrate 13
When AlN is used, the thermal conductivity and heat resistance are improved,
When Si ₃ N ₄ is used, strength and heat resistance are improved, and Al ₂ O ₃
When heat is used, heat resistance is improved. The heat sink 16
Is formed of a Cu, Al or AlSiC-based composite material, thereby effectively dissipating heat generated from a semiconductor chip or the like from the heat sink 16 to the outside.

The invention according to claim 5 is the invention according to claims 1 to 4
The invention according to any one of the above, wherein the aluminum foil 17 is 5
It is a ceramic circuit board with a heat sink having a thickness of about 500 μm. If the aluminum foil 17 is less than 5 μm, it becomes difficult to join the structure 14 and the heat sink 16, and if the aluminum foil 17 exceeds 500 μm, the thermal resistance increases.

[0009]

Next, a first embodiment of the present invention will be described in detail with reference to the drawings. (a) Structure As shown in FIGS. 1 and 5, structures 14 and 24 are formed on both surfaces of ceramic substrates 13 and 23 by first and second aluminum substrates.
Plates 11 and 12 or first and second copper plates 21 and 22 are laminated and bonded, respectively, and ceramic substrates 13 and 23 are formed.
Is formed of AlN, Si ₃ N ₄ or Al ₂ O ₃ . As shown in FIG. 1, in order to laminate and bond the first and second aluminum plates 11 and 12 on both sides of the ceramic substrate 13, an Al—Si brazing material (not shown) is placed on the first aluminum plate 11. In a state where the ceramic substrate 13, the Al-Si brazing material (not shown) and the second aluminum plate 12 are stacked,
A load of 0.5 to 5 kgf / cm ² is applied to these, and heating is performed at 600 to 630 ° C. in a vacuum. After lamination and bonding, the second aluminum plate 12 becomes a circuit having a predetermined pattern by etching. Al-Si brazing material is 9
An alloy of 0 to 95% by weight of Al and 5 to 10% by weight of Si is preferred. As shown in FIG. 5, in order to laminate and bond the first and second copper plates 21 and 22 on both sides of the ceramic substrate 23, the ceramic substrate 13 and the second copper plate 22 are stacked on the first copper plate 21. Load 0.5-2kgf
/ Cm ² and heated to 1065 to 1075 ° C. in a N ₂ atmosphere by a DBC (Direct Bond Copper) method, and the second copper plate 22 of the structure 24 becomes a circuit having a predetermined pattern by etching .

(B) Heat sink The heat sink 16 is formed of a Cu, Al or AlSiC-based composite material. When the heat sink is an AlSiC-based composite material, the AlSiC-based composite material is formed by pouring an Al alloy into gaps between the powders before firing the SiC powder before firing.

(C) Aluminum foil The aluminum foil 17 is an aluminum foil having a purity of 99% by weight or more. As shown in FIG. 2, Al melting point depressing layers 17a, 17a are formed on both surfaces. The aluminum foil 17 has a thickness of 5 to 500 μm, and the Al melting point lowering layer 17a has an Al—Si alloy layer, an Al—Cu alloy layer, an Al—Mg alloy layer, an Al—Ni alloy layer, and an Al—Ag alloy layer. Or Al-
A Ce alloy layer is exemplified. Note that the Al melting point lowering layer 17a
Is formed on the aluminum foil 17 as shown in FIG.
The melting point lowering layer 17a may be formed by coating the aluminum foil 17, or as shown in FIG. 3, an Al melting point lowering layer 17a in the form of fine particles may be formed on the aluminum foil 17 by vapor deposition or the like.

(D) Bonding of heat sink to first aluminum plate or first copper plate As shown in FIG. 4, the structure 1 in which the first aluminum plate 11 or the second copper plate 21 is placed on the bottom of the heat sink 16
4 and 24, and a load of 3 kgf / cm ² was applied thereto and heated and maintained at 520 to 570 ° C. in a vacuum to melt the Al alloy in the Al melting point depressed layer 17 a formed on both sides of the aluminum foil. The heat sink 16 is joined to the structures 14 and 24 via the aluminum foil 17. The first aluminum plate 11 or the first copper plate 21 is formed into a circuit having a predetermined pattern by etching, and the aluminum foil 17 is formed on the second aluminum plate 12 or the second copper plate 22.
The heat sink 16 may be joined via the heat sink.

[0013]

Next, examples of the present invention will be described in detail together with comparative examples. <Example 1> As shown in FIG. 1, a ceramic substrate 13 made of AlN having a length, width and thickness of 50 mm, 50 mm and 0.6 mm respectively, and a length, width and thickness of 30 mm, 30 mm and First and second aluminum plates 11, 12 formed of 0.4 mm Al;
The length, width and thickness are 30 mm, 30 mm and 0.3 mm, respectively.
Al-S which is an Al-7.5 wt% Si alloy of 03 mm
An i-type brazing material (not shown) was prepared, and the structure 14 was manufactured.

To manufacture the structure 14, first, an Al—Si brazing material, a ceramic substrate 13, an Al—Si brazing material, and a second aluminum plate 12 are placed on the first aluminum plate 11.
In a state in which the first and second aluminum plates 11 and 11 are attached to both sides of the ceramic substrate 13 by applying a load of 2 kgf / cm ² and heating the same to 630 ° C. in a vacuum.
12 were laminated and bonded. After the lamination and bonding, the second aluminum plate 12 was etched to obtain a structure 14 as a circuit having a predetermined pattern. Next, with this structure 14, the vertical, horizontal and thickness are 70 mm, 70 mm and 2.0 mm, respectively.
A heat sink 16 formed of an AlSiC-based composite material, and a vertical structure having an Al melting point depressed layer 17a formed on both surfaces.
30mm, 30mm and 0.1m respectively in width and thickness
An aluminum foil 17 having a purity of 99% by weight or more was prepared. Al-7.5 wt% Si is used for the Al melting point lowering layer 17a.
The alloy was formed on both surfaces of the aluminum foil 17 by coating to a thickness of 0.05 mm.

The joint surfaces between the first aluminum plate 11 of the structure 14 and the aluminum foil 17 of the heat sink 16 are each provided with a Ni plating 11a, 1 having a thickness of 0.005 mm.
6a was applied, and the structure 14 with the first aluminum plate 11 on the lower side was overlaid on the heat sink 16 via the aluminum foil 17. Load 2kgf / cm
² and then heated to 530 ° C. in a vacuum and left for 2 hours to remove the heat sink 16 from the first aluminum plate 11.
And a ceramic circuit board 10 with a heat sink.

<Example 2> Although not shown, the same structure and heat sink as in Example 1 were prepared. Next, as shown in FIG. 3, the length, width and thickness of the Al-melting point depressed layer 17a formed on both surfaces are 30 mm, 30 mm and 0.3 mm, respectively.
A 2 mm aluminum foil 17 having a purity of 99% by weight or more was prepared. The Al melting point lowering layer 17a is composed of Al-7.5% by weight.
Aluminum foil 17 with Si alloy powder (particle size 1.0 μm)
Crimped on top. Each of the joining surfaces of the first aluminum plate of the structure and the aluminum foil of the heat sink was plated with Ni having a thickness of 0.003 mm, and the first aluminum plate was placed on the lower side of the heat sink via the aluminum foil. Structure and superimposed. Load 2kgf
/ Cm ² and heated to 520 ° C. in a vacuum.
By leaving it for a while, the heat sink was bonded to the first aluminum plate via an aluminum foil to obtain a ceramic circuit board with a heat sink.

<Embodiment 3> Although not shown, the first structure
A ceramic circuit board with a heat sink was manufactured in the same manner as in Example 1 except that the respective joining surfaces of the aluminum plate and the heat sink with the aluminum foil were not plated with Ni. That is, the first aluminum plate of the structure and the aluminum foil of the heat sink are not subjected to any treatment, and the first aluminum plate is placed on the heat sink via the same aluminum foil as in the first embodiment. A heat sink was bonded to the first aluminum plate via an aluminum foil by stacking the lower structure and applying a load of 2 kgf / cm ² thereto and leaving the structure heated at 520 ° C. in vacuum for 2 hours. Thus, a ceramic circuit board with a heat sink was obtained.

Example 4 Although not shown, the same structure as in Example 1 was manufactured except that Si ₃ N ₄ was used for the ceramic substrate. That is, the vertical, horizontal and thickness are each 50 mm, 5
A ceramic substrate formed of 0 mm and 0.6 mm Si ₃ N ₄ , the same first and second aluminum plates and Al-Si brazing material as in Example 1 were prepared, and Al was placed on the first aluminum plate. -Si-based brazing material, a ceramic substrate made of Si ₃ N _4, in a laminated state Al-Si based brazing material and the second aluminum plate, these load 3 kgf / cm ² and heat to 640 ° C. in vacuo Thereby, the first and second aluminum plates were laminated and bonded to both surfaces of the ceramic substrate. After lamination and bonding, a structure was obtained as a circuit having a predetermined pattern by etching the second aluminum plate.

Next, a heat sink made of Al having a length, width and thickness of 70 mm, 70 mm and 2.0 mm, respectively, and an Al melting point depressed layer made of an Al-Cu alloy were formed on both sides together with this structure. Purity 99 with vertical, horizontal and thickness of 30mm, 30mm and 0.1mm respectively
A weight percent or more of aluminum foil 17 was prepared. Al-C
The u alloy was formed with a thickness of 0.008 mm on both surfaces of the aluminum foil 17 by coating an Al-5% by weight Cu alloy. Each of the joining surfaces between the first aluminum plate of the structure and the aluminum foil of the heat sink has a thickness of 0.1 mm.
005 mm of Ni plating was applied, and a structure having a first aluminum plate on the lower side was overlaid on a heat sink made of Al via an aluminum foil. A heat sink was bonded to the first aluminum plate via an aluminum foil by applying a load of 3 kgf / cm ² , heating to 570 ° C. in a vacuum, and allowing to stand for 2 hours to obtain a ceramic circuit board with a heat sink.

<Example 5> Although not shown, the same structure as in Example 1 was manufactured except that Al ₂ O ₃ was used for the ceramic substrate. That is, the vertical, horizontal and thickness are each 50 mm, 5
A ceramic substrate formed of Al ₂ O ₃ of 0 mm and 0.6 mm, the same first and second aluminum plates and Al-Si brazing material as in Example 1 were prepared, and Al was placed on the first aluminum plate. -Si-based brazing material, a ceramic substrate of Al ₂ O _3, in the state of extensive Al-Si based brazing material and the second aluminum plate, these load 2 kgf / cm ² and heat to 630 ° C. in vacuo Thereby, the first and second aluminum plates were laminated and bonded to both surfaces of the ceramic substrate. After lamination and bonding, a structure was obtained as a circuit having a predetermined pattern by etching the second aluminum plate.

Next, a heat sink formed of Cu having a length, width, and thickness of 70 mm, 70 mm, and 2 mm, respectively, with this structure, and a vertical heat sink having an Al-Mg alloy formed on both surfaces thereof, Aluminum foil 17 having a width and a thickness of 30 mm, 30 mm, and 0.2 mm, respectively, and having a purity of 99% by weight or more was prepared. The Al-Mg alloy was formed to a thickness of 0.004 mm on both surfaces of the aluminum foil 17 by coating an Al-6 wt% Mg alloy. A thickness of 0.001 mm is applied to each joint surface between the first aluminum plate of the structure and the aluminum foil of the heat sink.
An Ni plating of 8 mm was applied, and a structure having a first aluminum plate on the lower side was overlaid on a heat sink made of Cu via an aluminum foil. Load 3k on these
gf / cm ² was added, and the mixture was heated to 520 ° C. in a vacuum and allowed to stand for 3 hours to join a heat sink to the first aluminum plate via an aluminum foil to obtain a ceramic circuit board with a heat sink.

<Embodiment 6> As shown in FIG. 5, the height, width and thickness are each 50 m.
m, 50 mm and 0.6 mm ceramic substrate 13 formed of AlN, and each having a vertical, horizontal and thickness of 70
First and second copper plates 21 and 22 formed of Cu alloys of mm, 70 mm and 2 mm were prepared, and the structure 24 was manufactured. The structure 24 is manufactured by stacking the ceramic substrate 13 and the second copper plate 22 on the first copper plate 21 and applying a load of 0.5 to ² kgf / cm ² to them in an N ₂ atmosphere. DBC (Direct B)
performed by ond Copper) method, the second copper plate 22 is etching
Thus, the structure 24 was obtained as a circuit having a predetermined pattern.

Next, with this structure 24, A, 70 mm, and 3.0 mm A,
Heat sink 16 made of lSiC-based composite material
And an aluminum-melting point depressed layer made of an Al-Ni alloy is formed on both sides, and the length, width and thickness are 30 mm and 30 mm, respectively.
And a 0.3 mm aluminum foil 17 having a purity of 99% by weight or more. Al-Ni alloy is Al-3wt% Ni
The alloy was formed on both surfaces of the aluminum foil 17 by coating to a thickness of 0.05 mm. The joint surface between the first copper plate 21 of the structure 24 and the aluminum foil 17 of the heat sink 16 is subjected to Ni plating with a thickness of 0.005 mm, and the aluminum foil 17 is placed on the heat sink 16 made of an AlSiC-based composite material. And the structure 24 with the first copper plate on the lower side. Load 3k on these
gf / cm ² , heated to 530 ° C. in a vacuum and allowed to stand for 3 hours, so that the heat sink 16
Was bonded via an aluminum foil 17 to obtain a ceramic circuit board 20 with a heat sink.

<Example 7> Although not shown, the same structure as in Example 6 was manufactured except that Si ₃ N ₄ was used for the ceramic substrate. That is, S of 50 mm, 50 mm and 0.6 mm in length, width and thickness respectively.
A ceramic substrate formed of i ₃ N ₄ and the same first and second copper plates as in Example 6 were prepared, and Si was placed on the first copper plate.
_A load of 0.5 to ² kgf / cm ² is applied to the ceramic substrate made of ₃ N ₄ and the second copper plate in a state where they are stacked, and N ₂
After heating to 1065 to 1075 ° C. in an atmosphere for laminating and bonding, the structure was obtained as a circuit having a predetermined pattern by etching the second copper plate. Next, with this structure,
A heat sink formed of Al having a width and a thickness of 70 mm, 70 mm and 2 mm, respectively, and Al-A on both surfaces
Aluminum foil having a purity of 99% by weight or more having a length, a width and a thickness of 30 mm, 30 mm and 0.2 mm, respectively, on which an Al melting point depressed layer made of a g alloy was formed was prepared. Al-
The Ag alloy was formed by coating an Al-4% by weight Ag alloy on both surfaces of the aluminum foil with a thickness of 0.2 mm. The joint surface between the first copper plate of the structure and the aluminum foil of the heat sink is plated with 0.01 mm thick Ni, and the first copper plate is placed on the heat sink made of Al via the aluminum foil with the first copper plate facing down. With the structure. A heat sink was bonded to the first copper plate via an aluminum foil by applying a load of 3 kgf / cm ² thereto, heating to 530 ° C. in a vacuum, and allowing to stand for 5 hours.
A ceramic circuit board with a heat sink was obtained.

Example 8 Although not shown, the same structure as in Example 6 was manufactured except that Al ₂ O ₃ was used for the ceramic substrate. That is, A having a length, width and thickness of 50 mm, 50 mm and 0.6 mm, respectively.
A ceramic substrate made of l ₂ O ₃ and the same first and second copper plates as in Example 6 were prepared, and Al was placed on the first copper plate.
_In a state where the ceramic substrate made of ₂ O ₃ and the second copper plate are stacked, a load of 0.5 to ² kgf / cm ² is applied to them, and N ₂
After heating to 1065 to 1075 ° C. in an atmosphere for laminating and bonding, the structure was obtained as a circuit having a predetermined pattern by etching the second copper plate. Next, with this structure,
A heat sink formed of Cu having a width and a thickness of 70 mm, 70 mm and 2 mm, respectively, and Al-C
Aluminum foil having a purity of 99% by weight or more with a length, width and thickness of 30 mm, 30 mm and 0.1 mm, respectively, on which an Al melting point depressed layer made of an e-alloy was formed was prepared. Al-
The Ce alloy was formed by coating an Al-7% by weight Ce alloy on both surfaces of the aluminum foil with a thickness of 0.05 mm. The joining surface between the first copper plate of the structure and the aluminum foil of the heat sink has a thickness of 0.007 mm N
Each of them was subjected to i-plating, and a structure having the first copper plate on the lower side was overlaid on a heat sink made of Cu via an aluminum foil. A load of 4 kgf / cm ² is applied to these,
The heat sink was joined to the first copper plate via an aluminum foil by heating to 525 ° C. in a vacuum and left for 1 hour to obtain a ceramic circuit board with a heat sink.

Comparative Example 1 As shown in FIG. 6, a structure 4 having the same shape and size and the same material as the structure of Example 6 and a heat sink of Example 8 having the same shape and size. And a heat sink 8 made of the same material Cu and having a length, width and thickness of 30
mm, 30 mm, and 0.1 mm of solder 6 were prepared. First, the solder 6 and the first copper plate 1 are placed on the heat sink 8.
The heat sink 8 is joined to the first copper plate 1 by heating to 250 ° C. in a mixed gas atmosphere of N ₂ gas and H ₂ gas in a state where the structure 4 with the heat sink on the lower side is overlapped. Substrate 5 was used as Comparative Example 1.

<Comparative Example 2> Although not shown, except that the heat sink was formed of an AlSiC-based composite material and that the bonding surface of the heat sink was Ni-plated before joining the heat sink to the first copper plate 1 via solder. And Comparative Example 1
This ceramic circuit board with a heat sink was used as Comparative Example 2. Table 1 shows the configurations of the circuit boards of Examples 1 to 8 and Comparative Examples 1 and 2 described above.

<Comparative Test and Evaluation> The circuit boards of Examples 1 to 8 and Comparative Examples 1 and 2 were measured for thermal resistance and ceramic crack, respectively. The measurement of thermal resistance was performed by the following method, that is, Examples 1 to
20 mm × 15 mm on the upper surfaces of the second aluminum plate and the second copper plate of Comparative Example 1 and the copper plates of Comparative Examples 1 and 2.
The heating elements were bonded with silicone grease, and a radiator was attached to the lower surface of the heat sink. First, the heating element was heated at 30 W in this state, and the thermal resistance (the thermal resistance immediately before the temperature cycle) was measured between the heating element and the surrounding air. Next, the circuit boards of Examples 1 to 8 and Comparative Examples 1 and 2 were subjected to a temperature cycle of -55 ° C. to room temperature to 150 ° C. for 1000 cycles using a thermal shock tester. Furthermore, the thermal resistance (heat resistance after 1000 temperature cycles) was measured between the heating element and the surrounding air when the heating element was heated at 30 W after 1000 additional temperature cycles. Table 1 shows the results. The cracks of the ceramic substrate were measured by the following method, that is, the first and second aluminum plates, the first and second aluminum plates on the ceramic substrates of Examples 1 to 8 where the thermal resistance was measured after 1000 temperature cycles. The copper plate and the first and second copper plates on the ceramic substrates of Comparative Examples 1 and 2 are removed by etching , respectively.
This was performed by checking with a magnifying glass whether or not cracks had occurred in the ceramic substrate.

[0029]

[Table 1]

As apparent from Table 1, Examples 1 and 2
As a result, the Al melting point depressed layers formed on both surfaces of the aluminum foil showed substantially no change in coating or vapor deposition. Further, from the results of Example 1 and Example 3, it was found that bonding at a lower temperature can be achieved by Ni plating the respective bonding surfaces of the structure and the heat sink with the aluminum foil. In Examples 1 to 8, the thermal resistance after 1000 temperature cycles did not change from the thermal resistance immediately before the temperature cycle, whereas in Comparative Example 1, the thermal resistance after 1000 temperature cycles increased by about 77%. In Comparative Example 2, the thermal resistance after 1000 temperature cycles was about 98.
% Increased. Further, in Examples 1 to 8, no ceramic crack was generated even after 1000 temperature cycles, whereas in Comparative Examples 1 and 2, the temperature cycle was 100%.
After 0 times, it was confirmed that ceramic cracks occurred.

[0031]

As described above, according to the present invention, the structure and the heat sink are joined via the aluminum foil having a high thermal conductivity and having a purity of 99% by weight or more, having the Al melting point depressed layer formed on both surfaces. Therefore, heat radiation characteristics can be improved. Also, aluminum foil has low deformation resistance,
Even if a thermal cycle is applied to the circuit board, no cracks are generated in the ceramic board, and the life thereof can be extended. Also, by applying Ni plating to each of the bonding surfaces of the structure and the heat sink with the aluminum foil, the heat sink can be easily bonded to the aluminum plate or the copper plate at a relatively low temperature. Further, the ceramic substrate is
If the heat sink is formed of N, Si ₃ N ₄ or Al ₂ O ₃ and the heat sink is formed of Cu, Al or AlSiC-based composite material, the thermal conductivity, heat resistance, strength, etc. can be improved, and the semiconductor chip and the like can be improved. The generated heat can be effectively dissipated from the heat sink to the outside.

[Brief description of the drawings]

FIG. 1 is a sectional view of a ceramic circuit board with a heat sink according to the present invention.

FIG. 2 is a cross-sectional view of the aluminum foil on which the Al melting point lowering layer is formed.

FIG. 3 is a cross-sectional view of an aluminum foil on which another Al melting point lowering layer is formed.

FIG. 4 is a sectional view showing a state where the structure and the heat sink are joined via the aluminum foil.

FIG. 5 is a cross-sectional view of another ceramic circuit board with a heat sink according to the present invention.

FIG. 6 is a cross-sectional view corresponding to FIG. 1, showing a conventional ceramic circuit board with a heat sink;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 1st aluminum plate 11a, 16a Ni plating 12 2nd aluminum plate 13 ceramic board 14, 24 structure 16 heat sink 17 aluminum foil 17a Al melting | melting point depressed layer 21 1st copper plate 22 2nd copper plate

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Masato Otsuki 1-297 Kitabukuro-cho, Omiya-shi, Saitama Prefecture Mitsubishi Materials Research Institute (56) References JP-A-4-192341 (JP, A) Hei 4-363052 (JP, A) JP-A-8-23145 (JP, A) JP-A-8-83867 (JP, A) JP-A-3-57945 (JP, U) (58) Fields investigated (Int) .Cl. ⁷ , DB name) H01L 23/36 H01L 23/12 H01L 23/373 H01L 25/00

Claims (5)

(57) [Claims] The first and second aluminum plates (11, 12) or the first and second copper plates (2, 3) are provided on both sides of a ceramic substrate (13, 23).
Structures (14, 24), on which the heat sinks (1, 22) are laminated and bonded, respectively, via the aluminum plate (11) or the copper plate (21).
In the ceramic circuit board with a heat sink bonded to 6), the structure (14, 24) and the heat sink (16) are A
1. A ceramic circuit board with a heat sink, wherein said ceramic circuit board is bonded via an aluminum foil (17) having a purity of 99% by weight or more and having a melting point lowering layer (17a) formed thereon. 2. An Al melting point lowering layer (17a) comprising an Al—Si alloy layer, an Al—Cu alloy layer, an Al—Mg alloy layer, and an Al—Ni alloy layer.
The ceramic circuit board with a heat sink according to claim 1, which is an alloy layer, an Al-Ag alloy layer, or an Al-Ce alloy layer. 3. The bonding surfaces of the structure (14, 24) and the heat sink (16) with the aluminum foil (17) are Ni-plated.
The ceramic circuit board with a heat sink according to claim 1 or 2, wherein the ceramic circuit board is provided with (11a, 16a) . 4. The ceramic substrate (13, 23) is made of AlN, Si ₃
Formed by N ₄ or Al ₂ O _3, the heat sink (16) is Cu, Al, or AlSiC system according to claim 1 to the ceramic circuit board with 3 heat sink according to any one formed of a composite material. 5. The ceramic circuit board with a heat sink according to claim 1, wherein the aluminum foil has a thickness of 5 to 500 μm.