JP3456225B2 - High thermal conductive substrate and method of manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high thermal conductivity substrate and a method for manufacturing the same. More specifically, the present invention relates to a ceramics sintered body substrate containing aluminum nitride as a main component, which has a copper metallization layer or an aluminum metallization layer excellent in bonding strength and thermal shock resistance on its surface, and a method for producing the same.

[0002]

2. Description of the Related Art As the output, operating speed, degree of integration, etc. of various semiconductor devices and integrated circuits have been improved, obstacles due to heat generation thereof have become apparent. That is, when a high-performance semiconductor element or integrated circuit is mounted on a substrate made of a material having low thermal conductivity, the element or the like may overheat and the operating characteristics may deteriorate. Therefore, as a substrate for mounting a semiconductor device that generates a large amount of heat,
Substrates based on aluminum nitride, which has a high thermal conductivity, have been used.

When an aluminum nitride substrate is used as a substrate for mounting semiconductor devices, integrated circuits, etc., a metallized layer must be formed on the surface. In addition, a circuit may be formed by forming a circuit on the surface of the aluminum nitride substrate with the metallized layer. Conventionally, these metallized layers have been formed by directly applying a conductor paste such as a copper paste onto the surface of an aluminum nitride substrate and firing it.

[0004]

However, the metallized layer formed by the above-mentioned conventional method has a low adhesion strength, and therefore has a low bonding reliability. It is considered that this is due to the poor wettability between the glass component contained in the conductor paste and aluminum nitride. On the other hand, a method of improving the adhesion strength of a metallized layer by oxidizing the surface of aluminum nitride to form an alumina layer and forming a metallized layer on this alumina layer is disclosed in Japanese Patent Application Laid-Open No. 62-46986. It is disclosed in the official gazette. However, with this method, it is difficult to form a dense oxide film, and a strong adhesion strength cannot be obtained.

Further, JP-A-3-93683 discloses that a copper paste containing aluminum nitride, lead borosilicate glass having good wettability, and aluminum nitride and highly reactive cuprous oxide is used for adhesion. A method of forming a high strength metallized layer is disclosed. However, according to this method, the metallized layer at the site where thermal history and thermal stress are applied is likely to be peeled off. Similarly, DBC (DIRE
Even in the metallization method such as the CT BONDING COPPER) method, residual stress caused by the difference in thermal expansion between aluminum nitride and copper was generated, and there was a problem that the aluminum nitride was cracked.

It is therefore an object of the present invention to provide a high thermal conductivity substrate made of an aluminum nitride sintered body having a metallized layer with high adhesion and a method for manufacturing the same, which solves the problems of the prior art.

[0007]

According to the present invention, a ceramic sintered body containing aluminum nitride as a main component, a glass layer formed on the surface of the ceramic sintered body, and a copper metallization formed on the glass layer. A high thermal conductivity substrate is provided which comprises a layer or an aluminum metallization layer.

In the high thermal conductivity substrate of the present invention, the glass constituting the glass layer has a coefficient of thermal expansion of 3 × 10 ⁻⁶ to
It is preferably 10 × 10 ⁻⁶ ° C. ⁻¹ , and the thickness of the glass layer is preferably ¹ to 200 μm. Furthermore, in the high thermal conductive substrate of the present invention, it is preferable that the thickness of the glass layer at a portion to which thermal history and / or thermal stress is applied is made thicker than other portions. It is possible to prevent the metallized layer from being peeled off and the ceramics sintered body from being cracked even when added.

On the other hand, in the present invention, a high thermal conductivity substrate having a ceramic sintered body containing aluminum nitride as a main component and a copper metallized layer or an aluminum metallized layer disposed on the surface of the ceramic sintered body is manufactured. In the method, a step of applying a paste containing glass powder on the surface of the sintered aluminum nitride body, a step of firing the paste to form a glass layer, and forming a copper metallized layer or an aluminum metallized layer on the glass layer A method for manufacturing a high thermal conductivity substrate, comprising the steps of:

In the method of the present invention, the step of forming the copper metallization layer or the aluminum metallization layer comprises the steps of applying a copper paste or an aluminum paste to the surface of the glass layer and firing the copper paste or the aluminum paste. Or a step of adhering a copper foil, a copper plate, an aluminum foil or an aluminum plate to the surface of the glass layer may be included.

[0011]

The high thermal conductivity substrate of the present invention is characterized mainly in that it has a metallized layer of copper or aluminum on the glass layer on the surface of the ceramics sintered body containing aluminum nitride as a main component. Examples of the glass constituting the glass layer of the high thermal conductive substrate of the present invention include SiO ₂ and Ca.
At least 2 of the group consisting of O, Al ₂ O ₃ and B ₂ O ₃
It is preferable that the composition contains the seeds in the range of 1 to 70% by weight. In the high thermal conductive substrate of the present invention,
The coefficient of thermal expansion of the glass constituting the above glass layer is 3 ×
10 ^-6 to 10 × 10 ^-6 ℃ ^-1 is preferable, but the coefficient of thermal expansion of aluminum nitride (5.7 × 10 ^-6 ℃ ^-1 ) and that of copper (about 1.7 × 10 ^-5 ℃ ^-1 ) And a value close to the middle of the coefficient of thermal expansion of aluminum (about 2.3 × 10 ⁻⁵ ° C. ⁻¹ ) is preferable. When the coefficient of thermal expansion of glass is a value close to an intermediate value between the coefficients of thermal expansion of aluminum nitride and copper and the coefficients of thermal expansion of aluminum, the glass layer also functions as a stress relaxation layer, so durability against thermal history is improved. .

On the other hand, in the high thermal conductivity substrate of the present invention, the thickness of the glass layer is preferably 1 to 200 μm, more preferably 20 to 150 μm. This is because if the thickness of the glass layer is less than 1 μm, there is no effect of improving the adhesion of the metallized layer, and if it exceeds 200 μm, the heat dissipation property of the substrate decreases. That is, since the thermal conductivity of the glass layer is lower than that of aluminum nitride, if the glass layer is too thick, the temperature of the substrate may rise.

Further, in the high thermal conductivity substrate of the present invention, the thermal characteristics of the substrate can be changed site by region by partially changing the film thickness of the glass layer. That is, in the portion where the thermal resistance is desired to be reduced, it is possible to improve the heat dissipation property by reducing the film thickness of the glass layer having low thermal conductivity. On the other hand, the stress of the copper metallized layer or the aluminum metallized layer and the aluminum nitride can be relaxed by increasing the thickness of the glass layer in the portion to which the thermal history and the thermal stress are applied.

The present invention also provides a method for producing the above-described high thermal conductive substrate of the present invention. In the method of the present invention, first, a glass layer is formed on an aluminum nitride sintered body. The glass layer is preferably formed by the following steps. First, a paste obtained by adding an organic vehicle and a solvent to glass powder is applied to the aluminum nitride sintered body by screen printing. 100 after applying this glass paste
Dry at ~ 200 ° C and bake at 500 ~ 1000 ° C. Further, a copper paste or an aluminum paste is printed on the glass layer, dried and baked to form a metallized layer. Since the glass component and the copper metal in the copper paste or aluminum paste have good wettability with the underlying glass layer, stronger adhesion strength can be obtained as compared with the conventional method. Further, not only the copper paste or the aluminum paste but also the copper foil and the copper plate or the aluminum foil and the aluminum plate are bonded onto the glass layer to obtain a strong adhesion strength. The above glass paste contains SiO ₂ , CaO, Al ₂ O ₃ and B ₂ O.
It is preferable to use a glass powder having a composition containing at least two members selected from the group consisting of _{3 in} the range of 1 to 70% by weight. In addition, the above copper or aluminum paste is used as SiO ₂ and CaO, Al ₂ O ₃ , B ₂ O ₃ , CuO, C
It is preferable to contain a glass component such as u ₂ O.

In the high thermal conductive substrate of the present invention, the reason why the adhesion strength of the copper metallized layer or the aluminum metallized layer becomes strong is that the glass layer becomes a liquid phase during firing.
This is because the contact area between the copper powder or aluminum powder in the paste and the glass becomes large. Similarly, the glass layer is well wetted with aluminum nitride, and in particular, the adhesion area between the glass layer and aluminum nitride is larger than that in the conventional method, so that good adhesion strength can be obtained.

In the method of the present invention, the copper metallized layer or the aluminum metallized layer can also be formed by screen printing. According to this method, it is possible to form a fine line circuit pattern having a line width of about 70 μm. Furthermore, the electrical characteristics of the circuit can be adjusted by the film thickness of the copper metallized layer or the aluminum metallized layer.

Hereinafter, the present invention will be described in more detail with reference to examples, but the following disclosure is merely examples of the present invention and does not limit the technical scope of the present invention.

[0018]

【Example】

Example 1 A high thermal conductive substrate of the present invention was manufactured by the method of the present invention. First, an organic vehicle and a solvent were added to a glass powder having the following composition and an average particle diameter of 10 μm to form a paste, and the paste was applied to the surface of an aluminum nitride sintered body by screen printing. Composition SiO ₂ 50% by weight of glass CaO 5 〃 Al ₂ O ₃ 20 〃 B ₂ O ₃ 25 〃 above paste was dried at 0.99 ° C., was further fired at 1000 ° C. in air. The thickness of the glass layer after firing was 50 μm. On this glass layer, a copper paste of the following composition
It was applied to a thickness of μm and baked at 900 ° C. in a non-oxidizing atmosphere. Composition of copper paste Cu 90% by weight SiO ₂ 1 〃 CaO 2 〃 Al ₂ O ₃ 1 〃 CuO 3 〃 Cu ₂ O 3 〃

In order to evaluate the adhesion strength of the copper metallized substrate manufactured by the method of the present invention, the copper metallized surface after firing is plated with Ni having a thickness of 1 μm, and then the lead frame is brazed and peeled. I went. As a result, the adhesion strength was 12 kg / cm. Further, a peel test was conducted in the same manner on a substrate after the metallized firing was repeatedly subjected to thermal shock from 150 ° C. to −65 ° C. 15 times.
As a result, it was found that the adhesion strength was 10.5 kg / cm, and the adhesion strength was hardly affected by the heat history.

Example 2 A glass component having the same composition as in Example 1 was applied on an aluminum nitride sintered body to a thickness of 100 μm, dried and baked in the atmosphere at 1000 ° C. to form a glass layer. In this glass layer,
A 0.3 mm thick copper foil was attached and baked in a non-oxidizing atmosphere at 900 ° C. to manufacture the high thermal conductive substrate of the present invention. In order to evaluate the adhesion of this substrate, a thermal shock test similar to that of Example 1 was performed, and then a peel test similar to that of Example 1 was also performed. The adhesion strength of the substrate of this example is 7.9 kg / cm.
Met.

Example 3 According to the method of the present invention, a high thermal conductive substrate of the present invention having a structure different from those of Examples 1 and 2 was produced. First, an organic vehicle and a solvent were added to a glass powder having the following composition and an average particle diameter of 10 μm to form a paste, and the paste was applied to the surface of an aluminum nitride sintered body by screen printing. Composition of glass SiO ₂ 10% by weight CaO 10 〃 Al ₂ O ₃ 10 〃 B ₂ O ₃ 60 〃 MgO 5.0 〃 FeO 5.0 〃 The above paste was dried at 150 ℃ and further baked in the air at 650 ℃ . An aluminum paste having the following composition was applied to the glass layer of the glass layer after firing to a thickness of 50 μm and fired at 580 ° C. in a non-oxidizing atmosphere. Composition of aluminum paste Al 95 wt% SiO ₂ 1 〃 B ₂ O ₃ 4 〃

In order to evaluate the adhesion strength of the aluminum metallized substrate manufactured by the method of the present invention, a 1 μm thick Ni plating is applied to the aluminum metallized surface after firing, a lead frame is soldered, and a peel test is conducted. I went. As a result, the adhesion strength was 10.8 kg / cm. Further, a peel test was conducted on a substrate that was subjected to the same thermal shock as in Example 1 by the same method. As a result, the adhesion strength is
It was 9.3 kg / cm, and it was found that the adhesion strength was hardly affected by the heat history.

Example 4 A glass component having the same composition as in Example 3 was applied on an aluminum nitride sintered body to a thickness of 100 μm, dried and baked in the atmosphere at 650 ° C. to form a glass layer. In this glass layer,
A 0.25 mm-thick aluminum foil was attached and baked in a non-oxidizing atmosphere at 600 ° C. to manufacture the high thermal conductive substrate of the present invention. In order to evaluate the adhesiveness of this substrate, a peel test was conducted after Ni plating was performed as in Example 3. The adhesion strength of the substrate of this example was 7.1 kg / cm.

Comparative Example 1 An aluminum nitride sintered body was fired at 950 ° C. in the atmosphere to form an oxide film on the surface of the sintered body. A copper paste was printed to a thickness of 20 μm on the surface of the aluminum nitride sintered body on which this oxide film was formed, and dried and baked under the same conditions as in Example 1. The adhesion strength of the metallized layer to this copper metallized substrate was evaluated in the same manner as in Example 1, and the result was 2.1 kg / cm. Further, the adhesion strength after the thermal shock test was carried out in the same manner as in Examples 1 and 2 was 0.6 kg / cm, and practically sufficient adhesion strength could not be obtained.

[0025]

As described in detail above, according to the present invention, there is provided a high thermal conductivity substrate made of an aluminum nitride ceramics sintered body having a copper metallized layer or an aluminum metallized layer on its surface, and a method for manufacturing the same. The high thermal conductivity substrate of the present invention is superior to conventional ones in adhesion strength of a copper metallized layer or aluminum metallized layer and durability against thermal shock. Therefore, it can be advantageously used for VLSI packages and the like, which require particularly high heat dissipation.

─────────────────────────────────────────────────── --- Continuation of front page (56) References JP-A-3-93683 (JP, A) JP-A-5-330958 (JP, A) JP-A-62-216979 (JP, A) JP-A-62- 216983 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C04B 41/80-41/91

Claims (6)

(57) [Claims] 1. A ceramic sintered body containing aluminum nitride as a main component, a glass layer formed on the surface of the ceramic sintered body, and a copper metallized layer or an aluminum metallized layer formed on the glass layer. And the coefficient of thermal expansion of the glass constituting the glass layer is 3 × 10 ⁻⁶
High thermal conductivity substrate, which is a ~10 × 10 ^-6 ℃ ^-1. 2. The high thermal conductive substrate according to claim 1 , wherein the glass layer has a thickness of 1 to 200 μm. Wherein the thickness of said glass layer portions thermal history and / or thermal stress is applied is, high thermal conductivity substrate according to claim 1 or claim 2, characterized in that thicker than other portions. 4. A ceramics sintered body containing aluminum nitride as a main component, and a ceramics sintered body formed on the surface thereof.
In the method for producing a high thermal conductivity substrate having a glass layer and a copper metallized layer or an aluminum metallized layer arranged on the surface of the ceramic sintered body, thermal expansion is performed.
A step of applying a paste containing a glass powder having a coefficient of 3 × 10 ⁻⁶ to 10 × 10 ⁻⁶ ° C. ⁻¹ to the surface of the aluminum nitride sintered body , and a step of firing the paste to form a glass layer,
A step of forming a copper metallized layer or an aluminum metallized layer on the glass layer. 5. The step of forming the copper metallized layer or the aluminum metallized layer comprises applying a copper paste or an aluminum paste to the surface of the glass layer,
The method of manufacturing a high thermal conductive substrate according to claim 4 , comprising a step of firing the copper paste or the aluminum paste. 6. A step of forming the copper metallization layer or metallized aluminum layer, according to claim 4, characterized in that it comprises a step of bonding a copper foil or copper plate or aluminum foil or an aluminum plate on the glass layer surface For manufacturing a high thermal conductive substrate of.