JPH0483368A - Ceramic heat radiation substrate and its manufacture - Google Patents

Abstract

PURPOSE:To improve the heat radiation effect of electronic parts and package the electronic parts densely by keeping the porosity of a porous ceramic layer and that of the specified dense ceramic layers within specified ranges. CONSTITUTION:Dense ceramic layers 10b containing 90-99.5% of alumina are laminated on one or both faces of a porous ceramic layer 10a containing 90-99.5% of alumina and sintered into integrated form to make a ceramic heat radiation substrate 10 to radiate the heat of electronic parts 15 mounted on the dense ceramic layers 10b by passing refrigerant through the porous ceramic layer 10a. The porosity of the porous ceramic layer 10a is kept at 20-60% and that of the dense ceramic layers 10b is kept at 0.01-5%. A film of slurry for a porous layer is formed and dried to make a green sheet for a porous layer. Green sheets for a dense layer are bonded to one or both faces with bond and baked at 1,200-1,600 deg.C to obtain a laminated sintered body.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a semiconductor substrate material containing alumina as a main component and manufactured by a green sheet multilayer lamination method. More specifically, the present invention relates to a ceramic heat dissipation board for dissipating heat generated by electronic components and a method of manufacturing the same.

[Prior Art] Conventionally, this type of ceramic heat dissipation board has been manufactured by bonding Cu metal or Cu-W sintered alloy with high thermal conductivity to the surface of a densified alumina substrate in order to improve heat dissipation. There is.

However, when electronic components such as capacitors and resistor chips are mounted at high density on an alumina substrate bonded to the above sintered alloy, the heat generated by these electronic components is not sufficiently dissipated, and it is difficult to remove the heat even more efficiently. A way to do this was desperately needed.

In order to improve this point, a porous metal layer is bonded to the surface of the ceramic substrate, and a coolant is passed through the porous metal layer to remove the heat generated by the electronic components.

[Problems to be Solved by the Invention] However, since the ceramic substrate to which the porous metal layer is bonded requires a thickness of 200 μm or more for manufacturing purposes, electronic components may There was a problem that the heat dissipation effect was not sufficient. Furthermore, the ceramic heat dissipating substrate with the porous metal layer has a relatively thick wall and is heavy, which reduces the mounting space for electronic components and prevents high-density mounting of electronic components.

An object of the present invention is to provide a ceramic heat dissipation board that can be made thinner and lighter, and a method for manufacturing the same.

Another object of the present invention is to provide a ceramic heat dissipation board that has a high heat dissipation effect for electronic components and allows electronic components to be mounted at high density, and a method for manufacturing the same.

[Means for Solving the Problems] In order to achieve the above object, the heat dissipation substrate of the present invention has a porous ceramic layer having an alumina content of 90 to 99.5% on both sides or one side thereof. A ceramic heat dissipation board in which 5% dense ceramic layers are laminated and integrally sintered, and a coolant is flowed through the porous ceramic layer to dissipate heat generated by electronic components mounted on the dense ceramic layer, The porous ceramic layer has a porosity of 20
The porosity of the dense ceramic layer is in the range of 0.01 to 5%.

In addition, in the method for manufacturing a ceramic heat dissipation board of the present invention, first, a sintering aid and a water-soluble binder are added and mixed to alumina sol using water as a dispersion medium to prepare a slurry for a dense layer. The film is formed and dried to form a green sheet for a dense layer.

Next, a slurry for a porous layer is prepared by adding and mixing a water-soluble binder without adding a sintering aid to alumina sol using water as a dispersion medium, and this slurry for a porous layer is formed into a film and dried to form a porous layer. Form a green sheet for use. Next, the dense layer green sheet is adhered to both sides or one side of the porous layer green sheet using an adhesive, and the adhered green sheet is fired at 1200 to 1600°C to obtain a laminated sintered body.

The ceramic raw materials constituting the porous ceramic layer and the dense ceramic layer of the present invention both have an alumina content of 9.
It is alumina with a high purity of 0 to 99.5%. Both the slurry for the dense layer and the slurry for the porous layer mainly contain alumina sol using water as a dispersion medium. This alumina sol is preferably an alumina sol of fine colloidal particles prepared by a so-called sol-gel method, which is obtained by hydrolyzing aluminum alkoxide and peptizing it.

The difference between the preparation methods of the slurry for the dense layer and the slurry for the porous layer is that the sintering aid in the former is 100% by weight alumina sol.
0.05 to 10% by weight, whereas the latter contains no sintering aids at all or less than 0.1% by weight to increase the porosity of the ceramic layer. It is in. Examples of sintering aids for alumina include silicon dioxide, magnesium oxide, calcium oxide, magnesium acetate, and titanium dioxide.

The water-soluble binder is added in an amount of 10 to 80% by weight based on the solid content of the alumina sol in both the dense layer slurry and the porous layer slurry. Since this binder tends to generate pores in the ceramic layer due to removal of the binder during sintering, it is added to the alumina sol in a small amount within the above range to reduce the porosity. Examples of water-soluble binders include polyvinyl alcohol and water-soluble acrylic. The binder contained in the slurry for the dense layer may be different from the binder contained in the slurry for the porous layer.

Methods for forming dense layer slurry and porous layer slurry include the doctor blade method, extrusion molding method, roll rolling method, and slurry casting method, but these methods have low molding distortion and smoothness of the molded product. A good doctor blade method is preferred. When forming a slurry for a porous layer, ammonia or an alkaline substance such as amines may be added to the slurry to form a gel in the slurry, thereby increasing the porosity.

After forming the slurry for the dense layer and the slurry for the porous layer, they are dried at 30 to 95°C, respectively, to form a green sheet for the dense layer and a green sheet for the porous layer. The green sheet for the dense layer, which is the lowest layer, may be provided with holes through which the coolant passes.

Further, in order to enhance the heat dissipation effect, the green sheet for the porous layer may be subjected to metallization treatment such as Ni plating.

Next, adhesive is applied to both sides or one side of the green sheet for the porous layer, and 10 to 100 kg is coated at a temperature of 20 to 70°C.
The green sheet for the dense layer is adhered and laminated on the green sheet for the porous layer with a pressure of 1/cm''.

As this adhesive, an aqueous adhesive such as a cellulose derivative, an acrylic emulsion, or a vinyl acetate emulsion, or a non-aqueous adhesive such as an acrylic resin, a butyral resin, or a vinyl resin can be used.

In addition to the three layers in which dense layer green sheets are stacked on both sides of a porous layer green sheet, dense layers and porous layers may be stacked alternately depending on the purpose of the ceramic substrate. It is also possible to have multiple layers combined.

After the green sheets are laminated, they are cut into predetermined dimensions, placed in a firing furnace, and fired. Firing is performed at a temperature range of 1200 to 1600° C. for 1 to 2 hours under atmospheric pressure in order to obtain the desired porosity. The higher the firing temperature and the longer the firing time, the lower the porosity. When the temperature is less than 1200°C, the porosity of the dense ceramic layer exceeds 5%, and 1
When the temperature exceeds 600℃, the porosity of the porous ceramic layer decreases to 20
It is likely to be less than %. That is, in the multilayer ceramic substrate of the present invention, the porous ceramic layer has a porosity of 20 to 60%, and the dense ceramic layer has a porosity of 0.01 to 5%.
It is controlled within the range of .

Further, the ceramic heat dissipation substrate of the present invention is preferably an extremely thin substrate with a thickness of 10 to 200 μm in order to enhance the heat dissipation effect.

By mounting electronic components such as capacitors and resistor chips on the dense ceramic layer on the top layer of the ceramic heat dissipation board, which is a laminated sintered body, and passing a coolant through the porous ceramic layer,
Heat generated by electronic components can be dissipated.

As shown in FIGS. 1 to 4, metal tubes 11 and 12 are connected to both the front and rear ends of the ceramic heat dissipation substrate 10, and the coolant 13 is passed through the porous ceramic layer 10a of the substrate 10 to form a dense layer in the uppermost layer. As shown in FIGS. 5 and 6, a tube with a diameter of After drilling a through hole 27 of approximately 6 mm, insert the metal tubes 21 and 2 into the through hole 27.
2 perpendicularly to the layer 20b, and the coolant 23 is passed through the porous ceramic layer 20a of the substrate 20 to remove the heat generated by the electronic components 24 and 25 mounted on the uppermost dense ceramic layer 20b.

These metal tubes 11, 12, 21, and 22 are made of a metal material, such as a Kovar alloy, whose coefficient of thermal expansion is approximately the same as that of the alumina ceramic substrate.

These metal tubes are brazed with hard solder 16, such as silver solder, brass solder, copper solder, etc., and integrated with the substrate 10 or 20. The three-layer laminated ceramic heat dissipation board 10 shown in FIGS. 1 and 2 is inserted into the metal tubes 11 and 12, and the third
The five-layer laminated ceramic heat dissipating substrate 10 shown in FIGS. Figures 1 and 2
A through hole 17 having a diameter of 100 to 900 μm is formed in the dense ceramic layer 10b of the bottom layer of the substrate 10 shown in the figure, depending on the thickness of the layer 10b. Through hole 17 and the aforementioned through hole 27
are perforated in the green sheet state before firing.

Furthermore, a sealing layer 10c or 20c is formed on both side surfaces of the ceramic heat dissipation board 10 to which the metal tubes 11 and 12 are not connected, and on the circumferential side of the ceramic heat dissipation board 20, respectively, to prevent the coolant 13 or 23 from leaking. This sealing is performed by coating the stacked green sheets with a slurry for a dense layer and firing.

The substrate 10 in FIGS. 1 and 2 includes metal tubes 11 and 12.
A refrigerant gas, for example, Freon gas, is blown in from both sides and discharged from the through hole 17 through the porous ceramic layer 10a.

A refrigerant gas or cooling water is introduced into the substrate 10 of FIGS. 3 and 4 through a metal tube 11, and is discharged from a metal tube 12 through a porous ceramic layer 10a.

A refrigerant gas or cooling water is introduced into the substrate 20 of FIGS. 5 and 6 from a metal tube 21 and is discharged from a metal tube 22 through a porous ceramic layer 20a.

[Effects of the Invention] As described above, the ceramic heat dissipation board of the present invention has dense alumina layers laminated and sintered on both sides or one side of a porous alumina layer by the green sheet multilayer lamination method.
The substrate thickness can be reduced while maintaining a predetermined strength, and the substrate can be made lightweight.

This increases the heat dissipation effect of the electronic components and allows the electronic components to be mounted with high density.

[Example] Next, embodiments of the present invention will be described in detail based on the drawings.

<Example 1> Aluminum isopropoxide [AI (C3H?O)
8] to produce boehmite [AQOOH], which was peptized by adding water adjusted to pH 2 to 4 to obtain a stable pseudo-boehmite sol with an alumina concentration of 5% by weight.

In order to prepare a slurry for a dense layer, silica colloid, magnesium acetate, and calcium acetate were added as sintering aids to this sol, and polyvinyl alcohol was further added as a water-soluble binder. When these sintering aids are sintered into a dense ceramic layer, the composition ratio is AFL, 0*: 5in2: MgO: Ca0 = 92
: 7:2:1. The binder was added in an amount of 40% by weight based on the solid content. As a result, a slurry having a solid content of 10% by weight was prepared.

This slurry was coated on a high-density polyethylene tape as a moving carrier to a thickness of 1.2 mm using a doctor blade method, and then dried to remove water, which is the dispersion medium of the slurry, to a thickness of approximately 60 μm. A green sheet for dense layer was obtained.

On the other hand, a green sheet for a porous layer having a thickness of about 60 μm was obtained in the same manner as above except that no sintering aid was added to facilitate porosity. Nine through holes with a diameter of 100 μm were bored in the green sheet for the dense layer, which was the lowest layer. Next, an isopropyl alcohol solution of polyvinyl butyral with a concentration of 1% is applied as an adhesive to both sides of the green sheet for the porous layer, and the green sheet for the dense layer is superimposed on both sides of this sheet and adhered to form three layers. A laminated green molded body having a thickness of about 180 μm was obtained. This green molded body was cut into squares of 80 x 80 mm, and both sides were coated with a slurry for a dense layer, and then covered with a green sheet for a porous layer.

Next, this green molded body was placed in a firing furnace. At the same time, in order to examine the state of porosity formation, a green sheet for a porous layer, which is the same as the green sheet for a porous layer, and a green sheet for a dense layer, which is the same as the green sheet for a dense layer, are placed in a firing furnace. Green sheet at 1000℃, 1
Firing was performed at 200°C, 1300°C, 1400°C, and 1500°C for 1 hour each under atmospheric pressure. The dense alumina layer and porous alumina layer of the three-layer alumina substrate were alumina sintered layers with an alumina content of 92% and 995%, respectively. The bending strength of this three-layer alumina substrate is determined by the firing temperature of 1
000℃, 1200℃, 1300℃, 1400℃, 15
20.40.50.50.50kgf at 00℃ respectively
/mm”.

FIG. 7 shows the change in porosity depending on the firing temperature of a single-layer porous sintered alumina sheet and a single-layer dense alumina sintered sheet. According to FIG. 7, the porosity of the sintered sheet obtained by firing the dense layer green sheet alone is 0 to 0.
Since the porosity is in the range of 1%, it is inferred that the porosity of the dense alumina layer of the three-layer alumina substrate is also in the range of 0 to 1%.

Furthermore, since the porosity of the sintered sheet obtained by firing the porous layer green sheet alone is 40 to 60%, the porosity of the porous alumina layer of the three-layer alumina substrate is also 40 to 60%.
It is estimated to be 60%. Further, FIG. 8 shows the change in the porosity of the entire substrate depending on the firing temperature of the three-layer alumina substrate.

As shown in FIGS. 1 and 2, both front and rear ends of the laminated and sintered ceramic heat dissipation substrate 10 with a thickness of 100 μm are coated with Kovar alloy (Fe).
40%, Ni 40%, Co 20%) metal tube 11
and 12 and brazed with silver solder 16, Freon gas was blown into both the metal tubes 11 and 12 and discharged from the through hole 17 through the porous ceramic layer 10a. 10b showed an extremely high heat dissipation effect.

<Example 2> An alumina sol having an alumina concentration of 6% by weight was prepared using commercially available high purity alumina powder with an alumina content of 990% as a dispersed phase and water as a dispersion medium. This alumina sol 100% by weight
Magnesium acetate was used as a sintering aid at a concentration of 0.0% in terms of MgO.
05% by weight was added. Further, polyvinyl alcohol was added as a water-soluble binder in an amount of 40% by weight based on the solid content of the sol.

Below, the green sheet for the dense layer, which is the lowest layer, has a diameter of 4 m.
A three-layer alumina green sheet molded body was produced in the same manner as in Example 1 except that two through holes of tn were bored. This green molded body was cut into squares of 80×80 mm, and both sides were coated with a slurry for a dense layer, and covered with a green sheet for a porous layer.

Thereafter, this molded body was fired in the same manner as in Example 1.

As shown in FIGS. 5 and 6, Kovar alloy (Fe40%
, 40% Ni, 20% Co).
．． After inserting it into metal tube 2 and brazing it with silver solder 26,
When cooling water was poured into the tube 1 and discharged from the metal tube 22 through the porous ceramic layer 20a, the dense ceramic layer 20b as the uppermost layer showed an extremely high heat dissipation effect.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of the ceramic heat dissipation board of the present invention. FIG. 2 is a perspective view thereof. FIG. 3 is a sectional view of another ceramic heat dissipation board of the present invention. FIG. 4 is a perspective view thereof. FIG. 5 is a sectional view of yet another ceramic heat dissipation board of the present invention. FIG. 6 is a perspective view thereof. FIG. 7 is a diagram showing changes in porosity depending on firing temperature of a single-layer porous sintered alumina sheet and a single-layer dense alumina sintered sheet, respectively. FIG. 8 is a diagram showing changes in the porosity of the entire substrate depending on the firing temperature of the three-layer alumina substrate according to the example of the present invention. 10.20: Ceramic heat sink, 10a, 20a: Porous ceramic layer, 10b, 20b
:Dense ceramic layer, 13.23: Refrigerant. 0b Fig. Fig. Fig. Fig. 4 Fig. Fig. 8

Claims (1)

[Claims] 1) A porous ceramic layer with an alumina content of 90 to 99.5% on both sides or one side thereof.
A ceramic heat dissipation board in which dense ceramic layers are laminated and integrally sintered, and a coolant is flowed through the porous ceramic layer to dissipate heat generated by an electronic component mounted on the dense ceramic layer, the porous ceramic layer comprising: The porosity of the dense ceramic layer is in the range of 20 to 60%, and the porosity of the dense ceramic layer is in the range of 0.01 to 60%.
A ceramic heat dissipation board characterized by being in the range of 5%. 2) The ceramic heat dissipation substrate according to claim 1, wherein the substrate thickness is 10 to 200 μm. 3) Add and mix a sintering aid and a water-soluble binder to alumina sol using water as a dispersion medium to prepare a slurry for a dense layer, and form a film of this slurry for a dense layer and dry it to form a green sheet for a dense layer. A slurry for a porous layer is prepared by adding and mixing a water-soluble binder without adding a sintering aid to an alumina sol using water as a dispersion medium, and this slurry for a porous layer is formed into a film and dried. A green sheet for a porous layer is formed, the green sheet for a dense layer is adhered to both sides or one side of the green sheet for a porous layer, and the adhered green sheet is fired at 1200 to 1600°C. A method of manufacturing a ceramic heat dissipation substrate to obtain a laminated sintered body. 4) The method for manufacturing a ceramic heat dissipation substrate according to claim 3, wherein the alumina sol is an alumina colloid obtained by hydrolyzing aluminum alkoxide and then peptizing it.