JP2915114B2 - Manufacturing method of aluminum nitride metallized substrate - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a novel method for producing a refractory metal metallized aluminum nitride substrate having a metallized layer in close contact with an aluminum nitride substrate.

(Conventional technology) Aluminum nitride sintered body has high thermal conductivity, good electrical insulation, and excellent properties such as low coefficient of thermal expansion. Therefore, it is suitable for electronic industrial materials, especially printed wiring boards and semiconductor substrates. Used. In these applications, it is necessary to form a metal pattern, that is, a metallized layer on the surface of the aluminum nitride sintered body. LS with high integration
In the case of a substrate such as I, it has also been required that the substrate on which the pattern is formed as described above be multilayered.

Conventionally, means for manufacturing a ceramic substrate having a metallized layer include a method of forming a thin film by sputtering or vapor deposition on a ceramic substrate after sintering, a method of baking a metal paste, and a method of sintering a ceramic powder or a ceramic powder and a ceramic powder. If necessary, a green sheet is formed by adding an organic binder to the mixture of the agents, and after forming a pattern of a high melting point metal on the surface of the green sheet and degreased, the ceramic is sintered. At the same time, a so-called simultaneous firing method for forming a metallized layer is employed.

Of the above methods, the co-firing method is advantageous in that the number of steps is small, and an attempt has been made to manufacture an aluminum nitride substrate by the method.

(Problems to be Solved by the Invention) However, the adhesion of the metallized pattern of the aluminum nitride metallized substrate formed by the co-firing method may cause unevenness in the adhesion strength in the metallized pattern, or may cause fine wiring or fine electrodes. Has a problem that a practically sufficient adhesion strength may not be obtained.

(Means for Solving the Problems) As a result of repeated studies to solve the above problems, the present inventors have found that the adhesion of the aluminum nitride metallized substrate by the simultaneous firing method is improved by the simultaneous firing from the aluminum nitride substrate to the inside of the metallized layer. To be firmly maintained by the interface of the projections formed by the aluminum nitride grown on
Furthermore, by making the convex portions exist at a specific density over substantially the entire surface of the metallized pattern, there is no unevenness in adhesion strength, and a highly reliable aluminum nitride metallized substrate having a metallized pattern firmly adhered is obtained. The inventors have found that the present invention can be obtained, and have provided the present invention.

That is, the present invention forms a pattern with a high melting point metal paste on the surface of the aluminum nitride green sheet,
On the same surface as the pattern, on the surface of the green sheet near the pattern, or on the back surface of the pattern, on the surface of the green sheet where the pattern is located, a layer that limits the scattering of carbon in the degreasing layer. A method for manufacturing an aluminum nitride metallized substrate, comprising: providing, degreasing, and firing.

In the production method of the present invention, the aluminum nitride green sheet is not particularly limited to a known one basically composed of an aluminum nitride powder and an organic binder, and known materials and shapes are adopted without any limitation. You. For example, the material is basically composed of an aluminum nitride powder and an organic binder, and generally has a composition in which a sintering aid is blended as necessary.

Known organic binders and sintering aids are used without particular limitation. For example, as an organic binder, polyvinyl butyral, polymethyl acrylate, cellulose acetate butyrate, nitrocellulose, polyacrylate, polyvinyl alcohol, methyl cellulose, hydroxymethyl cellulose, and oxygen-containing organic polymers such as polyethylene oxide, etc. Hydrocarbon synthetic resins such as petroleum resin, polyethylene, polypropylene and polystyrene; polyvinyl chloride; acrylic resins and emulsions thereof; and organic polymers such as waxes and emulsions are used alone or in combination of two or more.

As the sintering aid, an alkaline earth metal compound, for example, an oxide such as calcium oxide, a compound composed of the elements yttrium and lanthanide, for example, an oxide such as yttrium oxide are preferably used.

The aluminum nitride powder may contain other sintering components in a range that does not inhibit the crystal grain growth of aluminum nitride in sintering described later. For example, the above-mentioned boron nitride, silicon carbide, silicon nitride and the like can be contained in an amount of 50% by weight or less.

In addition, as for the ratio of each component constituting the above-mentioned green sheet, a generally adopted mixing ratio is used without any particular limitation. For example, 0.1 to 10 parts by weight of an organic binder and 0.01 to 10 parts by weight of a sintering aid are suitable for 100 parts by weight of aluminum nitride powder.

In the method of the present invention, the high melting point metal constituting the high melting point metal paste is not particularly limited as long as it has a melting point higher than the sintering temperature of aluminum nitride.
Specifically, metals such as tungsten, molybdenum, platinum and rhenium are preferably used. For preparing the paste of the high melting point metal, a known method is employed without any particular limitation. For example, a method of mixing an organic binder such as ethyl cellulose and an organic solvent such as terpineol into a powder of a high melting point metal is generally used. In addition, a well-known method is also used without particular limitation for forming a pattern using the paste. For example, a method of screen-printing the paste is common. The pattern can be optionally present on the entire surface or a part of the green sheet as required. Further, a plurality of green sheets are generally laminated after the pattern is formed.

The method of the present invention is most characterized in that a layer for restricting the scattering of carbon at the time of degreasing is provided in a portion of the green sheet where the pattern of the high melting point metal paste is present.

That is, by providing the above layer and limiting the scattering of carbon, it is possible to increase the carbon concentration near the interface with the high melting point metallized layer of the degreased aluminum nitride molded article, and the high melting point metallized layer, The aluminum nitride sintered body grows at the interface between the refractory metal metallized layer and the aluminum nitride sintered body at the time of firing in the presence of such carbon, penetrates the metallized layer to form an acute projection, and the refractory metal The adhesion of the layer is improved. The formed protrusions are sharper than the protrusions formed by roughening the surface of the aluminum nitride sintered body by sandblasting or the like,
In addition, due to the high density, extremely high adhesion of the metallized layer is exhibited as compared with this method.

In the method of the present invention, the layer for restricting the scattering of carbon (hereinafter, also referred to as a carbon limiting layer) is provided in the vicinity of the pattern on the same surface as the green sheet on which the pattern of the high melting point metal paste is present, or Is formed at the portion where the pattern is located on the back surface of the green sheet in which.

In the method, wherein the carbon limiting layer is provided on the same green sheet surface as the pattern, the carbon limiting layer has a pattern area of 50% or more at intervals of 0.5 mm or less around the pattern,
Preferably, it is provided to be 60 to 100%.

In the method in which the carbon limiting layer is provided on the back surface of the green sheet on which the pattern is present, the carbon limiting layer is provided on the back surface of the green sheet on which the pattern is located at 50% or more of the area of the pattern, preferably Preferably, it is provided so as to be 100%. The carbon limiting layer is particularly effective when the thickness of the green sheet is 3 mm or less.

The aspect in which the carbon restriction layer is provided on the surface of the green sheet is particularly preferable because it does not affect the wiring of the metallized layer and can be easily removed as necessary.

In each of the above aspects, if the area of the carbon limiting layer is excessively increased, the residual carbon of the aluminum nitride degreased body increases,
It is not preferable because sintering inhibition at the time of heat sintering, warpage of the obtained sintered body, peeling of the metallized layer of the sintered body, high resistance, and the like occur. Therefore, the carbon limiting layer is preferably provided so as to keep the carbon concentration at the interface with the high melting point metallized layer and the high melting point metallized layer within the above range.

In the method of the present invention, the carbon limiting layer is used to limit the scattering of carbon in the decomposition gas generated by the thermal decomposition of the organic binder, and those that do not affect the sintering of aluminum nitride are used without any particular limitation. Is done. Preferred examples include a high melting point metal that limits the scattering of carbon in the decomposition gas,
For example, a paste of tungsten, molybdenum, rhenium, or the like can be given. This paste may be applied to the above-mentioned predetermined location with a predetermined area by screen printing or the like.

The thickness of the carbon restriction layer is not particularly limited, but may be 5
It is desirable to use in the range of 3030 μm.

In the method of the present invention, degreasing conditions and firing conditions are not limited, and known conditions are employed without any particular limitation.

For example, for degreasing, an inert gas such as nitrogen or argon,
It is generally carried out at 700 to 1200 ° C. in a reducing gas atmosphere comprising hydrogen or hydrogen and an inert gas.

In addition, the firing is performed under a inert gas atmosphere of nitrogen, argon, helium or the like, and the degreased molded body is heated at 1400 to 2100 ° C., preferably at a temperature of 1650 to 1900 ° C., and a method of firing is preferable. .

In the method of the present invention, after firing, the carbon limiting layer may be removed by etching or the like, if necessary.

(Function / Effect) As understood from the above description, according to the present invention, the metallized layer of the refractory metal has no unevenness in adhesion strength, and has a highly reliable aluminum nitride metallized with strong adhesion. A substrate is provided.

(Examples) The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

In addition, the tensile strength of the metallized pattern was measured as follows. First, after a Ni plating layer having a thickness of 2 μm was formed on the metallized surface, a solder-plated copper wire was soldered vertically. This was set on a strograph M2 manufactured by Toyo Seiki Seisaku-sho, Ltd., and the breaking strength when the copper wire was pulled in the vertical direction was measured. The diameter of the copper wire was 0.5 mm, and the pulling speed was 10 mm / min.

Example 1 An aluminum nitride green sheet having a thickness of about 0.6 mm
It was cut to 50 mm. Next, 2 parts by weight of ethyl cellulose was added to 100 parts by weight of tungsten powder having an average particle size of 2.5 μm,
Twenty parts by weight of terpineol are kneaded thoroughly with a rapier to form a paste, and screen printed to a green sheet
One line pattern of 0.8 mm width was printed. Further, a frame having a width of 1 mm was formed around the line pattern at an interval of 0.4 mm with the same paste as the pattern.

The printed aluminum nitride green sheet produced in this manner was heated and degreased at 1000 ° C. for 2 hours while flowing a mixed gas of 70% by volume of hydrogen and 30% by volume of nitrogen. After degreasing,
It was sintered at 1800 ° C. for 5 hours in a nitrogen atmosphere. The obtained aluminum nitride sintered substrate was divided into two parts at the center of the line pattern, and the tensile strength of the line pattern was measured for one of the cross sections. As a result, it was 5.8 kg / mm ² . Further, the tungsten metallized layer of the other fragments was removed by etching, and the aluminum nitride side of the interface was examined by a scanning electron micrograph. As a result, the entire surface where the line pattern was present had a height of about 6 μm and a width of about 2 μm. It was found that there were an average of five protrusions per 100 μm ² .

Comparative Example 1 An aluminum nitride sintered substrate was obtained in the same manner as in Example 1, except that no paste frame was formed around the line pattern.

Per sintered substrate obtained, similarly to tensile strength measurement, and results of protrusions observation of the interface, the tensile strength of the line pattern, at 1.1 Kg / mm ^2, at the interface metallized layer and the sintered body It was found that there was no protrusion having a height of 1 μm or more.

Example 2 In Example 1, instead of forming a paste frame around the line pattern, a 0.8-mm-wide line pattern was printed on the back surface of the position where the line pattern was printed. A bonded substrate was obtained.

Per sintered substrate obtained, similarly to tensile strength measurement, and results of protrusions observation of the interface, the tensile strength of the line pattern, at 5.2 kg / mm ^2, at the interface metallized layer and the sintered body , Height of about 5μm, width of about 1.5μm convex section is 100μ
It was found that there were an average of four per m ² .

Comparative Example 2 Using the same green sheet and tungsten paste as those used in Example 1, two 10 × 10 mm square patterns were printed on the green sheet at intervals of 20 mm, and then degreased and fired in the same manner as in Example 1. Thus, an aluminum nitride sintered substrate was obtained.

The obtained sintered substrate was divided into two such that each of the fragments had a square pattern, and the tensile strength of one of the fragments was measured. In the measurement of the tensile strength, the metallized layer was divided into 16 meshes by cutting to measure each strength. As a result, the strength of the section located on the outer periphery of the metallized layer is 2.
In 2 kg / mm ^2, the strength is located in the central portion was 6.3 kg / mm ^2.

Further, the metallized layer of the other fragments was removed by etching, and the aluminum nitride side of the interface was examined with a scanning electron micrograph. As a result, the height was about 8 μm and the width was about 2.5 μm at the center.
It was found that while there were seven protrusions per 100 μm ^{2 on} average, no protrusions having a height of 1 μm or more existed outside.

Example 3 An aluminum nitride sintered substrate was obtained in the same manner as in Comparative Example 2 except that the same paste was additionally printed on the entire back surface on which the pattern was printed using the same paste at an interval of 0.4 mm.

The obtained sintered substrate was subjected to the tensile strength measurement and the observation of the convex portion of the interface in the same manner as in Comparative Example 2, and as a result, the strength of the section located on the outer periphery of the metallized layer was 5.5 kg / mm ² , Was 6.7 kg / mm ² .

Furthermore, the metallization layer of another fragment removed by etching, were examined aluminum nitride side of the interface in the scanning electron micrograph, the outer periphery is average of 4 exists a height of about 6 [mu] m, the convex portion 100 [mu] m ² per a width of about 1.5μm And about 9 height in the center
It was found that there were an average of about 7 protrusions having a width of about 2.5 μm and a diameter of about μm.

[Brief description of the drawings]

FIG. 1 is a sectional view schematically showing an interface between an aluminum nitride sintered substrate and a metallized layer. In the figure, 1 indicates an aluminum nitride sintered substrate, 2 indicates a metallized layer, and a indicates the height of a convex portion.

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Claims (2)

(57) [Claims] 1. A pattern made of a paste of a high melting point metal is formed on the surface of a green sheet of aluminum nitride, and the pattern is formed on the same surface as the pattern, on the surface of the green sheet near the pattern, or on the back surface of the pattern. A method for producing an aluminum nitride metallized substrate, comprising: providing a layer for restricting the scattering of carbon during degreasing on the surface of a green sheet where a pattern is located; degreasing and firing; 2. The method according to claim 1, wherein the layer that limits the scattering of carbon during degreasing is made of a high melting point metal.