JPH02217383A - Sintered aluminum nitride and production thereof - Google Patents

Abstract

PURPOSE:To improve the electrical conductivity of a metallized layer without lowering the bonding strength of the metallized layer by using a material containing a nitride or oxynitride of a group V element as a metallized layer to be formed on the surface of sintered aluminum nitride. CONSTITUTION:The sintered aluminum nitride has a metallized layer on at least a part of the surface and the metallized layer contains at least one kind of substance selected from nitrides and oxynitrides of group V elements (Nb, V, Ta, etc.). The metallized layer is, for example, (1) a phase composed of at least one kind of nitride or oxynitride of Nb, V or Ta, (2) a mixed phase composed of a high-melting metal selected from Mo and W and at least one kind of nitride or oxynitride of Nb. V or Ta and (3) a mixed phase composed of at least one kind of nitride or oxynitride of Nb, V or Ta and at least one kind of a compound of group III element, group IVa element, group W element, rare-earth element and actinoid element.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an aluminum nitride sintered body having a metallized layer and a method for manufacturing the same.

(Prior art) Aluminum nitride sintered bodies have a thermal conductivity that is 5 to IO times higher than that of aluminum oxide sintered bodies, excellent heat dissipation, high electrical insulation properties, low dielectric constant, and corrosion resistance and heat resistance. Because it has various excellent properties such as excellent impact resistance, it is attracting attention as a material for various electronic and electrical parts and as a structural material. In particular, it has excellent heat dissipation and a thermal engraving coefficient of S.
Because it resembles an i-chip, it is expected to be used as an insulating substrate for semiconductor devices in place of alumina sintered bodies, which have insufficient heat dissipation properties, and beryllia sintered bodies, which are toxic and difficult to handle.

Specific applications include insulating substrates for high-frequency transistors and igniters that generate a large amount of heat by taking advantage of its excellent heat dissipation properties, and multilayer capacitors by taking advantage of its low dielectric constant. It is used as a material for electrical and electronic parts, and as a structural material, taking advantage of its translucent properties, it is being considered as a material for traveling wave tubes and electromagnetic wave transmitting windows for nuclear fusion reactors.

By the way, when an aluminum nitride sintered body is used as a substrate for mounting various electric/electronic components as mentioned above, it is essential to form a conductive layer on its surface, and when it is used as a structural material, it cannot be used as a metal member. It is essential to form a metallized surface that will serve as the bonding surface. Therefore, conventionally, a metallized layer has been formed on an aluminum nitride sintered body by the method shown below.

■ Place the Cu plate in contact with the aluminum nitride sintered body,
The so-called DBC method involves direct bonding by heating.

■ Thick film method using paste such as Cu s^SAg-Pd.

■ Mo! A method of forming a metallized layer by making a paste of a metallizing composition prepared by adding and mixing a nitride of an active metal such as TI to a high melting point metal such as W, and applying and firing the paste.

However, the metallized layer obtained using methods ① and ① above shows a significant decrease in bonding strength with the aluminum nitride sintered body when exposed to high temperatures, which causes a decrease in strength when soldering is performed at high temperatures. However, when parts that generate a large amount of heat are mounted on a tower, there are problems such as the metallized layer being prone to cracking due to the additional cooling and heating cycles.

On the other hand, the metallized layer formed by the method (■) above is
It has high bonding strength with respect to aluminum nitride sintered bodies, and there is almost no decrease in bonding strength even at high temperatures, making it excellent as a conductive layer for mounting various electronic components.

(Problems to be Solved by the Invention) However, although the metallized layer produced by the method (2) has excellent characteristics as described above, there are still many issues that require improvement.

In other words, using the Mo-TiN metallization composition as an example, TIN exhibits bonding strength to the aluminum nitride sintered body and serves as a conductive material in the metallization layer, but TIN alone does not have enough strength to form the metallization layer. Sufficient mechanical strength cannot be obtained, resulting in a brittle product. Therefore, MO is added to add strength and improve conductivity through its sintering power.
MO has a large shrinkage during firing, and if the amount of MO added is large, stress will be added to the aluminum nitride sintered body during firing, causing cracks, and even if cracks do not occur, it will cause a decrease in strength. .

On the other hand, increasing the amount of MO added can be expected to improve the electrical conductivity, but decreasing the amount of TIN will lead to a decrease in the bonding strength of the metallized layer.

In this way, the blending ratio of the Mo-TIN metallized composition must be selected in consideration of the bonding strength and conductivity of the metallized layer, the mechanical strength of the metallized layer, and the effect on the aluminum nitride sintered body. The challenge is to alleviate these issues. This problem also applies to V.

The present invention has been made to address such problems, and the first object of the present invention is to provide an aluminum nitride sintered body having a metallized layer with improved conductivity without reducing the bonding strength of the metallized layer, and The second objective is to provide an aluminum nitride sintered body having a metallized layer that suppresses adverse effects on the aluminum nitride sintered body without reducing the mechanical strength of the metallized layer, and its second purpose. An object of the present invention is to provide a manufacturing method.

[Structure of the Invention] (Means for Solving the Problems) That is, the aluminum nitride sintered body of the present invention is an aluminum nitride sintered body having a metallized layer on at least a part of the surface, wherein the metallized layer is made of a group V element. At least 1 selected from the group consisting of nitrides and oxynitrides
Ti! It is characterized by containing J.

Further, the method for manufacturing an aluminum nitride sintered body of the present invention includes:
At least 1 selected from the group consisting of simple substances and compounds of group V elements on the aluminum nitride sintered body.
The method is characterized in that a fluid material containing a metallizing composition containing seeds and an organic binder is applied and then fired in an inert atmosphere to form a metallized layer.

The aluminum nitride sintered body of the present invention is characterized by the metallized layer formed on its surface, and the physical properties, sintering method, and shape of the sintered body itself as a base material are There are no particular restrictions; for example, rare earth oxides such as yttrium oxide, alumina, calcium oxide, etc. are used as sintering aids, and common methods such as normal pressure sintering, atmospheric pressure sintering, and hot press sintering are used. The shape and physical properties are selected depending on the application. For example, when used as a substrate material, the thermal conductivity is 50w/11. or more is preferable.

Further, the aluminum nitride sintered body may be co-fired with the metallized layer.

The metallized layer formed on the aluminum nitride sintered body of the present invention is composed of at least nitrides and oxynitrides of group V elements. , that is, it contains Nb, V, Ta nitrides and oxynitride lFl,
Examples of specific constituent phases of the metallized layer are as shown below.

■ A phase consisting of at least one type of nitride or oxynitride of Nb, V, or Ta.

■ Mo or V high melting point metal, Nb, V STa
mixed phase with at least one kind of nitride or oxynitride.

■ A mixed phase of at least one type of nitride or oxynitride of Nb or V STa and at least one type of compound of a group ■ element, a group IVa element, a group II element, a rare earth element, or an actinide element.

In the above metallized layer (■), Nb5v, Ta nitride and oxynitride serve as components that firmly bond the metallized layer to the aluminum nitride sintered body, and also provide conductivity, and the high melting point metal improves conductivity. and contributes to improving mechanical strength.

In addition, in the metallized layer of (2) above, group (2) elements, N
Compounds of group A elements, group II elements, rare earth elements, and actinide elements serve as components that firmly bond the metallized layer to the aluminum nitride sintered body, as well as impart conductivity.
, V STa nitrides and oxynitrides not only reinforce the mechanical strength of the above-mentioned materials, but also contribute to improving bonding and conductivity.

The group Ⅰ elements, rVa group elements, group Ⅰ elements, rare earth elements, and actinide elements mainly exist as nitrides, oxides, oxynitrides, or complex compounds with Nbs V s Ta, for example. A.I.

Compounds such as Ga and In, compounds of T1, Zr, and Ilf, and Fe.

Compounds such as Cos, Rh, Pd, Se, Y
, compounds such as La5CesPrSS■, AcsT
It is a compound such as h.

These metallized layers include (a) Nb, V, Ta alone or nitride;
A metallizing composition consisting of a compound such as an oxynitride, (b
) (a) Moya W (7) High melting point metal and (0) Nb
.

A metallized composition containing V, Ta alone or a compound such as a nitride, oxynitride, or (C) (C) Nb%Vs Ta alone or a compound such as a nitride, oxynitride, etc. d) Using a metallizing composition containing compounds such as oxides, nitrides, and oxynitrides of group ■ elements, group IVa elements, group ■ elements, rare earth elements, and actinide elements, and adding an organic binder to these metallizing compositions. If necessary, add a solvent to make it into a paste to give it fluidity, then apply this fluid substance onto the aluminum nitride sintered body in the desired pattern shape by screen printing, etc., dry it, and then It is formed by firing in an inert atmosphere such as nitrogen gas.

The above firing temperature varies depending on the type of metallizing composition used and the blending ratio of each component therein.
) when using a metallizing composition of approximately 160
0°C to 1900°C, or approximately 1700°C to 1900°C when using the metallizing composition of (b) above.
When using the metallizing composition of (C) above, a suitable temperature is approximately 1600°C to 1900°C.

Further, it is preferable to use a metallizing composition having an average particle size of 2 μm or less, so that the surface of the metallized layer obtained can be kept smooth.

The surface roughness of the metallized layer is preferably 5 μm or less in terms of Rsax. This makes it possible to fully exhibit the high heat dissipation properties of the aluminum nitride sintered body when a semiconductor element or the like is mounted on the metallized layer.

The above-mentioned (a) component and (b) component in the above-mentioned (b) metallizing composition are 80: 2O-ts: 85 as a weight ratio of the (a) component and (b) component (however, the four components are the weight of the element It is preferable to mix within the range of (shown in terms of conversion). (b) If the component is less than 15 mm%, the electrical conductivity of the metallized layer obtained will decrease and the sinterability of the metallized layer will decrease, and if it exceeds 80 mm%, the bonding strength of the metallized layer to the aluminum nitride sintered body will decrease. decreases due to excessive shrinkage of the metal component.

By blending the (b) component in the metallized composition (b) as a metal, the shrinkage of the (b) component during firing can be alleviated, and the stress applied to the aluminum nitride sintered body side can be suppressed, and the firing temperature can be expected to decrease. Furthermore, when compounded as a compound such as a nitride, a metallized layer with excellent mechanical strength can be obtained due to its high sinterability.

In addition, the above-mentioned (c) component and (d) component in the above-mentioned (e) metallizing composition have a weight ratio of 95:5 to 20:80 (however, the weight ratio of each element It is preferable to mix within the range of (shown in terms of conversion). If the (c) component is less than 20% by weight, the bonding effect of the (c) component with the aluminum nitride sintered body will be almost eliminated, and the strength will be dominated by the (d) component, resulting in a decrease in strength of 95% by weight. If it exceeds this, excessive shrinkage will occur during the formation of the metallized layer, and variations in bonding strength will increase.

Component (iii) in this metallizing composition (C) is preferably blended as a metal. This can be expected to lower the firing temperature.

In addition, as the above-mentioned component (2), by using a group IVa compound such as Ti nitride, the reactivity can be increased and the bonding strength can be expected to be improved. By using this, lowering of the firing temperature can be expected. Furthermore, by using the component (2) in various combinations, such as the above-mentioned Ti compound and, for example, a CO compound, various improvements in properties can be expected.

The metallized layer in the present invention may be formed on an aluminum oxide layer formed on the surface of the aluminum nitride sintered body in advance. By forming a metallized layer on the aluminum oxide layer, the bonding strength of the metallized layer can be improved.

The aluminum oxide layer can be formed on the product by heat treating the aluminum nitride sintered body in an oxidizing atmosphere at a temperature of, for example, 900°C to 1400°C, or by thin film forming methods such as sputtering and thermal spraying. You may also use

Further, it is preferable to form a conductive protective layer on the metallized layer, and then use it for various purposes.

Materials for forming the conductive protective layer include N1, Ag, and Au.
, Cu, Cr5Pb, Sn, etc., which are used alone or in combination of 2FIi or more,
It is selected as appropriate depending on the purpose. Methods for forming this conductive protective layer include electroplating, electroless plating,
Various known methods such as a sputtering method and an evaporation method can be applied, and the appropriate thickness is about 1 μm to 10 μm.

By forming a conductive protective layer on the metallized layer in this way, it is possible to prevent the metallized layer from becoming brittle even in a reducing atmosphere containing hydrogen when other parts are brazed onto the metallized layer. , the reliability of the bonding is improved.

(Function) The metallized layer in the aluminum nitride sintered body of the present invention contains nitrides and oxynitrides of group V elements, and these may be used alone or with high melting point metals such as MO and V, or group elements, IVa group elements, group ■ elements, rare earth elements,
It constitutes a metallized layer together with a compound of actinide elements.

In the metallized layer formed together with the high melting point metal, the nitride or oxynitride of the group V element suppresses the shrinkage of the high melting point metal during firing, and alleviates the stress applied to the aluminum nitride sintered body. Therefore, it is possible to reliably ensure that the conductivity and mechanical strength are improved by the high melting point metal, and the reliability is improved. Further, since the nitride or oxynitride of the V group element itself has high sinterability, the mechanical strength of the metallized layer is also improved by this.

In addition, in a metallized layer formed with a compound of a group Ⅰ element, a group IVa element, a group Ⅰ element, a rare earth element, or an actinide element, the shrinkage of the nitride or oxynitride of the group V element itself is small; It is possible to improve the bonding strength and reduce the stress applied to the aluminum nitride sintered body, improving reliability.

Even in the case of a metallized layer made of a nitride or oxynitride of a group V element alone, the metallized layer becomes a sufficiently reliable metallized layer due to its high bonding strength to the aluminum nitride sintered body and sinterability.

(Example) Next, examples of the present invention will be described.

Example 1 First, 3% by weight of Y2O3 was added to ^IN powder as a sintering aid.
Using the added mixed powder, an AIN sintered body having a thermal conductivity of 270 W/s and a substrate shape of 50 m x 50 sm x O, 635 av was manufactured.

On the other hand, using MO powder and NbN powder, these were mixed with N.

35% by weight and ffi% of Nb65TII, and thoroughly mixed and pulverized in a pot mill to have an average particle size of 1.
A 5μ metallized composition was prepared. Next, an organic binder and a solvent were added to this metallizing composition and thoroughly mixed to prepare a metallizing paste.

Next, this metallizing paste was screen printed onto the above-mentioned AIN sintered body to a thickness of 8 μm after firing.
It was applied in a predetermined pattern shape as described above, and after drying, it was heated and baked at 1800° C. for 60 minutes in a nitrogen gas atmosphere to form a metallized layer.

When the constituent components of the metallized layer thus obtained were analyzed using a scanning electron microscope and an energy dispersive X-ray microanalyzer, it was found to consist of Mo and NbN.

Next, an old plating layer having a thickness of about 2 to 5 μl was formed as a conductive protective layer on this metallized layer, and annealing was performed in a homing gas at about 800° C. And this Nl plating layer is 2sw x 2m
An annealed copper wire pin with a length of 6011% and a diameter of 0.81 is bonded to the part m using 63Sn-Pb solder, and the AIN sintering of the metallized layer is applied with the tensile force when the pin is removed by applying a tensile force to this pin. The bonding strength to the solid body was evaluated. As a result, the bonding strength of the metallized layer was 2.5 kgf/
- It showed a good value.

Furthermore, after conducting a heat cycle test of 1000 cycles from -55°C to room temperature to 150°C on the AIN sintered body having the metallized layer, the bonding strength was similarly determined to be 81. At 3 kgf/ij, there was almost no decrease in the bonding strength, and the reliability against thermal history was also high.

On the other hand, for comparison with the present invention, rib powder and TIN powder were
They were mixed at a composition ratio (weight ratio) of 0:80, a binder was added to prepare a metallization paste, and a metallization layer was formed in the same manner as in Example 1.

The bonding strength of this metallized layer is 2.5kgf/-, and the bonding strength after the heat cycle test is 2.4kgr/-
Met.

Examples 2 to 23 Metallizing compositions were prepared using the compounding ratios shown in Table 1, and then metallizing pastes were prepared in the same manner as in Example 1. These metallizing pastes were applied onto the AIN sintered bodies shown in Table 2 in the same manner as in Example 1 to form metallized layers at the firing temperatures shown in Table 2.

As shown in Table 2, the bonding strengths of the obtained metallized layers all showed large values. Further, even after a heat cycle test under the same conditions as in Example 1, no decrease in bonding strength was observed.

(Margin below) Table 1 Examples 24 to 26 First, the AIN sintered body used in Example 1 was exposed to tt in the atmosphere.
Heat treatment was performed at a temperature of 0°C to 1200°C for 1 hour to form an Al2O3 layer with a thickness of 2 to 3 μm on the surface of the AIN sintered body. Next, on this Al2O3 layer, a and b shown in Table 1 were applied.
Example 1 using the metallizing compositions of and g, respectively.
A metallized layer was formed under the same conditions.

The bonding strength of the metallized layer obtained in this way was measured in Example 1.
When measured under the same conditions as
．． 2kgf'/m (, 2,9kgf'/mj, 2.
A strength improvement effect of 5 kgf/mj was observed.

Examples 27 to 29 On the metallized layer of the AIN sintered body having the metallized layer produced in Examples 16.8 and 5, an N1 plating layer and an Au plating layer were respectively formed in order, and a high frequency transistor (To- 220AB) were bonded together using Au-9l solder.

The output is 15 on the ^IN sintered body metalized in this way.
When the thermal resistance of the high-frequency transistor mounted on the 2.W high-frequency transistor was measured by the ΔvBE method, it was 3.3°C, 2.
Good values of 8° C./W and 8.2° C. were shown, confirming that the aluminum nitride sintered body of the present invention exhibits excellent characteristics as a substrate for a high-frequency transistor.

Example 30 In the same manner as in Example 17, an AIN sintered body having metallized layers on both sides was produced. Next, a Ni plating layer and an Au plating layer are sequentially formed on one of the metallized layers,
On top of that, there is an ignition timing control part for the igniter (Pa'y-I
C, V-30V, and IE-1, 5B A) were respectively bonded using Au-8l solder.

On the other hand, a Ni plating layer was similarly formed on the other metallized layer, and the Nl plating layer was joined to an aluminum die-cast container using Pb-8n solder to produce an igniter.

The temperature rise of 81 chips of the igniter thus obtained was measured. As a result, the temperature rise of the Sl chip is 1.1
It showed a good value of 4℃/V (standard 1.26℃/V),
It was confirmed that the aluminum nitride sintered body of the present invention has excellent properties as a substrate for an igniter.

Example 31 The metallizing paste used in Example 1 was applied onto an AIN substrate of 20 mm x 20 mm A ceramic substrate was obtained. The thickness of the metallized layer was about 10 μm. After this, nickel plating is applied to the surface of the metallized layer to a thickness of about 1-10 μ-
Annealing was performed at °C. Next, the AIN ceramic substrate having the metallized layer obtained as described above was laminated in multiple layers on the AIN ceramic substrate (without metallized layer) with the metallized layer facing down. Thereafter, the laminated metallized layers at predetermined positions were joined to an anode or a cathode via a conductive wire, and then packed in a case to obtain a capacitor.

Incorporate the capacitor obtained in this way into an RCL circuit,
Even when used for a long time at about 40° C., the AIN ceramic plate and the metallized layer formed on its surface had no similar change in appearance or properties such as insulation.

Example 32 A metallized layer was formed as a sealing part in the same manner as in Example 20 to a width of 8 cm at the peripheral edge of an AIN sintered body.

This AIN sintered body was used as a window member and bonded to a stainless steel frame using a heg-Cu-TI brazing material. When a helium leak test was conducted on this joint at high temperatures, good results were obtained.

[Effects of the Invention] As is clear from the above description, according to the present invention, conductivity can be improved while satisfying the bonding strength of the metallized layer, or aluminum nitride can be improved while satisfying the mechanical strength of the metallized layer in practical terms. It is possible to suppress negative effects on the sintered body, etc.
An aluminum nitride sintered body that satisfies various properties required for a metallized layer can be obtained. Therefore, it is possible to provide highly reliable -1 members as materials for various electronic/electrical parts and structural materials, such as mounting boards for high-frequency transistors and igniters, multilayer capacitors, and members for electromagnetic wave transmission windows.

Claims (12)

[Claims] (1) In an aluminum nitride sintered body having a metallized layer on at least a part of the surface, the metallized layer contains at least one member selected from the group consisting of nitrides and oxynitrides of group V elements. An aluminum nitride sintered body characterized by: (2) The aluminum nitride sintered body according to claim 1, wherein the metallized layer contains Mo and/or W. (3) The metallized layer includes a group III element, a group IVa element,
The aluminum nitride sintered body according to claim 1, characterized in that the aluminum nitride sintered body contains at least one member selected from the group consisting of compounds of group VIII elements, rare earth elements, and actinide elements. (4) The aluminum nitride sintered body according to claim 1, wherein the metallized layer is formed on the aluminum nitride sintered body with an aluminum oxide layer interposed therebetween. (5) The aluminum nitride sintered body according to claim 1, wherein a conductive protective layer is formed on the metallized layer. (6) A high frequency transistor substrate comprising the aluminum nitride sintered body according to claim 1. (7) An igniter substrate comprising the aluminum nitride sintered body according to claim 1. (8) A window member made of the aluminum nitride sintered body according to claim 1, wherein the surface metallized layer is provided as a sealing part on the peripheral edge of the aluminum nitride sintered body. (9) A capacitor formed by sequentially laminating a plurality of aluminum nitride sintered bodies according to claim 1. (10) A fluid substance containing an organic binder and a metallizing composition containing at least one selected from the group consisting of simple substances and compounds of Group V elements is applied onto the aluminum nitride sintered body, and then a fluid substance containing an organic binder is applied. A method for producing an aluminum nitride sintered body, which comprises firing in an active atmosphere to form a metallized layer. (11) The method for producing an aluminum nitride sintered body according to claim 10, wherein the metallizing composition contains at least one selected from the group consisting of Mo, W alone and compounds. (12) A claim characterized in that the metallizing composition contains at least one element selected from the group consisting of a group III element, a group IVa element, a group VIII element, a rare earth element, and an actinide element. Item 11. The method for producing an aluminum nitride sintered body according to item 10.