JP2007173608A - Aluminum nitride sintered body and ceramic circuit board employing it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aluminum sintered body in which the water resistance of aluminum nitride powder is raised by surface treatment and heat conductivity of a sintered body will not be deteriorated when the same is used as a sintered material, while having excellent appearance and prominent heat conductivity, and a ceramics circuit board employing it. <P>SOLUTION: The aluminum nitride sintered body employs aluminum nitride powder processed by aluminate series coupling agent as the material thereof, and the ceramics circuit board employs the aluminum nitride sintered body. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to an aluminum nitride sintered body and a ceramic circuit board using the same.

As circuit boards used for power modules and the like, ceramic substrates such as alumina, silicon nitride, and aluminum nitride are used from the viewpoint of thermal conductivity, cost, safety, and the like. These ceramic substrates are used as ceramic circuit substrates by joining metal circuits such as Cu and Al, and heat sinks. These ceramic circuit boards are characterized in that they are excellent in heat dissipation of heat generated from electronic components because of their high thermal conductivity compared to resin circuit boards and metal circuit boards using resin layers as insulating materials. Among these ceramic substrates, aluminum nitride has the highest thermal conductivity, and has attracted attention as a ceramic circuit substrate material for electronic components that generate a large amount of heat.

The aluminum nitride powder used as the aluminum nitride substrate material has a problem that it is easily hydrolyzed by moisture in the atmosphere. Therefore, in order to improve the water resistance of the aluminum nitride powder, a method of treating with an inorganic phosphoric acid compound (Patent Document 1), a method of forming a film with an aluminum sulfate (Patent Document 2), an aluminum oxide or phosphoric acid on the surface Water resistance of aluminum nitride powder by a method of adding an organosilicon coupling agent, an organophosphate coupling agent and a phosphate group-containing organotitanium coupling agent (Patent Document 3) Attempts have been made to improve performance.
Japanese Patent Laid-Open No. 2-141409 JP-A-7-33413 JP-A-7-33415

However, in the methods shown in Patent Documents 1 to 3, the water resistance of the aluminum nitride powder is improved, but when used as a sintering raw material, phosphorus, sulfur, silicon, titanium, etc. remain in the sintered body to conduct heat. There is a problem of reducing the sex. Furthermore, in the method of Patent Document 3, the productivity is lowered due to the coupling treatment after the film is once formed, the problem that phosphorus remains as described above, and the thermal conductivity is lowered by the formed aluminum oxide itself. There is a problem.

An object of the present invention is to provide an aluminum nitride sintered body having a good appearance and excellent thermal conductivity, and a ceramic circuit board using the same.

That is, the present invention is an aluminum nitride sintered body using aluminum nitride powder treated with an aluminate coupling agent as a raw material, and a ceramic circuit board using the aluminum nitride sintered body.

ADVANTAGE OF THE INVENTION According to this invention, the aluminum nitride sintered compact which was excellent in the thermal conductivity which has a favorable external appearance, and a ceramic circuit board using the same are provided.

The present invention will be described in detail. Examples of the aluminate coupling agent used in the present invention include acetoalkoxyaluminum diacetate. The addition amount of the aluminate coupling agent according to the present invention is preferably 0.5 to 5 parts by mass with respect to 100 parts by mass of the aluminum nitride powder.

The aluminum nitride powder according to the present invention is not particularly limited. For example, the powder is obtained by a direct nitriding method in which aluminum is heated in nitrogen, and is obtained by a reductive nitriding method in which aluminum oxide and carbon are heated in nitrogen. Powder or the like can be used.

The mixing method of the aluminate coupling agent and the aluminum nitride powder according to the present invention is not particularly limited, and may be a known mixing method using a Henschel mixer, a spar mixer, or the like.

An aluminum nitride sintered body using the aluminum nitride powder of the present invention and a method for producing a circuit board will be described.

Suitable examples of the sintering aid used in the present invention include alkaline earth metal compounds and transition metal compounds. Specifically, oxides, fluorides, chlorides, nitrates, sulfates of alkaline earth metals (Ca, Ba, Sr, etc.) and transition metals (Y, La, Sc, Pr, Ce, Nd, Gd, etc.) , Carbonates, etc. Among them, yttrium oxide and calcium oxide are preferable. These sintering aids react with oxygen in the aluminum nitride powder, that is, aluminum oxide, to form a liquid phase of a composite oxide (for example, 2Y ₂ O ₃ .Al ₂ O ₃ , Y ₂ O ₃ .Al ₂ O ₃ , 3Y ₂ O ₃ · 5Al ₂ O ₃ etc.), and this liquid phase brings about an increase in the density of the sintered body, and at the same time, extracts oxygen etc., which are impurities in the aluminum nitride particles, High thermal conductivity is brought about by segregating as a phase. If the amount of the sintering aid used is small, liquid phase sintering is insufficient. Conversely, if it is large, the proportion of crystal grain boundaries increases, and in either case, the thermal conductivity does not increase. In the present invention, the amount of the sintering aid used is preferably 1 to 5 parts by mass per 100 parts by mass of the aluminum nitride powder.

The mixing of the aluminum nitride powder and the sintering aid is not particularly limited, and a known mixing device such as a ball mill or a rod mill can be used. The mixed powder may be molded as it is, or may be molded after granulation by a spray dryer method, rolling granulation method or the like. The molding can be performed, for example, alone or in combination such as a dry press molding method and a cold isostatic press molding method (CIP method). The press pressure of the dry press molding is preferably 50 to 300 MPa, particularly preferably 100 to 250 MPa. In either case of the dry press molding method or the CIP method, an organic binder is used as necessary. Furthermore, it is also possible to mix aluminum nitride powder, a sintering aid, an organic binder, and, if necessary, a plasticizer, a dispersing agent, a solvent, etc., and to perform extrusion molding or doctor blade molding of this mixture.

As the organic binder, for example, polyvinyl butyral, polyacrylate, polymethyl methacrylate, methyl cellulose, polyethylene, wax and the like can be used.

In the present invention, in order to remove carbon and oxygen contained in the aluminate coupling agent, in order to further remove the organic binder, before firing, in an air stream such as nitrogen gas or air, 350 ~ Heat them at 700 ° C. for 1-10 hours to remove them from the compact.

Firing is preferably carried out in a non-oxidizing atmosphere such as nitrogen gas or argon gas, in a temperature range of 1600 to 1900 ° C. for 1 to 10 hours, preferably 2 to 7 hours. If the firing temperature is less than 1600 ° C., sintering may be insufficient and it may be difficult to produce an aluminum nitride sintered body having a thermal conductivity of 180 W / mK or more. On the other hand, if the firing temperature exceeds 1900 ° C., the vapor pressure of aluminum nitride in the furnace becomes high and densification may be difficult. The holding time is preferably the shortest time within which the sintered body density can be 98% or more within the above temperature range. When fired for a long time in a temperature range where the sintered body density is 98% or more, the aluminum nitride particles grow more than necessary and become coarse particles, which makes the volume of the two-particle interface relatively smaller than the triple point. This is because the grain boundary phase is segregated more at triple points than the two-particle interface of aluminum nitride, and the liquid phase of the aluminum composite oxide may ooze out on the surface of the sintered body.

The thickness of the aluminum nitride substrate according to the present invention varies depending on the purpose of use, but a thickness of about 0.3 to 3.0 mm is generally used as necessary.

When the aluminum nitride substrate of the present invention is used as a circuit substrate, copper, aluminum, tungsten, molybdenum, or the like can be used as the material of the metal circuit or the metal heat sink, but copper, aluminum, or an alloy thereof is common. is there. The thickness of a metal plate is not specifically limited, It determines suitably according to the electric current which flows. In general, those having a thickness of 0.1 to 1.0 mm are often used. As a joining method for joining the ceramic substrate and the metal plate, either the DBC method or the active metal brazing method can be employed. The brazing material used in the active metal brazing method contains silver and copper as main components and an active metal as a minor component. Specific examples of the active metal include titanium, zirconium, hafnium, niobium, tantalum, vanadium, and compounds thereof. Etching is performed after a circuit pattern is drawn on the metal plate with an etching resist. A known method can be used for the step of removing the etching resist. As the etching resist, a known ultraviolet curing type or thermosetting type can be used. Further, as the etching solution, a suitable etching solution is selected according to the type of the metal plate to be used. For example, when the metal is copper, a solution such as a ferric chloride solution, a cupric chloride solution, sulfuric acid, or a hydrogen peroxide solution is used. Preferred examples include a ferric chloride solution and a cupric chloride solution. It is done.

1 part by mass of an aluminate coupling agent was added to 100 parts by mass of aluminum nitride powder produced by direct nitriding, and mixed for 10 minutes with a Henschel mixer to obtain a coupling-treated aluminum nitride powder. 5 parts by mass of yttrium oxide powder as a sintering aid was added to 95 parts by mass of the aluminum nitride powder treated with the coupling agent, and mixed for 1 hour in a ball mill to obtain a raw material powder. 7 parts by mass of methyl cellulose as an organic binder, 5 parts by mass of glycerin as a plasticizer, 3 parts by mass of stearic acid emulsion as a dispersant, 2 parts by mass of oleic acid, and 7 parts by mass of ion-exchanged water as a solvent Were mixed with a Henschel mixer to obtain a mixture. The mixture was kneaded with a uniaxial kneader and then molded into a plate shape with a uniaxial extruder. The molded product was heated in an air stream at 570 ° C. for 5 hours to obtain a degreased body. The degreased body was heated in a nitrogen stream at 1780 ° C. for 2 hours to obtain a sintered body. The appearance and thermal conductivity of the sintered body were evaluated. The results are shown in Table 1.

(Comparative Example 1)
A sintered body was obtained in the same manner as in Example 1 except that the aluminum nitride powder was not treated with an aluminate coupling agent. The appearance and thermal conductivity of the sintered body were evaluated. The results are shown in Table 1.

(Comparative Example 2)
A sintered body was obtained in the same manner as in Example 1 except that the aluminum nitride powder was treated with a silane coupling agent. The appearance and thermal conductivity of the sintered body were evaluated. The results are shown in Table 1.

<Materials used>
Aluminum nitride powder: Aluminum nitride powder by direct nitriding obtained by heating aluminum powder in a nitrogen stream, finely dispersing aluminum droplets and reacting with nitrogen, or by reacting aluminum vapor with nitrogen and crushing “Average particle size: 1.5 μm, manufactured by Denki Kagaku Kogyo”
Aluminate coupling agent: Ajinomoto Co., Inc. Trade name “Plenact AL-M”
Silane coupling agent: Nippon Unicar Co., Ltd. trade name “A-137”
Yttrium oxide: Shin-Etsu Chemical Co., Ltd. Trade name “Yttrium oxide UU grade”
Methyl cellulose: manufactured by Shin-Etsu Chemical Co., Ltd.
Glycerin: Miyoshi oil and fat Product name “Purified Glycerin”
Stearic acid emulsion: Chukyo Yushi
Oleic acid: Reagent grade 1 manufactured by Kanto Chemical Co., Inc.

<Evaluation methods>
Thermal conductivity: Measured by a laser flash method using a device name (TC-7000 manufactured by Vacuum Riko Co., Ltd.).

According to the present invention, an aluminum nitride sintered body having a uniform color tone with no color unevenness can be obtained, and it can be suitably used as a circuit board.

Claims (2)

An aluminum nitride sintered body characterized by using an aluminum nitride powder treated with an aluminate coupling agent as a raw material. A ceramic circuit board using the aluminum nitride sintered body according to claim 1.