JP2000281460A - Metal powder brazing material and joining method between aluminum nitride member and metal member - Google Patents

Abstract

(57) [Problem] To prevent an outflow of a brazing material when joining an aluminum nitride member and a metal member with the brazing material. SOLUTION: (1) 100 parts by weight of a silver-copper eutectic alloy powder, (2) silver, copper, or a silver-copper alloy having a different composition ratio from (1) and having a melting point of (1). 60 ° C from melting point
Higher than the metal, the average particle size is 1 to 85 μm
10 to 60 parts by weight of metal powder , and (3) active metal powder,
For example, titanium powder or titanium hydride powder 0.1 to 5
A metal powder brazing material containing parts by weight is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal powder brazing material suitable for joining an aluminum nitride member and a metal member, and a method of joining the aluminum nitride member and the metal member via the brazing material.

[0002]

2. Description of the Related Art A joined body of a metal member and a ceramic member is
Various researches and utilizations as electronic circuits and structural materials.
Aluminum nitride substrate among ceramics
Because of its excellent insulation properties, a metal is bonded to this and the IGBT
In recent years, it has been widely used as a (high-power electronic circuit board). It is most advantageous to use copper as a metal for this purpose from the viewpoint of electrical characteristics and the like, and it is currently being actively studied.

As a joining method of a copper plate and an aluminum nitride substrate, an active metal method of joining using a brazing material to which an active metal having reactivity with aluminum nitride is added (for example, JP-A-60-32343). Or the surface oxidation treatment of an aluminum nitride substrate and a copper
_{What is} called D, which is joined by heating above the eutectic temperature of ₂ O-O
The BC method (for example, JP-A-59-40404) is known. The active metal method requires (1) no surface oxidation treatment of the aluminum nitride substrate, as compared with the DBC method. (2) The joining temperature is low, and the residual stress due to the difference in the coefficient of thermal expansion between the copper and the aluminum nitride sintered body is reduced. (3) There are few bonding defects and the bonding strength is stable. (4) Deterioration of the bonding layer is small even when heat treatment is performed in a hydrogen stream. There are advantages such as.

In order to make use of this property, a brazing material paste is printed in a desired pattern on an aluminum nitride substrate, and then a copper plate is bonded, and only an unnecessary portion of the copper plate is etched, whereby a desired conductive pattern is bonded on the substrate. There has been proposed a method for obtaining a coated aluminum nitride substrate.

[0005]

In general, when brazing, it is required that the brazing material and the joining member have good wettability. However, the joining portion where the metal is joined like a circuit board and the metal are joined. In the brazing of a substrate in which unbonded joints coexist, it is necessary to prevent the brazing material from unnecessarily flowing into the unbonded joints. However, when joining after forming the brazing material pattern, if the substrate is heated to a temperature equal to or higher than the melting point of the brazing material, a liquid phase will be generated and flow in the brazing material, and the insulation must be ensured. In other words, there has been a problem that the brazing material flows out to the non-joined portion and short-circuits between the patterns and defects such as the brazing material flow out to the insulating pattern portion.

[0006] Even when a brazing material is applied to an aluminum nitride substrate in a desired pattern and copper members are joined, it is important to prevent the brazing material from flowing out. A method has been proposed in which a metal having a higher melting point than the brazing filler metal component is added to the brazing filler metal (Japanese Patent Laid-Open No. Hei 2-
No. 6096). However, in this method, there is a problem that the brazing material layer is hardened by adding the high melting point metal and the thermal shock resistance of the joined body is reduced. However, in this method, the addition of the refractory metal hardens the brazing material layer, causing a problem that the thermal shock resistance of the joined body is reduced. As a method of suppressing the flow of other brazing material,
In the case of a Ti (or Nb, Zr) -Cu-Ag-based paste-like joining material, a technique has been proposed in which the particle size of the powder is controlled to prevent the powder from flowing out (JP-A-5-24677).
No. 0). However, according to the findings of the present inventors, the above-described method has a problem that the liquid phase generation rate is slow and there is a problem that voids are easily generated at the interface between the metal member and the brazing material or inside the brazing material. It has been clarified that in order to obtain a good bonding state at the interface, it is necessary that the brazing material is quickly melted during heating to form a liquid phase.

In addition, in the case of a brazing material containing an active metal, a method of adding a ceramic powder having reactivity with the active metal to the brazing material has been proposed as a method of suppressing the outflow thereof (Japanese Patent Laid-Open No. 4-108673). No.). However, in this method, a part of the ceramic powder is decomposed at the time of heat bonding to generate a gas of a non-metallic component, so that voids are easily generated inside the brazing material, causing a problem.

[0008]

Means for Solving the Problems The present inventors have made intensive studies to solve the above problems, and found that silver-copper eutectic alloy powder and silver, copper or the silver-copper eutectic The inventors have found that a metal powder consisting of a silver-copper alloy having a different composition ratio from the alloy and a brazing metal powder composed of an active metal powder may be used, and the present invention has been completed.

That is, the present invention relates to (1) 100 parts by weight of a silver-copper eutectic alloy powder, (2) silver, copper, or a silver-copper alloy having a different composition ratio from (1), and having a melting point of Is composed of a metal having a melting point of 60 ° C. or more higher than the melting point of (1), and has an average particle size of 1 to 8
A metal powder brazing material comprising 10 to 60 parts by weight of an alloy powder having a thickness of 5 μm and (3) 0.1 to 5 parts by weight of an active metal powder, and an aluminum nitride member and a metal member are joined via the brazing material. Is the way.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a silver-copper eutectic alloy is a crystal mixture which is simultaneously precipitated from a melt containing silver and copper, and a composition which forms a eutectic is called a eutectic composition.
The silver-copper eutectic alloy powder as the component (1) has a composition of silver 72
It is a powder of a crystal mixture having a eutectic composition of 28% by weight and 28% by weight of copper.

[0011] The average particle size of the silver-copper eutectic alloy powder is not particularly limited, but is 85% for screen printing.
μm or less is preferable, and 1 to 50 μm is more preferable.
The particle size of the silver-copper eutectic alloy powder can be measured using a centrifugal sedimentation method. In the centrifugal sedimentation method, when the form of the powder is irregular, it is not possible to distinguish between the major axis and the minor axis, and the average value is regarded as the particle size.In this specification, this average value is regarded as the particle size. No distinction is made between the major axis and the minor axis for the particle size. Further, the particle size in the present specification refers to a primary particle size, not an aggregate particle size.

There are various methods for producing the silver-copper eutectic alloy powder, such as an atomizing method and a pulverizing method, but the present invention is not limited to these methods at all. Further, the composition of the eutectic alloy powder may fluctuate due to manufacturing conditions and the like, and the melting point may increase.However, in the present invention, it is possible to sufficiently tolerate inadvertent fluctuation of the composition. However, there is no problem even if the melting point rises due to a change in composition as long as the rise is within 5 ° C.

The metal powder of the component (2) in the present invention comprises:
Silver, copper, or an alloy powder having a composition ratio different from that of (1), a metal having a melting point higher than that of (1) by 60 ° C. or more, and an average particle diameter of 1 to 85 μm; It is. In the case where the metal powder of the component (2) is a silver-copper alloy having a composition ratio different from that of the component (1), the melting point of the silver-copper eutectic alloy is not higher than the melting point of the silver-copper eutectic alloy of the component (1). When the alloy is melted, the metal powder of (2) melts at substantially the same time, and the outflow of the brazing material cannot be suppressed.

Although the metal powder of the component (2) does not substantially contain any metal other than the components constituting the silver-copper eutectic alloy powder, it is inevitable that Fe, Cr, Ni, Si, Mg, O, C, N
And the like.

The metal powder of the component (2) has an average particle diameter of 1 to 85 μm, preferably 5 to 45 μm. When the average particle size is larger than 85 μm, it is difficult to apply screen printing as a coating method, and when the average particle size is smaller than 1 μm, the effect of suppressing the flow of the brazing material melted at the time of joining to the insulating pattern portion is reduced.

In the present invention, the mixing ratio of the component (1) and the component (2) is based on 100 parts by weight of the component (1).
It is 10 to 60 parts by weight. When the component (2) is contained in an amount of 60 parts by weight or more, defects such as voids are likely to occur at the joining interface or inside the metal powder brazing material when joining is performed. The effect of suppressing the problem that the molten component of the material flows out to the insulating pattern portion is insufficient.

The metal powder brazing material of the present invention contains an active metal powder having reactivity with the aluminum nitride member in order to ensure wettability with the member made of the aluminum nitride sintered body during melting. . As the active metal, an element belonging to Group IVa of the periodic table and a hydride thereof can be used. In general, titanium, zirconium, and hafnium are used. Among them, titanium is particularly preferable because it has high reactivity with the aluminum nitride member and can extremely increase the bonding strength. If titanium hydride is used, it is not oxidized before the bonding step and the activity is not lost. Since the active metal titanium is obtained by the heat treatment in the step, a suitable bonding state can be obtained. The average particle size of the active metal powder is not particularly limited, but is preferably 85 μm or less, more preferably 1 to 50 μm for screen printing.

In order to maintain a sufficient bonding strength between the metal powder brazing material and the ceramic and to suppress a decrease in thermal shock resistance, the amount of the active metal powder added is 0 to 100 parts by weight of the silver-copper eutectic alloy powder. 0.1 to 5 parts by weight. The amount added is 0.
If the amount is less than 1 part by weight, the metal powder brazing material and the aluminum nitride member are not sufficiently wetted, and sufficient bonding cannot be obtained. If the amount is more than 5 parts by weight, there arises a problem that the thermal shock resistance of the joined aluminum nitride member is reduced.

It is preferable to apply the metal powder brazing material uniformly on the member.
Any method such as a roll coating method, spraying, and transfer is adopted. Generally, the screen printing method is the simplest, but if coarse particles are present in the metal powder brazing material, clogging of the screen or the like may occur and printing in a desired pattern may not be performed. Is preferred. When printing a finer pattern, a screen having a fine mesh must be used, and clogging is more likely to occur. Therefore, the maximum of components (1), (2) and (3) of the metal powder brazing material is required. The particle size is preferably controlled to 100 μm or less, more preferably 85 μm or less.

As a mixing method of each component constituting the metal powder brazing material, a known method is employed without any particular limitation. Generally, a known mixer such as a ball mill, an attritor, a planetary mixer, and a three-roll mill is used.

It is desirable that the metal powder brazing material is mixed with an organic solvent and a binder and kneaded into a paste so that a pattern can be easily formed by a method such as screen printing. When forming the paste, one or a mixture of two or more of methylcellosolve, ethylcellosolve, isophorone, toluene, ethyl acetate, terpineol, texanol, and the like are used as the organic solvent. Examples of the binder include oxygen-containing organic polymers such as ethyl cellulose, methyl cellulose, nitrocellulose, polyacrylate, and polymethyl methacrylate; petroleum resin,
Hydrocarbon synthetic resins such as polyethylene, polypropylene and polystyrene; polyvinyl chloride; organic polymers such as waxes and emulsions thereof are used alone or in admixture of two or more.

In order to screen-print a good pattern of the metal powder brazing paste, it is preferable to control the viscosity of the brazing paste to 20 to 300 kcps.
The ratio of the organic solvent to the whole brazing material paste is 5
By blending the binder in the range of 1 to 15% by weight and the binder in the range of 1 to 5% by weight, a metal powder brazing paste having excellent printability can be obtained. In addition, by blending the binder in the above range, the binder can be promptly removed in the degreasing step after printing, which is preferable.

When the brazing metal powder is made into a paste, a dispersant may be added to improve the dispersibility of each component. As the dispersant, for example, glycerin or sorbitol ester of fatty acid such as glycerin triolate and sorbitan triolate, natural fish oil, nonionic synthetic surfactant, higher fatty acid, benzenesulfonic acid and the like are used. The amount of the dispersant used depends on the type of the dispersant, the type of the mixed system to be added, and the like and cannot be unconditionally limited, but is generally 0.01 to 5% by weight, preferably 0.05% by weight, based on the whole of the paste. It is preferable to select from the range of 1 to 1% by weight.

By using the metal powder brazing material of the present invention, there is no outflow of the molten brazing material at the time of joining the aluminum nitride member and the metal member, and it is possible to perform good joining in a joined state, and to reduce the yield. improves.

The metal member to be joined to the aluminum nitride member via the metal powder brazing material is not particularly limited as long as it has a higher melting point than the joining temperature. Copper, copper alloy, silver, silver alloy, nickel, nickel alloy, molybdenum, tungsten, iron alloy, and the like can be used. Among them, it is most preferable to use copper as the metal member from the viewpoints of electrical resistance, stretchability, and low migration. In addition, it is preferable to use silver if electrical resistance is important, and if molybdenum or tungsten is used when reliability after bonding is more important than electrical characteristics, the coefficient of thermal expansion of the metal is reduced. Since the thermal expansion coefficient is close to that of aluminum, the thermal stress at the time of joining can be reduced, which is preferable.

The members joined by the metal powder brazing material of the present invention need not necessarily be in a bulk shape,
It can also be used for thin-film aluminum nitride or metal formed on a bulk surface of metal, glass, or the like. Also,
The metal powder brazing material of the present invention is not limited to use as a brazing material for joining a plurality of members or as a solder, but is applied to a single member such as aluminum nitride or metal and heated to form a metal layer. It can also be used in applications where

A general joining method using the metal powder brazing material of the present invention will be described below.

First, a metal powder brazing material paste is applied on a member by screen printing so as to form a desired pattern. The application form of the metal powder brazing material is not limited at all, such as application on an aluminum nitride member, application on a metal member, application on both an aluminum nitride member and a metal member.

After the application of the metal powder brazing material, it is generally desirable to perform degreasing to remove the binder component. The processing conditions such as heating temperature and time during degreasing vary depending on the binder component, but the active metal is oxidized if the processing is performed in a non-oxidizing atmosphere such as nitrogen or argon or in vacuum. Not suitable. Even in an oxidizing atmosphere, if the active metal is not unnecessarily oxidized by limiting the amount of oxygen, a suitable bonding state can be obtained even if degreasing is performed in an atmosphere where a trace amount of oxygen exists or in a wet atmosphere. it can. Here, the wet atmosphere is an atmosphere formed by passing a non-oxidizing atmosphere gas through water or hot water and then sending the gas to a processing chamber.

Next, the members are overlapped so that the degreased metal powder brazing material is disposed between the aluminum nitride member and the metal member, and joined at a temperature at which the metal powder brazing material melts. The joining temperature is 800 in order to sufficiently wet the aluminum nitride member and the metal member surface with the metal powder brazing material and to prevent a reduction in thermal shock resistance due to residual stress due to a difference in thermal expansion coefficient between the aluminum nitride member and the metal member. ~ 950 ° C is preferred. In order to prevent oxidation of the active metal powder and the metal member and to obtain a good bonding state, the bonding is performed in a vacuum of 1 × 10 ⁻⁴ Torr or less, or a non-oxidizing atmosphere of nitrogen, hydrogen, argon or the like having an oxygen concentration of 10 ppm or less. It is preferable to carry out below. 1-50 at the time of joining
By applying a load of g / cm ² , the metal powder brazing material can be more reliably brought into contact with the aluminum nitride member and the metal member, and a good joining state can be obtained.

The joined body thus obtained has a joint pattern similar to the pattern applied in the step of applying the metal powder brazing material. By successively performing the resist coating and the etching treatment, it is possible to manufacture an aluminum nitride joining member having no metal powder brazing component flowing out and having a metal circuit pattern having a good joining state.

When the metal circuit pattern is easily oxidized, a plating film such as electroless nickel may be formed on the metal surface after the etching process in order to prevent the metal from being oxidized.

The mechanism of exhibiting the effect when the metal powder brazing material of the present invention is used is presumed as follows. That is, when the mixture of the component (1) and the component (2) is heated to the melting temperature of the component (1), the component (1) is quickly melted and wets and spreads on the member to be joined. ) Has a melting point higher than that of the component (1) by 60 ° C. or more, and therefore exists in a solid state without melting and functions as a spacer for maintaining the thickness of the metal powder brazing layer containing the molten component (1).
For this reason, in the initial stage of melting of the metal powder brazing material, a favorable state of wet spreading between the metal powder brazing material and the member to be joined is obtained, and at the same time, the molten metal due to the joining pressure is applied to the insulating pattern portion. Is thought to be suppressed.

Further, in the step of heating to a temperature equal to or higher than the melting temperature of the component (1), the composition of the molten metal of the brazing metal powder is shifted because the component (2) dissolves in the liquid phase, so that the melting point is lowered. Going up. For this reason, it is considered that in the stage after the initial stage of melting of the metal powder brazing material, the effect of suppressing the decrease in the viscosity of the molten metal due to the temperature increase is added, and it is considered that the flow to the insulating pattern portion is suppressed.

[0035]

By joining the aluminum nitride member and the metal member by using the metal powder brazing material of the present invention, an aluminum nitride joining member having no metal circuit pattern with a good joining state without flowing out of the brazing material can be obtained. It can be manufactured with good yield.

[0036]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

Example 1 50 parts by weight of copper powder (melting point 1083 ° C.) and 100 parts by weight of eutectic alloy powder of silver and copper, and titanium hydride powder 1.
To the mixed powder to which 5 parts by weight were added, 8% by weight of terpineol, 3% by weight of polymethyl methacrylate, and 0.1% by weight of a dispersing agent in a proportion of the whole paste were blended, and then mixed using a planetary mixer, and 120 kcps. Was manufactured. The average particle size of the eutectic alloy powder of silver and copper and the copper powder were 8.0 μm and 1 μm, respectively.
1.6 μm, and the average particle size of the titanium hydride powder is 3.
The thing of 6 micrometers was used.

This metal powder brazing paste was 54 mm ×
A predetermined pattern was applied on a 36 mm aluminum nitride substrate by screen printing.

Thereafter, it was dried and degreased in a nitrogen atmosphere at 320 ° C. for 5 minutes. Further, after the copper member, the aluminum nitride member, and the copper member are stacked, the copper member and the aluminum nitride member are subjected to a heat treatment at 850 ° C. for 15 minutes in a vacuum (10 ⁻⁵ Torr) while applying a load of 10 g / cm ^2. Was joined. Thereafter, printing of the same resist pattern as the brazing material pattern and removal of unnecessary portions of the copper member were performed to produce a desired copper-aluminum nitride bonding member.

The frequency of the brazing material flowing out to the non-joined portion by visual observation was 0 out of 40 sheets. Observation of the bonding state with an ultrasonic flaw detector revealed that the frequency of void formation in which the area of the defective bonding portion due to void generation was 5% or more of the entire bonded portion area was 0 out of 40 sheets.

Examples 2 to 5 A metal powder brazing paste was prepared in the same manner as in Example 1 except that the materials shown in Table 1 were used.
An aluminum nitride joining member was manufactured. Here, silver powder (melting point: 960 ° C.) having an average particle diameter of 8.3 μm was used, and titanium powder having an average particle diameter of 4.2 μm was used.

The joining member obtained in this manner did not cause the brazing material to flow out to the non-printed portion, and the joining state was good even when observed with an ultrasonic probe. Table 1 shows the flow rate of the brazing filler metal and the frequency of void generation.

Comparative Examples 1 to 7 A metal powder brazing paste was prepared in the same manner as in Example 1 except that the materials shown in Table 1 were used as comparative examples. Was prepared. Here, Ag / Cu alloy powder having a weight ratio of 85/15 having an average particle diameter of 8.1 μm was used, and silver powder having an average particle diameter of 8.3 μm was used.

The joint member obtained in this manner showed a defect due to the occurrence of voids in the joint portion when the brazing material flowed out or was observed with an ultrasonic probe. The results are shown in Table 1.

[0045]

[Table 1]

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] April 7, 1999 (1999.4.7)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claim 1

[Correction method] Change

[Correction contents]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction contents]

[0006] Even when a brazing material is applied to an aluminum nitride substrate in a desired pattern and copper members are joined, it is important to prevent the brazing material from flowing out. A method has been proposed in which a metal having a higher melting point than the brazing filler metal component is added to the brazing filler metal (Japanese Patent Laid-Open No. Hei 2-
No. 6096). However, in this method, there is a problem that the brazing material layer is hardened by adding the high melting point metal and the thermal shock resistance of the joined body is reduced . Its other flowing out brazing material as a method of suppressing, Ti (or Nb, Z
In a method of r) -Cu-Ag based paste-like joining material, there has been proposed a method of controlling the particle size of the powder to suppress the outflow thereof (JP-A-5-246770). However, according to the findings of the present inventors, the above-described method has a problem that the liquid phase generation rate is slow and there is a problem that voids are easily generated at the interface between the metal member and the brazing material or inside the brazing material. It has been clarified that in order to obtain a good bonding state at the interface, it is necessary that the brazing material is quickly melted during heating to form a liquid phase.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction contents]

That is, the present invention relates to (1) 100 parts by weight of a silver-copper eutectic alloy powder, (2) silver, copper, or a silver-copper alloy having a different composition ratio from (1), and having a melting point of Is composed of a metal having a melting point of 60 ° C. or more higher than the melting point of (1), and has an average particle size of 1 to 8
A metal powder brazing material containing 10 to 60 parts by weight of a metal powder of 5 μm and (3) 0.1 to 5 parts by weight of an active metal powder, and an aluminum nitride member and a metal member are joined via the brazing material. Is the way.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction contents]

The metal powder of the component (2) in the present invention comprises:
Silver, copper, or a metal powder having a composition ratio different from that of (1), a metal having a melting point higher than that of (1) by 60 ° C. or more, and an average particle diameter of 1 to 85 μm; It is. In the case where the metal powder of the component (2) is a silver-copper alloy having a composition ratio different from that of the component (1), the melting point of the silver-copper eutectic alloy is not higher than the melting point of the silver-copper eutectic alloy of the component (1). When the alloy is melted, the metal powder of (2) melts at substantially the same time, and the outflow of the brazing material cannot be suppressed.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) B23K 103: 12 103: 18 F term (reference) 4G026 BA16 BB21 BB22 BF15 BF16 BF17 BF24 BF34 BF44 BG02 BH07

Claims (2)

[Claims] (1) 100 parts by weight of a silver-copper eutectic alloy powder, (2) silver, copper, or a silver-copper alloy having a different composition ratio from (1) and a melting point of (1) 60 ° C from the melting point of
A metal powder brazing material comprising 10 to 60 parts by weight of an alloy powder made of a high metal and having an average particle diameter of 1 to 85 μm, and (3) 0.1 to 5 parts by weight of an active metal powder. 2. A method for joining an aluminum nitride member and a metal member, wherein the brazing material according to claim 1 is applied to at least one joint surface of the aluminum nitride member or the metal member, and then the members are bonded together, and then heated. A method of joining an aluminum nitride member and a metal member.