CN115555669A

CN115555669A - Method for brazing aluminum nitride ceramic and kovar alloy

Info

Publication number: CN115555669A
Application number: CN202211020294.5A
Authority: CN
Inventors: 曹裕鹏; 崔海超; 庄焰
Original assignee: Shanghai Kelin Technology Development Co ltd
Current assignee: Shanghai Kelin Technology Development Co ltd
Priority date: 2022-08-24
Filing date: 2022-08-24
Publication date: 2023-01-03

Abstract

The invention relates to a method for brazing aluminum nitride ceramics and kovar alloy, which comprises the following steps: s1, pretreating the aluminum nitride ceramic and the kovar alloy; s2, preparing a Ti layer with the thickness of 5-10 mu m on the surface to be brazed of the aluminum nitride ceramic; s3, preparing a Ni layer with the thickness of 20-30 mu m on the Ti layer on the surface of the aluminum nitride ceramic to be brazed; s4, preparing a Ni layer with the thickness of 20-30 mu m on the surface to be brazed of the kovar alloy; s5, carrying out vacuum brazing on the aluminum nitride ceramic and the kovar alloy, adding AgCu28 powder brazing filler metal into a brazing gap, keeping the brazing temperature at 850-900 ℃ for 5min, and cooling the brazing gap to room temperature along with a brazing furnace after brazing. The method of the invention can carry out welding by adopting the commercially available brazing filler metal, and the brazing filler metal has better fluidity in the brazing seam and interface wettability, and the obtained brazing seam has larger area, high compactness and no defect.

Description

Method for brazing aluminum nitride ceramic and kovar alloy

Technical Field

The invention relates to the technical field of brazing, in particular to a method for brazing aluminum nitride ceramics and kovar alloy.

Background

With the rapid development of the electronic industry, electronic power devices are developed in a modularized and intelligent direction. Because the integration level is continuously improved, the unit deviceThe volume of the parts is also getting smaller and smaller, so people hope to have a ceramic material with high thermal conductivity to replace beryllium oxide and aluminum oxide so as to solve the heat dissipation problem of the components. The aluminum nitride ceramic has high thermal conductivity, is second to beryllium oxide and silicon carbide in ceramic materials, and has excellent properties of high mechanical strength, corrosion resistance, matching of thermal expansion coefficient with silicon, no toxicity and the like, so the aluminum nitride ceramic becomes a ceramic substrate material with the greatest development prospect at present. However, aluminum nitride ceramics is used as a heat dissipation substrate material, and effective sealing between aluminum nitride ceramics and other materials (metals, alloys, etc.) is required, and welding is a common method for realizing sealing between ceramics and metals. In the past, when the welding of ceramics and metals is researched, the welding of alumina ceramics and kovar alloy (Fe-Ni-Co) is more, mainly the thermal expansion coefficients of the alumina ceramics and the kovar alloy are similar, and the residual stress is smaller during the welding. When the Ag-Cu-Ti solder is adopted, the solder has better color-moistening performance with the ceramic due to the active Ti element, but the Ti element in the solder can diffuse to one side of the kovar alloy in the brazing process, and simultaneously the Ti element reacts with Fe and Ni in the kovar alloy to generate Fe ₂ Ni and Ni ₃ The Ti brittle compound reduces the wettability of the Ag-Cu-Ti solder and the ceramic; when the Ag-Cu brazing filler metal is adopted, the Cu in the Ag-Cu brazing filler metal is found to be spread along the grain boundary of the kovar alloy preferentially, and an island-shaped Cu-based solid solution area is formed at the front of spreading, but the Ag-Cu brazing filler metal has better wettability with the kovar alloy but has poorer wettability with ceramic than the Ag-Cu-Ti brazing filler metal.

Thus, a method of brazing aluminum nitride ceramics and kovar alloys is needed.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provides a method for brazing aluminum nitride ceramics and kovar alloy.

In order to achieve the purpose, the invention adopts the technical scheme that:

a method of brazing aluminum nitride ceramics and kovar alloys is provided, comprising the steps of:

s1, pretreating the aluminum nitride ceramic and the kovar alloy;

s2, preparing a Ti layer with the thickness of 5-10 mu m on the surface to be brazed of the aluminum nitride ceramic;

s3, preparing a Ni layer with the thickness of 20-30 mu m on the Ti layer on the surface to be brazed of the aluminum nitride ceramic;

s4, preparing a Ni layer with the thickness of 20-30 mu m on the surface to be brazed of the kovar alloy;

s5, carrying out vacuum brazing on the aluminum nitride ceramic and the kovar alloy, adding AgCu28 powder brazing filler metal into a brazing gap, keeping the brazing temperature at 850-900 ℃ for 5min, and cooling the brazing gap to room temperature along with a brazing furnace after brazing.

Preferably, the pre-treatment comprises: and (3) sequentially grinding, cleaning and drying the aluminum nitride ceramic and the kovar alloy.

Preferably, the smoothing comprises: and (5) flattening by adopting metallographic abrasive paper until the number of 2000# abrasive paper is obtained.

Preferably, the cleaning comprises: and cleaning with acetone in an ultrasonic cleaner for 10min.

Preferably, the method of preparing the Ti layer is a magnetron sputtering method.

Preferably, step S3 further comprises: before preparing the Ni layer, the aluminum nitride ceramic is cleaned in an ultrasonic cleaner by adopting acetone to remove surface impurities.

Preferably, the method of preparing the Ni layer is an electroplating method.

By adopting the technical scheme, compared with the prior art, the invention has the following technical effects:

the method can carry out welding by adopting the commercially available brazing filler metal, and the brazing filler metal has good fluidity in the brazing seam and interface wettability, and the obtained brazing seam has large area, high compactness and no defect; the reason is that: in the prior art, titanium and nickel are added into brazing filler metal, so that the titanium and the nickel are deviated at brazing seams during high-temperature brazing, the wettability of ceramic and kovar alloy is reduced, and the brazing seams are poor in compactness; the method of the invention prepares a titanium layer and a nickel layer on the surface of the aluminum nitride ceramic to be brazed in advance, and the nickel layer hinders the diffusion of titanium into the brazing filler metal to a certain extent, thereby ensuring the interface wettability of the aluminum nitride ceramic side; the nickel layer prepared on the surface to be brazed of the kovar alloy in advance can ensure that the interfaces on the two sides are nickel during brazing, so that the brazing filler metal has better fluidity in brazing seams, and the brazing seams are large in wetting area, compact in interface and free of defects; meanwhile, the thickness of the titanium layer and the nickel layer is controlled, so that the defects that the interface layer is not compact or holes are formed and the like due to the fact that titanium and nickel are separated from aluminum nitride ceramic or kovar alloy in high-temperature brazing are avoided.

Drawings

FIG. 1 shows the morphology of the interface structure after brazing in example 1 of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.

The invention is further described with reference to the following drawings and specific examples, which are not intended to be limiting.

Example 1

The present embodiment provides a method for brazing aluminum nitride ceramic and kovar alloy, comprising the steps of:

s1-1, grinding aluminum nitride ceramics with the size of 50mm multiplied by 2mm by adopting metallographic abrasive paper until 2000# abrasive paper is obtained; after being ground flat, the mixture is cleaned by adopting acetone in an ultrasonic cleaner for 10min; cleaning and drying;

s1-2, flattening the kovar alloy with the size of 50mm multiplied by 2mm by using metallographic abrasive paper until the size reaches 2000# abrasive paper; after being ground flat, the mixture is cleaned by adopting acetone in an ultrasonic cleaner for 10min; cleaning and then drying;

s2, preparing a Ti layer with the thickness of 5-10 microns on the surface to be brazed of the aluminum nitride ceramic by adopting a magnetron sputtering method; if the thickness of the Ti layer is less than 5 μm, ti on the interface diffuses into the brazing seam, which reduces the residual Ti on the interface layer and easily forms a void defect on the interface; if the thickness of the Ti layer is more than 10 μm, residual stress exists on the interface, so that the interface layer is easy to crack;

s3, cleaning the aluminum nitride ceramic in an ultrasonic cleaner by using acetone to remove surface impurities; after cleaning, preparing a Ni layer with the thickness of about 20 mu m on the Ti layer on the surface to be brazed of the aluminum nitride ceramic by adopting an electroplating method; if the thickness of the Ni layer is too thin, ni on the interface can diffuse with the brazing filler metal at high temperature, so that the compactness of the interface is poor, and the Ni has good fluidity; if the thickness of the Ni layer is too thick, the residual stress of the interface is large, and cracking can be caused;

s4, preparing a Ni layer with the thickness of about 20 mu m on the surface to be brazed of the kovar alloy by adopting an electroplating method; if the thickness of the Ni layer is too thin, ni on the interface can diffuse with the brazing filler metal at high temperature, so that the interface compactness is poor, because the Ni has better fluidity; if the thickness of the Ni layer is too thick, the residual stress of the interface is large, and cracking can be caused;

s5, carrying out vacuum brazing on the aluminum nitride ceramic and the kovar alloy, adding AgCu28 powder brazing filler metal into a brazing gap, keeping the brazing temperature at 900 ℃ for 5min, and cooling the brazing gap to room temperature along with a brazing furnace after brazing.

After brazing, the appearance of the interface structure is observed as shown in figure 1, and the brazing strength is 120MPa, the brazing seam interface compactness is good, no defect is generated, and the method can be used as a sealing welding method of aluminum nitride ceramics and kovar alloy.

The method can carry out welding by adopting the commercially available brazing filler metal, and the brazing filler metal has good fluidity in the brazing seam and interface wettability, and the obtained brazing seam has large area, high compactness and no defect; the reason is that titanium and nickel are added into brazing filler metal in the prior art, so that the titanium and the nickel are partially gathered at brazing seams during high-temperature brazing, the wettability of ceramic and kovar alloy is further reduced, and the brazing seams are poor in compactness; the method of the invention prepares a titanium layer and a nickel layer on the surface of the aluminum nitride ceramic to be brazed in advance, and the nickel layer hinders the diffusion of titanium into the brazing filler metal to a certain extent, thereby ensuring the interface wettability of the aluminum nitride ceramic side; the nickel layer prepared on the surface to be brazed of the kovar alloy in advance can ensure that the interfaces on the two sides are nickel during brazing, so that the brazing filler metal has better fluidity in brazing seams, and the brazing seams are large in wetting area, compact in interface and free of defects; meanwhile, the thickness of the titanium layer and the nickel layer is controlled, so that the defects that the interface layer is not compact or holes are formed and the like due to the fact that titanium and nickel are separated from aluminum nitride ceramic or kovar alloy in high-temperature brazing are avoided.

While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention.

Claims

1. A method of brazing aluminum nitride ceramics and kovar alloys, comprising the steps of:

s1, pretreating the aluminum nitride ceramic and the kovar alloy;

2. The method of claim 1, wherein the pre-processing comprises: and sequentially grinding, cleaning and drying the aluminum nitride ceramic and the kovar alloy.

3. The method of claim 2, wherein the smoothing comprises: and (5) flattening by adopting metallographic abrasive paper until the number of 2000# abrasive paper is obtained.

4. The method of claim 2, wherein the cleaning comprises: and cleaning with acetone in an ultrasonic cleaner for 10min.

5. The method of claim 1, wherein the method of preparing the Ti layer is magnetron sputtering.

6. The method of claim 1, wherein step S3 further comprises: before preparing the Ni layer, the aluminum nitride ceramic is cleaned in an ultrasonic cleaner by adopting acetone to remove surface impurities.

7. The method of claim 1, wherein the Ni layer is formed by electroplating.