Welding method for inhibiting blackening and resistance reduction of zirconia ceramic after welding

Abstract

The invention discloses a welding method for inhibiting blackening and resistance reduction of zirconia ceramic after welding, and relates to a zirconia ceramic welding method. The problems that existing zirconium oxide is blackened after brazing, and the resistance is reduced are solved. The method comprises the steps that composite brazing filler metal is placed between a to-be-welded face of zirconia ceramic and a to-be-welded face of an alloy material, and a to-be-welded piece is obtained after pressure is applied and fixed; and the to-be-welded part is placed in a brazing furnace for brazing, pressure is applied to the to-be-welded part in the brazing process, and heat preservation is conducted after the to-be-welded part is heated to the brazing temperature. On the premise of ensuring good connection of zirconium oxide and metal, blackening of zirconium oxide ceramic after welding can be avoided, resistance keeps an original insulation state, and meanwhile, the zirconium oxide ceramic has good shear strength. According to the method, the zirconia ceramic and the kovar alloy can be subjected to good active connection without changing the original electrical properties of the zirconia, and a guarantee is provided for wider application of the zirconia ceramic and the kovar alloy in the field of electronic devices.

Description

Technical Field

[0001] The invention relates to a zirconia ceramic welding method. Background Art

[0002] ZrO2 ceramics are important structural and functional ceramic materials. Due to their high strength and hardness, good toughness and impact resistance, high-temperature resistance, and excellent insulation properties, they have been widely used in the aerospace, machinery manufacturing, and electronics industries. However, like most advanced functional ceramics, ZrO2 ceramics are difficult to process into large, complex-shaped components and suffer from inherent defects that result in poor mechanical properties. Alloy materials, on the other hand, often possess excellent plasticity and toughness that complement ceramic materials. Therefore, joining the two through welding can achieve excellent overall performance.

[0003] To date, ceramic-metal joining methods include vacuum brazing, transient liquid phase bonding, and diffusion bonding. Among all available joining technologies, vacuum brazing is considered the primary method for ceramic-metal joining due to its convenience. Active brazing utilizes the chemical reaction between active elements in the brazing filler metal (such as Ti, V, Zr, etc.) and the ceramic material to promote wetting of the brazing filler metal on the ceramic, generating an interfacial reaction layer to achieve the desired connection. Active brazing offers advantages such as ease of operation and adaptability to a wide range of joint shapes and sizes, making it the preferred method for achieving reliable connections between ceramics and metals.

[0004] Active brazing of ceramics and metals is currently widely researched both domestically and internationally, with the use of Ti as the active element being the primary focus. For example, Lin Xiaochao et al. employed a self-designed Ag-Cu-TiH2 powder brazing filler metal to braze ZrO2 ceramics and Kovar alloys under vacuum conditions, leveraging the activation of TiH2. They discovered that the formation of a TiO-Cu2Ti4O reaction layer (blackening of the ceramic near the intermediate layer) upon contact between the filler metal and the zirconia ceramic was the primary factor in achieving the desired ceramic-brazing-filler metal connection.

[0005] The research shows that the blackening mechanism of zirconia ceramics is that ZrO2 loses oxygen after contact with Ti to form Zr 3+ , and a large number of oxygen vacancies are generated inside the ceramic. Researchers have also found that the resistance of zirconia ceramics drops significantly after blackening, becoming conductive. This limits the application of zirconia ceramics in electronic devices. However, there are few reports on how to prevent zirconia from changing color and maintaining an insulating state after active brazing. Therefore, developing a new active brazing process to control the phenomenon of zirconia blackening and resulting resistance drop has become an urgent problem to be solved. Summary of the Invention

[0006] In order to solve the problem of blackening and resistance reduction of existing zirconia after brazing, the present invention proposes a welding method for suppressing the blackening and resistance reduction of zirconia ceramics after welding. Under the premise of ensuring good connection between zirconia and metal, the zirconia ceramics can prevent blackening after welding and maintain the original insulation state of resistance.

[0007] The welding method of the present invention for suppressing the blackening and resistance drop of zirconia ceramics after welding is carried out according to the following steps:

[0008] A composite brazing material is placed between the to-be-welded surface of the zirconia ceramic and the to-be-welded surface of the alloy material, and pressure is applied to fix the parts to be welded; the parts to be welded are placed in a brazing furnace for brazing, and during the brazing process, pressure is applied to the parts to be welded and heated to the brazing temperature and then kept warm. After the holding period is completed, the parts are cooled to below 200°C in the furnace and taken out;

[0009] The composite solder is an Au-based composite solder, a Pt-based composite solder, a Pd-based composite solder or an Rh-based composite solder; the composite solder is formed by stacking a precious metal element foil, a melting element foil and an active element foil; when the welded parts are assembled, the active element foil in the composite solder is arranged on the side of the zirconia ceramic, and the melting element foil is arranged on the side of the alloy material.

[0010] The beneficial effects of the present invention are:

[0011] The present invention develops a new noble metal-based active brazing material and a supporting process, and adopts vacuum brazing to connect zirconia ceramics and alloys. The composite brazing material used in the present invention is a noble metal-based brazing material system. After being mixed with melting-reducing elements and active elements, the liquidus temperature of the composite brazing material is lower than the melting temperature of the base material. During the brazing process, Ti, Zr or V as active metals ensure that the brazing material can wet the ceramic to provide conditions for connection, which helps to improve the connection strength. The active elements react with zirconia to form non-stoichiometric zirconia, i.e., ZrO 2-x , which causes the ceramic to blacken. The addition of precious metals can absorb the excess Zr after oxygen loss, so that Zr returns to its normal stoichiometric ratio (Zr:O=1:2), and the ceramic is restored to its original white color. Therefore, precious metals are used to control the blackening phenomenon of zirconia due to contact with active elements, ensuring that the appearance of zirconia ceramics does not change color, maintains the initial insulating state, and has good shear strength.

[0012] The present invention can achieve good active connection between zirconia ceramics and Kovar alloy without changing the original electrical properties of zirconia, thus providing a guarantee for its wider application in the field of electronic devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a comparison of the appearance of Example 1 and the control group after welding;

[0014] Figure 2 The following is a comparison of the appearance of Example 2 and the control group after welding. DETAILED DESCRIPTION

[0015] The technical solution of the present invention is not limited to the specific implementation methods listed below, but also includes any reasonable combination of the specific implementation methods.

[0016] Specific embodiment 1: The welding method for suppressing the blackening and resistance drop of zirconia ceramics after welding in this embodiment is carried out according to the following steps:

[0017] A composite brazing material is placed between the to-be-welded surface of the zirconia ceramic and the to-be-welded surface of the alloy material, and pressure is applied to fix the parts to be welded; the parts to be welded are placed in a brazing furnace for brazing, and during the brazing process, pressure is applied to the parts to be welded and heated to the brazing temperature and then kept warm. After the holding period is completed, the parts are cooled to below 200°C in the furnace and taken out;

[0018] The composite solder is an Au-based composite solder, a Pt-based composite solder, a Pd-based composite solder or an Rh-based composite solder; the composite solder is formed by stacking a precious metal element foil, a melting element foil and an active element foil; when the welded parts are assembled, the active element foil in the composite solder is arranged on the side of the zirconia ceramic, and the melting element foil is arranged on the side of the alloy material.

[0019] This embodiment develops a new noble metal-based active brazing material and supporting process, and adopts vacuum brazing to connect zirconia ceramics and alloys. The composite brazing material used in the present invention is a noble metal-based brazing material system. After being mixed with melting-reducing elements and active elements, the liquidus temperature of the composite brazing material is lower than the melting temperature of the base material. During the brazing process, Ti, Zr or V as active metals ensure that the brazing material can wet the ceramic to provide conditions for connection, which helps to improve the connection strength. The active elements react with zirconia to form non-stoichiometric zirconia, i.e., ZrO 2-x , which causes the ceramic to blacken. The addition of precious metals can absorb the excess Zr after oxygen loss, so that Zr returns to its normal stoichiometric ratio (Zr:O=1:2), and the ceramic is restored to its original white color. Therefore, precious metals are used to control the blackening phenomenon of zirconia due to contact with active elements, ensuring that the appearance of zirconia ceramics does not change color, maintains the initial insulating state, and has good shear strength.

[0020] This embodiment can achieve good active connection between zirconia ceramics and Kovar alloy without changing the original electrical properties of zirconia, thus ensuring its wider application in the field of electronic devices.

[0021] Specific embodiment 2: This embodiment differs from specific embodiment 1 in that: the noble metal element foil in the Au-based composite solder is Au foil, the melting element foil is Cu foil, and the active element foil is Ti foil, Zr foil or V foil;

[0022] The mass fraction of the melting element foil in the Au-based composite solder is 19-20%, the mass fraction of the active element foil is 3.5-4.5%, and the balance is the precious metal element foil.

[0023] Specific embodiment three: This embodiment differs from specific embodiment one or two in that: the noble metal element foil in the Pt-based composite solder is Pt foil, the melting element foil is Sn foil, and the active element foil is Ti foil, Zr foil or V foil;

[0024] The mass fraction of the melting element foil in the Pt-based composite solder is 27-28%, the mass fraction of the active element foil is 3.5-4.5%, and the balance is the precious metal element foil.

[0025] Specific embodiment 4: This embodiment differs from any one of specific embodiments 1 to 3 in that: the noble metal element foil in the Pd-based composite solder is Pd foil, the melting element foil is Al foil, and the active element foil is Ti foil, Zr foil or V foil;

[0026] The mass fraction of the melting element foil in the Pd-based composite solder is 38-39%, the mass fraction of the active element foil is 3.5-4.5%, and the balance is the precious metal element foil.

[0027] Specific embodiment 5: This embodiment differs from any one of specific embodiments 1 to 4 in that: the noble metal element foil in the Rh-based composite solder is Rh foil, the melting element foil is Se foil, and the active element foil is Ti foil, Zr foil or V foil;

[0028] The mass fraction of the melting element foil in the Rh-based composite solder is 40-41%, the mass fraction of the active element foil is 3.5-4.5%, and the balance is the precious metal element foil.

[0029] Specific embodiment 6: This embodiment differs from any one of specific embodiments 1 to 5 in that: when the composite solder used in the brazing process is an Au-based composite solder, the brazing temperature is 1000-1100°C;

[0030] When the composite brazing material used in the brazing process is a Pt-based composite brazing material, the brazing temperature is 1150-1200° C.

[0031] When the composite brazing material used in the brazing process is a Pd-based composite brazing material, the brazing temperature is 1050-1100° C.

[0032] When the composite solder used in the brazing process is a Rh-based composite solder, the brazing temperature is 1000-1100°C.

[0033] Specific embodiment 7: This embodiment differs from specific embodiments 1 to 6 in that Ag foil or Sn foil is added to the composite solder, and is placed between the melting element foil and the alloy material. Ag or Sn is used to lower the liquidus and improve the solder's microstructure and properties.

[0034] Specific embodiment eight: This embodiment differs from the seventh embodiment in that the Ag foil or Sn foil accounts for 0-5wt% of the composite solder.

[0035] Specific embodiment 9: This embodiment differs from any one of specific embodiments 1 to 8 in that: the zirconia ceramic is YSZ ceramic; and the alloy is Kovar alloy.

[0036] Specific embodiment 10: This embodiment differs from the specific embodiments 1 to 9 in that during the brazing process, the vacuum degree of the brazing furnace is not less than 1×10 -3 Pa; the pressure applied to the workpiece to be welded is 5N / mm 2 ;The insulation time is 10-20min.

[0037] Example 1

[0038] The welding method of this embodiment for suppressing the blackening and resistance drop of zirconia ceramics after welding is carried out in the following steps:

[0039] A composite brazing material is placed between the surface to be welded of the zirconia ceramic and the surface to be welded of the alloy material, and pressure is applied to fix the parts to be welded; the parts to be welded are placed in a brazing furnace for brazing, and the vacuum degree of the brazing furnace is not less than 1×10 -3 Pa, 5N / mm is applied to the workpiece during brazing. 2 Pressurize and heat to 1050℃ and keep warm for 20min. After the heat preservation is completed, cool it to below 200℃ and take it out.

[0040] The composite solder is an Au-based composite solder, and the composition (by mass fraction) is: Au foil: 72%, Cu foil: 18%, Ti foil: 4.5%, Ag foil: 3.5%, Sn foil: 2%;

[0041] The composite brazing filler metal is composed of a stack of precious metal foil, a melting-reducing element foil, and an active element foil. When the weldment is assembled, the Ti foil in the composite brazing filler metal is placed on the zirconia ceramic side, and the Cu foil is placed on the alloy material side.

[0042] The zirconia ceramic is 3YSZ ceramic, and the metal is Kovar alloy 4J50;

[0043] Control group:

[0044] The control group brazed 3YSZ ceramics and Kovar alloy 4J50; the mass percentages of the active brazing filler metals used were: Ag: 68%, Cu: 27.5%, Ti: 4.5%, and the vacuum degree of the brazing furnace was not less than 1×10 -3 Pa, the pressure applied during brazing is 5N / mm 2 The brazing temperature is 880℃ and the holding time is 15min. After the holding time is completed, the parts are cooled to below 200℃ and taken out.

[0045] Figure 1 This is a comparison of the appearance of Example 1 and the control group after welding. The connector obtained by Example 1 using precious metal-based solder has no blackening phenomenon and maintains an insulating state (>20MΩ). The shear strength of the brazed joint obtained in Example 1 reaches 65.3MPa. The connector of the control group using traditional active solder has severe blackening phenomenon and the resistance is greatly reduced to 2.6KΩ.

[0046] Example 2: The welding method of this embodiment for suppressing the blackening and resistance drop of zirconia ceramics after welding is carried out according to the following steps:

[0047] A composite brazing material is placed between the surface to be welded of the zirconia ceramic and the surface to be welded of the alloy material, and pressure is applied to fix the parts to be welded; the parts to be welded are placed in a brazing furnace for brazing, and the vacuum degree of the brazing furnace is not less than 1×10 -3 Pa, 5N / mm is applied to the workpiece during brazing. 2 Press and heat to 1150℃ and keep warm for 20min. After the end of the heat preservation, cool it to below 200℃ and take it out.

[0048] The composite solder is a Pt-based composite solder, and (by mass fraction) is: Pt foil: 67%, Sn foil: 25%, Ti foil: 4.5%, Ag foil: 3.5%;

[0049] The composite brazing filler metal is composed of a stack of precious metal foil, a melting element foil, and an active element foil. When the welded parts are assembled, the Ti foil in the composite brazing filler metal is placed on the zirconia ceramic side, and the Sn foil is placed on the alloy material side.

[0050] The zirconia ceramic is 3YSZ ceramic, and the metal is Kovar alloy 4J50;

[0051] Control group:

[0052] The control group brazed 3YSZ ceramics and Kovar alloy 4J50; the mass percentages of the active brazing filler metals used were: Ag: 68%, Cu: 27.5%, Ti: 4.5%, and the vacuum degree of the brazing furnace was not less than 1×10 -3 Pa, the pressure applied during brazing is 5N / mm 2 The brazing temperature is 880℃ and the holding time is 15min. After the holding time is completed, the parts are cooled to below 200℃ and taken out.

[0053] Figure 2 This is a comparison of the appearance of Example 2 and the control group after welding. The connector obtained by Example 2 using precious metal-based solder has no blackening phenomenon and maintains an insulating state (>20MΩ). The shear strength of the brazed joint obtained in Example 2 reaches 61.5MPa. The connector of the control group using traditional active solder has severe blackening phenomenon and the resistance is greatly reduced to 2.6KΩ.

Claims

1. A welding method for suppressing blackening and resistance reduction of zirconia ceramics after welding, characterized by: The welding method to suppress the blackening and resistance drop of zirconia ceramics after welding is carried out in the following steps: A composite brazing material is placed between the to-be-welded surface of the zirconia ceramic and the to-be-welded surface of the alloy material, and pressure is applied to fix the parts to be welded; the parts to be welded are placed in a brazing furnace for brazing, and during the brazing process, pressure is applied to the parts to be welded and heated to the brazing temperature and then kept warm. After the holding period is completed, the parts are cooled to below 200°C in the furnace and taken out; The composite solder is an Au-based composite solder, a Pt-based composite solder, a Pd-based composite solder or an Rh-based composite solder; the composite solder is formed by stacking a precious metal element foil, a melting element foil and an active element foil; when the welded parts are assembled, the active element foil in the composite solder is arranged on the side of the zirconia ceramic, and the melting element foil is arranged on the side of the alloy material.

2. The welding method for suppressing blackening and resistance reduction of zirconia ceramics after welding according to claim 1, characterized in that: In the Au-based composite solder, the noble metal element foil is Au foil, the melting element foil is Cu foil, and the active element foil is Ti foil, Zr foil or V foil; The mass fraction of the melting element foil in the Au-based composite solder is 19-20%, the mass fraction of the active element foil is 3.5-4.5%, and the balance is the precious metal element foil.

3. The welding method for suppressing blackening and resistance reduction of zirconia ceramics after welding according to claim 1, characterized in that: In the Pt-based composite solder, the noble metal element foil is Pt foil, the melting element foil is Sn foil, and the active element foil is Ti foil, Zr foil or V foil; The mass fraction of the melting element foil in the Pt-based composite solder is 27-28%, the mass fraction of the active element foil is 3.5-4.5%, and the balance is the precious metal element foil.

4. The welding method for suppressing blackening and resistance reduction of zirconia ceramics after welding according to claim 1, characterized in that: The noble metal element foil in the Pd-based composite solder is Pd foil, the melting element foil is Al foil, and the active element foil is Ti foil, Zr foil or V foil; The mass fraction of the melting element foil in the Pd-based composite solder is 38-39%, the mass fraction of the active element foil is 3.5-4.5%, and the balance is the precious metal element foil.

5. The welding method for suppressing blackening and resistance reduction of zirconia ceramics after welding according to claim 1, characterized in that: The noble metal element foil in the Rh-based composite solder is Rh foil, the melting element foil is Se foil, and the active element foil is Ti foil, Zr foil or V foil; The mass fraction of the melting element foil in the Rh-based composite solder is 40-41%, the mass fraction of the active element foil is 3.5-4.5%, and the balance is the precious metal element foil.

6. The welding method for suppressing blackening and resistance reduction of zirconia ceramics after welding according to claim 1, characterized in that: When the composite solder used in the brazing process is Au-based composite solder, the brazing temperature is 1000-1100° C. When the composite brazing material used in the brazing process is a Pt-based composite brazing material, the brazing temperature is 1150-1200° C. When the composite brazing material used in the brazing process is a Pd-based composite brazing material, the brazing temperature is 1050-1100° C. When the composite solder used in the brazing process is a Rh-based composite solder, the brazing temperature is 1000-1100°C.

7. The welding method for suppressing blackening and resistance reduction of zirconia ceramics after welding according to claim 1, characterized in that: Ag foil or Sn foil is further added to the composite solder, and the Ag foil or Sn foil is arranged between the melting-reducing element foil and the alloy material.

8. The welding method for suppressing blackening and resistance reduction of zirconia ceramics after welding according to claim 7, characterized in that: Ag foil or Sn foil is 0-5wt% of the composite solder.

9. The welding method for suppressing blackening and resistance reduction of zirconia ceramics after welding according to claim 1, characterized in that: The zirconia ceramic is YSZ ceramic; the alloy is Kovar alloy.

10. The welding method for suppressing blackening and resistance reduction of zirconia ceramics after welding according to claim 1, characterized in that: During the brazing process, the vacuum degree of the brazing furnace is not less than 1×10 -3 Pa; the pressure applied to the workpiece to be welded is 5N / mm 2 ;The insulation time is 10-20min.

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