Novel composite brazing alloy material

Abstract

The invention discloses a novel composite brazing alloy material which is composed of four metal elements of Ag, Cu, In and Ni, and the mass percent range of the brazing alloy material is 50%-65% of Ag, 25%-35% of Cu, 5%-15% of In and 0.5%-5% of Ni. By optimizing brazing alloy components, the use amount of precious metal silver is reduced, so that the use cost is reduced, and meanwhile, the vacuum welding strength of nickel-plated metal ceramic and copper or iron-nickel alloy is enhanced. According to the brazing alloy, the welding temperature is reduced by adding indium (In), the solid-liquid temperature difference is reduced, the wettability is improved, the welding strength is enhanced by adding nickel (Ni), interface corrosion is inhibited, the binding force of a thin nickel plating layer is stabilized, and the process adaptability and the welding reliability can be considered through cooperation of indium and nickel.

Description

Technical Field

[0001] This invention relates to fields requiring silver-copper vacuum brazing, including the photovoltaic industry, new energy vehicles, vacuum electronic packaging, and other fields requiring vacuum brazing, and particularly to the field of vacuum welding of nickel-plated metallized ceramics and copper or iron-nickel alloys. Background Technology

[0002] Vacuum brazing technology, as an important material joining method, plays an irreplaceable role in semiconductor packaging, power electronic modules, aerospace devices, and new energy fields. In these fields, reliable bonding between metallized ceramics and metals is frequently required. To improve the solderability of ceramic surfaces, metallization treatment is typically performed, with nickel plating being a commonly used and economical process.

[0003] Silver-copper based brazing alloys, especially Ag-Cu eutectic brazing alloys represented by Ag72Cu28, have long been the mainstream choice in vacuum brazing due to their excellent wettability, electrical conductivity, thermal conductivity, and moderate melting point. However, the high Ag content in these alloys leads to high costs. With the rapid development of the photovoltaic, new energy vehicle, and semiconductor industries, there is a significant market demand for silver-copper brazing alloys, causing a rapid rise in the market price of silver. In 2025, the price of silver increased by 170% throughout the year. Therefore, it is necessary to optimize the composition of brazing alloys to reduce the amount of silver used, thereby optimizing costs and improving efficiency.

[0004] Meanwhile, when silver-copper based brazing alloys are used to weld nickel-plated metallized ceramics, the interfacial reaction between the Ag-Cu eutectic brazing alloy and the nickel layer is weak, resulting in a thin interfacial bonding layer. This leads to insufficient shear strength of the joint, making it prone to failure under thermal cycling or mechanical vibration loads. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a new type of composite brazing alloy material, which reduces the amount of precious metal silver used by optimizing the alloy composition design, thereby effectively reducing material costs.

[0006] Another objective of this invention is to provide a brazing alloy particularly suitable for vacuum brazing of nickel-plated metallized ceramics with copper or iron-nickel alloys. This brazing alloy, through a unique element ratio, undergoes a strong metallurgical reaction with the nickel layer at the brazing interface, forming a nickel-rich and tough interfacial reaction layer, thereby significantly improving the shear strength and reliability of the welded joint.

[0007] The objective of this invention is achieved through the following technical solutions.

[0008] A novel composite brazing alloy material is characterized in that it is composed of four metallic elements: Ag, Cu, In, and Ni.

[0009] Furthermore, the mass percentage of the four metallic elements in the brazing alloy is: Ag 50-65%, Cu 25-35%, In 5-15%, and Ni 0.5-5%.

[0010] Furthermore, the mass percentage of the four metallic elements in the brazing alloy is: Ag 58-63%, Cu 28-32%, In 8-12%, and Ni 1-3%.

[0011] Furthermore, the mass percentages of the four metallic elements in the brazing alloy are: Ag 63%, Cu 28%, In 8%, and Ni 1%.

[0012] Furthermore, the tensile strength of the brazing alloy is 350-450 MPa.

[0013] Furthermore, the wetting contact angle of the brazing alloy is 18-28°.

[0014] Furthermore, the solidus temperature of the brazing alloy is 750-760℃.

[0015] Furthermore, the liquidus temperature of the brazing alloy is 765-775℃.

[0016] This invention discloses a novel composite brazing alloy material. Based on the traditional silver-copper brazing alloy, it reduces the amount of precious metal Ag and adds In and Ni elements. The core function of In is to lower the welding temperature, reduce the solid-liquid temperature difference, and optimize wettability. The core function of Ni is to strengthen the joint, inhibit interface corrosion, and stabilize the bonding of the thin nickel plating layer. The synergy of the two can balance process compatibility and joint reliability.

[0017] Adding In to brazing alloys can lower the solid-liquid line temperature and reduce the solid-liquid temperature difference. In has a melting point of only 156.6℃ and forms an Ag-Cu-In ternary eutectic phase with Ag and Cu (its melting point is much lower than the 779℃ of the Ag-Cu binary eutectic). In hypoeutectic compositions, In accumulates at grain boundaries, lowering the liquidus line and reducing the solid-liquid temperature difference. Taking Ag50Cu50 as an example, adding 8% In can lower the liquidus line from 875℃ to around 755℃, reducing the solid-liquid temperature difference from 95℃ to 15℃.

[0018] Adding In to brazing alloys can also improve the wettability of the brazing alloy and optimize the brazing alloy spreading effect. In has a low surface tension (the surface tension of liquid In is about 550 mN / m, lower than that of Ag and Cu, where the surface tension of Ag is about 920 mN / m and that of Cu is about 1100 mN / m), which can reduce the interfacial tension between the brazing alloy and nickel-plated ceramics and oxygen-free copper, thus promoting the spreading of the brazing alloy; In can also form a low-melting-point Ni-In compound with nickel, enhancing interfacial wetting.

[0019] Adding indium (In) to brazing alloys can also control the coefficient of thermal expansion (CTE) and reduce thermal stress at the weld joint. Although In itself has a high CTE of 32 × 10⁻⁶... -6 / ℃, but the CTE of solid solutions formed with Cu and Ni (such as Cu-In and Ni-In) is relatively low, which can lower the overall CTE value of the brazing alloy. For example, the CTE of Ag50Cu50+8%In+1%Ni is about 16.5×10. -6 / ℃, which is closer to the CTE value of ceramics (7-8×10). -6 / ℃), reducing welding thermal stress.

[0020] Adding Ni to brazing alloys can enhance weld strength and suppress the formation of brittle phases. Ni forms a continuous solid solution with Cu, refining the brazing alloy grains and improving the matrix strength. Simultaneously, Ni can inhibit the formation of the brittle Ag3In phase from In, controlling the proportion of brittle phases to ≤5%. A formulation containing 1% Ni can achieve a tensile strength of up to 400 MPa, avoiding a significant strength decrease caused by In addition, and maintaining the fracture mode as ductile fracture of the brazing alloy matrix, thus meeting the mechanical requirements of structural components.

[0021] Adding Ni to the brazing alloy protects the thin nickel plating layer of the metallized ceramic and stabilizes the bonding strength at the weld interface. Ni forms a diffusion layer of the same material with the nickel plating layer, slowing down the "dissolution-erosion" of the nickel layer by the brazing alloy; at the same time, Ni forms a dense Ni3In and Ni-Cu-In compound layer at the interface, preventing the brazing alloy from penetrating into the ceramic metallization layer. After welding, the residual nickel layer thickness is ≥2.5μm, preventing the thin nickel layer from being eroded through and maintaining the bonding strength between the nickel layer and the ceramic.

[0022] Adding Ni to brazing alloys can also improve the corrosion resistance and high-temperature stability of the weld joints. Ni forms a passivation film on the surface of the brazing alloy, enhancing its resistance to salt spray and oxidation; brazing alloys containing 1% Ni showed no significant corrosion after 300 hours of salt spray testing, meeting the reliability requirements of long-term use of electronic ceramics. At high temperatures, Ni can also inhibit grain growth in the brazing alloy, improving the creep resistance of the joint.

[0023] Adding In and Ni to brazing alloys simultaneously can synergistically improve the overall performance of brazing alloys by utilizing their complementary properties.

[0024] Adding both In and Ni to the brazing alloy simultaneously can achieve a balance between the brazing alloy's temperature and strength. In lowers the temperature, while Ni supplements the strength, avoiding the contradiction that "lowering the temperature will inevitably lower the strength," allowing the brazing alloy to maintain a strength of over 180 MPa even at a welding temperature of 740-760℃.

[0025] Adding both In and Ni to the brazing alloy can achieve dual advantages in terms of interface and stress: In optimizes wetting, Ni stabilizes the interface, and together they regulate CTE, thus balancing the protection of the thin nickel layer and thermal stress matching.

[0026] This invention discloses a novel composite brazing alloy material with a reduced Ag content of 50%-65%. Compared with the traditional Ag72Cu28 alloy, the Ag content is reduced by 10%-30%, resulting in significant economic benefits when applied on a large scale.

[0027] This invention discloses a novel composite brazing alloy material, which significantly improves welding strength through a reasonable composition ratio. Due to the special interfacial strengthening effect of Ni, the brazing alloy of this invention can form a strong and tough metallurgical bonding layer at the interface when welding nickel-plated metallized ceramics, effectively solving the problem of joint delamination.

[0028] The present invention discloses a novel composite brazing alloy material with excellent wettability. The synergistic effect of In and Ni in the brazing alloy makes the wetting angle of the brazing alloy ≤28°. During the welding process, the brazing alloy spreads evenly, and the defect rate such as porosity and slag inclusion is significantly reduced. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below through specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0030] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0031] Example 1: A novel composite brazing alloy material, the composition and mass percentage of each component are: Ag 63%, Cu 28%, In 8%, Ni 1%. This brazing alloy can be made into powder or rolled into sheets.

[0032] In blocks are pre-cut into 1-2mm pieces, and Ni is made into filaments to shorten the melting time during smelting and reduce In exposure at high temperatures. During smelting, the In content is monitored in real time using a spectrometer. If it is below 8%, In can be added proportionally (addition amount = theoretical amount - actual measurement, error ≤0.05%). The powder / flake finished product is sealed and packaged under argon protection, and stored at a temperature ≤25℃ to prevent In from oxidizing and volatilizing due to long-term contact with air. The specific preparation method is as follows.

[0033] The preparation process of brazing alloy powder is as follows:

[0034] 1. Segmented melting + low-temperature In addition: First melt Ag / Cu → cool down and add In → finally add Ni, shortening the time In spends in the high-temperature zone. Ag / Cu melting temperature: 1000-1050℃; In addition temperature: 800-850℃; Ni addition temperature: 780-800℃. In volatility ≤0.3%, composition deviation ≤0.15%.

[0035] 2. Vacuum / Argon Gas Strong Protection: Argon gas is supplied throughout the process (flow rate 6-8L / min), and the vacuum degree of the melting furnace is ≥0.095MPa. The entire process of melting, heat preservation and casting is protected to prevent air convection from carrying away In vapor, reduce In oxidation and volatilization, and ensure that the In content deviation of the ingot is ≤0.2%.

[0036] 3. Shorten the heat preservation time: After adding In, keep warm for ≤3 minutes, and immediately atomize after stirring evenly. Mix quickly after adding In to avoid prolonged high temperature residence. The loss of In volatilization is reduced by 50% compared with conventional heat preservation.

[0037] 4. Rapid atomization: The dwell time before atomization is ≤1 minute to prevent In from evaporating at the nozzle;

[0038] 5. Nozzle and Cooling Optimization: Use an internal mixing nozzle with an atomization pressure of 0.6-0.8 MPa and liquid nitrogen as the cooling medium (cooling rate ≥10). 4 (℃ / s), the droplets rapidly solidify and lock in the components;

[0039] 6. Powder collection protection: The atomization tower is filled with argon gas, and the powder is collected in an argon atmosphere to prevent secondary volatilization of In on the surface of the high-temperature powder.

[0040] The process for preparing brazed alloy rolled sheets is as follows:

[0041] 1. Segmented melting + low-temperature In addition: First melt Ag / Cu → cool down and add In → finally add Ni, shortening the time In spends in the high-temperature zone. Ag / Cu melting temperature: 1000-1050℃; In addition temperature: 800-850℃; Ni addition temperature: 780-800℃. In volatility ≤0.3%, composition deviation ≤0.15%.

[0042] 2. Vacuum / Argon Gas Strong Protection: Argon gas is supplied throughout the process (flow rate 6-8L / min), and the vacuum degree of the melting furnace is ≥0.095MPa. The entire process of melting, heat preservation and casting is protected to prevent air convection from carrying away In vapor, reduce In oxidation and volatilization, and ensure that the In content deviation of the ingot is ≤0.2%.

[0043] 3. Shorten the heat preservation time: After adding In, keep warm for ≤3 minutes, stir evenly and pour immediately. Quick mixing after adding In avoids prolonged high temperature residence and reduces In volatilization loss by 50% compared to conventional heat preservation.

[0044] 4. Homogenization temperature control of ingots: 650℃×2h vacuum annealing (50℃ lower than ordinary silver-copper brazing alloy), water cooling instead of air cooling, to avoid In segregation and volatilization at grain boundaries during slow cooling;

[0045] 5. Rolling temperature control: Cold rolling is carried out at room temperature throughout to avoid In volatilization caused by heating; if hot rolling is required, the temperature should be ≤400℃ and the holding time should be ≤10min.

[0046] 6. Intermediate annealing protection: Argon gas is introduced during annealing at 400℃ for 30 minutes to prevent In from volatilizing from the material surface during the annealing process and to ensure the stability of the In content of the finished product.

[0047] The composition of other main embodiments and their mechanical properties compared with those of the Ag72Cu28 brazing alloy are shown in Table 1 below.

[0048] Table 1. Chemical composition of Examples 1-5 and comparison of mechanical properties with Ag72Cu28 brazing alloy.

[0049] Brazing alloy Ag (wt%) Cu (wt%) In (wt%) Ni (wt%) Tensile strength (MPa) Example 1 63 28 8 1 380-420 Example 2 65 29.5 5 0.5 350-400 Example 3 50 35 12 3 400-450 Example 4 55 25 15 5 350-400 Example 5 58 32 9 1 390-430 Ag72Cu28 72 28 0 0 250-360

[0050] As can be seen from Table 1, the tensile strength of the five compositions optimized is between 350-450 MPa, which is better than that of Ag72Cu28 (250-360 MPa).

[0051] Table 2. Performance comparison of Example 1 and brazing alloys doped with Sn and Zn.

[0052] Performance items Ag63Cu28In8Ni1 Ag60Cu32Sn8 Ag60Cu25Zn15 Performance superiority / inferiority conclusions Solidus temperature (°C) 750 - 760 705 - 715 680 - 690 Silver, copper, and tin, as well as silver, copper, and zinc, have lower melting points, but their low melting points can cause the brazing alloy to melt and be lost prematurely during welding. This invention has a moderate melting point, making it suitable for the heat resistance range of most metal substrates. Liquidus temperature (°C) 765 - 775 740 - 755 720 - 735 The melting temperature range of the silver-copper-tin solution reaches 35-50℃, and that of the silver-copper-zinc solution reaches 40-55℃, both significantly wider than the target formulation's 10-15℃ range. This makes component segregation more likely to occur during grouting. Tensile strength (MPa) 380- 420 230 - 300 260 - 320 The strength of this invention is far superior to that of the two competing products. Silver, copper, and tin are prone to brittle fracture due to the large amount of brittle β-Cu phase, while silver, copper, and zinc contain hard and brittle CuZn phases. Neither of these can meet the requirements of high-stress scenarios. Wetting contact angle (°) 18 - 28 35 - 45 40 - 50 This invention exhibits the best wettability. Silver, copper, and tin have poor wettability and are prone to voids. Silver, copper, and zinc suffer from uneven spreading due to the easy oxidation of Zn. Both are prone to welding defects during sealing. Crack filling performance The sealant is full and free of air bubbles, suitable for gaps of 0.1-0.5mm. Incomplete grouting can easily lead to shrinkage pores and gaps, and is only suitable for gaps larger than 0.5mm. It easily generates pores and brittle compounds, resulting in poor tightness of the brazing joint after filling, and is prone to leakage with long-term use. This invention is compatible with various gap specifications, offering enhanced sealing reliability. Competing products from two other categories suffer from numerous gap-filling defects and are unsuitable for welding precision components. Antioxidant properties Under argon protection, there is almost no oxidation, and the surface of the brazing seam is smooth. <![CDATA[It is easy to generate SnO2 oxide film on the surface during welding, and it is difficult to clean]]> Zn readily oxidizes to form ZnO fumes, resulting in a thick oxide layer on the surface of the brazing seam, which affects the joint's sealing performance. The present invention is simple to process after welding. The oxidation problem is most serious for silver, copper and zinc, followed by silver, copper and tin, all of which increase the cost of post-weld processing. Processing performance It can be smoothly rolled into thin strips, or the powder has no risk of breakage. It is brittle and prone to fracture during rolling, making it impossible to process into thin-sheet brazing alloys. During processing, the composition is prone to fluctuations due to Zn volatilization, resulting in a low yield. This invention offers superior processing stability, while the other two types of processing are limited and difficult to adapt to large-scale production.

[0053] As can be seen from Table 2, the brazing alloy Ag63Cu28In8Ni1, which is doped with both In and Ni, has the best overall performance and meets the actual industrial requirements.

[0054] This invention relates to a novel composite brazing alloy material that simultaneously adds In and Ni elements to a traditional silver-copper brazing alloy. Through a reasonable component ratio and preparation process, In and Ni exhibit a synergistic effect in the silver-copper brazing alloy, namely "functional complementarity, defect suppression, microstructure refinement, and performance enhancement": In dominates wetting and brittle phase suppression, while Ni dominates nucleation pinning and solid solution strengthening. The combined addition can simultaneously improve the joint strength, toughness, and high-temperature service performance while reducing the silver content by 30-50%.

[0055] In is a low-melting-point surface-active element. In can lower the melting point, making the brazing temperature more moderate and reducing the risk of thermal deformation; Ni can enhance mechanical strength, making the joint stronger. This synergistic effect allows the brazed joint to maintain good strength without causing deformation or performance degradation of the base material due to high temperatures.

[0056] In improves wettability, making the brazing alloy easier to spread and penetrate; Ni reduces segregation, making the alloy composition more uniform. The combined effect of both makes the brazing alloy spread more evenly on the base material surface, the interface bonding stronger, and avoids localized insufficient strength caused by segregation.

[0057] In enhances the density of brazed joints, reducing porosity and defects; Ni improves corrosion resistance, making the joint more durable in harsh environments. This synergistic effect significantly improves the long-term reliability and service life of brazed joints.

[0058] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A novel composite brazing alloy material, characterized in that: This novel composite brazing alloy material is composed of four metallic elements: Ag, Cu, In, and Ni.

2. The novel composite brazing alloy material according to claim 1, characterized in that: The mass percentages of the four metallic elements in the brazing alloy are: Ag 50-65%, Cu 25-35%, In 5-15%, and Ni 0.5-5%.

3. The novel composite brazing alloy material according to claim 1, characterized in that: The mass percentages of the four metallic elements in the brazing alloy are: Ag 58-63%, Cu 28-32%, In 8-12%, and Ni 1-3%.

4. The novel composite brazing alloy material according to claim 1, characterized in that: The mass percentages of the four metallic elements in the brazing alloy are: Ag 63%, Cu 28%, In 8%, and Ni 1%.

5. The novel composite brazing alloy material according to claim 1, characterized in that: The tensile strength of the brazing alloy is 350-450 MPa.

6. The novel composite brazing alloy material according to claim 1, characterized in that: The wetting contact angle of the brazing alloy is 18-28°.

7. The novel composite brazing alloy material according to claim 1, characterized in that: The solidus temperature of the brazing alloy is 750-760℃.

8. The novel composite brazing alloy material according to claim 1, characterized in that: The liquidus temperature of the brazing alloy is 765-775℃.