Ag-cu-pd quaternary metal brazing filler and design method thereof
By constructing a thermodynamic database of Ag-Cu-Pd quaternary metal brazing filler metals, optimizing the Ag/Cu ratio and Pd content, and introducing Ni element, the problems of melting temperature shift and phase composition inhomogeneity in brazing filler metals when reducing Pd content were solved, achieving cost optimization and performance maintenance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CENT SOUTH UNIV
- Filing Date
- 2026-04-13
- Publication Date
- 2026-07-10
AI Technical Summary
In the process of reducing the Pd content, existing Ag-Cu-Pd brazing fillers have excessively deviated melting temperatures, altered phase composition, and become uneven in phase structure, resulting in decreased wettability, reduced hardness, and unstable service structure, making them difficult to be compatible with existing brazing processes and service requirements.
By constructing a thermodynamic database of Ag-Cu-Pd quaternary metal solders, and using Gibbs energy models and phase equilibrium data, the Ag/Cu ratio and Pd content were optimized. Ni was introduced as a substitute element, and melting characteristics and microstructure phase composition were matched to ensure that the solder is consistent with commercial solders at the lowest cost.
It achieves a reduction of Pd usage by 8% to 25%, a cost reduction of 7.30% to 17.64%, a melting temperature deviation of no more than ±2.5 ℃, a melting range of no more than 5 ℃, a phase fraction deviation of no more than 3% at the service temperature, and a microhardness, wettability, and spreadability deviation of no more than 5%, significantly reducing the amount of precious metals added while maintaining the same properties.
Smart Images
Figure CN122369725A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a quaternary metal solder, specifically to an Ag-Cu-Pd quaternary metal solder and its design method, belonging to the field of solder material technology. Background Technology
[0002] Ag-Cu-Pd solders are preferred for vacuum electronic devices, precision structural components, and high-reliability connections due to their suitable melting point, good conductivity, excellent wettability, low vapor pressure, and good corrosion resistance. Pd (palladium) is a key precious metal element for maintaining the solder's microstructure stability, wettability, and long-term corrosion resistance. However, the high cost and price volatility of Pd raw materials have kept commercially available Pd287, Pd387, Pd481, Pd484, and Pd587 solders prohibitively expensive, severely limiting their industrial application. Current technologies often employ trial-and-error or empirical methods to simply reduce Pd content for cost optimization, but this frequently leads to excessive melting temperature deviations, altered solidification phase composition, phase imbalances, and uneven phase microstructure. This results in decreased wettability, reduced hardness, and unstable microstructure during service, making them incompatible with existing brazing processes and service requirements. Therefore, how to efficiently develop a solder system that maintains consistency with commercial solders in terms of melting characteristics, phase composition stability, wetting and spreading performance, and service reliability while reducing Pd content has become a pressing technical challenge in this field. Summary of the Invention
[0003] To address the problems existing in the prior art, the first objective of this invention is to provide an Ag-Cu-Pd quaternary metal solder. This solder reduces the amount of Pd used while maintaining key process performance characteristics. Tests show that compared to commercially available Ag-Cu-Pd solders, it reduces Pd usage by approximately 8% to 25% and lowers costs by 7.30% to 17.64%, achieving an economical replacement of precious metal solders.
[0004] The second objective of this invention is to provide a design method for Ag-Cu-Pd quaternary metal solders. This method constructs a quaternary thermodynamic database, targets commercially available solders, and sequentially performs melting characteristic matching and phase composition matching. Utilizing the lowest-cost constraint, it obtains the specific composition of the quaternary metal solder. This process significantly reduces the amount of precious metals added to the solder while ensuring consistency with existing commercial solders, achieving the technical objectives of equivalent process performance and optimal cost.
[0005] To achieve the above technical objectives, this invention provides a design method for Ag-Cu-Pd quaternary metal solders, comprising:
[0006] Step S1: Construct Gibbs energy models for each phase in the Ag-Cu-Pd quaternary metal system, calculate the thermodynamic parameters of pure components, binary and ternary components, and obtain a database of quaternary metal systems for predicting solidification paths, phase composition and phase transition temperatures.
[0007] Step S2: Initialize the Ag / Cu ratio range and Pd content in the Ag-Cu-Pd quaternary metal system. Using the remaining metal elements as control variables, calculate the equilibrium solidification through the database to obtain the melting temperature and melting range of the quaternary metal system.
[0008] Step S3: Based on the melting temperature and melting range of the quaternary metal system, match the melting characteristics with the target brazing filler metal, and obtain the as-cast and service microstructures of the quaternary metal system within the matching range;
[0009] Step S4: Based on the as-cast and service microstructure of the quaternary metal system in Step S3, match the microstructure and phase composition with the target brazing filler metal, and obtain the final quaternary metal brazing filler metal composition with the lowest cost as the constraint.
[0010] As a preferred embodiment, the target solder is one of the commercially available solders Pd287, Pd387, Pd481, Pd484, and Pd587. These commercially available solders are Ag-Cu-Pd ternary solders, all labeled according to ISO 17672:2024 (International Organization for Standardization), and their corresponding grades in the domestic standard GB / T 18762—2017 are BAg68CuPd, BAg58CuPd, BAg65CuPd, BAg52CuPd, and BAg54CuPd, respectively.
[0011] The Pd287 solder comprises the following components by mass percentage: Ag 68±1 wt.%, Cu 27±0.5 wt.%, Pd 5±0.5 wt.%; the Pd387 solder comprises the following components by mass percentage: Ag 58±1 wt.%, Cu 32±0.5 wt.%, Pd 10±0.5 wt.%; the Pd481 solder comprises the following components by mass percentage: Ag 65±0.5 wt.%, Cu 20±0.5 wt.%, Pd 15±0.5 wt.%; the Pd484 solder comprises the following components by mass percentage: Ag 52±0.5 wt.%, Cu 28±0.5 wt.%, Pd 20±0.5 wt.%; and the Pd587 solder comprises the following components by mass percentage: Ag 54±1 wt.%, Cu 21±0.5 wt.%, Pd 54±1 wt.%, Cu 21±0.5 wt.%, Pd 54±1 wt.%, Pd 587 wt.%, Pd 587 wt.%. 25±0.5 wt.%.
[0012] It should be noted that when the Ag-Cu-Pd quaternary metal solder provided by this invention is designed to be benchmarked against one of the aforementioned commercial solders, the Ag content during the initialization process varies by ±0.72 wt.% from the range of the original commercial solder, thereby ensuring that the basic composition of the quaternary metal system is consistent with that of the commercial solder.
[0013] As a preferred embodiment, the residual metal element M in the Ag-Cu-Pd quaternary metal system is one of Ni, In, and Sn. More preferably, the residual metal element M in the Ag-Cu-Pd quaternary metal system is Ni.
[0014] As a preferred embodiment, the construction process of the Ag-Cu-Pd quaternary metal system database is as follows:
[0015] (1) Establish the Gibbs energy functions of four pure components, Ag, Cu, Pd and M, in the standard element reference state, respectively, as the basic data of pure components;
[0016] (2) Based on pure component data, the liquid and solid phases in the Ag-Cu, Ag-Pd, Ag-M, Cu-Pd, Cu-M and Pd-M binary subsystems are described by the solution phase and the ordered-disorder model. The thermodynamic parameters of the Pd-Cu binary system are calculated from phase planar experimental data, while the other binary subsystems are from literature data.
[0017] (3) Based on the models and thermodynamic parameters of the liquid and solid phases in the binary subsystem, the thermodynamic parameters of each ternary system Ag-Pd-Cu, Ag-Pd-M, Pd-Cu-M and Ag-Cu-M are calculated using ternary phase equilibrium data;
[0018] (4) Integrate all binary and ternary subsystems to obtain the Ag-Cu-Pd quaternary thermodynamic database.
[0019] Further preferred, the Ag-Cu-Pd quaternary metal system is Ag-Cu-Pd-Ni, and the process of constructing its quaternary metal system database is as follows:
[0020] First, the Gibbs energy functions of pure components Ag, Cu, Pd, and Ni in the standard element reference state (SER) are established as the basic data for pure components. The SER state corresponds to the unique stable crystal structure of the element under the conditions of 298.15 K and 1 bar. Ag, Cu, Pd, and Ni are all Fcc_A1 structures under these conditions. The thermodynamic descriptions of pure elements Ag, Pd, Cu, and Ni are directly adopted from the Gibbs energy data given in the SGTE (Scientific Group Thermodata Europe) pure component database to ensure the reliability and consistency of the basic data.
[0021] Based on this, thermodynamic modeling was prioritized for six binary subsystems: Ag-Cu, Ag-Pd, Ag-Ni, Cu-Pd, Cu-Ni, and Pd-Ni. The Gibbs energies of the liquid and solid phases in these systems were described using a solution phase model and an order-disorder model. The thermodynamic parameters of the Pd-Cu system were obtained through optimized calculations based on experimentally determined phase equilibrium data. The thermodynamic parameters of the other binary subsystems were obtained from publicly available data in existing literature. This step ensured the accuracy of the binary models within the temperature and composition ranges, providing a solid foundation for modeling ternary and quaternary systems.
[0022] Subsequently, based on the obtained binary system model and parameters, and combined with ternary phase equilibrium data obtained through phase equilibrium experiments, the ternary thermodynamic parameters of the liquid and solid phases were optimized to improve the model's prediction accuracy within the multi-component range. Specifically, the thermodynamic parameters of the three ternary subsystems—Ag-Pd-Cu, Ag-Pd-Ni, and Pd-Cu-Ni—were obtained through thermodynamic optimization calculations based on experimental data; the Ag-Cu-Ni system underwent overall re-optimization calculations based on a unified binary subsystem to ensure its consistency and extrapolation stability in the quaternary system coupling process.
[0023] Finally, by unifying and integrating the optimized binary and ternary parameters, a self-consistent Ag-Cu-Pd-Ni quaternary thermodynamic database was constructed. This database can provide a full-temperature thermodynamic description of the liquid phase, α1 phase, and α2 phase, providing a reliable and quantifiable theoretical basis for subsequent large-scale composition screening, equilibrium and Hill solidification calculations, and cost-performance optimization.
[0024] As a preferred embodiment, the optimization calculation process for the binary and ternary thermodynamic parameters is as follows: experimental data on phase composition are obtained through XRD, and the accurate phase composition and components of the binary and ternary subsystems are determined by combining the data with electron probe microscopy analysis. Then, the experimental data are compiled into a readable file of Pandat software, and a global optimization algorithm is used to automatically search for the lowest point of Gibbs energy to obtain the most stable phase equilibrium result, which is the optimized binary and ternary thermodynamic parameters.
[0025] As a preferred embodiment, the Ag / Cu ratio in the initial Ag-Cu-Pd quaternary metal system ranges from 1.81 to 3.25.
[0026] As a preferred embodiment, the Pd content in the initial Ag-Cu-Pd quaternary metal system is 3~25 wt.%.
[0027] As a preferred embodiment, the remaining metal element in the Ag-Cu-Pd quaternary metal system is one of Ni, In, and Sn. More preferably, the remaining metal element in the Ag-Cu-Pd quaternary metal system is Ni. The metal element selected in this invention serves two purposes: firstly, to replace Pd, reducing the amount of Pd used while ensuring the solder's performance; and secondly, to improve the overall performance of the quaternary metal by forming a two-phase solid solution structure.
[0028] As a preferred embodiment, the process of matching the melting characteristics of the quaternary metal system with the target solder is as follows: by constraining the melting characteristics of the quaternary metal system to be highly consistent with those of the target solder, the range of melting characteristic components of the quaternary metal system is then selected.
[0029] As a preferred embodiment, the condition for highly consistent melting characteristics is that the melting temperature of the quaternary metal system and the target solder is within ±2.5 ℃, and the melting range is ≤5 ℃. This invention ensures consistent welding processes for the quaternary metal system and the target solder by matching melting characteristics, eliminating the need for additional adjustments to parameters such as heating rate, holding time, or cooling method. This improves the compatibility of the quaternary metal system and lowers the operational threshold.
[0030] As a preferred embodiment, the process for obtaining the as-cast and service microstructures of the quaternary metal system is as follows: using Hill solidification and full-temperature phase fraction calculations, the as-cast and service microstructures within the range of melting characteristic composition are obtained.
[0031] As a preferred embodiment, the process of matching the microstructure and phase composition of the quaternary metal system with the target brazing filler metal involves selecting the optimal composition range that is completely consistent with the as-cast microstructure of the target brazing filler metal and has a phase fraction deviation of ≤3% at the service temperature, based on the as-cast and service microstructures within the range of melting characteristics. This invention employs microstructure and phase composition matching, effectively ensuring the microstructure stability of the quaternary metal system during brazing and service, thereby guaranteeing brazing quality.
[0032] As a preferred embodiment, the as-cast and service microstructure of the quaternary metal system comprises a dark α1 phase, a grayish-white α2 phase, and fine (α1+α2) eutectic phases.
[0033] As a preferred embodiment, the (α1+α2) eutectic phase in the quaternary metal solder is inversely proportional to the Pd content in the quaternary metal system. When the Pd content is ≥23 wt.%, the (α1+α2) eutectic phase disappears.
[0034] The present invention also provides an Ag-Cu-Pd quaternary metal solder, obtained by the design method described in any one of the above.
[0035] Compared with the prior art, the beneficial technical effects of the technical solution provided by the present invention are as follows:
[0036] 1) The design method provided by this invention takes “melting characteristic matching - stable microstructure / phase composition - optimal cost” as an integrated constraint condition. It ensures that the quaternary metal brazing filler metal can maintain the same process window as the target brazing filler metal and significantly reduce the addition of precious metals. Furthermore, the method realizes predictable control of solidification path, phase composition and phase transformation temperature through database-driven approach, which can meet the technical requirements for quantitative design of precious metal brazing filler metals.
[0037] 2) The solder provided by this invention, through optimized composition design, significantly reduces the amount of precious metals added while ensuring high consistency with the process performance of the target solder, achieving the technical objective of optimal cost. Compared with the target solder, its melting temperature deviation does not exceed ±2.5 ℃, melting range does not exceed 5 ℃, phase fraction deviation at service temperature does not exceed 3%, and microhardness, wettability, and spreadability deviation does not exceed 5%. At the same time, the wetting angle and spread area on the Ni substrate are basically the same as or slightly improved with the target solder, and it has the technical advantages of "low cost, equal performance, and substitutability".
[0038] 3) The technical solution provided by this invention solves the core contradiction of "simply reducing Pd leading to performance degradation" in the prior art by combining the strategies of "Ag / Cu ratio control + Pd graded reduction + trace element substitution + thermodynamic database screening + optimal cost determination". On the one hand, the introduction of trace elements plays a role in refining grains and improving the uniformity of the microstructure. On the other hand, by graded and synergistically controlling the Ag / Cu mass ratio, Pd content and Ni content, the as-cast microstructure of the solder is stabilized into α1 phase, α2 phase and fine (α1+α2) eutectic phase, and the phase composition at the service temperature remains highly consistent with the target solder, thereby ensuring the microstructure stability and reliability of the solder during the welding process and long-term service. Attached Figure Description
[0039] Figure 1 The image shows a comparison of the as-cast microstructure characterization results of the quaternary metal solders obtained in Examples 1-6 of this invention and commercial Ag-Cu-Pd solders, including XRD patterns and corresponding BSE images.
[0040] in, Figure 1 (a) is a comparison of the XRD results of commercial solder 1-1# and quaternary metal solder 1-2#. Figure 1 (a-1) is a BSE image of the microstructure corresponding to commercial solder 1-1#. Figure 1 (a-2) is a BSE image of the microstructure corresponding to commercial solder #1-2;
[0041] Figure 1 (b) is a comparison of the XRD results of commercial solder 2-1# and quaternary metal solder 2-2#. Figure 1 (b-1) is a BSE image of the microstructure corresponding to commercial solder 2-1#. Figure 1 (b-2) is a BSE image of the microstructure corresponding to 2-2# commercial solder;
[0042] Figure 1 (c) is a comparison of the XRD results of commercial brazing filler metal 3-1# and quaternary metal brazing filler metal 3-2#. Figure 1 (a-1) is a BSE image of the microstructure corresponding to commercial solder 3-1#. Figure 1 (a-2) is a BSE image of the microstructure corresponding to 3-2# commercial solder;
[0043] Figure 1 (d) is a comparison of the XRD results of commercial brazing filler metal 4-1# and quaternary metal brazing filler metal 4-2#. Figure 1 (d-1) is the BSE image of the microstructure corresponding to commercial solder 4-1#. Figure 1 (d-2) is the BSE image of the microstructure corresponding to 4-2# commercial solder;
[0044] Figure 1 (e) is a comparison of the XRD results of commercial brazing filler metal 5-1# and quaternary metal brazing filler metal 5-2#. Figure 1 (e-1) is a BSE image of the microstructure corresponding to 5-1# commercial solder. Figure 1 (e-2) is a BSE image of the microstructure corresponding to 5-2# commercial solder;
[0045] Figure 2 This is a comparison chart of the Hill solidification calculation results of the quaternary metal brazing filler metals obtained in Examples 1-6 of this invention and commercial Ag-Cu-Pd brazing filler metals;
[0046] Figure 3 The image shows a comparison of the microhardness results of the quaternary metal brazing filler metals obtained in Examples 1-6 of this invention and commercial Ag-Cu-Pd brazing filler metals.
[0047] Figure 4 This is a comparison chart of the wettability results of the quaternary metal solders obtained in Examples 1-6 of the present invention and commercial Ag-Cu-Pd solders;
[0048] Figure 5 This is a comparison chart of the spreadability results of the quaternary metal brazing filler metals obtained in Examples 1-6 of the present invention and commercial Ag-Cu-Pd brazing filler metals;
[0049] Figure 6 The graph shows the calculated results of the phase composition of the quaternary metal solders obtained in Examples 1-6 of this invention and the commercial Ag-Cu-Pd solders as a function of temperature.
[0050] in, Figure 6 (a) shows the calculated phase composition of commercial brazing filler metal #1-1 as a function of temperature. Figure 6 (b) shows the calculated results of the phase composition of quaternary metal brazing filler metal #1-2 as a function of temperature. Figure 6 (c) shows the calculated phase composition of commercial brazing filler metal #2-1 as a function of temperature. Figure 6 (d) shows the calculated results of the phase composition of 2-2# quaternary metal brazing filler metal as a function of temperature. Figure 6 (e) shows the calculated phase composition of commercial brazing filler metal #3-1 as a function of temperature. Figure 6 (f) shows the calculated results of the phase composition of 3-2# quaternary metal brazing filler metal as a function of temperature. Figure 6 (g) shows the calculated phase composition of 4-1# commercial brazing filler metal as a function of temperature. Figure 6 (h) represents the calculated results of the phase composition of 4-2# quaternary metal brazing filler metal as a function of temperature. Figure 6 (i) shows the calculated phase composition of 5-1# commercial brazing filler metal as a function of temperature. Figure 6 (j) is the calculated result of the phase composition of 5-2# quaternary metal brazing filler metal as a function of temperature. Detailed Implementation
[0051] The following provides a detailed description of specific embodiments of the present invention. Obviously, the described embodiments and comparative examples are only a part of the present invention, and not all of it. All other examples based on the embodiments of the present invention, modified or refined by those skilled in the art, fall within the scope of protection of the present invention.
[0052] Example 1
[0053] The Ag-Cu-Pd quaternary metal solder provided in this embodiment is Ag-Cu-Pd-Ni, and its design method is as follows:
[0054] Step S1: Construct Gibbs energy models for each phase in the Ag-Cu-Pd-Ni quaternary metal system, calculate the thermodynamic parameters of pure components, binary and ternary components, and obtain a database for predicting solidification paths, phase composition and phase transition temperatures.
[0055] First, the Gibbs energy functions of pure components Ag, Cu, Pd, and Ni in the standard element reference state (SER) are established as the basic data for pure components. The SER state corresponds to the unique stable crystal structure of the element under the conditions of 298.15 K and 1 bar. Ag, Cu, Pd, and Ni are all Fcc_A1 structures under these conditions. The thermodynamic descriptions of pure elements Ag, Pd, Cu, and Ni are directly adopted from the Gibbs energy data given in the SGTE (Scientific Group Thermodata Europe) pure component database to ensure the reliability and consistency of the basic data.
[0056] Based on this, thermodynamic modeling was prioritized for six binary subsystems: Ag-Cu, Ag-Pd, Ag-Ni, Cu-Pd, Cu-Ni, and Pd-Ni. The Gibbs energies of the liquid and solid phases in these systems were described using a solution phase model and an order-disorder model. The thermodynamic parameters of the Pd-Cu system were obtained through optimized calculations based on experimentally determined phase equilibrium data. The thermodynamic parameters of the other binary subsystems were obtained from publicly available data in existing literature. This step ensured the accuracy of the binary models within the temperature and composition ranges, providing a solid foundation for modeling ternary and quaternary systems.
[0057] The specific process for obtaining the thermodynamic parameters of the Pd-Cu system is as follows:
[0058] Step S1-1: Prepare a Pd-Cu binary alloy in the key phase region, anneal it at a specific temperature, and hold it at that temperature for a period of time, as shown in Table 1.
[0059] Steps S1-2: After annealing, the six experimental alloys in Table 1 were prepared using standard metallographic methods, including grinding, polishing, and cleaning. The grinding process involved using 400-1200 mesh SiC sandpaper, followed by fine polishing with diamond polishing paste with a particle size of 2.5 μm. Finally, the samples were ultrasonically cleaned in anhydrous ethanol for 15 min and thoroughly dried. All polished samples were vacuum-preserved under clean, uncontaminated conditions to ensure the accuracy of subsequent microstructure observation and quantitative analysis. In addition, some as-cast and annealed phase equilibrium experimental alloys were ground into powder for phase analysis. The powder samples were then subjected to microstructure analysis at approximately 10⁻⁻⁶ mm. 4 The Pa was sealed in a quartz tube under vacuum conditions and annealed for 24 hours at the phase equilibrium experimental annealing temperature of the corresponding system to eliminate residual stress.
[0060] Steps S1-3: X-ray diffraction (XRD) is used to identify the phase composition of the as-cast and annealed phase equilibrium experimental alloy powders; electron probe microanalysis (EPMA) with a wavelength dispersive X-ray analysis system (WDX) is used to analyze the microstructure and phase composition of the as-cast and annealed phase equilibrium experimental alloys. The accurate phase composition and composition of the experimental alloys are determined by combining the results of XRD and EPMA.
[0061] Steps S1-4: Compile the above experimental data into a readable file in Pandat software, use a global optimization algorithm to automatically search for the lowest point of Gibbs energy, and obtain the most stable phase equilibrium result, which is the optimized binary thermodynamic parameter.
[0062]
[0063] Subsequently, based on the obtained binary system model and parameters, and combined with ternary phase equilibrium data obtained through phase equilibrium experiments, the ternary thermodynamic parameters of the liquid and solid phases were optimized to improve the model's prediction accuracy within the multi-component range. Specifically, the thermodynamic parameters of the three ternary subsystems—Ag-Pd-Cu, Ag-Pd-Ni, and Pd-Cu-Ni—were obtained through thermodynamic optimization calculations based on experimental data; the Ag-Cu-Ni system underwent overall re-optimization calculations based on a unified binary subsystem to ensure its consistency and extrapolation stability in the quaternary system coupling process.
[0064] The process of obtaining the ternary thermodynamic parameters is basically the same as that of the binary thermodynamic parameters. Specifically, the experimental data of the phase composition of the ternary subsystem is obtained by XRD, and the accurate phase composition and composition of the ternary subsystem are determined by combining the electron probe microanalysis data. Then, the experimental data is compiled into a readable file of Pandat software, and the global optimization algorithm is used to automatically search for the lowest point of Gibbs energy to obtain the most stable phase equilibrium result, which is the optimized ternary thermodynamic parameters.
[0065] Finally, by unifying and merging the optimized binary and ternary parameters, a quaternary thermodynamic database of Ag-Cu-Pd-Ni with consistency and extrapolation stability was constructed.
[0066] Step S2: Initialize the Ag / Cu ratio range and Pd content in the Ag-Cu-Pd-Ni quaternary metal system. Using Ni metal element as the control variable, calculate equilibrium solidification through the database to obtain the melting temperature and melting range of the quaternary metal system.
[0067] The Ag / Cu ratio in the initial Ag-Cu-Pd quaternary metal system ranges from 1.81 to 3.25.
[0068] The Pd content in the initial Ag-Cu-Pd quaternary metal system is 3~25wt%;
[0069] Step S3: Based on the melting temperature and melting range of the quaternary metal system, match the melting characteristics with commercial brazing filler metal, and obtain the as-cast and service microstructures of the quaternary metal system within the matching range.
[0070] The process of matching the melting characteristics of the quaternary metal system with commercial solder is as follows: by constraining the melting characteristics of the quaternary metal system to be highly consistent with those of the commercial solder, the range of melting characteristic components of the quaternary metal system is then selected.
[0071] The conditions for highly consistent melting characteristics are: the melting temperature of the quaternary metal system and the commercial solder is within ±2.5℃, and the melting range is ≤5℃;
[0072] The process for obtaining the as-cast and service microstructures of the quaternary metal system is as follows: using Hill solidification and full-temperature phase fraction calculations, the as-cast and service microstructures within the range of melting characteristic composition are obtained;
[0073] Step S4: Based on the as-cast and service microstructure of the quaternary metal system in Step S3, match the microstructure and phase composition with commercial brazing filler metal, and obtain the final quaternary metal brazing filler metal composition with the lowest cost as the constraint.
[0074] The process of matching the microstructure and phase composition of the quaternary metal system with commercial brazing filler metal is as follows: based on the as-cast and service microstructures within the range of melting characteristic composition, select the optimal composition range that is completely consistent with the as-cast microstructure of commercial brazing filler metal and has a phase fraction deviation of ≤3% at the service temperature.
[0075] In order to demonstrate the beneficial effects of the method provided by the present invention, quaternary metal solders with Pd287, Pd387, Pd481, Pd484 and Pd587 as benchmarks for commercial solders were designed through the above process, and their compositions are shown in Table 2.
[0076]
[0077] As shown in Table 2, by introducing a small amount of Ni, the present invention effectively reduces the amount of precious metals used. Specifically, the amount of Pd added is reduced by 8-25%, which directly leads to a cost reduction of 7-18%, demonstrating its excellent economic efficiency.
[0078] Example 2
[0079] This embodiment, based on the quaternary metal solder composition provided in Example 1, prepares a quaternary metal solder comparable to the commercial Pd287 solder. The process is as follows:
[0080] Using 99.99 wt.% Ag, 99.99 wt.% Pd, 99.999 wt.% Cu, and 99.995 wt.% Ni as raw materials, the materials were melted separately in a high-vacuum electric arc melting furnace and repeatedly turned more than 5 times to obtain two alloy ingots: one was commercially available Pd287 (1-1#, Ag68Cu27Pd5), and the other was Ag70.5Cu25.6Pd3.75Ni0.15 (1-2#) provided in this embodiment. Both 1-1# and 1-2# alloy ingots were divided into large-sized cuboid samples of different dimensions (7×7×3 mm and 2×2×3 mm) for observation of the as-cast microstructure and microhardness testing; smaller samples were homogenized and annealed at 700 ℃ for 1 day, then cooled to room temperature in the furnace for subsequent wettability testing. The as-cast and annealed brazing filler metals were mechanically ground sequentially using 400, 800, 1500, and 2000 grit sandpaper. The as-cast filler metals were then finely polished on a polishing cloth using 0.25 μm diamond polishing paste. Finally, all filler metals were ultrasonically cleaned in anhydrous ethanol for at least 15 minutes to remove residual contaminants.
[0081] Example 3
[0082] This embodiment prepares a quaternary metal solder that is comparable to commercial Pd387 solder based on the quaternary metal solder composition provided in Example 1. The process is completely consistent with that in Example 2. The difference is that the two alloy ingots obtained are different: one is commercial Pd387 (2-1#, Ag58Cu32Pd10), and the other is Ag59.5Cu31.6Pd 8.75Ni0.15 (2-2#).
[0083] Example 4
[0084] Based on the quaternary metal solder composition provided in Example 1, this embodiment prepares a quaternary metal solder that is comparable to the commercial Pd481 solder. The process is exactly the same as in Example 2, except that the two alloy ingots obtained are different: one is commercial Pd481 (3-1#, Ag65Cu20Pd15), and the other is Ag67Cu19.4Pd13.5Ni0.1 (3-2#).
[0085] Example 5
[0086] This embodiment prepares a quaternary metal solder that is comparable to commercial Pd484 solder, based on the quaternary metal solder composition provided in Example 1. The process is completely consistent with that in Example 2, except that the two alloy ingots obtained are different: one is commercial Pd484 (4-1#, Ag52Cu28Pd20), and the other is Ag54.5Cu27Pd18.25Ni0.25 (4-2#).
[0087] Example 6
[0088] This embodiment prepares a quaternary metal solder that is comparable to the commercial Pd484 solder, based on the quaternary metal solder composition provided in Example 1. The process is completely consistent with that in Example 2, except that the two alloy ingots obtained are different: one is commercial Pd587 (5-1#, Ag54Cu21Pd25), and the other is Ag57Cu19.7Pd23Ni0.3 (5-2#).
[0089] This invention uses X-ray diffraction (XRD) to analyze the phase composition of as-cast samples of two types of solder, 1-1#~5-1# and 1-2#~5-2#, in Examples 2-6; simultaneously, electron probe microanalysis (EPMA) is used to measure the elemental distribution and observe the microstructure of the samples to determine their microstructure and solidification path. The relevant results are as follows: Figure 1 As shown; furthermore, based on the Ag-Cu-Pd-Ni quaternary thermodynamic database provided in Example 1, Hill solidification calculations were performed on two types of solder, 1-1#~5-1# and 1-2#~5-2#, as follows: Figure 2 As shown, the calculated and predicted solidification path and phase composition are completely consistent with the experimental results.
[0090] Furthermore, this invention also employs an HVS-1000MZ touchscreen digital display microhardness tester to perform microhardness tests on two types of brazing filler metals: 1-1#~5-1# and 1-2#~5-2#. The test conditions are: load HV0.1, hold load for 15s, and the distance between the centers of two adjacent indentations is at least 5 times the length of the indentation diagonal. Ten independent and effective tests are performed on the same brazing filler metal in different areas to ensure the accuracy of the experimental measurements. After removing the maximum and minimum values, the average value is taken as the final hardness value, as shown in the figure. Figure 3 As shown in the figure, the quaternary metal brazing filler metal provided by this invention has a hardness highly similar to that of commercial brazing filler metals.
[0091] This invention also employs a DSAHT17C high-temperature contact angle measuring instrument to conduct high-temperature contact angle tests on two types of solder, 1-1#~5-1# and 1-2#~5-2#, after homogenization treatment. The test conditions were: pure Ni substrate (size: 20×20×2 mm), test temperature 935 ℃ (the soldering temperature of commercial solder Pd484), heating and cooling rate 10 ℃ / min, holding time 1 min, and vacuum degree 2.5×10⁻⁶. -3 Pa. Under the same experimental conditions, two types of solder, 1-1#~5-1# and 1-2#~5-2#, were each subjected to three independent and effective tests to ensure the accuracy of the experimental measurements. The average value was taken as the final wetting angle. The results are as follows: Figure 4 As shown. By Figure 4It can be seen that all five Ag-Pd-Cu-Ni alternative solders exhibited wetting angles that were comparable to or even slightly smaller than their commercial counterparts, indicating that wettability was maintained or even slightly improved despite a significant reduction in Pd content.
[0092] After the wettability test, the cooled droplet samples were removed and photographed. Image-ProPlus 6.0 software was used to quantitatively analyze the droplet profile and obtain its actual spreading area on the Ni substrate. The average of the data obtained from three parallel samples measuring the wetting angle for each solder was taken as the final actual spreading area. Using the ideal spreading area at full wetting as a benchmark, the spreading rates of two types of solders, 1-1#~5-1# and 1-2#~5-2#, were calculated. The results are as follows: Figure 5 As shown. By Figure 5 It can be seen that the spreading rate of all quaternary alternative solders is higher than that of their benchmark commercial solders, which is consistent with the wetting angle results and further confirms that quaternary solders have good wettability.
[0093] Furthermore, based on the Ag-Cu-Pd-Ni quaternary thermodynamic database constructed in Example 1, this invention calculates the phase composition changes with temperature for two types of solders, 1-1#~5-1# and 1-2#~5-2#, across the entire temperature range. The calculation results are as follows: Figure 6 As shown in the figure, the stable phase composition of the quaternary metal brazing filler metal provided by the present invention within the service temperature range is controlled within 3% of the phase fraction of the benchmark commercial brazing filler metal, with only a slight phase transition temperature shift, and the phase composition remains highly consistent.
[0094] The above test results show that the Ag-Cu-Pd-Ni quaternary solder provided by this invention is comparable to or even slightly improved over comparable commercial solders in terms of melting characteristics, microstructure stability, wettability, and spreading performance. It is important to emphasize that the cost optimization achieved by this invention is not obtained by simply reducing the Pd content. Instead, it relies on the constructed Ag-Cu-Pd-Ni quaternary thermodynamic database. Through systematic calculation and screening of approximately 35,888 alloy compositions, and under the constraints of melting characteristics and microstructure stability, multi-element synergistic optimization is achieved: while reducing the Pd content by 8-25%, through the synergistic regulation of Ag and Cu, and the trace addition of Ni, a cost reduction of approximately 7.30% to 17.64% is ultimately obtained.
Claims
1. A design method for Ag-Cu-Pd quaternary metal solders, characterized in that, include: Step S1: Construct Gibbs energy models for each phase in the Ag-Cu-Pd quaternary metal system, calculate the thermodynamic parameters of pure components, binary and ternary components, and obtain a database of quaternary metal systems for predicting solidification paths, phase composition and phase transition temperatures. Step S2: Initialize the Ag / Cu ratio range and Pd content in the Ag-Cu-Pd quaternary metal system. Using the remaining metal element M as the control variable, calculate the equilibrium solidification through the database to obtain the melting temperature and melting range of the quaternary metal system. Step S3: Based on the melting temperature and melting range of the quaternary metal system, match the melting characteristics with the target brazing filler metal, and obtain the as-cast and service microstructures of the quaternary metal system within the matching range. Step S4: Based on the as-cast and service microstructure of the quaternary metal system in Step S3, match the microstructure and phase composition with the target brazing filler metal, and obtain the final quaternary metal brazing filler metal composition with the lowest cost as the constraint.
2. The design method of an Ag-Cu-Pd quaternary metal solder according to claim 1, characterized in that: The target solder is one of the commercial solders Pd287, Pd387, Pd481, Pd484 and Pd587; the remaining metal element M in the Ag-Cu-Pd quaternary metal system is one of Ni, In and Sn.
3. The design method of an Ag-Cu-Pd quaternary metal solder according to claim 1, characterized in that: The construction process of the Ag-Cu-Pd quaternary metal system database is as follows: (1) Establish the Gibbs energy functions of four pure components Ag, Cu, Pd and M in the standard element reference state respectively, as the basic data of pure components; (2) Based on the pure component basic data, the liquid phase and the ordered-disorder model are used to describe the liquid phase and solid phase in the binary subsystems Ag-Cu, Ag-Pd, Ag-M, Cu-Pd, Cu-M and Pd-M. The thermodynamic parameters of the Pd-Cu binary system are calculated from the phase equilibrium experimental data, while the other binary subsystems are from the literature data. (3) Based on the models and thermodynamic parameters of the liquid and solid phases in the binary subsystem, the thermodynamic parameters of each ternary system Ag-Pd-Cu, Ag-Pd-M, Pd-Cu-M and Ag-Cu-M are calculated using ternary phase equilibrium data; (4) Integrate all binary and ternary subsystems to obtain the Ag-Cu-Pd quaternary thermodynamic database.
4. The design method of an Ag-Cu-Pd quaternary metal solder according to claim 1, characterized in that: The Ag / Cu ratio in the initial Ag-Cu-Pd quaternary metal system ranges from 1.81 to 3.25; the Pd content in the initial Ag-Cu-Pd quaternary metal system is 3 to 25 wt.%.
5. The design method of an Ag-Cu-Pd quaternary metal solder according to claim 1, characterized in that: The process of matching the melting characteristics of the quaternary metal system with the target solder is as follows: by constraining the melting characteristics of the quaternary metal system and the target solder to be highly consistent, the melting characteristic composition range of the quaternary metal system is screened; the condition for the high consistency of melting characteristics is that the melting temperature of the quaternary metal system and the target solder is within ±2.5 ℃, and the melting range is ≤5 ℃.
6. The design method of an Ag-Cu-Pd quaternary metal solder according to claim 5, characterized in that: The process for obtaining the as-cast and service microstructures of the quaternary metal system is as follows: using Hill solidification and full-temperature phase fraction calculations, the as-cast and service microstructures within the range of melting characteristic composition are obtained.
7. The design method of an Ag-Cu-Pd quaternary metal solder according to claim 6, characterized in that: The process of matching the microstructure and phase composition of the quaternary metal system with the target solder is as follows: based on the as-cast and service microstructures within the range of melting characteristics, select the optimal composition range that is completely consistent with the as-cast microstructure of the target solder and has a phase fraction deviation of ≤3% at the service temperature.
8. The design method of an Ag-Cu-Pd quaternary metal solder according to claim 1, characterized in that: The as-cast and service microstructure of the quaternary metal system consists of a dark black α1 phase, a grayish-white α2 phase, and fine (α1+α2) eutectic phases.
9. The design method of an Ag-Cu-Pd quaternary metal solder according to claim 1, characterized in that: The (α1+α2) eutectic phase in the quaternary metal solder is inversely proportional to the Pd content in the quaternary metal system. When the Pd content is ≥23 wt.%, the (α1+α2) eutectic phase disappears.
10. An Ag-Cu-Pd quaternary metal solder, characterized in that: Obtained by the design method described in any one of claims 1 to 9.