High-precision linear palladium alloy wire, preparation method thereof and high-precision probe

Abstract

A high-precision linear palladium alloy wire, its preparation method, and a high-precision probe are disclosed. The palladium alloy wire comprises, by weight percentage: Pd 38-43%, Cu 25-35%, Ag 20-32%, and trace elements 0.01-2%, selected from at least one of Zn, Ni, B, Al, and In. The palladium alloy wire is obtained by at least three stages of precision drawing using a drawing assembly with a surface roughness Ra below 0.05 μm. The wire has a diameter below 0.8 mm, a surface roughness Ra below 0.05 μm, a diameter tolerance within ±0.002 mm, and a roundness within 0.001 mm. This invention, through comprehensive optimization of the palladium alloy wire's composition design and processing path, enables it to maintain small diameter tolerance, good roundness, and low surface roughness even under micro-diameter conditions, thereby improving the quality uniformity, testing stability, and accuracy of the probe array.

Description

Technical Field

[0001] This invention belongs to the field of chip test probe technology, and relates to a high-precision linear palladium alloy wire and its preparation method, particularly to a high-precision linear palladium alloy wire for probes, its preparation method, and a high-precision probe. Background Technology

[0002] With the rapid development of semiconductor technology, chip packaging forms and integration levels are constantly improving, and probe arrays in chip testing fixtures are evolving towards miniaturization and high density. Chip test probes are core contact elements in the electrical performance testing process of semiconductor chips. On the one hand, they perform electrical signal transmission; on the other hand, they establish stable mechanical contact through elastic deformation. Their conductivity, corrosion resistance, hardness, and contact resistance stability directly affect the accuracy and repeatability of test data. Palladium alloys, possessing excellent conductivity, corrosion resistance, high hardness, and relatively stable contact resistance, have become one of the important materials used for high-end chip test probes. The diameter of the test probe directly determines the achievable probe pitch and density; therefore, the palladium alloy wires used to prepare probes have much higher technical requirements than ordinary metal wires in terms of diameter accuracy, roundness, straightness, and surface roughness.

[0003] In practical applications, the probe diameter limits the minimum spacing of the array and also affects the effective contact area and contact pressure distribution at the contact points. As the number of chip I / Os and the integration density of a single chip continue to increase, the demand for probe diameters is constantly shifting towards ultra-fine specifications below φ0.6mm. Palladium alloy wires with diameters of φ0.4mm, φ0.3mm, φ0.2mm, and even smaller are gradually becoming the mainstream specifications. For these micro-sized palladium alloy wires and the linear probes made from them, actual production and use not only require achieving small diameters but also maintaining a high degree of consistency in diameter tolerances, roundness, straightness, and surface roughness to ensure stable contact resistance and sufficient service life even under high-density probe array conditions.

[0004] In the prior art, for example, invention patent application CN117310234A discloses a palladium alloy probe sleeve for semiconductor chip testing and its manufacturing method. This method uses a Pd-Ag-Cu low-palladium content alloy system, and obtains a rod through melting, extrusion, rotary forging, and multi-pass drawing. Then, it uses precision turning, drilling, and heat treatment to produce a palladium alloy probe sleeve with thin walls and flanged limiting structures, balancing conductivity, strength, wear resistance, and material cost. However, this invention mainly focuses on optimizing the structure and material cost of the probe sleeve. It does not specifically limit the alloy system of the linear palladium alloy probe body that directly contacts the chip pads, nor does it specify the diameter tolerance, roundness, and surface roughness control under micro-diameter conditions. Under the current conditions of commonly used conventional wire drawing and general-purpose wire drawing dies, it is still difficult to meet the requirements of high geometric accuracy and stable contact resistance for the probe body in high-density chip testing.

[0005] Similarly, Chinese patent application CN118191384A discloses a linear probe and its manufacturing method. This method involves threading an ultrafine wire through a high-straightness capillary, straightening it under vacuum annealing, fixing it to a UV protective film, then using laser cutting to achieve high-precision length determination, and finally forming the tip through acid pickling and electrochemical etching. However, this invention primarily focuses on the straightening, cutting, and sharpening processes of existing wires, treating the wire as a substrate with already acceptable dimensions. It does not address the specific design requirements for the alloy system of high-performance probe materials such as palladium alloys used in chip testing, or the drawing and geometric precision control within the micro-diameter range. Given that existing wire preparation processes often employ ordinary wire drawing and grinding, problems such as large diameter fluctuations, excessive roundness deviations, and insufficient straightness persist.

[0006] Therefore, how to provide a palladium alloy wire that can still have high dimensional accuracy, excellent geometric accuracy and surface quality under micro-diameter conditions and is suitable for high-density chip test probes is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0007] To address the shortcomings of the existing technologies, this invention provides a high-precision linear palladium alloy wire, its preparation method, and a high-precision probe, suitable for high-density chip testing. Through comprehensive optimization of the palladium alloy wire in terms of composition design and processing path, it maintains high-precision characteristics such as small diameter tolerance, surface roughness, and good roundness even under micro-diameter conditions, thereby improving the stability, uniformity, and testing accuracy of the probe array.

[0008] In a first aspect, the present invention provides a high-precision linear palladium alloy wire, wherein the palladium alloy wire comprises the following components by weight percentage:

[0009] Pd 38-43%,

[0010] Cu 25-35%,

[0011] Ag 20-32%,

[0012] Trace elements, 0.01–2%, selected from at least one of Zn, Ni, B, Al, and In;

[0013] The high-precision linear palladium alloy wire is obtained by at least three stages of precision drawing using a drawing assembly with a surface roughness Ra of less than 0.05 μm;

[0014] The palladium alloy wire has a diameter of less than 0.8 mm, a surface roughness Ra of less than 0.05 μm, a diameter tolerance of within ±0.002 mm, and a roundness of within 0.001 mm.

[0015] In this invention, by limiting the composition of the palladium alloy wire to 38-43% Pd, 25-35% Cu, 20-32% Ag, and 0.01-2% trace elements, a balanced relationship is achieved between the alloy's conductivity, corrosion resistance, and mechanical properties. On the one hand, the Pd and Ag content within the aforementioned range ensures that the palladium alloy probe possesses conductivity and chemical stability suitable for chip testing, maintaining relatively stable contact resistance under multiple pressing cycles and complex testing environments. On the other hand, by limiting the Cu and trace element content, the overall strength and hardness of the alloy are suitable for multi-pass cold drawing and subsequent forming of fine-gauge alloy wires, reducing the likelihood of excessive plastic deformation due to insufficient strength, and avoiding processing cracks and brittle fractures caused by over-strengthening. This also helps maintain the controllability of the cross-sectional shape and size of the wire during the diameter reduction process.

[0016] Meanwhile, using high-precision palladium alloy wire with a diameter less than 0.8 mm, a surface roughness Ra less than 0.05 μm, a diameter tolerance within ±0.002 mm, and a roundness within 0.001 mm as the base material is the fundamental condition for fabricating high-precision linear palladium alloy probes. The smaller diameter, combined with strictly controlled diameter tolerances and roundness, facilitates small-pitch arrangement in high-density arrays and ensures consistency in the crimping stroke and stress state of each probe, reducing contact pressure differences and contact resistance dispersion caused by geometric errors. The lower surface roughness helps reduce microscopic damage and wear at the probe-pad or solder ball contact interface, slowing the evolution of surface defects into electrical performance failure. This improves the stability and lifespan of the probe under long-term repeated testing conditions, meeting the comprehensive requirements of high-end chip testing for dimensional consistency and contact reliability of linear palladium alloy probes.

[0017] Employing a precision drawing method with at least three stages of successive diameter reduction ensures a smoother and more uniform interface between the palladium alloy wire and the die wall during the diameter reduction process. This effectively reduces the risk of friction scratches and localized biting, minimizing the sources of surface defects during drawing. Simultaneously, multi-stage segmented drawing facilitates the rational distribution of the total reduction amount across each process stage, preventing cross-sectional instability and dimensional springback caused by excessive deformation in a single stage. This allows the wire to maintain good cross-sectional shape retention and a stable deformation trajectory during the successive diameter reduction process. Consequently, the resulting palladium alloy wire, even with a fine diameter, maintains low surface roughness and controlled diameter tolerances and roundness, ensuring the fabrication of linear palladium alloy probes with high dimensional accuracy and high surface quality.

[0018] Preferably, the diameter of the palladium alloy wire is less than 0.6 mm, and the diameter tolerance is within ±0.001 mm.

[0019] Secondly, the present invention also provides a method for preparing the high-precision linear palladium alloy wire, comprising the following steps:

[0020] Step 1: Melt, cast, and solution treat the raw material of palladium alloy wire to obtain alloy rods;

[0021] Step 2: Roll the alloy bar, rough draw it, and trim it into an intermediate billet;

[0022] Step 3: Using a drawing assembly with a surface roughness Ra of less than 0.05 μm, perform at least 3 stages of precision drawing on the intermediate billet to obtain high-precision palladium alloy wire. The drawing speed is 10-20 m / min, and the reduction rate of each stage is 25-80%.

[0023] Step 4: Use a laser diameter gauge to detect the diameter of the palladium alloy wire online.

[0024] The preparation method of this invention uses a process path of "melting, solution treatment, rolling / rough drawing, and multi-stage precision drawing" to gradually transform palladium alloy from cast bar stock into micro-sized wire: the first two steps ensure the basic alloy composition and microstructure, forming an intermediate billet with relatively uniform size and surface condition; on this basis, a drawing assembly with low inner surface roughness is used and the total reduction amount is distributed to at least 3 stages of drawing, making the diameter reduction process more stable and controllable, which is beneficial to obtain a small diameter while taking into account the control of diameter tolerance, roundness and surface roughness, thereby obtaining a high-precision palladium alloy wire suitable for preparing high-precision linear palladium alloy probes.

[0025] After the final stage of precision drawing, the diameter of the palladium alloy wire is detected in real time online without contact using the equipped laser diameter measuring instrument. The detection data is then fed back to the control system. If the diameter tolerance of the palladium alloy wire exceeds ±0.002mm, preferably ±0.001mm, the system will issue an early warning and automatically adjust the tension to achieve closed-loop control for high-precision processing.

[0026] Preferably, in step three, after fine drawing with a reduction rate of 55% or more, an intermediate annealing treatment is performed. The conditions for the intermediate annealing treatment include: holding at 700–900°C for 20–60 minutes in a protective atmosphere or vacuum. More preferably, the intermediate annealing treatment is performed in an argon atmosphere at 750–850°C for 20–60 minutes.

[0027] This invention, by incorporating intermediate annealing after the drawing stage with a large cumulative reduction in surface area, releases the work hardening and internal stress accumulated during the initial cold working process, restoring the alloy's plasticity and reducing the risk of cracks and wire breakage during further drawing. It also helps stabilize the deformation behavior during subsequent diameter reduction. Limiting the annealing temperature and holding time within the aforementioned range allows for the avoidance of abnormal grain growth while balancing recovery and recrystallization, thus maintaining the required strength and plasticity balance of the palladium alloy wire. This provides the microstructure basis for achieving the target dimensions and geometric accuracy during subsequent diameter reduction. Furthermore, annealing in an argon atmosphere within a narrow temperature range helps suppress or reduce surface oxides, improving the metallic finish of the palladium alloy wire surface and reducing the probability of friction and surface defect formation during subsequent drawing. This contributes to improving the surface quality and contact performance of the final high-precision palladium alloy wire and the linear palladium alloy probe made from it.

[0028] Preferably, the drawing assembly includes a high-polycrystalline diamond drawing die with a surface roughness Ra of less than 0.03 μm, and each drawing die includes a lubrication zone, a compression zone, a sizing zone and a discharge zone in sequence;

[0029] The pull-out component satisfies at least one of the following:

[0030] (1) The curvature radius R1 of the lubrication zone, the curvature radius R2 of the compression zone, the curvature radius R3 of the sizing zone and the curvature radius R4 of the discharge zone satisfy: R1≥R4>R2>R3;

[0031] (2) The inner wall of the lubrication zone is provided with several feeding holes, which are connected to the lubricant feeding system to uniformly supply lubricant to the intermediate billet;

[0032] (3) The compression cone angle in the compression zone is between 8° and 12°;

[0033] (4) The ratio of the length of the sizing zone to the inner diameter is between 0.4 and 0.6.

[0034] In the above structure, the lubrication zone uses a larger radius of curvature, which helps guide the intermediate blank smoothly into the die hole and fully carry the lubricant, reducing the impact and scraping at the entrance. The compression zone uses a relatively smaller radius of curvature, so that the reduction of cross-sectional area is mainly concentrated in this area, which makes it easier to control the amount and uniformity of deformation. The sizing zone has the smallest radius of curvature and mainly undertakes the function of dimensional correction. By limiting the effective length of the sizing zone, the alloy wire is kept stably attached in this area, thereby accurately limiting the final diameter and improving the consistency of roundness and diameter tolerance. The radius of curvature of the discharge zone is between that of the lubrication zone and the compression zone. It matches the length of the sizing zone and provides a smooth transition for the alloy wire to leave the die. This allows the drawn palladium alloy wire to gradually release the force during demolding, reducing local friction and surface damage at the exit end, suppressing dimensional deviation and straightness deterioration caused by elastic rebound, and leaving a channel for the discharge and circulation of lubricant. This is beneficial to the stability of the entire drawing process and the dimensional accuracy and surface quality of the final wire.

[0035] The aforementioned optional features allow for further optimization of lubrication, deformation, and sizing conditions during the drawing process. Specifically, a feeding hole connected to a lubricant feeding system is provided on the inner wall of the lubrication zone, ensuring continuous and uniform lubricant replenishment as the intermediate blank enters the die hole. This helps reduce drawing force and frictional heat generation, lowers the risk of surface scratches and pulls, improves the surface quality of the palladium alloy wire, and extends die life. Limiting the compression cone angle of the compression zone to the range of 8° to 12° ensures necessary surface reduction efficiency while avoiding excessive angle leading to increased drawing resistance and stress concentration, or excessively long deformation zone and increased friction due to insufficient angle, thus achieving more stable and uniform plastic flow. Controlling the ratio of the length to the inner diameter of the sizing zone to 0.4–0.6 facilitates cross-sectional shaping and dimensional correction within a suitable contact length, allowing the palladium alloy wire to fully adhere to the die in the sizing zone to achieve good roundness and diameter tolerance, while avoiding excessive friction and heat accumulation caused by an excessively long sizing zone, thereby improving the overall dimensional control and stability of the drawing process.

[0036] Preferably, the lubricant comprises 0.1 to 5.0 wt% nanoparticles, wherein the nanoparticles comprise at least one of MoS2 and carbon materials;

[0037] The lubricant is kept at 35-45°C, more preferably at 40±2°C, by a heat-insulating and pressurizing device, and pressurized to 40-150MPa, more preferably 80-100MPa, and sprayed onto the surface of the intermediate billet through the feeding hole.

[0038] Preferably, all drawing dies in each drawing stage are provided with feeding holes. More preferably, the amount of lubricant sprayed from the feeding hole of the first drawing die in each stage is 1.2 to 1.5 times that of the feeding holes of subsequent drawing dies, and the feeding amount of each subsequent drawing die can be supplied at a uniform flow rate to ensure uniform lubrication throughout the process.

[0039] Furthermore, the lubricant is mainly an oil-based extreme pressure lubricant, based on mineral oil / synthetic oil, with added sulfur and phosphorus extreme pressure agents, adapted to high-strength alloys such as palladium alloys, and formulated with appropriate concentration ratios, and a heating and cooling system to ensure stable viscosity and lubrication of the oil.

[0040] The kinematic viscosity of the lubricant at 40°C and normal pressure is 800–2000 mm³ / s. 2 The viscosity-pressure coefficient at 40℃ is 15–22 GPa / s. -1 .

[0041] The average primary particle size of the carbon material is 5–100 nm, including graphite particles, carbon nanotubes, and fullerene C. 60 At least one of them.

[0042] In this invention, by selecting an oil-based extreme pressure lubricant based on mineral oil and / or synthetic oil, and adding a small amount of MoS2 and / or carbon nanoparticles, a lubricating film with high load-bearing capacity and low shear resistance is formed between the die wall and the palladium alloy wire. This significantly reduces the coefficient of friction and drawing force, and minimizes surface defects such as scratches and pulls. Limiting the viscosity and viscosity-pressure coefficient of the lubricant within the specified range, and continuously spraying it onto the surface of the intermediate blank through the feeding hole under suitable temperature and pressure, helps maintain a stable oil film and good fluidity under high contact pressure conditions. This makes the drawing process more stable and controllable, reduces temperature rise and dimensional fluctuations, thereby improving the surface quality and dimensional stability of the palladium alloy wire, and extending the service life of the drawing die.

[0043] Preferably, in each compression stage, 3 to 8 high-polycrystalline diamond wire drawing dies are used to complete multiple deformation passes, and the inner diameter of the sizing zone of each wire drawing die in the same stage is gradually reduced so that the area reduction rate of each deformation pass is 6 to 15%.

[0044] By employing multiple drawing dies to sequentially reduce the diameter in the same compression stage, and controlling the reduction rate per pass within the range of 6% to 15%, the originally large total deformation can be broken down into several gentler deformation steps. This allows for a more uniform distribution of stress and strain levels in the palladium alloy during each pass, reducing the risk of cracking, wire breakage, or cross-sectional instability during a single drawing process. Simultaneously, the gradual reduction of the inner diameter of the sizing zone in each drawing die facilitates the gradual correction of the cross-sectional shape and size, resulting in smoother metal flow, reduced radial springback and dimensional fluctuations. This, in turn, improves the diameter tolerance and roundness consistency of the micro-palladium alloy wire while ensuring sufficient diameter reduction efficiency, providing a reliable dimensional basis for the fabrication of high-precision linear palladium alloy probes.

[0045] Preferably, a high-precision palladium alloy wire is obtained by five-stage compression, and the area reduction rates of the five-stage fine drawing are 50-80%, 30-50%, 35-60%, 25-40%, and 30-50%, respectively.

[0046] By distributing the total reduction area across five drawing stages and ensuring that the reduction rates at each stage fall within the aforementioned range, the main diameter reduction can be achieved in the initial drawing stage, improving production efficiency. Simultaneously, sufficient "finishing space" is reserved in the middle and later drawing stages for gradual correction of the cross-sectional shape and dimensions. This staged reduction design helps avoid wire breakage, cracking, or excessive dimensional springback caused by excessive reduction rates at any single stage. It makes the overall drawing process more stable and controllable, helping to achieve fine diameters while maintaining the stability of geometric accuracy such as diameter tolerance and roundness, thereby obtaining high-precision palladium alloy wire that meets the requirements of high-precision linear palladium alloy probes.

[0047] Preferably, in the final stage of fine drawing, the surface roughness Ra of the high-polycrystalline diamond wire drawing die is below 0.01 μm, the drawing speed is 10 to 15 m / min, and the reduction rate of the area per pass is 6 to 10%.

[0048] Limiting the single-pass reduction ratio to 6-10% in the final drawing stage allows this stage to primarily serve as a dimensional finishing and surface quality control phase. This results in a relatively gentle deformation process with more uniform stress distribution, preventing excessive deformation near the target diameter that could lead to significant cross-sectional springback, dimensional fluctuations, or new surface defects. A smaller range of pass reduction ratios facilitates precise adjustment of the final diameter and roundness of the palladium alloy wire, stable control of diameter tolerances, and, combined with the deformation accumulation from the previous drawing stages, further improves the dimensional consistency and reliability of the finished high-precision palladium alloy wire used in the fabrication of linear palladium alloy probes.

[0049] Thirdly, based on the aforementioned high-precision linear palladium alloy wire, the present invention also provides a high-precision probe, which is processed by the high-precision linear palladium alloy wire, or processed by the high-precision linear palladium alloy wire obtained by the aforementioned preparation method.

[0050] The high-precision linear palladium alloy wire, its preparation method, and the high-precision probe provided by this invention have at least the following beneficial effects:

[0051] (1) By limiting the composition of the palladium alloy and designing the size and precision of the high-precision palladium alloy wire, the present invention enables the probe to have suitable conductivity, corrosion resistance and mechanical strength under the condition of micro diameter, and has strictly controlled size and geometric precision, which is beneficial to realize small needle spacing, reduce contact resistance dispersion and improve service life in high-density chip testing.

[0052] (2) The present invention adopts the process route of “melting, casting, solution treatment, rolling / rough drawing, multi-stage precision drawing, and probe processing”. In particular, it adopts a high-polycrystalline diamond wire drawing die with low inner hole surface roughness and limits the curvature radius relationship of the lubrication zone, compression zone, sizing zone and discharge zone, and comprehensively coordinates the deformation and heat treatment paths of each stage, so that the stress and deformation in the drawing process are more uniform, reducing the risk of wire breakage and cross-sectional instability. It is beneficial to obtain a fine diameter while stably controlling the diameter tolerance and roundness, thereby improving the dimensional consistency of high-precision palladium alloy wire and linear palladium alloy probes made from it.

[0053] (3) This invention uses an oil-based extreme pressure lubricant made from mineral oil and / or synthetic oil and incorporating nanoparticles. After heat preservation and pressurization, the lubricant is continuously sprayed onto the surface of the intermediate blank through the feeding hole in the lubrication zone. This forms a stable and effective lubricating film between the die wall and the palladium alloy wire during the drawing process, significantly reducing friction and temperature rise, minimizing surface scratches and pulls, and extending the service life of the drawing die. Combined with a multi-die, multi-pass drawing process and a graded reduction in surface area design, the entire preparation process is stable and controllable, with high yield and batch consistency, facilitating the stable mass production of high-precision linear palladium alloy probes based on existing equipment. Attached Figure Description

[0054] Figure 1 This is a flowchart illustrating the preparation process of the high-precision linear palladium alloy wire of this invention.

[0055] Figure 2 This is a schematic diagram of the structure of the drawing assembly of the present invention;

[0056] Figure 3 This is a front view of the pull-out assembly of the present invention.

[0057] Figure 4 This is a schematic diagram of the structure of the present invention, which forms five deformations through a drawing assembly during a certain stage of compression;

[0058] Figure 5 This is a photograph of a high-precision linear palladium alloy wire sample from Example 9 of the present invention.

[0059] Explanation of reference numerals in the attached figures:

[0060] 1-Drawing assembly, 10-Drawing die, 11-Lubrication zone, 12-Compression zone, 13-Sizing zone, 14-Discharge zone, 111-Feeding hole, 20-Die frame, 30-Die base. Detailed Implementation

[0061] To better understand the above technical solutions, a detailed description of the solutions will be provided below in conjunction with the accompanying drawings and specific embodiments. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0062] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a,” “the,” and “the” as used in the embodiments of this invention and the appended claims are also intended to include the plural forms, and “multiple” generally includes at least two unless the context clearly indicates otherwise.

[0063] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that an article or device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or device. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or device that includes said element.

[0064] This invention provides a high-precision linear palladium alloy wire with a diameter of less than 0.8 mm, preferably less than 0.6 mm, a surface roughness Ra of less than 0.05 μm, a diameter tolerance within ±0.002 mm, preferably within ±0.001 mm, and a roundness within 0.001 mm. In one preferred embodiment, the high-precision palladium alloy wire is obtained by at least three stages of fine drawing using a drawing assembly 1 with a surface roughness Ra of less than 0.05 μm, preferably less than 0.03 μm.

[0065] The high-precision palladium alloy wire comprises the following components by weight percentage:

[0066] (1) Pd, 38-43%;

[0067] (2) Cu, 25-35%,

[0068] (3) Ag, 20-32%,

[0069] (4) Trace elements, 0.01-2%, selected from at least one of Zn, Ni, B, Al and In.

[0070] In a specific embodiment of the present invention, palladium alloy can be prepared into a high-precision palladium alloy wire and further processed into a probe through the following process, such as... Figure 1 As shown, it includes the following steps:

[0071] Step 1: Melt the raw materials of palladium alloy wire according to the above ratio, and cast the alloy rod in a vacuum or protective atmosphere at a casting speed of 5-8 mm / s to prepare the alloy rod.

[0072] Solution treatment is performed under vacuum or protective atmosphere conditions to obtain alloy bars with relatively uniform microstructure and composition;

[0073] Step 2: Roll and rough draw the alloy bar to gradually reduce the diameter of the bar. Then, finish the surface through straightening, turning or grinding processes to obtain an intermediate billet with straightness and surface condition suitable for precision drawing.

[0074] Step 3: Using drawing assembly 1 with a surface roughness Ra≤0.05μm, perform at least 3 stages of precision drawing on the intermediate billet, with a drawing speed of 10~20m / min, and control the surface reduction rate of each stage within the range of 25~80%, preferably within the range of 25~75%, to obtain high-precision palladium alloy wire;

[0075] Step 4: Use a laser diameter gauge to detect the diameter of the palladium alloy wire online;

[0076] Optional step five: Prepare a high-precision probe by cutting, end forming and cleaning a high-precision palladium alloy wire.

[0077] In one preferred embodiment, after fine drawing with a reduction rate of more than 60%, intermediate annealing is performed. The conditions for intermediate annealing include: holding at 700-900°C for 20-60 minutes in a protective atmosphere or vacuum.

[0078] See Figure 2 and Figure 3 As shown, in the embodiments of the present invention, the drawing assembly 1 and its respective drawing dies 10 have the following characteristics:

[0079] The drawing assembly 1 preferably includes a high-polycrystalline diamond drawing die 10. Each drawing die 10 is fixed in a corresponding die frame 20. The die hole of the drawing die 10 sequentially includes a lubrication area 11, a compression area 12, a sizing area 13, and a discharge area 14. The radius of curvature R1 of the lubrication area 11 is ( Figure 2 The radius of curvature R2 of the compression region 12 (corresponding to 2β) Figure 2 The radius of curvature R3 of the sizing zone 13 and the radius of curvature R4 of the discharge zone 14 (corresponding to 2α) Figure 2The relationship between R1 and R4 (corresponding to 2γ) satisfies R1≥R4>R2>R3. By setting the above curvature radius relationship, the intermediate billet is subjected to more stable force and flow during the process of entering the die hole, undergoing plastic deformation, completing sizing, and leaving the die. This helps to reduce friction and surface damage during the drawing process and improve the diameter accuracy, roundness, and surface quality of the final palladium alloy wire.

[0080] The inner wall of the lubrication zone 11 is provided with several feeding holes 111, which are connected to a lubricant feeding system (not shown) for uniformly supplying lubricant to the intermediate blank. In a preferred embodiment of the invention, the drawing lubricant is an oil-based extreme pressure lubricant with mineral oil and / or synthetic oil as the base oil. 0.1–5.0 wt% of nanoparticles may be added to the lubricant, including at least one of MoS2 and carbon materials; the average primary particle size of the carbon material is preferably 5–100 nm, for example, graphite particles, carbon nanotubes, or fullerene C60. The lubricant is kept at 35–45°C (preferably 40±2°C) and pressurized to 40–150 MPa (preferably 80–100 MPa) by a heat-insulating pressurizer, and then sprayed onto the surface of the intermediate blank through the feeding holes in the inner wall of the lubrication zone. This allows the lubricant to form a stable lubricating oil film between the die orifice and the palladium alloy wire, thereby reducing the coefficient of friction and drawing force, reducing the risk of surface scratches and pulls, and helping to extend the service life of the drawing die. In some embodiments, the kinematic viscosity of the lubricant at 40°C and normal pressure is controlled to be between 100 and 2000 mm³. 2 / s, viscosity-pressure coefficient controlled at 40℃ is 15~22GPa. -1 This ensures suitable flowability and load-bearing capacity even under high contact pressure conditions. In one preferred embodiment, during each compression stage, 3 to 8 high-polycrystalline diamond drawing dies are arranged sequentially to complete multiple deformation passes. The inner diameter of the sizing zone of each drawing die in the same stage gradually decreases, so that the reduction rate of each pass in that stage is controlled at 6% to 15%. Through the above-mentioned multi-die, multi-pass diameter reduction method, the deformation amount in a single pass is limited to a small range, making the diameter reduction process more stable, which helps to reduce the risk of wire breakage and improve the consistency of the final diameter and roundness.

[0081] The compression cone angle α of the compression zone 12 is set in the range of 8° to 12° to balance the surface reduction efficiency and deformation stability.

[0082] The ratio of the length L of the sizing zone 13 to the inner diameter D is controlled between 0.4 and 0.6. Since the diameter of the intermediate billet entering the multi-stage precision drawing is approximately 1.5 to 2.0 mm, according to the target diameter of the drawn alloy wire, the value of D in the drawing die is approximately 0.2 to 2.0 mm, that is, the value of L is approximately 0.08 to 1.2 mm, preferably 0.1 to 1 mm, so as to complete the cross-section shaping and dimensional correction within a moderate contact length, while avoiding excessive friction and heat generation.

[0083] like Figure 4 As shown, in some preferred embodiments, a multi-pass drawing method can be adopted in each stage of compression, where multiple drawing assemblies 1 are connected in series. That is, in the same stage of compression, 3 to 8 high-polycrystalline diamond drawing dies 10 are arranged sequentially to complete multiple passes of deformation, and are clamped and fixed by a die frame 30 to form a continuous drawing die group. The inner diameter of the sizing zone of each drawing die 10 in the same stage gradually decreases, so that the reduction rate of deformation in each pass in that stage is controlled within the range of 6% to 15%. By distributing the total reduction amount to multiple passes, the deformation in a single pass can be slowed down, the risk of wire breakage can be reduced, and it is beneficial to refine and stabilize the diameter and cross-sectional shape after each pass.

[0084] In a further preferred embodiment, a 5-stage precision drawing process is employed, with 3 to 8 high-polycrystalline diamond drawing dies 10 used in each stage of compression. The reduction rates of the surface area for each stage of precision drawing are sequentially set within the ranges of 50-80%, 30-50%, 35-60%, 25-40%, and 30-50%. Preferably, the reduction rates of the surface area for each stage of precision drawing are sequentially set within the ranges of 55-70%, 30-40%, 40-50%, 25-35%, and 30-40%. By rationally allocating the reduction rates at each stage, the initial stage of drawing completes the main diameter reduction task, while the middle and later stages of drawing balance diameter reduction with cross-sectional finishing, thereby improving processing efficiency while enhancing the geometric accuracy and dimensional stability of the high-precision palladium alloy wire.

[0085] In another preferred embodiment, in the final stage of fine drawing, the surface roughness Ra of the high-polycrystalline diamond wire drawing die is below 0.01 μm, the drawing speed is 10–15 m / min, and the reduction rate of deformation in each pass is controlled at 6–10%. The small reduction rate per pass allows the final stage of drawing to mainly play the role of dimensional finishing and shape correction, which is beneficial for finely adjusting the final diameter and roundness of the palladium alloy wire when approaching the target diameter. This ensures that the resulting high-precision linear palladium alloy probe can still meet the strict diameter tolerance and geometric accuracy requirements under micro-diameter conditions.

[0086] Preparation Examples A1-A7

[0087] Preparation examples A1-A7 differ in alloy composition; specific differences for each preparation example are shown in Table 1.

[0088] Table 1

[0089]

[0090] Examples 1-7

[0091] Step 1: Using the raw materials in the proportions of Preparation Examples A1-A7 respectively, palladium alloy casting rods are prepared by vacuum induction melting and casting process. The melting temperature is 1300℃ and the holding time is 30min to ensure uniform composition.

[0092] Solution treatment was performed at 800℃ in a vacuum, and the temperature was maintained for 2 hours. After water quenching, an initial bar with a diameter of 12mm was obtained.

[0093] Step 2: The palladium alloy bar is rolled into a square bar through multiple passes, then annealed, rough drawn, and finally peeled and trimmed to obtain an intermediate billet with a diameter of φ1.8mm.

[0094] Step 3: Using a drawing assembly 1 consisting of multiple high-polycrystalline diamond wire drawing dies 10 with a surface roughness Ra of less than 0.05 μm, the intermediate billet is subjected to three-stage precision drawing at a drawing speed of 10-20 m / min.

[0095] Each high-polycrystalline diamond wire drawing die 10 includes a lubrication zone 11, a compression zone 12, a sizing zone 13, and a discharge zone 14 in sequence; and the curvature radius R1 of the lubrication zone 11, the curvature radius R2 of the compression zone 12, the curvature radius R3 of the sizing zone 13, and the curvature radius R4 of the discharge zone 14 satisfy: R1≥R4>R2>R3.

[0096] The drawing assembly 1 has several feeding holes 111 on the inner wall of the lubrication zone of the drawing die 10, which are connected to a lubricant feeding system to uniformly supply lubricant to the intermediate blank. The lubricant is 2.0 wt% MoS2, which is kept at 40°C and pressurized to 100 MPa by a heat preservation and pressurization device and sprayed onto the surface of the intermediate blank through the feeding holes. The compression cone angle α of each drawing die parameter is approximately 10°, and the ratio of the length of the sizing zone to the inner diameter (L / D) is approximately 0.5.

[0097] The Level 3 precision drawing process is carried out in a clean room at a constant temperature (23±1℃), including:

[0098] The first-stage drawing process uses five high-polycrystalline diamond wire drawing dies with a surface roughness Ra below 0.05 μm, a drawing speed of 18 m / min, and a reduction in surface area per pass of approximately 13.4%, 13.6%, 14.8%, 13.6%, and 14.3% (controlled between 12% and 15%). The surface area reduction rate for the first-stage drawing is approximately 53%.

[0099] Two-stage drawing was performed using seven high-polycrystalline diamond dies with a surface roughness Ra below 0.03 μm. The drawing speed was 15 m / min, and the reduction in surface area per pass was approximately 11.8%, 11.6%, 11.2%, 11.0%, 10.5%, 10.2%, and 10.0% (controlled between 10% and 12%). The reduction in surface area for the two-stage drawing was approximately 55%. After the two-stage drawing, the bar was annealed in an argon atmosphere. The annealing temperature was adjusted between 750 and 850 °C according to the alloy composition and melting point of Examples 1-7, and the holding time was 30 min.

[0100] The process involves three stages of drawing, using six high-polycrystalline diamond dies with a surface roughness Ra below 0.01 μm, a drawing speed of 10 m / min, and a reduction rate of approximately 11.6%, 11.0%, 10.5%, 10.0%, 9.5%, and 8.5% per pass (controlled between 6% and 12%). The total reduction rate for the three stages of drawing is approximately 48%, resulting in a high-precision palladium alloy wire with a diameter of φ0.6 mm.

[0101] Step 4: The laser diameter gauge at the final stage of fine drawing shows that the diameter tolerance of the high-precision palladium alloy wire in Examples 1-7 can be controlled within ±0.001mm.

[0102] Example 8

[0103] The difference between this embodiment and Embodiment 1 is that the annealing treatment after the second-stage drawing is omitted in this embodiment. Laser diameter measuring instrument testing shows that the diameter tolerance of the high-precision palladium alloy wire in Embodiment 8 is within +0.0012 mm to -0.001 mm.

[0104] Example 9

[0105] The difference between this embodiment and Embodiment 1 is that a high-precision palladium alloy wire with a diameter of 0.4mm is obtained by performing three-stage precision drawing on an intermediate billet with a diameter of φ1.6mm, including:

[0106] The first stage of drawing was performed using five high-polycrystalline diamond wire drawing dies with a surface roughness Ra below 0.05 μm. The drawing speed was 18 m / min, and the reduction rate per pass was approximately 15%, 14.7%, 13.8%, 15%, and 14.1% (controlled between 12% and 15%). The reduction rate of the first stage of drawing was approximately 63.5%. The alloy wire was then annealed in an argon atmosphere at a temperature of 800℃ for 30 min.

[0107] Two-stage drawing was performed using seven high-polycrystalline diamond wire drawing dies with a surface roughness Ra below 0.03 μm. The drawing speed was 15 m / min, and the reduction rate per pass was approximately 13.7%, 14.3%, 14.8%, 13%, 15%, 14.7%, and 13.8% (controlled between 12% and 15%). The reduction rate for the two-stage drawing was approximately 66%. The alloy wire was then annealed in an argon atmosphere at 800℃ for 30 min.

[0108] Three-stage drawing is performed using seven high-polycrystalline diamond drawing dies with a surface roughness Ra below 0.01 μm. The drawing speed is 10 m / min, and the reduction rate per pass is approximately 8%, 8.7%, 9.5%, 10.5%, 11.8%, 10%, and 7% (controlled between 6% and 12%). The reduction rate of the three-stage drawing is approximately 50%, resulting in a high-precision palladium alloy wire with a diameter of φ0.4 mm.

[0109] Step 4: Laser diameter measuring instrument testing showed that the diameter tolerance of the high-precision palladium alloy wire in Example 9 was within the range of +0.0009 mm to -0.0007 mm, and the sample photograph showed that the palladium alloy wire had a uniform and smooth surface. Figure 5 .

[0110] Example 10

[0111] The difference between this embodiment and Embodiment 9 is that a high-precision palladium alloy wire with a diameter of 0.4mm is obtained by performing a 5-stage precision drawing on an intermediate billet with a diameter of φ1.6mm, including:

[0112] The first-stage drawing process uses six high-polycrystalline diamond wire drawing dies with a surface roughness Ra below 0.05 μm and a drawing speed of 18 m / min. The area reduction per pass is approximately 15%, 14.7%, 13.8%, 13.6%, 14.8%, and 14.7% (controlled between 12% and 15%). With slightly faster drawing, the area reduction per pass is approximately 61%. The alloy wire is then annealed in an argon atmosphere at 800℃ for 30 min.

[0113] Two-stage drawing was performed using four high-polycrystalline diamond dies with a surface roughness Ra below 0.03 μm. The drawing speed was 16 m / min, and the reduction rates per pass were approximately 10.8%, 10%, 11%, and 10.7% (controlled between 10% and 12%). The reduction rate for the two-stage drawing was approximately 36%.

[0114] The process involves three stages of drawing, using six high-polycrystalline diamond dies with a surface roughness Ra below 0.03 μm, a drawing speed of 15 m / min, and a reduction in surface area per pass of approximately 8.8%, 9.6%, 8.3%, 9%, 9.9%, and 9.7% (controlled between 8% and 10%). The total reduction in surface area across the three stages is approximately 44%.

[0115] Four-stage drawing is performed using three high-polycrystalline diamond wire drawing dies with a surface roughness Ra below 0.02 μm. The drawing speed is 12 m / min, and the area reduction rate per pass is approximately 10%, 11.1%, and 12.5% ​​(controlled between 10% and 15%). The area reduction rate for the four-stage drawing is approximately 30%.

[0116] Five-stage drawing is performed using six high-polycrystalline diamond drawing dies with a surface roughness Ra below 0.01μm. The drawing speed is 10m / min, and the reduction rate per pass is approximately 6.6%, 7.1%, 7%, 6.3%, 6.8%, and 9% (controlled between 6% and 10%). The reduction rate of the five-stage drawing is approximately 36%, resulting in a high-precision palladium alloy wire with a diameter of φ0.4mm.

[0117] Step 4: Laser diameter measuring instrument test results show that the diameter tolerance of the high-precision palladium alloy wire in Example 10 is within the range of +0.0007mm to -0.0005mm.

[0118] Example 11

[0119] The difference between this embodiment and Embodiment 9 is that the compression cone angle α of each drawing die compression zone is 15°. Laser diameter measuring instrument testing shows that the diameter tolerance of the high-precision palladium alloy wire in Embodiment 11 is within ±0.0012 mm.

[0120] Example 12

[0121] The difference between this embodiment and Embodiment 9 is that the ratio (L / D) of the length to the inner diameter of each wire drawing die sizing zone is 0.65. Laser diameter measuring instrument testing shows that the diameter tolerance of the high-precision palladium alloy wire in Embodiment 12 is within ±0.0013 mm.

[0122] Example 13

[0123] The difference between this embodiment and Embodiment 9 is that lubricant is provided only in the lubrication zone feed hole of the first drawing die in each stage of drawing. Laser diameter measuring instrument testing shows that the diameter tolerance of the high-precision palladium alloy wire in Embodiment 13 is within +0.0015mm to -0.0012mm.

[0124] Comparative Example 1

[0125] The difference between this embodiment and embodiment 9 is that step three uses a two-stage drawing process to reduce the surface area, including:

[0126] The first-stage drawing process employed eight high-polycrystalline diamond wire drawing dies with a surface roughness Ra below 0.05 μm. The drawing speed was 16 m / min, and the reduction in surface area per pass was approximately 19.5%, 18.6%, 18.3%, 18.7%, 17.2%, 18%, 18.6%, and 16.7% (controlled between 15% and 20%). The first-stage drawing yielded a surface area reduction of approximately 80%. The alloy wire was then annealed in an argon atmosphere at 800℃ for 30 minutes.

[0127] Two-stage drawing is performed using eight high-polycrystalline diamond wire drawing dies with a surface roughness Ra below 0.01 μm. The drawing speed is 10 m / min, and the reduction rate per pass is approximately 13.8%, 13%, 13.3%, 13.5%, 13.3%, 13.3%, 14.2%, and 13.4% (controlled between 12% and 15%). The reduction rate of the two-stage drawing is approximately 69%.

[0128] Laser diameter measuring instrument tests showed that the diameter tolerance of the palladium alloy wire in Comparative Example 1 was within +0.0040 mm to -0.0031 mm.

[0129] Comparative Example 2

[0130] The difference between Comparative Example 2 and Example 9 is that Comparative Example 2 uses a conventional wire drawing die (surface roughness Ra higher than 0.05 μm) for three-stage drawing. Laser diameter measuring instrument tests show that the diameter tolerance of the palladium alloy wire in Comparative Example 2 is within ±0.005 mm.

[0131] Test methods and results

[0132] 1. Dimensional error detection

[0133] The diameter of the samples from Examples 1-13 and Comparative Examples 1-2 was tested. Three samples were selected for each group, and the average of the three diameters measured at the front end, midpoint, and rear end of each sample along its length was taken as the sample diameter. The maximum error value was calculated based on the diameter of each sample.

[0134] 2. Roundness

[0135] Referring to the current roundness measurement standard, no less than 10 samples were randomly selected from the palladium alloy wires of each embodiment and comparative example. The cross-section of each wire was measured on a roundness meter, and the maximum true roundness deviation was recorded as the roundness value of the sample. The maximum and average roundness values ​​of the batch of samples were also calculated.

[0136] 3. Surface roughness Ra

[0137] Referring to current surface roughness measurement standards, such as using a contact surface roughness meter, select no less than 3 measurement positions along the axial direction on the outer surface of each sample wire, set appropriate sampling length and evaluation length, measure and record the Ra value, and take the average value of Ra at each measurement point as the surface roughness characterization of the sample.

[0138] The test results are shown in Table 2:

[0139] Table 2

[0140]

[0141] As can be seen from the comparison of test results of the embodiments and comparative examples, the present invention has the following advantages:

[0142] 1. Extremely high dimensional accuracy: Through the "short sizing" mold design, optimized drawing path and online detection feedback, this invention can stably produce palladium alloy wire for probes with diameter tolerance within ±0.002mm, especially within ±0.001mm (as in Examples 1-7, 9 and 10), with excellent roundness, which fully meets the stringent requirements of high-end chip test probes.

[0143] 2. Excellent surface quality: This invention utilizes the high hardness and high smoothness of polycrystalline diamond (PCD) wire drawing dies combined with an optimized lubrication zone design to ensure a defect-free wire surface. The roughness Ra value can be stably controlled below 0.05 μm, as shown in Examples 1-13. Figure 5 Furthermore, PCD molds have extremely high wear resistance, which is dozens of times higher than that of cemented carbide, greatly reducing the frequency of mold replacement and ensuring the stability and economy of mass production.

[0144] 3. Low wire breakage rate and high yield: Multi-stage precision drawing and reasonable reduction rate allocation, as well as timely online intermediate heat treatment, effectively manage the work hardening of materials, significantly reduce the risk of wire breakage during the micro-filament drawing process, and increase the yield by more than 20%.

[0145] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention. Clearly, those skilled in the art can make various alterations and modifications to the invention without departing from its spirit and scope. Thus, if these modifications and modifications of the invention fall within the scope of the claims and their equivalents, the invention is also intended to include these modifications and modifications.

Claims

1. A method for preparing a high-precision linear palladium alloy wire, characterized in that, The palladium alloy wire comprises the following components by weight percentage: Pd 38-43%, Cu 25-35%, Ag 20-32%, Trace elements, 0.01–2%, selected from at least one of Zn, Ni, B, Al, and In; The palladium alloy wire has a diameter of less than 0.8 mm, a surface roughness Ra of less than 0.05 μm, a diameter tolerance of within ±0.002 mm, and a roundness of within 0.001 mm. The preparation method includes the following steps: Step 1: Melt, cast, and solution treat the raw material of palladium alloy wire to obtain alloy rods; Step 2: Roll the alloy bar, rough draw it, and trim it into an intermediate billet; Step 3: Using a drawing assembly with a surface roughness Ra of less than 0.05 μm, at least three stages of precision drawing are performed on the intermediate billet to obtain high-precision palladium alloy wire. The drawing assembly includes a high-polycrystalline diamond drawing die, and each drawing die includes a lubrication zone, a compression zone, a sizing zone, and a discharge zone in sequence. In each compression stage, 3 to 8 high-polycrystalline diamond drawing dies are used to complete multiple deformation passes at a drawing speed of 10 to 20 m / min. The surface reduction rate of each stage is 25% to 80%. The inner diameter of the sizing zone of each drawing die within the same stage gradually decreases so that the surface reduction rate of each deformation pass is 6% to 15%. In the final precision drawing stage, the surface roughness Ra of the high-polycrystalline diamond drawing die is less than 0.01 μm. Step 4: Use a laser diameter gauge to detect the diameter of the palladium alloy wire online; The pull-out assembly meets the following requirements: The curvature radii R1 of the lubrication zone, R2 of the compression zone, R3 of the sizing zone, and R4 of the discharge zone satisfy the following condition: R1≥R4>R2>R3; The compression cone angle in the compression zone is between 8° and 12°; The ratio of the length L of the sizing zone to the inner diameter D is between 0.4 and 0.

6.

2. The preparation method according to claim 1, characterized in that, The diameter of the palladium alloy wire is less than 0.6 mm, and the diameter tolerance is within ±0.001 mm.

3. The preparation method according to claim 1, characterized in that, In step three, after fine drawing with a reduction rate of more than 55%, intermediate annealing is performed. The conditions for intermediate annealing include: holding at 700-900℃ for 20-60 minutes in a protective atmosphere or vacuum.

4. The preparation method according to any one of claims 1-3, characterized in that, The inner wall of the lubrication zone is provided with several feeding holes, which are connected to the lubricant feeding system to uniformly supply lubricant to the intermediate blank.

5. The preparation method according to claim 4, characterized in that, The lubricant comprises 0.1 to 5.0 wt% nanoparticles, wherein the nanoparticles include at least one of MoS2 and carbon materials.

6. The preparation method according to claim 5, characterized in that, The lubricant is kept at 35-45°C by a heat preservation and pressurization device, and then pressurized to 40-150MPa before being sprayed onto the surface of the intermediate billet through the feeding hole.

7. The preparation method according to any one of claims 1-3, characterized in that, High-precision palladium alloy wire is obtained by five-stage precision drawing, with the area reduction rates of the five stages being 50-80%, 30-50%, 35-60%, 25-40%, and 30-50%, respectively.

8. The preparation method according to claim 7, characterized in that, In the final stage of fine drawing, the drawing speed is 10-15 m / min, and the reduction rate of surface area per pass is 6-10%.

9. A high-precision probe, characterized in that, It is prepared by processing the high-precision linear palladium alloy wire obtained by the preparation method according to any one of claims 1-8.

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