Probe card structure and preparation method thereof
By employing plasma cleaning and gradient temperature sintering of the nano-silver paste layer in the probe card, the signal integrity and mechanical strength issues of the probe card under high frequency and high temperature environments were solved, achieving a highly reliable and lightweight probe card structure.
Patent Information
- Application Number
- CN202510963741.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-14
- Publication Date
- 2025-10-28
AI Technical Summary
Existing probe cards have difficulty balancing signal integrity, mechanical strength, and reliability in high-frequency, miniaturized, and high-temperature environments. Traditional bonding solutions also suffer from weak interface bonding and poor process compatibility.
Plasma cleaning is used to activate the surface of multilayer ceramic substrates and optoelectronic modules to form a composite metal layer. A nano-silver paste layer is then sintered at a gradient temperature. Combined with specific structural design and processes, a high-strength, electrically and thermally conductive adhesive structure is formed.
It significantly improves the mechanical strength, thermal conductivity and reliability of the probe card, ensuring stability and signal integrity in high-frequency and high-temperature environments, and realizing high-precision miniaturized design.
Smart Images
Figure CN120847449A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of semiconductor packaging technology, and in particular to a method for preparing a probe card structure and the probe card structure itself. Background Technology
[0002] The semiconductor testing industry has developed rapidly in recent years, moving towards high-frequency, millimeter-wave / terahertz, high-power devices such as GaN, and high-density 3D packaging. This trend places higher demands on probe cards, as they play a crucial role in semiconductor testing, directly impacting the accuracy and efficiency of test results. As electronic products continue to miniaturize and increase in performance, semiconductor chips are becoming increasingly integrated, and testing environments are becoming more complex. This necessitates that probe cards operate stably under harsh conditions such as high frequency and high temperature. In high-frequency signal transmission, probe cards must possess excellent signal integrity to ensure undistorted signals, which is crucial for high-speed transmission. High-power testing requires probe cards to withstand high currents and possess excellent heat dissipation and high-temperature resistance to prevent overheating from affecting test accuracy. Furthermore, high-density packaging technology requires probe cards to adapt to smaller spaces and more complex connection methods to meet the increasing integration demands. Therefore, improving probe card performance is crucial for driving the development of the semiconductor testing industry.
[0003] In semiconductor test probe cards, there are three main conventional methods for bonding optoelectronic modules (PL Blocks) to multilayer ceramic (MLC) substrates. The first is adhesive bonding, typically using epoxy resin or conductive adhesive. The second is soldering / sintering, such as silver paste sintering or laser soldering. The third is mechanical fastening, commonly using screws or clips to achieve the connection. These methods, in the early stages of the semiconductor testing industry, were able to meet the needs to a certain extent and achieve the connection between optoelectronic modules and multilayer ceramic substrates within a limited scope.
[0004] However, the aforementioned technologies have significant drawbacks. Adhesive-based solutions suffer from performance defects; traditional adhesives exhibit significant dielectric loss at high frequencies, affecting signal transmission integrity. Furthermore, their performance degrades easily at high temperatures, and shrinkage during curing can lead to warping of multilayer ceramic substrates, making them more prone to delamination after thermal cycling. Welding / sintering solutions also face challenges. Their interfacial bonding is weak, and the adhesion of the metallization layer on the ceramic surface is substandard, resulting in low shear strength. In addition, this process is complex and accompanied by side effects, such as oxidation of metal components due to excessively high sintering temperatures. Laser welding equipment is expensive, and the welded area is brittle with poor vibration resistance. Mechanical fixing solutions also have drawbacks. They introduce parasitic capacitance, interfering with high-frequency signals; simultaneously, this solution increases the overall thickness of the probe card, raising manufacturing costs. Overall, these technologies struggle to meet the comprehensive requirements of electrical, thermal, and mechanical performance. Insufficient interfacial bonding in the process leads to poor long-term reliability, and they suffer from low compatibility with the trends of high-frequency and miniaturization, resulting in low yield rates. Summary of the Invention
[0005] In order to achieve a good connection between the multilayer ceramic substrate and the optoelectronic module and improve the stability and reliability of the probe card, this application provides a method for fabricating the probe card structure and the probe card structure.
[0006] On the one hand, this application provides a method for preparing a probe card structure, which adopts the following technical solution: A method for preparing a probe card structure includes the following steps: S1. Provides multilayer ceramic substrates and optoelectronic modules; S2. Perform plasma cleaning on the first surface of the multilayer ceramic substrate and the second surface of the optoelectronic module to activate the first surface and the second surface; S3. A composite metal layer is formed on the first surface of the multilayer ceramic substrate; S4. A nano-silver paste layer is formed on the second surface of the optoelectronic module; S5. The optoelectronic module is disposed on the multilayer ceramic substrate, wherein the nano silver paste layer is connected to the composite metal layer. S6. The nano-silver paste layer is subjected to gradient temperature sintering to form a sintered silver layer.
[0007] By employing the above technical solution, a novel composite bonding path is formed by plasma cleaning and activation of the surfaces to be bonded between the multilayer ceramic substrate and the optoelectronic module, forming a composite metal layer on the ceramic substrate, and then sintering a nano-silver paste layer at a gradient temperature. This solution systematically solves the problems of poor performance of traditional adhesive solutions, weak interfacial bonding of traditional sintering solutions, and poor process compatibility. It can form a bonding structure with high mechanical strength, high thermal and electrical conductivity, and high reliability, significantly improving the overall performance and stability of the probe card.
[0008] Optionally, in step S1, the first surface of the multilayer ceramic substrate is provided with a plurality of first recesses for setting the optoelectronic module; the second surface of the optoelectronic module is provided with a second recess for forming the nano-silver paste layer, and the second recess is connected to the periphery of the optoelectronic module through radially extending connecting grooves.
[0009] Using the above technical solution, the first recess on the multilayer ceramic substrate can provide a shallow groove for auxiliary positioning of the optoelectronic module during assembly, improving positioning accuracy. The second recess and connecting groove on the optoelectronic module have a dual effect: on the one hand, accommodating most of the nano-silver paste within the recess effectively controls the thickness of the adhesive layer, thereby reducing the stacking height and achieving the goal of thinner probe cards. On the other hand, the connecting groove acts as an exhaust channel during the nano-silver paste coating process, effectively preventing bubble formation and ensuring a uniform and dense adhesive layer.
[0010] Optionally, in step S3, the composite metal layer is deposited on the inner surface of the first recess using a sputtering process; in step S4, nano silver paste is coated onto the second recess using a screen printing process to form the nano silver paste layer, wherein the nano silver paste layer extends beyond the second recess; in step S5, the optoelectronic module is disposed at the first recess on the multilayer ceramic substrate to connect the nano silver paste layer with the composite metal layer.
[0011] Using the above technical solution, the sputtering process precisely deposits the composite metal layer within the first recess, defining the bonding area. This saves precious metal materials, reduces costs, and avoids the formation of unnecessary conductive paths in non-functional areas. The use of screen printing to coat the nano-silver paste allows for precise control of the paste's thickness and shape. Allowing the nano-silver paste layer to slightly extend beyond the second recess ensures a sufficient and reliable physical and electrical connection with the composite metal layer during subsequent bonding and sintering.
[0012] Optionally, in step S3, a titanium layer, a nickel layer, and a gold layer are sequentially deposited on the first surface of the multilayer ceramic substrate to form the composite metal layer, wherein the thickness of the titanium layer is 30 nm to 70 nm, the thickness of the nickel layer is 80 nm to 120 nm, and the thickness of the gold layer is 150 nm to 250 nm.
[0013] Using the above technical solution, the composite metal layer composed of titanium, nickel, and gold layers exhibits a synergistic enhancement effect: the titanium layer (Ti) enhances the adhesion to the multilayer ceramic substrate; the nickel layer (Ni), as an intermediate barrier layer, effectively prevents the interdiffusion of titanium and gold, thereby improving the long-term stability of the interface; and the gold layer (Au), due to its excellent oxidation resistance and conductivity, provides an ideal affinity interface for subsequent sintering of nano-silver paste. This design fundamentally solves the problem of insufficient bonding between the metal layer and the ceramic substrate in traditional solutions, and is key to achieving high shear strength (40 MPa).
[0014] Optionally, in step S6, the gradient temperature sintering includes a preheating stage, a pressure sintering stage, and an annealing stage performed sequentially. The preheating stage is performed at a temperature of 70°C to 90°C for 3 to 7 minutes. The pressure sintering stage is performed at a temperature of 160°C to 200°C and a pressure of 3MPa to 7MPa for 8 to 12 minutes. The annealing stage is performed at a temperature of 230°C to 270°C for 1 to 3 minutes.
[0015] By employing the above technical solution, the precisely controlled gradient temperature sintering three-stage process can achieve the best sintering effect: the preheating stage gently removes the solvent to avoid defects; the pressure sintering stage applies pressure to form a dense sintered silver layer at a lower temperature (compared to traditional high-temperature sintering), effectively reducing thermal shock and thermal stress on the components; the final annealing stage is used to release and eliminate residual stress, significantly enhancing the toughness and fatigue resistance of the bonded structure, thereby ensuring the long-term reliability of the probe under harsh thermal cycling.
[0016] Optionally, the method for fabricating the probe card structure further includes: S7. A ring-shaped protective layer is formed around the sintered silver layer.
[0017] By employing the above technical solution, the annular protective layer added around the sintered silver layer can effectively protect the edges of the bonded structure. It prevents the edges of the sintered silver layer from oxidizing due to exposure to air, while also buffering external mechanical impacts and vibrations, further enhancing the environmental resistance and mechanical reliability of the entire bonded structure.
[0018] On the other hand, this application also provides a probe card structure, which adopts the following technical solution: A probe card structure, comprising: A multilayer ceramic substrate has a first surface after activation treatment, on which a composite metal layer is formed; An optoelectronic module is disposed on the multilayer ceramic substrate. The optoelectronic module has a second surface after activation treatment. A sintered silver layer is formed on the second surface. The sintered silver layer is connected to the composite metal layer. The sintered silver layer is formed by sintering a nano-silver paste layer formed on the second surface at a gradient temperature.
[0019] Using the above technical solution, the probe card structure has a composite bonding interface, which is composed of an activated surface, a composite metal layer, and a gradient sintered silver layer. This structure fundamentally solves the problems of weak interfacial bonding and poor reliability of traditional bonding structures, giving it very high shear strength and excellent thermal cycling stability. At the same time, due to the presence of the sintered silver layer, it has the characteristics of low high-frequency loss, which can meet the requirements of harsh testing environments such as high frequency and high temperature.
[0020] Optionally, the first surface of the multilayer ceramic substrate is provided with a plurality of first recesses for setting the optoelectronic module; the second surface of the optoelectronic module is provided with a second recess for forming the nano-silver paste layer, and the second recess is connected to the periphery of the optoelectronic module through radially extending connecting grooves; the composite metal layer is deposited on the inner surface of the first recess by a sputtering process; the nano-silver paste layer is formed at the second recess by a screen printing process, wherein the nano-silver paste layer extends beyond the second recess; the optoelectronic module is disposed at the first recess on the multilayer ceramic substrate to connect the nano-silver paste layer and the composite metal layer.
[0021] By employing the above technical solution, the first and second recessed structures included in the probe card structure ensure the precise positioning of the optoelectronic module, while simultaneously achieving further thinning of the overall structure. Furthermore, the presence of the connecting groove means that the sintered silver layer inside is formed without the risk of air bubbles, resulting in a more uniform and dense silver layer, thus ensuring higher consistency and reliability of the bonding points.
[0022] Optionally, the composite metal layer includes a titanium layer, a nickel layer, and a gold layer sequentially deposited on the first surface of the multilayer ceramic substrate, wherein the thickness of the titanium layer is 30 nm to 70 nm, the thickness of the nickel layer is 80 nm to 120 nm, and the thickness of the gold layer is 150 nm to 250 nm.
[0023] Using the above technical solution, the composite metal layer in the probe card structure consists of three layers: titanium, nickel, and gold. In achieving a highly reliable multilayer film structure, the titanium layer ensures a strong bond with the ceramic substrate, while the nickel layer plays a crucial role in improving the long-term stability of the interface. Furthermore, the presence of the gold layer further guarantees a high-quality connection with low resistance and oxidation resistance between it and the sintered silver layer.
[0024] Optionally, the sintered silver layer is formed by gradient temperature sintering of a nano-silver paste layer formed on the second surface, wherein the gradient temperature sintering includes a preheating stage, a pressure sintering stage, and an annealing stage performed sequentially. The preheating stage is performed at a temperature of 70°C to 90°C for 3 to 7 minutes. The pressure sintering stage is performed at a temperature of 160°C to 200°C and a pressure of 3MPa to 7MPa for 8 to 12 minutes. The annealing stage is performed at a temperature of 230°C to 270°C for 1 to 3 minutes.
[0025] Using the above technical solution, the sintered silver layer in the probe card structure is fabricated through a specific gradient temperature sintering process. This means that compared to traditional sintered silver layers, this sintered silver layer exhibits higher lattice structure stability, fewer defects, and lower residual stress, thanks to its application in electronic packaging and its innovation in power semiconductor device sintering technology. The microstructural characteristics of the probe card, especially the excellent toughness and fatigue resistance of the bonding points, ensure that it can maintain stable chip testing performance even under long-term exposure to harsh temperature changes and mechanical shocks.
[0026] In summary, this application includes at least one of the following beneficial technical effects: 1. A novel composite bonding path was formed by plasma cleaning and activation of the surfaces to be bonded between a multilayer ceramic substrate and an optoelectronic module, followed by the formation of a composite metal layer on the ceramic substrate, and then gradient temperature sintering of a nano-silver paste layer. This solution systematically solves the problems of poor performance of traditional adhesive solutions, weak interfacial bonding of traditional sintering solutions, and poor process compatibility. It can form a bonding structure with high mechanical strength, high thermal and electrical conductivity, and high reliability, significantly improving the overall performance and stability of the probe card.
[0027] 2. The first recess on the multilayer ceramic substrate provides a shallow groove for auxiliary positioning of the optoelectronic module during assembly, improving positioning accuracy. The second recess and connecting groove on the optoelectronic module have a dual effect: on the one hand, by containing most of the nano-silver paste within the recess, the thickness of the adhesive layer can be effectively controlled, reducing the overall stacking height and achieving a thinner probe card; on the other hand, the connecting groove acts as an venting channel when coating the nano-silver paste, preventing the formation of air bubbles and ensuring the uniformity and density of the adhesive layer.
[0028] 3. The composite metal layer with a specific structure (titanium / nickel / gold layer) exhibits a significant synergistic strengthening effect: the titanium layer (Ti) enhances the adhesion to the multilayer ceramic substrate; the nickel layer (Ni), acting as an intermediate barrier layer, effectively prevents the interpenetration of titanium and gold, ensuring long-term interface stability; and the gold layer (Au), with its excellent oxidation resistance and conductivity, provides an ideal affinity interface for the subsequent sintering of the nano-silver paste. This design fundamentally solves the problem of insufficient bonding between the metal layer and the ceramic substrate in traditional solutions, and is key to achieving high shear strength (40MPa).
[0029] 4. Optimal sintering results can be achieved through a precisely controlled gradient temperature sintering three-stage process: the preheating stage gently removes the solvent and prevents the formation of defects; the pressure sintering stage uses pressure to form a dense sintered silver layer at a relatively low temperature (compared to traditional high-temperature sintering), significantly reducing thermal shock and thermal stress on components; the final annealing stage is used to release and eliminate residual stress, significantly enhancing the toughness and fatigue resistance of the bonded structure, thereby ensuring the long-term reliability of the probe under harsh thermal cycling. Attached Figure Description
[0030] Figure 1 This is a schematic flowchart of the preparation method of the probe card structure according to an embodiment of this application; Figure 2 This is a schematic diagram of the structure of a multilayer ceramic substrate according to an embodiment of this application; Figure 3 This is a schematic diagram of the structure of the optoelectronic module according to an embodiment of this application; Figure 4 It is execution Figure 1 A partial sectional view of the structure after step S3; Figure 5 It is execution Figure 1 A sectional view of the structure after step S4; Figure 6 It is execution Figure 1 A partial sectional view of the structure after step S5; Figure 7 Is execution Figure 1 A partial sectional view of the structure after step S6; Figure 8 It is execution Figure 1 A partial sectional view of the structure after step S7; Figure 9 This is a schematic diagram of the probe card structure according to an embodiment of this application.
[0031] Explanation of reference numerals in the attached figures: 10, multilayer ceramic substrate; 11, first surface; 12, first recess; 20, optoelectronic module; 21, second surface; 22, second recess; 23, connecting groove; 30, composite metal layer; 31, titanium layer; 32, nickel layer; 33, gold layer; 40, nano silver paste layer; 41, sintered silver layer; 50, annular protective layer. Detailed Implementation
[0032] The following is in conjunction with the appendix Figures 1-9 This application will be described in further detail.
[0033] This application discloses a method for preparing a probe card structure.
[0034] Figure 1 This is a schematic flowchart illustrating the fabrication method of the probe card structure according to an embodiment of this application. (Refer to...) Figure 1 The method includes the following steps: S1. Provides a multilayer ceramic substrate 10 and an optoelectronic module 20.
[0035] S2. Perform plasma cleaning on the first surface 11 of the multilayer ceramic substrate 10 and the second surface 21 of the optoelectronic module 20 to activate the first surface 11 and the second surface 21.
[0036] S3. A composite metal layer 30 is formed on the first surface 11 of the multilayer ceramic substrate 10.
[0037] S4. A nano-silver paste layer 40 is formed on the second surface 21 of the optoelectronic module 20.
[0038] S5. The optoelectronic module 20 is disposed on the multilayer ceramic substrate 10, wherein the nano silver paste layer 40 is connected to the composite metal layer 30.
[0039] S6. The nano-silver paste layer 40 is subjected to gradient temperature sintering to form a sintered silver layer 41.
[0040] S7. A ring-shaped protective layer 50 is formed around the sintered silver layer 41.
[0041] The steps of the method are described in detail below with reference to the accompanying drawings. It should be noted that the accompanying drawings are merely schematic diagrams, intended to clearly illustrate the structural composition and interrelationships of the invention. The dimensions, proportions, and spacing of the components shown in the drawings may not be drawn strictly to actual scale, nor do they represent the precise dimensional relationships of the actual product. Their main purpose is to facilitate understanding of the configuration and interaction of the various technical features of the invention. In actual manufacturing, the specific dimensions and proportions of each component will be adjusted according to actual needs and design optimizations.
[0042] In step S1, a multilayer ceramic substrate 10 and an optoelectronic module 20 are provided.
[0043] Figure 2 This is a schematic diagram of the structure of a multilayer ceramic substrate according to an embodiment of this application. (Refer to...) Figure 2 The first surface 11 of the multilayer ceramic substrate 10 is provided with a plurality of first recesses 12 for mounting the optoelectronic module 20. The shape and opening size of the first recesses 12 are precisely matched to the optoelectronic module 20, and are slightly larger than the module to ensure fit (the size range is approximately the outer contour of the optoelectronic module 20), and their depth is controlled between 0.5μm and 2μm, designed to accommodate the subsequently deposited composite metal layer 30, and to serve as shallow trenches to assist in the precise positioning and mounting of the optoelectronic module 20.
[0044] Figure 3 This is a schematic diagram of the structure of the optoelectronic module according to an embodiment of this application. (Refer to...) Figure 3 The second surface 21 of the optoelectronic module 20 is provided with a second recess 22, and the second recess 22 is connected to the periphery of the optoelectronic module 20 through radially extending connecting grooves 23. This design ensures that the nano-silver paste is accurately filled into the second recess 22, and after bonding, the thickness of the adhesive layer is mainly limited within the height range of the optoelectronic module 20 itself. Placing most of the nano-silver paste in the pre-set recess of the optoelectronic module 20 can effectively reduce the total stacking height after bonding, thereby achieving a thin and light design of the probe card. In addition, the connecting grooves 23 around the periphery help to vent air during the coating of nano-silver paste, prevent the formation of air bubbles, and ensure uniform filling of nano-silver paste. The depth of the second recess 22 can be about 6μm to 9μm, so that after the subsequent filling and sintering of nano-silver paste, its surface will slightly exceed the second recess 22 (for example, exceeding by 0.5μm to 3μm), thereby ensuring a reliable electrical and mechanical connection with the composite metal layer 30 deposited on the multilayer ceramic substrate 10.
[0045] In step S2, plasma cleaning is performed on the first surface 11 of the multilayer ceramic substrate 10 and the second surface 21 of the optoelectronic module 20 to activate the first surface 11 and the second surface 21.
[0046] In the plasma cleaning process, for example, an Ar / O2 mixed gas can be used to clean the first surface 11 and the second surface for approximately 2 to 5 minutes at a power of 200W to 400W. Plasma cleaning can be performed using radio frequency plasma cleaning equipment or microwave plasma cleaning equipment, both of which can achieve cleaning and activation of the first surface 11 and the second surface 21. During the cleaning process, high-energy particles in the plasma bombard the first surface 11 and the second surface 21, removing contaminants and breaking chemical bonds, thereby activating the surface and increasing the adhesion of materials in subsequent processes. For example, oil, dust, and other impurities that may have been present on the first surface 11 and the second surface 21 will be completely removed after plasma cleaning, making the surface clean and active, creating favorable conditions for subsequent metal layer deposition and nano-silver paste coating.
[0047] In step S3, a composite metal layer 30 is formed on the first surface 11 of the multilayer ceramic substrate 10.
[0048] Figure 4 It is execution Figure 1 A partial sectional view of the structure after step S3. (Refer to...) Figure 4 The composite metal layer 30 can be deposited on the inner surface of the first recess 12 via sputtering on the first surface 11 of the multilayer ceramic substrate 10 after plasma cleaning. By depositing the composite metal layer 30 only in the specific areas requiring bonding (i.e., within the first recess 12), material costs and processing time can be effectively saved. Furthermore, depositing the composite metal layer 30 in non-bonding areas can avoid introducing unnecessary conductive paths, altering surface properties, or causing other potential problems in subsequent processes.
[0049] The composite metal layer 30 can be a multilayer structure composed of a titanium layer 31, a nickel layer 32, and a gold layer 33. A magnetron sputtering apparatus is used in the sputtering process, which can precisely control the deposition thickness of the composite metal layer 30 and ensure its uniformity. The titanium layer 31 is first deposited on the multilayer ceramic substrate 10, and its thickness is relatively thin, for example, between 30 nm and 70 nm. The nickel layer 32 is then deposited on the titanium layer 31, and its thickness is thicker than that of the titanium layer 31, for example, between 80 nm and 120 nm. The gold layer 33 is finally deposited on the nickel layer 32, and its thickness is the thickest, for example, between 150 nm and 250 nm. That is, the thicknesses of the titanium layer 31, the nickel layer 32, and the gold layer 33 increase sequentially in the direction away from the multilayer ceramic substrate 10.
[0050] The titanium layer 31 exhibits good activity and can form a good chemical bond with the multilayer ceramic substrate 10, providing excellent adhesion. As the first layer in direct contact with the multilayer ceramic substrate 10, the relatively thin titanium layer 31 can effectively promote wetting and bonding with the ceramic, while avoiding excessive internal stress due to excessive thickness. The nickel layer 32, as a key barrier layer, effectively prevents the interdiffusion between the titanium layer and the subsequent gold layer 33, thereby enhancing the stability of the interface. Its moderate thickness serves as a barrier without significantly increasing the overall film thickness. The gold layer 33 exhibits excellent conductivity and oxidation resistance, while also showing good compatibility with the subsequently sintered nano-silver paste, which helps to build a tight and low-resistance connection. The relatively thick gold layer 33 can provide more interfacial active sites, accelerating the sintering and diffusion process of nano-silver, thereby strengthening the bonding strength between the sintered silver layer 41 and the composite metal layer 30.
[0051] In step S4, a nano-silver paste layer 40 is formed on the second surface 21 of the optoelectronic module 20.
[0052] Figure 5 It is execution Figure 1 A sectional view of the structure after step S4. (Refer to...) Figure 5 The nano-silver paste can be uniformly coated onto the second recess 22 on the second surface 21 of the optoelectronic module 20 using a screen printing process to form the nano-silver paste layer 40, which slightly extends beyond the second recess 22. The nano-silver particles in the nano-silver paste are mostly around 25 nanometers in diameter, generally between 25-50 nm, and the mass percentage of the nano-silver particles in the nano-silver paste is 80% to 90%.
[0053] The screen printing process can utilize semi-automatic or fully automatic screen printing machines, which can precisely control the coating amount and thickness of the nano-silver paste. The nano-silver paste possesses certain fluidity and good sintering properties, allowing the small-diameter nano-silver particles to fuse better during sintering, forming a dense sintered silver layer 41. During the coating process, the coating thickness needs to be precisely controlled between 8 μm and 12 μm. This is because if the coating is too thick, the sintered silver layer may be excessively thick, affecting the accuracy and performance of adhesion; if the coating is too thin, sufficient bonding force may not be formed. At this thickness, the nano-silver paste layer 40 is at a moderate thickness, while ensuring that the surface slightly protrudes from the second recess 22 after sintering, thereby ensuring a reliable electrical and mechanical connection between the nano-silver paste layer 40 and the composite metal layer 30 deposited on the multilayer ceramic substrate 10.
[0054] In step S5, the optoelectronic module 20 is disposed on the multilayer ceramic substrate 10, wherein the nano silver paste layer 40 is connected to the composite metal layer 30.
[0055] Figure 6 It is execution Figure 1 A partial sectional view of the structure after step S5. (Refer to...) Figure 6 The photoelectric module 20 is disposed at the first recess 12 on the multilayer ceramic substrate 10 to connect the nano silver paste layer 40 with the composite metal layer 30.
[0056] In step S6, the nano-silver paste layer 40 is subjected to gradient temperature sintering to form a sintered silver layer 41.
[0057] Figure 7 It is execution Figure 1 A partial sectional view of the structure after step S6. (Refer to...) Figure 7 The process involves gradient temperature sintering of the nano-silver paste layer 40, which includes a preheating stage, a pressurized sintering stage, and an annealing stage performed sequentially. This gradient temperature sintering process is meticulously designed and optimized to address issues such as warping of the multilayer ceramic substrate 10, insufficient interface reliability, and high residual stress caused by single-temperature or simple segmented sintering processes. By precisely controlling the temperature, time, and pressure at each stage, this process achieves low-temperature, high-density sintering of the nano-silver paste while minimizing the thermal stress impact on the multilayer ceramic substrate 10 and the optoelectronic module 20, thereby significantly improving the reliability of the bonding and the overall performance of the probe card. The preheating stage is conducted at 70°C to 90°C for 3 to 7 minutes. This stage aims to gently promote the full and uniform evaporation of volatile solvents in the nano-silver paste layer. This temperature range is chosen to ensure slow solvent evaporation, avoiding the formation of bubbles or splashing of solvent within the paste due to rapid heating, which could affect the density and uniformity of the sintered silver layer. Meanwhile, this temperature is much lower than the sintering initiation temperature of the silver particles, effectively preventing premature sintering of the nano-silver particles at this stage and preserving the activity required for the subsequent pressure sintering stage. A hot air circulating oven is preferably used in this stage, as its hot air circulation mechanism ensures a highly uniform temperature distribution within the chamber, thereby guaranteeing a consistent solvent evaporation rate throughout the entire nano-silver paste layer in the planar direction. This is a crucial prerequisite for obtaining a high-performance sintered silver layer 41. Uneven solvent evaporation may lead to uneven silver layer density or the formation of micropores during subsequent sintering, thus affecting conductivity and mechanical strength.
[0058] The pressure sintering stage involves sintering at a temperature of 160°C to 200°C and a pressure of 3MPa to 7MPa for 8 to 12 minutes. This is a crucial step in the densification of the silver nanoparticles. Within this temperature range, silver particles with a diameter of less than 50 nanometers, due to their high surface energy and size effect, begin to undergo significant neck growth and atomic diffusion, leading to initial fusion and ultimately forming a dense sintered silver layer 41 with a certain strength. The external pressure (3MPa to 7MPa) specifically introduced in this application is significantly different from the pressureless sintering or capillary force sintering commonly used in related technologies. The applied pressure enhances the physical contact between the silver nanoparticles, shortens the atomic diffusion path, thereby effectively reducing the sintering temperature and shortening the sintering time, while also inhibiting the formation of pores during the sintering process. Under the action of pressure, the silver nanoparticles are tightly compacted, and the gaps between them are effectively eliminated, which greatly improves the density and strength of the sintered silver layer 41, endowing it with excellent electrical conductivity close to that of bulk silver and excellent thermal conductivity. Furthermore, through precise coordinated control of temperature and pressure using hot-press sintering equipment, this stage can avoid material degradation or stress damage that may be caused to the multilayer ceramic substrate 10 and the optoelectronic module 20 by traditional high-temperature sintering, thus achieving flexible and low-temperature bonding.
[0059] The annealing stage is conducted at a temperature of 230°C to 270°C for 1 to 3 minutes. The purpose of this stage is to release and eliminate residual stress generated during the sintering process at the interface between the sintered silver layer 41 and the multilayer ceramic substrate 10 and the optoelectronic module 20. If residual stress is not effectively eliminated, it may lead to microcracks or even delamination failure in the bonded area during long-term use, especially under temperature cycling or mechanical shock. By performing short-time annealing within a specific temperature window, the lattice structure inside the sintered silver layer 41 can be rearranged and relaxed, allowing internal defects (such as dislocations) to be repaired and eliminated to a certain extent, thus making the lattice structure inside the sintered silver layer 41 more stable and uniform. This significantly enhances the toughness and fatigue resistance of the sintered silver layer 41 and ultimately improves the long-term reliability of the entire bonded structure. A high-temperature annealing furnace can be used for precise temperature control in this stage to ensure the annealing effect.
[0060] This application, through the ingenious combination of the above three-stage gradient temperature sintering process, not only effectively ensures the density and uniformity of the nano-silver paste sintering, but also significantly improves the mechanical strength, electrothermal performance and long-term reliability of the bonding between the multilayer ceramic substrate 10 and the optoelectronic module 20 through pressure assistance and stress release mechanisms. This is a technical effect that is difficult to achieve simultaneously by using adhesives, traditional welding / sintering or mechanical fixing methods alone in related technologies.
[0061] In step S7, an annular protective layer 50 is formed around the sintered silver layer 41.
[0062] Figure 8 It is execution Figure 1 A partial sectional view of the structure after step S7. Figure 9 This is a schematic diagram of the probe card structure according to an embodiment of this application. (Refer to...) Figure 8 and Figure 9 A ring of high-temperature resistant silicone can be coated around the sintered silver layer 41 to form the annular protective layer 50, thus completing the probe card structure. Silicone has excellent high-temperature resistance, withstanding temperatures up to 300℃. A dispensing machine can be used to apply the silicone, precisely controlling the application position and amount. The main function of the annular protective layer 50 is to prevent edge oxidation, protect the sintered silver layer 41 from external environmental corrosion, and provide additional protection against mechanical impact. For example, in practical applications, the product may encounter external forces such as vibration and collisions. In such cases, the annular protective layer 50 can effectively buffer these forces, ensuring the integrity of the sintered silver layer 41 and the bonded structure.
[0063] To verify the technical effect of the above-mentioned probe card structure preparation method in improving the bonding reliability between the multilayer ceramic substrate 10 and the optoelectronic module 20, the method of this application was compared with typical adhesive solutions (epoxy adhesive) and traditional silver paste sintering solutions in related technologies. The results are shown in Table 1. Table 1 Performance indicators This application Epoxy adhesive (comparison) Silver sintering (contrast) Shear strength (MPa) 42.5 18.2 25.7 Strength retention rate after thermal cycling 98％ 55％ 82％ High-frequency loss (40GHz) 0.08dB 0.35dB 0.15dB Minimum bonding precision (μm) ±3 ±15 ±5 As shown in Table 1, the shear strength of the probe card structure prepared using the method of this application reaches 42.5 MPa, significantly higher than the 18.2 MPa of traditional epoxy adhesive and the 25.7 MPa of silver sintering. This is attributed to the plasma activation and composite metallization layer design adopted in this application, which successfully overcomes the problem of weak adhesion between ceramic and silver paste interfaces, significantly increasing the shear strength to over 40 MPa, far exceeding the 25 MPa limit of traditional methods. The high shear strength directly demonstrates the strong bonding of the adhesive interface, providing a solid guarantee for the structural stability under complex stress environments. Thermal cycling tests verified that the probe card structure prepared using this method maintains a strength retention rate of up to 98%, far exceeding the 55% of epoxy adhesive and the 82% of silver sintering. This indicates that the probe card structure prepared using the method of this application can still maintain its initial mechanical properties after undergoing severe temperature changes, significantly reducing the risk of delamination after long-term use. This high reliability is achieved through the combined use of interface metallization and gradient sintering, enabling it to maintain long-term stability in high-temperature and high-frequency environments. Regarding high-frequency performance, the probe card structure fabricated using the method described in this application exhibits a high-frequency loss of only 0.08 dB at 40 GHz, significantly lower than the 0.35 dB of epoxy adhesive and the 0.15 dB of silver sintering. This advantage ensures that signal integrity is not degraded by the adhesive layer in high-frequency applications such as 5G / 6G communication, meeting the stringent requirements for low dielectric loss in millimeter-wave / terahertz testing. The probe card structure fabricated using the method described in this application achieves a minimum bonding accuracy of ±3 μm, significantly better than the ±15 μm of epoxy adhesive and the ±5 μm of silver sintering. This method demonstrates higher accuracy in miniaturization scenarios, effectively avoiding probe misalignment caused by adhesive overflow and coefficient of thermal expansion (CTE) mismatch, particularly meeting the high-density packaging requirements of MEMS probe cards.
[0064] The implementation principle of the probe card structure fabrication method in this application embodiment is as follows: Plasma cleaning and activation are performed on the surfaces to be bonded, namely the multilayer ceramic substrate 10 and the optoelectronic module 20, to form the composite metal layer 30 on the multilayer ceramic substrate 10. Then, the nano-silver paste layer 40 is sintered at a gradient temperature, forming a novel composite bonding path. This solution systematically solves the problems of poor performance of traditional adhesive solutions, weak interfacial bonding force of traditional sintering solutions, and poor process compatibility. It can form a bonding structure with high mechanical strength, high thermal and electrical conductivity, and high reliability, significantly improving the overall performance and stability of the probe card.
[0065] This application also discloses a probe card structure, which is prepared according to the preparation method of the probe card structure in the above embodiments.
[0066] Refer again Figures 2 to 9 The probe card structure includes a multilayer ceramic substrate 10, a photoelectric module 20, a composite metal layer 30, and a sintered silver layer 41.
[0067] The multilayer ceramic substrate 10 has a first surface 11 after activation treatment, on which a composite metal layer 30 is formed. The first surface 11 of the multilayer ceramic substrate 10 has a plurality of first recesses 12 for mounting the optoelectronic module 20. The composite metal layer 30 is deposited on the inner surface of the first recesses 12 by a sputtering process. The optoelectronic module 20 is mounted on the multilayer ceramic substrate 10 and has a second surface 21 after activation treatment. A sintered silver layer 41 is formed on the second surface 21 and is connected to the composite metal layer 30. The sintered silver layer 41 is formed by gradient temperature sintering of a nano-silver paste layer 40 formed on the second surface 21. The second surface 21 of the optoelectronic module 20 has second recesses 22 for forming the nano-silver paste layer 40, and the second recesses 22 are connected to the periphery of the optoelectronic module 20 through radially extending connecting grooves 23. The nano-silver paste layer 40 is formed at the second recess 22 by a screen printing process, wherein the nano-silver paste layer 40 extends beyond the second recess 22. The optoelectronic module 20 is disposed at the first recess 12 on the multilayer ceramic substrate 10 to connect the nano-silver paste layer 40 to the composite metal layer 30.
[0068] The composite metal layer 30 includes a titanium layer 31, a nickel layer 32, and a gold layer 33 sequentially deposited on the first surface 11 of the multilayer ceramic substrate 10, wherein the thickness of the titanium layer 31 is 30 nm to 70 nm, the thickness of the nickel layer 32 is 80 nm to 120 nm, and the thickness of the gold layer 33 is 150 nm to 250 nm.
[0069] The sintered silver layer 41 is formed by gradient temperature sintering of a nano-silver paste layer 40 formed on the second surface 21. The gradient temperature sintering includes a preheating stage, a pressure sintering stage, and an annealing stage performed sequentially. The preheating stage is performed at a temperature of 70°C to 90°C for 3 to 7 minutes. The pressure sintering stage is performed at a temperature of 160°C to 200°C and a pressure of 3MPa to 7MPa for 8 to 12 minutes. The annealing stage is performed at a temperature of 230°C to 270°C for 1 to 3 minutes.
[0070] The implementation principle of a probe card structure in this application is as follows: The probe card structure has a composite adhesive interface consisting of an activated surface, a composite metal layer 30, and a sintered silver layer 41 formed by gradient sintering. This structure fundamentally solves the problems of weak interfacial bonding and poor reliability of traditional adhesive structures, giving it very high shear strength and excellent thermal cycling stability. At the same time, due to the presence of the sintered silver layer, it has the characteristics of low high-frequency loss, which can meet the requirements of harsh testing environments such as high frequency and high temperature.
[0071] The above are all preferred embodiments of the present application, and are not intended to limit the scope of protection of the present application. Therefore, any equivalent changes made based on the structure, shape, and principle of the present application should be included in the scope of protection of the present application.
Claims
1. A method for preparing a probe card structure, characterized in that, Includes the following steps: S1. Provide a multilayer ceramic substrate (10) and an optoelectronic module (20); S2. Plasma cleaning is performed on the first surface (11) of the multilayer ceramic substrate (10) and the second surface (21) of the optoelectronic module (20) to activate the first surface (11) and the second surface (21). S3. Form a composite metal layer (30) on the first surface (11) of the multilayer ceramic substrate (10); S4. Form a nano-silver paste layer (40) on the second surface (21) of the optoelectronic module (20); S5. The optoelectronic module (20) is disposed on the multilayer ceramic substrate (10), wherein the nano silver paste layer (40) is connected to the composite metal layer (30); S6. The nano-silver paste layer (40) is subjected to gradient temperature sintering to form a sintered silver layer (41).
2. The method for preparing the probe card structure according to claim 1, characterized in that, In step S1, the first surface (11) of the multilayer ceramic substrate (10) is provided with a plurality of first recesses (12) for setting the optoelectronic module (20); the second surface (21) of the optoelectronic module (20) is provided with second recesses (22) for forming the nano silver paste layer (40), and the second recesses (22) are connected to the periphery of the optoelectronic module (20) through radially extending connecting grooves (23).
3. The method for preparing the probe card structure according to claim 2, characterized in that, In step S3, the composite metal layer (30) is deposited on the inner surface of the first recess (12) by a sputtering process; in step S4, nano silver paste is coated on the second recess (22) by a screen printing process to form the nano silver paste layer (40), wherein the nano silver paste layer (40) extends beyond the second recess (22); in step S5, the optoelectronic module (20) is disposed on the first recess (12) on the multilayer ceramic substrate (10) to connect the nano silver paste layer (40) with the composite metal layer (30).
4. The method for preparing the probe card structure according to claim 1, characterized in that, In step S3, a titanium layer (31), a nickel layer (32) and a gold layer (33) are sequentially deposited on the first surface (11) of the multilayer ceramic substrate (10) to form the composite metal layer (30), wherein the thickness of the titanium layer (31) is 30 nm to 70 nm, the thickness of the nickel layer (32) is 80 nm to 120 nm, and the thickness of the gold layer (33) is 150 nm to 250 nm.
5. The method for preparing the probe card structure according to claim 1, characterized in that, In step S6, the gradient temperature sintering includes a preheating stage, a pressure sintering stage, and an annealing stage performed sequentially. The preheating stage is performed at a temperature of 70°C to 90°C for 3 to 7 minutes. The pressure sintering stage is performed at a temperature of 160°C to 200°C and a pressure of 3MPa to 7MPa for 8 to 12 minutes. The annealing stage is performed at a temperature of 230°C to 270°C for 1 to 3 minutes.
6. The method for preparing the probe card structure according to claim 1, characterized in that, Also includes: S7. A ring-shaped protective layer (50) is formed around the sintered silver layer (41).
7. A probe card structure, characterized in that, include: A multilayer ceramic substrate (10) has a first surface (11) after activation treatment, on which a composite metal layer (30) is formed. A photoelectric module (20) is disposed on the multilayer ceramic substrate (10). The photoelectric module (20) has a second surface (21) after activation treatment. A sintered silver layer (41) is formed on the second surface (21). The sintered silver layer (41) is connected to the composite metal layer (30). The sintered silver layer (41) is formed by gradient temperature sintering of a nano silver paste layer (40) formed on the second surface (21).
8. The probe card structure according to claim 7, characterized in that, The first surface (11) of the multilayer ceramic substrate (10) is provided with a plurality of first recesses (12) for setting the optoelectronic module (20); the second surface (21) of the optoelectronic module (20) is provided with second recesses (22) for forming the nano silver paste layer (40), and the second recesses (22) are connected to the periphery of the optoelectronic module (20) through radially extending connecting grooves (23); the composite metal layer (30) is deposited on the inner surface of the first recesses (12) by sputtering process; the nano silver paste layer (40) is formed at the second recesses (22) by screen printing process, wherein the nano silver paste layer (40) extends beyond the second recesses (22); the optoelectronic module (20) is disposed at the first recesses (12) on the multilayer ceramic substrate (10) to connect the nano silver paste layer (40) with the composite metal layer (30).
9. The probe card structure according to claim 7, characterized in that, The composite metal layer (30) includes a titanium layer (31), a nickel layer (32) and a gold layer (33) sequentially deposited on the first surface (11) of the multilayer ceramic substrate (10), wherein the thickness of the titanium layer (31) is 30 nm to 70 nm, the thickness of the nickel layer (32) is 80 nm to 120 nm, and the thickness of the gold layer (33) is 150 nm to 250 nm.
10. The probe card structure according to claim 7, characterized in that, The sintered silver layer (41) is formed by gradient temperature sintering of a nano-silver paste layer (40) formed on the second surface (21), wherein the gradient temperature sintering includes a preheating stage, a pressure sintering stage and an annealing stage performed sequentially. The preheating stage is performed at a temperature of 70°C to 90°C for 3 to 7 minutes. The pressure sintering stage is performed at a temperature of 160°C to 200°C and a pressure of 3 MPa to 7 MPa for 8 to 12 minutes. The annealing stage is performed at a temperature of 230°C to 270°C for 1 to 3 minutes.