A ceramic copper-clad substrate based on C-HPMS sputtering and silver-free solder paste low-temperature sintering and a preparation method thereof

Abstract

The application discloses a ceramic copper-clad substrate based on C-HPMS sputtering and silver-free solder paste low-temperature sintering and a preparation method thereof. The method comprises the following steps: pretreating and activating an Ar ion beam on a ceramic substrate; depositing a Ti adhesion layer and a Cu conductive layer in sequence by using a C-HPMS high-power magnetron sputtering technology with a ionization rate of more than 70%; screen printing a silver-free solder paste on the sputtered metallization layer, wherein the silver-free solder paste is composed of Cu 70-78wt%, Sn 18-25wt% and Ti 2-5wt% metal powder with an oxygen content of less than or equal to 500ppm and an organic carrier; after covering a copper foil, performing low-temperature pressure sintering at a vacuum degree of less than or equal to 5*10 ‑3 Pa, 750-850 DEG C, 1-5 MPa and keeping for 10-30 min. The application combines C-HPMS sputtering pre-metallization and silver-free active solder paste low-temperature pressure sintering to form a double-layer gradient interface structure of "sputtering transition layer + solder paste connecting layer", which can ensure high ceramic bonding strength, realize thick copper conductive connection and stress buffering, completely avoid the use of silver, and have the advantages of low cost, high reliability, environmental protection and thick copper conductive demand.

Description

Technical Field

[0001] This invention belongs to the field of electronic packaging materials technology, and in particular relates to a ceramic copper-clad substrate based on C-HPMS sputtering and low-temperature sintering with silver-free solder paste and its preparation method. Background Technology

[0002] Ceramic copper-clad laminates, with their high thermal conductivity, low coefficient of thermal expansion, excellent insulation properties, and mechanical strength, have become core packaging materials in fields such as power modules (e.g., IGBTs, SiC MOSFETs), high-power LED packaging, and electric drive systems. Especially with the large-scale application of third-generation semiconductor devices represented by silicon carbide (SiC) and gallium nitride (GaN), even more stringent requirements have been placed on the heat dissipation capacity, high-temperature reliability, and current carrying capacity of the packaging substrate.

[0003] Currently, the mainstream copper-clad ceramic substrate technologies mainly include three categories: direct copper-plated ceramic substrates (DPC), direct bonded copper ceramic substrates (DBC), and active metal brazing ceramic substrates (AMB). Each process route exhibits certain technical limitations when facing the aforementioned high-performance requirements.

[0004] The Direct Polymerization (DPC) process involves depositing a seed layer on a ceramic substrate using magnetron sputtering, followed by electroplating to thicken the copper conductive layer. This method offers low preparation temperatures (typically below 300°C) and high pattern precision, but the wastewater treatment costs from the electroplating process are high, and the copper layer thickness is generally limited to tens to hundreds of micrometers, making it difficult to meet the requirements of high-current power modules for thick copper conductivity. The Direct Polymerization (DBC) process utilizes the formation of a copper-oxygen eutectic liquid phase between copper and oxide ceramics at high temperatures to achieve direct bonding between the copper foil and the ceramic. This process is highly efficient, but the bonding temperature is typically in the range of 1065-1083°C, limiting the types of ceramic substrates (mainly oxide ceramics), and the peel strength is relatively low.

[0005] Traditional AMB (Active Metal Brazing) technology utilizes solder containing active metal elements (typically Ti) to achieve metallurgical bonding between ceramic and copper foil under vacuum conditions. Due to its higher bonding strength and excellent resistance to thermal cycling, it has become the mainstream solution for high-end power module packaging. However, existing AMB processes generally use Ag-Cu-Ti based silver solders, with Ag content typically exceeding 60%, resulting in high raw material costs. The soldering temperature is mostly between 850-950℃, making it prone to warping and deformation. Furthermore, silver elements pose an electrochemical migration risk during long-term service of power modules, potentially leading to device failure and reliability issues. Therefore, silver-free / low-silver active brazing technology has gradually become a research hotspot.

[0006] However, existing silver-free Cu-Sn-Ti solders still have significant shortcomings: conventional Cu-Sn-Ti systems have poor wettability on ceramic surfaces, and a large number of brittle intermetallic compound phases such as Cu3Ti and Cu4Ti are easily generated during the brazing process, resulting in low interface strength; at the same time, the brazing temperature required by the traditional AMB process is still as high as 850-950℃, and the copper foil and ceramic substrate are prone to warping and deformation due to the difference in thermal expansion coefficients during high temperature and cooling, making it difficult to guarantee the yield; in addition, the residual gas in the solder paste is not fully discharged during the sintering process, and the void ratio is difficult to effectively control below 0.3%, which cannot meet the stringent high reliability requirements of automotive-grade power modules.

[0007] The 2025 paper, "Effect of Gadolinium Content on Wetting Properties of CuSnTi Copper-Based Silver-Free Solder on Si3N4 Ceramic Substrates," reported the preparation of Cu-Sn-Ti copper-based silver-free solder via centrifugal stirring and investigated the effect of gadolinium content on the solder's wetting properties on ceramic substrates. The results showed that appropriate addition of Gd could promote the formation of interfacial TiN and Cu3Ti compound layers, thereby improving wetting performance. However, this study did not address the introduction of a sputtered pre-metallization layer.

[0008] Patent CN113795091A discloses a method for preparing ceramic circuit boards by low-temperature sintering. This method involves adding active metal particles to nano-metal particles to create a nano-active solder paste, followed by screen printing and low-temperature sintering (<300℃) to obtain a ceramic copper-clad laminate. While this method achieves direct bonding between copper foil and ceramic at low temperatures, the preparation process of the nano-active solder paste itself is complex and costly, and the sintering temperature below 300℃ limits further improvement in the density of the interfacial metallurgical bond.

[0009] In recent years, continuous high-power magnetron sputtering (C-HPMS) technology has been introduced into the field of ceramic substrate metallization, forming a new technology called direct sputtering of ceramic substrates (DSC). This technology utilizes C-HPMS, with its high ionization rate and high deposition efficiency, to directly deposit a conductive metal layer on the surface of a ceramic substrate, replacing the electroplating process in DPC (Digital Polymerization), achieving high bonding strength and green production. Compared to conventional magnetron sputtering and high-power pulsed magnetron sputtering (HiPIMS), C-HPMS employs a single-atom sputtering mode, resulting in high ionization and a continuously stable sputtering process. This produces a smooth and dense coating, increasing deposition efficiency by 10-20 times, while also enhancing the structural controllability of the thin film material. However, DSC technology is currently mainly used as a green alternative to the electroplating process in DPC, directly forming circuit patterns after sputtering. Limited by the sputtering deposition rate, the copper layer thickness is typically limited to tens of micrometers, and its use alone has limitations in thick copper, high-current applications.

[0010] In summary, there are currently no research reports on integrating C-HPMS pre-metallization sputtering as an intermediate interface layer with a silver-free active solder paste printing and sintering process to form a two-layer gradient bonding structure of "sputtering transition layer + solder paste bonding layer". Against this backdrop, this invention proposes a new technical approach to achieve multiple objectives, including high bonding strength, low cost, environmentally friendly process, and conductivity of thick copper. Summary of the Invention

[0011] This invention aims to address the following problems in existing ceramic copper-clad laminate manufacturing processes: Active metal brazing (AMB) relies on high-cost silver-based solder and carries the risk of silver electrochemical migration; Direct copper plating (DPC) has limited copper layer thickness and causes significant electroplating wastewater pollution; Direct copper bonding (DBC) has excessively high bonding temperatures and is limited in the types of ceramics it can be used with; and Single sputtering metallization (DSC) technology is difficult to implement in industrial applications of thick copper conductive layers. The purpose of this invention is to provide a ceramic copper-clad laminate based on C-HPMS sputtering and low-temperature sintering with silver-free solder paste, and its preparation method. This method can achieve a high-strength, high-reliability metallurgical bond between ceramic and thick copper foil at lower temperatures, while also considering low cost, environmental friendliness, and excellent thermal cycling reliability, meeting the stringent performance requirements of third-generation semiconductor power modules for packaging substrates.

[0012] To achieve the above objectives, the technical solution adopted by the present invention is as follows: This invention provides a method for preparing a ceramic copper-clad substrate based on C-HPMS sputtering and low-temperature sintering with silver-free solder paste, characterized by comprising the following steps: (1) The ceramic substrate was ultrasonically cleaned with acetone, ethanol and deionized water for 10 min each, and then activated with Ar ion beam. (2) The Ti adhesion layer and Cu conductive layer deposited on the surface of the ceramic substrate were treated by C-HPMS high-power magnetron sputtering technology, with a sputtering ionization rate of >70%; (3) Prepare Cu-Sn-Ti silver-free solder paste by gas atomization and screen print it on the surface of the ceramic substrate treated above. (4) Cover the solder paste layer with copper foil and apply a pre-pressure of 0.1~0.5MPa to remove bubbles; (5) The pre-pressed substrate is subjected to low-temperature vacuum pressure sintering at a vacuum degree ≤ 5×10 -3 Under the condition of Pa, heat to 750~850℃ at a heating rate of 5~10℃ / min, hold at 1~5MPa pressure for 10~30min, and cool with the furnace; (6) After ultrasonic cleaning, drying and performance testing, a compliant silver-free ceramic copper-clad substrate is obtained.

[0013] Furthermore, the process conditions for C-HPMS high-power magnetron sputtering in step (2) are: vacuum degree 1×10⁻⁶. -3 ~5×10 -3 Pa, power density 20~200W / cm³ 2 The thickness of the Ti adhesion layer is 50~200nm, and the thickness of the Cu conductive layer is 1~5μm.

[0014] Furthermore, in step (3), the mesh count of the screen printing plate is 200~300 mesh, and the thickness of the solder paste printing is 80~120μm.

[0015] Furthermore, the Cu-Sn-Ti silver-free solder paste in step (3) is prepared by the following steps: the metal alloy powder is prepared by gas atomization process, an organic carrier is prepared, the metal alloy powder and the organic carrier are mixed, and then vacuum stirred to remove bubbles and three-roll milling is performed to obtain the silver-free active solder paste.

[0016] Furthermore, the viscosity of the Cu-Sn-Ti silver-free solder paste is 80~120 Pa·s, and the mass fraction ratio is: 80~92 wt% alloy powder and 8~20 wt% organic carrier; Furthermore, the alloy powder has the following composition: Cu 70~78 wt%, Sn 18~25 wt%, Ti 2~5 wt%, and the powder oxygen content ≤500 ppm; Furthermore, the organic carrier is formulated with the following proportions: 50-70 wt% organic solvent, 10-25 wt% thickener, 3-8 wt% thixotropic agent, 1-3 wt% activator, 0.5-1.5 wt% corrosion inhibitor, and 0.3-1 wt% antioxidant. Furthermore, the organic solvent is selected from terpineol and / or diethylene glycol butyl ether; the thickener is ethyl cellulose; the thixotropic agent is fumed silica; the activator is selected from glutaric acid and / or salicylic acid; the corrosion inhibitor is benzotriazole; and the antioxidant is selected from butylated hydroxytoluene and / or vitamin E.

[0017] A ceramic copper-clad substrate based on C-HPMS sputtering and low-temperature sintering with silver-free solder paste is prepared by the above-mentioned method.

[0018] Furthermore, the ceramic copper-clad substrate includes a ceramic substrate, a Ti adhesion layer, a Cu conductive layer, a Cu-Sn-Ti sintered solder paste layer, and an oxygen-free copper foil; the thickness of the Ti adhesion layer is 50~200nm, the thickness of the Cu conductive layer is 1~5μm, the thickness of the Cu-Sn-Ti sintered solder paste layer is 80~120μm, and the thickness of the copper foil is 0.1~1.0mm.

[0019] Furthermore, the ceramic substrate is aluminum nitride ceramic or silicon nitride ceramic.

[0020] The technical principle of this invention is as follows: First, an Ar ion beam activation and C-HPMS high ionization rate (>70%) sputtering of a Ti adhesion layer are performed, causing a highly active Ti particle to undergo an interfacial chemical reaction with the ceramic surface, generating an in-situ TiN or TiO2-x nanoscale reaction layer, thus achieving chemical bonding between the sputtered metal layer and the ceramic substrate; subsequently, the printed Cu-Sn-Ti silver-free solder paste is sintered at a temperature of 750~850℃, where the Sn component melts first to form a liquid phase, filling the gaps between Cu particles under capillary action, and undergoing a solid-liquid diffusion reaction with Cu to generate intermetallic compound phases such as Cu6Sn5, achieving preliminary densification. Simultaneously, the Ti component participates in the interfacial reaction to strengthen the bond; under a vacuum degree ≤5×10 -3 Under the coupling effect of Pa and external mechanical pressure of 1~5MPa, the residual gas is effectively removed, and the liquid phase viscous flow further fills the micropores, resulting in a dense solder paste layer with low void ratio. Finally, a multi-layer gradient structure of "ceramic substrate (Si3N4 / AlN) / C-HPMS sputtered Ti adhesion layer / C-HPMS sputtered Cu conductive layer / Cu-Sn-Ti sintered solder paste layer / oxygen-free copper foil" is formed, so that the coefficient of thermal expansion gradually transitions from ceramic to copper foil, effectively dispersing thermal mismatch stress and giving the copper-clad substrate excellent bonding strength and resistance to thermal shock.

[0021] In summary, the innovative points of this invention are: 1. Collaborative Innovation in Processes: For the first time, a dual-layer gradient interface construction strategy of "C-HPMS sputtering pre-metallization + silver-free active solder paste printing and sintering" was proposed. This strategy organically integrates the advantages of high adhesion and low defect rate of sputtering metallization layer with the adjustability of solder paste sintering layer thickness and stress buffering capacity, solving the dual bottlenecks of insufficient thickness of single sputtering metallization copper layer and limited bonding force of single solder paste direct brazing interface.

[0022] 2. Material Innovation: A silver-free active solder paste composition highly compatible with the above-mentioned processes was developed. The solder paste metal powder uses a specific ratio, and the oxygen content of the powder is strictly controlled to ≤500ppm to ensure high reactivity during low-temperature sintering. Corrosion inhibitors and antioxidants are simultaneously introduced into the organic carrier formulation. Their synergistic effect effectively inhibits surface oxidation of the Ti-containing solder paste during storage, printing, and preheating stages, ensuring the process applicability of the solder paste and sufficient interfacial reaction during subsequent sintering. This silver-free solder paste eliminates the high cost and electromigration risks associated with silver-based solders at the source.

[0023] 3. Innovative Sintering Process: Low-temperature densification sintering at 750~850℃ was achieved by utilizing sputtering activation and pressure assistance. The highly active Ti layer deposited by sputtering and the Ti element in the solder paste work together at the ceramic interface to promote the rapid formation of the TiN reaction layer. At the same time, the Cu-Sn system in the solder paste can generate sufficient liquid phase at 750~850℃. Combined with mechanical pressure of 1~5MPa, residual gas is dispersed and the solder paste densification is promoted. Under conditions far lower than the traditional DBC process (>1065℃) and AMB brazing temperature (850~950℃), a high-density bonding layer with a void ratio of ≤0.3% is obtained, effectively avoiding thermal damage to the ceramic and copper foil caused by high temperature.

[0024] 4. Structural Innovation: A multi-layered gradient interface structure is formed, consisting of a ceramic substrate, a TiN reaction layer, a sputtered copper layer, a Cu-Sn-Ti intermetallic compound bonding layer, and a copper foil. The sputtered Ti / Cu layer provides an integrated metallurgical bonding foundation with the ceramic, while the solder paste sintering layer reliably connects the sputtered layer to the commercially available thick copper foil through the Cu-Sn-Ti intermetallic compound network. The coefficient of thermal expansion transitions gradually from ceramic to copper foil, significantly alleviating thermal mismatch stress and giving the copper-clad laminate excellent resistance to thermal shock.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. High bonding strength; 2. Excellent reliability in both hot and cold cycles; 3. Significant cost advantage; 4. Green and environmentally friendly; 5. Thick copper has strong electrical conductivity; 6. Ceramics have wide adaptability; 7. Low-temperature sintering results in minimal thermal damage. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the structure of a ceramic copper-clad substrate based on C-HPMS sputtering and low-temperature sintering with silver-free solder paste.

[0027] Figure 2 This is a flowchart illustrating the fabrication process of a ceramic copper-clad substrate based on C-HPMS sputtering and low-temperature sintering with silver-free solder paste. Detailed Implementation

[0028] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0029] It should be noted that, in all aspects of the present invention, the same components or terms in each aspect are described only once in one aspect and not repeatedly, and those skilled in the art should not understand this as a limitation of the present invention.

[0030] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0031] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0032] The present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto. Unless otherwise specified, the general process steps used in the following embodiments and comparative examples are as follows: (1) After ultrasonic cleaning in acetone, ethanol and deionized water for 10 min each, the ceramic substrate was activated by Ar ion beam treatment.

[0033] (2) The pretreated substrate is sent into the sputtering chamber and evacuated to a vacuum level ≤5×10. -3 Pa, employing continuous high-power magnetron sputtering technology, at power densities of 20~200 W / cm² 2 Under the condition of sputtering ionization rate > 70%, a Ti adhesion layer is deposited first, followed by a Cu conductive layer.

[0034] (3) Weigh out pure metal powders of Cu, Sn and Ti according to the proportions of each group, and use gas atomization to make powder and classify it so that the oxygen content of the powder is ≤500ppm and the particle size D is ≤500ppm. 50 =15~25μm; After mixing organic solvent, thickener, thixotropic agent, activator, corrosion inhibitor and antioxidant, metal powder is added, and the mixture is vacuum stirred to degas and then milled by three rollers to obtain a solder paste with a viscosity of 80~120 Pa·s.

[0035] (4) Use 200~300 mesh screen printing to print solder paste on the surface of the sputtered substrate. The thickness of the solder paste is controlled at 80~120μm. Cover the solder paste layer with copper foil of the required thickness and apply 0.1~0.5MPa pre-pressure to remove air bubbles.

[0036] (5) Place the copper foil-coated substrate in a vacuum hot press furnace and evacuate until the system pressure is ≤5×10. -3 Pa, heat to the set sintering temperature at a rate of 5~10℃ / min, apply the set pressure and hold for a certain time, then cool with the furnace.

[0037] (6) After sintering, the substrate is removed, ultrasonically cleaned and dried to obtain the finished ceramic copper-clad substrate.

[0038] In each embodiment and comparative example, performance testing was conducted according to the methods and standards described in Table 1.

[0039] Table 1 Performance Test Standards

[0040] Example 1 The experimental parameters for this embodiment are as follows: a Si3N4 ceramic substrate with a thickness of 0.32 mm and a thermal conductivity of 90 W / (m·K) is used; the thickness of the sputtered Ti adhesion layer is 100 nm, and the thickness of the Cu conductive layer is 2 μm; the solder paste composition is Cu-20Sn-3Ti, D 50 =22μm, oxygen content 380ppm. Sintering temperature 800℃, holding time 20min, applied pressure 3MPa, vacuum degree 3×10 -3 Pa.

[0041] Example 2 The experimental parameters for this embodiment are as follows: an AlN ceramic substrate with a thickness of 0.635 mm and a thermal conductivity of 230 W / (m·K) is used; the thickness of the sputtered Ti adhesion layer is 150 nm and the thickness of the Cu conductive layer is 3 μm; the solder paste composition is Cu-22Sn-4Ti; the sintering temperature is 820℃, the holding time is 25 min, and the applied pressure is 4 MPa.

[0042] Example 3 The experimental parameters for this embodiment are as follows: a Si3N4 ceramic substrate was used, and the thickness of the copper foil on both sides was 0.8 mm. The solder paste composition was Cu-18Sn-5Ti. The sintering temperature was 840℃, the holding time was 30 min, and the applied pressure was 5 MPa.

[0043] The performance test results of the ceramic copper-clad substrates prepared in Examples 1-3 are shown in Table 2.

[0044] Table 2 Performance test results of Examples 1-3

[0045] Comparative Example 1 The same Si3N4 ceramic substrate as in Example 1 was used, but without C-HPMS sputtering pre-metallization treatment; commercially available Ag-Cu-Ti active solder paste with a silver content of 68.8% was used, and brazing was performed at 890°C under vacuum without external pressure for 20 min. The performance comparisons of the resulting copper-clad ceramic substrates are shown in Table 3. Table 3 Performance comparison between the present invention and traditional AMB ceramic substrates

[0046] The comparison results show that the present invention completely eliminates the cost and migration risk of silver elements, while achieving a lower sintering temperature and a lower interface void ratio, and its overall performance is superior to that of the traditional AMB process.

[0047] Comparative Example 2 The process flow is exactly the same as in Example 1, except that the solder paste composition is Cu-28Sn-3Ti (i.e., the Sn content is 28wt%, which exceeds the 18~25wt% range specified in this invention).

[0048] Test results showed that the shear strength of the sample decreased to 62 MPa, and the interfacial porosity increased to 1.2%. Metallographic analysis indicated that a large number of coarse Cu6Sn5 and Cu3Sn brittle intermetallic compound phases were generated in the bonding layer, leading to embrittlement of the bonding layer and severely reducing its mechanical properties and density.

[0049] Comparative Example 3 The process flow is exactly the same as in Example 1, except that the solder paste composition is Cu-20Sn-1.5Ti (i.e., the Ti content is 1.5wt%, which is lower than the 2~5wt% range specified in this invention).

[0050] Test results showed that the sample had a shear strength of only 45 MPa and a significantly low peel strength. Interface microscopic analysis indicated that a continuous and effective TiN reaction layer could not be formed on the ceramic side, and the solder paste and ceramic were poorly wetted, making metallurgical bonding impossible.

[0051] As can be seen from the comparison between Examples 1-3 and Comparative Examples 2-3, the Sn and Ti contents in the solder paste must be strictly controlled within the range of Cu 70-78%, Sn 18-25%, and Ti 2-5% to achieve sufficient liquid-phase densification, avoid excessive precipitation of brittle phases, and obtain the best formation effect of the interface reaction layer. Meanwhile, the introduction of the C-HPMS sputtering pre-metallization layer and the low-temperature pressure sintering process in this invention are key to obtaining low void ratio, high bonding strength, and excellent thermal cycling reliability.

[0052] The embodiments described above are merely preferred embodiments of the present invention, but the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combining various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing a ceramic copper-clad substrate based on C-HPMS sputtering and low-temperature sintering with silver-free solder paste, characterized in that, Includes the following steps: (1) The ceramic substrate was ultrasonically cleaned with acetone, ethanol and deionized water for 10 min each, and then activated by Ar ion beam. (2) The Ti adhesion layer and Cu conductive layer deposited on the surface of the ceramic substrate were treated by C-HPMS high-power magnetron sputtering technology, with a sputtering ionization rate of >70%; (3) Preparation of Cu by gas atomization Sn Ti silver-free solder paste was screen-printed onto the surface of the above-treated ceramic substrate. (4) Cover the solder paste layer with copper foil and apply a pre-pressure of 0.1~0.5MPa to remove bubbles; (5) The pre-pressed substrate is subjected to low-temperature vacuum pressure sintering at a vacuum degree ≤ 5×10 -3 Under the condition of Pa, heat to 750~850℃ at a heating rate of 5~10℃ / min, hold at 1~5MPa pressure for 10~30min, and cool with the furnace; (6) After ultrasonic cleaning, drying and performance testing, a compliant silver-free ceramic copper-clad substrate is obtained.

2. The preparation method according to claim 1, characterized in that, The process conditions for C-HPMS high-power magnetron sputtering in step (2) are: vacuum degree 1×10 -3 ~5×10 -3 Pa, power density 20~200W / cm³ 2 The thickness of the Ti adhesion layer is 50~200nm, and the thickness of the Cu conductive layer is 1~5μm.

3. The preparation method according to claim 1, characterized in that, In step (3), the screen printing mesh number is 200~300 mesh, and the solder paste printing thickness is 80~120μm.

4. The preparation method according to claim 1, characterized in that, Cu in step (3) Sn Ti silver-free solder paste is prepared by the following steps: the metal alloy powder is prepared by gas atomization process, an organic carrier is prepared, the metal alloy powder and the organic carrier are mixed, and then vacuum stirred to remove bubbles and three-roll milling is performed to obtain the silver-free active solder paste.

5. The preparation method according to claim 3, characterized in that, The Cu Sn The viscosity of the Ti silver-free solder paste is 80~120 Pa·s, and the mass fraction ratio is: 80~92 wt% alloy powder and 8~20 wt% organic carrier; The alloy powder has the following composition: Cu 70~78 wt%, Sn 18~25 wt%, Ti 2~5 wt%, and the oxygen content of the powder is ≤500ppm; The organic carrier is formulated with the following proportions: 50-70 wt% organic solvent, 10-25 wt% thickener, 3-8 wt% thixotropic agent, 1-3 wt% activator, 0.5-1.5 wt% corrosion inhibitor, and 0.3-1 wt% antioxidant.

6. The preparation method according to claim 3, characterized in that, The organic solvent is selected from terpineol and / or diethylene glycol butyl ether; the thickener is ethyl cellulose; the thixotropic agent is fumed silica; the activator is selected from glutaric acid and / or salicylic acid; the corrosion inhibitor is benzotriazole; and the antioxidant is selected from butylated hydroxytoluene and / or vitamin E.

7. A ceramic copper-clad substrate based on C-HPMS sputtering and low-temperature sintering with silver-free solder paste, characterized in that, It is prepared by the preparation method according to any one of claims 1-3.

8. The ceramic copper-clad substrate according to claim 7, characterized in that, The structure of the ceramic copper-clad substrate is as follows: a ceramic substrate, a Ti adhesion layer, a Cu conductive layer, a Cu-Sn-Ti sintered solder paste layer, and an oxygen-free copper foil. The thickness of the Ti adhesion layer is 50~200nm, the thickness of the Cu conductive layer is 1~5μm, the thickness of the Cu-Sn-Ti sintered solder paste layer is 80~120μm, and the thickness of the copper foil is 0.1~1.0mm.

9. The ceramic copper-clad substrate according to claim 7, characterized in that, The ceramic substrate is aluminum nitride ceramic or silicon nitride ceramic.

Images