High thermal conductive composite metal material and preparation method thereof

Abstract

This invention discloses a high thermal conductivity composite metal material and its preparation method. The material includes an intermediate layer, which is one of a CuNiCu structure, a CuNiAuNiCu structure, or a CuNiAuInAuNiCu structure. The layers are connected by solid solution diffusion, without forming intermetallic compounds. The preparation method includes: using a Si wafer as a substrate, depositing a Cu layer and a transition layer using an electroplating process; if an Au or In layer is included, it is deposited using a sputtering device; finally, a top Cu layer is deposited, and the interlayer solid solution is bonded using an ultrasonic pressure welding process. This invention replaces traditional welding with solid solution diffusion bonding, avoiding the formation of brittle intermetallic compounds. The thermal conductivity can reach up to 402 W / (m·K), which is 119.4% higher than that of the traditional CuSn structure. The interface bonding is strong, and the long-term reliability is high. It is suitable for heat dissipation and packaging in high-performance chips, 5G RF devices, power modules, and aerospace electronic systems.

Description

Technical Field

[0001] This invention relates to composite metal materials, specifically to a high thermal conductivity composite metal material and its preparation method. Background Technology

[0002] With the rapid development of electronic devices towards high power density and miniaturization, their thermal management issues are becoming increasingly prominent. Metal-based composite layered materials are widely used in chip packaging and power module heat dissipation due to their excellent thermal and electrical conductivity. Currently, the closest existing technology to this invention is the bonding or brazing system using tin-based solders (such as pure Sn or eutectic solder), with a typical structure of Cu / Sn / Cu.

[0003] However, the traditional structures based on tin-based solders have gradually revealed their inherent limitations in practical applications. On the one hand, tin itself has a low thermal conductivity and is prone to violent diffusion reactions with copper during bonding and service, forming brittle intermetallic compound layers such as Cu6Sn5 and Cu3Sn. These compounds not only have much lower thermal conductivity than pure copper, but also induce microcracks and interface delamination during thermal cycling due to the mismatch in thermal expansion coefficients with adjacent materials, thus significantly increasing thermal resistance and threatening long-term reliability. On the other hand, traditional brazing processes often require high temperatures and long holding times, which not only consumes a lot of energy but may also cause potential damage to heat-sensitive components. Furthermore, the process control window is narrow, and it is extremely sensitive to surface condition and solder thickness. To improve these problems, the industry has successively tried to use solder systems with higher thermal conductivity, such as Au-Sn and Ag-Sn, or to introduce a nickel layer as a diffusion barrier to delay the growth of intermetallic compounds. However, most of these improvement solutions still rely on low-melting-point solder layers, failing to fundamentally eliminate the formation of intermetallic compounds. Furthermore, they often involve high costs of precious metals or complex processing requirements, resulting in significant bottlenecks in heat dissipation performance and long-term reliability. Meanwhile, solid solution diffusion bonding, as an ideal interface bonding method that theoretically avoids the formation of brittle phases and achieves properties close to the base material, has received widespread attention. However, its practical application faces numerous challenges: it requires not only sufficient mutual solid solubility of the material assemblies at the processing temperature but also precise preparation techniques and strict process control to achieve full diffusion of interface atoms while suppressing the precipitation of any intermetallic compounds. This places extremely high demands on material system design and manufacturing methods. Therefore, the current field of electronic heat dissipation materials urgently needs a new type of composite metal material and supporting process that can completely break free from dependence on traditional solders and achieve high-strength, high-thermal-conductivity interface bonding through controllable solid solution diffusion, simultaneously meeting the comprehensive requirements of high thermal conductivity, high reliability, and large-scale production. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to provide a high thermal conductivity composite metal material and its preparation method that eliminates brittle intermetallic compounds, achieves pure solid solution bonding at the interface, has extremely high thermal conductivity, strong structural stability, a wide process window, and is suitable for large-scale production. It aims to solve the problems of low thermal conductivity, high interfacial thermal resistance, and poor long-term reliability caused by the formation of brittle intermetallic compounds in traditional Cu / Sn and other composite metal structures.

[0005] Technical solution: The high thermal conductivity composite metal material of the present invention includes upper and lower substrates, with an intermediate layer disposed between the substrates; the intermediate layer is one of CuNiCu structure, CuNiAuNiCu structure or CuNiAuInAuNiCu structure; the materials of each layer are connected by solid solution diffusion and do not form intermetallic compounds.

[0006] The substrate includes, but is not limited to, a Si substrate. Other substrates, being part of the same encapsulation material system, can be directly applied by those skilled in the art.

[0007] Preferably, the CuNiCu structure is prepared by electroplating, wherein the Cu layer thickness is 4-6 μm and the Ni layer thickness is 0.24-0.26 μm, 0.39-0.41 μm or 0.49-0.51 μm.

[0008] Preferably, the CuNiCu structure is prepared by electroplating, wherein the Cu layer thickness is 5 μm and the Ni layer thickness is 0.25 μm, 0.4 μm or 0.5 μm.

[0009] Preferably, the CuNiAuNiCu structure is prepared by electroplating and sputtering, wherein the Cu layer has a thickness of 4-6 μm, the Ni layer has a thickness of 0.24-0.26 μm, and the Au layer is prepared by sputtering with a thickness of 90-110 nm, 140-160 nm, or 190-210 nm.

[0010] Preferably, the CuNiAuNiCu structure is prepared by electroplating and sputtering, wherein the Cu layer has a thickness of 5 μm, the Ni layer has a thickness of 0.25 μm, and the Au layer is prepared by sputtering with a thickness of 100 nm, 150 nm, or 200 nm.

[0011] Preferably, the CuNiAuInAuNiCu structure is prepared by electroplating and sputtering, wherein the Cu layer has a thickness of 4-6 μm, the Ni layer has a thickness of 0.24-0.26 μm, the Au layer has a thickness of 90-110 nm, and the In layer is prepared by sputtering with a thickness of 90-110 nm, 140-160 nm, or 190-210 nm.

[0012] Preferably, the CuNiAuInAuNiCu structure is prepared by electroplating and sputtering, wherein the Cu layer has a thickness of 5 μm, the Ni layer has a thickness of 0.25 μm, the Au layer has a thickness of 100 nm, and the In layer is prepared by sputtering with a thickness of 100 nm, 150 nm, or 200 nm.

[0013] The preparation method of the high thermal conductivity composite metal material of the present invention includes interlayer solid solution bonding using ultrasonic pressure welding process, controlling the welding temperature at 200-250 ℃, ultrasonic power at 300-500 W, pressure at 0.3-0.5 MPa, and welding time at 10-20 s.

[0014] Preferably, the preparation method specifically includes the following steps: S1. On the substrate surface, an electroplating process is used to sequentially deposit the bottom Cu layer and the corresponding transition layer; S2. When the intermediate layer is a CuNiAuNiCu structure or a CuNiAuInAuNiCu structure, after electroplating is completed, it is transferred to a sputtering device to deposit an Au layer and / or an In layer by controlling the process parameters. S3. Deposit the top Cu layer to complete the overall structure formation; S4. Ultrasonic pressure welding is used for interlayer solid solution bonding to ensure sufficient diffusion between layers and prevent the formation of intermetallic compounds.

[0015] Preferably, the electroplating process in S1 is as follows: metal layer electrodeposition is performed sequentially on the pretreated substrate surface, and the electroplating is carried out using a direct current electroplating method, with the current density controlled at 1-5 A / dm² during the electroplating process. 2 The electroplating temperature is 20-40℃.

[0016] Preferably, the process parameters in S2 are: vacuum degree better than 5.0 × 10⁻⁶. -4 The working pressure is 0.5-0.8 Pa, the sputtering power is 30-100 W, and the thickness of each layer is precisely grown by controlling the deposition time.

[0017] Preferably, the process parameters in S4 are as follows: an ultrasonic-assisted solid solution diffusion bonding process is used, the bonding temperature is controlled at 200-250 ℃, the ultrasonic power is 300-500 W, the applied pressure is 0.3-0.5 MPa, and the bonding time is 10-20 s, so as to achieve sufficient diffusion bonding between the intermediate layer metals and avoid the formation of intermetallic compounds.

[0018] Beneficial Effects: Compared with existing technologies, this invention has the following significant advantages: It provides a high thermal conductivity multilayer metal composite structure based on solid solution diffusion bonding, which does not generate brittle intermetallic compounds (IMCs). By optimizing the intermediate layer material system (e.g., Cu-Ni-Au-In) and using precise and controllable preparation processes (e.g., a combination of electroplating, sputtering, and ultrasonic pressure welding), it significantly improves the interlayer bonding stability and overall thermal conductivity. The composite metal material of this invention, through different intermediate layer structures and thickness parameters, utilizes solid solution diffusion bonding instead of traditional welding, avoiding the formation of IMCs. Compared to the traditional CuSn composite structure, the three structures of this invention exhibit improved thermal conductivity and stronger structural stability. Benefiting from the pure interface free of IMCs and the continuous pathways of highly thermally conductive metals such as Cu and Au, the overall thermal conductivity of the material is revolutionaryly improved. Tests show that its thermal conductivity can reach up to 402 W / (m·K), an improvement of 119.4% compared to the traditional CuSn structure. Simultaneously, the solid solution bonding interface is strong and the structure is stable, significantly improving the long-term reliability of the material under thermal cycling conditions. The fabrication process employs mature electroplating and sputtering technologies, combined with ultrasonic pressure welding to achieve solution bonding. This process offers strong controllability, moderate cost, and suitability for mass production. The material is particularly suitable for applications with stringent requirements for heat dissipation, reliability, and long-term stability, such as high-performance computing chips (CPU / GPU), 5G RF devices, power modules like insulated-gate bipolar transistors (IGBTs), and packaging and heat dissipation components for aerospace electronic systems. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the CuNiCu structure in Embodiment 1 of the present invention.

[0020] Figure 2 This is a schematic diagram of the CuNiAuNiCu structure in Embodiment 2 of the present invention.

[0021] Figure 3 This is a schematic diagram of the CuNiAuInAuNiCu structure in Embodiment 3 of the present invention. Detailed Implementation

[0022] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0023] Reference Figures 1-3 A high thermal conductivity composite metal material, specifically as follows: The composite metal material uses two layers of Si as the substrate, and the middle layer adopts three different multilayer composite structures, as shown below: Example 1

[0024] CuNiCu structure: Prepared using an electroplating process, the Cu layer thickness is fixed at 5 μm, while the Ni layer thickness is designed in three specifications: 0.25 μm, 0.4 μm, and 0.5 μm. Interlayer bonding is achieved through solid solution diffusion of Cu and Ni. (Refer to...) Figure 1 As shown. The thermal conductivity results are as follows: Ni=0.25 μm: thermal conductivity 320 W / (m·K), an improvement of 77.8% compared to the traditional CuSn structure; Ni=0.4 μm: thermal conductivity 305 W / (m·K), an improvement of 69.4% compared to the traditional CuSn structure; Ni=0.5 μm: thermal conductivity 290 W / (m·K), an improvement of 61.1% compared to the traditional CuSn structure.

[0025] Example 2

[0026] CuNiAuNiCu structure: A composite electroplating and sputtering process was used. The Cu layer (5 μm) and Ni layer (0.25 μm) were prepared by electroplating, while the Au layer was prepared by sputtering. Thicknesses of 100 nm, 150 nm, and 200 nm were achieved. Stable interlayer bonding was realized by utilizing the infinite solid solution properties of Au with Cu and Ni. (Refer to...) Figure 2 As shown. The thermal conductivity results are as follows: Au=100 nm: thermal conductivity 345 W / (m·K), an improvement of 91.7% compared to the traditional CuSn structure; Au=150 nm: thermal conductivity 360 W / (m·K), an improvement of 100% compared to the traditional CuSn structure; Au=200 nm: thermal conductivity 372 W / (m·K), an improvement of 106.7% compared to the traditional CuSn structure.

[0027] Example 3

[0028] The CuNiAuInAuNiCu structure employs a composite electroplating and sputtering process. The Cu layer (5 μm) and Ni layer (0.25 μm) are prepared by electroplating, while the Au layer (100 nm) and In layer are prepared by sputtering. The In layer thickness is available in three specifications: 100 nm, 150 nm, and 200 nm. The solid solution interaction between Au and In enhances the interlayer bonding and thermal conductivity. (Refer to...) Figure 3 As shown. The thermal conductivity results are as follows: In=100 nm: thermal conductivity 358 W / (m·K), an improvement of 98.9% compared to the traditional CuSn structure; In=150 nm: thermal conductivity 380 W / (m·K), an improvement of 111.1% compared to the traditional CuSn structure; In=200 nm: thermal conductivity 395 W / (m·K), an improvement of 119.4% compared to the traditional CuSn structure.

[0029] In each structure, all layers are connected by solid solution diffusion, without forming intermetallic compounds (IMC), thus avoiding the problems of decreased thermal conductivity and structural failure caused by IMC.

[0030] Example 4

[0031] The preparation methods of Examples 1-3 are as follows: S1. Substrate pretreatment: Clean and dry the Si substrate to remove surface impurities and ensure coating adhesion.

[0032] S2. Electroplating process: An electroplating equipment is used to deposit a bottom Cu layer on the Si substrate, with the thickness controlled at 5 μm; then, according to the intermediate layer structure, a Ni layer is electroplated, with the thickness controlled according to the design specifications.

[0033] S3. Sputtering process: For structures containing Au and In layers, the electroplated semi-finished product is transferred to a sputtering device, where Au and In layers are deposited sequentially in a vacuum environment, with precise control over the thickness of each layer.

[0034] S4. Top layer preparation: A Cu layer with a thickness of 5μm is deposited by electroplating to complete the stacking of the overall structure.

[0035] S5. Ultrasonic pressure welding: The laminated materials are placed in an ultrasonic pressure welding machine. The welding temperature is set to 220 ℃, the ultrasonic power to 500 W, the pressure to 0.4 MPa, and the welding time to 15 s. Through ultrasonic vibration and pressure, interlayer atomic diffusion is promoted to achieve solid solution bonding and ensure that no IMC is generated.

[0036] S6. Quality Inspection: The thickness of each layer is measured using a metallographic microscope or film thickness gauge, the interlayer structure is detected by XRD, and the thermal conductivity is tested by laser flash method.

[0037] Example 5

[0038] Refer to Table 1 for the solid solubility parameters of the materials (at room temperature), where: 1. Solid solubility data are based on standard room temperature (25 ℃) environment. The instantaneous high temperature (200-250 ℃) during ultrasonic pressure welding will slightly increase the solid solubility, but the solid solution structure will still be maintained and no intermetallic compounds will be formed. 2. Infinite solid solution refers to the ability of two metals to form a solid solution in any proportion, which is the core guarantee for a stable interlayer bond.

[0039] Table 1. Material Solid Solubility Parameters (Room Temperature Conditions)

[0040] To verify the feasibility of interlayer solid solution diffusion, Table 1 presents the solid solubility parameters of each composite system at room temperature (25 ℃). The table shows that Cu-Au and Ni-Au are infinite solid solution systems, capable of forming continuous solid solutions in any proportion without component segregation, which is the core guarantee for the absence of intermetallic compounds (IMCs) and tight bonding between layers. In the Au-In system, the solid solubility of In in Au reaches 15%, further enhancing the interlayer bonding force. In contrast, the solid solubility of the Cu-Sn system in the control group is only 0.7%, making it prone to IMC formation, which also confirms the shortcomings of the traditional structure. It should be noted that the instantaneous high temperature of 200-250 ℃ during ultrasonic pressure welding will slightly increase the solid solubility, but the solid solution structure is still maintained, and no intermetallic compounds are formed.

[0041] Example 6

[0042] To quantify the thermal conductivity of the material of this invention, a laser scintillation method was used to conduct simulation tests at room temperature (25 ℃). The results are shown in Table 2 (the comparison group is the industry-standard CuSn composite structure, with a thermal conductivity of 180 W / (m·K)). The data shows that the thermal conductivity of all three intermediate layer structures is significantly better than that of the traditional CuSn structure, with improvements ranging from 61.1% to 119.4%. Among them, the CuNiAuInAuNiCu structure (In=200 nm) has the highest thermal conductivity, reaching 395 W / (m·K), an improvement of 119.4%; the CuNiAuNiCu structure (Au=200 nm) is second, with a thermal conductivity of 372 W / (m·K), an improvement of 106.7%; even the basic CuNiCu structure (Ni=0.25 μm) has a thermal conductivity of 320 W / (m·K), an improvement of 77.8%, fully meeting the heat dissipation requirements of high-end electronic devices.

[0043] Table 2 Comparison of Thermal Conductivity Test Results for Different Composite Structures

[0044] Example 7 This embodiment provides a method for preparing a high thermal conductivity composite metal material, using a CuNiAuInAuNiCu structure, with specific parameters as follows: Cu layer thickness 4 μm, Ni layer thickness 0.24 μm, Au layer thickness 90 nm, and In layer thickness 90 nm. The preparation steps are basically the same as in Example 4, except that the parameters for the S5 ultrasonic pressure welding process are set as follows: welding temperature 200 ℃, ultrasonic power 300 W, pressure 0.3 MPa, and welding time 10 s.

[0045] Testing revealed that the obtained material exhibited excellent interlayer bonding, with no intermetallic compounds (IMC) formed. Its thermal conductivity was 352 W / (m·K), representing a 95.6% improvement compared to the traditional CuSn structure (180 W / (m·K)).

[0046] Example 8

[0047] This embodiment provides a method for preparing a high thermal conductivity composite metal material, employing a CuNiAuInAuNiCu structure, with specific parameters as follows: Cu layer thickness 6 μm, Ni layer thickness 0.26 μm, Au layer thickness 110 nm, and In layer thickness 210 nm. The preparation steps are basically the same as in Example 4, except that the parameters for the S5 ultrasonic pressure welding process are set as follows: welding temperature 250 ℃, ultrasonic power 500 W, pressure 0.5 MPa, and welding time 20 s.

[0048] Testing revealed that the resulting material exhibited further enhanced interlayer bonding strength, a pure interface, and no formation of any intermetallic compounds (IMCs). Its thermal conductivity reached 402 W / (m·K), a 123.3% improvement compared to the traditional CuSn structure (180 W / (m·K)).

Claims

1. A high thermal conductivity composite metal material, comprising upper and lower substrates, characterized in that, An intermediate layer is disposed between the substrates; the intermediate layer is one of CuNiCu structure, CuNiAuNiCu structure or CuNiAuInAuNiCu structure; the materials of each layer are connected by solid solution diffusion and do not form intermetallic compounds.

2. The high thermal conductivity composite metal material according to claim 1, characterized in that, The CuNiCu structure is prepared by electroplating, wherein the Cu layer thickness is 4-6 μm and the Ni layer thickness is 0.24-0.26 μm, 0.39-0.41 μm or 0.49-0.51 μm.

3. The high thermal conductivity composite metal material according to claim 2, characterized in that, The CuNiCu structure is prepared by electroplating, wherein the Cu layer has a thickness of 5 μm and the Ni layer has a thickness of 0.25 μm, 0.4 μm or 0.5 μm.

4. The high thermal conductivity composite metal material according to claim 1, characterized in that, The CuNiAuNiCu structure is prepared by electroplating and sputtering, wherein the Cu layer has a thickness of 4-6 μm, the Ni layer has a thickness of 0.24-0.26 μm, and the Au layer is prepared by sputtering with a thickness of 90-110 nm, 140-160 nm, or 190-210 nm.

5. The high thermal conductivity composite metal material according to claim 4, characterized in that, The CuNiAuNiCu structure is prepared by electroplating and sputtering, wherein the Cu layer has a thickness of 5 μm, the Ni layer has a thickness of 0.25 μm, and the Au layer is prepared by sputtering with a thickness of 100 nm, 150 nm, or 200 nm.

6. The high thermal conductivity composite metal material according to claim 1, characterized in that, The CuNiAuInAuNiCu structure is prepared by electroplating and sputtering. The Cu layer has a thickness of 4-6 μm, the Ni layer has a thickness of 0.24-0.26 μm, the Au layer has a thickness of 90-110 nm, and the In layer is prepared by sputtering with a thickness of 90-110 nm, 140-160 nm, or 190-210 nm.

7. The high thermal conductivity composite metal material according to claim 6, characterized in that, The CuNiAuInAuNiCu structure is prepared by electroplating and sputtering, wherein the Cu layer has a thickness of 5 μm, the Ni layer has a thickness of 0.25 μm, the Au layer has a thickness of 100 nm, and the In layer is prepared by sputtering with a thickness of 100 nm, 150 nm, or 200 nm.

8. A method for preparing the high thermal conductivity composite metal material according to claim 1, characterized in that, This includes using ultrasonic pressure welding for interlayer solution bonding, controlling the welding temperature at 200-250 ℃, ultrasonic power at 300-500 W, pressure at 0.3-0.5 MPa, and welding time at 10-20 s.

9. The method for preparing the high thermal conductivity composite metal material according to claim 8, characterized in that, Specifically, the following steps are included: S1. Electroplating process is used to sequentially deposit the bottom Cu layer and the corresponding transition layer on the substrate surface; S2. When the intermediate layer is a CuNiAuNiCu structure or a CuNiAuInAuNiCu structure, after electroplating is completed, it is transferred to a sputtering device to deposit an Au layer and / or an In layer by controlling the process parameters. S3. Deposit the top Cu layer to complete the overall structure formation; S4. Ultrasonic pressure welding is used for interlayer solid solution bonding to ensure sufficient diffusion between layers and prevent the formation of intermetallic compounds.

10. The method for preparing the high thermal conductivity composite metal material according to claim 9, characterized in that, The electroplating process described in S1 is as follows: metal layers are sequentially electrodeposited on the pretreated substrate surface. The electroplating is performed using direct current electroplating, and the current density is controlled to be 1-5 A / dm³ during the electroplating process. 2 The electroplating temperature is 20-40 ℃; the process parameters described in S2 are: vacuum degree better than 5.0×10 -4 The working pressure is 0.5-0.8 Pa, the sputtering power is 30-100 W, and the thickness of each layer is precisely grown by controlling the deposition time.

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