Diamond composite heat conduction structure based on Ag-Cu-Ti active brazing

Abstract

The invention discloses a diamond composite heat conduction structure based on Ag-Cu-Ti active brazing, and relates to the technical field of high heat conduction material connection, the diamond composite heat conduction structure comprises a diamond material layer, an Ag-Cu-Ti active brazing layer and a metal substrate layer, the diamond material layer is in a granular or block form, and the Ag-Cu-Ti active brazing layer is arranged on the metal substrate layer. A TiC transition layer is formed at the interface of the diamond material layer and the Ag-Cu-Ti active brazing layer, the thickness of TiC is 50-500 nm, and the Ag-Cu-Ti active brazing layer comprises the following components in percentage by weight: 60-70% of Ag, 25-35% of Cu, 3-8% of Ti and 0.5-2% of an additive. The prepared composite heat conduction structure can be widely applied to the related fields of high-power laser diode heat dissipation substrates, DBC substrates of IGBT / SiC modules, satellite phased array radar T / R assembly heat sinks and the like, the efficient welding bottleneck of diamond and metal is broken through through collaborative optimization of components and the technology, and the composite heat conduction structure has the advantages of being high in heat conduction and reliability and low in cost.

Description

Technical Field

[0001] The present invention relates to the technical field of high thermal conductivity material connection, and particularly relates to a diamond composite thermal conductive structure based on Ag-Cu-Ti active soldering. Background Art

[0002] Diamond has become an ideal thermal conductive material due to its ultra-high thermal conductivity (>2000 W / m·K). However, there are the following difficulties when welding it to metal or ceramic substrates: 1. Poor wettability: The surface of diamond is highly inert, and traditional solders (such as Sn-Ag, Pb-Sn) are difficult to form an effective bond.

[0003] 2. High interfacial thermal resistance: Microvoids and cracks are likely to occur at the welding interface, resulting in a decrease in the heat conduction efficiency by more than 30%.

[0004] 3. Insufficient high-temperature stability: Conventional solders have a low melting point (<300°C), which cannot meet the requirements of high-temperature devices (such as GaN-on-Diamond).

[0005] 4. Thermal expansion mismatch: The difference between diamond (CTE≈1×10 -6 / K) and copper substrate (CTE≈17×10 -6 / K) is large, and cracking is likely to occur after welding.

[0006] In the prior art, although the use of Ti / Au or Cr / Ni metallization layers can improve wettability, the process is complex and costly, and the metallization layers themselves have a low thermal conductivity (<200 W / m·K), becoming a new thermal resistance bottleneck. Summary of the Invention

[0007] The technical problem to be solved by the present invention is: to provide a diamond composite thermal conductive structure based on Ag-Cu-Ti active soldering, and its purpose is: through the synergistic optimization of composition and process, to break through the bottleneck of efficient welding of diamond and metal, and to have the advantages of high thermal conductivity, high reliability and low cost. The technical solution adopted by the present invention is as follows: A diamond composite thermal conductive structure based on Ag-Cu-Ti active soldering includes a diamond material layer, an Ag-Cu-Ti active soldering layer, and a metal substrate layer. The diamond material layer is in the form of particles or blocks. A TiC transition layer is formed at the interface between the diamond material layer and the Ag-Cu-Ti active soldering layer. The thickness of the TiC is 50 - 500 nm. The components and corresponding weight percentages in the Ag-Cu-Ti active soldering layer are Ag:Cu:Ti:additive = 60 - 70:25 - 35:3 - 8:0.5 - 2.

[0008] As a preferred technical solution, the diamond material layer is treated by hydrogen plasma etching, and the surface roughness Ra = 50 - 200 nm.

[0009] As a preferred technical solution, the additive is an oxide or metal powder of Zr, La or Ce.

[0010] As a preferred technical solution, the preparation steps of the composite heat conduction structure are as follows: a: Perform plasma etching and titanium pre-deposition on the diamond surface; b: Assemble the diamond prepared in step a with the brazing layer and the metal substrate layer, and then perform vacuum hot pressing.

[0011] c: Polish the structure assembled in step b.

[0012] In the preparation of the brazing layer of the present invention, the composition is optimized. Using 60-70 wt% Ag, 25-35 wt% Cu, 3-8 wt% Ti, and adding 0.5-2 wt% of Zr or rare earth elements such as La and Ce as raw materials, during the fusion process, the melting point is reduced to 750-850 °C, and at the same time, the interfacial reaction activity is enhanced. The Ti element reacts with the diamond surface to form a TiC transition layer, which is directly chemically bonded, and the interfacial thermal resistance is reduced to 5×10 -8 m²·K / W or less. When treating the diamond, the diamond particles or the substrate are first etched by hydrogen plasma to form a nanoscale rough surface with Ra = 50-200 nm, increasing the contact area of the filler metal. In a vacuum environment with a pressure less than <10 - ³, a 1-5 nm titanium layer is pre-deposited to promote the diffusion reaction of the Ti element in the filler metal. A "diamond particle + brazing layer + metal substrate" sandwich structure is adopted, where the diamond volume fraction is 40-70%. Through the hot pressing process, it is processed in an environment with a pressure of 5-20 MPa and a temperature of 800-900 °C, so that the filler metal penetrates into the diamond gaps to form a continuous heat conduction network. Finally, after welding, through rapid cooling with a cooling rate >50 °C / s, the overgrowth of the TiC layer can be inhibited, and the surface chemical mechanical polishing makes the roughness <1 μm, improving the adhesion to electronic devices. The diamond composite heat conduction structure based on Ag-Cu-Ti active brazing prepared by the present invention has a thermal conductivity of 400-800 W / m·K, which is 60%-100% higher than that of pure copper; the shear strength of the welding interface >100 MPa, and the strength retention rate still remains >90% in a high-temperature environment of 300 °C. The adjustable range of the thermal expansion coefficient is expanded to 5-12×10 -6 / K, which is compatible with mainstream semiconductor materials and can be widely applied to related fields such as high-power laser diode heat dissipation substrates, DBC substrates of IGBT / SiC modules, and heat sinks of satellite phased array radar T / R components. Through the synergistic optimization of composition and process, the bottleneck of efficient welding between diamond and metal is broken through, and it has the advantages of high thermal conductivity, high reliability and low cost. Description of the Drawings

[0013] Figure 1 Schematic diagram of the composite structure of the present invention Among them, 1 is the diamond material layer, 2 is the brazing layer, 3 is the metal substrate layer, and 4 is the TiC transition layer (4). Specific embodiments

[0014] In order to make the objectives, technical solutions and advantages of the present invention more clear and understandable, the present invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0015] If there is no special description, all the embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0016] If there is no special description, all the technical features and optional technical features of the present application can be combined with each other to form a new technical solution. Example 1

[0017] A diamond composite heat-conducting structure based on Ag-Cu-Ti active brazing includes a diamond material layer 1, an Ag-Cu-Ti active brazing layer 2 and a metal substrate layer 3. The diamond material layer 1 is in the form of particles or blocks. A TiC transition layer 4 is formed at the interface between the diamond material layer 1 and the Ag-Cu-Ti active brazing layer 2. The thickness of the TiC is 50-500 nm. The components and corresponding weight percentages in the Ag-Cu-Ti active brazing layer 2 are Ag:Cu:Ti:additive = 60-70:25-35:3-8:0.5-2.

[0018] As a preferred technical solution, the diamond material layer 1 is treated by hydrogen plasma etching, and the surface roughness Ra = 50-200 nm.

[0019] As a preferred technical solution, the additive is an oxide or metal powder of Zr, La or Ce.

[0020] As a preferred technical solution, the preparation steps of the composite heat-conducting structure are as follows: a: Perform plasma etching and titanium pre-deposition on the diamond surface; b: Assemble the diamond prepared in step a with the brazing layer (2) and the metal substrate layer (3), and then perform vacuum hot pressing.

[0021] c: Polish the structure assembled in step b. Example 2

[0022] In the process of preparing the composite heat-conducting structure, the copper substrate is reinforced by diamond particles, and the specific steps are as follows: Diamond particles with a particle size of 100 μm are mixed with Ag-65Cu-5Ti solder powder (particle size 10 μm) at a volume ratio of 6:4, and 0.5 wt% CeO 2 nanopowder is added; The mixture is filled into a graphite mold and sintered in a vacuum hot press furnace (850 °C / 15 MPa / 30 min).

[0023] The method steps other than this are the same.

[0024] After the composite component of Example 2 is polished after cooling, the measured thermal conductivity is 650 W / m·K, which is greatly improved compared with the thermal conductivity of 400 W / m·K of the pure copper substrate, and the shear strength is also increased to 120 MPa. Example 3

[0025] In the process of preparing the composite heat-conducting structure, by welding the diamond substrate), the specific steps are as follows: 1. A 5 nm titanium layer is pre-plated on the surface of a 1 mm thick CVD diamond substrate and a copper substrate; 2. A 50 μm thick Ag-70Cu-4Ti foil is clamped and bonded in a vacuum brazing furnace (800 °C / 10⁻³ Pa / 10 min).

[0026] For the composite component of Example 3, the measured interfacial thermal resistance is 3.2×10 -8 m²·K / W, and no delamination phenomenon is observed after 1000 thermal cycle tests at -55~250 °C.

[0027] Finally, it should be noted that: the above embodiments are only relatively preferred embodiments of the present invention to illustrate the technical solutions of the present invention, rather than limiting it, and certainly not limiting the patent scope of the present invention; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention; that is to say, any meaningless changes or polishings made in the main design concept and spirit of the present invention, as long as the technical problems solved are still the same as those of the present invention, should be included in the protection scope of the present invention; in addition, directly or indirectly applying the technical solutions of the present invention to other related technical fields shall also be included in the patent protection scope of the present invention by the same token.

Claims

1. A diamond composite thermal conductive structure based on Ag-Cu-Ti active brazing, characterized in that: The invention comprises a diamond material layer (1), an Ag-Cu-Ti active brazing layer (2) and a metal substrate layer (3), wherein the diamond material layer (1) is in the form of particles or blocks, a TiC transition layer (4) is formed at the interface between the diamond material layer (1) and the Ag-Cu-Ti active brazing layer (2), the thickness of the TiC transition layer (4) is 50 to 500 nm, and the components and corresponding weight percentages in the Ag-Cu-Ti active brazing layer (2) are Ag:Cu:Ti:additive=60 to 70:25 to 35:3 to 8:0.5 to 2.

2. The diamond composite thermal conductive structure based on Ag-Cu-Ti active brazing according to claim 1, characterized in that: The diamond material layer (1) is treated by hydrogen plasma etching, and the surface roughness Ra is 50-200 nm.

3. The diamond composite thermal conductive structure based on Ag-Cu-Ti active brazing according to claim 1, characterized in that: The additive is oxide or metal powder of Zr, La or Ce.

4. The diamond composite thermal conductive structure based on Ag-Cu-Ti active brazing according to claim 1, characterized in that: The preparation steps of the composite thermal conductive structure are as follows: a: Plasma etching and titanium pre-deposition on the diamond surface; b: vacuum hot pressing is performed after assembling the diamond prepared in step a with the brazing layer (2) and the metal substrate layer (3); c: Polish the structure assembled in step b.

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