Metal base material with nano-copper surface and preparation method of metal base material

Abstract

The invention relates to the technical field of metal materials, in particular to a metal base material with nano-copper on the surface and a preparation method of the metal base material. The preparation method comprises the following steps: mixing an initial metal base material with a metal salt solution, and carrying out a preliminary reaction to form a preliminarily modified metal base material; and mixing the modified metal base material with a reducing reagent for reaction to form the metal base material with the surface containing nano-copper. The metal base material with the nano-copper surface, provided by the embodiment of the invention, not only has oxidation resistance, but also has excellent sintering performance and bonding performance.

Description

Technical Field

[0001] The present invention relates to the technical field of metal materials, and in particular to a metal substrate with nano-copper on its surface and a preparation method thereof. Background Art

[0002] As electronic devices develop towards miniaturization, integration, and multifunctionality, device power density is gradually increasing, posing more severe challenges to chip packaging and system heat dissipation. Power devices such as third-generation semiconductors have the advantages of wide bandgap, high temperature resistance, and high energy conversion efficiency, and are widely used in aerospace, new energy vehicles, rail transportation, photovoltaics, and 5G communications. Traditional tin-based solder pastes have a low melting point and poor thermal conductivity, which cannot meet the heat dissipation and high-temperature service requirements of high-power devices. Therefore, there is an urgent need to develop high-temperature resistant and highly thermally conductive die-bonding materials. Nanometal solder pastes (such as nanosilver and nanocopper) have excellent electrical and thermal conductivity and a small size effect. They can be used to prepare high-temperature resistant interconnects at low temperatures, meeting the efficient heat dissipation and high-temperature service requirements of high-power devices. However, sintered silver has high porosity and high electromigration, which can easily reduce the reliability of the interconnect structure and even cause circuit failure. Compared with nanosilver paste, nanocopper paste not only has excellent electrothermal performance, but also has good electromigration resistance and cost-effectiveness. However, nano-copper is prone to spontaneous oxidation in the air, which increases the difficulty of practical application. At the same time, the sintering and bonding properties of existing nano-copper are also poor, which further limits its application.

[0003] In view of this, the present invention is proposed. Summary of the Invention

[0004] The present invention aims to provide a metal substrate with nano-copper on its surface and a method for preparing the same. The metal substrate with nano-copper on its surface provided by the embodiment of the present invention not only has excellent oxidation resistance, but also has excellent sintering and bonding properties.

[0005] The present invention is achieved in that:

[0006] In a first aspect, the present invention provides a method for preparing a metal substrate having nano-copper on its surface, comprising: mixing an initial metal substrate with a metal salt solution to perform a preliminary reaction to form a preliminarily modified modified metal substrate;

[0007] The modified metal substrate and a reducing agent are mixed and reacted to form a metal substrate containing nano-copper on the surface.

[0008] In an optional embodiment, the initial metal substrate is any one of micron copper particles, micron copper plates, millimeter copper plates, centimeter copper plates and decimeter copper plates.

[0009] In an optional embodiment, the metal salt solution includes a copper chloride solution;

[0010] The concentration of the copper chloride solution is 5-30 wt%.

[0011] In an optional embodiment, 5-30 ml of the metal salt solution is added per volume of the initial metal substrate.

[0012] In an optional embodiment, the conditions for forming the preliminarily modified modified metal substrate include: a reaction temperature of 20-100° C., and a reaction time of 1 minute to 24 hours.

[0013] In an optional embodiment, the reducing agent is an acidic solution;

[0014] Preferably, the acidic solution is selected from at least one of hydrochloric acid and formic acid.

[0015] In an optional embodiment, the concentration of the reducing agent is 1-20 wt %.

[0016] In an optional embodiment, before mixing the initial metal substrate with the metal salt solution, the initial metal substrate is pre-treated;

[0017] Preferably, the pre-treatment includes: cleaning and drying the initial metal substrate;

[0018] Preferably, the pre-treatment comprises: sequentially subjecting the initial metal substrate to copper cleaning solution, ultrasonic cleaning, alcohol cleaning and drying.

[0019] In an optional embodiment, the method comprises: treating the modified metal substrate before mixing with the reducing agent;

[0020] Preferably, the treatment comprises: cleaning the modified metal substrate.

[0021] In a second aspect, the present invention provides a metal substrate having a surface of nano-copper, which is prepared by the method for preparing a metal substrate having a surface of nano-copper as described in any one of the aforementioned embodiments;

[0022] Preferably, when the metal substrate is in granular form, the metal substrate is a core-shell structure, and the nano-copper serves as the shell;

[0023] When the metal substrate is non-granular, the surface of the metal substrate is a nano-copper structure.

[0024] The present invention has the following beneficial effects: Embodiments of the present invention provide a preparation method that preliminarily modifies an initial metal substrate by reacting it with a metal salt solution, and then reacting it with a reducing agent to form nano-copper on the surface. This ultimately improves the sintering performance, bonding performance, and oxidation resistance of the metal substrate, thereby expanding the application of the metal substrate. Specifically, the metal substrate formed by this process can achieve significantly improved shear strength, better electrical conductivity, and higher reliability in solder joints under the same process parameters, or achieve bonding strength comparable to that of traditional materials under conditions of lower sintering temperature and shorter sintering time. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0026] Figure 1 A schematic diagram of a process flow of a method for preparing a metal substrate having a nano-copper surface provided by an embodiment of the present invention;

[0027] Figure 2 This is a scanning electron microscope image of the morphology of the clean micron Cu particles provided in Example 1 of the present invention;

[0028] Figure 3 This is a scanning electron microscope image of the morphology of the preliminarily modified new micron Cu particles provided in Example 1 of the present invention;

[0029] Figure 4 This is a scanning electron microscope image of the Cu particles of the product provided in Example 1 of the present invention;

[0030] Figure 5 This is a scanning electron microscope image of the morphology of the clean copper plate provided in Example 2 of the present invention;

[0031] Figure 6 This is a scanning electron microscope image of the morphology of the copper plate with preliminary surface modification provided in Example 2 of the present invention;

[0032] Figure 7 This is a scanning electron microscope image of the morphology of a copper plate with nanoporous copper attached to the surface of the product provided in Example 2 of the present invention;

[0033] Figure 8 EDS spectra of the products provided in Examples 1 and 2 of the present invention;

[0034] Figure 9 This is a test result diagram provided for the test example of the present invention. DETAILED DESCRIPTION

[0035] To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, all are conventional products that can be purchased commercially.

[0036] In the first aspect, the present invention provides a method for preparing a metal substrate having a surface of nano-copper. Figure 1 ,include:

[0037] (1) The initial metal substrate is cleaned and dried. Specifically, the initial metal substrate is placed in a copper cleaning solution, then ultrasonically cleaned, and finally cleaned with an alcohol, such as anhydrous ethanol, and vacuum dried to obtain a clean initial metal substrate. The above cleaning is to remove copper oxides on the surface of the initial metal substrate, which is conducive to the subsequent formation of nano-copper on the surface.

[0038] The copper cleaning solution can be selected from an acid solution, such as but not limited to hydrochloric acid, acetic acid or formic acid. The amount of the copper cleaning solution added should not be too much, and the mass percentage of the acid solution is 1 to 30 wt%.

[0039] The initial metal substrate can be obtained from commercial sources. The initial metal substrate is any one of micron copper particles, micron copper plates, millimeter copper plates, centimeter copper plates, and decimeter copper plates.

[0040] (2) The clean initial metal substrate is mixed with a metal salt solution to perform a preliminary reaction to form a preliminarily modified modified metal substrate.

[0041] The metal salt solution may be a purchased metal salt dissolved in water. Alternatively, it may be a metal salt solution obtained by reacting a metal oxide with an acid. In this case, the metal oxide and the acid may be reacted first to form the metal salt solution, which may then be mixed with the initial metal substrate for reaction. Alternatively, the metal oxide and the acid may be directly mixed with the initial metal substrate for reaction.

[0042] The metal salt solution may be a copper salt solution, such as copper chloride. The concentration of the copper chloride solution may be 5-30 wt%, such as 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, or 30 wt%.

[0043] 5-30 ml of the metal salt solution is added to each volume of the initial metal substrate.

[0044] Conditions for forming the preliminarily modified modified metal substrate include: a reaction temperature of 20-100°C, such as any value between 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, and 100°C. A reaction time of 1 minute to 24 hours, such as any value between 1 minute, 5 minutes, 10 minutes, 15 minutes, 30 minutes, 1 hour, 10 hours, 15 hours, and 24 hours. In other words, the initial metal substrate and the metal salt solution can be mixed and reacted by soaking for a long time at room temperature or by rapidly reacting under heating conditions.

[0045] In the embodiments of the present invention, a chemical reaction occurs between the initial metal substrate and a metal salt solution by mixing, immersing, or heating the solution, thereby modifying the surface of the initial metal substrate. The inventors speculate that the reaction is a precipitation reaction, and the chemical substance formed is metal oxidation.

[0046] (3) The modified metal substrate is then treated, for example, by washing to remove any residual metal salt solution from the surface of the modified metal substrate. Specifically, for example, the new metal substrate is washed with 200 ml of pure water and 50 ml of anhydrous ethanol, respectively.

[0047] (4) The modified metal substrate and the reducing agent are mixed and reacted, so that the metal substrate attachment modified by the metal salt solution undergoes an oxidation-reduction reaction, and then a metal substrate containing nano-copper is formed on the surface.

[0048] The reducing agent is an acidic solution; for example, an acidic solution including but not limited to at least one of hydrochloric acid, formic acid and acetic acid.

[0049] At this time, the reducing agent treatment is carried out at room temperature for 1-10 minutes, and ultrasonic treatment can be added during the treatment.

[0050] The concentration of the reducing agent is 1-20 wt%, for example, 1 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, or any other value between 1-20 wt%. The concentration of the reducing agent should not be too high. The purpose of the reducing agent is to remove the metal oxides on the surface of the new metal substrate through an oxidation-reduction reaction, while allowing a portion of the copper oxide to be reduced, resulting in nano-metal particles that adhere to the surface of the original metal substrate.

[0051] In summary, the embodiments of the present invention form a large number of nano-metal ions through a metal salt solution, which are attached to the surface of the metal substrate. This significantly improves the sintering performance and structural density of the metal substrate compared to ordinary micron metal substrates. Furthermore, the metal substrate improved by the embodiments of the present invention has lower surface energy, lower active sites, and fewer unsaturated chemical bonds than nano-metal particles, thus having good antioxidant and bonding properties.

[0052] In a second aspect, the present invention provides a metal substrate having a surface of nano-copper, prepared by the method for preparing a metal substrate having a surface of nano-copper as described in any of the aforementioned embodiments; for example, when the metal substrate is granular, the metal substrate has a core-shell structure, with the nano-copper serving as the outer shell and the core of the initial metal substrate. When the metal substrate is non-granular, such as a plate-like structure, the metal substrate has a surface of nano-copper.

[0053] The features and performance of the present invention are further described in detail below with reference to the embodiments.

[0054] Example 1

[0055] An embodiment of the present invention provides a method for preparing a metal substrate having a nano-copper surface, comprising:

[0056] (1) Purchase micron Cu particles with an average size of 1 μm, and weigh 3 g of micron Cu particles, 25 ml of 25 wt% hydrochloric acid, and 5 ml of 15 wt% copper chloride solution.

[0057] (2) 3 g of micron Cu particles were placed in a reagent bottle, 25 ml of 20 wt% hydrochloric acid was added to the reagent bottle and ultrasonically cleaned for 5 minutes, then the micron Cu particles were eluted and placed in a clean reagent bottle, and washed two to three times with 30 ml of anhydrous ethanol, and then the reagent bottle was placed in a vacuum drying oven at 25 ° C for 30 minutes to obtain clean micron Cu particles. Figure 2 shown.

[0058] (3) The micron Cu particles treated in step 2 and 15 wt% copper chloride solution were placed in a crucible (wherein, 5 ml of copper chloride solution was added for each volume of micron Cu particles). The crucible was placed on a heating table, heated to 100°C, and heated for 5 minutes to obtain new micron Cu particles modified by the metal salt solution, such as Figure 3 shown.

[0059] (4) Soak the new micron Cu particles in step 3 in a reagent bottle containing 25 ml of 20 wt% hydrochloric acid solution for 2 minutes to achieve the preparation of micro-nano hierarchical structure Cu particles, such as Figure 4 shown.

[0060] The Cu particles are of a core-shell structure, the surface of which is a nanoparticle, the core of which is a shell structure, and the core of which is a micron Cu particle.

[0061] Example 2

[0062] An embodiment of the present invention provides a method for preparing a metal substrate having a nano-copper surface, comprising:

[0063] (1) Purchase a copper plate with a thickness of 1 mm, cut it into three pieces of 5 mm × 5 mm, and weigh 1 g of copper oxide particles, 50 ml of 20 wt% hydrochloric acid, and 25 ml of anhydrous ethanol.

[0064] (2) Place three copper plates in a reagent bottle, pour 25 ml of hydrochloric acid and 25 ml of anhydrous ethanol solution into the reagent bottle and perform ultrasonic cleaning for 5 minutes to obtain clean copper plates. Figure 5 shown.

[0065] (3) Place a clean copper plate and 1g of copper oxide particles into a reagent bottle, pour 25ml of hydrochloric acid into the reagent bottle, and let it stand for 15h to obtain a copper plate with preliminary surface modification, such as Figure 6 shown.

[0066] (4) The copper plate with preliminary surface modification was placed in a reagent bottle, and 25 ml of 5 wt% hydrochloric acid was poured into the reagent bottle for ultrasonic cleaning for 5 minutes to obtain a copper plate with nanoporous copper attached to the surface, such as Figure 7 shown.

[0067] The EDS spectrum of the metal substrate with nano-copper on the surface of the product provided in Example 1 and Example 2 of the present invention is shown in Figure 8 .

[0068] Example 3-Example 5

[0069] Examples 3 to 5 provide a method for preparing a metal substrate having nano-copper on its surface. The preparation method is substantially the same as the preparation method provided in Example 1, with the only difference being some of the conditions, as follows:

[0070] Example 3: The concentration of the copper chloride solution is 5wt%, and 12.5ml of the copper chloride solution is added per volume of clean micron Cu particles. The reaction temperature is room temperature, the reaction time is 14h, the reducing agent is 50ml of hydrochloric acid, the concentration of the reducing agent is 1wt%, and the treatment is 10 minutes.

[0071] Example 4: The concentration of the copper chloride solution is 5wt%, and 25ml of the copper chloride solution is added to each volume of clean micron Cu particles. The reaction temperature is room temperature, the reaction time is 8h, the reducing agent is 50ml of hydrochloric acid, the reducing agent concentration is 20wt%, and the treatment time is 1 minute.

[0072] Example 5: The concentration of the copper chloride solution is 5 wt %, and 30 ml of the copper chloride solution is added per volume of clean micron Cu particles. The reaction temperature is room temperature, the reaction time is 10 h, the reducing agent is 50 ml of hydrochloric acid, the reducing agent concentration is 15 wt %, and the treatment time is 6 minutes.

[0073] Test example

[0074] (1) The copper particles prepared in Example 1 and the unmodified initial clean micron Cu particles were printed on two identical copper sheets with the same mass and prepared into a sandwich structure. The sandwich structure was then bonded under the sintering conditions of 250°C, 5 MPa, and 20 min. After bonding, the samples were placed in a CondorSigma shearing machine and the shear head was set to a speed of 200 mm / s for testing. The shear force comparison results are shown in FIG. Figure 9 shown.

[0075] (2) The modified copper plate and the unmodified copper plate prepared in Example 2 were stacked up and down, and then bonded under the sintering conditions of 250°C, 15 MPa, and 20 min. After bonding, the samples were placed in a CondorSigma shearing machine and tested with a pusher head set at a speed of 200 mm / s. The shear force comparison results are shown in Figure 2. Figure 9 shown.

[0076] Depend on Figure 9 It can be seen that the shear strength of the modified micron Cu particles is improved; the shear strength of the modified copper plate is improved from almost no bonding strength to approximately 10 MPa.

[0077] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for preparing a metal substrate having a surface of nano-copper, characterized in that: include: mixing an initial metal substrate with a metal salt solution to perform a preliminary reaction to form a preliminarily modified modified metal substrate; The modified metal substrate and a reducing agent are mixed and reacted to form a metal substrate containing nano-copper on the surface.

2. The preparation method according to claim 1, characterized in that The initial metal substrate is any one of micron copper particles, micron copper plates, millimeter copper plates, centimeter copper plates and decimeter copper plates.

3. The preparation method according to claim 1, characterized in that The metal salt solution includes a cupric chloride solution; The concentration of the copper chloride solution is 5-30 wt%.

4. The preparation method according to any one of claims 1 to 3, characterized in that 5-30 ml of the metal salt solution is added to each volume of the initial metal substrate.

5. The preparation method according to claim 1, characterized in that The conditions for forming the preliminarily modified modified metal substrate include: a reaction temperature of 20-100° C., and a reaction time of 1 minute to 24 hours.

6. The preparation method according to claim 1, characterized in that The reducing agent is an acidic solution; Preferably, the acidic solution is selected from at least one of hydrochloric acid and formic acid.

7. The preparation method according to claim 1, characterized in that The concentration of the reducing agent is 1-20 wt%.

8. The preparation method according to claim 1, characterized in that Before mixing the initial metal substrate with the metal salt solution, pre-treating the initial metal substrate; Preferably, the pre-treatment includes: cleaning and drying the initial metal substrate; Preferably, the pre-treatment comprises: sequentially subjecting the initial metal substrate to copper cleaning solution, ultrasonic cleaning, alcohol cleaning and drying.

9. The preparation method according to claim 1, characterized in that include: treating the modified metal substrate prior to mixing with the reducing agent; Preferably, the treatment comprises: cleaning the modified metal substrate.

10. A metal substrate with nano-copper on its surface, characterized in that: It is prepared by the method for preparing a metal substrate having a nano-copper surface as described in any one of claims 1 to 9; Preferably, when the metal substrate is in granular form, the metal substrate is a core-shell structure, and the nano-copper serves as the shell; When the metal substrate is non-granular, the surface of the metal substrate is a nano-copper structure.

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