Copper-molybdenum-copper composite material with bending size requirement and flexible deep processing method thereof

Abstract

The application discloses a copper-molybdenum-copper composite material and a flexible deep processing method thereof, and comprises the following steps: adding pure molybdenum metal powder into a solvent and a dispersing agent, and after once ball milling, adding a thickening agent and a binder, and after twice ball milling and defoaming, molybdenum slurry for casting forming is obtained; the molybdenum slurry for casting forming is placed on a base strip, and after drying, a molybdenum film is obtained by adjusting a scraper height gap and a base strip speed; a certain thickness of copper slurry for printing is screen printed on upper and lower surfaces of the molybdenum film, and after drying and hot isostatic pressing, a copper-molybdenum-copper composite material flexible film is obtained; the copper-molybdenum-copper composite material flexible film is placed in a stamping die cavity to be bent, and after low-temperature curing, shaping and demolding, and after degumming and integrated co-firing, the copper-molybdenum-copper composite material with bending size requirements is obtained. The application has the advantages of simple process, precise component control, good precision, high finished product rate and the like.

Description

Technical Field

[0001] This invention relates to the field of copper-molybdenum-copper composite materials, specifically to a copper-molybdenum-copper composite material with bending dimension requirements and its flexible deep processing method. Background Technology

[0002] Heat sink materials are commonly used for heat dissipation when integrated circuits are combined with chips. Typical heat sink materials are represented by tungsten copper alloy, molybdenum copper alloy, copper-molybdenum copper, and copper-molybdenum copper-copper flat plate composite materials. These materials have advantages such as high thermal conductivity, low coefficient of thermal expansion, and compatibility with chips.

[0003] Currently, the main production methods for tungsten copper and molybdenum copper heat sink materials are melt infiltration and liquid phase sintering. Flat composite materials, on the other hand, are produced by rolling and thermal diffusion of the core material and double-sided copper layers. Further processing into products with precise structural dimensions and complex shapes suitable for chips requires machining or stamping processes. Due to the significant differences in plasticity, toughness, and hardness between the molybdenum core material and the copper layers on the upper and lower surfaces of the flat composite material, the different materials undergo non-cooperative deformation under stress during stamping and bending, resulting in material fracture during stamping and bending.

[0004] Existing technologies for preparing copper-molybdenum-copper composite materials involve complex processes, inaccurate composition control, and poor precision. In particular, the differences in mechanical properties between different materials make them unsuitable for precision stamping and hard machining. Summary of the Invention

[0005] In view of the above-mentioned shortcomings, the present invention provides a copper-molybdenum-copper composite material with bending dimension requirements and its flexible deep processing method. The present invention prepares a molybdenum preform film with good copper wettability through a water-based casting molding process. Copper paste is then applied to the upper and lower surfaces of the film material by screen printing. A thick film material with good flexibility of molybdenum-copper laminate is prepared by hot isostatic pressing. The flexible film is then placed in a designed mold for curing and shaping, followed by degumming, integrated co-firing, and finally shaping. This completes the flexible processing of flat composite materials with precision structure and complex shape, effectively solving the problem of fracture of hard composite materials after firing during stamping. It has the advantages of simple process, precise composition control, good precision, and high yield.

[0006] To achieve the above objectives, the present invention provides a flexible deep processing method for copper-molybdenum-copper composite materials with bending dimension requirements, comprising the following steps:

[0007] Step 1: Add pure molybdenum metal powder to solvent and dispersant, and after ball milling once, add thickener and binder, and after ball milling a second time and degassing, obtain molybdenum slurry for casting.

[0008] Step 2: Place the molybdenum slurry for casting on a base belt and obtain a molybdenum film by adjusting the doctor blade height gap and base belt speed after drying;

[0009] Step 3: A copper paste of a certain thickness is screen-printed on the upper and lower surfaces of the molybdenum film. After drying and hot isostatic pressing, a flexible copper-molybdenum-copper composite film is obtained. The copper paste is composed of copper powder, glass powder and organic carrier.

[0010] Step 4: Place the flexible diaphragm of copper-molybdenum-copper composite material into the stamping die cavity for bending, and after low-temperature curing and demolding, it is then degummed and co-fired to obtain copper-molybdenum-copper composite material with bending dimensions required; wherein, the low-temperature curing temperature is 150-350℃ and the time is 2-6h.

[0011] According to one aspect of the present invention, in step 1, the molybdenum slurry for casting has a pure molybdenum metal powder content of 70-80 wt%, a solvent content of 11-25 wt%, a dispersant content of 0.8-1.2 wt%, a thickener content of 1.2-2.8 wt%, and a binder content of 3-6 wt%.

[0012] According to one aspect of the present invention, in step 1, the particle size of the pure molybdenum metal powder is 2-10 μm; the solvent is deionized water; the dispersant is polyacrylic acid or Hypermer KD-1; the thickener is at least one of glycerol and polyethylene glycol; and the binder is one or more of PVA-2488, polymethyl methacrylate, and ethyl acrylate.

[0013] According to one aspect of the present invention, in step 1, the primary ball milling uses a nylon ball milling jar, with silicon nitride as the grinding medium, a ball-to-material ratio of 1:1, a milling time of 6–48 h, and a rotation speed of 150–250 r / min; the secondary ball milling uses a nylon ball milling jar, with silicon nitride as the grinding medium, a ball-to-material ratio of 1:1, a milling time of 6–48 h, and a rotation speed of 150–250 r / min; the degassing is performed under vacuum degassing conditions of 20–100 kPa for 5–20 min.

[0014] According to one aspect of the present invention, in step 2, the height gap of the scraper is 5 μm to 0.1 mm, the baseband speed is 2.0 to 2.5 mm / s, and the drying temperature is 20 to 30°C.

[0015] According to one aspect of the present invention, in step 3, the solid content of the copper paste for printing is 50-80%.

[0016] According to one aspect of the present invention, in step 3, the organic carrier is any one or more of terpineol, isopropanol, tributyl phthalate, ethyl cellulose, toluene, terephthalic acid, and castor oil.

[0017] According to one aspect of the present invention, in step 3, the screen printing method is as follows: first, copper paste is printed on one side and dried, then the other side is printed and dried, and the thickness of the single layer of screen printing is 0.1 to 10 μm.

[0018] According to one aspect of the present invention, the hot isostatic pressing is any one of hydrothermal isostatic pressing and oil-based isostatic pressing; the temperature of the hot isostatic pressing is 60-120°C, the pressure is 2000-5000 PSI, and the holding temperature is 60-100°C; the degumming is carried out in a hydrogen or nitrogen atmosphere, the degumming temperature is 300-600°C, and the degumming time is 8-24 hours; the integrated co-firing temperature is 800-1200°C, and the integrated co-firing time is 2-4 hours.

[0019] Based on the same inventive concept, the present invention also provides a copper-molybdenum-copper composite material with bending dimension requirements prepared by any of the above-mentioned flexible deep processing methods.

[0020] The beneficial effects of this invention are:

[0021] (1) The water-based casting slurry used in the water-based casting molding process of the present invention has a high solid content and strong interparticle bonding force. When the particle concentration reaches the degree of interparticle contact, it transforms into a three-dimensional spatial network structure of particles, and the material yield stress is greater.

[0022] (2) The casting paste of the present invention is a pseudoplastic fluid with moderate viscosity. The addition of plasticizer glycerol and binder PVA-2488 chain polar groups combines and encapsulates molecular chains, increases the intermolecular distance of the binder, forms a large number of cavities, increases the free volume, thereby reducing the glass transition temperature of the binder, making the brittle temperature range significantly lower than room temperature, thereby improving the flexibility of water-based casting sheets and meeting the processing requirements of rolling, cutting, stacking, bending and other processes.

[0023] (3) The intrinsic brittleness of molybdenum metal at room temperature and its insufficient strength at room temperature / high temperature limit the low-temperature processing performance of its molybdenum-copper alloy. However, this patent prepares a copper-molybdenum-copper composite material blank with good flexibility through tape casting and a lamination process. The interface is straight and does not introduce oxide impurities. At a certain temperature, the interfacial bonding between molybdenum and copper atoms is strengthened through the surface molybdenum-copper atomic metal bond composite mechanism. The bending shear force can be transferred between the molybdenum and copper metals through the good interfacial bonding, so that the deformation of the two phases tends to be consistent. At room temperature, the stress concentration at the interface between copper and molybdenum matrix is ​​greatly relieved through its own micro-scale plastic deformation, delaying the interface cracking. This enables the low-temperature ductility of functionally graded composite materials and good machinability of complex structures.

[0024] (4) The copper-molybdenum-copper composite material with bending dimension requirements prepared by the processing method of the present invention has a high pass rate and excellent mechanical properties. Attached Figure Description

[0025] Figure 1 This is a process flow diagram of the flexible deep processing method for copper-molybdenum-copper composite materials with bending dimension requirements as described in this invention.

[0026] Figure 2 This is a front view of the copper-molybdenum-copper composite material with bending dimension requirements prepared in Example 1 of the present invention;

[0027] Figure 3 This is a top view of the copper-molybdenum-copper composite material with bending dimension requirements prepared in Example 1 of the present invention;

[0028] Figure 4 This is a schematic diagram of the flexible processing of the copper-molybdenum-copper composite material with bending dimension requirements prepared in Example 1 of the present invention.

[0029] Explanation of reference numerals in the attached diagram: 1. Upper mold; 2. Lower mold. Detailed Implementation

[0030] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0031] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0032] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0033] To address the challenges of existing technologies for preparing copper-molybdenum-copper composites using methods such as hot pressing, rolling, and thermal diffusion, which involve complex processes, inaccurate composition control, and poor precision, especially given the unsuitability of precision stamping due to differences in the mechanical properties of the different materials, the inventors of this application provide a flexible deep-processing method for copper-molybdenum-copper composites with bending dimension requirements. The process flow diagram is shown below. Figure 1 As shown, it includes the following steps:

[0034] Step 1: Add pure molybdenum metal powder to solvent and dispersant, and after ball milling once, add thickener and binder, and after ball milling a second time and degassing, obtain molybdenum slurry for casting.

[0035] Step 2: Place the molybdenum slurry for casting on a base belt and obtain a molybdenum film by adjusting the doctor blade height gap and base belt speed after drying;

[0036] Step 3: A copper paste of a certain thickness is screen-printed on the upper and lower surfaces of the molybdenum film. After drying and hot isostatic pressing, a flexible copper-molybdenum-copper composite film is obtained. The copper paste is composed of copper powder, glass powder and organic carrier.

[0037] Step 4: Place the flexible diaphragm of copper-molybdenum-copper composite material into the stamping die cavity for bending, and after low-temperature curing and demolding, it is then degummed and co-fired to obtain copper-molybdenum-copper composite material with bending dimensions required; wherein, the low-temperature curing temperature is 150-350℃ and the time is 2-6h.

[0038] As an optional implementation, in step 1, the molybdenum slurry for casting contains 70-80 wt% pure molybdenum metal powder, 11-25 wt% solvent, 0.8-1.2 wt% dispersant, 1.2-2.8 wt% thickener, and 3-6 wt% binder.

[0039] As an optional implementation, in step 1, the particle size of the pure molybdenum metal powder is 2-10 μm; the solvent is deionized water; the dispersant is polyacrylic acid or Hypermer KD-1; the thickener is at least one of glycerol and polyethylene glycol; and the binder is one or more of PVA-2488, polymethyl methacrylate, and ethyl acrylate.

[0040] As an optional implementation, in step 1, the primary ball milling uses a nylon ball milling jar with silicon nitride as the grinding medium, a ball-to-material ratio of 1:1, a milling time of 6–48 hours, and a rotation speed of 150–250 r / min; the secondary ball milling uses a nylon ball milling jar with silicon nitride as the grinding medium, a ball-to-material ratio of 1:1, a milling time of 6–48 hours, and a rotation speed of 150–250 r / min; the degassing is performed under vacuum degassing at 20–100 kPa for 5–20 minutes.

[0041] As an optional implementation, in step 2, the height gap of the scraper is 5µm to 0.1mm, the baseband speed is 2.0 to 2.5mm / s, and the drying temperature is 20 to 30℃.

[0042] As an optional implementation, in step 3, the solid content of the copper paste for printing is 50-80%.

[0043] As an optional implementation, in step 3, the organic carrier is any one or more of terpineol, isopropanol, tributyl phthalate, ethyl cellulose, toluene, terephthalic acid, and castor oil.

[0044] As an optional implementation, in step 3, the screen printing method is as follows: first, print copper paste on one side and dry it, then print on the other side and dry it, and the thickness of the single layer of screen printing is 0.1 to 10 μm.

[0045] In this invention, screen printing can be repeated multiple times according to the required copper layer thickness. For example, if the film thickness is 5µm in a single print and the required single-sided copper layer thickness is 20µm, it needs to be printed 4 times.

[0046] As an optional implementation, the hot isostatic pressing can be either hydrothermal isostatic pressing or oil-based isostatic pressing; the temperature of the hot isostatic pressing is 60–120°C, the pressure is 2000–5000 PSI, and the holding temperature is 60–100°C; the degumming is carried out in a hydrogen or nitrogen atmosphere, with a degumming temperature of 300–600°C, preferably 550°C; the degumming time is 8–24 hours, preferably 16 hours; the integrated co-firing temperature is 800–1200°C, preferably 950°C; and the integrated co-firing time is 2–4 hours, preferably 2 hours.

[0047] As an optional implementation, any of the above flexible deep processing methods further includes:

[0048] Step 5: The copper-molybdenum-copper composite material with bending dimension requirements is machined to obtain workpieces with precise dimensions and complex structures.

[0049] In this invention, the above-mentioned machining processes include turning, milling, planing, drilling, grinding, etc.

[0050] The embodiments of the present invention also provide copper-molybdenum-copper composite materials with bending dimension requirements prepared by any of the above-mentioned flexible deep processing methods.

[0051] The specific implementation methods of this application have been described above. In order to objectively illustrate the technical effects produced by this application, the following examples and comparative examples will be used to describe them.

[0052] Example 1

[0053] One such Figure 2-3 The processing method for the copper-molybdenum-copper composite material parts shown is as follows:

[0054] (1) Pure molybdenum metal powder with a D50 of 2μm was added to a solvent (deionized water) and a dispersant (polyacrylic acid) at a mass ratio of 80:12:1 and ball-milled once in a nylon ball milling jar. The grinding balls were silicon nitride, the ball-to-material ratio was 1:1, the ball milling time was 24 hours, and the rotation speed was 200 r / min. Then, 5 wt% PVA-2488 and 2 wt% glycerol were added to the ball milling suspension and ball-milled a second time. The grinding balls were silicon nitride, the ball-to-material ratio was 1:1, the ball milling time was 24 hours, and the rotation speed was 200 r / min to obtain a second ball milling slurry. Then, vacuum degassing was performed for 10 minutes to obtain a molybdenum slurry for casting.

[0055] (2) Adjust the doctor blade gap to 45 μm, inject the water-based casting molding molybdenum slurry into the storage tank. During casting molding, the slurry flows from the bottom of the hopper to the forward-moving PET base belt. The thickness of the wet belt is controlled by the doctor blade gap. The base belt speed is 2.0 mm / s. The cast wet belt is dried in an air chamber (20-30°C) to obtain a molybdenum film.

[0056] (3) Using an automatic overlay printing machine to print a copper layer on a molybdenum film, specifically: add copper paste to a printing screen of the designed size, print a copper layer on the film, and dry it at 80°C. Repeat the printing and drying process four times to complete the copper layer printing on a single surface. Then repeat the above operation to complete the copper layer printing on the other side. The printed film is then subjected to hot isostatic pressing on a hydrothermal equalization press at 80°C and a maximum pressure of 5000 PSI for 10 minutes to complete the preparation of a double-sided copper-coated molybdenum core composite flexible thick film material. The copper paste used for printing consists of 75% copper powder, 3% glass powder, and 22% organic carrier (9% ethyl cellulose, 58% terpineol, 22% butyl carbitol acetate, 9% dibutyl phthalate, 0.5% castor oil, 0.5% polyamide wax, 0.5% terephthalic acid, and 0.5% ethanol), with a solid content of 75±3%.

[0057] (4) The above-mentioned flexible thick film material is placed in the die cavity of the designed shape and size to complete the bending process. The bent material is placed together with the die in a drying oven with a hydrogen atmosphere for low-temperature curing and shaping (temperature 180℃, time 2h). Then, it is demolded, and the shaped composite material part is sintered in a hydrogen atmosphere at a maximum sintering temperature of 950℃ for 2 hours to obtain the sintered copper-molybdenum-copper material; wherein, see Figure 4 The stamping die includes an upper die 1 and a lower die 2, as well as a stamping die cavity for placing flexible thick film material.

[0058] (5) Finally, the parts prepared by the sintered copper-molybdenum-copper material are machined and trimmed to complete the flexible deep processing of the parts with precision dimensions and complex shapes, and obtain copper-molybdenum-copper composite material with bending dimension requirements.

[0059] The above-mentioned copper-molybdenum-copper composite materials with bending dimension requirements were tested, and their mechanical properties are shown in Table 1 below. According to experimental statistics, the pass rate is over 99%.

[0060] Table 1:

[0061]

[0062] Comparative Example 1

[0063] Existing methods for preparing such Figure 2-3 The complex structure of the workpiece based on CMC composite material shown is processed by first reducing and annealing the core material (molybdenum metal) of calculated thickness to remove stress and reduce oxygen concentration and impurities. A copper layer of calculated thickness is then layered on both sides and bonded. Multiple passes of hot rolling, warm rolling, and cold rolling are then performed, combined with heat treatment to prepare the copper-molybdenum-copper composite material. Specifically: the thickness of the core material (molybdenum) (5mm) and the double-sided copper cladding (1.5mm) are calculated, and the three layers are bonded and welded. Next, multiple passes of hot rolling (700℃, 70% reduction in the first pass, 50% reduction in the second pass) and cold rolling (20%, 10%, 10%, 10% reduction in sequence) are performed, combined with heat treatment (550℃), to finally complete the preparation of a 0.3mm thick copper-molybdenum-copper composite material. The composite material is then cut and stamped using a designed stamping die.

[0064] The above-mentioned copper-molybdenum-copper composite materials with bending dimension requirements were tested, and their mechanical properties are shown in Table 2 below. According to experimental statistics, the failure rate is approximately 60% to 100%.

[0065] Table 2:

[0066]

[0067] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A flexible deep processing method for copper-molybdenum-copper composite materials with bending dimension requirements, characterized in that, Includes the following steps: Step 1: Pure molybdenum metal powder with a particle size of 2-10 μm is added to a solvent and a dispersant, and after one ball milling, a thickener and a binder are added. After a second ball milling and degassing, a molybdenum slurry for casting is obtained. The molybdenum slurry contains 70-80 wt% pure molybdenum metal powder, 11-25 wt% solvent, 0.8-1.2 wt% dispersant, 1.2-2.8 wt% thickener, and 3-6 wt% binder. The solvent is deionized water, and the dispersant is polyacrylic acid or hypermer. KD-1; the thickener is at least one of glycerol and polyethylene glycol; the binder is one or more of PVA-2488, polymethyl methacrylate, and ethyl acrylate; the primary ball milling uses a nylon ball mill jar, with silicon nitride as the grinding medium, a ball:material ratio of 1:1, a milling time of 6~48h, and a rotation speed of 150~250r / min; the secondary ball milling uses a nylon ball mill jar, with silicon nitride as the grinding medium, a ball:material ratio of 1:1, a milling time of 6~48h, and a rotation speed of 150~250r / min; Step 2: Place the molybdenum slurry for casting on a base belt and adjust the doctor blade height gap to 5μm~0.1mm and the base belt speed to 2.0~2.5mm / s. After drying at 20~30℃, a molybdenum film is obtained. Step 3: A copper paste of a certain thickness is screen-printed on the upper and lower surfaces of the molybdenum film. After drying and hot isostatic pressing, a flexible copper-molybdenum-copper composite film is obtained. The copper paste is composed of copper powder, glass powder, and an organic carrier. The solid content of the copper paste is 50-80%. The organic carrier is any one or more of terpineol, isopropanol, tributyl phthalate, ethyl cellulose, toluene, terephthalic acid, and castor oil. The screen printing method is as follows: first, the copper paste is printed on one side and dried, then the other side is printed and dried. The thickness of a single screen-printed layer is 0.1-10 μm. Screen printing is repeated multiple times according to the required copper layer thickness. Step 4: The flexible copper-molybdenum-copper composite diaphragm is placed in the stamping die cavity and bent. After low-temperature curing and shaping and demolding, it is then degummed and co-fired to obtain a copper-molybdenum-copper composite material with the required bending dimensions. The low-temperature curing temperature is 150~350℃ and the time is 2~6h. The degumming is carried out in a hydrogen or nitrogen atmosphere at a temperature of 300~600℃ for 8~24h. The co-firing temperature is 800~1200℃ and the co-firing time is 2~4h.

2. The flexible deep processing method for copper-molybdenum-copper composite materials with bending dimension requirements according to claim 1, characterized in that, In step 1, the degassing is performed under vacuum degassing at 20~100kPa for 5~20 minutes.

3. A copper-molybdenum-copper composite material with bending dimension requirements prepared by the flexible deep processing method of the copper-molybdenum-copper composite material with bending dimension requirements as described in any one of claims 1-2.

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