A thin miniaturized copper-molybdenum-copper composite material and a preparation method thereof

Abstract

The application discloses a kind of ultra-thin miniaturization copper-molybdenum-copper composite material and preparation method thereof, comprising: pure molybdenum metal powder is added into solvent and dispersing agent, and after once ball milling, thickening agent and binder are added, after twice ball milling, defoaming, obtain the molybdenum slurry for casting forming;Molybdenum slurry for casting forming is on base band, and by adjusting doctor blade height gap and base band speed, after drying, obtain molybdenum film piece;Molybdenum film piece is punched and filled with copper slurry for filling hole in hole, and then a certain thickness of printing copper slurry is screen printed on the upper and lower surfaces of molybdenum film piece filled with copper slurry, after drying, obtain laminated film piece;Layer film piece is subjected to hot isostatic pressing, cutting, degumming, integrated co-firing, to obtain thin miniaturization copper-molybdenum-copper composite material.The application has simple process, high preparation efficiency, greatly reduces the cost, and the prepared material has stable performance, excellent thermal conductivity performance, and is suitable for the miniaturization direction of composite material.

Description

Technical Field

[0001] This invention relates to the field of copper-molybdenum-copper composite materials, specifically to a thin, miniaturized copper-molybdenum-copper composite material and its preparation method. Background Technology

[0002] Copper-molybdenum-copper planar composite material is a composite material made by using molybdenum as the core material and oxygen-free copper as the top and bottom surfaces, and preparing it through rolling and thermal diffusion processes. It has both the low expansion properties of molybdenum and the high thermal conductivity of copper. However, because the pure molybdenum material is in the central sandwich layer, its thermal conductivity is far lower than that of the pure copper on the top and bottom surfaces. The heat conduction direction is mainly lateral, which makes it difficult for the composite material to achieve high overall thermal conductivity.

[0003] Common copper-molybdenum-copper composite materials often require molybdenum-copper composite materials as the core material to fully realize their performance advantages. However, the core molybdenum-copper material requires processes such as powder processing, pressing, melt infiltration sintering, and rolling. Then, the composite material with copper coating on the top and bottom surfaces is prepared by processes such as hot pressing composite and hot diffusion welding (CN103895286A). The process is complex, costly, and not suitable for the production of thin and miniaturized composite materials.

[0004] Existing technologies for preparing copper-molybdenum-copper composite materials using rolling, thermal diffusion, and other methods suffer from low processing precision, difficulty in controlling thickness and composition, numerous rolling processes, and low preparation efficiency, which greatly restricts the development of copper-molybdenum-copper composite materials.

[0005] Therefore, it is necessary to develop a method for preparing copper-molybdenum-copper composite materials that is simple in process, highly efficient in preparation, greatly reduces costs, produces materials with stable properties and excellent thermal conductivity, and is suitable for the miniaturization of composite materials. Summary of the Invention

[0006] In view of the above-mentioned shortcomings, the present invention provides a thin miniaturized copper-molybdenum-copper composite material and its preparation method, which has the advantages of simple process, high preparation efficiency, greatly reduced cost, stable material properties, excellent thermal conductivity, and suitability for the miniaturization of composite materials.

[0007] To achieve the above objectives, the present invention provides a method for preparing a thin, miniaturized copper-molybdenum-copper composite material, comprising the following steps: 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. Step 2: Apply the molybdenum slurry for casting onto a base belt and, by adjusting the doctor blade height gap and base belt speed, dry it to obtain a molybdenum film; Step 3: The molybdenum film is perforated and filled with copper paste for filling the holes. Then, a certain thickness of copper paste for printing is screen-printed on the upper and lower surfaces of the molybdenum film filled with copper paste. After drying, a laminated film is obtained. The copper paste for filling the holes and the copper paste for printing are both composed of copper powder, glass powder and organic carrier. Step 4: After hot isostatic pressing, cutting, degumming, and integrated co-firing, the thin and miniaturized copper-molybdenum-copper composite material is obtained.

[0008] 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%.

[0009] According to one aspect of the present invention, in step 1, the particle size of the pure molybdenum metal powder is 2~10μm; 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.

[0010] 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 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.

[0011] 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.

[0012] According to one aspect of the present invention, in step 3, the solid content of the copper paste for filling holes is 60-80%, and the solid content of the copper paste for printing is 50-80%.

[0013] 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.

[0014] According to one aspect of the present invention, in step 3, the perforation method is laser perforation or stamping; the perforation filling equipment is a thin film automatic filling machine; the screen printing method is: 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 0.1~10μm.

[0015] According to one aspect of the present invention, in step 4, 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℃, the pressure is 2000~6000 PSI, and the holding time is 5~20 min; the degumming is carried out in a hydrogen or nitrogen atmosphere, the degumming temperature is 300~600℃, and the degumming time is 8~24 h; the temperature of the integrated co-firing is 800~1200℃, and the integrated co-firing time is 2~4 h.

[0016] Based on the same inventive concept, the present invention also provides a thin miniaturized copper-molybdenum-copper composite material prepared by any of the above preparation methods.

[0017] The beneficial effects of this invention are: (1) The copper-molybdenum-copper composite material prepared by the present invention through the ephemeral printing of paste is simple to prepare, has high preparation efficiency, saves processing and material costs, and the material composition is easy to control and adjust. It can realize the design and production of thin and miniaturized material thickness. The copper paste is filled in the molybdenum core film to realize the three-layer penetration of copper material, which greatly improves the thermal conductivity. The material has high density and is suitable for mass production. (2) The molybdenum slurry for ducting of the present invention uses a binder to encapsulate metal particles and achieve sedimentation equilibrium in the solvent, and forms a strong three-dimensional dendritic structure through self-curing; the molybdenum slurry for ducting of the present invention uses a plasticizer to lower the glass transition temperature Tg of the material, thereby enhancing the mobility of the polymer chains and improving the flexibility of the film material after casting; the molybdenum slurry for ducting of the present invention uses a dispersant to adsorb onto the surface of the metal powder, generating site repulsion and steric hindrance to promote the dispersion of the powder in the organic solvent; the molybdenum slurry for ducting of the present invention uses a solvent to regulate suitable rheological properties; (3) Compared with the traditional method of rolling thinning copper-molybdenum-copper composite materials, the present invention uses copper paste to coat copper on the surface of a thick molybdenum film through screen printing, which is an additive process. The thickness of the copper layer can be controlled more precisely, the copper layer has good uniformity, and composite heat sinks with small size, thin film thickness, high thermal conductivity and electrical conductivity, and high density can be prepared. At the same time, the preparation process is simple and controllable, with low cost and short cycle. Attached Figure Description

[0018] Figure 1 This is a process flow diagram of the preparation method of the thin miniaturized copper-molybdenum-copper composite material described in this invention; Figure 2 This is a cross-sectional schematic diagram of the thin, miniaturized copper-molybdenum-copper composite material described in this invention.

[0019] Explanation of reference numerals in the attached figures: 1. Copper paste for printing on the upper surface; 2. Copper paste for filling holes; 3. Molybdenum paste for casting; 4. Copper paste for printing on the lower surface. Detailed Implementation

[0020] 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.

[0021] 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.

[0022] 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.

[0023] To address the problems of low processing precision, difficulty in controlling thickness and composition, numerous rolling steps, and low production efficiency in existing copper-molybdenum-copper composite materials prepared by rolling, thermal diffusion, and other methods, the inventors of this application provide a method for preparing thin, miniaturized copper-molybdenum-copper composite materials. The process flow diagram is shown in the figure, and includes the following steps: 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. Step 2: Apply the molybdenum slurry for casting onto a base belt and, by adjusting the doctor blade height gap and base belt speed, dry it to obtain a molybdenum film; Step 3: The molybdenum film is perforated and filled with copper paste for filling the holes. Then, a certain thickness of copper paste for printing is screen-printed on the upper and lower surfaces of the molybdenum film filled with copper paste. After drying, a laminated film is obtained. The copper paste for filling the holes and the copper paste for printing are both composed of copper powder, glass powder and organic carrier. Step 4: After hot isostatic pressing, cutting, degumming, and integrated co-firing, the thin and miniaturized copper-molybdenum-copper composite material is obtained.

[0024] As an optional implementation, 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%.

[0025] As an optional implementation, in step 1, the particle size of the pure molybdenum metal powder is 2~10μm; 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.

[0026] 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.

[0027] As an optional implementation, in step 2, the height gap of the scraper is 5um~0.1mm, the baseband speed is 2.0~2.5mm / s, and the drying temperature is 20~30℃.

[0028] As an optional implementation, in step 3, the solid content of the copper paste for filling holes is 60-80%, and the solid content of the copper paste for printing is 50-80%.

[0029] 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.

[0030] As an optional implementation, in step 3, the perforation method is laser perforation or stamping; the perforation filling equipment is a thin film automatic filling machine; the screen printing method is: 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 0.1~10μm.

[0031] 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.

[0032] As an optional implementation, in step 4, 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℃, the pressure is 2000~6000 PSI, and the holding time is 5~20 min; the degumming is carried out in a hydrogen or nitrogen atmosphere, the degumming temperature is 300~600℃, preferably 550℃; the degumming time is 8~24 h, preferably 16 h; the integrated co-firing temperature is 800~1200℃, preferably 950℃; the integrated co-firing time is 2~4 h, preferably 2 h.

[0033] As an optional implementation, step 4 also includes machining, which includes turning, milling, planing, drilling, grinding, etc.

[0034] In embodiments of the present invention, a thin, miniaturized copper-molybdenum-copper composite material prepared by any of the above-described preparation methods is also provided, as shown in the cross-sectional schematic diagram below. Figure 2 As shown, it includes copper paste 1 for printing on the upper surface, copper paste 2 for filling holes, molybdenum paste 3 for casting, and copper paste 4 for printing on the lower surface.

[0035] 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.

[0036] Example 1 A method for preparing a thin, miniaturized copper-molybdenum-copper composite material (size 2*2*0.06mm, thickness ratio 1:4:1): Step 1: Pure molybdenum metal powder with a D50 of 2μm is 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 mill jar. The grinding balls are silicon nitride, the ball-to-material ratio is 1:1, the ball milling time is 24 hours, and the rotation speed is 200 r / min to complete the first ball milling. Then, 5 wt% PVA-2488 and 2 wt% glycerol are added to the ball milling suspension for a second ball milling. The grinding balls are silicon nitride, the ball-to-material ratio is 1:1, the ball milling time is 24 hours, and the rotation speed is 200 r / min to obtain the second ball milling slurry. Then, vacuum degassing is performed for 10 minutes to obtain the casting slurry.

[0037] Step 2: Adjust the doctor blade gap to 45um, inject the water-based casting slurry into the storage tank. During casting, 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 2.0mm / s. The cast wet belt is dried in an air chamber (20~30℃). Finally, it is automatically cut at the tail end to obtain a cast sheet (molybdenum film) of 120*120*0.04mm.

[0038] Step 3: Drill holes (0.02mm in diameter) in the cast film (molybdenum film) using a laser machine, then fill the holes with copper paste using an automatic hole-filling machine. Print the copper layer using an automatic overlay printing machine. Place the film with the holes filled on a hard alloy carrier plate and fix it at the four corners. Add copper paste to the printing screen of the designed size, print the copper layer on the film, and dry it at 80℃. Repeat the printing and drying process four times to complete the copper layer printing on one side. Then repeat the above operation to complete the copper layer printing on the other side, obtaining a copper-molybdenum film. The copper paste for filling holes consists of 70% copper powder, 3% glass powder, and 27% organic carrier (55% terpineol, 23% isopropanol, 10% tributyl phthalate, 8% ethyl cellulose, 2% toluene, 1% terephthalic acid, and 1% castor oil), with a solid content of 75±3%. The copper paste 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%.

[0039] Step 4: The printed copper-molybdenum-copper film is hot isostatically pressed on a hydrothermal equalization press at 80℃ and a maximum pressure of 5000 PSI for 10 minutes. The hot isostatically pressed film is then cut on an automatic cutting machine to a size of 2.2*2.2mm to obtain copper-molybdenum-copper laminated blocks. The blocks are then degummed and co-fired. Degumming is completed in a hydrogen atmosphere at a maximum temperature rise of 600℃ for a total time of 16 hours. Similarly, sintering is completed in a hydrogen atmosphere at a maximum sintering temperature of 950℃ for 2 hours to obtain a thin, miniaturized copper-molybdenum-copper composite material.

[0040] The thin, miniaturized copper-molybdenum-copper composite material prepared above was tested and found to have a thickness of 60 μm, an expansion coefficient of 5.0E-6 / K (50℃), and a density of 9.56 g / cm³. 3 Its thermal conductivity is 230 W / (m*K).

[0041] Comparative Example 1 Existing methods for preparing copper-molybdenum-copper composite materials: First, the thickness of the core material molybdenum (10mm) and the double-sided copper cladding (3mm) are calculated according to the proportions, and the three layers of materials are bonded and welded together. Then, multiple hot rolling processes (temperature 700℃, first pass reduction of 70%, second pass reduction of 50%) and cold rolling processes (sequential rolling reduction of 20%, 10%, 10%, 10%) are carried out, combined with heat treatment (550℃) process, to finally complete the preparation of a 1.55mm thick copper-molybdenum-copper composite material.

[0042] The copper-molybdenum-copper composite material prepared above was tested and found to have a thickness of 1.8 mm, an expansion coefficient of 5.5E-6 / K (50℃), and a thermal conductivity of 180 W / (m*K).

[0043] 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 method for preparing a thin, miniaturized copper-molybdenum-copper composite material, characterized in that, Includes the following steps: Step 1: Pure molybdenum metal powder 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 content of pure molybdenum metal powder in the molybdenum slurry is 70-80 wt%, the content of solvent is 11-25 wt%, the content of dispersant is 0.8-1.2 wt%, the content of thickener is 1.2-2.8 wt%, and the content of binder is 3-6 wt%. The particle size of the pure molybdenum metal powder is 2-10 μm. Step 2: The molybdenum slurry for casting is applied to a base belt and dried by adjusting the doctor blade height gap and the base belt speed to obtain a molybdenum film; wherein the doctor blade height gap is 5μm~0.1mm and the base belt speed is 2.0~2.5mm / s; Step 3: A molybdenum film is perforated and filled with copper paste for filling the holes. Then, a certain thickness of copper paste for printing is screen-printed onto the upper and lower surfaces of the molybdenum film filled with copper paste. After drying, a laminated film is obtained. Both the copper paste for filling the holes and the copper paste for printing are composed of copper powder, glass powder, and an organic carrier. The solid content of the copper paste for filling the holes is 60-80%, and the solid content of the copper paste for printing is 50-80%. The perforation method is laser perforation or stamping. The equipment for filling the holes is an automatic thin-film filling machine. 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. 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: After hot isostatic pressing, cutting, debinding, and integrated co-firing, the laminated film is obtained as a thin, miniaturized copper-molybdenum-copper composite material. The hot isostatic pressing temperature is 60-120℃, the pressure is 2000-6000 PSI, and the holding time is 5-20 min. The debinding is carried out in a hydrogen or nitrogen atmosphere at a temperature of 300-600℃ for 8-24 h. The integrated co-firing temperature is 800-1200℃, and the integrated co-firing time is 2-4 h.

2. The method for preparing the thin, miniaturized copper-molybdenum-copper composite material according to claim 1, characterized in that, In step 1, 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.

3. The method for preparing the thin, miniaturized copper-molybdenum-copper composite material according to claim 1, characterized in that, 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.

4. The method for preparing the thin, miniaturized copper-molybdenum-copper composite material according to claim 1, characterized in that, In step 2, the drying temperature is 20~30℃.

5. The method for preparing the thin, miniaturized copper-molybdenum-copper composite material according to claim 1, characterized in that, In step 3, the organic carrier is any one or more of terpineol, isopropanol, tributyl phthalate, ethyl cellulose, toluene, terephthalic acid, and castor oil.

6. The method for preparing the thin, miniaturized copper-molybdenum-copper composite material according to claim 1, characterized in that, In step 4, the hot isostatic pressing can be either hydrothermal isostatic pressing or oil-based isostatic pressing.

7. A thin, miniaturized copper-molybdenum-copper composite material prepared by the preparation method according to any one of claims 1-6.

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