CN105921753A - Method for preparing near-net-shape parts with complex shapes from diamond-copper composite material - Google Patents

Abstract

The invention belongs to the field of composite materials, and relates to a method for preparing a near-net shape part of a complex shape from a high thermal conductivity diamond-copper composite material. The method includes the following steps in sequence: 1. Pretreatment of the surface of the diamond powder; 2. Titanium plating on the surface of the diamond powder ; 3. Parts prefabricated; 4. Forming. Adopting the present invention can directly realize the near-net forming of parts with complex shapes, less raw material loss, lower raw material cost, and at the same time solve the difficult problem of subsequent mechanical processing of DCC materials, the preparation process is short, the production efficiency is high, and the production cost is low; the present invention The invention solves the problem of body collapse and deformation caused by the "bridge" phenomenon in the molding process of traditional injection molding technology, improves the strength and thermal conductivity of the material, and the strength of the obtained parts can reach more than 245MPa, and the thermal conductivity is higher than 430W/mk. The coefficient of thermal expansion is lower than 6.5X10 ^‑6 K ^‑1 .

Description

Method for preparing near-net-shape parts with complex shapes from diamond-copper composite materials

technical field

The invention belongs to the field of composite materials, and relates to a method for preparing near-net shape parts with complex shapes from high thermal conductivity diamond-copper composite materials.

Background technique

Diamond has the highest thermal conductivity (700～2000W.m ^-1 .K ^{－ 1} ) among all substances, its hardness is as high as 1.0X10 ⁵ MPa, and its thermal expansion coefficient is about 0.8—1.0X10 ^-6 K ^-1 . At the same time, diamond also has a series of advantages such as non-magnetic, poor electrical conductivity, stable chemical properties, and high wear resistance. As a widely used engineering material, copper has excellent electrical conductivity and high thermal conductivity, its thermal conductivity is 400W.m ^-1 .K ^－ , and its thermal expansion coefficient is 17X10 ^-6 K ^-1 . Therefore, according to the Maxwell composite theory, the composite material (DCC, Diamond-Copper Composites) composed of diamond particles and copper will have excellent thermal conductivity and small thermal expansion coefficient, which is the most promising new generation for high-performance electronic equipment. One of the packaging materials. At present, the relatively mature preparation methods of DCC materials mainly include high temperature and high pressure sintering method, gas pressure infiltration method, mechanical pressure infiltration method and SPS sintering method. However, these methods can only produce samples with simple shapes, which cannot meet the development needs of the ever-changing electronic equipment technology.

Contents of the invention

The purpose of the present invention is to solve the problem that traditional production methods can only produce samples with simple shapes, and provide a method for preparing near-net shape parts with complex shapes from high thermal conductivity diamond-copper composite materials. High-performance DCC composite parts with shape and high dimensional accuracy.

In order to achieve the purpose of the present invention, the present invention provides a kind of method that high thermal conductivity diamond-copper composite material prepares the near-net shape part of complex shape, comprises the following steps successively:

1. Diamond powder surface pretreatment: degreasing and sensitizing diamond powder with an average particle size of 110 μm;

2. Titanium coating on the surface of diamond powder: mix diamond powder and titanium powder with an average particle size of 40 μm in a mass ratio of 1:4, mix the mixed powder thoroughly and place it in a magnesium oxide crucible, then cover the mixed powder with NaCl salt, Insulate at 850-950°C for 2-3 hours under vacuum conditions, then dissolve the molten salt with water to obtain modified diamond powder;

3. Part prefabricated parts: Mix the modified diamond powder and the copper powder with a particle size of 4-5 μm at a mass ratio of 1:1 on a ball mill and mix evenly, then add a binder with a mass ratio of 5-8% and mix evenly Feed for injection molding, the binder is paraffin wax (PW), low density polyethylene (LDPE) and stearic acid (SA) with a mass ratio of 75:20:5, and then injection molded into complex shape parts The preform is vacuum degreased and sintered to obtain a diamond-copper part blank with higher strength and density;

4. Molding: Place the copper block above the green body and put them together in a vacuum infiltration furnace to heat up to 1350-1450°C for 2-3 hours for infiltration treatment, and cool to room temperature with the furnace to obtain diamond-copper composite materials Component.

Compared with the prior art, the present invention has the following advantages:

1. By adopting the present invention, the near net forming of parts with complex shapes can be directly realized, the loss of raw materials is small, and the cost of raw materials is reduced. At the same time, the difficult problem of subsequent mechanical processing of DCC materials is solved, and the preparation process is short. Therefore, the production efficiency is high and the production cost is low. Low;

2. Composite materials composed of diamond particles and copper have not been able to directly prepare near-net-shape parts with complex shapes for a long time. Although injection molding technology is one of the processing methods for alloy parts, due to the irregular shape of diamond particles, during the molding process This problem has not been solved because the "bridging" phenomenon will cause the body to collapse and deform. In the present invention, one is to fully fill the gaps between diamond particles by designing the ratio of copper powder with a small average particle size, and at the same time adopt low molecular weight multi-component binders, and use their good fluidity to ensure forming The smooth forming of the billet, the second is that the removal of the binder can be completed at a lower temperature, which avoids the high volatilization rate of the binder at a higher temperature and easily causes cracking and deformation of the billet, and at the same time, it is carried out under vacuum. Degreasing and sintering to prevent the oxidation of the product, so as to realize the near net forming of complex shape parts;

3. The present invention not only can directly realize the near net forming of parts with complex shapes, but also effectively guarantees the advantages of this type of product. The surface of diamond powder is modified, and a titanium coating with a thickness of 0.1-2 μm is formed on the surface of diamond powder, which not only improves the holding force of the matrix metal to diamond, but also reduces the interface thermal resistance, thereby improving the strength and thermal conductivity of the material. The strength of the obtained part can reach more than 245MPa, the thermal conductivity is higher than 430W/mk, and the thermal expansion coefficient is lower than 6.5X10 ^-6 K ^-1 .

Description of drawings

Fig. 1 is the SEM photograph of the titanium-coated layer on the surface of modified diamond powder in embodiment 1.

detailed description

The present invention will be described in detail below with reference to the drawings and embodiments.

The present invention adopts the vacuum salt bath plating technology to modify the surface of diamond with titanium plating, forming a composite coating structure with TiC as the inner layer and Ti as the outer layer, so as to improve the wettability between diamond and liquid copper, and improve the contact between diamond and copper. The bonding strength between diamond and copper is reduced, and then the diamond-copper composite material preform is prepared by injection molding, and then the diamond-copper part blank with higher strength and density is obtained by vacuum degreasing and sintering Finally, the liquid copper is uniformly infiltrated into the diamond-copper part blank with a certain porosity by vacuum infiltration method, so as to obtain a DCC composite material part with a uniform and dense structure.

Example 1:

The near-net shape parts of diamond-copper composite materials were prepared at 1450 °C, and the preparation process was as follows:

1. Surface pretreatment of diamond powder: surface cleaning of diamond powder, that is, degreasing and sensitization treatment;

2. Titanium coating on the surface of diamond powder: mix artificial diamond powder with an average particle size of 110 μm and titanium powder with an average particle size of 40 μm at a weight ratio of 1:4, mix on a drum mill for 12 hours, and place the mixed powder on the In a magnesia crucible, cover the mixed powder with NaCl salt, heat it to 850°C under vacuum for 2 hours, take out the crucible and dissolve and separate the modified diamond powder.

3. Part prefabricated parts: add the modified diamond powder to the copper powder with a particle size of 4-5μm at a mass ratio of 1:1, mix it on a ball mill for 12 hours to fully mix it evenly, and then add a mass ratio of 5%. The binder is uniformly mixed into injection molding feed, and then injection molded into prefabricated parts with complex shapes (injection temperature 155°C, injection pressure 90MPa, holding pressure 70MPa, holding time 10S). The binder here is (mass ratio): paraffin wax (PW): low-density polyethylene (LDPE): stearic acid (SA) = 75:20:5.

Put the preform in a vacuum furnace to realize the integration of degreasing and sintering, and raise the temperature to 500°C at a heating rate of 2°C/min and keep it for 0.5 hours. This stage is mainly for degreasing, and raise the temperature to 700°C at a heating rate of 2°C/min Heat preservation for 1.5 hours. At this stage, pre-sintering is mainly carried out, and a certain strength is given to the green body while all the binders are removed. Then the temperature was raised to 1050°C at a heating rate of 4°C/min and kept for 2 hours. This stage was mainly sintering and densification, and a diamond-copper part blank with high strength and density was obtained.

4. Molding: Place a copper block with a purity of 99.999%, which accounts for about 10% of the blank, above the diamond-copper blank, and place it together in a vacuum infiltration furnace to raise the temperature to 1450°C and hold it for 90 minutes, that is A diamond-copper composite near-net shape part is obtained.

Referring to Figure 1, it can be seen that the structure of the titanium-coated layer on the surface of the diamond powder is uniform and dense.

After testing: the strength of the part is 258MPa, the thermal conductivity is 450W/mk, and the thermal expansion coefficient is 6.5X10 ^-6 K ^-1 .

This embodiment is the best embodiment.

Example 2:

The near-net shape parts of diamond-copper composite materials were prepared at 1350 °C, and the preparation process was as follows:

1. Surface pretreatment of diamond powder: surface cleaning of diamond powder, that is, degreasing and sensitization treatment;

2. Mix artificial diamond particles with an average particle size of 110 μm and titanium powder with an average particle size of 40 μm at a weight ratio of 1:4, and mix them on a drum mill for 12 hours. Put the mixed powder of diamond and titanium in a magnesia crucible, then cover the mixed powder with NaCl salt, heat it to 950°C under vacuum for 2 hours, take out the crucible and dissolve and separate the modified diamond powder.

3. Add the modified diamond powder to copper powder with a particle size of 4-5 μm at a mass ratio of 1:1, mix it on a ball mill for 10 hours to fully mix it, and then add a binder with a mass ratio of 8% and mix it evenly to form a Injection molding feed, and then injection molding to make prefabricated parts with complex shapes (injection temperature 155°C, injection pressure 90MPa, holding pressure 70MPa, holding time 10S).

The binder here is (mass ratio): paraffin wax (PW): low-density polyethylene (LDPE): stearic acid (SA) = 75:20:5.

The preform is placed in a vacuum furnace to realize the integration of degreasing and sintering, and the specific process is the same as in Example 1.

4. Place the copper block, which accounts for about 20% of the part volume and has a purity of 99.999%, above the diamond-copper part body, and put it together in a vacuum infiltration furnace to raise the temperature to 1350 ° C and keep it for 90 minutes to obtain diamond- Copper composite near-net-shape parts.

After testing: the strength of the part is 245MPa, the thermal conductivity is 430W/mk, and the thermal expansion coefficient is 6.8X10 ^-6 K ^-1 .

Example 3:

The near-net shape parts of diamond-copper composite materials were prepared at 1400 °C, and the preparation process was as follows:

1. Surface pretreatment of diamond powder: surface cleaning of diamond powder, that is, degreasing and sensitization treatment;

2. Mix artificial diamond particles with an average particle size of 110 μm and titanium powder with an average particle size of 40 μm at a weight ratio of 1:4, and mix them on a drum mill for 12 hours. Put the mixed powder of diamond and titanium in a magnesia crucible, then cover the mixed powder with NaCl salt, heat it to 850°C under vacuum for 3 hours, take out the crucible and dissolve and separate the diamond particles.

3. Add the modified diamond powder to the copper powder with a particle size of 4-5μm at a mass ratio of 1:1, mix it on a ball mill for 12 hours to fully mix, and then add a binder with a mass ratio of 6% to mix evenly Feed into injection molding, and then make prefabricated parts with complex shapes through injection molding (injection temperature 155°C, injection pressure 90MPa, holding pressure 70MPa, holding time 10S).

The binder here is (mass ratio): paraffin wax (PW): low-density polyethylene (LDPE): stearic acid (SA) = 75:20:5.

The preform is placed in a vacuum furnace to realize the integration of degreasing and sintering, and the specific process is the same as that in Example 1.

4. Place the copper block which accounts for about 15% of the part volume and has a purity of 99.999% above the diamond-copper part body, and put it together in a vacuum infiltration furnace to raise the temperature to 1400 ° C and keep it warm for 90 minutes to obtain diamond- Copper composite near-net-shape parts.

After testing: the strength of the part is 252MPa, the thermal conductivity is 440W/mk, and the thermal expansion coefficient is 6.3X10 ^-6 K ^-1 .

The content of the present invention is not limited to the examples listed, and any equivalent transformation of the technical solution of the present invention adopted by those of ordinary skill in the art by reading the description of the present invention is covered by the claims of the present invention.

Claims (1)

1. the method that diamond carbon/carbon-copper composite material prepares complicated shape nearly end form part, it is characterised in that:

Comprise the steps: successively

One, diamond dust surface preparation: the diamond dust that particle mean size is 110 μm is carried out oil removing and sensitized treatment；

Two, diamond dust ti coat on diamond: with the titanium valve that average grain diameter is 40 μm, diamond dust is used mass ratio is that 1:4 mixes, mixed-powder is sufficiently mixed and is placed on magnesia crucible, NaCl salt is covered again on mixed-powder, 850 950 DEG C of insulation 2 3h under vacuum, then take off fused salt with water-soluble, obtain modified diamond dust；

Three, part prefabricated blank system: modified diamond dust is sufficiently mixed uniformly with the copper powders that granularity is 45 μm that mass ratio is 1:1 on ball mill, then add the binding agent that mass ratio is 5 8% and be uniformly mixed into injection molding feedstock, described binding agent be mass ratio be the paraffin of 75:20:5, low density polyethylene (LDPE) and stearic acid, complicated shape part prefabricated blank is made again through injection moulding, then through vacuum degreasing and sintering, the diamond copper part base of higher-strength and consistency is obtained；

Four, shaping: be placed in by copper billet above base substrate and be placed in together in infiltration in vacuum stove and be warming up to 1,350 1450 DEG C of insulations and carry out infiltration process in 23 hours, is cooled to room temperature with stove, i.e. obtains diamond carbon/carbon-copper composite material part.