CN102586704A - High thermal conductivity graphite whisker/copper composite and preparation method thereof - Google Patents

Abstract

The invention belongs to the research field of metal matrix composite materials, and relates to a high thermal conductivity graphite whisker/copper composite material and a preparation method thereof. The composite material is composed of matrix pure copper and plated reinforced phase high thermal conductivity graphite whiskers, in which the volume fraction of pure copper is 40%-70%, and the volume fraction of graphite whiskers after plating is 30%-60% %. The production process steps of the composite material are as follows: first, copper or molybdenum is plated on the surface of graphite whiskers by chemical plating or salt bath plating to form a 1-2 μm thick coating; then the plated graphite whiskers are combined with copper The powder is mixed evenly at the ratio of 30-60:70-40, and then sintered at 820-980°C by SPS powder metallurgy to obtain graphite whisker/copper composite material. The invention provides a method for preparing a graphite whisker/copper composite material used in the field of electronic packaging, which has many advantages such as high thermal conductivity, controllable thermal expansion coefficient, high density, and easy processing to meet the requirements of the modern electronic packaging field .

Description

A kind of preparation method of high thermal conductivity graphite whisker/copper composite material

technical field

The invention belongs to the technical field of metal matrix composite materials, and relates to a preparation method of a high thermal conductivity graphite whisker/copper composite material. the

Background technique

The development and design of electronic packaging materials has always been an important part of the thermal management of electronic equipment. Modern thermal management requires electronic packaging materials to have high thermal conductivity (TC), low coefficient of expansion (CTE), good processability and low price. Traditional materials such as Cu/Mo, Cu/W, Al/SiC, and AlN are often used in the field of electronic packaging. These materials have certain limitations, such as Cu/Mo, Cu/W density is too high, Al/SiC, AlN Diamond composite materials with high CTE and high thermal conductivity are limited by price and processing performance.

The new generation of graphite whiskers has low thermal expansion coefficient, high longitudinal thermal conductivity, the highest thermal conductivity can reach 1100 W/(m K), low density, and its good physical properties are suitable for metal-based electronic packaging materials. enhanced phase. The isotropic high thermal conductivity composite material prepared by compounding graphite whiskers and copper matrix by powder metallurgy technology has excellent thermal conductivity, low thermal expansion coefficient, light weight and easy processing, simple preparation process and low cost, and has a wide range of applications. application prospects.

During the preparation of composite materials, the interface bonding between the reinforcement phase and the matrix has a great influence on the performance of composite materials. Studies have shown that when copper and carbon are combined, the thermal conductivity of the composite material is poor due to poor interfacial wettability. Therefore, how to strengthen the interfacial bonding is the key to improving the performance of composite materials.

Contents of the invention

The purpose of this invention is to provide a method for preparing copper-based electronic packaging composite parts with adjustable thermal expansion coefficient and high thermal conductivity by using high thermal conductivity and low expansion graphite whisker as a reinforcing phase.

The present invention adopts chemical plating or salt bath plating method to metallize the surface of whiskers, increase the wettability between copper and carbon, effectively improve the interface bonding between whiskers and copper, and then combine the treated whiskers with copper powder Mix evenly, and finally prepare a high-performance graphite whisker/copper-based composite material by using a plasma discharge sintering process.

A preparation method of a high thermal conductivity graphite whisker/copper composite material is characterized in that the high thermal conductivity graphite whisker is used as a reinforcing phase, and a layer of copper or molybdenum is first plated on the surface of the graphite whisker by electroless plating or salt bath plating , and then compounded with copper powder through SPS powder metallurgy process to prepare high-performance graphite whisker reinforced copper matrix composite material;

The reinforcing phase used is graphite whisker with high thermal conductivity and low expansion, the aspect ratio is between 10-70, and the surface of the whisker is coated with copper or molybdenum with a thickness of 0.1-2 μm;

The volume ratio of the selected coated graphite whiskers to copper powder is 30-60:70-40, and they should be mixed on a ball mill before compounding. The speed of the ball mill is 110-150 rpm, and the time is 1.5-3 hours.

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Firstly, the surface metal plating is carried out on the graphite whisker. The main process route of copper plating is: degreasing─coarsening─sensitization─activation─electroless plating. The composition of the plating solution: copper sulfate pentahydrate 15g/L, formaldehyde 5g/L L. Potassium sodium tartrate 14g/L, EDTA 19.5g/L, sodium hydroxide 14.5g/L, bipyridine 0.02g/L, potassium ferrocyanide 0.01g/L. Copper plating process conditions: the pH of the plating solution is 12.0-12.5, the plating temperature is 40-50°C, and the plating time is 2-15 minutes.

The main process route of molybdenum plating is: degreasing-powder mixing-vacuum micro-evaporation plating. Put the graphite whisker after degreasing and the NaCl/KCl mixed salt with a certain amount of ammonium paramolybdate into the ball mill and mix for 30 minutes. The molar ratio of NaCl and KCl in the mixed salt is 1:1, and the paramolybdic acid in the mixed salt The mass fraction of ammonium is 10%. After mixing evenly, the mixture is heated to 900°C-1100°C under a protective atmosphere to form a molybdenum layer on the surface of the graphite whiskers.

The coated graphite whiskers and copper powders of different particle sizes are mixed in a ball mill for 1.5-3 hours according to a certain ratio, the ball mill speed is 110-150 rpm, and the volume ratio of graphite whiskers to copper powder is 30-60 :70-40, copper powders of different particle sizes can be freely matched according to the mass ratio.

Finally, put the mixed powder into the graphite mold, place it in the SPS sintering furnace, and use the SPS powder metallurgy process to prepare composite material parts. The sintering temperature is 820-980°C, the pressure is 20-70MPa, and the holding time is 2-5 minutes.

The technology of the invention adopts the plasma discharge sintering method (SPS) to prepare the preparation method of graphite whisker reinforced copper matrix composite material. By adding an intermediate layer of molybdenum or copper, the wettability of the whiskers and copper is increased, the interface state between the reinforcement phase and the matrix is improved, and the interface thermal resistance is greatly reduced. Especially the addition of the molybdenum layer makes the original reinforcement phase A weak mechanical bond to the substrate becomes a chemical bond. The graphite whiskers/composites prepared by this method have excellent performance, and its advantages include:

1) It has good thermal conductivity and can dissipate the heat generated by the semiconductor chip in time;

2) Adjustable coefficient of thermal expansion, matching with chip materials such as Si or GaAs, to avoid thermal stress damage of the chip;

3) Composite materials have low density and certain strength and rigidity;

4) The performance of the product is isotropic, easy to process, and the production cost is low;

5) The metal plating treatment on the surface of the whisker improves the interface state between the reinforcement phase and the matrix, and greatly improves the comprehensive performance of the composite material.

Description of drawings

Fig. 1 is the flow chart of this process.

Detailed ways

The technical scheme of the present invention will be described in further detail below in conjunction with examples:

Example 1:

Electroless copper plating is used to plate a 1 μm copper layer on the surface of graphite whiskers: First, put graphite whiskers in 20% NaOH solution and boil for 15 minutes, then rinse with distilled water until neutral. Then put it into 20% HNO ₃ solution and boil for 15 minutes, rinse with distilled water until neutral. Put the washed graphite whiskers into 20ml/LHCl+20g/LSnCl ₂ solution and stir vigorously for 15 minutes. When the solution turns blue-gray, the reaction is complete. After washing, add 20ml/L HCl+0.5g/LPdCl to the graphite whiskers ₂ The solution was vigorously stirred for 15 minutes, and the reaction was complete when the solution turned light brown. Pour the sensitized and activated graphite whiskers into the copper plating solution. The formula of the solution is copper sulfate pentahydrate 15g/L, potassium sodium tartrate 14g/L, EDTA 19.5g/L, bipyridine 0.02g/L, Potassium ferrocyanide 0.01g/L. And add formaldehyde [w (HCHO) = 36%] 10ml/L for surface copper plating treatment, the plating pH is 12, the temperature is 45 ℃, and the plating time is 3 minutes. Add 1000ml of distilled water after plating to dilute the plating solution. After the plating solution is filtered out by vacuum filtration, a large amount of distilled water is added to wash the copper-plated whiskers until neutral, and then put into a drying oven for drying. Graphite whiskers whose surfaces were plated with 1 μm of copper were obtained.

The above-mentioned copper-coated graphite whiskers were mixed with copper powder with a particle size of 40 μm in a volume ratio of 30:70 in a planetary ball mill for 2 hours, and the speed of the ball mill was 120 rpm. After mixing evenly, put the mixed powder into a plasma sintering furnace (SPS) for sintering, the sintering temperature is 890°C, the sintering pressure is 30MPa, and the temperature is kept for 3 minutes. That is, the graphite whisker/copper composite material is obtained.

Example 2

A molybdenum layer with a thickness of 1.5 μm was coated on the graphite whisker surface by salt bath plating. Graphite whiskers and NaCl/KCl mixed salt with a certain amount of ammonium paramolybdate added were put into the ball mill and mixed for 30 minutes. The molar ratio of NaCl and KCl in the mixed salt was 1:1, and the mass fraction of ammonium paramolybdate in the mixed salt was 10%. After mixing evenly, put it into a tube furnace with a protective atmosphere and heat it to 1000°C, keep it warm for 120 minutes and then cool it with the furnace. The coated whiskers are washed with water and then sieved to remove excess impurities to obtain molybdenum-coated graphite whiskers. Using this process, a molybdenum layer with a thickness of 1.5 μm is uniformly plated on the surface of the graphite whisker, and the graphite whisker and the molybdenum layer react to form a molybdenum carbide layer.

Copper powder with a particle size of 40 μm and molybdenum-coated graphite whiskers were mixed in a planetary ball mill at a ratio of 70:30 by volume for 2 hours, and the speed of the ball mill was 120 rpm. After mixing evenly, put the mixed powder into a plasma sintering furnace (SPS) for sintering, the sintering temperature is 900°C, the sintering pressure is 50MPa, and the temperature is kept for 5 minutes. That is, the graphite whisker/copper composite material is obtained.

Example 3

A molybdenum layer with a thickness of 1 μm was plated on the surface of graphite whiskers by salt bath plating. Graphite whiskers and NaCl/KCl mixed salt with a certain amount of ammonium paramolybdate added were put into the ball mill and mixed for 30 minutes. The molar ratio of NaCl and KCl in the mixed salt was 1:1, and the mass fraction of ammonium paramolybdate in the mixed salt was 10%. After mixing evenly, put it into a tube furnace with a protective atmosphere and heat it to 1000°C, keep it warm for 60 minutes and then cool it with the furnace. The coated whiskers are washed with water and then sieved to remove excess impurities to obtain molybdenum-coated graphite whiskers. Using this process, a molybdenum layer with a thickness of 1 μm is evenly plated on the surface of the graphite whisker, and the graphite whisker and the molybdenum layer react to form a molybdenum carbide layer.

Copper powder with a particle size of 20 μm and molybdenum-coated graphite whiskers were mixed in a planetary ball mill at a ratio of 50:50 by volume for 2 hours, and the speed of the ball mill was 130 rpm. After mixing evenly, put the mixed powder into a plasma sintering furnace (SPS) for sintering, the sintering temperature is 900°C, the sintering pressure is 50MPa, and the temperature is kept for 5 minutes. That is, the graphite whisker/copper composite material is obtained.

Example 4

A molybdenum layer with a thickness of 0.5 μm was coated on the surface of graphite whiskers by salt bath plating. Graphite whiskers and NaCl/KCl mixed salt with a certain amount of ammonium paramolybdate added were put into the ball mill and mixed for 30 minutes. The molar ratio of NaCl and KCl in the mixed salt was 1:1, and the mass fraction of ammonium paramolybdate in the mixed salt was 10%. After mixing evenly, put it into a tube furnace with a protective atmosphere and heat it to 1000°C, keep it warm for 40 minutes and then cool down with the furnace. The coated whiskers are washed with water and then sieved to remove excess impurities to obtain molybdenum-coated graphite whiskers. Using this process, a molybdenum layer with a thickness of 0.5 μm is uniformly plated on the surface of the graphite whisker, and the graphite whisker and the molybdenum layer react to form a molybdenum carbide layer.

Get particle size and be that the copper powder of 20 μ m, the molybdenum-coated graphite whisker of copper powder of 70 μ m are mixed in planetary ball mill for 3 hours by volume ratio graphite whisker: copper (20 μ m): the ratio of copper (70 μ m)=50:10:40, The rotational speed of the ball mill was 150 rpm. After mixing evenly, put the mixed powder into a plasma sintering furnace (SPS) for sintering, the sintering temperature is 890°C, the sintering pressure is 30MPa, and the temperature is kept for 5 minutes. That is, the graphite whisker/copper composite material is obtained.

Claims (4)

1. the preparation method of a high conductive graphite whisker/carbon/carbon-copper composite material; It is characterized in that using high conductive graphite whisker to make wild phase; The method plating layer of copper or the molybdenum that plate with electroless plating or salt bath on the graphite whisker surface earlier; Carry out compoundly then through SPS powder metallurgical technique and copper powder, prepare high-performance graphite whisker copper matrix composites reinforced;

Used wild phase is high heat conduction, the graphite whisker of low bulk, length-to-diameter ratio between 10-70, copper or the molybdenum of whisker coating surface thickness 0.1-2 μ m;

The volume ratio of selected graphite whisker of plating and copper powder is 30-60:70-40, will on ball mill, mix before compound, and drum's speed of rotation is 110-150 rev/min, and the time is 1.5-3 hour.

2. according to the preparation method of the described high conductive graphite whisker/carbon/carbon-copper composite material of claim 1; It is characterized in that: adopt the SPS powder metallurgical technique that the graphite whisker and the copper powder of metal lining coating are carried out compound tense, temperature is that 820-980 ℃, pressure are 20-70MPa, soaking time 2-5 minute.

3. according to the preparation method of the described high conductive graphite whisker/carbon/carbon-copper composite material of claim 1; It is characterized in that: adopt the SPS powder metallurgical technique that the graphite whisker and the copper powder of metal lining coating are carried out compound tense; Selected copper powder granularity is at 17-80 μ m, and different Cu powder degree volume proportion can be allocated arbitrarily.

4. according to the preparation method of the described high conductive graphite whisker/carbon/carbon-copper composite material of claim 1; It is characterized in that: at first carry out the surface metal plating at graphite whisker; Copper-plated operational path is: oil removing-alligatoring-sensitization-activation-electroless plating, the composition of plating bath: cupric sulfate pentahydrate 15g/L, formaldehyde 5g/L, Seignette salt 14g/L, EDTA 19.5g/L, sodium hydroxide 14.5g/L, second bipyridine 0.02g/L, yellow prussiate of potash 0.01g/L; The copper-plating technique condition is: plating bath pH is 12.0-12.5, plating temperature 40-50 ℃, plating time 2-15 minute;

The little evaporation plating of vacuum that the operational path of plating molybdenum is: oil removing-mixing powder-; Graphite whisker after the oil removing put into the NaCl/KCl mixing salt that is added with a certain amount of ammonium paramolybdate mix 30 minutes in the ball mill; The mol ratio of NaCl and KCl is 1:1 in the mixing salt, and the massfraction of ammonium paramolybdate is 10% in the mixing salt; After mixing, mixture is heated to 900 ℃-1100 ℃ under protective atmosphere, forms molybdenum layer on the graphite whisker surface.

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