WO2015143907A1

WO2015143907A1 - Method for preparing high thermal conductive graphite film-copper composite material

Info

Publication number: WO2015143907A1
Application number: PCT/CN2014/095456
Authority: WO
Inventors: 赖优萍
Original assignee: 苏州格优碳素新材料有限公司
Priority date: 2014-03-26
Filing date: 2014-12-30
Publication date: 2015-10-01
Also published as: CN103864067B; CN103864067A

Abstract

The present invention relates to a method for preparing a high thermal conductive graphite film-copper composite material. A macromolecular film is used as a major raw material; the surface groups of the film are activated through a plasma treatment, and then the factors of atmosphere, pressure etc. are controlled while increasing the temperature in stages to prepare a crystalline carbon foam film with a major component of carbon element, which further undergoes a rolling or laminating process to obtain a high thermal conductive graphite film having a soft and smooth surface and a uniform thickness; a layer of copper having a smooth surface and fine crystals is obtained on the surface of this graphite film through a chemical copper plating method; and subsequently, a layer of copper is further electroplated so as to prepare the high thermal conductive graphite film-copper composite material. The graphite film-copper composite material prepared using the method of the present invention has an axial thermal conductivity coefficient which can reach 60 W/mK.

Description

Method for preparing high thermal conductivity graphite film-copper composite material

Technical field

The invention particularly relates to a method for preparing a highly thermally conductive graphite film-copper composite.

Background technique

With the rapid development of semiconductor technology and the increasing requirements for portable products of digital products (such as mobile phones, tablet computers, etc.), there is an urgent need for manufacturers to improve the utilization of internal space of electronic products, but generated during operation. The heat is not easily discharged, and it is easy to accumulate quickly to form a high temperature. Obviously, high temperature will reduce the performance, reliability and service life of electronic equipment. Therefore, the current electronic industry is increasingly demanding heat-dissipating materials as the core components of the thermal control system. There is an urgent need for a highly efficient heat-conducting, lightweight material to quickly transfer heat out to ensure the normal operation of electronic equipment.

The traditional heat dissipating material is a high thermal conductivity metal such as copper, silver or aluminum. However, as the heat generation of electronic components increases, the product needs cannot be met, and the natural graphite film has higher thermal conductivity and lower density. , good material stability, so gradually in the electronics industry is widely used.

The natural graphite film is made of natural flake graphite or coal tar pitch. After acidifying the raw material, the natural graphite layer is expanded by heating to obtain a worm-like structure, and then calendered under high temperature and high pressure conditions with the bonding material to obtain a film-like graphite sheet. However, the thermal conductivity of natural graphite film generally does not exceed 400W/(m•K), and there are disadvantages such as easy powder drop, so it is increasingly unable to meet the heat dissipation requirements of current portable digital products.

At present, in order to meet the requirements of heat dissipation, a synthetic graphite film has also been under development. The patent application No. 201210227634.8 discloses a method for manufacturing a highly thermally conductive graphite film, which uses the most raw material of polyimide film, and is carbonized and graphite. The two processes are as follows: a. Selecting a polyimide film as a raw material, adding graphite paper between each layer of polyimide film; b, a polyimide layer separated by graphite paper at intervals The amine film is placed in a carbonization furnace and carbonized in a nitrogen or argon atmosphere at a carbonization temperature of 100 ° C to 1400 ° C for a period of time ranging from 1 hour to 6 hours; c, graphitization after carbonization, and graphitization in a nitrogen or argon atmosphere In the middle, the temperature is controlled at about 2500 ° C -3000 ° C, controlled within 12 hours.

The graphite film is a layered crystal material, and the planar thermal conductivity of the synthetic graphite film can reach 1400-1800 W/(m•K). However, its axial thermal conductivity is only 5-10 W/(m•K).

Summary of the invention

The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and to provide a preparation method of a highly thermally conductive graphite film capable of significantly improving the axial thermal conductivity of a graphite film.

In order to solve the above technical problems, the technical solution adopted by the present invention is:

A method for preparing a high thermal conductivity graphite film-copper composite material comprises the following steps:

a plasma treatment of the original film;

b Put the treated original film in step a into a high temperature furnace, close the furnace, raise the temperature and control the temperature at 300 °C-700 °C, and keep the pressure inside the furnace at 0.05 Pa-15. Pa, time control is 1-10 hours;

c continue to heat up, control the temperature of the high temperature furnace at 700 ° C -1200 ° C, into the high temperature furnace into the inert gas, keep the pressure inside the furnace at 10 Pa-50 Pa, time control is 1-10 hours;

d continue to heat up, control the temperature of the high temperature furnace at 1600 ° C -2500 ° C, continue to pass inert gas into the high temperature furnace, keep the pressure inside the furnace at 5 Pa-30 Pa, time control is 1-10 hours;

e continue to heat up, control the temperature of the high temperature furnace at 2500 ° C -3000 ° C, increase the flow of inert gas into the high temperature furnace, keep the pressure inside the furnace at 0.5 Atm-1.5 atm, time control is 1-10 hours, after natural cooling and cooling, a carbon foam film is obtained;

f rolling or laminating the carbon foam film obtained in the step e to obtain a high thermal conductive graphite film;

g electroless copper plating on the surface of the graphite film obtained in step f;

h Further electroplating the graphite film on the basis of step g to obtain a high thermal conductivity graphite film-copper composite.

Preferably, the original film in the step a is one of a polyamide film or a polyimide film.

Preferably, the original film is fixed with a graphite frame in a high temperature furnace.

Preferably, in step f, the tension is controlled between 0.1 kg and 20 kg.

Preferably, in step f, the plating solution for performing electroless copper plating has a pH of 11.0-12.0.

Preferably, in step g, the plating temperature of the electroless copper plating is from 45 ° C to 50 ° C.

Preferably, in step g, the plating time of the electroless copper plating is performed for 1-10 minutes.

Preferably, the inert gas in step c is nitrogen, the inert gas in step d is argon, and the inert gas in step e is argon.

Preferably, the high temperature furnaces in step b, step c, step d and step e are the same.

Preferably, the high temperature furnaces in step b, step c, step d and step e are not the same.

In step g, the plating solution for performing electroless copper plating contains a copper salt, a reducing agent, a complexing agent, a stabilizer, a pH adjuster, and an additive.

The main function of the copper salt is to provide copper ions. The copper salt may be copper sulfate, copper chloride, basic copper carbonate, copper tartrate or copper acetate. The present application is preferably copper sulfate pentahydrate.

The complexing agent may be selected from sodium potassium tartrate, sodium citrate, sodium gluconate, triethanolamine, tetrahydroxypropylethylenediamine, glycerol, glycolic acid, EDTA, and is preferably EDTA.

The reducing agent may be selected from the group consisting of formaldehyde, sodium hypophosphite, sodium borohydride, hydrazine, and dimethylaminoborane. The present application is preferably sodium hypophosphite.

The stabilizer may be selected from the group consisting of methanol, sodium cyanide, thiourea, alkyl mercaptan, dihydroxy nitrogenbenzene, and bipyridine. The present application is preferably a bipyridine.

Additives and surfactants can be used as additives.

The electroplating copper process of the present application is: pickling→plating copper→2-3 grade pure water washing→drying→2-3 grade pure water washing→drying. The main components of the plating solution include: copper sulfate, sulfuric acid, hydrochloric acid, brightener and leveling agent.

The specific steps for electroplating copper are as follows:

Pickling: The graphite film was immersed in a 5% dilute sulfuric acid solution for 12 hours.

Electroplating copper: concentration of sulfuric acid 2mol/l, concentration of copper sulfate 0.7mol/l, Add a small amount of hydrochloric acid and leveling agent, the current density is 0.02A/cm2, and pay attention to replenish the consumed material during the electroplating process.

Washing: Use deionized water and rinse repeatedly.

Dry: Store in a cool, dry place and air dry.

Washing: Rinse with deionized water repeatedly.

Drying: Place in an infrared oven for 30 minutes.

The invention adopts a polymer film as a main raw material, activates a surface group of the film by plasma treatment, and then heats the temperature in stages and simultaneously controls factors such as atmosphere and pressure to prepare a crystalline carbon foam film whose main component is carbon element, and then passes through rolling. Or a lamination process to obtain a highly thermally conductive graphite film having a soft surface and a uniform thickness. On the surface of the graphite film, a layer of copper having a smooth surface and fine crystals is obtained by electroless copper plating, followed by electroplating a layer of copper. A high thermal conductivity graphite film-copper composite material, which can significantly improve the axial thermal conductivity of the graphite film.

Due to the adoption of the above technical solutions, the present invention has the following advantages compared with the prior art:

(1) Plasma treatment makes the surface of the original film clean and surface activated, and at the same time, the shrinkage rate of the graphite film and the surface spot defects can be reduced.

(2) Fixing the original film with a graphite frame can reduce the shrinkage rate during the processing of the original film.

(3) A carbon foam film having a good self-foaming effect can be obtained by using different atmospheres and pressures (inert atmosphere or reduced pressure) and temperature changes in different time periods during the heating process.

(4) The present invention can obtain a smooth and smooth copper plating layer of about 10 micrometers, and the axial thermal conductivity of the graphite film-copper composite material can reach 60 W/mK.

detailed description

The present invention will be further described in detail below in conjunction with specific embodiments. The embodiments are intended to be illustrative of the basic principles, main features and advantages of the invention, and the invention is not limited by the scope of the following embodiments. The implementation conditions employed in the examples can be further adjusted according to specific requirements, and the unspecified implementation conditions are usually the conditions in the conventional experiment.

Example 1

The polyamide film is used as the original film, and the treated polyamide film is fixed by a graphite frame in a high-temperature furnace for heat treatment, and the heat treatment is performed in the same high-temperature furnace. The process is: closing the high-temperature furnace, The temperature in the furnace was raised to 500 ° C, and the pressure was reduced to 10 Pa using a vacuum pump. The temperature was maintained for 1 hour and then the temperature was raised, and the temperature was raised to 2 hours. At 1000 ° C, nitrogen gas is introduced into the high temperature furnace, while the vacuum pump is continuously used to maintain the pressure in the furnace at 40 Pa. The temperature is maintained for 2 hours, the temperature is increased, and the temperature is raised to 2400 ° C in 3 hours. Argon gas is introduced into the high temperature furnace to maintain the furnace. The internal pressure is 30Pa, the temperature is maintained for 2 hours, and the temperature is raised to 2900 °C in one hour. The argon flow rate is increased and the vacuum pump displacement is reduced. The pressure in the furnace is controlled at 1.5 atm for 3 hours, and then naturally cooled and cooled. Foamed graphite film, finally, the foamed graphite film is rolled, the tension is controlled at 8kg, and a highly thermally conductive graphite film with a soft surface is obtained. Electroless copper plating is performed on the obtained graphite film to control electroless copper plating. The bath has a pH of 11.0 and is plated for 1 minute at a plating temperature of 45 ° C. The electroless copper plating bath includes copper sulfate pentahydrate, EDTA, sodium hypophosphite, surfactant, bipyridine and pH. The adjusting agent, after the electroless copper plating is completed, continues to electroplating copper to obtain a high thermal conductivity graphite film-copper composite material, wherein the process of electroplating copper is: pickling→plating copper→2-3 grade pure water washing→drying→ 2-3 grade pure water wash → dry, The main components of the plating solution include: copper sulfate, sulfuric acid, hydrochloric acid, brightener and leveling agent.

The thickness of the copper plating layer was 10 μm, and the axial thermal conductivity of the graphite film-copper composite was ≥40 W/mK.

Example 2

The polyimide film is used as the original film, and the treated polyamide film is fixed by a graphite frame in a high-temperature furnace for heat treatment, and the heat treatment is performed in the same high-temperature furnace. The process is: closing the high-temperature furnace , the temperature in the furnace was raised to 300 ° C, and the pressure was reduced to 1 Pa using a vacuum pump, and the temperature was maintained for 5 hours, and the temperature was raised to 2 hours. At 720 ° C, nitrogen gas was introduced into the high temperature furnace, while the vacuum pump was continuously used to maintain the pressure in the furnace at 10 Pa. The temperature was maintained for 3 hours, and the temperature was raised to 1600 ° C in 3 hours. The nitrogen gas was continuously introduced into the high temperature furnace to maintain the furnace. The internal pressure is 10Pa, the temperature is maintained for 2 hours, the temperature is increased to 2600 ° C in 1 hour, the nitrogen flow rate is increased and the vacuum pump displacement is reduced, the pressure in the furnace is controlled at 0.5 atm, the time is maintained for 3 hours, and then the natural cooling is cooled and the hair is obtained. The foamed graphite film is finally rolled into a foamed graphite film, and the tension is controlled at 2 kg to obtain a highly thermally conductive graphite film having a soft and smooth surface. Electroless copper plating is performed on the obtained graphite film to control the electroless copper plating. The bath has a pH of 12.0 and is plated for 10 minutes at a plating temperature of 50 ° C. The electroless copper plating bath includes copper sulfate pentahydrate, EDTA, sodium hypophosphite, surfactant, bipyridine and pH adjustment. After the electroless copper plating is completed, the copper plating is continued to obtain a high thermal conductivity graphite film-copper composite material, wherein the process of electroplating copper is: pickling acid → electroplating copper → 2-3 grade pure water washing → drying Dry → 2-3 grade pure water wash → dry, The main components of the plating solution include: copper sulfate, sulfuric acid, hydrochloric acid, brightener and leveling agent.

Example 3

The polyimide film is used as the original film, and the treated polyamide film is fixed by a graphite frame in a high temperature furnace for heat treatment, and the heat treatment is performed in different high temperature furnaces. The process is as follows: In a high temperature furnace, the high temperature furnace is closed, the temperature in the furnace is raised to 650 ° C, and the pressure is reduced to 15 Pa using a vacuum pump. The temperature is maintained for 1 hour and then the temperature is raised, and the temperature is raised to 2 hours. At 1100 ° C, argon gas was introduced into the high temperature furnace while continuing to use the vacuum pump to maintain the pressure in the furnace at 50 Pa for 1 hour; then in the second high temperature furnace, the high temperature furnace was closed and the temperature in the furnace was raised within 2 hours. At 2400 ° C, argon gas is introduced into the high temperature furnace, while the vacuum pump is continuously used to maintain the pressure in the furnace at 30 Pa, and the temperature is maintained for 1 hour, and the temperature is raised to 2900 ° C in one hour to increase the flow rate of the argon gas and reduce the displacement of the vacuum pump. The pressure in the furnace is controlled at 1.5 atm for 2 hours, and then naturally cooled down to obtain a foamed graphite film. Finally, the foamed graphite film is rolled, and the tension is controlled at 10 kg to obtain a soft and smooth surface. The thermally conductive graphite film is subjected to electroless copper plating on the basis of the obtained graphite film, and the plating solution for controlling electroless copper plating has a pH of 11.0, and is plated at a plating temperature of 48 ° C for 5 minutes, wherein the electroless copper plating solution includes Copper sulfate pentahydrate, EDTA, sodium hypophosphite, surfactant, bipyridine and pH adjuster, after electroless copper plating is completed, electroplating copper is continued to obtain a high thermal conductivity graphite film-copper composite material, wherein Copper electroplating process: electroless copper plating → pickling → pure water washing → drying stage 2-3 2-3 → pure water washing → drying stage, The main components of the plating solution include: copper sulfate, sulfuric acid, hydrochloric acid, brightener and leveling agent.

Comparative example 1

A polyimide film is used as a raw material, graphite paper is added between each layer of polyimide film, and a polyimide film which is cross-laminated with graphite paper is placed in a carbonization furnace to be carbonized and carbonized in a nitrogen atmosphere. The temperature is 1200 ° C, the time is controlled at 3 hours; the graphitization is carried out in an argon atmosphere, the temperature is controlled at about 2800 ° C, and the temperature is controlled at 5 hours. The experimental results show that the plane of thermal conductivity of the graphite film is ≥1600 W/mK; vertical direction 5.3 W/mK.

The present invention has been described in detail above, and the description of the embodiments is only to assist in understanding the method of the present invention and its core idea, and the purpose of the present invention is to enable those skilled in the art to understand the contents of the present invention and implement it. This limits the scope of protection of the present invention. Equivalent variations or modifications made in accordance with the spirit of the invention are intended to be included within the scope of the invention.

Claims

A method for preparing a high thermal conductivity graphite film-copper composite material, comprising the steps of:

a plasma treatment of the original film;

d continue to raise temperature, control the temperature of the high temperature furnace at 1600 °C -2500 °C, continue to pass inert gas into the high temperature furnace, keep the pressure inside the furnace at 5 Pa-30 Pa, time control is 1-10 hours;

e continue to heat up, control the temperature of the high temperature furnace at 2500 ° C -3000 ° C, increase the inert gas flow to the high temperature furnace, keep the pressure inside the furnace at 0.5 atm-1.5 Atm, the time is controlled in 1-10 hours, after natural cooling and cooling, a carbon foam film is obtained;

2. The method for producing a highly thermally conductive graphite film-copper composite according to claim 1, wherein the original film in the step a is one of a polyamide film or a polyimide film.

3. The method for producing a highly thermally conductive graphite film-copper composite according to claim 1, wherein the original film is fixed by a graphite frame in the high temperature furnace.

4. The method for preparing a high thermal conductivity graphite film-copper composite according to claim 1, wherein in the step f, the tension is controlled at 0.1 kg-20 Kg.

5. The method for preparing a high thermal conductivity graphite film-copper composite according to claim 1, wherein in the step g, the plating solution for performing electroless copper plating has a pH of 11.0-12.0.

6. The method for producing a highly thermally conductive graphite film-copper composite according to claim 1, wherein in the step g, the plating temperature of the electroless copper plating is 45 ° C to 50 ° C.

7. The method for producing a highly thermally conductive graphite film-copper composite according to claim 1, wherein in the step g, the plating time of the electroless copper plating is 1-10 minutes.

8. The method for preparing a high thermal conductivity graphite film-copper composite according to claim 1, wherein the inert gas in the step c is nitrogen, the inert gas in the step d is argon, and the inert gas in the step e is argon. gas.

9. The method for preparing a high thermal conductivity graphite film-copper composite according to claim 1, wherein the high temperature furnaces in the step b, the step c, the step d and the step e are the same.

10. The method for preparing a high thermal conductivity graphite film-copper composite according to claim 1, wherein the high temperature furnaces in the step b, the step c, the step d and the step e are not the same.