Preparation method of a high thermal conductivity diamond / copper composite conductive thin film material and corresponding material

Abstract

The present invention relates to the technical field of conductive thin films, and relates to a preparation method of a high thermal conductivity diamond / copper composite conductive thin film material and the corresponding material, including: preparing an organic carrier mixed solution; preparing an organic carrier / diamond powder mixed solution by using diamond powder and the organic carrier mixed solution; preparing a bonded glass powder by successively performing vitrification treatment and refinement treatment on an inorganic mixed powder obtained by mixing silicon dioxide, sodium oxide and calcium oxide; preparing a diamond / copper composite conductive paste by using copper powder, the organic carrier / diamond powder mixed solution and the bonded glass powder; coating the diamond / copper composite conductive paste on the surface of a ceramic substrate and performing vacuum leveling treatment, and placing the obtained diamond / copper composite conductive paste coating and leveling assembly in a protective atmosphere to successively perform degreasing treatment and sintering treatment to prepare a high thermal conductivity diamond / copper composite conductive thin film material. The present invention can prepare a diamond / copper composite conductive thin film with both high thermal conductivity and low resistivity.

Description

Technical Field

[0001] The present invention relates to the technical field of conductive thin films, and particularly to a preparation method of a high thermal conductivity diamond / copper composite conductive thin film material and a corresponding material. Background Art

[0002] A high-temperature printed circuit board (PCB) is an electronic material prepared by printing conductive copper paste on a ceramic substrate and then subjecting it to high-temperature degreasing and sintering. Different from normal-temperature PCB materials, high-temperature PCB materials need to withstand higher ambient temperatures during use. Therefore, in addition to having good electrical conductivity and bonding strength, they also need to have higher thermal conductivity to meet stringent heat dissipation requirements. The thermal conductivity of PCB materials is mainly determined by the copper conductive paste on the surface and the substrate material. Since the thermal conductivity of copper metal paste is much higher than that of the ceramic substrate, further increasing the thermal conductivity of the conductive paste plays an important role in improving the thermal conductivity of PCB materials.

[0003] Currently, the main method to improve copper conductive paste is to add high-thermal-conductivity materials such as gold and graphene to conductive copper powder. The Chinese invention patent with the publication number CN113481491B discloses a copper / graphene composite thin film material and its preparation method. By co-depositing metallic copper and single-layer graphene on the surface of the substrate, a copper / graphene composite thin film material is obtained, and a composite thin film material with high thermal conductivity is obtained. However, raw materials such as gold and graphene are expensive and not conducive to large-scale application in the industrial field. In contrast, diamond powder materials, which also have high thermal conductivity and low price, have greater application prospects in copper conductive paste. However, the electrical conductivity of diamond is extremely low, and directly adding it to the conductive copper paste will greatly reduce the electrical conductivity of the conductive paste.

[0004] Therefore, how to dope diamond in copper conductive paste to increase the thermal conductivity while maintaining high electrical conductivity has become an urgent technical problem to be solved. Summary of the Invention

[0005] In view of this, in order to overcome the deficiencies of the prior art, the present invention provides a preparation method of a high thermal conductivity diamond / copper composite conductive thin film material and a corresponding material.

[0006] According to one aspect of the present invention, the present invention provides a preparation method of a high thermal conductivity diamond / copper composite conductive thin film material, and the method includes the following steps:

[0007] Step 1: Preparation of organic carrier / diamond powder mixture

[0008] Prepare a first mixed material by using terpineol, polyethylene glycol 400, ethyl cellulose, and polyoxypropylene according to the ratio, and perform a first water bath stirring treatment on the prepared first mixed material to obtain an organic carrier mixture;

[0009] Prepare a second mixed material by mixing diamond powder and an organic carrier mixture according to the ratio, and perform a second water bath stirring treatment on the prepared second mixed material to obtain an organic carrier / diamond powder mixture;

[0010] Step Two: Preparation of Diamond-Copper Composite Conductive Paste

[0011] Mix silicon dioxide, sodium oxide, and calcium oxide according to the ratio to obtain an inorganic mixed powder, and successively perform vitrification treatment and refinement treatment on the obtained inorganic mixed powder to obtain a bonding glass powder;

[0012] Prepare a third mixed material by mixing copper powder, the organic carrier / diamond powder mixture, and the bonding glass powder according to the ratio, and perform a third water bath stirring treatment on the prepared third mixed material to obtain a diamond / copper composite conductive paste;

[0013] Step Three: Preparation of High-Thermal-Conductivity Diamond-Copper Composite Conductive Film Material

[0014] Coat the diamond / copper composite conductive paste on the surface of a ceramic substrate, and perform a vacuum leveling treatment on the ceramic substrate coated with the diamond / copper composite conductive paste to obtain a diamond / copper composite conductive paste-coated and leveled assembly;

[0015] Place the diamond / copper composite conductive paste-coated and leveled assembly in a protective atmosphere and successively perform degreasing treatment and sintering treatment to obtain a high-thermal-conductivity diamond / copper composite conductive film material.

[0016] Preferably, in the preparation method of the high-thermal-conductivity diamond / copper composite conductive film material of the present invention, in Step One, prepare a first mixed material by mixing terpineol, polyethylene glycol 400, ethyl cellulose, and polyoxypropylene according to the ratio, and perform a first water bath stirring treatment on the prepared first mixed material, including: preparing the first mixed material by using 70-80 parts by weight of terpineol, 14-24 parts by weight of polyethylene glycol 400, 3 parts by weight of ethyl cellulose, and 3 parts by weight of polyoxypropylene, and performing water bath stirring on the prepared first mixed material at a temperature of 80-100 °C for 1-3 h.

[0017] Preferably, in the preparation method of the high-thermal-conductivity diamond / copper composite conductive film material of the present invention, in Step One, prepare a second mixed material by mixing diamond powder and an organic carrier mixture according to the ratio, and perform a second water bath stirring treatment on the prepared second mixed material, including: preparing the second mixed material by using 1-4 parts by weight of diamond powder and 14-18 parts by weight of an organic carrier mixed solution, and performing water bath stirring on the prepared second mixed material at a temperature of 60-80 °C for 2-4 h, and the average particle size of the diamond powder is 0.2-0.25 μm.

[0018] Preferably, in the preparation method of the high thermal conductivity diamond / copper composite conductive thin film material of the present invention, in step two, mixing silica powder, sodium oxide powder and calcium oxide powder according to the ratio to obtain an inorganic mixed powder, including: mixing 70-85 parts by weight of silica powder, 10-20 parts by weight of sodium oxide and 5-10 parts by weight of calcium oxide powder to obtain an inorganic mixed powder.

[0019] Preferably, in the preparation method of the high thermal conductivity diamond / copper composite conductive thin film material of the present invention, in step two, the obtained inorganic mixed powder is subjected to vitrification treatment and refinement treatment in sequence to prepare a bonding glass powder, including:

[0020] The obtained inorganic mixed powder is roll-milled for 12-18 h and then heated to 1000-1200 °C, held for 1-3 h and then water-cooled to obtain a vitrified material;

[0021] Under the condition of a ball-to-material ratio of 20:1, the vitrified material is ball-milled for 24-36 h, and the ball-milled material is screened to obtain a bonding glass powder.

[0022] Preferably, in the preparation method of the high thermal conductivity diamond / copper composite conductive thin film material of the present invention, in step two, a third mixed material is prepared by using copper powder, an organic carrier / diamond powder mixture and a bonding glass powder according to the ratio, and the prepared third mixed material is subjected to a third water bath stirring treatment, including: mixing 70-78 parts by weight of copper powder with 6-10 parts by weight of bonding glass powder by roll-milling for 6 h, mixing the roll-milled mixed material with 15-22 parts by weight of an organic carrier / diamond powder mixture and then stirring in a water bath at a temperature of 60-80 °C for 2-4 h, and the average particle size of the copper powder is 3-5 μm.

[0023] Preferably, in the preparation method of the high thermal conductivity diamond / copper composite conductive thin film material of the present invention, in step three, the diamond / copper composite conductive paste is coated on the surface of a ceramic substrate, including: printing the diamond / copper composite conductive paste on the surface of a ceramic substrate by using a 200-mesh screen, and the ceramic substrate is made of alumina material with a purity of not less than 99%, and the average surface roughness of the ceramic substrate is not greater than Ra0.8.

[0024] Preferably, in the preparation method of the high thermal conductivity diamond / copper composite conductive thin film material of the present invention, in step three, the ceramic substrate coated with the diamond / copper composite conductive paste is subjected to vacuum leveling treatment, including: placing the ceramic substrate coated with the diamond / copper composite conductive paste in a vacuum and heating it to 80-120 °C, and holding it for 10-50 min.

[0025] Preferably, in the preparation method of the high thermal conductivity diamond / copper composite conductive thin film material of the present invention, in step three, the diamond / copper composite conductive paste coating and leveling assembly is placed in a protective atmosphere for degreasing treatment and sintering treatment in sequence, including: placing the diamond / copper composite conductive paste coating and leveling assembly in a protective atmosphere, heating it at a heating rate of 1-3 °C / min to 500 °C and then holding for 2-5 h, and heating it at a heating rate of 5-10 °C / min to 700-900 °C and then holding for 0.5-2 h.

[0026] According to another aspect of the present invention, the present invention provides a high thermal conductivity diamond / copper composite conductive thin film material, and the high thermal conductivity diamond / copper composite conductive thin film material is prepared by the above method.

[0027] The preparation method of the high thermal conductivity diamond / copper composite conductive thin film material of the present invention and the corresponding material have the following beneficial effects:

[0028] 1. By preparing an organic carrier mixture solution and mixing it with diamond powder to form an organic carrier / diamond powder mixture solution, the sub-micron diamond powder is evenly dispersed in the organic carrier, so that the diamond powder in the conductive thin film is concentrated in the gaps formed after the organic carrier volatilizes, and the conductive channels of the conductive thin film are not damaged;

[0029] 2. By preparing a bonding glass powder with a low coefficient of thermal expansion and uniformly mixing it with copper powder and the organic carrier / diamond powder mixture solution to form a diamond / copper composite conductive paste, the prepared conductive thin film has a high thermal deformation resistance, thereby improving the thermal stability of the composite conductive thin film;

[0030] 3. Through the vacuum leveling, degreasing and sintering processes, the conductive paste is prepared into a diamond / copper composite conductive thin film with both high thermal conductivity and low resistivity;

[0031] 4. The prepared high thermal conductivity diamond / copper composite conductive thin film material has strong heat dissipation, can withstand a high working temperature, and is suitable for application in high-precision integrated circuits. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required to be used in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0033] Figure 1 It is a flowchart of the preparation method of the high thermal conductivity diamond / copper composite conductive thin film material of exemplary embodiments 1-5 of the present invention;

[0034] Figure 2 SEM morphology diagram of the high thermal conductivity diamond / copper composite conductive thin film material prepared in Example 1 of the present invention;

[0035] Figure 3 SEM morphology diagram of the high thermal conductivity diamond / copper composite conductive thin film material prepared in Example 2 of the present invention;

[0036] Figure 4 SEM morphology diagram of the high thermal conductivity diamond / copper composite conductive thin film material prepared in Example 3 of the present invention;

[0037] Figure 5 SEM morphology diagram of the high thermal conductivity diamond / copper composite conductive thin film material prepared in Example 4 of the present invention;

[0038] Figure 6 SEM morphology diagram of the high thermal conductivity diamond / copper composite conductive thin film material prepared in Example 5 of the present invention;

[0039] Figure 7 SEM morphology diagram of the copper conductive thin film material prepared in Example 6 (comparative example) of the present invention;

[0040] Figure 8 EDS spectrum of a local area of the high thermal conductivity diamond / copper composite conductive thin film material prepared in Example 3 of the present invention;

[0041] Figure 9 EDS spectrum of a local area of the high thermal conductivity diamond / copper composite conductive thin film material prepared in Example 5 of the present invention;

[0042] Figure 10 TMA curve of the bonding glass powder and the ceramic substrate in Example 5 of the present invention. Detailed implementation manners

[0043] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0044] It should be noted that, without conflict, the following embodiments and the features in the embodiments may be combined with each other; and, based on the embodiments in the present disclosure, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present disclosure.

[0045] It should be noted that the following description pertains to various aspects of embodiments within the scope of the appended claims. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any specific structure and / or function described herein is merely illustrative. Based on this disclosure, those skilled in the art should understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects described herein can be used to implement a device and / or practice a method. Additionally, this device can be implemented and this method can be practiced using other structures and / or functionality in addition to one or more of the aspects described herein.

[0046] In the present invention, submicron ultrafine diamond powder is uniformly mixed with an organic carrier mixture to form an organic carrier / diamond powder mixture. The diamond powder is doped into the gaps of micron copper powder through the organic carrier mixture to prepare a diamond / copper composite conductive paste with both high thermal conductivity and low resistivity. Through vacuum leveling treatment, degreasing treatment, and sintering treatment, a high thermal conductivity diamond / copper composite conductive thin film material is prepared. Figure 1 It is a flowchart of the preparation method of the high thermal conductivity diamond / copper composite conductive thin film material for exemplary embodiments 1 - 5 of the present invention. Embodiments 1 to 5 of the present invention are implemented Figure 1 in the manner shown.

[0047] Example 1

[0048] Preparation of high thermal conductivity diamond / copper composite conductive thin film material:

[0049] Step 1. Preparation of organic carrier / diamond powder mixture

[0050] According to the ratio, terpineol, polyethylene glycol 400, ethyl cellulose, and polyoxypropylene are used to prepare a first mixed material. The prepared first mixed material is subjected to a first water bath stirring treatment. Specifically, 80 parts by weight of terpineol, 14 parts by weight of polyethylene glycol 400, 3 parts by weight of ethyl cellulose, and 3 parts by weight of polyoxypropylene are used to prepare the first mixed material. The prepared first mixed material is water bath stirred at 80 °C for 1 h to obtain an organic carrier mixture;

[0051] According to the ratio, diamond powder and the organic carrier mixture are used to prepare a second mixed material. The prepared second mixed material is subjected to a second water bath stirring treatment. Specifically, 1 part by weight of diamond powder with an average particle size of 0.2 - 0.25 μm and 14 parts by weight of the organic carrier mixed solution are used to prepare the second mixed material. The prepared second mixed material is water bath stirred at 60 °C for 2 h to obtain an organic carrier / diamond powder mixture;

[0052] Step 2. Preparation of diamond / copper composite conductive paste

[0053] Mix silicon dioxide, sodium oxide, and calcium oxide according to the ratio to obtain an inorganic mixed powder. Then, perform vitrification treatment and refinement treatment on the obtained inorganic mixed powder. Specifically, mix 85 parts by weight of silicon dioxide powder, 10 parts by weight of sodium oxide, and 5 parts by weight of calcium oxide powder to obtain an inorganic mixed powder; roll-mill the obtained inorganic mixed powder for 12 h and then heat it to 1000 °C, hold for 1 h, and then cool it with water to obtain a vitrified material; under the condition of a ball-to-material ratio of 20:1, ball-mill the vitrified material for 24 h, and screen the ball-milled material with a 200-mesh sieve to prepare a bonding glass powder.

[0054] Prepare a third mixed material by using copper powder, an organic carrier / diamond powder mixture, and a bonding glass powder according to the ratio, and perform a third water-bath stirring treatment on the prepared third mixed material. Specifically, prepare a third mixed material by using copper powder, an organic carrier / diamond powder mixture, and a bonding glass powder according to the ratio, and perform a third water-bath stirring treatment on the prepared third mixed material, including: roll-mill and mix 70 parts by weight of copper powder with an average particle size of 3 - 5 μm and 6 parts by weight of the bonding glass powder for 6 h, mix the roll-milled and mixed material with 15 parts by weight of the organic carrier / diamond powder mixture, and then perform water-bath stirring at 60 °C for 2 h to prepare a diamond / copper composite conductive paste.

[0055] Step 3: Preparation of a high-thermal-conductivity diamond / copper composite conductive thin-film material

[0056] Coat the diamond / copper composite conductive paste on the surface of a ceramic substrate, and perform vacuum leveling treatment on the ceramic substrate coated with the diamond / copper composite conductive paste. Specifically, use a 200-mesh wire mesh to print the diamond / copper composite conductive paste on a ceramic substrate made of alumina material with a purity of not less than 99% and a surface average roughness of not more than Ra0.8, place the ceramic substrate coated with the diamond / copper composite conductive paste in a vacuum and heat it to 80 °C, hold for 10 min, to obtain a diamond / copper composite conductive paste-coated and leveled assembly.

[0057] Place the diamond / copper composite conductive paste-coated and leveled assembly in a protective atmosphere and perform degreasing treatment and sintering treatment in sequence. Specifically, place the diamond / copper composite conductive paste-coated and leveled assembly in a protective atmosphere, heat it at a heating rate of 3 °C / min to 500 °C and hold for 2 h, and then heat it at a heating rate of 10 °C / min to 700 °C and hold for 0.5 h to prepare a high-thermal-conductivity diamond / copper composite conductive thin-film material.

[0058] Example 2

[0059] Preparation of a high-thermal-conductivity diamond / copper composite conductive thin-film material:

[0060] Step 1: Preparation of organic carrier / diamond powder mixture

[0061] Prepare the first mixed material with terpineol, polyethylene glycol 400, ethyl cellulose, and polyoxypropylene according to the ratio, and perform the first water bath stirring treatment on the prepared first mixed material. Specifically, prepare the first mixed material with 76 parts by weight of terpineol, 18 parts by weight of polyethylene glycol 400, 3 parts by weight of ethyl cellulose, and 3 parts by weight of polyoxypropylene, and stir the prepared first mixed material in a water bath at 90 °C for 1.5 h to obtain the organic carrier mixture;

[0062] Prepare the second mixed material by mixing diamond powder with the organic carrier mixture according to the ratio, and perform the second water bath stirring treatment on the prepared second mixed material. Specifically, prepare the second mixed material with 1 part by weight of diamond powder with an average particle size of 0.2 - 0.25 μm and 14 parts by weight of the organic carrier mixed solution, and stir the prepared second mixed material in a water bath at 70 °C for 3 h to obtain the organic carrier / diamond powder mixture;

[0063] Step 2: Preparation of diamond / copper composite conductive paste

[0064] Mix silica, sodium oxide, and calcium oxide according to the ratio to obtain an inorganic mixed powder, and perform vitrification treatment and refinement treatment on the obtained inorganic mixed powder in sequence. Specifically, mix 85 parts by weight of silica powder, 10 parts by weight of sodium oxide, and 5 parts by weight of calcium oxide powder to obtain an inorganic mixed powder; roll-mill the obtained inorganic mixed powder for 14 h and then heat it to 1000 °C, keep it warm for 1 h and then cool it with water to obtain a vitrified material; ball-mill the vitrified material for 28 h under the condition of a ball-to-material ratio of 20:1, and screen the ball-milled material with a 200-mesh sieve to obtain the bonding glass powder;

[0065] Prepare the third mixed material with copper powder, organic carrier / diamond powder mixture, and bonding glass powder according to the ratio, and perform the third water bath stirring treatment on the prepared third mixed material. Specifically, prepare the third mixed material with copper powder, organic carrier / diamond powder mixture, and bonding glass powder according to the ratio, and perform the third water bath stirring treatment on the prepared third mixed material, including: roll-mill and mix 72 parts by weight of copper powder with an average particle size of 3 - 5 μm and 6 parts by weight of bonding glass powder for 6 h, mix the roll-milled mixed material with 15 parts by weight of the organic carrier / diamond powder mixture and then stir it in a water bath at 70 °C for 3 h to obtain the diamond / copper composite conductive paste;

[0066] Step 3: Preparation of high thermal conductivity diamond / copper composite conductive thin film material

[0067] The diamond / copper composite conductive paste is coated on the surface of the ceramic substrate, and the ceramic substrate coated with the diamond / copper composite conductive paste is subjected to vacuum leveling treatment. Specifically, the diamond / copper composite conductive paste is printed on a ceramic substrate made of alumina material with a purity of not less than 99% and a surface average roughness of not more than Ra0.8 using a screen with a pore size of 200 meshes. The ceramic substrate coated with the diamond / copper composite conductive paste is placed in a vacuum and heated to 90 °C and held for 20 min to obtain a diamond / copper composite conductive paste-coated and leveled component;

[0068] The diamond / copper composite conductive paste-coated and leveled component is placed in a protective atmosphere and subjected to degreasing treatment and sintering treatment in sequence. Specifically, the diamond / copper composite conductive paste-coated and leveled component is placed in a protective atmosphere, heated to 500 °C at a heating rate of 2 °C / min and held for 2 h, and then heated to 700 °C at a heating rate of 10 °C / min and held for 0.5 h to obtain a high thermal conductivity diamond / copper composite conductive thin film material.

[0069] Example 3

[0070] Preparation of high thermal conductivity diamond / copper composite conductive thin film material:

[0071] Step 1. Preparation of organic carrier / diamond powder mixture

[0072] According to the ratio, terpineol, polyethylene glycol 400, ethyl cellulose and polyoxypropylene are used to prepare the first mixed material, and the prepared first mixed material is subjected to the first water bath stirring treatment. Specifically, 72 parts by weight of terpineol, 22 parts by weight of polyethylene glycol 400, 3 parts by weight of ethyl cellulose and 3 parts by weight of polyoxypropylene are used to prepare the first mixed material, and the prepared first mixed material is stirred in a water bath at 100 °C for 2 h to obtain an organic carrier mixture;

[0073] According to the ratio, diamond powder and the organic carrier mixture are used to prepare the second mixed material, and the prepared second mixed material is subjected to the second water bath stirring treatment. Specifically, 2 parts by weight of diamond powder with an average particle size of 0.2 - 0.25 μm and 16 parts by weight of the organic carrier mixed solution are used to prepare the second mixed material, and the prepared second mixed material is stirred in a water bath at 80 °C for 4 h to obtain an organic carrier / diamond powder mixture;

[0074] Step 2. Preparation of diamond / copper composite conductive paste

[0075] Mix silica, sodium oxide, and calcium oxide according to the ratio to obtain an inorganic mixed powder. Then, perform vitrification treatment and refinement treatment on the obtained inorganic mixed powder. Specifically, mix 80 parts by weight of silica powder, 15 parts by weight of sodium oxide, and 5 parts by weight of calcium oxide powder to obtain an inorganic mixed powder. After roller milling the obtained inorganic mixed powder for 16 h, heat it to 1100 °C, keep it warm for 2 h, and then cool it with water to obtain a vitrified material. Under the condition of a ball-to-material ratio of 20:1, ball mill the vitrified material for 32 h, and screen the ball-milled material with a 200-mesh sieve to prepare a bonding glass powder.

[0076] Prepare a third mixed material by using copper powder, an organic carrier / diamond powder mixture, and a bonding glass powder according to the ratio. Then, perform a third water bath stirring treatment on the prepared third mixed material. Specifically, prepare a third mixed material by using copper powder, an organic carrier / diamond powder mixture, and a bonding glass powder according to the ratio. The third water bath stirring treatment on the prepared third mixed material includes: roller mill and mix 74 parts by weight of copper powder with an average particle size of 3 - 5 μm and 8 parts by weight of the bonding glass powder for 6 h. After mixing the roller-milled and mixed material with 18 parts by weight of the organic carrier / diamond powder mixture, perform water bath stirring at 80 °C for 4 h to prepare a diamond / copper composite conductive paste.

[0077] Step 3. Preparation of a high-thermal-conductivity diamond / copper composite conductive thin film material

[0078] Coat the diamond / copper composite conductive paste on the surface of a ceramic substrate, and perform vacuum leveling treatment on the ceramic substrate coated with the diamond / copper composite conductive paste. Specifically, use a 200-mesh silk screen to print the diamond / copper composite conductive paste on a ceramic substrate made of alumina material with a purity of not less than 99% and a surface average roughness of not more than Ra0.8. Place the ceramic substrate coated with the diamond / copper composite conductive paste in a vacuum and heat it to 100 °C, keep it warm for 30 min to obtain a diamond / copper composite conductive paste-coated and leveled assembly.

[0079] Place the diamond / copper composite conductive paste-coated and leveled assembly in a protective atmosphere and perform degreasing treatment and sintering treatment in sequence. Specifically, place the diamond / copper composite conductive paste-coated and leveled assembly in a protective atmosphere, heat it to 500 °C at a heating rate of 2 °C / min and keep it warm for 3 h, then heat it to 700 °C at a heating rate of 8 °C / min and keep it warm for 1 h to prepare a high-thermal-conductivity diamond / copper composite conductive thin film material.

[0080] Example 4

[0081] Preparation of a high-thermal-conductivity diamond / copper composite conductive thin film material:

[0082] Step 1. Preparation of an organic carrier / diamond powder mixture

[0083] Prepare the first mixed material by using terpineol, polyethylene glycol 400, ethyl cellulose and polyoxypropylene according to the ratio, and conduct the first water bath stirring treatment on the prepared first mixed material. Specifically, prepare the first mixed material by using 70 parts by weight of terpineol, 24 parts by weight of polyethylene glycol 400, 3 parts by weight of ethyl cellulose and 3 parts by weight of polyoxypropylene, and conduct water bath stirring on the prepared first mixed material at 100 °C for 2.5 h to obtain an organic carrier mixed solution;

[0084] Prepare the second mixed material by using diamond powder and the organic carrier mixed solution according to the ratio, and conduct the second water bath stirring treatment on the prepared second mixed material. Specifically, prepare the second mixed material by using 4 parts by weight of diamond powder with an average particle size of 0.2 - 0.25 μm and 16 parts by weight of the organic carrier mixed solution, and conduct water bath stirring on the prepared second mixed material at 80 °C for 4 h to obtain an organic carrier / diamond powder mixed solution;

[0085] Step Two: Preparation of Diamond / Copper Composite Conductive Paste

[0086] Mix silica, sodium oxide and calcium oxide according to the ratio to obtain an inorganic mixed powder, and conduct vitrification treatment and refinement treatment on the obtained inorganic mixed powder in sequence. Specifically, mix 75 parts by weight of silica powder, 15 parts by weight of sodium oxide and 10 parts by weight of calcium oxide powder to obtain an inorganic mixed powder; subject the obtained inorganic mixed powder to roll grinding treatment for 18 h and then heat it to 1100 °C, keep it warm for 2 h and then cool it with water to obtain a vitrified material; under the condition of a ball-to-material ratio of 20:1, ball mill the vitrified material for 36 h, and screen the ball-milled material with a 200-mesh sieve to obtain a bonded glass powder;

[0087] Prepare the third mixed material by using copper powder, the organic carrier / diamond powder mixed solution and the bonded glass powder according to the ratio, and conduct the third water bath stirring treatment on the prepared third mixed material. Specifically, prepare the third mixed material by using copper powder, the organic carrier / diamond powder mixed solution and the bonded glass powder according to the ratio, and conduct the third water bath stirring treatment on the prepared third mixed material, including: conduct roll grinding and mixing of 76 parts by weight of copper powder with an average particle size of 3 - 5 μm and 10 parts by weight of the bonded glass powder for 6 h, mix the roll-ground and mixed material with 20 parts by weight of the organic carrier / diamond powder mixed solution and then conduct water bath stirring at 80 °C for 4 h to obtain a diamond / copper composite conductive paste;

[0088] Step Three: Preparation of High Thermal Conductivity Diamond / Copper Composite Conductive Film Material

[0089] The diamond / copper composite conductive paste is coated on the surface of the ceramic substrate, and the ceramic substrate coated with the diamond / copper composite conductive paste is subjected to vacuum leveling treatment. Specifically, the diamond / copper composite conductive paste is printed on the ceramic substrate made of alumina material with a purity of not less than 99% and a surface average roughness of not more than Ra0.8 using a screen with a pore size of 200 meshes. The ceramic substrate coated with the diamond / copper composite conductive paste is placed in a vacuum and heated to 110 °C and kept warm for 40 min to obtain a diamond / copper composite conductive paste coated and leveled assembly;

[0090] The diamond / copper composite conductive paste coated and leveled assembly is placed in a protective atmosphere and subjected to degreasing treatment and sintering treatment in sequence. Specifically, the diamond / copper composite conductive paste coated and leveled assembly is placed in a protective atmosphere, heated to 500 °C at a heating rate of 1 °C / min and kept warm for 4 h, and then heated to 800 °C at a heating rate of 6 °C / min and kept warm for 1.5 h to obtain a high thermal conductivity diamond / copper composite conductive thin film material.

[0091] Example 5

[0092] Preparation of high thermal conductivity diamond / copper composite conductive thin film material:

[0093] Step 1. Preparation of organic carrier / diamond powder mixture

[0094] The first mixed material is prepared according to the ratio using terpineol, polyethylene glycol 400, ethyl cellulose and polyoxypropylene, and the prepared first mixed material is subjected to the first water bath stirring treatment. Specifically, the first mixed material is prepared using 70 parts by weight of terpineol, 24 parts by weight of polyethylene glycol 400, 3 parts by weight of ethyl cellulose and 3 parts by weight of polyoxypropylene, and the prepared first mixed material is stirred in a water bath at 100 °C for 3 h to obtain an organic carrier mixture;

[0095] The second mixed material is prepared according to the ratio using diamond powder and the organic carrier mixture, and the prepared second mixed material is subjected to the second water bath stirring treatment. Specifically, the second mixed material is prepared using 4 parts by weight of diamond powder with an average particle size of 0.2 - 0.25 μm and 18 parts by weight of the organic carrier mixed solution, and the prepared second mixed material is stirred in a water bath at 80 °C for 4 h to obtain an organic carrier / diamond powder mixture;

[0096] Step 2. Preparation of diamond / copper composite conductive paste

[0097] Mix silica, sodium oxide, and calcium oxide according to the ratio to obtain an inorganic mixed powder. Then, perform vitrification treatment and refinement treatment on the obtained inorganic mixed powder. Specifically, mix 70 parts by weight of silica powder, 20 parts by weight of sodium oxide, and 10 parts by weight of calcium oxide powder to obtain an inorganic mixed powder. After roller milling the obtained inorganic mixed powder for 18 h, heat it to 1200 °C, keep it warm for 3 h, and then cool it with water to obtain a vitrified material. Under the condition of a ball-to-material ratio of 20:1, ball mill the vitrified material for 36 h, and screen the ball-milled material with a 200-mesh sieve to obtain a bonding glass powder.

[0098] Prepare a third mixed material by using copper powder, an organic carrier / diamond powder mixture, and a bonding glass powder according to the ratio. Perform a third water bath stirring treatment on the prepared third mixed material. Specifically, prepare a third mixed material by using copper powder, an organic carrier / diamond powder mixture, and a bonding glass powder according to the ratio. The third water bath stirring treatment on the prepared third mixed material includes: roller mill and mix 78 parts by weight of copper powder with an average particle size of 3 - 5 μm and 10 parts by weight of the bonding glass powder for 6 h. After mixing the roller-milled mixed material with 22 parts by weight of the organic carrier / diamond powder mixture, perform water bath stirring at 80 °C for 4 h to obtain a diamond / copper composite conductive paste.

[0099] Step Three: Preparation of a high-thermal-conductivity diamond / copper composite conductive thin film material

[0100] Coat the diamond / copper composite conductive paste on the surface of a ceramic substrate, and perform vacuum leveling treatment on the ceramic substrate coated with the diamond / copper composite conductive paste. Specifically, use a 200-mesh wire mesh to print the diamond / copper composite conductive paste on a ceramic substrate made of alumina material with a purity of not less than 99% and a surface average roughness of not more than Ra0.8. Place the ceramic substrate coated with the diamond / copper composite conductive paste in a vacuum and heat it to 120 °C, keep it warm for 50 min to obtain a diamond / copper composite conductive paste-coated and leveled component.

[0101] Place the diamond / copper composite conductive paste-coated and leveled component in a protective atmosphere and perform degreasing treatment and sintering treatment in sequence. Specifically, place the diamond / copper composite conductive paste-coated and leveled component in a protective atmosphere, heat it to 500 °C at a heating rate of 1 °C / min and keep it warm for 5 h, then heat it to 900 °C at a heating rate of 5 °C / min and keep it warm for 2 h to obtain a high-thermal-conductivity diamond / copper composite conductive thin film material.

[0102] Example 6 (comparative example)

[0103] Preparation of a copper conductive thin film material:

[0104] Step One: Preparation of an organic carrier mixture

[0105] Prepare the first mixed material by using terpineol, polyethylene glycol 400, ethyl cellulose and polyoxypropylene according to the ratio, and conduct the first water bath stirring treatment on the prepared first mixed material. Specifically, prepare the first mixed material by using 80 parts by weight of terpineol, 14 parts by weight of polyethylene glycol 400, 3 parts by weight of ethyl cellulose and 3 parts by weight of polyoxypropylene, and stir the prepared first mixed material in a water bath at 80 °C for 1 h to obtain an organic carrier mixed solution;

[0106] Step 2: Preparation of copper conductive paste

[0107] Mix silicon dioxide, sodium oxide and calcium oxide according to the ratio to obtain an inorganic mixed powder, and conduct vitrification treatment and refinement treatment on the obtained inorganic mixed powder in sequence. Specifically, mix 85 parts by weight of silicon dioxide powder, 10 parts by weight of sodium oxide and 5 parts by weight of calcium oxide powder to obtain an inorganic mixed powder; heat the obtained inorganic mixed powder to 1000 °C after roll grinding for 12 h, keep it warm for 1 h and then cool it with water to obtain a vitrified material; ball mill the vitrified material for 24 h under the condition of a ball-to-material ratio of 20:1, and screen the ball-milled material with a 200-mesh sieve to obtain a bonded glass powder;

[0108] Prepare the third mixed material by using copper powder, organic carrier mixed solution and bonded glass powder according to the ratio, and conduct the third water bath stirring treatment on the prepared third mixed material. Specifically, prepare the third mixed material by using copper powder, organic carrier mixed solution and bonded glass powder according to the ratio, and conduct the third water bath stirring treatment on the prepared third mixed material, including: roll grind and mix 70 parts by weight of copper powder with an average particle size of 3 - 5 μm and 6 parts by weight of bonded glass powder for 6 h, mix the roll-ground and mixed material with 14 parts by weight of organic carrier / diamond powder mixed solution, and then stir in a water bath at 60 °C for 2 h to obtain a diamond / copper composite conductive paste;

[0109] Step 3: Preparation of copper conductive thin film material

[0110] Coat the copper conductive paste on the surface of the ceramic substrate, and conduct vacuum leveling treatment on the ceramic substrate coated with the copper conductive paste. Specifically, print the copper conductive paste on a ceramic substrate made of alumina material with a purity of not less than 99% and a surface average roughness of not more than Ra0.8 by using a 200-mesh screen, place the ceramic substrate coated with the copper conductive paste in a vacuum and heat it to 80 °C, keep it warm for 10 min to obtain a copper conductive paste-coated and leveled component;

[0111] The copper conductive paste coating and leveling component is placed in a protective atmosphere and subjected to degreasing treatment and sintering treatment in sequence. Specifically, the copper conductive paste coating and leveling component is placed in a protective atmosphere, heated to 500 °C at a heating rate of 3 °C / min and then held for 2 h, and then heated to 700 °C at a heating rate of 10 °C / min and held for 0.5 h to obtain a copper conductive thin film material.

[0112] Example 7

[0113] The high thermal conductivity diamond / copper composite conductive thin film materials prepared in Examples 1-5 and the copper conductive thin film material prepared in Example 6 (comparative example) were characterized by SEM micrographs and EDS. The SEM micrographs of the high thermal conductivity diamond / copper composite conductive thin film materials prepared in Examples 1-5 are sequentially referred to Figure 2 , Figure 3 , Figure 4 , Figure 5 and Figure 6 , and the SEM micrograph of the copper conductive thin film material prepared in Example 6 (comparative example) is referred to Figure 7 ; the local area EDS spectrum of the high thermal conductivity diamond / copper composite conductive thin film material prepared in Example 3 is referred to Figure 8 , and the local area EDS spectrum of the high thermal conductivity diamond / copper composite conductive thin film material prepared in Example 5 is referred to Figure 9 .

[0114] Figure 2 is the SEM micrograph of the high thermal conductivity diamond / copper composite conductive thin film material prepared in Example 1 of the present invention; Figure 3 is the SEM micrograph of the high thermal conductivity diamond / copper composite conductive thin film material prepared in Example 2 of the present invention; Figure 4 is the SEM micrograph of the high thermal conductivity diamond / copper composite conductive thin film material prepared in Example 3 of the present invention; Figure 5 is the SEM micrograph of the high thermal conductivity diamond / copper composite conductive thin film material prepared in Example 4 of the present invention; Figure 6 is the SEM micrograph of the high thermal conductivity diamond / copper composite conductive thin film material prepared in Example 5 of the present invention; Figure 7 is the SEM micrograph of the copper conductive thin film material prepared in Example 6 (comparative example) of the present invention; as Figure 7 shown, there are more gaps inside the conductive thin film without doped diamond powder, which indicates that the conductive and heat conduction channels of the copper conductive thin film are imperfect and not conducive to improving the electrical conductivity and thermal conductivity of the thin film; as Figure 2 shown, after doping diamond powder, some gaps in the copper thin film are filled with diamond powder to form a diamond / copper composite conductive thin film, and the heat conduction channel of the thin film is improved without destroying the conductive channel of the thin film; as Figure 3As shown, reducing the heating rate in the degreasing stage is beneficial for the more complete volatilization of the organic carrier, and the increase in the proportion of copper in the thin film is conducive to improving the electrical conductivity and thermal conductivity of the conductive thin film; as Figure 4 shown, after increasing the doping of diamond powder, a large number of gaps in the conductive thin film are filled with diamond powder, and the heat conduction channels of the conductive thin film are more complete; as Figures 5 to 6 shown, after continuously increasing the doping of diamond powder, the vast majority of the gaps in the conductive thin film are filled with diamond powder, forming a very perfect heat conduction channel inside the thin film. At the same time, with the increase of the sintering temperature and time, the conductive channels formed by the connection of copper particles are denser, which is conducive to improving the electrical conductivity and thermal conductivity of the conductive thin film.

[0115] Figure 8 This is the local area EDS spectrum of the high - thermal - conductivity diamond / copper composite conductive thin - film material prepared in Example 3 of the present invention; Figure 9 This is the local area EDS spectrum of the high - thermal - conductivity diamond / copper composite conductive thin - film material prepared in Example 5 of the present invention; as Figure 8 shown, after doping diamond powder into the copper conductive paste, the corresponding C element appears in the EDS spectrum of the prepared composite conductive thin film, and the C element is concentrated in the gaps of Cu, which indicates that the doped diamond powder can effectively supplement the heat conduction channels of the conductive thin film, thereby improving the thermal conductivity of the conductive thin film; as Figure 9 shown, with the increase of diamond powder in the conductive paste, the gaps of Cu are almost completely filled with the C element, and the C element shows a continuous distribution, which indicates that a very perfect heat conduction channel is formed inside the composite conductive thin film. Therefore, doping diamond powder into the copper conductive paste is beneficial to the preparation of high - thermal - conductivity diamond / copper composite conductive thin - film materials.

[0116] The thermal expansion coefficients of the bonding glass powder and the ceramic substrate used in Example 5 of the present invention were respectively measured by using a German STA 449F3 type synchronous thermal analyzer, and the obtained TMA curve is shown in Figure 10 . Figure 10 This is the TMA curve of the bonding glass powder and the ceramic substrate in Example 5 of the present invention. By comparing the thermal expansion coefficients of the bonding glass powder and the ceramic substrate, it can be seen that under the condition that the temperature does not exceed 400 °C, the thermal expansion coefficient of the bonding glass powder is extremely low, and it has a high consistency with the thermal expansion coefficient of the ceramic substrate, which is beneficial to improving the thermal deformation resistance of the copper conductive paste and the thermal stability of the PCB material.

[0117] Table 1 shows the performance parameters of the high thermal conductivity diamond / copper composite conductive thin film materials prepared in Exemplary Embodiments 1-5 of the present invention and the copper conductive thin film material prepared in Example 6 (comparative example). The resistivity was obtained by the four-probe test method. The measuring instrument was a CXT 2516 type resistivity meter, and the reference test standard was "GB / T 17473-2008 Part 3: Determination of Sheet Resistance", where mΩ / □ represents milliohm per square centimeter; the bonding strength was measured by a ZQ-21A type tensile testing machine, and the reference test standard was "GB / T 17473-2008 Part 4: Determination of Adhesion"; the thermal conductivity was measured by an LFA457 laser thermal conductivity meter, and the reference test standard was "GB / T 10294-2008 Test Method for Thermal Conductivity - Method for Determination of Thermal Conductivity".

[0118] As Figures 2 to 6 well as the corresponding performance parameters in Table 1, it can be seen that by introducing submicron diamond powder with high thermal conductivity, doping it into the gaps between the conductive fillers through the organic carrier / diamond powder mixture, and improving the thermal expansion coefficient of the bonding glass powder and other comprehensive measures, the thermal conductivity of the high thermal conductivity diamond / copper composite conductive thin film material has been significantly improved while maintaining a low sheet resistance value.

[0119] From Figure 4 and Figure 6 the corresponding sheet resistance in Table 1, it can be seen that the submicron diamond powder inside the thin film is mainly distributed in the pores between the micron copper particles, without damaging the conductive channels formed by the connection of copper particles, so that the high thermal conductivity diamond / copper composite conductive thin film material maintains a low resistivity.

[0120] From Figure 4 and Figure 6 the corresponding thermal conductivity in Table 1, it can be seen that by increasing the weight fraction of diamond powder in the conductive paste, the thermal conduction channels of the conductive thin film can be further improved, and the thermal conductivity of the high thermal conductivity diamond / copper composite conductive thin film material can be increased.

[0121] Table 1

[0122]

[0123]

[0124] A preparation method of a high thermal conductivity diamond / copper composite conductive thin film material according to an embodiment of the present invention and the corresponding material have the following beneficial technical effects:

[0125] 1. By preparing an organic carrier mixture and mixing it with diamond powder to form an organic carrier / diamond powder mixture, the submicron diamond powder is evenly dispersed in the organic carrier, so that the diamond powder in the conductive thin film is concentrated in the gaps formed after the evaporation of the organic carrier, and the conductive channels of the conductive thin film are not damaged;

[0126] 2. By preparing a bonding glass powder with a low coefficient of thermal expansion and uniformly mixing it with copper powder and an organic carrier / diamond powder mixture, a diamond / copper composite conductive paste is formed, enabling the prepared conductive film to have a high thermal deformation resistance, thereby improving the thermal stability of the composite conductive film;

[0127] 3. Through vacuum leveling, degreasing, and sintering processes, the conductive paste is prepared into a diamond / copper composite conductive film with both high thermal conductivity and low resistivity;

[0128] 4. The prepared high - thermal - conductivity diamond / copper composite conductive film material has strong heat dissipation performance, can withstand a high working temperature, and is suitable for application in high - precision integrated circuits.

[0129] As described above, this is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A method for preparing a high thermal conductivity diamond / copper composite conductive film material, characterized in that: The method comprises: A first mixed material is prepared by using terpineol, polyethylene glycol 400, ethyl cellulose and polyoxypropylene according to a ratio, and the prepared first mixed material is subjected to a first water bath stirring treatment to prepare an organic carrier mixed solution; A second mixed material is prepared by using a mixture of diamond powder and an organic carrier according to a ratio, and the prepared second mixed material is subjected to a second water bath stirring treatment to obtain an organic carrier / diamond powder mixed solution; Mixing silicon dioxide, sodium oxide and calcium oxide according to a ratio to obtain an inorganic mixed powder, and sequentially performing vitrification treatment and refinement treatment on the obtained inorganic mixed powder to obtain a bonding glass powder; A third mixed material is prepared by using copper powder, organic carrier / diamond powder mixed solution and bonding glass powder according to a ratio, and the prepared third mixed material is subjected to a third water bath stirring treatment to obtain a diamond / copper composite conductive slurry; The diamond / copper composite conductive slurry is coated on the surface of the ceramic substrate, and the ceramic substrate coated with the diamond / copper composite conductive slurry is subjected to vacuum leveling treatment to obtain a diamond / copper composite conductive slurry coated leveling component; The diamond / copper composite conductive slurry coated leveling component is placed in a protective atmosphere for degreasing treatment and sintering treatment in sequence to obtain a high thermal conductivity diamond / copper composite conductive film material.

2. The method for preparing the high thermal conductivity diamond / copper composite conductive film material according to claim 1, characterized in that: A first mixed material is prepared by using terpineol, polyethylene glycol 400, ethyl cellulose and polyoxypropylene according to a ratio, and the prepared first mixed material is subjected to a first water bath stirring treatment, including: preparing the first mixed material by using 70-80 parts by weight of terpineol, 14-24 parts by weight of polyethylene glycol 400, 3 parts by weight of ethyl cellulose and 3 parts by weight of polyoxypropylene, and stirring the prepared first mixed material in a water bath at a temperature of 80-100° C. for 1-3 hours.

3. The method for preparing the high thermal conductivity diamond / copper composite conductive film material according to claim 1, characterized in that: A second mixed material is prepared by using a mixed solution of diamond powder and an organic carrier according to a ratio, and the prepared second mixed material is subjected to a second water bath stirring treatment, including: preparing the second mixed material by using 1-4 parts by weight of diamond powder and 14-18 parts by weight of an organic carrier mixed solution, stirring the prepared second mixed material in a water bath at a temperature of 60-80° C. for 2-4 hours, wherein the average particle size of the diamond powder is 0.2-0.25 μm.

4. The method for preparing the high thermal conductivity diamond / copper composite conductive film material according to claim 1, characterized in that: The inorganic mixed powder is obtained by mixing silicon dioxide powder, sodium oxide powder and calcium oxide powder according to a ratio, including: mixing 70-85 parts by weight of silicon dioxide powder, 10-20 parts by weight of sodium oxide and 5-10 parts by weight of calcium oxide powder to obtain the inorganic mixed powder.

5. The method for preparing the high thermal conductivity diamond / copper composite conductive film material according to claim 1, characterized in that: The obtained inorganic mixed powder is subjected to vitrification treatment and refinement treatment in sequence to prepare bonding glass powder, including: The obtained inorganic mixed powder is roller-milled for 12-18 hours, heated to 1000-1200°C, kept warm for 1-3 hours, and then water-cooled to obtain a vitrified material; The vitrified material is ball-milled for 24-36 hours at a ball-to-material ratio of 20:1, and the ball-milled material is screened to obtain a bonding glass powder.

6. The method for preparing the high thermal conductivity diamond / copper composite conductive film material according to claim 1, characterized in that: A third mixed material is prepared by using copper powder, an organic carrier / diamond powder mixed solution and a bonding glass powder according to a ratio, and the prepared third mixed material is subjected to a third water bath stirring treatment, including: roller milling 70-78 parts by weight of copper powder and 6-10 parts by weight of bonding glass powder for 6 hours, mixing the roller-milled mixed material with 15-22 parts by weight of an organic carrier / diamond powder mixed solution, and then stirring in a water bath at a temperature of 60-80°C for 2-4 hours, wherein the average particle size of the copper powder is 3-5μm.

7. The method for preparing the high thermal conductivity diamond / copper composite conductive film material according to claim 1, characterized in that: The diamond / copper composite conductive slurry is coated on the surface of a ceramic substrate, comprising: using a screen with an aperture of 200 meshes to print the diamond / copper composite conductive slurry on the surface of the ceramic substrate, wherein the ceramic substrate is made of an aluminum oxide material with a purity of not less than 99%, and the average surface roughness of the ceramic substrate is not greater than Ra0.

8.

8. The method for preparing the high thermal conductivity diamond / copper composite conductive film material according to claim 1, characterized in that: The ceramic substrate coated with diamond / copper composite conductive slurry is subjected to vacuum leveling treatment, comprising: placing the ceramic substrate coated with diamond / copper composite conductive slurry in vacuum, heating it to 80-120° C., and keeping the temperature for 10-50 minutes.

9. The method for preparing the high thermal conductivity diamond / copper composite conductive film material according to claim 1, characterized in that: Placing the diamond / copper composite conductive slurry coated leveling component in a protective atmosphere and sequentially performing degreasing treatment and sintering treatment, including: placing the diamond / copper composite conductive slurry coated leveling component in a protective atmosphere, heating the temperature to 500°C at a heating rate of 1-3°C / min and then keeping the temperature for 2-5h, heating the temperature to 700-900°C at a heating rate of 5-10°C / min and then keeping the temperature for 0.5-2h.

10. A high thermal conductivity diamond / copper composite conductive film material, characterized in that: The high thermal conductivity diamond / copper composite conductive film material is prepared according to any one of the methods described in claims 1-9.

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