CN115608990A - A welding method of diamond-copper composite materials for ultra-high thermal conductivity microchannels - Google Patents

Abstract

The invention discloses a method for welding diamond-copper composite materials for ultra-high thermal conductivity microchannels, which comprises the following steps: S100, using SiC sandpaper to polish the diamond-copper surface. Clean the diamond copper with ion water and alcohol; S200, put the graphite mold and diamond copper into the discharge plasma sintering furnace in turn for welding, the welding pressure is 7.5~12.5MPa, the heating rate is 20~50℃/min, and the welding temperature is 700~ 800°C, the holding time is 30-90min, and the atmosphere in the furnace is vacuum. After the welding is completed, the sample is cooled with the furnace in a vacuum environment. After cooling to room temperature, the welded diamond-copper composite material is taken out. The invention can make diamond-copper Welding does not destroy the connection surface between diamond and copper in the composite material; compared with traditional diffusion welding, the present invention can realize rapid heating, welding and cooling, and realize reliable welding while ensuring the heat dissipation performance of diamond copper.

Description

A welding method of diamond-copper composite materials for ultra-high thermal conductivity microchannels

technical field

The invention relates to the technical field of material welding, in particular to a method for welding diamond-copper composite materials for ultra-high thermal conductivity microchannels.

Background technique

With the improvement of electronic chip performance and miniaturization of size, higher and higher requirements are put forward for the heat dissipation performance of microelectronic systems. The average heat flux density of GaN chip level has reached 500W/cm2, and the local heat flux density may even exceed 1000W. /cm2. Traditional electronic packaging materials such as metals, alloys, ceramics, etc. have been unable to meet the requirements of high-performance chips due to their low thermal conductivity (<400W/(m·K)). The research results show that the heat generated by the chip can be taken away by the cooling liquid in the microchannel heat sink by introducing the microchannel heat sink; at the same time, the representative diamond/copper composite material of the new first-generation electronic device thermal management material has a high thermal conductivity. Conductivity (>500W(m K)), low thermal expansion coefficient (matched with semiconductor chips) and density, it is one of the best heat sink materials. The diamond/copper high thermal conductivity material is used as the heat sink, and the heat sink structure with micro-channel cooling is designed, which is expected to solve the heat dissipation problem of ultra-high heat flux density of microelectronic chips.

The reliable connection between the heat sink microchannels, that is, the diamond copper, directly determines the reliability of the high heat flux density chip. Poor packaging of the contact surface of the diamond copper heat sink will cause the following effects: First, it will increase the contact thermal resistance during heat dissipation, which will greatly reduce the heat dissipation effect; second, the coolant in the microchannel may leak, causing the device to burn and burn. Corrosion damage to solder joints and cables.

At present, conventional channel sealing is mainly brazing, which has certain advantages in formability and cost, but it will cause microchannel inclination, narrowing, and virtual welding when forming microchannels. The advantages of packaging by laser welding and electron beam welding are energy concentration, fast welding speed, and small heat-affected zone. However, the fusion welding technology will cause damage to the interface between diamond and copper and destroy the heat dissipation performance of the heat sink. Diffusion welding technology can be used to heat and press the material to be welded and keep it warm for a period of time under vacuum conditions, and form a reliable connection surface through atomic diffusion at the interface of the material to be welded. However, traditional diffusion welding requires the overall heating of the heating furnace, resulting in long heating time and high temperature, which will cause graphitization of the diamond surface and reduce the heat dissipation performance.

In order to solve the heat dissipation problem of electronic chips, it is urgent to develop a new welding technology for diamond-copper composite materials.

Contents of the invention

For this reason, the present invention provides a method for welding diamond-copper composite materials for ultra-high thermal conductivity microchannels, so as to solve the above-mentioned defects in the prior art.

A method for welding diamond-copper composite materials for ultra-high thermal conductivity microchannels, comprising the following steps:

S100. Use SiC sandpaper to polish the diamond copper surface. After the polishing is completed, use an ultrasonic cleaner to clean the diamond copper with acetone, deionized water, and alcohol in sequence;

S200. Put the graphite mold and diamond copper into the discharge plasma sintering furnace in turn for welding. The welding pressure is 7.5-12.5MPa, the heating rate is 20-50°C/min, the welding temperature is 700-800°C, and the holding time is 30-200°C. After 90 minutes, the atmosphere in the furnace is vacuum. After the welding is completed, the sample is cooled with the furnace in a vacuum environment. After cooling to room temperature, the welded diamond-copper composite material is taken out.

Preferably, in the S200, the welding temperature is 750-800° C., and the holding time is 60-90 minutes.

Preferably, before performing the S100, the diamond copper to be polished can be pre-cleaned, that is, the diamond copper is cleaned with ionized water using an ultrasonic cleaner, and then the cleaned diamond copper is pickled, and finally cleaned with water Rinse the surface of the diamond copper clean.

Preferably, the formulation of the pickling solution used in the pickling treatment is 15% sulfuric acid by volume and 85% water by volume.

Preferably, in said S100, the diamond copper cleaned with alcohol is dried in a vacuum drying oven.

Preferably, in the S100, the diamond copper is polished step by step with 400 mesh, 800 mesh, 1200 mesh, and 2000 mesh SiC sandpaper in sequence.

Preferably, in S200, a layer of graphite paper is used to separate the graphite mold and the diamond copper, or boron nitride is sprayed on the contact surface between the graphite mold and the diamond copper.

Preferably, in S200, during welding, the peak current of the pulsed current should be increased step by step with the increase of temperature, so as to avoid instantaneous liquefaction of copper in the composite material due to excessive instantaneous current.

Preferably, during welding, the duty cycle of the pulsed current is 18ms:18ms˜18ms:3ms.

The present invention has the following advantages:

(1) The present invention can make diamond copper be welded in solid state, does not destroy the connection surface of diamond and copper in composite material;

(2) Compared with traditional diffusion welding, the present invention can realize rapid heating, welding and cooling, and realize reliable welding while ensuring the heat dissipation performance of diamond copper.

Description of drawings

Fig. 1 is the mold assembly schematic diagram of diamond copper SPS diffusion welding;

Fig. 2 is the diamond copper surface to be welded observed by SEM;

Fig. 3 is the heating curve of SPS diffusion welding;

Figure 4 is the pulse current curve during the SPS diffusion welding process;

Figure 5 is the shear strength and deformation rate of welded joints;

Figure 6 shows the interface of the diamond brazed joint observed by SEM.

In the picture:

1-upper head; 2-first upper mold; 3-second upper mold; 4-diamond copper; 5-second lower mold; 6-first lower mold; 7-lower pressure head; 8-heat shield ; 9 - thermocouple.

detailed description

In order to make the technical means, creative features, goals and effects achieved by the present invention easy to understand, the present invention will be further described below in conjunction with specific embodiments.

As shown in Figures 1 to 6, the present invention provides a method for welding diamond-copper composite materials for ultra-high thermal conductivity microchannels, comprising the following steps:

S100. Use 400 mesh, 800 mesh, 1200 mesh, and 2000 mesh SiC sandpaper to grind and polish the diamond copper surface step by step. After polishing, use an ultrasonic cleaning machine to clean the diamond copper and alcohol in sequence with acetone, deionized water, and alcohol. The cleaned diamond copper is dried in a vacuum drying oven;

Before performing said S100, the diamond copper to be polished can also be pre-cleaned, that is, the diamond copper is cleaned with ionized water using an ultrasonic cleaning machine, and then the cleaned diamond copper is pickled. The formula of the pickling solution is 15% by volume of sulfuric acid and 85% by volume of water. Finally, rinse the surface of the diamond copper with clean water.

S200, putting the graphite mold and the diamond copper into a spark plasma sintering furnace in sequence for welding.

Before welding, use a layer of graphite paper between the graphite mold and the diamond copper, or spray a small amount of boron nitride on the contact surface between the graphite mold and the diamond copper.

The welding pressure is 7.5-12.5MPa, the heating rate is 20-50°C/min, the welding temperature is 700-800°C, and the holding time is 30-90min.

During welding, the peak current of the pulsed current should be increased step by step with the increase of temperature, so as to avoid the instantaneous current being too high, which will cause the copper in the composite material to liquefy instantaneously. The duty cycle of the pulsed current is 18ms: 18ms-18ms: 3ms.

More preferably, in the S200, the welding temperature is 750-800° C., and the holding time is 60-90 minutes.

The atmosphere in the furnace is a vacuum. After the welding is completed, the sample is cooled with the furnace in a vacuum environment. After cooling to room temperature, the welded diamond-copper composite material is taken out.

Example 1

Pretreatment of the specimens to be welded includes grinding, polishing and cleaning. Grind the welded surface with SiC sandpaper to remove the oxide film and stains on the surface. When grinding, use 400 mesh, 800 mesh, 1200 mesh, and 2000 mesh sandpaper in sequence, and the sanding time is 5 minutes each time. After the polishing is completed, the sample is cleaned in an ultrasonic cleaner. When cleaning, it is first cleaned with acetone for 10 minutes, then with deionized water for 10 minutes, and finally with alcohol for 10 minutes. After cleaning, the samples were put into a vacuum drying oven to dry for later use.

Figure 2 is the microscopic morphology of the diamond copper surface to be welded at this time.

As shown in Figure 1, the boron nitride of one deck about 0.5mm is sprayed on the surface of the second upper mold 3, the second lower mold 5 and the contact surface of the diamond copper 4 in the middle, so as to prevent the welding process temperature from being higher, and the diamond copper 4 and the The second upper mold 3 and the second lower mold 5 are welded together. After the boron nitride is dried, the surface to be welded of the diamond copper 4 is pasted on the second lower mold 5, put into the SPS vacuum sintering furnace together with the mold, and the thermocouple 9 is lapped on the diamond copper 4. In order to ensure uniform force, it is necessary to ensure the midline between the upper and lower indenters 1 and the lower indenter 7, the midline between the first upper mold 2 and the first lower mold 6, and the second upper mold 3 and the second The centerline between the lower dies 5 and the center of the diamond copper 4 are on a straight line. After the mold and the diamond copper are installed, close the heat shield 8 and the furnace door, and then vacuumize after the furnace door is closed. When the vacuum degree is less than 5×10 ^-3 Pa, start to pass in pulse current for heating. During welding, the SPS upper indenter 1 and lower indenter 7 give the sample a constant pressure of 10MPa, the heating rate of pulse current is 50°C/min, the cooling rate is 50°C/min, and the duty ratio of pulse current is 18ms:18ms, The holding temperature is 750°C, and the holding time is 90 minutes (see Figure 3 for the heating curve).

The pulse current curve during the welding process is shown in Figure 4. It can be seen from the figure that the pulse current increases with the increase of time in the heating stage, and the diamond copper produces plastic deformation in the heat preservation stage, the contact parts of the welding interface increase, and the pulse current gradually decreases. stabilized afterwards. After the welding is completed, the sample is taken out after cooling to room temperature with the furnace.

The welded joint obtained according to the scheme of Example 1 was subjected to a compression shear test. The shear test was carried out on a Sansi Zongheng UMT5000 microcomputer-controlled electronic universal testing machine. The loading rate of the testing machine was set at 0.5mm/min, and the maximum shear force was divided by the shear The cut area value is the evaluation standard of shear strength, and the deformation rate is the ratio of the thickness difference before and after welding divided by the thickness before welding. As shown in Figure 5, the shear strength of the welded joint in Example 1 is 48.83 MPa, and the deformation rate is 5.25%. Cut the welded joint of Example 1 perpendicular to the welded surface, observe the welded interface with SEM after sample preparation and polishing, as shown in Figure 6, it can be seen that there are no obvious welds and holes after welding, and the combination of diamond and copper is good , which indicates that the welded diamond copper ensures the heat dissipation performance of diamond copper while ensuring the welding strength.

Example 2

Grind the welded surface with SiC sandpaper to remove the oxide film and stains on the surface. When grinding, use 400 mesh, 800 mesh, 1200 mesh, and 2000 mesh sandpaper in sequence, and the sanding time is 5 minutes each time. After the polishing is completed, the sample is cleaned in an ultrasonic cleaner. When cleaning, it is first cleaned with acetone for 10 minutes, then with deionized water for 10 minutes, and finally with alcohol for 10 minutes. After cleaning, the samples were put into a vacuum drying oven to dry for later use.

Spray a layer of boron nitride of about 0.5mm on the surface of the second upper mold 3, the second lower mold 5 and the contact surface of the middle diamond copper 4, and put the mold and diamond copper into the SPS furnace after the boron nitride is dried. After the furnace door is closed, vacuumize. When the vacuum degree is less than 5×10 ^-3 Pa, the pulse current heating starts. During welding, the SPS upper indenter 1 and lower indenter 7 give the sample a constant pressure of 10MPa, the heating rate of pulse current is 50°C/min, the cooling rate is 50°C/min, and the duty ratio of pulse current is 18ms:18ms, The holding temperature is 750°C, and the holding time is 60 minutes.

Compared with Example 1, this example reduces the incubation time from 90min to 60min. As shown in Figure 5, the shear strength reduction of the welded joint in Example 2 is 44.94 MPa, and the deformation rate is 4.25%.

Example 3

Grind the welded surface with SiC sandpaper to remove the oxide film and stains on the surface. When grinding, use 400 mesh, 800 mesh, 1200 mesh, and 2000 mesh sandpaper in sequence, and the sanding time is 5 minutes each time. After the polishing is completed, the sample is cleaned in an ultrasonic cleaner. When cleaning, it is first cleaned with acetone for 10 minutes, then with deionized water for 10 minutes, and finally with alcohol for 10 minutes. After cleaning, the samples were put into a vacuum drying oven to dry for later use.

Spray a layer of boron nitride of about 0.5mm on the surface of the second upper mold 3, the second lower mold 5 and the contact surface of the middle diamond copper 4, and put the mold and diamond copper into the SPS furnace after the boron nitride is dried. After the furnace door is closed, vacuumize. When the vacuum degree is less than 5×10 ^-3 Pa, the pulse current heating starts. During welding, the SPS upper indenter 1 and lower indenter 7 give the sample a constant pressure of 10MPa, the heating rate of the pulse current is 50°C/min, the cooling rate is 50°C/min, and the duty ratio of the pulse current is 18ms: 3ms. The holding temperature is 750°C, and the holding time is 60 minutes.

Compared with Embodiment 2, this example changes the pulse current duty cycle from 18ms:18ms to 18ms:3ms. As shown in Figure 5, the shear strength of the welded joint in Example 3 is 45.02 MPa, and the deformation rate is 4.75%.

Example 4

Grind the welded surface with SiC sandpaper to remove the oxide film and stains on the surface. When grinding, use 400 mesh, 800 mesh, 1200 mesh, and 2000 mesh sandpaper in sequence, and the sanding time is 5 minutes each time. After the polishing is completed, the sample is cleaned in an ultrasonic cleaner. When cleaning, it is first cleaned with acetone for 10 minutes, then with deionized water for 10 minutes, and finally with alcohol for 10 minutes. After cleaning, the samples were put into a vacuum drying oven to dry for later use.

Spray a layer of boron nitride of about 0.5mm on the surface of the second upper mold 3, the second lower mold 5 and the contact surface of the middle diamond copper 4, and put the mold and diamond copper into the SPS furnace after the boron nitride is dried. After the furnace door is closed, vacuumize. When the vacuum degree is less than 5×10 ^-3 Pa, the pulse current heating starts. During welding, the SPS upper indenter 1 and lower indenter 7 give the sample a constant pressure of 10MPa, the heating rate of pulse current is 50°C/min, the cooling rate is 50°C/min, and the duty ratio of pulse current is 18ms:18ms, The holding temperature is 800°C, and the holding time is 60 minutes.

Compared with Example 2, this example increases the holding temperature from 750°C to 800°C. As shown in Figure 5, the shear strength of the welded joint in Example 4 is 46.51MPa, and the deformation rate is 5.5%.

Example 5

Use an ultrasonic cleaning machine to clean the diamond copper sample. The cleaning solution is deionized water. Clean for 10 minutes. After the cleaning is completed, pickle for 3 minutes. . After the pickling is completed, rinse the surface of the diamond copper sample with water, and polish the surface to be welded with SiC sandpaper to remove the oxide film and stains on the surface. When polishing, use 400 mesh, 800 mesh, 1200 mesh, and 2000 mesh sandpaper in sequence. The grinding time is 5 minutes. After the polishing is completed, the sample is cleaned in an ultrasonic cleaner. When cleaning, it is first cleaned with acetone for 10 minutes, then with deionized water for 10 minutes, and finally with alcohol for 10 minutes. After cleaning, the samples were put into a vacuum drying oven to dry for later use.

Spray a layer of boron nitride of about 0.5mm on the surface of the second upper mold 3, the second lower mold 5 and the contact surface of the middle diamond copper 4, and put the mold and diamond copper into the SPS furnace after the boron nitride is dried. After the furnace door is closed, vacuumize. When the vacuum degree is less than 5×10 ^-3 Pa, the pulse current heating starts. During welding, the SPS upper indenter 1 and lower indenter 7 give the sample a constant pressure of 10MPa, the heating rate of pulse current is 50°C/min, the cooling rate is 50°C/min, and the duty ratio of pulse current is 18ms:18ms, The holding temperature is 750°C, and the holding time is 90 minutes.

Compared with Example 1, in this example, the pretreatment of the sample is changed to pickling first, and then polishing with sandpaper.

The present invention can weld diamond copper in a solid state without damaging the connection surface between diamond and copper in the composite material; compared with traditional diffusion welding, the present invention can realize rapid heating, welding and cooling, ensuring the heat dissipation performance of diamond copper and realizing reliable welding.

Although the present invention has been described in detail above with general descriptions and specific examples, it will be obvious to those skilled in the art that some modifications or improvements can be made on the basis of the present invention. Therefore, the modifications or improvements made on the basis of not departing from the spirit of the present invention all belong to the protection scope of the present invention.

Claims (9)

1. A welding method of diamond-copper composite material for ultra-high thermal conductivity microchannel, characterized in that: comprise the following steps: S100. Use SiC sandpaper to polish the diamond copper surface. After the polishing is completed, use an ultrasonic cleaner to clean the diamond copper with acetone, deionized water, and alcohol in sequence; S200. Put the graphite mold and diamond copper into the discharge plasma sintering furnace in turn for welding. The welding pressure is 7.5-12.5MPa, the heating rate is 20-50°C/min, the welding temperature is 700-800°C, and the holding time is 30-200°C. After 90 minutes, the atmosphere in the furnace is vacuum. After the welding is completed, the sample is cooled with the furnace in a vacuum environment. After cooling to room temperature, the welded diamond-copper composite material is taken out. 2. A method for welding diamond-copper composite materials for ultra-high thermal conductivity microchannels according to claim 1, characterized in that: in the S200, the welding temperature is 750-800° C., and the holding time is 60-90 minutes. 3. the welding method of a kind of ultra-high thermal conductivity microchannel diamond-copper composite material according to claim 1, is characterized in that: before carrying out described S100, the diamond copper to be polished can be carried out pre-cleaning, promptly use ultrasonic wave earlier The cleaning machine uses ionized water to clean the diamond copper, then pickles the cleaned diamond copper, and finally rinses the surface of the diamond copper with clean water. 4. the welding method of a kind of ultra-high thermal conductivity microchannel diamond-copper composite material according to claim 3, is characterized in that: the formula of the pickling liquid that described pickling process adopts is 15% volume ratio sulfuric acid, 85% volume than water. 5. A method for welding diamond-copper composite materials for ultra-high thermal conductivity microchannels according to claim 1 or 3, characterized in that: in the S100, the diamond copper after alcohol cleaning is dried in a vacuum drying oven. 6. the welding method of a kind of ultrahigh thermal conductivity microchannel diamond-copper composite material according to claim 1, is characterized in that: in described S100, adopt 400 order, 800 order, 1200 order, 2000 order SiC sandpaper successively to Diamond copper is ground and polished step by step. 7. the welding method of a kind of ultra-high thermal conductivity microchannel with diamond-copper composite material according to claim 1, is characterized in that: in described S200, use one deck graphite paper to separate between graphite mold and diamond copper , or spray boron nitride on the contact surface between graphite mold and diamond copper. 8. the welding method of a kind of ultra-high thermal conductivity microchannel diamond-copper composite material according to claim 1, is characterized in that: in the described S200, when welding, the peak current of the pulsed current that feeds in should increase with temperature. The rise is increased step by step to prevent the instantaneous current from being too high, which will cause the copper in the composite material to liquefy instantaneously. 9 . The method for welding diamond-copper composite materials for ultra-high thermal conductivity microchannels according to claim 1 , characterized in that: during welding, the duty cycle of the pulsed current is 18ms: 18ms～18ms: 3ms.

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