CN106756849A - A kind of PCB with transition metal boride coating micro- brills and preparation method thereof - Google Patents

Abstract

The invention provides a method for preparing a micro-drill for PCB with a transition metal boride coating, which includes cleaning the micro-drill substrate, loading the cleaned micro-drill into a sputtering coating device, vacuuming, and turning on heating The device heats the micro-drill substrate, and then performs ion bombardment cleaning on the surface; then, while the ion source is still working, deposits the transition metal boride coating by sputtering, and during the deposition process, by adjusting the deposition temperature The adjustment of thermal stress and growth stress can be achieved by using the negative bias voltage set on the substrate, so as to obtain a transition metal boride coating with low stress or even zero stress. The coating is smooth and compact, has a low coefficient of friction, strong binding force with the substrate, and is not easy to peel off, and is suitable for the preparation of a hard wear-resistant coating on a micro-drill for PCB. The invention also provides a micro drill for PCB with transition metal boride coating.

Description

A micro-drill for PCB with transition metal boride coating and preparation method thereof

technical field

The invention relates to the technical field of printed circuit board (PCB) micro-drill coating, in particular to a micro-drill for PCB with a transition metal boride coating and a preparation method thereof.

Background technique

Printed Circuit Board (PCB) is the core component of the electronics industry. The quality of micro-drills for PCB conduction, which consumes billions of pieces each year, has become the core issue of PCB manufacturing technology innovation. With the development of downstream electronic products in the direction of lightness, thinness and smallness, high precision, high integration and thinness have become important development trends of PCB boards, especially with the application and application of difficult-to-process materials such as halogen-free PCB boards and flexible PCB boards Due to the high-speed technical requirements, ordinary carbide micro-drills are difficult to meet the processing requirements of PCB boards, and are prone to problems such as drill wear, breakage, poor hole wall processing quality, and short service life.

In order to improve the processing performance of PCB micro-drills, arc deposition technology is usually used to prepare one or more layers of wear-resistant coatings with high hardness (such as TiN, CrN, TiAlN, diamond-like carbon, etc.) on the surface of micro-drills. However, due to the spraying of droplets during the arc deposition process, the problem of forming large particles on the surface of PCB micro-drills with a diameter as small as 0.1mm still exists, which increases the surface roughness of the coating, which is not conducive to chip removal, and easily causes friction. The temperature rise will lead to the melting of low melting point substances on the PCB board, and the knife sticking phenomenon will occur, which will greatly reduce the processing quality of the hole wall. In addition, the high-energy bombardment during the deposition process leads to high residual compressive stress in the coating, which causes the coating to peel off easily, and the film-base bonding force is low. High residual stress easily leads to bending of the drill body with a smaller diameter. prone to brittle fracture. Therefore, how to reduce the residual stress of hard-coated micro-drills and improve the bonding strength of the film base is a key problem that needs to be solved urgently for coated PCB micro-drills.

Contents of the invention

In view of this, the present invention provides a low-stress transition metal boride coating micro-drill for PCB and its preparation method to solve the problem of high residual stress of PCB hard coating in the prior art, easy peeling of the film layer, and combination of film and base. The problem of low intensity.

In a first aspect, the present invention provides a micro-drill for PCB with a transition metal boride coating, including a micro-drill substrate, and a transition metal boride coating disposed on the micro-drill substrate, the transition metal boride The absolute value of the residual stress of the compound coating is less than 0.3GPa.

Preferably, the absolute value of the residual stress of the transition metal boride coating is 0.05-0.1 GPa, more preferably 0 GPa.

Preferably, the transition metal boride coating has a thickness of 0.2-4 μm. More preferably, it is 0.3 to 3.5 μm. When the deposition rate is constant, the thickness of the coating is mainly determined by the deposition time, the longer the deposition time, the greater the thickness of the coating.

More preferably, the thickness of the transition metal boride coating is 0.8-2 μm.

Preferably, in the transition metal boride coating, the grain size of the transition metal boride is 10-50 nm.

Preferably, the micro-drill for PCB with transition metal boride coating has a hardness of 20-40GPa under a load of 10gf.

Preferably, the fracture toughness of the transition metal boride coating on the PCB micro-drill is 2-4 MPa·m ^1/2 .

Preferably, using GCr15 as the friction pair, the friction coefficient of the transition metal boride coating on the PCB micro-drill is 0.2-0.5 under a load of 10N.

Preferably, the material of the micro-drill substrate is cemented carbide. Cemented carbide can be a powder metallurgy product sintered with high-hardness refractory metal carbide (tungsten carbide, titanium carbide) micron powder as the main component and sintered with cobalt, nickel or molybdenum as the binder. The mass content in is generally 6wt.%-10wt.%.

In the present invention, the cemented carbide can be one of tungsten carbide-based cemented carbide, titanium carbide-based cemented carbide, titanium carbonitride-based cemented carbide, and chromium carbide-based cemented carbide.

Preferably, the material of the transition metal boride coating is titanium diboride, zirconium diboride, vanadium diboride, niobium diboride, tantalum diboride, chromium diboride, molybdenum diboride and diboride One or more of tungsten borides. Titanium diboride is more preferred. The thermal expansion coefficient of the transition metal boride coating is greater than the thermal expansion coefficient of the micro-drilling substrate, forming a thermal stress with a state of tensile stress, which just cancels out the growth stress with a state of compressive stress (the thermal internal force is opposite to the direction of the growth stress, and the value approach), which can effectively reduce the residual stress of the coating.

The first aspect of the present invention provides a micro-drill for PCB with a transition metal boride coating, by depositing a transition metal boride coating on the micro-drill substrate, the coating is smooth and dense, and the coefficient of friction is low, and the coating and the substrate The combination is strong, high hardness, good toughness, can improve the service life of the micro drill.

In a second aspect, the present invention provides a method for preparing a micro-drill for PCB with a transition metal boride coating, comprising the following steps:

(1) Take the micro-drill substrate for PCB and clean it;

Place the cleaned micro-drill substrate in the vacuum chamber of the sputter coating equipment, pump the air pressure of the vacuum chamber below 5× ^10-3 Pa, and start heating the vacuum chamber to make the substrate temperature reach 350-600 ℃;

Turn on the ion source, pass in argon gas, and perform ion bombardment cleaning on the substrate for 10-30 minutes;

(2) keep the ion source to continue to work, feed argon gas, adopt transition metal boride as sputtering target material, deposit transition metal boride coating on the substrate surface after described ion bombardment cleaning by sputtering, wherein , loading a negative bias voltage on the substrate during the deposition process, the negative bias voltage is 0V～-300V, the deposition temperature is 350～600°C; the power density of the sputtering target is 2～20W/cm ² ; the ion The operating current of the source is 20-30A, and the operating voltage is 50-100V; by adjusting the deposition temperature and negative bias voltage, the absolute value of the residual stress of the transition metal boride coating is less than 0.3GPa;

(3) After the deposition is finished, the sample is cooled to obtain a micro-drill for PCB with a transition metal boride coating.

Preferably, the cleaning treatment of the micro-drill substrate includes: ultrasonically cleaning the micro-drill substrate sequentially with acetone, ethanol, and water, and blowing it dry.

In the present invention, before sputtering the transition metal boride coating, the purpose of using ion bombardment cleaning is to remove the pollutants and oxide film on the surface of the workpiece to expose a fresh surface for better subsequent film deposition.

Preferably, when the ion source is turned on, the air pressure in the vacuum chamber is below 3×10 ^-3 Pa.

Preferably, in step (1), the working pressure of the argon gas is 0.5-1.0 Pa.

Preferably, in step (1), during ion bombardment cleaning, the flow rate of the argon gas is 100-200 sccm.

Preferably, during the ion bombardment cleaning, the working current of the ion source is 20-30A, and the working voltage is 50-100V.

Preferably, the sputtering method is unbalanced magnetron sputtering deposition.

In this application, a bias voltage refers to an applied potential on a substrate. Connecting the negative pole of the bias power supply on the deposited substrate is called negative bias.

In the sputtering deposition process of the transition metal boride coating, the application uses an ion source for auxiliary deposition, which improves the ionization rate and the plasma density in the deposition area. Due to the negative bias during the deposition process, it can Effective positive ion bombardment on the surface of the substrate is beneficial to increase the kinetic energy of the deposited particles (mainly referring to the target atoms, atomic groups, etc. sputtered from the surface of the sputtering target and deposited on the surface of the substrate), so that the continuous deposition on the surface of the substrate The metallurgical bonding between the particles and the surface atoms enhances the diffusion ability of the atoms adsorbed on the substrate surface on the substrate surface, thereby effectively improving the film-base bonding strength of the coating.

Preferably, in step (2), the gas flow rate of the argon is 60-100 sccm.

Preferably, the material of the micro-drill substrate is cemented carbide.

Preferably, the transition metal boride is selected from titanium diboride, zirconium diboride, vanadium diboride, niobium diboride, tantalum diboride, chromium diboride, molybdenum diboride and tungsten diboride one or more of.

The residual stress of the coating is mainly composed of thermal stress and growth stress. The thermal stress is mainly caused by the mismatch between the thermal expansion coefficient of the coating and the substrate, while the growth stress is due to the non-equilibrium characteristics of physical vapor deposition technology and ion stress. Lattice distortions, defects, dislocations, etc. introduced by the bombardment. Reducing thermal stress usually requires lowering the deposition temperature of the coating, and lower deposition temperature will deteriorate the microstructure and mechanical properties of the coating; the subsequent annealing treatment of the coating also has a certain effect on reducing the growth stress of the coating, but The low-temperature annealing takes a long time, increases the manufacturing cost, and is not suitable for the production of micro-drills for PCBs.

Since the thermal expansion coefficient of transition metal borides (such as TiB ₂ ) is 8.1×10 ^-6 /K, the thermal expansion coefficient of cemented carbide is about 4.5×10 ^-6 /K, because the thermal expansion coefficient of TiB ₂ is greater than that of cemented carbide, so After sputtering deposition at a temperature higher than room temperature, the thermal stress in the resulting coating is tensile stress, while the growth stress is compressive stress, and the directions of tensile stress and compressive stress are opposite. To realize the adjustment of thermal stress and growth stress, so as to obtain transition metal boride coating with low residual stress or even zero residual stress.

In the present application, the temperature during the deposition process is 350-600°C, and the negative bias voltage set on the substrate during the deposition process is 0V-200V.

Preferably, the temperature in the deposition process is 450-550°C.

Further preferably, when the transition metal boride coating is titanium diboride, the deposition temperature is 450-550° C., and the negative bias voltage is -10-100V.

Furthermore, when the deposition temperature is 550°C, the thermal stress can reach 1.29GPa, the negative bias voltage used at this time is preferably -50～-100V, the growth stress is -1.17～-1.45GPa, and the residual stress of the obtained coating can be It reaches 0.12～-0.16GPa, more preferably, the negative bias voltage is preferably -60～-80V, at this time, the growth stress is -1.226～-1.338GPa, and the residual stress of the obtained coating can reach 0.064～-0.048GPa. More preferably, when the negative bias voltage is -71V, the residual stress of the resulting coating can reach 0GPa.

Further, when the deposition temperature is 500°C, the thermal stress can reach 1.17GPa, the negative bias voltage used at this time is preferably -30～-70V, the growth stress is -1.058～-1.282GPa, and the residual stress of the obtained coating can be It reaches 0.112～-0.112GPa, more preferably, the negative bias is preferably -40～-60V, at this time, the growth stress is -1.114～-1.226GPa, and the residual stress of the obtained coating can reach 0.056～-0.056GPa. More preferably, when the negative bias voltage is -50V, the residual stress of the resulting coating can reach 0GPa.

Further, when the deposition temperature is 450°C, the thermal stress can reach 1.04GPa, the negative bias voltage used at this time is preferably -10～-40V, the growth stress is -0.946～-1.114GPa, and the residual stress of the obtained coating can be It reaches 0.094～-0.074GPa, more preferably, the negative bias is preferably -20～-30V, at this time, the growth stress is -1.002～-1.058GPa, and the residual stress of the obtained coating can reach 0.038～-0.018GPa. More preferably, when the negative bias voltage is -27V, the residual stress of the obtained coating can reach 0GPa.

Preferably, the transition metal boride coating has a thickness of 0.2-4 μm. More preferably, it is 0.3 to 3.5 μm.

In one embodiment of the present invention, when the transition metal boride coating is tungsten diboride and the deposition temperature is 450° C., the negative bias voltage is -15V. At this time, the residual stress of the tungsten diboride coating is close to 0GPa.

In one embodiment of the present invention, when the transition metal boride coating is chromium diboride, and the deposition temperature is 550° C., the negative bias voltage is -255V. At this time, the residual stress of the chromium diboride coating is close to 0GPa.

In the method provided by the second aspect of the present invention, when sputtering the transition metal boride coating, an ion source is used for auxiliary deposition, an appropriate deposition temperature is adopted, and the negative bias voltage loaded on the substrate is adjusted according to different deposition temperatures , to achieve the adjustment of thermal stress and growth stress, so that they almost cancel each other, so as to obtain a smooth and dense transition metal boride coating with low stress or even zero stress, and then make the coating and the substrate have a stronger bonding force. It is not easy to peel off in the process. It does not affect the microstructure of the coating, does not need to increase the annealing process, and is not limited by the size of the cavity, the hanger and the amount of the furnace. The method is very suitable for the preparation of micro-drill hard wear-resistant coatings for PCBs.

The advantages of the present invention will be partly clarified in the following description, and part of them will be obvious from the description, or can be known through the implementation of the embodiments of the present invention.

Description of drawings

Fig. 1 is the schematic structural representation of the PCB micro-drill with transition metal boride coating in the embodiment of the present invention, and in Fig. 1, 20 is micro-drill substrate, and 10 is transition metal boride coating;

Fig. 2 is the front view of the PCB micro-drill with transition metal boride coating obtained in the embodiment of the present invention;

Fig. 3 is the relationship curve of the thermal stress of the TiB coating _on the YG6 cemented carbide substrate as a function of temperature in Example 1 of the present invention;

Fig. 4 is the relationship curve of the growth stress of the TiB coating _on the YG6 cemented carbide substrate as the negative bias changes in Example 1 of the present invention;

Fig. 5 is the scanning electron microscope (SEM) photo of transition metal boride coating in the embodiment 1 of the present invention;

FIG. 6 is an optical morphology characterization diagram of the transition metal boride coating obtained by the Rockwell indentation method in Example 1 of the present invention.

detailed description

The following descriptions are preferred implementations of the embodiments of the present invention. It should be pointed out that those skilled in the art can make some improvements and modifications without departing from the principles of the embodiments of the present invention. These improvements And retouching are also regarded as the scope of protection of the embodiments of the present invention.

Example 1

A preparation method for a PCB micro-drill with a transition metal boride coating, comprising the following steps:

(1) Pretreatment: Use the YG6 (WC-6% Co) cemented carbide micro-drill sold in the domestic market as the substrate, first put the micro-drill into the acetone solution for ultrasonic cleaning for 10-20 minutes, and then put it into the alcohol solution Ultrasonic cleaning for 10 to 20 minutes, then dry the surface with dry nitrogen, and then put the blade in a vacuum drying oven to dry;

(2) Furnace loading: open the vacuum chamber door of the sputter coating equipment, and clamp the micro drill on the fixture;

(3) Vacuuming: close the door of the vacuum chamber, open the water cooler to connect the magnetron target, molecular pump, and the water circuit of the vacuum chamber, turn on the main power supply of the air compressor and coating machine, and then turn on the mechanical pump and the fore-stage valve for molecular Pump vacuum, when the vacuum of the front stage of the molecular pump is below 3Pa, start the molecular pump; then close the front valve, and open the rough valve to rough the vacuum chamber; when the pressure in the vacuum chamber reaches below 10Pa, open the front stage The valve simultaneously pumps the vacuum chamber and the molecular pump to a low vacuum. When the pressure in the vacuum chamber reaches below 3Pa, close the rough pump valve and open the slide valve to pump the vacuum chamber to a high vacuum;

(4) Heating: When the high vacuum reaches 5.0×10 ^-3 Pa, turn on the heating device to heat and bake the vacuum chamber so that the temperature of the micro-drill substrate reaches 500°C, and turn on the turret system during the heating process to make the sample conduct public autobiography;

(5) Ion etching cleaning: When the vacuum degree of the vacuum chamber reaches below 3.0×10 ^-3 Pa, argon gas of 150 sccm is introduced, and the working pressure is 0.8 Pa, and then the ion source is turned on for etching cleaning, and the working current of the ion source is 30A, working voltage 100V, ion source etching and cleaning time 20min;

(6) Coating deposition: Keep the ion source to continue to work, and at the same time turn on the TiB ₂ sputtering target to deposit the TiB ₂ coating. During the deposition process, the working current of the ion source is 30A, and the working voltage is 100V. The power density of the shooting target is 10W/cm ² , the negative bias voltage loaded on the substrate is -50V, the deposition temperature is 500°C, and the thickness of the obtained coating is 2μm;

(7) Out of the furnace: after the coating deposition is completed, turn off the sputtering power supply and the bias power supply, then turn off the gas mass flowmeter, the main valve of the gas cylinder and the pressure reducing valve; set the cooling program, and turn off the vacuum pump after the temperature drops below 100°C group and exhaust valve, then turn off the water cooler and the main power supply of the equipment; open the vent valve, and when the pressure in the vacuum chamber is consistent with the external air pressure, open the door of the vacuum chamber, and then take out the processed micro-drill to obtain a transition metal boride Coated PCB with micro drill.

Fig. 1 is the schematic structural representation of the PCB micro-drill with transition metal boride coating in the embodiment of the present invention, among the figure, 20 is micro-drill substrate, and 10 is transition metal boride coating (TiB in the present embodiment ₂ ) , 10 layers with a thickness of 2 μm. Fig. 2 is a front view of the micro drill for PCB with transition metal boride coating obtained in the embodiment of the present invention.

The microscopic morphology of the transition metal boride coating in the embodiment of the present invention was characterized by a scanning electron microscope (SEM), and the results are shown in FIG. 5 . It can be seen from Figure 5 that the obtained transition metal boride coating is smooth and dense, with low roughness, and there is no problem of large particles caused by arc ion plating technology.

The transition metal boride coating prepared in this embodiment was tested by the Rockwell indentation method, and the results are shown in FIG. 6 . The Rockwell indentation test in Figure 6 shows that the film-base bonding strength of the coating can reach HF1 level (that is, there are cracks and no peeling off). The measured residual stress of the coating is close to 0GPa, the film/substrate bonding strength (scratch bonding force) can reach 60N, and the surface composite hardness (coating + substrate) can reach 24GPa under a load of 10gf; GCr15 is used as the friction pair. The coefficient of friction under a load of 10N was 0.3.

The above results show that the transition metal boride coating prepared by the preparation method provided by the invention has higher film/substrate bonding strength, the film layer is not easy to peel off, and the service life of the micro drill for PCB can be improved.

In addition, under the same conditions as this implementation, when the deposition temperature is 550°C, the thermal stress can reach 1.29GPa. At this time, when the negative bias applied to the substrate is -71V, the growth stress can also reach -1.29GPa. GPa, the residual stress of the resulting coating can reach 0GPa. When the deposition temperature is 450°C, the thermal stress can reach 1.04GPa. At this time, when the negative bias applied to the substrate is -27V, the growth stress can also reach -1.04GPa, and the residual stress of the obtained coating can reach 0GPa.

Fig. 3 is the relationship curve of the thermal stress of the TiB2 coating _on the YG6 cemented carbide substrate in the embodiment of the present invention with temperature; Fig. ₄ is the growth stress of the TiB2 coating on the YG6 cemented carbide substrate in the embodiment of the present invention The relationship curve of negative bias voltage change. Among them, Fig. 3 is calculated according to the thermal stress formula, and Fig. 4 is the magnitude of residual stress under different bias voltages (wherein, residual stress = thermal stress + growth stress (considering their direction), so the residual stress is subtracted from The thermal stress under the designated deposition temperature just can obtain the growth stress under different bias.It should be noted that, the direction of the thermal stress with tensile stress state is defined as positive in the present invention (can be understood as XY plane outward along a direction Tensile), growth stress with compressive stress state is negative.

Wherein, in Fig. 3, the linear relationship between thermal stress Y1 and deposition temperature T is Y1 = 0.00245T-0.06; in Fig. 4, the linear relationship between growth stress Y2 and negative bias U (absolute value) is Y2 = -0.0056 U-0.89.

Example 2

A preparation method for a PCB micro-drill with a transition metal boride coating, comprising the following steps:

(1) Pre-treatment: Use the YG8 (WC-8% Co) cemented carbide micro-drill sold in the domestic market as the substrate, first put the micro-drill into the acetone solution for ultrasonic cleaning for 10 minutes, and then put it into the alcohol solution for further cleaning. Ultrasonic cleaning for 15 minutes, then dry the surface with dry nitrogen, and then put the blade in a vacuum drying oven to dry;

(2) Furnace loading: open the vacuum chamber door of the sputter coating equipment, and clamp the micro drill on the fixture;

(3) Vacuuming: close the door of the vacuum chamber, open the water cooler to connect the magnetron target, molecular pump, and the water circuit of the vacuum chamber, turn on the main power supply of the air compressor and coating machine, and then turn on the mechanical pump and the fore-stage valve for molecular Pump vacuum, when the vacuum of the front stage of the molecular pump is below 3Pa, start the molecular pump; then close the front valve, and open the rough valve to rough the vacuum chamber; when the pressure in the vacuum chamber reaches below 10Pa, open the front stage The valve simultaneously pumps the vacuum chamber and the molecular pump to a low vacuum. When the pressure in the vacuum chamber reaches below 3Pa, close the rough pump valve and open the slide valve to pump the vacuum chamber to a high vacuum;

(4) Heating: After the high vacuum is pumped to 5.0×10 ^-3 Pa, turn on the heating device to heat and bake the vacuum chamber so that the temperature of the micro-drill substrate reaches 450°C, and turn on the turret system during the heating process to make the sample conduct public autobiography;

(5) Ion etching cleaning: When the vacuum degree of the vacuum chamber reaches below 3.0×10 ^-3 Pa, argon gas is introduced, the working pressure is 0.8Pa, and then the ion source is turned on for etching cleaning. The working current of the ion source is 25A , the working voltage is 80V, and the ion source etching and cleaning time is 10min;

(6) Coating deposition: Keep the ion source to continue to work, and at the same time turn on the two tungsten oxide WB ₂ sputtering targets to deposit the WB ₂ coating. During the deposition process, the working current of the ion source is 20A, and the working voltage is 90V. The power density of the shooting target is 8W/cm ² , the negative bias applied to the substrate is -15V, the deposition temperature is 450°C, and the resulting coating thickness is 3μm;

(7) Out of the furnace: after the coating deposition is completed, turn off the sputtering power supply and the bias power supply, then turn off the gas mass flowmeter, the main valve of the gas cylinder and the pressure reducing valve; set the cooling program, and turn off the vacuum pump after the temperature drops below 100°C group and exhaust valve, then turn off the water cooler and the main power supply of the equipment; open the vent valve, and when the pressure in the vacuum chamber is consistent with the external air pressure, open the door of the vacuum chamber, and then take out the processed micro-drill to obtain a transition metal boride Coated PCB with micro drill.

After testing, in the WB ₂ coating, the grain size of WB ₂ is 40nm, the residual thermal stress of the coating is 0GPa, and the obtained film base of the micro-drill for PCB with transition metal boride coating under the load of 10gf The combined hardness is 40GPa; the fracture toughness is 3MPa·m ^1/2 ; with GCr15 as the friction pair, the friction coefficient under the load of 10N is 0.5.

Example 3

A YT15 cemented carbide micro _- drill was used, and CrB2 was used as a sputtering target to deposit a CrB2 coating _on the micro-drill. The working current of the ion source is 30A, the working voltage is 75V, the sputtering target power is 8W/cm ² , the negative bias voltage is 255V, the deposition temperature is 550°C, and the coating thickness is 2.5μm.

Example 3

A preparation method for a PCB micro-drill with a transition metal boride coating, comprising the following steps:

(1) Pretreatment: Using the YT15 cemented carbide micro-drill bit sold in the domestic market as the substrate, first put the micro-drill into acetone solution for ultrasonic cleaning for 10 minutes, then put it into alcohol solution for ultrasonic cleaning for 15 minutes, and then dry it with Nitrogen blows the surface dry, and then puts the blade in a vacuum drying oven to dry;

(2) Furnace loading: open the vacuum chamber door of the sputter coating equipment, and clamp the micro drill on the fixture;

(3) Vacuuming: close the door of the vacuum chamber, open the water cooler to connect the magnetron target, molecular pump, and the water circuit of the vacuum chamber, turn on the main power supply of the air compressor and coating machine, and then turn on the mechanical pump and the fore-stage valve for molecular Pump vacuum, when the vacuum of the front stage of the molecular pump is below 3Pa, start the molecular pump; then close the front valve, and open the rough valve to rough the vacuum chamber; when the pressure in the vacuum chamber reaches below 10Pa, open the front stage The valve simultaneously pumps the vacuum chamber and the molecular pump to a low vacuum. When the pressure in the vacuum chamber reaches below 3Pa, close the rough pump valve and open the slide valve to pump the vacuum chamber to a high vacuum;

(4) Heating: When the high vacuum reaches 5.0×10 ^-3 Pa, turn on the heating device to heat and bake the vacuum chamber so that the temperature of the micro-drill substrate reaches 550°C, and turn on the turret system during the heating process to make the sample conduct public autobiography;

(5) Ion etching cleaning: When the vacuum degree of the vacuum chamber reaches below 3.0×10 ^-3 Pa, argon gas is introduced, the working pressure is 0.8Pa, and then the ion source is turned on for etching cleaning. The working current of the ion source is 30A , the working voltage is 75V, and the ion source etching and cleaning time is 10min;

(6) Coating deposition: Keep the ion source to continue to work, and at the same time turn on the CrB ₂ sputtering target to deposit the CrB ₂ coating. During the deposition process, the working current of the ion source is 30A, the working voltage is 75V, and the power of the sputtering target The density is 8W/cm ² , the negative bias applied to the substrate is -255V, the deposition temperature is 550°C, and the thickness of the obtained CrB ₂ coating is 2.5μm;

(7) Out of the furnace: after the coating deposition is completed, turn off the sputtering power supply and the bias power supply, then turn off the gas mass flowmeter, the main valve of the gas cylinder and the pressure reducing valve; set the cooling program, and turn off the vacuum pump after the temperature drops below 100°C group and exhaust valve, then turn off the water cooler and the main power supply of the equipment; open the vent valve, and when the pressure in the vacuum chamber is consistent with the external air pressure, open the door of the vacuum chamber, and then take out the processed micro-drill to obtain a transition metal boride Coated PCB with micro drill.

After testing, in the CrB ₂ coating, the crystal grain size of CrB ₂ is 30nm, and the residual thermal stress of the coating is 0GPa, and the obtained film base of the micro-drill for PCB with transition metal boride coating under 10gf load The combined hardness is 30GPa; the fracture toughness is 2.5MPa·m ^1/2 ; with GCr15 as the friction pair, the friction coefficient under the load of 10N is 0.4.

The above examples illustrate that the thermal stress and growth stress of the coating can be controlled by adjusting the deposition temperature and deposition negative bias, and the thermal stress and growth stress can be offset by parameter optimization to prepare a transition metal boride coating with low stress. In addition, plasma assistance was introduced in the sputter deposition process to increase the ionization rate and the energy of deposited particles, thereby improving the film-substrate bonding strength of the coating.

It should be noted that, according to the disclosure and explanation of the above description, those skilled in the art to which the present invention belongs may also make changes and modifications to the above implementation manners. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some equivalent modifications and changes to the present invention should also fall within the protection scope of the claims of the present invention. In addition, although some specific terms are used in this specification, these terms are only for convenience of description and do not constitute any limitation to the present invention.

Claims (10)

1. a kind of PCB with transition metal boride coating preparation methods of micro- brill, it is characterised in that including following step Suddenly：

(1) PCB is taken with micro- brill matrix, and cleaning treatment is carried out to it；

Micro- brill matrix after by the cleaning is placed in the vacuum chamber of sputtering coating equipment, and the air pressure of vacuum chamber is evacuated into 5 × 10^{- 3}After below Pa, heating is carried out to vacuum chamber makes substrate temperature reach 350~600 DEG C；

Ion gun is opened, argon gas is passed through, 10~30min of icon bombardment cleaning is carried out to matrix；

(2) ion gun is kept to work on, using transition metal boride as sputtering target material, to sputter mode described Matrix surface deposition transition metal boride coating after icon bombardment cleaning, wherein, loaded on matrix in deposition process and born Bias, the back bias voltage is 0~-300V, and depositing temperature is 350~600 DEG C；The power density of the sputtering target is 2~20W/ cm²；The operating current of the ion gun is 20~30A, and operating voltage is 50~100V；By adjusting the depositing temperature and bearing Bias makes the absolute value of the residual stress of the transition metal boride coating be less than 0.3GPa；

(3) after deposition terminates, cooling sampling obtains the micro- brills of the PCB with transition metal boride coating.

2. preparation method as claimed in claim 1, it is characterised in that during the icon bombardment cleaning, the work of the ion gun Make electric current for 20~30A, operating voltage is 50~100V.

3. preparation method as claimed in claim 1, it is characterised in that the transition metal boride is selected from titanium diboride, two One or more in zirconium boride, vanadium diboride, niobium dioxide, tantalum diboride, two chromium borides, molybdenum diboride, wolfram diboride.

4. preparation method as claimed in claim 1, it is characterised in that when the transition metal boride coating is titanium diboride When, the depositing temperature is 350~600 DEG C, and the back bias voltage is -10~-100V.

5. preparation method as claimed in claim 4, it is characterised in that when the depositing temperature is 550 DEG C, the back bias voltage It is -50~-100V, the residual stress of the transition metal boride coating is 0.12~-0.16GPa；

When the depositing temperature be 500 DEG C when, the back bias voltage be -30~-70V, the transition metal boride coating it is residual Residue stress is 0.112~-0.112GPa；

When the depositing temperature be 450 DEG C when, the back bias voltage be -10~-40V, the transition metal boride coating it is residual Residue stress is 0.094~-0.074GPa.

6. preparation method as claimed in claim 3, it is characterised in that the transition metal boride coating is wolfram diboride, When the depositing temperature is 450 DEG C, the back bias voltage is -15V, and the residual stress of the transition metal boride coating is approached 0GPa。

7. preparation method as claimed in claim 3, it is characterised in that the transition metal boride coating is two chromium borides, When the depositing temperature is 550 DEG C, the back bias voltage is -255V, and the residual stress of the transition metal boride coating connects Nearly 0GPa.

8. a kind of micro- brills of the PCB with transition metal boride coating, it is characterised in that including micro- brill matrix, and set In micro- transition metal boride coating bored on matrix, the absolute value of the residual stress of the transition metal boride coating Less than 0.3GPa.

9. micro- brills of PCB as claimed in claim 1, it is characterised in that the thickness of the transition metal boride coating is 0.2 ~4 μm.

10. micro- brills of PCB as claimed in claim 1, it is characterised in that using GCr15 as friction pair, the micro- brills of the PCB On coefficient of friction of the transition metal boride coating under 10N load be 0.2-0.5；The transition metal boride coating Fracture toughness is 2-4MPam^1/2。