Micro drill bit and preparation method and application thereof

Abstract

The invention provides a microbit and a preparation method and application thereof. The micro drill bit comprises a drill bit base body and a superhard wear-resistant diamond coating arranged on the surface of the drill bit base body, and the diameter of the drill bit base body is 0.08-4 mm. The diameter of an existing diamond film-coated micro drill bit is mostly larger than 1 mm, the existing diamond film-coated micro drill bit is difficult to adapt to a packaging substrate with a smaller substrate size and thinner substrate holes, the micro drill bit comprises a drill bit base body and a diamond coating arranged on the surface of the drill bit base body, the thickness of the diamond coating is uniform, the diameter of the drill bit base body is only 0.08-4 mm, and the diameter of the diamond coating is smaller than 1 mm. And the development and processing trend of the packaging substrate is met. According to the miniature drill bit, the diameter of the drill bit base body is only 0.08 mm-4 mm, the miniature drill bit belongs to a drill bit with the extremely small diameter, the uniform diamond coating is further arranged on the drill bit with the extremely small diameter, and good drilling and cutting machining performance is achieved. The invention further provides a preparation method and application of the microbit.

Description

Technical Field

[0001] The invention belongs to the technical field of micro drill bits, and in particular relates to a micro drill bit and a preparation method and application thereof. Background Art

[0002] With the rapid development of the electronics and communications industries, various electronic products tend to be multifunctional, miniaturized and portable. Therefore, one of the development directions of packaging substrates is that the substrate size is smaller, the holes of the substrate are finer, and the components are mounted more densely. The diameter of the corresponding micro drill bits for micro hole processing is also getting smaller and smaller. With the rise of high-performance computing, one of the development directions of packaging substrates is to develop in the direction of thickening. This means that the thickness-to-diameter ratio of the micro hole increases, and the aspect ratio of the micro drill bits for processing such micro holes becomes larger. The aspect ratio demand for thickened packaging substrate micro drill bits has exceeded 20. The high-frequency and high-speed transmission of signals also makes the use of packaging substrates develop in the direction of high thermal conductivity, low dielectric constant (Dk), low dielectric loss (Df), and low coefficient of thermal expansion (CTE).

[0003] In order to meet the above characteristics, the packaging substrate material usually prefers high-hardness ceramic fillers, modified glass fiber cloth and modified resin as the main components. A high proportion of hard fillers will increase the wear of the micro drill bit, sharply reduce the life of the micro drill bit, and the micro-hole processing quality of the packaging substrate cannot be guaranteed.

[0004] Therefore, a micro drill still needs to be developed to adapt to the packaging substrate with an increasing aspect ratio. Summary of the invention

[0005] The present invention aims to solve at least one of the above technical problems existing in the prior art. To this end, the present invention provides a micro drill that can meet the development trend of packaging substrate processing and is suitable for processing fine-hole substrates.

[0006] The invention also provides a method for preparing a packaging substrate.

[0007] The invention also provides an application of a packaging substrate.

[0008] A first aspect of the present invention provides a micro drill, comprising a drill base and a diamond coating disposed on the surface of the drill base, wherein the diameter of the drill base is 0.08 mm to 4 mm.

[0009] One of the technical solutions of the present invention regarding the micro drill has at least the following beneficial effects:

[0010] The diameter of existing diamond-coated micro drill bits is mostly above 1 mm, which is difficult to adapt to packaging substrates with smaller substrate sizes and finer holes. The micro drill bit of the present invention includes a drill bit base and a diamond coating provided on the surface of the drill bit base. The thickness of the diamond coating is uniform, and the diameter of the drill bit base is only 0.08 mm to 4 mm, which meets the development and processing trend of packaging substrates.

[0011] The micro drill of the present invention has a drill base with a diameter of only 0.08 mm to 4 mm, and belongs to an extremely small diameter drill. The extremely small diameter drill is also provided with a uniform diamond coating, and has good drilling processing performance.

[0012] According to some embodiments of the present invention, the diameter of the drill bit base is only 0.1 mm to 1.0 mm.

[0013] According to some embodiments of the present invention, the drill bit substrate is made of cemented carbide.

[0014] According to some embodiments of the present invention, the material of the drill bit base includes YG6, YG6X and YG8.

[0015] According to some embodiments of the present invention, the thickness of the diamond coating is 100 nm to 10 μm.

[0016] If the thickness of the diamond coating is less than 100nm, it is too thin and may affect the drilling performance; if it is greater than 10μm, the bonding force between the diamond coating and the drill bit substrate will decrease. Therefore, 100nm to 10μm is the appropriate diamond coating thickness range.

[0017] According to some embodiments of the present invention, at least one of micron-sized diamond grains, submicron-sized diamond grains and nano-sized diamond grains is distributed in the diamond coating.

[0018] In the micro drill bit of the present invention, the size of the diamond grains in the diamond coating is controllable, and the size range of the diamond grains distributed in the diamond coating can be selected as required.

[0019] The second aspect of the present invention provides a method for preparing the micro drill bit, comprising dividing the drill bit base into a cutting zone and a chip removal zone along the axial direction, performing electrostatic self-assembly pre-crystal planting and hot wire chemical vapor deposition on the drill bit base after pre-treatment with an alkaline solution, and forming the diamond coating on the surface of the drill bit base, wherein the alkaline solution pretreatment time of the cutting zone is greater than the alkaline solution pretreatment time of the chip removal zone.

[0020] A technical solution in the method for preparing a micro drill bit of the present invention has at least the following beneficial effects:

[0021] Diamond-coated micro drills have become the most promising micro-hole processing tools due to the ultra-high hardness, high wear resistance, low friction and low chemical affinity between the diamond coating and the processed material. However, due to the small diameter and high aspect ratio of the micro drill, the micro drill itself has low strength and is easy to break. Due to the extremely small characteristic size and large aspect ratio of the micro drill used in high-end packaging substrates, the micro drill itself has low strength and is easy to break. How to achieve uniform diamond coating while maintaining the strength of the micro drill substrate is a key challenge in the preparation of coated micro drills.

[0022] At present, the diameter of diamond-coated micro drills is mostly above 1mm, and few are below 1mm. There is no diamond-coated micro drill with a diameter of 0.1mm. For micro drills with a diameter range of 0.15mm to 10mm, a multi-step deposition method can be used to control the hot wire to pass through the chemical vapor deposition diamond film. However, when the diameter of the micro drill is very small, such as less than 1mm, there will be strength problems.

[0023] If only the front cutting part of the drill bit base body (about 2mm from the front end of the tool tip) is pretreated with alkaline solution, although a substantial decrease in the strength of the micro drill bit can be avoided, the chip removal part will be greatly worn due to continuous extrusion and friction with the dense debris drilled during use, which will affect the life of the micro drill bit. Therefore, it is necessary to perform weak corrosion on the chip removal part so that diamonds can grow. At the same time, the chip removal part does not need to bear a lot of force, and the diamond coating with slightly poor bonding force deposited under weak corrosion is not easy to fall off. The alkaline solution pretreatment time of the cutting area is longer than that of the chip removal area, which can ensure the strength of the tool head, prevent it from being weakened during processing, and prevent the drill bit from breaking.

[0024] If the alkaline solution pre-treatment corrodes the cutting part and the chip removal part at the same time, the corrosion of the substrate caused by corrosion and the subsequent acid corrosion will reduce the cobalt element in the binder, and the drill part will be corroded as a whole, which will cause a significant decrease in the strength of the micro drill and make it easy to break during use.

[0025] The acid-base two-step method is an effective means to roughen the surface of cemented carbide tools, remove the surface cobalt element, and inhibit the generation of harmful graphite phases on the interface. However, for micro drills with very small diameters, such as those less than 1 mm, if the amount of cobalt element removal is improperly controlled, the fracture strength of the micro drill will be significantly reduced, seriously affecting the drilling performance and life of the micro drill. The present invention adopts a method of regional treatment to ensure the strength during drilling, that is, the drill will not break. Specifically, the present invention divides the drill base into a cutting zone and a chip removal zone along the axial direction, and treats the cutting zone and the chip removal zone with an alkaline solution for different times, thereby controlling the cobalt content on the surface of the micro drill and the different strength weakening distributions, and then carries out acid solution corrosion to remove the cobalt content, so as to achieve the purpose of ensuring the strength during drilling, that is, the drill will not break. Then, the drill base is pre-planted by electrostatic self-assembly, and nano-diamond particles are uniformly and densely adsorbed on the surface of the drill with complex shapes to enhance the nucleation density, so that there are no holes at the interface of the film, and the interface bonding strength is improved. Finally, through hot-wire chemical vapor deposition, the distance between the filament and the drill bit substrate and the growth parameters were adjusted to prepare a diamond coating with controllable grain size and thickness on the surface of an extremely small diameter micro drill bit. A uniform diamond coating was deposited while maintaining the strength of the micro drill bit substrate.

[0026] "Extremely small diameter micro drill" may refer to a micro drill with a diameter less than 1 mm.

[0027] Furthermore, "ultra-small diameter micro drill" can also refer to a micro drill with a diameter of about 0.1 mm.

[0028] According to some embodiments of the invention, the alkaline solution comprises an inorganic base, ferrocyanide and water.

[0029] The mass ratio of the inorganic base, ferrocyanide and water is 1:0.5-1.5-5-15.

[0030] According to some embodiments of the present invention, the alkaline solution pretreatment time of the cutting area is 5 min to 50 min.

[0031] According to some embodiments of the present invention, the alkaline solution pretreatment time of the cutting area is 5 min to 15 min.

[0032] According to some embodiments of the present invention, the alkaline solution pretreatment time of the cutting area is 5 min to 10 min.

[0033] According to some embodiments of the present invention, the cutting zone refers to a region ranging from 2 mm to 3 mm distributed axially starting from the top of the drill bit base body.

[0034] According to some embodiments of the present invention, the alkaline solution pretreatment time of the chip removal area is 2 minutes to 20 minutes.

[0035] According to some embodiments of the present invention, the alkaline solution pretreatment time of the chip removal area is 2 minutes to 5 minutes.

[0036] According to some embodiments of the present invention, the alkaline solution pretreatment time of the chip removal area is 3 minutes to 5 minutes.

[0037] According to some embodiments of the present invention, the chip removal zone refers to a region ranging from 2 mm to 3 mm distributed axially starting from the cutting zone.

[0038] According to some embodiments of the present invention, ultrasound may be applied during the alkaline solution pretreatment of the cutting zone and the chip removal zone.

[0039] According to some embodiments of the present invention, the frequency range of ultrasound is 80 Hz to 120 Hz.

[0040] According to some embodiments of the present invention, the electrostatic force self-assembly pre-crystal planting method is: immersing the drill bit substrate in a diamond crystal planting solution, and adsorbing diamond particles on the surface of the drill bit substrate.

[0041] According to some embodiments of the present invention, the diamond crystal growth solution includes a surfactant and purified diamond powder.

[0042] According to some embodiments of the present invention, in the diamond crystal growth solution, the mass fraction of the purified diamond powder is 0.05wt% to 0.2wt%.

[0043] According to some embodiments of the invention, the surfactant comprises sodium dodecylbenzene sulfonate.

[0044] The concentration of the sodium dodecylbenzene sulfonate is 10 -6 mol / L~10 -5 mol / L.

[0045] In common pre-crystal planting technology, the adsorption density of diamond seeds on the tool surface is low, which easily leads to the formation of interface cavities and cracks in the subsequent nucleation and growth process, seriously affecting the bonding strength of the interface, especially for micro drills with very small diameters, such as micro drills with diameters less than 1 mm. Due to their extremely small characteristic sizes, diamond seeds are difficult to adsorb, and the interface problem is more prominent. The electrostatic force self-assembly pre-crystal planting method of the present invention is suitable for high-density uniform pre-crystal planting of micro drills with very small diameters of various specifications and sizes.

[0046] According to some embodiments of the present invention, the method of hot wire chemical vapor deposition is: adjusting the distance between the top of the drill bit substrate and the hot wire, after vacuuming, introducing a mixed gas, heating the filament, and depositing a growing diamond coating on the surface of the drill bit substrate.

[0047] According to some embodiments of the present invention, the distance between the top of the drill base and the hot wire is 15 mm to 25 mm.

[0048] According to some embodiments of the present invention, the mixed gas includes hydrogen, methane and argon.

[0049] According to some embodiments of the present invention, the temperature of the filament is 1500°C to 2800°C.

[0050] According to some embodiments of the present invention, the time for the deposition and growth of the diamond coating is 1 h to 5 h.

[0051] According to some embodiments of the present invention, the method further comprises etching the drill bit matrix with an acid solution after the pretreatment with the alkaline solution.

[0052] According to some embodiments of the present invention, the method for preparing the micro drill bit comprises the following specific steps:

[0053] S1: Chemical pretreatment of carbide micro drills;

[0054] S2: Carbide micro drill bits are subjected to diamond pre-grafting treatment;

[0055] S3: Using hot wire chemical vapor deposition method, hydrogen, methane and argon are introduced into the reaction chamber to deposit diamond coating on the pretreated substrate.

[0056] According to some embodiments of the present invention, in step S1, the specific process is as follows:

[0057] (1) Prepare an alkaline solution (alkaline mixed solution of K3Fe(CN)6, KOH, and H2O). Immerse the cutting area of ​​the carbide micro drill in the alkaline solution and ultrasonicate it in an ultrasonic bath for 5 to 50 minutes. Continue to immerse the micro drill downward into the solution so that the chip removal area is immersed in the alkaline solution and continue to corrode for 2 to 20 minutes.

[0058] (2) taking out the hard alloy precision grinding tool in (1) and ultrasonically cleaning it with deionized water for multiple times, each time for 10 to 20 minutes;

[0059] (3) preparing a mixed acid solution (a mixture of sulfuric acid and hydrogen peroxide);

[0060] (4) placing the hard alloy micro drill bit in (2) in a mixed acid solution and corroding it for 5s to 30s;

[0061] (5) taking out the carbide micro drill bit (4) and ultrasonically cleaning it with deionized water for multiple times, each time for 10 to 20 minutes;

[0062] (6) Blow dry the cleaned carbide micro drill with nitrogen.

[0063] According to some embodiments of the present invention, in step S2, the specific process is as follows:

[0064] (1) Prepare diamond crystal solution. The particle size of diamond powder is 60nm to 120nm. Pour the diamond powder into concentrated nitric acid to make a mixed solution with a mass fraction of 0.1wt% to 0.2wt%. Seal the solution with a sealing film and add a magnetic stirrer to oxidize for 2h to 6h. Then centrifuge and wash. After washing, add 10 -6 mol / L-10 -5 mol / L of anionic surfactant sodium dodecylbenzene sulfonate, prepared into a diamond crystal solution with a mass fraction of 0.05wt% to 0.2wt%, and then adjusted to a pH of 6-10;

[0065] (2) immersing the corrosion-cleaned carbide micro drill bit in the diamond crystal planting solution prepared in (1) and ultrasonically planting the diamond crystal for 5 minutes to 20 minutes;

[0066] (3) Rinse the carbide micro drill bit that has been planted in (2) with clean water for a few times and blow dry with nitrogen.

[0067] According to some embodiments of the present invention, in step S3, the specific process is as follows:

[0068] (1) Insert the carbide micro drill evenly into the perforated copper plate and place it under the outlet of the hot wire chemical vapor deposition. Adjust the distance from the top of the carbide precision grinding tool to the hot wire to 15 mm to 25 mm, and then evacuate;

[0069] (2) After (1) is evacuated to a vacuum, hydrogen, methane and argon are introduced, wherein the methane accounts for 1% to 5% of the total gas volume, the argon accounts for 10% to 40% of the total gas volume, and the gas pressure is maintained at 1 kPa to 5 kPa;

[0070] (3) Turn on the hot filament power supply, the filament temperature range is 1500℃~2800℃, and the growth continues for 1h~5h;

[0071] (4) After growth is completed, turn off the gas, turn off the power, and evacuate the room.

[0072] The third aspect of the present invention provides the use of the micro drill bit and the micro drill bit made by the method in packaging substrate processing.

[0073] The present invention provides a technical solution for the application of the micro drill bit and the micro drill bit obtained by the method in the processing of packaging substrates, which has at least the following beneficial effects:

[0074] The size of the packaging substrate is smaller, the holes of the substrate are finer, and the components are mounted more densely. The diameter of the corresponding micro drill bit for micro hole processing is also getting smaller and smaller. In particular, the packaging substrate is also developing in the direction of thickening. This means that the thickness-to-diameter ratio of the micro hole increases, the length-to-diameter ratio of the micro drill bit for processing such micro holes becomes larger, and the length-to-diameter ratio of the micro drill bit for thickening the packaging substrate is required to be greater. The application of the micro drill bit of the present invention in the processing of the packaging substrate adapts to the development trend of the packaging substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0075] Figure 1 It is a schematic diagram of the step-by-step corrosion area.

[0076] Figure 2 These are the breaking strength test results of Examples 10-12.

[0077] Figure 3 It is the surface morphology of pre-grafted nano-diamond grains on the surface of cemented carbide tool.

[0078] Figure 4 This is a microscopic morphology of the micron-scale diamond coating of Example 46.

[0079] Figure 5 This is a microscopic morphology of the submicron diamond coating of Example 48.

[0080] Figure 6 This is a microscopic morphology of the nanoscale diamond coating of Example 50. DETAILED DESCRIPTION

[0081] The following are specific embodiments of the present invention, and the technical solutions of the present invention are further described in conjunction with the embodiments, but the present invention is not limited to these embodiments.

[0082] In some embodiments of the present invention, the present invention provides a micro drill, comprising a drill base and a diamond coating disposed on the surface of the drill base, wherein the diameter of the drill base is 0.08 mm to 4 mm.

[0083] It can be understood that the diameter of existing diamond-coated micro drill bits is mostly above 1 mm, which is difficult to adapt to packaging substrates with smaller substrate sizes and finer holes. The micro drill bit of the present invention includes a drill bit base and a diamond coating provided on the surface of the drill bit base. The thickness of the diamond coating is uniform, and the diameter of the drill bit base is only 0.08 mm to 4 mm, which meets the development and processing trend of packaging substrates.

[0084] The micro drill of the present invention has a drill base with a diameter of only 0.08 mm to 4 mm, and belongs to an extremely small diameter drill. The extremely small diameter drill is also provided with a uniform diamond coating, and has good drilling processing performance.

[0085] In some embodiments of the present invention, the diameter of the drill bit base is only 0.1 mm to 1.0 mm.

[0086] In some embodiments of the present invention, the drill bit substrate is made of cemented carbide.

[0087] In some embodiments of the present invention, the material of the drill bit base body includes YG6, YG6X and YG8.

[0088] YG6 is a common cemented carbide grade, mainly composed of tungsten carbide (WC) and a small amount of cobalt binder. It has good hardness, strength and wear resistance, and is suitable for processing metals such as steel and iron and some non-metallic materials.

[0089] YG6X is an improved model of cemented carbide, also known as YG6A. It is slightly adjusted on the basis of YG6 to improve its hardness and wear resistance, and is more suitable for some high hardness materials.

[0090] YG8 is another common cemented carbide grade, which contains a higher cobalt content, usually around 8%. Because it contains more cobalt binder, YG8 is slightly better than YG6 and YG6X in toughness and impact resistance, but the hardness may be slightly lower. YG8 is suitable for some applications that require higher toughness and impact resistance.

[0091] In some embodiments of the present invention, the thickness of the diamond coating is 100 nm to 10 μm.

[0092] If the thickness of the diamond coating is less than 100nm, it is too thin and may affect the drilling performance; if it is greater than 10μm, the bonding force between the diamond coating and the drill bit substrate will decrease. Therefore, 100nm to 10μm is the appropriate diamond coating thickness range.

[0093] In some embodiments of the present invention, at least one of micron-sized diamond grains, submicron-sized diamond grains and nano-sized diamond grains is distributed in the diamond coating.

[0094] In the micro drill bit of the present invention, the size of the diamond grains in the diamond coating is controllable, and the size range of the diamond grains distributed in the diamond coating can be selected as required.

[0095] In some other embodiments of the present invention, a method for preparing the micro drill bit of the present invention is provided, comprising dividing the drill bit base into a cutting zone and a chip removal zone along the axial direction, performing electrostatic self-assembly pre-crystal planting and hot wire chemical vapor deposition on the drill bit base after pre-treatment with an alkaline solution, and forming a diamond coating on the surface of the drill bit base, wherein the alkaline solution pretreatment time of the cutting zone is greater than the alkaline solution pretreatment time of the chip removal zone.

[0096] It is understandable that diamond-coated micro drills have become the most promising micro-hole processing tools due to the ultra-high hardness, high wear resistance, low friction and low chemical affinity between the diamond coating and the processed material. However, due to the small diameter and high aspect ratio of the micro drill, the micro drill itself has low strength and is easy to break. Due to the extremely small characteristic size and large aspect ratio of the micro drill used in high-end packaging substrates, the micro drill itself has low strength and is easy to break. How to achieve uniform diamond coating while maintaining the strength of the micro drill substrate is a key challenge in the preparation of coated micro drills.

[0097] It should be noted that, currently, the diameter of diamond-coated micro drills is mostly above 1mm, and few are below 1mm. There is no diamond-coated micro drill with a diameter of 0.1mm. For micro drills with a diameter range of 0.15mm to 10mm, a multi-step deposition method can be used to control the hot wire to pass through the chemical vapor deposition diamond film. However, when the diameter of the micro drill is very small, such as less than 1mm, there will be strength problems.

[0098] If only the front cutting part of the drill bit base body (about 2mm from the front end of the tool tip) is pretreated with alkaline solution, although a substantial decrease in the strength of the micro drill bit can be avoided, the chip removal part will be greatly worn due to continuous extrusion and friction with the dense debris drilled during use, which will affect the life of the micro drill bit. Therefore, it is necessary to perform weak corrosion on the chip removal part so that diamonds can grow. At the same time, the chip removal part does not need to bear a lot of force, and the diamond coating with slightly poor bonding force deposited under weak corrosion is not easy to fall off. The alkaline solution pretreatment time of the cutting area is longer than that of the chip removal area, which can ensure the strength of the tool head, prevent it from being weakened during processing, and prevent the drill bit from breaking.

[0099] If the alkaline solution pre-treatment corrodes the cutting part and the chip removal part at the same time, the corrosion of the substrate caused by corrosion and the subsequent acid corrosion will reduce the cobalt element in the binder, and the drill part will be corroded as a whole, which will cause a significant decrease in the strength of the micro drill and make it easy to break during use.

[0100] The acid-base two-step method is an effective means to roughen the surface of cemented carbide tools, remove the surface cobalt element, and inhibit the formation of harmful graphite phases on the interface. However, for micro drills with very small diameters, such as those less than 1 mm, if the amount of cobalt element removal is improperly controlled, the fracture strength of the micro drill will be significantly reduced, seriously affecting the drilling performance and life of the micro drill. The present invention adopts a method of regional treatment to ensure the strength during drilling, that is, the drill will not break. Specifically, the present invention divides the drill base into a cutting zone and a chip removal zone along the axial direction, and treats the cutting zone and the chip removal zone with an alkaline solution for different times, thereby controlling the cobalt content on the surface of the micro drill and the different strength weakening distributions, and then carries out acid solution corrosion to remove the cobalt content, so as to achieve the purpose of ensuring the strength during drilling, that is, the drill will not break. Then, the drill base is pre-grafted by electrostatic self-assembly, and nano-diamond particles are uniformly and densely adsorbed on the surface of the drill with complex shapes to enhance the nucleation density, so that there are no holes at the interface of the film, and the interface bonding strength is improved. Finally, through hot-wire chemical vapor deposition, the distance between the filament and the drill bit substrate and the growth parameters were regulated to prepare a diamond coating with controllable grain size and thickness on the surface of an extremely small diameter micro drill bit. While maintaining the strength of the micro drill bit substrate, a uniform ultra-hard and wear-resistant diamond coating was deposited.

[0101] "Extremely small diameter micro drill" may refer to a micro drill with a diameter less than 1 mm.

[0102] Furthermore, "ultra-small diameter micro drill" can also refer to a micro drill with a diameter of about 0.1 mm.

[0103] In some embodiments of the present invention, the alkaline solution includes an inorganic base, ferrocyanide and water.

[0104] In some embodiments of the present invention, the mass ratio of the inorganic base, ferrocyanide and water is 1:0.5-1.5-5-15.

[0105] In some embodiments of the present invention, the alkaline solution pretreatment time of the cutting area is 5 minutes to 50 minutes.

[0106] In some embodiments of the present invention, the alkaline solution pretreatment time of the cutting area is 5 minutes to 15 minutes.

[0107] In some embodiments of the present invention, the cutting zone refers to a region ranging from 2 mm to 3 mm distributed axially starting from the top of the drill bit base body.

[0108] In some embodiments of the present invention, the alkaline solution pretreatment time of the chip removal area is 2 minutes to 20 minutes.

[0109] In some embodiments of the present invention, the alkaline solution pretreatment time of the chip removal area is 2 minutes to 5 minutes.

[0110] In some embodiments of the present invention, the chip removal zone refers to a region ranging from 2 mm to 3 mm distributed axially starting from the chip removal zone.

[0111] In some embodiments of the present invention, the electrostatic force self-assembly pre-crystal planting method is: immersing the drill bit substrate in diamond crystal planting liquid, and adsorbing diamond particles on the surface of the drill bit substrate.

[0112] In some embodiments of the present invention, the diamond seeding solution includes a surfactant and purified diamond powder.

[0113] In some embodiments of the present invention, the mass fraction of purified diamond powder in the diamond crystal growth solution is 0.05wt% to 0.2wt%.

[0114] In some embodiments of the present invention, the surfactant includes sodium dodecylbenzene sulfonate.

[0115] The concentration of sodium dodecylbenzene sulfonate is 10 -6 mol / L~10 -5 mol / L.

[0116] In common pre-crystal planting technology, the adsorption density of diamond seeds on the tool surface is low, which easily leads to the formation of interface cavities and cracks in the subsequent nucleation and growth process, seriously affecting the bonding strength of the interface, especially for micro drills with very small diameters, such as micro drills with diameters less than 1 mm. Due to their extremely small characteristic sizes, diamond seeds are difficult to adsorb, and the interface problem is more prominent. The electrostatic force self-assembly pre-crystal planting method of the present invention is suitable for high-density uniform pre-crystal planting of micro drills with very small diameters of various specifications and sizes.

[0117] In some embodiments of the present invention, the method of hot wire chemical vapor deposition is: adjusting the distance between the top of the drill bit substrate and the hot wire, after vacuuming, introducing a mixed gas, heating the filament, and depositing a diamond coating on the surface of the drill bit substrate.

[0118] In some embodiments of the present invention, the distance between the top of the drill bit base and the hot wire is 15 mm to 25 mm.

[0119] In some embodiments of the present invention, the mixed gas includes hydrogen, methane and argon.

[0120] In some embodiments of the present invention, the temperature of the filament is 1500°C to 2800°C.

[0121] In some embodiments of the present invention, the deposition and growth time of the diamond coating is 1 hour to 5 hours.

[0122] In some embodiments of the present invention, the method further comprises etching the drill bit matrix with an acid solution after the pretreatment with the alkaline solution.

[0123] In some embodiments of the present invention, the method for preparing the micro drill bit of the present invention comprises the following specific steps:

[0124] S1: Chemical pretreatment of carbide micro drills;

[0125] S2: Carbide micro drill bits are subjected to diamond pre-grafting treatment;

[0126] S3: Using hot wire chemical vapor deposition method, hydrogen, methane and argon are introduced into the reaction chamber to deposit diamond coating on the pretreated substrate.

[0127] In some embodiments of the present invention, in step S1, the specific process is as follows:

[0128] (1) Prepare an alkaline solution (alkaline mixed solution of K3Fe(CN)6, KOH, and H2O). Immerse the cutting area of ​​the carbide micro drill in the alkaline solution and ultrasonicate it in an ultrasonic bath for 5 to 50 minutes. Continue to immerse the micro drill downward into the solution so that the chip removal area is immersed in the alkaline solution and continue to corrode for 2 to 20 minutes. Figure 1 As shown;

[0129] (2) taking out the hard alloy precision grinding tool in (1) and ultrasonically cleaning it with deionized water for multiple times, each time for 10 to 20 minutes;

[0130] (3) preparing a mixed acid solution (a mixture of sulfuric acid and hydrogen peroxide);

[0131] (4) placing the hard alloy micro drill bit in (2) in a mixed acid solution and corroding it for 5s to 30s;

[0132] (5) taking out the carbide micro drill bit (4) and ultrasonically cleaning it with deionized water for multiple times, each time for 10 to 20 minutes;

[0133] (6) Blow dry the cleaned carbide micro drill with nitrogen.

[0134] In some embodiments of the present invention, in step S2, the specific process is as follows:

[0135] (1) Prepare diamond crystal solution. The particle size of diamond powder is 60nm to 120nm. Pour the diamond powder into concentrated nitric acid to make a mixed solution with a mass fraction of 0.1wt% to 0.2wt%. Seal the solution with a sealing film and add a magnetic stirrer to oxidize for 2h to 6h. Then centrifuge and wash. After washing, add 10 -6 mol / L-10 -5mol / L of anionic surfactant sodium dodecylbenzene sulfonate, prepared into a diamond crystal solution with a mass fraction of 0.05wt% to 0.2wt%, and then adjusted to a pH of 6-10;

[0136] (2) immersing the corrosion-cleaned carbide micro drill bit in the diamond crystal planting solution prepared in (1) and ultrasonically planting the diamond crystal for 5 minutes to 20 minutes;

[0137] (3) Rinse the carbide micro drill bit that has been planted in (2) with clean water for a few times and blow dry with nitrogen.

[0138] In some embodiments of the present invention, in step S3, the specific process is as follows:

[0139] (1) Insert the carbide micro drill evenly into the perforated copper plate and place it under the outlet of the hot wire chemical vapor deposition. Adjust the distance from the top of the carbide precision grinding tool to the hot wire to 15 mm to 25 mm, and then evacuate;

[0140] (2) After (1) is evacuated to a vacuum, hydrogen, methane and argon are introduced, wherein the methane accounts for 1% to 5% of the total gas volume, the argon accounts for 10% to 40% of the total gas volume, and the gas pressure is maintained at 1 kPa to 5 kPa;

[0141] (3) Turn on the hot filament power supply, the filament temperature range is 1500℃~2800℃, and the growth continues for 1h~5h;

[0142] (4) After growth is completed, turn off the gas, turn off the power, and evacuate the room.

[0143] In some other embodiments of the present invention, there is provided application of the micro drill bit of the present invention and the micro drill bit made by the method of the present invention in processing packaging substrates.

[0144] It should be noted that the size of the packaging substrate is smaller, the holes of the substrate are finer, and the components are mounted more densely. The diameter of the corresponding micro drill bit for micro hole processing is also getting smaller and smaller. In particular, the packaging substrate is also developing in the direction of thickening. This means that the thickness-to-diameter ratio of the micro hole increases, the length-to-diameter ratio of the micro drill bit for processing such micro holes becomes larger, and the length-to-diameter ratio of the micro drill bit for thickening the packaging substrate is required to be greater. The application of the micro drill bit of the present invention in the processing of the packaging substrate adapts to the development trend of the packaging substrate.

[0145] The technical solution of the present invention will be better understood with reference to specific embodiments below.

[0146] In order to verify that the corrosion method used in the present invention can effectively ensure that the micro-drill with a very small diameter (0.1 mm) maintains a high fracture strength, the following experiments were conducted (see Examples 1 to 24), as shown in Tables 1 and 2.

[0147] The alkaline solution and acid solution used in the examples in Table 1 and Table 2 are consistent, and the time gradient of corrosion is consistent. The only difference is that Table 1 adopts regional corrosion, while Table 2 does not adopt regional corrosion.

[0148] After the corrosion was completed, the fracture strength test was carried out. The fracture strength of Examples 10 and 12 was as follows: Figure 2 The specific corrosion steps are as follows:

[0149] Experimental steps of the example in Table 1: First, prepare the alkaline solution by weighing 10 g of potassium ferrocyanide and 10 g of potassium hydroxide, and dissolving them in 100 mL of deionized water to prepare the alkaline solution.

[0150] The cutting area of ​​the cemented carbide micro-drill was immersed in an alkaline solution and subjected to ultrasonic etching in an ultrasonic bath (100 Hz) for different time periods.

[0151] The chip removal area of ​​the cemented carbide micro-drill is also immersed in the alkaline solution and the corrosion is continued for different time periods.

[0152] The medium-hard alloy precision grinding tool was then taken out and ultrasonically cleaned with deionized water for 3 times, each time for 10 minutes.

[0153] Prepare a mixed acid solution by weighing 5 mL of concentrated sulfuric acid solution and 50 mL of hydrogen peroxide solution, and pouring them into 50 mL of deionized water.

[0154] The cemented carbide micro-drill was placed in a mixed acid solution for several minutes for etching. The cemented carbide micro-drill was then taken out and ultrasonically cleaned with deionized water for 3 times, each time for 10 minutes. Finally, the cleaned cemented carbide micro-drill was blown dry with nitrogen.

[0155] Experimental steps of the example in Table 2: First, prepare the alkaline solution by weighing 10 g of potassium ferrocyanide and 10 g of potassium hydroxide, and dissolving them in 100 mL of deionized water to prepare the alkaline solution.

[0156] Immerse the carbide micro-drill cutting area and chip removal area in an alkaline solution and perform ultrasonic etching in an ultrasonic bath for several minutes. Then take out the medium carbide precision grinding tool and ultrasonically clean it with deionized water for 3 times, 10 minutes each time. Prepare a mixed acid solution, weigh 5mL of concentrated sulfuric acid solution and 50mL of hydrogen peroxide solution, and pour them into 50mL of deionized water.

[0157] The carbide micro drill is placed in the mixed acid solution for etching for several minutes.

[0158] The cemented carbide micro-drill was then taken out and ultrasonically cleaned with deionized water for 3 times, each time for 10 minutes. Finally, the cleaned cemented carbide micro-drill was blown dry with nitrogen.

[0159] Table 1 Corrosion of extremely small diameter micro-drills (0.1 mm)

[0160]

[0161] Table 2 Corrosion of very small diameter micro drill (0.1mm) without partition

[0162]

[0163] From Table 1 and Table 2 and the comparison between them, it can be seen that the fracture strength of the micro-drill with very small diameter decreases with the increase of alkali corrosion time and decreases with the increase of acid corrosion time. And under the same corrosion conditions, the fracture strength of the partitioned corrosion is greater than that of the non-partitioned corrosion. When the fracture strength is greater than 0.40N, the micro-drill with very small diameter can be guaranteed to have sufficient working strength. It can be seen that the partitioned corrosion adopted by the present invention can effectively ensure that the micro-drill with very small diameter has sufficient fracture strength.

[0164] The diamond crystal planting liquid prepared by the present invention can perform high-density crystal planting on the cemented carbide material used for micro-drilling. Examples are shown in Table 3. The examples in Table 3 are the particle size and potential of the diamond crystal planting liquid prepared by using diamond powder of different particle sizes, different oxidation times, and whether a surfactant is added, as well as the crystal planting density results of the crystals planted by the diamond crystal planting liquid prepared above. The specific experimental steps are as follows:

[0165] Weigh 0.05g diamond powder (different particle sizes), weigh 50ml concentrated nitric acid solution, pour the diamond powder into the concentrated nitric acid, seal with a sealing film, add a magnetic stirrer to oxidize for different times. Then centrifuge for 3 times at a speed of 7000r / min, each time for 8 minutes. After cleaning, choose to add or not add 50ml of 10 -6 mol / L sodium dodecylbenzene sulfonate (SDBS) organic solution, adjust the pH to 6. The cleaned carbide micro drill is immersed in the prepared diamond crystal planting solution and ultrasonically planted for 10 minutes. The planted carbide micro drill is simply rinsed with clean water several times and blown dry with nitrogen.

[0166] Table 3 Crystallization solutions prepared with different parameters

[0167]

[0168] From Table 3, we can see that the particle size of the crystal-planting solution becomes smaller and the potential becomes larger after adding the surfactant, which indicates that the performance of the crystal-planting solution is improved. From the crystal-planting density, we can see that the crystal-planting density of the crystal-planting solution obtained by different diamond powders and different oxidation times is also improved after adding the surfactant. Figure 3 As can be seen from (a) in the figure, diamond particles are scattered and sparsely distributed on the surface. By calculating the number of diamond grains per unit area, the planting density is about 109 cm -2 . Figure 3 As can be seen from (b), the surface is densely distributed with diamond particles, and the diamond particles are very small, with a planting density of about 5×10 10 cm -2 The comparison between the two shows that the crystal planting solution after adding surfactant dispersion is better than the crystal planting solution directly dispersed by adding water, and the crystal planting density is one order of magnitude higher. Both have achieved high-density crystal planting effect (10 10 / cm 2 ~10 11 / cm 2 ). This indicates that the patented method can effectively perform high-density crystal planting on cemented carbide materials for extremely small diameter micro-drills.

[0169] The method of the present invention can realize the growth of diamond coating on the surface of different cemented carbide substrate materials, and the controllable growth of diamond coating can be achieved by adjusting the growth temperature (wire bottom distance), methane content, argon content and growth time, so as to obtain diamond coatings of different thicknesses and different grain sizes. The example variable parameters and coating growth conditions are shown in Table 4, and other parameters remain the same. The specific steps are as follows:

[0170] Step 1: Prepare an alkaline solution, weigh 10g of potassium ferrocyanide and 10g of potassium hydroxide, and dissolve them in 100ml of deionized water to make a Murakami alkaline solution. Immerse the cutting area of ​​the carbide micro-drill (0.1mm) in the alkaline solution and ultrasonically corrode it in an ultrasonic tank (100Hz) for 15 minutes. Then immerse the chip removal area of ​​the carbide micro-drill in the alkaline solution and continue to corrode it for 5 minutes. Then take out the medium-hard alloy precision grinding tool and ultrasonically clean it with deionized water for 3 times, 10 minutes each time. Prepare a mixed acid solution, weigh 5ml of concentrated sulfuric acid solution and 50ml of hydrogen peroxide solution, and pour them into 50ml of deionized water. Put the carbide micro-drill into the mixed acid solution and corrode it for 30 seconds. Take out the carbide micro-drill and ultrasonically clean it with deionized water for 3 times, 10 minutes each time. Blow dry the cleaned carbide micro-drill with nitrogen.

[0171] Step 2: Prepare diamond crystal solution. Weigh 0.2g diamond powder (particle size 100nm), weigh 100ml concentrated nitric acid solution, pour the diamond powder into the concentrated nitric acid, seal with a sealing film, add a magnetic stirrer to oxidize for 6 hours. Then centrifuge and clean 3 times at a speed of 7000r / min, each time for 8 minutes. After cleaning, add 100ml of 10 -6mol / L organic solution of sodium dodecylbenzene sulfonate (SDBS), adjusted to pH 10. The cleaned carbide micro-drill is immersed in the prepared diamond crystal planting solution and ultrasonically planted for 10 minutes. The planted carbide micro-drill is simply rinsed with clean water for several times and blown dry with nitrogen.

[0172] Step 3: Insert the carbide micro drill evenly into the perforated copper plate, place it under the outlet of the hot wire chemical vapor deposition, evacuate, and set different growth temperatures. After evacuating, introduce hydrogen, methane, and argon, and control and adjust the percentage of methane and argon content, and keep the gas pressure at 5kPa. Turn on the hot wire power supply, continue to grow for different times, and when the growth is completed, turn off the gas, turn off the power supply, and evacuate.

[0173] Table 4 Different growth parameters and coating growth conditions

[0174]

[0175] It can be seen from Table 4 that the method of the present invention can achieve the growth of diamond coatings with different thicknesses and different grain sizes on the surfaces of different cemented carbide substrates. Figure 4 , Figure 5 and Figure 6 They are micron-scale diamond coating (Example 46), submicron-scale diamond coating (Example 48) and nano-scale diamond coating (Example 50). It can be seen that the corresponding diamond coatings are successfully deposited on the surface of the micro-drill, and the coatings are deposited evenly, densely, without gaps, and the coating quality is high.

[0176] The present invention has been described in detail above in conjunction with the embodiments, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge scope of ordinary technicians in the relevant technical field without departing from the purpose of the present invention.

Claims

1. A micro drill, characterized in that: The drill bit comprises a drill base and a diamond coating arranged on the surface of the drill base. The diameter of the drill base is 0.08 mm to 4 mm.

2. The micro drill according to claim 1, characterized in that: The thickness of the diamond coating is 100nm-10μm.

3. The micro drill according to claim 1 or 2, characterized in that: At least one of micron-sized diamond grains, submicron-sized diamond grains and nano-sized diamond grains is distributed in the diamond coating.

4. A method for preparing the micro drill according to any one of claims 1 to 3, characterized in that: The method comprises dividing the drill bit base into a cutting zone and a chip removal zone along the axial direction, performing electrostatic self-assembly pre-crystal planting and hot wire chemical vapor deposition on the drill bit base after pre-treatment with an alkaline solution, and forming the diamond coating on the surface of the drill bit base, wherein the alkaline solution pretreatment time of the cutting zone is greater than the alkaline solution pretreatment time of the chip removal zone.

5. The method according to claim 4, characterized in that The alkaline solution comprises an inorganic base, ferrocyanide and water; preferably, the mass ratio of the inorganic base, ferrocyanide and water is 1:0.5-1.5-5-15.

6. The method according to claim 4, characterized in that The alkaline solution pretreatment time of the cutting area is 5 minutes to 50 minutes.

7. The method according to claim 4, characterized in that The alkaline solution pretreatment time of the chip removal area is 2 minutes to 20 minutes.

8. The method according to claim 4, characterized in that The electrostatic force self-assembly pre-crystal planting method comprises: immersing the drill bit base body in diamond crystal planting liquid, and adsorbing diamond particles on the surface of the drill bit base body.

9. The method according to claim 8, characterized in that The diamond crystal planting solution comprises a surfactant and purified diamond powder.

10. The method according to claim 9, characterized in that In the diamond crystal planting solution, the mass fraction of the purified diamond powder is 0.05wt% to 0.2wt%.

11. The method according to claim 9, characterized in that The surfactant includes sodium dodecylbenzene sulfonate; preferably, the concentration of the sodium dodecylbenzene sulfonate is 10 -6 mol / L~10 -5 mol / L.

12. The method according to claim 4, characterized in that The method of hot wire chemical vapor deposition is: adjusting the distance between the top of the drill base and the hot wire, after vacuuming, introducing mixed gas, heating the filament, and depositing and growing a diamond coating on the surface of the drill base.

13. The method according to claim 12, characterized in that The distance between the top of the drill base and the hot wire is 15 mm to 25 mm.

14. The method according to claim 12, characterized in that The mixed gas includes hydrogen, methane and argon.

15. The method according to claim 12, characterized in that The temperature of the filament is 1500℃~2800℃.

16. The method according to claim 12, characterized in that The deposition and growth time of the diamond coating is 1h to 5h.

17. The method according to any one of claims 4 to 16, characterized in that The method further comprises subjecting the drill bit matrix to acid solution corrosion after the pretreatment with the alkaline solution.

18. Use of the micro drill bit according to any one of claims 1 to 3 or the micro drill bit produced by the method according to any one of claims 4 to 17 in processing packaging substrates.

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