Miniature drill bit, and preparation method therefor and use thereof

Abstract

A miniature drill bit, and a preparation method therefor and the use thereof. The miniature drill bit comprises a drill bit substrate and a superhard wear-resistant diamond coating arranged on a surface of the drill bit substrate, wherein the diameter of the drill bit substrate is 0.08-4 mm. The diameter of the drill bit substrate makes it an extremely-small-diameter drill bit, and a uniform diamond coating is further arranged on the extremely-small-diameter drill bit; therefore, the drill bit has good drilling machining performance and meets the development and machining trend of a packaging substrate. The invention solves the problems of most of the traditional diamond-coated miniature drill bits having a diameter of 1 mm or more, and having difficulties in terms of adapting to packaging substrates having a smaller size and finer holes.

Description

A micro drill bit and its preparation method and application Technical Field

[0001] The present 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 are becoming more multifunctional, miniaturized, and portable. Consequently, one development trend for packaging substrates is toward smaller substrates, finer substrate holes, and denser component placement. Correspondingly, the diameter of microdrill bits used for microhole processing is also decreasing. With the rise of high-performance computing, one development trend for packaging substrates is toward thicker substrates. This means that the aspect ratio of the microholes increases, and the aspect ratio of the microdrill bits used to process these microholes also increases. The demand for aspect ratios for thicker packaging substrates has already exceeded 20. High-frequency and high-speed signal transmission is also driving the use of packaging substrate materials toward high thermal conductivity, low dielectric constant (Dk), low dielectric loss (Df), and low coefficient of thermal expansion (CTE).

[0003] To meet these requirements, package substrate materials typically utilize high-hardness ceramic fillers, modified fiberglass cloth, and modified resin as their primary components. A high proportion of hard fillers can increase wear on microdrills, significantly reducing their lifespan and compromising the quality of micro-hole machining on package substrates.

[0004] Therefore, a micro drill bit still needs to be developed to adapt to the increasingly larger aspect ratio of packaging substrates. Technical issues

[0005] Package substrate materials typically utilize high-hardness ceramic fillers, modified fiberglass cloth, and modified resin as their primary components. A high proportion of hard fillers can increase wear on microdrills, dramatically reducing their lifespan and compromising the quality of micro-hole machining on package substrates. Technical Solutions

[0006] The present invention provides a micro drill bit, which can meet the development trend of packaging substrate processing and is suitable for processing fine-pore substrates.

[0007] The present invention also provides a method for preparing a packaging substrate.

[0008] The present invention also provides an application of a packaging substrate.

[0009] A first aspect of the present invention provides a micro drill comprising a drill base and a diamond coating provided on the surface of the drill base, wherein the diameter of the drill base is 0.08 mm to 4 mm.

[0010] One of the technical solutions of the present invention regarding the micro drill has at least the following beneficial effects:

[0011] The diameter of existing diamond-coated micro drill bits is mostly over 1 mm, which makes it difficult to adapt to packaging substrates with smaller substrate sizes and finer substrate 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 diamond coating has a uniform thickness, 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.

[0012] The micro drill bit of the present invention has a drill base with a diameter of only 0.08 mm to 4 mm, and is an extremely small-diameter drill bit. The extremely small-diameter drill bit is also provided with a uniform diamond coating, and has good drilling processing performance.

[0013] According to some embodiments of the present invention, the diameter of the drill bit base is only 0.1 mm to 1.0 mm.

[0014] According to some embodiments of the present invention, the drill bit substrate is made of cemented carbide.

[0015] According to some embodiments of the present invention, the material of the drill bit base includes YG6, YG6X and YG8.

[0016] According to some embodiments of the present invention, the thickness of the diamond coating is 100 nm to 10 μm.

[0017] 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 strength between the diamond coating and the drill substrate will decrease. Therefore, the appropriate diamond coating thickness range is 100nm~10μm.

[0018] According to some embodiments of the present invention, at least one of micron-sized diamond grains, submicron-sized diamond grains, and nanometer-sized diamond grains is distributed in the diamond coating.

[0019] 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 needed.

[0020] 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, pre-treating the drill bit base with an alkaline solution, performing electrostatic self-assembly pre-crystal deposition and hot wire chemical vapor deposition on the drill bit base, 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.

[0021] A technical solution in the method for preparing a micro drill bit of the present invention has at least the following beneficial effects:

[0022] Diamond-coated microdrills are the most promising micro-hole machining tools due to their exceptional hardness, high wear resistance, low friction, and low chemical affinity with the material being machined. However, the small diameter and high aspect ratio of ultra-small microdrills result in low strength and brittle fracture. The extremely small feature sizes and large aspect ratios of microdrills used in high-end packaging substrates result in low strength and brittle fracture. Achieving uniform diamond coating while maintaining the strength of the microdrill substrate is a key challenge in the preparation of coated microdrills.

[0023] Currently, most diamond-coated micro drill bits have diameters above 1mm, with few below 1mm. Diamond-coated micro drill bits with diameters of 0.1mm and 0.1mm are not yet available. For micro drill bits with diameters ranging from 0.15mm to 10mm, a multi-step deposition method can be used to control the flow of a hot wire through a chemical vapor deposition process to deposit diamond films. However, when the micro drill bit diameter is very small, such as less than 1mm, strength issues arise.

[0024] While alkaline pretreatment of only the front cutting portion of the drill bit (approximately 2mm from the front of the tip) can prevent a significant drop in the microdrill's strength, the chip removal area, constantly squeezed and rubbed against the densely drilled debris, experiences significant wear during use, shortening the lifespan of the microdrill. Therefore, a mild etch treatment of the chip removal area is necessary. This allows diamond growth to occur while also minimizing the stress on the chip removal area and preventing the weaker diamond coating deposited under mild etch from detaching. Pre-treating the cutting area with alkaline solution for a longer period than the chip removal area ensures the strength of the drill bit, preventing it from weakening during machining and preventing the drill from breaking.

[0025] If the alkaline solution pretreatment corrodes the cutting part and the chip removal part at the same time, the corrosion of the substrate caused by corrosion and the subsequent reduction of the cobalt element in the binder by acid corrosion, and the overall corrosion of the drill bit will lead to a significant decrease in the strength of the micro drill bit, and the micro drill bit will be easily broken during use.

[0026] The acid-base two-step method is an effective means of roughening the surface of cemented carbide tools, removing surface cobalt, and inhibiting the formation of harmful graphite phases at the interface. However, for micro drill bits with very small diameters, such as those less than 1 mm, improper control of the amount of cobalt removed can significantly reduce the fracture strength of the micro drill bit, seriously affecting the drilling performance and life of the micro drill bit. The present invention adopts a regional treatment method to ensure the strength during drilling, that is, the drill bit will not break. Specifically, the present invention divides the drill bit 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 time periods to control the cobalt content on the surface of the micro drill bit and the different strength reduction distributions. Then, an acid solution is used to etch and remove the cobalt content to achieve the purpose of ensuring the strength during drilling, that is, the drill bit will not break. The drill bit base is then subjected to electrostatic self-assembly pre-crystalization, and nano-diamond particles are uniformly and densely adsorbed on the complex-shaped drill bit surface to enhance the nucleation density, eliminate holes at the film interface, and improve the interface bonding strength. Finally, through hot-filament chemical vapor deposition, the distance between the filament and the drill bit substrate and the growth parameters were controlled 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.

[0027] "Extremely small diameter micro drill" may refer to a micro drill with a diameter of less than 1 mm.

[0028] Furthermore, "ultra-small diameter micro drill" can also refer to a micro drill with a diameter of about 0.1 mm.

[0029] According to some embodiments of the present invention, the alkaline solution comprises an inorganic base, ferricyanide and water.

[0030] The mass ratio of the inorganic base, ferricyanide and water is 1:0.5~1.5~5~15.

[0031] According to some embodiments of the present invention, the alkaline solution pretreatment time of the cutting area is 5 minutes to 50 minutes.

[0032] According to some embodiments of the present invention, the alkaline solution pretreatment time of the cutting area is 5 minutes to 15 minutes.

[0033] According to some embodiments of the present invention, the alkaline solution pretreatment time of the cutting area is 5 minutes to 10 minutes.

[0034] According to some embodiments of the present invention, the cutting zone refers to an area ranging from 2 mm to 3 mm distributed axially starting from the top of the drill base body.

[0035] According to some embodiments of the present invention, the alkaline solution pretreatment time of the chip removal area is 2 minutes to 20 minutes.

[0036] According to some embodiments of the present invention, the alkaline solution pretreatment time of the chip removal area is 2 minutes to 5 minutes.

[0037] According to some embodiments of the present invention, the alkaline solution pretreatment time of the chip removal area is 3 minutes to 5 minutes.

[0038] According to some embodiments of the present invention, the chip removal zone refers to an area ranging from 2 mm to 3 mm distributed axially starting from the cutting zone.

[0039] 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.

[0040] According to some embodiments of the present invention, the frequency range of ultrasound is 80 Hz to 120 Hz.

[0041] According to some embodiments of the present invention, the electrostatic self-assembly pre-crystal planting method comprises: immersing the drill bit base in a diamond crystal planting solution, and adsorbing diamond particles on the surface of the drill bit base.

[0042] According to some embodiments of the present invention, the diamond crystallization solution includes a surfactant and purified diamond powder.

[0043] According to some embodiments of the present invention, in the diamond crystal growth solution, the mass fraction of the purified diamond powder is 0.05 wt % to 0.2 wt %.

[0044] According to some embodiments of the invention, the surfactant comprises sodium dodecylbenzenesulfonate.

[0045] The concentration of the sodium dodecylbenzenesulfonate is 10 -6 mol / L~10 -5 mol / L.

[0046] Conventional pre-graining techniques result in a low adsorption density of diamond seeds on the tool surface, which can easily lead to the formation of interface voids and cracks during subsequent nucleation and growth, severely impacting the interface bonding strength. This is particularly true for extremely small micro-drill bits, such as those less than 1 mm, where diamond seeds have difficulty adsorbing due to their extremely small characteristic dimensions, making interface issues more prominent. The electrostatic self-assembly pre-graining method of the present invention is suitable for high-density, uniform pre-graining of extremely small micro-drill bits of various specifications and sizes.

[0047] According to some embodiments of the present invention, the hot filament chemical vapor deposition method is: adjusting the distance between the top of the drill bit base and the hot filament, after vacuuming, introducing a mixed gas, heating the filament, and depositing a diamond coating on the surface of the drill bit base.

[0048] 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.

[0049] According to some embodiments of the present invention, the mixed gas includes hydrogen, methane and argon.

[0050] According to some embodiments of the present invention, the temperature of the filament is 1500°C to 2800°C.

[0051] According to some embodiments of the present invention, the deposition growth time of the diamond coating is 1 hour to 5 hours.

[0052] According to some embodiments of the present invention, the method further comprises etching the drill bit base body with an acid solution after the pretreatment with the alkaline solution.

[0053] According to some embodiments of the present invention, the method for preparing the micro drill bit comprises the following specific steps:

[0054] S1: Chemical pretreatment of carbide micro drill bits;

[0055] S2: Carbide micro drill bits are subjected to diamond pre-graining treatment;

[0056] S3: Using hot wire chemical vapor deposition, hydrogen, methane and argon are introduced into the reaction chamber to deposit a diamond coating on the pretreated substrate.

[0057] According to some embodiments of the present invention, in step S1, the specific process is as follows:

[0058] (1) Prepare an alkaline solution (an 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 in the solution, immersing the chip removal area in the alkaline solution, and continue etching for 2 to 20 minutes.

[0059] (2) Take out the carbide precision grinding tool in (1) and ultrasonically clean it with deionized water for multiple times, each time for 10 minutes to 20 minutes;

[0060] (3) Preparation of a mixed acid solution (a mixture of sulfuric acid and hydrogen peroxide);

[0061] (4) Place the carbide micro drill bit in (2) into the mixed acid solution and corrode for 5s to 30s;

[0062] (5) Take out the carbide micro drill bit (4) and clean it ultrasonically with deionized water for multiple times, each time for 10 to 20 minutes;

[0063] (6) Use nitrogen to blow dry the cleaned carbide micro drill bit.

[0064] According to some embodiments of the present invention, in step S2, the specific process is as follows:

[0065] (1) Prepare diamond crystal solution. The particle size of diamond powder is 60nm~120nm. Pour the diamond powder into concentrated nitric acid to make a mixture with a mass fraction of 0.1wt%~0.2wt%. Seal the mixture with a sealing film and add a magnetic stirrer to oxidize for 2h~6h. Then centrifuge and wash. After washing, add 10 -6 mol / L-10 -5 mol / L of anionic surfactant sodium dodecylbenzenesulfonate, prepared into a diamond crystal solution with a mass fraction of 0.05wt%~0.2wt%, and then adjusted to pH 6-10;

[0066] (2) Immerse the cleaned carbide micro drill bit in the diamond crystal planting solution prepared in (1) and perform ultrasonic crystal planting for 5 to 20 minutes;

[0067] (3) Rinse the carbide micro drill bit that has been crystallized in (2) briefly with clean water and blow dry with nitrogen.

[0068] According to some embodiments of the present invention, in step S3, the specific process is as follows:

[0069] (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 between the top of the carbide precision grinding tool and the hot wire to 15 mm to 25 mm, and then evacuate.

[0070] (2) After (1) is evacuated to a vacuum, hydrogen, methane, and argon are introduced, with methane accounting for 1% to 5% of the total gas volume, and argon accounting for 10% to 40% of the total gas volume, and the gas pressure is maintained at 1 kPa to 5 kPa;

[0071] (3) Turn on the hot filament power supply, the filament temperature range is 1500℃~2800℃, and the growth continues for 1h~5h;

[0072] (4) After growth is completed, turn off the gas, turn off the power, and evacuate.

[0073] A third aspect of the present invention provides the use of the micro drill bit and the micro drill bit manufactured by the method in processing packaging substrates. Beneficial effects

[0074] The present invention provides a technical solution for the application of the micro drill bit and the micro drill bit produced by the method in the processing of packaging substrates, which has at least the following beneficial effects:

[0075] As packaging substrates become smaller and their holes become finer, component placement becomes more dense. The diameter of the corresponding microdrill bits used for microhole machining is also decreasing. In particular, packaging substrates are becoming thicker. This means that the aspect ratio of the microholes increases, and the aspect ratio of the microdrill bits used to machine these microholes increases, leading to a greater demand for microdrill bits with thicker aspect ratios. The application of the present microdrill bits in packaging substrate machining aligns with this development trend. BRIEF DESCRIPTION OF THE DRAWINGS

[0076] Figure 1 is a schematic diagram of the step-by-step corrosion area.

[0077] FIG2 shows the breaking strength test results of Examples 10-12.

[0078] FIG3 is a surface morphology of pre-grown nanodiamond grains on the surface of a cemented carbide tool.

[0079] FIG4 is a microscopic morphology of the micron-scale diamond coating of Example 46.

[0080] FIG5 is a microscopic morphology of the submicron diamond coating of Example 48.

[0081] FIG6 is a microscopic morphology of the nano-diamond coating of Example 50. Best Mode for Carrying Out the Invention

[0082] 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.

[0083] In some embodiments of the present invention, the present invention provides a micro drill bit, comprising a drill bit base and a diamond coating provided on the surface of the drill bit base, wherein the diameter of the drill bit base is 0.08 mm to 4 mm.

[0084] It can be understood that the diameter of existing diamond-coated micro drill bits is mostly above 1 mm, which makes it difficult to adapt to packaging substrates with smaller substrate sizes and finer substrate 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.

[0085] The micro drill bit of the present invention has a drill base with a diameter of only 0.08 mm to 4 mm, and is an extremely small-diameter drill bit. The extremely small-diameter drill bit is also provided with a uniform diamond coating, and has good drilling processing performance.

[0086] In some embodiments of the present invention, the diameter of the drill bit base is only 0.1 mm to 1.0 mm.

[0087] In some embodiments of the present invention, the drill bit substrate is made of cemented carbide.

[0088] In some embodiments of the present invention, the material of the drill bit base body includes YG6, YG6X and YG8.

[0089] YG6 is a common cemented carbide grade, primarily composed of tungsten carbide (WC) with a small amount of cobalt as a binder. It offers excellent hardness, strength, and wear resistance, making it suitable for machining metals such as steel and iron, as well as some non-metallic materials.

[0090] YG6X is an improved type of cemented carbide, also known as YG6A. It is slightly adjusted based on YG6 to improve its hardness and wear resistance, making it more suitable for some high-hardness materials.

[0091] YG8 is another common cemented carbide grade with a higher cobalt content, typically around 8%. Because it contains a higher amount of cobalt as a binder, YG8 offers slightly better toughness and impact resistance than YG6 and YG6X, but may be slightly lower in hardness. YG8 is suitable for applications requiring higher toughness and impact resistance.

[0092] In some embodiments of the present invention, the thickness of the diamond coating is 100 nm to 10 μm.

[0093] 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 strength between the diamond coating and the drill substrate will decrease. Therefore, the appropriate diamond coating thickness range is 100nm~10μm.

[0094] In some embodiments of the present invention, at least one of micron-sized diamond grains, submicron-sized diamond grains, and nanometer-sized diamond grains is distributed in the diamond coating.

[0095] 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 needed.

[0096] 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, pre-treating the drill bit base with an alkaline solution, and then subjecting the drill bit base to electrostatic self-assembly pre-crystal deposition and hot wire chemical vapor deposition to form 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.

[0097] Understandably, diamond-coated microdrills are the most promising micro-hole machining tools due to the diamond coating's ultra-high hardness, high wear resistance, low friction, and low chemical affinity with the material being machined. However, the small diameter and high aspect ratio of ultra-small microdrills result in inherently low strength and brittle fracture. The extremely small feature sizes and large aspect ratios of microdrills used in high-end packaging substrates result in inherently low strength and brittle fracture. Achieving uniform diamond coating while maintaining the strength of the microdrill substrate is a key challenge in the preparation of coated microdrills.

[0098] It should be noted that currently, most diamond-coated micro drill bits have diameters above 1mm, with few below 1mm. Diamond-coated micro drill bits with diameters of 0.1mm and 0.1mm are not yet available. For micro drill bits with diameters ranging from 0.15mm to 10mm, a multi-step deposition method can be used to control the flow of a hot wire through chemical vapor deposition to deposit diamond films. However, when the micro drill bit diameter is very small, such as less than 1mm, strength issues arise.

[0099] While alkaline pretreatment of only the front cutting portion of the drill bit (approximately 2mm from the front of the tip) can prevent a significant drop in the microdrill's strength, the chip removal area, constantly squeezed and rubbed against the densely drilled debris, experiences significant wear during use, shortening the lifespan of the microdrill. Therefore, a mild etch treatment of the chip removal area is necessary. This allows diamond growth to occur while also minimizing the stress on the chip removal area and preventing the weaker diamond coating deposited under mild etch from detaching. Pre-treating the cutting area with alkaline solution for a longer period than the chip removal area ensures the strength of the drill bit, preventing it from weakening during machining and preventing the drill from breaking.

[0100] If the alkaline solution pretreatment corrodes the cutting part and the chip removal part at the same time, the corrosion of the substrate caused by corrosion and the subsequent reduction of the cobalt element in the binder by acid corrosion, and the overall corrosion of the drill bit will lead to a significant decrease in the strength of the micro drill bit, and the micro drill bit will be easily broken during use.

[0101] The acid-base two-step method is an effective means to roughen the surface of cemented carbide tools, remove surface cobalt elements, and inhibit the formation of harmful graphite phases on the interface. However, for micro drill bits with very small diameters, such as those less than 1 mm, if the amount of cobalt removed is not properly controlled, the fracture strength of the micro drill bit will be significantly reduced, seriously affecting the drilling performance and life of the micro drill bit. The present invention adopts a regional treatment method to ensure the strength during drilling, that is, the drill bit will not break. Specifically, the present invention divides the drill bit 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 time periods, thereby controlling the cobalt content on the surface of the micro drill bit and the different strength weakening distributions. Then, an acid solution is used to corrode and remove the cobalt content to achieve the purpose of ensuring the strength during drilling, that is, the drill bit will not break. The drill bit base is then subjected to electrostatic self-assembly pre-crystalization, and nano-diamond particles are uniformly and densely adsorbed on the surface of the drill bit with a complex shape to enhance the nucleation density, so that there are no holes at the film interface 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.

[0102] "Extremely small diameter micro drill" may refer to a micro drill with a diameter of less than 1 mm.

[0103] Furthermore, "ultra-small diameter micro drill" can also refer to a micro drill with a diameter of about 0.1 mm.

[0104] In some embodiments of the present invention, the alkaline solution includes an inorganic base, ferricyanide, and water.

[0105] In some embodiments of the present invention, the mass ratio of the inorganic base, ferricyanide and water is 1:0.5~1.5~5~15.

[0106] In some embodiments of the present invention, the alkaline solution pretreatment time of the cutting area is 5 minutes to 50 minutes.

[0107] In some embodiments of the present invention, the alkaline solution pretreatment time of the cutting area is 5 minutes to 15 minutes.

[0108] In some embodiments of the present invention, the cutting zone refers to an area ranging from 2 mm to 3 mm distributed axially starting from the top of the drill base body.

[0109] In some embodiments of the present invention, the alkaline solution pretreatment time of the chip removal area is 2 minutes to 20 minutes.

[0110] In some embodiments of the present invention, the alkaline solution pretreatment time of the chip removal area is 2 minutes to 5 minutes.

[0111] In some embodiments of the present invention, the chip discharge area refers to an area starting from the chip discharge area and distributed in the axial direction with a range of 2 mm to 3 mm.

[0112] In some embodiments of the present invention, the electrostatic self-assembly pre-crystal planting method is as follows: immersing the drill bit substrate in diamond crystal planting liquid, and adsorbing diamond particles on the surface of the drill bit substrate.

[0113] In some embodiments of the present invention, the diamond growing solution includes a surfactant and purified diamond powder.

[0114] In some embodiments of the present invention, the mass fraction of the purified diamond powder in the diamond crystal growth solution is 0.05wt% to 0.2wt%.

[0115] In some embodiments of the present invention, the surfactant includes sodium dodecylbenzenesulfonate.

[0116] The concentration of sodium dodecylbenzenesulfonate is 10 -6 mol / L~10 -5 mol / L.

[0117] Conventional pre-graining techniques result in a low adsorption density of diamond seeds on the tool surface, which can easily lead to the formation of interface voids and cracks during subsequent nucleation and growth, severely impacting the interface bonding strength. This is particularly true for extremely small micro-drill bits, such as those less than 1 mm, where diamond seeds have difficulty adsorbing due to their extremely small characteristic dimensions, making interface issues more prominent. The electrostatic self-assembly pre-graining method of the present invention is suitable for high-density, uniform pre-graining of extremely small micro-drill bits of various specifications and sizes.

[0118] In some embodiments of the present invention, the hot filament chemical vapor deposition method is: adjusting the distance between the top of the drill bit base and the hot filament, after vacuuming, introducing a mixed gas, heating the filament, and depositing a diamond coating on the surface of the drill bit base.

[0119] 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.

[0120] In some embodiments of the present invention, the mixed gas includes hydrogen, methane, and argon.

[0121] In some embodiments of the present invention, the temperature of the filament is 1500°C to 2800°C.

[0122] In some embodiments of the present invention, the deposition growth time of the diamond coating is 1 hour to 5 hours.

[0123] In some embodiments of the present invention, the method further comprises etching the drill bit base body with an acid solution after the pretreatment with the alkaline solution.

[0124] In some embodiments of the present invention, the method for preparing the micro drill bit of the present invention comprises the following specific steps:

[0125] S1: Chemical pretreatment of carbide micro drill bits;

[0126] S2: Carbide micro drill bits are subjected to diamond pre-graining treatment;

[0127] S3: Using hot wire chemical vapor deposition, hydrogen, methane and argon are introduced into the reaction chamber to deposit a diamond coating on the pretreated substrate.

[0128] In some embodiments of the present invention, in step S1, the specific process is as follows:

[0129] (1) Prepare an alkaline solution (an 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, immersing the chip removal area in the alkaline solution, and continue etching for 2 to 20 minutes, as shown in Figure 1.

[0130] (2) Take out the carbide precision grinding tool in (1) and ultrasonically clean it with deionized water for multiple times, each time for 10 minutes to 20 minutes;

[0131] (3) Preparation of a mixed acid solution (a mixture of sulfuric acid and hydrogen peroxide);

[0132] (4) Place the carbide micro drill bit in (2) into the mixed acid solution and corrode for 5s to 30s;

[0133] (5) Take out the carbide micro drill bit (4) and clean it ultrasonically with deionized water for multiple times, each time for 10 to 20 minutes;

[0134] (6) Use nitrogen to blow dry the cleaned carbide micro drill bit.

[0135] In some embodiments of the present invention, in step S2, the specific process is as follows:

[0136] (1) Prepare diamond crystal solution. The particle size of diamond powder is 60nm~120nm. Pour the diamond powder into concentrated nitric acid to make a mixture with a mass fraction of 0.1wt%~0.2wt%. Seal the mixture with a sealing film and add a magnetic stirrer to oxidize for 2h~6h. Then centrifuge and wash. After washing, add 10 -6 mol / L-10 -5mol / L of anionic surfactant sodium dodecylbenzenesulfonate, prepared into a diamond crystal solution with a mass fraction of 0.05wt%~0.2wt%, and then adjusted to pH 6-10;

[0137] (2) Immerse the cleaned carbide micro drill bit in the diamond crystal planting solution prepared in (1) and perform ultrasonic crystal planting for 5 to 20 minutes;

[0138] (3) Rinse the carbide micro drill bit that has been crystallized in (2) briefly with clean water and blow dry with nitrogen.

[0139] In some embodiments of the present invention, in step S3, the specific process is as follows:

[0140] (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 between the top of the carbide precision grinding tool and the hot wire to 15 mm to 25 mm, and then evacuate.

[0141] (2) After (1) is evacuated to a vacuum, hydrogen, methane, and argon are introduced, with methane accounting for 1% to 5% of the total gas volume, and argon accounting for 10% to 40% of the total gas volume, and the gas pressure is maintained at 1 kPa to 5 kPa;

[0142] (3) Turn on the hot filament power supply, the filament temperature range is 1500℃~2800℃, and the growth continues for 1h~5h;

[0143] (4) After growth is completed, turn off the gas, turn off the power, and evacuate.

[0144] In some other embodiments of the present invention, applications of the micro drill bit of the present invention and the micro drill bit manufactured by the method of the present invention in processing packaging substrates are provided.

[0145] It should be noted that packaging substrates are becoming smaller, the holes in the substrates are becoming finer, and the components are being mounted more densely. The diameter of the corresponding microdrill bits used for micro-hole processing is also becoming smaller and smaller. In particular, packaging substrates are also developing in the direction of thickening. This means that the thickness-to-diameter ratio of the micro-holes is increasing, and the aspect ratio of the micro-drill bits used to process such micro-holes is increasing. The demand for aspect ratios of micro-drill bits for thickening packaging substrates is even greater. The application of the micro-drill bits of the present invention in packaging substrate processing adapts to the development trend of packaging substrates.

[0146] The technical solution of the present invention will be better understood with reference to specific embodiments below.

[0147] In order to verify that the corrosion method used in the present invention can effectively ensure that the micro-drill with an extremely 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.

[0148] The alkaline solution and acid solution used in the examples in Table 1 and Table 2 are consistent, and the corrosion time gradient is consistent. The only difference is that Table 1 adopts regional corrosion, while Table 2 does not adopt regional corrosion.

[0149] After the corrosion was completed, the fracture strength test was carried out. The fracture strength of Examples 10-12 is shown in Figure 2. The specific corrosion steps are as follows:

[0150] 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.

[0151] The carbide micro-drill cutting area was immersed in an alkaline solution and subjected to ultrasonic etching in an ultrasonic bath (100 Hz) for different times.

[0152] The chip removal area of ​​the carbide micro-drill is also immersed in the alkaline solution and continues to be corroded for different times.

[0153] 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.

[0154] 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.

[0155] Place the carbide micro-drill in a mixed acid solution and etch it for several minutes. Then remove it and ultrasonically clean it with deionized water three times, 10 minutes each time. Finally, blow dry the cleaned carbide micro-drill with nitrogen.

[0156] 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.

[0157] Immerse both the cutting and chip removal areas of the carbide microdrill in an alkaline solution and ultrasonically etch for several minutes in an ultrasonic bath. Remove the medium-carbide precision grinding tool and ultrasonically clean it three times in deionized water for 10 minutes each. Prepare a mixed acid solution by weighing 5 mL of concentrated sulfuric acid solution and 50 mL of hydrogen peroxide solution and pouring both into 50 mL of deionized water.

[0158] Place the carbide micro drill in the mixed acid solution and etch it for several minutes.

[0159] The carbide micro-drill was then taken out and ultrasonically cleaned with deionized water for 3 times, each time for 10 minutes. Finally, the cleaned carbide micro-drill was blown dry with nitrogen.

[0160] Table 1 Corrosion of extremely small diameter micro drills (0.1 mm)

[0161]

[0162] Table 2 Corrosion of extremely small diameter micro drill (0.1mm) without partition

[0163]

[0164] From Tables 1 and 2, and their comparison, we can see that the fracture strength of the micro-drills decreases with increasing alkaline corrosion time and decreases with increasing acid corrosion time. Furthermore, under the same corrosion conditions, the fracture strength of the zoned corrosion is greater than that of the non-zoned corrosion. A fracture strength greater than 0.40 N ensures sufficient working strength for the micro-drills. This shows that the zoned corrosion method employed in the present invention can effectively ensure sufficient fracture strength for the micro-drills.

[0165] The diamond seeding solution prepared by the present invention can achieve high-density seeding of cemented carbide materials used in micro-drills. Examples are shown in Table 3. Table 3 shows the particle size and potential of diamond seeding solutions prepared using different diamond powder particle sizes, different oxidation times, and whether or not a surfactant was added, as well as the seeding density of crystals seeded using the diamond seeding solutions prepared above. The specific experimental steps are as follows:

[0166] 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 and clean three 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 dodecylbenzenesulfonate (SDBS) organic solution, adjusted to pH 6. The cleaned carbide micro-drill was immersed in the prepared diamond crystal growth solution and ultrasonically grown for 10 minutes. The planted carbide micro-drill was briefly rinsed with clean water several times and blown dry with nitrogen.

[0167] Table 3 Crystallization solutions prepared with different parameters

[0168] As can be seen from Table 3, the particle size of the crystallization solution becomes smaller and the potential becomes larger after adding the surfactant, which indicates that the performance of the crystallization solution has been improved. From the crystallization density, it can be seen that the crystallization solution obtained by adding surfactants and different diamond powders and different oxidation times has also been improved after adding surfactants. As can be seen from Figure 3 (a), the surface is sparsely distributed with diamond particles. By calculating the number of diamond grains per unit area, the crystallization density is about 10 9 cm -2As can be seen from Figure 3 (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 effect of the crystal planting solution after adding surfactant dispersion is better than that of the crystal planting solution directly dispersed with 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 shows that this 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 grow diamond coatings on the surfaces of various cemented carbide substrates. By adjusting conditions such as the growth temperature (wire-to-base distance), methane content, argon content, and growth time, the diamond coating's growth can be controlled, resulting in diamond coatings of varying thicknesses and grain sizes. The example variable parameters and coating growth results are shown in Table 4, while other parameters remained constant. 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 ​​a carbide microdrill (0.1mm) in the alkaline solution and ultrasonically etch it in an ultrasonic bath (100Hz) for 15 minutes. Then, immerse the chip removal area of ​​the carbide microdrill in the alkaline solution and continue etching for 5 minutes. Remove the medium-carbide precision grinding tool and ultrasonically clean it three times with deionized water, each for 10 minutes. Prepare a mixed acid solution by weighing 5ml of concentrated sulfuric acid solution and 50ml of hydrogen peroxide solution. Pour both into 50ml of deionized water. Place the carbide microdrill in the mixed acid solution and etch it for 30 seconds. Remove the carbide microdrill and ultrasonically clean it three times with deionized water, each for 10 minutes. Blow dry the cleaned carbide microdrill 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 wash 3 times at a speed of 7000r / min, each time for 8 minutes. After washing, add 100ml of 10 -6 mol / L sodium dodecylbenzenesulfonate (SDBS) organic solution, adjusted to pH 10. The cleaned carbide micro-drill was immersed in the prepared diamond seeding solution and seeded with ultrasound for 10 minutes. The seeded carbide micro-drill was briefly rinsed with clean water and dried with nitrogen.

[0172] Step 3: Evenly insert the carbide microdrill into the perforated copper plate and place it under the outlet of the hot-filament chemical vapor deposition (CVD) system. Evacuate the plate and set different growth temperatures. After evacuating the plate, introduce hydrogen, methane, and argon, adjusting the methane and argon percentages and maintaining a pressure of 5 kPa. Turn on the hot-filament power supply and continue growth for varying lengths of time. Once growth is complete, turn off the gases, turn off the power supply, and evacuate the plate.

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

[0174]

[0175] As can be seen from Table 4, the method of the present invention can achieve the growth of diamond coatings of varying thicknesses and grain sizes on the surfaces of various cemented carbide substrates. Figures 4, 5, and 6 show a micron-scale diamond coating (Example 46), a submicron-scale diamond coating (Example 48), and a nanoscale diamond coating (Example 50), respectively. It can be seen that the corresponding diamond coatings were successfully deposited on the micro-drill surface. The coatings were uniform, dense, and free of gaps, and the coatings were of high quality.

[0176] The present invention has been described in detail above with reference to the embodiments. However, the present invention is not limited to the above embodiments. Various changes can be made within the scope of knowledge possessed by ordinary technicians in the relevant technical field without departing from the spirit 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 5min~50min.

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

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%~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 15mm~25mm.

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~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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