Copper deposition process of DPC deep-hole ceramic substrate

Abstract

The invention discloses a copper deposition process of a DPC deep-hole ceramic substrate, and relates to the technical field of advanced semiconductor packaging, optoelectronic device manufacturing and precision electronic assembly, and the copper deposition process comprises the following steps: carrying out laser drilling on a ceramic substrate in a spiral drilling mode; and then sequentially carrying out porcelain slag cleaning, magnetron sputtering, chemical copper deposition and thick copper electroplating on the ceramic substrate. According to the method, copper can be coated on the inner wall of the deep hole of the ceramic substrate with the hole depth ratio exceeding 5 without depending on ionized physical vapor deposition and atomic layer deposition, the welding requirement and the bonding performance are met, and meanwhile the cost needed by three-dimensional interconnection packaging manufacturing is greatly reduced.

Description

Technical Field

[0001] This invention relates to the fields of advanced semiconductor packaging, optoelectronic device manufacturing and precision electronic assembly technology, specifically a copper plating process for DPC deep hole ceramic substrates. Background Technology

[0002] As electronic devices evolve towards higher performance, miniaturization, and multifunctionality, traditional two-dimensional planar wiring can no longer meet market demands, making three-dimensional integration and system-in-package (SIP) an inevitable trend. This requires vertical circuit interconnection within the ceramic substrate, i.e., connecting circuits on the upper and lower surfaces through through-holes penetrating the substrate.

[0003] In direct current plasma (DCP) processes, "deep vias" typically refer to through-holes with a diameter <150μm and a depth-to-diameter ratio >2, which are crucial for achieving vertical circuit interconnection within ceramic substrates. Currently, DCP processes often use magnetron sputtering to form a conductive "seed layer" to achieve thicker electroplating. Traditional magnetron sputtering processes face the following problems in deep via structures: the seed layer is not sputtered in the center of the via, leading to via breakage; uneven sputtering of the seed layer within the via makes it susceptible to erosion during water plating, resulting in via cracking.

[0004] Therefore, developing a copper plating process for DPC deep-hole ceramic substrates is of great significance. Summary of the Invention

[0005] The purpose of this invention is to provide a copper plating process for DPC deep-hole ceramic substrates to solve the problems mentioned in the prior art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A copper plating process for DPC deep-hole ceramic substrates includes the following steps: S1: Laser drilling is performed on the ceramic substrate using a spiral drilling method; S2: Clean the ceramic substrate prepared in step S1 by removing ceramic slag; S3: Perform magnetron sputtering on the ceramic substrate prepared in step S2; S4: Perform chemical copper plating on the ceramic substrate prepared in step S3; S5: Electroplating thick copper onto the ceramic substrate prepared in step S4.

[0007] Further, in step S1, the ceramic substrate is one or more of aluminum nitride substrate and aluminum oxide substrate; the laser drilling parameters are: frequency of 300-800kHz, pulse energy of 10-200μJ, short pulse width of 20-100ns; and the diameter of the laser-drilled hole is 10-100μm.

[0008] Further, in step S2, the ceramic slag cleaning process is as follows: the ceramic slag at the orifice position on the surface of the laser-treated ceramic substrate is ground off, placed in a phosphoric acid solution, soaked at 65-85℃ for 1-2 hours, then cleaned with an acidic piranha solution for 1 minute, then cleaned with a strong oxidizing alkaline solution for 10 minutes, neutralized and cleaned with citric acid solution, ultrasonically washed with water, and dried to obtain the cleaned ceramic substrate.

[0009] Further, the concentration of the phosphoric acid solution is 15%-20% v / v; the acidic piranha solution is composed of concentrated sulfuric acid and hydrogen peroxide, with a mass ratio of concentrated sulfuric acid to hydrogen peroxide of (3-4):1; the strong oxidizing alkaline solution is composed of ammonia, hydrogen peroxide, and deionized water, with a mass ratio of ammonia, hydrogen peroxide, and deionized water of 1:(1-2):(3-5); the concentration of citric acid is 3-5% v / v; the ceramic slag cleaning parameters are: ultrasonic frequency of 20-40 kHz; drying temperature of 120-180℃; and drying time of 1-3 h.

[0010] Furthermore, in step S3, the thickness of the titanium layer sputtered by magnetron sputtering is 0.1-0.15 μm, and the thickness of the copper layer is 1-2 μm; the magnetron sputtering parameters are: Ti target and Cu target, temperature 300-305℃, argon atmosphere, and pressure 0.10-0.15 Pa.

[0011] Furthermore, in step S4, the chemical copper plating process includes either vertical immersion copper plating or chemical copper plating.

[0012] Furthermore, the vertical immersion copper plating process employs an alkaline formaldehyde system containing dual stabilizers and highly dispersible surfactants; the highly dispersible surfactant is a fluorinated surfactant, specifically a perfluoroalkyl or partially fluorinated alkyl chain; the stabilizer is a thiourea derivative and molybdate, specifically tetramethylthiourea and sodium molybdate; the vertical immersion copper plating process flow is: pre-immersion → water washing → activation → water washing → accelerated treatment → water washing → copper plating → water washing → drying; the activation time is 240-580s; the accelerated treatment time is 80-180s; during the copper plating process, air flotation is added every 5s in the copper plating tank, and the tank is oscillated back and forth, supplemented by 50Hz / 30W side vibration for 5s + stop for 5s and 30Hz / 15W bottom vibration for 10s + stop for 10s.

[0013] Further, the electroless copper plating process is as follows: S1: Copper sulfate, sodium citrate, and tetrahydroxypropylethylenediamine are dissolved in deionized water at 50-60℃, stirred and mixed, and the pH is adjusted to 12.5 with sodium hydroxide. Then, sodium 3-mercapto-1-propanesulfonate, potassium ferrocyanide, sodium dodecyl sulfate, fatty alcohol polyoxyethylene ether, and butynediol ethoxylate are added in sequence. Finally, formaldehyde is added while stirring to obtain the electroless copper plating solution. S2: Place the ceramic substrate prepared in step S3 in a potassium permanganate mixture for pre-immersion for 3-5 minutes, wash with water, then place it in a colloidal palladium activation solution and activate it in a water bath at 50-55℃ for 120-360 seconds. Wash with water, and then accelerate it at room temperature for 100-200 seconds with an accelerating solution. After that, place it in a chemical copper plating solution and perform chemical copper plating at 20-40℃ with a deposition rate of 1-2 μm / h to obtain a chemically plated copper ceramic substrate.

[0014] Furthermore, in the preparation process of the chemical copper plating solution, by mass fraction, the following components are present: copper sulfate 0.8-1%, sodium citrate 2.5-3.5%, tetrahydroxypropyl ethylenediamine 1-1.5%, sodium 3-mercapto-1-propanesulfonate 0.0003-0.0005%, potassium ferrocyanide 0.001-0.002%, sodium dodecyl sulfate 0.003-0.005%, fatty alcohol polyoxyethylene ether 0.001-0.003%, butynediol ethoxylate compound 0.003-0.005%, and formaldehyde 1-1.5%.

[0015] Furthermore, in step S5, the electroplating of thick copper is carried out using a DC electroplating process; the thickness of the electroplated copper is 20-30 μm.

[0016] Furthermore, in step S5, the thickness of the electroplated copper is 20-30 μm.

[0017] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention introduces an inductively coupled plasma source into the magnetron sputtering process to increase the metal ionization rate of sputtered titanium and copper atoms, activate the surface of the ceramic substrate, promote the deposition of titanium and copper on the ceramic substrate surface to form a dense film, and reduce the generation of voids. Simultaneously, a planetary rotation method is adopted, namely, rotation of the dual cylindrical target + rotation of the rotating frame + rotation of the substrate on the rotating frame, which effectively improves the uniformity of hole wall coverage.

[0018] 2. This invention introduces a dual stabilizer, thiourea derivative and molybdate, into the vertical immersion copper deposition process. On one hand, the sulfur and nitrogen atoms in the thiourea derivative can provide lone pairs of electrons to coordinate with molybdate and copper. On the other hand, the molybdenum (VI) provided by molybdate is partially reduced to mixed valence states (such as Mo(V), Mo(IV)) in an alkaline reducing environment, giving the molybdenum oxygen clusters or ions abundant coordination ability. This promotes the coordination of the thiourea derivative with molybdate ions, forming a soluble pre-structured complex that can selectively adsorb onto the surface of the through-holes of the ceramic substrate activated by colloidal palladium. Simultaneously, the thiourea derivative is strongly anchored to the palladium / copper surface through sulfur atoms, while molybdenum acts on the palladium / copper surface in the form of oxygen clusters or ions. This forms a loose, porous, yet dense network film around the colloidal palladium catalytic center, effectively controlling the copper deposition process and improving the uniformity and density of the copper coating.

[0019] 3. This invention introduces sodium dodecyl sulfonate and fatty alcohol polyoxyethylene ether as highly dispersible surfactants in the chemical copper plating process, effectively reducing the surface tension of the copper plating solution, improving its wettability, and promoting the escape of hydrogen gas during the chemical copper plating process, thereby increasing the density of the coating. This invention also introduces butynediol ethoxylate as a leveling agent into the chemical copper plating solution, which not only promotes a smooth and uniform coating morphology but also works synergistically with potassium ferrocyanide and sodium 3-mercapto-1-propanesulfonate to improve the stability of the chemical copper plating solution. Furthermore, the chemical copper plating process incorporates air flotation, back-and-forth rocking, side vibration, and bottom vibration to promote solution exchange, thereby depositing a dense and stable copper layer on the inner wall of the pores.

[0020] 4. This invention introduces a dual process of magnetron sputtering and chemical copper deposition into the DPC process. First, this invention achieves high-density interconnection of DPC ceramic substrates, effectively avoiding functional problems such as hole breakage and damage caused by the limitations of magnetron sputtering itself. It enables metallization of high aspect ratio vias, ensuring 100% copper layer coverage within the vias, eliminating voids, maintaining uniform thickness, and exhibiting low resistivity and suppression, thereby achieving low-loss, high-fidelity vertical electrical signal transmission. Second, this invention improves the high-frequency, high-power performance of DPC ceramic substrates. While ensuring the bonding strength between the copper layer and ceramic, it achieves micron-level apertures and high aspect ratio vertical conductive vias, enhancing thermal conductivity and heat dissipation capabilities to meet the urgent needs of high-frequency signal transmission integrity and high-power device heat dissipation. Finally, this invention improves the reliability and stability of DPC ceramic substrates. The strong bonding strength between copper and ceramic, as well as the excellent resistance to electromigration and thermomechanical fatigue of the copper pillars themselves, ensures long-term stable operation of the package in harsh environments. Furthermore, this invention is low-cost and highly efficient, offering significant advantages for large-scale manufacturing. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of a copper plating process for a DPC deep hole ceramic substrate according to the present invention. Figure 2 This is a schematic diagram of the copper layer structure of the hole wall of the DPC deep hole ceramic substrate prepared in Example 1 of the present invention; Figure 3 This is a schematic diagram of the copper structure of the hole wall of the DPC deep hole ceramic substrate prepared in Example 1 of the present invention; Figure 4 This is a schematic diagram of the copper structure of the hole wall of the DPC deep hole ceramic substrate prepared in Comparative Example 1 of the present invention. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] In the following examples, the CAS number of citric acid is 77-92-9; the CAS number of sodium citrate is... 68-04-2; CAS number for tetrahydroxypropyl ethylenediamine is 102-60-3; CAS number for sodium 3-mercapto-1-propanesulfonate is 17636-10-1; CAS number for potassium ferrocyanide is 13943-58-3; CAS number for sodium dodecyl sulfate is 151-21-3; the model number for fatty alcohol polyoxyethylene ether is AEO-9; CAS number for butynediol ethoxylate is 1606-85-5.

[0024] Example 1: A copper plating process for a DPC deep hole ceramic substrate: Step 1: Laser drilling: At a frequency of 600kHz, a single pulse energy of 150μJ, and a short pulse width of 80ns, a spiral drilling method is used to perform laser drilling on the aluminum nitride ceramic substrate to make the hole diameter 20μm, thus obtaining a laser-treated ceramic substrate. Step Two: Cleaning Porcelain Shards The ceramic slag at the orifice of the laser-treated ceramic substrate was removed by grinding. The substrate was then immersed in a 15% phosphoric acid solution at 75°C for 2 hours. After that, it was cleaned with an acidic piranha solution of concentrated sulfuric acid and hydrogen peroxide in a mass ratio of 3:1 for 1 minute. Then, it was cleaned with a strong oxidizing alkaline solution of ammonia, hydrogen peroxide and deionized water in a mass ratio of 1:2:5 for 10 minutes. The substrate was then neutralized and cleaned with a 5% citric acid solution, ultrasonically washed with water at 20kHz, and dried at 150°C for 2 hours to obtain the cleaned ceramic substrate. Step 3: Perform magnetron sputtering: The cleaned ceramic substrate was placed in a dual-target pulsed interleaved sputtering apparatus. Under argon protection, at 0.15 Pa and 300 °C, inductively coupled plasma was used for activation and glow discharge to provide pulse power. Ti and Cu targets were used as targets, and Ti / Cu was sputtered on the surface of the cleaned ceramic substrate in a planetary rotation manner to make the titanium layer thickness 0.1 μm and the copper layer thickness 1 μm, thus obtaining a magnetron sputtered ceramic substrate. Step 4: Perform chemical copper plating: S1: Take a magnetron sputtered ceramic substrate for chemical copper plating. A vertical immersion process is used. The system is an alkaline formaldehyde system containing tetramethylthiourea, sodium molybdate and perfluoroalkyl, combined with a dual stabilizer + highly dispersible surfactant + gantry line for copper plating. The process flow is: pre-immersion → water washing → activation → water washing → acceleration → water washing → copper plating → water washing → drying. S2: During the copper plating process, colloidal palladium is used for catalytic activation for 360s, and accelerated processing for 150s. In the copper plating tank, air flotation is added every 5s to top out, while oscillating back and forth. A combination of 50hz / 30W side vibration and 30hz / 15W bottom vibration is used, and the process is carried out according to the process of side vibration 5s + stop 5s and bottom vibration 10s + stop 10s. Step 5: Perform thick copper electroplating: A DC electroplating process was used to electroplat a chemical copper-plated ceramic substrate to achieve a copper plating thickness of 25 μm, resulting in a DPC deep-hole ceramic substrate.

[0025] Example 2: A copper plating process for a DPC deep hole ceramic substrate: Step 1: Laser drilling: At a frequency of 400kHz, a single pulse energy of 100μJ, and a short pulse width of 60ns, a spiral drilling method is used to perform laser drilling on the aluminum nitride ceramic substrate to make the hole diameter 20μm, thus obtaining a laser-treated ceramic substrate. Step Two: Cleaning Porcelain Shards The ceramic slag at the orifice of the laser-treated ceramic substrate was removed by grinding. The substrate was then immersed in a 20% phosphoric acid solution at 75°C for 2 hours. After that, it was cleaned with an acidic piranha solution of concentrated sulfuric acid and hydrogen peroxide in a mass ratio of 4:1 for 1 minute. Then, it was cleaned with a strong oxidizing alkaline solution of ammonia, hydrogen peroxide and deionized water in a mass ratio of 1:1:4 for 10 minutes. The substrate was then neutralized and cleaned with a 3% citric acid solution, ultrasonically washed with water at 20kHz, and dried at 150°C for 2 hours to obtain the cleaned ceramic substrate. Step 3: Perform magnetron sputtering: The cleaned ceramic substrate was placed in a dual-target pulsed inter-sputtering apparatus. Under argon protection, at 0.15 Pa and 300 °C, Ti / Cu was sputtered on the surface of the cleaned ceramic substrate using inductively coupled plasma activation and glow discharge pulse power supply. The titanium layer was 0.1 μm thick and the copper layer was 1 μm thick, resulting in a magnetron sputtered ceramic substrate. Step 4: Perform chemical copper plating: S1: Dissolve 0.8 parts copper sulfate, 2.5 parts sodium citrate, and 1 part tetrahydroxypropyl ethylenediamine in deionized water at 55°C, stir and mix well, adjust the pH to 12.5 with sodium hydroxide, then add 0.0003 parts sodium 3-mercapto-1-propanesulfonate, 0.001 parts potassium ferrocyanide, 0.003 parts sodium dodecyl sulfate, 0.001 parts fatty alcohol polyoxyethylene ether, and 0.003 parts butynediol ethoxylate compound in sequence. Finally, add 1 part formaldehyde while stirring to obtain the chemical copper plating solution. S2: The magnetron sputtered ceramic substrate was placed in a stannous chloride-hydrochloric acid mixture for 5 min, washed with water, and then placed in a colloidal palladium activation solution for 360 s activation in a 50 ℃ water bath. After washing with water, it was accelerated at room temperature for 150 s with an accelerator solution. Then it was placed vertically in a chemical copper plating solution and chemical copper plating was performed at 40 ℃ with a deposition rate of 2 μm / h to obtain a chemical copper plating ceramic substrate. Step 5: Perform thick copper electroplating: A DC electroplating process was used to electroplat a chemical copper-plated ceramic substrate to achieve a copper plating thickness of 25 μm, resulting in a DPC deep-hole ceramic substrate.

[0026] Example 3: A copper plating process for a DPC deep hole ceramic substrate: Step 1: Laser drilling: At a frequency of 600kHz, a single pulse energy of 150μJ, and a short pulse width of 80ns, a spiral drilling method is used to perform laser drilling on the aluminum nitride ceramic substrate to make the hole diameter 20μm, thus obtaining a laser-treated ceramic substrate. Step Two: Cleaning Porcelain Shards The ceramic slag at the orifice of the laser-treated ceramic substrate was removed by grinding. The substrate was then immersed in a 15% phosphoric acid solution at 75°C for 2 hours. After that, it was cleaned with an acidic piranha solution of concentrated sulfuric acid and hydrogen peroxide in a mass ratio of 3:1 for 1 minute. Then, it was cleaned with a strong oxidizing alkaline solution of ammonia, hydrogen peroxide and deionized water in a mass ratio of 1:2:5 for 10 minutes. The substrate was then neutralized and cleaned with a 5% citric acid solution, ultrasonically washed with water at 20kHz, and dried at 150°C for 2 hours to obtain the cleaned ceramic substrate. Step 3: Perform magnetron sputtering: The cleaned ceramic substrate was placed in a dual-target pulsed interleaved sputtering apparatus. Under argon protection, at 0.15 Pa and 300 °C, inductively coupled plasma was used for activation and glow discharge to provide pulse power. Ti and Cu targets were used as targets, and Ti / Cu was sputtered on the surface of the cleaned ceramic substrate in a planetary rotation manner to make the titanium layer thickness 0.1 μm and the copper layer thickness 1 μm, thus obtaining a magnetron sputtered ceramic substrate. Step 4: Perform chemical copper plating: S1: Dissolve 0.9 parts copper sulfate, 3 parts sodium citrate, and 1.2 parts tetrahydroxypropyl ethylenediamine in deionized water at 55°C, stir and mix well, adjust the pH to 12.5 with sodium hydroxide, then add 0.0004 parts sodium 3-mercapto-1-propanesulfonate, 0.0015 parts potassium ferrocyanide, 0.004 parts sodium dodecyl sulfate, 0.002 parts fatty alcohol polyoxyethylene ether, and 0.004 parts butynediol ethoxylate compound in sequence. Finally, add 1.2 parts formaldehyde while stirring to obtain the chemical copper plating solution. S2: The magnetron sputtered ceramic substrate was placed in a stannous chloride-hydrochloric acid mixture for 5 min, washed with water, and then placed in a colloidal palladium activation solution for 360 s activation in a 50 ℃ water bath. After washing with water, it was accelerated at room temperature for 200 s with an accelerator solution, and then placed vertically in a chemical copper plating solution for chemical copper plating at 40 ℃ with a deposition rate of 2 μm / h to obtain a chemical copper plating ceramic substrate. Step 5: Perform thick copper electroplating: A DC electroplating process was used to electroplat a chemical copper-plated ceramic substrate to achieve a copper plating thickness of 25 μm, resulting in a DPC deep-hole ceramic substrate.

[0027] Example 4: A copper plating process for a DPC deep hole ceramic substrate: Step 1: Laser drilling: At a frequency of 600kHz, a single pulse energy of 150μJ, and a short pulse width of 80ns, a spiral drilling method is used to perform laser drilling on the aluminum nitride ceramic substrate to make the hole diameter 20μm, thus obtaining a laser-treated ceramic substrate. Step Two: Cleaning Porcelain Shards The ceramic slag at the orifice of the laser-treated ceramic substrate was removed by grinding. The substrate was then immersed in a 15% phosphoric acid solution at 75°C for 2 hours. After that, it was cleaned with an acidic piranha solution of concentrated sulfuric acid and hydrogen peroxide in a mass ratio of 3:1 for 1 minute. Then, it was cleaned with a strong oxidizing alkaline solution of ammonia, hydrogen peroxide and deionized water in a mass ratio of 1:2:5 for 10 minutes. The substrate was then neutralized and cleaned with a 5% citric acid solution, ultrasonically washed with water at 20kHz, and dried at 150°C for 2 hours to obtain the cleaned ceramic substrate. Step 3: Perform magnetron sputtering: The cleaned ceramic substrate was placed in a dual-target pulsed interleaved sputtering apparatus. Under argon protection, at 0.15 Pa and 300 °C, inductively coupled plasma was used for activation and glow discharge to provide pulse power. Ti and Cu targets were used as targets, and Ti / Cu was sputtered on the surface of the cleaned ceramic substrate in a planetary rotation manner to make the titanium layer thickness 0.1 μm and the copper layer thickness 1 μm, thus obtaining a magnetron sputtered ceramic substrate. Step 4: Perform chemical copper plating: S1: Dissolve 1 part copper sulfate, 3.5 parts sodium citrate, and 1.5 parts tetrahydroxypropyl ethylenediamine in deionized water at 55°C, stir and mix well, adjust the pH to 12.5 with sodium hydroxide, then add 0.0005 parts sodium 3-mercapto-1-propanesulfonate, 0.002 parts potassium ferrocyanide, 0.005 parts sodium dodecyl sulfate, 0.003 parts fatty alcohol polyoxyethylene ether, and 0.005 parts butynediol ethoxylate compound in sequence. Finally, add 1.5 parts formaldehyde while stirring to obtain the chemical copper plating solution. S2: The magnetron sputtered ceramic substrate was placed in a stannous chloride-hydrochloric acid mixture for 5 min, washed with water, and then placed in a colloidal palladium activation solution for 360 s activation in a 50 ℃ water bath. After washing with water, it was accelerated at room temperature for 200 s with an accelerator solution, and then placed vertically in a chemical copper plating solution for chemical copper plating at 40 ℃ with a deposition rate of 2 μm / h to obtain a chemical copper plating ceramic substrate. Step 5: Perform thick copper electroplating: A DC electroplating process was used to electroplat a chemical copper-plated ceramic substrate to achieve a copper plating thickness of 25 μm, resulting in a DPC deep-hole ceramic substrate.

[0028] Comparative Example 1: A copper plating process for a DPC deep hole ceramic substrate: Step 1: Laser drilling: At a frequency of 600kHz, a single pulse energy of 150μJ, and a short pulse width of 80ns, a spiral drilling method is used to perform laser drilling on an aluminum nitride ceramic substrate to make the hole diameter 20μm, thus obtaining a laser-treated ceramic substrate. Step Two: Cleaning Porcelain Shards The ceramic slag at the orifice of the laser-treated ceramic substrate was removed by grinding. The substrate was then immersed in a 15% phosphoric acid solution at 75°C for 2 hours. After that, it was cleaned with an acidic piranha solution of concentrated sulfuric acid and hydrogen peroxide in a mass ratio of 3:1 for 1 minute. Then, it was cleaned with a strong oxidizing alkaline solution of ammonia, hydrogen peroxide and deionized water in a mass ratio of 1:2:5 for 10 minutes. The substrate was then neutralized and cleaned with a 5% citric acid solution, ultrasonically washed with water at 20kHz, and dried at 150°C for 2 hours to obtain the cleaned ceramic substrate. Step 3: Perform magnetron sputtering: The cleaned ceramic substrate was placed in a dual-target pulsed interleaved sputtering apparatus. Under argon protection, at 0.15 Pa and 300 °C, a glow discharge pulse power supply was provided. Ti and Cu targets were used as targets. Ti / Cu was sputtered on the surface of the cleaned ceramic substrate by rotating the frame and rotating the dual cylindrical targets. The titanium layer thickness was 0.15 μm and the copper layer thickness was 1 μm, resulting in a magnetron sputtered ceramic substrate. Step 4: Perform chemical copper plating: S1: Take a magnetron sputtered ceramic substrate for chemical copper plating. A vertical immersion process is used. The system is an alkaline formaldehyde system containing tetramethylthiourea, sodium molybdate and perfluoroalkyl, combined with a dual stabilizer + highly dispersible surfactant + gantry line for copper plating. The process flow is: pre-immersion → water washing → activation → water washing → acceleration → water washing → copper plating → water washing → drying. S2: During the copper plating process, the copper is activated by colloidal palladium for 360s, accelerated for 150s, and the copper is ejected by air flotation every 5s in the copper plating tank, while oscillating back and forth; the process is carried out according to the process of 50hz / 30W side vibration for 10s + stop for 10s. Step 5: Perform thick copper electroplating: A DC electroplating process was used to electroplat a chemical copper-plated ceramic substrate to achieve a copper plating thickness of 25 μm, resulting in a DPC deep-hole ceramic substrate.

[0029] Comparative Example 2: A copper plating process for a DPC deep hole ceramic substrate: Step 1: Laser drilling: At a frequency of 600kHz, a single pulse energy of 150μJ, and a short pulse width of 80ns, a spiral drilling method is used to perform laser drilling on the aluminum nitride ceramic substrate to make the hole diameter 20μm, thus obtaining a laser-treated ceramic substrate. Step Two: Cleaning Porcelain Shards The ceramic slag at the orifice of the laser-treated ceramic substrate was removed by grinding. The substrate was then immersed in a 15% phosphoric acid solution at 75°C for 2 hours. After that, it was cleaned with an acidic piranha solution of concentrated sulfuric acid and hydrogen peroxide in a mass ratio of 3:1 for 1 minute. Then, it was cleaned with a strong oxidizing alkaline solution of ammonia, hydrogen peroxide and deionized water in a mass ratio of 1:2:5 for 10 minutes. The substrate was then neutralized and cleaned with a 5% citric acid solution, ultrasonically washed with water at 20kHz, and dried at 150°C for 2 hours to obtain the cleaned ceramic substrate. Step 3: Perform magnetron sputtering: The cleaned ceramic substrate was placed in a dual-target pulsed interleaved sputtering apparatus. Under argon protection, at 0.15 Pa and 300 °C, inductively coupled plasma was used for activation and glow discharge to provide pulse power. Ti and Cu targets were used as targets, and Ti / Cu was sputtered on the surface of the cleaned ceramic substrate in a planetary rotation manner to make the titanium layer thickness 0.1 μm and the copper layer thickness 1 μm, thus obtaining a magnetron sputtered ceramic substrate. Step 4: Perform chemical copper plating: S1: Dissolve 1 part copper sulfate, 3.5 parts sodium citrate, and 1.5 parts tetrahydroxypropyl ethylenediamine in deionized water at 55°C, stir and mix well, adjust the pH to 12.5 with sodium hydroxide, then add 0.002 parts potassium ferrocyanide, 0.005 parts sodium dodecyl sulfate, and 0.005 parts butynediol ethoxylate in sequence, and finally add 1.5 parts formaldehyde while stirring to obtain the chemical copper plating solution; S2: The magnetron sputtered ceramic substrate was placed in a stannous chloride-hydrochloric acid mixture for 5 min, washed with water, and then placed in a colloidal palladium activation solution for 360 s activation in a 50 ℃ water bath. After washing with water, it was accelerated at room temperature for 200 s with an accelerator solution, and then placed vertically in a chemical copper plating solution for chemical copper plating at 40 ℃ with a deposition rate of 2 μm / h to obtain a chemical copper plating ceramic substrate. Step 5: Perform thick copper electroplating: A DC electroplating process was used to electroplat a chemical copper-plated ceramic substrate to achieve a copper plating thickness of 25 μm, resulting in a DPC deep-hole ceramic substrate.

[0030] Comparative Example 3: A copper plating process for a DPC deep hole ceramic substrate: Step 1: Laser drilling: At a frequency of 600kHz, a single pulse energy of 150μJ, and a short pulse width of 80ns, a spiral drilling method is used to perform laser drilling on an aluminum nitride ceramic substrate to make the hole diameter 20μm, thus obtaining a laser-treated ceramic substrate. Step Two: Cleaning Porcelain Shards The ceramic slag at the orifice of the laser-treated ceramic substrate was removed by grinding. The substrate was then immersed in a 15% phosphoric acid solution at 75°C for 2 hours. After that, it was cleaned with an acidic piranha solution of concentrated sulfuric acid and hydrogen peroxide in a mass ratio of 3:1 for 1 minute. Then, it was cleaned with a strong oxidizing alkaline solution of ammonia, hydrogen peroxide and deionized water in a mass ratio of 1:2:5 for 10 minutes. The substrate was then neutralized and cleaned with a 5% citric acid solution, ultrasonically washed with water at 20kHz, and dried at 150°C for 2 hours to obtain the cleaned ceramic substrate. Step 3: Perform magnetron sputtering: The cleaned ceramic substrate was placed in a dual-target pulsed interleaved sputtering apparatus. Under argon protection, at 0.15 Pa and 300 °C, a glow discharge pulse power supply was provided. Ti and Cu targets were used as targets. Ti / Cu was sputtered on the surface of the cleaned ceramic substrate by rotating the frame and rotating the dual cylindrical targets. The titanium layer thickness was 0.15 μm and the copper layer thickness was 1 μm, resulting in a magnetron sputtered ceramic substrate. Step 4: Perform thick copper electroplating: A DC electroplating process was used to electroplat a chemical copper-plated ceramic substrate to achieve a copper plating thickness of 25 μm, resulting in a DPC deep-hole ceramic substrate.

[0031] Testing and experiments: The ceramic substrate samples prepared in the above examples and comparative examples were subjected to high-temperature thermal shock testing and cross-sectional analysis. High-temperature thermal shock test: Place the ceramic substrate sample on a heating platform and subject it to thermal shock at 350°C for 5 minutes. Observe whether there are phenomena such as blistering and peeling. Slice analysis: The ceramic substrate sample was cut into thin slices of 4×4×0.635mm, and the integrity of the copper layer inside the holes of the ceramic substrate was observed using an electron microscope.

[0032] The experimental data are shown in Table 1 below.

[0033] Table 1 Performance Test Data of DPC Ceramic Substrate

[0034] Conclusion: By employing a dual process of magnetron sputtering and chemical copper plating, and optimizing the composition of the chemical copper plating solution, high aspect ratio through-hole metallization can be achieved on DPC ceramic substrates, improving the uniformity of the plating layer within the through-holes, thereby ensuring product stability and reliability.

[0035] In Comparative Example 1, the magnetron sputtering process uses only glow discharge plasma as the plasma source, which reduces the ionization rate of titanium and copper atoms, thereby decreasing the adhesion between the metal layer and the ceramic substrate. Simultaneously, the sputtering of titanium and copper layers using a rotating stand and a dual-cylindrical target reduces the uniformity of the coating on the inner wall of the hole, thus affecting the transmission of vertical electrical signals. Furthermore, in the chemical copper plating process, only bottom vibration is used, slowing down solution exchange and affecting the density and stability of the copper layer on the inner wall of the hole.

[0036] In Comparative Example 2, the electroless copper plating solution used only potassium ferrocyanide as a stabilizer and sodium dodecyl sulfate as a surfactant, which not only reduced the stability of the electroless copper plating solution but also reduced the uniformity of the plating layer inside the hole.

[0037] In Comparative Example 3, only magnetron sputtering was used to prepare the DPC ceramic substrate, which increased the risk of deep hole fracture and breakage in the ceramic substrate, affecting the vertical electrical signal transmission, heat dissipation and thermal conductivity of the DPC ceramic substrate and its stability in use.

[0038] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A copper plating process for DPC deep-hole ceramic substrates, characterized in that: The copper plating process Includes the following steps: S1: Laser drilling is performed on the ceramic substrate using a spiral drilling method; S2: Clean the ceramic substrate prepared in step S1 by removing ceramic slag; S3: Perform magnetron sputtering on the ceramic substrate prepared in step S2; S4: Perform chemical copper plating on the ceramic substrate prepared in step S3; S5: Electroplating thick copper onto the ceramic substrate prepared in step S4.

2. The copper plating process for a DPC deep-hole ceramic substrate according to claim 1, characterized in that: In step S1, the ceramic substrate is one or more of aluminum nitride substrate and aluminum oxide substrate; the laser drilling parameters are: frequency of 300-800kHz, pulse energy of 10-200μJ, short pulse width of 20-100ns; and the diameter of the laser-drilled hole is 10-100μm.

3. The copper plating process for a DPC deep-hole ceramic substrate according to claim 1, characterized in that: In step S2, the ceramic slag cleaning process is as follows: the ceramic slag at the orifice position on the surface of the laser-treated ceramic substrate is ground off, placed in a phosphoric acid solution, soaked at 65-85℃ for 1-2 hours, then cleaned with an acidic piranha solution for 1 minute, then cleaned with a strong oxidizing alkaline solution for 10 minutes, neutralized and cleaned with citric acid solution, ultrasonically washed with water, and dried to obtain the cleaned ceramic substrate.

4. The copper plating process for a DPC deep-hole ceramic substrate according to claim 3, characterized in that: The concentration of the phosphoric acid solution is 15%-20% v / v; the acidic piranha solution is composed of concentrated sulfuric acid and hydrogen peroxide, with a mass ratio of concentrated sulfuric acid to hydrogen peroxide of (3-4):1; the strong oxidizing alkaline solution is composed of ammonia, hydrogen peroxide, and deionized water, with a mass ratio of ammonia, hydrogen peroxide, and deionized water of 1:(1-2):(3-5); the concentration of the citric acid is 3-5% v / v; the ceramic slag cleaning parameters are: ultrasonic frequency of 20-40 kHz; drying temperature of 120-180℃; and drying time of 1-3 h.

5. The copper plating process for a DPC deep-hole ceramic substrate according to claim 1, characterized in that: In step S3, the thickness of the titanium layer by magnetron sputtering is 0.1-0.15 μm, and the thickness of the copper layer is 1-2 μm; the magnetron sputtering parameters are: Ti target and Cu target, temperature 300-305℃, argon atmosphere, and pressure 0.10-0.15 Pa.

6. The copper plating process for a DPC deep-hole ceramic substrate according to claim 1, characterized in that: In step S4, the chemical copper plating process includes either vertical immersion copper plating or chemical copper plating.

7. The copper plating process for a DPC deep-hole ceramic substrate according to claim 6, characterized in that: The vertical immersion copper plating process uses an alkaline formaldehyde system containing a dual stabilizer and a highly dispersible surfactant; the highly dispersible surfactant is a fluorinated surfactant, and the dual stabilizer is a thiourea derivative and a molybdate.

8. The copper plating process for a DPC deep-hole ceramic substrate according to claim 6, characterized in that: The electroless copper plating process is as follows: S1: Dissolve copper sulfate, sodium citrate, and tetrahydroxypropylethylenediamine in deionized water at 50-60℃, stir and mix well, adjust the pH to 12.5 with sodium hydroxide, then add sodium 3-mercapto-1-propanesulfonate, potassium ferrocyanide, sodium dodecyl sulfate, fatty alcohol polyoxyethylene ether, and butynediol ethoxy compound in sequence, and finally add formaldehyde while stirring to obtain the electroless copper plating solution; S2: Place the ceramic substrate prepared in step S3 in a potassium permanganate mixture for pre-immersion for 3-5 minutes, wash with water, then place it in a colloidal palladium activation solution and activate it in a water bath at 50-55℃ for 120-360 seconds. Wash with water, and then accelerate it at room temperature for 100-200 seconds with an accelerating solution. After that, place it in a chemical copper plating solution and perform chemical copper plating at 20-40℃ with a deposition rate of 1-2 μm / h to obtain a chemically plated copper ceramic substrate.

9. The copper plating process for a DPC deep-hole ceramic substrate according to claim 8, characterized in that: In the preparation of the chemical copper plating solution, by mass fraction, the following components are present: copper sulfate 0.8-1%, sodium citrate 2.5-3.5%, tetrahydroxypropyl ethylenediamine 1-1.5%, sodium 3-mercapto-1-propanesulfonate 0.0003-0.0005%, potassium ferrocyanide 0.001-0.002%, sodium dodecyl sulfate 0.003-0.005%, fatty alcohol polyoxyethylene ether 0.001-0.003%, butynediol ethoxylate compound 0.003-0.005%, and formaldehyde 1-1.5%.

10. The copper plating process for a DPC deep-hole ceramic substrate according to claim 1, characterized in that: In step S5, the thick copper plating is performed using a DC electroplating process; the thickness of the electroplated copper is 20-30 μm.

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