Glass via fill method and glass substrate

Abstract

The application discloses a glass via hole filling method and a glass substrate. The glass via hole filling method comprises the following steps: providing a glass substrate with a via hole; cleaning the via hole and performing a hole wall activation treatment; placing conductive glue in the via hole; performing vacuumizing treatment on the glass substrate with the conductive glue; performing thermal curing on the conductive glue to form a conductive glue filling layer in the via hole; and performing planarization treatment on the glass substrate. The application adopts the process of filling with conductive glue combined with vacuumizing and exhausting and thermal curing, so that the process window is greatly widened, the manufacturing cost is reduced, and the via hole is filled with high quality without cavities.

Description

Technical Field

[0001] This invention relates to the field of glass adapter plate technology, and in particular to a glass through-hole filling method and a glass substrate. Background Technology

[0002] With the rapid development of high-performance computing technology, integrated circuits are evolving towards high density, multifunctionality, and three-dimensional stacking. Through-glass via (TGV) technology, with its excellent high-frequency electrical performance (low dielectric loss), thermal expansion coefficient (CTE) similar to silicon, and low-cost potential, is gradually becoming the mainstream vertical interconnect solution to replace through-silicon vias (TSV). A typical TGV fabrication process includes: precision drilling of glass substrates (such as laser-induced etching, plasma etching, etc.), hole wall cleaning and activation, seed layer deposition (usually Ti / Cu), copper plating filling, and chemical mechanical polishing (CMP) planarization. Among these, the metallization filling of microvias with a high aspect ratio (≥ 10:1) is the core challenge in ensuring the electrical performance and reliability of the device.

[0003] In existing TGV metallization processes, electrochemical deposition (copper plating) is commonly used to fill vias. However, conventional DC plating faces significant challenges for microvias with aspect ratios ≥10:1. Due to uneven electric field distribution and limited ion diffusion, copper ions tend to deposit rapidly at the opening of the via, forming a so-called "overburden effect," leading to premature closure of the via opening. This not only traps residual air and old plating solution at the core of the via, forming difficult-to-eliminate closed voids, but also hinders the replenishment of subsequent ions, resulting in insufficient deposition at the bottom of the via. Although the industry has attempted to use pulse reverse plating technology to improve the ion distribution inside and outside the via by adjusting the current waveform and utilizing additives, aiming to achieve a "bottom-up" "butterfly wing" filling morphology, it is still difficult to completely eliminate micron-level micro-crack defects under extremely high aspect ratios. In addition, existing electroplating processes have extremely stringent requirements on the concentration ratio of additives in the plating solution and the current parameter window. The process stability during mass production is poor, the yield is difficult to control at an acceptable level, and the high equipment and maintenance costs also limit its large-scale application.

[0004] Therefore, how to design a method that can achieve void-free and high-quality filling of glass through holes is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] To address the shortcomings of existing glass through-hole electroplating filling methods, which easily produce voids within the holes and are difficult to control in terms of process management, this invention proposes a glass through-hole filling method and a glass substrate. It adopts conductive adhesive filling combined with vacuum degassing and thermosetting processes, which can achieve high-quality filling of through holes without voids while significantly widening the process window and reducing manufacturing costs.

[0006] The technical solution adopted in this invention is to design a glass through-hole filling method, which includes the following steps: Provide a glass substrate with through holes; The through-holes are cleaned and the hole walls are activated. The conductive adhesive is placed inside the through hole; Vacuum treatment is performed on the glass substrate with conductive adhesive. The conductive adhesive is thermosetting to form a conductive adhesive filling layer inside the through-hole; The glass substrate is planarized.

[0007] This design, through a combination of vacuuming and thermosetting, pre-extracts residual gas from the through-holes before curing, effectively preventing air bubbles from forming voids after the conductive adhesive cures, thus solving the density problem of high aspect ratio through-hole filling. Simultaneously, using conductive adhesive as the filling medium instead of traditional pure electroplating broadens the process control window and reduces equipment complexity and manufacturing costs. The conductive adhesive filling layer prepared using this glass through-hole filling method has a dense structure without voids and bonds tightly to the hole walls.

[0008] Furthermore, the thermosetting process is a stepped thermosetting process, which includes: preheating at 60~100℃ for 20~30 minutes to remove bubbles and level the surface, and then raising the temperature to 150~160℃ and holding for 20~30 minutes to complete the curing.

[0009] This design employs a phased thermosetting process. First, a preheating stage at 60-100℃ utilizes lower viscosity to promote bubble expulsion and adhesive leveling. Then, a high-temperature stage at 150-160℃ completes cross-linking and curing. This temperature gradient effectively prevents internal stress or secondary bubbles from forming in the adhesive due to rapid temperature increases, ensuring the density and structural stability of the conductive adhesive filler layer.

[0010] In some embodiments of the present invention, conductive adhesive is disposed within the through hole, including: Conductive adhesive is uniformly coated onto the surface of the glass substrate and the walls of the through holes using an inkjet printer. The coating thickness on the walls of the through holes is 2μm to 10μm.

[0011] This design uses inkjet printing to form a conductive adhesive layer with a thickness of 2μm to 10μm on the hole wall. This ensures good conductivity of the hole wall while maximizing the preservation of the central flow cross-section of the through hole and reducing the amount of conductive adhesive used. This thin-layer coating method provides sufficient physical space for subsequent electroplating and hole-filling steps, while ensuring the adhesion between the hole wall and the metal layer.

[0012] In some embodiments of the present invention, after forming a conductive adhesive filling layer inside the through-hole, the method further includes: An auxiliary substrate is bonded to the side of the glass substrate opposite to the through-hole opening; Fill the through holes with electroplating; After the holes are filled, remove the auxiliary substrate.

[0013] This design provides a flat and stable support and conductive foundation for the subsequent electroplating and via filling process by bonding an auxiliary substrate to the back of the glass substrate, preventing warping and deformation of the glass substrate during electroplating. This step allows the thin conductive layer, which was originally only coated on the hole walls, to successfully undergo high-current via filling electroplating, improving the yield and efficiency of deep hole electroplating.

[0014] Based on this, the preferred option is to use a DC power supply for hole filling electroplating, with a current density of 1~2A / dm² and an electroplating time of 70~90min.

[0015] This design, by limiting the current density and time parameters of DC electroplating, enables metal ions to be uniformly deposited within the vias under the influence of an electric field, gradually filling the pores. This parameter range is adapted to the electroplating environment supported by an auxiliary substrate, which helps to obtain a smooth surface and a dense internal copper-filled layer. After the vias are filled, the auxiliary substrate can be easily peeled off without affecting the glass substrate itself.

[0016] In some embodiments of the present invention, conductive adhesive is disposed within the through-hole, including: The conductive adhesive was filled into the through holes using an inkjet printer.

[0017] This design completely fills the through-holes with conductive adhesive, eliminating gaps within the holes. It eliminates the need for complex processes such as electroplating and auxiliary carriers, forming a conductive path through a single filling and curing process, significantly reducing equipment investment and manufacturing costs.

[0018] In some embodiments of the present invention, after forming a conductive adhesive filling layer within the through-hole based on the conductive adhesive filling the through-hole, the method further includes: A femtosecond laser is used to create micropores with a diameter smaller than that of a through hole in the conductive adhesive filler layer; A process combining bridging electroplating and hole-filling electroplating is used to electroplat and fill micropores.

[0019] This design incorporates micropores within a fully filled conductive adhesive layer. This retains the adhesive's support and protection of the pore walls while simultaneously introducing electrolyte channels and current paths for subsequent electroplating. By combining bridging and via-filling electroplating processes, a composite conductor structure of a conductive adhesive sleeve and a central copper pillar is constructed. This structure utilizes the outer cured conductive adhesive layer to buffer the difference in thermal expansion coefficients between the glass and metal, significantly improving thermal cycling reliability, while the central electroplated copper pillar ensures the low resistance characteristics of the core conductive path.

[0020] Based on this, the preferred option is a femtosecond laser with a pulse energy of 100~200μJ and a pulse width of 200~800fs; The bridging electroplating uses a pulse power supply with a forward current density of 0.1~0.3A / dm², a forward to reverse current-time ratio of 1:3~1:5, and an electroplating time of 3~4h. The hole-filling electroplating uses a DC power supply with a current density of 1~2A / dm² and an electroplating time of 70~90min.

[0021] This design defines the specific parameters for femtosecond laser, bridging plating, and via-filling plating. The specific pulse parameters of the femtosecond laser ensure the precision of micro-hole processing and the quality of the hole walls, preventing crack formation. The bridging plating stage uses a pulsed power supply and a specific forward / reverse time ratio, which helps improve the distribution of metal ions within the hole. The subsequent DC via-filling stage quickly fills the remaining space based on the bridging, balancing filling quality and production efficiency.

[0022] Furthermore, the pore wall activation treatment is plasma treatment, with the following process parameters: using a box-type plasma device, a vacuum degree of 0.5~0.9Pa, introducing an argon-oxygen mixture, a power of 1~3kW, and a treatment time of 1~3min.

[0023] Plasma treatment with specific vacuum levels, gas compositions, and power effectively removes organic contaminants and weak boundary layers from the pore walls and introduces active functional groups onto the glass surface. This significantly enhances the wettability and adhesion between the conductive adhesive and the glass substrate, preventing delamination or peeling during subsequent processes.

[0024] Furthermore, the diameter of the through hole is 20~50μm, and the depth-to-width ratio is ≥10:1.

[0025] This design clarifies the specific technical scenarios to which this invention is applicable. The size range covers common glass via specifications in the current packaging field, demonstrating the effectiveness and process compatibility of this invention in addressing the challenges of filling high aspect ratio microvias.

[0026] In some embodiments, the conductive adhesive is a copper-based conductive adhesive.

[0027] The present invention also provides a glass substrate comprising: A glass substrate body having through holes; A conductive adhesive filling layer is disposed inside the through hole. The outer peripheral surface of the conductive adhesive filling layer is tightly fitted to the hole wall of the through hole, and the interior of the conductive adhesive filling layer has a dense, non-porous structure.

[0028] This structure significantly reduces the resistance of the vertical interconnect path, improves the integrity of signal transmission and the long-term reliability of the device, and is suitable for high-performance three-dimensional system integration packaging.

[0029] In some embodiments, the conductive adhesive filler layer fills the internal space of the through-hole.

[0030] In other embodiments, the thickness of the conductive adhesive filling layer is 2μm to 10μm, and a metal filling layer is provided on the inner peripheral side of the conductive adhesive filling layer, and the conductive adhesive filling layer and the metal filling layer fill the internal space of the through hole.

[0031] In some other embodiments, the conductive adhesive filler layer has micropores with a diameter smaller than that of the through hole, and the micropores are filled with a metal plating layer, so that the conductive adhesive filler layer and the metal plating layer fill the internal space of the through hole.

[0032] Compared with the prior art, the present invention has at least one of the following beneficial effects: 1. The process route of conductive adhesive filling combined with vacuum degassing and thermosetting is adopted. Before thermosetting, the residual gas in the through hole is removed by vacuuming, which effectively avoids the problem of air bubbles forming voids inside the conductive adhesive layer after curing. At the same time, the conductive adhesive replaces the traditional pure electroplating metal filling medium, eliminating the need to rely on electroplating additives with strict control windows, greatly relaxing the process requirements, reducing equipment investment and process costs, and is especially suitable for high-difficulty through hole filling scenarios with a depth-to-width ratio ≥10:1. 2. An inkjet printing device is used to form a conductive adhesive layer with a thickness of 2μm~10μm on the hole wall. The thin layer design of 2μm~10μm occupies only a very small space inside the hole, leaving sufficient deposition margin for subsequent hole filling electroplating. 3. The conductive adhesive completely fills the through-hole, forming a dense support structure on its own. There is no need to prepare an additional metal seed layer, which avoids defects such as hole capping and micro gaps in the hole caused by uneven ion distribution during the electrochemical deposition process. The filling process is not limited by electric field distribution and ion diffusion rate. The density and structural consistency of the filling layer are better than those of the electroplated filling layer. 4. Micropores are created in the fully filled conductive adhesive layer, forming a stable channel for electrolyte flow and current conduction; bridging electroplating facilitates the preferential deposition of metal ions at the bottom of the micropores, achieving a bottom-up growth mode and effectively avoiding the capping effect of premature closure of the orifice; subsequent DC filling electroplating improves process efficiency while ensuring filling quality, and the process stability is significantly better than traditional electroplating solutions. Attached Figure Description

[0033] The present invention will now be described in detail with reference to the embodiments and accompanying drawings, wherein: Figure 1 This is a schematic diagram of the spraying of conductive adhesive in Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of the thermosetting process in Embodiment 1 of the present invention; Figure 3 This is a schematic diagram of CMP polishing in Embodiment 1 of the present invention; Figure 4 This is a schematic diagram of the spraying of conductive adhesive in Embodiment 2 of the present invention; Figure 5 This is a schematic diagram of the thermosetting process in Embodiment 2 of the present invention; Figure 6 This is a schematic diagram of attaching an auxiliary substrate according to Embodiment 2 of the present invention; Figure 7 This is a schematic diagram of DC electroplating in Embodiment 2 of the present invention; Figure 8 This is a schematic diagram of CMP polishing in Embodiment 2 of the present invention; Figure 9 This is a schematic diagram of the spraying of conductive adhesive in Embodiment 3 of the present invention; Figure 10 This is a schematic diagram of the thermosetting process in Embodiment 3 of the present invention; Figure 11 This is a schematic diagram of laser-driven hole opening in Embodiment 3 of the present invention; Figure 12 This is a schematic diagram of the hole-filling electroplating in Embodiment 3 of the present invention; Figure 13 This is a schematic diagram of CMP grinding in Embodiment 3 of the present invention. Detailed Implementation

[0034] To make the technical problems, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0035] This invention provides a glass through-hole filling method, particularly suitable for glass through-hole filling scenarios with a ratio of ≥10:1. The basic filling process begins with cleaning and activating the hole walls of the glass substrate. This process removes contaminants from the hole walls and introduces active groups, enhancing the adhesion of the subsequent conductive adhesive. Next, conductive adhesive is placed within the through-hole. The glass substrate coated with conductive adhesive is then vacuumed to remove air bubbles trapped within the through-hole. The conductive adhesive is then thermally cured, forming a dense conductive adhesive filling layer within the through-hole. Finally, the glass substrate is polished to achieve surface planarization. The conductive adhesive filling layer prepared using this glass through-hole filling method has a dense structure, is free of voids, and bonds tightly to the hole walls.

[0036] In practical applications, borosilicate glass substrates with through-holes of 20-50 μm in diameter can be selected as the processing target. Commercially available copper-based conductive adhesives can be used. These adhesives use micron-sized copper powder as conductive filler. After curing, the copper filler is evenly distributed in the adhesive layer. The portion that overflows from the glass surface during filling forms the copper layer that needs to be removed in the subsequent planarization process after curing.

[0037] The pore wall activation treatment can be performed using a box-type plasma device, with the vacuum level controlled at 0.5~0.9Pa, an argon-oxygen mixture introduced, the power set at 1~3kW, and the treatment time at 1~3min. This can effectively remove organic contaminants and weak boundary layers from the pore walls and introduce active functional groups onto the glass surface.

[0038] The thermosetting process can be further improved by using a staged curing method. Specifically, preheating at 60~100℃ for 20~30 minutes allows for bubble removal and leveling, followed by raising the temperature to 150~160℃ and holding for 20~30 minutes to complete curing. The 60~100℃ preheating temperature range is based on experimental data: below 60℃, the viscosity is too high, making bubble removal difficult; above 100℃, premature curing may result in residual bubbles. The preheating stage reduces the viscosity of the conductive adhesive, promoting the removal of residual bubbles and leveling of the adhesive. The high-temperature stage ensures complete cross-linking and curing of the conductive adhesive, forming a stable filling structure.

[0039] See Figures 1 to 3 As shown, this invention provides Embodiment 1, which uses a basic process to achieve filling. The specific steps are as follows: Step 1: Prepare a glass substrate 100. The glass substrate 100 has through holes with a diameter of 20~50μm. Step 2: Cleaning the glass through-hole and activating the hole wall; The glass substrate 100 is placed in an ultrasonic cleaning tank filled with deionized water to remove surface dust and processing debris, and then dried with high-purity nitrogen and placed in a clean and dry environment for later use. The pore wall activation is performed using a box-type plasma device. Before the process, the chamber is evacuated to a vacuum of 0.5~0.9Pa, and an argon-oxygen mixture with a volume ratio of 1:1~2:1 is introduced as the process gas. The power supply is set to 1~3kW. During the process, high-energy plasma particles bombard the hole walls, removing residual organic contaminants while introducing a large number of active hydroxyl groups on the glass surface, thereby improving the wettability and adhesion of the subsequent conductive adhesive. Step 3: Apply conductive adhesive; The coating is performed using an inkjet printer. First, a layer of conductive adhesive (e.g., 2μm thick) is evenly sprayed onto the upper and lower surfaces of the glass substrate 100. Then, the inside of the through holes is sprayed to ensure that the conductive adhesive completely covers the hole walls without any missed areas and that the through holes are filled with conductive adhesive. After the spraying is completed, the glass substrate 100 is left to stand, allowing the conductive adhesive to flow and level naturally under gravity, initially filling the micro gaps in the through holes. Step 4: Fill the conductive holes; After the coating is completed, the substrate is placed in a vacuum chamber and the vacuum is evacuated to ≤100Pa. The pressure is maintained for 5~15 minutes. The pressure difference forces the air bubbles trapped in the through holes to burst and overflow, ensuring that the conductive adhesive completely wets the hole walls. Then, thermosetting is performed to fill the holes: First, preheat at 60~100℃ for 20min~30min to reduce the viscosity of the conductive adhesive by using low temperature to promote the further discharge of residual air bubbles and leveling of the adhesive layer. Then, heat up to 150~160℃ and keep warm for 20~30min to allow the conductive adhesive to complete cross-linking and curing, forming a dense and void-free conductive adhesive filling layer 200 in the through hole. Step 5: CMP flattening; After the conductive adhesive is filled and cured, the glass substrate is subjected to chemical mechanical polishing (CMP) to achieve surface planarization; finally, it is dried with high-purity nitrogen to obtain a glass substrate 100 with a smooth surface and densely filled through holes.

[0040] The process steps in Example 1 are the most streamlined, requiring no complex processes such as electroplating and auxiliary carrier plates. A conductive path can be formed through a single filling and curing process, which significantly reduces equipment investment and manufacturing costs. At the same time, the thermal expansion coefficient of the conductive adhesive can be flexibly adjusted through the filler, resulting in good compatibility with the glass substrate. Furthermore, the curing temperature is low, effectively avoiding glass warping and thermal stress problems caused by high-temperature processes. This makes it particularly suitable for cost-sensitive scenarios where signal rate requirements are not high.

[0041] Considering the varying requirements for conductivity and structural strength of the filler layer in different application scenarios, the coating method of the conductive adhesive can be optimized accordingly. One optimization scheme is to form a thin conductive layer only on the walls of the vias. During operation, an inkjet printer is used to uniformly coat the conductive adhesive on the surface of the glass substrate and the walls of the vias. The coating thickness on the walls of the vias is controlled to be 2μm~10μm. This thickness ensures the continuity of conductivity on the walls of the vias without occupying too much space inside the vias, leaving sufficient margin for subsequent processes.

[0042] See Figures 4 to 8 As shown, the present invention also provides Embodiment 2, which achieves filling based on an optimized scheme of thin coating on the hole wall. The specific steps are as follows: Step 1: Prepare a glass substrate 100. The glass substrate 100 has through holes with a diameter of 20~50μm. Step 2: Cleaning the glass through-hole and activating the hole wall; The glass substrate 100 is placed in an ultrasonic cleaning tank filled with deionized water to remove surface dust and processing debris, and then dried with high-purity nitrogen and placed in a clean and dry environment for later use. The pore wall activation is performed using a box-type plasma device. Before the process, the chamber is evacuated to a vacuum of 0.5~0.9Pa, and an argon-oxygen mixture with a volume ratio of 1:1~2:1 is introduced as the process gas. The power supply is set to 1~3kW. During the process, high-energy plasma particles bombard the hole walls, removing residual organic contaminants while introducing a large number of active hydroxyl groups on the glass surface, thereby improving the wettability and adhesion of the subsequent conductive adhesive. Step 3: Apply conductive adhesive; The coating is performed using an inkjet printer. First, a layer of conductive adhesive is evenly sprayed on the upper and lower surfaces of the glass substrate 100. Then, the inside of the through hole is sprayed to ensure that the conductive adhesive completely covers the hole wall without any missed areas. Only 2μm of the hole wall is sprayed inside the through hole. After the spraying is completed, the glass substrate 100 is left to stand, allowing the conductive adhesive to flow and level naturally under gravity, initially filling the micro gaps in the through holes. Step 4: Fill the conductive holes; The coated glass substrate 100 is placed in a vacuum chamber and evacuated to a vacuum level of ≤100Pa. The pressure is maintained for 5~15 minutes. The pressure difference forces the residual air bubbles trapped in the through hole to break and overflow, ensuring that the conductive adhesive completely wets the surface of the hole wall. Step 5: After vacuuming, the conductive adhesive is subjected to step heat curing. First, it is preheated at 80℃ for 20 minutes to reduce the viscosity of the conductive adhesive and promote the further discharge of residual air bubbles and leveling of the adhesive layer. Then, the temperature is raised to 160℃ and kept for 20~30 minutes to allow the conductive adhesive to complete cross-linking and curing, forming a dense and void-free conductive adhesive filling layer 200 in the through holes. Step 6: After the above process is completed, temporarily bond an auxiliary substrate (either a ceramic substrate or a resin substrate) 300 to the side of the glass substrate opposite to the through hole opening; use temporary bonding adhesive to bond the auxiliary substrate to the glass substrate. Subsequently, a DC electroplating process was used to fill the holes. An acidic sulfate copper plating solution was selected, and the temperature of the electroplating solution was controlled at 25~30℃ and the pH value was 3.5~4.5. A DC current of 1~2A / dm² was applied and electroplating was carried out for 70~90 minutes to allow the metallic copper to be deposited evenly from the bottom of the through hole upwards, gradually filling the space inside the through hole that was not occupied by the conductive adhesive. Step 7: After the hole filling is completed, remove the auxiliary substrate 300, remove the temporary bonding adhesive by heating or chemical dissolution, and separate the auxiliary substrate; after the peeling is completed, clean the glass substrate 100 and blow dry the surface with high-purity nitrogen. Step 8: CMP flattening; Planarization was achieved using chemical mechanical polishing equipment to remove the conductive adhesive from the surface of the glass substrate 100. After polishing, the surface of the glass substrate 100 was rinsed with deionized water to thoroughly remove residual polishing liquid and abrasive debris. Finally, it was dried with high-purity nitrogen gas to obtain a glass substrate with a smooth surface and densely filled through holes.

[0043] This embodiment 2 utilizes conductive adhesive as a pre-placed conductor at the bottom, combined with the physical support of the auxiliary substrate and the full electroplating filling process. Ultimately, the inside of the through hole is completely filled with high-purity copper pillars, exhibiting excellent electrical and thermal conductivity as well as anti-electromigration capabilities. The auxiliary substrate acts as a physical barrier to effectively block the leakage of electroplating solution, while the pre-filling of conductive adhesive improves the electric field distribution within the high aspect ratio through hole, reducing the nucleation difficulty and void risk in deep hole electroplating. It solves the problem that simple electroplating cannot completely fill deep holes, significantly improving process stability and yield, and is suitable for scenarios with high electrical performance requirements.

[0044] Another optimization method involves completely filling the vias with conductive adhesive. This method creates a filling layer with high structural strength, which can be used as an independent conductive interconnect. During operation, an inkjet printer is used to inject sufficient conductive adhesive into the vias until it completely occupies the entire physical space. After filling, micropores can be created in the conductive adhesive layer to provide conductive and electrolyte channels for subsequent electroplating. Micropore fabrication is achieved using a femtosecond laser. Micropores are created in the central region of the conductive adhesive filling layer, and their diameter is smaller than the original via diameter, thus balancing the construction of conductive channels with the preservation of structural strength. The micropores are then filled using a combination of bridging electroplating and via-filling electroplating. For example, in the bridging electroplating stage, a pulse power supply is used, with the forward current density controlled at 0.1~0.3A / dm², the ratio of forward to reverse current time set at 1:3~1:5, and the electroplating time at 3~4 hours. This allows for preferential deposition at the bottom of the micropores, preventing premature closure of the pore openings and the formation of capping defects. In the via-filling electroplating stage, a DC power supply is switched, with the current density set at 1~2A / dm² and the electroplating time at 70~90 minutes. This allows for rapid filling of the remaining pores, balancing filling quality and process efficiency.

[0045] See Figures 9 to 13 As shown, the present invention also provides Embodiment 3, which achieves filling based on an optimized scheme of fully filled conductive adhesive. The specific steps are as follows: Step 1: Prepare a glass substrate 100. The glass substrate 100 has through holes with a diameter of 20~50μm. Step 2: Cleaning the glass through-hole and activating the hole wall; The glass substrate 100 is placed in an ultrasonic cleaning tank filled with deionized water to remove surface dust and processing debris, and then dried with high-purity nitrogen and placed in a clean and dry environment for later use. The pore wall activation is performed using a box-type plasma device. Before the process, the chamber is evacuated to a vacuum of 0.5~0.9Pa, and an argon-oxygen mixture with a volume ratio of 1:1~2:1 is introduced as the process gas. The power supply is set to 1~3kW. During the process, high-energy plasma particles bombard the hole walls, removing residual organic contaminants while introducing a large number of active hydroxyl groups on the glass surface, thereby improving the wettability and adhesion of the subsequent conductive adhesive. Step 3: Apply conductive adhesive; The coating is performed using an inkjet printer. First, a layer of conductive adhesive is evenly sprayed on the upper and lower surfaces of the glass substrate 100. Then, the inside of the through hole is sprayed to ensure that the conductive adhesive completely covers the hole wall without any missed areas. Only 2~10μm of the hole wall is sprayed inside the through hole. After the spraying is completed, the glass substrate 100 is left to stand, allowing the conductive adhesive to flow and level naturally under gravity, initially filling the micro gaps in the through holes. Step 4: Fill the conductive holes; The coated glass substrate is placed in a vacuum chamber and evacuated to a vacuum level of ≤100Pa. The pressure is maintained for 5~15 minutes. The pressure difference forces the residual air bubbles trapped in the through holes to burst and overflow, ensuring that the conductive adhesive completely wets the surface of the hole wall. Step 5: After vacuuming, the conductive adhesive is subjected to step heat curing. First, it is preheated at 60~100℃ for 20min~30min to reduce the viscosity of the conductive adhesive and promote the further discharge of residual air bubbles and leveling of the adhesive layer. Then, the temperature is raised to 150~160℃ and held for 20~30min to allow the conductive adhesive to complete cross-linking and curing, forming a dense and void-free conductive adhesive filling layer 200 in the through hole. Step 6: After the above process is completed, use a femtosecond laser pulse energy of 100~200μJ and a pulse width of 200~800fs. If the femtosecond laser pulse energy is too low (e.g., <100μJ), it cannot effectively remove the conductive adhesive material; if it is too high (e.g., >200μJ), it may damage the glass substrate. If the pulse width exceeds the range of 200~800fs, the heat-affected zone increases, affecting the micro-hole processing accuracy. Using the central axis of the through hole as the positioning reference, process a micro-hole (e.g., 20μm in diameter) at the geometric center of the conductive adhesive filling layer 200. The diameter of this micro-hole is smaller than that of the original through hole, which will not damage the overall structural strength of the filling layer, and can simultaneously construct an electrolyte flow channel and a current conduction path, solving the problem of obstructed electroplating ion transport after full filling of conductive adhesive. Step 7: After the above process is completed, use the bridging + filling electroplating method. The electroplating solution can be an acidic sulfate copper plating solution. During the bridging electroplating stage, the pulse power supply is started, and the forward current density is set to 0.1~0.3A / dm². The ratio of forward energizing time to reverse energizing time is controlled at 1:3~1:5. In the initial stage of energizing, copper ions preferentially deposit on the conductive adhesive filling layer in the center of the micropore. During the reverse energizing period, the excess copper layer deposited at the orifice is directionally dissolved, effectively inhibiting the orifice from being sealed prematurely. Electroplating continues for 3~4 hours until the central plating layer grows to the same diameter as the through hole, forming a blind hole, and there are no abnormal protrusions at the orifice, at which point the bridging electroplating stage ends. Next, the hole-filling electroplating stage is performed: the pulse power supply is turned off, the power mode is switched to DC, the current density is set to 1~2A / dm², and after the power is turned on, copper ions are rapidly and uniformly deposited on the conductive network built in the bridging stage, gradually filling the remaining pores; electroplating continues for 70min~90min, during which the current stability is monitored in real time to ensure uniform deposition rate and no local overheating or burning. Step 8: CMP flattening; Planarization is achieved using chemical mechanical polishing equipment to remove the conductive adhesive on the surface of the glass substrate 100. After polishing, the surface of the glass substrate 100 is rinsed with deionized water to thoroughly remove residual polishing liquid and abrasive debris. Finally, it is dried with high-purity nitrogen gas to obtain a glass substrate 100 with a smooth surface and densely filled through holes.

[0046] This embodiment 3 constructs a composite conductor structure of conductive adhesive sleeve + central copper pillar. It utilizes the outer cured conductive adhesive layer to buffer the difference in thermal expansion coefficients between glass and metal, greatly improving thermal cycling reliability. At the same time, the central electroplated copper pillar ensures the low resistance characteristics of the core conductive path. The laser drilling process is highly precise on the conductive adhesive and does not easily damage the glass substrate, achieving the best balance between electrical performance and thermomechanical reliability. It is particularly suitable for high-end packaging fields that need to withstand extreme temperature changes.

[0047] The glass substrates prepared by the above embodiments have a tight bond between the conductive adhesive filling layer in the through holes and the hole walls, with no void defects, and stable vertical interconnect performance. They can meet the manufacturing needs of various high-precision electronic devices such as 5G communication devices, three-dimensional system-in-package, and MEMS sensors. Moreover, they have a wide process window and strong mass production stability. Compared with traditional electroplating filling processes, they can significantly reduce equipment investment and maintenance costs.

[0048] In addition, the CMP flattening step in this article can be set according to actual needs. For ease of understanding, an example of a feasible solution of the present invention is provided. CMP planarization includes the following steps: First, rough polishing is performed until a copper layer of 2-3 μm remains on the glass surface to prevent the glass surface from being directly impacted by polishing; then, fine polishing is performed to continue removing the remaining copper layer until the glass substrate surface is completely exposed; next, over-polishing is performed to finish the process, using a very short controlled over-polishing process with abrasive-free or low-abrasive polishing fluid to control the copper depression at the via opening to within a range of less than 70-100 nm, ensuring that the surface roughness (Ra) after polishing is less than 0.5 nm and the height difference between the copper surface and the glass surface is less than 5 nm; finally, post-CMP cleaning is performed, which includes the following steps in sequence: megasonic cleaning, PVA brush scrubbing, and SC1 or dilute acid chemical cleaning. Megasonic cleaning is used to physically remove nanoscale abrasive particles, PVA brush scrubbing is used to mechanically remove loose particles on the surface, and SC1 or dilute acid chemical cleaning is used to dissolve residual copper ions and remove organic contaminants, thoroughly removing residual copper ions and polishing abrasive particles, and avoiding copper shavings remaining on the glass surface.

[0049] The present invention also proposes a glass substrate, comprising: a glass substrate body and a conductive adhesive filling layer 200, wherein a through hole is formed on the glass substrate body, the conductive adhesive filling layer 200 is disposed in the through hole, the outer peripheral surface of the conductive adhesive filling layer 200 is tightly attached to the hole wall of the through hole, and the interior of the conductive adhesive filling layer 200 has a dense non-porous structure. This conductive adhesive filling layer 200 can be prepared by the glass through hole filling method described above.

[0050] See Figures 1 to 3 As shown, in some embodiments, the conductive adhesive filling layer 200 fills the internal space of the through hole, and this structure can be prepared by Example 1 above.

[0051] See Figures 4 to 8 As shown, in some other embodiments, the thickness of the conductive adhesive filling layer 200 is 2μm to 10μm, and a metal filling layer is provided on the inner peripheral side of the conductive adhesive filling layer 200. The conductive adhesive filling layer 200 and the metal filling layer fill the internal space of the through hole. This structure can be prepared by Example 2 above.

[0052] See Figures 9 to 13 As shown, in some other embodiments, the conductive adhesive filling layer 200 has micropores with a diameter smaller than that of the through-hole, and the micropores are filled with a metal plating layer. The conductive adhesive filling layer 200 and the metal plating layer fill the internal space of the through-hole. This structure can be prepared by Example 3 above.

[0053] It should be noted that the terminology used above is for describing specific embodiments only and is not intended to limit the exemplary embodiments of the present invention. When the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof. The order of execution of actions, steps, etc., in the apparatus and methods shown in the specification can be implemented in any order unless a specific order is expressly specified, and as long as the output of a previous process is not used in a subsequent process. Similar sequential terms used for ease of description do not imply that such an order must be followed.

[0054] Techniques, methods, and apparatus known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and apparatus should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0055] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for filling glass through-holes, characterized in that, Includes the following steps: Provide a glass substrate with through holes; The through holes are cleaned and the hole walls are activated. Conductive adhesive is placed inside the through hole; Vacuum treatment is performed on the glass substrate with conductive adhesive. The conductive adhesive is thermo-cured to form a conductive adhesive filling layer inside the through hole; The glass substrate is planarized.

2. The glass through-hole filling method according to claim 1, characterized in that, The thermosetting process is a stepped thermosetting process, which includes: preheating at 60~100℃ for 20~30 minutes to remove bubbles and level the surface, and then raising the temperature to 150~160℃ and holding for 20~30 minutes to complete the curing.

3. The glass through-hole filling method according to claim 1, characterized in that, Placing conductive adhesive within the through-hole includes: The conductive adhesive is uniformly coated onto the surface of the glass substrate and the walls of the through holes using an inkjet printer, with the coating thickness on the walls of the through holes being 2μm to 10μm.

4. The glass through-hole filling method according to claim 3, characterized in that, After forming a conductive adhesive filling layer within the through-hole, the method further includes: An auxiliary substrate is bonded to the side of the glass substrate opposite to the through-hole opening; The through holes are filled by electroplating; After the holes are filled, the auxiliary substrate is removed.

5. The glass through-hole filling method according to claim 4, characterized in that, The hole-filling electroplating uses a DC power supply with a current density of 1~2A / dm² and an electroplating time of 70~90min.

6. The glass through-hole filling method according to claim 1, characterized in that, Placing conductive adhesive within the through-hole includes: The conductive adhesive is used to fill the through-holes using an inkjet printer.

7. The glass through-hole filling method according to claim 6, characterized in that, After forming a conductive adhesive filling layer within the through-hole, the method further includes: A femtosecond laser is used to create micropores with a diameter smaller than the through holes in the conductive adhesive filler layer; The micropores are electroplated and filled using a combination of bridging electroplating and hole-filling electroplating.

8. The glass through-hole filling method according to claim 7, characterized in that, The femtosecond laser has a pulse energy of 100~200μJ and a pulse width of 200~800fs; The bridging electroplating uses a pulse power supply with a forward current density of 0.1~0.3A / dm², a forward to reverse current-time ratio of 1:3~1:5, and an electroplating time of 3~4h. The hole-filling electroplating uses a DC power supply with a current density of 1~2A / dm² and an electroplating time of 70~90min.

9. The glass through-hole filling method according to claim 1, characterized in that, The pore wall activation treatment is plasma treatment, and the process parameters are as follows: a box-type plasma device is used, the vacuum degree is 0.5~0.9Pa, an argon-oxygen mixture is introduced, the power is 1~3kW, and the treatment time is 1~3min.

10. The glass through-hole filling method according to any one of claims 1 to 9, characterized in that, The diameter of the through hole is 20~50μm, and the aspect ratio is ≥10:

1.

11. The glass through-hole filling method according to any one of claims 1 to 9, characterized in that, The conductive adhesive is a copper-based conductive adhesive.

12. A glass substrate, characterized in that, include: A glass substrate body, wherein through holes are formed on the glass substrate body; A conductive adhesive filling layer is disposed within the through hole. The outer peripheral surface of the conductive adhesive filling layer is tightly fitted to the hole wall of the through hole, and the interior of the conductive adhesive filling layer has a dense, non-porous structure.

13. The glass substrate according to claim 12, characterized in that, The conductive adhesive filler layer fills the internal space of the through hole.

14. The glass substrate according to claim 12, characterized in that, The thickness of the conductive adhesive filling layer is 2μm~10μm, and a metal filling layer is provided on the inner peripheral side of the conductive adhesive filling layer. The conductive adhesive filling layer and the metal filling layer fill the internal space of the through hole.

15. The glass substrate according to claim 12, characterized in that, The conductive adhesive filling layer has micropores with a diameter smaller than that of the through hole, and the micropores are filled with a metal plating layer. The conductive adhesive filling layer and the metal plating layer fill the internal space of the through hole.

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