Conductive silver paste, glass via substrate and method of making same

Abstract

The application belongs to the technical field of conductive silver paste, and relates to a conductive silver paste, a glass via substrate and a preparation method thereof. The conductive silver paste comprises silver powder and siloxane modified epoxy resin. The glass via substrate comprises a glass substrate and a conductive column, the glass substrate comprises a via penetrating in the thickness direction of the glass substrate; the conductive column is filled in the via, and the components of the conductive column comprise silver powder and siloxane modified epoxy resin. The application solves the problem of CTE mismatch cracking between the conductive silver paste and the glass substrate.

Description

Technical Field

[0001] This application relates to the field of conductive silver paste technology, specifically to a conductive silver paste, a glass through-hole substrate, and a method for preparing the same. Background Technology

[0002] With its advantages of high flatness, low dielectric loss, and high dimensional stability, glass through-hole substrates are gradually replacing traditional FR-4 type printed circuit boards (FR-4PCBs) and becoming the core integrated interconnect component for high-density interconnection in the consumer electronics field.

[0003] Glass through-hole substrates use high-purity glass (such as quartz glass, borosilicate glass, etc.) as the core substrate. Vertical through-holes (TGV) are created inside the glass substrate using micro-hole processing technology. By filling with conductive media (silver pillars, electroplated copper, etc.) and precise wiring on the surface, glass-based printed circuit boards can achieve three-dimensional electrical signal conduction in the vertical (Z-axis) and horizontal (XY-axis) directions.

[0004] Silver pillars are typically obtained by curing low-temperature conductive silver paste. Due to the low process temperature, the absence of high-temperature sintering, and compatibility with heat-sensitive devices, low-temperature conductive silver paste has become the mainstream conductive medium for silver pillars.

[0005] The silver pillars fill the through-holes in the glass substrate and are microscopically composed of an epoxy resin matrix and metallic silver. The coefficient of thermal expansion (CTE) of epoxy resin is 50ppm / ℃ to 80ppm / ℃, the CTE of silver is about 19ppm / ℃, and the CTE of the glass substrate is only 3.3ppm / ℃. The huge difference in CTE among the three will generate strong interfacial thermal stress during thermal cycling, causing the silver pillars to delaminate and detach from the glass hole walls, and even inducing microcracks in the glass hole walls, which seriously restricts the long-term reliability of the product. Summary of the Invention

[0006] This application addresses the aforementioned issues and aims to provide a conductive silver paste, a glass through-hole substrate, and a method for preparing the same. It solves the problem of CTE mismatch and cracking between the conductive silver paste and the glass substrate.

[0007] To achieve the above objectives, this application provides the following technical solution.

[0008] The first aspect of this application discloses a conductive silver paste, which includes silver powder and siloxane-modified epoxy resin.

[0009] In some embodiments, the siloxane-modified epoxy resin includes an epoxy resin backbone and trimethoxysiloxane groups grafted onto the active sites of the epoxy resin backbone; the molar percentage of the trimethoxysiloxane groups is 10% to 20% based on the total number of molars of active sites on the epoxy resin backbone.

[0010] In some embodiments, the silver powder satisfies at least one of the following: (1) the silver powder comprises main phase silver powder and nano silver powder, wherein the volume average particle size D of the main phase silver powder is... V50 The volume average particle size D of the silver nanoparticles ranges from 2 μm to 3 μm. V50 (1) The mass ratio of the main phase silver powder to the nano silver powder is 50 nm to 100 nm; (2) The mass ratio of the main phase silver powder to the nano silver powder is 5.67 to 11.5; (3) The sphericity of the main phase silver powder is greater than or equal to 95%.

[0011] In some embodiments, the conductive silver paste further includes at least one of cellulose acetate butyrate resin, a curing agent, and a toughening agent.

[0012] In some embodiments, the silver powder accounts for 70% to 78% of the mass of the conductive silver paste; the cellulose acetate butyrate resin accounts for 1% to 2% of the mass of the conductive silver paste; and the curing agent includes phthalic anhydride, accounting for 1% to 3% of the mass of the conductive silver paste.

[0013] In some embodiments, the toughening agent satisfies at least one of the following: (1) the toughening agent comprises organosilicon microspheres with at least a portion of their surface having an epoxy coating; (2) the average particle size of the organosilicon microspheres is 1 μm to 2 μm; and (3) the organosilicon microspheres account for 1% to 3% of the mass of the conductive silver paste.

[0014] In some embodiments, the conductive silver paste further includes a first organic solvent with a boiling point of 180°C to 200°C and a second organic solvent with a boiling point of 250°C to 300°C, wherein the mass ratio of the first organic solvent to the second organic solvent is 1:(2 to 3).

[0015] In some embodiments, the conductive silver paste satisfies at least one of the following: (1) the thixotropic index of the conductive silver paste is 3.0 to 4.0; (2) the high shear apparent viscosity of the conductive silver paste is 10 Pa. s to 20Pa s; (3) The low shear apparent viscosity of the conductive silver paste is 40 Pa. s to 80Pa s.

[0016] A second aspect of this application discloses a glass through-hole substrate, comprising a glass substrate and conductive pillars. The glass substrate includes through-holes extending through its thickness direction. The conductive pillars are filled within the through-holes, and the components used in the conductive pillars include silver powder and siloxane-modified epoxy resin. The thickness from the central axis of the conductive pillar to its outer surface is denoted as H. The region within a thickness range of 0.1H from the center is denoted as a first region of the conductive pillar, and the region within a thickness range of 0.1H from the outer surface is denoted as a second region of the conductive pillar. The mass percentage of silver powder in the first region is greater than that in the second region. The mass percentage of siloxane-modified epoxy resin in the second region is greater than that in the first region.

[0017] The third aspect of this application discloses a method for preparing a glass through-hole substrate, comprising the following steps: S1, filling conductive silver paste into the through-hole of a glass substrate to obtain a filled glass substrate, wherein the conductive silver paste includes silver powder, siloxane-modified epoxy resin and solvent; S2, fixing the filled glass substrate in a centrifuge for centrifugation treatment, so that the siloxane-modified epoxy resin contained in the conductive silver paste migrates towards the inner wall of the through-hole, and the silver powder contained in the conductive silver paste migrates towards the central axis of the through-hole, thereby obtaining an intermediate; S3, heating the intermediate to solidify the conductive silver paste, thereby obtaining a glass through-hole substrate.

[0018] This application has the following effects: The silver powder in the conductive silver paste of this application can overlap to form a continuous conductive path, giving the cured / sintered conductive silver paste low resistance and achieving electrical conductivity. The siloxane-modified epoxy resin has better flowability. When the conductive silver paste is filled into the through-holes of the glass substrate, under the action of centrifugal force, the siloxane-modified epoxy resin preferentially spreads on the surface of the through-holes compared to the silver powder. Furthermore, the siloxane-modified epoxy resin enriches on the surface of the through-holes and forms hydrogen bonds with the silanol groups on the surface of the through-holes, further enhancing the bonding strength between the cured conductive silver paste and the glass substrate. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of a glass through-hole substrate provided in one embodiment of this application.

[0020] Figure 2 yes Figure 1 A schematic diagram of the through-hole.

[0021] Explanation of reference numerals in the attached figures 1. Glass through-hole substrate; 2. Through-hole. Detailed Implementation

[0022] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of a conductive silver paste, a glass via substrate, and a method for preparing the same, according to this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of essentially identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0023] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0024] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0025] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0026] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0027] Unless otherwise specified, the terms used in this application have the common meanings as commonly understood by those skilled in the art.

[0028] Unless otherwise specified, the values ​​of the parameters mentioned in this application can be determined using various testing methods commonly used in the art, for example, according to the testing methods given in this application.

[0029] To address these issues, existing industry solutions mainly fall into two categories: The first is a formulation modification approach, which involves adding toughening phases such as silicone elastic powder and rubber particles to the conductive silver paste to absorb thermal stress through elastic deformation. However, in this approach, the elastic particles are dispersed phases, resulting in uneven stress absorption, and the insulating particles can disrupt the conductive path, leading to increased resistivity. Furthermore, the particles are prone to interfacial debonding with the resin matrix, becoming new stress concentration sources and limiting long-term reliability improvements. The second approach is an additional filling approach, which involves filling the hole walls with an organic buffer layer such as PI (polyimide) or phenelzine before filling the conductive silver paste. This approach offers excellent buffering performance, but requires additional filling, curing, and etching processes, significantly increasing process complexity and cost. Moreover, a clear heterogeneous interface still exists between the buffer layer and the silver pillars, posing a risk of delamination under long-term thermal cycling.

[0030] Currently, there is no technical solution that can fundamentally solve the CTE mismatch and cracking problem between low-temperature TGV silver paste and glass substrate without adding new processes or significantly losing conductivity. This is also one of the core bottlenecks for the large-scale deployment of consumer electronics-grade glass-based circuits.

[0031] The first aspect of this application provides a conductive silver paste comprising silver powder and a siloxane-modified epoxy resin. The silver powder in the conductive silver paste can interlock to form continuous conductive pathways, resulting in low resistance and electrical conductivity after curing / sintering. The siloxane-modified epoxy resin has better flowability. When the conductive silver paste is filled into the through-holes 2 of a glass substrate, under centrifugal force, the siloxane-modified epoxy resin preferentially spreads on the surface of the through-holes 2 compared to the silver powder. Furthermore, the siloxane-modified epoxy resin accumulates on the surface of the through-holes 2, forming hydrogen bonds with the silanol groups on the surface of the through-holes 2, further enhancing the bonding strength between the cured conductive silver paste and the glass substrate.

[0032] In some embodiments, the siloxane-modified epoxy resin includes an epoxy resin backbone and trimethoxysiloxane groups grafted onto the active sites of the epoxy resin backbone. The trimethoxysiloxane groups can form hydrogen bonds with the silanol groups on the through-hole 2, improving the bonding strength between the conductive silver paste and the glass substrate, thereby preventing the conductive silver paste from falling off.

[0033] In some embodiments, the molar percentage of trimethoxysiloxane groups is 10% to 30% based on the total number of molar active sites on the epoxy resin backbone.

[0034] The term "molar percentage" mentioned in this article refers to the proportion of a certain component in a mixture, and the calculation formula is: (number of moles of a certain substance / total number of moles of all substances) × 100%.

[0035] In this application, the molar percentage of trimethoxysiloxane groups can be 10%, 15%, 20%, 25%, 30%, or any value between two of these. Preferably, it can be 10% to 20%. If the molar percentage of trimethoxysiloxane groups is less than 10%, the total number of trimethoxysiloxane groups decreases, resulting in fewer hydrogen bonds, fewer interfacial bonding points, and weaker bonding strength. If the molar percentage of trimethoxysiloxane groups is greater than 30%, although the siloxane-modified epoxy resin has sufficient trimethoxysiloxane groups, excessive grafting of trimethoxysiloxane groups into the epoxy resin will also lead to poorer skeletal stability of the epoxy resin and increased raw material costs. Therefore, a molar percentage of trimethoxysiloxane groups within the above range ensures sufficient bonding strength between siloxane-modified epoxy resins and sufficient stability of the epoxy resin skeleton.

[0036] In some embodiments, the silver powder comprises a main phase silver powder and nano-silver powder, wherein the volume average particle size D of the main phase silver powder is... V50 The volume average particle size D of the silver nanoparticles ranges from 2 μm to 3 μm. V50 The wavelength range is 50nm to 100nm. The silver powder employs a gradation of main phase silver powder and nano-silver powder, using micron-sized main phase silver powder. This ensures that the main phase silver powder has sufficient inertial migration effect compared to the nano-silver powder during centrifugation, resulting in it remaining more in the central region of the conductive pillar (the conductive pillar will be discussed later). The nano-silver powder is lighter and, flowing with the siloxane-modified epoxy resin, can fill the interparticle gaps in the central region of the conductive pillar, increasing the density of the central region.

[0037] The term "primary phase silver powder" mentioned in this article refers to the silver powder with the highest mass content in the slurry, which undertakes the core conductive function, and is called primary phase silver powder.

[0038] The term "D" mentioned in this article V50 "" refers to the average particle size of the powder as a volumetric metric, and is the most critical quality control parameter for silver powder particle size.

[0039] In this application, the volume average particle size D of the main phase silver powder is... V50The particle size can be 2 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm, 2.9 μm, 3 μm, or any value between two of these. The volume average particle size D of the main phase silver powder. V50 Within the aforementioned range, the main phase silver powder can have sufficient inertia, thereby ensuring that most of the main phase silver powder will not flow to the through hole 2 along with the siloxane-modified epoxy resin.

[0040] In this application, the volume average particle size D of the nano-silver powder is... V50 The value can be 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, or any value between two of these. The volume average particle size D of the silver nanoparticles... V50 Within the aforementioned range, the nano-silver powder can fill the interparticle gaps in the central region of the conductive pillar as the siloxane-modified epoxy resin flows, thereby increasing the density of the central region of the conductive pillar.

[0041] In some embodiments, the mass ratio of the main phase silver powder to the nano-silver powder is 5.67 to 11.5; the mass ratio can be 5.67, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 11.5, or any value between two of these. A mass ratio of the main phase silver powder to the nano-silver powder within the above range ensures that the silver powder possesses sufficient inertia while also increasing the density of the central region of the conductive pillar.

[0042] In some implementations, the sphericity of the main phase silver powder is greater than or equal to 95%.

[0043] The term "sphericity" mentioned in this article refers to a dimensionless shape factor that characterizes the degree to which the geometry of a particle approaches a perfect sphere. It is equal to the surface area of ​​an ideal sphere of the same volume as the particle, divided by the actual external surface area of ​​the particle itself.

[0044] In this application, the sphericity of the main phase silver powder can be greater than or equal to 95%. When the sphericity of the main phase silver powder is within the above range, the surface of the main phase silver powder has sufficient smoothness. Under the action of centrifugal force, the main phase silver powder has sufficient inertial migration effect, and the silver powder is more concentrated and aggregated in the central region of the conductive pillar.

[0045] In some embodiments, the conductive silver paste further includes at least one of cellulose acetate butyrate resin, a curing agent, and a toughening agent. In this application, cellulose acetate butyrate coats flake silver powder, which spreads and arranges itself as the conductive silver paste flows. The curing agent may include dicyandiamide-based curing agents, anhydride-based curing agents, or microencapsulated curing agents, specifically phthalic anhydride. This type of curing agent maintains the stability of the paste at room temperature and, upon heating, crosslinks and cures with siloxane-modified epoxy resin, improving the adhesion of the conductive silver paste. The toughening agent introduces flexible segments after curing, enhancing the surface flexibility of the conductive silver paste, improving its bending resistance, and allowing it to better absorb thermal stress through elastic deformation.

[0046] In some embodiments, the mass percentage of silver powder is 70% to 78% based on the mass of the conductive silver paste. The mass percentage of silver powder can be 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, or any value between two of these ranges. A silver powder mass percentage within the above range is considered appropriate, allowing the conductive pillars to balance conductivity and high density.

[0047] In some embodiments, the mass percentage of cellulose acetate butyrate resin, based on the mass of the conductive silver paste, is 1% to 2%. This mass percentage can be 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, or any value between these two ranges. Maintaining the mass percentage of cellulose acetate butyrate resin within this range allows the resin to effectively coat the sheet-like silver powder while ensuring that excessive silver powder does not accumulate on the through-holes 2.

[0048] In some embodiments, the curing agent accounts for 1% to 3% of the mass of the conductive silver paste. The curing agent mass percentage can be 1%, 1.5%, 2%, 2.5%, 3%, or any value between these two ranges. Within this range, the curing agent can balance the resistivity of the conductive silver paste with its adhesion to the via 2.

[0049] In some embodiments, the toughening agent comprises silicone microspheres with at least a portion of their surface coated with an epoxy layer. The silicone microspheres improve the toughness of the conductive silver paste by relying on the good compatibility of the outer shell with the siloxane-modified epoxy resin and the internal silicon core buffering the curing stress. The mass percentage of the silicone microspheres, based on the mass of the conductive silver paste, can be 1%, 1.5%, 2%, 2.5%, 3%, or any value within a range of two. Within the above range, the silicone microspheres, as a toughening agent, can impart a certain degree of toughness to the conductive silver paste, allowing it to absorb thermal stress through elastic deformation.

[0050] In some embodiments, the average particle size of the silicone microspheres is between 1 μm and 2 μm; the average particle size of the silicone microspheres can be 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2 μm, or any value between the two. An average particle size of silicone microspheres within the above range allows for better dispersion in the conductive silver paste, thereby improving the toughness of the conductive silver paste.

[0051] In some embodiments, the conductive silver paste further includes a first organic solvent with a boiling point of 180°C to 200°C and a second organic solvent with a boiling point of 250°C to 300°C. The first organic solvent may include an alcohol ether solvent, which may include dipropylene glycol monomethyl ether (DPM). The second organic solvent may include an alcohol ether ester solvent, which may include ethylene glycol butyl ether acetate and diethylene glycol butyl ether acetate. The solvents are a blend of high and low boiling points. The first organic solvent (low-boiling-point solvent) assists in moderate thickening and shaping during centrifugation, while the second organic solvent (high-boiling-point solvent) ensures the fluidity of the conductive silver paste during filling, preventing rapid solvent evaporation that could lead to voids.

[0052] In this application, the boiling point of the first organic solvent can be 180°C, 182°C, 184°C, 186°C, 188°C, 190°C, 192°C, 194°C, 196°C, 198°C, 200°C, or any value between two of these. Since the boiling point of the first organic solvent is within the above range, it can volatilize at low temperatures, thus allowing for appropriate thickening and shaping of the conductive silver paste.

[0053] In this application, the boiling point of the second organic solvent can be 250°C, 255°C, 260°C, 265°C, 270°C, 275°C, 280°C, 285°C, 290°C, 295°C, 300°C, or any value between two of these. The boiling point of the second organic solvent being within the above range ensures sufficient fluidity of the conductive silver paste during the filling process, preventing rapid evaporation of the solvent as the temperature rises, which could lead to voids.

[0054] In this application, the mass ratio of the first organic solvent to the second organic solvent is 1:(2 to 3). The mass ratio of the first organic solvent to the second organic solvent can be 1:2, 1:2.1, 1:2.2, 1:2.3, 1:2.4, 1:2.5, 1:2.6, 1:2.7, 1:2.8, 1:2.9, 1:3, or any value within a range of both. A mass ratio of the first organic solvent to the second organic solvent within the above range allows the solvent to achieve both thickening and shaping properties as well as fluidity. For example, the first solvent can be diethylene glycol butyl ether, and the second solvent can be diethylene glycol butyl ether acetate.

[0055] In some embodiments, the conductive silver paste has a thixotropic index of 3.0 to 4.0. The thixotropic index can be 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, or any value between these ranges. A thixotropic index within this range allows the conductive silver paste to possess suitable viscosity and flowability.

[0056] The term "thixotropic index" (TI) mentioned in this article, also known in the industry as the shear-thinning index, is a dimensionless parameter that quantitatively characterizes the strength of shear-thinning in non-Newtonian fluids; it is equal to the apparent viscosity at low shear rates divided by the apparent viscosity at high shear rates.

[0057] In this application, the thixotropic index, high shear apparent viscosity, and high shear apparent viscosity can all be measured with reference to GB / T17473-2025 "Test Methods for Performance of Electronic Pastes".

[0058] In some embodiments, the conductive silver paste satisfies a high shear apparent viscosity of 10 Pa. s to 20Pa s; Low shear apparent viscosity is 40 Pa s to 80Pa The high shear apparent viscosity can be 10 Pa. s, 11Pa s, 12Pa s, 13Pa s, 14Pa s, 15Pa s, 16Pa s, 17Pa s, 18Pa s, 19Pa s, 20Pa The value is s or any value between the two. High shear apparent viscosity within the above range allows conductive silver paste to possess suitable flowability.

[0059] The term "high shear apparent viscosity" mentioned in this article refers to the apparent viscosity of the slurry measured under high shear rate / high rotation speed conditions, corresponding to the stress state during screen printing and high-speed stirring.

[0060] In some embodiments, the conductive silver paste satisfies a low shear apparent viscosity of 40 Pa. s to 80Pa The low shear apparent viscosity can be 40 Pa. s, 50Pa s, 60Pa s, 70Pa s, 80Pa The value of s or any value between the two can give the conductive silver paste a suitable viscosity.

[0061] The term "low shear apparent viscosity" mentioned in this article refers to the apparent viscosity of the slurry measured under extremely low shear rate / low rotation speed conditions, corresponding to the rheological state of the slurry during static storage, printing stoppage, and wet film formation stages.

[0062] like Figure 1 and Figure 2 As shown, a second aspect of this application provides a glass through-hole substrate 1, including a glass substrate, conductive pillars, a first region, and a second region. The glass substrate includes a through-hole 2 extending through its thickness direction. The conductive pillars are filled within the through-hole 2, and the conductive pillars are composed of silver powder and siloxane-modified epoxy resin. The thickness from the central axis of the conductive pillar to its outer surface is denoted as H. The region within a thickness range of 0.1H from the center is denoted as the first region of the conductive pillar, and the region within a thickness range of 0.1H from the outer surface is denoted as the second region of the conductive pillar. The mass percentage of silver powder in the first region is greater than that in the second region. The mass percentage of siloxane-modified epoxy resin in the second region is greater than that in the first region.

[0063] The term "first region" mentioned in this article refers to the region inside the through hole 2 that is close to the center of the conductive post. The entire region is 1 / 10 of the distance from the central axis of the conductive post to the outer surface of the inner wall of the through hole 2.

[0064] The term "second region" mentioned in this article refers to the region inside the through hole 2 that is close to the inner wall of the through hole 2. The entire region is 9 / 10 of the distance from the central axis of the conductive post to the outer surface of the inner wall of the through hole 2.

[0065] In this application, the conductive silver paste, after curing and sintering, forms conductive pillars, which can prevent electrode short circuits and leakage, and can also form strong hydrogen bonds with the conductive pillars. Near the inner wall of the through-hole 2, siloxane-modified epoxy resin accumulates to form a buffer layer, while silver powder accumulates in the center of the through-hole 2 to form the conductive pillars. The two are in a continuous transition without a clear interface, simultaneously achieving stress buffering and high conductivity. Due to the inertial lift force within the through-hole 2, the silver powder spontaneously accumulates towards the center of the conductive pillars, ultimately forming a radial concentration gradient with a high concentration of silver powder in the center and a low concentration near the inner wall of the hole. This gradient, together with the siloxane-modified resin layer enriched on the wall surface, constitutes a continuous gradient structure. Since most of the siloxane-modified resin is bonded to the glass surface, most of the siloxane-modified epoxy resin will be in the second region.

[0066] A third aspect of this application provides a method for preparing a glass through-hole substrate 1, comprising the following steps: S1, filling conductive silver paste into the through-hole 2 of a glass substrate to obtain a filled glass substrate, wherein the conductive silver paste includes silver powder, siloxane-modified epoxy resin and solvent; S2, fixing the filled glass substrate in a centrifuge for centrifugation (using a two-stage centrifugation process, the first stage centrifugation speed is 1000 rpm to 1500 rpm, the first stage centrifugation time is 30 s to 60 s; the second stage centrifugation speed is 2500 rpm to 3000 rpm, the second stage centrifugation time is 30 s to 60 s), so that the siloxane-modified epoxy resin contained in the conductive silver paste migrates towards the inner wall of the through-hole 2, and the silver powder contained in the conductive silver paste migrates towards the central axis of the through-hole 2, to obtain an intermediate; S3, subjecting the intermediate to heat treatment (pre-curing temperature 80℃ to 100℃, pre-curing time 10 s). The process involves curing the conductive silver paste from 180°C to 20°C for 30 to 60 minutes, followed by a complete curing temperature of 180°C to 200°C and a complete curing time of 30 to 60 minutes, to obtain a glass through-hole substrate 1.

[0067] Example The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0068] Example 1 1. Preparation of conductive silver paste (1) Weigh each raw material according to the total mass percentage, and the proportion is as follows: 72.5% graded spherical silver powder, 11.5% siloxane modified epoxy resin, 1% cellulose acetate butyrate, 2% curing agent (phthalic anhydride), 8% composite solvent, 3% functional additives, and 2% epoxy-coated organosilicon microspheres.

[0069] Based on the total molar number of active sites in the epoxy resin skeleton, the trimethoxysiloxane group accounts for 20% of the molar percentage; the silver powder is a composite of main phase silver powder and nano silver powder, with the main phase silver powder D... V50 =2.5μm, nano silver powder D V50 =80nm, the mass ratio of main phase silver powder to nano silver powder is 9:1, and the sphericity of the main phase silver is 96%; the toughening agent is epoxy-coated organosilicon microspheres with an average particle size of 1.5μm; the composite solvent is diethylene glycol butyl ether (first organic solvent) and diethylene glycol butyl ether acetate (second organic solvent), with a mass ratio of 1:2.5; the functional additives include 1.2% dispersant, 0.5% defoamer, 0.8% leveling agent, and 0.5% adhesion promoter.

[0070] (2) Mix siloxane-modified epoxy resin, cellulose acetate butyrate resin, curing agent, composite solvent and organosilicon microspheres, and stir and dissolve them at a constant temperature to obtain a uniform resin base.

[0071] (3) The graded silver powder is slowly added to the resin base in multiple batches and pre-dispersed at low speed for 45 minutes to eliminate powder agglomeration and obtain premixed slurry.

[0072] (4) The premixed slurry is fed into a three-roll mill and ground to a fineness of ≤4μm. Then, it is degassed under vacuum at room temperature until there are no obvious bubbles in the slurry, thus obtaining conductive silver paste.

[0073] 2. Fabrication of glass through-hole substrate 1 S1. Apply the above-mentioned conductive silver paste evenly to the surface of the glass substrate with through holes 2, so that the conductive silver paste completely fills the through holes 2 that penetrate the thickness direction of the glass substrate, and obtain the glass substrate after filling.

[0074] S2. The glass substrate after filling is fixed horizontally in a centrifuge and centrifuged in two stages: 1200 rpm for 40 seconds and 2800 rpm for 40 seconds. During the centrifugation process, the components migrate by gravity difference. The siloxane-modified epoxy resin migrates and accumulates to the inner wall of the through hole 2 (second region), and the silver powder accumulates to the central axis of the through hole 2 (first region), thus producing a fractionated intermediate.

[0075] S3. Segmented stepwise heating and curing of intermediates: First, pre-curing at 90℃ for 15 minutes to lock the radial component gradient formed by centrifugation, then heating to 200℃ and holding for 40 minutes to complete cross-linking and curing, and then cooling to obtain the target glass through-hole substrate 1.

[0076] Examples 2 to 4 Examples 2 to 4 were prepared using the same method as Example 1 to prepare conductive silver paste. The difference was that the component mass ratio in Table 1-1 was used. The method for preparing glass through-hole substrate 1 was the same as that in Example 1. The test results are shown in Table 1-2.

[0077] Comparative Example 1 Comparative Example 1 and Example 1 used the same method to prepare conductive silver paste, the difference being that Comparative Example 1 only replaced the siloxane-modified epoxy resin with ordinary bisphenol A epoxy resin and silane coupling agent (KH-560). The ordinary bisphenol A epoxy resin accounted for 11% of the mass, and the silane coupling agent accounted for 0.5% of the mass, totaling 11.5%. The method for preparing the glass through-hole substrate 1 was the same as that in Example 1. The test results are shown in Tables 1-2.

[0078] Table 1-1

[0079] Table 1-2

[0080] As shown in Examples 1 to 4, all examples employed siloxane-modified epoxy resin combined with a two-stage centrifugal process, resulting in a continuous and uniform gradient buffer layer within the through-hole 2. After 1000 cycles of thermal cycling from -40℃ to 125℃, the delamination rate remained ≤1.6% for all cycles, and the resistivity was stably maintained at 13.7 μΩ. cm to 14.9μΩ Within a 1 cm range, both conductivity and resistance to thermal cracking are considered. The addition of silicone microspheres (toughening agent) forms a dual crack-resistant system of a continuous buffer layer and micro-elastic particles, improving initial hole wall pull-out strength and delamination rate after 1000 thermal cycles. Therefore, the bonding strength between the cured conductive silver paste and the glass substrate can be further enhanced.

[0081] As can be seen from Example 1 and Comparative Example 1, even with the same centrifugation process, the improvement of ordinary epoxy resin combined with silane coupling agent is limited due to the weak adsorption of the resin to glass and poor silver powder migration. The "siloxane-modified epoxy resin" in Example 1 provides better chemical bonding with the glass substrate (reaction of silanol groups with glass) and toughness buffering.

[0082] Examples 5 to 9 Examples 5 to 9 were prepared using the same method as Example 1 to prepare conductive silver paste, except that the component ratios in Table 2-1 were used. The method for preparing the glass through-hole substrate 1 was the same as that in Example 1, and the test results are shown in Table 2-1.

[0083] Table 2-1

[0084] Table 2-2

[0085] As shown in Examples 1, 5 to 9, adjusting only the proportions in Table 2-1 can create a continuous and uniform gradient structure. The ratio range of the main phase silver powder to nano-silver ensures normal centrifugal migration of the silver powder. When the proportion of nano-silver powder exceeds 10%, the fine particles have weak inertia, poor migration effect, increased resistivity, and a significant increase in delamination rate. A silver powder gradation within a reasonable range can balance conductivity and crack resistance. A moderate proportion of siloxane groups can optimize interfacial bonding.

[0086] Examples 10 to 13 Examples 10 to 13 use the same method as Example 1 to prepare conductive silver paste. The difference in the method for preparing glass through-hole substrate 1 is that the preparation process in Table 3-1 is used. The test results are shown in Table 3-2.

[0087] Comparative Example 2 Comparative Example 2 and Example 1 used the same method to prepare conductive silver paste. The difference in the method for preparing glass through-hole substrate 1 was that vacuum coating was used instead of the two-stage centrifugal process. The test results are shown in Table 3-2.

[0088] Table 3-1

[0089] Results in Table 3-2

[0090] As shown in Examples 1, 10 to 13, the two-stage centrifugation process allows for more complete wall-laying of the siloxane-modified epoxy resin and aggregation of silver powder, resulting in a more uniform buffer layer and better initial pore wall pull-out strength compared to single-stage centrifugation. The low-temperature pre-curing step stabilizes the gradient structure and reduces delamination. The two-stage centrifugation process and stepped curing are key processes for ensuring the stability of the gradient structure.

[0091] As shown in Example 1 and Comparative Example 2, although the silver powder and siloxane-modified epoxy resin in the pores of Comparative Example 2 are uniformly mixed, there is no radial gradient structure, and the delamination rate during thermal cycling reaches 37.6%. Therefore, traditional pore-filling processes such as vacuum coating lack the driving force for graded layering and cannot form a uniform gradient buffer layer, resulting in poor reliability during thermal cycling. The two-stage centrifugal process can form a gradient buffer structure and improve crack resistance reliability.

[0092] As shown in Examples 1 to 13, a buffer layer is formed by the enrichment of siloxane-modified epoxy resin near the inner wall of the through-hole 2, while a conductive pillar is formed by the enrichment of silver powder in the center of the through-hole 2. The two are in a continuous transition without a clear interface, achieving both stress buffering and high conductivity. Due to the inertia of the silver powder in the conductive silver paste, it spontaneously accumulates towards the central region of the through-hole 2, ultimately forming a radial concentration gradient with a high concentration of silver powder in the center of the through-hole 2 and a low concentration of silver powder near the inner wall of the hole. This gradient, together with the siloxane-modified resin layer enriched on the wall surface, constitutes a continuous gradient structure. Since most of the siloxane-modified resin is bonded to the surface of the glass through-hole substrate 1, most of the siloxane-modified epoxy resin is in the second region.

[0093] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A conductive silver paste, characterized in that, The conductive silver paste comprises silver powder and siloxane-modified epoxy resin.

2. The conductive silver paste according to claim 1, characterized in that, The siloxane-modified epoxy resin includes an epoxy resin backbone and trimethoxysiloxane groups grafted onto the active sites of the epoxy resin backbone. The molar percentage of the trimethoxysiloxane group is 10% to 30% based on the total number of molar active sites on the epoxy resin backbone.

3. The conductive silver paste according to claim 1, characterized in that, The silver powder satisfies at least one of the following: (1) The silver powder comprises main phase silver powder and nano silver powder, wherein the volume average particle size D of the main phase silver powder is V50 The volume average particle size D of the silver nanoparticles is 2 μm to 3 μm. V50 The range is from 50nm to 100nm; (2) The mass ratio of the main phase silver powder to the nano silver powder is 5.67 to 11.5; (3) The sphericity of the main phase silver powder is greater than or equal to 95%.

4. The conductive silver paste according to claim 1, characterized in that, The conductive silver paste also includes at least one of cellulose acetate butyrate resin, curing agent, and toughening agent.

5. The conductive silver paste according to claim 4, characterized in that, The silver powder accounts for 70% to 78% of the mass of the conductive silver paste; and / or The cellulose acetate butyrate resin accounts for 1% to 2% of the mass of the conductive silver paste; and / or Based on the mass of the conductive silver paste, the curing agent includes phthalic anhydride, and the phthalic anhydride accounts for 1% to 3% of the mass.

6. The conductive silver paste according to claim 4, characterized in that, The toughening agent satisfies at least one of the following: (1) The toughening agent includes organosilicon microspheres with at least a portion of their surface having an epoxy coating; (2) The average particle size of the organosilicon microspheres is 1 μm to 2 μm; (3) The mass percentage of the organosilicon microspheres is 1% to 3% based on the mass of the conductive silver paste.

7. The conductive silver paste according to claim 1, characterized in that, The conductive silver paste further includes a first organic solvent with a boiling point of 180°C to 200°C and a second organic solvent with a boiling point of 250°C to 300°C, wherein the mass ratio of the first organic solvent to the second organic solvent is 1:(2 to 3).

8. The conductive silver paste according to claim 1, characterized in that, The conductive silver paste satisfies at least one of the following: (1) The thixotropic index of the conductive silver paste is 3.0 to 4.0; (2) The high shear apparent viscosity of the conductive silver paste is 10 Pa. s to 20Pa s; (3) The low shear apparent viscosity of the conductive silver paste is 40 Pa. s to 80Pa s.

9. A glass through-hole substrate, characterized in that, include: A glass substrate, the glass substrate including a through hole extending through its thickness direction; A conductive pillar, which fills the through hole, and the components used in the conductive pillar include silver powder and siloxane-modified epoxy resin. The thickness from the central axis of the conductive post to its outer surface is denoted as H. The region within the thickness range of 0.1H from the center is denoted as the first region of the conductive post, and the region within the thickness range of 0.1H from the outer surface is denoted as the second region of the conductive post. The mass percentage of silver powder in the first region is greater than the mass percentage of silver powder in the second region; The mass percentage of the siloxane-modified epoxy resin in the second region is greater than the mass percentage of the siloxane-modified epoxy resin in the first region.

10. A method for preparing a glass through-hole substrate, characterized in that, Includes the following steps: S1. The conductive silver paste is filled into the through holes of the glass substrate to obtain the filled glass substrate. The conductive silver paste includes silver powder, siloxane-modified epoxy resin and solvent. S2. The filled glass substrate is fixed in a centrifuge for centrifugation, so that the siloxane-modified epoxy resin contained in the conductive silver paste migrates towards the inner wall of the through hole, and the silver powder contained in the conductive silver paste migrates towards the central axis of the through hole, thus obtaining an intermediate. S3. Perform a stepped heating treatment on the intermediate to solidify the conductive silver paste and obtain a glass through-hole substrate.

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