Low-thermal-expansion high-temperature-resistant novolac epoxy resin hole plugging ink and preparation method thereof

Abstract

The invention discloses low-thermal-expansion high-temperature-resistant novolac epoxy resin hole-plugging ink and a preparation method thereof, polyfunctional group novolac epoxy resin F51 is used as a matrix, epoxy propyl phenyl ether (PGE) is used as a reactive diluent, modified boron nitride (BN) and zirconium oxide (ZrO2) high-temperature-resistant filler and diethyl toluenediamine (DETDA) are added as curing agents, and F51 / PGE / DETDA series hole-plugging ink is prepared through curing. Wherein the thermal expansion coefficient of the Z / B50-50 hole-plugging ink is 6.54 * 10 <-5 > / DEG C, the glass-transition temperature is 168.71 DEG C, the temperature of 5% thermal weight loss is 348.31 DEG C, and the performance index of the Z / B50-50 hole-plugging ink is superior to that of a market ink product. The Z / B50-50 hole plugging ink has the hole plugging yield of 91.11% in the printed circuit board with the high thickness-diameter ratio (40: 1), the defects of cavities, cracks and the like do not occur in hole plugging, and the hole plugging use requirements of the printed circuit board with the high thickness-diameter ratio are met.

Description

Technical Field

[0001] This application belongs to the field of phenolic epoxy resin technology, and particularly relates to a low thermal expansion, high temperature resistant phenolic epoxy resin pore-filling ink and its preparation method. Background Technology

[0002] Printed circuit boards (PCBs) are the support structures and electrical connection carriers for electronic components, providing electrical interconnections between components. They are widely used in automotive, artificial intelligence, communications, medical, and big data industries. Resin-filled vias are a key process in PCB manufacturing. This involves filling the PCB vias with via-hole filling ink, followed by curing to fill the vias, thereby improving the PCB's reliability, electrical performance, and process adaptability.

[0003] As electronic products increasingly penetrate various fields, the demand for PCBs and the requirements for their precision are also rising. PCB integration has reached new heights, moving towards smaller hole diameters (less than 0.3 mm), higher aspect ratios (board thickness / hole diameter), finer pitch, higher lead arrays, and high-density interconnects (HDI). Currently available via-filling inks are insufficient to meet the via-filling needs and usage requirements of high aspect ratio PCBs. Therefore, the development of via-filling inks for high aspect ratio and multifunctional printed circuit PCBs is of great significance in addressing these issues. Summary of the Invention

[0004] The purpose of this application is to provide a low thermal expansion, high temperature resistant phenolic epoxy resin via-filling ink and its preparation method, in order to solve the above-mentioned technical problems and meet the via-filling requirements and usage requirements of high aspect ratio PCB boards.

[0005] To achieve the above-mentioned objectives, the technical solution adopted in this application is as follows: In a first aspect, embodiments of this application provide a method for preparing a low-thermal-expansion, high-temperature-resistant phenolic epoxy resin pore-filling ink, which includes the following steps: S1 and BN nanopowders were added to a 5 mol / L sodium hydroxide solution and mechanically suspended and stirred at 90°C for 12 h. After stirring, the mixture was filtered, washed with deionized water until neutral, dried under vacuum, and then ground to obtain hydroxylated boron nitride (BN-OH) powder. S2. Add hydroxylated boron nitride (BN-OH) powder to an ethanol solution of silane coupling agent KH-570, stir at 40°C for 3 hours, cool, filter and wash with anhydrous ethanol and deionized water in sequence to remove residual silane coupling agent, dry under vacuum, and grind to obtain modified BN powder. S3. Add the modified BN and ZrO2 powders to a beaker containing anhydrous ethanol and stir to disperse them evenly in the anhydrous ethanol to obtain a mixture ①. S4. In phenolic epoxy resin F51, diluent glycidyl phenyl ether (PGE), mixture ①, defoamer and dispersant are added in sequence. The mixture is mechanically stirred at 1500 r / min for 4 h at 50 °C. Curing agent diethyltoluene diamine (DETDA) and leveling agent are added in proportion. The mixture is mechanically stirred for another 1 h and then ultrasonically dispersed for 20 min to obtain mixture ②. S5. After grinding the mixture ② three times with a three-roll mill, degas it by vacuuming at 50°C for 25 minutes to obtain F51 / PGE / DETDA plugging ink.

[0006] Optionally, in step S1, the size of the BN nanopowder is 200-500 nm.

[0007] Optionally, in step S2, the mass ratio of KH-570 to hydroxylated boron nitride (BN-OH) is 4%-10%.

[0008] Optionally, in step S3, the size of the ZrO2 powder is 20-50 μm, and the mass ratio of ZrO2 to BN in the mixture ① is 3:7-7:3.

[0009] Optionally, in step S4, the mass fraction of glycidyl phenyl ether (PGE) in mixture ② is 10wt%-20wt%, the total mass of ZrO2 and BN in mixture ② is 6wt%-15wt%, the mass ratio of phenolic epoxy resin F51 to diethyltoluene diamine (DETDA) is 20:1-10:1, and the mass fraction of defoamer, dispersant, and leveling agent in mixture ② is 0.5wt%-2wt%.

[0010] Secondly, embodiments of this application provide a low thermal expansion, high temperature resistant phenolic epoxy resin pore-filling ink, which is obtained by the above-described preparation method.

[0011] Thirdly, this application provides an application of the above-mentioned low thermal expansion and high temperature resistant phenolic epoxy resin via-filling ink in resin via-filling of PCB boards. The F51 / PGE / DETDA via-filling ink is poured into the fine holes of a high aspect ratio PCB board, pre-cured at 120°C for 1-2 hours, cured at 160°C for 2-3 hours, and post-cured at 220°C for 0.5-1.5 hours to complete the resin via-filling process for a high aspect ratio PCB board.

[0012] As an optional implementation of the above technical solution: Step 1: Preparation of modified boron nitride (BN) filler. 2 g of BN nanoparticles were added to a four-necked flask containing 60 mL of 5 mol / L sodium hydroxide solution and mechanically stirred at 90 °C for 12 h. After stirring, the mixture was filtered, and the product was repeatedly washed with deionized water until neutral. After vacuum drying, it was ground to obtain hydroxylated boron nitride (BN-OH) powder.

[0013] Subsequently, KH-570 (5% of the mass of BN-OH powder) was added to 5 g of deionized water and 50 g of anhydrous ethanol, and the mixture was stirred at 40 °C for 3 h to allow the silane coupling agent to be fully hydrolyzed. 2 g of BN-OH was added, and the reaction was continued for 3 h. After cooling, the mixture was filtered and washed with anhydrous ethanol and deionized water to remove residual silane coupling agent. After vacuum drying, the mixture was ground to obtain modified BN powder.

[0014] Step 2: Preparation of F51 / PGE / DETDA ink. Modified BN and ZrO2 powders were added to a beaker containing anhydrous ethanol and stirred until evenly dispersed. Then, in phenolic epoxy resin F51, diluent glycidyl ether (PGE), modified BN and ZrO2 ethanol solution, defoamer (BYK-110), and dispersant (BYK-057) were added sequentially. The mixture was mechanically stirred at 1500 r / min for 4 h at 50 ℃, while evaporating the anhydrous ethanol. Curing agent diethyltoluene diamine (DETDA) and leveling agent (BYK-333) were added in proportion, and mechanical stirring continued for 1 h. After stirring, the ink was ultrasonically dispersed for 20 min to ensure uniform mixing of all components.

[0015] The ink was rolled and ground three times using a three-roll mill, and then placed in a vacuum drying oven and degassed at 50 °C for 25 min to obtain F51 / PGE / DETDA plugging ink.

[0016] The addition ratios of F51 / PGE / DETDA inks are shown in Table 1, where Z / B represents the addition ratio of micron-sized ZrO2 and nano-sized BN.

[0017] Table 1. Formulation of F51 / PGE / DETDA Low Thermal Expansion High Temperature Resistant Ink

[0018] Step 3: Resin plugging. F51 / PGE / DETDA ink is poured into the fine holes of the high aspect ratio (40:1) PCB board, pre-cured at 120℃ for 1 hour, cured at 160℃ for 2 hours, and then post-cured at 220℃ for 1 hour, completing the resin plugging process for the PCB board. Testing showed that Z / B50-50 ink achieved a resin plugging yield of up to 91.11% on the high aspect ratio (40:1) PCB board.

[0019] Compared with the prior art, the beneficial effects of the embodiments of this application are: This application provides a low thermal expansion, high-temperature resistant phenolic epoxy resin plugging ink and its preparation method. The Z / B50-50 ink from the F51 / PGE / DETDA series has a thermal expansion coefficient and tensile strength of 6.54 × 10⁻⁶. -5 With a thermal expansion coefficient of 60.1 MPa and a thermal expansion coefficient of 34%, 26%, and 39% lower than PSM-66, PHP-3F-DS, and PHP-900, respectively, Z / B50-50 exhibits higher tensile strength, 5%, 25%, and 55% higher tensile strength compared to these products. Dynamic thermomechanical testing shows that Z / B50-50 has a glass transition temperature of 168.71℃, which is higher than that of PSM-66 (142.38℃), PHP-3F-DS (139.17℃), and PHP-900 (136.32℃). Thermogravimetric analysis indicates that Z / B50-50 ink demonstrates superior high-temperature resistance compared to other inks on the market. Therefore, Z / B50-50 ink exhibits superior overall performance compared to currently available inks, making it an ideal low-thermal-expansion, high-temperature resistant resin-based pore-filling ink. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 The average coefficient of thermal expansion for inks with different components.

[0022] Figure 2 Thermogravimetric curves of inks with different components are shown.

[0023] Figure 3 Thermogravimetric curves for market ink products.

[0024] Figure 4 Thermomechanical analysis curves of inks with different components.

[0025] Figure 5 Thermomechanical analysis curves for market ink products.

[0026] Figure 6 The cross-section of the Z / B50-50 resin plug is shown.

[0027] Figure 7 The effect of different amounts of diluent on the viscosity and impact strength of phenolic epoxy resin.

[0028] Figure 8 The effect of total filler addition on ink flexural strength.

[0029] Figure 9 The effect of the BN / ZrO2 addition ratio on the tensile strength of ink. Detailed Implementation

[0030] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0031] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.

[0032] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0033] Phenolic resins possess excellent heat resistance, stability, mechanical properties, low shrinkage, and flame retardancy. Introducing epoxy groups into phenolic resins can prepare phenolic epoxy resins. Due to the introduction of epoxy groups into their structure, phenolic epoxy resins not only possess the heat resistance of phenolic resins but also the adhesiveness and adhesion properties of epoxy resins. Boron nitride (BN) has advantages such as high mechanical strength, low fluorescence quenching, high thermal conductivity, low biotoxicity, high stability, and chemical inertness, making it promising for applications in the manufacture of electronic devices and optical components. Zirconia (ZrO2) has resistance to chemical and microbial attack, and is also resistant to acids and alkalis. It has good dispersibility, excellent thermochemical stability, and high strength and toughness, with good mechanical and thermal properties, and is widely used in thermal barrier coatings, high-temperature devices, and composite materials.

[0034] This invention uses phenolic epoxy resin F51 as the resin matrix and adds glycidyl ether (PGE) as an active diluent to adjust the viscosity of the ink system. Modified boron nitride and zirconium dioxide powder are used as fillers, and diethyltoluene diamine (DETDA) is used as a curing agent to prepare an F51 / PGE / DETDA via-filling ink with low thermal expansion coefficient and high temperature resistance. This ink can be used for resin via-filling on high aspect ratio (40:1) PCBs with high thermal performance requirements and can also meet the requirements for use in high-temperature environments, thereby ensuring the service life and reliability of high aspect ratio (40:1) PCBs.

[0035] To illustrate the technical solution described in this application, specific embodiments are provided below. Example 1

[0036] Step 1: Preparation of modified boron nitride (BN) filler. 2 g of 300 nm BN powder was added to a four-necked flask containing 60 mL of 5 mol / L sodium hydroxide solution and mechanically stirred at 90 °C for 12 h. After stirring, the mixture was filtered, and the product was repeatedly washed with deionized water until neutral. After vacuum drying, it was ground to obtain hydroxylated boron nitride (BN-OH) powder.

[0037] Subsequently, 0.1 g of KH-570 was added to 5 g of deionized water and 50 g of anhydrous ethanol, and the mixture was stirred at 40 °C for 3 h to allow the silane coupling agent to be fully hydrolyzed. 2 g of BN-OH was added, and the reaction was carried out for 3 h. After cooling, the mixture was filtered and washed with anhydrous ethanol and deionized water to remove residual silane coupling agent. After vacuum drying, the mixture was ground to obtain modified BN powder.

[0038] Step 2: Preparation of F51 / PGE / DETDA ink. 1 g of modified BN and 1 g of 30 μm ZrO2 powder were added to a beaker containing 20 g of anhydrous ethanol and stirred until evenly dispersed, yielding 22 g of mixture ①. Subsequently, 2 g of diluent glycidyl phenyl ether (PGE), mixture ①, 0.3 g of defoamer (BYK-110), and 0.3 g of dispersant (BYK-057) were added sequentially to 20 g of phenolic epoxy resin F51. The mixture was mechanically stirred at 1500 r / min for 4 h at 50 ℃, while evaporating the anhydrous ethanol. 2.3 g of curing agent diethyltoluene diamine (DETDA) and 0.1 g of leveling agent (BYK-333) were added, and mechanical stirring continued for 1 h. After stirring, the ink was ultrasonically dispersed for 20 min to ensure uniform mixing of all components.

[0039] The ink was rolled and ground three times using a three-roll mill, and then placed in a vacuum drying oven at 50°C for 25 minutes to remove bubbles, thus obtaining F51 / PGE / DETDA plugging ink.

[0040] Step 3: Resin plugging. F51 / PGE / DETDA ink is poured into the fine holes of the high aspect ratio (40:1) PCB board, pre-cured at 120℃ for 1 hour, cured at 160℃ for 2 hours, and post-cured at 220℃ for 1 hour to complete the resin plugging process of the PCB board.

[0041] The coefficient of thermal expansion of the plugging ink obtained in this embodiment is 6.54 × 10⁻⁶. -5 / ℃, glass transition temperature is 168.71℃, and temperature at which 5% thermal weight loss occurs is 348.31℃. Example 2

[0042] Step 1: Same as Step 1 in Example 1.

[0043] Step 2: Preparation of F51 / PGE / DETDA ink. 1.4 g of modified BN and 0.6 g of 20 μm ZrO2 powder were added to a beaker containing 20 g of anhydrous ethanol and stirred until evenly dispersed, yielding 22 g of mixture ①. Subsequently, 2.2 g of diluent glycidyl phenyl ether (PGE), mixture ①, 0.2 g of defoamer (BYK-110), and 0.2 g of dispersant (BYK-057) were added sequentially to 20 g of phenolic epoxy resin F51. The mixture was mechanically stirred at 1500 r / min for 4 h at 50 °C, while evaporating the anhydrous ethanol. 2.5 g of curing agent diethyltoluene diamine (DETDA) and 0.15 g of leveling agent (BYK-333) were added, and mechanical stirring continued for 0.5 h. After stirring, the ink was ultrasonically dispersed for 30 min to ensure uniform mixing of all components.

[0044] The ink was rolled and ground three times using a three-roll mill, then placed in a vacuum drying oven and degassed under vacuum to obtain F51 / PGE / DETDA plugging ink.

[0045] Step 3: Same as step 3 in Example 1.

[0046] The coefficient of thermal expansion of the plugging ink obtained in this embodiment is 7.12 × 10⁻⁶. -5 / ℃, glass transition temperature is 159.44℃, and temperature at which 5% thermal weight loss occurs is 334.94℃. Example 3

[0047] Step 1: Same as Step 1 in Example 1.

[0048] Step 2: Preparation of F51 / PGE / DETDA ink. 0.2 g of modified BN and 1.8 g of 30 μm ZrO2 powder were added to a beaker containing 20 g of anhydrous ethanol and stirred until evenly dispersed, yielding 22 g of mixture ①. Subsequently, 2.2 g of diluent glycidyl phenyl ether (PGE), mixture ①, 0.15 g of defoamer (BYK-110), and 0.25 g of dispersant (BYK-057) were added sequentially to 20 g of phenolic epoxy resin F51. The mixture was mechanically stirred at 1500 r / min for 4 h at 50 °C, while evaporating the anhydrous ethanol. 2.8 g of curing agent diethyltoluene diamine (DETDA) and 0.12 g of leveling agent (BYK-333) were added, and mechanical stirring continued for 0.5 h. After stirring, the ink was ultrasonically dispersed for 30 min to ensure uniform mixing of all components.

[0049] The ink was rolled and ground three times using a three-roll mill, then placed in a vacuum drying oven and degassed under vacuum to obtain F51 / PGE / DETDA plugging ink.

[0050] Step 3: Same as step 3 in Example 1.

[0051] The coefficient of thermal expansion of the plugging ink obtained in this embodiment is 8.96 × 10⁻⁶. -5 / ℃, glass transition temperature is 150.52℃, and temperature at which 5% thermal weight loss occurs is 343.88℃.

[0052] The average coefficient of thermal expansion of various components of the ink in this experiment, such as Figure 1 As shown in the figure, the average coefficient of thermal expansion of the ink first decreases and then increases, with Z / B50-50 having the lowest average coefficient of thermal expansion at 6.54 × 10⁻⁶. -5 / ℃, superior to market-grade ink product PSM-66 (9.91×10 -5 / ℃), PHP-3F-DS (8.86×10 -5 / ℃) and PHP-900 (10.59×10 -5 / ℃). Phenolic epoxy resin F51 itself has low shrinkage, and the modified filler forms an interface with the resin, which can restrict the thermal expansion movement of the internal molecular chains of the epoxy resin. The modulus of the filler is much higher than that of the resin, and the thermal stress will be preferentially transferred through the rigid filler network rather than released through the extension of the resin chains, thereby effectively reducing the thermal expansion coefficient of the ink.

[0053] Thermogravimetric analysis (TGA) tests were conducted on inks with different components and commercially available ink products. The test results are as follows: Figure 2 and Figure 3 The temperatures at which the ink products and market products PSM-66, HP-3F-DS, and PHP-900 experienced weight loss of 5%, 10%, and 50% in this experiment are detailed in Table 2.

[0054] Table 2. Thermogravimetric data of experimental inks and products

[0055] The thermogravimetric analysis (TGA) curves of the ink of this invention are similar to those of commercial products at different temperatures. Component Z / B50-50 exhibits significantly better TGA temperatures at 5%, 10%, and 50% weight loss compared to commercial products. The nano-BN in the formulation of this invention is itself an inorganic nanoparticle with good inherent thermal stability. Upon addition to the system, it forms a strong interaction with the ink resin matrix, leading to an increase in the weight loss temperature. Furthermore, the BN modified with a silane coupling agent readily bonds with the resin matrix, forming a cross-linked network structure. The fully dispersed nanoparticles and micron-sized particles intertwine within the ink, restricting chain segment movement and effectively improving thermal stability.

[0056] Figure 4 and Figure 5 The figures show the Tanδ-T curves for experimental inks and market products, respectively. As can be seen from the figures, within the test temperature range of 35-200℃, both experimental inks and market products exhibit only one Tanδ peak, corresponding to only one glass transition temperature. Tg This indicates that the BN and ZrO2 fillers and the resin system are thermodynamically compatible cured products.

[0057] With the increase of nano-BN addition, the ink's... Tg The glass transition temperature initially moves towards higher temperatures, then subsequently towards lower temperatures. The experimental ink Z / B50-50 exhibited the highest glass transition temperature at 168.71℃, exceeding that of products PSM-66 (142.38℃), PHP-3F-DS (139.17℃), and PHP-900 (136.32℃). This is because phenolic epoxy resin possesses high thermal stability and high-temperature resistance, along with numerous epoxy functional groups and a high crosslinking density in the cured product. Furthermore, the fillers in the ink may also interact physically with the resin molecular chains on their surfaces, restricting the movement of polymer chain segments and resulting in a high glass transition temperature.

[0058] Table 3 lists the different via-filling effects and yields of the F51 / PGE / DETDA low thermal expansion, high-temperature resistant via-filling ink formulation on PCB test boards with ratios of 0.25 (20:1), 0.2 (25:1), 0.15 (35:1), and 0.13 (40:1). The Z / B50-50 ink formulation showed the best via-filling effect, achieving a via-filling yield of 91.11% for high aspect ratio (40:1) PCB boards.

[0059] Table 3. Through-hole plugging yield of ink on PCBs with different hole diameters

[0060] Z / B50-50 Resin Pore Plug Section Analysis Metallurgical microscopy was used to characterize the resin-filled via cross-section of the Z / B50-50 ink formulation in the 0.13 mm aperture area of ​​a PCB sample. The local characterization results are as follows: Figure 6 As shown in the figure, the ink has good filling properties in the holes after plugging and curing. No depressions appeared at the hole openings, and no defects such as resin cracks or hole-filling voids appeared inside the through holes. This indicates that the ink formula Z / B50-50 has a good resin plugging effect on the through holes of PCB boards with a thickness-to-diameter ratio of 40:1.

[0061] The reactive diluent glycidyl phenyl ether can both reduce ink viscosity and participate in resin curing. Experiments were conducted by adding different amounts of diluent to phenolic epoxy resin and testing the effects of different amounts on ink viscosity and impact strength to determine the optimal amount of diluent. The results are as follows: Figure 7 As shown.

[0062] Without filler, the viscosity of phenolic epoxy resin is 35 Pa·s. With increasing diluent addition, the resin viscosity continuously decreases, and the impact strength of the cured product initially increases and then decreases. Epichlorohydrin contains epoxy groups and, like phenolic epoxy resin, participates in curing, increasing the crosslinking density. Under impact, it can buffer energy to a greater extent, hindering resin crack propagation and preventing destructive fracture. Therefore, to ensure mechanical properties and low viscosity, the diluent addition was controlled at 15 wt%. At this addition, the viscosity and impact strength of the phenolic epoxy resin reached 16.3 Pa·s and 12.3 KJ / m², respectively. 2 .

[0063] Effect of Total BN / ZrO2 Filler Addition on the Mechanical Properties of Ink To determine the effect of BN / ZrO2 filler addition on the flexural properties of ink, modified BN and ZrO2 powders were mixed in equal mass and added to the ink at addition amounts of 2wt%, 4wt%, 6wt%, 8wt%, 10wt%, and 12wt%, respectively. After curing, the flexural strength was tested, and the results are as follows: Figure 8 As shown.

[0064] As the filler content increases, the flexural strength of the cured ink initially increases and then decreases, reaching a maximum of 88.3 MPa when the filler content reaches 8 wt%. Excessive filler content can cause agglomeration, increase internal defects, and reduce the stability of the cross-linked network structure, leading to a decrease in flexural strength. Therefore, the total filler content should be controlled at 8 wt%.

[0065] Effect of BN / ZrO2 addition ratio on the mechanical properties of ink To determine the specific addition ratio of BN and ZrO2 fillers in the ink, tensile strength tests were conducted on cured inks with different BN / ZrO2 addition ratios. The effects of the addition ratio of modified nano-BN and micron-sized ZrO2 on the tensile strength of the ink are as follows: Figure 9 As shown.

[0066] Depend on Figure 9 It can be seen that with the increase of nano-BN addition, the tensile strength of the ink first increases and then decreases, and the tensile strength and error differ significantly among the components. The Z / B50-50 component exhibits the highest tensile strength at 60.1 MPa, which is 5%, 25%, and 55% higher than that of PSM-66, PHP-3F-DS, and PHP-900, respectively. Modified nano-BN powder can form a good interfacial bond with the resin matrix. Under tensile stress, this interface effectively disperses stress. Furthermore, the high strength of the nanoparticles themselves allows for better dispersion within the ink resin matrix, resulting in enhanced tensile strength. Conversely, excessive BN addition may lead to excessive density and agglomeration, causing stress concentration and reducing tensile strength and elongation at break. Unmodified micron-sized ZrO2, with a particle size much larger than nano-BN, is prone to agglomeration and poor dispersibility in inks when added in excessive amounts, also leading to a decrease in tensile strength.

[0067] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A method for preparing a low thermal expansion, high-temperature resistant phenolic epoxy resin pore-filling ink, characterized in that, Includes the following steps: S1 and BN nanopowders were added to a 5 mol / L sodium hydroxide solution and mechanically suspended and stirred at 90°C for 12 h. After stirring, the mixture was filtered, washed with deionized water until neutral, dried under vacuum, and then ground to obtain hydroxylated boron nitride (BN-OH) powder. S2. Add hydroxylated boron nitride (BN-OH) powder to an ethanol solution of silane coupling agent KH-570, stir at 40°C for 3 hours, cool, filter and wash with anhydrous ethanol and deionized water in sequence to remove residual silane coupling agent, dry under vacuum, and grind to obtain modified BN powder. S3. Add the modified BN and ZrO2 powders to a beaker containing anhydrous ethanol and stir to disperse them evenly in the anhydrous ethanol to obtain a mixture ①. S4. In phenolic epoxy resin F51, diluent glycidyl phenyl ether (PGE), mixture ①, defoamer and dispersant are added in sequence. The mixture is mechanically stirred at 1500 r / min for 4 h at 50 °C. Curing agent diethyltoluene diamine (DETDA) and leveling agent are added in proportion. The mixture is mechanically stirred for another 1 h and then ultrasonically dispersed for 20 min to obtain mixture ②. S5. After grinding the mixture ② three times with a three-roll mill, degas it by vacuuming at 50°C for 25 minutes to obtain F51 / PGE / DETDA plugging ink.

2. The preparation method according to claim 1, characterized in that: In step S1, the size of the BN nanoparticles is 200-500 nm.

3. The preparation method according to claim 1, characterized in that: In step S2, the mass ratio of KH-570 to hydroxylated boron nitride (BN-OH) is 4%-10%.

4. The preparation method according to claim 1, characterized in that: In step S3, the ZrO2 powder has a size of 20-50 μm, and the mass ratio of ZrO2 to BN in the mixed solution ① is 3:7-7:

3.

5. The preparation method according to claim 1, characterized in that: In step S4, the mass fraction of glycidyl phenyl ether (PGE) in mixture ② is 10wt%-20wt%, the total mass of ZrO2 and BN in mixture ② is 6wt%-15wt%, the mass ratio of phenolic epoxy resin F51 to diethyltoluene diamine (DETDA) is 20:1-10:1, and the mass fraction of defoamer, dispersant, and leveling agent in mixture ② is 0.5wt%-2wt%.

6. A low thermal expansion, high temperature resistant phenolic epoxy resin pore-filling ink, characterized in that: It is obtained by the preparation method described in any one of claims 1-5.

7. The application of the low thermal expansion, high temperature resistant phenolic epoxy resin via-sealing ink as described in claim 6 in resin via-sealing of PCB boards, characterized in that: F51 / PGE / DETDA via-filling ink is poured into the fine holes of a high aspect ratio PCB board, pre-cured at 120℃ for 1-2 hours, cured at 160℃ for 2-3 hours, and post-cured at 220℃ for 0.5-1.5 hours to complete the resin via-filling process for the high aspect ratio PCB board.

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