Low dielectric filling adhesive for packaging chip and preparation method thereof

Abstract

This invention relates to the field of semiconductor packaging materials technology, specifically disclosing a low-dielectric filler for packaging chips and its preparation method. The invention uses fluorosilicone-modified benzoxazine, fluorosilicone-modified alicyclic epoxy resin and dicyclopentadiene cyanate prepolymer crosslinking to form a low-viscosity polymer, and then adds low-dielectric filler F-mesoporous SiO2 and functional additives. The resulting low-dielectric filler has low viscosity, can fill ultrafine gaps well, and after curing, the filler has low volume shrinkage and good high-frequency dielectric properties.

Description

Technical Field

[0001] This invention relates to the field of semiconductor packaging materials technology, specifically to a low-dielectric filler for packaging chips and its preparation method. Background Technology

[0002] With the continuous development of industries such as aerospace and intelligent communications, the precision requirements for electronic devices are becoming increasingly stringent. For high-precision, high-reliability electronic devices in aerospace, the key performance indicators such as circuit board integration, signal stability, and environmental tolerance far exceed those of civilian equipment. Therefore, the underfill adhesive used for circuit board chip packaging in aerospace electronic equipment needs to overcome four major technical obstacles simultaneously. Specifically, this manifests in four aspects: filler content, dielectric properties, curing shrinkage, and tolerance to extreme environments. In high-density filling of ultra-fine gaps (5-20μm), the filler's insufficient flowability and large particle size result in insufficient filling rate in these gaps, creating filling blind zones and causing pin short circuits. In 10GHz high-frequency operating environments, the filler's high dielectric constant and dielectric loss lead to severe signal attenuation, failing to meet the low-loss transmission requirements of broadband signals. Aerospace electronic equipment circuit boards often employ a composite stacked structure of multilayer PCBs and ceramic substrates. The significant difference in thermal expansion coefficients between the layers and the ceramic substrate means that excessive volume shrinkage during curing can generate significant internal stress, causing overall circuit board warping or even chip pin breakage. Aerospace and special applications require materials to maintain stable performance in alternating cold and hot environments, as well as in environments with strong radiation and corrosive chemicals. However, ordinary fillers have limited adaptability to extreme environments and struggle to maintain good performance. It is evident that developing a low-dielectric filler for packaging chips with high ultra-fine gap filling rate, good dielectric properties in high-frequency operating environments, low curing shrinkage rate, and good adaptability to extreme environments is crucial for promoting the development of electronic devices for aerospace applications. Summary of the Invention

[0003] The purpose of this invention is to provide a low-dielectric filler for chip packaging and its preparation method, which solves the problems of low filling rate of ordinary fillers in ultra-fine gaps, poor dielectric properties in high-frequency working environments, high curing shrinkage rate, and insufficient adaptability to extreme environments.

[0004] To solve the above-mentioned technical problems, the present invention provides the following technical solution: A method for preparing a low-dielectric filler for packaging chips, specifically comprising: Step 1: Using p-trifluoromethylphenol, γ-aminopropyltrimethoxysilane and paraformaldehyde as raw materials, fluorosilicone-modified benzoxazine was synthesized; Step 2: Using alicyclic epoxy resin, terminal epoxy polydimethylsiloxane and perfluorooctyltriethoxysilane as raw materials, F-Si-alicyclic EP is synthesized; Step 3: Using F-Si-alicyclic EP, fluorosilicone-modified benzoxazine and dicyclopentadiene cyanate as raw materials, a fluorosilicone-modified low-viscosity CE-BZ-EP prepolymer was synthesized. Step 4: Modify mesoporous silica with perfluorooctyltriethoxysilane to obtain F-mesoporous SiO2; Step 5: Add F-mesoporous SiO2 and functional additives to the fluorosilicone modified low-viscosity CE-BZ-EP prepolymer to prepare a low-dielectric filler for packaging chips.

[0005] As a limitation of this invention, the preparation method of the fluorosilicone modified benzoxazine is as follows: Under nitrogen protection, p-trifluoromethylphenol and γ-aminopropyltrimethoxysilane were added to toluene and stirred at 200-300 rpm for 20-30 min. Then, paraformaldehyde was added, and the mixture was stirred at 300-400 rpm for 6-8 h in an oil bath at 80-90 °C. After the reaction was completed, the mixture was cooled and filtered. The solvent was removed by rotary evaporation at 55-65 °C, and the filtrate was dried under vacuum at 40-50 °C for 6-8 h to obtain fluorosilicone modified benzoxazine.

[0006] As a limitation of the present invention, the mass ratio of p-trifluoromethylphenol, γ-aminopropyltrimethoxysilane, and paraformaldehyde is (50-60):(55-65):(20-30).

[0007] Under heating conditions, a Mannich condensation reaction occurs between p-trifluoromethylphenol, γ-aminopropyltrimethoxysilane, and paraformaldehyde. Paraformaldehyde depolymerizes to generate reactive formaldehyde. The amino group in γ-aminopropyltrimethoxysilane reacts with the reactive formaldehyde to generate an N-hydroxymethyl intermediate. The N-hydroxymethyl intermediate dehydrates to form an imine cation, which reacts with the phenolic hydroxyl group of p-trifluoromethylphenol to form a benzoxazine ring structure, thus yielding a fluorosilicone-modified benzoxazine.

[0008] Fluorosilicone-modified benzoxazine contains a para-trifluoromethyl group and a trimethoxysilane group bonded to a nitrogen atom. The benzoxazine ring contains a Mannich bridge structure, resulting in low intrinsic dielectric constant and dielectric loss. Simultaneously, the strongly electron-withdrawing trifluoromethyl group further reduces the electronic polarizability of benzoxazine through inductive and conjugation effects. The synergistic effect of these two factors gives the fluorosilicone-modified benzoxazine monomer excellent dielectric properties. The nitrogen-bonded trimethoxysilane group is a flexible long-chain segment that can reduce viscosity and absorb and disperse internal stress during crosslinking and curing. Furthermore, the ring-opening polymerization of benzoxazine is an atomic rearrangement reaction that does not produce small molecule byproducts, resulting in extremely low curing volume shrinkage. The synergistic effect of these two factors reduces the curing shrinkage rate of the filler adhesive system, thereby reducing the risk of circuit board warping. In addition, the trimethoxysilane can condense with hydroxyl groups on the surface of silica fillers or substrates during curing to form covalent bonds, enhancing the compatibility between the filler and the matrix resin and strengthening the adhesion between the filler adhesive and the substrate.

[0009] As a limitation of this invention, the preparation method of the F-Si-alicyclic EP is as follows: Under nitrogen protection, alicyclic epoxy resin and terminally epoxy polydimethylsiloxane were added to toluene and stirred at 200-300 rpm for 20-30 min. Perfluorooctyltriethoxysilane and Karstedt catalyst were then added, and the mixture was stirred at 80-90 °C and 300-400 rpm for 6-8 h. After the reaction was completed, the mixture was cooled, activated carbon was added to adsorb and remove the catalyst, and the mixture was filtered. The filtrate was washed with deionized water and separated. The organic phase was dried with anhydrous magnesium sulfate, filtered, and the solvent was removed by rotary evaporation at 50-60 °C. The mixture was then vacuum dried at 60-70 °C for 6-8 h to obtain F-Si-alicyclic EP.

[0010] As a limitation of the present invention, the mass ratio of the alicyclic epoxy resin, terminal epoxy polydimethylsiloxane, perfluorooctyltriethoxysilane and Karstedt catalyst is (100-120):(20-24):(10-14):(0.1-0.2).

[0011] Under the action of Karstedt catalyst, the epoxy groups of terminal epoxy polydimethylsiloxane and alicyclic epoxy resin undergo ring-opening and hydrosilylation reaction with the silane-hydrogen bonds on perfluorooctyltriethoxysilane. Perfluorooctyltriethoxysilane and terminal epoxy polydimethylsiloxane are chemically grafted onto the alicyclic epoxy resin. The grafted perfluorooctyltriethoxysilane segments have extremely low electronic polarizability, low intrinsic dielectric constant and low dielectric loss, significantly improving the dielectric properties of alicyclic epoxy resin. The grafted polydimethylsiloxane segments are flexible long chains, which can reduce the viscosity of the resin bulk and improve the flowability during resin processing. After the filler is cross-linked, it can also absorb and disperse stress, increase the flexibility of the cured system, reduce the curing shrinkage rate of the filler system, and reduce the risk of circuit board warpage.

[0012] As a limitation of this invention, the preparation method of the fluorosilicone modified low-viscosity CE-BZ-EP prepolymer is as follows: Under nitrogen protection and in an oil bath at 70-80℃, F-Si-alicyclic EP was mixed with fluorosilicone-modified benzoxazine and stirred at 200-300 rpm for 20-30 min. The mixture was then stirred at 100-110℃ and 300-400 rpm for 0.5-1 h. After the reaction was completed, the temperature was lowered to 70-80℃, and dicyclopentadiene cyanate and iron triacetylacetone catalyst were added. The mixture was stirred at 120-130℃ and 300-400 rpm. The viscosity of the system was monitored during the reaction. After the reaction was completed, heating was stopped, and the reactive system was transferred to an ice-water bath and rapidly cooled to room temperature to obtain fluorosilicone-modified low-viscosity CE-BZ-EP prepolymer.

[0013] As a limitation of this invention, the mass ratio of the F-Si-alicyclic EP, fluorosilicone-modified benzoxazine, dicyclopentadiene cyanate, and catalyst iron triacetylacetone is (20-30):(40-50):(60-70):(0.1-0.2); the viscosity of the system is monitored during the reaction, and the reaction is complete when the viscosity of the reaction system at 90°C is 2500-3000 mPa·s, and heating is stopped.

[0014] Under heating conditions at 100℃, the benzoxazine ring of fluorosilicone-modified benzoxazine partially undergoes ring-opening to generate a Mannich structure containing phenolic hydroxyl groups and secondary amine groups. The phenolic hydroxyl groups undergo ring-opening addition reactions with the epoxy groups of F-Si-alicyclic EP to form ether bonds. Under heating conditions at 120℃ and catalyzed by the catalysts triacetylacetone iron and the phenolic hydroxyl groups generated by the ring-opening of benzoxazine, the cyanate ester trimerizes to form an intrinsically low-polarity triazine ring. Furthermore, the polybenzoxazine self-polymerized by benzoxazine crosslinks with the triazine ring to form a chemically bonded crosslinked low-viscosity prepolymer. Prepolymerization ensures the uniform distribution of triazine rings, fluorine atoms, and siloxane segments in the resin matrix, avoiding phase separation that is easily caused by simple blending and eliminating the high polarity regions generated by phase separation, thereby enhancing the dielectric properties of the filler adhesive system. During prepolymerization, the active groups undergo cross-linking reactions, and the volume of the prepolymer changes, reducing the volume shrinkage caused by cross-linking during complete curing. At the same time, the resulting oligomer network has better deformation capabilities. The two work synergistically to reduce the residual stress inside the material after complete curing. Prepolymerization also prevents monomers from crystallizing or self-polymerizing during storage, ensuring the stability of the raw materials.

[0015] As a limitation of the present invention, the preparation method of the F-mesoporous SiO2 is as follows: Under nitrogen protection, mesoporous silica was added to anhydrous ethanol and stirred at 200-300 rpm for 20-30 min. Perfluorooctyltriethoxysilane and deionized water were added to adjust the pH to 4-5. The reaction was carried out at 70-80℃ and stirred at 300-400 rpm for 6-8 h. After the reaction was completed, the mixture was cooled, filtered, and the filtrate was washed with ethanol and dried under vacuum at 70-80℃ for 6-8 h to obtain F-mesoporous SiO2. The mass ratio of mesoporous silica to perfluorooctyltriethoxysilane is (100-120):(3-4).

[0016] The silanol generated from the hydrolysis of perfluorooctyltriethoxysilane undergoes a condensation reaction with the silanols on the surface of mesoporous silica, forming Si-O-Si covalent bonds. Perfluorooctyltriethoxysilane is then grafted onto the surface of the mesoporous silica. After modification, the surface energy of the mesoporous silica surface is close to that of the modified resin matrix, exhibiting excellent compatibility. The synergistic effect of its mesoporous structure and fluorinated surface significantly reduces the dielectric constant and dielectric loss of the filler adhesive system.

[0017] As a limitation of this invention, the functional additives include alicyclic glycidyl ether as a diluent, KH-560 as a coupling agent, phenyl silicone oil as a dielectric modifier, UV-329 as a UV absorber, 1010 as an antioxidant, BYK-333 as a leveling agent, BYK-055 as a defoamer, dicyandiamide as a curing agent, and 2-methylimidazole as an accelerator; by weight, the low dielectric filler for the encapsulation chip includes 100-120 parts of fluorosilicone-modified low-viscosity CE-BZ-EP prepolymer, 4... 5-55 parts F-mesoporous SiO2, 20-40 parts diluent alicyclic glycidyl ether, 1-2 parts coupling agent KH-560, 2-3 parts dielectric modifier phenyl silicone oil, 0.3-0.5 parts ultraviolet absorber UV-329, 0.3-0.5 parts antioxidant 1010, 0.2-0.4 parts leveling agent BYK-333, 0.2-0.4 parts defoamer BYK-055, 3-5 parts curing agent dicyandiamide, and 3-5 parts accelerator 2-methylimidazole.

[0018] A low-dielectric filler for packaging chips is prepared using any of the above-described preparation methods.

[0019] Compared with the prior art, the beneficial effects of the present invention are: This invention uses a fluorosilicone-modified benzoxazine, a fluorosilicone-modified alicyclic epoxy resin, and a dicyclopentadiene cyanate copolymer prepolymer as the resin matrix for the filler adhesive. Benzoxazine and alicyclic epoxy resins have low intrinsic dielectric constants and dielectric losses. Fluorosilicone modification further reduces electronic polarizability, enhancing dielectric properties. Simultaneously, the flexible silane chains reduce the bulk viscosity of the resin, improving its flowability during processing. During prepolymerization, the active groups undergo cross-linking reactions, causing changes in the prepolymer volume and reducing volume shrinkage caused by cross-linking during complete curing. The resulting oligomer network also exhibits better deformation capabilities. These two factors work synergistically to reduce residual stress within the material after complete curing. Furthermore, prepolymerization prevents monomer crystallization or self-polymerization during storage, ensuring the stability of the raw materials. Detailed Implementation

[0020] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. The terminology used in the embodiments is for describing specific implementation schemes, not for limiting the scope of protection of the present invention. The dosages in the embodiments are laboratory-scale tests and can be scaled up proportionally. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Mesoporous silica (pore size: 15nm, particle size: 1μm), alicyclic epoxy resin (viscosity: 500mPa·s (@25℃), epoxy equivalent: 120g / eq).

[0022] The preparation method of F-mesoporous SiO2 is as follows: Under nitrogen protection, 100g of mesoporous silica was added to 500mL of anhydrous ethanol and stirred at 200rpm for 20min. Then, 3g of perfluorooctyltriethoxysilane and 10mL of deionized water were added to adjust the pH to 5. The mixture was stirred at 70℃ and 400rpm for 8h. After the reaction was completed, the mixture was cooled, filtered, and the filtrate was washed with ethanol and dried under vacuum at 80℃ for 8h to obtain F-mesoporous SiO2. Example 1: A method for preparing a low-dielectric filler for packaging chips, specifically as follows: Step 1: Under nitrogen protection, 50g of p-trifluoromethylphenol and 55g of γ-aminopropyltrimethoxysilane were added to 400mL of toluene. After stirring at 200rpm for 20min, 20g of paraformaldehyde was added. The mixture was stirred at 400rpm for 6h in an oil bath at 85℃. After the reaction was completed, the mixture was cooled and filtered. The solvent was removed by rotary evaporation at 60℃ and the filtrate was dried under vacuum at 40℃ for 8h to obtain fluorosilicone modified benzoxazine. Step 2: Under nitrogen protection, 100g of alicyclic epoxy resin and 20g of terminal epoxy polydimethylsiloxane were added to 400mL of toluene and stirred at 200rpm for 20min. Then, 10g of perfluorooctyltriethoxysilane and 0.1g of Karstedt catalyst were added and the mixture was stirred at 90℃ and 400rpm for 8h. After the reaction was completed, the mixture was cooled, activated carbon was added to adsorb and remove the catalyst, and the mixture was filtered. The filtrate was washed with deionized water and separated. The organic phase was dried with anhydrous magnesium sulfate, filtered, and the solvent was removed by rotary evaporation at 50℃. The mixture was then vacuum dried at 60℃ for 6h to obtain F-Si-alicyclic EP. Step 3: Under nitrogen protection and an 80°C oil bath, 20g of F-Si-alicyclic EP and 40g of fluorosilicone-modified benzoxazine were mixed and stirred at 200rpm for 20min. The mixture was then stirred at 100°C and 400rpm for 1h. After the reaction was completed, the temperature was lowered to 80°C, and 60g of dicyclopentadiene cyanate and 0.1g of triacetylacetone iron catalyst were added. The mixture was stirred at 120°C and 400rpm. The viscosity of the system was monitored during the reaction. When the viscosity of the reaction system reached 2500mPa·s (@90°C), heating was stopped, and the reactive system was transferred to an ice-water bath and rapidly cooled to room temperature to obtain fluorosilicone-modified low-viscosity CE-BZ-EP prepolymer. Step 4: Under nitrogen protection and stirring at 200 rpm, add 25g of alicyclic glycidyl ether (diluent), 1g of coupling agent KH-560, 2g of dielectric modifier phenyl silicone oil, 0.3g of UV absorber UV-329, and 0.3g of antioxidant 1010 to 100g of fluorosilicone modified low-viscosity CE-BZ-EP prepolymer in sequence. After the addition is complete, continue stirring for 20 minutes, then increase the speed to 1500 rpm and add 45g of [unspecified ingredient] in sequence. F-mesoporous SiO2 (added in 3 portions), 0.2g leveling agent BYK-333 and 0.2g defoamer BYK-055 were added. After the addition was completed, the mixture was stirred for 30 minutes. Finally, the speed was reduced to 200 rpm, and 3g curing agent dicyandiamide and 3g accelerator 2-methylimidazole were added in sequence. The mixture was stirred for 40 minutes. The mixture was then filtered through a 5μm pore size filter and degassed under vacuum at -0.095MPa for 10 minutes to obtain a low-dielectric filler for encapsulating chips.

[0023] Example 2: A method for preparing a low-dielectric filler for packaging chips, specifically as follows: Step 1: Under nitrogen protection, 55g of p-trifluoromethylphenol and 60g of γ-aminopropyltrimethoxysilane were added to 400mL of toluene. After stirring at 200rpm for 20min, 25g of paraformaldehyde was added. The mixture was stirred at 400rpm for 6h in an oil bath at 85℃. After the reaction was completed, the mixture was cooled and filtered. The solvent was removed by rotary evaporation at 60℃ and the filtrate was dried under vacuum at 40℃ for 8h to obtain fluorosilicone modified benzoxazine. Step 2: Under nitrogen protection, 110g of alicyclic epoxy resin and 22g of terminal epoxy polydimethylsiloxane were added to 400mL of toluene and stirred at 200rpm for 20min. Then, 12g of perfluorooctyltriethoxysilane and 0.1g of Karstedt catalyst were added and the mixture was stirred at 90℃ and 400rpm for 8h. After the reaction was completed, the mixture was cooled, activated carbon was added to adsorb and remove the catalyst, and the mixture was filtered. The filtrate was washed with deionized water and separated. The organic phase was dried with anhydrous magnesium sulfate, filtered, and the solvent was removed by rotary evaporation at 50℃. The mixture was then vacuum dried at 60℃ for 6h to obtain F-Si-alicyclic EP. Step 3: Under nitrogen protection and an 80°C oil bath, 25g of F-Si-alicyclic EP and 45g of fluorosilicone-modified benzoxazine were mixed and stirred at 200rpm for 20min. The mixture was then stirred at 100°C and 400rpm for 1h. After the reaction was completed, the temperature was lowered to 80°C, and 65g of dicyclopentadiene cyanate and 0.1g of triacetylacetone iron catalyst were added. The mixture was stirred at 120°C and 400rpm. The viscosity of the system was monitored during the reaction. When the viscosity of the reaction system reached 2700mPa·s (@90°C), heating was stopped, and the reactive system was transferred to an ice-water bath and rapidly cooled to room temperature to obtain fluorosilicone-modified low-viscosity CE-BZ-EP prepolymer. Step 4: Under nitrogen protection and stirring at 200 rpm, add 30g of alicyclic glycidyl ether (diluent), 1g of coupling agent KH-560, 2g of dielectric modifier phenyl silicone oil, 0.3g of UV absorber UV-329, and 0.3g of antioxidant 1010 to 110g of fluorosilicone modified low-viscosity CE-BZ-EP prepolymer in sequence. After the addition is complete, continue stirring for 20 minutes, then increase the speed to 1500 rpm and add 50g of [unspecified ingredient] in sequence. F-mesoporous SiO2 (added in 3 portions), 0.2g leveling agent BYK-333 and 0.2g defoamer BYK-055 were added. After the addition was completed, the mixture was stirred for 30 minutes. Finally, the speed was reduced to 200 rpm, and 3g curing agent dicyandiamide and 3g accelerator 2-methylimidazole were added in sequence. The mixture was stirred for 40 minutes. The mixture was then filtered through a 5μm pore size filter and degassed under vacuum at -0.095MPa for 10 minutes to obtain a low-dielectric filler for encapsulating chips.

[0024] Example 3: A method for preparing a low-dielectric filler for packaging chips, specifically as follows: Step 1: Under nitrogen protection, 60g of p-trifluoromethylphenol and 65g of γ-aminopropyltrimethoxysilane were added to 400mL of toluene. After stirring at 200rpm for 20min, 30g of paraformaldehyde was added. The mixture was stirred at 400rpm for 6h in an oil bath at 85℃. After the reaction was completed, the mixture was cooled and filtered. The solvent was removed by rotary evaporation at 60℃ and vacuum dried at 40℃ for 8h to obtain fluorosilicone modified benzoxazine. Step 2: Under nitrogen protection, 120g of alicyclic epoxy resin and 24g of terminal epoxy polydimethylsiloxane were added to 400mL of toluene and stirred at 200rpm for 20min. Then, 14g of perfluorooctyltriethoxysilane and 0.1g of Karstedt catalyst were added and the mixture was stirred at 90℃ and 400rpm for 8h. After the reaction was completed, the mixture was cooled, activated carbon was added to adsorb and remove the catalyst, and the mixture was filtered. The filtrate was washed with deionized water and separated. The organic phase was dried with anhydrous magnesium sulfate, filtered, and the solvent was removed by rotary evaporation at 50℃. The mixture was then vacuum dried at 60℃ for 6h to obtain F-Si-alicyclic EP. Step 3: Under nitrogen protection and an 80°C oil bath, 30g of F-Si-alicyclic EP and 50g of fluorosilicone-modified benzoxazine were mixed and stirred at 200rpm for 20min. The mixture was then stirred at 100°C and 400rpm for 1h. After the reaction was completed, the temperature was lowered to 80°C, and 70g of dicyclopentadiene cyanate and 0.1g of triacetylacetone iron catalyst were added. The mixture was stirred at 120°C and 400rpm. The viscosity of the system was monitored during the reaction. When the viscosity of the reaction system reached 2500mPa·s (@90°C), heating was stopped, and the reactive system was transferred to an ice-water bath and rapidly cooled to room temperature to obtain fluorosilicone-modified low-viscosity CE-BZ-EP prepolymer. Step 4: Under nitrogen protection and stirring at 200 rpm, add 35g of alicyclic glycidyl ether (diluent), 1g of coupling agent KH-560, 2g of dielectric modifier phenyl silicone oil, 0.3g of UV absorber UV-329, and 0.3g of antioxidant 1010 to 120g of fluorosilicone modified low-viscosity CE-BZ-EP prepolymer in sequence. After the addition is complete, continue stirring for 20 minutes, then increase the speed to 1500 rpm and add 55g of [unspecified ingredient] in sequence. F-mesoporous SiO2 (added in 3 portions), 0.2g leveling agent BYK-333 and 0.2g defoamer BYK-055 were added. After the addition was completed, the mixture was stirred for 30 minutes. Finally, the speed was reduced to 200 rpm, and 3g curing agent dicyandiamide and 3g accelerator 2-methylimidazole were added in sequence. The mixture was stirred for 40 minutes. The mixture was then filtered through a 5μm pore size filter and degassed under vacuum at -0.095MPa for 10 minutes to obtain a low-dielectric filler for encapsulating chips.

[0025] Based on Example 1, the following comparative experiments were conducted, specifically Comparative Example 1, Comparative Example 2, and Comparative Example 3, as described below: Comparative Example 1: This comparative example relates to a method for preparing a low-dielectric filler for packaging chips. The difference from Example 1 lies in the benzoxazine non-fluorosilicone modification treatment, specifically: Step 1: Under nitrogen protection, 100g of alicyclic epoxy resin and 20g of terminal epoxy polydimethylsiloxane were added to 400mL of toluene and stirred at 200rpm for 20min. Then, 10g of perfluorooctyltriethoxysilane and 0.1g of Karstedt catalyst were added and the mixture was stirred at 90℃ and 400rpm for 8h. After the reaction was completed, the mixture was cooled, activated carbon was added to adsorb and remove the catalyst, and the mixture was filtered. The filtrate was washed with deionized water and separated. The organic phase was dried with anhydrous magnesium sulfate, filtered, and the solvent was removed by rotary evaporation at 50℃. The mixture was then vacuum dried at 60℃ for 6h to obtain F-Si-alicyclic EP. Step 2: Under nitrogen protection and an 80°C oil bath, 20g of F-Si-alicyclic EP and 40g of benzoxazine were mixed and stirred at 200rpm for 20min. The mixture was then stirred at 100°C and 400rpm for 1h. After the reaction was completed, the temperature was lowered to 80°C, and 60g of dicyclopentadiene cyanate and 0.1g of triacetylacetone iron catalyst were added. The mixture was stirred at 120°C and 400rpm. The viscosity of the system was monitored during the reaction. When the viscosity of the reaction system reached 2500mPa·s (@90°C), heating was stopped, and the reactive system was transferred to an ice-water bath and rapidly cooled to room temperature to obtain fluorosilicone modified low-viscosity CE-BZ-EP prepolymer. Step 3: Under nitrogen protection and stirring at 200 rpm, add 25g of alicyclic glycidyl ether (diluent), 1g of coupling agent KH-560, 2g of dielectric modifier phenyl silicone oil, 0.3g of UV absorber UV-329, and 0.3g of antioxidant 1010 to 100g of fluorosilicone modified low-viscosity CE-BZ-EP prepolymer in sequence. After the addition is complete, continue stirring for 20 minutes, then increase the speed to 1500 rpm and add 45g of [unspecified ingredient] in sequence. F-mesoporous SiO2 (added in 3 portions), 0.2g leveling agent BYK-333 and 0.2g defoamer BYK-055 were added. After the addition was completed, the mixture was stirred for 30 minutes. Finally, the speed was reduced to 200 rpm, and 3g curing agent dicyandiamide and 3g accelerator 2-methylimidazole were added in sequence. The mixture was stirred for 40 minutes. The mixture was then filtered through a 5μm pore size filter and degassed under vacuum at -0.095MPa for 10 minutes to obtain a low-dielectric filler for encapsulating chips.

[0026] Comparative Example 2: This comparative example relates to a method for preparing a low-dielectric filler for packaging chips. The difference from Example 1 is that the alicyclic epoxy resin is not modified with fluorosilicone, specifically: Step 1: Under nitrogen protection, 50g of p-trifluoromethylphenol and 55g of γ-aminopropyltrimethoxysilane were added to 400mL of toluene. After stirring at 200rpm for 20min, 20g of paraformaldehyde was added. The mixture was stirred at 400rpm for 6h in an oil bath at 85℃. After the reaction was completed, the mixture was cooled and filtered. The solvent was removed by rotary evaporation at 60℃ and the filtrate was dried under vacuum at 40℃ for 8h to obtain fluorosilicone modified benzoxazine. Step 2: Under nitrogen protection and an 80°C oil bath, 20g of alicyclic epoxy resin and 40g of fluorosilicone-modified benzoxazine were mixed and stirred at 200rpm for 20min. The mixture was then stirred at 100°C and 400rpm for 1h. After the reaction was completed, the temperature was lowered to 80°C, and 60g of dicyclopentadiene cyanate and 0.1g of triacetylacetone iron catalyst were added. The mixture was stirred at 120°C and 400rpm. The viscosity of the system was monitored during the reaction. When the viscosity of the reaction system reached 2500mPa·s (@90°C), heating was stopped, and the reactive system was transferred to an ice-water bath and rapidly cooled to room temperature to obtain the fluorosilicone-modified low-viscosity CE-BZ-EP prepolymer. Step 3: Under nitrogen protection and stirring at 200 rpm, add 25g of alicyclic glycidyl ether (diluent), 1g of coupling agent KH-560, 2g of dielectric modifier phenyl silicone oil, 0.3g of UV absorber UV-329, and 0.3g of antioxidant 1010 to 100g of fluorosilicone modified low-viscosity CE-BZ-EP prepolymer in sequence. After the addition is complete, continue stirring for 20 minutes, then increase the speed to 1500 rpm and add 45g of [unspecified ingredient] in sequence. F-mesoporous SiO2 (added in 3 portions), 0.2g leveling agent BYK-333 and 0.2g defoamer BYK-055 were added. After the addition was completed, the mixture was stirred for 30 minutes. Finally, the speed was reduced to 200 rpm, and 3g curing agent dicyandiamide and 3g accelerator 2-methylimidazole were added in sequence. The mixture was stirred for 40 minutes. The mixture was then filtered through a 5μm pore size filter and degassed under vacuum at -0.095MPa for 10 minutes to obtain a low-dielectric filler for encapsulating chips.

[0027] Comparative Example 3: This comparative example relates to a method for preparing a low-dielectric filler for packaging chips. The difference from Example 1 is that no prepolymerization treatment is performed. Specifically: Step 1: Under nitrogen protection, 50g of p-trifluoromethylphenol and 55g of γ-aminopropyltrimethoxysilane were added to 400mL of toluene. After stirring at 200rpm for 20min, 20g of paraformaldehyde was added. The mixture was stirred at 400rpm for 6h in an oil bath at 85℃. After the reaction was completed, the mixture was cooled and filtered. The solvent was removed by rotary evaporation at 60℃ and the filtrate was dried under vacuum at 40℃ for 8h to obtain fluorosilicone modified benzoxazine. Step 2: Under nitrogen protection, 100g of alicyclic epoxy resin and 20g of terminal epoxy polydimethylsiloxane were added to 400mL of toluene and stirred at 200rpm for 20min. Then, 10g of perfluorooctyltriethoxysilane and 0.1g of Karstedt catalyst were added and the mixture was stirred at 90℃ and 400rpm for 8h. After the reaction was completed, the mixture was cooled, activated carbon was added to adsorb and remove the catalyst, and the mixture was filtered. The filtrate was washed with deionized water and separated. The organic phase was dried with anhydrous magnesium sulfate, filtered, and the solvent was removed by rotary evaporation at 50℃. The mixture was then vacuum dried at 60℃ for 6h to obtain F-Si-alicyclic EP. Step 3: Under nitrogen protection and stirring at 200 rpm, add 25g of diluent alicyclic glycidyl ether, 1g of coupling agent KH-560, 2g of dielectric modifier phenyl silicone oil, 0.3g of UV absorber UV-329, and 0.3g of antioxidant 1010 sequentially to a mixture of 16g ​​F-Si-alicyclic EP, 32g of fluorosilicone-modified benzoxazine, and 50g of dicyclopentadiene cyanate. After the addition is complete, continue stirring for 20 minutes, then increase the stirring speed to 1500 rpm and add 45g of [unspecified ingredient]. F-mesoporous SiO2 (added in 3 portions), 0.2g leveling agent BYK-333 and 0.2g defoamer BYK-055 were added. After the addition was completed, the mixture was stirred for 30 minutes. Finally, the speed was reduced to 200 rpm, and 3g curing agent dicyandiamide and 3g accelerator 2-methylimidazole were added in sequence. The mixture was stirred for 40 minutes. The mixture was then filtered through a 5μm pore size filter and degassed under vacuum at -0.095MPa for 10 minutes to obtain a low-dielectric filler for encapsulating chips.

[0028] Testing experiment: Low-dielectric filler for packaging chips was prepared according to each embodiment and comparative example as the test object. Meanwhile, a commercially available high-precision low-dielectric filler was used as comparative example 4 to perform viscosity test, thermal expansion coefficient test, energy storage modulus test, curing shrinkage rate test, gap filling rate test, high-frequency dielectric performance test, and post-radiation dielectric performance test.

[0029] Viscosity test: 0.5 mL of low dielectric filler was injected into the measuring cup of the rotational viscometer, the constant temperature bath was controlled at 25℃, and the shear rate was set to 10 s. -1 The viscosity fluctuation of the low dielectric filler was observed and recorded continuously for 72 hours.

[0030] Curing shrinkage test: After measuring the density of the low dielectric filler at 25℃ before curing, it was filled into a mold of known volume and cured. The curing process was: room temperature → 80℃ (5℃ / min, 30min) → 120℃ (3℃ / min, 45min) → 180℃ (2℃ / min, 150min). After curing, the filler was demolded and the density of the cured filler was measured with a densitometer. The volumetric curing shrinkage rate of the filler was calculated.

[0031] Gap fill rate testing, high-frequency dielectric performance testing, and post-radiation dielectric performance testing: A vision-guided jet dispensing machine (positioning accuracy ±0.005mm, pressure 0.3-0.5MPa) was used to dispense adhesive onto aerospace circuit boards with a 5-20μm gap. The dispensing path was set to a serpentine path (pitch ≥0.2mm, start / end point 0.5mm from chip edge). Dispensing parameters included: 5-10μm gap (0.1-0.2mL / min, 1mm / s), 10-20μm... The gap was 0.2-0.3 mL / min, 1.5 mm / s. After dispensing, the adhesive was allowed to stand for 5 minutes to level. The curing process was: room temperature → 80℃ (5℃ / min, 30 min) → 120℃ (3℃ / min, 45 min) → 180℃ (2℃ / min, 150 min). After curing, the adhesive was allowed to cool naturally to room temperature and inspected using an X-ray flaw detector (accuracy: 0.01 mm resolution). The 5-20 μm gap filling rate of the filler was calculated. The dielectric constant and dielectric loss of the low-dielectric filler were measured at 10 GHz using a vector network analyzer. The adhesive was then exposed to a radiation environment (radiation source: 137 Cs radiation (radiation intensity of 1 krad / h) for 180 h was used to test its dielectric loss rate after radiation.

[0032] Conclusion: The test data shows that the filler adhesive provided by this invention can effectively fill ultra-fine gaps of 5-20μm. After curing, the filler adhesive has a low volume shrinkage rate, good dielectric properties, and can maintain a low dielectric constant and dielectric loss under high-frequency conditions. It also has good radiation resistance, with low dielectric loss after 180krad γ radiation, and can still maintain good dielectric properties. It can solve the problems of low ultra-fine gap filling rate, poor dielectric properties in high-frequency working environments, high curing shrinkage rate, and insufficient adaptability to extreme environments of ordinary filler adhesives.

[0033] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A method for preparing a low-dielectric filler for packaging chips, characterized in that: Specifically: Step 1: Using p-trifluoromethylphenol, γ-aminopropyltrimethoxysilane and paraformaldehyde as raw materials, fluorosilicone-modified benzoxazine was synthesized; Step 2: Using alicyclic epoxy resin, terminal epoxy polydimethylsiloxane and perfluorooctyltriethoxysilane as raw materials, F-Si-alicyclic EP is synthesized; Step 3: Using F-Si-alicyclic EP, fluorosilicone-modified benzoxazine and dicyclopentadiene cyanate as raw materials, a fluorosilicone-modified low-viscosity CE-BZ-EP prepolymer was synthesized. Step 4: Modify mesoporous silica with perfluorooctyltriethoxysilane to obtain F-mesoporous SiO2; Step 5: Add F-mesoporous SiO2 and functional additives to the fluorosilicone modified low-viscosity CE-BZ-EP prepolymer to prepare a low-dielectric filler for packaging chips.

2. The method for preparing a low-dielectric filler for packaging chips according to claim 1, characterized in that: The preparation method of fluorosilicone modified benzoxazine is as follows: Under nitrogen protection, p-trifluoromethylphenol and γ-aminopropyltrimethoxysilane were added to toluene and stirred at 200-300 rpm for 20-30 min. Then, paraformaldehyde was added, and the mixture was stirred at 300-400 rpm for 6-8 h in an oil bath at 80-90 °C. After the reaction was completed, the mixture was cooled and filtered. The solvent was removed by rotary evaporation at 55-65 °C, and the filtrate was dried under vacuum at 40-50 °C for 6-8 h to obtain fluorosilicone modified benzoxazine.

3. The method for preparing a low-dielectric filler for packaging chips according to claim 2, characterized in that: The mass ratio of p-trifluoromethylphenol and γ-aminopropyltrimethoxysilane to paraformaldehyde is (50-60):(55-65):(20-30).

4. The method for preparing a low-dielectric filler for packaging chips according to claim 1, characterized in that: The preparation method of F-Si-alicyclic EP is as follows: Under nitrogen protection, alicyclic epoxy resin and terminally epoxy polydimethylsiloxane were added to toluene and stirred at 200-300 rpm for 20-30 min. Perfluorooctyltriethoxysilane and Karstedt catalyst were then added, and the mixture was stirred at 80-90 °C and 300-400 rpm for 6-8 h. After the reaction was completed, the mixture was cooled, activated carbon was added to adsorb and remove the catalyst, and the mixture was filtered. The filtrate was washed with deionized water and separated. The organic phase was dried with anhydrous magnesium sulfate, filtered, and the solvent was removed by rotary evaporation at 50-60 °C. The mixture was then vacuum dried at 60-70 °C for 6-8 h to obtain F-Si-alicyclic EP.

5. The method for preparing a low-dielectric filler for packaging chips according to claim 4, characterized in that: The mass ratio of alicyclic epoxy resin, terminal epoxy polydimethylsiloxane, perfluorooctyltriethoxysilane and Karstedt catalyst is (100-120):(20-24):(10-14):(0.1-0.2).

6. The method for preparing a low-dielectric filler for packaging chips according to claim 1, characterized in that: The preparation method of fluorosilicone modified low-viscosity CE-BZ-EP prepolymer is as follows: Under nitrogen protection and in an oil bath at 70-80℃, F-Si-alicyclic EP was mixed with fluorosilicone-modified benzoxazine and stirred at 200-300 rpm for 20-30 min. The mixture was then stirred at 100-110℃ and 300-400 rpm for 0.5-1 h. After the reaction was completed, the temperature was lowered to 70-80℃, and dicyclopentadiene cyanate and iron triacetylacetone catalyst were added. The mixture was stirred at 120-130℃ and 300-400 rpm. The viscosity of the system was monitored during the reaction. After the reaction was completed, heating was stopped, and the reactive system was transferred to an ice-water bath and rapidly cooled to room temperature to obtain fluorosilicone-modified low-viscosity CE-BZ-EP prepolymer.

7. The method for preparing a low-dielectric filler for packaging chips according to claim 6, characterized in that: The mass ratio of F-Si-alicyclic EP, fluorosilicone-modified benzoxazine, dicyclopentadiene cyanate, and catalyst iron triacetylacetone is (20-30):(40-50):(60-70):(0.1-0.2). The viscosity of the system is monitored during the reaction. When the viscosity of the reaction system at 90℃ is 2500-3000 mPa·s, the reaction is complete and heating is stopped.

8. The method for preparing a low-dielectric filler for packaging chips according to claim 1, characterized in that: The preparation method of F-mesoporous SiO2 is as follows: Under nitrogen protection, mesoporous silica was added to anhydrous ethanol and stirred at 200-300 rpm for 20-30 min. Perfluorooctyltriethoxysilane and deionized water were added to adjust the pH to 4-5. The reaction was carried out at 70-80℃ and stirred at 300-400 rpm for 6-8 h. After the reaction was completed, the mixture was cooled, filtered, and the filtrate was washed with ethanol and dried under vacuum at 70-80℃ for 6-8 h to obtain F-mesoporous SiO2. The mass ratio of mesoporous silica to perfluorooctyltriethoxysilane is (100-120):(3-4).

9. The method for preparing a low-dielectric filler for packaging chips according to claim 1, characterized in that: Functional additives include alicyclic glycidyl ether as a diluent, KH-560 as a coupling agent, phenyl silicone oil as a dielectric modifier, UV-329 as a UV absorber, 1010 as an antioxidant, BYK-333 as a leveling agent, BYK-055 as a defoamer, dicyandiamide as a curing agent, and 2-methylimidazole as an accelerator; by weight, the low-dielectric filler for the encapsulation chip includes 100-120 parts of fluorosilicone-modified low-viscosity CE-BZ-EP prepolymer and 45-55 parts of F - Mesoporous SiO2, 20-40 parts diluent alicyclic glycidyl ether, 1-2 parts coupling agent KH-560, 2-3 parts dielectric modifier phenyl silicone oil, 0.3-0.5 parts ultraviolet absorber UV-329, 0.3-0.5 parts antioxidant 1010, 0.2-0.4 parts leveling agent BYK-333, 0.2-0.4 parts defoamer BYK-055, 3-5 parts curing agent dicyandiamide and 3-5 parts accelerator 2-methylimidazole.

10. A low-dielectric filler for packaging chips, characterized in that: It is prepared by any one of the preparation methods according to claims 1-9.

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